It is expected that the offset for each CCD's pulse-height calibration will depend on the actual light background, which is a function of the aspect of the telescope. rgsoffsetcalc utilizes the simultaneously transmitted diagnostic mode data (the Q-dumps) and determines the offset per diagnostic dataset. These are written together with time stamps into a calibration data file, which must be explicitly presented to the CAL by each task that would have them override the static calibration data. The time tags allow for potential interpolations of drifts of the offsets during an exposure. These calibrations are computed separately for each instrument, but not for each exposure, and so this step is skipped if the file already exists in the current working directory. To force construction of fresh offsets the user must manually delete this file before running rgsproc. Providing these calibrations to rgsenergy is not recommended currently, and the default is to skip this step altogether (parameter calcoffsets=no).
