In the paper, the concept of a new prospective Russian spectrometer intended for Earth atmosphere monitoring in the visible and near-UV spectral ranges from board of a spacecraft is presented. The goal of the instrument is to measure total ozone and other gases in the vertical column of the atmosphere. Its wide field of view (100°) makes it possible to provide global mapping of measured components of the atmosphere every day. So far the optical modeling of the whole instrument as well as its units has been done. In this paper, the optical design of the spectrometer is presented in details. The instrument consists of an entrance unit, two spectral channels and calibration unit. The modeling results of the image of entrance slit on the detector are demonstrated. They confirm the characteristics specified: spectral resolution 0.3 nm in the range 0.3–0.4 μm and 0.5 nm in the range 0.4–0.8 μm. Spatial resolution is approximately equal to 0.5° in both channels, which corresponds to a resolvable element about 6 km near Earth surface when measuring at nadir direction from the altitude of 700 km.