PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
CONTACT: James H. Wilson
FOR IMMEDIATE RELEASEMarch 29, 1996
RADAR TELESCOPE OBSERVES NUCLEUS OF COMET HYAKUTAKE
The nucleus of Comet Hyakutake, observed by radar at a
distance of 16 million kilometers (10 million miles) on March 24
and 25, is apparently 1-3 kilometers (less than 2 miles) across,
a NASA radar scientist reported.
"This is the first and, so far as I know, only direct
detection of the nucleus of comet Hyakutake," said Jet Propulsion
Laboratory radar astronomer Steven J. Ostro. "We have touched
the heart and soul of the comet," he added.
The observations were made with the 70-meter (230-ft)
antenna at the NASA/JPL Goldstone Deep Space Communication
Complex. The radar telescope also detected particles flying away
from the nucleus at speeds of at least 10 meters per second (22
Ostro pointed out that five other comets have been detected
in the NASA radar astronomy program, but this is the first comet
radar detection since Halley was observed from the Arecibo radar
telescope in 1985.
Several transmit-receive cycles were made on each of the two
nights, he said. The echoes were received an average of 104
seconds after the 480-kilowatt radar signal was beamed at the
comet. The power in the echo received from the comet was less
than one billionth of a billionth of a milliwatt.
The radar echoes reveal that the comet's coma, the large
visible cloud, must contain a great many particles not much
smaller than a centimeter (about half an inch). Ostro noted that
there seems to be about ten times as much radar echo power from
these particles as from the nucleus itself.
The radar astronomy sessions were sandwiched between radio
communication passes for the Galileo and Voyager missions, and
were limited by system difficulties and the faintness of the
radar echoes. The Goldstone antenna is part of the Deep Space
Network, developed and operated for NASA by JPL.