OBJECT = MISSION MISSION_NAME = "GALILEO" OBJECT = MISSION_INFORMATION MISSION_NAME = "GALILEO" MISSION_START_DATE = 1977-10-01 MISSION_STOP_DATE = 1997-11-11 MISSION_ALIAS_NAME = "JUPITER ORBITER-PROBE (JOP)" MISSION_DESC = " Mission Overview ================ The Galileo mission utilizes a single launch of a combined Orbiter and Probe using the space shuttle Atlantis and an inertial upper stage (IUS) to inject the Galileo spacecraft on its interplanetary trajectory to Jupiter. The launch window occurs from October 12, 1989 to November 21, 1989. Since the IUS does not have the energy to inject Galileo on a direct trajectory to Jupiter, the spacecraft will instead be launched first towards Venus for the first leg of its Venus-Earth-Earth gravity assist (VEEGA) trajectory to Jupiter. Target-of-opportunity science observations will be made at Venus (closest approach February 10, 1990), the first Earth encounter (closest approach to Earth and Moon December 8, 1990), the asteroid Gaspra (closest approach October 29, 1991), the second Earth encounter (closest approach to Earth and Moon December 8, 1992), and the asteroid Ida (closest approach August 28, 1993). At about 150 days before Galileo arrives at Jupiter, the Probe is separated from the Orbiter. From this moment in time, the Probe is on a ballistic trajectory to the Probe entry point, about 6 degrees north latitude, into the atmosphere of Jupiter. Using its 400 Newton engine for the first time, the Orbiter executes an Orbiter deflection maneuver to keep from following the Probe into the atmosphere of Jupiter, and to retarget the Orbiter to the proper encounter conditions required for the Jupiter Orbit Insertion phase of the mission. A close flyby (about 1,000 kilometer altitude) of the Jovian satellite Io occurs in this phase for the purpose of science observations as well as to slow the Orbiter down relative to Jupiter by nearly 200 meters/second in order to reduce the propellant required during the Jupiter Orbit Insertion (JOI) 400 Newton engine burn to capture Galileo into Jupiter's orbit. Perijove of about 4 Jupiter radii occurs about 4 hours after Io encounter. A few minutes after perijove passage, the Probe entry and beginning of the relay of data from the Probe to the Orbiter occurs. The Probe mission and data relay lasts 75 minutes, after which JOI is performed, slowing the Orbiter down relative to Jupiter by about 630 meters/second. The initial orbit period is about 200 days. A large 400 Newton engine burn is performed at the first apojove in order to raise perijove from 4 Jupiter radii to about 9 Jupiter radii, thus allowing at least 11 orbits with 10 targeted satellite encounters to be completed by the Orbiter without exceeding the allowed total accumulated radiation exposure at the spacecraft. Only three orbits would be allowed before exceeding this limit if perijove were allowed to stay at 4 Jupiter radii, where the radiation environment is very severe. Also during this perijove raise maneuver, Galileo is targeted to the satellite Ganymede, the first of its Galilean satellite encounters following JOI. At this point, the targeting to satellite encounters begins, such that a satellite tour consisting of a minimum of 10 targeted satellite encounters is achieved within the 23 month period allotted for the satellite tour. During the course of the satellite tour, the orientation, shape and size of the spacecraft orbits around the Jovian system, referred to as petals because of how the spacecraft orbits appear on a plan view of the Jovian satellite tour trajectory, is controlled almost exclusively by gravity assists of the satellites themselves. The orbit periods are pumped down by successive encounters with the satellites from the initial 200 days to approximately 35-40 days between encounters. At the 8th orbit, when the orbit petal orientation is approximately in the anti-sun direction, the period is again pumped up to about 100 days, allowing one of the primary objectives, probing the Jovian magnetotail, to be accomplished. After this magnetotail orbit, the period is again pumped down, by gravity assist encounters with the Jovian satellites, to 35-40 days for the final 2-3 targeted encounters. (Refer to O'Neil, 1991; the Galileo Science Requirements Document, PD 625-50; and Wolf, et al, IOM GLL-NAV-92-90, May 