The Recent Advances of Satellites

Nicole B. / Physics 336 / 20 April 1997
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Satellites are used in many fields today. Scientists use satellites to observe and determine many different features of the earth. Scientists use satellites to observe different types of radiation and celestial objects. Weather satellites are used to determine many different weather conditions and locations of weather. Satellite navigation systems help pilots and ship navigators to also locate things. Communication satellites are used to transmit data to different places of the world, while military satellites are also used to transmit data but for the purpose of protecting our country.

Scientific Satellites

Scientists use satellites to observe different features of the earth including different kinds of radiation. "Satellites provide colonized images of the outgoing-long-wave radiation, a quantity that can aid in detection of long-term warming or cooling" (McGinley 10). Satellites are also used to monitor the atmospheric ozone, which is a gas that protects the earth from harmful solar radiation. Modern satellites are sent up with multi-channel high-resolution radiometers that cover a wide range of infrared and microwave wavelengths. Radiometers sense cloudy and clear air, atmospheric temperatures, and ocean winds and provide visual imagery as well. Sensors that measure radiation are used to get a more complete picture of the atmosphere by measuring in an area beyond visual red, where ground surface or cloud top temperature can be determined.

Today earth-orbiting satellite observatories can observe celestial objects without the interference caused by the earth's atmosphere. "The orbiting astronomical observatories, and the International Ultraviolet Explorer, for example studied faint astronomical objects in the ultraviolet region of the electromagnetic spectrum" (15).

The National Reconnaissance Office (NRO), one of America's space agencies was able to observe a celestial object without interference caused by the earth's atmosphere. The NRO demonstrated the motion and survivability of tethers in low earth orbit, littered with micro-meteoroids as well as space stuff. "The tether is about two and one half miles long and is made of white yarn that is wrapped in braided Spectra 1000, a tough white fiber used in bullet proof vests and fish lines, that is one tenth of an inch thick" (Miles 2). On both ends of the tips of the tether is an aluminum hexagonal box covered with 18 laser reflectors. The box containing the NASA-donated unreeling device and long-dead electronics has a mass of 83 pounds. The other box is 23 pounds. The names of the boxes are Ralph and Norton, after Ralph Kramden, and Ed Norton of the Honeymooners.

This is the longest-lasting space tether yet, which has a great cost of 4 million dollars. It is also the first unclassified, ongoing space project in the 36-year history of the National Reconnaissance Office. The NRO usually flies spy satellites. The NRO is not willing to say much about the experiment, but it did say that on June 20, 1996, the Tether Physics and Survivability experiment called tips was ejected from a classified military satellite, into a 635-mile-high orbit that swings as far north as Alaska and as far south as Chile's Cape Horn. A few hours later the yarn (all 2 1/2 miles ) was unreeled from a spool, weighing 12 pounds, and was swung like a jump rope and eventually straightened out. It has been orbiting the earth for 9 months, and is observed by the NRO by ground-based laser, radar and telescope observations. NRO officials say if the tether isn't broken by a micrometeroid or other debris it could orbit as long as 27 years before plunging through the atmosphere and burning up. The NRO hopes that some day they could use tethers to connect clusters of small satellites so they could communicate much like a computer network. Tethers could also be used to power space craft by generating electricity as the conductive cords sweep through earth's magnetic field to propel spacecraft's into different orbits and to drop experiments from a space station.

Weather Satellites

Satellites are used by scientists to determine many different weather conditions and the various locations of weather. The meteorologist, by noting past locations, apparent qualitative strength, jet streams and storms, and by using the satellite-improved model generated forecast, is able to make more accurate weather predictions for a particular location. Through the use of sensors, the satellites data provides details of individual thunderstorms and maintains coverage over a specific location on earth at time intervals from 5 minutes to 12 hours. "Heavy snows or rains associated with large cyclones are often produced by mesoscale, sized thunderstorm systems that can be easily seen and traced by visual and infrared satellite imagery" (McGinley 20).

