ACE Weekly 09/17/2008 - 09/23/2008 All ACE spacecraft subsystems are performing nominally. ============================================================================ Orbit/Attitude: Type Attitude SK-48 Date 09/22/2008 09/22/2008 DOY 266 2008 266 2008 Thrusters 2R 4R+ 4R- 1A 2A Duration 14:40 min 54.281 sec Start 13:36:15z 15:10:43z Stop 13:50:55z 15:11:38z HGAStart -6.59deg 7.40deg HGAStop 7.40deg 7.43deg SunStart 7.96deg 11.39deg SunStop 11.39deg 11.56deg Nutation 0.20deg 1.34deg Firing 74 pulses Continuous FuelUsed 0.2401lbs 0.1980lbs FuelRemain 147.5832lbs 147.3852lbs FinalSCMass 1381.843lbs 1381.645lbs Note, the nutation for SK-48 was larger than expected (nutation=1.34deg, expected < 0.5deg). Further information is provided in Anomaly Report #S08-0004 (below) The next attitude maneuver is scheduled for Monday 10/13/2008. =========================================================================== OCRs: DOY 263 (09/19/2008) SEP-071 30kV Discharge Flag Cleared The SBS30KVRESET command to clear the 30kV discharge flag was sent 14:04:09z. The flag was set on DOY 258 2008 at 02:32:52z. SSS30KV and SSS30KI, however, remained at nominal values (4.04V and 39.7mA). ============================================================================ Activities: Data Capture: 99.99% DOY 258-264 2008 A 4 second gap (260 04:17:10 - 04:17:13) due to gaps during the redumps. Note, the redumps are not redumped. ============================================================================ Anomalies: DOY 263 09/19/2008 S-ACE-0352 G08-0088 ROBOTT/C&C Froze At 1434z, the ACE MOC automation software (ROBOTT/C&C) froze for unknown reasons. The Real-Time Monitor restarted the software at 1451z and commanding was available at 1456z. The last reboot of the automation software for unknown reasons occurred on 05/05/2008 (AR#G08-0054). IMPACT: Minimal. No commanding was needed during the 20 minutes. DOY 264 09/20/2008 S-ACE-0353 G08-0089 DSS-46 Ranging Pass DSS-46 was unavailable for a Range Only support due to problems with the transmitter. IMPACT: Minimal. There were 8 other southern hemisphere ranging supports between the maneuvers on 09/02/2008 and 09/22/2008 for the orbit determination team. DOY 266 09/22/2008 S-ACE-0354 S08-0089 SK-48 Nutation The nutation (half-angle) for SK-48 was larger than expected (nutation=1.34deg, expected < 0.5deg). The nutation occurred during the first few seconds (<5sec) of the maneuver and remained constant throughout the rest of the maneuver (duration=54.281sec). This maneuver used the top deck thrusters (1A 2A). The following table shows the nutation for the past 21 station keeping maneuvers. Maneuvers that use the top deck thrusters (indicated by ***) tend to have larger nutation than maneuvers using the bottom deck (3A 4A). Investigation will continue as time can be scheduled. IMPACT: Nutation took an additional ~2 hours to dampen to nominal post-maneuver nutation levels. Date DOY duration nutation thrusters (seconds) (degrees) 02/14/2003 045 SK-28 104.8 0.10 3A 4A 06/23/2003 174 SK-29 79.1 0.44 1A 2A *** 11/21/2003 325 SK-30 54.9 0.50 1A 2A *** 02/26/2004 057 SK-31 59.5 0.07 3A 4A 05/27/2004 148 SK-32 98.7 0.32 3A 4A 08/20/2004 233 SK-33 63.8 0.50 1A 2A *** 12/06/2004 341 SK-34 58.6 0.14 3A 4A 03/17/2005 076 SK-35 51.2 0.20 3A 4A 05/25/2005 145 SK-36 64.6 0.32 3A 4A 09/28/2005 271 SK-37 41.2 0.76 1A 2A *** 12/22/2005 356 SK-38 30.4 0.15 3A 4A 04/05/2006 095 SK-39 21.9 0.27 1A 2A *** 06/26/2006 177 SK-40 41.2 0.23 3A 4A 09/19/2006 262 SK-41 7.7 0.62 1A 2A *** 12/13/2006 347 SK-42 23.9 0.21 3A 4A 04/02/2007 092 SK-43 13.4 1.01 1A 2A *** 06/21/2007 172 SK-44 53.6 0.19 1A 2A *** 09/06/2007 249 SK-45 53.6 0.31 3A 4A 01/17/2008 017 SK-46 52.1 0.15 3A 4A 05/20/2008 141 SK-47 54.2 0.30 3A 4A 09/22/2008 266 SK-48 54.3 1.34 1A 2A ***