Image restoration using the point spread function of the Halley Multicolour Camera

Abstract

The optical resolution of the Halley Multicolour Camera (HMC) is limited by its finite aperture, by minute mechanical degradations within the instrument, and by the high speed time delay and integration (TDI) illumination method adapted to the spin of the spacecraft. The sum of all implies a visible loss of image sharpness. The smearing effect has been calibrated using images of a star which can be considered as a point source. The images were superimposed in the frequency domain with subpixel accuracy. With these means the point spread function (PSF) has been determined and applied to the received images using Fourier methods. The effectiveness of the scheme is demonstrated on images of the earth and comet Halley.