Astrometric Reduction of Cassini ISS Images of Enceladus in 2015 Based on Gaia DR1

The Gaia DR1 catalogue stars are taken as reference ones to reduce the Cassini ISS images of Enceladus in 2015, and a total of 494 Cassini-centered astrometric observation are obtained in right ascension(α) and declination (δ) in the international Celestial Reference Frame(ICRF). Compared with JPL ephemerides SAT367, we derive that their mean residuals are a few tens meters in α*cos(δ) and a few kilometers in δ, and their standard deviation is not over 2 kilometers. Compared with the results from UCAC4 catalogue stars, The Gaia DR1 has the equivalent precision of reduction.