ACE Weekly 02/20/2014 - 02/25/2014

All ACE spacecraft subsystems are performing as expected.

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Orbit/Attitude:

	Type         Attitude
	Date         02/25/2014
	DOY          056 2014
	Thrusters    2R 4R+ 4R-
	Duration     7:18 min
	Start        15:39:07z
	Stop         15:46:25z
	HGAStart     -8.80 deg
	HGAStop      +8.89 deg
	SunStart     17.71 deg
	SunStop      13.63 deg
	SpinStart    4.9801 rpm
	SpinStop     4.9805 rpm
	Nutation      0.09 deg
	Firing       37 pulses
	FuelUsed       0.1209 lbm
	FuelRemain   108.6492 lbm
	FinalSCMass  1342.909 lbm

The next attitude maneuver is scheduled for Tuesday 03/04/2014.

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OCRs:

None

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Activities:

Data Capture:  100%  DOY 047-054 2014

FDF has analyzed four WS1 range tests.  The range bias is less than
10meters.
	02/10/2014  1450-1535z  WS1  -6.3m (average range residual)
	02/10/2014  1614-1650z  WS1  -5.1m
	02/17/2014  2055-2255z  WS1  -4.5m
	02/18/2014  2145-2245z  WS1  -1.5m

The remaining range tests with WS1 and Santiago will be analyzed with
the 02/19 - 02/25 (maneuver to maneuver) orbit determination arc.

Two more Santiago range certification tests are scheduled for the coming
week
	Thu 2/27  059  1700-1800z  AGO  ACE
	Fri 2/28  060  1700-1800z  AGO  ACE

The certification tests are specifically for the DSCOVR mission.  ACE is
also interested in using Santiago if FDF determines that the Santiago
ranging is sufficient to supplement or replace the DSN Canberra southern
hemisphere ranging.


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Anomalies:

Update for S13-0001 - B1 Fuel Tank Temperature Anomaly 
The fuel tank heaters continue to turn off for ~30 minutes every 2
hours.  The Tank B1 temperature has been fluctuating 4-5C, but the other
tanks have been stable and only fluctuating ~1C.  The tank heater off/on
started 12/22/2013 2053z, with brief periods (2-12 hours) when the fuel
tank heaters remained on.  We had expected the tank heaters to return to
the normal condition of staying on as the sun-spacecraft distance
increases (perihelion 1/4/2014).  It remains unknown why the B1 tank
temperature increased (9/19/2013 & 11/05/2013) and is now fluctuating
more than the other tanks.

Two suggestions have been discussed with Space Science Mission
Operations:
1) Load an autonomy bin to close the latch valves if the fuel tank
pressure drops unexpectedly.
2) Turn off the primary propulsion heaters and let the temperature drop
to the point where the backup propulsion thermostats would turn on.
This may also reduce the temperature of the instrument deck (maybe).


Update for G14-0001 (02/19/2014) - ITOS event log database problem
Deleting the event log database and recreating it successfully resolved
the problems.  Since the event log is saved at the end of every pass,
there is no impact to recreating the event log database.