NORTH AMERICAN weather watchers have less than their normal satellite view as the Atlantic hurricane season gets under way. But they still have plenty of storm-tracking power. One of the two GOES satellites that orbit 22,300 miles above the equator to keep tabs on the Pacific and Atlantic Oceans lost its vision last January. It had outlived its five-year design lifetime by nearly a year. But data from United States polar orbiting satellites and perhaps also from European and Japanese weather eyes can help make up for this loss.
The European data could be particularly helpful. The National Oceanic and Atmospheric Administration (NOAA) expects soon to move the remaining GOES to 98 degrees west longitude. There it can see from Hawaii to the middle North Atlantic. But it can't see over to the African coast where the tropical disturbances that may grow into hurricanes originate. The European Organisation for Meteorological Satellites' Meteosat 4, positioned at zero degrees longitude, can fill this gap. It sees from the Atlantic to the Middle East.
Leroy Spayd in the office of NOAA's assistant administrator for satellite and information services explains that taking advantage of Meteosat this year will be a little tricky. NOAA is upgrading its computer and communications systems to make foreign satellite data routinely available. That routine access won't be ready for this hurricane season. However, Mr. Spayd says, ``We'll try our hardest to get European data into our system'' in some interim manner that will help the National Hurricane Center.
The weather eyes' utility depends partly on their orbits. GOES stands for Geostationary Operational Environmental Satellite. Geostationary means it travels in an equatorial orbit 22,300 miles high at the same rate at which Earth spins. Essentially, it remains fixed at a given longitude. Most satellite pictures shown on TV weather reports come from geosynchronous satellites.
Polar orbiting satellites, on the other hand, travel at much lower altitudes and view a given area only twice a day. They are valuable for surveying polar latitudes where geosynchronous satellites have, at best, a limited slanting view. The US NOAA-10 and NOAA-11 orbit 540 miles high in near polar orbits to circle Earth every 102 minutes. Their twice-a-day views will help Hawaiian forecasters see weather that lies to their west.
These two types of satellites are linked in an international data-exchange network that covers the planet. This includes a Japanese geosynchronous satellite and Soviet polar orbiting satellites, as well as the US and European facilities. NOAA's computer/communications upgrade is aimed at taking advantage of this network.
The satellites send back more than cloud pictures. They can relay data from automatic instruments on land and on buoys at sea. Sensing infrared radiation, some of them can track atmospheric moisture even when it isn't condensed into clouds. They can measure temperatures at different atmospheric levels. Indeed, the failed GOES satellite lost only its vision. It still can perform some of these other functions, such as surface instrument readout.
NOAA has no more satellites to orbit in the current GOES series. It expects to launch a series of improved satellites starting next year. The nominal launch date for the first new GOES is July 1990. But Spayd notes that the development and checkout of the new instrument designs have led to schedule slippages already.