Telescopes are one of the common types of satellite payloads. They are used both for Earth and astronomical observations. By using space telescopes it is possible to eliminate the negative effect of the atmosphere on image quality. Additionally, observations in some spectral ranges can be performed only from space due to absorption of certain wavelengths in the atmosphere. One such range is UV below 300 nm, which is of particular interest when it comes to the investigation of hot objects. Reflective telescopes are commonly used in this spectral range, although many classical designs are limited in their useful field of view to values below 1°. In this paper a hybrid refractive-diffractive telescope design working in a 200 nm – 300 nm spectral range with a field of view 10°×10° is proposed. Its performance is compared to purely refractive and reflective systems and significant improvement in the imaging quality of the system and decrease of its size is shown. The choice of the diffractive element type is explained. Parameters of the systems are based on the requirements for a proposed Polish mission UVSat which aims to enable long-term observations of a large number of stars exhibiting UV variance.

Diffractive optical elements (DOEs) may be used as a single optical component with dedicated functionality (e.g. focusing), or as one of the elements in complex hybrid optical systems to reduce the number of the elements and improve imaging quality. It is desirable to cover DOE’s surface with antireflective coating. In this paper, we show the results of simulations using the Fourier modal method and measure the efficiency of a diffractive lens with antireflective (AR) coating. Results were compared with a previously proposed model of AR covered DOE by Mao et al. [Opt. Express 25, 11673 (2017)10.1364/OE.25.011673]. Contrary to the previously published model, we have not observed a shift of the efficiency curve. Our findings prove that AR coatings improve the efficiency of DOEs and it is not necessary to take them into account when calculating optimal profile height.

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