Conference 7.286::space

See RENDEZVOUS WITH RAMA, Arthur C. Clarke, for another good reason to have such
detection equipment available.

Burns

    	That is almost as close as the planetoid Hermes came towards Earth
    in 1937 (400,000 miles).
    
    	To keep this Topic in tune with the Conference, I agree that a 
    space platform should be built to destroy any errant planetoids which
    could strike Earth (remember the small one that skimmed 36 miles above
    Earth's surface in 1972?  If it had hit, it would have created an
    explosion more powerful than several hydrogen bombs).  This would be
    done by putting a nuclear device aboard a rocket on the platform,
    which would be launched at the planetoid to fragment and/or deflect
    it away from Earth.
    
    	A possible better solution would be to find a way to deflect it and 
    then use it for scientific and mineral purposes.  
    
    	There would also have to be a way to keep the planetoid platform
    from being turned into a weapon against targets on Earth, or for
    deflecting the planetoids on enemy targets!  See Topic 165.
    
    	Larry
    

    .2 notwithstanding, I don't think we have the technology to deflect,
    much less break up, a rock 1/2 mile (2,640 feet) in diameter.  In
    some parts of the United States, such a rock would be considered a
    mountain.  Hitting it with an H-bomb will likely only cause a
    radioactive crater to be included with the package when it is
    "delivered".
        John Sauter

re:< Note 530.3 by SAUTER::SAUTER "John Sauter" >

In all honesty, it depends on how good we are at finding the asteroids 
on collision course and how fast we react.

It may be true that, in the terminal phases, it might do you no good to try 
and deflect the asteroid, but when an object is, say 5 or more revolutions 
from impact, even a small deflection (10 megatonnes?) should be sufficient.

With that kind of time frame, it may even be possible to have several 
tries using a penetrator type warhead.  A penetrating warhead is 
presently envisioned for command posts and should enable the bomb to 
explode in the bulk of the asteroid, firmly smashing it to pieces. 

I'm not even sure that a 10 megatonne bomb would be useless in the 
terminal phases, as I think I read somewhere that the crater from a 10 
megatonne ground burst is something like 1/2 mile in diameter.  You 
would still get damage, but nothing compared to 20,000 megatonnes!

If you doubt our ability to compute orbital mechanics may I just remind 
you that voyager II was something less than one second off on hitting 
uranus after playing cosmic billiard balls at jupiter and saturn.

The problem with asteroids is most definately detection, not prediction 
or destruction/deflection.

Tony

    I don't doubt our ability to compute orbital mechanics, I doubt our
    ability to deliver a heavy bomb to an asteroid in solar orbit, in
    time to deflect it.
    
    Consider the 1/2 mile asteriod.  How far away can we detect such an
    object?  I don't have the figures on me, but I suspect it can be
    detected only in the last few weeks of its approach, given current
    technology.  Care to bet on our ability to put a mission comparable to
    the Halley's Comet missions together in a few weeks?  Remember that a
    10-megaton bomb is heavy.  I don't know how much it weighs, but it's
    got to be more than a scientific payload.
    
    If the asteriod is large enough that we can detect it five revolutions
    away, it's probably so big that we can't launch a bomb big enough to
    deflect it a measurable amount.  It would be real embarassing to
    deflect it from a Pacific strike to, say, New York.
    
    Now I don't doubt that our technology will improve.  Someday we'll be
    able to detect smaller objects further away, and soft-land rockets that
    can push for a long time, making a significant change in the orbit of a
    moderate-sized asteriod.  My point is that we don't have the technology
    to do it today.  We don't even know how to clean the trash out of
    near-Earth orbit!
        John Sauter

    	This is why we should prepare now and start taking the time we
    have to get these planetoid "deflectors" into space one at a time,
    until they're fully operational and ready to go at a moments notice.
    I agree it would be foolish to try and send up a bomb from Earth's
    surface at a fast-approaching target, and not have backup defenses
    to boot.
    
    	As a side note, I would like to know why the announcement of this
    near-miss was delayed a month after it happened, and for how long
    did astronomers know of its approach?  Also, what planetoid was it,
    or is this a newly discovered one?
    
    	Larry
            

    Uh, just how would we detect an object that was only 10's of km or less
    in diameter when it is heading straight toward us?
    
    re warheads
    
    The Titan 2 carried at 25MT warhead and since the velocity requirement
    for LEO is similar to that for an ICBM, I think we could place a
    moderate sized warhead on an escape trajectory with existing launch
    vehicles.
    
    re .6
    
    A news item I caught last night said it was a new asteroid and that it
    was detected as is passed by. I suspect they didn't announce it until
    they had a good idea of it's orbital parameters since the obvious
    question is 'will it come back?'. I don't think there is any kind of
    'asteroid conspiracy' :-)
    
    gary
             

Re: Last two.

I read a newspaper account this morning that said it was not detected until
over a week after it had passed and "was a fast receding spot of light".

				Bill

    re: pity if we deflect it from the Pacific to New York.
    
    I wouldn't doubt that a strike on New York would be messy, however,
    a British astronomer suggested on television the other day, that
    a water strike would have generated a tidal wave over 1 mile high.
    She didn't suggest the radius of the effected zone, but a strike
    anywhere would seem to have dire consequences.
    
    Did anyone hear that the object was optically visable? Where did
    the reports originate, anyway? 

    re: .9---I didn't say "pity", I said "embarassing".  There are some who
    feel that the U.S. would be better off if New York City would simply
    vanish into the sea, and I didn't want to offend those people.
    
    A tidal wave over a mile high would effect all coastal areas,
    world-wide.  I don't have the numbers at my fingertips, but I don't
    believe Krakatoa's tidal wave was that large, and it went half-way
    around the world.  (To be sure, it wasn't destructive when it was only
    one foot high, but you did say "effected".)
    
    A shock that would cause a 5000-foot wave would also produce other
    effects, it seems to me.  Certainly atmospheric disturbances, and
    possibly an earthquake.
    
    My only knowledge of this incident comes from this conference, so I was
    amused to learn that it was only detected after its passage.  So much
    for our ability to detect close calls weeks in advance.
        John Sauter

    	According to a newspaper report I read, a 1983 study done in
    Colorado showed that a nuclear device with *half* the explosive force
    of the atomic bomb (Little Boy) dropped on Hiroshima in 1945 could
    deflect and/or destroy a planetoid one kilometer (0.6 mile) in
    diameter - and this planetoid was half a mile in size.
    
    	Now if we could start establishing some sort of early warning
    system in space, it seems that we could defend ourselves from what
    could become a major catastrophe.
    
    	I have the very sad feeling, though, that nothing will be done
    until a planetoid smashes into Earth and does serious damage, just 
    like no one puts up a stoplight at a dangerous intersection until
    someone gets hit and killed.
    
    	Even if it is a very small planetoid, there are fears that such
    a hit could be considered a first strike, and set off a nuclear war.
    
    	Larry
    

    I don't know what the status is today, but from 1969-1971 I worked
    on the Safeguard anti-missle system at Bell Labs before coming to
    DEC.  Of the two missiles used, the Spartan could hit an incoming
    asteroid with a nuclear warhead above the atmosphere.  Now, I think
    the treaty only allowed for a limited deployment between the USSR
    and USA.  If those things are stil operational at Grand Forks and
    Maltrsom (sp?), we have a limited capability today.
    
    Joe
    

    I doubt very much that the asteroid was visible without powerful
    optics.  Consider: it was very tiny, and twice as far away as the moon
    at its closest approach.

Re: .12

I believe the U.S. ABM facilities were put into mothballs in the early '80s.

- dave

    	As I said before, a space-based surveillance and defense platform
    is our best bet against a planetoid striking Earth.
    
    	Larry
    

re several:  I don't doubt that there is enough energy in bombs that are
within our technology to deflect fairly large asteroids nor that we easily
have the technology to do the orbital computations given the data.  The
data is the problem.  How massive is the asteroid, for example.  I would
think that a big problem would be how to prevent the asteroid from spending
most of the energy imparted to it in fracturing rather than changing course.
It's not clear to me that 1000 somewhat smaller, but still supstantial
pieces are that much better than one gigantic one.

re around .2:  What is this about a meteor/asteroid skimming 30-some miles
above the earth?  That must have been some moving to avoid getting slowed
down by friction and dragged down if it got that low.

Burns

    	In August of 1972 a meteor streaked through Earth's atmosphere just
    36 miles above the surface of North America in the daytime before 
    skimming back out into interplanetary space.  In the minute or so that 
    it was visible, an Air Force satellite tracked it, thousands of people 
    saw it, dozens took still photos of it, and one man even got a motion 
    picture film of it.  A 1974 issue of SKY AND TELESCOPE (I forget the 
    month, sorry), has a detailed article on the meteor, complete with
    stills from the motion picture film. 
    
	Larry
    

re:< Note 530.16 by DECWIN::FISHER "Burns Fisher 381-1466, ZKO3-4/W23" >

>The data is the problem.  

I agree with this.

>How massive is the asteroid, for example.  

Actually, this isn't really a problem, given one or two revolutions, 
with accurate locations, the mass of a body at about one a.u. will 
easily fall out of the equations.

>I would
>think that a big problem would be how to prevent the asteroid from spending
>most of the energy imparted to it in fracturing rather than changing course.
>It's not clear to me that 1000 somewhat smaller, but still supstantial
>pieces are that much better than one gigantic one.

Let me try and explain:  As you break the asteroid up into tiny pieces, 
you almost don't change the total volume, but you dramatically increase 
the surface area.  Frictional heating is porportional to surface area.  
So by increasing the surface area, you will increase the fraction of the 
asteroid vaporized by friction with the atmosphere.

Tony

    re .18:
    
    For mass determination, do you mean that within
    a few revolutions, the perturbations of *other
    object's orbits* can be meaured accurately enough
    to calculate the asteroid's mass ?? I don't understand.
    

re:< Note 530.19 by HYDRA::MCALLEN >
    
>    For mass determination, do you mean that within
>    a few revolutions, the perturbations of *other
>    object's orbits* can be meaured accurately enough
>    to calculate the asteroid's mass ?? I don't understand.
    
Well, either that way (assuming we have instruments sensitive enough, 
which I doubt), or certainly easier, the perturbation of the 
asteroids orbit by other massive bodies that it approaches.

Tony

From: [email protected] (Steve Willner P-316 x57123)
Newsgroups: sci.astro,sci.space
Subject: Asteroid Nearby
Keywords: asteroid collision
Date: 23 Apr 89 06:51:33 GMT
 
Paula Cleggett-Haleim
Headquarters, Washington, D.C.                     April 19, 1989
(Phone:  202/453-1548)
 
    NASA ASTRONOMER DISCOVERS "NEAR-MISS" ASTEROID THAT PASSED EARTH
 
     An asteroid, a half-mile or more in diameter, passed within a half 
million miles of Earth - about twice the distance to the Moon - on March 23, 
the National Aeronautics and Space Administration said today. 
 
     "On the cosmic scale of things, that was a close call," said Dr.
Henry Holt.  Holt is a University of Arizona astronomer who discovered
the asteroid while working on a U.S. Geological Survey (USGS) project,
funded by NASA, to detect and track unknown asteroids that cross the
orbit of Earth.  The project is headed by Dr. Eugene Shoemaker, USGS. 
 
     Dr. Bevan French, advanced program scientist for NASA's Solar
System Exploration Division, Washington, D.C., said that if the
asteroid had collided with Earth, the impact would have been
equivalent to the explosion of 20,000 hydrogen bombs creating a crater
5 to 10 miles in diameter - "enough to destroy a good-sized city." 
Landing in the ocean could have been worse since huge tidal waves
could have been created that would sweep over coastal regions, he said. 
 
     Although scientists do not know the asteroid's exact size, they
believe it to be over a half-mile in diameter.  A 6-mile-diameter
asteroid hit Earth about 65 million years ago.  It is popularly theorized 
that this caused a global catastrophe that destroyed the dinosaurs. 
 
     The asteroid, currently designated 1989FC, came closer to Earth
than any recorded since Hermes in l937, according to Dr. Brian
Marsden, director of the Minor Planets Center at the Smithsonian
Astrophysical Observatory, Cambridge, Mass.  Hermes passed Earth at
approximately the same distance as 1989FC.  [400,000 miles away.]
 
     The observatory, which is the international clearinghouse for
such discoveries, recorded the discoveries of about 1,800 asteroids
[This sounds far too high to me.  Maybe it includes recoveries of
previously known asteroids.  Or maybe I'm all wet.--SW] in l988.  In
the designation l989FC, l989 is the year of discovery; F indicates
discovery in the sixth half-month of the year (i.e. the end of March);
C indicates that the asteroid was the third discovered in that period.
If the asteroid is successfully observed on two subsequent approaches
to Earth, Holt will be entitled to name it. 
 
     Holt discovered the asteroid on a series of photographic plates
taken March 31 using the 18-inch Schmidt telescope at the California
Institute of Technology's Mount Palomar Observatory in California. 
 
    The object - estimated to be travelling 46,000 miles an hour -
appeared as a trail of light in two photographs of the sky near the
constellation Coma Berenices.  They were taken an hour apart.  The
asteroid was detected when the two photographic plates were examained
under a stereo microscope.  "I knew it was travelling fast by the
elliptical spot that it created," said Holt. 
 
    During the week following the discovery, subsequent observations
of l989FC were made by Holt and other astronomers to determine its
orbit.  Like Earth, l989FC takes about a year to go around the Sun. 
But its orbit is highly elliptical and extends past the orbit of Mars
and inward past the orbit of Venus.  Asteroid 1989FC is now moving
rapidly away from Earth and Sun.  It will return, crossing Earth's
orbit again in early October 1989, this time at a greater distance
from Earth. 
 
     Asteroid l989FC is only one of about 30 Earth-crossing asteroids
that have been discovered, although there may be many more.  Estimates
range from several hundred to more than a thousand.  Holt and Shoemaker 
regularly observe the sky during the "dark of the Moon," the period just 
before and just after the new Moon phase.
 
Steve Willner            Phone 617-495-7123         Bitnet:   willner@cfa
60 Garden St.            FTS:      830-7123           UUCP:   willner@cfa
Cambridge, MA 02138 USA                 Internet: [email protected]
 

    re Safeguard
    
    The Safeguard system was brought to fully operational status and stayed
    that way for 24 hours before being decommisioned. The series 'War &
    Peace in the Nuclear Age' had a segment on Safeguard and the site at
    Grand Forks AFB in its last episode. They claimed it was operational
    for a month. I prefer the 24 hour version, but either way it was
    completed as a proof of concept  rather than an operational base.
    
    The ABM treaty allowed for one or two bases with a limited number of
    missiles. The Soviets still have an ABM system protecting Moscow.
    
    Yes, Spartan could hit something at around LEO altitude and with the
    current SOTA of detection/monitoring it would probably be the most
    effective thing we could throw at an asteroid. The warhead may have to
    change as the Spartan warhead was optimised for a high X-Ray flux, not
    blast effects.
    
    gary

re .19:

    
>Well, either that way (assuming we have instruments sensitive enough, 
>which I doubt), or certainly easier, the perturbation of the 
>asteroids orbit by other massive bodies that it approaches.

I think Galileo showed that if the smaller object's mass is negligible
compared to the larger that the larger will affect the smaller's motion
independent of the smaller's mass.  This would mean that you would have
to determine the asteroid's mass by its interaction on bodies comparable
in size to its own (or smaller).  If it did not go near such, then you
would have to depend on things like assumptions about its composition
and albedo or size measurement.

As to breaking it up:  Yes, I understand that there would be more surface
area and therefore more burning away.  That may be an improvement over an
absolutely certain direct hit.  However, if the known data is incomplete,
the hit may well be only a probability.  Then we have to do risk/benefit
analyses like, "If I know I can move this thing without fracturing it,
I'd better do it.  However, if I fracture it, which is the greater:  The
probability of a direct hit times great damage, or the higher probability
of a hit by some big chunks times less damage?  That's why I say we might
be worse off if we fracture it.  (Or maybe the big one hits Antarctica
or Siberia while the little ones hit all over the place)


Anyway, it's an interesting question.  We should be doing something about
it.

Burns

    Here's what we do:
    
    1. Identify the threat:
    
    We give some money to the USGS to beef up their search.  If you read
    Sky & Telescope you known that some amateurs have built automatic
    telescopes for monitoring binary stars.  These machines run a program
    every usable night that positions the scope, locks in on a series of
    target stars and takes brightness measurements that are recorded by a
    computer. A similar system could be used to systematicly search for
    asteroids. 
    
    2. Save the Earth:
    
    When a likely asteroid is found launch an international manned mission
    well in advance of it's approach to Earth.  The mission would be well
    equipped with a variety of nuclear explosives of varying yield.
    These are used to stabilize the rock and slow it down using the
    explosives for thrust like the Orion nuclear propulsion system.
    The rock is maneuvered into a safe capture orbit and takes up residence
    around Earth.
    
    3. Build houses:
    
    Given the raw material already in orbit ways can be found to process
    material in situ to build space stations and what have you.
    
    
    This is all stock SF stuff, but none of it's been mentioned here.
    The assumption has been that the best thing to do is to smash the
    thing or knock it aside and that we will get only one try at it,
    like in the movies.  I wanted to point out alternatives.
    
    Mike Hughes

    Re. breaking it up: Unless you can reduce it to pebble sized pieces,
    I doubt that it would make much difference. Meteorites pass through
    the atmosphere too quickly for more than a shallow surface layer
    to burn off, up to a cm or two I think. I understand that large
    bodies entering the atmosphere break up anyway, due to the immense
    pressures to which they are subjected; however, the pieces do not
    have time to move apart, and the material acts as if it were still
    a single body. The energy still has to go somewhere; it has been
    suggested that the Tunguska event (Siberia 1908) was due to the
    airburst of a substantial body, since no evidence of a crater was
    found. This seems to have been a very glancing blow, much like the
    1972 event, but probably through lower and denser levels of the
    atmosphere. The air, unable to escape around the object due to its
    speed, would pile up in front of it as a tremendous 'bow wave';
    when it slowed sufficiently, the enormous pressure would be released
    as a colossal explosion. Like a nuclear bomb, such an explosion
    could actually do more damage than a groundburst, where much of
    the energy is expended in digging a crater and throwing material
    upwards.
      On deflection; LEO is not far enough out to be of much use, the
    body will probably be no more than seconds away from impact. The
    further away you can hit it the better. A deflection that at 10E6
    miles would cause it to miss by 10e4 miles would, if applied at
    10e3 miles, alter its point of impact by just 10 miles; about the
    width of the crater.
      On the 65,000,000 year ago event-no crater has ever been found.
    It has occurred to me that a likely point of impact is the area
    now occupied by the Hawaian islands. These are a somewhat anomalous
    hotspot in the middle of an ocean plate, and this hotspot has been
    around for a very long time, generating a chain of volcanoes the
    remains of which are found all the way across the plate (for those
    not familiar with plate tectonics, the hotspot is in the mantle
    beneath the crust, and the ocean crust is moving over it). A body
    of 10+km diameter would act as an enormous piston; air and seawater
    in its way would be forced, at enormous temperature and pressure,
    down through the ocean crust and into the mantle below. Much would
    of course promptly explode outwards again, together with the pulverized
    material of the asteroid; but even a couple of km� of volatiles
    might have a dramatic effect upon the chemistry of the mantle for
    a long time afterwards. There is no crater now, because that particular
    bit of the ocean crust has long since moved away, and been subducted;
    I think in the general area of Northern Japan/Sakhalin. Anyone with
    more knowledge of geology care to comment?

    re: .25---On the last point, about the Hawaiian Islands.  My geology
    knowledge is pretty weak, but I think that Hot Spot has been around a
    lot longer than 65e6 years.
        John Sauter

    re: .25---  Most experts believe that if there was a asteroid impact 
65e06 years ago that Iceland is a high probabity result of the impact.  
As I recall, it seems as if Iceland is the magic 65e06 years old and 
also very vulcanic.

