Development of a Lunar Scintillometer as part of the National Large Optical Telescope Site Survey

TL;DR

This paper presents the development and deployment of a lunar scintillometer for measuring ground layer turbulence, crucial for astronomical site assessment, with detailed design, noise analysis, and multi-year observational results.

Contribution

It introduces a new lunar scintillometer instrument, including design, noise mitigation, and software, and reports its successful multi-year deployment at Mount Saraswati, Hanle.

Findings

Effective measurement of ground layer turbulence achieved

Instrument design improves noise resistance and data analysis

Multi-year data collection validates the instrument's performance

Abstract

Ground layer turbulence is a very important site characterization parameter used to assess the quality of an astronomical site. The Lunar Scintillometer is a simple and effective site-testing device for measuring the ground layer turbulence. It consists of a linear array of photodiodes which are sensitive to the slight variations in the moon's brightness due to scintillation by the lower layers of the Earth's atmosphere. The covariance of intensity values between the non-redundant photodiode baselines can be used to measure the turbulence profile from the ground up to a height determined by the furthest pair of detectors. The six channel lunar scintillometer that has been developed at the Indian Institute of Astrophysics is based closely on an instrument built by the team led by Andrei Tokovinin of Cerro Tololo Inter-American Observatory (CTIO), Chile. We have fabricated the instrument based on the existing electronic design, and have worked on the noise analysis, an EMI (Electromagnetic Induction) resistant PCB design and the software pipeline for analyzing the data from the same. The results from the instrument's multi-year campaign at Mount Saraswati, Hanle is also presented.