Conference 7.286::space

    	I heard that Hipparcos was placed into a geosynchronous transfer
    orbit by its Ariane launcher but that the spacecraft's kick motor has
    failed to ignite on the first couple of attempts (as of last week).
    Efforts are being made to determine the cause of the failure of the
    kick motor and to figure out how to make it ignite. If all attempts to
    place Hipparcos into its intended geosynchronous orbit fail, there is
    still the possibility that it could conduct a somewhat limited survey.
    
    				Drew
    

From: [email protected] (Mark James)
Newsgroups: sci.space
Subject: Hipparcos in trouble
Date: 21 Aug 89 16:37:40 GMT
Distribution: sci.space
Organization: GIP ALTAIR,c/o INRIA, Rocquencourt, FRANCE
 
    The following article appeared in the Paris daily _Liberation_
dated Friday, 18 August 1989, and is reproduced here without
permission. My apologies for the quick and dirty translation; terms of
rocketry, in particular, are rendered literally, and probably don't
read at all like the author knows what he's talking about.  This is
entirely my own ignorance, not his. 
 
    IGNITION FAILURES CONTINUE FOR HIPPARCOS
 
    Fourth try, fourth failure.  Yesterday at 2 PM [Paris time, 1200
UT], a new attempt to ignite the apogee thrusters of the astronomical
satellite Hipparcos failed once again.  And the source of the fault,
which has prevented the star-hunting satellite, launched by an Ariane
rocket on 9 August, from attaining its final orbit -- a circular
geostationary orbit at an altitude of 36,000 kilometers -- remains a
mystery. 
 
    One thing is certain:  This problem has occurred exactly where it
was least expected.  The Mage II apogee thrusters, built by SEP
(Societe Europeenne de Propulsion), functioned perfectly during 25
tests (13 on the ground, 12 at launch).  Since the onset of Hipparcos'
illness, engineers have been focusing on a possible fault in the
electric power supply leading to the small pyrotechnic charges; these,
when lit, should create a spark powerful enough to fire the thruster. 
Could there have been a short-circuit in one of the supply lines,
while a second, redundant line remained intact? 
 
    Yesterday, engineers sent about 80 powerful signals to Hipparcos,
trying to force their way into the satellite's circuitry by injecting
a current of six or seven amperes, instead of the one ampere normally
needed.  Failure.  Failure once more for an attempt to modify the
internal conditions of the satellite by cutting in half its rotation
speed, and thus its centrifugal force.  It had been hoped that this
would detach any poorly-insulated cables that might have been pressed
together into a short circuit.  Nothing came of it. 
 
    Next Tuesday, 22 August, at 9 AM [0700 UT], a fifth try will take
place, not much different from the last one.  Engineers will try to
``kick'' the satellite by firing one of its attitude thrusters, giving
its overall motion a bit more complexity.  Objective:  to shake Hipparcos 
a little (but not too much), in order to shift its internal circuits. 
 
    While awaiting the results of this last effort, scientists are
working on a compromise solution:  If the apogee thruster cannot
propel the satellite into a good curcular orbit, it would be left in a
strongly elliptical orbit (like its present one), except that the
lowest point of this orbit -- the perigee -- would be lifted by
several hundred kilometers, using the hydrazine thrusters.  After this
manoeuver, Hipparcos would orbit the Earth once every ten and a half hours. 
 
    According to mission chief Mike Perryman, Hipparcos would still
function, but the quality of its work ``would depend entirely on the
life span of the satellite''.  A life of six months would not
accomplish much, because ``the satellite is designed to sweep the sky
once every six months'', says Perryman.  A single observation is not
enough to add much to what we already know.  If the satellite
functions for a year, or even better two, the results will be
significant.  Recall that the principal mission of Hipparcos is to
measure not only the positions of a hundred thousand stars, but also
changes in those positions, due to stellar motion and to parallax. 
 
    In the worst case, if all goes really badly for this satellite
that cost the ESA 2.5 billion francs [$600 million US], it would be
possible to construct a second Hipparcos.  For the moment, no real
copy is planned, but a number of spare parts of the satellite are
already in existence and could be used. 
 
              Dominique Leglu
 
    *** End of article ***
 
    In _Le Monde_ the next day (Saturday, 19 August 1989), the
reporter (the article is signed ``Ca. V.'') is less optimistic about
this backup plan.  (Note:  Perigee is currently 210 km.) 
 
    ``Even raising its perigee by 400 to 600 km with the help of its
hydrazine jets, as the ESA project leaders envisage, Hipparcos would
only be able to observe each star three or four times, instead of the
eighty times originally planned.  For this last-chance scenario,
Hipparcos would need another Earth station, its orbit remaining
elliptical and not circular. 
 
    ``In addition to the principal station at Odenwald, in West
Germany, the Australian control center in Perth could thus be equipped
with the high-speed links necessary to receive the scientific data
transmitted by the `surveyor of the skies'.'' 
 
    All in all, then, not real good news for us astronuts.
 
### T. Mark James           #### opinions, errors etc are my own ###
### [email protected]  #### "Sure, living in the future is like
### +33 (1) 39 63 53 93     ####  having bees live in your head.
################################  But, there they are..."

From: [email protected] (Giggles Gonzaga -- Prophetess of Wisdom and Truth)
Newsgroups: sci.space
Subject: Re: Hipparchos (Was Re: European Space Agency)
Date: 23 Aug 89 13:41:46 GMT
Organization: Space Telescope Science Institute, Baltimore, MD 21218

    A guy named Peter Bunclark has been posting some very interesting
information on HIPPARCOS in our local Space Telescope Science
Institute bulletin board. Here are excerpts from his articles -- 
------------------------------------------------------------------------
    Date: 14 Aug 89 10:20:05 EDT
 
   "Hipparcos was successfully launched just after midnight on the 8/9 August.
   This placed the satellite into a transfer orbit with a perigee height of
   800 km and an apogee height of 41,000 km. The satellite was successfully
   spun up and all systems were described as nominal. On Thursday 10 August at
   1420 the apogee boost motor was supposed to fire and place Hipparcos into
   a geostationary orbit. It didn't. This was at the 4th apogee of the
   satellite. At the 6th apogee (Friday 11th 0930) another unsuccessful
   attempt occurred. Technical evaluations were being carried out."
 
