Twenty years of Chandra operations: telescope thermal performance and application of lessons learned to the Lynx mission

The Chandra X-ray Observatory has been operating successfully on orbit for 20 years, providing outstanding astrophysics data to the science community. The telescope’s mission life has been extended well past its required five years due to the robust system design as well as the mission planning skills of the engineers and scientists at the Chandra Operations Control Center (OCC) in Massachusetts. Lessons learned in designing and operating Chandra can significantly benefit the Lynx mission, one of the NASA Strategic Mission concepts under consideration by the 2020 Decadal Survey. This paper reviews the design features that have enabled Chandra’s long mission life, with emphasis on the performance of the thermal and mechanical designs. Impacts of the aging exterior thermal finish are discussed, including drifting internal temperatures and a corresponding loss of the 10C cold bias design surrounding the High Resolution Mirror Assembly (HRMA). Also addressed are the resulting changes to the radiative cold heat sink for the Aspect Determination System (ADS); the increased potential for contamination on optical and focal plane surfaces; and consequences of putting components close to their upper temperature limit. Actions to address the changing conditions by the flight operations team at the OCC are described, showing how thermal constraints have been accommodated. Lessons learned, optimized operations, and new thermal design options are presented as methods to ensure a long life for the Lynx mission.