The Canadian Astro-H metrology system

The Hard X-ray Telescopes on Astro-H have a 12-meter focal length. In order to achieve this long focal length and still fit compactly in the H-IIA launch fairing, the detectors are mounted at the end of an extendable optical bench that will be deployed in orbit. Once in operation, the spacecraft will experience distortions primarily due to thermal fluctuations in low-earth orbit and it is important that the misalignment between the telescopes and instruments is accurately measured. The Canadian Astro-H Metrology System (CAMS) is a laser alignment system that will measure optical alignment deviations. The CAMS is compact, consumes little power, and is stable over a wide temperature range. The system will be used to measure lateral (X/Y) displacement as well as rotational shifts in the optical bench. In addition, the CAMS data can be used to enhance the quality of the hard X-ray images that will have been degraded by structural deformations. A description of the CAMS hardware and the relevant data processing algorithms are provided.