Weather
Satellite Systems
Several months
ago, I published an article on Global Positioning System (GPS). I am following
it up with this article on weather satellite systems. Neither the GPS or
these weather satellite systems are communication systems per se, but they
are interesting milestones of the satellite industry.
During the
soccer season, I become much interested in weather forecasts: I just want
to know whether I will get my practices and games in for that week. Trying
to catch the 5 minutes forecast on the daily news on television is not
very satisfying. Well, for a spare $20,000 I can have my very own weather
station in my home.
Weather satellites
come in two basic forms: geostationary and polar orbiting. Geostationary
Operational Environmental Satellites (GOES) orbit the Earth at a distance
of some 19,337 nautical miles. These satellites can view a sector of the
Earth approximately + 600 in latitude and + 600 in longitude. Pictures
from these satellites are often seen on TV weather reports. Large and precisely-aimed
antennas are required to insure reliable reception of GOES weather pictures.
Television
and Infrared Observation Satellites (TIROS), on the other hand, orbit the
Earth at an altitude of only 450 nautical miles. TIROS are Low Earth Orbit
(LEO) satellites. While GOES station on the equator, TIROS are set up to
circle the poles. With two active satellites in orbit, every point on the
surface of the Earth is scanned four times each day. Transmission from
TIROS are made on a number of radio frequencies. These signals, which only
have to traverse a few hundred miles to reach the Earth from orbit, can
be received with simple, non-directional antennas that are much more practical
for use on boats or on mobile vehicles. Equipment required to receive and
process the satellite information costs $900 to $1,000, plus the cost of
the computer and its display/printer and power supply. A complete system
can be assembled for less than $2,500, the salary of the meteorologist
not included
One of the
latest weather-related product to hit the market is 'Weather for Windows'
from Canada's Global Meteorological Technologies Ltd (GMT). The product
uses a 486 PC connected to an INMARSAT-C terminal. Information is sent
via INMARSAT's Fleetnet service. The display is a near real- time graphical
weather map of the world that can be zoomed to show local areas. Weather
ships and buoys can be highlighted to display the weather information for
that specific station. Maps can be configured to display ice formation
or possible fish shoal locations. A complete system (INMARSAT-C terminal,
486 PC, Weatherwise software and access to Fleetnet) will cost Canadian
$20,000. An additional $16.40 will be charged for the use of the service
per voyage day. GMT receives the original weather data from NOAA (TIROS/GOES),
constructs the graphical data and broadcasts to the ships via Fleetnet.
For around
100,000 French Francs (approximately US $20,000), yachtsmen and fishermen
can procure a 'Sea Mac' system (INMARSAT-C terminal, Apple Macintosh computer,
and software) from the French firm Informatique et Mer, that will display
a range of weather data (wind speed and direction, wave height, barometric
pressure, water temperature etc.) in a graphical format. The system allows
zooming into a specific area of the globe for detailed weather information.
The system will also provide a five days forecast in an animated weather
map.
Viet-Dung
Hoang, Ph.D.
[email protected]
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Copyright
© 1994 - 1997 by VACETS and Viet-Dung Hoang
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