Investigation of three-mirror objectives for Earth remote sensing operating with an off-axis field of view

Abstract

The design, investigation, and enhancement of telescope objectives used as the principal optical instrument in Earth remote sensing systems are relevant because of the wide application range of the data obtained by such systems. Three-mirror systems can be used as objectives to ensure the set of parameters required for modern instruments (a focal distance of up to 5 m, an angular field of up to 2°–3°, a maximum spatial resolution of up to 0.75–2 m). However, the primary factor affecting the image quality in traditional compact centered systems is the obscuration of the pupil. A method for designing three-mirror flat-field anastigmats operating with an off-axis field of view without obscuration is presented in this paper, together with a discussion of peculiarities and a possible method for evaluating the complexity of calculation of such systems using a complexity coefficient. Objectives with focal distances of 1000 and 1600 mm, f-number of 4–5, and angular field of up to 1°–2° are designed.