ACE Weekly 09/17/2008 - 09/23/2008
All ACE spacecraft subsystems are performing nominally.
============================================================================
Orbit/Attitude:
Type Attitude SK-48
Date 09/22/2008 09/22/2008
DOY 266 2008 266 2008
Thrusters 2R 4R+ 4R- 1A 2A
Duration 14:40 min 54.281 sec
Start 13:36:15z 15:10:43z
Stop 13:50:55z 15:11:38z
HGAStart -6.59deg 7.40deg
HGAStop 7.40deg 7.43deg
SunStart 7.96deg 11.39deg
SunStop 11.39deg 11.56deg
Nutation 0.20deg 1.34deg
Firing 74 pulses Continuous
FuelUsed 0.2401lbs 0.1980lbs
FuelRemain 147.5832lbs 147.3852lbs
FinalSCMass 1381.843lbs 1381.645lbs
Note, the nutation for SK-48 was larger than expected (nutation=1.34deg,
expected < 0.5deg). Further information is provided in Anomaly Report
#S08-0004 (below)
The next attitude maneuver is scheduled for Monday 10/13/2008.
===========================================================================
OCRs:
DOY 263 (09/19/2008) SEP-071 30kV Discharge Flag Cleared
The SBS30KVRESET command to clear the 30kV discharge flag was sent
14:04:09z. The flag was set on DOY 258 2008 at 02:32:52z. SSS30KV and
SSS30KI, however, remained at nominal values (4.04V and 39.7mA).
============================================================================
Activities:
Data Capture: 99.99% DOY 258-264 2008
A 4 second gap (260 04:17:10 - 04:17:13) due to gaps during the redumps.
Note, the redumps are not redumped.
============================================================================
Anomalies:
DOY 263 09/19/2008 S-ACE-0352 G08-0088 ROBOTT/C&C Froze
At 1434z, the ACE MOC automation software (ROBOTT/C&C) froze for unknown
reasons. The Real-Time Monitor restarted the software at 1451z and
commanding was available at 1456z. The last reboot of the automation
software for unknown reasons occurred on 05/05/2008 (AR#G08-0054).
IMPACT: Minimal. No commanding was needed during the 20 minutes.
DOY 264 09/20/2008 S-ACE-0353 G08-0089 DSS-46 Ranging Pass
DSS-46 was unavailable for a Range Only support due to problems with the
transmitter.
IMPACT: Minimal. There were 8 other southern hemisphere ranging supports
between the maneuvers on 09/02/2008 and 09/22/2008 for the orbit
determination team.
DOY 266 09/22/2008 S-ACE-0354 S08-0089 SK-48 Nutation
The nutation (half-angle) for SK-48 was larger than expected
(nutation=1.34deg, expected < 0.5deg). The nutation occurred during the
first few seconds (<5sec) of the maneuver and remained constant throughout
the rest of the maneuver (duration=54.281sec). This maneuver used the top
deck thrusters (1A 2A). The following table shows the nutation for the past
21 station keeping maneuvers. Maneuvers that use the top deck thrusters
(indicated by ***) tend to have larger nutation than maneuvers using the
bottom deck (3A 4A). Investigation will continue as time can be scheduled.
IMPACT: Nutation took an additional ~2 hours to dampen to nominal
post-maneuver nutation levels.
Date DOY duration nutation thrusters
(seconds) (degrees)
02/14/2003 045 SK-28 104.8 0.10 3A 4A
06/23/2003 174 SK-29 79.1 0.44 1A 2A ***
11/21/2003 325 SK-30 54.9 0.50 1A 2A ***
02/26/2004 057 SK-31 59.5 0.07 3A 4A
05/27/2004 148 SK-32 98.7 0.32 3A 4A
08/20/2004 233 SK-33 63.8 0.50 1A 2A ***
12/06/2004 341 SK-34 58.6 0.14 3A 4A
03/17/2005 076 SK-35 51.2 0.20 3A 4A
05/25/2005 145 SK-36 64.6 0.32 3A 4A
09/28/2005 271 SK-37 41.2 0.76 1A 2A ***
12/22/2005 356 SK-38 30.4 0.15 3A 4A
04/05/2006 095 SK-39 21.9 0.27 1A 2A ***
06/26/2006 177 SK-40 41.2 0.23 3A 4A
09/19/2006 262 SK-41 7.7 0.62 1A 2A ***
12/13/2006 347 SK-42 23.9 0.21 3A 4A
04/02/2007 092 SK-43 13.4 1.01 1A 2A ***
06/21/2007 172 SK-44 53.6 0.19 1A 2A ***
09/06/2007 249 SK-45 53.6 0.31 3A 4A
01/17/2008 017 SK-46 52.1 0.15 3A 4A
05/20/2008 141 SK-47 54.2 0.30 3A 4A
09/22/2008 266 SK-48 54.3 1.34 1A 2A ***