    Date: 17 Aug 89 12:26:40 EDT
 
   "The cause of the problem that has led to the failure
   of the apogee boost motors has been traced to a short circuit.
   The spin rate of the satellite was halved to see if this would
   have any affect on the short circuit. A further attempt at
   firing the motors was tried at 1300 (BST) today (17th). This
   was unsuccessful. The next attempt will be on Monday 21st at
   1110 (BST).
   
   If all attempts are unsuccessful the planned revised mission will
   take place in the current highly elliptical orbit (210km-36000km).
   It is possible that the perigee will be raised several hundred kms
   by using the hydrazine boosters. There are fears now that even
   this mission will not be as successful as first thought. Originally
   it should have lasted 6 months or more. Now the timescale is
   thought to be 3 to 4 months. This will mean that we will not even
   be able to get full sky coverage."
   
    Date: 21 Aug 89 10:27:16 EDT
 
   "It would seem that there are 2 faults in the firing systems
   of the satellite. With the 2nd firing system it seems that the
   first stage of the circuitry is working fine but it's not
   proceeding to the second stage. In addition to the 1110 attempt
   on Monday to fire the motor there will also be one on Tuesday.
    
   There are also more problems with the alternative observing
   programme than first thought. Due to the lack of continuous
   contact with the ground stations it makes it very difficult to
   work out the attitude of the satellite (needed to better than
   1" accuracy) if it observes in a manner similar to the original
   mission. An alternative is that the spin axis points towards
   the Sun all the time. This leads to problems with the Solar
   panels overheating. Even if the ground station at Kourou is
   used we would only get ~70% coverage. There is also the problem
   that the detectors must be switched off when the satellite is
   below 10,000km. This is for about 2 hours every orbit.
   
   Another problem is that the satellite will spend longer stretches
   of time in the Earth's shadow due to it being in the current orbit.
   These periods will be longer than the backup batteries can cope
   with, so that during the March/April eclipse season the satellite
   will have to be placed in a dormant state. It could be that the
   satellite will not recover from this.
   
   There will also be a delay of 2 months (plus) before this alternative
   mission gets started while ESOC ground control carrys out various
   reprogramming that has to be done."
 ______________________________________________________________________________
Shireen Gonzaga/Space Telescope Science Inst./3700 San Martin Dr., Baltimore,
MD21218/tel301-338-4412/ARPA [email protected]/SPAN SCIVAX::GONZAGA/sometimes 
you just have to give in to the absurd -- Picard in ST-TNG "Up the Long Ladder"

    Shoot me down, or back me up, but (aside from schedule constraints)
    could the space shuttle recover or repair HIPPARCOS?
    
    jim
    

    Re: .4
    	I'm going to shoot you down: Hipparcos is in an elliptical
    geosynchronous transfer orbit (something like 240 km by 35,000 km). The
    Space Shuttle can't get into this kind of orbit.
    	Even if the Shuttle could reach it, the schedule is so tight that
    it couldn't be recovered by the Shuttle. NASA had enough trouble trying
    to schedule a recovery of LDEF and couldn't schedule a recovery for
    Solar Max.
    
    					Drew
    

    I figured as much, but you can't find the good solutions unless
    you are willing to address the, seemingly, impossible ones...
    
    jim
    

Newsgroups: sci.space
Subject: NASA Headline News for 08/30/89 (Forwarded)
Date: 31 Aug 89 00:55:38 GMT
Reply-To: [email protected] (Peter E. Yee)
Organization: NASA Ames Research Center, Moffett Field, CA

-----------------------------------------------------------------
                          NASA Headline News
Wednesday, August 30, 1989                     Audio:202-755-1788
-----------------------------------------------------------------
 
    This is NASA Headline News for Wednesday, August 30:
 
    The star tracking satellite HIPPARCOS, launched by the European
Space Agency (ESA) on August 8 is being called a failure, according to
an official of the Italian Space Agency.  The spacecraft has not yet
reached its proper orbit, and there have been five unsuccessful
attempts to start its kick motor.  The official said his agency is
prepared to ask ESA for funds to replace the satellite. 
 
    A service of the Internal Communications Branch, (LPC), NASA 
Headquarters.

From: [email protected] (Hermann Schneider)
Newsgroups: sci.space
Subject: HIPPARCOS status report
Date: 22 Sep 89 12:06:03 GMT
Organization: ESOC - European Space Operations Centre
 
    Hipparcos status report (This is an exert from the ESOC news letter)

    Five firing attempts of Apogee Boost Motor between 10th and 25th
Aug 89. A definite understanding of the reasons for the failure could
not be be obtained. On-board investigations have been given up. Ground
laboratory test now to reproduce failure. 
 
    Mission is redefined. Orbit change to a perigee between 450 and
550 km and apogee between 35800 and 35900 km. Orbital period
10h40mins. Last orbit adjustments on 18th Sept. Solar arrays + fill in
antenna deployed on 12 Sept. First payload telemetry data expected for
last week Sept. Additional ground stations needed (Perth is in, Kourou
?). Lifetime depends on solar array degradation due to Van Allen
belts. Expected life time is until June 1990. Position measurements
for about 100.000 stars will be obtained with an accuracy far
exceeding those of on-ground observations. 
 
    Regards, Hermann Schneider

        (Communication Systems Programer)
        ESOC (European Space Agency's Operations Center)

Newsgroups: sci.space
Subject: Hipparcos Status Report
Date: 30 Sep 89 14:19:41 GMT
Reply-To: [email protected] (Neil Dixon)
Organization: ESTEC/YCV, Noordwijk, The Netherlands
 
    The following is reproduced from 'Estec News' (28th Sep 1989),
published by ESTEC Public Relations Office. 
  
