Simulating diffraction effects in heliospheric imagers

Abstract

In this paper, we consider the modelling of diffracted stray light in heliospheric imagers. The emphasis is on the imagers proposed by RAL Space as part of the phase A/B1 study for ESA’s Vigil (formerly called Lagrange) L5 monitoring mission. In order to handle the extreme diffraction angles, a one-dimensional version of the PROPER diffraction modelling library has been developed. This is used to compute patterns at the lens aperture, and the standard two-dimensional version is then used to continue propagation to the sensor plane. The effects of key instrument and modelling parameters are analysed with a view to optimize accuracy of the modelling and the diffraction performance of the instrument.