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Subject: SPACE Digest V12 #604

SPACE Digest                                     Volume 12 : Issue 604

Today's Topics:
		      Galileo Fact Sheet (long)

Administrivia:

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Date: 29 Nov 90 17:57:45 GMT
From: csus.edu!wuarchive!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucdavis.ucdavis.edu  (Ron Baalke)
Subject: Galileo Fact Sheet (long)


  	       GALILEO FACT SHEET/PROJECT BACKGROUND
	                November 29, 1990
 
SUMMARY

     Galileo is a NASA spacecraft mission to Jupiter, launched
October 18, 1989, and designed to study the planet's atmosphere,
satellites and surrounding magnetosphere.  It was named for the
Italian Renaissance scientist who discovered Jupiter's major
moons in 1610 with the first astronomical telescope. 
     This mission will be the first to make direct measurements
from an instrumented probe within Jupiter's atmosphere, and the
first to conduct long-term observations of the planet and its
magnetosphere and satellites from orbit around Jupiter. It will
be the first orbiter and atmospheric probe for any of the outer
planets.
     The Jet Propulsion Laboratory designed and
developed the Galileo Jupiter orbiter spacecraft and is
operating the mission; NASA's Ames Research Center developed
the atmospheric probe with Hughes Aircraft Company as prime
contractor.  The German government is a partner in the
mission through its provision of the spacecraft propulsion
subsystem, scientific instruments on both orbiter and probe,
and ground operations support.
     In order to reach Jupiter, Galileo must pick up the
necessary speed by flying past Venus and twice by the Earth,
using the gravity-assist technique employed by Voyager to
reach the planets Saturn, Uranus and Neptune. 
     These gravity-assist encounters have provided the
opportunity for Galileo to conduct brief scientific
observations of Venus (closest approach February 10, 1990)
and the Earth-Moon system (December 8, 1990 and 1992). 
Designed to measure and observe Jupiter's atmosphere,
magnetosphere and satellites, Galileo's instruments can add
to knowledge of the inner bodies, supplementing previous
spacecraft data and complementing the Venus surface studies
by the Magellan project.
     In addition, Galileo's flight through the asteroid
belt provides opportunities for the first close-up
observation of an asteroid.  In late October 1991 it will
encounter the asteroid Gaspra, and a second potential
opportunity occurs in August 1993, with the asteroid Ida.
     In December 1995 the Galileo atmospheric probe will conduct 
a direct examination of Jupiter's atmosphere, while the larger 
part of the craft, the orbiter, begins a 22-month, 10-orbit tour 
of the major satellites and the magnetosphere, including long-
term observations of Jupiter throughout this phase.
     The 2-1/2-ton (2,222-kilogram) Galileo orbiter
spacecraft carries 10 scientific instruments; there are
another six on the 750-pound (340-kilogram) probe.  The
spacecraft radio link to Earth and the probe-to-orbiter radio
link serve as instruments for additional scientific
investigations.
     Galileo communicates with its controllers and
scientists through the Deep Space Network, using tracking
stations in California, Spain and Australia.

LAUNCH OPERATIONS

     The Galileo spacecraft was carried into Earth
orbit on October 18, 1989, by Space Shuttle Atlantis,
commanded by Donald E. Williams and piloted by Michael J.
McCulley.  Mission specialists Shannon W. Lucid, Ellen S.
Baker and Franklin R. Chang-Diaz deployed Galileo and its IUS
(Inertial Upper Stage) booster from the shuttle.  The two-
stage IUS solid rocket accelerated the spacecraft out of
Earth orbit toward the planet Venus. 
     The Galileo mission was previously designed for a direct 
flight of about 2-1/2 years to Jupiter.  Changes in the launch 
system after the Challenger accident, including replacement of 
the Centaur upper-stage rocket with the IUS, precluded this 
direct flight.  Trajectory engineers designed a new 
interplanetary flight path using gravity assists, once with Venus 
and twice with Earth, to build up the speed to reach Jupiter, 
taking a total of just over 6 years.  This is called the Venus-
Earth-Earth-Gravity-Assist or VEEGA trajectory.
 
