A measurement of the systematic astrometric error in GeMS and the short-term astrometric precision in ShaneAO

From National Research Council Canada

DOIResolve DOI: https://doi.org/10.1117/12.2057233
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Name affiliation
  1. National Research Council of Canada. National Science Infrastructure
FormatText, Article
Proceedings titleAdaptive Optics Systems IV
Series titleProceedings of SPIE; no. 9148
ConferenceAdaptive Optics Systems IV, June 22-27, 2014
ISSN0277-786X
1996-756X
ISBN9780819496164
Article number91481J
SubjectDegrees of freedom (mechanics); Linear transformations; Mathematical transformations; Stars; Systematic errors; Tomography; astrometry; Brown dwarfs; M92; multi-conjugate; NGC 1851; Adaptive optics
Abstract
We measure the long-term systematic component of the astrometric error in the GeMS MCAO system as a function of field radius and Ks magnitude. The experiment uses two epochs of observations of NGC 1851 separated by one month. The systematic component is estimated for each of three field of view cases (15'' radius, 30'' radius, and full field) and each of three distortion correction schemes: 8 DOF/chip + local distortion correction (LDC), 8 DOF/chip with no LDC, and 4 DOF/chip with no LDC. For bright, unsaturated stars with 13 < Ks < 16, the systematic component is < 0.2, 0.3, and 0.4 mas, respectively, for the 15'' radius, 30'' radius, and full field cases, provided that an 8 DOF/chip distortion correction with LDC (for the full-field case) is used to correct distortions. An 8 DOF/chip distortion-correction model always outperforms a 4 DOF/chip model, at all field positions and magnitudes and for all field-of-view cases, indicating the presence of high-order distortion changes. Given the order of the models needed to correct these distortions (∼8 DOF/chip or 32 degrees of freedom total), it is expected that at least 25 stars per square arcminute would be needed to keep systematic errors at less than 0.3 milliarcseconds for multi-year programs. We also estimate the short-term astrometric precision of the newly upgraded Shane AO system with undithered M92 observations. Using a 6-parameter linear transformation to register images, the system delivers ∼0.3 mas astrometric error over short-term observations of 2-3 minutes.
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PublisherSPIE
LanguageEnglish
Peer reviewedYes
NPARC number21275455
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