Rejected Flight Grades: Raw Mode Analysis

(Based on analysis by Bev LaMarr)

Data: Raw Mode, ObsID 62273, external calibration source, -120 C

49012 events, 916 telemetered frames of 10 sec each, 20 x 1024 pixel strip

Of the grades currently rejected onboard, only ACIS grade 66 has spectral features that correspond to the Mn-K lines in the external calibration source.

Statistics of Flight Rejected Grades
ACIS GradeASCA GradeCount rate (cts/sec/CCD) Percent of total eventsSpectrum
24 7 1.0 0.3PS Plot
66 7 11.5 3.8PS Plot
107 7 24.9 8.2PS Plot
214 7 26.7 8.8PS Plot
255 7 121.6 40.2PS Plot

Flight Grades with more than 1 percent of total events
ACIS GradeASCA GradePercent of total eventsRejected?Spectrum
0 0 9.2 No PS Plot
2 2 1.6 No PS Plot
64 2 12.8 No PS Plot
66 7 3.8 Yes PS Plot
72 6 1.1 No PS Plot
80 6 1.2 No PS Plot
104 6 1.2 No PS Plot
107 7 8.2 Yes PS Plot
208 6 1.1 No PS Plot
214 7 8.8 Yes PS Plot
255 7 40.2 Yes PS Plot

The grade 66 events include some X-rays from the cal source as can be seen by the small Mn-K peak in the spectrum of these events. An estimate of the number of events in the Mn-K peak is 611 out of 1869 total events (between 1175 and 1625 ADU). This corresponds to a rate of 3.8 cts/sec/CCD in X-rays and 7.8 cts/sec/CCD in background events from the grade 66 events.

Applying the same criteria to G02346 data, there are 9057 counts in the Mn-K peak (55.9 cts/sec/CCD). Assuming that g66 is the only non-G02346 grade that includes substantial X-rays, approximately 6% of the X-ray events at Mn-Ka are being lost to g66 events.

Last updated March 21, 2000
Web page by Catherine E. Grant ( cgrant@space.mit.edu )
Center for Space Research
Massachusetts Institute of Technology
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