ACE Weekly 04/16/2014 - 04/22/2014
All ACE spacecraft subsystems are performing as expected.
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Orbit/Attitude:
Type Attitude
Date 04/22/2014
DOY 112 2014
Thrusters 2R 4R+ 4R-
Duration 9:30 min
Start 15:04:06z
Stop 15:13:33z
HGAStart -9.02 deg
HGAStop +10.80 deg
SunStart 11.06 deg
SunStop 15.71 deg
SpinStart 4.9926 rpm
SpinStop 4.9945 rpm
Nutation 0.18 deg
Firing 48 pulses
FuelUsed 0.1526 lbm
FuelRemain 107.4528 lbm
FinalSCMass 1341.713 lbm
The next attitude maneuver is scheduled for Tuesday 04/22/2014. Station
Keeping maneuver #69 is scheduled for 05/13/2014.
This maneuver targeted a spacecraft antenna angle (HGA) of 11 degrees
(10.80 degrees achieved). The ~3 dB drop in the downlink signal due to
the increased antenna angle is in-line with expectations.
antenna angle Signal to Noise Ratio (DSN 34m antenna)
4/15 8.13 deg 15 dB
4/15 9.73 deg 12.5 dB
4/22 9.02 deg 13.5 dB
4/22 10.80 deg 10.6 dB
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OCRs:
The following OCRs are for the S3DPU recovery (latchup
2014-107-00:14:11). The procedures were converted from TPOCC (old ACE
MOC) to ITOS (new MMOC).
DOY 108 (04/18/2014) SWICS/SWIMS-033 Restore volatile parameters
SWICS recovery 1500-1507z
SWIMS recovery 1510-1512z
SWICS NQ parameters 1513-1516z
DOY 108 (04/18/2014) 1516-1518z SWICS-037 Change event prioritization
Reloading event prioritization which had previously been loaded
7/15/2013.
DOY 108 (04/18/2014) 1519z SWICS-038 Set adc_trigger=4
Reset trigger mode to 4 which had previously been set 3/21/2014.
DOY 108 (04/18/2014) 1521-1538z S3D-004 Patch 4X-SWIMS Deadtime
Patch 4X will extend SWIMS Deadtime. Originally loaded 1/27/1999.
DOY 108 (04/18/2014) 1540z S3D-003 Patch 2 for SWICS PHA
Change the scheme used by S3DPU to identify which of three solid state
detectors were triggered by an ion and in which classification range it
falls. Originally loaded 3/10/1998.
DOY 108 (04/18/2014) 1540-1555z S3D-002 Patch 3.1.3.b-SWICS Deadtime
To extend SWICS deadtime (time DPU does not analyze PHA Data) for the
period when Stepping voltage changes from lowest value to highest value.
Originally loaded 7/8/1998.
DOY 108 (04/18/2014) 1555-1610z S3D-005 Patch 5-Anti Reset Patch
S3D-005 Patch 5 allows SEPICA to be in Engineering Mode without
affecting SWICS and SWIMS. Originally loaded 4/9/2004.
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Activities:
Data Capture: 100% DOY 103-110 2014
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Anomalies:
DOY 107 04/17/2014 S-ACE-0679 S14-0001 S3DPU Latchup
The Data Processing Unit for SWICS, SWIMS and SEPICA (S3DPU), had its
fourth latchup at 00:14:11z. The standard procedures for restoring
volatile parameters and S3DPU patches were performed on Friday 4/18/2014
(1500-1610z) ... just in time for the CME on 4/19/2014.
DOY 137 2002 11:20:51z SSDLUCNT = 1
DOY 137 2005 19:51:57z SSDLUCNT = 2
DOY 347 2006 10:08:40z SSDLUCNT = 3
DOY 107 2014 00:14:11z SSDLUCNT = 4
DOY 112 04/22/2014 S-ACE-0680 G14-0007 DSS-24 Transmitter problem
The DSN station encountered problems with the Uplink Exciter Control
Software at 1512z. Uplink was re-established 31 minutes later at 1543z.
IMPACT: The problem occurred at the end of the attitude maneuver. The
attitude maneuver ended successfully, but real-time data was lost for 2
minutes as the spacecraft had switched from coherent to non-coherent
downlink. Lack of uplink resulted in a post-maneuver thruster abort.
Background on post-maneuver thruster abort: Before every maneuver, a
THRUSTER_ABORT command is loaded to execute 30 minutes after the
expected end of the maneuver. The preloaded post-maneuver
THRUSTER_ABORT command has never been needed, but is loaded for an
abundance of caution. The THRUSTER_ABORT is usually cleared with a
ground command when the maneuver has completed. There is no impact from
executing a THRUSTER_ABORT when no maneuver is in progress, i.e. the sun
pulse processing problem does not occur.
Update for S13-0001 - B1 Fuel Tank Temperature Anomaly
The fuel tank heaters had been powering off for ~30 minutes every ~2
hours. The updated theory is that the heater thermostat has become
detached from the B1 tank. Review is ongoing for switching to the
backup propulsion heater system which has the thermostat attached to
Tank A1.
But with the spacecraft cooling (moving away from perihelion since
January 2014), the primary heater thermostat (Tank B1--assumed detached)
has kept the tank heaters on continuously since 4/2/2014. This is the
normal propulsion heater configuration. Nevertheless, the review for
switching to the backup propulsion heater system continues.