Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) Thermal Design 2003-01-2638
This paper documents the thermal design of the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), an infrared and near infrared instrument going to Mars as a payload on the 2005 Mars Reconnaissance Orbiter (MRO). The CRISM instrument requires a complex thermal design with multiple thermal regions. The instrument is made up of three boxes, the Optical Sensing Unit (OSU), the Data Processing Unit (DPU) and the Gimbal Motor Electronics (GME). The OSU is the main box in the instrument and it holds the telescope, the spectrometer housing, the IR focal plane, the visible near infrared (VNIR) focal plane, the heat pipes, and the RICOR mechanical coolers.
The OSU thermal design is the most complex of the three boxes. It is approximately 17 inches long, 10 inches wide and 6 inches tall and it consists of 6 distinct thermal regions.
This paper will focus on the thermal design of the OSU and the difficulties in maintaining the different thermal regions. One example of this is the IR focal plane. The mechanical coolers and heat pipes are used to cool the IR focal plane to it's operating temperature. The problem is that the coolers have a heat lift capacity of approximately 750mW and therefore, the heat leak into the IR focal plane needs to be kept below this number. Among other things, this paper will discuss the selection of diode heat pipes to reduce heat leak from the off pipes and a detailed suspension system that was conceived to isolate the focal plane from the spectrometer housing that it is mounted to.