yee@trident.arc.nasa.gov (Peter E. Yee) (09/30/89)
FOLLOWING IS THE TEXT OF THE STS-34 PRESS KIT. EACH NASA FIELD CENTER
NEWSROOM HAS RECEIVED A MASTER COPY OF THE KIT WITH ILLUSTRATIONS FOR
USE AT THEIR CENTER.
SPACE SHUTTLE MISSION STS-34
PRESS KIT
OCTOBER 1989
PUBLIC AFFAIRS CONTACTS
Sarah Keegan/Barbara Selby
Office of Space Flight
NASA Headquarters, Washington, D.C.
Charles Redmond/Paula Cleggett-Haleim
Office of Space Science and Applications
NASA Headquarters, Washington, D.C.
Jim Ball
Office of Commercial Programs
NASA Headquarters, Washington, D.C.
Lisa Malone
Kennedy Space Center, Fla.
Kyle Herring
Johnson Space Center, Houston, Texas
Jerry Berg
Marshall Space Flight Center, Huntsville, Ala.
Mack Herring
Stennis Space Center, Bay St. Louis, Miss.
Nancy Lovato
Ames-Dryden Flight Research Facility, Edwards, Calif.
Robert J. MacMillin
Jet Propulsion Laboratory, Pasadena, Calif.
Jim Elliott
Goddard Space Flight Center, Greenbelt, Md.
GENERAL RELEASE
RELEASE: 89-151
SHUTTLE ATLANTIS TO DEPLOY GALILEO PROBE TOWARD JUPITER
Space Shuttle mission STS-34 will deploy the Galileo planetary
exploration spacecraft into low-Earth orbit starting Galileo on its journey
to explore Jupiter. Galileo will be the second planetary probe deployed
from the Shuttle this year following Atlantis' successful launch of
Magellan toward Venus exploration in May.
Following deployment about 6 hours after launch, Galileo will be
propelled on a trajectory, known as Venus-Earth-Earth Gravity Assist
(VEEGA) by an Air Force-developed, inertial upper stage (IUS). Galileo's
trajectory will swing around Venus, the sun and Earth before Galileo
makes it's way toward Jupiter.
Flying the VEEGA track, Galileo will arrive at Venus in February 1990.
During the flyby, Galileo will make measurements to determine the
presence of lightning on Venus and take time-lapse photography of Venus'
cloud circulation patterns. Accelerated by Venus' gravity, the spacecraft
will head back to Earth.
Enroute, Galileo will activate onboard remote-sensing equipment to
gather near-infrared data on the composition and characteristics of the
far side of Earth's moon. Galileo also will map the hydrogen distribution
of the Earth's atmosphere.
Acquiring additional energy from the Earth's gravitational forces,
Galileo will travel on a 2-year journey around the sun spending 10 months
inside an asteroid belt. On Oct. 29, 1991, Galileo wlll pass within 600
miles of the asteroid Gaspra.
On the second Earth flyby in December 1992, Galileo will photograph
the north pole of the moon in an effort to determine if ice exists.
Outbound, Galileo will activate the time-lapse photography system to
produce a "movie" of the moon orbiting Earth.
Racing toward Jupiter, Galileo will make a second trek through the
asteroid belt passing within 600 miles of asteroid Ida on Aug. 29, 1993.
Science data gathered from both asteroid encounters will focus on surface
geology and composition.
Five months prior to the Dec. 7, 1995, arrival at Jupiter, Galileo's
atmospheric probe, encased in an oval heat shield, will spin away from the
orbiter at a rate of 5 revolutions per minute (rpm) and follow a ballistic
trajectory aimed at a spot 6 degrees north of Jupiter's equator. The probe
will enter Jupiter's atmosphere at a shallow angle to avoid burning up like
a meteor or ricocheting off the atmosphere back into space.
