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Lunar Prospector Status Report #7

January 12, 1998 - 10:00 a.m. EST (7:00 a.m. PST)

The Mission Control Center at NASA's Ames Research Center reports that the Lunar Prospector spacecraft has now been successfully commanded through 2/3 of the maneuvers required to put it into its final desired mapping orbit configuration approximately 62 miles (100 km) above the lunar surface. That was achieved with this morning's second lunar orbit insertion (LOI) burn. That burn began at 5:58 a.m. EST (2:58 a.m. PST), concluding 27 minutes later at 6:25 a.m. EST (3:25 a.m. PST) with the spacecraft in its scheduled 3.5-hour period orbit. The spacecraft continues to perform precisely as planned.

During LOI #2, the closest approach (periselene) altitude of the spacecraft was approximately 52 miles (83 km), and the furthest distance (aposelene) altitude was an estimated 1170 miles (1870 km). Closest approach during the second LOI burn occured at 6:12 a.m. EST (3:12 a.m. PST). Periapsis is about 30 degrees north and the orbit plane is currently almost perpendicular to the Earth-Moon line, so that if one is looking at the Moon one could see the entire orbit, with periapsis to the upper right and the aposelene about one-half a lunar diameter away from the Moon to the lower left. This means that the spacecraft never gets behind the Moon as seen from Earth and continuous communications can be maintained.

The third and final LOI burn is scheduled for tomorrow morning, beginning at approximately 6:27 a.m. EST (3:27 a.m. PST) and continuing for approximately 30 minutes. Following that burn, mission operations personnel report that they will be experiencing 20-minute occultations during each 2-hour orbit, increasing to 47 minutes within a week. The orbit plane is also perpendicular to the Moon-Sun line, so that the spacecraft will not go behind the Moon into shadow. The first eclipses start about 9 days after LOI burn # 3.

The current spacecraft configuration is: all science instruments on, 3600 bps on the omni antenna, spinning at 12.15 rpm with the spin axis in the LOI burn attitude. To date, the spacecraft has burned 57.95% of its initial fuel load of 138 kg (approx. 304 lbs). Tomorrow's LOI burn is expected to use another 17.4%, leaving 34 kg (approx. 75 lbs). This is sufficient to maintain the spacecraft's mapping orbit under predicted circumstances throughout its primary and extended missions.

A one-hour press conference and status briefing summarizing activities and accomplishments to date and highlighting upcoming events and scientific expectations for the Lunar Prospector mission is scheduled for the main auditorium at NASA Ames Research Center on Tuesday morning, Jan. 13, 1998 beginning at 9 a.m. PST (12 noon EST). The briefing will be carried live on NASA Television.

David Morse
Ames Research Center
Moffett Field, CA 94035