Photonics Leads the Way to a Stellar Alignment

Charlie Atkinson, Eastman Kodak Co.

Stationed on 18-m towers in New York and California, a one-of-a-kind photonic device has played a crucial role aligning eight cylindrical mirrors and the telescope assembly for the Advanced X-ray Astrophysics Facility, NASA's newest space-based X-ray imaging observatory. Only photonics could provide the measurement accuracy that could ensure the alignment of critical optical components.
After an August 1998 launch aboard the Space Shuttle Columbia, the observatory's internal propulsion system will place it in a highly elliptical Earth orbit, where it will capture never-before-seen X-ray images of deep space phenomena, such as black holes and galaxy clusters, while revealing much about the origins of the universe. The observatory's optics can focus X-ray light from a source in space onto a spot less than 0.5 arcsec in radius at the 10-m focal plane, equivalent to the resolution of the Hubble Space Telescope.
To accomplish this resolution, metrologists at Eastman Kodak Co. used a custom-made laser metrology tool to align each of the observatory's mirrors in five degrees of freedom to within 0.1 arcsec of tilt, 0.001 mm lateral displacement and 0.016 mm in axial position. They then used the device, called the centroid detector assembly, to align the mirrors' focus with the focal plane of the observatory's scientific instrumentation module.