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Topic: Satellite constellation

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	Satellite Phones \| Satellite Cell Phones
		The reason that satellite phones are still working in situations where other phones don’t is that satellite phones rely on satellites in space for their functioning.
		One important thing to keep in mind with satellite phones is that the phone or the phone’s antenna must be located in the open to allow it to have an unobstructed view of the sky.
		Satellite phones require a clear line-of-sight view of the satellite to be able to send and receive signals from the satellite.
	www.satellitephonesite.com (585 words)

	Satellite constellation - Wikipedia, the free encyclopedia
		Such a constellation can be considered to be a number of satellites with coordinated ground coverage, operating together under shared control, synchronised so that they overlap well in coverage and complement rather than interfere with other satellites' coverage.
		Low Earth orbiting satellites (LEOs) are often deployed in satellite constellations, because the coverage area provided by a single LEO satellite covers a small area, and the satellite travels at a high angular velocity to maintain its orbit.
		Satellite constellation coverage and geometry – determining the minimum number of satellites needed to provide a service, and their orbits – is a field in itself.
	en.wikipedia.org /wiki/Satellite_constellation (290 words)

	Wave based satellite constellation (US5911389)
		The satellites (1-27) orbit a celestial body (110) along a plurality of orbits (120-128), which are located at a substantially common altitude and have a substantially common inclination.
		The satellites (1-27) may be positioned based on a Walker code T/P/F, where T is the total number of satellites (1-27) in a full Walker rosette corresponding to the Walker code, P is the number of distinct orbits (120-128), and F/T is the phase shift between adjacent orbits (120-128).
		A constellation comprising a plurality of man-made satellites, wherein:
	www.delphion.com /details?pn=US05911389__ (553 words)

	Constellation Models
		The fourth plot (middle right) shows that the 24-satellite constellation is less sensitive than the 21-satellite constellation to a single satellite failure.
		The sixth plot (bottom right) shows that the 27-satellite constellation is less sensitive than the 24-satellite constellation to a dual satellite failure.
		Hence, the ability of the constellation to withstand sudden satellite failures improves as the size of the nonuniform constellations increases.
	www.aero.org /publications/crosslink/summer2002/03_sidebar1.html (192 words)

	Fixed ground track satellite constellation and user terminal (US6556808)
		A satellite communication system includes a constellation of non-geostationary orbiting satellites following a fixed ground track on the earth, and ground terminals having substantially continuous visibility to at least one of the satellites in a single ground track.
		Non-geostationary orbit satellite constellation for continuous coverage of northern latitudes above 25° and its extension to global coverage tailored to the distribution of populated land masses on earth
		Satellite communication method using satellites on substantially circular orbit, inclined to the equatorial plane with period matching the earth period
	www.delphion.com /details?pn=US06556808__ (526 words)

	Communications satellite - Wikipedia, the free encyclopedia
		A satellite in a geostationary orbit appears to be in a fixed position to an earth-based observer.
		Low earth orbiting satellites are less expensive to position in space than geostationary satellites and, because of their closer proximity to the ground, require lower signal strength (Recall that signal strength falls off as the square of the distance from the source, so the effect is dramatic).
		The first satellite of Molniya series was launched on April 23, 1965 and was used for experimental transmission of TV signal from Moscow uplink station to downlink stations, located in Siberia and Russian Far East, in Norilsk, Khabarovsk, Magadan and Vladivostok.
	en.wikipedia.org /wiki/Communications_satellite (2546 words)

	Constellation (ECCO) - Satellite Intelligence
		The 12 satellites to be manufactured by Orbital represent the first of two phases of satellites authorized for CCI in July 1997 by the U.S. Federal Communications Commission.
		The satellites will be capable of providing telephony services to more than one million subscribers located within a band spanning the Earth between 23 degrees north latitude and 23 degrees south latitude.
		Scheduled to be constructed by early 2001 and operational by the third quarter, the ECCO Equatorial satellite constellation will provide voice and data services to subscribers via hand-held, vehicle-mounted or stationary telephones.
	www.comlinks.com /satcom/constel.htm (539 words)

	Iridium Flares (Site not responding. Last check: )
		Knowing the satellite's position, its orientation, the relative Sun angle to the satellite, the reflective properties of a mirror and the observers position on Earth, a program can be developed to calculate the projected specular reflection of the Sun from the Main Mission Antennae to an observer.
		Iridium 27 (inoperable) was the fourth satellite to reenter on Feb 1, 2002.
		Two Iridium satellites are tentatively planned to be launched aboard a Eurockot on a Rokot KM vehicle (a modified RS-18 ICBM) from Plesetsk, Russia in June 2002.
	www.satobs.org /iridium.html (1843 words)

	LEO Communications Satellites: The Iridium Constellation
		Because the satellites all reside in near polar orbits, the cost of launch was huge due to the large amounts of fuel needed to obtain such and orbit.
		It seemed that the satellites were doomed to be de-orbited before their time because of a near failure in finding a possible buyer for the system.
		Data is transmitted between the satellites and from the ground stations to the satellites on Ka-band frequencies while data is transmitted from the satellites to the handheld devices using L-band frequencies.
	ccar.colorado.edu /asen5050/projects/projects_2000/redlin (1678 words)