EARTH TO JUPITER

     Galileo makes three planetary encounters in the
course of its gravity-assisted flight to Jupiter.  These
provide opportunities for scientific observation and
measurement of Venus and the Earth-Moon system.  The mission
also has a chance to fly close to one or two asteroids,
bodies which have never before been observed close up, and to
obtain data on other phenomena in interplanetary space.
     The instruments designed to observe Jupiter's
atmosphere from afar can also improve our knowledge of the
atmosphere of Venus; sensors designed for the study of
Jupiter's moons can add to information about our own planet
and its satellite. 
 
VENUS

     The planet Venus is approximately the size and
density of the Earth, and it has a solid surface beneath a
cloudy atmosphere, but it does not otherwise resemble our
planet.  The atmosphere is deep and dense; cloud tops are
some 40 miles above the surface, where the atmospheric
pressure is more than 90 times that on Earth and the
temperature near 900 degrees Fahrenheit.
     The clouds are essentially opaque to visible light,
and the surface can be observed only by radar from Earth or
spacecraft or by a spacecraft hardy enough to land and
survive on the surface.  Many observations of these types
have been made, but they have been of limited scope or
resolution; NASA's Magellan mission, in orbit around Venus,
is making a global high-resolution radar survey.  Many
features of the atmosphere remain unknown, including details
of the motion of the upper regions, the form of deeper
clouds, and the existence of lightning storms. 
     The Galileo spacecraft approached Venus February 9,
1990 from the night side and passed across the sunlit
hemisphere.  Closest approach was about 10 p.m. PST, or
about 1 a.m. EST February 10, at a distance of 10,000 miles
(16,000 kilometers) above the cloudtops.  For a day before
and several days after closest approach Galileo scientists
collected measurements of charged particles, dust and
magnetism, infrared and ultraviolet spectral observations,
data for infrared lower-atmosphere maps, and 81 camera
images. 
     Virtually all these data had to be tape-recorded on
the spacecraft for playback in November 1990, because
Galileo's capabilities are constrained during this early
phase of flight.  
     The spacecraft was originally designed to operate
between Earth and Jupiter; at Jupiter, sunlight is 25 times
weaker than at Earth and temperatures are much lower.  The
VEEGA mission has exposed the spacecraft to a hotter
environment from Earth to Venus and back; spacecraft
engineers devised a set of sunshades to protect the craft.
For this system to work, the top of the spacecraft was
pointed close to the Sun, with the main antenna furled
(precluding high-rate communications) for protection from the
Sun's rays, until well after the first Earth flyby in
December 1990.  Therefore, scientists had to wait until the
spacecraft is close to Earth to receive the recorded Venus
data, transmitted through a low-gain antenna.
 
EARTH (FIRST PASS)

     Approaching Earth for the first time about 14
months after launch, the Galileo spacecraft will have the
opportunity to measure the magnetic tail far above the dark
side of Earth and parts of both the near and far sides of
the Moon.  After passing Earth, Galileo will observe its
sunlit side.  At this short range, scientific data can be
transmitted at higher rates using only the spacecraft's low-
gain antennas.  The high-gain antenna is to be unfurled like
an umbrella about 5 months after the first Earth encounter.
 
FIRST ASTEROID: GASPRA

     Nine months after the Earth passage, Galileo will
enter the asteroid belt, and 2 months after that it will
perform the world's first asteroid encounter.  Gaspra is
believed to be a fairly representative main-belt asteroid,
about 10 miles or 15 kilometers across, probably similar in
composition to stony meteorites.
     The spacecraft will pass about 900 miles (1,600
kilometers) from Gaspra at a relative speed of about 18,000
miles per hour; scientists expect to collect several pictures
of Gaspra, and measurements to indicate composition and
physical properties.  The exact flyby geometry has not yet
been selected.
 
EARTH (SECOND PASS)

     Thirteen months after the Gaspra encounter, the
spacecraft will have completed its 2-year elliptical orbit
around the Sun and will arrive back at Earth.  It will need a
much larger elliptical orbit (with a 6-year period) to
reach as far as Jupiter, and the second flyby of Earth will
pump the orbit up to that size.
     Passing about 185 miles (300 kilometers) above the
surface, 25 miles above the altitude at which it was deployed
from the Space Shuttle more than 3 years before, Galileo
will use Earth's gravity to change its flight direction
and pick up about 8,000 miles per hour.
     Each gravity-assist flyby requires several rocket-
thrusting sessions, using Galileo's onboard propulsion
module, to refine the flight path. (Asteroid encounters may
require similar maneuvers to obtain the best observing
conditions.)
     Passing the Earth for the last time, the spacecraft's
scientific equipment can make observations of the planet, both
for comparison with Venus and Jupiter and to aid in Earth
studies.  It can also observe the north polar regions of our
Moon, for comparison with Jupiter's satellites and to obtain new
data on lunar regions never explored before.

