An Evaluation of the Hubble Space Telescope Thermal Design in Preparation for the Final Servicing Mission

Having been in operation for over 15 years, the Hubble Space Telescope (HST) had experienced significant changes in both hardware upgrades and operational modes. The changes were necessary to improve performance of some equipment and to replace failed electronics in others. Hardware replacements were done in several servicing missions. To accommodate the change in physical condition of HST, alterations in the way the telescope is operated were also required. The final opportunity to make any hardware changes on HST is during Servicing Mission 4 (SM-4) which is currently scheduled for December of 2007. It is important to make the most appropriate changes in order to ensure that HST will be in good operating condition until its planned termination.

In order to provide manifest input to the HST project for the final servicing mission, the HST thermal team must conduct careful evaluation of every single piece of hardware on HST. The objective of the evaluation is to identify components with temperatures approaching or exceeding their operational limits. For those components with temperatures approaching limits, a thermal analysis must be conducted to predict future temperature rise under a given environment. For components with temperatures exceeding limits, thermal analyses are done to advise the HST project on operational alternatives which will maintain them within limit. Because SM-4 will be the last servicing mission to the HST, this evaluation takes on a much more significant role. The thermal team must make sure that the recommended changes will render HST in good working condition thermally until 2015. This paper describes the process of thermal evaluation and planning for HST's final servicing mission. Thermal analysis and temperature predictions are presented.