S/2004 S 1 and S/2004 S 2

C. C. Porco, CICLOPS, Space Science Institute, Boulder; and the Cassini Imaging Science Team (cf. Porco et al. 2004, Science, in preparation) report the discovery of two new satellites of Saturn, S/2004 S 1 and S/2004 S 2, both orbiting between Saturn I (Mimas) and Saturn II (Enceladus). Revolution periods, orbital semimajor axes, and estimated satellite diameters are as follows: S/2004 S 1, 1.01 days, 194000 km, 3 km; S/2004 S 2, 1.14 days, 211000 km, 4 km. There is a slight possibility that S/2004 S 1 is identical with S/1981 S 14, observed in a single Voyager image on 1981 Aug. 23 (IAUC 6162), but this is still under investigation. Both orbits appear to be approximately circular and equatorial. Estimated diameters assume disk-integrated reflectivities of 0.15 at a phase angle of 67 degrees. Visual magnitudes seen from the earth are estimated to be in the range of about 22-23. The objects were first discovered in imaging sequences taken on 2004 June 1 that were specifically designed to search for new satellites in the inner saturnian system. In these sequences, S/2004 S 1 was observed over 6.0 hr, while S/2004 S 2 was observed over 9.3 hr. All exposures were 4.6 s and taken with the narrow-angle camera through the clear filters (Porco et al. 2004, Space Sci. Rev., in press). S/2004 S 1 was subsequently found in other Cassini narrow- angle camera images taken three weeks earlier with exposure times of 18 s.