Cryogenic (70K) measurement of an all-composite 2-meter diameter mirror

Brian Catanzaro, Steven Connell, Mark Mimovich, Stan Backovsky, Grant Williams, James A. Thomas, Dan Barber, Roger Johnston, Joe Hylton, Kelly Dodson, Eri Cohen

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

The Herschel Space Observatory (formerly known as FIRST) consists of a 3.5 m space telescope. As part of a JPL-funded effort to develop lightweight telescope technology suitable for this mission, COI designed and fabricated a spherical, F/1, 2 m aperture prototype primary mirror using solely carbon fiber reinforced polymer (CFRP) materials. To assess the performance of this technology, optical metrology of the mirror surface was performed from ambient to an intended operational temperature for IR-telescopes of 70K. Testing was performed horizontally in a cryogenic vacuum chamber at Arnold Engineering Development Center (AEDC), Tennessee. The test incorporated a custom thermal shroud, a characterization and monitoring of the dynamic environment, and a stress free mirror mount. An IR-wavelength phase shifting interferometer (IR PSI) was the primary instrument used to measure the mirror surface. From an initial surface figure of 2.1 microns RMS at ambient, a modest 3.9 microns of additional RMS surface error was induced at 70K, The thermally induced error was dominated by low-order deformations, of the type that could easily be corrected with secondary or tertiary optics. In addition to exceptional thermal stability, the mirror exhibited no significant change in the figure upon returning to room temperature.

Original languageEnglish (US)
Pages (from-to)238-255
Number of pages18
JournalProceedings of SPIE-The International Society for Optical Engineering
Volume4444
DOIs
StatePublished - Jan 1 2001
Externally publishedYes

Keywords

  • Composite Materials
  • Cryogenic Testing
  • High Spatial Frequency Errors
  • Lightweight Mirrors
  • Phase Shifting Interferometer
  • Quilting
  • Thermal Shroud
  • Vacuum Test Chamber
  • Vibration Measurements

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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