Mission Life Enhancing Studies and Results for the Imaging X-ray Polarimetry Explorer (IXPE)

Launched in 2021, the Imaging X-ray Polarimetry Explorer (IXPE) program now approaches an extended scientific mission. The measurements to date of X-ray polarization of astronomical bodies have been groundbreaking with over 21 discovery papers published to date from data produced by IXPE’s three imaging polarimeters. In an effort to continue to collect this data for as long as possible, the IXPE mission is proactively examining ways to enhance the lifetime of its spacecraft. The IXPE spacecraft is a single-string platform designed for a 2-year life that supports the science payload by providing pointing, power, data storage and downlink, and thermal control. One limiting factor to spacecraft life is the wet chemistry of IXPE’s lithium ion battery, which degrades over time as a function of its temperature, the number of charge and discharge cycles, and the level of charge and discharge. The resultant degradation reduces stored energy and the end of discharge voltage, an important parameter for the space vehicle electrical loads and fault protection monitoring system. This paper reports how the factors affecting battery life can be modified while maintaining the current level of instrument performance. Heater setpoint adjustments are described as well as modifications to the on-orbit concept of operations.