ACE Weekly 05/21/04 - 05/27/04

All ACE spacecraft subsystems are performing nominally.  Attitude and 
stationkeeping maneuvers were successfully executed on 05/27/04.  The next 
attitude maneuver is scheduled for 06/11/04.

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

The ACE transit of the old Solar Exclusion Zone (SEZ) will continue through 
06/14/04. For the first time ever, ACE will transit the solar disk on 
06/01/04. On that date, the Sun's angular radius is 0.2629 degree (as seen 
from Earth's center). The solar transit will last nearly 21 hours (again, 
as seen from Earth's center). The main features of this transit are given 
in the following table (times are UTC).

5/19    01:42   4.75 deg inbound
5/27    07:45   2.0 deg inbound
5/30    23:39   0.63 deg inbound
6/01    01:18   0.2629 deg (kissing solar disk inbound)
6/01    10:46   0.197 deg (radius of closest approach to solar center)
6/01    22:14   0.2629 deg (kissing solar disk outbound)
6/02    23:28   0.63 deg outbound
6/06    11:15   2.0 deg outbound
6/14    07:18   4.75 deg outbound

The 0.63 deg epochs are included because that radius represents the closest 
approach during our last transit in February/March. ACE will spend almost 
exactly 3 days within this zone.

********************************

 From Craig Roberts (FDF):
ACE stationkeeping maneuver SK-32 was successfully performed on 05/27/04 
following a successful attitude reorientation maneuver earlier in the same 
pass.  Continuous-mode firing of the aft-end axial jets 3A and 4A commenced 
at 16:45:45 UTC and ended at 16:47:24.  The key burn parameters were:

-- delta-V = 0.5358 m/sec (Sunward)
-- burn duration = 98.7061 sec
-- fuel used  = 0.37132 lbm (0.1684 kg)

As was expected, the spin rate decreased during the SK burn.  It dropped 
from 4.9372 rpm to 4.9142 rpm, a decrease of 0.023 rpm and very close to 
the prediction.  As 4.9142 rpm is sufficiently within constraints, no 
spin-up burn was performed today (a spin-up burn is very likely come the 
next stationkeeping maneuver, however).

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

NONE

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

TAPS:
- Transition from GTAS to TAPS occurred on 03/18/04. All trending 
activities are being accomplished using TAPS.
- Installation of TAPS release 4.3 is tentatively scheduled for the first 
week of July 2004.  All open DRs will be fixed in this release.
- An additional DR has been opened.  The FOT found that TAPS drops 3 frames 
per every 152 frames processed for product generation.

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

- Release 0.6 installed on String 1 on 05/13/04.  Operations has moved to 
String 2.
   -- 22 DRs have been verified out of 25 reported fixed in this release.
   -- 1 new DR opened this week.
   -- 17 DRs have been opened as a result of FOT testing of Release 0.6.
- 20 DRs are OPEN to date.
-  It has been determined that Release 0.6 will not be used operationally, 
however testing will continue until Release 0.7 is delivered.
- SUG development is ongoing.  A DRAFT version has been delivered and is 
still being reviewed by the FOT.  Comments will be provided to the developer.
- FOT training on ROBOTT began 05/05/04 and additional sessions are being 
developed.

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

NONE

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

DOY 04142 (05/21/04)  ACE Anomaly G04-0042 - GDS 26m (DSS-16) Telemetry Outage
At 16:03:20, the FOT lost telemetry from DSS-16.  Telemetry resumed at 
16:04:30.  Station reported the problem was with the X-axis in auto track 
mode.  Station switched to Program Mode of tracking and achieved solid 
telemetry lock.  IMPACT:  None.   Telemetry was subsequently retrieved via 
recorder dump.  DR# G104427

DOY 04144 (05/23/04)  ACE Anomaly G04-0043 - MAD 26m (DSS-66) Incorrect 
Command Modulation Index
During G_INITIAL_CONTACT, the FOT noticed RCVR_A/B_AGC limit 
violations.  After successfully running the procedure the FOT checked the 
DSNMON 0158 data for the value of the carrier suppression (command 
modulation index).  The value was going from 0 dB to 7.16 dB, which is 
incorrect.  The FOT informed DSS-66 of the possible problem and requested 
they confirm their command modulation index value.  DSS-66 stated they had 
a modulation index value of 0.60 radians (nominal value is 0.86).  The FOT 
requested the operator  change the value to 0.86 radians.  The value was 
changed and the FOT sent a /no_op to confirm a good command 
link.  IMPACT:  Delayed pass activities.  DR# G104439

DOY 04146 (05/25/04)  ACE Anomaly G04-0044 - GDS 26m (DSS-16) MFR Swap
Telemetry dropped out from 14:48:50 - 14:50:30.  Contacted DSS-16 and they 
were looking into the problem.  The MFR2 dropped lock for unknown reasons 
causing TCP1 TS1 & TS2 to also drop Telemetry lock.  They had to switch to 
MFR3 to solve the problem.  IMPACT:  Delayed pass activities.  Telemetry 
was subsequently retrieved via recorder dump. DR# G104436

DOY 04147 (05/26/04)  ACE Anomaly G04-0045 - GDS 26m (DSS-16) Commands Not 
Getting to Spacecraft
Attempt to send initial NO-OP command at beginning of pass was 
unsuccessful.  DSS-16 notified of problem.  Station found composite at .87 
vice 1.29.  Operator manually entered mil directive and commands were 
successfully received by the spacecraft.  IMPACT:  Delayed pass 
activities.  DR# G104439



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~