Lunar Prospector Status Report #80

April 30, 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 have been 8 (of 13) occurrences of the battery
voltage reaching the yellow low-voltage limit (24.5 V) during an eclipse
while the propellant tank heater was on.

On April 28, 14 commands were sent to configure the MAG/ER instrument to
collect high resolution data during full moon. Since the solar magnetic
field is much stronger than the lunar magnetic field, the best lunar
magnetic field data is collected during full moon, when the earth is
between the sun and the moon, blocking the solar magnetic field, and the
moon's field is more easily measured. Full moon will occur April 30. All
commands executed nomi.

Current spacecraft state (0000 GMT 4/30/99, DOY 120):

Orbit: 5863
Downlink: 3600 bps
Spin Rate: 12.00 rpm

Spin Axis Attitude (ecliptic):
Latitude: -88.5 deg
Longitude: 040 deg

Trajectory:
Periapsis Alt: 23.7 km
Apoapsis Alt: 36.3 km
Period: 111 min

Occultations: 49 minutes
Eclipses: 48 minutes
Propellant Remaining: 12.47 kg

The next orbit maintenance burn is scheduled for May 5. This maneuver will put the spacecraft into a similar 30-km average altitude orbit, but one that will have periapsis on the far side of the moon for most of the time, rather than the near side of the moon as the current orbit has. Maneuvers will then continue once every 28 days through the end of mission.