2 Types

There are basically two types of meteorological satellites: geostationary and polar orbiting.

Geostationary weather satellites orbit the Earth above the equator at altitudes of 22,300 miles (35,880 kilometres). Because of this orbit, they remain stationary with respect to the rotating Earth and thus can record or transmit images of the entire hemisphere below continuously with their visual and infrared sensors. The news media uses the geostationary photos in their daily weather presentation as single images or made into movie loops.

Several geostationary meteorological spacecraft are in operation. The United States has three in operation; GOES-9, GOES-10 and GOES-12. GOES-12 is designated GOES-East, over the Amazon River and provides most of the U.S. weather information. GOES-10 is GOES-West over the eastern Pacific Ocean. GOES-9 is on loan to Japan over the mid Pacific as part of a multinational agreement since the Japanese satellite GMS-5 reached the end of its life and the failed launch of the replacement satellite MTSAT-1. The Europeans have METEOSAT-6, METEOSAT-7 and METEOSAT-8 over the Atlantic Ocean and METEOSAT-5 over the Indian Ocean. The Russians operate the GOMS over the equator south of Moscow. India also operate geostationary satellites which carry instruments for meteorological purposes.

Polar orbiting weather satellites circle the Earth at altitudes of from 450 miles to 500 miles (~720 - 800 km) in a north to south or vice versa path passing over the poles in their continuous flight. These sun synchronous vehicles take picture of the same location once every day and night. The United States, China, India and Russia have polar orbiting meteorological satellites.

Visual images from weather satellites are easy to interpret even by the layman; clouds, cloud systems such as fronts and tropical storms, lakes, forests, mountains, snow ice, fires, and pollution such as smoke, smog, oil slicks, dust and haze are readily apparent. Even wind can be determined by cloud patterns, alignments and movement from successive photos.

The thermal or infrared images recorded by the weather satellite sensors called scanning radiometers enable a trained analyst to determine cloud heights and types, to calculate land and surface water temperatures, and to locate ocean surface features. These infrared pictures depict offshore pollution, ocean eddies or vortices and map currents such as the Gulf Stream valuable to the shipping industry hoping to save precious fuel by using the ocean movements wisely. Fishermen and farmers want to know land and water temperatures to protect their crops against frost or increase their catch from the sea. Even El Niño phenomena can be spotted. Using color-digitized techniques, the gray shaded thermal images can be converted to color for easier identification of desired information.

Snowfield monitoring, especially in the Sierra Nevada, can be helpful to the hydrologist keeping track of how much snow is available for runoff vital to the water sheds of the western United States. This information is gleaned from existing satellites of all agencies of the U.S. government (in addition to local, on-the-ground, measurements). Ice floes, packs and bergs can also be located and tracked from weather space craft.

Even man-made pollution can be pinpointed. The visual and infrared photos show pollution plumes from the areas over the entire earth. Aircraft and rocket pollution (contrails) can also be spotted. Oil well ruptures in the oceans of our planet are captured by weather satellites, but, more important, the ocean current and low level wind information gleaned from the space photos helped predict spill coverage and movement.

Almost every summer, sand and dust from the Sahara Desert in Africa drifts across the equatorial regions of the Atlantic Ocean. GOES-EAST photos enabled meteorologists to observe, track and forecast this sand cloud. In addition to reducing visibilities, causing respiratory problems, sand clouds suppress hurricane formation by modifying the solar radiation balance of the tropics. Other dust storms in Asia and mainland China are common and easy to spot and monitor with recent examples of dust moving across Pacific ocean and reaching North America.

The United States Department of Defense's Meteorological Satellite ( DMSP) can "see" the best of all weather vehicles with its ability to detect objects almost as small as an oil tanker. In addition, of all the weather satellites in orbit, only DMSP can "see" at night in the visual. Some of the most spectacular photos have been recorded by the night visual sensor; city lights, volcanoes, fires, lightning, meteors, oil field burn-offs, as well as the Aurora Borealis and Aurora Australis have been captured by this 450-mile-high space vehicle's low moonlight sensor.

At the same time, energy monitoring as well as city growth can be accomplished since both major and even minor cities, as well as highway lights, are conspicuous. Astronomers can use this information as light pollution. The United States is the largest user of electrical energy for lighting, and this is apparent on the nighttime views of the United States. Over 40 percent of the electrical energy in New York City goes for lighting. The DMSP satellite's nighttime views bear this out. Other developed and underdeveloped countries, while large in population, show limited lighting usage especially in their major cities. The New York Blackout of 1976 was captured by one of the night orbiter DMSP space vehicles.

In addition to monitoring city lights, these photos are a life saving asset in the detection and monitoring of fires. Not only do the satellites see the fires visually day and night, but the thermal and infrared scanners on board these weather satellites detect potential fire sources below the surface of the Earth where smoldering occurs. Once the fire is detected, the same weather satellites provide vital information about wind that could fan or spread the fires. These same cloud photos from space tell the firefighter when it will rain.

In remote areas of the world where population is not readily available to detect fires, these satellites could be tremendous asset where millions of acres rage out of control for days or weeks before they are discovered. These nighttime photos also clearly show the colossal waste of burn-off in the gas and oil fields of the Middle East and African countries. With the energy loss resulting from the burn-off, unusually large amounts of pollutants are being thrown into the atmosphere.

The most dramatic photos provided by all the weather satellites, but even more definitive were the DMSP night visual pictures of the 700 oil well fires that Iraq started on 23 February 1991 as they fled Kuwait. These fires were vividly illustrated as huge flashes on the night visual pictures far outstripping the glowing cities of the larger populated areas. The last of the 700 fires which spewed millions of gallons of oil, was doused on November 6. During the February to November time frame, the amount of black smoke put into the atmosphere created immeasurable damage to that region's ecological system, damage to human, animal and plant life, and went so far as to suppress normal 1991 hurricane activity in the eastern Atlantic.

3 External link

• Near realtime composite of satellite image of the Earth

Meteorology

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