ACE Weekly 04/09/2014 - 04/15/2014

All ACE spacecraft subsystems are performing as expected.

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Orbit/Attitude:

	Type         Attitude
	Date         04/15/2014
	DOY          105 2014
	Thrusters    2R 4R+ 4R-
	Duration     9:28 min
	Start        15:41:44z
	Stop         15:51:12z
	HGAStart     -8.13 deg
	HGAStop      +9.73 deg
	SunStart     11.00 deg
	SunStop      14.18 deg
	SpinStart    4.9906 rpm
	SpinStop     4.9927 rpm
	Nutation      0.18 deg
	Firing       48 pulses
	FuelUsed       0.1527 lbm
	FuelRemain   107.6056 lbm
	FinalSCMass  1341.866 lbm


This maneuver targeted a spacecraft antenna angle (HGA) of 10 degrees
(9.73 degrees achieved).  The ~2.5 dB drop in the downlink signal due to
the increased antenna angle is in-line with expectations.  Next week's
maneuver will target a spacecraft angle of 11 degrees.  Refer to OCR
ACE-337 below.
	antenna angle    Signal to Noise Ratio
	8.13 deg         15 dB
	9.73 deg         12.5 dB

The next attitude maneuver is scheduled for Tuesday 04/22/2014.

Station Keeping maneuver #69 is scheduled for 05/13/2014.  Note that
there are 4 months, instead of the usual 3 months, since the last
station keeping maneuver.  This is because the observed delta-V from
SK-68 on 1/15/2014 had exactly matched the planned delta-V.  The
variation in thruster performance is usually between -2 to +2%, but it
is pleasant to note when the maneuver is right-on.

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OCRs:

ACE-337  Increase antenna constraint from 9 to 11 degrees for summer
With DSN's decommission of DSS-27 (12/23/2013), ACE has been using the
better 34m antennas.  And during the summer, DSN northern hemisphere
views are longer (9 out of 12 DSN antennas are in the northern
hemisphere), which reduces the need for ACE using WS1 (21m).  Turning
the spacecraft an additional 2 degrees will improve the SWEPAM-I density
measurement by ~10%.  We expect that the instrument deck temperature
will increase slightly (~0.2C), but that is more than offset by the 2-4C
drop that occurs due to aphelion (7/3/2014).  Attitude maneuvers will
target an 11 degree spacecraft antenna angle and drift back to 11
degrees on the day after the next scheduled maneuver, which allows the
attitude maneuver to slip a day if needed.  Although WS1 will not be
able to acquire the high-rate telemetry with the spacecraft at 11
degrees, the range-only passes with WS1 and Santiago can still continue.

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Activities:

Data Capture:  100%  DOY 096-103 2014

The Near Earth Network performed one more Santiago range test.
	04/09/2014  099  1300-1400  AGO

FDF's certification status for the complete week of WS1 and Santiago
range passes (3/26/2014 - 4/1/2014) has not yet been delivered.

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Anomalies:

Update on Anomaly #G14-0005 (S-ACE-0677) DSS-15 Earth Receive Time (ERT)

The DSN Earth Receive Time continues to have occasional problems, but
DSN's halting and re-acquiring the TLP has corrected it when it occurs.
There have been no problems with the clock reports sent to ASC and NOAA.

Fri 4/11/2014  DSS-15  no problem found
Sat 4/12/2014  DSS-15  17:56:36 ERT -0.182 sec.  Corrected 17:56:51
Sun 4/13/2014  DSS-15  21:29:31 ERT -0.363 sec.  Corrected 21:29:47
Mon 4/14/2014  DSS-15  no problem found

Background Info:  The ERT is behind by an integer multiple of telemetry
frames (high-rate = 0.091 seconds per frame).  This occurs after the
spacecraft's data-rate change (from low-rate RTSW to high-rate).  This
is an intermittent problem (DR# G114836/AR 118839) with the Receiver,
Ranging, and Telemetry (RRT) software v11.3.6 that is currently
undergoing soak testing at DSN's Goldstone site.