Galileo Orbiter

Launch data: Designation  20298 / 89084B Launch date  18 Oct 1989 - 16:53:40 UT Launch site  KSC, LC-39B Launch vehicle  Shuttle STS-34 (IUS) Mission  Venus Flyby, Asteroid Flyby, Earth Flyby, Jupiter Orbiter Heliocentric orbit Perihelion / Aphelion   Incl. to ecliptic   ° Period   min

Galileo - Credit: NASA.

STS-34 Galileo spacecraft / IUS deployment sequence in OV-104's payload bay - Credit:NASA.

STS-34 Galileo spacecraft / inertial upper stage (IUS) deployment - Credit: NASA.

Galileo diagram

Description:

• Galileo was designed to perform in-depth studies of Jupiter's atmosphere, satellites, and surrounding magnetosphere. The mission was named in honour of Galileo Galilei, the Italian Renaissance scientist who discovered Jupiter's major moons in 1610. The spacecraft's primary mission was the deployment of an atmospheric probe into Jupiter's atmosphere (Dec.7, 1995). Following deployment, the vehicle went into orbit around Jupiter to continue its investigations. During its interplanetary cruise, the planned deployment of Galileo's high gain antenna failed, forcing use of the its low gain antennas at much lower than planned data rates. Despite the failure, it is believed approximately 70% of the original science objectives will be achieved. During its flight to Jupiter, Galileo also performed the 1st and 2nd asteroid flybys - Gaspra (Oct.1991) and Ida (Aug.1993). Galileo was also the only vehicle in a position to obtain images of the far side of Jupiter when more than 20 fragments of Comet Shoemaker-Levy plunged into Jupiter's atmosphere in July 1994.
• Spacecraft: Orbiter: Dual-spin stabilised. Spinning section (3 rpm) houses fields and particles instruments, antennas, propulsion system, computers, most other support systems. Despun section provides fixed orientation for remote sensing instruments, star scanner, gyros. Bipropellant propulsion system (HHM, NTO) from Federal Republic of Germany uses 12 10N thrusters, 1 400N main engine. S-band communications through 2 omni LGAs (40 bps typical), deployable 4.8 meter wire mesh HGA failed to deploy (planned downlink rate >100 kbps). Redundant flight computers with high level of fault protection. Powered by 2 RTGs (570W BOL, 485W EOL).11 meter deployable boom for some science instruments.
• Probe: Deceleration module, consisting of aeroshell and aft cover, to slow initial descent and provide thermal control.2.5 m parachute controls descent following deceleration module release. Descent module contains redundant L-band transmitters, instrument package, batteries. Downlink to Orbiter at 128 bps. Primary lithium-sulphur batteries (18 Ahr total) provide power during descent.
• Payload: Orbiter: Near-Infrared Mapping Spectrometer (NIMS) - makes multispectral images for atmosphere and surface chemical analysis, Ultraviolet Spectrometer (UVS) - studies gases, Solid-State Imager (SSI) - visible imaging with 800 x 800 array CCD, Photopolarimeter (PPR) - measures radiant and reflected energy, Magnetometers (MAG), Dust Detection Experiment (DDE), Plasma Investigation (PLS), Energetic Particle Detector (EPD), Plasma Wave Investigation (PWS), Radio Science Probe: Atmosphere Structure Experiment - measures temperature, pressure and deceleration, Probe Mass Spectrometer - atmospheric composition studies, Helium Abundance Detector - atmospheric composition studies, Probe Nephelometer - cloud location and cloud-particle observations, Net Flux Radiometer - measures the difference, upward versus downward, in radiant energy flux at each altitude, Lightning and Energetic Particles - measures light and radio emissions associated with lightning and energetic particles in Jupiter's radiation belts.

Mission details:

• Deployed from STS-34 18 Oct 1989.
• The Galileo spacecraft flew 960 km from Earth at 20:35 UT on Dec 8, 1990 in a gravity assist maneuver.
• The Antenna release failed on April 11, 1991 and subsequent attempts to release it failed, reducing data return rate by an order of magnitude.
  

