Theoretical analysis of collimators on the geometrical calibration of wide field-of-view radiometer

The wide field-of-view optics of radiometers usually has different entrance pupil diameters and entrance pupil positions due to the optical aberrations for different spectral bands and different viewing directions. A model for determining the diameters of collimators in the geometrical calibration of wide field-of-view radiometer was presented. The results of numerical computation show that the least diameter of the collimators is dependent on the positions of the overlapping areas enlightened by all the collimators and of the radiometer relative to the ORG.