Released simultaneously by the National Science
Foundation and Cornell University
NSF PR 98-18 - March 18, 1998
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New Pact Protects Radio Astronomy Frequency from Interference
A new agreement extends some protection to astronomers
who use the Arecibo Radio Telescope in Puerto Rico
and have been concerned about potential interference
from the commercial satellite system IRIDIUM. The
memorandum of understanding signed between the National
Astronomy and Ionosphere Center, which operates Arecibo,
and Motorola, Inc., which operates IRIDIUM, guarantees
eight hours of observing time each day "unpolluted"
by interference. The NAIC is headquartered at Cornell
University and funded by the National Science Foundation.
The agreement, which took five years to hammer out,
addresses IRIDIUM's potential interference with reception
of faint radio signals at a key frequency for astronomers:
1612 Megahertz. Hydroxyl, one of most common interstellar
molecules, emits radiation at this frequency. This
simple molecule can be produced in the atmospheres
of old red giant stars; gas can blow off and eventually
be swept up into new stars. Hydroxyl also appears
in interstellar clouds, which are seedbeds of young
stars and solar systems. Tracing the path of this
gas is one thread in reconstructing how our own galaxy
evolved.
"This agreement is a good compromise in protecting
astronomers' ability to observe at this frequency,"
said Paul Goldsmith, Cornell University astronomer
and NAIC director. "Some radio astronomers may have
felt that they were entitled to 24 hours a day, but
I'm happy that both sides could agree to eight. The
agreement should help radio astronomy and communications'
use of the spectrum to coexist productively."
"We're very pleased that the agreement will help us
fully exploit the newly upgraded Arecibo telescope,"
said Hugh Van Horn, NSF director of astronomy. "The
telescope's ability to observe across a much greater
range of frequencies, and its enhanced sensitivity,
will enable a vast new range of astronomical observations
of sources from asteroids to distant galaxies. But
careful protection of the radio spectrum is absolutely
essential to use the telescope to its fullest potential."
The IRIDIUM satellite system, planned to become operational
in the fall of 1998, will employ 66 satellites in
low earth orbit to enable portable telephone communication
anywhere in the world, directly by satellite instead
of by local cellular networks.
The protected time period of astronomical observation
will span the period from 10:00 p.m. to 6:00 a.m.,
Eastern Time. The agreement also specifies that radio
astronomers may be allotted protected slots at other
times of the day if special scientific opportunities
arise.
Radio interference remains an ongoing and increasing
threat to astronomy. "We must worry about interference
with observations at other frequencies and at other
radio telescopes as well," said Michael Davis, chair
of the National Research Council's Committee on Radio
Frequencies. "It's vital to protect access to these
very faint whispers of natural radiation that tell
us so much about the universe."
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