Constrained modelling of instrumental radial velocity drift in precision Radial Velocity Spectrometers: Application to HPF

Abstract

For precise measurement of the radial velocity change in a star, the precision of the wavelength solution is 4 orders more important than accuracy of the wavelength solution. Since the absolute wavelength solution model of a multi-order echelle spectrographs require a large number of parameters, it is better to track the change in wavelength solution over time instead of refitting the complete wavelength solution without any constrains. For stabilized spectrographs like The Habitable-Zone Planet Finder (HPF) and NEID, these changes in wavelength solution are significantly low order and can be modeled with only a few parameters. Table 1, shows an example of low order changes to dispersion solution we expect from various physical mechanisms in HPF or NEID