ACE Weekly 09/16/2009 - 09/22/2009

All ACE spacecraft subsystems are performing nominally.

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Orbit/Attitude:

No maneuvers were completed this week.  The next attitude maneuver and
Station-Keeping #52 are scheduled for Thursday 09/24/2009.

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OCRs:

None

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Activities:

DOY 259 09/16/2009 - Multi-Mission Operations Center (MMOC) Test
The MMOC was able to command to ACE using DSS-27.  The MMOC received ACE
realtime data.  There were no problems when data forwarding was
configured for just NOAA Space Weather.  The ACE Science Center (ASC)
system has not yet been configured to receive data from the MMOC
computers.  During commanding, the TwosComplementChecksum was not
populated in the READ_S0 command sent to the spacecraft using the new
MMOC mission software (ITOS).  The command had been successfully built
in previous releases of ITOS, but was not correct for the version of
ITOS used during the test.  The SSR ignored the command and flagged the
error (AR#S09-0006).  Another ITOS delivery is scheduled for 09/28/2009.


Data Capture:  100%  DOY 256-263 2009

DSN availability continues to be limited with the increased LCROSS usage
and the DSS-24/DSS-54 downtime.  SSR playback was finally caught up on
DOY 264.  Unfortunately, there was no pass on DOY 265.  SSR Playback
will continue to not be finished until the following pass.

There is a scenario that will cause data loss with the automated SSR
procedures.  If the data to be dumped from the previous pass exceeds the
length the next pass (+40 minutes for setup and SSR swap); then the SSR
procedures will not dump all of the data carried over from the previous
pass.  That scenario will occur on DOY 266 (88 minutes leftover from the
previous dump and the next pass is only 95 minutes).  The pass on DOY
266 will be taken manually to avoid the ~8 hours of data loss.  Note
that ACE passes are usually 210 minutes long, but have been shortened
due to LCROSS and limited DSN availability.

Another consequence of the limited DSN availability is the reduced
ranging data following the station keeping maneuver on DOY 267.  After a
station keeping maneuver, 3-4 1-hour range passes are taken so that FDF
can determine the results of the maneuver.  There are no additional
ranging passes for this station keeping maneuver.  The daily tracking
passes have been kept as ranging supports; but this will delay SSR
playback from being completed.  Also, there will not be any southern
hemisphere ranging for 7 days following the station keeping maneuver.


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Anomalies:

DOY 259  09/16/2009  S-ACE-0460  S09-0006  Invalid Checksum in READ_S0
The READ_S0 command was sent to the spacecraft from ITOS 803-0 in the
MMOC during a test. The command did not have the SSR checksum
calculated.
	/com.read_s0 ssrb, offset=0, size=5242880
	sent:    0d 0a 000c 4c11 00000000 00500000 0000
	correct: 0d 0a 000c 4c11 00000000 00500000 b39f
Impact:  The SSR ignored the command and flagged the error
(LAST_COM_INV_B, ERROR_CT_B and SYS_ERR_CODES_B).