First On-Sky Demonstration of a Scintillation Correction technique using Tomographic Wavefront Sensing

Hartley, Kathryn E; Farley, Oliver JD; Townson, Matthew J; Osborn, James; Wilson, RW

Abstract

Scintillation noise significantly limits high precision ground-based photometry of bright stars. In this paper we present the first ever on-sky demonstration of scintillation correction. The technique uses tomographic wavefront sensing to estimate the spatial-temporal intensity fluctuations induced by high altitude optical turbulence. With an estimate of the altitudes and relative strengths of the turbulent layers above the telescope, the wavefront sensor data from multiple guide stars can be combined to estimate the phase aberrations of the wavefront at each altitude through the use of a tomographic algorithm. This 3D model of the phase aberrations can then be used to estimate the intensity fluctuations across the telescope pupil via Fresnel propagation. The measured photometric data for a given target within the field of view can then be corrected for the effects of scintillation using this estimate in post-processing. A simple proof-of-concept experiment using a wavefront sensor and a stereo-SCIDAR turbulence profiler attached to the 2.5m Isaac Newton Telescope was performed for a range of exposure times using the Orion Trapezium cluster as the reference stars. The results from this on-sky demonstration as well as simulations estimating the expected performance for a full tomographic AO system with laser guide stars are presented. On-sky the scintillation index was reduced on average by a factor of 1.9, with a peak of 3.4. For a full tomographic system we expect to achieve a maximum reduction in the scintillation index by a factor of ∼25.

Citation

Hartley, K. E., Farley, O. J., Townson, M. J., Osborn, J., & Wilson, R. (2023). First On-Sky Demonstration of a Scintillation Correction technique using Tomographic Wavefront Sensing. Monthly Notices of the Royal Astronomical Society, 520(3), 4134-4146. https://doi.org/10.1093/mnras/stad420

• Journal Article Type: Article
• Acceptance Date: Feb 2, 2023
• Online Publication Date: Feb 20, 2023
• Publication Date: 2023-04
• Deposit Date: Feb 8, 2023
• Publicly Available Date: Feb 13, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 520
• Issue: 3
• Pages: 4134-4146
• DOI: https://doi.org/10.1093/mnras/stad420