ACE Weekly 10/08/2008 - 10/14/2008

All ACE spacecraft subsystems are performing nominally.

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Orbit/Attitude:

	Type        Attitude
	Date        10/13/2008
	DOY         287 2008
	Thrusters   2R 4R+ 4R-
	Duration    14:20 min
	Start       20:19:32z
	Stop        20:33:52z
	HGAStart    -6.95deg
	HGAStop     +7.32deg
	SunStart    13.16deg
	SunStop      6.79deg
	Nutation     0.20deg
	Firing      72 pulses
	FuelUsed      0.2348lbs
	FuelRemain  147.1504lbs
	FinalSCMass 1381.410lbs

The next attitude maneuver is scheduled for Friday 10/31/2008.

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OCRs:

None

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Activities:

Data Capture:  100%  DOY 279-286 2008

DSN shut down the Goldstone antenna complex on DOY 285 0020-0820z to repair
the power distribution system.  The WIND mission was impacted and was
expected to lose 23 hours of data.  ACE took a shortened pass and SOHO moved
their pass to give WIND time with DSS-46 (Canberra 26m antenna).  WIND does
not schedule 26m antenna, but it was determined the best chance to capture
data given the limited DSN antenna time and loaded dump schedule.
Unfortunately, DSS-46 was only able to capture 1 frame of WIND data and all
23 hours of data was lost.  ACE SSR playback was slowly caught up over the
next 3 passes.


The risk of data loss has again increased for the October-February time
frame.  Several missions are competing for the same antenna time (daylight
hours).  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.
* Mars (MRO, MEX, M01O, etc), Dawn, Rosetta, New Horizons and Voyager1 are
on the opposite side of the sun.  Messenger is at Mercury.  The viewperiods
for these missions are at the same time as the L1 missions (SOHO, WIND,
ACE).  The overlap of the viewperiods is the most extreme in December 2008.
Note, the Mars overlap occurs every 2 years.
* In the winter months, viewperiods from antennas in the northern hemisphere
are shorter.  Since 4 of the 6 antennas are in the northern hemisphere
(Madrid, Spain & Goldstone, California), overall antenna time is reduced.
* DSN continues a maintenance schedule where every antenna is unavailable
during daylight hours one day each week.
* DSS-66 was decommissioned September 29, 2008.

During December 2006-January 2007 4.2 hours of ACE science data was lost
During December 2007-January 2008 1.9 hours of ACE science data was lost


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Anomalies:

DOY 287  10/13/2008  S-ACE-0358  G08-0093  Front-End Workstation Failure
AC1FE1A started generating errors performing unix directives.  The
workstation froze at 2100z.  This also impacted the string 1 gateway and
prevented communication to the automation Real-Time Monitor.
IMPACT:  The attitude maneuver was completed at 2033z.  String 2 was
available as a backup, but required a manual failover due to the network
problems.  However, AR#G08-0094 made a failover irrelevant.

DOY 287  10/13/2008  S-ACE-0359  G08-0094  DSS-27 Antenna Stop
DSS-27 Complex Supervisor Software (CSS) incorrectly configured to SOHO
Pass# 3820 at 2117z.  TLM restored at 2151z (14 minutes before EOT).  It was
decided not to re-establish the uplink for the last 10 minutes.
IMPACT:  34 minute telemetry outage.  SWEPAM calibration, SSR Redumps and
final state of health checks were not performed.  These were performed on
following pass (Tuesday DOY 288).

DOY 287  10/13/2008  S-ACE-0360  G08-0095  AC3WS3 Monitor Failure
The display monitor on string 3 failed.  Hardware maintenance will be
notified.
IMPACT:  Minimal.  String 3 is currently not being used as a backup.