Verification of straylight rejection of optical science payloads using a pulsed laser source

The performance of astronomical space telescopes can be greatly impacted by straylight. That is why characterizing the straylight in such telescopes before they are deployed is paramount. Nowadays such characterization can be done by simulation or by test. Simulation can provide very useful information on the origin of straylight, helping devise solutions to reduce it and improve the performance of the telescope. However, simulation suffers from limitations due to processing power needed and assumptions made in the model which can lead to simulation results quite far from the actual performances. Standard straylight tests on the other hand provide accurate measurement of the straylight but without any insight about its origin, making it difficult to mitigate.
Emerging technologies now offer new possibilities for straylight measurement using time-of-flight technics to help identify the origin of the straylight. Such technologies were reviewed and analysed in a first activity called TRIPP (Time-Resolved Imaging of Photon Paths). The results and outcome of this study are presented in the first chapter of this paper. A second chapter then presents the ongoing status of a second activity, SLOTT (Straylight Lidar Ogse verificaTion Tool) which aims to develop a demonstrator for such a time-resolved straylight verification system.
With the development and test of such a tool, CSEM and its partners (TAS-CH, Difrotec, CSL, LusoSpace), supported by ESA, hopes to establish new methods to characterize and reduce the straylight propagation in future space-based telescopes.