An experimental technique to resolve the Landsat-7 spacecraft heater debond issue

Results of thermal vacuum testing of simulated 100% debonded equipment panel heaters revealed that with the primary heater on all the time and an 80/spl deg/C heat sink, the worst case maximum heater temperature is 166/spl deg/C for a 448 W/cm/sup 2/ heater power density, and 223/spl deg/C for a 0.673 W/cm/sup 2/ heater power density. All the heaters on the equipment panels of the Landsat-7 spacecraft have a maximum heater power density of 0.460 W/cm/sup 2/ or less, with only either the primary or redundant heater turned on. The equipment panel heaters have a 200/spl deg/C maximum allowable temperature in the manufacturer´s specifications. The maximum heater temperature for a 100% debonded heater in the worst case is 170/spl deg/C, which has a 30/spl deg/C margin. In order to exceed the 200/spl deg/C maximum allowable temperature, the maximum heater power density needs to be higher than 0.589 W/cm/sup 2/. Data from the tests to induce heater failure showed that the heater failed after it had reached 250/spl deg/C to 253/spl deg/C for 25 minutes. In order to exceed 250/spl deg/C, the maximum heater power density needs to be higher than 0.9 W/cm/sup 2/. For these reasons, there was no need to replace the equipment panel heaters which were suspected to have debonded.