Tony

re:< Note 530.25 by REPAIR::RICKETTS "Have you tried kicking it?" >

>    Re. breaking it up: Unless you can reduce it to pebble sized pieces,
>    I doubt that it would make much difference. 

One technology developed for taking out hardened command sites was a 
penetrating nuclear warhead.

There are also a very effective terminal guidance systems available, 
e.g. the u.s. a-sat system and the recent star wars, sdi test.

I cannot do more than guess at the effect of a say 10 megatonne warhead 
exploding, say 100 yards deep in a 1/2 mile diameter asteroid.  I think 
a LOT would be vaporized instantly, maybe as much as 1/2 of it.  I think 
a lot of what's left would be pebble sized or smaller and I think all 
the pieces would all be moving away from each other quite fast.

I've got to believe that this type of "attack" would be far preferable 
to a direct strike by the asteroid and quite easy to do.

Tony

    A detection system that is required would be rader systems scanning
    the sky.  They would not have to be that powerful to detect a target.
    
    Can todays IBM's hit anything in space ?

 Re 26: The hotspot may have been around a lot longer, but I don't think
    there's any evidence for it. I don't think there is any ocean crust
    quite that old on that particular plate; it has all been subducted.
    
 Re 27: An asteroid impact could be responsible for Iceland, but much
    more recent, I'm sure the place is not that old. (The figure
    3X10e6 years springs to mind, but I'm open to correction.) There
    are no subduction zones in the North Atlantic, so any evidence on
    the seabed or in the ocean crust should still be (relatively!)
    accessible, so long as it isn't actually underneath Iceland. Remember
    that Iceland is on a mid-ocean ridge, and the two sides of the Atlantic
    are moving apart; any impact features formed there 65X10e6 years
    ago would now be halfway between Iceland and either Scotland or
    Greenland.
    
  Re 28: Probably right, I expect it would be *very* difficult to reduce
    it to pebble-sized bits without the pieces going in all directions
    rather than continuing together. Not sure how the warhead would
    take the impact though; the missile would have to be travelling
    at or near escape velocity if it were fired from earth, while the
    asteroid would be coming towards us at anything from 20 to 70 km/s.
    Wouldn't the initial impact simply vaporize the warhead before it
    had a chance to penetrate? These things are designed to hit the
    surface of the earth at speeds orders of magnitude below the likely
    closing velocity of an asteroid. Of course, if you could detect
    it far enough out, you could loop round and hit it from the side
    or rear, and might then be able to penetrate rather than explode
    on impact. Depends on its composition as well; irons are rarer,
    but would probably be much more difficult to penetrate or shatter
    than stones.  

        According to the May 1989 issue of the Boston L5/NSS SPACE NEWS
    newsletter on page 2, a relatively large meteorite struck the Soviet
    Union on February 12, 1947 only 400 kilometers (250 miles) from the
    city of Valivostok with the force of an atomic bomb.

        This event was unknown to me until this article.  Does anyone 
    have any further information on this meteorite strike?

        Larry

re:< Note 530.30 by REPAIR::RICKETTS "Have you tried kicking it?" >

> Re 27: An asteroid impact could be responsible for Iceland, but much
>    more recent, I'm sure the place is not that old. (The figure
>    3X10e6 years springs to mind, but I'm open to correction.) 

Sorry, if I wasn't clear enough.  I heard Dr. Louis Alverez, of the 
iridium layer fame speak.  He stated in his talk that he thought Iceland 
was the most likely evidence of an asteroid strike 65 m yrs ago

>Remember
>    that Iceland is on a mid-ocean ridge, and the two sides of the Atlantic
>    are moving apart; any impact features formed there 65X10e6 years
>    ago would now be halfway between Iceland and either Scotland or
>    Greenland.

I certainly am no geologist and I don't pretend to know the ages of the 
mid-ocean ridges, but what if the asteroid impact caused the ridge?

Tony

>I certainly am no geologist and I don't pretend to know the ages of the 
>mid-ocean ridges, but what if the asteroid impact caused the ridge?
    
    As was stated, these ridges are caused by upwelling of material as
    tectonic plates move apart.  The 100's-of-miles-long ridges are found
    all over the earth.
    
John

From:	DECWRL::"[email protected]"  "3-May-89 0922 EDT" 4-MAY-1989 
        17:33:14.29 
To:	[email protected]
Subj:	Searching for Asteroids.

    The most recent issue of FINAL FRONTIER has a few paragraphs about
a fellow named Zook at NASA who is working on an automated wide-field
camera for asteroid searching.  It seems very similar to the idea I
mentioned before in this list:  Electronic imaging tied to software
motion detection. 
 
    According to Zook, the system will be able to see down to 23rd
magnitude, seeing 1 meter diameter objects out to the Moon and 100 m
diameter objects out to 0.5 AU (at opposition, presumably). 
 
    This system, if it is built and if it works, should locate many
thousands of small near Earth asteroids.  An excellent use for NASA
funds, IMHO.  The more asteroids we know about, the easier is it to
plan multiple fly-bys by a single spacecraft, and the more accessible
the best candidate will be. 
 
	Paul F. Dietz
	[email protected]
 
	Not too much faith should be put in experimental results
	until they are confirmed by theory.
 

From: [email protected] (Greg Goebel)
Newsgroups: sci.space
Subject: Re: Re: Asteroid Encounter
Date: 1 May 89 15:21:48 GMT
 
    Dealing With Threats From Space
 
   Michael Lemonick
 
   TIME / 9 JUN 86 / P 65
 
   It is a sunny afternoon in Karachi, and streets of Pakistan's largest
   city are crowded with shoppers, apparently unconcerned about the rising
   tension between Pakistan and India.  Suddenly a second sun bursts into
   view overhead, so bright it temporarily blinds thousands and so hot it
   blisters the skin.  Thirty seconds later, the shock wave hits, 
   crumbling buildings and throwing people to the ground.  To the 
   Pakistanis, only one explanation is possible for the tremendous blast:
   India has launched a nuclear attack.  They immediately order their bombers,
   armed with atomic bombs, to strike back at India, which responds in kind.
   Only later do the surviving officials learn of their mistake.  The 
   object that exploded over Karachi was not a nuclear weapon but a large
   meteor hurtling in from outer space.
 
    Though this sounds like the plot for a TV movie, Eugene Shoemaker,
a respected US Geological Survey scientist, is concerned that just
such an event -- and an unwarranted reaction -- could occur. 
Shoemaker expressed his fears at a Baltimore meeting of the American
Geophysical Union (AGU):  "The effect of a meteor blast appears the
same as a high-altitude nuclear explosion," he said. "If this happens
in the wrong place, people will think they've been nuked." 
 
    Meteors, which are asteroids or cometary debris that has entered
the atmosphere, continually shower Earth.  Most of them are small
and either break up or are burned to ash by friction.  But, explains
Shoemaker, the incineration of larger asteroids is far more violent. 
As asteroid 80 feet across, striking the atmosphere at 50,000 MPH,
compresses the air in its path so much that in effect the asteroid is
stopped dead in its path, converting kinetic energy almost
instantaneously into heat, light, and a powerful shock wave.  That
causes a tremendous explosion, in this case equivalent to a
one-megaton bomb. 
 
    If a meteor were to burst in the atmosphere tomorrow, Shoemaker
says, "the Soviets and the US would know what it was" and not react
militarily.  Their detectors could distinguish between a nuclear
explosion -- which generates million-degree temperatures, X-rays, and
gamma rays -- and an exploding meteor -- which would produce
considerably lower temperatures and no deadly radiation. But smaller
nations, unaware of the nature of the blast, might react violently.
Says Shoemaker:  "Suppose it happens over Syria or Pakistan?"  He
proposes that the US immediately try to determine whether the
explosion was of cosmic origin and notify the affected nation. 
 
    Since 1973, Shoemaker has been photographing the sky in search of
asteroids that periodically cross Earth's orbit and thus pose a
danger of collision. To date, he says, 57 such asteroids at least 1 km
in diameter have been catalogued.  In addition, about three
Earth-crossing comets are detected each year.  From the rate at which
new Earth-crossers are detected, Shoemaker estimates that there are
some 2,000 asteroids in this category and that 100 comets intersect
Earth's orbit every year. 
 
    His calculations suggest that asteroids packing the explosive
energy of one megaton should enter the atmosphere on an average of
once every 30 years, larger asteroids with a 20-megaton punch every
400 years, and a 1 km, 10,000 megaton comet or asteroid once in
100,000 years. 
 
    This century has already seen a major meteorite blast.  In 1908,
either an asteroid or comet exploded about five miles above the remote
Stony Tunguska River region of Siberia, igniting and flattening trees
over hundreds of square miles.  From descriptions of the blast and
photographs of the damage, scientists have estimated that the object
was at least 200 feet across and caused a 12-megaton explosion. 
 
    Depending on their velocity, size, and composition, some meteors
survive the fiery trip through the atmosphere at hit the ground, at
which point they are called meteorites.  Most are in the form of
pebbles or small rocks, but occasionally they are much larger. 
Scientists think it was a 130-foot chunk of meteoric iron that hit
Arizona with a force of 15 megatons between 20,000 and 50,000 years
ago, digging a crater three-quarters of a mile across and 600 feet deep. 
 
    But even greater menace lurks in the darkness of space. 
Scientists have speculated that objects as large as several miles
across have crashed into Earth, spewing millions of tons of debris
into the atmosphere, blotting out the Sun for months or years, and
causing mass extinctions of life -- including, many believe, the
dinosaurs.  Of the known larger Earth-crossers, none seem to pose a
threat in the near future.  But, says Shoemaker, "until we have
tracked all of them, something could sneak up on us." 
 
    What if a large asteroid or comet is discovered heading for Earth?  
At the AGU meeting, Shoemaker and colleage Alan Harris, of the Jet 
Propulsion Laboratory in Pasadena, California, suggested that the
intruder could be diverted by landing a thrusting device on it.  As a
last-ditch effort, a small nuclear warhead could be detonated on or
near it.  Says Shoemaker:  "We have the technology to do that right
now."  But if the explosion simply broke the meteorite into large
chunks, the danger would only be multiplied.  "The more prudent
solution," says Harris, "is to burrow a substantial charge into the
object and blow it to smithereens." 
  

From: [email protected] (John Sahr)
Newsgroups: sci.space
Subject: Re: Rendezvous with Rama (was Re: Re: Asteroid Encounter)
Date: 15 May 89 15:20:05 GMT
 
    In article <[email protected]> [email protected]
(Henry Spencer) writes: 
>In article <[email protected]> [email protected] (Wayne 
>D. T. Johnson) writes:
>>It would be interesting to know how far an Earth based radar can reach with
>>the accuracy to detect killer rocks?
>
>For radars of practical size with practical power output, the range is
>zero on an astronomical scale.  The trouble is that radar return is an
>inverse *fourth power* function of distance, since the inverse-square law
>gets you once in each direction.  And you thought inverse square was bad...
>Arecibo, with the biggest dish on Earth (not even vaguely steerable) and
>a monstrously powerful custom-built transmitter, can get useful radar
>echos from *planets*... but it's not easy.  The biggest conventional
>radars on Earth have trouble tracking inert objects out at Clarke-orbit
>distances, one-tenth of the way to the Moon.  For a 100m rock at
>planetary distances, forget it.  Optical tracking is much better -- it's
>only inverse-square, since the Sun supplies the illumination.
 
    Actually, the "inverse fourth power law" only applies to point
targets, that is, targets which are much smaller than the radar beam. 
Other types of targets are inverse square laws, such as ionospheres,
which fill the radar beam, and there are even a few inverse cube laws,
such as E-region backscatter (fills the beam one direction, but not
two directions (sometimes)). 
 
    Asteroids are "inverse fourth power" objects, as Henry states.
 
    Arecibo also does duty as an incoherent scatter (atmospheric)
radar.  For ball park estimates, these radars could spot a Canadian
dime at a distance of a thousand kilometers or so.  I'll point out
that although the Arecibo dish is not steerable, the antenna is
somewhat steerable, because the feed can be moved around.  There is
another big radar in Peru, whose "dish" is somewhat _larger_ than
Arecibo's, the Jicamarca Radio Observatory near Lima.  However,
Arecibo has higher gain because of its higher radar operating
frequency, and there are other important differences. 
 
    Food for thought:  Suppose the maximum killer asteroid speed is
100 km/s. If the entire sky is examined once a day, then to have at
least a one day warning for a "bullseye" asteroid, you need to be able
to spot them when they are about 8e6 km away, which is about 20 times
the distance to the Moon. 
 
    Arecibo gathers signals from Io over about an hour. "But Io is
really far away, so that's pretty good, right?"  Well, no doubt about
it, radar observation of Io is neat, but Io is right where you expect
it to be, and it is as big as the Moon, and it isn't moving very fast,
or rather, its speed is known precisely ahead of time.  None of the
above are true for asteroids, and it makes a big difference for
radars.  In fact, if all you knew about Io was that it was "out
there," it probably wouldn't be found (by radar).  Yet Galileo found
Io with a binocular power telescope, and even he happened to be
looking at Jupiter at the time---he knew where to look.  Asteroids are
solitary wanderers. 
 
    More food:  The mass (kinetic energy) of an asteroid varies as
r^3, while its radar cross section varies as r^2 (r is the asteroid
radius). From the inverse-fourth power law for point targets, the
range R at which an asteroid of radius r is first detectable varies as
r^(-1/2).  If you think about it, this says that you'll always start
seeing asteroids at about the same distance, at least the ones that
are worth seeing.  I won't go into it, but this has implications for
the utility of Stealth technology. 
 
    Upshot:  Current radars are not even close to being able to
usefully spot the next author of a Meteor Crater or even of a Hudson's
Bay.  Optical searches are still the way to go. 
 
>Mars in 1980s:  USSR, 2 tries, |     Henry Spencer at U of Toronto Zoology
>2 failures; USA, 0 tries.      | uunet!attcan!utzoo!henry [email protected]

John Sahr,       Dept. of Electrical Eng., Cornell University, Ithaca, NY 14853
ARPA: [email protected]; UUCP: {rochester,cmcl2}!cornell!calvin!johns
 

    Moved by moderator -
    
             <<< VIKA::SYS$SYSDEVICE:[NOTES$LIBRARY]SPACE.NOTE;1 >>>
                             -< Space Exploration >-
================================================================================
Note 651.0                        Is this true                         4 replies
35847::RECUPAROR                                     27 lines  28-AUG-1990 09:43
--------------------------------------------------------------------------------
    Can anybody confirm this.
    Thanks in advance.
    Rick
    
    
                 <<< OCTAVE::DJA1:[NOTES$LIBRARY]UFOS.NOTE;2 >>>
                    -< Unidentified Flying Objects (UFOS) >-
================================================================================
Note 162.41                   The End of the World                      41 of 51
VAXRIO::MARCOS                                       15 lines  24-AUG-1990 12:40
                                     -< y >-
--------------------------------------------------------------------------------
I've just heard that Aussie astronomers discovered MU 1990, a big asteroid
which according to Duncan Steel at Adelaide University can crash on Earth in 2
years causing earthquakes, seaquakes and a cloud of dust which could freeze the
planet. Does any one know anything about it?

fearful sights and great signs shall there be from heaven
the sea and the waves roaring
the sun shall be darkened, and the moon shall not give her light

Hummmmmm

What has urged Dan Quayle to ask NASA to assess the orbits of some asteroids?

M.E.

    
             <<< VIKA::SYS$SYSDEVICE:[NOTES$LIBRARY]SPACE.NOTE;1 >>>
                             -< Space Exploration >-
================================================================================
Note 651.3                        Is this true                            3 of 4
42110::RICKETTS "Have you tried kicking it?"         38 lines  28-AUG-1990 11:25
                             -< LDPSCI::ASTRONOMY >-
--------------------------------------------------------------------------------
    This is the note from the ASTRONOMY conference. As you can see,
    Dr Olsen-Steel's original comment seems a little less apocalyptic.
    
    
                    <<< LDP::DJA1:[NOTES$LIBRARY]ASTRONOMY.NOTE;1 >>>
                         -< Astronomical Discussions >-
================================================================================
Note 628.17                Asteroid 1989FC, near miss                   17 of 17
ADVAX::KLAES "All the Universe, or nothing!"         26 lines  17-AUG-1990 13:40
                 -< Another "close" call - Planetoid 1990 MU >-
--------------------------------------------------------------------------------

  Reut 08/17 1056 AUSTRALIAN ASTRONOMERS FIND ASTEROID CROSSING EARTH'S PATH
 
   SYDNEY (AUG.  17) REUTER - Australian astronomers said on Friday they had
discovered an asteroid several hundred metres (yards) long which crossed
Earth's orbital path in June.

   The asteroid, temporarily named 1990MU, came within two million km
(1.2 million miles) of Earth's surface and intersected the planet's
path around the Sun.

   It was found by astronomers Robert McNaught and Doctor Duncan
Olsson-Steel using telescopes at the Siding Spring Observatory near
Coonabarabran, New South Wales.

   They estimate 1990MU to be hundreds of metres (yards) long and say it
should cross Earth's path again in two years.

   "I believe at the next cycle it will be a lot closer to the Earth,"
Olsson-Steel said by telephone from Adelaide.  "But the chances of it
hitting the Earth within the next thousand or million years are extremely
remote."

   About 70 asteroids which cross Earth's path have been found, but
scientists estimate 1,000 exist.  Most asteroids in the solar system are
grouped between the orbits of Mars and Jupiter.
 

             <<< VIKA::SYS$SYSDEVICE:[NOTES$LIBRARY]SPACE.NOTE;1 >>>
                             -< Space Exploration >-
================================================================================
Note 651.4                        Is this true                            4 of 4
3168::BIRO                                            9 lines  28-AUG-1990 13:33
                                -< Footfall... >-
--------------------------------------------------------------------------------
    Gee, all SF books have them landing in the Middle East,
    I wonder If we can wait that long  :*)
    
    All kiding asside, the big news will be a mining mission
     It will be a wonderful oportunity to try such a mission
     but who will be able to do it...
    
    john
    

Article: 36830
From: [email protected] (Robert M. Unverzagt)
Newsgroups: sci.space
Subject: Re: Near miss with Earth?
Date: 27 Oct 91 19:36:36 GMT
Sender: [email protected]
Organization: The Aerospace Corporation, El Segundo, CA
 
In article <[email protected]> [email protected]
(Dave Tholen) writes: 

>Tom von Alten writes:
>
>>Someone mentioned to me that there was a near miss between the Earth and
>>another sizable chunk of rock in the last few days.  He said that it
>>was 6hrs, or 400,000 miles away.
>
>1991 TU passed less than 500,000 miles from Earth on October 8.  This
>object is another in the 10 meter size range.  It was discovered by the
>same instrument (Spacewatch Camera on Kitt Peak) as was 1991 BA in
>January (the 10 meter rock that missed by a bit over 100,000 miles).
 
I heard that 1991 BA was due back in Earth's neighborhood early
next year.  Is this true?  Does anybody have the orbital elements
of this chunk of rock?  Will the next near-Earth encounter be
as close?
 