At approximately Mach 1 speed, the probe's pilot parachute will deploy,
removing the deceleration module aft cover. Deployment of the main
parachute will follow, pulling the descent module out of the aeroshell to
expose the instrument-sensing elements. During the 75-minute descent
into the Jovian atmosphere, the probe will use the orbiter to transmit
data back to Earth. After 75 minutes, the probe will be crushed under the
heavy atmospheric pressure.
The Galileo orbiter will continue its primary mission, orbiting around
Jupiter and four of its satellites, returning science data for the next 22
months.
Galileo's scientific goals include the study of the chemical
composition, state and dynamics of the Jovian atmosphere and satellites,
and the investigation of the structure and physical dynamics of the
powerful Jovian magnetosphere.
Overall responsibility for management of the project, including orbiter
development, resides at NASA's Jet Propulsion Laboratory, Pasadena,
Calif. The NASA Ames Research Center, Mountain View, Calif., manages
the probe system. JPL built the 2,500-lb. spacecraft and Hughes Aircraft
Co. built the 740-lb. probe.
Modifications made to Galileo since flight postponement in 1986
include the addition of sunshields to the base and top of the antenna, new
thermal control surfaces, blankets and heaters. Because of the extended
length of the mission, the electrical circuitry of the thermoelectric
generator has been revised to reduce power demand throughout the
mission to assure adequate power supply for mission completion.
Joining Galileo in the payload bay of Atlantis will be the Shuttle Solar
Backscatter Ultraviolet (SSBUV) instrument. The SSBUV is designed to
provide calibration of backscatter ultraviolet instruments currently being
flown on free-flying satellites. SSBUV's primary objective is to check the
calibration of the ozone sounders on satellites to verify the accuracy of
the data set of atmospheric ozone and solar irradiance data.
The SSBUV is contained in two Get Away Special canisters in the
payload bay and weighs about 1219 lbs . One canister contains the SSBUV
spectrometer and five supporting optical sensors. The second canister
houses data, command and power systems. An interconnecting cable
provides the communication link between the two canisters.
Atlantis also will carry several secondary payloads involving radiation
measurements, polymer morphology, lightning research, microgravity
effects on plants and a student experiment on ice crystal growth in space.
Commander of the 31st Shuttle mission is Donald E. Williams, Captain,
USN. Michael J. McCulley, Commander, USN, is Pilot. Williams flew as
Pilot of mission STS 51-D in April 1985. McCulley will be making his
first Shuttle flight.
Mission Specialists are Shannon W. Lucid, Ph.D.; Franklin R. Chang-Diaz,
Ph.D.; and Ellen S. Baker, M.D. Lucid previously flew as a Mission
Specialist on STS 51-G in June 1985. Chang-Diaz flew as a Mission
Specialist on STS 61-C in January 1986. Baker is making her first Shuttle
flight.
Liftoff of the fifth flight of orbiter Atlantis is scheduled for 1:29 p.m.
EDT on Oct. 12 from Kennedy Space Center, Fla., launch pad 39-B, into a
160-nautical-mile, 34.3-degree orbit. Nominal mission duration is 5
days, 2 hours, 45 minutes. Deorbit is planned on orbit 81, with landing
scheduled for 4:14 p.m. EDT on Oct. 17 at Edwards Air Force Base, Calif.
Liftoff on Oct. 12 could occur during a 10-minute period. The launch
window grows each day reaching a maximum of 47 minutes on Nov. 2. The
window then decreases each day through the remainder of the launch
opportunity which ends Nov. 21. The window is dictated by the need for a
daylight landing opportunity at the trans-Atlantic landing abort sites and
the performance constraint of Galileo's inertial upper stage.
After landing at Edwards AFB, Atlantis will be towed to the NASA
Ames-Dryden Flight Research Facility, hoisted atop the Shuttle Carrier
Aircraft and ferried back to the Kennedy Space Center to begin processing
for its next flight.
- end -
GENERAL INFORMATION
NASA Select Television Transmission
NASA Select television is available on Satcom F-2R, Transponder 13,
C-band located at 72 degrees west longitude, frequency 3960.0 MHz,
vertical polarization, audio monaural 6.8 MHz.
