ACE Weekly 08/27/04 - 09/02/04

All ACE spacecraft subsystems are performing nominally.  An attitude 
maneuver was successfully executed on 08/27/04.  The next attitude maneuver 
is scheduled for 09/03/04.

============================================================================
Orbit Events:

 From Craig Roberts (FDF) regarding SK-33:
The ACE L1 Lissajous orbit stationkeeping maneuver SK-33 was executed 
successfully on Friday, August 20, 2004 following a scheduled attitude 
reorientation maneuver during the same pass on DSS-16.  Key data concerning 
the burn follows.

-- Burn Start:  16:34:32 UTC
-- Burn Stop:  16:35:36 UTC
-- Delta-V = 0.3642 m/sec (anti-Sunward)
-- Burn Duration = 63.7559 sec (continuous firing)
-- Fuel Usage = 0.2434 lbm (0.1104 kg)
-- Final Fuel Mass per tank = 44.1972 lbm (times 4 tanks)
-- Fuel remaining = 176.7888 lbm (80.1896 kg)
-- Thrusters:  Top-deck Axials 1A and 2A
-- Spin axis right ascension = 154.02 deg
-- Spin axis declination = 15.91 deg
-- Initial spin rate = 5.0103 rpm
-- Final spin rate = 4.9888 rpm
-- Spin rate change = -0.0215 rpm

Real-time Doppler measurement of the line-of-sight delta-V component, which 
was expected to be -0.3623 m/sec, showed the burn to be just 0.22 percent 
hot.  This represents a performance deviation of 0.8 millimeter/sec.  A 
very short-arc (approx. 5 days) post-burn orbit determination solution has 
since confirmed that SK-33 went well.

ACE's Lissajous orbit has now transitioned to an opening pattern, so the 
ACE motion will now be counterclockwise about L1 (and for that matter, the 
Sun) for quite a long time to come.

+++++++++++++++++++++++++++++++++++++++++

The ACE transit of the Solar Exclusion Zone (SEZ) continue through 
09/11/04.  The minimum Sun angular radius was 0.32 degrees (as seen from 
Earth's center) on 08/30/04.  Features of this transit are given in the 
following table.

8/18    4.96 deg inbound
8/25    2.13 deg inbound
8/29   0.61 deg inbound
8/30    0.32 deg  minimum SEZ angle this transit
8/31   0.41 deg outbound
9/05    2.30 deg outbound
9/11    4.78 deg outbound

More data regarding the transit will be included in coming weeklies.

=====================================================================
OCRs Executed:

None

=====================================================================
Ongoing Activities:

TAPS:
- Installation of TAPS release 4.3 occurred on 07/20/04.  FOT testing of 
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.

----------------------------------------------------------------------------
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 
monitoring and noting any discrepancies.
- Testing of v0.8.1 by the FOT will continue on String 2.
   -- To date all DRs fixed in this release have been tested.  One (1) DR
has failed and five (5) new DRs have been written.

============================================================================
Extra Spacecraft Activities:

None

=====================================================================
Anomalies:

DOY 04239 (08/26/04) ACE Anomaly G04-0100 - GDS 26m (DSS-16) Receiver B 
Out-of-Lock
DSS-16 ended their sweep for the uplink at 14:35:55, however the second 
receiver on the spacecraft (RCVR B) lost its lock on the uplink.  FOT 
requested DSS-16 resweep and receiver B locked up on 
signal.  IMPACT:  Since Automation did not see a good active foward link 
C&C would have not continued.  DSN would have not know of the problem 
because it is not a part of the two-way loop.  None of the activities would 
have started that day.  C&C had to be rebooted after receiver B 
locked.  DR# N102329     (Left off previous weekly)

DOY 04243 (08/30/04) ACE Anomaly G04-0088 (Appended) - ADS Failure
Received error when attempting to start ADS.  Killed processes on 
workstation and rebooted the software.  IMPACT:  Delayed pass activities.

DOY 04245 (09/01/04) ACE Anomaly G04-0101 - GDS 34m (DSS-27)  Reliable 
Network Server (RNS) Problem
AT 14:15 the FOT received extensive VC2 Errors (BOT 14:05).  Notified JPL 
Comm.  Telemetry good at 15:05:40.  IMPACT:  Delayed SSR activities during 
SEZ transit.  Data had to be retrieved via CDR file.  DR# N102342

DOY 04245 (09/01/04) ACE Anomaly S04-0007 - SSR-B Full/Failover
SSR B Full due to inability to dump recorder during SEZ transit.  Autonomy 
Bin 42 failover occurred as expected.  IMPACT:  None.

DOY 04246 (09/02/04) ACE Anomaly G04-0102 - GDS 34m (DSS-27)  Reliable 
Network Server (RNS) Problem
AT 14:03 FOT received telemetry dropouts (BOT 14:05).  Queried station for 
TLM dropouts, and station indicated that errors were due to their RNS. 
Station performed TLP re-initialization at ~14:06.  Team experienced 
momentary TLM dropouts until telemetry returned reliably at 
14:27:58.  IMPACT:  Delayed pass activities.  Data had to be retrieved via 
CDR file.  DR# G104777
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~