The Galileo Probe Mission Events Timeline
The Galileo Probe Mission Events Timeline
- OCTOBER 18, 1989: LAUNCH
- The Galileo Orbiter and Probe are launched on the Space Shuttle
Atlantis. The Probe was attached to the Orbiter and two-way
communication occured between the two spacecraft via an umbilical
cable. Three status checks of the Probe and a system function test were
conducted during the approximately six year cruise together.
- JULY 13, 1995: 5:29 GMT: PROBE SEPARATION FROM ORBITER
- DISTANCE FROM JUPITER: 81,520,000 km (50,660,000 miles).
SPEED RELATIVE TO JUPITER: 20,448 km/hour ( 12, 706 mph )
The Galileo Orbiter/Probe was spun up to 10.5 rpm to provide
rotational stabilization of the Probe. The spin axis was precisely
aligned with its trajectory. The separation velocity of the
Probe was chosen so the gravitational pull of the Sun and
Jupiter alone would successfully guide it into Jupiter's
atmosphere on December 7, 1995. The Probe has no rocket engines for
course corrections. It will enter Jupiter's atmosphere at an
angle of 8.3 degrees to the horizontal. A 1.5 degree shallower angle
would cause the Probe to skip off back into space; a 1.5 degree
steeper angle would overheat the spacecraft and destroy it.
During and after separation the Galileo Probe remains in a dormant
state with only a Coast Timer operating. No communication from the Probe
until after atmospheric entry.
- DECEMBER 7, 1995 GALILEO PROBE ATMOSPHERIC ENTRY
- All the times listed below are relative to the time of atmospheric
entry (E). All altitudes listed below are relative to the level in
Jupiter's atmosphere where the atmospheric (barometric) pressure
equals Earth's sea level atmospheric pressure ( 1 bar of pressure,
14.7 lbs/square inch ). Atmospheric entry for the Galileo Probe is
defined to occur at an altitude of 450 km. At the atmospheric entry
level, the atmosphere is becoming thick enough to influence
the Probe's motion.
- ATMOSPHERIC ENTRY TIME (E): 22:04 GMT ( 2:04 PM PST )
- E - 6 hours: COAST TIMER INITIATES PROBE OPERATION
- DISTANCE FROM JUPITER = 600,000 km ( 373,000 miles )
SPEED RELATIVE TO JUPITER = 76,700 km/hour ( 47,600 mph )
HIGHLIGHTS: Warm-up and calibration of Probe scientific and engineering
instruments begins. "g-switches" are used to sense the deceleration of the Probe by
atmosphere as backup for timer malfunction.
- E - 3 hours: MEASUREMENTS OF JUPITER'S INNER RADIATION BELTS BEGIN
- DISTANCE FROM JUPITER = 360, 000 km ( 224,000 miles )
SPEED RELATIVE TO JUPITER = 97,200 km/hour ( 60,400 mph )
HIGHLIGHTS: The Energetic Particles Investigation begins measurements
of the energetic electrically charged particles trapped in a part of
Jupiter's intense radiation belts/ magnetic field not previously
explored. Four minute sample sets are taken at E-180 minutes, E-140 minutes, E-96 minutes, E-60 minutes, and continuing sample sets are acquired thereafter until entry.
- E: ATMOSPHERIC ENTRY
- ALTITUDE = 450 km ( 280 miles )
VELOCITY = 170,700 km/ hour ( 106,100 miles/hour )
INCIDENCE ANGLE= 8.3 degrees below horizontal.
LATITUDE = 6.5 degrees North (planetocentric)
LONGITUDE= 4.4 degrees West.
HIGHLIGHTS: Atmospheric Structure Instrument begins continuously
recording deceleration of Probe due to upper atmosphere. Atmospheric
density, pressure, and temperature can be inferred from such data.
- E + 56 seconds: PEAK AERODYNAMIC STRESS
- ALTITUDE = 100 km ( 62 miles )
VELOCITY = 99,200 km/hour ( 61,600 miles/hour )
ATMOSPHERIC PRESSURE = 0.007 bar
ATMOSPHERIC TEMPERATURE = -119 degrees Centigrade (C)
HIGHLIGHTS: As the Probe enters Jupiter's atmosphere, aerodynamic
forces quickly decelerate the Probe. The Probe experiences a force
equivalent to 230 times the strength of gravity at Earth's surface.
Largest aerodynamic force ever on a spacecraft entering the atmosphere
of a planet.
