Final acceptance testing of the LSST monolithic primary/tertiary mirror

Michael T. Tuell, James H. Burge, Brian Cuerden, William Gressler, Hubert M. Martin, Steven C. West, Chunyu Zhao

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

9 Scopus citations


The Large Synoptic Survey Telescope (LSST) is a three-mirror wide-field survey telescope with the primary and tertiary mirrors on one monolithic substrate1. This substrate is made of Ohara E6 borosilicate glass in a honeycomb sandwich, spin cast at the Steward Observatory Mirror Lab at The University of Arizona2. Each surface is aspheric, with the specification in terms of conic constant error, maximum active bending forces and finally a structure function specification on the residual errors3. There are high-order deformation terms, but with no tolerance, any error is considered as a surface error and is included in the structure function. The radii of curvature are very different, requiring two independent test stations, each with instantaneous phase-shifting interferometers with null correctors. The primary null corrector is a standard two-element Offner null lens. The tertiary null corrector is a phase-etched computer-generated hologram (CGH). This paper details the two optical systems and their tolerances, showing that the uncertainty in measuring the figure is a small fraction of the structure function specification. Additional metrology includes the radii of curvature, optical axis locations, and relative surface tilts. The methods for measuring these will also be described along with their tolerances.

Original languageEnglish (US)
Title of host publicationAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation
EditorsColin R. Cunningham, Ramon Navarro, Allison A. Barto
ISBN (Electronic)9780819496195
StatePublished - 2014
Externally publishedYes
EventAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation - Montreal, Canada
Duration: Jun 23 2014Jun 27 2014

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


OtherAdvances in Optical and Mechanical Technologies for Telescopes and Instrumentation


  • Active optics
  • Asphere
  • Computer-generated hologram (CGH)
  • Force and temperature compensation
  • Interferometry
  • Measurement uncertainty
  • Null corrector
  • Structure function

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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