12, 1992). Mission Phases ============== LAUNCH ------ Galileo was launched on October 18, 1989 at 1654 GMT aboard the Space Shuttle Atlantis (OV-104), flight STS-34. An Inertial Upper Stage (IUS-19) placed Galileo on its Earth-to-Venus trajectory. Following the IUS burn, Galileo configured itself for solo flight and separated from the IUS on October 19, 1989 at 0107 GMT. (Refer to O'Neil, 1991). Spacecraft Id : GO Target Name : VENUS Mission Phase Start Time : 1989-10-18T00:00:0 Mission Phase Stop Time : 1989-10-19T00:00:0 Spacecraft Operations Type : FLYBY INTERPLANETARY CRUISE --------------------- The trajectory of the spacecraft from Earth to Jupiter was dictated by the limited propulsion capability allowed within the Space Shuttle to boost the spacecraft from earth orbit to an interplanetary trajectory. This limit prevented a direct trajectory from Earth to Jupiter; instead a 'VEEGA' trajectory was used to achieve the energy necessary to send Galileo to Jupiter. The acronym VEEGA is from the trajectory description: Venus-Earth- Earth Gravity Assist. In this trajectory, Galileo passes Venus once, then flies by Earth twice, thus obtaining three gravity assists before heading toward Jupiter. (Refer to D'Amario, et al, Space Science Reviews, 1992.) Spacecraft Id : GO Target Name : JUPITER Mission Phase Start Time : 1989-10-19T00:00:0 Mission Phase Stop Time : 1995-10-08T00:00:0 Spacecraft Operations Type : FLYBY EARTH-VENUS CRUISE ------------------ End of Launch sequence to March 5, 1990. This phase includes the encounter with the planet Venus. Spacecraft Id : GO Target Name : VENUS Mission Phase Start Time : 1989-10-19T00:00:0 Mission Phase Stop Time : 1990-03-05T00:00:0 Spacecraft Operations Type : FLYBY VENUS ENCOUNTER --------------- A 10 day single load sequence provided the sequencing resources for the Venus encounter. The data gathered was put entirely onto the onboard tape recorder, since the high gain antenna had to remain furled behind its sunshade during this near-sun activity, and the low gain antenna did not have the performance for real-time science data transmission to Earth during the Venus encounter. The Venus encounter data was played back to Earth in November 1990, when Galileo was close enough to Earth that science data rates could be achieved over the low gain antenna. Upstream energetic particles were detected, bowshock crossings were indicated, and the plasma wave instrument saw evidence of lightning discharges. Eighty-one images by the Solid State Imaging experiment were taken, which proved useful in atmospheric motion studies. (Refer to O'Neil, 1991). Spacecraft Id : GO Target Name : VENUS Mission Phase Start Time : 1990-02-06T00:00:0 Mission Phase Stop Time : 1990-02-16T00:00:0 Spacecraft Operations Type : FLYBY VENUS-EARTH CRUISE ------------------ Interplanetary cruise from Venus, around the sun, and back to and past the Earth. This phase includes the first Earth encounter. Spacecraft Id : GO Target Name : EARTH Mission Phase Start Time : 1990-02-19T00:00:0 Mission Phase Stop Time : 1991-04-29T00:00:0 Spacecraft Operations Type : FLYBY EARTH1 ENCOUNTER ---------------- Following Voyager's Neptune encounter in 1989, every planet in the solar system had been encountered and explored from deep space by an Earth-launched spacecraft except Pluto and Earth. The first Earth encounter by Galileo in December 1990 left only Pluto thus unexplored. The spacecraft trajectory took Galileo virtually up the Earth's magnetotail, providing unprecedented opportunity for fields and particles measurements of the magnetotail. The plasma science experiment results brought into question the validity of the previous assumption that the bulk flows of the ion and electron plasmas in the distant magnetotail are identical. Spectral mapping observations of Australia and Antarctica were made by the near infrared mapping spectrometer. A first ever time lapse movie, in six colors, of the rotating Earth over a period slightly greater than one day was made by the solid state imaging experiment. Multispectral imaging of the western nearside and eastern farside of the Moon were obtained by the SSI. This data showed that Orientale Basin ejecta deposits are similar to typical highlands deposits such as the soils at the Apollo 16 site, while observations of the South