The schedule for tv transmissions from the orbiter and for the
change-of-shift briefings from Johnson Space Center, Houston, will be
available during the mission at Kennedy Space Center, Fla.; Marshall Space
Flight Center, Huntsville, Ala.; Johnson Space Center; and NASA
Headquarters, Washington, D.C. The schedule will be updated daily to
reflect changes dictated by mission operations.
TV schedules also may be obtained by calling COMSTOR, 713/483-5817.
COMSTOR is a computer data base service requiring the use of a telephone
modem. Voice updates of the TV schedule may be obtained by dialing
202/755-1788. This service is updated daily at noon EDT.
Special Note to Broadcasters
In the 5 workdays before launch, short sound bites of astronaut interviews
with the STS-34 crew will be available to broadcasters by calling
XXX/YYY-ZZZZ between 8 a.m. and noon EDT.
Status Reports
Status reports on countdown and mission progress, on-orbit activities and
landing operations will be produced by the appropriate NASA news center.
Briefings
An STS-34 mission press briefing schedule will be issued prior to launch.
During the mission, flight control personnel will be on 8-hour shifts.
Change-of-shift briefings by the off-going flight director will occur at
approximately 8-hour intervals.
LAUNCH PREPARATIONS, COUNTDOWN
AND LIFTOFF
Processing activities began on Atlantis for the STS-34 mission on May
16 when Atlantis was towed to Orbiter Processing Facility (OPF) bay 2
after arrival from NASA's Ames-Dryden Flight Research Facility in
California. STS-30 post-flight deconfiguration and inspections were
conducted in the processing hangar.
As planned, the three main engines were removed the last week of May
and taken to the main engine shop in the Vehicle Assembly Building (VAB)
for the replacement of several components including the high pressure
oxidizer turbopumps. The engines were reinstalled the first week of July,
while the ship was in the OPF. Engine 2027 is installed in the number one
position, engine 2030 is in the number two position and engine 2029 is in
the number three position.
The right hand Orbital Maneuvering System (OMS) pod was removed in
mid-June for repairs. A propellant tank needed for Atlantis' pod was
scheduled for delivery too late to support integrated testing. As a result,
Discovery's right pod was installed on Atlantis about 2 weeks later. The
left OMS pod was removed July 9 and reinstalled 2 1/2 weeks later. Both
pods had dynatubes and helium isolation valve repairs in the Hypergolic
Maintenance Facility.
About 34 modifications have been implemented since the STS-30
mission. One significant modification is a cooling system for the
radioisotope thermoelectric generators (RTG). The RTG fuel is plutonium
dioxide which generates heat as a result of its normal decay. The heat is
converted to energy and used to provide electrical power for the Galileo
spacecraft. A mixture of alcohol and water flows in the special cooling
system to lower the RTG case temperature and maintain a desired
temperature to the payload instrumentation in the vicinity of the RTGs.
These cooling lines are mounted on the port side of the orbiter from the
aft compartment to a control panel in bay 4.
Another modification, called "flutter buffet," features special
instrumentation on the vertical tail and right and left outboard elevons.
Ten accelerometers were added to the vertical tail and one on each of the
elevons. These instruments are designed to measure in-flight loads on the
orbiter's structure. Atlantis is the only vehicle that will be equipped with
this instrumentation.
Improved controllers for the water spray boilers and auxiliary power
units were installed. Other improvements were made to the orbiter's
structure and thermal protection system, mechanical systems, propulsion
system and avionics system.
Stacking of solid rocket motor (SRM) segments for flight began with
the left aft booster on Mobile Launcher Platform 1 in the VAB on June 15.
Booster stacking operations were completed by July 22 and the external
tank was mated to the two boosters on July 30.
Flight crew members performed the Crew Equipment Interface Test on
July 29 to become familiar with Atlantis' crew compartment, vehicle
configuration and equipment associated with the mission.
