<title>Solar intrusion thermal analysis</title>

Abstract

During the Fall of 1994 eclipse season, GOES-8 Sounder telescope secondary mirror temperature exceeded qualification limits, while operating normally in the vicinity of the Sun. Based on a simple conservative thermal analysis, which was performed in January of 1995, it was determined that there was a health and safety issue with operating Imager or Sounder in the vicinity of the Sun. As a result, a set of operating constraints were levied on both instrument normal operations, limiting them from scanning in the vicinity of the Sun. Since the simple thermal analysis was believed to be conservative, ITT was tasked to develop a detailed model of the secondary assembly and to determine the effect of focused energy on the secondary assembly critical components. The detailed model of the secondary assembly was developed and several full disk frame cases were analyzed to determine if the keep out zone may be eliminated or reduced. In addition to the full disk frame cases several CEI initialization cases were also analyzed for the Imager post eclipse instrument urn on scenario. The results of the detailed analysis indicates that the simple thermal analysis done in January of 1995 was in fact not conservative. It was determined that the Imager secondary temperature will far exceed the mission allowable temperature of 47C, while performing full disk frames in the vicinity of the Sun. The maximum inner baffle temperature was predicted to get as high as 130C for the worst full disk frame case analyzed. The thermal modeling effort as well as the results of the analysis and recommendations for future instrument qualification test and design changes will be documented in this paper.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.