Conference warhed::astronomy

                  I N T E R O F F I C E   M E M O R A N D U M

                                        Date:     27-Jan-1997 07:27pm GMT 
                                        From:     VMSmail User "astro@store-forw
                                                  "[email protected]"@VBORMC@MRGATE@RDGMTS
                                        Dept:      
                                        Tel No:    

TO:  [email protected]@VBORMC@MRGATE@RDGMTS

Subject: This Week on Galileo

                            THIS WEEK ON GALILEO
                       January 27 - February 2, 1997

As Galileo emerges from behind the Sun, DSN antennas on Earth are once again
able to hear Galileo's radio signal. The further Galileo gets from the Sun
in the sky, the clearer the signal will get. This week the Sun's affect on
Galileo's radio signal is small enough to restart the playback of recorded
data.

This week's playback includes a variety of observations taken during
Galileo's first close encounter with Europa. Most prominent in this week's
plans are observations taken of features in Jupiter's atmosphere known as
Hot Spots. The observations scheduled for playback this week were taken by
SSI, NIMS and PPR. Recall that Hot Spots are areas of the atmosphere where
the clouds are relatively clear. These clear regions allow energy from the
deeper, warmer layers to escape into space. These observations are the
deepest Galileo will be able to "see" into Jupiter's atmosphere. Also recall
that Galileo's atmospheric probe penetrated Jupiter's atmosphere very near a
Hot Spot back in December 1995.

Observations of Io make up most of the remaining portion of the playback
plans. A global 6-color observation of Io by SSI, global thermal day and
night side observations by PPR and spatial and spectral observations by NIMS
are all returned during this week. Recall that during the last encounter,
Galileo's flyby of Io was the second closest (after the pass during the
Callisto-3 orbit) of the orbital tour.

This week's playback plans are rounded off by observations designed to
increase the global and regional imagery of selected targets. A regional map
of Europa, a global 4-color map of Amalthea and a global 3-color map of
Thebe are all scheduled for transmission to Earth. All of these were taken
by SSI.

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% Date: Mon, 27 Jan 1997 16:37:44 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 29-JAN-1997 21:36:31.32
To:	[email protected]
CC:	
Subj:	New Galileo Infrared Image of Europa

NEW GALILEO INFRARED IMAGE OF EUROPA
January 29, 1997

Today's image release on the Galileo home page is an infrared view of
Europa taken during the spacecraft's flyby of that satellite last month.

http://www.jpl.nasa.gov/galileo/

The caption file to the new image is appended below.

Ron Baalke
---------------------------------------------------------------------------

IMAGE TITLE:  Infrared Observations of Europa's Trailing Side

IMAGE CAPTION:  During the first targeted encounter of the icy        
  satellite Europa, the Near Infrared Mapping Spectrometer (NIMS) performed 
  high resolution spectral mapping of the trailing side, a region thought to
  have minerals other than water ice. For each pixel of the image, there is 
  a corresponding spectrum of several hundred wavelengths which is used to  
  identify the types of material present. The excellent resolution (about 10
  km) of the NIMS data shown on the right allows one to isolate the spectral
  signatures of the different types of terrain, which seem to consist of    
  water frost and hydrated minerals in various proportions. The NIMS image  
  is shown for a wavelength of 0.7 micrometers; a corresponding Voyager     
  image for visible light is shown on the left. 

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% Date: Wed, 29 Jan 1997 16:35:47 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: New Galileo Infrared Image of Europa
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 10-FEB-1997 17:28:07.61
To:	[email protected]
CC:	
Subj:	This Week on Galileo - February 10-16, 1997


                            THIS WEEK ON GALILEO
                            February 10-16, 1997

This week is the final week for data playback from Galileo's previous
encounter with Europa. This can only mean one thing! It is time for another
satellite encounter. At the end of this week, on the evening of February 16
(PST), Galileo will start executing the sequence of commands required to
perform another encounter with Europa, the second of three scheduled during
the orbital tour.

In the final scramble for data from the previous encounter, the playback
plans for this week include a variety of data from many different
observations. Some of the data returned during this week will again be used
to fill in gaps caused by solar conjunction. Other portions will expand on
partial data sets already return in earlier weeks. New data sets complete
the plans for this week.

Europa data includes high resolution observations of dark material and
regions with maculas as well as observations taken to map Europa at a global
level. High resolution fields and particles data from Galileo's flyby of
Europa are also returned this week. These data will be used to understand
the interaction between Europa and Jupiter's magnetosphere.

Io observations are returned containing data used to monitor volcanic
activity while others will be used to understand what happens on the surface
of Io as it moves in and out of sunlight as occurs when sunlight is blocked
from getting to Io by Jupiter. Observations of Jupiter continue to include
data describing the "hot spots" in Jupiter's atmosphere. Playback plans are
rounded off by including observations of Jupiter's main ring, and the minor
satellites Amalthea and Thebe.

Preparations continue this week to prepare for Galileo's next encounter.
Early in the week, the spacecraft will perform an turn designed to keep it
pointed toward earth. These attitude maintenance turns are required
periodically as the spacecraft and the earth drift relative to each other in
the sky. The first set of commands for the next encounter will be sent to
the spacecraft this week. This set of commands will control Galileo's
activity from February 16 through the end of February 20. A second set of
commands will be sent to the spacecraft before February 20 to control the
spacecraft through the end of the encounter (February 22). Optical
navigation images will continue to be taken this week. These images will aid
navigators in determining how well the spacecraft is following the desired
path through Jupiter's system. This type of information will be used to plan
the next orbit trim maneuver.

Well, that's it for this week! With a new encounter comes the return of
Today on Galileo. Come back and visit on Sunday, February 16!

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Mon, 10 Feb 1997 15:35:48 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
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% Subject: This Week on Galileo - February 10-16, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 17-FEB-1997 01:10:51.68
To:	[email protected]
CC:	
Subj:	Today on Galileo - February 16, 1997

                              TODAY ON GALILEO
                         Sunday - February 16, 1997

This afternoon Galileo starts executing the first set of commands of its
second consecutive encounter with Europa. This set of commands will control
the spacecraft's activity through the end of the fifth day of the encounter
period. During this encounter, Galileo will continue its close-up study of
Europa which will be highlighted with a flyby at a targeted altitude of only
586 km, even closer than its previous encounter with this moon. The
observations of Jupiter's atmosphere scheduled for this encounter are of
features known as White Ovals. Other targets for this encounter are Io,
Thebe, Amalthea, Ganymede and Callisto. The survey of the magnetosphere
performed by Fields and Particles instruments continues during this orbit
but also includes a high-rate observation as Galileo crosses through the
magnetic equator of the magnetosphere. All in all another exciting encounter
with Jupiter's system.

Today, the encounter sequence of commands starts to execute in the latter
part of the day, at about 3:05 pm (Pacific Standard Time). During this
encounter the radio signals from Galileo will take about 50 minutes to reach
Earth. By about 3:55 pm, the Galileo team will receive the first signals
indicating that the encounter sequence of commands has begun to execute.
First on the schedule is to finish off residual playback plans from the
previous encounter. Recall that Galileo's playback plans were hampered by
the effects of solar conjunction. Playback plans have been extended a few
hours into the next encounter in order to get as much of that data down
before writing over it with a whole new set of data. Once playback plans
have been completed, the Fields and Particles survey for this encounter will
be initiated. This survey will continue through out the entire encounter
period. At the end of the day, the spacecraft will start to perform a tape
recorder conditioning activity.

Come back tomorrow to learn more about tape recorder conditioning and what
else Galileo will be doing.

For more information on the Galileo and its mission to Jupiter, please visit
the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Sun, 16 Feb 1997 23:42:39 GMT
% From: Ron Baalke <[email protected]>
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 17-FEB-1997 19:12:47.89
To:	[email protected]
CC:	
Subj:	Today on Galileo - February 17, 1997

                              TODAY ON GALILEO
                         Monday - February 17, 1997

Galileo's morning will be spent completing the majority of the tape recorder
conditioning activity it started last night. These tape recorder
conditioning activities are performed more or less twice per orbit, both
immediately preceding an encounter (the current situation) and about
half-way through each orbit, near apoapsis, the point in the orbit that the
spacecraft is furthest away from Jupiter. Like any piece of equipment, the
tape recorder requires a normal maintenance plan, and these conditioning
activities are it. During the activity, the tape recorder is run from one
end to the next which re-packs the tape around the reels. This re-packing
keeps the tape in the right position on the reel and prevents possible
damage to the other parts of the tape recorder. The conditioning activity
was previously required only every 90 days. The current plan results in a
conditioning activity about every 30 days. This more frequent schedule was
put into place after the tape recorder anomaly in December 1996 and is
believed to alleviate some of the conditions that could lead to a
reoccurrence.

The first set of observations of this encounter are performed today during
the latter half of the day. These observations are remote Io torus
observations performed by the ultraviolet spectrometer in colaboration with
the extreme ultraviolet spectrometer. If you recognize this observation, it
is because a new set of remote Io torus observations is performed on almost
every orbit as the spacecraft approaches the Jupiter system. These
observations are part of a continued effort to map Io torus activity. Every
observation opportunity occurs a different time and exposes Galileo to a
different part of the torus . These observations continue into tomorrow.

Toward the end of the day, the Galileo team is scheduled to transmit
commands that will instruct the spacecraft to execute the final orbit trim
maneuver prior to the Europa encounter. This is the last opportunity the
navigators have to fine tune the path the spacecraft will take as it flys
through Jupiter's system. The orbit trim maneuver is scheduled to execute
tomorrow.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/


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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 18-FEB-1997 18:01:53.56
To:	[email protected]
CC:	
Subj:	Today on Galileo - February 18, 1997

                              TODAY ON GALILEO
                        Tuesday - February 18, 1997

As Galileo nears the Jupiter system, we see more science related activities
on the spacecraft's daily schedule. After completing its remote observations
of the Io Torus, the ultraviolet / extreme ultraviolet spectrometer
combination turns its attention to Jupiter. The day is filled with
observation of Jupiter's auroral regions performed by both instruments while
maps of Jupiter's dark and bright sides are performed by the ultraviolet
spectrometer alone.

The auroral observations will provide data at new longitudes of Jupiter's
atmosphere. These data will allow scientists to determine the energy of the
electrons that are falling from the magnetosphere into Jupiter's atmosphere,
thus causing the auroral phenomena. The bright side maps are used to
determine the distribution of energy (in the ultraviolet range of the
electromagnetic spectrum) on a global Jupiter level. Finally, the dark side
map, along with other observations, is used to map the distribution of
hydrogen in Jupiter's atmosphere. Combined with measurements from previous
orbits, this orbit's set of data will nearly complete the first full map of
the distribution of hydrogen on Jupiter's dark side. These hydrogen
distribution maps are used to determine and study the transfer of energy and
dynamic processes in Jupiter's upper atmosphere.