The Galileo probe arrived at the Spacecraft Assembly and
Encapsulation Facility (SAEF) 2 on April 17 and the spacecraft arrived on
May 16. While at SAEF-2, the spacecraft and probe were joined and tested
together to verify critical connections. Galileo was delivered to the
Vertical Processing Facility (VPF) on Aug. 1. The Inertial Upper Stage
(IUS) was delivered to the VPF on July 30. The Galileo/IUS were joined
together on Aug. 3 and all integrated testing was performed during the
second week of August.
The Shuttle Solar Backscatter Ultraviolet (SSBUV) experiment,
contained in two Get Away Special (GAS) canisters, was mounted on a
special GAS beam in Atlantis' payload bay on July 24. Interface
verification tests were performed the next day.
Atlantis was transferred from the OPF to the VAB on Aug. 21, where it
was mated to the external tank and SRBs. A Shuttle Interface Test was
conducted in the VAB to check the mechanical and electrical connections
between the various elements of the Shuttle vehicle and onboard flight
systems.
The assembled Space Shuttle vehicle was rolled out of the VAB aboard
its mobile launcher platform for the 4.2 mile trip to Launch Pad 39-B on
Aug. 29. Galileo and its IUS upper stage were transferred from the VPF to
Launch Pad 39-B on Aug. 25. The payload was installed in Atlantis'
payload bay on Aug. 30.
The payload interface verification test was planned for Sept. 7 to
verify connections between the Shuttle and the payload. An end-to-end
test was planned for Sept. 8 to verify communications between the
spacecraft and ground controllers. Testing of the IUS was planned about 2
weeks prior to launch in parallel with Shuttle launch preparations.
A Countdown Demonstration Test, a dress rehearsal for the STS-34
flight crew and KSC launch team, is designed as a practice countdown for
the launch. At press time, it was planned for Sept. 14 and 15.
One of the unique STS-34 processing milestones planned was a
simulation exercise for the installation of the RTGs. Simulated RTGs
were to be used in the 2-day event scheduled within the first week after
Atlantis arrives at the launch pad. The test is designed to give workers
experience for the installation of the RTGs, a first in the Shuttle program.
In addition, access requirements will be identified and procedures will be
verified.
Another test scheduled at the pad is installation of the flight RTGs and
an associated test and checkout of the RTG cooling system planned for the
third week of September. This test will verify the total RTG cooling
system and connections. The RTGs will be removed at the completion of
the 3-day cooling system test and returned to the RTG facility. The two
flight RTGs will be reinstalled on the spacecraft 6 days before launch.
Launch preparations scheduled the last 2 weeks prior to launch countdown
include final vehicle ordnance activities, such as power-on stray-voltage
checks and resistance checks of firing circuits; loading the fuel cell
storage tanks; pressurizing the hypergolic propellant tanks aboard the
vehicle; final payload closeouts; and a final functional check of the range
safety and SRB ignition, safe and arm devices.
The launch countdown is scheduled to pick up at the T-minus 43-hour
mark, leading up to the STS-34 launch. Atlantis' fifth launch will be
conducted by a joint NASA/industry team from Firing Room 1 in the Launch
Control Center.
MAJOR COUNTDOWN MILESTONES
Countdown Event
T-43 Hours Power up Space Shuttle vehicle.
T-34 Hours Begin orbiter and ground support
equipment closeouts for launch.
T-30 Hours Activate orbiter's navigation aids.
T-27 Hours (holding) Enter first built-in hold for 8 hours.
T-27 Hours (counting) Begin preparations for loading fuel
cell storage tanks with liquid oxygen
and liquid hydrogen reactants.
T-25 Hours Load orbiter's fuel cell tanks with
liquid oxygen.
T-22 Hours, 30 minutes Load orbiter's fuel cell tanks with
liquid hydrogen.
T-22 Hours Perform interface check between
Houston Mission Control and Merritt
Island Launch Area (MILA) tracking
station.
T-20 Hours Activate and warm up inertial
measurement units (IMU).
T-19 Hours (holding) Enter 8-hour built-in hold. Activate
orbiter communications system.
