2. Introduction <ul><li>Initial proposal called for 77 satellites in the constellation </li></ul><ul><li>Iridium name was derived from the element Iridium having atomic no. 77 </li></ul><ul><li>Later studies indicated that only 66 satellites were adequate </li></ul> 4. <ul><li>Disadvantages of GEO: </li></ul><ul><li>The first and foremost limitation of GEO satellites is round trip latency </li></ul><ul><li>The second limitation of GEO schemes is cost. Because the orbit is 36,000 km above the equator, you need to use a big satellite with powerful transmitters, high performance receivers and large antennas </li></ul><ul><li>Increasing complexity the potential for hardware failure increases </li></ul><ul><li>poor performance in the polar regions </li></ul> 5. <ul><li>Low earth orbit (LEO) is used for iridium </li></ul><ul><li>Advantages of LEO: </li></ul><ul><li>LEO model satellites are placed into a circular inclined orbit several hundred kilometres above the earth's surface </li></ul><ul><li>This model are very low launch costs per satellite </li></ul><ul><li>Modest demands on antenna, receiver and transmitter performance </li></ul><ul><li>Very low propagation latency times . </li></ul> 6. <ul><li>Disadvantages of LEO </li></ul><ul><li>Global coverage will require many satellites </li></ul><ul><li>Cannot build a LEO constellation to cover one part of the world alone </li></ul><ul><li>The limited life of the satellites </li></ul> 8. <ul><li>Arrangement of iridium satellites </li></ul><ul><li>The 66 satellites are grouped in six orbitals planes,11 active satellites in each plane </li></ul><ul><li>The satellite has a circular orbit at an altitude of 783km from the earth surface </li></ul><ul><li>The distance between the corotating planes is 31.6 ° and counterrotating plane is 22° </li></ul> 11. <ul><li>History </li></ul><ul><li>Iridium communications service was launched on November 1 , 1998 and went into bankruptcy on August 13 , 1999 </li></ul><ul><li>The first Iridium call was made by then- Vice President of the United States Al Gore </li></ul><ul><li>Motorola provided the technology and major financial backing. </li></ul> 12. <ul><li>Downfall </li></ul><ul><li>Insufficient demand for the service, coupled with a massive initial capital cost </li></ul><ul><li>The increased coverage of terrestrial cellular networks (e.g. GSM ) and the rise of roaming agreements </li></ul><ul><li>The cost of service was also prohibitive for many users </li></ul><ul><li>The bulkiness and expense of the handheld devices </li></ul><ul><li>Mismanagement has also been cited as a major factor </li></ul> 13. <ul><li>Present status </li></ul><ul><li>Iridium Satellite LLC claims to have 203,000 subscribers as of June 30, 2007 </li></ul><ul><li>Revenue for the second quarter of 2007 was $66.7 million with EBITDA of $20.2 million </li></ul><ul><li>Used extensively by the U.S. Department of Defense </li></ul><ul><li>Total bandwidth is 28.8 kbit/s, making real time e-mail conversations finally possible. </li></ul><ul><li>Iridium operates at 2200 to 3800 baud </li></ul><ul><li>Iridium claims data rates up to 10 kilobits per seconds for their 'direct internet' service </li></ul> 21. THANK YOU