Toward the end of the day, the first Io observation of the encounter is
performed by the camera. A plume monitoring observation of the volcano Pele,
it is part of the continuing campaign to map and observe active volcano
plumes on Io's bright limb against the black sky background.

Also today on Galileo, in the morning, the tape recorder, having completed
its conditioning activity just yesterday, is positioned at its starting
location for this encounter. If you visited Today on Galileo yesterday, you
would know that the last orbit trim maneuver prior to the Europa encounter
was also scheduled for around 10 a.m. (PST). It turns out that the
spacecraft's path did not require a final fine tuning and this maneuver has
been canceled.

Finally, at the end of the day, the Galileo team is scheduled to transmit
the set of commands that will instruct the spacecraft through the latter
half of the encounter period. This set of commands will start to execute
late Thursday and will continue through Saturday evening.


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% From: Ron Baalke <[email protected]>
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 19-FEB-1997 17:22:29.19
To:	[email protected]
CC:	
Subj:	Today on Galileo - February 19, 1997

                              TODAY ON GALILEO
                       Wednesday - February 19, 1997

Jupiter continues to be the one of the main focuses of the science
activities. More importantly we see scheduled the first observations of the
selected feature of Jupiter's atmosphere. Recall that these selected
features are important enough for all four remote sensing instruments to
coordinate their observations of them. The feature selected for this orbit
is know as a White Oval. These ovals are easily seen from Earth and, like
the Great Red Spot, some are very long lived - so long that some of them
have been given names: BC, FA, DE (not very interesting names, but
nevertheless names). These ovals are typically found to roll around in the
boundary regions between two opposing zonal jet streams. One of the more
interesting questions about these ovals is: How can they last for so long?
What provides them with the energy they need to keep going? The coordinated
observations of these features should provide some of the answers to these
questions. The data gathered by the remote sensing instruments will provide
information on cloud particles distributions, thermal characteristics as
well as images and maps at different visible and near infra red wavelengths,
thus providing a full characterization of these features. In support of
these observations, two Jupiter North-South strip observations are also
performed today. Recall that these observations are designed to provide data
on the global characteristics of Jupiter's atmosphere in the same time
period that the selected feature observations are taken.

Other Jupiter observations performed today are a single Hot Spot observation
performed by NIMS (Near Infrared Mapping Spectrometer). This is the only Hot
Spot observation of this orbit. Hot Spots were the featured track during
Galileo's previous encounter period. The last of the Jupiter aurora
observations is performed today, and, to compliment the dark side
observation taken yesterday, a "fixed local time" map is also performed
today. This observation is said to have a "fixed local time" when the angle
between the instrument view direction and the Sun is constant - like if you
were floating in space and were able to look at the Earth such that it was
always 5 p.m. in the places you were looking at.

The second main focus for today's observing activity is Io. The last remote
Io torus observations are performed today, but new observations of Io while
eclipsed by Jupiter and observations designed to monitor Io's volcanic
activity take their place. Finally a single observation of the minor moon
Thebe is performed by SSI (Galileo's imaging camera).

Tune in tomorrow for the big day of flybys: Io, Europa and Jupiter.


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% From: Ron Baalke <[email protected]>
% To: [email protected]
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 20-FEB-1997 16:46:47.66
To:	[email protected]
CC:	
Subj:	Today on Galileo - February 20, 1997 (Encounter Day!)

                           TODAY ON GALILEO
                      Thursday, 20 February 1997

Galileo passes its closest point (for this orbit) to Io, Europa and Jupiter
during today's set of activities.  As you know from the name of this encounter,
only one of these flybys is close enough to be called an encounter.  The flyby
of Europa will occur at approximately 9:06 a.m. (PST).  The spacecraft will fly
at an altitude of only 586 km, even closer than its last encounter!  This flyby
is preceded by the closest approach to Io at about 4:03 a.m. (at an altitude of
about 400,000 kilometers), and is followed by the Jupiter closest approach at
about 12:54 p.m. (at a distance of 9.1 Rj, Rj = Jupiter radii, 1 Rj = 71492 km).

As can be expected, the majority of the science activity is focused on Europa. 
However, observations of Jupiter's White Ovals, monitoring of volcanic activity
on Io, observations of Io's bright side, maps of Io's topography and
observations of Amalthea and Ganymede are used to make this a very busy
observing day for Galileo.  Of particular interest during this days activity is
a high-rate recording of Fields and Particles instrument data as Galileo flies
through Jupiter's magnetic equator.  As Galileo whips past Jupiter, it passes
through the heart of the magnetosphere, a region where fresh plasma is
constantly being generated and transported away to the outer boundaries of the
magnetosphere.  This observation will allow scientists to study these generation
and transportation processes and understand how they affect the rest of the
magnetosphere.

Europa observations are performed over unique areas at small solar phase angles
(meaning that the Sun is behind Galileo and most of Europa will be lit).  This
geometry is good for observations that will provide data on the surface
composition of Europa.  High resolution observations for this orbit concentrate
on lineated regions and bright plains.  The global, regional and high resolution
observations performed during this encounter are expected to provide an exciting
fresh view of new regions on Europa's surface.

During closest approach to Europa, the Earth and Sun will become blocked from
Galileo's line of sight by Europa itself.  The Radio Science team will take
advantage of this loss of signal to track Galileo's signal as it gets blocked by
Europa and as it comes out from behind Europa.  These measurements will allow
scientists to determine the distribution of free electrons around Europa's
surface and determine if it has a detectable ionosphere.  In addition, the
measurements will allow a more accurate determination of Europa's diameter. 
Also planned for closest approach is another high-rate Fields and Particles
observation.  This recording will provide data regarding the interaction of
Europa with Jupiter's magnetosphere.

At the end of the day, the first set of commands that was sent to the spacecraft
for this encounter will end.  But having sent up the second set of commands, the
spacecraft will continue to perform the encounter activities as planned.

Two more days to the encounter period and a satellite closest approach on each
of them.  Come back tomorrow!

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/
          OR
http://galileo.ivv.nasa.gov/


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% Subject: Today on Galileo - February 20, 1997 (Encounter Day!)
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 20-FEB-1997 20:16:17.29
To:	[email protected]
CC:	
Subj:	Galileo Returns To Europa For Another Close Look

PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 
http://www.jpl.nasa.gov
          
Contact:  Jane Platt
          
FOR IMMEDIATE RELEASE                          February 19, 1997

GALILEO RETURNS TO EUROPA FOR ANOTHER CLOSE LOOK 

     NASA's Galileo spacecraft will make an encore appearance at 
Jupiter's icy moon, Europa, on Thursday, Feb. 20, marking the 
closest planned Europa flyby of the initial two-year mission.

     The encounter will be Galileo's closest flyby yet of Europa.  
The craft will swoop past the Jovian moon at an altitude of 580 
kilometers (360 miles) on Thursday, Feb. 20, at 9:06 a.m. Pacific 
time (12:06 p.m. Eastern time).

     Galileo made its first pass of Europa in December 1996, 
revealing remarkable detail of that moon's terrain. This week's 
flyby will look at other areas of Europa's surface, which is 
covered by ice and a series of criss-crossed, dark lines.  Europa 
holds great fascination for scientists because of the possibility 
that liquid oceans may be hidden underneath the icy surface. The 
presence of liquid water would boost the odds that Europa could 
host some form of life.

     "I think this flyby may provide additional clues regarding 
the prospect of  liquid water oceans on Europa," said Galileo 
Mission Director Bob Mitchell. 

     With its diameter of 3,138 kilometers (1,946 miles), Europa 
is just slightly smaller than Earth's moon.  Because the geometry 
of the upcoming flyby will be somewhat different from the path 
taken by Galileo's previous Europa encounter, it will yield data 
and images of different portions of the moon.

     "This position will allow for high resolution of different 
terrain," said Mitchell. "It will help us learn more about 
Europa's structure and surface and how the surface was formed."  

     The current Europa encounter phase began on Sunday, Feb. 16, 
and will continue through Saturday, Feb. 22.  The spacecraft has 
already begun returning real-time encounter data, with recorded 
data scheduled to be transmitted to Earth beginning on the 
evening of Saturday, Feb. 22 (Pacific time).

     This encounter will include the return of magnetospheric 
measurements from Europa's vicinity.  Other science highlights 
will include the study of surface features of Europa's lineated 
regions, images of two other, smaller Jovian moons, Thebe and 
Amalthea, and studies of such Jovian atmospheric features as the 
south equatorial belt-zone boundary and the aurora borealis.  

     This flyby provides a period of radio occultation, when 
Europa crosses between Earth and Galileo, temporarily cutting off 
the spacecraft's radio signal.  This affords a prime opportunity 
for Galileo to study atmospheric data just before and after radio 
contact is lost, when the signal passes through the Europa's 
atmosphere.      

     "As the fifth encounter in Galileo's series of 10 flybys, 
this marks the approximate halfway point for this series, which 
began in June 1996," said Galileo Project Manager Bill O'Neil.  
"It's been eight months since then, and it will be another eight 
months before the series' final encounter." 

     A third Europa flyby is planned for Nov. 6, 1997, and JPL 
has asked NASA to extend the Galileo mission by two years to 
include eight more Europa flybys and ultimately a flyby of Io.  
The proposed extended mission might be shortened if the 
spacecraft's operations were to deteriorate as a result of its 
continuous exposure to Jupiter's extreme radiation environment.

     "NASA has assured us that the extended mission will be 
funded," said O'Neil.  "The $30 million needed for the extension 
will come from within the existing NASA budget, enabled by cost 
savings due to improved efficiencies in JPL's spacecraft tracking 
and mission operations."

     The 2,223-kilogram (2-1/2 ton) Galileo orbiter spacecraft 
was launched aboard Space Shuttle Atlantis on October 18, 1989.  
JPL manages the Galileo Project for NASA's Office of Space 
Science, Washington, D.C.

     Additional information on the Galileo mission and its 
results can be found on the World Wide Web at 
http://www.jpl.nasa.gov/galileo.

