DEA-A Anomalous Shutdown¶

What is it?¶

The DEA-A shuts down anomalously, presumably due to a spurious command.

When did it happen before?¶

The DEA-A has shutdown only once in the mission, in 2005:

• September 15, 2005, 2005:258:23:31:29, obsid 6221

Will it happen again?¶

It appears it could happen again, but one occurrence provides little guidance.

How is this Anomaly Diagnosed?¶

Within a major frame (32.2 seconds), one should see:

• 1DEPSA (DEA-A Power Supply On/Off) change from 1 to 0 (On to Off)
• All DEA-A Analog Voltages (1DEP3AVO, 1DEP2AVO, 1DEP1AVO, 1DEP0AVO, 1DEN0AVO, 1DEN1AVO) drop to 0.0 +/- 0.5 V
• 1DEICACU (DEA-A Input Current) drop to < 0.2 A (this value is noisy, so take an average)
• DEA-A POWER should go to zero
• 1DE28AVO (DEA-A +28V Input Voltage) is expected to have a small uptick, ~0.5 V, consistent with the load suddenly dropping to zero

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 first 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 DEA-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 previous occurrences. If yes, it should appear as if in one frame the DEA-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 DEA-A anomalies, proceed with the recovery. If the diagnosis is not consistent with previous DEA-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:
  • Power on the DEA side A (SOP_61036_DEAA_ON)
  • Warm boot the BEP and restart housekeeping (SOP_ACIS_WARMBOOT_DEAHOUSEKEEPING)
  • Set the focal plane temperature to -121 \(^{\circ}\rm{C}\) (SOT_SI_SET_ACIS_FP_TEMP_TO_M121C)
• Execute the CAP at the next available comm.
• Write a shift report and distribute to sot_shift to inform the project that ACIS is restored to its default configuration.

Impacts¶

• Until the DEA is powered back on, science operations will be interrupted.
• After DEA is powered back on, the focal plane temperature will be unregulated and possibly uncalibrated. Recovery requires a BEP warmboot and setting the focal plane temperature to -121 \(^{\circ}\rm{C}\).
• 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.

Relevant Procedures¶

Relevant Notes/Memos¶

• Flight Note 572 (includes SOT memo “ACIS DEA-A Off anomaly” by Edgar & Germain)
• ACIS - DEA ADC Reset (Dorothy Gordon)