We have prepared a simple 7 node mathematical thermal model of the CUBIC payload and a more comprehensive 73 node model. Both have been subjected to external conditions that simulate the range of temperatures expected for a typical orbit. Because the electronics boxes are closely coupled to the CUBIC baseplate, which we have assumed is closely coupled to the SAC-B spacecraft, we do not expect the electronics to experience extreme temperatures. Some results of our models are shown in Figures 25 and 26, and a complete listing of one of our detailed thermal runs is given in Appendix 3. The passive cooling of the radiation plate is predicted to achieve an average temperature of less than -35 C for a low inclination orbit. The back side of the TEC will be about 8 C warmer than the cold plate.
We have performed laboratory tests to verify the mathematical thermal model. These tests have been done by building a mockup of the flight cold finger and connecting it to a plate held at -40 C by LN2 coils. The entire assembly was operated at vacuum to eliminate thermal conduction and convection from the air. The tests agreed well with our thermal models. We predict that the CCD operating temperature will be between -80 C and -85 C, depending on the thermal case. Performance during the SAC-B thermal-vacuum tests at INPE in July 1995 was consistent with these predictions.