  Galileo passed less than 1600 km from minor planet (951) Gaspra at 22:37 UT on Oct 29, 1991. Data from the encounter will be stored on board and returned to Earth in late 1992. The Galileo probe flew 2400 km from minor planet (243) Ida at 16:22 UTC on Aug 28, 1993. This is Galileo's second and last minor planet encounter. The greatest discovery from the Galileo fly-by was that Ida has a natural satellite. Although Galileo flew past Ida in August 1993, the discovery wasn't made until late in February 1994 when images stored on the spacecraft's tape recorder were finally transmitted to Earth. The moon has been named Dactyl by the International Astronomical Union. Dactyl is the first natural satellite of an asteroid ever discovered and photographed

  
  
• The Galileo probe made a TCM (Trajectory Correction Maneuver) from Oct 4 to Oct 8, 1993 (in five daily segments). The reboost of the Compton Observatory's orbit is proceeding; after the first two burns the orbit had been raised from 337 km to 355 km; the original orbit was 452 km high.
• The Galileo Probe separated from the Orbiter at 0530 UTC on Jul 13, 1995 and entered Jupiter's atmosphere on Dec 07, 1995.
• The Galileo Orbiter successfully completed the ODM maneuver on Jul 27, 1995. This was the first major firing of the main liquid propellant engine which will be used for orbit insertion. The Orbiter is now targeted for its flyby of Io, while the Probe is on a Jovian impact trajectory.
• Galileo Orbiter was at 2153 UTC on Dec 7, 1995 at a distance of 214600 km from the center of the giant planet. Closest approach to Europa was 30921 km at 1309 UTC Dec 7, and to Io was 892 km at 1745 UTC. Galileo has now entered orbit around Jupiter. The S400 liquid apogee engine ignited at 0027 UTC Dec 8 and completed its burn at 0116 UTC on Dec 8. Galileo's first orbit was planned to have a perijove of 2 Jupiter radii and an apojove of 250 Jupiter radii.
• The Galileo orbiter made a perijove raise burn at apojove on Mar 14, 1996 changing its orbit from 185000 x 19000000 km to 670000 x 19000000 km; and successfully completed its flyby of Ganymede on Jun 27, 1996.
• The Galileo Orbiter flew again past Ganymede at a distance of 262 km from the surface on Sep 6, 1996. The probe's third close approach to Jupiter was on Sep 7 at a distance of 10.7 Jovian radii.
• Galileo made a close flyby of Callisto on Nov 4, 1996 at 1334 UTC at a distance of 1118 km, and reached perijove on orbit 3 two days later. Next orbit it will fly by Europa, on Dec 19.
• Galileo completed its orbit 6 Europa encounter on Feb 20, 1997. It flew 587 km from Europa. Its next orbit will take it past Ganymede on Apr 5.
• The Galileo Orbiter had a safemode event at around 1814 UTC on Jul 20, 1998 during its inbound approach to the inner Jovian system, causing loss of almost all the data from the Europa 16 encounter. Telemetry from the spacecraft has now resumed. Galileo passed 1837 km from Europa's surface at 0507 UTC on Jul 21, just after perijove at 632000 km radius, at 0019 UTC on Jul 21.
• The Galileo probe made another flyby of Europa at 0210 UTC on Feb 1, 1999 at an altitude of 1495 km, and on Jul 1,1999 Galileo flew past Callisto again.
• Galileo made a 300 km flyby of Io on Nov 26, 1999 at 0400 UTC. Galileo is probably now in a 407000 x 6200000 km x 1.3 deg orbit around Jupiter.
• Galileo safely completed the Europa-26 encounter on Jan 3, 2000. At 1800 UTC on Jan 3 Galileo passed 343 km from Europa; at 0333 on Jan 4 it flew 343000 km from Jupiter's cloud tops; at 0656 on Jan 4 it flew 214000 km from Io. The Galileo Europa Mission ends on Jan 31, 2000.