Shag
-- 
--------------------------------------------------------------------------
        Rob Unverzagt        |   "They put a hot wire to my head
   [email protected]   |    Because of the things I did and said..."
--------------------------------------------------------------------------

Article: 36835
From: [email protected] (Dave Tholen)
Newsgroups: sci.space
Subject: Re: Near miss with Earth?
Date: 27 Oct 91 21:39:03 GMT
Sender: [email protected]
Organization: Institute For Astronomy, Hawaii
 
Robert M. Unverzagt writes:
 
> I heard that 1991 BA was due back in earth's neighborhood early
> next year.  Is this true?  Does anybody have the orbital elements
> of this chunk of rock?  Will the next near-earth encounter be
> as close?
 
Not true.  The orbital period of 1991 BA is 3.2 years, so it's still
heading out toward aphelion, which it will reach on 1992 October 13.
Nowhere near Earth at the moment, and fainter than magnitude 30.
 
Lots of astronomers have the orbital elements for 1991 BA, including
myself.  To low precision, a = 2.2 AU, e = 0.7, and i = 2 deg.  Do
you need the full-blown precision?
 
Depends on what you mean by the "next" Earth encounter.  I haven't run
an extended ephemeris, but I don't believe the next few minima in
geocentric distance are nearly as small as the previous one.  Some of
those minima in geocentric distance are quite large, however, so they
may not correspond to your idea of an "encounter".

Article: 17867
From: [email protected] (Nick Szabo)
Newsgroups: sci.space,sci.astro,sci.geo.geology
Subject: Scientific American article: origin of the asteroids
Date: 27 Oct 91 20:18:43 GMT
Organization: TECHbooks of Beaverton Oregon - Public Access Unix
 
October's Scientific American has an excellent article on the origin
of asteroids, by Richard Binzel, M. Antonietta Barucci, and Marcello
Fulchignoni.  Highly recommended.  Under fair use for educational
purposes, I have digested a summary: 
 
It was once thought that asteroids were the debris of a shattered planet.  
Actually, asteroids are remnants of a planet that failed to form. 
 
Calculations indicate there are about one million main belt asteroids
with diameters greater than one kilometer.   Depletions occur in
regions where the orbital period of a body would be an integer ratio
of Jupiter's orbital period.  The increase in asteroid eccentricity
and splitting into resonances caused by Jupiter prevented the
accretion of a planet.  Jupiter also perturbs many asteroids into
collision with each other, at an average speed of 5,000 meters per
second, pulverizing them. 
 
Jupiter also perturbs many asteroids into flyby trajectories or
collisions with itself.  Flybies accelerated the asteroids, much like
the Voyager spacecraft, ejecting them out of the solar system. Jupiter
flybies and collisions may have cleared the asteroid zone of most of
its original mass, leaving behind the remnants observed today. A small
number of asteroids have been captured by Jupiter, becoming moons. 
 
Furthermore, Mars perturbs some asteroids towards Earth.  These
near-Earth asteroids live only 10-100 million years -- far shorter
than the 4,500 million year age of the solar system.  They disappear
because of collisions with Earth, Venus, or Mars, or near misses which
result in a flyby trajectory and ejection from the solar system.  Some
near-Earth asteroids are probably the remains of comets whose volatiles 
have been evaporated by the Sun, at least from their surface.  Meteor 
showers originate from the dust of comets, but one major shower, the 
Geminid, is associated with the asteroid 3200 Phaethon. 
 
A large collision with Earth may have initiated the mass extinctions
of the dinosaurs et. al. 65 million years ago.  Smaller impacts,
occuring about once a century, release the energy of a small nuclear
warhead.  A large object hit Tungaska in 1908, and there have been
several near misses since.  This past January observers discovered the
asteroid 1991BA just hours before it passed within 0.0011 AU -- less
than half the distance from Earth to the Moon. 
 
The rotation of irregularly shaped asteroids causes cycles in
reflected sunlight.  The rotation rate can be deduced by observing the
variations, and from rotation rates astronomers can infer the kinds of
collisions an asteroid has experienced.  Each noncatastrophic
collision adds a random rotational energy.  Small asteroids spin
quickly, larger asteroids more slowly.  This trend reverses for
asteroids greater than 125 km diameter, because their gravity either
keeps them intact or causes the shattered fragments from catastrophic
collisions to reaccumulate.  Many of these large bodies are believed
to be rubble piles, shattered to the core. 
 
IRAS, the infrared telescope satellite, measured 2,000 catalogued and
many more uncatalogued asteroids.  IRAS showed that large asteroids
are brighter in the infrared than small asteroids. This implies a
compositional difference, supporting the theory that many smaller
asteroids are fragments originating in the interiors of larger parent
bodies.  IRAS also discovered dust bands in the asteroid belt,
confirming the collisions occur frequently. 
 
Asteroids have been classified into the following categories:
 
* Primitive, including the C, D, and P types.  Primarily rich in
  carbon and water; found mostly in the outer belt.
 
* Metamorphic, including the F, G, and B, and T types.  These
  are similar to primitive asteroids except that they have fewer
  volatiles, implying that they have been heated.  Peak in the
  middle of the belt.
 
* Igneous, including the S, M, and E types.  Found mostly in the 
  inner belt; appear to have formed from a melt and contain complex 
  mineral assemblages.
 
Heating may have been due to a large primordial solar wind, decay
of aluminum-26 from a supernova, and/or asteroid collision.  
 
Knowledge of asteroids is quite incomplete.  Observed differences in
the distribution of meteorites and asteroids have not been resolved.
Telescopic observations and meteorite studies remain the main methods
of exploration.  Planned upgrades to Arecibo and Hubble should provide
new knowledge.  The Galileo Gaspra flyby, and the proposed Italian
Piazza and U.S. Discovery small satellite missions to near-Earth
asteroids will enable us to explore asteroids from up close. 
-- 
[email protected]  ...!{tektronix!nosun,uunet}techbook!szabo
Public Access UNIX at (503) 644-8135 (1200/2400) Voice: +1 503 646-8257
Public Access User --- Not affiliated with TECHbooks

Article: 17864
From: [email protected] (David Oesper)
Newsgroups: sci.astro
Subject: FTP Asteroid File?/Gene Roddenberry/Excellent Asteroid Book
Date: 27 Oct 91 23:40:38 GMT
Sender: [email protected] (USENET News System)
Organization: Iowa State University, Ames IA
 
Is there a file of all named asteroids available via FTP?
 
By the way, did you know there is an asteroid named 2309 Mr. Spock?
Fascinating.  I'd like to suggest that an asteroid be named in honor
of the late Gene Roddenberry.  Asteroid Roddenberry would be a fitting
tribute to this visionary man who brought us Star Trek.  May Gene's
legacy live long and prosper! 
 
For an excellent introduction to the minor planets, I highly recommend
ASTEROIDS: THEIR NATURE AND UTILIZATION by Charles T. Kowal. Mr.
Kowal's passion for this subject really shows, and this combined with
his friendly, not-overly-technical style makes this a classic! 
 
David Oesper  (S Per)
Ames Area Amateur Astronomers
Ames, Iowa

Article: 17877
From: [email protected]
Newsgroups: sci.astro
Subject: Re: FTP Asteroid File?
Date: 28 Oct 91 12:52:18 GMT
Sender: [email protected] (Uutis Ankka)
Organization: University of Helsinki
 
In article <[email protected]>, [email protected]
(David Oesper) writes:
 
> Is there a file of all named asteroids available via FTP?
 
    There are eg. minor planet catalogs made by Jost Jahn.
    There are also names of there asteroids.  I don't know
    how new version the listing is, but I think Jost can 
    comment this himself (e-mail: [email protected]).
 
    These files are available in following ftp sites:
 
    ftp.funet.fi      /pub/astro/pc/dbases      (SFX archives for PC)
    mandarin.mit.edu  /astro/data.etc/asteroids (Compressed unix files)
 
				Veikko Makela
				Computing Centre
				Helsinki University
				<[email protected]>

Article: 17928
From: [email protected] (Bruce Scott)
Newsgroups: sci.astro
Subject: Re: Scientific American article: origin of the asteroids
Date: 29 Oct 91 17:51:24 GMT
Organization: Max Planck Institut fuer Plasmaphysik
 
Re: the statement to the effect that Jupiter's presence affected asteroid
formation:
 
The summary, quite understandably, compiled present-day beliefs concerning
the mechanism of asteroid formation. One should be careful, however. It is
also conventionally believed that accretion timescales rise with distance
from the sun in the solar nebula (accepting that the sun formed, quickly,
first). Please observe that the gas giants are the farthest away. We *must*
speak about gas-rich accretion since the gas-giant cores had to accrete
and then capture gas (this is due to the decidedly non-solar composition)
as per Mizuno (Icarus late 1970s or ca. 1980). Any model which addresses
Jupiter as a cause for events in the inner solar system as the latter forms
must state how the gas giants form first. Possibilities: ordering by gas/fluid
motions in the nebula disk (an old idea which waits for better computations
than those yet done), maybe ice sticks better giving an earlier start (I'm
sure this has been thought of, but by whom, and what has been done?), or
something resulting from the fact that vertical convection is strong really
only in the outer disk regions where ice grains give an opacity function
rising fast enough with temperature (B Scott, Astr Ap, v247, p419, 1991).
 
My pet belief is somewhat different, springing from the situation of
convection in disk regions where the ice condensation temperature is
between those at the disk midplane and radiative surface. Details will
be in a paper to be published next year (the work is done). The upshot:
no vertical convection in these regions(!) Someone else will have to tell
me what this contrast might mean for planetesimal formation. If, as is
likely, planetesimals need fluid dynamical help to get going in the
disk lifetime (ca. 10^6 yrs), we have a possible explanation. I believe
the presence of gas giant *formation regions* had nothing to do with
asteroid formation. Criticism is welcome.
-- 
Gruss,                                  The deadliest bullsh*t is
Bruce D. Scott                           odorless and transparent.
bds at dgaipp1s.bitnet                      -- William Gibson
Max Planck Institut fuer Plasmaphysik

Date: 1 Dec 91 21:31:38 GMT
From: (Bruce Watson)
Subject: Mysterious Space Object an Asteroid

    From the Dec 1, 1991 Denver Post:

    MYSTERIOUS SPACE OBJECT AN ASTEROID
                              
    A small object discovered last month hurtling through space turned
out to be a tiny asteroid.  The rock -- 30-feet in diameter -- is one of
the smallest asteroids yet detected, said University of Arizona scientist 
Tom Gehrels.  Astronomers thought it might have been a man-made object. 

Article: 18850
From: [email protected] (Tom Sullivan)
Newsgroups: alt.alien.visitors,sci.astro
Subject: Mystery Object of Thursday, 12/5
Date: 11 Dec 91 17:00:40 GMT
Sender: [email protected] (Usenet Administration)
Organization: NSDD, Data General Corp.
 
I've seen nothing on the net regarding this, but I found this in the Globe:
 
Without permission from the Boston Globe, 12/7, page 13:
 
Mystery object eludes astronomers
 
By David L. Chandler, Globe Staff
 
	The unidentified object that hurtled past Earth before dawn on
Thursday remains a mystery, astronomers said yesterday, and it
apparently slipped by without them getting a good look.

	A week ago, astronomers had decided that the tiny object,
which passed slightly farther away from Earth than the moon's distance
of 240,000 miles, was probably an asteroid -- a chunk of
interplanetary rock probably less than 30 feet across [BUT, read on!].

	But observations on Monday by European astronomers working in
Chile showed dramatic variations in brightness which suggest an
irregularly shaped, tumbling object with great variations in its
surface reflectivity, much more so than expected for a natural object
like an asteroid, said Brian Marsden, an astronomer.

	Marsden, director of the Cambridge-based International
Astronomical Union's Bureau for Astronomical Telegrams and Minor
Planet Center, said yesterday that the variation in brightness "means
we are dealing with some very peculiar object.  I would say man-made.
I think it wold be hard to explain this kind of variation with a
natural object, even a small one."

	But Marsden and others are still puzzling over what kind of
man-made object it is.

	Marsden said two weeks ago that it was probably the leftover
Centaur rocket used in 1974 to launch a sun-observing satellite called
Helios.  But more precise calculations of the object's orbit, based on
the latest observations, show that, traced backwards, it never quite
meets Earth, as it should if it had been launched from Earth.

	There is a possible explaination for that descrepancy, Marsden
said:  Centaur rockets sometimes contain leftover hydrogen fuel after
they reach orbit, and this fuel could continue to leak out, perhaps
for years.  This could propel the rocket in unpredictable directions,
like air escaping from a balloon that send it careening aound a room.

	During its closest approach to Earth on Thursday, the object
was too far south to be visible from anywhere in the northern
hemisphere.  Astronomers at the European Southern Observatory in Chile
tried to get pictures of it shortly after its closest approach in
order to get more precise data on its exact path and to make further
measurements of its brightness variations.

	But as of yesterday, they were unable to find any sign of the
object in their pictures.

	Because of the difficulty of the observation and the faintness
of the object, astronomers Richard West and Oliver Hainaut at the
observatory in the Chilean Andes continued to examine their images
carefully yesterday.

	These observations are essential to guarantee the success of a
planned radar observation of the object when it returns to visibility
in the northern hemisphere next week.  A successful radar observations
"would clinch it" as to whether the object is natural or artificial,
Marsden said.

	"I was hoping it would be natural," said Marsden, because that
would make it a very unusual type of asteroid and the smallest ever
detected, and therefore interesting to astronomers.  But because of
the brightness changes seen this week, he is now "90 percent sure"
that it is artificial.

	Because of the uncertain movements of a rocket leaking
leftover fuel, however, it may never be possible to identify it as a
specific rocket.

	If it is artificial but not any known rocket, that might
explain the astronomers' inability to locate it in their pictures,
Marsden joked.

	"Maybe that's why they couldn't be found last night," he said.
"Maybe they landed."
  
Tom

Article: 19026
From: [email protected] (Daniel Fischer)
Newsgroups: sci.astro,sci.space,alt.alien.visitors
Subject: The famous Dr. Steel on 1991 VG [Forwarded]
Date: 17 Dec 91 17:39:15 GMT
Sender: [email protected]
Organization: Max Planck Institut fuer Radioastronomie
 
From [email protected] Tue Dec 17 05:49:11 1991 ...

.... did I get the following paper which he asked me to post to the net:
 
==========================================================================
 
		A ROCK OR A ROCKET?
 
On November 6th astronomers operating the Spacewatch telescope at Kitt
Peak in Arizona found what was at first assumed to be a small rocky
asteroid.  It was given the code-name 1991 VG.  More recent
observations from Chile have indicated that this body, which raised a
flurry in the world's media when it flew close (on an astronomical
scale) by the Earth on December 5th, may in fact be an old rocket body
returning to our planet's vicinity. 
 
Spacewatch, operated by Tom Gehrels, Jim Scotti and David Rabinowitz
(University of Arizona) is a relatively small (91 cm aperture)
telescope which has been fitted with a large CCD array and programmed
to search for objects such as asteroids and comets which approach the
Earth.  They do this by letting the sidereal rotation of the Earth
cause the instrument to scan across the sky, with the same area being
returned to later, and again once more as a check.  Any objects which
have moved between scans are picked up by the software, and the
operator may then make a visual inspection of the data and calculate a
preliminary orbit for the new-found object.  Especially for the
fainter detections many of the orbits turn out to be geocentric, a
piece of man-made debris being indicated.  However some very small
asteroids have been discovered in this way: 1991 BA last January (the
closest-ever observed miss of our planet, at 170,000 km) and 1991 TU
in October (at 750,000 km).  1991 VG is the second-closest observed
fly-by, at 450,000 km, or just further away than the Moon.  All three
of these objects were estimated to be about 5--10 metres in size, and
are therefore the smallest and intrinsically-faintest items ever
observed telescopically above the atmosphere. 
 
However, 1991 VG was soon realized to be in an unusual orbit for an
asteroid: its path is very similar to that of the Earth, being almost
circular (eccentricity 0.08), the size of its orbit just 5\% larger
than that of the Earth (so that it takes just a few weeks longer than
a year to circuit the Sun), and, critically, an extremely small
inclination to the ecliptic, the plane of the Earth's orbit.  The
latter parameter has a value (about a quarter of a degree only) which
is consistent with a man-made spacecraft.  Initial computations by
Brian Marsden (Harvard-Smithsonian Center for Astrophysics) indicated
that it might be an upper stage from the U.S. Centaur rocket which put
the German Helios 1 satellite into a heliocentric orbit in December
1974, since tracing the orbit of 1991 VG back in time showed a close
approach about then.  A Soviet craft was also a possibility.  However,
as better astrometric data for 1991 VG came in it was possible for its
orbit to be improved, and Marsden found that he could not identify a
close approach to the Earth since the beginning of the space age, and
so the `rocket' option was discounted. Since there are about a billion
asteroids of this size or larger believed to orbit in the inner solar
system, the chances are that some of them will have orbits very
similar to the Earth, and in fact these are much more likely to be
detected by telescopes like Spacewatch.  From the opposite point of
view a calculation of the probability of a collision by such an object
with our planet indicates that its lifetime against such an event is
only about 250,000 years, which means that it must have arrived in its
present orbit in the astronomically-recent past.  Marsden suggested
that it might be an object which had spent most of its life in a
so-called `Trojan' orbit, having exactly the same orbital period as
the Earth but keeping 60 degrees ahead or behind of the planet at all
times, until it recently slipped that mooring.  Many Trojan asteroids
are seen in association with Jupiter, and in 1990 a Mars Trojan was
discovered. 
 
However, close to the fly-by of 1991 VG Richard West (European
Southern Observatory) collected time-resolved images of the object
using the Danish 1.54 m telescope in Chile: the path taken at that
time was over the South Pole and therefore out of the reach of most
northern telescopes.  He found that the brightness of 1991 VG varies
rapidly and has a period of about 7--8 minutes, with several extremely
bright flashes being detected.  These are as expected for a rotating,
shiny spacecraft which occasionally renders a specular reflection in
the direction of the viewer.  Such a short period also seems
inconsistent with a natural rocky asteroid, since it is unlikely that
such an object of 5--10 m diameter could have a spin period of less
that one hour without flying apart: its cohesive strength would be too
low.  In addition the relative brightnesses in different regions of
the visible spectrum were essentially solar, warranting for a
colourless object rather than a reddish asteroidal reflection
spectrum.  West concludes that 1991 VG is most likely an artificial
object rotating about more than one axis. 
 
This being the case it opens up a problem for dynamicists: if 1991 VG
is indeed the Centaur rocket body launched in 1974 then how has its
orbit been perturbed so as to bring it back to our vicinity now?  One
possibility is that excess fuel has escaped and therefore had a
rocket-effect without being ignited.  It also seems inevitable that it
will also soon be claimed as being an alien spacecraft left by
extraterrestrial visitors, even though science will undoubtedly be
able to provide a plausible solution.  If it is a rocket then 1991 VG
also provides an example of mankind's ability to pollute not only his
own planet and immediate space environment, but interplanetary space
as well: the prevention of such pollution was the subject of a
resolution of the International Astronomical Union at its General
Assembly in Buenos Aires last August. 
 
So is 1991 VG a rock or a rocket?  An answer to this may be gained
over the next week when Steve Ostro (Jet Propulsion Laboratory)
attempts to get radar echoes from it using the giant radar at Arecibo
(Puerto Rico).  An attempt from Goldstone (California) on December
12th was unsuccessful.  The radio reflection properties of metal are
very different to those of rock, so that a spacecraft would give a
much stronger echo; its structure would also affect the returned
polarization.  Even then the answer may not be  definitive since it is
known that many asteroids, like meteorites, are made of nickel-iron. 
 
