ACE Weekly 12/19/2007 - 12/25/2007 All ACE spacecraft subsystems are performing nominally. ============================================================================ Orbit/Attitude: No maneuvers were completed this week. The next attitude maneuver is scheduled for Friday 12/28/2007. Station-Keeping #46 has been tentatively scheduled for Thursday 01/17/2008. ============================================================================ OCRs: None ============================================================================ Activities: 34m HEF S-Band Transmitter DSN has requested additional ACE test passes to verify fixes implemented with the new S-Band 250W transmitters at DSS-45 and DSS-65. The following tests have been scheduled. Date DOY Station Test Fri 12/28 362 DSS-45 S-Band XMTR, SLE and range data The risk of data loss has again increased for the December-January time frame. 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. * In the winter months, our viewperiods from antennas in the northern hemisphere are shorter. Since 4 of the 6 antennas are in the northern hemisphere (Madrid, Spain & Goldstone, California), our overall available time is reduced. * SOHO has a 60-day continuous campaign from 12/03/2008 through 02/03/2008. * Ulysses Nutation Season continues until February 2008. * DSN has implemented a maintenance schedule where every antenna is unavailable during daylight hours one day each week. This has the biggest impact on L1 missions, reducing available antenna time by 14% (1/7). * DSS-45 and DSS-65 will eventually be available after the S-Band transmitter installation is complete. However, these antennas are already utilized by other missions. During December-January last year, there were several late-night reschedulings, 3 SSR failovers due to lost passes, and a cumulative 4.2 hours of science data lost. ============================================================================ Anomalies: DOY 355 12/21/2007 S-ACE-0257 G07-0109 DSS-46 Commanding Delayed DSS-46 TCP1 CMD STAT read "waiting for start ack". After several reboots and TCP swaps, TCP1 CMD STAT went to "waiting for data". DR#C106064 IMPACT: Activities delayed 1 hour 40 minutes. Additional DSN time was not available. It would take until 12/24/2007 (DOY 358) for SSR playback to be caught up and back on schedule. DOY 358 12/24/2007 S-ACE-0258 G07-0110 DSS-27 Antenna Stop Antenna stopped tracking unexpectedly (1532z). Station returned to track within 11 minutes (1543z) and uplink established at 1546z. DR#G108252 IMPACT: SSR playback had not yet caught up. Since automation does not redump the redumps, this resulted in 1.9 hours of cumulative data loss (DOY 357 1805-2026z).