                              #####

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% From: Ron Baalke <[email protected]>
% To: [email protected]
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% Subject: Galileo Returns To Europa For Another Close Look
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 21-FEB-1997 17:22:54.26
To:	[email protected]
CC:	
Subj:	Today on Galileo - February 21, 1997

                              TODAY ON GALILEO
                         Friday - February 21, 1997

Galileo passes its closest approach to Ganymede today at 08:27 a.m. (PST).
At a distance of 320,000 kilometers, only a few observations are dedicated
to obtain more data of this moon. Global observations and day/dark side maps
of Ganymede are taken by SSI (Sold State Imaging camera), NIMS (Near
Infrared Mapping Spectrometer) and PPR (Photopolarimeter-Radiometer). A
final pair of observations of Europa are performed by PPR. These particular
observations are performed in PPR's polarimetry mode which will result in a
data set that can be used to get more information on the texture and light
scattering properties of Europa's surface.

Several observations are performed to continue to monitor Io's volcanic
activity. Observations of Jupiter's While Ovals as well as another set of
North-South strip observations are also performed throughout the day. The
first of the Callisto observations for this orbit is performed at the end of
the day. It is a global color observation performed by SSI.

During the day, starting about 7 a.m. PST, the Galileo team transmit the set
of commands that will instruct the spacecraft through the first half of the
cruise/playback period. This set of commands will begin to execute tomorrow
evening.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/



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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 23-FEB-1997 00:49:42.43
To:	[email protected]
CC:	
Subj:	Today on Galileo - February 22, 1997


                              TODAY ON GALILEO
                        Saturday - February 22, 1997

Galileo makes its final close approach pass for this encounter period today.
At 2:55 p.m. (PST), Galileo will fly 276,000 kilometers from Callisto's
surface. The observation period for this encounter will end about two and
half hours later, at 5:30 p.m.

Today's final observation schedule is relatively light. In the morning, the
NIMS (Near Infrared Mapping Spectrometer) instrument will perform the last
of the Jupiter White Oval observations. Observations of Callisto round off
the observing schedule for this encounter. Performed by NIMS and PPR
(Photopolarimeter-Radiometer), these observations will map regions that are
unique in Galileo's orbital tour. The data obtained will allow continued
investigation of surface composition and thermal properties.

Thanks for tuning in to this encounter's Today on Galileo. This Week on
Galileo will return on Monday, February 24, 1997.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/



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% Date: Sat, 22 Feb 1997 23:43:46 GMT
% From: Ron Baalke <[email protected]>
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% Subject: Today on Galileo - February 22, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 24-FEB-1997 16:49:58.08
To:	[email protected]
CC:	
Subj:	This Week on Galileo - Feb 24-Mar 2, 1997

                            THIS WEEK ON GALILEO
                        24 February - 02 March 1997

The first week after its second encounter with Europa is still quite busy
for the Galileo spacecraft. Having just flown through the Jovian system, the
spacecraft will pass through three Earth occultations (by Europa, Jupiter
and Io) and one Solar occultation (Jupiter/Io). An occultation is a period
of time when the view to one celestial body is blocked by the body of
another. Earth occulations are of particular interest to the Radio Science
investigators. When Galileo starts passing behind Jupiter or one of its
moons, its radio signal must travel through the outermost layers of the
body's atmosphere. The atmosphere refracts (essentially, bends) and weakens
Galileo's radio signal. As the spacecraft moves more and more behind the
body, the radio signal must travel through more and more layers of
atmosphere, which weaken the signal even more until it can no longer be
detected (of course, when the spacecraft is behind the planet or moon
itself, that completely blocks the signal). On the other side, the radio
signal will gain strength and will be bent less as the spacecraft
re-emerges. The data gathered while monitoring Galileo's radio signal along
with trajectory information will be processed by the investigators and
ultimately result in temperature and wind profiles of the body's atmosphere.

At the beginning of the week, the spacecraft is scheduled to perform the
first orbit trim maneuver after its encounter with Europa. Each of these
post-encounter maneuvers are important because they are used to correct the
amount of "gravity assist" energy transferred to the spacecraft during the
satellite flyby. For example, to examine only one of the variables, if the
flyby is a little lower in altitude than planned the spacecraft receives
more energy and if the flyby is a little higher than planned the spacecraft
receives less energy. These maneuvers are used to add or subtract energy as
required by the flyby conditions and send the spacecraft on the right path
toward the next encounter.

Galileo continues gathering magnetospheric data from its fields and
particles instruments through the middle of the week. In addition, the first
observations from the encounter are returned to earth. In general, the order
of playback follows the order in which the data was recorded on the tape
recorder. As such, this week's playback focuses mainly on observations of Io
and Jupiter. Europa observations start to be returned toward the end of the
week and into next week. A single image of Thebe is returned about half-way
through the week.

The observations of Io included in this week's playback concentrate mainly
on the continual effort to monitor plume activity and surface changes.
Observations of Pele, Loki and Ra Patera were specifically taken in hopes of
observing a plume in action. Surface changes are hoped to be characterized
by determining the changes in the chemistry of Io's surface as well as the
spatial, temporal and spectral variability of the surface.

Jupiter observations returned this week are all of the selected atmospheric
feature for this encounter--White Ovals. Remember, from last week's Today on
Galileo, white ovals are huge storms easily seen from Earth. They are
usually found in the boundary regions between two opposing zonal jet streams
and some of these are very long lived. What provides energy to these storms
is only one of the many questions scientists hope to answer with Galileo's
observations.

The Europa observations returned toward the end of this week are mostly
regional in resolution. Global and regional observations performed by SSI
and NIMS (Near Infrared Mapping Spectrometer) are part of campaigns that 
span the different Europa enconters
(orbit 4 and orbit 11) and are designed to result in complete global images
and maps. An observation performed by SSI (Solid State Imaging camera) 
of a region showing the
intersection of two dark lineae is the final observation on this week's
playback schedule. This region is believed to represent a stress-controlled
eruption or intrusion of material originating from beneath Europa's surface.

More Europa observations are on next week's schedule.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% From: Ron Baalke <[email protected]>
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 10-MAR-1997 02:09:58.88
To:	[email protected]
CC:	
Subj:	This Week on Galileo - March 10-16, 1997

                            THIS WEEK ON GALILEO
                             March 10-16, 1997

Galileo continues returning data from its previous pass through Jupiter's
system. The playback focus moves away from Europa and back to Jupiter, the
magnetosphere, and the other moons. On Thursday evening, the spacecraft is
scheduled to perform the next orbit trim maneuver. This maneuver will fine
tune the spacecraft's path and put it on the right course for its next
encounter in early April. In addition, on Sunday night, the spacecraft will
perform another turn to keep its radio antenna pointed toward earth.

The Jupiter observations returned during this week once again contain data
on the white ovals in Jupiter's atmosphere. These particular observations
were taken by NIMS (Near Infrared Mapping Spectrometer) and PPR
(Photopolarimeter- Radiometer). Many of these observations are taken over a
range of solar phase angles, from 95 deg to 150 deg. Remember that small
solar phase angles occur when the sun is directly behind the spacecraft and
most of the target is lit by the sun. These medium to high phase angles mean
the sun is lighting Jupiter from the side and from behind. The range of
phase angles allows the instruments to look at different types of reflected
light which allows scientists to identify different properties of the
particles in Jupiter's atmosphere. North-south strip observations are also
returned this week. These observations provide data that allow scientists to
place the white oval observations in the context of what was happening in
the rest of Jupiter's atmosphere.

The fields and particles instruments' high-rate recording as Galileo flew
through Jupiter's magnetic equator is also scheduled to be returned this
week. In this region of the magnetosphere, it is thought that fresh plasma
is constantly being generated and transported away to the outer boundaries
of the magnetosphere. This data will provide information on the heart of the
magnetosphere - how the plasma is generated and transported away, and what
effect activity here has on the rest of the magnetosphere.

The remaining observations returned this week are comprised of observations
of Io, Ganymede and Amalthea. Io observations include the completion of a
surface map from the Europa-4 encounter, chemical monitoring and the search
for volcanic hot spots. The Ganymede observations are part of multi- orbit
campaigns to characterize the surface of Ganymede and fill in gaps in data
obtained during the Voyager spacecraft flybys of the Jupiter system.
Finally, the Amalthea observation is also one of many performed and planned
during the orbit tour that will be used to determine the global shape and
morphology of Amalthea.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Mon, 10 Mar 1997 0:59:10 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
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% Subject: This Week on Galileo - March 10-16, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 14-MAR-1997 21:58:43.61
To:	[email protected]
CC:	
Subj:	Galileo Update - 03/13/97

     PUBLIC INFORMATION OFFICE
     JET PROPULSION LABORATORY
     CALIFORNIA INSTITUTE OF TECHNOLOGY
     NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
     PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
     http://www.jpl.nasa.gov
     
     GALILEO MISSION STATUS
     March 13, 1997
     
     Playback from the latest Europa encounter on February 20 is proceeding 
     on schedule, returning data from Galileo's most recent pass close to 
     Jupiter and its satellites.  The data include observations of white 
     oval atmospheric features taken by the spacecraft's near infrared 
     mapping spectrometer and photopolarimeter-radiometer over a range of 
     solar phase angles.  
     
     This week's data return will also include fields and particles 
     instruments' high data rate recording as Galileo made its closest 
     approach while flying through Jupiter's magnetic equator.  Much of the 
     plasma in Jupiter's inner magnetosphere is confined to the equatorial 
     region and is whisked away to the outer boundaries of the 
     magnetosphere through various processes. This data will help 
     scientists understand more about those processes.
     
     Other observations expected to be returned this week include chemical 
     monitoring of volcanic hot spots on Io and a surface map from the 
     Europa encounter. Ganymede observations to be returned are part of 
     multi-orbit efforts to characterize the moon's surface and flesh out 
     information obtained when the Voyager spacecraft flew by the Jovian 
     system.  New observations of the small moon Amalthea will be used to 
     determine the body's global shape and morphology.
     
     Last week's playback focused on Europa observations, the prime target 
     of last month's flyby. During the approach to Europa, most of the 
     satellite was illuminated by the Sun. This vantage point enabled 
     Galileo to gather information on the icy moon's surface composition 
     and shape, as well as crater feature observations which may offer 
     clues to what lies underneath Europa's surface.  Near infrared mapping 
     spectrometer data included observations of a lineated region and icy 
     regions of varying ages.
     
     A previous magnetometer glitch on Galileo has been corrected, and it's 
     now believed the failure was caused by radiation effects. Although 
     there are indications that the same radiation-induced faults have 
     occurred with the magnetometer and the spectrometer, in each case, a 
     reloading procedure has corrected the problem.
     
