Two pathfinder tests of high precision astrometry on-sky

S. Mark Ammons, Eduardo A. Bendek, Olivier Guyon, Bruce Macintosh, Christian Marois, Dmitry Savransky, Benoit Neichel, Raphael Galicher

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

Abstract

MCAO systems on ELTs should deliver the best available relative astrometric precision from the ground, which may be sufficient to detect exo-earths orbiting nearby brown and red dwarfs (< 30 μas). Yet despite the success of AO astrometry on large telescopes, we still do not understand the systematic errors that may dominate long-term astrometric stability with MCAO, such as dynamic optical distortion and differential atmospheric refraction (DAR). We present results from two on-sky pathfinders intended to characterize longterm systematic errors in MCAO systems. The first is an astrometric monitoring program of bright stars in 2013A on the GEMS LGS MCAO system. We isolate the effects of dynamic optical distortion by using narrow filters to counter atmospheric refraction and observing sparse fields to avoid crowding errors. Initial results on stable astrometric calibrator stars in sparse fields (less than 10 stars per square arcminute) suggest the presence of systematic errors of at most 0.4 milliarcseconds on short time baselines of a few days. The second pathfinder is an on-sky test of the diffractive pupil concept on a 1-meter telescope at Lick Observatory, intended to calibrate changing optical distortion with diffracted light from the target star (Guyon et al. 2012). We show that the diffractive pupil stabilizes the instrumental distortion to at least the precision of the experiment (~1 mas over 3').

Original languageEnglish (US)
Title of host publication3rd AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes
PublisherINAF - Osservatorio Astrofisico di Arcetri Largo Enrico Fermi
ISBN (Print)9788890887604
DOIs
StatePublished - 2013
Event3rd Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2013 - Florence, Italy
Duration: May 26 2013May 31 2013

Publication series

Name3rd AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes

Other

Other3rd Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2013
CountryItaly
CityFlorence
Period5/26/135/31/13

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics

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