Location: webtextbook > weather>satellites Unifying Concept: S.C.H.3.4.4 know that funds for science research come from federal government agencies, industry, and private foundations and that this funding often influences the areas of discovery. SATELLITES Before the advent of today's weather satellite technology, information about the atmosphere was collected via time honored instruments such as the wind vane, anemometer, barometer, rain gauge, etc. But using just these instruments alone, much information was missing. Imagine the meteorologist's surprise when the first images of the earth where transmitted from space. For the first time they saw swirls of clouds associated with low pressure systems, fronts, as well as the cloudless areas of high pressure and fair weather systems. These first weather satellites were very limited in their ability to image the earth. Satellites now provide the meteorologist with information on:
Today the United States operates two different type of weather satellites. One is the Polar Orbiting Environmental Satellites (POES [NOAA 14]) and the other is the Geosynchronous Orbiting Environmental Satellites (GOES [GOES 8 & 9]). POES satellites are designed to observe the same area of the earth twice a day, once in sunlight and once at night. They orbit the earth over the north and south poles as the earth revolves underneath them. Their orbital time is approximately 100-115 minutes with each successive orbit further west.The following are the hardware specifications of the POES satellite: AVHRR (Advanced Very High Resolution Radiometer)
TOVS: TIROS Operational Vertical Sounder
Click on this 0.58-0.68 micron image which was produced by NOAA 14. It is a visible (VIS) image of a cold front approaching Florida , Alabama, and Georgia from the west. Notice the details in the cloud structures. Details can be seen due to the low orbit (approximately 650 miles) and the 1 km resolution of the satellite .
The GOES satellite sits approximately 22,500 miles above the equator. With the satellite sitting at this altitude, it will make one revolution of the earth per 24 hours. This is the same as the revolution of the earth and therefore allows the satellite to be "parked" over the same equatorial spot on the earth. Orbiting like this, the imager can provide successive views of weather systems. Because the imager can produce a picture every 30 minutes or sooner, the added advantage to using GOES satellites, is the ability to loop the successive images so that weather systems can be animated. The following are the hardware specifications of the five GOES satellite imager:
Click on this infrared (IR) image which was produced by GOES 8. Infrared images indicate heat intensities. It is not as detailed as the NOAA 14 image. Because its orbital speed is the same as the rotating speed of the earth, its position above the equator is always the same. To learn more about how satellite images are produced and transmitted, go to the following satellite page and study the seven page tutorial. On the last page of the tutorial there is an interactive portion on combining different spectral bands.
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