The detector material is shown for all bands in table 3.2. The InSb, the Si:As (BIBIB) and the Si:Ga detectors are operated at a temperature of 4-5 K; the Si:Sb detectors for the FP are heated to 10 K (FP); and the Ge:Be detectors are cooled by a thermal conductor to the 2 K cryostat heat sink. The detectors are used with integrating pre-amplifiers with non-destructive read-out, employing heated JFET's.
As photons fall onto the detectors the current generated charges up a capacitor (one per detector). The voltage across this capacitor is read-out non-destructively 24 times a second and digitised into a bit value between 0 and 4095. After a set interval the capacitor is discharged with a destructive readout (basically short-circuited). The time interval between two detector resets is automatically determined from the user's input data (flux and SNR, or execution speed) and is either 1, 2 or 4 seconds. This destructive readout affects the readout electronics, which then take some time to return to normal.
Figures 5.7 and 5.9 give examples of data in which the individual datapoints from the non-destructive readouts and reset pulses can be seen.
To observe faint sources, integrations over several reset intervals are used. Raw data is saved in an Edited Raw Data (ERD) file, with an ERD file for one second consisting of an array of 52 ramps of 24 read-out's each. The Standard Processed Data (SPD) and Auto-Analysis Results (AAR) files contain for each detector a single flux estimate for each reset interval. As mentioned previously, normally only a subset of the array will contain clearly interpretable data.
Examples of ERD, SPD and AAR for each AOT are shown in sections 4.2 to 4.5 with the processing chain that generates SPD & AAR from ERD discussed in chapter 8.