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IAUC 5052: 1990i; SATURN

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                                                  Circular No. 5052
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505

     H. Kosai, National Astronomical Observatory of Japan, reports
the independent discoveries of a new comet by Kiyoshi Tsuchiya and
Tsuruhiko Kiuchi, as follows:

     1990 UT           R.A. (1950) Decl.        m1       Observer
     July 13.522      12 31.8      +31 15       8        Tsuchiya
          16.506      12 25.0      +30 15       9        Kiuchi

K. Tsuchiya (Asahikawa, Hokkaido).  f/4 camera + T-Max film.
T. Kiuchi (Usuda, Nagano).  25x150 binoculars.

     M. R. Showalter, NASA Ames Research Center, writes that,
following the analysis (Showalter et al. 1986, Icarus 66, 297; see
also Cuzzi and Scargle 1985, Ap.J. 292, 276) of Voyager 2 observations
of transitory optical-depth variations near the edges of the
Encke Gap in Saturn's A ring in terms of the gravitational attraction
of a single satellite in the Gap, he has been able to identify
images of the predicted satellite, designated 1981 S13, in eleven
Voyager 2 frames spanning 48 hr before the Saturn encounter in 1981.
The satellite is estimated to have radius about 10 km and geometric
albedo 0.4-0.7, and its longitude (equinox 1950.0, measured along
the earth's equatorial plane to the ascending node of Saturn's ring
plane and thence along the ring plane) is given by L = 141 deg +
(626.0 +/- 0.1 deg) x (JD - 2444842.568).
     F. Colas, Bureau des Longitudes, Paris; J. Lecacheux, Observatoire
de Paris; P. Laques and R. Despiau, Observatoire du Pic-du-Midi,
telex:  "CCD observers at Pic-du-Midi Observatory (1.05-m reflector)
report that a tiny bright oval spot is present on the Saturnian polar
cap at planetocentric latitude +73 deg.  The preliminary period of
rotation is found near 10h39m, but the period possibly increased by a
few min during July 4-12.  The spot, whose apparent size is about
0".7, or 4500 km (resolved on the best CCD images), is detected in
Johnson VRI bands but is easier in I.  Methane filters reveal high
contrast against the surroundings in the molecular absorption at
0.89 micron, but low contrast in the nearby continuum at 0.83 micron.
This spectral behavior denotes an uncommon high-altitude cloud."

1990 July 16                   (5052)             Daniel W. E. Green

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