The world's first artificial (man made) satellite, the Sputnik 1, was launched by the Soviet Union in 1957. Since then, thousands of satellites have been launched into orbit around the Earth by more than 40 countries.

About a thousand satellites are currently operational, whereas thousands of unused satellites and satellite fragments orbit the Earth as space debris. Of the 1000 operating satellites, approximately 500 satellites are in low-Earth orbit, 50 are in medium-Earth orbit (at 20,000 km), the rest are in geostationary orbit (at 36,000 km).

Satellites are used for a large number of purposes including military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, and research satellites.

An amateur radio satellite is an artificial satellite built and used by amateur radio operators using amateur radio frequency allocations to communicate with other amateur radio operators.

Many amateur-satellites are called OSCAR, (Orbiting Satellite Carrying Amateur Radio). These satellites can be used for free by licensed amateur radio operators for voice and data communications.

Currently, over 5 fully operational amateur-satellites in orbit can be used to repeat radio signals from one radio operator to another radio operator, within the satellite footprint, using VHF, UHF and microwave frequencies. OSCAR satellites can also store and forward packets of digital information all around the world.

Low orbit satellites are the easiest to use requiring low power radio signals and small antennas.

A software program called Orbitron can be used to track satelittes, including the ISS, as they orbit the earth.

The BLUEsat Group is a collection of undergraduate students at University of NSW (UNSW), dedicated to creating easy-to-access space technology.

BLUEsat was started in 1997 as the Basic Low-Earth Orbit UNSW Experimental Satellite (BLUEsat) project, aimed at designing, building and launching the first undergraduate satellite in Australia.

The team aims to build a 10x10x20cm3 nano-satellite for space research, capable of performing various space-related experiments.

The current team consists of roughly thirty electrical, software and mechanical engineering and commerce students. BLUEsat members a chance to work hands-on to design, build and test the subsystems that allow satellites to survive, navigate and operate in one of the harshest environments found in engineering.

Many of the BLUEsat team are also amateur radio operators as the nano-satellites use amateur radio frequencies to communicate with the earth station.

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