Lunar Prospector Status Report #13

January 21, 1998 - 08:00 p.m. EST (5:00 p.m. PST)

Mission Control at NASA's Ames Research Center reports that the status of the Lunar Prospector spacecraft as of 4 p.m. PST (7 p.m. EST) on Wed., Jan. 21, 1998 is as follows:

The vehicle is in its 113th orbit of the moon. It is currently rotating at the desired 12.08 revolutions per minute. The spin axis shows the vehicle to be at longitude -- 223 degrees; latitude -- 87.8 degrees. The downlink data rate continues at 3600 bps, as planned. All science instruments are continuing to operate nominally and return excellent data.

The current trajectory of the spacecraft shows that it is in an orbit with a periselene (closest approach to the lunar surface) of 80 km and an aposelene of 120 km. The orbit has inevitably experienced some degradation from the optimal circular mapping orbit of 100 km (attained on Jan. 15) due to small perturbations in the lunar gravity field. However, the vehicle is still within its prescribed mapping boundary conditions. Mission operations personnel are learning about the effects of lunar gravitation on the Lunar Prospector spacecraft as the mission progresses. They will assess the need to undertake thruster burns to put the vehicle into an orbit closer to the 100 km circular optimum as they further assess the impact of lunar gravity. The time duration of each orbit remains the same -- at the planned 118 minutes per period.

Mission Control will, necessarily, be paying very close attention to the spacecraft's power parameters as the current series of eclipses (where the vehicle's solar arrays are in darkness and, therefore, not charging) become longer in length. Upcoming events include some configuration commanding of the Magnetometer and Electron Reflectometer science instruments -- an event that is currently scheduled for the afternoon of Thurs., Jan. 22, 1998.

David Morse
Ames Research Center
Moffett Field, CA 94035