- E + 112 seconds: PILOT PARACHUTE DEPLOYED
- ALTITUDE = 50 km ( 31 miles )
VELOCITY = 3,200 km/hour ( 1,990 miles/hour )
ATMOSPHERIC PRESSURE = 0.07 bar
ATMOSPHERIC TEMPERATURE = -160 C
- E +114 seconds: MAIN PARACHUTE DEPLOYED
- ALTITUDE = 50 km ( 31 miles )
VELOCITY = 3,120 km/hour ( 1,940 mph )
ATMOSPHERIC PRESSURE = 0.07 bar
ATMOSPHERIC TEMPERATURE = -160 C
- E + 122 seconds: DECELERATION MODULE JETTISONED
- ALTITUDE = 48 km ( 30 miles )
VELOCITY = 1,630 km/hour ( 1,010 mph )
ATMOSPHERIC PRESSURE = 0.09 bar
ATMOSPHERIC TEMPERATURE = -160 C
- E + 126 seconds: DIRECT SCIENTIFIC MEASUREMENTS BEGIN
- ALTITUDE = 48 km ( 30 miles )
VELOCITY = 1,540 km/hour ( 960 mph )
ATMOSPHERIC PRESSURE = 0.09 bar
ATMOSPHERIC TEMPERATURE = -160 C
- E + 135 seconds: RADIO TRANSMISSION TO ORBITER BEGINS
- ALTITUDE = 40 km ( 25 miles )
VELOCITY = 890 km/hour ( 550 mph )
ATMOSPHERIC PRESSURE = 0.1 bar
ATMOSPHERIC TEMPERATURE = -160 C
HIGHLIGHTS: Data stored in memory up to this point in the mission is
transmitted along with the new measurements. To provide a backup to
the communications link with the Orbiter, the data is radioed to the
Orbiter in two nearly identical transmissions produced by separate
electronics and transmitters on the Probe.
- E + 4 minutes (approximate): VISIBLE CLOUD TOPS OF JUPITER REACHED
- ALTITUDE = 26 km ( 16 miles )
VELOCITY = 454 km/hour ( 282 mph )
ATMOSPHERIC PRESSURE = 0.3 bar
ATMOSPHERIC TEMPERATURE = -150 C
HIGHLIGHTS: The visible clouds of Jupiter are believed to be made
of frozen ammonia crystals.
- E + 8 minutes: ATMOSPHERIC PRESSURE SAME AS EARTH'S SEA-LEVEL PRESSURE
- ALTITUDE = 0 km ( 0 miles )
VELOCITY = 295 km/hour ( 183 mph )
ATMOSPHERIC PRESSURE = 1.0 bar
ATMOSPHERIC TEMPERATURE = -107 C
- E + 13 minutes (highly uncertain): A SECOND MAJOR CLOUD DECK IS ENCOUNTERED
- ALTITUDE = -21 km ( -13 miles )
VELOCITY = 234 km/hour ( 145 mph )
ATMOSPHERIC PRESSURE = 2.0 bar
ATMOSPHERIC TEMPERATURE = -67 C
HIGHLIGHTS: The existence and nature of these clouds is highly
uncertain.
- E + 24 minutes (highly uncertain): ENTER CLOUDS OF WATER
- ALTITUDE = -57 km ( -35 miles )
VELOCITY = 170 km/hour ( 106 mph )
ATMOSPHERIC PRESSURE = 5.0 bar
ATMOSPHERIC TEMPERATURE = 0 C
- E + 30 minutes: TEMPERATURE EQUALS ROOM TEMPERATURE ON EARTH
- ALTITUDE = -71 km ( -44 miles )
VELOCITY = 154 km/hour ( 96 mph )
ATMOSPHERIC PRESSURE = 6.7 bar
ATMOSPHERIC TEMPERATURE = 25 C
- E + 42 minutes: SUNSET OCCURS AT PROBE ENTRY SITE
- ALTITUDE = -100 km ( -62 miles )
VELOCITY = 126 km/hour ( 78 mph )
ATMOSPHERIC PRESSURE = 11.7 bars
ATMOSPHERIC TEMPERATURE = 79 C
- E + 60 minutes: END OF BASELINE MISSION
- ALTITUDE = -135 km ( - 84 miles )
VELOCITY = 104 km/hour ( 65 mph )
ATMOSPHERIC PRESSURE = 20 bars
ATMOSPHERIC TEMPERATURE = 140 C
HIGHLIGHTS: Below this level, effects of pressure and temperature on
Probe systems, limited battery capacity, and difficulty of radio
signal transmission through dense atmosphere and clouds may lead to
degraded Probe operation and data.
- E + 75 minutes: END OF PROBE DATA RECEPTION BY ORBITER
- ALTITUDE = -159 km (-99 miles)
VELOCITY = 92 km/hour (57 mph)
ATMOSPHERIC PRESSURE = 28 bars
ATMOSPHERIC TEMPERATURE = 185 C
HIGHLIGHTS: Determined by need to prepare Orbiter for Jupiter Orbit
Insertion.
Site Last Modified: November 30, 1995
Problems with this Web page should be directed to:
Curator: Gaye Graves
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Author: Julio Magalhães
magalhaes@galileo.arc.nasa.gov
Responsible NASA Official: Marcie Smith
marcie_smith@qmgate.arc.nasa.gov
Responsible NASA Official: Rich Young
ryoung@humbabe.arc.nasa.gov