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                                                  Circular No. 3338
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM     Telephone 617-864-5758

     T. Johnson, Jet Propulsion Laboratory, communicates the following
on behalf of the Voyager Team: "On Mar. 4d19h50m UT the Voyager
1 spacecraft passed through Jupiter's equatorial plane.  A 672-s
exposure taken with the narrow-angle camera (focal length 150 cm)
from a distance of 1.2 x 10**6 km revealed evidence for a faint Jovian
ring, extending out to 128 300 +/- 100 km from Jupiter.  The ring,
the width of which is less than 30 km, was identified primarily by
its parallactic motion against background stars as the spacecraft
moved.  The magnitude of the ring is very roughly estimated at 12 +/-
0.5 mv per pixel (8.56 x 10**-11 radian**2), and the spectral type is G.
Analysis of images of Jupiter I (Io) obtained on Mar. 4 and 5 has
revealed several active volcanic eruptions.  At least five areas
have been identified as active to date (at longitudes relative to
the subjovian meridian of ~ 310o, 260o, 170o, 145o and 110o west);
further analysis is revealing several other possibly active regions.
Infrared radiometry performed by the infrared spectrometer (IRIS)
indicates that the feature at 310o has elevated temperatures (at
least 200 K above background surface temperature, ~ 120 K, depending
on the size of the active region assumed) and is roughly circular,
~ 200 km across.  Other active areas may have similar temperatures,
and the infrared observations also show several hot spots
that could be plumes.  The attention of ground- and space-based
observers is drawn to these observations.  Surveys of Io-related
emissions, both optical and infrared, over a long timebase, are
obviously needed to establish the degree of variability in surface
activity and interactions with the Jovian magnetosphere."

     E. E. Becklin, C. G. Wynn-Williams, C. B. Pucher and J. S.
Morgan, University of Hawaii, report: "We have detected Jupiter's
ring on both sides of the planet at 2.2 um using the 224-cm Mauna
Kea telescope.  The flux through a 5" diaphragm located 13" above
the limb is 1.5 mJy; i.e., K = 14, some 11 magnitudes fainter than
Saturn's rings as measured through the same diaphragm.  Observations
obtained on Jan. 26 and Feb. 15 with the Cassegrain image-tube
spectrograph show [O II] emission at 3726 and 3729 A.  The
emission is concentrated in the plane of Jupiter's magnetic equator
near Io's orbit.  The intensity ratio I_3726/I_3729 >> 1, consistent
with observations of the "nebular" [S II] line.  The "transauroral"
[S II] lines at 4068 and 4076 A were also detected on these plates."

1979 March 16                  (3338)              Brian G. Marsden

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