Is it so unlikely that a spacecraft would come back to Earth?  In
fact, using the orbit of 1991 VG prior to the recent encounter (a =
1.05 AU, e = 0.075, i = 0.22 deg) the chance of this object hitting
the Earth converts to a lifetime of only 250,000 years (other
Earth-crossing asteroids have lifetimes more like 100 million years). 
Increasing the cross-section to that having a radius equal to the miss
distance of 450,000 km implies that an object in such an orbit would
fly-by the Earth by that distance or less once per 20 years or so:
pretty frequent. 
 
Duncan Steel,
Anglo-Australian Observatory,
Coonabarabran, NSW.
 
From [email protected] Tue Dec 17 13:20:36 1991
Received: from sun02 by mpirbn.mpifr-bonn.mpg.de (5.64/7.0)
	id AA05616; Tue, 17 Dec 91 13:20:29 +0100
Received: from shark.mel.dit.csiro.au by mpifrrouter (4.1/SMI-4.0)
	id AA03006; Tue, 17 Dec 91 13:18:51 +0100
Received: from aaocbn.oz.au by shark.mel.dit.csiro.au with SMTP id AA17832
  (5.65c/IDA-1.4.4/DIT-1.3 for <[email protected]>); Tue, 17 Dec 
  1991 23:18:13 +1100
Message-Id: <[email protected]>
Date: Tue, 17 Dec 91 23:17 EST
From: [email protected]
Subject: NOT HELIOS 1?
To: [email protected]
X-Vms-To: IN%"[email protected]"
Status: R
 
                                               1991 December 17th.
Dear Daniel,
 
Thanks for the message.  I believe that Brian Marsden identified a
COSMOS craft from earlier in 1974 as a possibility, but at that time
he was looking for returns around that time (prior to a good orbit for
1991 VG being available).  Now no return to the Earth's vicinity is
found purely from gravitation: some have looked at the possibilities
of radiation pressure for a large hollow object (or a panel), or fuel
escaping.  It is not possible, it seems, to  narrow down to a
candidate if the year (even) when the object was last close to the
Earth is not known. 
 
I believe that the Helios 1 booster is still listed in the Satellite
Situation Report (i.e. return to Earth's surface NOT indicated)
although I will need to check on that tomorrow. 
 
Duncan Steel
=====================================================================
Dr Duncan Steel,
Anglo-Australian Observatory,
Private Bag,
Coonabarabran, NSW 2357,
Australia.
 
"[email protected]" or "[email protected]" or "PSI%AAOCBN.OZ.AU::DIS"
 
Telephone:  +61 (0)68 426 314 (AEST is 10 hours ahead of GMT/UT)
            +61 (0)68 426 220 (home)
Fax:        +61 (0)68 842 298 
=====================================================================

Article: 20808
From: [email protected] (Len Bucuvalas x5363)
Newsgroups: sci.astro
Subject: Answers on 1992CS
Date: 5 Mar 92 22:17:01 GMT
Sender: [email protected]
 
In all fairness .... here are 2 answers from what seems to be
intelligent and respected professionals in the industry.....I used to
live in Mass so I can tell you that MIT's requirements for researchers
are MOST stringent! 
 
Len
 
----- Begin Included Message -----
 
>From [email protected] Wed Mar  4 06:46:12 1992
Date: Wed, 04 Mar 92 09:47:09 -0500
 
Rumors of an imminent impact have no basis.  Rick Binzel certainly
does not know of any likely asteroid impacts in the next few years,
and that is one of his major studies.  In fact, he just helped write a
paper studying the likelihood of any such impact over some large
stretch of time (100 years? I'm not sure).  There are no asteroids
currently known which are likely to impact the earth in the forseeable
future.  The paper also has a proposal for a national policy for
searching for asteroids on an impact course.  I haven't read the
report, but from what I recall from his talks, he expects that it
would take nearly a century to identify most of the asteroids which
have any possibility of approaching the earth, if we had a systematic
search program underway.  Another conclusion I recall is that the
likelihood of any individual being killed by an asteroid/meteor is
much lower than many other risks we take for granted.  While a major
meteor strike would kill many people, they happen extremely rarely, so
the probability of you being killed by one is very very small.  As
Rick puts it, he's not losing any sleep over it.  It is simply
something we should start looking into; sometime in the future, maybe
a hundred years, maybe a thousand, there will be a major impact, but
perhaps by that time we can predict it and even do something about it.
 
In the meantime, put your fears to rest.  There is no evidence of a
major impact imminent.  The chance of a major impact happening in your
lifetime, or even your grandchildren's lifetime, are extremely low,
and we cannot predict asteroid orbits accurately enough that far in
the future even for those asteroids for which we have "good" orbits. 
These rumors of an imminent impact sound very much like typical
end-of-the-world or government-conspiracy rumors.  Last year someone
claimed there would be a devastating earthquake in Missouri, and lots
of people got concerned in spite of geologists statements that there
was no evidence for an imminent earthquake.  The earthquake did not
happen on the claimed date, and people have forgotten about it.  I
expect the same thing to happen to this rumor. 
 
					Steve McDonald
					Earth, Atmospheric & Planetary Science
					Massachusetts Institute of Technology
					[email protected]
 
>From [email protected] Wed Mar  4 01:43:42 1992
Date: Tue, 3 Mar 92 23:39:48 HST
From: [email protected] (Dave Tholen)
Subject: Re: Asteroid CS1992
Newsgroups: sci.astro
Organization: Institute for Astronomy, Hawaii
 
There is no asteroid designated CS1992.  This isn't even a proper
asteroid designation.  If "some circles" are using this designation,
and if it is an unusual object in any way, then it would have been
reported to the Minor Planet Center and received a real designation by
now.  1992 CS is a real designation, but if it were unusual, I would
have heard about it by now. 
 
Regarding the destruction of an asteroid using a nuclear warhead,
there is ample scientific explanation.  It is well known that
asteroids have collided with the Earth in the past, and will continue
to do so as long as there is a supply (the main belt) and a mechanism
for putting them into Earth crossing orbits (perturbations by
Jupiter).  A collision with a sufficiently large asteroid could cause
widespread devastation, something that most people would like to
avoid.  Such a catastrophe could be avoided by either diverting the
asteroid or destroying it.  Nuclear warheads offer sufficient energy
to do the job. 
 
I know of no connection to a tract of land in Australia.
 
Jost Jahn posts the periodic Earth-crossing asteroid ephemerides, but
the answer was from someone at MIT (and probably hasn't made it across
the Usenet yet, so I'll include it here). 
 
================================================================
From: [email protected] (Steve McDonald)
Newsgroups: sci.astro
Subject: Re: Asteroid CS1992
Date: Tue, 3 Mar 92 17:38:46 EST
Sender: [email protected] (News system)
Organization: Massachusetts Institute of Technology
 
In article <[email protected]>
[email protected] (Len Bucuvalas x5363) writes: 

>We are looking for exact scientific information regarding an 
>asteroid, that has in some circles been named CS1992.
>
>In particular, we wish to know its current position, its orbital elements,
>and future orbital path, including any possible interceptions with the
>orbit of the Earth and any possible 'near' misses in the next 20 years.
>
> [lots of stuff about anti-meteorite icbm's and rumored 1000-occupancy
>  survival shelters in Australia]
 
CS1992 doesn't sound right; perhaps you mean 1992CS, which is a proper
form for an asteroid designation?  CS1992 is not a proper form. 
 
I have not seen any IAU circular on anything designated 1992CS (or
CS1992). Nor has Rick Binzel, a major asteroid specialist, heard of
it.  But if there is an asteroid designated 1992CS, we can immediately
infer several things about it.  First, it was only discovered in the
first half of February this year.  Newly discovered asteroids follow a
very specific naming sequence; 1992 is the year of discovery, C means
first 15 days of February, and S means it was discovered after 1992CR.
 Next, we can immediately infer that we know very little about it.  It
has only been under observation for a little over two weeks.  You can
get a preliminary orbit calculation from three observations, but it
takes much more than that to be able to confidently recover it a year
later.  And it takes many years of observations before the orbit is
refined enough to list it with the asteroids with confidently known
orbits (at which time it gets a permanent number and a name).  So
predicting earth approaches even just a year or two from now with only
two weeks of observations is ridiculous. The error bars are absolutely
huge.  It is impossible to blame any of the things this author
mentions on such a recently discovered asteroid. 
 
					Steve McDonald
					Earth, Atmospheric & Planetary Sciences
					Massachusetts Institute of Technology
					[email protected]
 
----- End Included Message -----

From: [email protected]
Newsgroups: sci.physics
Subject: "What's New" March-13-1992
Date: 13 Mar 92 21:43:16 GMT
Lines: 66

Received: from Forsythe.Stanford.EDU by faraday.phys.psu.edu
	(4.1/PSUCS-1.0-PHYS) id AA05280; Fri, 13 Mar 92 15:58:57 EST
Return-Path: <[email protected]>
Message-Id: <[email protected]>
Date:      Fri, 13 Mar 92 12:58:32 PST
To: [email protected]
From: "CHRISTINE REES" <[email protected]>
Subject: What's New for March 13, 1992
Status: R

WHAT'S NEW, Friday, 13 March 1992                  Washington, DC

2. THERE IS AN URGENT NEED TO REDIRECT U.S. WEAPONS SCIENTISTS as
well. In Los Alamos on 4 Feb 1992, one speaker called for a fleet of
1200 powerful new missiles to be made ready and armed with the world's
entire arsenal of nuclear warheads!  And Edward Teller urged
development of a superbomb, 10,000 times more powerful than the 65
megaton monster the Soviets exploded in 1960!  Lowell Wood became so
excited he could not contain himself; from the back of the auditorium
he shouted "Nukes forever!"  The enemy?  A killer comet.  One might be
discovered any day, headed for a collision with Earth.  Those who had
defended the free world from the evil empire, far from becoming
irrelevant, would now save Earth from cosmic disaster.  Congress
directed NASA to conduct workshops on both detection (WN 6 Mar 92) and
interception of near-Earth objects.  The organizers of the Los Alamos
interception workshop regretted that the press had been mistakenly
barred. 

Robert L. Park  [email protected]      The American Physical Society

To:  WHATSNEW (Personal Dist. List)

------------------------------

From: [email protected] (Jim Carr)
Newsgroups: sci.physics
Subject: Bob Park vs. the Star Warriors
Summary: NYTimes opEd page, 25 March 92
Date: 25 Mar 92 19:42:37 GMT
Sender: [email protected]
Reply-To: [email protected] (Jim Carr)
Distribution: usa

Those of you interested in Asteroids and Lowell Wood should not miss
the lengthy opEd piece by Bob Park in today's (Wed, 3/25) NYTimes.  He
leads with the story of Lowell Wood's "nukes forever" cheer at a Los
Alamos conference and closes with a question about who will stop him. 

In between he makes it clear that he supports the general concept of
the NASA proposal to spend 50 M$ in capital and 10 M$/yr operating a
tracking network that would identify possible risks over a tens of
years time scale, but questions (not quite strong enough word, I
think) the wisdom of building a 1,200 missle fleet armed with giga-ton
warheads. 

That last line is not a misprint.  Apparently it was mention of the
possible need for bombs 10,000 times stronger than the largest ever
tested (and the first test was in the 10 Megaton range, so they are
talking about 100 Gigaton to perhaps 1 Teraton bombs) that
interested/excited Dr. Wood.  We were reading this at lunch, where it
was noted that 1 Teraton is about 10^{15} kg while the mass of the
Moon is a bit less than 10^{23} kg.  Thats a lot of TNT. 

--
J. A. Carr                                    |  "The New Frontier of which I  
[email protected]                           |  speak is not a set of promises
Florida State University  B-186               |  -- it is a set of challenges."
Supercomputer Computations Research Institute |   John F. Kennedy (15 July 60)

  So is this guy Lowell Wood some famous scientist who has turned into a wacko
or was he just a wacko to begin with? 

  Obviously the odds that these gaziga tons of neucs would be miss used on
Earth far out weighs the small chances that they would be used to save us from
any cosmic disaster. 

  George

    re .48
    
>  Obviously the odds that these gaziga tons of neucs would be miss used on
>Earth far out weighs the small chances that they would be used to save us from
>any cosmic disaster. 
    
    Why do you think that the nukes *wouldn't* be used to save us from a
    collision? Do you mean the odds of the collision itself are very low?
    
    I agree with your first point that there are risks of mis-use. What if
    the nukes are pre-orbited somewhere out where they would be needed
    anyway and fitted with civilian aeroplane like transponders - the idea
    being that if anyone starts to move one any interested party will know
    about it.
    
    How are we going to test them? Nuclear test ban treaties aside, I'm not
    volunteering my backyard and I wouldn't want the defense of my planet
    depending on something completely untested. Space testing, I suppose?

    re .49
    
    I think the problem is that Los Alamos is proposing 1200 HUGE nuclear
    weapons to hit earth orbit intersecting asteroids.
    
    BEFORE WE EVEN KNOW IF ONE IS GOING TO HIT WITHIN THE NEXT MELENIUM!
    
    Before we know how many of thease weapons woudl be required to do the
    job (wouldn't 1 do?).
    
    I firmly believe that action is needed.  I think building or perhaps
    even designing the nuclear weapons is way premature.  We need the
    telescope network and computer analysis to determine the risky objects,
    first.  Then we need to find out what it would take to make the risky
    objects safe.  That is the time to be quoting warhead yield and number.
    
    One kind of gets the impression that the scientists at Los Alamos want
    to keep a nuclear force for the U.S., disguised in the name of defense
    for the entire earth from asteroids.
    
    Tony

  I don't think this contraption would be used successfully for several
reasons. 

  1). The probability of a large asteroid hitting Earth is very small and not
      likely to happen in our life time or any time within the next thousand
      years. Most likely it would never be used.

  2). Even if an asteroid came right toward us the chance that we would detect
      it in time are small. In fact one missed us by several thousand miles a
      few years ago and no one saw it until it had already passed. Since the
      save guards on this system would be great it would probably have to
      be seen months ahead of collision for there to be time to do the
      politics necessary to activate the system.

  3). Even if we hit it, the chances are small that it would do any good.
      turning a multi-megaton slug into a multi-megaton of buck shot might
      result in more damage if it hit a wider area. Then again maybe not,
      but who knows?

  4). The political controversy that would result from attempting to build
      this system would result in so many delays, changes and compromises
      that the system would be at best expensive and at worst useless.

  When you stack these problems up against the danger of the system being
miss-used it's a big loser all around. The only way this system would ever
save us would be if a 1 in 1 million coincidence occurred. The chances of
it being miss-used over it's several hundred year life would be much larger
than that.

  All and all, we are much safer without it.

  George

    I have to disagree with George JUST a slight amount, but only a slight
    amount, I think he is mostly right on.
    
    The detection part can be improved.  We currently don't look for
    anything like small asteroids.  With the appropriate telescope net and
    computer resources, we should be able to plot out all the orbits for
    earth crossing asteroids within 10 years.  The article mentioned
    something like $50 million capital and $10 million per year operating
    would be all that was required to catalouge all asteroids and calculate
    their orbits.
    
    We should only consider building something to change a probable hit
    AFTER that is accomplished, when we know what we have to build.  
    
    George is concerened that if you just fracture the thing you might
    wind up doing more damage.  His concern is justified, that is why you
    want to perturb the orbit way before the object is to strike the earth,
    perturb the orbit away from colision, not destroy the asteroid.
    
    Tony

Article: 648
From: [email protected] (Peter E. Yee)
Newsgroups: sci.space.news
Subject: NASA completes asteroid workshop studies (Forwarded)
Date: 1 Apr 92 20:29:55 GMT
Sender: [email protected]
Organization: NASA Ames Research Center, Moffett Field, CA
 
Michael Braukus
Headquarters, Washington, D.C.     March 31, 1992
(Phone:  202/453-1549)
 
RELEASE:  92-43
 
NASA COMPLETES ASTEROID WORKSHOP STUDIES
 
     NASA today presented Congress with summaries of workshop studies
on detecting Earth-orbit-crossing asteroids and determining how to
deal with such threats.  The two workshops were in response to a
congressional request included in the Fiscal Year 1991 NASA
authorization bill. 
 
     The NASA-sponsored Near-Earth-Object Detection Workshop judged
asteroids with diameters 1 km or larger the most dangerous objects in
terms of potential for causing catastrophic global effects on Earth. 
Impacts of such asteroids are extremely rare and can be detected with
current ground-based technology, most likely decades in advance of any
collision. 
 
     The workshop's proposed detection plan builds on research
programs that NASA has funded for a number of years.  The plan calls
for a coordinated international network of specialized ground-based
telescopes for detecting Earth-approaching asteroids. 
 
     The Near-Earth-Object Interception Workshop was hosted by the
Department of Energy's Los Alamos National Laboratory in January 1992.
Participants at this three-day workshop discussed various schemes for
preventing an asteroid from colliding with Earth. 
 
Editors Note:
 
     General summaries of these two reports can be obtained from the
NASA Headquarters Newsroom by calling 202/453- 8400.  The detailed
findings of the Detection Workshop will be available from the NASA
Newsroom on April 2, 1992.  The detailed findings and technical papers
presented at the Interception Workshop will be available from the Los
Alamos National Laboratory, 505/667-7000, in the summer of 1992. 

Article: 21768
Newsgroups: sci.space,sci.astro,sci.geo.geology
From: [email protected] (Ron Baalke)
Subject: Asteroid Lectures at Griffith Observatory
Sender: [email protected] (Usenet)
Organization: Jet Propulsion Laboratory
Date: Mon, 20 Apr 1992 08:28:45 GMT
 
     The Griffith Observatory in Los Angeles, California, in
cooperation with The Planetary Society, are sponsoring a series of
evening lectures by JPL experts on asteroids.  The lectures are held
on Mondays at 7:30 PM at the following location: 
 
                           Planetarium Theater
                           Griffith Observatory
                           2800 East Observatory Road
                           Los Angeles, CA
                           Phone: (213) 664-1191
 
     Admission is $3.50 and tickets are sold at the Griffith
Observatory one half hour before the lecture.  The following lectures
are scheduled: 
 
     April 20 - Investigating Asteriods by Radar - Dr. Steven Ostro
 
                Bouncing radar beams off asteroids and studying the echoes
                give us surpising and useful information about asteroids'
                sizes, shapes, surface structures and orbits. Improvments
                will soon let us see near-Earth asteroids with the clarity
                of Galileo's images of minor planet Gasrpa.  This lecture
                shows recent results and describes new radar experiments
                being planned.
 
     April 27 - Asteroids and the Dinosaur Extinctions - Dr. Paul Weissman
 
                This talk explores the theory that the impact of a
                six-mile-diameter asteroid or comet 65 million years ago was
                responsible for the extinction of the dinosaurs and many other
                species.  The event could be repeated -- fossil records show
                that major impacts happended frequently in the past and will
                continue into the future.
 
     June 1   - Galileo Encounters Gaspra - Dr. Torrence Johnson
 
                The chief scientist for Galileo reviews the exciting results
                of our first closeup look at a minor planet -- Gaspra --
                visited by Galileo last autumn while enroute to Jupiter.
                Dr. Johnson discusses how we observe asteroids by spacecraft
                and what we learned about Gaspra.  Highlights include the
                latest pictures of Gaspra.

