Lunar Prospector Status Report #39

July 1, 1998 - 1:00 p.m. EST (10:00 a.m. PST)

No commanding was done this week. Although there were many changes to the tracking schedule due to the recovery efforts for the SOHO spacecraft, LP tracking was still very good and we had only a few short (~1 hour) outages throughout the week.

NOTE: The Solar and Heliospheric Observatory (SOHO) mission is a joint undertaking of European Space Agency (ESA) and NASA. The spacecraft was launched aboard an Atlas II rocket on 2 December,1995 from the Cape Canaveral Air Station in Florida. Mission operations are directed from the control center at NASA Goddard Space Flight Center in Maryland, USA. On the 26th of June, 1998 during routine maintenance operations, ground controllers lost contact with the SOHO spacecraft and the satellite went into Emergency Sun Reacquisition (ESR) mode. The ESR mode is activated when an anomaly occurs and the spacecraft loses its orientation towards the Sun. When this happens, the spacecraft automatically tries to point itself towards the Sun again by firing its attitude control thrusters under the guidance of an onboard Sun sensor.

Efforts to re-establish nominal operations did not succeed and telemetry was lost. Subsequent attempts using the full NASA Deep Space Network(DSN) capabilities have so far been unsuccessful. ESA and NASA engineers are continuing with the task of re-establishing contact with the spacecraft.

Because LP's tracking is also handled through the DSN, the attempts to reestablish communication with SOHO have affected LP's tracking schedule.

Current spacecraft state (0000 GMT 7/1/98):

Orbit: 2069
Downlink: 3600 bps
Spin Rate: 12.01 rpm

Spin Axis Attitude (ecliptic):
Latitude: 90.6 deg
Longitude: 164 deg

Trajectory:
Periapsis Alt: 90.6 km
Apoapsis Alt: 109.3 km

Inclination: 91.0 deg
Period: 118 min
Occultations: 47 minutes
Eclipses: none