Orbital Communication satellites

The first experiments with the thermal electric engine were conducted in Russia in 1929 by its inventor, Valentin P. Glushko, who later became a world-famous authority in rocket propulsion. For more than forty years, the United States and Russia have devoted many resources to research and development of various kinds of EREs. First tested in space by the Russians in 1964, these engines have found some limited applications in modern space technology. For more than two decades Russian weather and communication satellites have regularly used electric rocket engines for orbital stabilization. The first spacecraft to employ ERE for main propulsion was the American asteroid exploration probe Deep Space 1, launched in 1998. The performance of... 

The effects of the radiation flux in space on polymer materials is now of considerable importance due to the increasing use of communications satellites. Geosynchronous orbit corresponds to the second Van Allen belt of radiation, which comprises mainly electrons and protons of high energy. 

The nickel-cadmium battery (Ni-Cd) is the most common battery used in communication satellites, in Earth orbiters, and in space probes. The chemical reactions are ... 

Ni-Hy batteries have been used in several Earth and planetary orbiting missions since the first commercial flight by INTELSAT V in 1983. Because of its demonstrated long life in GEO, this battery has been the workhorse for commercial communications satellites over the past 20 years. NASA first utilized Ni-H2 batteries in a LEO orbit when it launched the HST mission. These batteries, operating at a low 10 % DOD, have performed flawlessly since 1990. 

He ordered the flight computer to establish communications circuits with the small number of low-orbit observation satellites remaining. The image they provided built up quickly. 

It was as though the possessed shared a communal unease at inflicting the necessary suffering in full view of each other and the low-orbit sensor satellites. Breaking a person s spirit was as private as sex. 

On April 30,1999, at 12 30 EDT, a Titan IV B-32 booster equipped with a Centaur TC-14 upper stage was launched from Cape Canaveral, Florida. The mission was to place a Milstar-3 satellite into geosynchronous orbit. Milstar is a joint services satellite communications system that provides secure, jam-resistant, worldwide communications to meet wartime requirements. It was the most advanced military communications satellite system to that date. The first Milstar satellite was launched February 7,1994, and the second was launched November 5,1995. This mission was to be the third launch. 

High earth orbit (HEO) satellites typically have a perigee at 500 km above the surface of the Earth and an apogee as high as 50,000 km. The orbits are inclined at 63.4° in order to provide communications services to locations at high northern latitudes. 

These communications satellites are suspended around the Earth in different types of orbits, depending on the communication requirements. 

In 2011, there are more than 2,000 communications satellites orbiting the Earth. 

There are at least nineteen Orbiting Satellite Carrying Amateur Radio (OSCAR). These artificial communication satellites have been launched by individuals. 

Several forms of radio communications—satellites, cellular radio, and Wi-Fi— are commonly in use. Satellite communications can be used for voice, television, or data. When used for voice, satellites often result in an undesirable confusion because the time required to bounce a signal off a satellite (parked at an altitude of 22,300 miles, in geostationary orbit) is 0.125 second each way. Therefore, there is a built-in 0.25-second delay in any conversation. 

Vanes were used in the Orbital Communication (ORBCOMM) satellites, which were responsible for handling low data transfer, limiting the communications to non-time sensitive information. These satellites allowed two-way data communication, position determination, emergency alerting, and alphanumeric messaging (Decket, 1994). The design of the satellite was a simple disk with deployable solar panels and antenna (Stoltz et al., 1996). Vanes were used primarily for low thrust station keeping. 

Batteries are being developed for a variety of applications including Low Earth Orbit (LEO) Satellite Batteries, Military Communications Batteries, Aircraft and Heart-Assist Pump Batteries. Table 30.5 shows the requirement for the LEO Satellite battery shown in Fig. 30.19. Charge-discharge cycles for a single-cell battery at different points in the cycle life are shown in Fig. 30.20 at 40% depth of discharge. Five thousand cycles have been demonstrated in test cells at 40% DOD while over ten thousand cycles have been obtained at 25% DOD. Batteries are also being developed for the other applications described above. 

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