Calibration Access and Data Handbook

Procedure

Provides a list of thresholds per CCD.

For GRADE-one events (single pixel events) REJTHRESH is applied such that any pixel with PI below this threshold is strictly ignored by rgsevents, and will not be further processed. ACCTHRESH is used such that any event with no pixels at or above this threshold will be marked with the BELOW_ACCEPTANCE rejection flag.

These thresholds REJTHRESH & ACCTHRESH are not directly applicable to pixels with grade larger than one. In order to apply them in such cases a set of three empirically determined charge-splitting ratios is included in QSPLITR2/3/4, one for each of the grades between two and four. The charge-splitting ratio is the average proportion of the total energy belonging to the pixel with the largest individual energy in a reconstructed event. This ratio is used to adjust the threshold to account for the extra energy in pixels from on-board reconstruction.

For GRADE-one events (single pixel events), ${\tt QSPLITR1}=1$. For ${\tt GRADE}>1$ events, the thresholds are scaled according to

$${\tt REJ\_THRESH(GRADE,NODE)}={\tt REJTHRESH}/{\tt QSPLITR(GRADE-1)}\ ,$$

and

$${\tt ACC\_THRESH(GRADE,NODE)}={\tt ACCTHRESH}/{\tt QSPLITR(GRADE-1)}\ .$$

GRADE ranges from 1-4, and ${\tt QSPLITR2/3/4}\le 1$.