Accuracy of laser tracker measurements of the GMT 8.4-m off-axis mirror segments

Tom L. Zobrist; James H. Burge; Hubert M. Martin

doi:10.1117/12.856520

19 July 2010 Accuracy of laser tracker measurements of the GMT 8.4 m off-axis mirror segments

Tom L. Zobrist, James H. Burge, Hubert M. Martin

Proceedings Volume 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation; 77390S (2010) https://doi.org/10.1117/12.856520
Event: SPIE Astronomical Telescopes + Instrumentation, 2010, San Diego, California, United States

Abstract

We have developed a metrology system that is capable of measuring rough ground and polished surfaces alike, has limited sensitivity to the nominal surface shape, and can accommodate surfaces up to 8.4 m in diameter. The system couples a commercial laser tracker with an advanced calibration technique and a system of stability references to mitigate numerous error sources. This system was built to guide loose abrasive grinding and initial polishing of the off-axis primary mirror segments for the Giant Magellan Telescope (GMT), and is also being used to guide the fabrication of the Large Synoptic Survey Telescope primary and tertiary mirrors. In addition to guiding fabrication, the system also works as a verification test for the GMT principal optical interferometric test of the polished mirror segment to corroborate the measurement in several low-order aberrations. A quantitative assessment of the system accuracy is presented, along with measurement results for GMT, including a comparison to the optical interferometric test of the polished surface.8

Citation Download Citation

Tom L. Zobrist, James H. Burge, and Hubert M. Martin "Accuracy of laser tracker measurements of the GMT 8.4 m off-axis mirror segments", Proc. SPIE 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, 77390S (19 July 2010); https://doi.org/10.1117/12.856520

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