T-19 hours (counting) Resume countdown. Continue preparations to load
external tank, orbiter closeouts and preparations
to move the Rotating Service Structure (RSS).
T-11 Hours (holding) Start 14-hour, 40 minute built-in hold
orbiter flight and middecks.
T-11 Hours (counting) Retract RSS from vehicle to launch
position.
T-9 Hours Activate orbiter's fuel cells.
T-8 Hours Configure Mission Control communications
for launch. Start clearing
blast danger area.
T-6 Hours, 30 minutes Perform Eastern Test Range open
loop command test.
T-6 Hours (holding) Enter 1-hour built-in hold. Receive
management "go" for tanking.
T-6 Hours (counting) Start external tank chilldown and
propellant loading.
T-5 Hours Start IMU pre-flight calibration.
T-4 Hours Perform MILA antenna alignment.
T-3 Hours (holding) 2-hour built-in hold begins. Loading
of external tank is complete and in a
stable replenish mode. Ice team
goes to pad for inspections. Closeout
crew goes to white room to begin
preparing orbiter's cabin for flight
crew's entry. Wake flight crew
(launch minus 4 hours, 55 minutes).
T-3 Hours (counting) Resume countdown.
T-2 Hours, 55 minutes Flight crew departs O&C Building for
Launch Pad 39-B (Launch minus 3
hours,15 minutes).
T-2 Hours, 30 minutes Crew enters orbiter vehicle (Launch
minus 2 Hours, 50 minutes).
T-60 minutes Start pre-flight alignment of IMUs.
T-20 minutes (holding) 10-minute built-in hold begins.
T-20 minutes(counting) Configure orbiter computers for
launch.
T-10 minutes White room closeout crew cleared
through launch danger are a
roadblocks.
T-9 minutes (holding) 40-minute built-in hold begins.
Perform status check and receive
Launch Director and Mission
Management Team "go."
T-9 minutes (counting) Start ground launch sequencer.
T-7 minutes, 30 seconds Retract orbiter access arm.
T-5 minutes Pilot starts auxiliary power units. Arm
range safety, solid rocket booster
(SRB) ignition systems.
T-3 minutes, 30 seconds Orbiter goes on internal power.
T-2 minutes, 55 seconds Pressurize liquid oxygen tank for
flight and retract gaseous oxygen
vent hood.
T-1 minute, 57 seconds Pressurize liquid hydrogen tank.
T-31 seconds "Go" from ground computer for
orbiter computers to start the
automatic launch sequence.
T-28 seconds Start SRB hydraulic power units.
T-21 seconds Start SRB gimbal profile test.
T-6.6 seconds Main engine start.
T-3 seconds Main engines at 90 percent thrust.
T-0 SRB ignition, holddown post
release and liftoff.
T+7 seconds Shuttle clears launch tower and
control switches to JSC.
Note: This countdown timeline may be adjusted in real time as necessary.
TRAJECTORY SEQUENCE OF EVENTS
__________________________________________________________
RELATIVE
EVENT MET VELOCITY MACH ALTITUDE
(d:h:m:s) (fps) (ft.)
__________________________________________________________
Launch 00/00:00:00
Begin Roll Maneuver 00/00:00:09 165 .15 627
End Roll Maneuver 00/00:00:17 374 .33 2,898
SSME Throttle Down to 65% 00/00:00:34 833 .75 11,854
Max. Dyn. Pressure (Max Q)00/00:00:52 1,260 1.2 28,037
SSME Throttle Up to 104% 00/00:01:01 1,499 1.49 38,681
SRB Staging 00/00:02:04 4,316 3.91 153,873
Negative Return 00/00:03:54 6,975 7.48 317,096
Main Engine Cutoff (MECO) 00/00:08:27 24,580 22.41 366,474
Zero Thrust 00/00:08:33 24,596 22.17 368,460
ET Separation 00/00:08:45
OMS 2 Burn 00/00:39:48
Galileo/IUS Deploy (orb 5)00/06:21:36
Deorbit Burn (orbit 81) 05/01:45:00
Landing (orbit 82) 05/02:45:00
Apogee, Perigee at MECO: 157 x 39 nm
Apogee, Perigee post-OMS 2: 161 x 161 nm
Apogee, Perigee post deploy: 177 x 161 nm
SPACE SHUTTLE ABORT MODES
Space Shuttle launch abort philosophy aims toward safe and intact recovery
of the flight crew, orbiter and its payload. Abort modes include:
* Abort-To-Orbit (ATO) -- Partial loss of main engine thrust late enough to
permit reaching a minimal 105-nautical mile orbit with orbital
maneuvering system engines.
