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A method for calculating a “spectral” diffractive lens, which ensures the preservation of the focal position at several prescribed wavelengths is proposed. The method is based on minimizing the function characterizing the difference between the complex transmission functions of the spectral lens for given wavelengths and the complex transmission functions of diffraction lenses calculated separately for each of the given wavelengths. As examples, spectral diffractive lenses are calculated for three and seven wavelengths. The simulation results of the calculated lenses confirm good performance of the proposed method.

Launched in March 2021, the 3U CubeSat nanosatellite was the first ever to use an ultra-lightweight harmonic diffractive lens for Earth remote sensing. We describe the CubeSat platform we used; our 10 mm diameter and 70 mm focal length lens synthesis, design, and manufacturing; a custom 3D-printed camera housing built from a zero-thermal-expansion metal alloy; and the on-Earth image post-processing with a convolutional neural network resulting in images comparable in quality to classical refractive optics used for remote sensing before.