1 Introduction

In 1987 our photographic observing programs aimed at obtaining astrometric data on the eight major satellites of Saturn were commenced on the 1-metre reflector at the Yunnan observatory. After the first successful observing run, a series of exposures on the photographic plate was obtained between 1988 and 1993 at the above-mentioned place and at the Sheshan Station near Shanghai (Longitude E121.18417, Latitude N31.09611). A section of the data has been collected into "A catalogue of ground-based observations of the eight major satellites of Saturn, 1874-1989", see Strugnell & Taylor (1990).

With the coming of the CASSINI mission and the need for long-term dynamic predictions of Saturn's satellites to be based on precise astrometric observations, it is becoming more and more important to collect high quality observations and to reduce the many new observations made with CCD cameras. In the 90's Charge Coupled Device technology has been in common use in natural satellite astrometry due to a series of advantages such as high quantum efficiency, good linear response, large dynamical range, low noise and broad spectral response. During the days near to the opposition of 1994 we experimented with the use of CCD as an alternative to photographic plate. The preliminary success in achieving similar results in precision to photo-plate enhances our enthusiasm to continue such observations using the same observational technique in the next two years.

In this paper we publish all of our CCD observations of the positions of the Saturnian major satellites made during observing campaigns in 1994, 1995 and 1996. These observations were compared with positions calculated using the theories given by Taylor & Shen (1988), Harper & Taylor (1993), Duriez & Vienne (1991, 1992) and Dourneau (1987, 1993) respectively. By an iterative least square process to optimize the residuals from the four reductions a set of better calibration parameters was solved. Finally, the anticipated precise observations are generated.