SECOND ASTEROID POSSIBILITY

     Nine months later, Galileo could have a second
asteroid-observing opportunity, if this were determined to be
the best use of spacecraft propellant reserves.  Ida is about
20 miles or 30 kilometers across; like Gaspra, it is believed
to represent the majority of main-belt asteroids in
composition, though there are believed to be differences
between the two. 
     Relative velocity for this flyby would be nearly
28,000 miles per hour.  

Approaching Jupiter

     Some 2-1/2 years after leaving Earth for the third
time and 5 months before reaching Jupiter, Galileo's
probe must separate from the orbiter which has been carrying
it since before launch.
     The spacecraft precisely adjusts its trajectory to
establish the atmospheric probe's 5-month free flight to
Jupiter, and then turns to orient the probe so that it will
enter the atmosphere in the correct attitude.  Finally, it
spins up to 10 rpm and releases the spin-stabilized probe. 
Several days later the Galileo orbiter readjusts its
trajectory to aim for its own Jupiter encounter. 
 
AT JUPITER

     Early in December 1995 the Galileo orbiter and
probe will approach Jupiter separately. They will have
travelled about 2-1/2 billion miles (4 billion kilometers) in
a complex multiple looping path for more than 6 years. For
the last 60 days of the approach, the orbiter carries out a
comprehensive program of observations of Jupiter and
measurements of its environment in space.
     The probe will enter the atmosphere to make direct
measurements.  The orbiter will fly close by Io, receive the
probe signals for relay to Earth and go into orbit around
Jupiter, all in a period of about 7 hours.
     While the probe is still approaching Jupiter, the
orbiter will have its first two satellite encounters.  After
passing within 20,000 miles (33,000 kilometers) of Europa, it
will fly about 600 miles (1,000 kilometers) above Io's
volcano-torn surface, about 1/20 the closest flyby altitude
of Voyager in 1979. 
     A few hours later, the probe will enter the upper
atmosphere, about 6 degrees north of Jupiter's equator, at
more than 100,000 miles per hour or about 47 kilometers per
second, and slow by aerodynamic braking for about 2 minutes
before deploying its parachute and dropping its heat shields. 
Then it will float down about 125 miles or 200 kilometers
through the clouds, passing from a pressure of 1/10 that on
Earth's surface to about 25 Earth atmospheres in 75 minutes. 
The probe batteries are not expected to last beyond this
point, and the radio-communications link will be terminated.
     About 133,000 miles (214,000 kilometers) above,
the orbiter will receive, store and transmit the probe's
science data.  Next, the orbiter must thrust with its main
engine to go into orbit around Jupiter.  
     This orbit, the first of 10 planned, will have a
period of about 8 months.  Additional maneuvers and the first
Ganymede close flyby in July 1996 will shorten the orbit, and
each time the orbiter returns to the inner zone of satellites
it will make a gravity-assist close pass over one of them to
change its orbit while making close observations.  These
satellite encounters will be at altitudes as close as 125
miles (200 kilometers) above the surfaces of the moons,
typically about 100 times closer than the Voyagers' satellite
flybys.  Throughout the 22-month orbital phase, Galileo will
continue observing the planet and the satellites and
gathering data on the magnetospheric environment. 

SCIENTIFIC ACTIVITIES

     Galileo's scientific experiments are being carried out by 
more than 100 scientists from six nations.   These are supported
by dedicated instruments and the radio subsystems on the Galileo 
orbiter and probe.  NASA has appointed 13 interdisciplinary 
scientists whose studies reach across more than one Galileo
instrument data set.  The experiments and principal scientists 
are listed at the end of this fact sheet.
 
SPACECRAFT

     The Galileo mission and systems were designed to
investigate three broad aspects of the Jupiter system:  the
planet's atmosphere, the satellites and the magnetosphere.
The spacecraft was constructed in three segments, which help
focus on these areas:  the atmospheric probe; a non-spinning
section of the orbiter carrying cameras and other remote
sensors; and the spinning main section of the orbiter
spacecraft which includes the fields and particles
instruments, designed to sense and measure the environment
directly as the spacecraft flies through it.  The spinning
section also carries the main communications antenna, the
propulsion module, flight computers and most support systems.

