Design and analysis for interferometric measurements of the GMT primary mirror segments

J. H. Burge, L. B. Kot, H. M. Martin, R. Zehnder, C. Zhao

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

68 Scopus citations


The Giant Magellan Telescope (GMT) uses seven 8.4-m diameter segments to create a giant primary mirror, 25 meters across with focal ratio f/0.7. The off-axis segments will be difficult to measure accurately, as they have 14.5 mm departure from the nearest fitting sphere! The test configuration adopted uses a large 3.75-m powered mirror to fold the light path and provide most of the aspheric correction, with a smaller mirror and computer generated hologram (CGH) providing the additional correction. These optics will be aligned to a vibration-insensitive interferometer using a combination of optical references created by the CGH and metrology with a laser tracker. Some key challenges for this system are presented here including, the system alignment, the large fold mirror, and the mechanical structure. Analysis of the optical test shows that it will meet GMT specifications, including the difficult requirement that the separate segments have matching radius of curvature. Additional corroborative testing will be performed to assure that the mirror segments are correctly figured.

Original languageEnglish (US)
Title of host publicationOptomechanical Technologies for Astronomy
StatePublished - 2006
Externally publishedYes
EventOptomechanical Technologies for Astronomy - Orlando, FL, United States
Duration: May 24 2006May 31 2006

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume6273 I
ISSN (Print)0277-786X


OtherOptomechanical Technologies for Astronomy
Country/TerritoryUnited States
CityOrlando, FL


  • Aspheres
  • Optical fabrication
  • Optical testing
  • Telescopes

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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