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Space Craft ( Satellites)

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Satellites, or SpaceCraft, can be divided into five primary types: Research, Communications, Weather, Navigational, and Military Applications.

Let’s take a brief look at their functions and how their services directly affect you in your daily life.

Research Satellites:

Research SpaceCraft measure fundamental properties of outer space. Some of these include magnetic fields, the flux of cosmic rays and micrometeorites, and properties of celestial objects that are difficult or nearly impossible to observe from the earth. Early research satellites included a series of orbiting observatories designed to study radiation from the sun, light and radio emissions from distant stars, and the earth’s atmosphere. Notable research satellites include the Hubble Space Telescope,  the Compton Gamma-Ray Observatory, the Chandra X-ray Observatory, the Infrared Space Observatory, and the Solar and Heliospheric Observatory. Major contributors to scientific research were the experiments conducted by the astronauts and cosmonauts aboard the space stations launched by the United States (Skylab) and the Soviet Union (Salyut and Mir). These stations researchers worked for months at a time on scientific or technical projects. The International Space Station, currently under construction, will continue this work.

Space Craft ( Satellites)

Communications Satellites

These types of SpaceCraft provide a worldwide linkup of radio, telephone, and television. The first communications satellite was Echo 1; launched in 1960. Echo 1 was a large metallized balloon that reflected radio signals striking it. This passive mode of operation soon gave way to the active or repeater mode, in which complex electronic equipment aboard the SpaceCraft receives a signal from the earth, amplifies it, and transmits it to another point on the earth. Relay 1 and Telstar 1, both launched in 1962, were the very first active communications satellites. Telstar 1 relayed the first live TV broadcast across the Atlantic Ocean. However, SpaceCraft in the Relay and Telstar program were not in geosynchronous orbits, which is the industry secret to continuous communications networks. Syncom 3, launched in 1964, was the first stationary earth satellite. It was used to telecast the 1964 Olympic Games in Tokyo to the United States, the first television program to cross the Pacific Ocean. In principle, three geosynchronous satellites located symmetrically in the plane of the earth’s equator can provide complete coverage of the earth’s surface.  In practice, many more are used in order to increase the system’s message-handling capacity. The first commercial based geosynchronous satellite, Intelsat 1, was launched by COMSAT in 1965. A network of 19 Intelsat satellites in geosynchronous orbit now provides instantaneous communications throughout the world. In addition, numerous communications satellites have been orbited by commercial organizations and individual nations for a variety of telecommunications tasks.

Weather Satellites:

Meteorological satellites, or weather satellites, provide continuous, up-to-date information about large-scale atmospheric conditions to include cloud cover and temperature profiles. Tiros 1, the first such SpaceCraft, was launched in 1960; it transmitted infrared TV pictures of the earth’s cloud cover and could also detect the development of hurricanes, as well as chart their destructive paths. The Tiros series was followed by the Nimbus series, which carried 6 cameras for more detailed scanning, and also the Itos series, which was able to transmit night photographs. Other weather satellites include the Geostationary Operational Environmental Satellites (GOES). GOES sends weather data and pictures that cover a section of the United States; China, Japan, India, and the European Space Agency have orbited similar SpaceCraft. Todays weather satellites can transmit visible or infrared photos, focus on a narrow or wide area, and maneuver in outerspace to obtain maximum coverage.

Navigational Satellites:

Navigation satellites primarily developed to satisfy the need for a navigation system that nuclear submarines could use to update their inertial navigation system. Pretty cool. With this in mind the U.S. Navy established the Transit program in 1958; the system was declared operational in 1962 after the launch of Transit 5A. Transit satellites provided a constant up/downlink signal by which aircraft and ships could determine their positions with great pin point accuracy. In 1967 civilians were able to enjoy the benefits of Transit technology. However, the Transit system had a problematic limitation. The combination of the small number of Transit SpaceCraft and their polar orbits meant there were some areas of the globe that were not continuously covered. As a result, the users had to wait until a satellite was properly positioned before they could obtain navigational information. The limitations of the Transit system sparked the next advance in satellite navigation: the availability of 24-hour worldwide positioning information or GPS System.  The Navigation Satellite for Time and Ranging/Global Positioning Satellite System (Navstar/GPS) consists of 24 satellites approximately 11,000 miles above the surface of the earth in six different orbital tracks. The GPS has distinct advantages over the Transit system: It provides greater accuracy in a shorter time; GPS users can obtain information 24 hours a day; and users are always in view of at least five satellites. This allows for highly accurate location information (a direct readout of position accurate to within a few yards) including altitude. In addition, because of technological improvements, the GPS system has user equipment that is smaller and less complex. The former Soviet Union established a Navstar equivalent system known as the Global Orbiting Navigation Satellite System (GLONASS). GLONASS uses the same number of satellites and orbits similar to those of Navstar. Many of todays handheld GPS receivers can also use the GLONASS data if equipped with the proper processing software.

Military Satellites:

Military Satellites utilize infrared sensors to track missile launches; electronic sensors that eavesdrop on classified conversations; and optical and other sensors that aid military in military surveillance.  These types of reconnaissance SpaceCraft have also proved to have civilian benefits, such as commercially available satellite photographs showing surface features and structures in great detail, and fire sensing in remote forested areas. The United States has launched several Landsat Remote-Imaging SpaceCraft to survey the earth’s resources by means of special television cameras and radiometric scanners. Russia and other nations have also launched such satellites; the French SPOT SpaceCraft provides higher-resolution photographs of the earth.