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ARRL Satellite Bulletin ARLS006 (1999)

ARLS006 Hams, SWLs invited to monitor eclipse propagation

QST de W1AW  
Space Bulletin 006  ARLS006
From ARRL Headquarters  
Newington, CT  August 6, 1999
To all radio amateurs

ARLS006 Hams, SWLs invited to monitor eclipse propagation

NASA is inviting Amateur Radio operators and shortwave listeners to
monitor radio propagation during the total solar eclipse August 11
and to report their findings. Scientists expect nighttime conditions
to be manifested as the eclipse crosses Earth's surface--creating an
''audio eclipse.''

The August 11 eclipse will be the last total solar eclipse of the
20th century. The trajectory of the moon's shadow will carry it
across central Europe, Turkey, the Middle East, Pakistan and India.

As the path of totality slices through Earth's atmosphere, ions and
electrons in the vicinity of the shadow will begin to recombine. The
reflecting F layer may not be greatly affected, but ionization in
the attenuating D layer could vanish. Shortwave radio stations that
were restricted in range to sites in Europe just moments earlier may
be able to skip over the horizon and be heard on the other side of
the Atlantic.

The eclipse will begin over Europe around 1010 UTC when it is still
dark over most of North America. Thus, when the daytime ionosphere
begins to diminish over Europe, there is a good chance that European
shortwave broadcast stations will be able to propagate great
distances into the Western Hemisphere. NASA suggests experimenting
with different stations at frequencies between 5 and 15 MHz that are
favorable for probing changes in the D layer.  The best ones for
eclipse listening will be transmitters that can be heard at night,
but not at all during the day.

NASA requests that participating listeners report the time, station
frequency and signal strength at night and during the local time of
the eclipse for a week centered on August 11. Send logs, any audio
recordings, and your latitude and longitude to Marshall Space Flight
Center's Eclipse mailbox, The data will be
analyzed to help determine ionospheric properties.

For additional details, visit the Science@NASA site,

The Royal Belgium Amateur Radio Society (UBA) is mounting a similar
program aimed at European amateurs. For more information, visit


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