Off-axis point spread function characterization in laser guide star adaptive optics systems

• Type: Article in International Scientific Journal
• Date: 2018

Authors

Beltramo Martin, O (Author) Other; Correia, CM (Author) Other; Mieda, E (Author) Other; Neichel, B (Author) Other; Fusco, T (Author) Other; Witzel, G (Author) Other; Lu, JR (Author) Other; Véran, JP (Author) Other

Journal

Title: Monthly Notices of the Royal Astronomical Society

Vol. 478

Pages: 4642-4656

ISSN: 0035-8711

Publisher: Oxford University Press

Indexing

ISI Web of Knowledge - 10 Citations

Scopus - 14 Citations

Other information

Authenticus ID: P-014-ZC6

DOI: 10.1093/mnras/sty1103

Abstract (EN): Adaptive optics (AO) restore the angular resolution of ground-based telescopes, but at the cost of delivering a time- and space-varying point spread function (PSF) with a complex shape. PSF knowledge is crucial for breaking existing limits on the measured accuracy of photometry and astrometry in science observations. In this paper, we concentrate our analyses of the anisoplanatism signature only on to the PSF. For large-field observations (20 arcmin) with single-conjugated AO, PSFs are strongly elongated due to anisoplanatism that manifests itself as three different terms for laser guide star (LGS) systems: angular, focal and tilt anisoplanatism. First, we propose a generalized model that relies on a point-wise decomposition of the phase and encompasses the non-stationarity of LGS systems. We demonstrate that it is more accurate and less computationally demanding than existing models: it agrees with end-to-end physical-optics simulations to within 0.1 per cent of PSF measurables, such as the Strehl ratio, FWHM and the fraction of variance unexplained (FVU). Secondly, we study off-axis PSF modelling with respect to the Cn2(h) profile (heights and fractional weights). For 10-mclass telescopes, PSF morphology is estimated at the 1 per cent level as long as we model the atmosphere with at least seven layers, whose heights and weights are known with precisions of 200 m and 10 per cent, respectively. As a verification test, we used the Canada's National Research Council - Herzberg NFIRAOS Optical Simulator (HeNOS) testbed data, featuring four lasers. We highlight the capability of retrieving off-axis PSF characteristics within 10 per cent of the FVU, which complies with the expected range from the sensitivity analysis. Our new off-axis PSF modelling method lays the groundwork for testing on-sky in the near future.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 15