The Focal Plane Instrumentation Of The ROSAT Telescope

The ROSAT telescope is equipped with two different kinds of X-ray image converters: two redundant position sensitive proportional counters (PSPC) and one high resolution imager (HRI), based on microchannel plates. The detectors and part of their front-end electronics as well as the gas supply system for the PSPC's are mounted onto a carrousel, which allows positioning of the desired imager in the focus of the telescope. All instruments, electronics, mechanisms, etc. are accommodated in the focal plane housing, which is mounted to the optical bench of the mirror system. We will give an overview of the focal plane instrumentation and present the performance of the X-ray image converters.