JET-X attitude monitor for the Spectrum-RG mission

The Joint European Telescope for X-ray astronomy, JET-X, is one of the core instruments in the scientific payload of the Russian Spectrum-Roentgen-Gamma high energy astrophysics mission. JET-X consists of two co-aligned x-ray imaging telescopes, each with a spatial resolution of better than 20 arcseconds. Cooled x-ray sensitized CCDs in the focal plane of each telescope are designed to provide imaging with 150 eV spectral resolution over the energy band 0.3 - 10 keV. A typical observation of 10 5 seconds comprises many short (2.5 second) CCD exposures, thus enabling the detection and energy determination of individual photon events. If the full imaging resolution of the instrument is to be realized, a post facto, time-resolved attitude reconstruction of the telescope's pointing direction will be required, so that the effects of thermal distortion within the telescope structure and attitude drift of the spacecraft can be corrected when combining the multiple x-ray images obtained during an observation. JET-X will therefore generate its own aspect solution through pointing measurements with a purpose- designed Attitude Monitor: a cooled, slow-scan CCD TV camera with data processing electronics.