ACE Weekly 04/24/2012 - 04/30/2012

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 Friday 05/04/2012.

For the 5/4/2012 maneuver, the spacecraft attitude will have the sun
angle dropping to 3 degrees over the subsequent week.  There will be no
impact to the sun pulse generation (nutation will be zero).  The sun
angle during the February 2012 sun crossing had gone down to 1.45
degrees and the sun pulse generation was not impacted.  Since this
week's Solar Exclusion Zone transit is farther from the sun (0.68
degrees versus crossing the sun), a 3 degree sun angle is best for
optimizing the High-Gain Antenna pointing towards Earth.


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OCRs:

MOCR 428 has been submitted for Mission Director approval for the sun
angle to go below 4 degrees from Tuesday 5/8/2012 1900z  to Sunday
5/13/2012 2300z.  The minimum sun angle will be 3 degrees.

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Activities:

Data Capture:  100%  DOY 113-120 2012

The next Solar Exclusion Zone transit (SEZ) is next week with a minimum
Sun-Earth-Vehicle angle (SEV) of 0.67 degrees on Sunday 5/6/2012.  No
problems are expected with current solar radio flux levels (<150 sfu).

WS1 ranging test on Monday 04/30/2012.  WS1 found that their ranging
software was storing values with 32 bits, which was insufficient to
store the larger values associated with L1 (ACE/L1 ~1,500,000km;
LRO/moon ~385,000km).  WS1 has upgraded their software (dll's) and
testing continues.

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Anomalies:

DOY 119 04/28/2012  S-ACE-0641  G12-0004  DSN Replacement Router and SLE
The MMOC SLE connection was successfully established at 20 minutes
before BOT (2020z).  DSN installed a replacement router (2032z) and the
MMOC SLE connection was lost.  The MMOC SLE telemetry processes (RT+PB)
subsequently crashed.  The DSN replacement router was taken offline and
the ACE pass procedure was restarted from scratch (2106z).
IMPACT:  Activities delayed 30 minutes.  FOT needed to come in for
manual intervention (Saturday).

Update on AR#S12-0001  S-ACE-0639  SWEPAM-E Overcount Alarm
The SWEPAM-Electron Overcount Alarm stopped flagging on DOY 117
07:48:38z.  The instrument team is working the next course of action,
but their time is limited.  IMPACT:  The instrument automatically
reduces voltages when the overcount alarm occurs.