All modes can optionally include a focal plane chopper.
The backbone of the photometric calibration are internal standard sources checked against celestial primary standards. The instrument is in excellent condition with all components functioning properly. There is increased detector noise due to the ionizing cosmic radiation affecting the detectability of the faintest sources. All lessons learnt from operating the instrument in space are continously being implemented in the standard data reduction software packages available to every observer. Particular strengths of the instrument include the detectability of very cold sources, high resolution mapping and fast spectrophotometry.