     An orbital trim maneuver will begin today to put Galileo on track for 
     its next destination, Ganymede. The flyby occurs on April 4 (PST).  
     Galileo has five additional encounters of Jupiter's moons scheduled 
     during its two-year primary journey through the Jovian system. 

                                     #####
     
      

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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 17-MAR-1997 20:45:21.43
To:	[email protected]
CC:	
Subj:	This Week on Galileo - March 17-23, 1997

                            THIS WEEK ON GALILEO
                             March 17-23, 1997

Playback plans for this week start with the second pass through the data
stored on Galileo's tape recorder during its previous encounter with the
Jupiter system back in February. This second opportunity allows scientists
to return new data that they initially thought they might not have enough
time to return. Other data can fill in small gaps in already played-back
data caused by transmission and reception problems. The second pass also
allows scientists to re-play parts of observations that have been identified
as being interesting enough for a second look - in particular , observations
of Jupiter's atmosphere, White Ovals for this orbit. But why would a re-play
of the data be required for a second look?

Given the low data rates Galileo transmits to earth, compression algorithms
play a big part in determining the total amount of data that can be gathered
from a particular tapeload of observations. Higher compression can transmit
more data. Unfortunately, high compression can produce what are know as
compression artifacts. You may have noticed some blocky looking regions in
some of the images that have been posted here on our home page. These are
compression artifacts . These compresion artifacts can and do sometimes hide
some of the more interesting features and information that can be extracted
from some of the observations. This type of compression can also be known as
"lossy" compression because it creates "loss" of some data.

Once a region has been identified as being of significant scientific value,
the data recorded on the tape recorder can be transmitted again to earth
with lower compression ratios or with a different compression algorithm that
does not create compression artifacts. This would be known as "lossless"
compression. The lossless compression is only used sparingly as it would
take too much time to transmit the complete observations. This preview /
re-play plan has been successful in allowing scientists to confirm the
existence of features that were believed to exist since the Voyager flybys,
but had not been seen directly due to insufficient resolution in the
observations.

In a similar manner, the second pass allows scientists to use lossy
compression data return to locate small objects, like the minor satellites -
whose orbits are not so well known, in an observation. Once the object is
located, the relevant data is transmitted with lossless compression. This
method prevents having to return a lot of empty sky at lower compression
ratios which would wast valuable data return time. The minor satellite
observation returned during this week is a single image of Thebe.

Other data returned during this week are NIMS (Near Infrared Mapping
Spectrometer) and PPR (Photopolarimeter Radiometer) observations of White
Ovals, Io observations by SSI (Solid State Imaging camera) and NIMS,
Callisto observations by NIMS and PPR, and Europa observations by NIMS, SSI
and PPR. Next week is the last week of playback prior to Galileo's next
encounter on April 4th with Ganymede.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo


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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 24-MAR-1997 04:33:16.50
To:	[email protected]
CC:	
Subj:	This Week on Galileo - March 23-30, 1997


                            THIS WEEK ON GALILEO
                             March 24-30, 1997

This week contains the final days for playback of the data gathered during
Galileo's Europa 6 encounter period. In this final week, a variety of
observations are transmitted to earth. Included in this set is a fields and
particles observation of Europa's interaction with Jupiter's magnetosphere
and an observation of the equatorial region of the magnetosphere. Europa
data contains information regarding the composition of Europa's surface
(NIMS - Near Infrared Mapping Spectrometer) including an observation that
should allow scientists to distinguish between new and old ice and images of
bright plains and craters (SSI - Solid State Imaging camear) that should
shed light on the formation processes of these features. Io observations
include data on the changes in Io's surface (SSI), Io's surface while
eclipsed from the sun by Jupiter (SSI), surface chemistry (NIMS) and
volcanic activity (NIMS).

A single Amalthea observation (SSI), a White Oval (NIMS) observation, and a
North-South strip thermal observation of Jupiter's atmosphere (NIMS) are
also returned this week. Finally, global observations (SSI, NIMS) of
Ganymede and Callisto are also on the playback schedule.

Preparations for Galileo's next satellite encounter occur toward the end of
the week. The encounter period is scheduled to start on Sunday, March 30th.
The main encounter will be with Ganymede on Friday, April 4th at an altitude
of about 3100 km. Playback is completed this Friday and is followed by some
maintenance activities: flushing the thruster lines (to prevent the lines
from becoming blocked by debris) and conditioning the tape recorder.

Eight optical navigation images of the Jupiter system are taken on Friday
and Saturday. Remember that these images allow navigators to better
determine the path of the spacecraft and decide whether it has to be
adjusted prior to its Ganymede flyby. These are expected to be the last of
the optical navigation images for the remainder of Galileo's mission at
Jupiter. After several months of navigating around Jupiter's system, the
models of the orbits of the Galilean satellites have been significantly
improved. Specifically, the optical navigation images have reduced the
uncertainties in the satellite positions (and velocities). These reductions
have allowed navigators to better determine the spacecraft's flight path and
more accurately predict satellite encounter conditions. At this point,
optical navigation images are beginning to lose their value and will no
longer be required.

The encounter set of commands is transmitted to the spacecraft on Saturday
and becomes active on Sunday. Stay tuned for the return of Today on Galileo.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo


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% Date: Mon, 24 Mar 1997 3:22:03 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: This Week on Galileo - March 23-30, 1997
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PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

GALILEO MISSION STATUS
March 27, 1997

     This is the final week for playback of data gathered during 
Galileo's February 20th Europa encounter.  Included in the 
potpourri of Europa information is data on surface composition, 
an observation expected to help scientists distinguish between 
new and old ice, images of bright plains and craters that may 
help explain the formation of these features, and a fields and 
particles observation of Europa's interaction with Jupiter's 
magnetosphere.  

     The playback also features Io observations of surface 
chemistry, volcanic activity, and the surface while eclipsed from 
the Sun.  Observations of two of Jupiter's white ovals, global 
observations of Ganymede and Callisto, and a single Amalthea 
observation have also be transmitted.

     With the wrap-up of Europa 6 playback, the end of this week 
marks the start of preparations for Galileo's next encounter, a 
Ganymede flyby at 11:11 p.m. Pacific Standard Time on Friday, 
April 4. An orbital trim maneuver is planned for Monday, March 
31, one day after the beginning of the Ganymede encounter period.  
Maintenance activities will also be performed, including the 
flushing of the thruster lines to prevent debris blockage, and 
conditioning of the tape recorder.

     After this next Ganymede flyby, Galileo has four more 
encounters of Jupiter's moons scheduled during its two-year 
primary journey through the Jovian system.  A planned two-year 
continuation of the mission, referred to as the Galileo Europa 
Mission (GEM), will include eight more Europa flybys and an Io 
flyby, as long as the spacecraft remains healthy.

                             #####

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% From: Ron Baalke <[email protected]>
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% Subject: Galileo Update - 03/27/97
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                              TODAY ON GALILEO
                          Sunday - March 30, 1997

The encounter period for Galileo's return to Ganymede starts today at 8 am
(PST). During the next eight days, the spacecraft will once again fly
through the Jupiter system and perform observations of Jupiter, its
magnetosphere, all of the Galilean moons and some minor satellites. On the
evening of April 4th, the spacecraft will fly by Ganymede, the featured
satellite for this orbit, at an altitude of 3095 km. The encounter period
also includes a non-targeted (not the "intended" satellite target) flyby of
Europa. The Europa closest approach will occur on the evening of April 3rd
at an altitude of approximately 25,000 km.

The first day of the encounter period features the resumption of the
magnetosphere survey being performed by the fields and particles
instruments. In addition, the fields and particles instruments will perform
a high rate observation of the magnetosphere as the spacecraft flies across
the region known as the plasma sheet (ionized matter which is confined to a
thin "sheet". Together with observations performed in previous orbits -
which occurred at different locations of the magnetosphere, the data will
allow scientists to understand how the plasma is distributed and how it
moves around in the magnetosphere.

Also today, the UVS (Ultraviolet Spectrometer) instrument will be performing
remote observations of the "neutral torus" regions around the orbits of
Callisto and Ganymede. It is believed that neutral particles are somehow
being stripped from these satellites and that these particles then remain in
the orbits of the satellites. These observations are expected to find if the
particles are there, what they are, and possibly explain how and why they
remain in the satellite orbits.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Subject: Today on Galileo - March 30, 1997
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                              TODAY ON GALILEO
                          Monday - March 31, 1997

Galileo continues with its UVS (Ultraviolet Spectrometer) observations of
Ganymede and Callisto's neutral torii. Earlier in the day, three optical
navigation images of Adrastea will be taken and transmitted to earth.
Although they will not be used to navigate the spacecraft, the information
gathered from these images will allow the models of Adrastea's orbit to be
improved by reducing the uncertainties in Adrastea's orbital position and
velocity. These improvements will make it easier to plan future observations
of Adrastea. You could say that the images will be used to navigate the
instruments!

During the day the flight team will transmit the commands required to
perform the last orbital trim maneuver prior to the spacecraft's encounter
with Ganymede. Remember that last Friday and Saturday were spent taking
optical navigation images used to help navigators determine whether the
spacecraft's path required a final adjustment. The orbit trim maneuver will
begin executing tonight and will complete executing tomorrow morning.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Mon, 31 Mar 1997 17:52:56 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
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% Subject: Today on Galileo - March 31, 1997
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                              TODAY ON GALILEO
                           Tuesday, April 1, 1997

Early this morning, Galileo finishes its execution of the final orbit trim
maneuver before its encounter with Ganymede later this week. The remainder
of the day is spent performing remote observations of the Io torus with the
UVS (Ultraviolet Spectrometer) and EUV (Extreme Ultraviolet Spectrometer)
instruments and a magnetosphere radiation observation by the PWS (Plasma
Wave) instrument.

The remote Io torus observations are part of an ongoing set of observations
that provide information required to map and characterize the energy
distribution within the Io torus. The PWS observation is gathering
information on the radiation that is believed to exist in the lobes of
Jupiter's magnetosphere. The lobes are the regions of the magnetosphere that
are between the magnetopause (the boundary between normal space and the
magnetosphere) and the plasma sheet. This region is believed to contain much
lower concentrations of plasma, and very little is known about how the
plasma in this region behaves.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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                              TODAY ON GALILEO
                          Wednesday, April 2, 1997

The fourth encounter day of this seventh orbit features a distant flyby of
Callisto. At a range of over 637,000 kilometers, the flyby is noted by
global observations performed by the SSI (Solid State Imaging camera) and
the NIMS (Near Infrared Mapping Spectrometer) instruments. The primary
purpose of these observations is to fill gaps in data obtained during the
Voyager missions. The goal of such observations is to create a complete
global map of each of the Galilean satellites.

