The NEAR Shoemaker spacecraft in orbit about the asteroid Eros continues to function in near perfect condition with only one instrument giving mission control problems.
During this past week, NEAR Shoemaker remained in Operational Mode with Flight Computer #1 and Attitude Interface Unit #2 in control of spacecraft attitude.
With two exceptions, the spacecraft instrument suite remained “ON” and operational throughout the week. The exceptions involved the Near-Infrared Spectrograph (NIS), which remains “OFF”, and the X-Ray/Gamma Ray Spectrometer (XGRS), which suffered a three-day outage early in the week, but has been returned to operational mode.
NEAR Shoemaker is presently in a nominal 50 km circular orbit around Eros. The spacecraft entered this orbit April 30, 2000 at 16:15 UTC when Orbit Correction Maneuver 6 (OCM 6) was executed. According to the current long term trajectory plan, NEAR Shoemaker will remain in this orbit conducting Science observations until July 7, 2000 at 18:00 UTC when Orbit Correction Maneuver 7 (OCM 7) will initiate the 50 km x 35 km transfer orbit.
Since the next planned OCM is not scheduled until July 7, weekly Momentum Correction Maneuvers (MCM) are required to manage spacecraft system momentum. Beginning May 10, these maneuvers are scheduled every Wednesday until June 28. The forth MCM of this period, MCM 6, was successfully executed this past Wednesday, May 31, at 16:00 UTC. The achieved momentum was well within operational tolerances, and the imparted delta V was minor.
The XGRS autonomously turned off Thursday, DOY 146, at MET 134688448 (18:10:19 UTC) when the Disaster Code was asserted by the instrument, tripping the XGRS Disaster Code autonomy rule.
The following day, Friday May 26 at MET 134778798 (19:16:09 UTC) the XGRS was turned back ON for a one minute test, to collect a complete set of XGRS subcommutated telemetry.
Exactly one minute after turning the instrument ON, it was commanded OFF as planned. XGRS telemetry indicated the instrument was OK.
The next day, Saturday May 27 at MET 134857380 (17:05:51 UTC) the XGRS was once again turned ON. Subsequently, XGRS DPU macros were loaded and the normal warmup macro executed.
During execution of this macro, the calibration source motor was successfully homed. The XGRS recovery plan leaves the instrument in this state for approximately 24 hours before turning the high voltage power supplies ON.
Finally, Sunday May 28 at MET 134946483 (17:50:54 UTC) the X-Ray and Gamma Ray high voltage power supplies were reconfigured. Telemetry looked good and the instrument was judged to be operational once again.
The NIS instrument remains disabled. The instrument was disabled a week ago Saturday, DOY 134, when an excessive power converter current was detected.
NIS instrument engineers and scientists are analyzing relevant data to determine possible explanations for the over current condition and propose a plan of attack.
The NIS will be re-enable June 5 for approximately one minute to collect a snapshot of NIS science and housekeeping telemetry.
Except for the NIS, science activities conducted this week included Eros observations by the full instrument suite: MSI, MAG, XGRS and NLR. Please consult science timelines for more details.
Upcoming Spacecraft Activities:
In addition to regular Eros Science and Optical Navigation, the following are operationally significant activities planned for the NEAR Shoemaker mission operation:
