30, 20, and 10 Years Ago in OPN

“Astronomical mirrors are back in the news with a new test facility for large mirrors and NASA’s Advanced X-ray Astrophysics Facility … It’s not quite a stairway to heaven, but it comes close. The Large Optical Segment (LOS) Test Facility, a seven-story, 75-ton tower located in Lexington, Mass., can be used to manufacture and test very large telescope mirrors or mirror segments, 13 feet or more in diameter, for spaceborne applications … Metrology equipment in the LOS facility provides crosschecks to guard against errors like those found in the Hubble Space Telescope.”