Preliminary on-sky results of the next generation GMT phasing sensor prototype

Derek Kopon, Brian McLeod, Antonin Bouchez, Daniel Catropa, Marcos A. Van Dam, Danielle Frostig, Jan Kansky, Ken McCracken, William Podgorski, Stuart McMuldroch, Joseph D'Arco, Laird Close, Jared R. Males, Katie Morzinski

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

9 Scopus citations


The Active optics, Guiding, and Wavefront Sensing system (AGWS), currently being designed by SAO, will use J-band dispersed fringe sensors (DFS) to phase the GMT to a fraction of an imaging wavelength. These phasing sensors will use off-axis guide stars to measure phase shifts at each of 12 segment boundaries. The fringes produced at each boundary will be dispersed in the perpendicular direction using an array of high-index doublet prisms. Inter-segment phase shifts will appear as tilts in the dispersed fringes, which can be measured in the Fourier domain. In order to avoid atmospheric blurring of the fringes, we require a J-band detector capable of fast, low-noise readout, which mandates the use of a SAPHIRA e-APD array. We built a DFS prototype that we tested on-sky at the Magellan Clay telescope behind the MagAO adaptive optics system in May 2018.

Original languageEnglish (US)
Title of host publicationAdaptive Optics Systems VI
EditorsDirk Schmidt, Laura Schreiber, Laird M. Close
ISBN (Print)9781510619593
StatePublished - 2018
EventAdaptive Optics Systems VI 2018 - Austin, United States
Duration: Jun 10 2018Jun 15 2018

Publication series

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


OtherAdaptive Optics Systems VI 2018
Country/TerritoryUnited States


  • Active optics
  • Giant Magellan Telescope
  • adaptive optics
  • dispersed fringe sensor
  • e-APD array
  • phasing

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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