Optical ray tracing of echelle spectrographs applied to the wavelength solution for precise radial velocities

TL;DR

This paper introduces 'moes', a ray tracing software for echelle spectrographs, demonstrating high-precision wavelength solutions and environmental influence modeling to predict radial velocity systematics at 1 m/s accuracy.

Contribution

The paper presents a novel ray tracing software that improves wavelength calibration precision and models environmental effects for radial velocity measurements.

Findings

Achieved residuals of 0.024 pixels in wavelength calibration

Predicted radial velocity systematics at the 1 m/s level

Set a new standard for spectrograph wavelength solution accuracy

Abstract

We present $\texttt{moes}$, a ray tracing software package that computes the path of rays through echelle spectrographs. Our algorithm is based on sequential direct tracing with Seidel aberration corrections applied at the detector plane. As a test case, we model the CARMENES VIS spectrograph. After subtracting the best model from the data, the residuals yield an rms of 0.024 pix, setting a new standard to the precision of the wavelength solution of state-of-the-art radial velocity instruments. By including the influence of the changes of the environment in the ray propagation, we are able to predict instrumental radial velocity systematics at the 1 m/s level.