CCD centroiding experiment for JASMINE and ILOM

JASMINE and ILOM are space missions which are in progress at the National Astronomical Observatory of Japan. These two projects need a common astrometric technique to obtain precise positions of star images on solid state detectors to accomplish the objectives. We have carried out measurements of centroid of artificial star images on a CCD to investigate the accuracy of the positions of the stars, using an algorithm for estimating them from photon weighted means of the stars. We find that the accuracy of the star positions reaches 1/300 pixel for one measurement. We also measure positions of stars, using an algorithm for correcting the distorted optical image. Finally, we find that the accuracy of the measurement for the positions of the stars from the strongly distorted image is under 1/150 pixel for one measurement.