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1993-04-23
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PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA (91109). PHONE (2l3) 354-50ll
Dr. Stephen P. Synnott of the Jet Propulsion
Labora-
tory has found evidence for the existence of four, and
possibly
as many as six, new satellites of Saturn, using data from the
Voyager 2 Saturn encounter.
The discoveries bring the number of known Saturnian
satellites to between 21 and 23. The two "possible"
satellites
were seen in only one observation each, so their orbits are
not yet confirmed.
The innermost satellite found by Synnott moves at
about the same orbital distance from Saturn as the already-
known satellite, Mimas. The object was originally suggested
by data from charged-particle instruments aboard Voyager 2.
Synnott and JPL planetary scientist Richard Terrile found
the satellite.
A third (and possibly fourth) companion of the sat-
ellite Tethys appear to move in what Synnott calls a "horse-
shoe" orbit. Synnott says that he is sure an object is there.
But he is not certain yet, because of resolution limits in
the î
photos, whether it is one or two objects. Satellites in
"horse-
shoe" orbits trade orbits as they approach each other.
Another satellite was found by Synnott at a point
about 60 degrees ahead of the satellite Dione. That is the
second found in that region. The first was discovered in
Earth-based observations in 1980.
Synnott found yet another satellite about 350,000
kilometers (217,000 miles) from Saturn, between the orbits
of Tethys and Dione. It circles Saturn once in 2.44 days.
Synnott's final observation, a faint streak in a
Voyager 2 photo, indicates a satellite (the "possible sixth")
may exist about 470,000 kilometers (292,000 miles) from Sat-
urn, between the orbits of Dione and Rhea. Its period would
be, Synnott calculates, 3.8 days.
The object that shares the orbit of Mimas is about
10 kilometers (6 miles) in diameter. All the others are about
15 to 20 kilometers (nine to 12 miles) in diameter.
Synnott, a member of the Voyager navigation team,
also found two new satellites at Jupiter in photos he studied
after the Voyager encounters in 1979.
Two Voyager spacecraft were launched in 1977 to
perform flyby encounters with Jupiter, in 1979, and Saturn
in 1980 and 1981. The Voyager project is managed for NASA
by the Jet Propulsion Laboratory. î
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