Lunar Prospector Status Report #81

May 7, 1999 - 1:00 p.m. EST (10:00 a.m. PST)

The Lunar Prospector spacecraft continues to collect good science data in the extended mission orbit. All five science instruments are on: the Gamma Ray Spectrometer (GRS), the Neutron Spectrometer (NS), the Magnetometer (MAG), the Electron Reflectometer (ER), and the Alpha Particle Spectrometer (APS). Data continues to be collected for the Doppler Gravity Experiment (DGE) as well.

During the last week, there were 2 occurrences where the battery voltage dropped to below the red limit during eclipse with the propellant tank heater on. Since these events (DOY 121 and 123), the transmitter has been cycled off during heater event eclipses if the battery has not been fully recharged.

On May 2, the MAG/ER was reconfigured for normal data collection, as the full moon period ended.

On May 5, the 5th orbit burn sequence to maintain the extended mission orbit was executed. This maneuver moved periapsis to the far side, where it will generally remain through the end of mission. A timeline is given below (transmit times in HHMM GMT on Day of Year 125).

125/1707 EM/Pressure transducer ON
125/1709 thruster A1/A2 heaters on
125/1714 maneuver parameters loaded
125/1735 fire part 1 delta-V, A1/A2 for 25.5 sec, 4.0 m/s, 0.33 kg fuel)
125/1742 thruster A1/A2 heaters on
125/1755 maneuver parameters loaded
125/1833 fire part 2 delta-V, A1/A2 for 26.0 sec, 4.1 m/s, 0.33 kg fuel)
125/1834 thrusters safed

All commands (58 total) executed normally this week

Current spacecraft state (0000 GMT 5/7/99, DOY 127):

Orbit: 5954
Downlink: 3600 bps
Spin Rate: 12.05 rpm

Spin Axis Attitude (ecliptic):
Latitude: -88.5 deg
Longitude: 039 deg

Trajectory:
Periapsis Alt: 21.4 km
Apoapsis Alt: 38.6 km
Period: 111 min

Occultations: 21 minutes
Eclipses: 48 minutes
Propellant Remaining: 11.81 kg