			Hipparcos Status Report
 
    Hipparcos was launched on August 9, 1989 from Kourou, French
Guiana, on an Ariane 4 launcher. The launch was a success but at the
4th apogee, 37 hours after the launch, on 10 August, the satellite's
Apogee Boost Motor (ABM) did not ignite.  ABM firing attempts were
repeated between 10 and 25 August at the 6th, the 11th, the 20th and
again at the 38th apogee, always with no result. 
 
    Like all geostationary satellites, Hipparcos was launched in a so
called transfer orbit, that is a highly elliptical orbit with a
perigee of approximately 200 km and an apogee of about 36,000 km. As
the satellite approaches the apogee (the furthest position from the
Earth in the elliptical orbit) its Apogee Boost Motor is ignited in
order to inject the spacecraft into the circular geostationary orbit
at a constant altitude of about 36,000 km. In such an orbit the
satellite moves eastward with a period of 24 hours and from Earth
it appears fixed in the sky always at the same place so that only one
ground station (Odenwald, near Darmstadt, in the case of Hipparcos) is
enough to control and get data from the satellite. 
 
    Attempts to fire the ABM were subsequently abandoned and on 4
September it was decided to terminate the original scientific mission
and to proceed with a "revised mission". The on board hydrazine was
used to raise the perigee of the highly elliptical orbit from 250 km
to 540 km, the apogee remaining at about 36,000 km. The solar arrays
and the fill-in antenna (used to complete the coverage of the main
antenna) were successfully deployed on 12 September. The two telescope
baffles successfully opened on 25 September: stars can be seen
crossing the star mapper grid.... 
 
    The revised mission, expected to start around mid-October, will
allow a considerable part of the Hipparcos mission to be implemented
in spite of the spacecraft not having reached a geostationary orbit. 
 
    In its elliptical orbit, approximately every ten hours, the
satellite goes though the Van Allen Belts. There, at some 5,000 km over
the equator, the solar cells are bombarded by a heavy shower of high
energy protons and electrons captured by the solar wind. Under these
circumstances, the solar arrays get easily "damaged" and their
degradation shortens the mission lifetime of the spacecraft: reliable
measurements are not yet available, but it is expected that the lifetime 
could be somewhat less than the 30 months originally foreseen. 
 
    The longer the mission the more scientists will be able to get out
of it.  Positions of a large amount of stars (75,000 if the mission
lasts 4 months, 110,000 for a revised mission lasting 18 months,
against the 120,000 in the original baseline) can still be detected.
But with a mission lasting only 4 months, for instance, each star is
observed only 10 times or less instead of 80, and this means that
proper motions and parallaxes are not estimable and the overall
positional measurement will be probably a factor ten less than
expected. Scientists are confident to achieve a positional accuracy 15
times higher than that attainable from any ground based observation.
However, for a mission lifetime significantly shorter than the 2.5
years originally foreseen, the degraded precision of the parallaxes
and proper motions would considerably reduce the astrophysical return
of the mission. 
 
    Another draw-back to the satellite's performance is related to
ground station coverage. If Hipparcos would have reached its
geostationary orbit, the Odenwald ground station would have been in
continuous contact with the satellite. In its present orbit Hipparcos
is instead viewed by Odenwald for only 30% of the time. For this
reason the ESA ground station in Perth (West Australia) has been
equipped with high-rate data links in order to retrieve scientific
data. Data acquisition time would thus raise to 62%, and if the CNES
station in Kourou is also added to the chain, the coverage would be
eventually brought to about 81%. 
 
    Despite the large amount of data which has been downlinked and
analysed, it has not been possible so far to fully understand the
reasons for the Apogee Boost Motor failure.  (The investigations
indicate that the ABM firing orders have been properly executed
on-board. The failure must have occurred downstream the firing relays
either in the electrical or the pyro-technic chain.) An enquiry board
has been formed to investigate the failure. The board will issue a
report on their findings by mid-October 1989. 
-- 
Neil Dixon <[email protected]> UUCP:...!mcvax!esatst!neil, BITNET: NDIXON@ESTEC
Thermal Control & Life Support Division (YC) 
European Space Research and Technology Centre (ESTEC),
Noordwijk, The Netherlands.

Newsgroups: sci.space
Subject: NASA Headline News for 10/13/89 (Forwarded)
Date: 15 Oct 89 04:15:26 GMT
Reply-To: [email protected] (Peter E. Yee)
Organization: NASA Ames Research Center, Moffett Field, CA
 
-----------------------------------------------------------------
Friday, Oct. 13, 1989                        Audio:  202/755-1788
-----------------------------------------------------------------
 
    This is NASA Headline News for Friday, October 13:
 
    Aerospace Daily reports that the European Space Agency's HIPPARCOS
star-mapper satellite has sent back extremely accurate data despite
its less than satisfactory orbit.  HIPPARCOS has remained in an
ellipical orbit because its apogee kick motor failed to place the
spacecraft in a geostationary orbit.  The data is five times more
accurate than anything available from ground telescopes. 
-----------------------------------------------------------------
These reports are filed daily, Monday through Friday, at 12 noon, 
Eastern time.
-----------------------------------------------------------------
A service of the Internal Communications Branch (LPC), NASA 
Headquarters, Washington, D.C.

Newsgroups: sci.space
Subject: Hipparcos: The present status
Date: 15 Feb 90 13:44:37 GMT
Reply-To: [email protected] (Neil Dixon)
Organization: ESTEC/YCV, Noordwijk, The Netherlands
 
The following is reproduced from ESTEC News:
 
---------------------------------------------------------------------
Published by ESTEC Public Relations Office  14 Feb. 1990
 
Hipparcos: The present status
 
Subsequent to the perigee raising manoeuvres performed last September,
the satellite operations have continued smoothly after much intensive
work by the ESOC Operations Team and members of the Project Team. The
outlook for the mission is much better than it was in the days and
weeks following the apogee boost motor failure. It Is worth noting
that, while the present elliptical orbit has posed many unforeseen
operational difficulties and will inevitably result in a somewhat
degraded scientific mission (compared with the nominal mission for any
given operational lifetime), a geostationary orbit was not mandatory
from the point of view of the astrometric measurements, and this
explains why it has been possible to implement a revised mission.
 
