Mid-Infrared Drift Scanning Up The SNR Slope

TL;DR

This paper explores drift scanning as a potential alternative to chopping in mid-infrared observations, aiming to improve signal-to-noise ratio and reduce mechanical and operational constraints for large telescopes.

Contribution

The study demonstrates the feasibility of drift scanning with CanariCam, providing insights for future mid-infrared instrumentation without secondary mirror chopping.

Findings

Drift scanning can potentially replace chopping in MIR observations.

Experiments show promising SNR improvements with drift scanning.

Implications for large telescopes like 30m class are discussed.

Abstract

Mid-infrared (MIR) observations are typically accomplished from the ground through oscillating the secondary mirror a few times a second. This chopping serves to remove the fast time variable components of (a) sky variation and (b) array background. However, there is a significant price to pay for this, including reduced on-object photon collection time, stringent demands on the secondary mirror, nodding the telescope to remove the radiative offset imprinted by the chopping, and an often-fixed chop-frequency regardless of the sky conditions in the actual observations. Worse, in the era of 30m telescopes it is wholly impracticable to chop the secondary mirror. If the array is stable enough, drift scanning holds the promise to remove the necessity of chopping. In this paper we report our experiments using the CanariCam MIR instrument on the 10.4m GranTeCan and the implications to future instruments and experiments.