Atmospheric Probe

     The probe weighs about 750 pounds (340 kilograms),
and includes a deceleration module to slow and protect the
descent module, which carries out the scientific mission.  
     The deceleration module consists of an aeroshell
and an aft cover, designed to block the heat generated by
slowing from the probe's arrival speed of about 100,000 miles
per hour to subsonic speed in less than 2 minutes.
     After the aft cover is released, the descent 
module deploys its 8-foot (2.5-meter) parachute and drops the
aeroshell; its radio-relay transmitter and all six of its
instruments go to work (two instruments started storing data
on the way in).  Each operating at 128 bits per second, the
dual L-band transmitters send nearly identical streams of
scientific data to the orbiter.  Probe electronics are
powered by batteries with an estimated capacity of about 18
amp-hours on arrival at Jupiter.
     Probe instruments include an atmospheric structure
instrument group measuring temperature, pressure and
deceleration; a neutral mass spectrometer and a helium-
abundance interferometer supporting atmospheric composition
studies; a nephelometer for cloud location and cloud-particle
observations; a net-flux radiometer measuring the difference,
upward versus downward, in radiant energy flux at each
altitude; and a lightning/radio-emission instrument with an
energetic-particle detector, measuring electromagnetic waves
(light and radio-frequency) associated with lightning and
energetic particles in Jupiter's radiation belts.

Galileo Orbiter

     The orbiter, in addition to supporting the probe
activities, will support all the scientific investigations of
Jupiter's satellites and magnetosphere, and remote
observation of the giant planet itself, including those
carried out on the way to Jupiter.
     The orbiter weighs about 4,900 pounds (2,222
kilograms), including about 2,035 pounds or 925 kilograms of
rocket propellant.  This is used in almost 30 relatively
small maneuvers during the long gravity-assisted flight to
Jupiter, three large thrust maneuvers including the one that
puts the craft into its Jupiter orbit, and the 30 or so trim
maneuvers planned for the satellite tour phase.
     The propulsion module consists of 12 10-newton thrusters, a 
single 400-newton engine, and the fuel, oxidizer, and 
pressurizing-gas tanks, tubing, valves and control equipment.  (A 
thrust of 10 newtons would support a weight of about 1 kilogram 
or 2.2 pounds at Earth's surface.)  The propulsion system was 
developed and built by Messerschmitt-Bolkow-Blohm (MBB) and 
provided by the Federal Republic of Germany as a partner in 
Project Galileo.
     The orbiter's maximum communications rate is 134
kilobits per second (the equivalent of about one black-and-
white image per minute); there are other data rates, down to
10 bits per second, for transmitting engineering data when
the Earth-spacecraft geometry makes communication difficult. 
The Galileo spacecraft acquires and transmits a total of
1,418 engineering measurements (temperatures, voltages,
computer states and counts, and the like).  The spacecraft
transmitters operate at S-band and X-band (2,295 and 8,415
megahertz) frequencies.
     The high-gain antenna is a 16-foot (4.8-meter)
umbrella-like reflector unfurled after the first Earth
flyby.  Two low-gain antennas (one pointed forward and one
aft, both mounted on the spinning section) are provided to
support communications duri9g the Earth-Venus-Earth leg of
the flight and whenever the main antenna is not deployed and
pointed at Earth.  The despun section of the orbiter carries
a radio relay antenna for receiving the probe's data
transmissions.
     Because the time delay in radio signals from Earth
to Jupiter and back is more than 1 hour, the Galileo
spacecraft was designed to operate from programs sent to it
in advance and stored in spacecraft memory.  A single master
sequence program can cover from weeks to months of quiet
operations between planetary and satellite encounters. 
During busy encounter operations, one program covers only a
few days or less.  
     These sequences operate through flight software
installed in spacecraft computers in various subsystems and
scientific instruments. In the command and data subsystem,
there are about 35,000 lines of code, including 7,000 lines
of automatic fault protection software, which operates to put
the spacecraft in a safe state if an untoward event such as
an onboard computer glitch were to occur.  The articulation
and attitude control flight software has about 37,000 lines
of code, including 5,500 lines devoted to fault protection.
     Electrical power is provided to Galileo's
equipment by two radioisotope thermoelectric generators. 
Heat produced by natural radioactive decay of plutonium is
converted to approximately 500 watts of electricity (570
watts at launch, 485 at the end of the mission) to operate
the orbiter equipment for its 8-year baseline mission. 
This is the same type of power source used by the Voyager and
Pioneer Jupiter spacecraft in their outer-planet missions.
     Most spacecraft are stabilized in flight either by
spinning around a major axis, or by maintaining a fixed
orientation in space, referenced to the Sun and another star. 
Galileo represents a combination of these techniques, and is
the first dual-spin planetary spacecraft.  A spinning section
rotates at 3 rpm, and a "despun" section is counter-rotated
to provide a fixed orientation for cameras and other remote
sensors.  A star scanner on the spinning side is used to
determine orientation and spin rate; gyros are used for
turns and instrument pointing.
     Instruments which measure fields and particles,
together with the main antenna, the power supply, the
propulsion module, most of the computers and control
electronics, are mounted on the spinning section.  The
instruments include magnetometer sensors mounted on a 36-
foot (11-meter) boom to escape interference from the
spacecraft; a plasma instrument detecting low-energy charged
particles and a plasma-wave detector to study waves generated
by the particles; a high-energy particle detector; and a
detector of cosmic and Jovian dust.  It also carries the Heavy
Ion Counter, an engineering experiment added to assess the
potentially dangerous charged-particle environments the
spaceraft flies through, and an added Extreme Ultraviolet
detector associated with the UV spectrometer on the scan
platform.
     The despun section carries instruments and other
equipment whose operation depends on a steady pointing
capability.  The instruments include the camera system; the
near-infrared mapping spectrometer to make multispectral
images for atmosphere and surface chemical analysis; the
ultraviolet spectrometer to study gases; and the
photopolarimeter-radiometer to measure radiant and reflected
energy.  The camera system is expected to obtain images of
Jupiter's satellites at resolutions from 20 to 1,000 times
better than Voyager's best.  
     This section also carries a dish antenna to track
the probe in Jupiter's atmosphere to pick up its signals for
relay to Earth. 