In the new orbit, the satellite was commissioned and its overall
performance was found to be nominal or better than specified.
 
On 1 November 1989, the nominal scanning law acquisition was completed
and the satellite is now following its pre-defined scanning of the
celestial sphere. Further payload calibrations were carried out
between 1-25 November and the nominal mission commenced on 26
November. Star observations (more than 10 000 stars are observed each
day, along with some minor planets - even Venus has already been
observed) are now proceeding routinely.
 
Ground station data coverage is now provided by a combination of the
Darmstadt, Perth (Australia), and Kourou ground stations. A fourth
station at Goldstone, USA, is planned to be operational by the end of
March thus raising the coverage from the present value of about 70% to
about 90%.
 
The most critical parameter in any assessment of the expected
scientific accuracy of the revised Hipparcos mission is still the
satellite lifetime, which will be determined by the degradation of the
solar panels due to the high-energy proton radiation environment in
the present elliptical orbit. Estimates now suggest that a total
lifetime of about 30 months might be achievable - this estimate has
been continually refined as further satellite measurements are
accumulated and as progress has been made in matching the on-board
measurements to the theoretical predictions.
 
A further complication with the present orbit is that the eclipse
durations experienced by the satellite can be much longer than the 72
minute maximum expected for the nominal mission. The first such
extended eclipse period will be encountered around February and March
1990, with eclipses lasting up to about 100 min. Plans are being
formulated to ensure the survival of the satellite throughout these
periods, and to maximise the amount of scientific data acquisition and
engineering check-outs that can be carried out during this eclipse
period.
 
It is evident that the payload performance in all areas is extremely
good, with the instrumental parameters and (along-scan) star positions
already being determined to milli-arcsecond precision. There is still
some way to go before the mission can be considered to be a complete
scientific success, but in terms of satellite performance and
operational procedures made necessary through the implementation of
the 'recovery' mission, the future is looking promising.
-- 
Neil Dixon <[email protected]> UUCP:...!mcvax!esatst!neil, BITNET: NDIXON@ESTEC
Thermal Control & Life Support Division (YC) 
European Space Research and Technology Centre (ESTEC),
Noordwijk, The Netherlands.

Newsgroups: sci.astro
Subject: Astrometry in the 1990s (was Re: Hubble Predictions)
Date: 2 May 90 18:37:33 GMT
Reply-To: [email protected] (Daniel Fischer)
Organization: Max-Planck-Institut fuer Radioastronomie, Bonn
 
    Dan Briggs <[email protected]> writes in <[email protected]; 29
Apr 10:29 GMT>: 

> I believe that the modified mission plan will return something like 60% of the
> original data planned... if we're lucky we might get *most* of the data back.

    On March 13 I talked with Hipparcos' mission manager Mike Perryman
at ESTEC. He told me they now believe that Hipparcos will survive for
3 years as its solar cells are unexpectedly resistant to the van Allen
belts. He was "absolutely" sure that the satellite will be able to
fulfill its name-giving objective of measuring parallaxes (and thus
absolute distances) of roughly 100000 stars, at the originally
envisioned precision of 0.002 arcsec. If the funding crisis is
mastered and ESA gets all the ground stations it wants for > 3 years
(at the moment the coverage is 90% of the time, according to ESA PRESS
RELEASE of March 27) chances are that *all* the mission objectives can
be met. (Wouldn't that be a first in space history:a satellite
designed for GSO does all its work at GTO?) 

    Dan further asked about the astrometrical capabilities of
Hipparcos, Hubble and observatories on Earth. As far as I've
understood the fundamental objective of the Hipparcos mission (see
e.g. ESA BULLETIN #58(May 1989) 76-87, GEMINI #24 (June 1989) 1-4 and
NATURE 13 July 1989 111-116) is to pin a - for a while - ultimate
*absolute* reference system on the sky ("Global Astrometry"). That's
why they put on board this unique mirror that combines light from two
areas in the sky 58 degrees apart: an incredible amount of relative
angular measurements of 0.002" precision all over the sky will, after
having solved numerous equa= tions, yield all star positions in *one*
system. This should be the most fundamental result of this mission
(which, however, won't be available much before the year 2000, I've
heard from Hipp people). 

    The other objectives, measuring stellar distances and motions
("Small-Field Astrometry") are equally important, especially because
of the 100,000+ stars observed, but when it comes to *individual*
stars, other facilities might do better than Hipparcos. A fine review
that just appeared in SKY & TELESCOPE (May 1990 493-497) describes
these different aspects of astrometry and mentions the tremendous
capabilities _interferometric_ techniques have in measuring double
stars (sub-milliarcsec precision). 

    That is also where Hubble might contribute most to astrometry (and
not so much with its cameras, as even the FOC will 'only' reach 0.015
arc sec; see my March 14 and 21 postings on sci.astro/SPACE Digest):
its interferometric Fine Guidance Sensors are designed to allow
small-field astrometry at 0.0016" (and with repeated measurements even
0.0003") angular resolution - they want to measure light deflection by
Jupiter and similar esoteric stuff this way. So there's really no
telling at the moment whether sophisticated ground-based
interferometry (like on Mt.Wilson and in Southern France) or space
approaches will yield better results. None of them however can match
the 'global' power of Hipparcos: it is about 20 times more precise
than any global astrometry observatory on the ground. 

+- [email protected] --- Daniel Fischer --- [email protected] -+
| Max-Planck-Institut f. Radioastronomie, Auf dem Huegel 69, D-5300 Bonn 1,FRG |
+----- Enjoy the Universe - it's the only one you're likely to experience -----+

I'm confused; is this last note about Hippa***, or is it about
Hubble?  Mainly, does Hubble do the precise measurement, or does,
Hippa****, or do they both do the measurement?  That guy could
sure use an editor!

