The cosmic background explorer observatory (COBE) underwent a thermal vacuum/thermal balance (TV/TB) test in the space environment simulator (SES) at the Space Simulation Test Laboratory, Goddard Space Flight Center. This was the largest and most complex test ever accomplished at this facility. The 4 × 4 m (13 × 13 ft) spacecraft weighed approximately 2223 kg (4900 lb) for the test. The test setup included simulator panels for the inboard solar array panels, simulator panels for the, flight cowlings, sun and earth sensor stimuli, thermal/radio frequency shield heater stimuli, and a cryopanel for thermal control in the attitude control system/shunt dissipator area. The fixturing also included a 4.3 m (14 ft) diameter gaseous helium cryopanel which provided a 20° Kelvin (K) (-253° C) environment for the calibration of one of the spacecraft's instruments, the differential microwave radiometer. This cryogenic panel caused extra contamination concerns so a special method was developed and written into the test procedure to prevent the high buildup of condensibles on the panel, which could have led to backstreaming of the thermal vacuum chamber. The test was completed successfully with a high-quality simulated space environment provided to the spacecraft. This paper describes the test requirements, test setup, special fixturing requirements, related contamination concerns, and a general discussion of the test and test results.

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