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

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

Research output: Chapter in Book/Report/Conference proceedingConference contribution

11 Scopus citations


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)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsA.E. Hatheway
Number of pages18
Publication statusPublished - 2001
Externally publishedYes
EventOptomechanical Design and Engineering 2001 - San Diego, CA, United States
Duration: Aug 2 2001Aug 3 2001


OtherOptomechanical Design and Engineering 2001
CountryUnited States
CitySan Diego, CA



  • 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

  • Electrical and Electronic Engineering
  • Condensed Matter Physics

Cite this

Catanzaro, B., Connell, S., Mimovich, M., Backovsky, S., Williams, G. G., Thomas, J. A., ... Cohen, E. (2001). Cryogenic (70K) measurement of an all-composite 2-meter diameter mirror. In A. E. Hatheway (Ed.), Proceedings of SPIE - The International Society for Optical Engineering (Vol. 4444, pp. 238-255)