CMA1 Temperature and Detector StabilityDuring the early phase of the mission, the CMA1 detector/HT supply combination commonly exhibited unstable behaviour (ref. EXPRESS No. 3 p.3 ) at elevated detector temperatures. Operational procedures were instituted to maintain a low average CMA1 temperature, namely a systematic switch off of the 28V power supply (A1 line, analogue electronics and HT convertors) for maneouvres, perigee passes and some non-LE prime observations, and a restriction of the maximum solar aspect angle to![]() These procedures have reduced to practically zero the occurrence of instability and indeed long observations in the second half of 1984 have demonstrated that there is no immediately obvious degradation in performance if the temperature is maintained below 27°C.
In order to see how these constraints affect the total allowed duration of an
observation it is important to quantify the CMA1 detector temperature
behaviour as a function of the
Figure 1 shows five of these curves, covering the typical range 90°
Fig. 2 shows the derivatives of the temperature curves for
Maximum observation duration for 110°<
Maximum observation duration for 95°<
Basically unrestricted duration for
Figure 1
Figure 2
Page authors: Lorella Angelini Jesse Allen HEASARC Home | Observatories | Archive | Calibration | Software | Tools | Students/Teachers/Public Last modified: Thursday, 26-Jun-2003 13:48:32 EDT |