A less technical definition for VSAT is as follows. “VSAT, short for Very Small Aperture Terminal is an earthbound station used in satellite communications of data, voice and video signals, excluding broadcast television. A VSAT consists of two parts, a transceiver that is placed outdoors in direct line of sight to the satellite and a device that is placed indoors to interface the transceiver with the end user's communications device, such as a PC. The transceiver receives or sends a signal to a satellite transponder in the sky. The satellite sends and receives signals from a ground station computer that acts as a hub for the system. Each end user is interconnected with the hub station via the satellite, forming a star topology. The hub controls the entire operation of the network. For one end user to communicate with another, each transmission has to first go to the hub station that then retransmits it via the satellite to the other end user's VSAT. VSAT can handle up to 56 Kbps.” The VSAT industry started around 1985.
Three different types of satellites used in telecommunications are low earth orbit (LEO) ranging from 400 to 1,000 miles above the earth, medium or middle earth orbit (MEO) ranging from 1,000 to 22,300 miles above the earth and geosynchronous or geostationary earth orbit (GEO) orbiting at 22,300 miles above the earth.
LEOs are used primarily for data communication such as e-mail, paging and videoconferencing. Because LEOs are not fixed in space in relation to the rotation of the earth, they move at very high speeds and therefore data being transmitted via LEOs must be handed off from one satellite to the next as the satellites move in and out of range of the earth-bound transmitting stations that are sending the signals into space. LEO telecommunication systems are a promising technology because they provide the ability for underdeveloped territories to acquire satellite telephone service in areas where it is either too costly or not geographically possible to lay land lines.
MEOs are mostly used for geographical positioning systems (GPS) and are not stationary in relation to the rotation of the earth. GEOs are tied to the earth's rotation and are therefore in a fixed position in space in relation to the earth's surface. The satellite goes around once in its orbit for every rotation of the earth. The advantage of a GEO system is that the transmission station on earth needs to point to only one place in space in order to transmit the signal to the GEO satellite. GEO systems are used for transmissions of high-speed data, television signals and other wideband applications.
Source for all above: http://isp.webopedia.com/TERM/V/VSAT.html
www.comsys.co.uk/vsatnets.htm contains various diagrams of VSAT systems in various configurations. The major configurations are star, mesh, and hybrid. Comsys maintains a big database of both confidential and public information regarding VSATs.
www.comsys.co.uk/vsatstat.htm is a site that contains many statistics regarding VSATs, including the number of different systems in use, the major vendors with Hughes Network Systems maintaining over half the market and market growth.
http://www.comsys.co.uk/vsatuser.htm lists a number of both large and smaller customers around the world and the number of sites in service. ©comsys
www.comsys.co.uk/acronyms.htm contains a huge listing of acronyms pertaining to the VSAT industry and mostly all different types of communications systems in use.
www.gvf.org/solutions/studies/index.cfm is a location for the Global VSAT forum. At this particular site, you can read about a number of case studies demonstrating how VSATs are being put to use.
www.qpcomm.com/vsat_info.html explains again what a VSAT system is and lists
different ways in which a VSAT system can be used. It also identifies what
types of companies use these systems.
http://server5550.itd.nrl.navy.mil/projects/HDRSATCOM/ contains some good pictures of different VSAT satellites in use. Take a look at the photo galleries. It also lists a number of articles and publications on the subject (very technical, at least for me).
www.nwfusion.com/news/2002/0204specialfocus.html contains a good article on VSATs and some new uses for this product. It is also a good site for information on network systems. I found a bunch of white papers here.
http://www.spacedaily.com/news/vsat-02f.html contains an article relating to installing VSATs in the Upper Amazon. It also is the site for various articles regarding space (Spacewar, Terradaily, Space Travel). A very interesting and informative site. Recommended.