GEOMETRIC CALIBRATION OF THE MICAS CCD SENSOR ON THE DS1 (DEEP SPACE ONE) SPACECRAFT: LABORATORY VS. IN-FLIGHT DATA ANALYSIS

We have carried out a geometric calibration of the CCD sensor of MICAS (Miniature Integrated Camera Spectrometer), a 4-inch aperture reflecting telescope on board the DS1 (Deep Space One) spacecraft, using laboratory data and in-flight images of star fields. The images suffer from significant distortion up to 4 pixels near the margins, an effect which we modelled by two-dimensional polynomials of 10th degree. The focal length of the camera is determined to be f = 686.55 +/- 0.05 mm, clearly above the nominal design value. In-flight images show that the geometric properties of the camera essentially have not changed. Following image geometric corrections on the basis of the laboratory data, positions of stars in the images can be predicted to within 0.5 pixels (1 σ). The analysis demonstrates that ground calibration data which can be obtained and processed very rapidly constitutes an important basis for the evaluation of camera geometric properties