* Abort-Once-Around (AOA) -- Earlier main engine shutdown with the
capability to allow one orbit around before landing at Edwards Air Force
Base, Calif.; White Sands Space Harbor (Northrup Strip), N.M.; or the Shuttle
Landing Facility (SLF) at Kennedy Space Center (KSC), Fla.
* Trans-Atlantic Abort Landing (TAL) -- Loss of two main engines midway
through powered flight would force a landing at Ben Guerir, Morocco; Moron,
Spain; or Banjul, The Gambia.
* Return-To-Launch-Site (RTLS) -- Early shutdown of one or more engines
and without enough energy to reach Ben Guerir, would result in a pitch
around and thrust back toward KSC until within gliding distance of the SLF.
STS-34 contingency landing sites are Edwards AFB, White Sands, KSC, Ben
Guerir, Moron and Banjul.
SUMMARY OF MAJOR ACTIVITIES
Day One
Ascent
Post-insertion checkout
Pre-deploy checkout
Galileo/Inertial Upper Stage (IUS) deploy
Detailed Secondary Objective (DSO)
Polymer Morphology (PM)
Sensor Technology Experiment (STEX) activation
Day Two
Galileo/IUS backup deploy opportunity
DSO
IMAX
PM
Shuttle Solar Backscatter Ultraviolet (SSBUV) activation
Shuttle Student Involvement Program (SSIP)
Day Three
DSO
IMAX
Mesoscale Lightning Experiment (MLE)
PM
Day Four
DSO
IMAX
MLE
PM
SSBUV deactivation
Day Five
DTO/DSO
GHCD operations
PM
STEX deactivation
Flight control systems (FCS) checkout
Cabin stow
Landing preparations
Day Six
PM stow
Deorbit preparation
Deorbit burn
Landing at Edwards AFB
LANDING AND POST LANDING OPERATIONS
Kennedy Space Center, Fla., is responsible for ground operations of the
orbiter once it has rolled to a stop on the runway at Edwards Air Force
Base, Calif. Those operations include preparing the Shuttle for the return
trip to Kennedy.
After landing, the flight crew aboard Atlantis begins "safing" vehicle
systems. Immediately after wheel stop, specially garbed technicians will
first determine that any residual hazardous vapors are below significant
levels for other safing operations to proceed.
A mobile white room is moved into place around the crew hatch once it
is verified that there are no concentrations of toxic gases around the
forward part of the vehicle. The flight crew is expected to leave Atlantis
about 45 to 50 minutes after landing. As the crew exits, technicians enter
the orbiter to complete the vehicle safing activity.
Once the initial aft safety assessment is made, access vehicles are
positioned around the rear of the orbiter so that lines from the ground
purge and cooling vehicles can be connected to the umbilical panels on the
aft end of Atlantis.
Freon line connections are completed and coolant begins circulating
through the umbilicials to aid in heat rejection and protect the orbiter's
electronic equipment. Other lines provide cooled, humidified air to the
payload bay and other cavities to remove any residual fumes and provide a
safe environment inside Atlantis.
A tow tractor will be connected to Atlantis and the vehicle will be
pulled off the runway at Edwards and positioned inside the Mate/Demate
Device (MDD) at nearby Ames-Dryden Flight Research Facility. After the
Shuttle has been jacked and leveled, residual fuel cell cryogenics are
drained and unused pyrotechnic devices are disconnected prior to returning
the orbiter to Kennedy.
