On-sky demonstration of the GMT dispersed fringe phasing sensor prototype on the Magellan Telescope
van Dam, Marcos A.
AffiliationUniv Arizona, Steward Observ
MetadataShow full item record
PublisherSPIE-INT SOC OPTICAL ENGINEERING
CitationDerek Kopon ; Brian McLeod ; Marcos A. van Dam ; Antonin Bouchez ; Ken McCracken ; Daniel Catropa ; William Podgorski ; Stuart McMuldroch ; Alan Conder ; Laird Close ; Jared Males ; Katie Morzinski and Timothy Norton " On-sky demonstration of the GMT dispersed fringe phasing sensor prototype on the Magellan Telescope ", Proc. SPIE 9909, Adaptive Optics Systems V, 990946 (September 2, 2016); doi:10.1117/12.2232942; http://dx.doi.org/10.1117/12.2232942
JournalADAPTIVE OPTICS SYSTEMS V
Rights© 2016 SPIE
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractThe GMT is an aplanatic Gregorian telescope consisting of 7 primary and secondary mirror segments that must be phased to within a fraction of an imaging wavelength to allow the 25.4 meter telescope to reach its diffraction limit. When operating in Laser Tomographic Adaptive Optics (LTAO) mode, on-axis guide stars will not be available for segment phasing. In this mode, the GMT's Acquisition, Guiding, and Wavefront Sensing system (AGWS) will deploy four pickoff probes to acquire natural guide stars in a 6-10 arcmin annular FOV for guiding, active optics, and segment phasing. The phasing sensor will be able to measure piston phase differences between the seven primary/secondary pairs of up to 50 microns with an accuracy of 50 nm using a J-band dispersed fringe sensor. To test the dispersed fringe sensor design and validate the performance models, SAO has built and commissioned a prototype phasing sensor on the Magellan Clay 6.5 meter telescope. This prototype uses an aperture mask to overlay 6 GMT-sized segment gap patterns on the Magellan 6.5 meter primary mirror reimaged pupil. The six diffraction patterns created by these subaperture pairs are then imaged with a lenslet array and dispersed with a grism. An on-board phase shifter has the ability to simulate an arbitrary phase shift within subaperture pairs. The prototype operates both on-axis and 6 arcmin off-axis either with AO correction from the Magellan adaptive secondary MagAO system on or off in order to replicate as closely as possible the conditions expected at the GMT.
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