ACE Weekly 09/10/04 - 09/16/04

All ACE spacecraft subsystems are performing nominally.  A "Dog-Leg"=20
attitude maneuver was successfully executed on 09/10/04 but not without=20
problems (see Anomalies section).  The next attitude maneuver is scheduled=
=20
for 09/17/04.

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Orbit Events:

The ACE transit of the Solar Exclusion Zone (SEZ) concluded on=20
09/11/04.  The minimum Sun angular radius was 0.32 degrees (as seen from=20
Earth's center) on 08/30/04.  The next SEZ crossing will occur in the=20
Nov-Dec time frame.

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OCRs Executed:

None

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Ongoing Activities:

TAPS:
- Installation of TAPS release 4.3 occurred on 07/20/04.  FOT testing of=20
this release is ongoing.
   -- Of the 6 DRs fixed in release 4.3, all have been verified.
   -- Two (2) new DRs have been opened to date and additional DRs may=20
follow based on recent findings.

----------------------------------------------------------------------------
Automation (ROBOTT):

- On 08/25/04, ROBOTT v0.8.1 was installed on String 1 (OCR GND-143).
   -- Operations is being conducted in the "auto" mode with the FOT closely=
=20
monitoring and noting any discrepancies.
   --  ROBOTT is NOT being used for maneuvers.
- ROBOTT v0.9 is scheduled for delivery to Strings 2 & 3 on 09/21/04.

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Extra Spacecraft Activities:

None

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Anomalies:

DOY 04254 (09/10/04) ACE Anomaly S04-0008 - Ordinance Fire Component Red=20
High Limit Violation
At 16:34:42  Mnemonics ORD_AB_P1 and ORD_AB_P2 violated their Red High=20
limits. At 16:34:44  both mnemonics came back within their high/low=20
limits.  During the time of 16:34:42 - 16:34:44 the FOT was conducting an=20
Attitude Maneuver.  This violation also occurred  on DOY 03157 (S03-0011)=20
and DOY 03267 (S03-0020).  IMPACT: None

DOY 04254 (09/10/04) ACE Anomaly S04-0009 - Thruster Firings Every Other=20
Rotation
During the 2nd attitude maneuver on DOY 254 2004, thruster firings occurred=
=20
at every other rotation.  When this occurs the nutation of the spacecraft=20
increases significantly.  The nutation after the maneuver was approximately=
=20
7=B0 and dropped to 1=B0 within 4 hours.  Nutation after a nominal maneuver=
 is=20
typically 0.5=B0.  The reasons for the thrusters firing every other rotation=
=20
is being investigated.  The same maneuver conditions have been used=20
successfully in the past.  Possible reasons include a longer time for=20
spacecraft relay switching or a spin rate different than that reported by=20
the star scanner.  IMPACT:  All thruster firings were completed and the=20
spacecraft is at the correct attitude.  No data loss occurred.  The science=
=20
center has been notified so that they can assess the impact to data quality.

DOY 04256 (09/12/04) ACE Anomaly G04-0104 - GDS 26m (DSS-16) Command Mod=20
Index Reset
Commands were not getting into the S/C and FOT requested DSS-16 to reset=20
the command mod index.  Once reset, commands were received and processed by=
=20
the S/C.  IMPACT:  Delayed pass activities.  Had the FOT not been=20
monitoring, ROBOTT would have paused C&C and no other pass=20
activities/commands would have been executed.  DR# G104798

DOY 04257 (09/13/04) ACE Anomaly G04-0105 - MAD 26m (DSS-66) Wrong Command=
=20
Mod Index
FOT noticed extremely low AGC levels during commanding (-130db) and=20
requested DSS-66 manually enter the correct Command Mod Index.  Nominal AGC=
=20
levels were reported after change made.  IMPACT:  Delayed pass=20
activities.  Had the FOT not been monitoring, ROBOTT would have paused C&C=
=20
and no other pass activities/commands would have been executed.  DR# =
 M102735

DOY 04258 (09/14/04) ACE Anomaly G04-0106 - GDS 26m (DSS-16) Command Mod=20
Index Reset
Commands were not getting into the S/C and FOT requested DSS-16 to reset=20
the command mod index.  Once reset, commands were received and processed by=
=20
the S/C except the C&DH B Poke which was never verified.  That problem is=20
under-investigation.  IMPACT:  Delayed pass activities.  Had the FOT not=20
been monitoring, ROBOTT would have paused C&C and no other pass=20
activities/commands would have been executed.  DR#  G104806

DOY 04259 (09/15/04) ACE Anomaly G04-0107 - ROBOTT C&C Failure During=
 G_ACEUP
C&C never acquired CC privilege and paused during the execution of=20
procedure G_ACEUP.  IMPACT:  By the time the problem was fixed by the FOT=20
data was online so the procedure G_PRECAL was not able to be executed.  Had=
=20
the FOT not been monitoring, ROBOTT would have paused C&C and no other pass=
=20
activities/commands would have been executed.  DR CDSID 21015

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Glen A. Miller
ACE Flight Operations Observatory Engineer
Honeywell Technology Solutions Inc.
Goddard Space Flight Center
Building 14, Room W10A
Mail Stop 428.2
Greenbelt, MD 20771

Office: 301-286-7071
Pager: 800-425-3174
Fax:    301-286-1729
gamiller@pop500.gsfc.nasa.gov
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~