The SXS Filter Wheel Development

The Department of Astronomy of the University of Geneva participates in the Hitomi (formerly ASTRO-H) mission in collaboration with SRON (Netherlands) by developping a filter wheel for the SXS. In order to maintain the energy resolution of the detector, the X-ray counting rate needs to be kept below a few counts per second and per pixel, because of the slow time constant (~ 10 ms) of the signals. For observations of bright X-ray sources with high energy resolution, a filter wheel is an essential apparatus which controls the X-ray flux thanks to its various filters. In addition the filter wheel is equipped with electronically controlled X-ray source developed by SRON, in order to allow the monitoring of the gain of the instrument.

The filter wheel will be fairly large (around 40 cm in diameter), because of its being mounted on the optical bench middle plate, i.e. far from the focus point. Environmental conditions are standard for low-orbit missions, without any particularly hard constraints in temperature range or radiation levels.

 

FWM QM-bottom

Qualification model (QM) of the filter wheel mechanism