CCD Housing Temperature Monitor

Since the switch to STIS CCD Side 2 electronics (see ISR 2001-03) on 2001-Jul-10, it has not been possible to actively stabilize the CCD operating temperature, due to the lack of a temperature sensor on Side 2. Therefore, to control the thermal environment, a constant current is applied to the CCD thermo-electric cooler. This, however, allows small variations in CCD temperature. These variations are tracked indirectly by a temperature sensor in the CCD housing, so that temperature-dependent calibration can be performed.

The following plot shows the history of the CCD housing temperature since the repair of Side 2 in May 2009. The x-axis gives the date in years, while the y-axis gives the CCD housing temperature in degrees Celsius. The diamonds are the housing temperature as measured from the dark and bias calibration observations. This amounts to three points per day. The solid black (triangles very close together) curve is the sun time*solor intensity as a function of time. This curve tracks the orbital precession of HST and matches well the periodicity found in the housing temperature.

The following plot shows the history of the CCD housing temperature from the switch to Side 2 to the Side 2 failure in 2004. The dots are the temperatures for each of the CCD observations. The filled diamonds are the medians per calendar month.