Euclid end-to-end straylight performance assessment

In the Euclid mission the straylight has been identified at an early stage as the main driver for the final imaging quality of the telescope. The assessment by simulation of the final straylight in the focal plane of both instruments in Euclid’s payload have required a complex workflow involving all stakeholders in the mission, from industry to the scientific community. The straylight is defined as a Normalized Detector Irradiance (NDI) which is a convenient definition tool to separate the contributions of the telescope and of the instruments. The end-to-end straylight of the payload is then simply the sum of the NDIs of the telescope and of each instrument. The NDIs for both instruments are presented in this paper for photometry and spectrometry.