• The Galileo probe made its encounter G28 perijove pass of the Jupiter system on May 30-31, 2000. Reported closest approach to Jupiter was 479000 km at 0553 UTC on May 31; this is probably distance above cloud tops rather than from Jupiter center (an extra 71000 km). The main event was a Ganymede flyby at an altitude of 808 km at 1010 UTC on May 30. Galileo is now apparently in a high eccentricity orbit which will bring it back for its next perijove on Dec 28. It will be in a record high apojove of 20.7 million kilometers on September 8, inside the orbits of the outermost Jovian moons.
• Galileo made a 2326 km altitude flyby of Ganymede at 0825 UTC on Dec 28, 2000. Perijove was 464030 km at 0326 UTC Dec 29. Galileo is now in a 0.53 x 15.47 Gm orbit with next perijove around May 23.
• Galileo reached perijove flying 450400 km above the Jovian cloud tops at 1734 UTC on 2001 May 23. Closest approach to Io was 341771 km at 1718 UTC; Europa was at 718513 km at 2351 UTC on May 23 and Ganymede was passed at 358700 km at 1120 UTC on May 24.
  A close 123 km pass of Callisto will occur on May 25 at around 1124 UTC, reducing Galileo's perijove on its next orbit to target it for an Io flyby.
• Galileo passed Io at a distance of 200 km at 0459 UTC on Aug 6, 2001. Closest approach to Jupiter on this orbit was an altitude of 350000 km at 0452 UTC on Aug 6.
• Galileo completed the Io 32 flyby on Oct 16, 2001. It passed 343000 km from Jupiter's cloud tops at 2252 UTC on Oct 15, and only 181 km from Io's south polar region at 0223 UTC on Oct 16. It will retreat to 11 million km from Jupiter by Nov 23 before coming back in for an equatorial pass of Io on Jan 17, 2002.
• Galileo made a 102 km flyby of Io on Jan 17, 2002 at 1409 UTC. Unfortunately the harsh radiation environment made the spacecraft safemode at 1341 UTC; it was reactivated at 0400 UTC on Jan 18. Closest approach to Jupiter was 322000 km at 1622 UTC on Jan 17. Galileo is now on its way back to an apoapsis of about 25 million km, and will fall back in to flyby Jupiter V (Amalthea) on Nov 5.
• Galileo passed 160 km from Amalthea (Jupiter V) on its final Jovian moon flyby. Closest approach was at 0618 UTC on Nov 5, 2002; perijove was at 0724 UTC at 71500 km above the cloud tops. A safemode at about 0648 UTC caused loss of some data from the encounter.
• Galileo is now in an orbit which will reach an apojove of 26.4 million km in Apr 2003. The Sun's gravity perturbs the orbit and causes the current orbit periapsis height of 71000 km to slowly drop, becoming negative in Jun 2003; Galileo will fall back to destructive entry into the Jovian clouds on Sep 2003 with a final Jovicentric/ecliptic orbit at that time of -9700 x 25434600 km x 1.7 deg.
• The Galileo Orbiter spacecraft entered the Jovian atmosphere on Sep 21, 2003 at 1857 UTC. Entry was at 48.2 km/s from an orbit with a periapsis 9700 km below the 1-bar atmospheric layer (used by convention as the nominal 'surface' of Jupiter). The spacecraft continued transmitting at least until it passed behind the limb of Jupiter at 1850:54 UTC, at which point it was 9283 km above the 1-bar level, surprising Galileo veterans who feared it might enter safemode due to the high radiation environment. It crossed the orbit of Callisto at around 1100 UTC on Sep 20, the orbit of Ganymede at around 0500 UTC on Sep 21, Europa's orbit at about 1145 UTC, Io's orbit at about 1500 UTC, Amalthea's orbit at 1756 UTC, and the orbits of Adrastea and Metis at 1825 UTC. No close approaches were made to any of the moons during this final suicide dive. Galileo was destroyed to prevent the possibility that its orbit would eventually be perturbed in such a way that it would crash on and biologically contaminate Europa, which is considered a possible place to search for life. Light travel time from Jupiter to Earth was 52 min 20 sec at the time of impact, and the final signal reached Earth at 1943:14 UTC.