Capture Satellite Weather Images at Home

You can tap into international weather satellites with an antenna and a computer to capture satellite weather images. Learn how to make accurate weather forecasts at home.


| October/November 1993



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Both polar-orbiting and geostationary satellites take weather photographs 24 hours a day.


HANK BRANDLI

An early season cold front is expected to hit the state tomorrow and you decide to harvest a bit earlier to avoid crop damage. Or a forecast of weekend rain coincides with your long-awaited fishing trip, and you're not sure whether it's worth risking the two-hour drive. Sure, the weather bureau or local television station can tell you what to expect—in general. But in many circumstances, their regional reports are not comprehensive enough to be of real use, especially to those whose livelihood depends upon an accurate forecast. Forecasts produced by weather stations are no longer the property of million-dollar media centers. They are available inexpensively to anyone who owns a personal computer and has a healthy interest in the skies.

Predicting the weather reliably requires information. Where is the nearest cloud formation? What kinds of clouds does it contain? What's the temperature within the formation? In what direction is the prevailing wind? Meteorologists answer these questions largely by using one critical tool: the satellite photograph.

Unmanned meteorological satellites provide some of the most spectacular and useful visual information, surpassing both the predictions of the weather bureau and television for sheer volume of information. There are innumerable ways to use the data: Agriculturists use the photos to inform the farming community when weather conditions are most favorable for planting, fertilizing, and harvesting; hydrologists use them to evaluate rainfall conditions, predict areas of flooding, and provide safety warnings; the construction industry uses them to detect rain, lightning, and snow, aiding workers at construction sites .... The list is endless.

Polar-orbiting weather satellites circle the Earth approximately every 100 minutes, providing coverage of the entire world. Each day and night, these 450-mile-high, polar-orbiting weather satellites of the United States, Russia, and China can "see" far enough to show you the weather heading your way up to 48 hours in advance. These 1,000- to 1,600-mile belts of imagery are transmitted via automatic picture transmission (APT) systems, whose media are simple radio waves. Most take both visual and infrared (thermal) images during the day, and only infrared at night; the images can be received from any of these satellites when the spacecraft is above your horizon. They can be captured and observed as easily from the home, business, classroom, boat, or aircraft as from any television station.

There are also several high-altitude satellites, following a geostationary orbit, that photograph the Earth from 22,000 miles, but their signals can be received only with expensive equipment. A simple antenna, preamplifier (which amplifies weak signals), and receiver, together with a home computer, is all you'll need to receive detailed and accurate weather data from polar-orbiting satellites. Even without a computer, there are other ways to display the images and have the thrill of making your own local forecast.

Weather Birds

Three American NOAA (National Oceanic and Atmospheric Administration) polar-orbiting weather satellites in sun synchronous orbits (satellites that come over at the same local time respective to the Sun) transmit 1,600-mile-wide images of the same location at approximately 8 A.M. and 8 P.M. , 2 A.M. and 2 P.M. , and 5 A.m. and 5 P.M. China's Feng Yuri, similar to the NOAA satellites, takes images at 9 A.m. and 9 P.m. The several Russian meteor spacecraft transmit mostly 1,200-mile-wide pictures. Their near-polar paths allow photo-taking at opposite times during the day. Unlike the satellites of China and America, Russia's satellites remain at a high latitude and therefore work on a different schedule. So if the satellites take a picture at 11 A.M. one day, the next day they may take pictures at either 11:30 or 12:30. NOAA satellites can pinpoint areas of clouds as small as two miles wide; Russia's can record features on the Earth as small as one mile wide.





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