72 S Kumar Another method to classify existing satellite systems is by their functions. Voice communications. These universal satellites provide telecommunication services consisting of not only voice, but also data, fax, and paging. The providers nclude iridium. GlobalStar and IcO Satellite radio. There are two major satellite radios providing music on demand aiming to niche markets i.e. coast-to-coast drivers who like to stick to their favourite channels wherever they go. Thus, XM Radio allied with eneral Motors(GM)to install receivers in its cars, while Sirius Radio partnered with Ford Motor and BMW to put Sirius radios in their cars. In the portable electronics segment, Sony and Sharp are also interested in embracing XM Satellite Radio in their Walkmans [6 Broadband networking. In 2005, Teledesic will offer broadband data services through the current 288(rather than 840 as originally designed) satellites orbiting about 500 miles away from earth. The in-operational rival, SkyBrigde-a satellite-based broadband access system- has started offering internet access and videoconference services since 2000 Data messaging Orbcomm provides narrow band two-way digital messaging, data communications and global positioning services Geodesy Navigation Global Positioning System( GPS)is a space-based triangulation system utilising satellites and terrestrial computers to measure positions anywhere on earth. It was first and foremost developed by the US Department of Defense for navigation purposes. Now, the system is more utilised in the public sector for positioning persons or objects that carry transmitters. Gona a GPs in Soviet version, is mainly utilised in military and aviation units in the former Ussr Remote sensing. The remote sensing market has traditionally been the domain of single specialist dedicated satellites for sensing global climates and natural events Comprising of 12 satellites, FUEGO is devoted to wild fire detection and named Forest Fire Earth Watch. RapidEye, a satellite-based geo-information service, provides global climate information, i.e. hail, storm, frost, drought, etc, as well as agricultural produce prediction services. Cosmo-Skymed provides remote sensing services, such as disaster monitoring. urban monitoring law infringement and environmental and agricultural monitoring, only to customers living around the Mediterranean sea able 5 compares and contrasts some important satellite communication systems72 S. Kumar Another method to classify existing satellite systems is by their functions. • Voice communications. These universal satellites provide telecommunication services consisting of not only voice, but also data, fax, and paging. The providers include Iridium, GlobalStar, and ICO. • Satellite radio. There are two major satellite radios providing music on demand aiming to niche markets, i.e. coast-to-coast drivers who like to stick to their favourite channels wherever they go. Thus, XM Radio allied with General Motors (GM) to install receivers in its cars, while Sirius Radio partnered with Ford Motor and BMW to put Sirius radios in their cars. In the portable electronics segment, Sony and Sharp are also interested in embracing XM Satellite Radio in their Walkmans [6]. • Broadband networking. In 2005, Teledesic will offer broadband data services through the current 288 (rather than 840 as originally designed) satellites orbiting about 500 miles away from earth. The in-operational rival, SkyBrigde – a satellite-based broadband access system – has started offering internet access and videoconference services since 2000. • Data messaging. Orbcomm provides narrow band two-way digital messaging, data communications and global positioning services. http://www.orbcomm.com/about.htm • Geodesy & Navigation. Global Positioning System (GPS) is a space-based triangulation system utilising satellites and terrestrial computers to measure positions anywhere on earth. It was first and foremost developed by the US Department of Defense for navigation purposes. Now, the system is more utilised in the public sector for positioning persons or objects that carry transmitters. Glonass, a GPS in Soviet version, is mainly utilised in military and aviation units in the former USSR. • Remote sensing. The remote sensing market has traditionally been the domain of single specialist dedicated satellites for sensing global climates and natural events. Comprising of 12 satellites, FUEGO is devoted to wild fire detection and named ‘Forest Fire Earth Watch’. RapidEye, a satellite-based geo-information service, provides global climate information, i.e. hail, storm, frost, drought, etc., as well as agricultural produce prediction services. Cosmo-Skymed provides remote sensing services, such as disaster monitoring, urban monitoring, law infringement and environmental and agricultural monitoring, only to customers living around the Mediterranean Sea. Table 5 compares and contrasts some important satellite communication systems