The STS-125 Atlantis astronauts retrieved the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) during a very successful and final servicing mission to the HST in May 2009. The radiator attached to WFPC2 has dimensions of 2.2 m by 0.8 m. Its outermost layer is a 4-mm-thick aluminum, curved plate coated with white thermal paint.
This radiator has been exposed to space since the deployment of WFPC2 in 1993. Due to its large surface area and long exposure time, the radiator serves as a unique witness plate for the micrometeoroid and orbital debris (MMOD) environment between 560 and 620 km altitude.
The NASA Orbital Debris Program Office is leading an effort, with full support from the Hypervelocity Impact Technology Facility, Meteoroid Environment Office, and Astromaterials Acquisition and Curation Office, conducted an MMOD impact survey of the WFPC2 radiator in 2009. The goal is to use the data to validate or improve the near-Earth MMOD environment definition. This effort is also very well supported by the HST Development Project Office located at the NASA Goddard Space Flight Center.