ACE Weekly 11/14/2012 - 11/20/2012

All ACE spacecraft subsystems are performing as expected.  

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Orbit/Attitude:

	Type        Attitude       SK-63
	Date        11/19/2012     11/19/2012
	DOY         324 2012       324 2012
	Thrusters   2R 4R+ 4R-     1A 2A
	Duration    9:58 min       56.016 sec
	Start       15:54:49z      17:15:35z
	Stop        16:04:47z      17:16:31z
	HGAStart    -8.46deg       +9.08deg
	HGAStop     +9.08deg       +9.28deg
	SunStart     9.16deg       15.22deg
	SunStop     15.22deg       15.39deg
	SpinStart   5.0856rpm      5.0881rpm
	SpinStop    5.0881rpm      5.0704rpm
	Nutation     0.15deg        0.23deg
	Firing      51 pulses      Continuous
	FuelUsed      0.1609lbs      0.1952lbs
	FuelRemain  118.0996lbs    117.9044lbs
	FinalSCMass 1352.359lbs    1352.164lbs

The next attitude maneuver is scheduled for Tuesday 11/27/2012.


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OCRs:

DOY 320 (11/15/2012) 2053-2058z SIS-049 5 cmds
Disabled noisy M1B HV strips # 18 & 30 and raise their threshold.  As
the instrument is warmer (Oct-Mar near perihelion), some strips have
increased leakage current and noisy data.  There are a total of 512
strips in the two SIS telescopes.  So far 40 strips have been disabled
since launch and 2 VLSI readout channels were not working at launch.
M1B detector now has maximum number of strips that can be disabled and
the threshold on all M1B strips has been raised.

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Activities:

Data Capture:  100%  DOY 316-323 2012

We have had limited DSN antenna time this past week.  Viewperiods from
several missions are beginning to overlap.  A new moon meant that the
GRAIL viewperiod overlapped with L1.  And winter months give reduced
views for Northern Hemisphere antennas (Goldstone & Madrid).  When we
are behind in the playback, we don't worry about redumping every small
gap.  On DOY 322, there were 2 gaps resulting in 4 seconds of missing
data.  But by coincidence, we were in a pass for the corresponding time
and have real-time science data to cover the playback gaps.  Therefore
we continue our current streak of 5+ months of perfect data capture
(since 5/9/2012).

The WS1 certification test on 11/20/2012 was successful.  No DSN time
was available for this day, the data was successfully converted and sent
to ASC for level-zero processing.  We have found a solution to the NOAA
processing of SIS data.  By holding onto the telemetry for a few seconds
before sending it, NOAA successfully processed the SIS data.  WS1 is
delivering the data to the MMOC much faster than DSN.  On a somewhat
related note, there may be some issues between data forwarding and the
mmoc_fanout that should be investigated.


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Anomalies:

DOY 320  11/13/2012  S-ACE-0655  G12-0016  IN_TASK set after SIS OCR
The ITOS system is configured with an IN_TASK variable so that other
tasks know if they can start.  After the SIS commanding, a known ITOS
issue contributed to the IN_TASK variable to be set to one.  (The ITOS
issue is that critical commands cause ITOS to "go" through wait
statements in halted procs.)  The only commanding left was end-of-pass
state of health checks and recorder redumps.  These were performed on
the following pass.
IMPACT:  Manual intervention to clean up proc after pass.  No data loss.

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Average Sun Angles With Weekly Attitude Maneuvers

Dates        Avg SEV  Avg Sun  Sun-SEV (indicates extra s/c tilt)
-----------  -------  -------  ----------------------------------
10/18-10/23  5.1deg   11.0deg  5.9deg
10/23-10/28  3.3deg    9.3deg  6.0deg
10/28-11/06  2.0deg    7.3deg  5.3deg
11/06-11/13  3.8deg    8.4deg  4.6deg
11/13-11/20  6.3deg   10.3deg  4.0deg

ACE is moving away from the sun-earth line (larger sun-earth-vehicle
angle, SEV) which allows for larger sun angles over the next 5 weeks.
After mid-December, the L1 orbit will bring ACE back towards the
sun-earth line (smaller SEV angles).

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 sun angle can be kept ~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.