The aerodynamic tail cone is installed over the three main engines,
and the orbiter is bolted on top of the 747 Shuttle Carrier Aircraft for the
ferry flight back to Florida. Pending completion of planned work and
favorable weather conditions, the 747 would depart California about 6 days
after landing for the cross-country ferry flight back to Florida. A refueling
stop is necessary to complete the journey.
Once back at Kennedy, Atlantis will be pulled inside the hangar-like
facility for post-flight inspections and in-flight anomaly troubleshooting.
These operations are conducted in parallel with the start of routine
systems reverification to prepare Atlantis for its next mission.
GALILEO
Galileo is a NASA spacecraft mission to Jupiter to study the planet's
atmosphere, satellites and surrounding magnetosphere. It was named for
the Italian renaissance scientist who discovered Jupiter's major moons by
using 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. On the way to Jupiter, Galileo also will
observe Venus, the Earth-moon system, one or two asteroids and various
phenomena in interplanetary space.
Galileo will be boosted into low-Earth orbit by the Shuttle Atlantis and
then boosted out of Earth orbit by a solid rocket Inertial Upper Stage. The
spacecraft will fly past Venus and twice by the Earth, using gravity assists
from the planets to pick up enough speed to reach Jupiter. Travel time from
launch to Jupiter is a little more than 6 years.
In December 1995, the Galileo atmospheric probe will conduct a brief,
direct examination of Jupiter's atmosphere, while the larger part of the
craft, the orbiter, begins a 22-month, 10-orbit tour of major satellites and
the magnetosphere, including long-term observations of Jupiter throughout
this phase.
The 2-ton Galileo orbiter spacecraft carries 9 scientific instruments.
There are another six experiments on the 750-pound probe. The spacecraft
radio link to Earth serves as an additional instrument for scientific
measurements. The probe's scientific data will be relayed to Earth by the
orbiter during the 75-minute period while the probe is descending into
Jupiter's atmosphere. Galileo will communicate with its controllers and
scientists through NASAUs Deep Space Network, using tracking stations in
California, Spain and Australia.
GALILEO MISSION EVENTS
Launch Window (Atlantis and IUS) Oct. 12 to Nov. 21, 1989
(Note: for both asteroids, closes in mid-October)
Venus flyby ( 9,300 mi) *Feb. 9, 1990
Venus data playback Oct. 1990
Earth 1 flyby ( about 600 mi) *Dec. 8, 1990
Asteroid Gaspra flyby (600 mi) *Oct. 29, 1991
Earth 2 flyby (200 mi) *Dec. 8, 1992
Asteroid Ida flyby (600 mi) *Aug. 28, 1993
Probe release July 1995
Jupiter arrival Dec. 7, 1995
(includes Io flyby, probe entry and relay, Jupiter orbit insertion)
Orbital tour of Galilean satellites Dec '95-Oct '97
*Exact dates may vary according to actual launch date
EARTH TO JUPITER
Galileo will make 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 been observed close up, and obtain data on other
phenomena of interplanetary space.
Scientists are currently studying how to use the Galileo scientific
instruments and the limited ability to collect, store and transmit data
during the early phase of flight to make the best use of these opportunities.
Instruments designed to observe Jupiter's atmosphere from afar can
improve our knowledge of the atmosphere of Venus and sensors designed for
the study of Jupiter's moons can add to our information about our own moon.
VENUS
The Galileo spacecraft will approach Venus early in 1990 from the night
side and pass across the sunlit hemisphere, allowing observation of the
clouds and atmosphere. Both infrared and ultraviolet spectral observations
are planned, as well as several camera images and other remote
measurements. The search for deep cloud patterns and for lightning storms
will be limited by the fact that all the Venus data must be tape-recorded on
the spacecraft for playback 8 months later.
