Simulating diffraction effects in heliospheric imagersS J Tappin, J A Davies, C J Eyles
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.