Approximately 15,000 man made objects have been placed in orbit since Sputnik I was launched in 1957. As of 30 October 1985 - 5,783 are still in orbit. Almost three-quarters of these objects are space debris, or "space junk." Of the 1,500 or so objects not considered junk, only about one-fifth are operable. Some of these objects may be satellites (in some form of orbit), or probes which may fly by or land on another celestial body. In general these devices can be grouped by function:
COMMUNICATION SATELLITES: The first true communications satellite, Telstar I funded by AT&T, was launched into low Earth orbit on 10 July 1962. Since that time communication "live via satellite" has been accepted as part of everyday life. Telephone, television, radio, and telex have all improved dramatically, becoming more efficient and less expensive through the use of the present day Intelsat, Westar, Telstar, SBS, and Galaxy satellites. The military uses these and dedicated military communications satellites for their command and control networks.
NAVIGATION SATELLITES: Today's navigation satellites allow a soldier on the battle field to pinpoint his location to within 2 meters, position a ballistic missile submarine (or its missiles in flight), guide a freighter through a reef, or allow a sailor to know his position day or night, rain or shine.
SCIENCE SATELLITES: Weather reporting, atmospheric research, cartography, agriculture, oceanography, forestry, mining, earthquake detection, solar and planetary probes - these are just a few of the scientific uses in which satellites are employed. The first weather observation from space was via a family of satellites known as TIROS (Television and Infrared Observation Satellite), launched in the period from 1960 to 1965. The weather satellite is now an established tool of the meteorologist in most countries of the world. The study of weather and the atmosphere prompted scientists to look more closely at other planetary uses (as those listed above) and inspired the creation of a whole family of Earth resource satellites. The U.S. made initial launches with the Landsat and Seasat series and the U.S.S.R. launched the Salyut and Cosmos series.
ENGINEERING ACTIVITIES: Engineering experiments are carried out using various special purpose satellites, probes, habitats, and Orbiter flights. The Surveyor probe tested soft landing techniques for the Apollo lunar landings, the Long Duration Exposure Facility (LDEF) allows material testing, and the SkyLab/SpaceLab flights conducted important materials research. Construction experiments were tested and performed in the first SkyLab and during several Orbiter flights. In the case of the Skylab program the construction performed was for actual use; if the techniques had failed the program would have failed.
SPACE PROBES: Orbital space exploration began in low Earth orbit with Sputnik and Explorer satellites in the late 1950's. During the 1960's spacecraft orbited and landed on the moon while others approached Venus and Mars. The 1970's saw additional planetary exploration of Mercury, Jupiter, and Saturn by the Mariner, Pioneer, Viking, and Voyager probes. The 1980's witnessed the fly-bys of comets, asteroids, and a visit of Voyager 2 to both Uranus and Neptune. The world's first engineering study of an unmanned "starship" (named Daedalus) was made between 1973 and 1977 by a technical group of the British Interplanetary Society. Just as the early satellites helped to prepare us for space walks and moon landings, so too these deep space probes will provide information to help prepare for the time when starships will no longer be science fiction, but a reality. MILITARY SATELLITES: From the beginnings of space flight military uses have been saught for space vehicles. The Military employs a great deal of the available capacity of the navigation, weather, and communication satellites. In addition, distinctly military applications are pursued such as reconnaissance and targeting. The U.S. Discoverer, Big Bird, Vela, and Key Hole satellites are known to be related to these activities, as are many Russian Vostok and Cosmos flights. The names of any current military vehicles are closely guarded secrets as demonstrated by the cloak of secrecy around recent Space Shuttle flights.
ASATs (Anti-Satellite systems), designed specifically to destroy satellites or to significantly impair their performance, came into being in the middle to late 1960's. These have been tested and/or used by both the U.S. and U.S.S.R. Since much of the world has come to depend upon satellites for both civilian and military applications, a large debate has centered on the development of these types of defense systems, the most controversial being President Reagan's Strategic Defensive Initiative (commonly called "Star Wars"). Most ASAT weapons are of the "kamikaze" variety; that is, they collide with the target in order to destroy it. Current research is being conducted by both the U.S. and U.S.S.R. on laser and particle beam weapon systems. Lasers inflict damage by heating a target's sensors, antennas or power systems. Particle beams destroy an object by focusing high amounts of energy and radiation on the target. This energy tends to heat the target, like a laser, and the radiation ruins the electronics. America's Space Shuttle has considerable military significance. It is thought that it may be used for external inspection and possible internal examination of the components of most low orbiting satellites. This is understandably considered "unacceptable espionage" by most other countries. The next generation of U.S. reconnaissance satellites is being designed for deployment and recovery by the Shuttle System. To outfit any of the Shuttles with real weapons is unlikely as the Orbiters are very fragile and few in number.
