Geo-Stationary Satellites
Geo-Stationary Satellites circle the Earth in a geosynchronous orbit, which means they orbit the equatorial plane of the Earth at a speed matching the Earth's rotation. Because of this, certain areas of the world are better covered by the geostationary satellites than others, and polar areas are always covered poorly. These types of satellites orbit the earth at an altitude of about 35,785 km (22,235 mi.) above the equator which in turn allows them to monitor almost half of the Earth from their orbit. The geostationary satellites take images over a period of a few minutes (up to 26 minutes for a GOES-8 full earth scan) to scan the earth line by line. The GOES Satellites are operated by NOAA, National Oceanic and Atmospheric Administration, and are used by many other organizations in both the public and private sectors. Originally launched in 1975 the GOES satellites keep a constant eye on the world. GOES 8 and 10 are the two currently used satellites with GOES 11 being used as a potential back-up to 8 or 10. The imagery captured by the satellites are useful in weather forecasting, rain and snowfall estimation and observing the movement of sea and lake ice.
|
|
|
|
GOES-8 information: |
• Geostationary Operational Environmental Satellite (GOES)- 8.
• Operationally positioned at 75° west longitude and 0° latitude.
• Satellite was launched on April 13, 1994.
• Satellite operational on June 1, 1995. |
| |
| GOES-10 information: |
• Geostationary Operational Environmental Satellite (GOES)- 10.
• Operationally positioned at 135° west longitude and 0° latitude.
• Satellite was launched on May 23, 1995.
• Satellite operational on January 22, 1996. |
| |
|
|
Polar Satellites
Poloar Satellite system offers the advantage of daily global coverage, by making nearly polar orbits roughly 14.1 times daily. Polar Operational Environmental Satellites are satellites that are much closer to the earth than the geostationary satellites and move over different portions of the Earth on an orbit over the poles. Because of this, they do not capture as much as the higher Geo-Stationary satellites. Because of the polar orbiting nature of the POES series satellites, these satellites are able to collect global data on a daily basis for a variety of land, ocean, and atmospheric applications. Data from the POES series supports a broad range of environmental monitoring applications including weather analysis and forecasting, climate research and prediction, global sea surface temperature measurements, atmospheric soundings of temperature and humidity, ocean dynamics research, volcanic eruption monitoring, forest fire detection, global vegetation analysis, search and rescue, and many other applications. NOAA uses two polar orbiting satellite to capture a full picture of the earth and ensure that no data is older than 6 hours old.
|
| Polar Operational Environmental Satellite (POES).
Altitude above Earth - 700 to 800 km (440 to 500 miles), depending on time of day.
Orbital period is 98 to 102 minutes with 14 complete orbits per day. |
|
|
Visible Satellite Imagery
Visible Satellite show the visible light that is reflected off of clouds and the surface of the earth. They show all types of clouds and are the best type of images for seeing low level systems, which do not show up well on infrared imagery. Visible imagery is only taken during the day (in the area where the satellite is located). Areas of white indicate clouds while shades of gray indicate generally clear skies.
Visible images represent the amount of sunlight being scattered back into space by the clouds, atmospheric gases, and the Earth's surface. Thicker clouds have a higher reflectivity (or albedo) and appear brighter than thinner clouds on a visible image. However, it is difficult to distinguish among low, middle, and high level clouds in a visible satellite image, since they can all have a similar albedo and for this distinction, infrared satellite images are useful.
|
|
Infrared Satellite Imagery
Infrared Satellite show the amount of heat energy emitted by the different cloud features and the surface of the earth. Within an infrared image, warmer objects appear darker than colder objects. The following IR image shows the clouds that have colder temperatures as the greens to red colors (reds being the coldest). Thus the warmer areas show up as the grays. Presumably, the colder the clouds, the higher they appear in the atmosphere and the taller the cloud tops become. Taller cloud tops tend to produce more severe weather than lower cloud tops.
|
|
Water Vapor Satellite Imagery
Water Vapor Satellite show water vapor in the upper troposphere. The troposphere is the only area of the atmosphere generally important in everyday weather forecasting. The systems shown by water vapor images are upper level systems and are often different from those found at the surface. These systems have a large effect on the systems that are found at the surface. Water vapor is essentially the fuel that storm systems need to develop and survive. The areas shown in the image below with dark gray represent lower moisture than the bright white areas which represent areas of high moisture content.
|
|
