Event data stops being reported for one or more CCD/FEP combinations and the delta overclock values are peculiar, large and negative for the first three output nodes and large and positive for the fourth output node.
It appears likely it could happen again.
Both of the following symptoms will be noticed:
deltaOverclock
values reported from these FEPs are large and negative
for the first three output nodes and large and positive for the fourth output
node. If one sees this, this is a clear indication of the Hi/Lo Pixel Anomaly
and not a FEP Anomalous Reset.Both of these symptoms can be observed from one of the PMON pages. We should also receive red alert emails and text messages from PMON which say “Repeated consecutive overclock values of 0 or 4095” and/or “Repeated consecutive delta-overclocks outside expected range”.
If you happen to observe the incident on PMON, send a warning email to
CXCDS Ops (send to operators@cfa
or ascdsops@head
). Importantly,
we have a SOP
written to intervene if the observation with the anomaly is still in
progress to dump diagnostic data. If the analysis confirms the anomaly,
then send an email to the Flight Directors alerting them of the incident.
Otherwise, the most likely scenario is that we will be notified by CXCDS Ops that data collection on one or more of the CCDs stopped during an observation. We need to:
initialOverclock
and deltaOverclock
values will be
consistent with zero for the first three output nodes and will be close to
a value of 4095 for the last output node.WSPOW00000
command should clear the problem. However, any run immediately following
which executes WSVIDALLDN
instead (such as an event histogram or
no-bias run) may be affected, since in this case the anomaly may persist.