Design of a compact multispectral telescope consisting of a Cassegrain telescope and a concave elliptical grating.

In this paper we design a high-performance multispectral telescope with a concave elliptical grating for a field of view of 3° in the VNIR spectral range of 0.48-0.82 µm, at an altitude of 760 km from the ground, with total length of 140 mm, which has a small volume and a simple structure. The paper reports on the MTF, spot, and field curvature diagrams, which show that it can achieve spectral and spatial resolutions of 25 nm and 5.5 m, respectively, with good image quality (MTF value for all wavelengths is higher than 0.2 at Nyquist frequency of 217 cycles per mm) and has the least possible aberrations, without the need for any lenses.