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The Spatial Block simulates the recorded pixel information when the TOA radiance arrives to the instrument detector elements. This Block is applicable to Imagers and Radiometers. Spectrometers will be modelled by the Spectral Behaviour .The Spatial Block performs the spatial resampling to the final ground sampling distance, taking into account the real instrument Modulation Transfer Function and spatial non-uniformity sources. The process is characterized by the convolution of the spectral surface information with filter functions along and across orbit representing the sensor specific Point Spread Functions (PSF). This needs to incorporate optical, detector, vibration and spacecraft motion characteristics.The Spatial Block simulates the spatial domain of the image, which is correlated with the instrument type (whiskbroom, pushbroom or frame). Pushbroom and frame instruments can be considered as particular types of whiskbroom instruments in which the acquisition of a group of pixels (line in pushbroom instruments or 2D array in frame instruments) is taken at the same time. In the optical phase, there are several errors to be taken into account. Some of them are:• High frequency vibrations or Jitter.• Pixelation• Smearing• Time Delay Integration• StraylightThe steps to process an image Block at the optical stage are:1. Convert Block Radiances at Instrument input to Irradiances on the Focal Plane.2. Perform a 2D Fourier Transform3. Multiply the image in Fourier domain by the two-dimensional MTF4. Perform the inverse Fourier Transform