Coating the HRMA mirrors at Optical Coating Laboratories, Inc. in preparation for the Chandra mission

ChandraXX: A Ground-breaking Mirror in Space

The many scientific discoveries made by the Chandra X-ray Observatory since its launch more than 20 years ago would not have been possible without its advanced X-ray optical system, the High Resolution Mirror Assembly. The High Resolution Mirror Assembly, or HRMA (prounced "her-ma") is the most advanced X-ray mirror system that has ever been built or flown on a spacecraft. X-ray imaging is much more difficult than imaging visible light because the energy of even the lowest energy X-rays is hundreds of times larger than the energy of visible photons. Because of their high energy, the only way that X-ray photons can be reflected efficiently from a mirror is if the X-ray hits the mirror at a very shallow angle, effectively skipping off the mirror surface like a stone skips off the surface of a lake. X-ray mirror systems like HRMA are thus shaped like a large barrel, with additional concentric smaller barrels nested within. The HRMA consists of four pairs of these concentric, barrel-shaped mirrors so that X-rays passing down the axis of the barrel can be deflected and brought to a focus some ten meters behind the HRMA at the exquisite imaging detectors that are part of the Science Instrument Module. Chandra's X-ray mirrors can create the most beautiful X-ray images possible because they are exceptionally large and exceptionally smooth. Chandra's mirrors were first shaped to an extreme precision, then were polished so that there are no bumps in the mirrors larger than a few atoms - as if the earth was smoothed so that the tallest mountain was no more than a few feet high. Chandra's mirrors are also excepionally clean: at launch there was no more than a single speck of dust on an area as large as the typical computer screen. The mirrors making up the HRMA are the most accurate, smoothest and cleanest ever made, and because of this, Chandra produces for us the sharpest and clearest images of the X-ray Universe.
Published: September 30, 2019

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Page Author: Dr. Michael F. Corcoran
Last modified Monday, 07-Oct-2019 16:28:06 EDT