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A four mirror anastigmat collimator design for optical payload calibration

Rolt, Stephen and Calcines, Ariadna and Lomanowski, Bart A. and Bramall, David G. (2016) 'A four mirror anastigmat collimator design for optical payload calibration.', in Proceedings Volume 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave. .


We present here a four mirror anastigmatic optical collimator design intended for the calibration of an earth observation satellite instrument. Specifically, the collimator is to be applied to the ground based calibration of the Sentinel-4/UVN instrument. This imaging spectrometer instrument itself is expected to be deployed in 2019 in a geostationary orbit and will make spatially resolved spectroscopic measurements of atmospheric contaminants. The collimator is to be deployed during the ground based calibration only and does not form part of the instrument itself. The purpose of the collimator is to provide collimated light within the two instrument passbands in the UV-VIS (305 – 500 nm) and the NIR (750 – 775 nm). Moreover, that collimated light will be derived from a variety of slit like objects located at the input focal (object) plane of the collimator which is uniformly illuminated by a number of light sources. The collimator must relay these objects with exceptionally high fidelity. To this end, the wavefront error of the collimator should be less than 30 nm rms across the collimator field of view. This field is determined by the largest object which is a large rectangular slit, 4.4° x 0.25°. Other important considerations affecting the optical design are the requirements for input telecentricity and the size (85 mm) and location (2500 mm ‘back focal distance’) of the exit pupil. The design of the instrument against these basic requirements is discussed in detail. In addition an analysis of the straylight and tolerancing is presented in detail.

Item Type:Book chapter
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Publisher statement:Copyright (2016) Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Date accepted:No date available
Date deposited:18 January 2023
Date of first online publication:29 July 2016
Date first made open access:18 January 2023

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