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The Institute of Optical Sensor Systems (OS) at the Robotics and Mechatronics Center of the German Aerospace Center (DLR) has more than 35 years of experience with high-resolution imaging and imaging technology. This paper shows the institute’s scientific results of a hardware driven method to validate the image quality and keep it constant over the whole mission life time. This technology is applicable for highest resolution systems as well as for systems which are foreseen to measure reproducible data series over years. The technology is applicable for panchromatic and multispectral instrument designs. The paper will first define image quality, which is described by modulation transfer function, signal to noise ratio, spatial and spectral resolution, linearity and other key parameters. They are shown the differences in the quality assessment compared to the classic image-based methods. Within an in-orbit initialization phase of the instrument, the full electrical channel is validated by generating a defined amount of electrons instead of electrons coming from the photodiode. The approach is based on charge injection with a reproducible number of electrons which is driving the complete vertical pixel chain. The basic idea is to generate a periodic signal in orbit which can be analyzed with respect to radiation influences. The control timing of the FPGA sensor controller can be operated from ground via commanding. This procedure includes also the initialization mode by controlling the phase adjustment of the CDS sampling. The possible image degradation as a result of typical radiation effects over the mission life time is described in the paper as well as how such effects can be avoided in future by implantation of the proposed method. This new approach enables e.g. linearity test, analysis and alignment and shows the relevance of such a validation technology for high-resolution optical space instruments.
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