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