    Re:.13
    
    Dear Confused,
    	Reply .12 is primarily about Hipparcos. Evidently the original
    author was asked to compare Hipparcos' astrometric performance with that 
    of HST and ground observatories. The conclusion was that Hipparcos can
    determine the position of a star to within 2 milliarc seconds relative
    to the sky's absolute frame of reference. This is by far the best ever
    position measurment relative to the sky's absolute frame of reference.
    The author goes on to point out that HST is capable of determining the
    position of a star to as good as 0.3 milliarc seconds relative to
    neighboring stars (i.e. relative to a small region of the sky). The two
    spacecraft essentially have complementary capabilities.
    
    				Drew
    

OK. Thanks Drew.  As I read the article it implied that HST could
do the measurement better than Hipparcos, because of the .3
milliarc seconds vs 2 milliarc seconds, but I missed the
different references.

From: [email protected] (Steve Willner, OIR)
Newsgroups: sci.space,sci.astro
Subject: Hipparcos Update
Message-ID: <[email protected]>
Date: 23 May 90 20:42:00 GMT


[Following is condensed from the April 1990 issue of Astronews, the ESA
Astrophysics Division newsletter.  The original article is by Michael
Perryman of ESTEC.]

On-board systems function well.  Payload now fully commissioned and
calibrated.  Payload being used to determine spacecraft attitude and
improve detector pointing.  Lifetime predictions for solar arrays
revised upward to 2.5-3.0 years.  Longest eclipse in February/March was
105 minutes; batteries had 5 minutes of margin, so data completely
unaffected.  Data being acquired 55-60% of time through mid-March.
Goldstone station now on-line, but data link from Goldstone to ESOC
flaky.  Expect efficiency 70-75% when problems solved, compared to 30%
at start of mission and 90% if correct orbit had been achieved.  Data
analysis proceeding smoothly.

"If the mission survives 3 years at current performance levels (useful
data fraction, present data quality, etc.), the original astrometric
(and hence scientific) goals (2 milli-arcsec for positions, parallaxes,
and annual proper motions) could still be achievable."
-------------------------------------------------------------------------
Steve Willner            Phone 617-495-7123         Bitnet:   willner@cfa
Cambridge, MA 02138 USA                 Internet: [email protected]

From: [email protected] (Harm Munk)
Newsgroups: sci.space
Subject: ESA announces publication of Hipparcos Input Catalogue
Date: 19 Feb 91 09:25:59 GMT
Organization: Philips CFT
 
In the last issue of the ESA-Journal, a leaflet was inserted with
the following text. Please forward all further inquiries to Dr.
C. Turon, MESIOA::TURON (SPAN), or TURON@FRMEU51 (EARN) (see also
end of article), NOT to the poster of this article.
 
=================================================================
                 Pre-Publication Announcement
                 THE HIPPARCOS INPUT CATALOGUE
a catalogue of 118 000 star positions and associated astronomical
                             data
           will be published by ESA on behalf of the
                INCA Consortium in Spring 1991
 
This notice gives details of this important star catalogue, and
   an opportunity to order printed copies, for individual or
         institutional use, at a pre-publication price
-------------------------------------------------------------
The Hipparcos Input Catalogue has been compiled, over the period
1982-1990, as the definitive observational catalogue for the European
Space Agency's Hipparcos astrometry satellite, which was launched on 8
August 1989.  The Catalogue's compilation has been carried out by an
international astronomical team, the INCA Consortium, endorsed by ESA,
and led by Dr. Catherine Turon of the Observatoire de Paris, France. 
The Input Catalogue contains the most up-to-date information on all
stars to be observed by Hipparcos.  As a source of stellar
astronomical data, its completeness and accuracy are of unprecedented
quality. It will be a valuable reference for research activities to be
undertaken with the final Hipparcos astrometric data. The Input
Catalogue will be available in printed form, on magnetic tape through
the Strasbourg Stellar Data Centre, and probably also on CD-ROM. The
printed version will comprise approximately 2500 tabulated pages, and
is being published by ESA on behalf of the INCA Consortium. 
 
Stellar Content: the Catalogue contains data on each star included for
observation by the Hipparcos satellite. The star list comprises about
55 000 stars brighter than, and essentially complete to, between V=7.3
and 9 mag (dependent on galactic latitude and colour index), with a
roughly uniform sky distribution. A further 60 000 stars, selected on
the basis of their astrometric and astrophysical interest, lie between
this completeness limit and the satellite observability limit of about
V=12.4 mag. The stars selected for inclusion in the Hipparcos
observing programme, and therefore contained in the Hipparcos Input
Catalogue, were selected on the basis of more than 200 scientific
proposals submitted to ESA in 1982, ranked and supplemented by a peer
scientific selection committee, takin into account the observing
capabilities of the satellite. 
 
Data content: the Input Catalogue does _NOT_ contain data derived from
the Hipparcos satellite observations (these data will only be
available at the end of the data analysis phase, probably around
1995). It comprises the best-available ground based astronomical data
for each programme star, verified and reduced to homogeneous systems,
as measured or compiled by the INCA Consortium.  It includes the
following information, when available (including, where appropriate,
formal errors and sources of the data), and ordered by right ascension: 

     Hipparcos Input Catalogue (HIC) running number
     Cross-identification to HD, DM, FK5, AGK3, and SAO
     catalogues*
     Position for equinoxes J2000 & B1950*
     Proper motion*
     Parallax
     Radial velocity
     Magnitudes (B, V and 'Hipparcos')*
     Spectral type and luminosity class
     Variability information*
     Multiplicity information* (including an Annex containing
     more detailed information
     Proper motion and cluster identifiers*
     A supplementary "Atlas" of finding charts for approximately
     10 000 fainter stars*
 
* indicates that the entries include newly-observed, measured,
or compiled data.
 
