Influence of the System MTF on the lossless compression of hyperspectral raw data

This paper investigates the influence of the MTF of an acquisition system on lossless compression algorithms of raw hyperspectral data sets, in the framework of the SMART project funded by Tuscany Region. Notwithstanding there are several other constraints that drive the design of the MTFs, it is of increasing interest to quantify its impact on the performances of data compressors with the aim of reducing both transmission bandwith/power and on-board mass storage. Such an analysis is expected to be relevant especially in the case of minisatellites, whose constraints regarding compactness are particularly demanding. In this perspective, a simulated acquisition system of low-resolution images has been obtained by considering already acquired data at higher resolution as a reference image, in order to reproduce an hypothetical scene to be digitalized by a low-weight sensor. To this end, standard CCSDS Aviris 2006 data have been chosen, due to their spatial resolution of 17m, which is adequate for simulating acquired data whose resolution is foreseen to be between 50 and 150m. MTF requirements are usually provided on the basis of the cut-off value at the Nyquist frequency, which is defined as a half of the sampling frequency. Typically, a cut-off value between 0:2 and 0:3 ensures that a sufficient amount of information is delivered from the scene to the acquired image, whereas, for lower cut-off parameters, the images are usually too smoothed and, for higher values, an excessive aliasing distortion can degrade the data. The reported analysis allows to choose a suitable cut-off value that ensures both a sufficient quality and a low quantity of bits to be transmitted to the ground station. As a first approximation, the MTF shapes have been obtained by considering Gaussian-like functions.