ACE Weekly 07/29/2015 - 08/04/2015

All ACE spacecraft subsystems are performing as expected.

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Attitude/Orbit:


Type               Attitude
Date             08/04/2015
DOY                216 2015
Thrusters        2R 4R+ 4R-
Duration      16:03 minutes
Start             14:30:19z
Stop              14:46:22z
ra,decStart    117.66,26.24
ra,decStop     121.72,11.79
ra,decExpect   121.95,11.22
Deviation          0.61 deg (-3.9%)
HGAStart          -8.79 deg
HGAStop           -8.34 deg
SunStart          17.76 deg
SunStop           13.32 deg
SpinStart        5.0096 rpm
SpinStop         5.0139 rpm
Nutation           0.19 deg
Firing            81 pulses
FuelUsed         0.2409 lbm
FuelRemain      96.7656 lbm
FinalSCMass    1331.025 lbm

Note: The previous week attitude maneuver (DOY 209) incorporated planning
for the upcoming (quarterly) crossing of the ecliptic, and targeted an
initial HGA angle of 4 degrees (reaching ~11 degrees by DOY 216). This plan
provided the maximum average sun angle for the week while nearing the
ecliptic crossing - fortunately, also rendering the usage of WS1 for the
ground anomaly recovery on DOY 210 feasible (see below under the Anomalies
section).

- The next attitude maneuver is scheduled for Tuesday, 08/11/2015

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OCRs:

None

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Activities:

Data Capture:  100%  DOY 207-214 2015

MMOC: Quarterly (3Q) security scans performed on the MMOC operational
systems on 07/30/2015.

Operational System Failover: The FOT performed a switch to the primary
operational system (mmocops1p) on 07/30/15. Both ASC and WS were informed
of the IP address change.

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Anomalies:

-  DOY 210 07/29/2015 S-ACE-33: Procedure Stuck Waiting for Command
   Verification

At 2015/210/11:41:32z, shortly after the beginning of the 11:35z-14:55z
DSS-65 pass, the ground system experienced an anomaly that halted the
ace_pass procedure just after starting recording on SSR-B. This event led
to no playback of SSR-A data and both recorders continued to record from
that point onwards. To resolve the issue, the FOT added a WS1 pass at
BOT 2015/210/20:20:00z.

The FOT planned to manually set SSR-B from recording to idle before
normal SSR activities and continue the pass as normal. Effectively,
this would yield the same result as if the DSS-65 pass was lost.

Based on the evaluation of the ground system observables, the ITOS command
graph component is suspect, but the confirmed root cause of the anomaly is
still under investigation.

IMPACT:
WS1 contact scheduled. Additionally, the 3Q security scans were delayed one
day due to addition of the WS1 support.


- DOY 210 07/29/2015 (SOAR IDs TBD): WS1 Loss of TLM Capability

A WS1 pass was added on 2015-210 (BOT:20:20:00z) to workaround the MMOC
ground anomaly experienced during the previous DSS-65 contact, which caused
both SSR-A and SSR-B to remain on RECORD state. Following initial
(successful) commanding and telemetry capabilities, at approximately
~20:35:12z, the MMOC stopped receiving ACE telemetry. Automation paused
(as expected) waiting for verification of RECORD_S0 command, and the
command was retransmitted every 60 seconds.

A series of re-sweeps were performed (one from WS1, another via Wallops)
in conjunction with a re-start of the ace_pass procedure with no success
(i.e., poor signal to noise per bit achieved). WS Systems Engineering then
performed a reset of the WS1 receiver(s), which allowed the station to
lock up successfully on the signal.

The FOT re-established telemetry around 21:59:44z and proceeded to
configure SSR-B from record to idle and started the playback of SSR-A.
The SSR-A dump was shortened from 201 to 43 slices and the remaining 158
slices (approx. 40 minutes) were carried-over to the next pass on DOY 211.

The FOT will follow-up with WS personnel to obtain more information
regarding the root cause of the anomaly.

IMPACT:
The FOT worked with WS and WAPS operations/engineering personnel
to troubleshoot the problem (re-starting the MMOC pass procedure) and
re-establish telemetry following the receiver reset. Lastly, the FOT
confirmed post-pass that there were no (VC4) DOY 210 data losses.