GROUND SYSTEMS

     Galileo communicates with Earth via NASA's Deep
Space Network (DSN), which has a complex of large antennas
with receivers and transmitters located in the California
desert, in Australia and in Spain, linked to a network
control center at JPL in Pasadena, California.  The
spacecraft receives commands, sends science and engineering
data, and is tracked by doppler and ranging measurements
through this network.  The German Space Operations Center and 
tracking station at Weilheim will also support Galileo
cruise science activities beginning in September 1991.  
     At JPL, mission controllers including about 275
scientists, engineers and technicians supported the mission
at launch; nearly 400 will support Jupiter operations.  Their
responsibilities include commanding the spacecraft,
interpreting the engineering and scientific data it sends in
order to understand how it is performing and responding, and
analyzing navigation data obtained by the Deep Space Network. 
The controllers use a set of complex computer programs to
help them control the spacecraft and interpret the data.
     As indicated above, the Galileo spacecraft carries
out its complex operations, including maneuvers, scientific
observations and communications, in response to stored
sequences which are sent up to the orbiter periodically
through the Deep Space Network in the form of command loads.
     Designing these sequences is a complex process
balancing the desire to make certain scientific observations
with the need to safeguard the spacecraft and mission.  The
sequence design process itself is supported by software
programs, for example, which display to the scientist maps of
the instrument coverage on the surface of a satellite for a
given spacecraft orientation and trajectory.  Notwithstanding
these aids, a typical 3-day satellite encounter will take
efforts spread over many months to design, check and recheck. 
The controllers also use software designed to check the
command sequence further against flight rules and
constraints.
     The spacecraft regularly reports its status and
health through an extensive set of engineering measurements. 
Interpreting these data into trends and averting or working
around equipment failures is a major task for the Galileo
flight team.  Conclusions from this activity become an
important input, along with scientific plans, to the sequence
design process.  This too is supported by computer programs
written and used in the mission support area.
     Navigation is the process of estimating, from radio
range and doppler measurements, the position and velocity of
the spacecraft to predict its flight path and to design
course-correcting maneuvers.  These calculations must be done
with computer support.  The Galileo mission, with its complex
gravity-assist flight to Jupiter and 10 gravity-assist
satellite encounters in the Jovian system, is extremely
dependent on consistently accurate navigation. 
     In addition to the programs which directly operate
the spacecraft and are periodically transmitted to it, the
mission operations team uses software amounting to 650,000
lines of programming code in the sequence design process;
1,615,000 lines in the telemetry interpretation; and 550,000
lines of code in navigation.  These all had to be written,
checked, tested, used in mission simulations and, in many
cases, revised before the mission could begin.
     Science investigators are located variously at JPL
or at their home laboratories, linked by computer
communications.  From either location, they are involved in
developing the sequences affecting their experiments and, in
some cases, helping to change preplanned sequences to follow
up on unexpected discoveries with second looks.

