Archive for August, 2008

Satellite Communications Systems – SatCom

Tuesday, August 26th, 2008

Satellite communications systems (or satcoms as they are referred to in short) help in providing a communication link. This is carried out through artificial satellites which are positioned in different kinds of orbits in space. Satellite communications systems use one or more of these five kinds of orbits – geostationary orbits, low (non-polar and polar) Earth (LEO) orbits, medium earth orbits (MEO), highly elliptical orbits (HEO) and Molniya orbits.

Defense Satellite Communications System

Tuesday, August 19th, 2008

The first important landmark in defence satellite communications system and especially U.S. defense satellite communications system was when the U.S. army established radar contact with the moon. The navy started to experiment with the moon as a sort of reflector in 1954 and in 1959 it successfully established a communication link between Washington D.C. and Hawaii.

Mobile Satellite Communications and MSS

Tuesday, August 12th, 2008

Mobile satellite services (MSS), also known as mobile satellite communications, are commonly referred to as satellite communication systems that use portable terrestrial terminals rather than fixed satellite services (FSS). FSS use fixed terrestrial terminals where the location of the ground stations do not change frequently. Consumer satellite television (or cable television) uses FSS. MSS terminals may be placed in planes, ships and vehicles or may be carried by individuals. Satellite telephones use MSS. The three major kinds of MSS are as follows: land MSS (LMSS), aeronautical MSS (AMSS) and maritime MSS (MMSS).

 

Communications Satellites

Friday, August 1st, 2008

Our daily lives are affected regularly by communications satellites. Communications satellites provide an effective way to connect people and business from the most remote areas of the world to civilization. Many forms of business use communications satellites, like newspapers, gas stations, Internet service providers and even emergency management officials.

What makes communications satellites so useful is the frequency range at which these systems operate. Communications satellites operate near or in the microwave frequency range. This frequency range is optimum for carry large quantities of data. They are also best suited for line of sight (LOS) communications. LOS means the antennas have to see each other for the signal to be received. These frequencies are not reflected or absorbed by the Earth’s atmosphere like in the case of HF signals reflected by the ionosphere.