The first Jupiter observations of the encounter are performed today. Jupiter
aurora are observed in a coordinated effort between the UVS (Ultraviolet
Spectromter), NIMS and SSI instruments. Jupiter fixed time local, darkside,
and fixed longitude maps are also performed. These observations should sound
familiar because they are repeated during each encounter. They look at
Jupiter's atmosphere in unique ways, attempting to understand the
distribution and dynamics of energy and hydrogen on a global scale.

The first observations of a small red spot, the selected feature of
Jupiter's atmosphere for this orbit, are also performed today. Originally
selected for this orbit were features know as Brown Barges. Brown Barges
were visually clear regions seen during the Voyager flybys and were of
significant scientific interest. Unfortunately, Hubble Space Telescope
images appear to show that they have disappeared. The selected small red
spot is, however, just as interesting: It is about 40 degrees north of the
equator and has been seen in Jupiter's atmosphere for a very long time.
Remember that the observations of selected features are coordinated amongst
all of Galileo's remote sensing instruments in order to obtain a complete
characterization.

Completing the observation plans for today are observations of Europa while
eclipsed from the Sun by Jupiter, and the first observations for monitoring
Io's volcanic activity. During the day, the flight team will transmit the
second set of commands for this encounter. This set will be active from
tomorrow until the end of the encounter on Sunday.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  4-APR-1997 21:40:13.98
To:	[email protected]
CC:	
Subj:	Today on Galileo - April 4, 1997

                              TODAY ON GALILEO
                           Friday, April 4, 1997

Two more flybys are on today's schedule of activities for the spacecraft.
The first, occurring early in the morning, occurs when the spacecraft
reaches its closest point to Jupiter at a range of 9.1 Rj, or Jupiter radii
(1 Rj is about 71490 kilometers). The second occurs late at night, just
prior to midnight (PST), when the spacecraft will fly by Ganymede at an
altitude of only 3095 kilometers.

The first three quarters of the day are mainly spent performing various
observations of Jupiter. A few more hot spot observations are taken by the
NIMS (Near Infrared Mapping Spectrometer) and the PPR (Photopolarimeter
Radiometer)instruments. Regional and east-west strip observations are
performed through the day by the PPR instrument. This provides context
information for the small red spot observations performed during this
encounter, a new set of which are taken toward the end of the day. The PPR
instrument will also perform a couple of observations of the Great Red Spot.
The non-Ganymede observations for today are rounded out by a few
observations monitoring Io's volcanic activity and images of Adrastea and
Metis. The latter couple of observations, like yesterday's observation of
Thebe, are designed to help in the construction of global maps by the end of
Galileo's primary mission.

Observations of Ganymede are scheduled to start about 5 pm (PST) and
continue through tomorrow morning. These observations will serve primarily
to fill in regions that have not been previously observed. They cover a
variety of bright, dark and dark-rayed (like the Kittu crater) regions with
the goal of determining surface composition and studying the effects of high
energy impacts. Observations by NIMS and SSI (Solid State Imaging camera)
focus on these high energy impact regions (circles, domes, grooves) and what
roles the impactors have played in their formation and characteristics. The
observations will also provide information on any role volcanism might have
played in the resurfacing of craters. There is even an opportunity to
perform some comparative planetology with craters on Mars.

Global observations by the NIMS and UVS (Ultraviolet Spectrometer)
instruments will allow for the determination of the surface composition of
Ganymede which can be used to compare Ganymede with the other satellites.
PPR darkside and dayside maps performed are part of campaigns to map surface
thermal properties over the entire globe. High resolution samples taken by
PPR are expected to provide information about the temperature and physical
properties of Ganymede's surface and help determine whether any material is
being lost to space. A recording of fields and particles instrument data
taken during closest approach continues the investigation of the interaction
between Ganymede and the magnetosphere.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Fri, 4 Apr 1997 19:07:51 GMT
% From: Ron Baalke <[email protected]>
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% Subject: Today on Galileo - April 4, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  6-APR-1997 03:06:42.19
To:	[email protected]
CC:	
Subj:	Today on Galileo - April 5, 1997

                              TODAY ON GALILEO
                          Saturday, April 5, 1997

After yesterday's close encounter with Ganymede, the last flyby of this
encounter period, the observation schedule begins to lighten. The morning
contains a few residual observations of Ganymede while the rest of the day
is scattered with observations of Io, Europa, Callisto and Jupiter's
atmosphere. The first cruise set of commands is transmitted to the
spacecraft in preparation for the end of the encounter period, less than two
days away.

Jupiter observations once again focus on the selected small red spot, but
also include north-south and east-west strip observations to provide context
information. The observations of Io, Europa and Callisto are performed by
the PPR (Photopolarimeter Radiometer) instrument in polarimetry mode. These
observations are taken to provide information on surface texture and light
scattering properties.

For more informaton on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/
http://galileo.ivv.nasa.gov/

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% Date: Sun, 6 Apr 1997 1:08:04 GMT
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  7-APR-1997 00:08:15.88
To:	[email protected]
CC:	
Subj:	Today on Galileo - April 6, 1997

                              TODAY ON GALILEO
                           Sunday, April 6, 1997

As we spring forward into daylight savings time today (here in the U.S.),
the encounter period for Ganymede-7 comes to an end. Two more PPR
(Photopolarimeter Radiometer) polarimetry observations are performed, one of
Callisto and one of Europa. The last of the small red spot observations are
completed just prior to the end of the encounter. The fields and particles
instruments continue their survey of Jupiter's magnetosphere into the
playback period. The cruise period commands begin to execute at about 10 am
(PDT).

Come back tomorrow to learn about the playback plans for this orbit with the
return of This Week on Galileo.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/
http://galileo.ivv.nasa.gov/

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% Date: Sun, 6 Apr 1997 21:48:04 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
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% Subject: Today on Galileo - April 6, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  7-APR-1997 17:42:35.26
To:	[email protected]
CC:	
Subj:	This Week on Galileo - April 7-13, 1997

                            THIS WEEK ON GALILEO
                              April 7-13, 1997

With only about a month before Galileo's next encounter, playback was
initiated immediately following the end of the Ganymede encounter period.
The fields and particles instruments will continue to survey the
magnetosphere during this week and navigators will execute the first orbit
trim maneuver to correct the spacecraft's path for any residual errors from
the satellite encounter flyby.

Once again, the playback plans contain a variety of different observations -
a reflection of the many different types of experiments that are possible
with a spacecraft like Galileo. The fields and particles plasma sheet
observation is first in line to be transmitted to earth. Remember from
"Today on Galileo" that the collection of these observations (performed in
different orbits) will be used to map the distribution of plasma and to
understand it varies in different parts of the magnetosphere.

Global observations of Callisto performed by SSI (Solid State Imaging
camera) and NIMS (Near Infrared Mapping Spectrometer) will also be played
back this week. They are part of the mission-long goal to completely map the
surface of all the Galilean satellites (did you catch the composite - global
image of Io recently posted on the Galileo WWW page? -
http://www.jpl.nasa.gov/galileo/ganymede/p48496.html) and are the first to
include the Valhalla multi-ring structure. In addition to a global image of
Thebe, the first Europa images from the non-targeted flyby, a Europa image
while eclipsed by Jupiter and an Europa global image taken 12 hours prior to
closest approach, are also scheduled for transmission during this week.

Jupiter observations returned during the week are comprised mostly of SSI
and NIMS observations of the small red spot feature selected for this past
encounter. These observations are expected to provide more information
regarding long lasting storms in Jupiter's atmosphere. Images of aurora
comprise the remaining portion of the week's return of Jupiter observations.

Finally, a large set of Io monitoring observations performed by NIMS, SSI
and PPR (Photopolarimeter Radiometer) are also on the playback schedule.
These observations will provide information regarding the changes in Io's
surface: chemistry, composition, temperature, new hot spots, etc. They are
all part of the goal to understand the volcanic processes on Io.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/
http://galileo.ivv.nasa.gov/

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% Date: Mon, 7 Apr 1997 15:47:39 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: This Week on Galileo - April 7-13, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 14-APR-1997 15:15:03.07
To:	[email protected]
CC:	
Subj:	This Week on Galileo - April 14-20, 1997


                            THIS WEEK ON GALILEO
                             April 14-20, 1997

The fields and particles survey of the magetosphere continues in this, the
second week of "cruise" following Galileo's last encounter with Ganymede. In
addition to playback, this week's activities include a spacecraft turn
(Friday) to keep the spacecraft's antenna pointed near the Earth and the
transmission of commands (Sunday) required to execute the next orbit trim
maneuver which will occur early next week.

Observations from the spacecraft's non-targeted flyby of Europa seem to be
one of the main spotlights of this week's playback. NIMS (Near Infrared
Mapping Spectrometer) returns an observation taken at regional resolution as
part of the tour-long campaign to completely map all Galilean satellites.
This portion of the map is centered around the lineated feature known as
Flexus Linea. PPR (Photopolarimeter Radiometer) returns various thermal
observations including both dayside and darkside maps. SSI (Solid State
Imaging camera) returns low solar phase angle photometry (measurements of
the intensity of light) observations and observations of crater features
near the terminator (the dividing line between day and night). Of particular
interest is a NIMS observation of the region known as Tyre Macula. This
observation aims to search for differences in the mineral compostion of the
region in an attempt to understand the origin of this circular feature. A
set of observations of this region was coordinated amongst all four remote
sensing instruments (UVS, PPR and SSI).

The playback schedule also includes the transmission of Jupiter observations
taken by NIMS and PPR. NIMS will return obseravtions of the small red spot
featured in this past encounter and of a hot spot near the same latitude as
that of the atmospheric probe entry site. PPR also returns observations of
the small red spot, but also returns a couple of observations taken of the
Great Red Spot. Io observations by NIMS (thermal and chemical), SSI
(topographical) and PPR (thermal) continue to be returned during the week.
Finally, a global observation by NIMS and a thermal observation by PPR, both
of Ganymede, complete the playback plans for this week.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Tue, 20 May 1997 13:21:30 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: This Week on Galileo - April 14-20, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 18-APR-1997 18:41:38.43
To:	[email protected]
CC:	
Subj:	Galileo Update - 04/17/97

PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

GALILEO MISSION STATUS
April 17, 1997

     The Galileo spacecraft is operating normally in its second 
week of "cruise" following the craft's latest encounter with 
Ganymede at 11:10pm Pacific Standard Time on April 4, with the 
signal received on the ground 46 minutes later.  Galileo flew by 
the satellite at an altitude of 3,102 kilometers. 

