ACE Weekly 10/08/2008 - 10/14/2008 All ACE spacecraft subsystems are performing nominally. ============================================================================ Orbit/Attitude: Type Attitude Date 10/13/2008 DOY 287 2008 Thrusters 2R 4R+ 4R- Duration 14:20 min Start 20:19:32z Stop 20:33:52z HGAStart -6.95deg HGAStop +7.32deg SunStart 13.16deg SunStop 6.79deg Nutation 0.20deg Firing 72 pulses FuelUsed 0.2348lbs FuelRemain 147.1504lbs FinalSCMass 1381.410lbs The next attitude maneuver is scheduled for Friday 10/31/2008. =========================================================================== OCRs: None ============================================================================ Activities: Data Capture: 100% DOY 279-286 2008 DSN shut down the Goldstone antenna complex on DOY 285 0020-0820z to repair the power distribution system. The WIND mission was impacted and was expected to lose 23 hours of data. ACE took a shortened pass and SOHO moved their pass to give WIND time with DSS-46 (Canberra 26m antenna). WIND does not schedule 26m antenna, but it was determined the best chance to capture data given the limited DSN antenna time and loaded dump schedule. Unfortunately, DSS-46 was only able to capture 1 frame of WIND data and all 23 hours of data was lost. ACE SSR playback was slowly caught up over the next 3 passes. The risk of data loss has again increased for the October-February time frame. Several missions are competing for the same antenna time (daylight hours). If there are problems with the passes, it may not be possible to acquire additional DSN time. The following discusses some of the issues involved. * Mars (MRO, MEX, M01O, etc), Dawn, Rosetta, New Horizons and Voyager1 are on the opposite side of the sun. Messenger is at Mercury. The viewperiods for these missions are at the same time as the L1 missions (SOHO, WIND, ACE). The overlap of the viewperiods is the most extreme in December 2008. Note, the Mars overlap occurs every 2 years. * In the winter months, viewperiods from antennas in the northern hemisphere are shorter. Since 4 of the 6 antennas are in the northern hemisphere (Madrid, Spain & Goldstone, California), overall antenna time is reduced. * DSN continues a maintenance schedule where every antenna is unavailable during daylight hours one day each week. * DSS-66 was decommissioned September 29, 2008. During December 2006-January 2007 4.2 hours of ACE science data was lost During December 2007-January 2008 1.9 hours of ACE science data was lost ============================================================================ Anomalies: DOY 287 10/13/2008 S-ACE-0358 G08-0093 Front-End Workstation Failure AC1FE1A started generating errors performing unix directives. The workstation froze at 2100z. This also impacted the string 1 gateway and prevented communication to the automation Real-Time Monitor. IMPACT: The attitude maneuver was completed at 2033z. String 2 was available as a backup, but required a manual failover due to the network problems. However, AR#G08-0094 made a failover irrelevant. DOY 287 10/13/2008 S-ACE-0359 G08-0094 DSS-27 Antenna Stop DSS-27 Complex Supervisor Software (CSS) incorrectly configured to SOHO Pass# 3820 at 2117z. TLM restored at 2151z (14 minutes before EOT). It was decided not to re-establish the uplink for the last 10 minutes. IMPACT: 34 minute telemetry outage. SWEPAM calibration, SSR Redumps and final state of health checks were not performed. These were performed on following pass (Tuesday DOY 288). DOY 287 10/13/2008 S-ACE-0360 G08-0095 AC3WS3 Monitor Failure The display monitor on string 3 failed. Hardware maintenance will be notified. IMPACT: Minimal. String 3 is currently not being used as a backup.