     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [email protected]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Denial is always the first
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | sympton.
|_____|/  |_|/       |_____|/                     | 
 
Article: 21736
From: [email protected] (Nick Szabo)
Newsgroups: sci.astro,sci.space
Subject: Re: comet approaching?
Date: 18 Apr 92 04:48:49 GMT
Organization: TECHbooks of Beaverton Oregon - Public Access Unix
 
In article <[email protected]>
[email protected] (be here now) writes: 
 
>I've heard stories about an approaching comet or meteor that is
>to pass quite close to Earth, sometime in December 1992.
 
This sounds like asteroid 4179 Toutatis (formerly called 1989AC). It
is predicted to pass 0.025 AU (about 3.8 million km) from Earth on
December 8, 1992.  1 AU is the distance from Earth to Sun.  Toutatis
is estimated to be 6 km (4 miles) in diameter: a mountain flying at us
at 50,000 miles an hour.  It will reach 9th magnitude, very bright for
an asteroid, making it a great opportunity for astronomers to learn
about the near-Earth asteroids.  Get those spectrometers ready! 
 
Toutatis' orbital parameters are perihelion=0.90 AU, a=2.60 AU,
e=.654, inclination=00.5.  Has anybody classified this asteroid yet
(eg silicate, carbonaceious, etc.)? 
 
The Galileo spacecraft, flying around the planets on its meandering
path to Jupiter, coincidentally flies by Earth on the same day. The
Galileo navigation team has been aware of Toutatis and has computed a
close approach distance of more than 1 million km on December 11th.
The asteroid will be easy to see from Earth but too small for
Galileo's telescope. 
 
>A couple of days ago I saw a short blurb on CNN about scientists
>taking seriously, the notion of putting together some sort of anti-
>meteor defense system so if there was a meteor on collision course,
>it could be blasted or moved out of harm's way.  Just how serious
>is this kind of reasoning.  Is there precedence??
 
A large object, about 100,000 tons, hit Siberia in 1908.  Much larger
objects have hit Earth over geologic time.  The one that wiped out the
dinosaurs was probably about the same size as Toutatis. There is good
reason to spend about $70 million -- about 4% the cost of the Hubble
Space Telescope -- on the Spacewatch telscope network so that we can
predict whether anything like this will happen during the next few
centuries.  Due to such telescopes, we have computed the orbit of
Toutatis well enough to know that it won't hit us.  But did not even
know it was coming until 1989! 
 
Diverting such an asteroid would be quite a bit more expensive than
merely predicting whether they will hit, but feasible if we know several 
years ahead of time -- hopefully more than 3 years ahead of time! 
 
Tracking these Earth-crossing asteroids is also important to science
and to prospecting for space resources, so even without a threat there
is good reason to find and study them.  There is no space-related
project I can think of that can produce as much value for as few
dollars as Spacewatch. 
-- 
[email protected]  Public Access User --- Not affiliated with TECHbooks
Public Access UNIX and Internet at (503) 644-8135 (1200/2400, N81) 

Article: 21770
From: [email protected] (Hugh Miller)
Newsgroups: sci.astro,sci.space
Subject: Re: comet approaching?
Date: 20 Apr 92 02:11:03 GMT
Sender: [email protected] (System PRIVILEGED Account)
Organization: Loyola University Chicago
 
In <[email protected]>
[email protected] (Dave Tholen) writes: 
 
>Arnold Gill writes:
 
>>     Perhaps you could enlighten me.  What was this 1978 blast over open
>>     water that was attributed to a comet in the atmosphere?  I have not
>>     heard anything of this.
 
>I'm not sure how much information is available that isn't classified, but
>in 1978, a spy satellite detected a blast of approximately 100 kilotons
>in the South Atlantic.  At the time, there was speculation that it was the
>result of a South African-Israeli nuclear test, but intelligence was unable
>to confirm that speculation.  So speculation currently centers around the
>hypothesis that the blast was produced by a Tunguska-like event, involving
>the collision with either an asteroid or comet.  There's not enough
>information to prove exactly was it really was, but collisions like these
>do happen on average once a decade, and the energy release is plausible,
>and because the nuclear test hypothesis has no intelligence to support it,
>the collision hypothesis appears to be the favored interpretation at this
>time.
 
    As I recall from rereading the publically available information 3
years ago for some research on S.A. and the bomb, Carter
administration experts testified loudly that the light flash picked up
by the Vela satellite could not be a lightning or other nonartificial
burst, since it had the peculiar "double-pulse" signature of a nuclear
explosion - a double-humped luminance curve with peaks about 1 sec.
apart.  Neither atmospheric nor Earth-impact meteoritic traces exhibit
this signature. 

    When the Reagan administration came into power, the clamps came
down on the incident.  The CIA President's administration has been
similarly close-lipped.  Go figure. 
-- 
Hugh Miller         | Dept. of Philosophy | Loyola University of Chicago
Voice: 312-508-2727 |  FAX: 312-508-2292  |    [email protected]
"Read broadly, think scientifically, speak briefly, and sell the goods!"
            -- Sinclair Lewis, _The Man Who Knew Coolidge_

Article: 21775
From: [email protected] (Nick Szabo)
Newsgroups: sci.astro,sci.space
Subject: Re: comet approaching?
Date: 20 Apr 92 08:20:09 GMT
Organization: TECHbooks of Beaverton Oregon - Public Access Unix
 
In article <[email protected]>
[email protected] (Josh 'K' Hopkins) writes: 
 
>	3) As a rule, asteroids don't go anywhere interesting. 
 
There may be exceptions.  Several "Jupiter family" short-period comets
have perihelion near 1 AU and aphelion near 5 AU.  They are
essentially in Earth-Jupiter transfer orbits.  The windows are rare:
if we have a 100 day window at aphelion and a 10 day window at
perihelion (just guesses), this gives a 2.3% chance of getting to
Jupiter and 2.7% of getting from Earth, or 6.3/100th of 1% chance of a
coincidence of the two, for each comet orbit.  If there are 10,000
undiscovered objects in these orbits, and an object's orbit is 5
years, that gives us a launch window every year once we have
discovered the objects.  The current number of active Jupiter-family
comets and their short lifetimes imply such a large population of
dark, dead objects, though many may have evolved into Apollo-Amor orbits. 
 
Similarly, some Apollo-Amor asteroids are close to Earth-Mars transfer
orbits (q = 1.0, Q = 1.5 AU), but windows will again be quite rare
unless we have discovered a large number of such objects. 
 
_Pioneering the Space Frontier_ suggested "cycling stations" in
continual transfer orbit between Earth and Mars to provide radiation
shielding during the trip.  An asteroid in such an orbit is a natural
cycling station. 
 
Since asteroids themselves are the most interesting destinations, :-)
the most interesting transfer orbits are those that take us out to the
Main Belt.  These are also the most numerous, since most Apollo-Amor
apohelions lie in the Belt.  I suspect we could even now find several
good Earth-to-Belt-via-Apollo transfer windows per year if we are not
picky about which asteroid is our destination. 
 
I note that while many objects may be _close_ to being in
planet-planet transfer orbits, few will be _exact_, since their
lifetime before colliding with one of the planets or being thrown by
it into a different orbit will (on a geological timescale) be shorter.
Any theorists out there want to compute how much shorter?  Using
something close but not exact (eg 2102 Tantalus q = 0.90, Q = 1.7 AU
for Earth-Mars) will add a small delta-v penalty, but being able to
use the object en route might make up for this.  Alternatively, we can
move a few tons of regolith for shielding from the asteroid to the
optimum transfer orbit. 
-- 
[email protected]  Public Access User --- Not affiliated with TECHbooks
Public Access UNIX and Internet at (503) 644-8135 (1200/2400, N81) 

Article: 22093
Newsgroups: sci.astro,sci.space
From: [email protected] (Daniel Fischer)
Subject: Re: DESTROYING/DEFLECTING COMETS - Here's the *official* opinion !!!
Sender: [email protected]
Organization: Max Planck Institut fuer Radioastronomie
Date: Mon, 27 Apr 1992 12:22:02 GMT
 
In <[email protected]>
[email protected] (Craig D. Berry) writes: 
 
>I was just reviewing the thread about the possibility of using rocket
>delivered nuclear bombs to nudge an oncoming asteroid or comet out of
>an Earth-impacting trajectory.  A question occurred to me:  Given the [...]
 
All those resurrecting the BIG sci.astro/sci.space thread about
fighting Earth-crossing asteroids would do good to read the papers
first that were actually written for the U.S. congress to study
exactly this problem - and which became public just 4 weeks ago! A
phone call to NASA's number (given in an announcement that came on 31
March on sci.space.news) sufficed to get *all* those papers to my home
here in Germany *for*free* - and these papers, based on 3 astronomical
conferences in 1991 and a military workshop in 1992, are much more
realistic than any of the concepts regarding asteroid-fighting I've
seen on Usenet in the past months. I shall give a very brief summary
of the findings (and apologize in case that someone has posted similar
stuff in the past few days; postings take up to 2 weeks to reach our
site...:-): 
 
  <> There is only need to find and fight asteroids with diameters
greater than 1 km. Impacts from those would cause a global-scale
disaster, killing perhaps billions and wiping out civilization (but
not the whole of mankind; we're still orders of magnitude below
crashes like the event 65 Myr ago). 
 
  <> There is a 1:10000 chance that such a body hits Earth during our life.
 
  <> There are approximately 2000 of these bodies in the inner solar
system at any given time that could in principle (through orbital
perturbations) go on Earth collision course. Less than 10% of these
have been discovered so far. 
 
  <> But to find nearly all of these (90% or more) would be possible
with a telescope network called The Spaceguard Survey (name taken from
A.C. Clarke's Rendezvous with Rama - they confess that in the
report!), consisting of six 2...3-meter telescopes with (2048
Pixel)^2-CCDs and real-time software that detects and tracks unknown
moving objects. This is an extension of the already very successful
Spacewatch on Kitt Peak; J.Scotti has reported here about its
successes repeatedly (do 1991 BA and 1991 VG ring a bell?) - to build
the Spaceguard would cost $50m, to run it an annnual $10-15m, and it
would have to operate for 25 years to reach said 90% completeness.
With a limiting mag. of 22mag Spaceguard would find any 1km asteroid
within 200 million km's. 
 
  <> The chance that even one of these is on collision course within
the next centuries is remote (much less than one percent), and the
chance that it will hit soon, i.e. within months, is still much much
smaller (figure not given). 
 
  <> Therefore it does not make sense and would be tremendous waste of
money to build an asteroid defense system that could knock down an
object close to Earth on short notice. *If* there's a killer lurking
out there, it is highly probable that it will be several years if not
decades till it crashes. 
 
  <> Thus a cool and systematic scenario of response is possible and
recommen= ded: 1) Observe its orbit and physical characteristics in
detail from Earth. 2) Send one or more reconnaissance spacecraft to
the body and study its composition, rotation parameters etc. in
detail. 3) And when it passes its perihelion, it is the right moment
for the actual intercept. 
 
  <> This intercept should consist of placing an (as yet unspecified,
but I bet they mean nuclear) 'powerful explosive device' close to the
asteroid to give it a kick. That should do the job and make it miss
Earth. All sophisticated ideas like putting a solar sail or a rocket
motor on the target body as well as overkill scenarios like Ed
Teller's idea of a megabomb to pulverize the body are science fiction.
(There must have been heavy fighting between the astrono= mers and
some old cold warriors and SDI freaks during spring: according to
reports in SCIENCE, SPACE NEWS and the INTERNAT.HERALD TRIBUNE many of
the defense people wanted the 'Intercept Study' to contain weird
weapon proposals - but NOTHING of that can be found in the summary
that was presented now; perhaps we'll find more in a detailed report
due in summer from the LANL.) 
 
That's in a nutshell what the world's top experts in asteroidology and
space weapons came up with in 18 months of work. Some aspects I
missed:  The Detection Study mentions Earth-crossing long-period comets
several times as possible hazards with only months or weeks warning
time (obviously; the role of amateur comet hunters is emphasized,
BTW!) - but the Interception Study does not mention how to fight them.
Also I do not quite get how an anti-asteroidal 'stand-off' weapon
works: if you explode a nuclear bomb not on but close to a body, the
latter will get only hot (there's no pressure wave generated) - how
will this constitute a kick? The Study warns of exploding a device on
or in the surface as this could break off a piece of the asteroid and
double the danger. 

And a thing that's nowhere mentioned in the reports:  What happens
next? Is congress forced to act on them or can they just ignore them?
The Spaceguard proposal notes that no money has been put aside to
finance it but fails to provide a detailed scenario of how to pay and
who should do it (it only stresses that the whole world should
participate). Any details released on that so far? 
 
+ [email protected] - Daniel  Fischer - [email protected] +
| Max-Planck-Institut f. Radioastronomie, Auf dem Huegel 69, W-5300 Bonn 1,FRG |
+----- Enjoy the Universe - it's the only one you're likely to experience -----+

Interesting!  Re "how does standoff weapon work", I would think that momentum
would be transferred to the asteroid simply by having fragments/gas from the
explosive device crash into it at high speed.  Of course, one would have to do
some calculating to determine whether the much smaller mass of the bomb x the
much higher speed of the fragments (but the fact that they would not all have
vectors in the correct direction!) would constitute create a significant velocity
change in the asteroid.

So let's do it!

Burns

    Re:.56
    
    	I don't know the details of why they want to use a stand off weapon
    but my geuss is they are not counting on the propulsive force of the
    explosion per se. Instead they are likely using the heat the bomb would
    generate to vaporize a portion of the asteroid and use that for
    propelling it out of the way.
    
    					Drew
     

Article: 26703
From: [email protected] (Bill Higgins-- Beam Jockey)
Newsgroups: sci.space,sci.astro
Subject: NEAR asteroid mission (but wait! There's more!)
Date: 24 Sep 92 14:12:12 GMT
Sender: [email protected]
Organization: Fermi National Accelerator Laboratory
 
Let's talk about the New, Improved NASA, with Secret Ingredient FCB!
 
Robert Farquhar, the wizard of ICE/ISEE-3 and the guy who suggested
Giotto's visit to a second planetoid, has left NASA Goddard and joined
the Applied Physics Laboratory at Johns Hopkins University.  APL has a
long track record of building modestly-sized spacecraft, especially
for the U.S. Navy.  Farquhar gave a talk at the World Space Congress
in one of the COSPAR sessions on a new project:  The Near Earth
Asteroid Rendezvous (NEAR).  It's part of something called the
"Discovery" series of lower-cost spacecraft NASA wants to do; I think
the figure $150 million was mentioned. 
 
I came into the talk late, but apparently caught most of it. 
 
Prime target is a 1998 launch to 4660 Nereus, an asteroid with an
orbit similar to Earth's, requiring a delta-V of 1.165 km/sec.  Launch
7 January 1998, arrive 16 January 2000. Spacecraft would go into an
orbit around the asteroid, distant at first, then sneaking in to lower
and lower orbits as Nereus's gravity field is better understood.  NEAR
would orbit in a plane perpendicular to the spacecraft-Earth line, so
its antenna always points at Earth, and rotate once per orbit, so its
instruments always point toward the asteroid. 
 
The Announcement of Opportunity is due about a year from now, but the
strawman payload includes visible imager, gamma-ray spectrometer,
imaging spectrograph (I presume seeing deep into the infrared),
magnetometer, and laser altimeter.  This last instrument is needed for
navigation, not just science, to get a good close orbit, and would
have a 20 km range.   The gamma-ray spectrometer would provide
information on the surface composition, but it needs a long
integration time (nominially one year for decent signal-to-noise), and
a fairly close orbit helps its spatial resolution. 
 
How does the spacecraft look?  Imagine a square cardboard box, 1.5 m
on a side (I moved to a condo last weekend, I've been looking at a lot
of these), a little shallower than a cube.  Open the four top flaps. 
These are the solar panels in a cross-shaped array.  Put a dish in the
center of the box. 
 
The fixed 1.5 m X-band dish allows (at 1 AU from Earth) 20.8 kbits/sec
using DSN's 34-meter ground stations, 83.8 kb/sec with the 70-m
dishes.  Solid-state data recorder would  hold 5E5 bits. (Now that I
look at my notes, that seems a bit small! Maybe I transcribed it
incorrectly.  Think that 5 coulda been an 8?)
 
They're trying to design for a Delta launch using the 8-foot fairing. 
Dry mass would be 400 kg, experiments taking up 60 kg of that, and
there would be 300 kg of propellants.  A bipropellant propulsion
system has a big 450-N (100-pound) thruster and twelve 22-N thrusters.
 
Solar panels would provide 300 watts of electricity at 2 AU.  They are
fixed, but Earth is within 30 degrees of the Sun during the mission, 
so there is plenty of sunlight available in Earth-pointing mode.
 
Now for the fun part.  You say you want to visit more than one
asteroid? There's one on the way, 2019 Van Albada, and for an extra 16
m/sec of delta-V NEAR can see it.  1.7 AU perihelion, 2.61 AU
aphelion, inclined 4.0 degrees, 17 km diameter.  Zip by in July of
1998, take a few pictures.  Then head for Nereus.
 
What's that?  You say you've been orbiting Nereus for nine months, and
you're tired of looking at it?  For an extra delta-V of just 69 m/sec,
we can leave orbit on 12 September 2000 and fly past the Earth in
February 2002.  Pick up a little speed, come back next year to the
Earth, pick up a little more speed, and on 16 November 2003 you'll be
sailing past Comet Encke!
 
Or!  Do three swingbys of Earth, an Encke flyby, then return for two
Earth swingbys, and you can go on to the asteroid Eros on 18 August 2005.  
 
Instead of Eros, you could go to comet Tempel-1 or another I wrote
down as S.W.3.  Or, if you prefer, you could do a flyby of the
mysterious major asteroid Vesta with three Earth swingbys!  This would
give you a "small-body grand tour" for a total delta-V cost of 158
meters per second beyond the Nereus-orbit budget.
 
If you miss Nereus, or you want to buy extra copies of the NEAR
spacecraft, there are launch opportunities to 3361 Orpheus in March
1998 and another to Nereus in January 2000.  Obviously Farquhar
prefers the January 1998 window, and taking plenty of propellant along
(like maybe 375 kg instead of 300 kg).
 
In article <[email protected]>,
wingo%[email protected] (Dennis "I've Got The World On
A String" Wingo) writes: 

> I saw an awesome presentation at the WSC about a
> faster cheaper better asteriod mission that boggles the mind [...]
> I wonder if Bill bought the paper on that one.  
 
I sure would have! Alas, unlike IAF sessions, COSPAR does not have
papers (!).  I am trying to get some pictures of the spacecraft, as I
think asteroid missions would be a good topic for my next pop-science
slideshow.  The Morrison report on the asteroid-collision threat is
now out, and I grabbed a copy of that at WSC.
 
> It was from JPL  
 
No, APL... 
 
> and was a laugh a minute as this guy
> tossed out several variations of the mission that would take the 
> probe to several asteroids and comets.  He spoke in the manner of a
> vacuum cleaner salesman and although he was funnin, it was a joy to hear.  
 
Dennis caught the spirit of it pretty well.  And Farquhar's track
record suggests he may be able to deliver on these outlandish
promises, if the hardware holds up. 
 
"Do you know the asteroids, Mr.Kemp?...    Bill Higgins
Hundreds of thousands of them.  All        
wandering around the Sun in strange        Fermilab
orbits.  Some never named, never
charted.  The orphans of the Solar         [email protected]
System, Mr. Kemp."
                                           [email protected]
"And you want to become a father."
  --*Moon Zero Two*                        SPAN/Hepnet: 43011::HIGGINS

Article: 27070
Newsgroups: sci.space,sci.astro
From: [email protected] (Ron Baalke)
Subject: Asteroid Toutatis Closes In On Earth
Sender: [email protected] (Usenet)
Organization: Jet Propulsion Laboratory
Date: Tue, 6 Oct 1992 05:21:44 GMT
 
Paula Cleggett-Haleim
Headquarters, Washington, D.C.                 October 5, 1992
(Phone:  202/358-1547)
 
Jim Doyle
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  818/354-5011)
 
RELEASE:  92-164
 
ASTEROID'S ORBIT "CLOSES IN" ON EARTH
 
     One of the largest near-Earth objects, an asteroid named
"Toutatis," will make a close Earth approach on Dec. 8, 1992, passing
by at about 2.2 million miles (3.6 million kilometers) distance. 
 
     Dr. Donald Yeomans, Head of the Near Earth Object Center at
NASA's Jet Propulsion Laboratory, Pasadena, Calif., said the object,
formally known as Asteroid 4179 Toutatis, passes Earth less than one
degree above Earth's orbital plane every 4 years, making it an excellent 
object for study.  The asteroid, at 2 miles (3.5 kilometers) diameter, 
is one of the largest to cross Earth's orbit on a regular basis. 
 
     Yeomans said the ground-based viewing conditions will be
excellent for infrared optical and radar observations just before,
during and well after the close Earth passage, and he notes that
astronomers in many areas of the world simultaneously will study the
body using several different techniques. 
 
     Toutatis again will make close Earth approaches in 1996 and 2000.
In 2004, it will come as close as about four Earth-Moon distances or
about a million miles (about 1.6 million kilometers).  Its orbit takes
it almost to the distance of Jupiter's orbit before the Sun's
gravitational attraction pulls it back. 
 
     The approach of Toutatis this year and the one in 2004 represent
the two closest Earth passages of any known asteroid for the next 30
years, said Yeomans. 
 
     Toutatis was discovered Jan. 4, 1989, by Astronomer Christian
Pollas at Caussols, France, and was named after a Gallic deity called
"protector of the tribe." 
 
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [email protected]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Einstein's brain is stored
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | in a mason jar in a lab
|_____|/  |_|/       |_____|/                     | in Wichita, Kansas.
 

Article: 3688
From: [email protected] (UPI)
Newsgroups: clari.tw.space,clari.local.florida,clari.tw.science
Subject: Two-mile wide asteroid approaching Earth
Date: 26 Nov 92 16:54:01 GMT
 
	GAINESVILLE, Fla. (UPI) -- A University of Florida astronomer
says a two-mile wide asteroid is approaching Earth and will give
astronomers a rare close-up view on Dec. 8. 

	The asteroid Toutatis poses no threat when it crosses Earth's
orbit on this encounter, coming within 2.2 million miles of the
planet, said UF astronomer Dan Durda. 

	But the flyby of the large rock brings home the possibility
that someday Toutatis could smash into Earth with devastating force,
possibly dramatically altering the planet's climate, he said. 

	``Because asteroids are a significant hazard, it behooves us
to understand them,'' Durda said. 

	What makes Toutatis distinctive is that the asteroid is
relatively bright and astronomers have been able to calculate its
orbit in advance, allowing them to plan observations throughout the
world in early December, he said. 

	``There are many smaller, fainter asteroids, which are harder
to see, and often we don't know about them until they have already
passed the Earth,'' Durda said. 

	The timing of this asteroid is easy to remember because it
appears every four years, within a month or two of presidential
elections, he said. 

	Toutatis will be visible through a telescope as a faint
star-like object near the Sun above the southeast horizon shortly
before sunrise. 

	Pinpointing the asteroid's precise location is difficult
because it will be faint and will move very rapidly across the sky,
especially around Dec. 8, its closest approach. 

	``That happens to be the same date that NASA's Galileo
spacecraft will make its second and last Earth flyby on its way to
Jupiter, giving us two space visitors in one day,'' Durda said. 

	Asteroids are the remnants of rocky fragments that formed the
planets 4.5 billion years ago, and today most congregate in a belt
between Mars and Jupiter. Toutatis, named for a Gaulish god and tribe
protector, has been thrown into an unusual Earth-crossing orbit by the
gravitational pull of Jupiter, he said. 

	Many scientists are convinced that the impact of an asteroid
or comet striking Earth was responsible for the extinction of the
dinosaurs some 65 million years ago. Scientists have quibbled about
whether it was an asteroid or a comet, but a much smaller rocky object
slammed into northern Siberia in 1908, detonating into the lower
atmosphere and creating an explosion a thousand times more powerful
than the atomic bomb that leveled Hiroshima, he said. 

	More recently, an object the size of a small room narrowly
missed Earth, skimming though the atmosphere over Utah in 1972, he said. 

	These objects frequently pass Earth over the course of
hundreds or thousands of years, but they have received little
publicity because no major strikes have been documented in populated
areas in modern times, he said. 

	If an asteroid as large as Toutatis were to hit Earth, it
would create an explosion many times more powerful than all the
world's nuclear weapons detonating, Durda said. 

	``There is absolutely no danger of Toutatis striking the Earth
on this passage or at any time during the next couple of hundred
years,'' he said. ``But it is a good candidate to hit the Earth at
some time in the future because of its close approaches.'' 

	Asteroids that make close approaches to Earth could someday be
a valuable source of mineral resources, he said. 

	Astronomers will observe Toutatis through ground-based
telescopes, radar and the Hubble Space Telescope, Durda said. By
viewing Toutatis, scientists hope to learn more about the asteroid's
size, shape and rotation rate, he said. 

Article: 3721
From: [email protected] (UPI)
Newsgroups: clari.tw.space,clari.tw.science,clari.news.interest,clari.news.top
Subject: Nuclear blast could prevent asteroid collision, researchers say
Date: Wed, 2 Dec 92 15:08:01 PST
 
	WASHINGTON (UPI) -- If an asteroid ever threatens to collide with
Earth, a nuclear blast detonated in space could knock the object off
course and avert catastrophic destruction, researchers said Wednesday.

	A nuclear charge smaller than the one dropped on Hiroshima could be
fired from Earth on a rocket to explode above the oncoming asteroid,
diverting it enough to avoid colliding with Earth, the researchers said.

	The rocket would have to be launched about a decade before the
collision would occur, said Thomas Ahrens of the California Institute of
Technology and Alan Harris of the Jet Propulsion Laboratory in Pasadena,
Calif.

	Scientists estimate that about 2,000 asteroids that are large enough
to cause widescale destruction if they collided with Earth travel in
orbits that cross Earth's path. An asteroid of that size, about 1 mile
in diameter, probably strikes Earth about every 100,000 years.
Scientists believe such an impact contributed to the extinction of the
dinosaurs 65 million years ago.

	``That's the minimum size that would cause global destruction,''
Ahrens said in a telephone interview.

	In recent years, scientists have begun developing strategies for
preventing such a collision, including surveying space for such objects
and developing plans to prevent an impact.

	In the journal Science, Ahrens and Harris estimate that if such an
object collided with Earth, massive destruction would ensue and about 25
percent of Earth's population would be killed. To put the peril in
perspective, the chances of an individual being killed by such a
collision is about equivalent to perishing in a commercial airline
crash, they said.

	The pair then calculated that the best strategy to prevent such a
collision would be to fire a rocket into space before the impact
carrying a nuclear explosive device equivalent to about half the power
of the bombs dropped on the Japanese cities of Hiroshima and Nagasaki in
World War II.

	The explosion would be detonated above the asteroid, knocking it off
course enough to prevent a collision with Earth, they said. ``We think
this is the best way because it seems to be least sensitive to detailed
knowledge of the asteroid and is the one least likely to break it up
into several large but lethal pieces,'' he said.

	The pair stopped short of recommending building such a rocket, saying
instead that the issue should be studied more.

Article: 3849
From: [email protected] (UPI)
Newsgroups: clari.tw.space,clari.tw.science,clari.news.interest
Subject: Astronomers obtain images of Earth-approaching asteroid
Date: Sun, 3 Jan 93 13:04:35 PST
 
	PASADENA, Calif. (UPI) -- Using a large radar antenna,
astronomers at the Jet Propulsion Laboratory in Pasadena have obtained
the sharpest images ever of an asteroid as it approached Earth,
officials said Sunday. 

	The radar images of the asteroid, 4179 Toutatis, were made as it
passed within 2.2 million miles from Earth on Dec. 8. The distance is
less than 10 times farther away than the moon.

	``This is our first clear look at one of the many thousands of
asteroids whose orbits can intersect Earth's orbit,'' said Dr. Steven
Ostro, a senior research scientist at JPL and the leader of the radar team.

	The images revealed Toutatis to be a contact binary asteroid,
consisting of two irregularly shaped, cratered objects about 2.5 miles
and 1.6 miles in average diameter.

	It also has a jagged, cratered surface, which indicates a complex
history of collisions, he said.

	``The binary nature of Toutatis is the most important single result
of this radar experiment,'' Ostro said.

	Previous radar images taken in 1989 of another Earth-approaching
asteroid, 4769 Castalia, by Ostro and other scientists were too crude to
reveal surface details.

	But radar images contained hints of contact-binary configurations,
Ostro said.

	``Three years ago we were startled by the initial evidence for
contact-binary asteroids,'' Ostro said. ``Now it seems that double bodies 
might be very common in the Earth-approaching asteroid population.''

	The abundance of contact-binaries could be the key to theories of the
origin and evolution of asteroids and meteorite source bodies, he said.

	Toutatis was discovered by French astronomers on Jan. 4, 1989.
Almost nothing was known about Toutanis before the radar images were
taken, he said. 

	The radar data will be fully processed during the next few
months.  Eventually, a detailed three-dimensional computer model of the
object will be constructed from the data, Ostro said. 

Images discussed in .62 are available:


   pragma::public:[nasa]toutatis.gif
                                .info


- dave

Article: 30816
From: [email protected] (Ron Baalke)
Newsgroups: sci.space,sci.astro,alt.sci.planetary
Subject: Toutatis Captured by Radar Images
Date: 20 Jan 93 01:46:56 GMT
Organization: Jet Propulsion Laboratory
 
From the "JPL Universe"
January 15, 1993
 
Earth-approaching asteroid captured by radar images
By Mary Hardin
 
     Using a large radar antenna at the Goldstone Dep Space
Communications Complex in the Mojave desert, JPL astronomers 
have obtained the sharpest images yet of an Earth-approaching
asteroid, 4179 Toutatis, as it passed extremely close to Earth
last month.

     "This is our first clear look at one of the many thousands
of asteroids whose orbits can intersect Earth's orbit," said Dr.
Steven Ostro of the Geology and Planetary Section 326 and leader
of the radar team.

     The radar images reveal Toutatis to be a "contact binary"
asteroid, consisting of two irregularly shaped, cratered objects
about 4 and 2.5 kilometers (2.5 and 1.6 miles) in average
diameter and rotating with a period between 10 and 11 days.
Toutatis passed 4 million kilometers (2.5 million miles) from
Earth on Dec. 8 -- less than 10 times farther away than the Moon.

     Discovered by French astronomers on Jan. 4, 1989, almost
nothing was known about Toutatis before the radar images were
taken. The asteroid has now been shown to have a jagged, cratered
surface which indicates a complex history of collisions.

     "The binary nature of Toutatis is the most important single
result of this radar experiment," Ostro said.

     Previous radar images taken by Ostro and his colleagues of
another Earth-approaching asteroid, 4769 Castalia (1989 PB), were
too crude to reveal surface details but did show the object to be
bifurcated into two 1-kilometer (0.6 mile) lobes. Radar echoes
bounced off of other asteroids have also contained hints of
contact-binary configurations. 

     "Three years ago we were startled by the initial evidence
for contact-binary asteroids," Ostro said. "Now it seems that
double bodies might be very common in the Earth-approaching
asteroid population. If so, then their abundance has important
implications for theories of the origin and evolution of
asteroids and meteorite source bodies.

     "For example, sub-catastrophic collisions might play an
important role in delivering asteroidal bodies into the inner
solar system from the main asteroid belt between Mars and
Jupiter," he said.

     The two components of Toutatis probably joined in a
relatively gentle collision, but their origins and the times and
circumstances of events leading up to the asteroid's current
configuration are unknown, Ostro continued.

     "Toutatis may be two pieces of a much larger asteroid that
once orbited in the main belt between Mars and Jupiter, but was
disrupted in a catastrophic collision with another large object,"
Ostro speculated. Another possible scenario is that Toutatis was
split into two parts by a collision not quite energetic enough to
completely pulverize it.

     The best way to study the history of Toutatis would be
through the analysis of samples returned from both Toutatis
components. While there are no plans yet to rendezvous with
Toutatis, Ostro said it and dozens of other near-Earth asteroids
are leading candidates for robotic flyby, rendezvous and sample-
return missions because of the asteroids' small gravitational
fields and because of the ease of maneuvering spacecraft between
the orbits of Earth and the asteroids.

     For most of the radar observations, a 400,000-watt coded
radio transmission was beamed at Toutatis from Goldstone's main
70-meter (230-foot) antenna. The echoes, which took as little as
24 seconds to travel to Toutatis and back, were received by the
new 34-meter (112-foot) antenna and relayed back to the 70-meter
station where they were decoded and processed into images.

     Full processing of the Toutatis radar data over the next few
months is expected to reveal details of surface features less
than 100 meters (330 feet) across. Eventually a detailed three-
dimensional computer model of the object will be constructed from
the data, Ostro said. In addition to Ostro, members of the JPL
radar team include Dr. Raymond Jurgens, Keith Rosema, Ron
Winkler, Denise Howard, Randy Rose, Dr. Martin Slade and Dr.
Donald Yeomans.

     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [email protected]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Every once in a while,
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | try pushing your luck.
|_____|/  |_|/       |_____|/                     |

Article: 62999
Newsgroups: sci.space
From: [email protected] (Martin Connors)
Subject: Re: Near Miss Asteroids (Q)
Sender: [email protected]
Organization: University Of Alberta, Edmonton Canada
Date: Tue, 18 May 1993 19:59:30 GMT
 
In article <[email protected]> [email protected] (THE ARTSTONE  
COLLECTIVE) writes:

> I am interested in Asteroids that have passed close to the Earth.
> 
> 	1. When have these occured in modern times ?
- Look in the articles which follow....
> 	2. Where might I find articles ?
 
1. Spratt, C. E.      J. Roy. Astron. Soc. Can., 81, 8-18 (1987).
 
 Chris Spratt has written several interesting asteroid reviews in this  
Canadian journal. This one is on Apollo objects which count for most NEAs.
 
2. Binzel, R., S. Xu, S. J. Bus, & E. Bowell, Science, 257, 779-782 (1992).
 
 'The Origin of NEAs' - good source of recent references
 
3. Wisdom, J.   Nature, 315, 731-733 (1985).
 
 The mechanism of how material gets from the asteroid belt to Earth.
 
5. Ostro, S. J.    Bull. Am. astr. Soc., 24, 934 (1992).
 
 Abstract about radar imaging possibilities for Toutatis (later done  
during near pass on Dec. 8 1992)
 
8. Greenberg, R. & Nolan, M. C. in Asteroids II (eds. Binzel, R. P.,  
Gehrels, T., & Matthews, M. S.) 778-804 (U. of Arizona Press, Tucson, 1989)
 
 Asteroids II is a valuable all-round reference
 
10. Milani, A., M. Carpino, G. Hahn, & M. Nobili, Icarus, 78, 212-269 (1989).
 
 Project Spaceguard - classifies all types of orbital behaviour.
 
There have been a number of NEA articles in Sky & Tel., Astronomy, but I  
don't have a list in e-form.
 
Try to get (perhaps from JPL)
The Spaceguard Survey, Report of the NASA International Near-Earth-Object  
Detection Workshop, by David Morrison, Jan. 25, 1992
 
Also note:
Near miss of the Earth by a small asteroid, by Scotti, Rabinowitz,  
Marsden, Nature v354, p 287 (28 Nov 1991)
 
and Asteroid and Comet orbits using radar data, Astronomical Journal,  
v103,
p303, which gives a list of upcoming near encounters
 
I see I got carried away but hopefully the list will be useful.
--
Martin Connors         |
Space Research         | [email protected]  (403) 492-2526
University of Alberta  |

Date: 3 Jun 93 10:21:17 -0600
From: Bill Higgins-- Beam Jockey <[email protected]>
Subject: Clem2 Whacks Toutatis(was Re: Big Rock Can Hit Earth in Yr 2000)
Newsgroups: sci.space,sci.astro

In article <[email protected]>,
[email protected] (Mike Fraietta) writes: 

> This is the first I've heard of a second Clementine mission.  Does
> this mission have the same goals as the first?  That is to test new
> lightweight sensors in a space radiation environment as well as
> demonstrating autonomous navigation and spacecraft operation.
> 
> Where can one find out more details of this second mission?

Coming right up, Mike... here's an abstract by R. J. Boain (I infer
he's from the Jet Propulsion Laboratory) from a recent workshop on
advanced instrumentation for planetary missions.  "SDIO" is the
Strategic Defense Initiative Organization, recently degraded and
renamed the Ballistic Missile Defense Organization. 

"Do you know the asteroids, Mr.Kemp?...    Bill Higgins
Hundreds of thousands of them.  All        
wandering around the Sun in strange        Fermilab
orbits.  Some never named, never
charted.  The orphans of the Solar         [email protected]
System, Mr. Kemp."
                                           [email protected]
"And you want to become a father."
  --*Moon Zero Two*                        SPAN/Hepnet: 43011::HIGGINS
=============

 Boain R. J.
  Clementine II: A Double Asteroid Flyby and Impactor Mission

Recently JPL was asked by SDIO to analyze and develop a preliminary
design for a deep-space mission to fly by two near-Earth asteroids,
Eros and Toutatis.  As a part of this mission, JPL was also asked to
assess the feasibility of deploying a probe on approach to impact
Toutatis.  This mission is a candidate for SDIO's Clementine II. 
 
SDIO's motivations were to provide further demonstrations of
precision, autonomous navigation for controlling the flight paths of
both a spacecraft and a probe.  NASA's interest in this mission is
driven by the opportunity to obtain the first close-up images and
other scientific measurements from a spacecraft of two important
near-Earth objects.  For Toutatis this is especially important since
it was observed and imaged extensively just last December using
Earth-based radar; Clementine II will provide the opportunity to
corroborate the radar data and validate the ultimate potential of the
radar technique. 
 
Scientifically, the probe impact at Toutatis will allow the
acquisition of data pertaining to the dynamic strength of surface
material, data on the properties of the regolith and on stratification
below the surface, and will potentially allow the measurement of
thermal diffusivity between the interior and the surface.  These
determinations will be accomplished by means of high-resolution
imagery of the impact crater and its surroundings invisible,
ultraviolet, and infrared wavebands from the spacecraft flying by some
30 min after the probe strike.  In addition, if the spacecraft can be
equipped with a lightweight mass spectrometer and dust analyzer, the
potential also exists to measure the particle sizes and distribution
and the composition of the ejecta cloud. 
 
This mission is planned to be launched in July of 1995, with the Eros
encounter on March 13, 1996, and the Toutatis flyby on October 4,
1996, some 440 days after launch.  The Eros encounter is characterized
by a flyby speed of 8.4 km/sec and a Sun-target-spacecraft phase angle
of 120 degrees.  Thus, the principal visible light images of Eros
will be obtained after closest approach.  The Eros miss distance is
nominally set at 30 km.  For Toutatis, the encounter is characterized
by an approach speed of 17.8 km/sec and a phase angle of 20 degrees.
With this approach geometry, Toutatis presents a sunlit face to the
spacecraft and probe.  The probe will hit the asteroid at approximately
18 km/sec.  To facilitate imagery of the impact crater and to assure
continuous line-of-sight tracking through encounter, the closest
approach distance at Toutatis is selected to be 50.0 km. 

