ACE Weekly 02/07/2012 - 02/13/2012

All ACE spacecraft subsystems are performing as expected.

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Orbit/Attitude:

No maneuvers were completed this week.  The next attitude maneuver is
scheduled for Tuesday 02/21/2012.

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OCRs:

None

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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.

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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