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This work summarizes the results from an extensive test campaign in which space-based laser optics were qualified for the upcoming ESA ADM-Aeolus mission. 14 different types of optical components from different suppliers were tested at the Nd:YAG laser wavelength according to the ISO standard 11 254 -2 for multiple pulse testing. A new technique based on transient pressure sensing was developed to monitor the occurrence of damage on a sample surface exposed to a vacuum environment. Parallel testing of reference samples showed a distinct degradation under vacuum compared to atmospheric or pressurized environment. For all samples tested we found a typical behavior in the characteristic damage curves attained: A sharp drop in LIDT for small pulse numbers followed by a smooth decrease for larger pulse numbers (laser fatigue effect).

The paper focuses on the aliasing phenomenon that may produce distortions on remotely sensed images acquired by hyper-spectral push-broom sensors and that arises because of its sampling rate. The analysis is performed on images recorded over different targets at a resolution that is high for the sensor under investigation. A model for the system modulation transfer function of PRISM hyper-spectral push-broom sensor is developed by taking into account the different contributions due to optical layout, electronics, detector, satellite motion. By using the sensor model, the high resolution images are pre-filtered and spatially re-sampled in order to obtain simulated images of the sensor. Such images are compared with those obtained by an ideal pre-filtering and re-sampling process in order to evidence possible aliasing effects. Quantitative indexes are adopted in order to assess the presence of aliasing. Filtering procedures are utilized to mitigate aliasing effects; to this aim multi-resolution filtering and a fuzzy filtering scheme are evaluated by means of the adopted indexes and by visual inspection. Quantitative and qualitative results show that, due to the efficacy of the proposed filters, aliasing mitigation is obtained with negligible penalties on spatial resolution.

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