ACE Weekly 12/05/2012 - 12/11/2012

All ACE spacecraft subsystems are performing as expected.  

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Orbit/Attitude:

	Type        Attitude
	Date        12/11/2012
	DOY         346 2012
	Thrusters   2R 4R+ 4R-
	Duration    7:39 min
	Start       22:31:25z
	Stop        22:39:04z
	HGAStart    -8.78deg
	HGAStop     +8.95deg
	SunStart    14.04deg
	SunStop     18.80deg
	SpinStart   5.0738rpm
	SpinStop    5.0756rpm
	Nutation     0.09deg
	Firing      39 pulses
	FuelUsed      0.1265lbs
	FuelRemain  117.4928lbs
	FinalSCMass 1351.753lbs

The next attitude maneuver is scheduled for Tuesday 12/18/2012.

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OCRs:

None


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Activities:

Data Capture:  100%  DOY 337-344 2012

ACE had an operational pass with WS1 on Friday 12/7/2012 (DOY 342).
There was a data flow issue with mmoc_fanout in the first ~10 minutes of
the pass.  The problem was resolved by restarting ACE data forwarding
and didn't recur.  Time will be needed to resolve the issue.

Antenna time with WS1 was requested for Wednesday 12/19/2012.  There are
4 hours from the beginning of the ACE view to the beginning of the LRO
passes, but a 45 minute Themis D pass sits in the middle of that time.
We'll keep the shortened 2.5 hour pass with DSS-27 and catch up on the
science playback a few days later.

As reported last week, we are currently in a period of limited antenna
time (12/9-12/14 and 12/17-12/20).  Playback will fall behind by 30-60
minutes (5-10 hours of science data).  No data loss is expected.  The
reasons for limited antenna time are:
* GRAIL viewperiod at DSN overlaps ACE (new moon)
* LRO viewperiod at WS1 overlaps ACE (new moon)
* DSN DSS-54 antenna down for repairs
* Short northern hemisphere views (Goldstone & Madrid) during winter
* Mission views overlapping in December and January (Mars,Voyager,etc)

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Anomalies:

None

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Average Sun Angles With Weekly Attitude Maneuvers

Dates         Avg Sun    Avg SEV   Sun-SEV (indicates extra s/c tilt)
-----------   -------    -------   ----------------------------------
10/18-10/23   11.0deg     5.1deg    5.9deg
10/23-10/28    9.3deg     3.3deg    6.0deg
10/28-11/06    7.3deg     2.0deg    5.3deg
11/06-11/13    8.4deg     3.8deg    4.6deg
11/13-11/20   10.3deg     6.3deg    4.0deg
11/20-11/27   12.7deg     8.6deg    4.1deg
11/27-12/04   14.9deg    10.1deg    4.8deg
12/04-12/11   16.0deg    10.9deg    5.1deg

The following is background information that will be included in each
weekly report.
The project has accepted the SWEPAM team proposal to keep the spacecraft
at larger sun angles with weekly attitude maneuvers.  The SWEPAM-Ion
instrument has a series of channel electron multipliers (CEMs) and
larger sun angles allows more responsive CEMs to measure the solar wind.
The maximum sun angle follows the Sun-Earth-Vehicle angle (SEV).  The
SEV angle is determined by the size/shape of the orbit around L1.  When
the spacecraft antenna is pointed directly towards earth, the
spacecraft's sun angle will be equal to the Sun-Earth-Vehicle angle.
With weekly maneuvers, the average sun angle can be kept 4-6deg more
than the SEV angle.  This results in the spacecraft antenna aspect angle
being kept between 5 and 9 degrees and never pointing directly back at
earth.  For reference, the SWEPAM team prefers sun angles above 13
degrees.  With the current size of the L1 orbit, the sun angle will be
above 13 degrees for ~45% of the time.