JUPITER'S SYSTEM

     Jupiter is the largest and fastest-spinning planet
in the solar system.  Its radius is more than 11 times
Earth's, and its mass is 318 times that of our planet.  It is
made mostly of light elements, principally hydrogen and
helium.  Its atmosphere and clouds are deep and dense, and a
significant amount of energy is emitted from its interior. 
The earliest Earth-based telescopic observations showed bands
and spots in Jupiter's atmosphere; one storm system, the Red
Spot, has been seen to persist over 3 centuries.  Atmospheric 
forms and dynamics were observed in increasing detail with the 
Pioneer and Voyager flyby spacecraft, and Earth-based infrared 
astronomers have recently studied the nature and vertical 
dynamics of deeper clouds. 
     Sixteen satellites are known.  The four largest,
discovered by the Italian scientist Galileo in 1610, are
about the size of small planets.  The innermost of these,
Io, has active sulfurous volcanoes, discovered by Voyager 1
and further observed by Voyager 2 and Earth-based infrared
astronomy.  Io and Europa are about the size and density of
Earth's moon (3-4 times the density of water) and probably
mostly rocky inside.  Ganymede and Callisto, further out from
Jupiter, are the size of Mercury but less than twice as dense
as water; their interiors are probably about half-and-half
ice and rock, with mostly ice or frost surfaces.
     Of the others, eight (probably captured asteroids)
orbit irregularly far from the planet, and four (three
discovered by the Voyager mission in 1979) are close to the
planet.  Voyager also discovered a thin ring system at
Jupiter in 1979.
     Jupiter has the strongest planetary magnetic field
known; the resulting magnetosphere is a huge teardrop-shaped, 
plasma-filled cavity in the solar wind pointing away from the
Sun.  The inner part of the magnetic field is doughnut-
shaped, but farther out it flattens into a disk.  The
magnetic poles are offset and tilted relative to Jupiter's
axis of rotation, so the field appears to wobble around with
Jupiter's rotation (just under 10 hours), sweeping up and
down across the inner satellites and making waves throughout
the magnetosphere.

MANAGEMENT

     The Galileo Project is managed for NASA's Office of Space 
Science and Applications by the Jet Propulsion Laboratory, a 
division of the California Institute of Technology.  This 
responsibility includes designing, building, testing, operating 
and tracking Galileo.  William J. O'Neil is project manager, 
Torrence V. Johnson is project scientist, Clayne M. Yeates is 
science and mission design manager, Neal E. Ausman Jr. is mission 
director, and Matthew R. Landano is deputy mission director.  The 
Federal Republic of Germany has furnished the orbiter's retro-
propulsion module and some of the instruments and is 
participating in the scientific investigations.  The radioisotope 
thermoelectric generators were designed and built by the General 
Electric Company for the U.S. Department of Energy.
     NASA's Ames Research Center, Moffett Field,
California, is responsible for the atmosphere probe, which
was built by Hughes Aircraft Company, El Segundo, California. 
At Ames, the probe manager is Benny Chin and the probe
scientist is Richard E. Young.