The Input Catalogue amounts to five printed volumes. A sixth volume
contains finding charts for approximately 10 000 fainter stars. 
 
Orders for the Printed Version of the Hipparcos Input Catalogue
 
The Catalogue will be published as ESA SP-1136 in April 1991. Orders
received before 31 March will be accepted at a special pre-publication
price. 
 
Orders for the printed version of the Hipparcos Input Catalogue should
be made on a special order form (or photocopies of the form). The form
must be accompanied by a cheque, or an international banker's draft,
or proof of a bank transfer, for the appropriate amount in Dutch
guilders, made payable to"ESA Publications Division", as follows: 
 
- Individuals certifying that the Catalogue is for private use:
for orders received before 31 March 1991: 120 Dfl, for orders
received after 1 April 1991: 180 Dfl
- Libraries, observatories and other institutes: for orders
received before 31 March 1991: 360 Dfl, for orders received after
1 April 1991: 540 Dfl
 
 (The prices include postage: outside Europe, delivery will be
                     made by surface mail)
 
Further information (and further copies of the order form) can
be obtained from:
 
     Dr. C. Turon,                 Tel: (33) 1 4507 7837
     INCA Consortium Leader        MESIOA::TURON (SPAN)
     Observatoire de Paris,        TURON@FRMEU51 (EARN)
      Section d'Astrophysique,
     F-92195 Meudon Cedex, France.
==============================================================

Article: 17394
From: [email protected] (Garrelt Mellema)
Newsgroups: sci.astro,sci.space
Subject: Hipparcos status
Date: 9 Oct 91 14:31:11 GMT
Sender: [email protected] (System PRIVILEGED Account)
Organization: Leiden University, the Netherlands.
 
A few weeks ago someone asked about the status of the Hipparcos
mission.  I talked with someone involved in the project and the
following is a summary of what he told me: 
 
-At the end of this year there will be a special Hipparcos issue of
 Astronomy & Astrophysics. Preprints of these articles are already
 available. Turon et al. compare the results of the first
 12 weeks of observations of the star mapper with the data of the 
 input catalogue. They show that the (ground based) input catalogue 
 is pretty good and that the first results confirm the suspicions about
 systematic errors in the best ground based coordinate systems.
 These first results also show the merits of having the data being
 reduced by two independent consortia.
 
-Hipparcos is still measuring and will continue to do so till it dies.
 Expected causes of death are: a) running out of maneuvering gas (2 yrs),
 b) failure of solar pannels (3-4 yrs), c) unexpected calamities.
 
-The data will not be available for another 4 years. At the moment there 
 are not really any first results articles being planned, they'll just 
 do the full reduction and then everybody gets their data. 
 
-The performance of the satellite itself is as good or better as expected. 
 Only: It is in the wrong orbit and this causes problems while measuring: 
 Data gets lost or is of less quality while measuring in the radiation belts 
 for example.
 
-The goal of obtaining an accurate coordinate system will be made.  The
 areas where Hipparcos will probably fail to live up to its expectations 
 are proper motions and parallaxes.  It will be especially hard to 
 accurately discern between the two (the closest stars have on average a 
 larger proper motion).
 
Hipparcos doesn't seem to get a lot of attention.  This strikes me as
odd, since this is a mission that despite accidents is really going to
produce results.  Apparently the ESA has no need for publicity or
thinks that Hipparcos is not really interesting for the public.  Part
of the problem is of course that there are still no results to show. 
 
Garrelt Mellema
Leiden Observatory, Leiden, the Netherlands

Article: 25294
Newsgroups: sci.space,sci.astro
From: [email protected] (Ron Baalke)
Subject: Hipparcos Emergency - 08/05/92
Sender: [email protected] (Usenet)
Organization: Jet Propulsion Laboratory
Date: Thu, 6 Aug 1992 00:07:32 GMT
 
                       HIPPARCOS SPACECRAFT EMERGENCY
                            August 5, 1992
 
     ESOC (European Space Operations Center) declared a spacecraft
emergency on the Hipparcos spacecraft on August 4 at 1424Z.  The
project reported that the prime AOCS (Attitude Orbit Control System)
had failed.  DSS-16 (the 26 meter antenna in Goldstone, California)
was configured for support and was on point at 1445Z.  After further
analysis of the spacecraft condition, the project reported the backup
AOCS was working.  Hipparcos is in a Sun acquisition mode and will
remain in this mode until further analysis of the problem on the prime
AOCS.  The project lifted the spacecraft emergency at 1830Z on August
4.  DSS-16 continued tracking until the end of the scheduled support
at 0006Z on August 5. 

     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [email protected]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | You can't hide broccoli in
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | a glass of milk - 
|_____|/  |_|/       |_____|/                     | anonymous 7-year old.
 

Article: 31341
From: [email protected] (Bill Higgins-- Beam Jockey)
Newsgroups: sci.astro
Subject: Re: Hipparchos Status ?
Date: 1 Feb 93 17:42:30 -0600
Organization: Fermi National Accelerator Laboratory
 
In article <[email protected]>, [email protected] (Dave
Michelson) writes: 

> In article <[email protected]> [email protected] () writes:
>>I'm reading a 1989 text by Bohm-Vitense That mentions
>>an astrometric satellite named Hipparchos. 
..
> Yes, it was launched but it ended up in a far lower orbit than desired.
> ESA project managers devised an alternative mission plan and, at the time,
> believed that a good fraction of the original objectives could be met.
 
Dave is right. Early scientific results are reported in *ESA Bulletin*
no. 69, February 1992. I don't have that handy, but I do have "The
Hipparcos Mission-- On the Road to Recovery," bye H. Hassan, K.
Clausen, M.A.C. Perryman, J. van der Ha, and D. Heger, *ESA Bulletin*
no. 64, p. 59-66. Also, the project status in issue 70 says that
Hipparcos (note correct spelling) completed two years of data-taking
in November 1991, data quality is high, and they are able to collect
60% of the data despite the wrong-orbit problem.
 