------------------------------

    Joseph De Lalande, French Academician, reporting on his
  calculations on the possibility of flying in 1782: 

    "...you would need wings of tremendous dimensions and they would
  have to be moved at a speed of three feet per second.  Only a fool
  would expect such a thing to be realized."

------------------------------

Article: 38434
From: [email protected]
Newsgroups: sci.astro
Subject: DSP sees asteroids
Date: 28 Jun 93 16:39:02 PST
Organization: Science Applications Int'l Corp./San Diego
 
On DSP detections of asteroid impacts:
 
Asteroid Flyby Proposed using LEAP Penetrators
by Jeffrey M. Lenorovitz
Aviation Week and Space Technology
28 June 1993, pp.27-28
[EXCERPTS]
 
"...the U.S. Space Command has begun regular monitoring with early
warning satellites to detect asteroid explosions in the Earth's
atmosphere.  One Defense Dept. official estimates there are 10-30
asteroid impacts per year in the upper atmosphere, with blasts
equivalent to the force of a 1-kiloton bomb or larger.  Some of them
are equal to an air burst of a 30-kiloton bomb, he said. 
    
     "Atmospheric observations by the early warning satellites'
classified sensors have detected asteroid explosions for years, but
individual system operators decided whether the events were logged or
not.  'The [early warning satellite network] is an older system that
is very manual, so if there was no reason to believe there was a
ballistic missile launch, the operators tended to ignore the asteroid
explosion data,'  one Air Force officer said.  'We're now exploiting
the data on a regular basis.' 
 
["Exploiting the data" ?  Who's doing it and how?  Will the results be 
sumbitted to a peer-reviewed journal?] 
 
     "Air Force officers said the Russians have offered to make their
early warning radars available to detect asteroids in the Earth's
vicinity.  'If programmed right, these radars can see halfway to the
Moon,'  one officer said. 
 
     "Defense Dept. officials said these elements are part of a growing 
movement to use military resources for scientific- and civilian-oriented 
programs.  'It's time for a more concerted effort to use the billions of 
dollars spent on sensors, radars, composite materials, propulsion 
systems and computers for new applications,' one BMDO officer said... 
 
[Amen. My favorite candidates for this are the large geosynchronous 
SIGINT satellites we (the U.S.) are supposed to have been flying since 
the 1970s.  A couple of these with the right receiver package could 
revolutionize radioastronomy.] 
 
     "BMDO officers admit it sometimes is a challenge to seek high-level 
military support for asteroid detection and tracking.  'It's difficult 
to be taken seriously when asking for money to find out whether 'the sky 
is falling,''  one officer said,  'There really is a sober side to all 
of this, despite the 'giggle factor' associated with it.' 
 
     "The destructive force of a collision is illustrated by the 1908 
atmospheric explosion of an asteroid 5 mi. above Tunguska, Siberia.  The 
blast had a force equal to that of a 12-megaton bomb, leveling forest 
for 700 sq. mi.
 
     "A small asteroid estimated to be about 30 ft. in diameter passed 
within 90,000 mi. of Earth in May, according to Stephen Moran, an 
astronomer with the American Astronomical Society.  A mile-wide asteroid 
came to within 500,000 mi. from the planet in 1937, and another 'near 
miss' was reported in March, 1989, when a half-mile wide asteroid flew 
past the Earth at a distance of 700,000 mi." 
 
Allen Thomson                  SAIC, Inc.                    McLean, VA
--------------------------------------------------------------------------
Although I would be happy to have SAIC adopt my opinions as corporate
positions, there is absolutely no reason to think that it has done so.
 

Article: 3782
Newsgroups: talk.politics.space
From: [email protected] (Rob Whitely)
Subject: Asteroid discussion
Sender: [email protected]
Organization: Institute For Astronomy, Hawaii
Date: Mon, 13 Sep 1993 09:51:08 GMT
 
Keywords:Asteroids
 
I'm not sure who posted what arguments, or when, but I was intrigued by
this discussion on asteroids.  I was particularly thrilled to learn that
people consider crashing asteroids into the earth as a good idea. 
Hmmm....  The person who originally suggested this as a means of
recovering metals from asteroids was somewhat offbase on a couple of
things, and unfortunately, someone else took this hair-brained idea and
ran with it.  In case anyone cares:
 
	1)  A simple examination of orbital dynamics would demonstrate that
slowing down an asteroid so it can impact safely with the earth is just
not feasible.  How does one slow down an object travelling 8-10
miles/sec.?  What does one do with the hundreds of megatons or gigatons
of energy of an object at those speeds?  Even if you could "control" the
infall speed of an asteroid, we still don't know much about the upper
atmospheric dynamics of impacts.  I think it safe to say that any use of
asteroids will have to be at a safe distance from earth.

	2)  The real utility of extraterrestrial materials lies not in their
uses on our planet.  What an absurd idea, bringing these materials back
after mining them from an asteroid!!  There's no way, first of all, to
make that competitive with earth-based mining, as someone already
pointed out.  The best use for these materials is right where they are,
in space.  Consider that launch costs for low orbit insertion are
running several thousand dollars a POUND on the space shuttle.  If you
want to build cities in orbit, moonbases, long range spacecraft, space
stations and the like, why in the hell would you drag all the materials
up out of earth's gravity well when you could just snag one of the
metallic asteroids on an earth-crossing orbit?  As someone already
pointed out, the up-front cost of sucha mission would be pretty steep. 
But then, the returns from such a mission might well be enormous.

	  It's extremely difficult to get really good data on asteroids
because, of course, they don't really do anything but reflect light. 
Reflection spectroscopy is OK, but with it we can't really tell how
"pure" a nickel-iron asteroid might be.  I've actually read somewhere
that such an asteroid might be 75% nickel-iron.  That is WAY better than
any ore on earth, if that number is to be believed.  But even if that
number is 10 times too high, it still seems fairly certain that the
metallic asteroids are much purer than ores from our crust.  This means
that refining such ore will be, in some ways, simpler than on earth.  Of
course, you have all of the familiar space problems to complicate
things.  So is this venture possible, or even worthwile?

	Consider an asteroid with a diameter of 500 meters.  Such objects are
thought to number in the thousands or tens of thousands in the inner
solar system.  Most of them lie in the ecliptic, or close to it, and a
large fraction of these are probably earth-crossing.  Assume a typical
spherical asteroid with a nickel-iron content of 10%, in an orbit
accessible to us.  Such an object would contain roughly 3 million cubic
meters of nickel and iron!  A cubic meter of such metal has a mass of 10
metric tons.  I don't know what the market value of 30 million metric
tons of iron and nickel is, but the launch costs of putting that much
material into a useful orbit are staggering.  That much material would
sustain man's efforts in space for a long time.  So much for the
question of being worthwile.

	  In all likelihood, there are several dozens of gold mines just
waiting to be grabbed.  This brings up the second question: Can it be
done?  The answer is yes, if we are willing to be patient, and are
willing to sink a lot of money into doing it.  The most daunting problem
has already been alluded to, which is the slowing and placement of the
asteroid into a safe, useful orbit.  The solution that I've heard the
most about is the placement of a series of mass drivers on the surface
of the target asteroid.  These would be used to gradually nudge the
orbit of the asteroid into one close to the earth.  I haven't really
heard of, or even considered the pros and cons of exactly where to place
the asteroid once under control.  Maybe someone more knowledgeable than
me could comment on this.  I guess it would be much easier to let the
asteroid continue in a solar orbit, rather than making it a satellite of
the earth.  How convenient this would be for mining purposes I don't
know.  In any case, this solution is feasible, if one is willing to
spend the money, and wait for 10 years for the asteroid to be nudged
into a useful orbit.  Unfortunately, people investing large sums of
capital are not typically patient enought to wait so long for their
investment to pay off.  Especially not American investors.

	If anyone has anything of interest to add to these recent discussions,
please feel free.

						Rob Whiteley
 

re: 'catching' asteroids for mining...

> The most daunting problem has already been alluded to, which is the
> slowing and placement of the asteroid into a safe, useful orbit.  The
> solution that I've heard the most about is the placement of a series of
> mass drivers on the surface of the target asteroid.  These would be used
> to gradually nudge the orbit of the asteroid into one close to the earth.
> I haven't really heard of, or even considered the pros and cons of
> exactly where to place the asteroid once under control.  


But the earth DOES have its very own, built-in, 'asteroid velocity
reduction system':  The moon!  Why not let the moon catch it?  Let 'em slam
into the dark side!  Or sell advertising rights to help fund the efforts
and let the asteroids impact in the desired dot-matrix pattern on the
bright side! ;-)

- jeff

Article: 77384
Newsgroups: sci.space
From: Jim Kinnison <[email protected]>
Subject: NEAR Program Review Schedule
Sender: [email protected]
Organization: The Johns Hopkins Applied Physics Lab
Date: Tue, 9 Nov 1993 13:54:50 GMT
 
In article <[email protected]> Pat, [email protected] writes:

> 	has the Spacecraft basic architecture then been approved.
> 	could you post it?  and  has the mission plan been
> 	finalized, or are they still mulling about on
> 	which asteroids to visit?
> 
> pat
 
Our normal program review cycle consists of three major reviews -
conceptual, preliminary, and critical design reviews - along with
smaller preintegration reviews,etc.  The Conceptual Design Review
(CoDR) is where the mission objectives and basic configuration are
established.  This is currently scheduled for Dec 1-2, 1993, here at
APL.  The Preliminary Design Review (PDR) is where the baseline
designs for each system are reviewed.  This will be held about six
months after the CoDR.  The final major review is the Critical Design
Review (CDR), where the design is fixed and fabrication is begun. 
After the CDR, changing a design becomes a Big Deal, so we take pains
to make sure everything is right beforehand. Each system, as well as
the entire mission, undergoes a review cycle like this. 
 
Our Chief Engineer manages this process, and he reads this news group,
so he may be able to answer more detailed questions. 
 
Jim
 
=========================================================================
Jim Kinnison                  |  "Oy! Ten thousand years can give you
The Johns Hopkins University  |    such a crick in the neck!"
Applied Physics Laboratory    | 
                              |  Yes, I have a three-year-old, and  
[email protected]        |     _Aladdin_ is all he wants to watch.
                              |

Article: 77391
Newsgroups: sci.space
From: Jim Kinnison <[email protected]>
Subject: NEAR Configuration (longish)
Sender: [email protected]
Organization: The Johns Hopkins Applied Physics Lab
Date: Tue, 9 Nov 1993 14:37:40 GMT
 
I'm taking the information given below from "Near-Earth Asteroid 
Rendezvous: A Small Satellite Approach" by Andrew Sando and Andrew Cheng 
given at the Seventh AIAA/Utah State University Conference on Small 
Satellites.  Preprints are available on request.
 
Top-Level Science Objectives:
	 
	 - to characterize an asteroid's physical and geological properties
	   and to infer its elemental and mineralogical composition.
	 
	 - to clarify the relationship between asteroids, comets, and 
           meteorites.
	 
	 - to advance the understanding of processes and conditions during the 
	   formation and early evolution of the planets.
	 
Primary Measurement Objectives:
 
	- to measure the asteroid's gross physical properties, including size, 
	  shape, mass, density, and spin state.
	
	- to determine the surface elemental and mineralogical composition with 
	  sufficient accuracy to enable comparisons with major meteorite types.
	
	- to characterize the morphology of the asteroid surface.
	
Secondary Science Objectives:
 
	- to determine regolith properties and texture through imaging on 
	  sub-meter scales.
	
	- to search for intrinsic magnetization and to constrain the nature of 
	  the solar wind interaction.
	
	- to search for evidence of cometary activity as indicated by gas or 
	  dust around the asteroid.
	
	- to investigate the internal mass distribution through measurements of 
	  the gravity field and/or time dependent spin state.
	
Several asteroids were considered for this mission, and Eros was
chosen. It is the largest near-Earth asteroid with dimensions of about
36 km by 15 km by 13 km.  The spacecraft will launch in February 1996,
fly by the main delt asteroid Iliya in August 1996, and rendezvous
with Eros in December 1998. The satellite will orbit Eros beginning at
about 100 km altitude, and slowly decrease to about 50 km.  The study
phase will take about 8 months. 
 
The instrument suite is made up of a visible imager, X/gamma spectrometer, 
near-IR spectrograph, magnetometer, and a laser altimeter. 
 
Overall design philosophy is consistent with small satellite design:
 
	- Modularity among subsystems 
 
	- Functional, rather than one-for-one, redundancy
	
	- Maximize use of off-the-shelf components
	
	- Use of standard data interface bus, in this case Mil-Std-1553
 
Any errors in the above summary are definitely mine.  More detailed info 
about the mission are given in the paper, but I have to run to a meeting, 
and can't transcribe it all! 8^]
 
Jim
 
=========================================================================
Jim Kinnison                  |  "Oy! Ten thousand years can give you
The Johns Hopkins University  |    such a crick in the neck!"
Applied Physics Laboratory    | 
                              |  Yes, I have a three-year-old, and  
[email protected]        |     _Aladdin_ is all he wants to watch.
                              |

From:	US1RMC::"[email protected]" "MAIL-11 Daemon" 18-FEB-1994 
To:	[email protected]
CC:	
Subj:	HQ94-26 / Computer Model of Asteroid

Don Savage
Headquarters, Washington, D.C.                                                 
February 17, 1994
(Phone:  202/358-1547)

James H. Wilson
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  818/354-5011)

Stephen Lyons
Washington State University, Pullman, Wash.
(Phone:  509/335-5095)

RELEASE:  94-26

COMPUTER MODEL OF NEAR-EARTH ASTEROID SHOWS "DOUBLE OBJECT"

Two NASA-sponsored scientists have produced the first-ever detailed, 
three-dimensional reconstruction of one of the thousands of asteroids in 
the solar system whose orbits bring them extremely near to Earth. 

Scott Hudson of Washington State University in Pullman, Wash., and 
collaborator Steven Ostro of NASA's Jet Propulsion Laboratory (JPL), 
Pasadena, Calif., created the computer model of the double-lobed asteroid 
4769 Castalia from radar data obtained in 1989 by Ostro and others, using 
the Arecibo Observatory in Puerto Rico.  The asteroid was discovered by 
Eleanor Helin of JPL at the Palomar Observatory in 1989. 

Hudson and Ostro's computer model and the resulting pictures appear in 
the Feb. 18 issue of Science magazine. 

"This computer model of Castalia represents the first detailed, three-
dimensional reconstruction of a solar system body from radar data," 
Hudson said.  The effective resolution in this reconstruction is about 
330 feet (100 meters). 

At about a mile (just under 2 kilometers) across, Castalia is smaller 
than any solar system object for which spacecraft images have been taken 
-- including the two asteroids, Gaspra and Ida, recently imaged by NASA's 
Galileo spacecraft. 

Ostro said that previously it was very difficult to interpret radar 
images of small, irregularly-shaped bodies.  But with the development of 
this new reconstruction technique, the scientific value of radar 
observations has been dramatically enhanced. 

"I hope that the Castalia model will enhance interest in a program of 
exploration of these small bodies, including both Earth-based 
observations and spacecraft missions," he said.  "A radar-derived model 
of a target asteroid would make close maneuvering easier, and the mission 
easier and cheaper." 

Ostro also noted that the Castalia model verifies the suspicion of many 
astronomers that the near-Earth asteroids would prove to be the most 
irregularly shaped worlds in the solar system. 

"Understanding the origins of those shapes, especially the detailed role 
of collisions, is an important theoretical challenge," he said.  The 
scientists believe that the double-lobed shape of Castalia shown by the 
model resulted from a gentle collision between two separate asteroids 
some time in the past. 

Nearly 300 near-Earth asteroids are currently known.  It is thought that 
more than 1,000 as large as Castalia, plus 100 million as large as a 
house, remain to be discovered.  Most of them are thought to have been 
thrown into the inner solar system from the main asteroid belt, between 
Mars and Jupiter, by long periods of gravitational interaction with the 
planets. 

With unstable orbits, they eventually might be thrown out of the solar 
system by the same forces or possibly collide with planets. 

The scientists believe that continuing improvements in radar telescopes, 
expanded optical programs to search for near-Earth asteroids and modeling 
techniques like this one will provide greatly increased knowledge of the 
properties and histories of these strange, nearby worlds. 

The research was part of the Innovative Research Program, the Planetary 
Geology and Geophysics Program and the Planetary Astronomy Program of 
NASA's Office of Space Science, Washington, D.C. 

NOTE TO EDITORS:  A photograph of asteroid Castalia is available to media 
representatives by calling NASA's Broadcast and Imaging Branch on 
202/358-1900. 

B&W:  94-H-67

From:	US1RMC::"[email protected]" "JPL Public Information" 
        18-FEB-1994 12:54:28.86
To:	[email protected]
CC:	
Subj:	JPL/Radar-imaged near-Eart asteroid

See the note at bottom regarding availability of a GIF.

PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109.  TELEPHONE (818) 354-5011

Contact: James H. Wilson

EMBARGOED FOR RELEASE FEBRUARY 18, 1994

     Two NASA-sponsored scientists have produced the first-ever
detailed, three-dimensional reconstruction of one of the thousands of
asteroids in our solar system whose orbits bring them extremely near
to Earth. 

     Dr. Scott Hudson of Washington State University in Pullman,
Washington, and collaborator Dr. Steven Ostro of NASA's Jet Propulsion
Laboratory created the computer model of the double- lobed asteroid
4769 Castalia using radar data obtained in 1989 by Ostro and others,
using the Arecibo Observatory in Puerto Rico. The asteroid was
discovered by Eleanor Helin of JPL at the Palomar Observatory in 1989.

     Hudson and Ostro's computer model and the resulting pictures
appeared in the February 18 issue of Science.

     "This computer model of Castalia represents the first detailed,
three-dimensional reconstruction of a solar system body from radar
data," Hudson said.  "It provides our most conclusive evidence to date
of a contact-binary asteroid."  The effective resolution in this
reconstruction is about 100 meters (300 feet). 

     At a little under two kilometers across (about a mile), Castalia
is smaller than any solar system object for which spacecraft images
have been taken -- including the two asteroids, Gaspra and Ida,
recently imaged by NASA's Galileo spacecraft. 

     Ostro said that previously it was very difficult to interpret
radar images of small, irregularly shaped bodies.  But with the
development of this new reconstruction technique, the scientific value
of radar observations has been dramatically enhanced. 

     "I hope that the Castalia model will enhance interest in a
program of exploration of these small bodies, including both
Earth-based observations and spacecraft missions," he said. "A
radar-derived model of a target asteroid would make close maneuvering
easier, and the mission easier and cheaper." 

     Ostro also noted that the Castalia model verifies the suspicion
of many astronomers that the near-Earth asteroids would prove to be
the most irregularly shaped worlds in the solar system. 

     "Understanding the origins of those shapes, especially the
detailed role of collisions, is an important theoretical challenge,"
he said.  The scientists believe that the double- lobed shape of
Castalia shown by the model resulted from a gentle collision between
two separate asteroids some time in the past. 

     Nearly 300 near-Earth asteroids are currently known.  It is
thought that more than a thousand as large as Castalia, plus 100
million as large as a house, remain to be discovered. Most of them are
thought to have been thrown into the inner solar system from the main
asteroid belt between Mars and Jupiter by long periods of
gravitational interaction with the planets. 

     With unstable orbits, they might eventually be thrown out of the
solar system by the same forces, or possibly collide with planets. 