	GALILEO MISSION EVENTS
 
     Launch: STS-34 Atlantis and IUS             October 18, 1989
     First trajectory-change maneuver         November 9-11, 1989
     Venus flyby (about 10,000 mi altitude)     February 10, 1990
     Venus data playback                     November 19-21, 1990
     Earth 1 flyby (about 590 mi)                December 8, 1990
     Asteroid Gaspra flyby (about 900 mi)        October 29, 1991
     Earth 2 flyby (about 200 mi)                December 8, 1992
     Asteroid Ida flyby                           August 28, 1993
     Probe release                                      July 1995
     Jupiter arrival (includes                   December 7, 1995
       Io flyby at about 600 mi, Probe entry
       and relay, Jupiter orbit insertion)
     Orbital tour of Galilean satellites          Dec '95-Oct '97
     Europa, Ganymede, Callisto
     First Ganymede encounter                           July 1996

	SPACECRAFT CHARACTERISTICS
 
                               Orbiter                 Probe
Mass, lb (kg)                 4,890 (2,222 kg)       750 (340 kg)
Usable propellant, lb (kg)    2,035 (925)                --
Height (in-flight)            20.5 feet (6.15 m)    34 in. (86cm)
Inflight span (exc. mag boom) 30 feet (9.2 m)            -- 
Instrument payload            12 experiments        6 experiments
Payload mass, lb (kg)         260 (118)                   66 (30)
Electric power                RTGs, 570-480 watts  Lithium-sulfur
                              Battery, 730 w-h

	GALILEO SCIENTIFIC ESPERIMENTS
 
Experiment/Instrument   Principal Investigator   Objectives

PROBE
Atmospheric Structure, Alvin Seiff, NASA Ames RC, Temperature, 
pressure, density, molecular weight profiles
Neutral Mass Spectrometer, Hasso Niemann, NASA Goddard SFC, 
Chemical composition, helium abundance; Ulf von Zahn, Bonn 
University, FRG, Helium/hydrogen ratio
 
Nephelometer, Boris Ragent, NASA Ames RC, Clouds, solid/liquid 
particles

Net Flux Radiometer, L. A. Sromovsky, Univ. of Wisconsin, 
Thermal/solar energy profiles; Lightning/energetic particles, 
Louis Lanzerotti, Bell Laboratories, Detect lightning, measure 
energetic particles


ORBITER (DESPUN)
Solid-State Imaging Camera, Michael Belton, NOAO, (Team Leader) 
Galilean satellites at 1-km resolution or better, other bodies 
correspondingly 

Near-Infrared Mapping Spectrometer, Robert Carlson, JPL, 
Surface/atmospheric composition, thermal mapping

Ultraviolet Spectrometer (includes extreme UV sensor on spun 
section), Charles Hord, Univ. of Colorado, Atmospheric gases, 
aerosols, etc. 

Photopolarimeter Radiometer, James Hansen, Goddard Institute for 
Space Studies, Atmospheric particles, thermal/reflected radiation 

ORBITER (SPINNING)
Magnetometer, Margaret Kivelson, UCLA, Strength and fluctuations 
of magnetic fields; Energetic Particles, Donald Williams, Johns 
Hopkins APL, Electrons, protons, heavy ions in atmosphere; 
Plasma, Louis Frank, Univ. of Iowa, Composition, energy, 
distribution of ions; Plasma Wave, Donald Gurnett, Univ. of Iowa, 
Electromagnetic waves and wave-particle interactions; Dust, 
Eberhard Grun, Max Planck Inst. fur Kernphysik, Mass, velocity, 
charge of submicron particles

Radio Science:  Celestial Mechanics, John Anderson, JPL, (Team 
Leader), Masses and motions of bodies from spacecraft tracking

Radio Science:  Propagation, H. Taylor Howard, Stanford Univ., 
Satellite radii, atmospheric structure, from radio propagation

Engineering Experiment:  Heavy Ion Counter, Edward Stone, 
Caltech, Spacecraft charged-particle environment


	INTERDISCIPLINARY INVESTIGATORS
 
Fraser P. Fanale, University of Hawaii
Peter Gierasch, Cornell University
Donald M. Hunten, University of Arizona
Andrew P. Ingersoll, California Institute of Technology
David Morrison, University of Hawaii
Michael McElroy, Harvard University
Glenn S. Orton, NASA Jet Propulsion Laboratory
Toby Owen, State University of New York
James B. Pollack, NASA Ames Research Center
Christopher T. Russell, University of California at Los Angeles
Carl Sagan, Cornell University
Gerald Schubert, University of California at Los Angeles
James Van Allen, University of Iowa
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | baalke@mars.jpl.nasa.gov
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | baalke@jems.jpl.nasa.gov
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

End of SPACE Digest V12 #604
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