[mmaimcal] MM frequency protection

[Al Wootten]

ASTRONOMERS WIN PROTECTION FOR KEY PART OF SPECTRUM

     Astronomers using the millimeter-wave region of the radio spectrum
have won crucial protection for their science.  The 2,500 delegates to the
World Radiocommunication Conference (WCR 2000) have given final approval
to dedicated spectrum allocations for radio astronomy.  The delegates
recently concluded a month of deliberations in Istanbul, Turkey.

     The new millimeter-wave allocations represent the culmination of more
than three years of cooperative planning by radio astronomers in many
countries.

     Millimeter waves - high-frequency radio waves - have come of age as
an astronomical tool in the last ten years.  They are one of the last
technological frontiers for astronomers.

     WRC-00 has protected for science all the frequencies between 71 and
275 Gigahertz that radio astronomers currently use, adding more than 90
GHz of spectrum to the 44 GHz already set aside in
this frequency range.  As a result, radio astronomy is now allocated most
of the frequencies between 71 and 275 GHz that can get through the earth's
atmosphere.

     "We have formal access to all three atmospheric 'windows,' apart from
their very edges," said Tom Gergely of the National Science Foundation's
(NSF) Astronomy Division, one of the U.S. delegates to WRC-2000.

     The WRC also changed the frequencies allocated to satellite downlinks
within the 71-275 GHz range to frequencies not used for science.  Since no
satellites yet operate at these high frequencies, no equipment needs to be
altered.

     "Commercial technologies are not fully developed above 50 GHz," said
Klaus Ruf, chairman of the Inter-Union Commission for the Allocation of
Frequencies.  "The WRC's actions mean that, when they are, radio
astronomers should be able to share this part of the spectrum with most
terrestrial services."

     The World Radiocommunication Conference is held every two to three
years.   Member countries of the International Telecommunication Union
meet at the WRC to parcel out the radio frequency spectrum between
radio-based applications such as personal communications, satellite
broadcasting, GPS and amateur radio, and the sciences of radio astronomy,
earth exploration and deep space research.  The WRC also coordinates
sharing between these services in the same radio bands.

     WRC decisions are incorporated into the Radio Regulations that govern
radio services worldwide.

     The new spectrum allocations for radio astronomy are the first since
1979.  Millimeter-wave astronomy was then in its infancy and many of its
needs were not yet known.  As astronomers began to explore this region of
the spectrum they found spectral lines from many interesting molecules in
space.  Many of those lines had not fallen into the areas originally set
aside for astronomy, but most will be under the new allocations.

     "It's a win for millimeter-wave science," said John Whiteoak of the
Australia Telescope National Facility, Australian delegate to WRC-2000.
"This secures its future."

     The protection is a significant step for both existing
millimeter-wave telescopes and new ones such as the Atacama Large
Millimeter Array (ALMA) now being planned by a US-European consortium.
Even at its isolated site in Chile's Atacama Desert, ALMA would be
vulnerable to interference from satellite
emissions.  Sensitive radio astronomy receivers are blinded by these
emissions, just as an optical telescope would be by a searchlight.

     "There is more energy at millimeter and sub-millimeter wavelengths
washing through the universe than there is of light or any other kind of
radiation," said ALMA project scientist, Al Wootten of the National Radio
Astronomy Observatory.  "Imaging the sources of this energy can tell us a
great deal about the
formation of stars and galaxies, and even planets."

     The changes were welcomed by Johannes Andersen, General Secretary of
the International Astronomical Union, which represents astronomers
worldwide.

     "Protecting our ability to observe the universe is the top priority
for the International Astronomical Union," Andersen said.  "This action
shows that international bodies accept the need for environmental emission
standards in space as well as on Earth, for the benefit of all."

-NSF-