Engineers conduct a "Center of Curvature" test.
Mikrolar Helps NASA Complete Center of Curvature Pre-Test
Mikrolar's R3000 Rotopod assisted NASA with the calibration of the eighteen primary mirrors on the James Webb Space Telescope, NASA's premier observatory of the next decade, serving thousands of astronomers worldwide. Launched into space on December 25th, 2021, the James Webb is an infrared observatory designed to compliment the famous Hubble Space Telescope with longer wavelength coverage and greatly improved sensitivity.
The Center of Curvature test measures the shape of the James Webb's main mirror by comparing light reflected off of it with light from a computer-generated hologram that represents what Webb's mirror ideally should be. By interfering the beam of light from James Webb with the beam from the hologram reference, and interferometer accurately compares the two by measuring the difference to incredible precision. "interferometry using a computer-generated hologram is a classic modern optical test used to measure mirrors," said Ritva Keski-Kuha, the test lead and NASA's Deputy Telescope Manager for Webb at NASA's Goddard Space Flight Center in Greenbelt, Maryland. This platform (shown in the image above) allows ultra-precise positioning for the test.
With the largest mirror of any space telescope, taking this measurement is a challenge. "We have spent the last four years preparing for this test," said David Chaney, Webb's primary mirror metrology lead at Goddard. "The challenges of this test include the large size of the primary mirror, the long radius of curvature, and the background noise. Our test is so sensitive that we can measure the vibrations of the mirrors due to people simply talking while in the same room."
View of the Facility at NASA.