Geosynchronous Orbit (GEO) Satellites
GEO Satellite Definition:
A satellite in geosynchronous (or geostationary) are positioned a fixed point at approximately 35,786 kilometers (19,323 nautical miles or 22,241 statute miles) above the earth's surface. At this fixed height, the satellite matches the Earth’s rotation speed and allows the satellites a full-disc view at a stationary position. To stay over the same spot on earth, a geostationary satellite also has to be directly above the equator. Otherwise, from the earth the satellite would appear to move in a north-south line every day.
GEO satellites primary purpose is weather imagery to optimize forecasting. In addition to weather imagery, these satellites include instrumentation used in environmental monitoring communications via a relay system. In the United States, this relay system is known as the GOES Data Collection System (DCS). The world network of GEO satellites used with weather imagery and environmental monitoring communications are as follows:
GEO Satellites (country of operations):
GOES - Geostationary Operational Environmental Satellites ( USA)
http://www.oso.noaa.gov/goes/
GOES - Information on the GOES Data Collection System (DCS)
http://noaasis.noaa.gov/DCS/
GMS - Geostationary Meteorological Satellites ( Japan)
http://ghrc.msfc.nasa.gov:5721/source_documents/gms_source.html
MeteoSat (European Community)
http://www.eumetsat.int/
INSAT – Indian National Satellite System ( India)
http://www.bharat-rakshak.com/SPACE/space-satellite3.html
GOMS – Geostationary Operational Meteorological Satellite ( Russia)
http://margotte.univ-paris1.fr/cgms/en/ap9-08.htm
Feng Yun ( China)
http://www.fas.org/spp/guide/china/earth/fy-2.htm
(Note: Polar Orbiting Satellites, which are not GEO satellites, are not discussed in this background)
Purpose of GEO Satellites:
GEO satellites provide the kind of continuous monitoring necessary for intensive data analysis. By orbiting the equatorial plane of the Earth at a speed matching the Earth's rotation, these satellites can continuously stay above one position on the Earth's surface. Because they stay above a fixed spot on the surface, they provide a constant vigil for the atmospheric "triggers" for severe weather conditions such as tornadoes, flash floods, hail storms, and hurricanes. When these conditions develop these GEO satellites are able to monitor storm development and track their movements.
The United States normally operates two meteorological satellites in geostationary orbit over the equator – named GOES West and GOES East. GOES is defined as Geostationary Operational Environmental Satellite. Each satellite views almost a third of the Earth's surface:
Other instruments on board these satellites are a Search and Rescue transponder, a data collection and relay system for ground-based data platforms, and a space environment monitor.
The environmental monitoring market (and in the United States home land security applications) uses the data collection and relay system for data communications.
A Data Collection Platform (DCP) consists of sensor connected to a data logger and the data logger connected to a GEO transmitter. Stevens Water Monitoring Systems, Inc. designs and manufactures a certified GEO transmitter and a variety of sensors and data loggers. Data Collection Platforms (DCP) are used in remote and isolate regions to gather important weather, hydrological or other environmental data. As a result, users can efficiently monitor various environmental data related to the earth and its natural phenomena and transmit this data via the GEO satellite being targeted by the respective remote station. The GEO satellite functions as a repeater of the data back to an earth ground stations. Stevens also designs and manufactures a GEO receive system called a Direct Readout Ground Station (DRGS) and also provides an alternative Internet Access to the GOES data using Stevens service called www.GOESLink.com.
Advantages of GEO Satellite Telemetry
- Low communications cost (Free for GOES)
- Low maintenance
- Emergency event-driven capability
- Ideal for remote locations
- Data easily shared among government users
- Very reliable data transmissions as system is supported governmental agencies
- Available for environmental or home-land security monitoring applications
Disadvantages of GEO Satellite Telemetry
- Scheduled transmission times assigned by governmental agency and based on Channel/Time availability
- Interference detection difficult
- Troubleshooting capabilities minimal
- Data is available to Government and public
- Hardware cost more expensive than other telemetry costs
- One-way transmissions
- No acknowledgement of successful data transmission.
- If a transmission fails, it cannot be repeated at a later time.
- Primarily available only to Federal, state or local governmental agencies or government sponsored environmental monitoring applications.
For application or more information on the GOES DCS - http://noaasis.noaa.gov/DCS/