An innovative thermal balance test for Landsat-7 ETM+ instrument: cheaper, faster, unusual, successful

A thermal balance test with cold vacuum chamber walls is needed at the instrument level for the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) instrument. The initial approaches for the thermal balance test had significant impacts on the cost and schedule. This paper presents an innovative approach, which is cheaper, faster and better. It consists of two modifications to the baseline thermal vacuum (T/V) test profile, and will maintain the total test time in the vacuum chamber the same as the baseline. The first modification is to change the chamber wall temperature from 0/spl deg/C to -90/spl deg/C and enable the standby and safehold flight heaters during the 2.6-day radiative cooler cooldown to perform a cold thermal balance. The second modification is to reverse the order of 20% and 30% ETM+ duty cycles during orbital simulations in orbits 36 through 44, and change the chamber wall temperature from 0/spl deg/C to -90/spl deg/C and increase the duty cycle from 30% to 36% during orbital simulations in orbits 25 through 40 to perform a hot thermal balance. Reversing the order of 20% and 30% duty cycles in orbits 36 through 44 increases the time for 30% duty cycle continuous simulation by 0.3 day, and has a better chance of reaching a dynamic equilibrium. The innovative thermal balance test requires some extra test preparation time for adding kapton film heaters, kapton tape and a 0.0508 mm thick aluminized kapton cover to the Thematic Mapper Calibrator (TMC) test fixture.