ACE Weekly 02/07/2012 - 02/13/2012 All ACE spacecraft subsystems are performing as expected. ======================================================================== Orbit/Attitude: No maneuvers were completed this week. The next attitude maneuver is scheduled for Tuesday 02/21/2012. ======================================================================= OCRs: None ======================================================================== Activities: Data Capture: 99.99% DOY 036-043 2012 DOY 039 15:15:00-15:15:30 31 seconds during SSR failover ACE crossed in front of the sun from 2100z Tuesday 2/7/2012 to 2100z Wednesday 2/8/2012. The ACE Lissajous orbit has a sun crossing every 8 years, the last crossing was 6/1/2004. The sun was quiet this week. The solar radio flux as measured by F10.7 was between 100 and 120 and had dropped to 97 while ACE was in front of the sun. The low solar radio noise allowed the NOAA SWPC network of 11-meter antennas to track ACE even while it was in front of the sun with only a ~1 hour outage around 1600z on 2/8. Allowing ACE to drift to a smaller sun/antenna angle also helped the signal strength. The spacecraft continued to generate sun pulses as the sun angle dropped to 1.45 degrees. The sun sensor has a resolution of 0.5 degrees and the exact sun angle is only available as the sun sensor transitions between values (or during ADC format). The following table gives the values when the sun angle was 4 degrees and less. Date DOY UTC Sun Angle (degrees) -------- --- -------- ------------------- Sun 2/05 036 13:40:26 4.02 Mon 2/06 037 03:51:30 3.51 Mon 2/06 037 15:57:46 3.01 Tue 2/07 038 05:53:30 2.51 Tue 2/07 038 22:19:14 2.01 Thu 2/09 040 01:43:22 1.50 Thu 2/09 040 ~09:00:00 ~1.45 Thu 2/09 040 16:26:10 1.50 Fri 2/10 041 19:50:26 2.01 Sat 2/11 042 12:17:37 2.51 Sun 2/12 043 02:14:33 3.01 Sun 2/12 043 14:22:57 3.51 Mon 2/13 044 04:35:21 4.02 Allowing the spacecraft to drift to a smaller sun angles will also help in the future and further approval will be discussed with management. ======================================================================== Anomalies: DOY 012 01/12/2012 S-ACE-0523 S10-0007 Increase in SBE_CT_B SSR B Single Bit Error Count (SBE_CT_B) increased from 11639 to 11714 between 2/6/2012 and 2/10/2012. SBE_CT_B again increased from 11714 to 12086 between 2/10/2012 and 2/12/2012. SBE_CT is tracked as a measure of SSR health. IMPACT: Minimal. Single Bit Errors are automatically corrected by the SSR. No non-correctable errors (Hard Single Bit Errors & Double Bit Errors) have occurred throughout the mission. SBE_CT_A SBE_CT_B 1999 15 2000 2001 2002 2003 270 286 2004 858 2005 2006 2118 2007 510 3238 2008 4533 2009 525 6839 2010 780 7339 2011 10995 2012 11714