The spacecraft was originally designed to operate between Earth and
Jupiter, where sunlight is 25 times weaker than at Earth and temperatures
are much lower. The VEEGA mission will expose 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 front
end of the spacecraft must be aimed precisely at the Sun, with the main
antenna furled for protection from the Sun's rays until after the first Earth
flyby in December 1990. This precludes the use of the Galileo high-gain
antenna and therefore, scientists must wait until the spacecraft is close to
Earth to receive the recorded Venus data, transmitted through a low-gain
antenna.
FIRST EARTH PASS
Approaching Earth for the first time about 14 months after launch, the
Galileo spacecraft will observe, from a distance, the nightside of Earth and
parts of both the sunlit and unlit sides of the moon. After passing Earth,
Galileo will observe Earth's sunlit side. At this short range, scientific data
are transmitted at the high rate using only the spacecraft's low-gain
antennas. The high-gain antenna is to be unfurled like an umbrella, and its
high-power transmitter turned on and checked out, about 5 months after the
first Earth encounter.
FIRST ASTEROID
Nine months after the Earth passage and still in an elliptical solar orbit,
Galileo will enter the asteroid belt, and two months later, will have its
first asteroid encounter. Gaspra is believed to be a fairly representative
main-belt asteroid, about 10 miles across and probably similar in
composition to stony meteorites.
The spacecraft will pass within about 600 miles at a relative speed of
about 18,000 miles per hour. It will collect several pictures of Gaspra and
make spectral measurements to indicate its composition and physical
properties.
SECOND EARTH 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 ellipse (with a 6-year period) to reach as
far as Jupiter. The second flyby of Earth will pump the orbit up to that
size, acting as a natural apogee kick motor for the Galileo spacecraft.
Passing about 185 miles above the surface, near the altitude at which it
had been deployed from the Space Shuttle almost three years earlier,
Galileo will use Earth's gravitation to change the spacecraft's flight
direction and pick up about 8,000 miles per hour in speed.
Each gravity-assist flyby requires about three rocket-thrusting
sessions, using Galileo's onboard retropropulsion module, to fine-tune the
flight path. The asteroid encounters require similar maneuvers to obtain
the best observing conditions.
Passing the Earth for the last time, the spacecraft's scientific
equipment will make thorough observations of the planet, both for
comparison with Venus and Jupiter and to aid in Earth studies. If all goes
well, there is a good chance that Galileo will enable scientists to record
the motion of the moon about the Earth while the Earth itself rotates.
SECOND ASTEROID
Nine months after the final Earth flyby, Galileo may have a second
asteroid-observing opportunity. Ida is about 20 miles across. Like Gaspra,
Ida 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 will be nearly 28,000 miles per hour, with a
planned closest approach of about 600 miles.
APPROACHING JUPITER
Some 2 years after leaving Earth for the third time and 5 months before
reaching Jupiter, Galileo's probe must separate from the orbiter. The
spacecraft turns to aim the probe precisely for its entry point in the
Jupiter atmosphere, spins up to 10 revolutions per minute and releases the
spin-stabilized probe. Then the Galileo orbiter maneuvers again to aim for
its own Jupiter encounter and resumes its scientific measurements of the
interplanetary environment underway since the launch more than 5 years
before.
While the probe is still approaching Jupiter, the orbiter will have its
first two satellite encounters. After passing within 20,000 miles of
Europa, it will fly about 600 miles above Io's volcano-torn surface, twenty
times closer than the closest flyby altitude of Voyager in 1979.
AT JUPITER
The Probe at Jupiter
The probe mission has four phases: launch, cruise, coast and
entry-descent. During launch and cruise, the probe will be carried by the
orbiter and serviced by a common umbilical. The probe will be dormant
during cruise except for annual checkouts of spacecraft systems and
instruments. During this period, the orbiter will provide the probe with
electric power, commands, data transmission and some thermal control.
Six hours before entering the atmosphere, the probe will be shooting
through space at about 40,000 mph. At this time, its command unit signals
"wake up" and instruments begin collecting data on lightning, radio
emissions and energetic particles.
A few hours later, the probe will slam into Jupiter's atmosphere at