     The scientists believe that continuing improvements in radar
telescopes, expanded optical programs to search for near-Earth
asteroids and modeling techniques like this one will provide greatly
increased knowledge of the properties and histories of these strange
nearby worlds. 

     The research was part of the Innovative Research Program, the
Planetary Geology and Geophysics Program, and the Planetary Astronomy
Program of NASA's Office of Space Science, Washington, D.C. 

                              #####

2-18-94 JHW
# 9412 

Note:  A GIF image file for this story is available under filename
CASTALIA.GIF at the JPL Info public access site (Internet anonymous
ftp to jplinfo.jpl.nasa.gov (137.78.104.2), or by dialup modem to +1
(818) 354-1333)).  New files are kept in the directory `news' for
about 30 days and are then moved to the directory `images.' 

Article: 3292
From: [email protected] (JPL Public Information)
Newsgroups: sci.space.science,alt.sci.planetary
Subject: Digital CASTALIA.GIF now available
Date: Tue, 15 Mar 1994 20:51:22 GMT
Organization: Jet Propulsion Laboratory
 
A new version of the image file depicting a three-dimensional
reconstruction of the asteroid 4769 Castalia is now available at the
JPL Info public access computer site. 
 
The file, CASTALIA.GIF, is in the directories `news' and `images.'
Created digitally from original data, it replaces a previous version
scanned from a hardcopy print. 
 
The image was provided by Dr. Scott Hudson of Washington State
University and Dr. Steven Ostro of JPL. 
 
JPL Info may be accessed via Internet with anonymous ftp to
jplinfo.jpl.nasa.gov (137.78.104.2); or by dialup modem to +1 (818)
354-1333, N-8-1, 14.4kbps. 
 

Article: 5269
From: [email protected] (Reuters)
Newsgroups: clari.world.asia,clari.tw.space,clari.tw.science
Subject: Asteroid Narrowly Misses Earth, Scientist Says
Date: Thu, 17 Mar 94 2:40:04 PST
 
	 SYDNEY (Reuter) - An asteroid missed Earth on Tuesday,
passing by at less than half the distance to the Moon, an
Australian-based astronomer said Thursday. 

	 The asteroid, estimated to be up to 22 yards across and
traveling at 43,000 miles per hour, passed by March 15 between 100,000
and 112,000 miles away. 

	 ``In the cosmic scale of things that really is right in our
backyard,'' Duncan Steel of the Anglo-Australian Observatory in Sydney
said in a radio interview. 

	 Steel said the asteroid was one of only three observed to
pass the Earth that closely in the past three years. 

	 But there was only one telescope capable of spotting such
objects -- at the University of Arizona in the United States -- and it
only covered a small area of sky. 

	 Therefore astronomers believed what they call near-hits
happened ``more or less every day,'' said Steel. ``It's likely we're
missing more than 99 percent of these things.'' 

	 Steel said if an asteroid less than 111 yards across was on a
collision course with the Earth, it would blow up in the atmosphere,
the shock wave causing considerable damage. 

	 ``We've estimated that in this particular case the explosion
would be equivalent to about 20 Hiroshima bombs but at relatively high
altitude, five to ten kilometers up,'' said Steel. 

	 ``It would only affect a relatively small region of the
Earth, and the chances are it would be over an unpopulated region such
as the ocean or desert.'' 

	 ``Our main search which we carry out here is for the rather
bigger ones, which if they hit would be a real global catastrophe
affecting everybody on the face of the Earth,'' Steel said. 

	 Steel said there were 19 asteroid impact craters in Australia
alone, four of them being less than 5,000 years old. 

Article: 54780
From: [email protected] (Dwight Decker)
Newsgroups: sci.astro,sci.space
Subject: Old kiddie space book with mission to Eros
Date: 22 Mar 1994 14:24:08 -0700
Organization: AG Communication Systems, Phoenix, Arizona
 
Hmmm...the recent announcement of a space probe to be sent past the
asteroid Eros stirred up a vague memory.  Back when I was a wee tyke,
I read a kiddie-level book on space travel that opened with what
seemed to me a very strange scene.  Instead of an expedition to the
Moon or Mars, which seemed to me more interesting targets (this was
about 1961 and I would have been nine), the book described a manned
landing on the asteroid Eros. What's more, I recall that the scene
wasn't the landing itself, but a group of college students sitting in
a dorm lounge watching the event on a big flat-screen wall-mounted TV
(in 1975 or so), incidentally chatting among themselves and reviewing
what they knew about asteroids outside the main belt for the reader's
benefit. The whole thing was a mind-stretcher for me at the time, as
it introduced Earthgrazing asteroids to me for the first time, even
gave one a name, and the author seemed to have excellent reasons for
sending a spaceship there (an extraterrestrial body that does us the
favor of coming a heck of a lot closer than Mars ever does would be
easier to reach than Mars and still provide many of the research
opportunities of Going to Another Planet). 

	Well, here it is 1994, the space program isn't going much of
anywhere, let alone Eros, and we don't even have wall-mounted
flat-screen TVs like that one in every home. Still, even sending a
robot out to take a look at Eros might be useful, so maybe that book
author of long ago wasn't completely off the mark. 

	Does anyone else remember the book I'm so ineptly trying to
remember well enough to describe? 
 
 --Dwight R. Decker

Article: 4000
From: [email protected] (Reuter/Deborah Zabarenko)
Newsgroups: clari.news.features,clari.news.top,clari.tw.space
Subject: Fireball in Pacific Sky Points up Death Risk
Date: Thu, 28 Apr 94 7:10:06 PDT
 
	 WASHINGTON (Reuter) - In the dead of winter, fishermen in
the tropical Pacific reported an extraordinary sight: a big
fireball, brighter than the morning sun, that left an hour-long
trail of dusty debris falling to Earth.

	 They didn't know it then, but they were watching an
astronomical event that has reverberated around the world and
pointed up what astronomers say is a very real risk of getting
killed by an asteroid.

	 What the fishermen saw February 1 was a previously
undetected meteorite or asteroid that exploded in flames about
12 miles above the Earth's surface near the island of Kosrae,
also known as Kusaie, part of the Caroline Islands.

	 ``The flame was reddish and bluish in color and very
bright,'' according to an eyewitness report compiled in
Kosrae. ``(The fishermen) heard no explosion nor did they notice
any unusual bright flashes beyond the horizon ... The tailing
smoke remained for about one hour.''

	 What made the fireball significant, U.S. astronomers say,
was its large size. At about 33 feet in diameter, this object --
formally termed a bollide -- was the largest ever detected by
satellites posted around the world.

	 The amount of energy released was at least comparable to the
nuclear bomb dropped on Hiroshima, the scientists agree. Some
estimate the energy was 10 times that much.

	 And therein lies some confusion.

	 The fireball's massive airburst tripped orbiting military
sensors around the globe, and at least one member of the U.S.
astronomic community maintains these sensors were unable to tell
the difference between this natural phenomenon and a possible
nuclear strike.

	 One scientist, who spoke on condition of anonymity, said
President Clinton was awakened and briefed on the incident, but
only two hours after the sensors picked it up. This, the
scientist contends, constitutes an unacceptable delay in the
event of a real atomic attack.

	 The White House has categorically denied that this happened,
and officials at Patrick Air Force Base in Florida -- where
military satellite traffic is monitored -- said the sensors
accurately determined the fireball's origins.

	 Cliff Jacobs, a scientist at Sandia National Laboratory in
New Mexico, said that the story of a late-night call to the
president probably got started in one of the remote sensor
sites, but it never happened.

	 Even without a White House connection, the Pacific fireball
points up current worries over asteroids and meteorites.

	 One of the most eye-popping -- and hard-to-swallow --
asteroid statistics provided by the U.S. space agency is the
estimate that the average human has one chance in 20,000 of
being killed by an asteroid, about the same as the chance of
dying in a plane crash.

	 David Morrison, a scientist with the National Aeronautics
and Space Administration in Mountain View, California, admits
the odds are a bit complicated to explain.

	 The danger from asteroids lies in their potential to alter
life on Earth, killing millions or even billions of people in
the event of a direct hit of a big asteroid, Morrison said.

	 ``It's not the danger of getting hit on the head by a
rock,'' Morrison said in a telephone interview.

	 ``It's the danger that somewhere on Earth there will be an
impact so large that will affect the climate of the whole
planet, putting so much (debris) into the stratosphere that
temperatures drop and crops die,'' Morrison said.

	 The Pacific fireball was big enough that it might have
caused massive damage if it had crashed into the Earth's
surface, but because it flamed out far above it, only the
fishermen saw it, and nobody got hurt.

From:	US4RMC::"ASTRO%[email protected]" "Astronomy Discussion 
        List" 26-JUL-1994 10:14:01.12
To:	Multiple recipients of list ASTRO <ASTRO%[email protected]>
CC:	
Subj:	New name for asteroid

Does anybody have any more information on the following:

From the Tampa Tribune (7/25/94)

Besieged by letters and e-mail, a Cambridge, Mass. astronomy
organization named an asteroid that orbits between Jupiter and Mars
"Zappafrank" after the late musician. "I don't recall a lobby quite 
as extensive as this one" said Brian G. Marsden, Director of the
International Astronomical Union's Minor Planet Center. The asteroid,
actually a tiny planet, as appropriately named because it was
discovered in 1980 by a Czech astronomer and Zappa symbolized artistic
freedom to youngsters growing up in Communist Eastern Europe. He was
friends with Vaclav Havel, the dissident playwright who became Czech
president. Since there are a number of asteroids the names of which
begin with "frank" and there's one named Zappala after the Italian
discoverer, Marsden decided on "Zappafrank" to distinguish the musician. 

                _\\///_
               (' O-O ')
     ---------ooO-(_)-Ooo----------
    |                              |
    |          Chris Cook          |
    |                              |
    |    [email protected]   |
    |                              |
    |  Views, opinions are my own  |
    |      & not my employers.     |
     ------------------------------

% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% Date:         Tue, 26 Jul 1994 06:16:18 PDT
% Reply-To: Astronomy Discussion List <ASTRO%[email protected]>
% Sender: Astronomy Discussion List <ASTRO%[email protected]>
% From: Chris Cook <[email protected]>
% Subject:      New name for asteroid
% To: Multiple recipients of list ASTRO <ASTRO%[email protected]>

From:	US4RMC::"ASTRO%[email protected]" "Astronomy Discussion 
        List" 26-JUL-1994 11:47:34.28
To:	Multiple recipients of list ASTRO <ASTRO%[email protected]>
CC:	
Subj:	Re: New name for asteroid

More info?  Sure--what did you want to know?   I'm the public affairs
specialist at the Harvard-Smithsonian Center for Astrophysics, where
the IAU's Minor Planet Center is headquartered.  The name was proposed
by a Phoenix, AZ psychiatrist (and Zappa fan).  He originally wanted
to name one of the recently-discovered planets orbiting the pulsar in
Virgo after Zappa.  But the IAU has no official committee to name
objects outside the solar system.  So Marsden suggested a minor planet
instead--one that was discovered at Klet Observatory in S. Bohemia.
The official designation reads as follows: 

"Named in memory of Frank Zappa (1940-1993), rock musician and
composer of innovative contemporary symphonic, chamber and electronic
music.  Zappa was an eclectic, self-trained artist and composer with
incredible energy and a biting wit, and his music transcends the usual
music barriers.  Before 1989 he was regarded as a symbol of democracy
and freedom by many people in Czechoslovakia." 

FYI, there are also asteroids named after all of the Beatles, Bob
Hope, and Bing Crosby. 

% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% Date:         Mon, 25 Jul 1994 11:17:24 EDT
% Reply-To: Astronomy Discussion List <ASTRO%[email protected]>
% Sender: Astronomy Discussion List <ASTRO%[email protected]>
% From: Julie <[email protected]>
% Organization: Center for Astrophysics
% Subject:      Re: New name for asteroid
% X-To:         ASTRO%[email protected]
% To: Multiple recipients of list ASTRO <ASTRO%[email protected]>

From:	US4RMC::"ASTRO%[email protected]" "Astronomy Discussion 
        List"  3-AUG-1994 16:52:38.79
To:	Multiple recipients of list ASTRO <ASTRO%[email protected]>
CC:	
Subj:	NASA Creates Near-Earth Object Search Committee

Donald L. Savage
Headquarters, Washington, D.C.
August 3, 1994
(Phone:  202/358-1547)

RELEASE:  94-128

NASA APPOINTS NEAR-EARTH OBJECT SEARCH COMMITTEE

        NASA today announced the establishment of a committee
which will develop a plan to identify and catalogue, to the
extent practicable within 10 years, all comets and asteroids
which may threaten Earth.

        Dr. Eugene Shoemaker was appointed as Chairman of the
eight-member Near-Earth Object Search Committee.  Shoemaker,
an astronomer with the Lowell Observatory and professor
emeritus with the U.S. Geological Survey, also was co-
discoverer of Comet Shoemaker-Levy 9 which collided with
Jupiter last month.

        The committee was formed in response to Congressional
direction to NASA to develop a plan in coordination with the
Department of Defense and the space agencies of other
countries.  The plan's objective is to identify and
catalogue, to the extent practicable, the orbital
characteristics of all comets and asteroids greater than
about 1/2 mile (1 kilometer) in diameter in orbit around the
sun that cross the orbit of the Earth.  The plan is to
include estimated budgetary requirements for fiscal years
1996 through 2000.

        The Chairman of the House Committee on Science, Space
and Technology, Representative George Brown, introduced the
legislation as an amendment to the NASA Authorization Bill.
The amendment calls for the NASA Administrator to submit the
plan to the Congress by Feb. 1, 1995.  Also appointed to the
committee are:

     Dr. Jurgen H. Rahe, Executive Secretary, NASA Headquarters, Wash., D.C.
     Dr. Gregory Canavan, Dept. of Energy Los Alamos National Laboratory, N.M.
     Dr. Alan J. Harris, NASA Jet Propulsion Laboratory, Pasadena, Calif.
     Dr. David Morrison, NASA Ames Research Center, Mountain View, Calif.
     Dr. David L. Rabinowitz, Carnegie Institution, Wash., D.C.
     Dr. Michael J. Mumma, NASA Goddard Space Flight Center, Greenbelt, Md.
     Col. Simon P. Worden, U.S. Air Force Space Command, Colorado Springs, Colo.

- end -

NOTE TO EDITORS':  Copies of the Jan. 25, 1992, report of the
NASA International Near-Earth Detection Workshop called "The
Spaceguard Survey" are available to news media by calling the
NASA Newsroom at 202/358-1600.

% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% Date:         Wed, 3 Aug 1994 20:33:07 +0000
% Reply-To: Astronomy Discussion List <ASTRO%[email protected]>
% Sender: Astronomy Discussion List <ASTRO%[email protected]>
% From: Ron Baalke <[email protected]>
% Subject:      NASA Creates Near-Earth Object Search Committee
% X-To:         [email protected]
% To: Multiple recipients of list ASTRO <ASTRO%[email protected]>

Article: 68217
From: [email protected] (enews)
Newsgroups: sci.astro
Subject: Issues in Science and Technology
Date: 14 Aug 1994 15:57:16 -0400
Organization: Express Access Online Communications, Greenbelt, MD USA
 
The featured article from the summer issue of Issue in Science and 
Technology looks at the effects of collisions in space. Here is an 
excerpt from Carl Sagan and Steven J. Ostro's article "Long-Range 
Consequences of Interplanetary Collisions."
______________________________________________________________________________
 
     As Comet Shoemaker-Levy 9 races toward its mid-July collision
with the planet Jupiter, considerable public attention is being
focused on catastrophic impacts with the Earthein the past and in the
future. In recent years calls have been made to develop technologies
that could deflect any asteroid or comet found to be on a collision
course with Earth. But before devoting resources to this scheme,
careful consideration must be given to the nature and time scale of
the risk and to the cost-effectiveness and possible booby traps in the
suggested means of mitigation. 
 
     Comets have been associated with catastrophes in almost all
cultures and since remotest antiquity. The first such argument with a
modern scientific flavor was offered by Edmund Halley in 1688. He
wondered if the Noachic flood could have been caused by tidal effects
from a grazing collision (or an actual impact) of a comet with the
Earth and proposed in effect a comet-induced tsunami. Since then the
impact danger of small worlds has been a common motif in popular
culture. Scientists have, until recently, generally responded with
reassurances about the improbability of perilous collisions. This
summeres impact with Jupiter reminds us that improbable is not
impossible. 
 
     We now know that the Earth orbits the Sun amid a swarm of small
bodies. Some 200 Earth-orbit-crossing asteroids (ECAs) and a much
smaller number of Earth-orbit-crossing comets have been discovered,
almost entirely by a handful of observers using small telescopes.
These limited searches, in tandem with analyses of the lunar and
terrestrial cratering records, have established that the ECA
population awaiting detection is enormous. There are thought to be
some 2,000 objects as large as 1 kilometer in diameter, 320,000 as
large as 100 meters, and 150,000,000 as large as 10 meters. 
 
     It is a straightforward consequence of orbital mechanics and
probability theory that, through its long history, the Earth will be
struck, at typical velocities of 20 kilometers per second, many times
by these objects. Collisions with the larger members of this
population are catastrophic. The greatest danger is from impacts
energetic enough to inject so much pulverized soil and rock into the
stratosphere as to darken and cool most of the Earth, regardless of
the impact location. 
 
     Unlike most familiar hazards, the impact threat works on many
different time scales, all much longer than a human lifetime. On
average, every millennium there will be a collision event as energetic
as the highest-yield nuclear weapon ever detonated (the result of an
impact of an object a few tens of meters in diameter); every 10,000
years, one that may have global climatic effects (the result of an
impact of an object 200 meters in diameter); and every million years,
an impact event tens of times more energetic than the aggregate yield
of the worldes current nuclear arsenal (the result of an impact of an
object 2.5 kilometers in diameter)eenough to cause a global
catastrophe and kill a significant fraction of the human species. 
______________________________________________________________________________
 
So begins this issue's featured article from Issues in Science and Technology.
 
This article and others from Issues in Science and Technology and additional 
publications can be viewed at no charge on The Electronic Newsstand, a 
service which collects articles, editorials, and table of contents from 
over 130 magazines and provides them to the Global Internet community.
 
Access to The Electronic Newsstand is available 24 hours a day, 7 days a 
week via Gopher, an information navigation and retrieval technology from the
University of Minnesota.
 
For those without a local Gopher client program, The Electronic Newsstand
provides a telnet account which will allow you to use a text based Gopher
client to access our service.
 
To access The Electronic Newsstand, 
 
	via Local Gopher Client:
 
		Hostname:	gopher.enews.com
		Port:		2100
 
	via the Gopher Home Menu at U of Minn:
 
		Other Gopher and Information Servers/
		  North America/
		    USA/
		      General/
			The Electronic Newsstand (tm)
 
	via Gopher Link Information:
 
		Name=The Electronic Newsstand
		Type=1
		Port=2100
		Path=1/
		Host=gopher.enews.com
 
	via Telnet:
 
		Hostname: 	gopher.enews.com
		Loginname:	enews
		Password:	<not required>
 
	via World Wide Web:
 
		URL:		gopher://gopher.enews.com/
 
HTTP World Wide Web pages coming soon, and retrieval service for users 
with email only. We are also available for America Online users in the 
Gopher area under Literature and Books.
 
If you have any suggestions on how we might improve this 
service, or need more information, please email  [email protected]
 
	--The Electronic Newsstand Staff
 
    "Men, it appears, would rather believe than know.  They would rather 
  have the void of purpose...than be void of purpose." - Edward O. Wilson