     The fields and particles survey of Jupiter's magnetosphere 
continues.  Other scheduled activities include one of the 
periodic spacecraft turns to keep the antenna pointed near Earth, 
and transmission of commands to prepare for next week's orbit 
adjustment.

     This week's playback includes observations taken by the 
spacecraft during its non-targeted flyby of the increasingly-
popular moon Europa.  The playback includes a near-infrared 
mapping spectrometer (NIMS) observation at regional resolution, 
part of a plan to map all the Galilean satellites.  Another 
spectrometer observation was designed to look for differences in 
the mineral composition of the Tyre Macula region, a circular 
feature.  Return from other instruments will include thermal 
observations and images of crater features near the terminator, 
the dividing line between day and night.

     The playback schedule also features the return of 
observations of Jupiter's Great Red Spot, a smaller red spot, and 
a hot spot near the same latitude as the atmospheric probe entry 
site.

     Galileo will return for another Ganymede flyby on May 7, 
with two Callisto encounters and another Europa flyby planned for 
the final orbits of Galileo's primary mission.  A planned two-
year continuation of the mission, known as the Galileo Europa 
Mission (GEM), will include eight more Europa flybys and one or 
two Io flybys, as long as the spacecraft remains healthy.
     
                           #####

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% Date: Sat, 24 May 1997 16:26:22 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: Galileo Update - 04/17/97
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 21-APR-1997 08:20:54.38
To:	[email protected]
CC:	
Subj:	[ASTRO] This Week on Galileo - April 21-27, 1997

                            THIS WEEK ON GALILEO
                             April 21-27, 1997

This week marks the midpoint between encounters for Galileo. While passing
through apojove (the farthest point from Jupiter during any given orbit),
the spacecraft is scheduled to execute another orbit trim maneuver. This
maneuver will begin correcting errors the spacecraft's path in preparation
for it next encounter with the Jupiter system.

The fields and particles survey of Jupiter's magnetosphere for this orbit
ends early this week. It is schedule to resume just prior to Galileo's next
encounter. However, two fields and particles observations recorded during
the last encounter are scheduled for transmission to Earth this week. The
first is an observation of the magnetosphere plasma sheet (ionized matter
which is confined to a thin "sheet"). Together with observations performed
during other orbits at different locations of the magnetosphere, this data
will allow scientists to understand how the plasma is distributed and how it
moves around in the magnetosphere. The second is an observation performed
during closest approach to Ganymede. This observation will provide
information regarding the interaction between Ganymede and the
magnetosphere.

Observations performed during closest approach to Ganymede are highlighted
this week on the playback schedule. These observations were designed to
obtain data on a variety of bright, dark and dark-rayed regions. These
regions and the features within them are believed to be associated with high
energy impacts. The regions are circular, dome-shaped and contain grooves.
Of particular interest is figuring out what these regions are made of and
whether any of their characteristics are due to the remains of the impacting
bodies. The role of volcanism in the resurfacing of these features may also
be determined from the observations. These high resolution samples are
complimented by data obtained during a global observation of Ganymede
performed by NIMS (Near Infrared Mapping Spectrometer) and a darkmap
observation performed by PPR (Photopolarimeter Radiometer)-- both also on
the playback schedule this week.

Observations of Jupiter's small red spot continue to be returned this week,
as are additional observations of Jupiter's atmosphere in the form of strips
running North-South and East-West. These additional observations not only
provide context information for the small red spot observations but also
contribute to the construction of a global map of Jupiter, with regional
resolutions.

The remaining schedule for this week is comprised of global observations of
Europa and Callisto, observations of Europa and Io while eclipsed from the
sun by Jupiter, and an observation of Thebe, all performed by SSI (Solid
State Imaging camera). Observations monitoring Io's volcanic activity by SSI
and NIMS are also returned this week. Finally, the playback schedule also
includes a series of photometry (measurements of the intensity of light)
observations performed by PPR of Io, Europa and Callisto at different solar
phase angles.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Tue, 27 May 1997 4:43:00 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: [ASTRO] This Week on Galileo - April 21-27, 1997
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TO:  [email protected]@VBORMC@MRGATE@RDGMTS

Subject: [ASTRO] This Week on Galileo - April 28 - May 3, 1997

                            THIS WEEK ON GALILEO
                           April 28 - May 3, 1997

This week is the final week for playback of data from Galileo's previous
encounter with Ganymede. Observations taken during closest approach to
Ganymede are again highlighted on this week's playback schedule. These data
include observations of the bright, dark and dark-rayed regions popular with
the remote sensing instruments, and high resolution magnetospheric data
acquired by the fields and particles instruments for an hour or so around
the closest approach to Ganymede.

Other data returned this week include observations from the flyby of Europa.
Close enough for regional observations, these data are comprised of lineated
and circular regions and will be used to determine the origin of these
features. At the same time, the data will be used in the construction of a
global map of Europa at regional resolution. Regional observations of
Jupiter are also returned this week. These data will be used in the
construction of a global map of Jupiter. A few remaining observations from
the remote sensing instrument campaign to study a small red spot in
Jupiter's atmosphere, a couple observations of a hot spot on Jupiter and a
single image of Adrastea complete the playback plans for the week.

For its next encounter, Galileo will have another close flyby of Ganymede;
the last for the remainder of the orbital tour. The flight team will
transmit the first set of commands for the encounter to the spacecraft this
Thursday. The fields and particles instrument survey of Jupiter's
magnetosphere is resumed on Friday. This resumption also marks the start of
the second magnetosphere mini-tour (a "mini-tour" is a portion of the fields
and particles survey that is more than one complete orbit in duration). On
Sunday, just prior to the start of the encounter observations, the commands
for the last orbit trim maneuver prior to the Ganymede flyby will also be
transmitted to the spacecraft. Encounter observations are scheduled to start
late Sunday night.

Come back Sunday for the return of Today on Galileo!

For more information on the Galileo spacecraft and its mission to
Jupiter, please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/


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% Date: Mon, 28 Apr 1997 5:47:56 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: [ASTRO] This Week on Galileo - April 28 - May 3, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 29-APR-1997 19:37:02.82
To:	[email protected]
CC:	
Subj:	[ASTRO] Galileo Update - 04/28/97

PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

GALILEO MISSION STATUS
April 28, 1997

     As the Galileo spacecraft prepares for another encounter 
with Jupiter's largest moon, Ganymede, playback of data from the 
craft's previous Ganymede flyby on April 4 Pacific Standard Time 
is nearing completion.

     This final batch of data return from the April flyby will 
conclude around noon Pacific Daylight Time on Saturday, May 3.  
It includes observations of Ganymede's bright, dark and dark-
rayed regions from the remote sensing instruments, and high 
resolution fields and particles data on the magnetospheres around 
Jupiter and Ganymede and the interaction between the two.

     Playback also includes observations of Europa's lineated 
circular regions.  This will be used to help determine how these 
features originated and to construct a global map of Europa at 
regional resolution. Regional observations of Jupiter to be 
returned this week will also be used for a global map of Jupiter.

     A few Jupiter observations from the remote sensing 
instruments will be returned, including a study of a small red 
spot in the Jovian atmosphere, a hot spot on the planet and a 
single image of Adrastea, one of Jupiter's small inner moons.  
The fields and particles instruments' survey of Jupiter's 
magnetosphere will resume on Friday, marking the start of the 
second magnetospheric "mini-tour."

     The Galileo flight team will transmit the first set of 
encounter sequence commands to the spacecraft later this week, as 
it prepares for the next encounter with Ganymede on May 7.  This 
will be Galileo's final close flyby of Ganymede.

                           #####

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% Date: Tue, 29 Apr 1997 17:59:44 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: [ASTRO] Galileo Update - 04/28/97
% Sender: [email protected]
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  6-MAY-1997 00:22:26.63
To:	[email protected]
CC:	
Subj:	[ASTRO] Today on Galileo - May 5, 1997


                              TODAY ON GALILEO
                            Monday, May 5, 1997

The day's activities start with the completion of the UVS (Ultraviolet
Spectrometer) observations of the Ganymede neutral torus. Later, a couple
observations of Callisto are performed. The first, again by the UVS
instrument, observes Callisto at solar phase angles not visible from Earth.
The second, by the NIMS (Near Infrared Mapping Spectrometer) instrument, is
a global observation that will be used to further investigate Callisto's
mineralogy and determine the distribution of the different materials on
Callisto's surface. Most of the day, however, is spent with the UVS
performing remote Io torus observations. Remember that these observations
are used to determine the temperature of electrons and characterize the
distribution of energy in the Io torus.

Early in the day, the spacecraft turns in order to improve the viewing
geometry for remote sensing observations of Io. Without the turn, these
observations would be carried out with the instruments looking back through
the spacecraft booms (magnetometer and RTGs). Since the booms are mounted on
the spinning side of the spacecraft, a boom would pass through the
instrument view fields about once every 7 seconds. The turn moves the booms
out of the way and eliminates the risk of observations being lost due to
boom blockage. The spacecraft stays in this special orientation through
Wednesday afternoon.

At the end of the day, the flight team will transmit the second set of
commands for the encounter period to the spacecraft. This set will begin to
execute late Tuesday.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/


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% Date: Mon, 5 May 1997 14:29:35 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: [ASTRO] Today on Galileo - May 5, 1997
% Sender: [email protected]
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  5-MAY-1997 04:26:55.27
To:	[email protected]
CC:	
Subj:	[ASTRO] Today on Galileo - May 4, 1997


                              TODAY ON GALILEO
                            Sunday, May 4, 1997

Today, Galileo starts its next set of observations of the Jupiter system.
Ganymede is the featured satellite for this orbit. This will be Galileo's
last close flyby of Ganymede -- scheduled to occur Wednesday morning at an
altitude of just under 1600 kilometers. The encounter period also includes a
non-targeted flyby of Callisto on Tuesday morning. The set of computer
commands that starts executing today will run through late Tuesday. The
second set, transmitted to the spacecraft in the next couple of days, will
run through the end of the encounter period next Sunday.

