The laser antenna surface scanning instrument

Pedro Salas; Paul Marganian; Joseph Brandt; John Shelton; Nathan Sharp; Dennis Egan; Nathaniel D. Sizemore; Carla Beaudet; Laura Jensen; Marty Bloss; Andrew Seymour; Frederic R. Schwab; Felix J. Lockman

doi:10.1117/12.2560393

13 December 2020 The laser antenna surface scanning instrument

Pedro Salas, Paul Marganian, Joseph Brandt, John Shelton, Nathan Sharp, Dennis Egan, Nathaniel D. Sizemore, Carla Beaudet, Laura Jensen, Marty Bloss, Andrew Seymour, Frederic R. Schwab, Felix J. Lockman

Author Affiliations +

Proceedings Volume 11445, Ground-based and Airborne Telescopes VIII; 114456C (2020) https://doi.org/10.1117/12.2560393
Event: SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only

Conference Poster

Abstract

To carry out astronomical observations in the molecule rich 3 mm window the Green Bank Telescope (GBT) compensates for gravitational and weather induced deformations of its primary reflector. Terrestrial laser scanners (TLSs) offer a fast and reliable means of measuring these deformations, but their use has been limited to measuring gravitational deformations thus far due to the large systematics inherent to their construction. The laser antenna surface scanning instrument (LASSI) on the GBT uses a TLS to measure weather induced deformations. The LASSI removes the TLS systematics by taking the difference between scans. We use the active surface (AS) on the GBT to validate this strategy and find that the LASSI can accurately measure deformations corresponding to different Zernike polynomials with amplitudes between 60 μm and 550 μm. We estimate that the wavefront error introduced by the LASSI to the surface is 100 ± 30 μm, root-mean-squared (rms), which would result in a total surface error of 250 μm rms. This suggests that using the LASSI to measure, and the AS to correct, for weather induced deformations is a viable method to efficiently carry-out day time 3 mm observations with the GBT.

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Pedro Salas, Paul Marganian, Joseph Brandt, John Shelton, Nathan Sharp, Dennis Egan, Nathaniel D. Sizemore, Carla Beaudet, Laura Jensen, Marty Bloss, Andrew Seymour, Frederic R. Schwab, and Felix J. Lockman "The laser antenna surface scanning instrument", Proc. SPIE 11445, Ground-based and Airborne Telescopes VIII, 114456C (13 December 2020); https://doi.org/10.1117/12.2560393

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