DEA Sequencer Reset During a Science Observation
What is it?
The DEA sequencer crashes, resulting in loss of science data from all
video boards for the rest of the science run.
When did it happen before?
The DEA Sequencer has reset three times during the mission; most recently in 2013:
- June 22, 2004: 2004:174:20:49, obsid 5008
- February 13, 2009: 2009:044:00:14, obsid 10275
- July 30, 2013: 2013:211:05:42, obsid 15474
Will it happen again?
It appears likely that the anomaly will occur again.
How is this Anomaly Diagnosed?
- The science run will be terminated, sending a
scienceReport packet that will contain
non-zero fepErrorCodes and a non-zero terminationCode.
- Within a major frame (32.2 seconds), there will be a slight drop in DPA Input Current A and/or B,
(1DPICACU and/or 1DPICBCU) ~0.2-0.3 A. The drop in two input currents depends on which side is
running which FEPs.
- Within a major frame, the 1STAT1ST bilevel will toggle off (science idle).
- DEA Housekeeping will show sharp drops in the temperatures of FEP 0 and/or FEP 1, if they are
running.
What is the first response?
Most likely we will be notified by CXCDS Ops that data ceased prematurely for an
observation. We need to:
- Send an e-mail to the ACIS team (including Peter Ford, Bob Goeke, Mark Bautz,
and Bev LaMarr) to alert them to the existence of the anomaly.
- Examine data from the next observation because the setup for the next
observation should clear the problem. This can be done from the realtime
SW pages.
- Process the dump data and get access to the CXC products to verify that this
anomaly looks identical or similar to previous occurrences.
- Convene a telecon with the ACIS engineering team at the next reasonable moment
to review the data and diagnosis.
Impacts
- The last portion of the science run will be lost. The following science run should be unaffected.
Relevant Notes/Memos
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Open access, full memo: