ACE Weekly 12/12/2012 - 12/18/2012

All ACE spacecraft subsystems are performing as expected.  

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Orbit/Attitude:

	Type        Attitude
	Date        12/18/2012
	DOY         353 2012
	Thrusters   2R 4R+ 4R-
	Duration    7:49 min
	Start       16:15:19z
	Stop        16:23:08z
	HGAStart    -8.96deg
	HGAStop     +9.04deg
	SunStart    14.97deg
	SunStop     19.19deg
	SpinStart   5.0755rpm
	SpinStop    5.0771rpm
	Nutation     0.16deg
	Firing      40 pulses
	FuelUsed      0.1294lbs
	FuelRemain  117.3636lbs
	FinalSCMass 1351.623lbs

The next attitude maneuver is scheduled for Thursday 12/27/2012.

The spacecraft reached a peak Sun-Earth-Vehicle angle (11.3 degrees) in
its L1 orbit on Saturday 12/15/2012.  For the next 1.5 months, the SEV
angle will decrease as ACE moves closer to the Sun-Earth line; reaching
2.2 degrees on 1/27/2012.

With the SEV angle at a peak, the post-maneuver sun angle (19.19
degrees) is the largest we'll see until the spacecraft reaches the other
end of the L1 orbit in 3 months (March 2013).

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OCRs:

None

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Activities:

Data Capture:  100%  DOY 344-351 2012

There has been no data loss so far as we go through this period limited
DSN antenna time (12/9-12/20).  The science playback is behind by 30-60
minutes (5-10 hours of science data), but we'll be caught up on Friday
12/21/2012.  Looking ahead in the schedule, the next period of very
limited antenna time for ACE is 1/30/2013-2/4/2013.

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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
12/11-12/18   16.8deg    11.3deg    5.5deg

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.