Polar orbiting satellites globally monitor temperature, moisture and cloud patterns associated with these systems. The satellite measurements are combined with other weather data to initialize computer-run mathematical models which routinely provide forecasts for these major cyclones. Satellite monitoring of polar ice caps helps identify important seasonal variations. Ice caps in areas where vegetation is decreasing because of drought or human exploitation, modify fractions of incident radiation reflected and influence the effective solar radiation reaching the earth. Meteorological satellites can measure radiation in a wide spectrum of electromagnetic wavelengths. This provides the meteorologist with a supplemental source of data including cloud imagery from visual sensors, ground surface, cloud, and atmospheric layer temperatures, and water vapor concentration from infrared sensors.

Navigation Satellites

Satellite navigation systems are used to help many pilots and ship navigators locate different things in various places. By knowing the position of several satellites from their signals, it is possible to determine the exact location of a ship on earth. A modern system uses laser-beam signals and can determine the position to within less than one inch. Omega, a navigation system developed originally for ships, uses very low frequency radio beams sent out by eight ground-based stations across the globe, and is picked up by global positioning satellites to provide two or three dimensional fixes on military planes. These systems permit the pilot to do his or her own navigation, so navigation officers are not needed for commercial flights.

The techniques used by navigation satellites are also used to make accurate maps of remote areas of earth. The US Lands System provides data to ground stations around the world. Geologists and other specialists use this data for mineral exploration, crop forecasting, flood control, and land management.

Communication Satellite

Many different communication sources such as telephone companies, television companies, newspapers and magazines use communication satellites to transmit data to various parts of the globe. A group of satellites used in communication among earth stations forms a satellite communications system. Such systems provide international communication like The International Telecommunications Satellite Organization (INTELSAT), or provide domestic communication like Canada's Telesat System. Intelsat is in 400 earth stations in 150 countries. The constellation of Intelsat satellites over the Atlantic, Pacific and Indian Oceans relays telegraph and TV transmissions and over two thirds of all international phone calls.

Communications satellites are responsible for instantaneous television coverage of events all over the globe, for the speed of international banking and finance, for the almost-immediate delivery of vast amounts of information, and for international "E" mail and telephone service to all parts of the earth. Almost any transfer of information that depends on cables, lines, or antennas can not be communicated through satellite. One large communications satellite can carry at the same time over 100,000 phone calls and several television signals.

Military Satellites

The military uses satellites for many purposed including protecting the country. Countries use military surveillance and reconnaissance, or spy satellites to monitor the activity of other nations. The US Big Bird and the Soviet Cosmos satellites were used to take photos of military activity. The Ferret satellite also reported radio and radar transmissions.

Long distance communications satellites for the military were introduced in the late 1060's by the US and the Soviet Union and in the 1070's by the North Atlantic Treaty Organization (NATO) and the United Kingdom. Capabilities of these satellites have greatly improved. For example, the US Navy's FltSatCom (Fleet Satellite Communication) system provides for world-wide high-priority communications between naval aircraft, ships, submarines, and ground stations.

The purpose of military navigation satellites is to determine the position of ground troops, aircraft, missiles, ships and submarines accurately.


Satellites are used to observe and determine things in many different fields today. Satellites are used to observe radiation and different features of earth. Weather satellites are used to determine many weather conditions and location of weather. Satellites are also used for communication purposes so information can be transmitted throughout the globe in a very short amount of time. Navigation satellites help pilots and ship navigators determine the exact location of things on earth. Military satellites are used to protect the country by using military surveillance and spy satellites to monitor activity of other nations. As stated above, satellites are what make this world united and without them we would face many difficulties.



Demis Richard. "Artificial Satellites." Compton's Encyclopedia and Fact Index. vol. 21 pg. 72-73 Chicago: Compton's Learning Company, 1996.

Jobanek, Michael. "Aircraft." The New Grolier Multimedia Encyclopedia. CD-ROM. Danbury, CT: Groiler Electronic Publishing, Inc., 1993.

McGinley, John A. "Satellite Meteorology." McGraw-Hill Encyclopedia of Science and Technology. New York: McGraw, 1992.

"Miles of Yarn are an Experiment in Orbit." NewsDay 25 Mar. 1997: B 27.