Today's observation schedule is relatively light. The fields and particles
instrument survey of the Jupiter magnetosphere continues through the
encounter and into cruise contributing to the second "mini-tour" of the
orbital tour (recall that a "mini-tour" is a portion of the fields and
particles survey that is more than one complete orbit in duration). The UVS
(Ultraviolet Spectrometer) instrument performs remote observations of the
Ganymede neutral torus. The neutral torus is believed to be formed when
neutral (i.e. with no electrical charge) particles are stripped off of
Ganymede and then remain trapped in the same orbit as Ganymede. Starting
late in the afternoon and continuing into early evening, the UVS
observations are interrupted by the final orbit trim maneuver prior to the
close Ganymede flyby.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Sun, 4 May 1997 23:10:55 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: [ASTRO] Today on Galileo - May 4, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  7-MAY-1997 03:58:58.77
To:	[email protected]
CC:	
Subj:	[ASTRO] Today on Galileo - May 6, 1997


                              TODAY ON GALILEO
                            Tuesday, May 6, 1997

Today Galileo passes through its point of closest approach to Callisto for
this encounter. In the middle of the morning, the spacecraft will fly past
Callisto at a range of about 35,500 kilometers. Today's schedule of
observations is extremely varied in nature. Passage through the closest
approach to Callisto brings on a series of observations performed by the
remote sensing instruments. The observation geometry for this flyby will
provide views of the satellite that are complimentary to those obtained
during the Voyager flybys and the previous Galileo flyby of Callisto during
Galileo's third orbit. The observation opportunities also provide good views
of Callisto's south pole and opportunities for higher resolution
observations of the cratered regions of Buri and Adlinda.

The day starts out with the completion of the UVS (Ultraviolet Spectrometer)
remote observations of the Io torus. Another remote observation of the torus
is performed early in the afternoon. Observations to monitor volcanic
activity on Io start today. This orbit's set includes an extensive campaign
by the SSI (Solid State Imaging camera) to monitor volcanic plumes on Io.
Ten different plume regions will be observed during this orbit. Each of
these observations involve looking at each region when it is on Io's bright
limb against the dark sky background. These images will be taken in three or
four colors and will provide resolutions ranging from 10-20 kilometers per
pixel.

The first observation of the selected feature of Jupiter's atmosphere for
this orbit, the boundary of the south pole region, is performed by the SSI.
Remember that these atmospheric features are selected for complete
characterization by all four remote sensing instruments. A series of UVS
observations of Jupiter's atmosphere are taken through out the day. These
include an East-West strip and a Central Meridian region used to provide
context information for the featured observations and to aid in the
construction of global Jupiter maps at regional resolution. UVS will also
take fixed longitude and darkmaps of Jupiter's atmosphere. These look at
Jupiter's atmosphere to understand the distribution and dynamics of energy
and hydrogen on a global scale. Finally, the UVS observations will look at
aurora on Jupiter. These observations (along with others from NIMS - Near
Infrared Mapping Spectrometer) are coordinated with a high resolution fields
and particles observation of Jupiter's magnetosphere taken as the spacecraft
punches through the plasma sheet (ionized matter which is confined to a thin
"sheet"). This particular plasma sheet recording is, approximately two and a
half hours, the longest of the orbital tour.

The day's set of observations is closed out by an observation of Ganymede
performed by the UVS at solar phase angles not visible from Earth.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Tue, 6 May 1997 14:22:06 GMT
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  8-MAY-1997 01:41:10.84
To:	[email protected]
CC:	
Subj:	[ASTRO] Today on Galileo - May 7, 1997


                              TODAY ON GALILEO
                           Wednesday, May 7, 1997

On this fourth day of the encounter period, Galileo passes the point of
closest approach to Io at a distance of 956,000 kilometers (about 594,000
miles) before speeding by the surface of Ganymede at an altitude of only
1596 kilometers (about 990 miles) and a speed of 8.6 kilometers per second
(over 19,000 miles per hour). Early in the afternoon, the viewing geometry
of Io will have changed sufficiently so that the spacecraft can be turned
back to an earth pointed orientation and the instruments no longer have to
look through the spacecraft booms to see Io.

As can be expected, the day's science activities focus primarily on this
close flyby of Ganymede. On the way toward Ganymede approximately two-thirds
of the satellite is illuminated by the sun. After closest approach, only
one-third is lit up. The remote sensing instruments perform high-resolution
studies of a variety of different surface morphological (shape) and albedo
(reflected light) features. The regions included in these observations are
Osiris (dome structure), Uruk Sulcus (craters, grooves and furrows), a
multi-ringed structure, light-dark material, caldera-like features,
palimpsest and dark floor craters. The fields and particles instruments
perform a high-resolution recording of the magnetosphere for about 45
minutes centered at closest approach. This particular recording is unique as
the orbital path takes the spacecraft through a region upstream from the
satellite wake (the wake is the region created in front of a satellite as
the charged particles that co-rotate with the magnetosphere sweep past the
satellites). The observation will provide additional data on Ganymede's
magnetic field and will help further understand the interaction between
Ganymede and the Jovian magnetosphere. Finally, because of the geometry of
the encounter, Ganymede blocks the spacecraft's view of the earth and the
sun for about 7 minutes. The radio science team will take this opportunity
to measure the changes in Galileo's radio signal through this period. These
measurements will allow scientists to further study the temperature and wind
profiles in Ganymede's tenuous atmosphere.

Also on today's observing schedule are Io observations, as Galileo continues
monitoring surface changes and plume activity. Another remote Io torus
observation is performed by the UVS (Ultraviolet Spectrometer). Observations
of Jupiter's south pole region also continue today, and another north-south
strip is added to the growing map of Jupiter's atmosphere. Finally, a few
observations of Europa are performed by UVS, NIMS (Near Infrared Mapping
Spectrometer) and PPR (Photopolarimeter Radiometer).

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Wed, 7 May 1997 14:45:05 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
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% Subject: [ASTRO] Today on Galileo - May 7, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  8-MAY-1997 21:18:18.25
To:	[email protected]
CC:	
Subj:	[ASTRO] Today on Galileo - May 8, 1997


                              TODAY ON GALILEO
                           Thursday, May 8, 1997

The last two closest approach points are passed today on Galileo, both
within the first six hours of the day. Europa closest approach occurs at a
range of just under 1.3 million kilometers (about 0.8 million miles).
Jupiter closest approach follows about two hours later at a distance just
over 660,000 kilometers (about 410,000 miles).

Today's observation schedule is highly geared toward Jupiter's atmosphere.
Observations of Jupiter's south pole region are performed throughout the
day. However, starting mid-morning, observations, performed primarily by the
PPR (Photopolarimeter Radiometer), include photometry observations (looking
at light intensities), north-south strips, regional maps, Great Red Spot,
and hot spot observations (together with NIMS - Near Infrared Mapping
Spectrometer). In addition, the UVS (Ultraviolet Spectrometer) performs more
observations looking for aurora on Jupiter.

Also today, Europa is observed by NIMS and Metis is observed by SSI (Solid
State Imaging camera). Lastly, PPR performs a series of polarimetry
observations on all four Galilean satellites. These observations are part of
a campaign to obtain samples over all solar phase angles at less than 10
degree phase angle resolution. They will provide information on surface
texture and light scattering properties.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/


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% Date: Thu, 8 May 1997 15:08:53 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
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% Subject: [ASTRO] Today on Galileo - May 8, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  9-MAY-1997 13:29:19.54
To:	[email protected]
CC:	
Subj:	[ASTRO] Today on Galileo - May 9, 1997


                              TODAY ON GALILEO
                            Friday, May 9, 1997

As the encounter period starts to wind down today, the flight team will
transmit the cruise period set of commands to the spacecraft. These commands
will begin to execute Sunday morning.

The morning starts with the completion of the UVS (Ultraviolet Spectrometer)
Jupiter aurora observations that were initiated yesterday evening. Also, PPR
(Photopolarimeter Radiometer) performs another regional observation of
Jupiter's atmosphere this morning. Throughout the day, NIMS (Near Infrared
Mapping Spectrometer) joins PPR in performing a few more observations of
Jupiter's south pole region.

PPR continues its polarimetry campaign by observing Io, Callisto and Europa.
Completing today's set of observations, the UVS performs a final remote Io
torus observation.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Fri, 9 May 1997 5:44:35 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
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% Subject: [ASTRO] Today on Galileo - May 9, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 10-MAY-1997 14:57:05.38
To:	[email protected]
CC:	
Subj:	[ASTRO] Today on Galileo - May 10-11, 1997


                              TODAY ON GALILEO
                              May 10-11, 1997

In the last two days of the encounter period, the level of science activity
continues to settle down. Saturday's activity consists of only two final
NIMS (Near Infrared Mapping Spectrometer) observations of Jupiter's south
pole region and one PPR (Photopolarimeter Radiometer) polarimetry
observation of Io. Sunday consists of only a remote Callisto neutral torus
observation performed by the UVS (Ultraviolet Spectrometer). As the cruise
period begins, remember that the fields and particles survey of the
magnetosphere continues as part of the second Galileo "mini-tour".

On Saturday the flight team will transmit the commands required to perform
the post flyby orbit trim maneuver. This maneuver is used to correct any
errors in the spacecraft's path due to small differences in the planned
flyby path and the actual flyby path. This maneuver starts to execute
Saturday night and continues into Sunday morning. It finishes executing just
prior to the Callisto neutral torus observations.

Don't forget to come back on Monday, May 12 for the return of This Week on
Galileo!

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Sat, 10 May 1997 6:20:03 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: [ASTRO] Today on Galileo - May 10-11, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 13-MAY-1997 02:44:43.96
To:	[email protected]
CC:	
Subj:	[ASTRO] This Week on Galileo - May 12-18, 1997

                            THIS WEEK ON GALILEO
                              May 12-18, 1997

Playback of encounter data from the just completed Ganymede encounter starts
immediately and comprises the bulk of activity on Galileo for this week.
There are approximately 40 playback days before the start of the next
encounter (with Callisto) scheduled to start on June 22. This week's
playback highlights observations of the non-targeted flyby of Callisto that
occured early in the encounter period. In addition, the fields and particles
survey of the magnetosphere, part of the second "mini-tour" of the mission,
continues through the playback period.

The NIMS (Near Infrared Mapping Spectrometer) observations returned during
this week include a global observation of Callisto and an observation of
Callisto's south pole region. These observations were designed to
investigate and determine what materials and minerals reside on the surface
of Callisto and how these materials are distributed on said surface. NIMS
also returns higher resolution observations of the cratered regions of Buri
and Adlinda with the same objectives of being able to establish the
composition and structure of the regions.

The SSI (Solid State Imaging camera) observations included in the playback
include a medium resolution image of a region of the surface of Callisto
that was not seen during the Voyager flybys. A medium resolution image of
the south pole region of Callisto is also returned. This region was seen
poorly both by Voyager and elsewhere in Galileo's satellite tour. Finally, a
medium resolution single-color image of the Adlinda region complements data
obtained by other remote sensing instruments.