Hipparcos was launched in the summer of 1989.  Its mission is to
measure the postions and motion of stars very precisely--
"astrometry." It was supposed to go into geosynchronous orbit, so only
one ground station would be needed to gather its data.  The Ariane
launcher put it into an  an elliptical transfer orbit, but the
satellite's apogee kick motor failed to fire, so instead of entering a
high circular orbit Hipparcos was stuck in the transfer orbit.
 
This not only put the spacecraft out of view of the ground station for
long periods, but brought it through thick parts of the Van Allen
belts (which are bad for the electronics and solar panels) and plunged
it into darkness in the Earth's shadow far more often than planned
(which is bad for the batteries).
 
ESA had to invent a whole new set of operating procedures for
Hipparcos in a big hurry.  Having determined that they could still
accomplish much of the mission in the bogus orbit, they added a couple
more ground stations and raised the perigee.  It's been a pretty
brilliant recovery.  There is enough hydrazine to last until mid-1994,
and they are hoping to get approval to keep operating Hipparcos until
it dies. 
 
Maybe I will send copies of this to some ESA and Hipparcos people and
invite further comment.
 
Reviewing *Time Trax*: "In this future  | Bill Higgins, Beam Jockey    
police have gotten more technical,      | Fermilab                     
computers have gotten much smaller,     | Bitnet: [email protected]  
criminals have become much cleverer,    | Bitnet: [email protected]  
and matte painters                      | SPAN/Hepnet: 43011::HIGGINS  
have lost the secrets of their ancestors." --Mark Leeper 

Article: 31466
From: [email protected] (Bill Higgins-- Beam Jockey)
Newsgroups: sci.astro
Subject: Hipparcos update from Project Scientist (was Re: Hipparchos Status ?)
Date: 3 Feb 93 12:32:05 -0600
Organization: Fermi National Accelerator Laboratory
 
In article <[email protected]>, [email protected]
(Bill Higgins-- Beam Jockey) writes: 

> Maybe I will send copies of this to some ESA and Hipparcos people and
> invite further comment.
 
I received a nice reply from Dr. M.A.C. Perryman, the Hipparcos
Project Scientist at ESA's ESTEC center in Noordwijk, Holland.  I
quote him below.
 
Bill Higgins, Beam Jockey              | The restaurant's architect
Fermi National Accelerator Laboratory  | said every effort had been
Bitnet:           [email protected]  | made to build McDonald's
Internet:       [email protected]  | 15th outlet in Italy 
SPAN/Hepnet:           43011::HIGGINS  | in harmony with Pompeii.
                                       | --Reuters story in *Chicago 
                                       |  Sun-Times*, 18 June 92
 
=======[begin Perryman quote]==========================
 
Hipparcos has completed three years of high-quality data collection,
i.e. exceeding the originally planned mission lifetime. This appears
to have fully compensated for the reduced data collection efficiency
(60 per cent achieved compared with 90 per cent anticipated). Approval
has been given to fund operations until the end of consumables (cold
gas for the attitude control) which is expected some time in the first
quarter of 1994. The most serious technical problems have been the
progressive loss of three of the original five gyros. The satellite
has been operating on only two gyros for the last four months (in the
attitude determination around the spin axis, needed to about 1 arcsec,
the gyro data is effectively replaced by a dynamical model based on
the perturbing torques acting on the satellite). Contingency plans
exist for a zero-gyro operation, although it is not too clear how well
this mode will really function. 
 
Data analysis has treated just over the first 18 months of mission
data, and is now quickly catching up with the satellite production.
Around 1Gbit per day enters the global astrometric solution. We are
confident that the original mission goals will be attained (2 milli-
arcsec on the positions, parallaxes and annual proper motions at 9 mag)
for the 120000 programme stars, and in many cases exceeded.
 
The catalogue derived from the star mapper observations should contain
just over a million objects, down to about 11-12 mag, with a positional
precision of around 0.03 arcsec.
 
Several thousand new double systems have been detected.
 
Photometry is obtained at several hundred distinct epochs throughout
the three-year mission, yielding broad-band photometry at the
milli-mag level per observation for the stars observed by the main
mission, and two-colour (close to B and V) photometry at the 0.03 mag
level at each observation for the million objects observed by the
star mapper.
 
=======[end Perryman quote]============================

 
I picked this up recently, and hope people here find it interseting and useful.
As MO has troubles, its good to see that a mission that had initial problems
can still cmoe good in the end!
 
Dave
 
Press Release Nr.37-93
Paris, 17 August 1993
 
 
Hipparcos: mission accomplished
 
 
 
After more than three years of efficient and successful
operations, communications with ESA's scientific
satellite Hipparcos were terminated on 15 August 1993.
The Hipparcos satellite, a purely European undertaking,
and the first space experiment dedicated to the highly
accurate measurements of star positions, distances, and
space motions, was launched in August 1989. Targeted
for an operational lifetime of two and a half years,
more than three years of high quality star measurements
were eventually accumulated, and all of the original
scientific goals of the mission have been fully
accomplished.
 
During the last few months of its life, as the high
radiation environment to which the satellite was
exposed took its toll on the on-board system, Hipparcos
was operated with only two of the three gyroscopes
normally required for such a satellite, following an
ambitious redesign of the on-board and on-ground
systems. Plans were in hand to operate the satellite
without gyroscopes at all, and the first such "gyro-
less" data had been acquired, when communication
failure with the on-board computers on 24 June 1993 put
an end to the relentless flow of 24000 bits of data
that have been sent down from the satellite each
second, since launch. Further attempts to continue
operations proved unsuccessful, and after a short
series of sub-systems tests, operations were terminated
four years and a week after launch.
 
An enormous wealth of scientific data was gathered by
Hipparcos. Even though data analysis by the scientific
teams involved in the programme is not yet completed,
it is clear that the mission has been an overwhelming
success. "The ESA advisory bodies took a calculated
risk in selecting  this complex but fundamental
programme" said Dr. Roger Bonnet, ESA's Director of
Science, "and we are delighted to have been able to
bring it to a highly successful conclusion, and to have
contributed unique information that will take a
prominent place in the history and development of
astrophysics".
 
