Lunar Prospector Status Report #64

January 8, 1999 - 1:00 p.m. EST (10:00 a.m. PST)

The Lunar Prospector spacecraft is operating well and all instruments continue to collect good data. The project celebrated the completion of the first year after launch this week; the science data has been of higher resolution than expected and all baseline mission objectives have been met.

There was no commanding this week.

The lunar gravity model has been updated using Doppler data collected in the 40-km altitude orbit. This model will be used to plan for extended mission operations. The magnetometer has already seen an order of magnitude increase in signal level due to the lower transition orbit, and they are looking forward to even higher resolution data in the extended mission orbit.

The final orbit for the extended mission was decided upon last week after a review of the lunar topography data with the Clementine team. Although a very low orbit (25-km average altitude) would provide somewhat higher resolution data, the project decided that a 30-km average altitude orbit would be used for the extended mission. The Clementine terrain data is very accurate (100 m), but there are large spatial gaps in the data (as large as 100 km), which mean that there could be mountain peaks on the order of several kilometers higher than the terrain maps indicate. The 30-km average altitude orbit will maintain a clearance of 9 km above known terrain, providing significant margin above the actual terrain.

The maneuver to go to the extended mission orbit is scheduled for January 15, 1999 (January 16 0200 GMT). Trajectory correction burns will be required every 28 days to maintain this orbit.

Current spacecraft state (0000 GMT 01/8/99):

Orbit: 4415
Downlink: 3600 bps
Spin Rate: 12.00 rpm

Spin Axis Attitude (ecliptic):
Latitude: -87.3 deg
Longitude: 229 deg

Trajectory:
Periapsis Alt: 31 km
Apoapsis Alt: 49 km
Period: 112 min

Occultations: 49 minutes
Eclipses: none
Propellant Remaining: 17.45 kg