AUTOMATED DESIGN OF KORSCH ORTHOSCOPIC ASPHERICAL MIRROR TELESCOPES FOR NANOSATELLITES

Abstract

This study presents the results of an automated parametric synthesis of a series of orthoscopic aspheric optical systems of mirror telescopes with different focal lengths, built according to the Korsch scheme. In order to ensure compactness of the design, these systems consist of three second-order aspheric mirrors and three folded flat mirrors. The obtained optical systems have a focal length ranging from 480 mm to 960 mm, an angular field of view ranging from 1.2° to 2.4°, an aperture number ranging from 6 to 12, an entrance aperture with a diameter of 80 mm, and an axial length of no more than 170 mm, which is within the dimensions of a 2U CubeSat. The maximum linear size of the image detector's sensitive area is 20 mm in all considered systems. The mirror telescopes do not have chromatic aberrations, enabling the capture of images within the visible spectrum and multiple infrared sub-bands. The provided aberration analysis demonstrates the high image quality of the considered optical systems. Specifically, for a wavelength of 0.546 μm, thediffraction modulation transfer function values both in the meridional and sagittal planes across the entire field exceed 0.53 for a spatial frequency of 30 mm-1, and 0.3 for a spatial frequency of 50 mm-1. The maximum relative distortion in the designed systems is 0.005%, corresponding to an absolute displacement of 0.5 μm. The presented telescopes are capable of covering an observation band of Earth's surface with linear dimensions ranging from 12.6 km to 25.1 km when a satellite track height is 600 km. By applying multi-element image detectors with a pixel size of 5 μm and achieving diffraction-limited image quality in the optical systems, both the geometric and diffraction resolution limits on Earth's surface will not exceed 10 m.