Extremely accurate positions of more than one hundred
thousand stars, precise distance measurements (in most
cases for the first time), and accurate determinations
of the stars' velocity through space have been derived.
The resulting HIPPARCOS Star Catalogue, expected to be
completed in 1996, will be of unprecedented accuracy,
achieving results  some 10-100 times more accurate than
those routinely determined from ground-based
astronomical observatories. A further star catalogue,
the Thyco Star Catalogue of more than  a million stars,
is being compiled from additional data accumulated by
the satellite. These catalogues will be of enormous
value in astronomers' attempts to understand and
describe the properties and evolution of stars, and the
dynamical motion of these stars within our Galaxy. In
the process, HIPPARCOS has discovered many thousands of
new binary star systems, measured the precise light
variations of many hundreds of thousands of stars over
its operational lifetime, and has provided an accurate
and independent validation of the predictions of
General Relativity.
 
Scientists working with ESA on the HIPPARCOS programme,
were at ESOC on 13-14 July to review the progress of
the data processing, and to examine whether any further
efforts might allow the satellite to continue
operating. "All of us are sorry to see the end of this
remarkable satellite" said Dr. Michael Perryman, ESA
scientist responsible for HIPPARCOS, "On the other end,
we are delighted that it has delivered substantially
more than it had been originally designed for. When our
final results are published, some very interesting new
insights into the nature of our Galaxy, its structure
and its evolution, will emerge" he added.
 
A large team of scientists from the various ESA member
states are responsible for the analysis and
interpretation of the vast amount of data that has been
generated by the HIPPARCOS satellite, in what is
considered to be the largest single data processing
challenge ever undertaken in astronomy. Working with
ESA since the time of the mission acceptance in 1980,
their immediate work will only end with the publication
of the HIPPARCOS and Tycho Star Catalogues later this
decade. Only then will an astrophysical exploitation of
the results commence. Proposals have already been
submitted to ESA to follow up its successful
breakthrough into space astrometry with new missions
proposed for launch early in the next millennium.
 
 
 
 
Note for Editors :
 
The Hipparcos mission was accepted within the ESA
mandatory scientific programme in 1980. With overall
management by ESA, the system prime contractor was
Matra Marconi Space (France), also responsible for the
payload and the on-board software development: with
Alenia (Italy) responsible for the procurement of the
spacecraft, as well as integration and testing of the
complete satellite. A total of 35 European firms were
involved in the satellite construction. The satellite
was launched by Ariane 4 on 8 August 1989.
Hipparcos was named after the pioneer Greek astronomer
Hipparchus who compiled a detailed star map in around
120 BC and, by comparing it with observations made by
his predecessors, established that the Earth's rotation
axis slowly changed its direction in space.
 
The Hipparcos satellite carried out its measurements in
a highly elliptical 10-hour orbit, ranging between 500
km and 36,000 km above the Earth's surface, resulting
from non-functioning of the satellite's apogee boost
motor shortly after launch. A redesign of the on-board
attitude control system, and the addition of two more
ground stations into the control network, nevertheless
allowed ESA's operations team at ESOC (Darmstadt,
Germany) to operate the satellite with close to full
efficiency.
 
For the 20-strong operations team at ESOC and the
ground station teams in Perth (Australia), Goldstone
(USA) and Kourou (French Guiana) the mission has been
highly interesting, challenging and very demanding.
"After more than three years of excellent performance,
underlining the remarkable quality of the satellite's
design and construction, it was showing its age in
several areas" said Dietmar Heger, ESOC's Spacecraft
Operations Manager for Hipparcos. "The orbit was
subjected to very significant levels of high energy
electron and proton radiation, much higher than those
expected in its intended geostationary orbit. We cannot
be surprised or disappointed that the satellite has
finally ceased to function" he said.
 
The scientific activities associated with the Hipparcos
mission are under the responsibility of four European
scientific teams, together comprising about 100
scientists from universities and scientific institutes,
and led by Professor Erik Hoeg (Copenhagen University
Observatory, Denmark), Professor Jean Kovalevsky
(Observatoire de la C:te d'Azur, France), Dr. Lennart
Lindegren (Lund Observatory, Sweden) and Dr. Catherine
Turon (Observatoire de Meudon, France).
 
Final accuracies on the stellar positions, distances
and annual motions measured by Hipparcos, are in the
range 1-2 milli-arcsec (i.e. 1-2 thousandths of a
second of arc, equivalent to the angular size of a golf
ball viewed from the other side of the Atlantic Ocean).
Distances of stars many millions of times further away
than our own Sun are being measured, and their
velocities are being measured with accuracies of a few
hundred metres per second. A further million stars will
be contained in the accompanying Tycho Catalogue, with
positions not as accurate as those derived from the
main experiment, although still considerably more
accurate than those measurable from the ground.
 
At the heart of the satellite was an extremely accurate
optical telescope, which measured the separations
between stars in different parts of the sky as the
satellite turned slowly around its axis. The telescope
mirrors on Hipparcos were so accurately polished that,
if scaled up to the size of the Atlantic Ocean,
deviations of the surface would nowhere exceed 10 cm in
height. The global positional accuracies determined by
Hipparcos are impossible to achieve from the Earth's
surface, where the atmosphere, the temperature
variations, instrument flexure, and the absence of all-
sky visibility provide insurmountable barriers to
ground-based observers.
 
The Hipparcos results will represent a milestone in
mankind's understanding of the structure and evolution
of our Galaxy, and an invaluable legacy to future
generations of astronomers.
 
-- 
================================================================================
Dave Clements, Oxford University Astrophysics Department
================================================================================
clements @ uk.ac.ox.vax			|  Umberto Eco is the *real* Comte de
dlc      @ uk.ac.ox.astro		|           Saint Germain...
================================================================================