Heidelberg Joint Astronomical Colloquium

The Hubble Space Telescope (HST) has been a major astronomical facility over the last two decades, and it still is now (early 2012)! As a joint project of NASA and ESA, it was deployed on its 600 km altitude orbit by the Space Shuttle in April 1990. The plan was then to visit it every 3 to 4 years by Space Shuttle crews to perform maintenance and repairs, if needed, and also to keep it as an up to date scientific instrument by exchanging focal scientific instruments. Five such missions were performed in total. They were all very successful, and the remarkable success record of the orbiting observatory is largely due to this unique on-orbit servicing capability. In this presentation, I will explain the philosophy of HST on-orbit servicing, and describe the execution of these missions as well as the related challenges. I was a crew member on the first and the third servicing missions, and spacewalked on the third to exchange the Telescope's main computer and one of three Fine Guidance Sensors.