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 ***