Two image-processing techniques are developed to measure precisely the positions of Jupiter and its Galilean satellites. Tests based on 133 frames of CCD images we have obtained show that these techniques allow us to obtain as good as 0.03 arcsec precision for the positions of the center of Jupiter as well as those of the satellites. We are encouraged by the obtained internal precision. Investigators who are interested in the data processing are expected to check the observations using the original raw pixel positions and related records on request. It is believed that these techniques could be used in CCD astrometric observation and forthcoming mutual phenomena (occultation) observation. Further improvement in the edge-detection of Jupiter needs to be made in future when the planet is not near opposition. Perhaps, only the lamb on the sunward could be used to fit by an ellipse after the edge detection, since the edge on the terminator of Jupiter is not sharp enough at this time. Besides, in order to obtain high accuracy in astrometric positions of Jupiter and its Galilean satellites, we should be careful to use the "Brighter Moon Calibration'' method and better calibration methods deserve to be investigated.
Copyright ESO 2003