The Physical Model in Action: Quality Control for X-Shooter

TL;DR

This paper discusses the use of a physical model in the X-Shooter data reduction pipeline to improve wavelength calibration and optical distortion correction, enhancing quality control and instrument diagnostics.

Contribution

It introduces a physical model-based approach for calibration and quality control in the X-Shooter spectrograph, linking physical parameters to instrument diagnostics.

Findings

Physical model improves wavelength calibration accuracy.

Monitoring physical parameters aids in instrument diagnostics.

Correlations found between physical model parameters and temperature readings.

Abstract

The data reduction pipeline for the VLT 2nd generation instrument X-Shooter uses a physical model to determine the optical distortion and derive the wavelength calibration. The parameters of this model describe the positions, orientations, and other physical properties of the optical components in the spectrograph. They are updated by an optimisation process that ensures the best possible fit to arc lamp line positions. ESO Quality Control monitors these parameters along with all of the usual diagnostics. This enables us to look for correlations between inferred physical changes in the instrument and, for example, instrument temperature sensor readings.