Pole-Aitken basin interior contain characteristics that appear distinctively different from that of nearside maria, thus providing new information on mare deposits on the limb and farside of the Moon. (Refer to Clarke, 1988; Clarke and Fanale, 1989; Fanale, 1990; Head et al, 1991; Chapman, 1991; Ingersoll, 1991; Frank, 1991; and O'Neil, 1991). Spacecraft Id : GO Target Name : EARTH Target Name : MOON Mission Phase Start Time : 1990-11-08T00:00:0 Mission Phase Stop Time : 1990-12-16T00:00:0 Spacecraft Operations Type : FLYBY EARTH-EARTH CRUISE ------------------ Interplanetary cruise from Earth, around the sun, and back to and past the Earth a second time. This phase includes both the encounter with the asteroid Gaspra and the second Earth encounter. Spacecraft Id : GO Target Name : EARTH Mission Phase Start Time : 1991-04-29T00:00:0 Mission Phase Stop Time : 1993-04-12T00:00:0 Spacecraft Operations Type : FLYBY GASPRA ENCOUNTER ---------------- On 29 October 1991 Galileo passed Gaspra at a distance of approximately 1,600 km and a speed of approximately 30,000 km per hour. Color and black and white images were taken of Gaspra as well as measurements to indicate composition and physical properties. The data were stored on the spacecraft tape recorder and later played back to Earth. Spacecraft Id : GO Target Name : GASPRA Mission Phase Start Time : 1991-10-29T00:00:0 Mission Phase Stop Time : 1991-10-29T00:00:0 Spacecraft Operations Type : FLYBY EARTH2 ENCOUNTER ---------------- On 8 December 1992 Galileo flew by Earth the second time for its third and last gravity assist on its flight to Jupiter. Galileo flew past the north pole of the moon at an altitude of approximately 111,000 km. Galileo's speed increased by approximately 13,300 km per hour. Critical instrument and spacecraft calibrations needed for the Jupiter mission were carried out, as were observations of the Moon and Earth. These included the first-ever near infrared observation of the Moon's North pole, and observations of Indonesia, Australia, Antarctica and the Earth's aurora. Spacecraft Id : GO Target Name : EARTH Target Name : MOON Mission Phase Start Time : 1992-11-08T00:00:0 Mission Phase Stop Time : 1992-12-20T00:00:0 Spacecraft Operations Type : FLYBY " MISSION_OBJECTIVES_SUMMARY = " Mission Objectives Summary ========================== The Galileo mission has three major and co-equal general science objectives. They are (1) to investigate the chemical composition and physical state of Jupiter's atmosphere, (2) to investigate the chemical composition and physical state of the Jovian satellites, and (3) to investigate the structure and physical dynamics of the Jovian magnetosphere. (Refer to Galileo Project Plan, PD 625-1). " END_OBJECT = MISSION_INFORMATION OBJECT = MISSION_HOST INSTRUMENT_HOST_ID = GO OBJECT = MISSION_TARGET TARGET_NAME = EARTH END_OBJECT = MISSION_TARGET END_OBJECT = MISSION_HOST OBJECT = MISSION_HOST INSTRUMENT_HOST_ID = GO OBJECT = MISSION_TARGET TARGET_NAME = GASPRA END_OBJECT = MISSION_TARGET END_OBJECT = MISSION_HOST OBJECT = MISSION_HOST INSTRUMENT_HOST_ID = GO OBJECT = MISSION_TARGET TARGET_NAME = JUPITER END_OBJECT = MISSION_TARGET END_OBJECT = MISSION_HOST OBJECT = MISSION_HOST INSTRUMENT_HOST_ID = GO OBJECT = MISSION_TARGET TARGET_NAME = MOON END_OBJECT = MISSION_TARGET END_OBJECT = MISSION_HOST OBJECT = MISSION_HOST INSTRUMENT_HOST_ID = GO OBJECT = MISSION_TARGET TARGET_NAME = VENUS END_OBJECT = MISSION_TARGET END_OBJECT = MISSION_HOST OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "CHAPMAN1991" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "CLARKE1988" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "CLARKE1989" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "FANALE1990" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "FRANK1991" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "GLLIOM1992" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "GLLMS1991" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "GLLPP1985" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "GLLSRD1989" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "HEAD1991B" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "INGERSOLL1991" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "SSR1992" END_OBJECT = MISSION_REFERENCE_INFORMATION END_OBJECT = MISSION END