Are there specific signs of good data (or, the converse)?
(2/4/92)
- a master veto rate less than 170 indicates good data (master veto rate is defined
in the "count-rates" question); above 170 counts/sec, there are
unpredictable background "enhancements". These enhancements largely
affect the lowest 15 channels. The enhancements are not yet understood.
- Look closely at the image of the full photon file (PSPC data).
You should see ONE spoke on either side of the main support ring.
This spoke is relatively sharp as it was parallel to the wobble
direction. The other spokes should be faintly visible at intervals of
45 degrees. A faint spoke appearing closer than 45 degrees from
another spoke is the sign of a different aspect solution or a
different roll angle. Likely, it will be a relatively brief exposure
done well before or well after the bulk of the observations. For an
on-axis source, it will not be a problem. For an off-axis source, you
will need to be careful not to include those photons in as
"background" (especially if you define your background as an annulus
about the source).
- the presence of scattered solar x-rays appears as an upwardly-going
"exponential" curve in a count rate versus time plot, and usually
appears at the start or the end of an observation sequence as Earth
block starts/ends.
- an upturn in the background spectrum in the lowest channels
indicates a contribution from afterpulses (pulses generated following
a strong pulse). These times and events must be filtered out of the
data.
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