DPA-A Anomalous Shutdown
What is it?
The DPA-A shuts down anomalously, presumably due to a spurious command.
Note
The diagnosis and response to this anomaly presented in this document assumes that the
active BEP is powered by DPA side A.
When did it happen before?
The DPA-A has shut down 4 times over the mission:
- October 26, 2000: 2000:300:15:40, obsid 979
- December 19, 2002: 2002:353:20:26, obsid 60915
- January 12, 2015: 2015:012:00:01, obsid 52186
- December 9, 2016: 2016:344:07:40, obsid 17615
Will it happen again?
It appears likely that the anomaly will occur again if the mission continues.
How is this anomaly diagnosed?
Within a major frame (32.2 seconds), one should see:
- 1DPPSA (DPA-A Power Supply On/Off) change from 1 to 0 (On to Off)
- 1DPP0AVO (DPA-A +5V Analog Voltage) drop to 0.0 +/- 0.3 V
- 1DPICACU (DPA-A Input Current) drop to < 0.2 A (this value is noisy, so take an average)
- DPA-A POWER should go to zero
- 1DP28AVO (DPA-A +28V Input Voltage) is expected to have a small uptick, ~0.5 V, consistent with
the load suddenly dropping to zero
- The software and hardware bilevels will likely not have normal values if BEP side A is active.
All other hardware telemetry should be nominal. The current values for these can be found
on our Real-Time Telemetry pages. Older data can be examined from the dump files or the
engineering archive.
What is the response?
Our real-time web pages will alert us and the Lead System Engineer will call us. We need to:
- Send an email to the ACIS team at the official anomaly email address. If it is off-hours, call
Peter and Bob.
- Send an email to
sot_red_alert
announcing that the ACIS team is aware of the DPA-A shutdown
and is investigating, and that a telecon will be called when more information is available.
- Contact the GOT Duty Officer to inform that we need the dump data as soon as possible and to
email or call us when the dump file is available.
- Process the dump data and make sure that there is nothing anomalous in the data BEFORE
the shutdown. We want to know if a new occurrence looks just like the previous occurrences.
If yes, it should appear as if in one frame the DPA-A turned off.
- Once analysis of the dump data is complete, convene a telecon at the next reasonable moment
with the ACIS team and review the diagnosis. The MIT ACIS team (Peter Ford, Bob Goeke, Mark
Bautz, and Bev LaMarr) should also be included in the discussion, either in the telecon or
via email. If the diagnosis is consistent with previous DPA-A anomalies, proceed with the
recovery. If the diagnosis is not consistent with previous DPA-A anomalies, stop and start a
more involved analysis with the ACIS team.
- As soon as the time of the shutdown is known, inform
sot_yellow_alert
.
- Identify whether or not additional comm time is needed and if so ask the OC/LSE to request it.
- Send an email to
sot_red_alert
and call a telecon with the FOT, SOT, and FDs to brief
them on the diagnosis and the plan to develop a CAP to recover.
- Prepare a CAP and submit it for review to capreview AT ipa DOT harvard DOT edu, and cc: acisdude.
It will also be necessary to call the OC/CC to determine which number should be used for the CAP.
This CAP will have the following steps:
- Execute the CAP at the next available comm. Reloading the flight software patches can take
a half an hour, so ensure that there is enough time in the comm to execute the entire procedure.
- Write a shift report and distribute to
sot_shift
to inform the project that ACIS is restored
to its default configuration.
Note
As of this writing, the latest ACIS Flight Software Patch is F, Optional Patch G. Before preparing
the CAP, the latest version of the procedure should be checked.
Impacts
- Until the DPA-A is powered back on, science operations will be interrupted.
- The warmboot of the BEP will reset the parameters of the TXINGS patch to their defaults.
They can be updated in the weekly load through a SAR.
- After recovery from a DPA-A shutdown, the power status may be in an unusual state (e.g., lower
than expected input current) due to FEPs being off. This situation should resolve itself with
the next observation.
Relevant Procedures
FOT Procedures
SOP_ACIS_DPAA_ON
(PDF) (DOC)
SOP_ACIS_SW_STDFOPTG
(PDF) (DOC)
SOT_SI_SET_ACIS_FP_TEMP_TO_M121C
(PDF) (DOC)
CAPs
- CAP 1407 (DPA-A Poweroff Recovery) (PDF) (DOC)
- CAP 1342 (DPA-A Poweroff Recovery) (PDF) (DOC)
- CAP 818 (DPA-A Side Recovery from Enabled/Powered Off State) (PDF)