Last on the playback schedule and continuing into next week, the high
resolution fields and particles observation of the plasma sheet of Jupiter's
magnetosphere is transmitted to earth. This recording, taken for two and a
half hours and centered on the crossing of the plasma sheet, will be
correlated with Jupiter aurora observations taken by the UVS (Ultraviolet
Spectrometer) instrument.

For additional information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Mon, 12 May 1997 14:49:38 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: [ASTRO] This Week on Galileo - May 12-18, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 27-MAY-1997 04:33:27.19
To:	[email protected]
CC:	
Subj:	[ASTRO] This Week On Galileo - May 26 - June 1, 1997


                            THIS WEEK ON GALILEO
                           May 26 - June 1, 1997

Playback of data from Galileo's previous encounter with Ganymede and the
Jupiter system continues through the week but is interrupted mid-week to
perform regular maintenance and conditioning of the spacecraft's tape
recorder. In addition, as the spacecraft approaches apojove, its furthest
point from Jupiter for this orbit, navigators begin to prepare for the next
orbit trim maneuver, scheduled to be sent to the spacecraft and executed
next week.

Observations from the Io volcanic activity monitoring campaign continue to
be transmitted to earth this week. NIMS (Near Infrared Mapping Spectrometer)
returns a few more observations containing data on hot spots, thermal
anomalies, hot outbursts and chemical changes on Io's surface. SSI (Solid
State Imaging camera) returns another observation from its plume monitoring
campaign. This particular observation is of the region known as Marduk.

On this week's playback schedule we begin to see observations taken during
the spacecraft's flyby of Ganymede. Remote sensing observations focus on
high- resolution sampling of a variety of surface features with different
shapes (morphology) and different light reflection (albedo) characteristics.
NIMS observations returned this week include craters with large central
domes, dark rays, and dark halos. Other NIMS observations look at grooves
and furrows, and dark and light region boundaries.

Similar SSI observations will provide data on the resurfacing and
deformation of dark regions, the formation of light regions, and the
relative ages of these regions (dark regions are believed to be older than
lighter regions). A few other SSI observations provide information on the
shape and characteristics of craters (including a multi-ringed crater),
grooves and caldera like features. The features observed in this set of
observations include the Osiris crater, Uruk Sulcus, Marius Regio, Tiamat
Sulcus, Anshar Sulcus, Erech Sulcus and Mashu Sulcus. In addition, a PPR
(Photopolarimeter Radiometer) observation of the south pole region of
Ganymede is returned this week.

Taken during the 45 minutes centered at closest approach to Ganymede, the
high-time-resolution recording of fields and particles data is also returned
this week. Remember that the flyby geometry for this encounter was such that
the spacecraft flew through the upstream region of the Ganymede wake (the
wake is the region created in front of a satellite as the charged particles
that co- rotate with the magnetosphere sweep past the satellites). These
data are expected to provide additional information regarding the
interaction between Ganymede and it magnetic field and Jupiter's
magnetosphere.

The remainder of the playback schedule contains another couple of
observations of the Jupiter south pole region, the selected feature of
Jupiter's atmosphere for this past orbit. This observation was taken by NIMS
and is one of 16 observations of this region. Also returned by NIMS is an
observation of a secondary feature of Jupiter's atmosphere, a region at a
temperate latitude (50 degrees South). PPR contributes to the Jupiter data
by returning data from a strip of atmosphere running North-South. These
strip observations are designed to provide context information for the
selected feature observations. Finally, PPR returns three polarimetry
observations, two of Ganymede and one of Europa. These observations are part
of a campaign to obtain polarimetry samples over all solar phase angles and
will provide information on surface texture and light scattering properties.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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% Date: Mon, 26 May 1997 2:34:25 GMT
% From: Ron Baalke <[email protected]>
% To: [email protected]
% Message-Id: <[email protected]>
% Subject: [ASTRO] This Week On Galileo - May 26 - June 1, 1997
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From:	VBORMC::"[email protected]" "MAIL-11 Daemon" 24-MAY-1997 03:03:08.53
To:	[email protected]
CC:	
Subj:	[ASTRO] Galileo Returns New Insights Into Callisto and Europa

Douglas Isbell
Headquarters, Washington, DC              May 23, 1997
(Phone: 202/358-1753)

Jane Platt
Jet Propulsion Laboratory, Pasadena, CA
(Phone: 818/354-5011)

RELEASE: 97-110

GALILEO RETURNS NEW INSIGHTS INTO CALLISTO AND EUROPA 

    Jupiter's icy moon Europa has a metallic core and layered 
internal structure similar to the Earth's, while the heavily 
cratered moon Callisto is a mixture of metallic rock and ice 
with no identifiable central core, according to new results 
from NASA's Galileo mission. 

    In addition, recent plasma wave observations from Galileo 
show no evidence of a magnetic field or magnetosphere around 
Callisto, but do hint at the prospect of a tenuous atmosphere.

    These peer-reviewed findings, reported in today's issue of 
Science magazine and the May 16 issue of Nature magazine, are 
based on data gathered during Galileo's Nov. 4, 1996, flyby of 
Callisto and its Europa encounters on Dec. 19, 1996, and Feb. 
20, 1997.

    "Before Galileo, we could only make educated guesses about 
the structure of the Jovian moons," said Dr. John Anderson, a 
planetary scientist at NASA's Jet Propulsion Laboratory (JPL), 
Pasadena, CA. "Now, with the help of the spacecraft, we can 
measure the gravitational fields of the satellites and 
determine their interior structure and density. We can 
determine how the matter is distributed inside." 

    While scientists use seismic waves to study Earth's 
interior, Galileo performs remote studies of Jupiter's moons by 
measuring small changes in the spacecraft's trajectory as it 
passes each body. 

    "These new results from the gravity data are very 
consistent with the idea of subsurface oceans on Europa," 
Anderson said. "We know that Europa has a very deep layer of 
water in some form, but we don't yet know whether that water is 
liquid or frozen." 

    In an article appearing in the May 23 edition of Science, 
Dr. Margaret Kivelson, principal investigator for Galileo's 
magnetometer, reports that during its December 1996 pass by 
Europa, the magnetometer detected what she described as "a 
substantial magnetic signature," and also found that Europa's 
north magnetic pole is pointed in an odd direction. Based on 
these observations, Kivelson, a professor at the University of 
California at Los Angeles, said Europa may have a magnetic 
field about one-quarter the strength of Ganymede's magnetic field. 

    Although the magnetometer was malfunctioning during 
Galileo's Europa flyby in February 1997, Kivelson said the 
problem is corrected and the device is expected to return 
valuable data during its upcoming Europa flybys. The next 
Europa encounter is scheduled for November, with a series of 
flybys planned during a two-year Galileo extended mission. 

    Galileo's findings on the Jovian moon Callisto revealed a 
much different structure than Europa. Scientists believe that 
because Callisto is the Galilean moon located farthest from 
Jupiter, it was never subjected to the same gravitational pull 
as the inner moons and, therefore, never experienced enough 
heating to form different layers. 

    "Callisto had a much more sedate, predictable and peaceful 
history than the other Galilean moons," Anderson explained, 
"and, therefore, it is a more typical solar system object." The 
findings indicate Callisto has no core, but instead has a 
homogeneous structure, with 60 percent of its ingredients being 
rock, including iron and iron sulfide, and 40 percent made of 
compressed ice.

    Dr. Donald Gurnett, principal investigator for the Galileo 
spacecraft's plasma wave instrument, said the instrument 
displayed a very minor response from Callisto and, 
consequently, showed no evidence of a magnetic field or 
magnetosphere. The latest issue of Nature magazine contains 
these findings, as well as supportive data from magnetometer 
studies of Callisto, as reported by Dr. Krishan Khurana of UCLA. 

    However, Gurnett added, "There is some evidence of a plasma 
source on Callisto, which might indicate a very tenuous 
atmosphere." Gurnett is a professor at the University of Iowa 
at Iowa City. 

    The Galileo spacecraft was launched in October 1989 and 
entered orbit around Jupiter on Dec. 7, 1995. The Galileo 
mission is managed by JPL for NASA's Office of Space Science, 
Washington, DC. 

    Images and other data from Galileo are posted on the 
Galileo mission home page on the World Wide Web at URL: 

           http://www.jpl.nasa.gov/galileo. 

                       -end-


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From:	VBORMC::"[email protected]" "MAIL-11 Daemon"  1-JUN-1997 22:05:56.99
To:	[email protected]
CC:	
Subj:	[ASTRO] This Week on Galileo - June 2-8, 1997


                            THIS WEEK ON GALILEO
                               June 2-8, 1997

This week commands for an orbit trim maneuver are transmitted to the
spacecraft. This maneuver, executed late Monday night, will correct the
spacecraft's orbit so that it arrives along the planned path for its next
encounter with the Jupiter system later this month. A few hours prior to the
maneuver, by chance, as it is required about once every 23 days, regular
maintenance is performed on the spacecraft's propulsion system.

Playback continues in the days surrounding the orbit trim maneuver. This
week's playback is comprised primarily of data taken of features in
Jupiter's atmosphere. The selected feature for the past encounter was the
south pole boundary region. Eleven observations of this region performed by
NIMS (Near Infrared Mapping Spectrometer) and two observations performed by
PPR (Photopolarimeter Radiometer) are returned this week. Four NIMS
observations of a secondary feature, a temperate region near 50 degrees
south latitude, are also returned this week. Regional observations of
Jupiter's atmosphere are also on the week's playback schedule. Strips
running from pole to pole, known as North-South strip observations, are
returned from both PPR and NIMS. Hot spot observations from PPR and NIMS and
a regional map taken by PPR that includes the Great Red Spot are also
returned this week.

PPR continues to return observations from its polarimetry map campaign. This
week's contribution includes six observations of Io, four observations of
Europa and two observations of Callisto. SSI's (Solid State Imaging camera)
return of a full-disk observation of Metis, one of the minor moons,
completes the first round of playback through the data stored on the tape
recorder from the last encounter.

The second pass through the previous encounter's data starts on Friday.
Recall that this second opportunity to get at the data is used by the
science community and playback planners to return new data that they
initially thought they might not have enough time to return, fill in small
gaps in already played-back data caused by transmission and reception
problems, and to re-play parts of observations that have been identified as
being interesting enough for a second look.

The second pass starts with a return to observations of Callisto. The second
pass data on this week's schedule includes a global observation performed by
NIMS, a south pole maps by PPR, NIMS and SSI, a Voyager gap-fill observation
by SSI, and a NIMS observation of the cratered region of Adlinda.

For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:

http://www.jpl.nasa.gov/galileo/

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