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1993-05-03
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PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011
Scientists and engineers from Caltech's Jet
Propulsion Laboratory (JPL) and the National Radio Astronomy
Observatory (NRAO) are working together in the high plains of
central New Mexico to improve our hearing from the planet
Neptune. The researchers are testing a new deep-space
communications system, starting in late June, with the
Voyager 2 spacecraft which will fly past the eighth planet
next year.
When Voyager 2 reaches Neptune in August 1989 to
take close-up pictures and thousands of other measurements,
the spacecraft will be nearly three billion miles from home;
its signal received on Earth will be extremely faint.
Adding the 27 radio telescopes of the NRAO's Very
Large Array (VLA) to JPL's Deep Space Network, which
communicates with interplanetary spacecraft, will more than
double the ability to capture Voyager's signal during the
eight hours per day that Voyager and Neptune will be above
the horizon at the desert site during 40 days of the summer
1989 encounter. Special equipment must be added to let the
VLA hear Voyager.
Under an agreement between NASA and the National
Science Foundation, which sponsors NRAO, engineers are î
installing new receivers and microwave horns, tuned to
Voyager's X-Band radio frequency, on all the 82-foot dish
antennas at the VLA. NASA has also provided an independent
power plant for the array, which is sometimes cut off the air
by summer lightning storms. Special signal-processing and
communication equipment has been added so that the VLA will
be linked by satellite to the Network's Deep Space
Communications Complex at Goldstone, California.
The new X-Band receiver systems were designed and
built cooperatively by JPL, the NRAO's Central Development
Laboratory at Charlottesville, Virginia, and the VLA at
Socorro, New Mexico. Like those of the DSN, the advanced
receiver circuits are kept chilled with liquid helium to
suppress internal electronic noise.
This month's system test is the first and probably
the last chance to preview Neptune operations with the whole
worldwide communication system, including elements at the
VLA. The Voyager spacecraft, now 2.4 billion miles from
Earth, will transmit in its planetary encounter mode, at data
rates up to 21,600 bits per second (the rate used at Uranus
in 1986). Linked electronically, the 20 or more VLA antennas
which now have their X-Band receivers and the 113-foot and
230-foot dishes at Goldstone will function as a single
receiving system.
The VLA, located about 100 miles southwest of
Albuquerque, has since 1980 enabled radio astronomers to
study distant stars, nebulae, and galaxies by collecting and î
analyzing radio emissions from these objects. The 27 mobile
dishes are arrayed along a Y-shaped railroad track and can be
rearranged for different observations. William D. Brundage
is VLA project engineer and responsible for Voyager
preparations at Socorro.
Voyager 2 was launched in August 1977, and has
explored Jupiter, Saturn, and Uranus since then.
The Deep Space Network has been developing and
operating as a NASA system for nearly 30 years. It has
communicated with spacecraft and astronauts on the Moon in
addition to unmanned spacecraft sent to explore comets, six
of the nine planets, and the outer reaches of the solar
system. Besides the Goldstone complex, the network includes
stations in Spain and Australia, where Australia's Parkes
Radio Telescope linked with the Deep Space Network to support
Voyager 2 in 1986 and will again next year. JPL's Donald W.
Brown is interagency arraying manager for the network, with
overall responsibility for the Socorro link.
VLA/Socorro contact: Terry Romero, Box 0, Socorro, NM 87801
Telephone (505) 772-4284