ACE Weekly 12/10/2008 - 12/16/2008 All ACE spacecraft subsystems are performing nominally. ============================================================================ Orbit/Attitude: Type Attitude SK-49 Date 12/10/2008 12/10/2008 DOY 345 2008 345 2008 Thrusters 2R 4R+ 4R- 1A 2A Duration 9:28 min 36.851 sec Start 15:49:53z 18:03:15z Stop 15:59:21z 18:03:53z HGAStart -2.22deg +7.40deg HGAStop +7.40deg +7.52deg SunStart 8.74deg 5.54deg SunStop 5.54deg 5.42deg Nutation 0.13deg 0.16deg Firing 48 pulses Continuous FuelUsed 0.1617lbs 0.1345lbs FuelRemain 146.1408lbs 146.0064lbs FinalSCMass 1380.401lbs 1380.267lbs The next attitude maneuver is scheduled for Friday 12/19/2008. =========================================================================== OCRs: DOY 351 (12/16/2008) 2040-2050z SIS-042 M1B HV strip #17 was disabled due to a saturated leakage current that caused oscillations in SIS RTSW data. There are a total of 512 strips in the M1 and M2 detectors in the two SIS telescopes. 25 strips have been disabled since launch (2 VLSI readout channels were not working at launch). ============================================================================ Activities: Data Capture: 100% DOY 342-349 2008 There is a higher than normal risk of data loss from October 2008 through February 2009. If there are problems with the passes, it may not be possible to acquire additional DSN time. This higher-risk period has been occurring every winter for the past couple of years. For more information refer to 10/14/2008 weekly. The FDF timing coefficient file delivered on 12/1/2008 was missing the 1/1/2009 leap second. This was corrected with the 12/15/2008 timing coefficient file and no problems are expected. Errors in the ACE Clock Calibration would have an impact on the ACE Science Center's data processing. ============================================================================ Anomalies: DOY 345 12/10/2008 S-ACE-0393 S08-0006 S3DPU_I limit violation S3DPU current (S3DPU_I) briefly violated the red high limit (RH > 145mA). The S3DPU Idle Counter (SSDIDLECTR) was at 33. 2008-345:23:33:35 - 23:34:07. 148.176-149.744mA IMPACT: The last brief S3DPU_I violation was 2007-316-21:59:36. S3DPU_I is higher when the instruments are processing more data as indicated by a low SSDIDLECTR. DOY 346 12/11/2008 S-ACE-0392 G08-0126 DSS-46 CMD/SLE Problems DSS-46 was unable to maintain a bound state for SLE commanding at Beginning Of Track (BOT). The station rebooted and reloaded the equipment several times before the problem was resolved. DR#C106686 IMPACT: Activities delayed 30 minutes. The playback was completed on the next day. DOY 349 12/14/2008 S-ACE-0394 G08-0127 DSS-46 TCP Configuration The TCP was not configured to send high-rate data to the ACE MOC (low latency). The FOT contacted the Ops Chief and relayed the information to the station. DR#C106699. This same problem occurred on 10/15/2008 (AR#G08-0096 DR#C106579) and 10/30/2008 (AR#G08-0104 DR#C106604). DSN is reviewing the desktop/TCP configuration. IMPACT: Manual intervention required. Activities delayed 56 minutes. The playback was completed on the next day. DOY 351 12/16/2008 S-ACE-0395 G08-0128 DSS-27 Red DSS-27 was unavailable due to problems with the transmitter. DSN Maintenance released their time with DSS-46 and the pass was taken 2 hours later. One of the advantages of ACE automation is that passes can be easily rescheduled. In this particular case, manual intervention was required to simply update the DSN schedule. IMPACT: There will only be 2 northern hemisphere ranging passes between the maneuvers on DOY 345 and 354. There will be 9 southern hemisphere ranging passes. This should be sufficient for orbit determination, but additional northern hemisphere ranging passes would have helped. Also, if the additional time was not acquired, it would have taken 3 days to catch up on the SSR playback.