Performance of the center-of-curvature optical assembly during cryogenic testing of the James Webb Space Telescope
Autor: | David Chaney, Tony Whitman, Joseph Cosentino, Michael Zarella, James B. Hadaway, Gene Olczak, Mark Waldman, Randal Telfer, Mark Connolly, Conrad Wells |
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Rok vydání: | 2018 |
Předmět: |
Physics
business.industry James Webb Space Telescope Astrophysics::Instrumentation and Methods for Astrophysics Center of curvature 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences law.invention 010309 optics Primary mirror Telescope Interferometry Optics law 0103 physical sciences Calibration Piston (optics) 0210 nano-technology Adaptive optics business |
Zdroj: | Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave. |
Popis: | The James Webb Space Telescope (JWST) primary mirror (PM) is 6.6 meters in diameter and consists of 18 hexagonal segments, each 1.5 meters point-to-point. Each segment has a 6 degree-of-freedom hexapod actuation system and a radius-of-curvature (ROC) actuation system. The full telescope was tested at its cryogenic operating temperature at Johnson Space Center (JSC) in 2017. This testing included center-of-curvature measurements of the PM wavefront error using the Center-of-Curvature Optical Assembly (COCOA), along with the Absolute Distance Meter Assembly (ADMA). The COCOA included an interferometer, a reflective null, an interferometer-null calibration system, coarse and fine alignment systems, and two displacement measuring interferometer systems. A multiple-wavelength interferometer was used to enable alignment and phasing of the PM segments. By combining measurements at two laser wavelengths, synthetic wavelengths up to 15 millimeters could be achieved, allowing mirror segments with millimeter-level piston errors to be phased to the nanometer level. The ADMA was used to measure and set the spacing between the PM and the focus of the COCOA null (i.e., the PM center-of-curvature) for determination of the ROC. This paper describes the COCOA, the PM test setup, the testing performed, the test results, and the performance of the COCOA in aligning & phasing the PM segments and measuring the final PM wavefront error. |
Databáze: | OpenAIRE |
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