	Satellite Constellation Survey, July 1998
		Some of the proposed L-band LEO constellations are of particular concern to RA due to the fact that their emissions are not spatially grouped like the GEO satellites, and their lower orbit allows their transmissions to reach RA receivers at higher instantaneous power flux density levels.
		The Celestri System is a proposed communications network formed from an integrated family of advanced communcations satellites, ground stations and terrestrial equipment that is designed to provide a broad range of multimedia, video and data services to communications carriers, multinational corporations, small- and medium-sized business, as well as telecommuters and other customers throughout the world.
		The third SBS satellite became the first to be placed in space by NASA's Space Shuttle on November 11, 1982, during its premier commercial flight.
	www.vla.nrao.edu /astro/rfi/surveys/satellite (2468 words)

	Constellation Management
		While uniform constellations are effective at maximizing the number of satellites in view to users, they are not always effective at providing the best geometry to minimize position-estimate errors.
		Spare satellites were not launched until the primary satellites had aged enough to present a strong probability of failure.
		For example, in a six-plane constellation, it is better to fly a large constellation without spares rather than a small constellation with spares because failures are unpredictable and the number of spares required to cover all orbit planes is costly.
	www.aero.org /publications/crosslink/spring2005/04.html (3452 words)

	Satellite Constellation History
		Satellites first began orbiting in the late 1950’s when Russia launched Sputnik 1, circular in shape and only 23 inches in diameter.
		Since 1964 most communications satellites are geo-stationary, meaning that they keep and orbit over the same spot above the Earth’s equator at an altitude of 22,200 miles.
		Although relatively newly established, we each have each learned from the rise of the satellite industry in the early 90's as well as felt the harsh fall of the telecommunications industry since 2000.
	www.constellationnetcorp.com /history.htm (205 words)

	Globalstar Satellite Phone News - Explorer Satellite
		Eight additional ground spare satellites are scheduled to be launched in 2007 and will be utilized to replenish the constellation over time as necessary until the second-generation Globalstar satellites are available for service, which the Company currently projects will be in late 2009.
		Although our first generation constellation does not have substantial remaining net book value due to its age and the effects of our restructuring a few years ago, we are still required to look at its valuation at least annually.
		We have recently completed a realignment of the satellites to maintain the best possible service level and to prepare for the launch of our eight additional satellites, which are scheduled to be launched within months.
	www.explorersatellite.com /Globalstar/globalstar_files_8k.htm (2073 words)

	ESA - Navigation - The future - Galileo - Galileo system
		The altitude of the satellites has been chosen to avoid gravitational resonances so that, after initial orbit optimisation, station-keeping manoeuvres will not be needed during the lifetime of a satellite.
		The position constraints for individual satellites are set by the need to maintain a uniform constellation, for which it is specified that each satellite should be within +/- 2° of its nominal position relative to the adjacent satellites in the same orbit plane and should be within 2° of the orbit plane.
		The spare satellite in each orbit plane ensures that in case of failure the constellation can be repaired quickly by moving the spare to replace the failed satellite.
	www.esa.int /esaNA/SEM5K8W797E_galileo_2.html (1034 words)

	Satellites Constellation
		The satellites' constellation domain consists of a group of low-Earth orbiting satellites that have cross-link communication capability, each carrying nearly the same suite of instruments.
		In a general way, satellites whose missions involve observations and/or communication with the ground must take into account access windows, which are intervals of opportunity defined by when the satellite is in view of the target on the ground.
		Each LEO satellite has a revolution period round the Earth of about 99 minutes and they can receive or emit data from or to a tracking station only when it is inside of one of the red circles.
	homepages.inf.ed.ac.uk /s0125683/satellites/index.html (2907 words)

	System for providing optimal satellite communication via a MEO/LEO satellite constellation - Patent 6684056
		Presently known satellite communication networks use either low-earth orbit (LEO), medium-earth orbit (MEO) or geosynchronous (GEO) satellite constellations to transfer voice, data or video signals from a source to a destination.
		The third option for deciding which constellation to route the communication session through is implemented by having the satellites themselves perform this decision function.
		A particular feature of the present invention is the decision as to which satellite constellation to use; derived from a decision algorithm.
	www.freepatentsonline.com /6684056.html (2701 words)

	spacetoday.net: Globalstar plans revised satellite constellation
		Satellite communications provider Globalstar announced this week will reconfigure its existing satellites in orbit into a new constellation in response to several satellite failures.
		The new constellation uses five satellites in each of eight orbital planes, instead of six satellites per plane in the original constellation.
		The company does have eight spare satellites on the ground it acquired earlier this year in a settlement with Loral, but Globalstar has no plans to launch the satellites in the foreseeable future.
	www.spacetoday.net /Summary/1857 (352 words)

	Crystal Communications - Satellite Telephones and Communications
		Iridium Satellite LLC’s management team is comprised of seasoned executives from the satellite and aviation industries, several of whom were involved in the development of the original Iridium technology and the satellite constellation’s deployment.
		The satellites are in a near-polar orbit at an altitude of 485 miles (780 km).
		Each satellite is cross-linked to four other satellites; two satellites in the same orbital plane and two in an adjacent plane.
	www.crystalcommunications.net /iridium/about_iridium.htm (673 words)

	SaVi satellite constellation visualization - user manual
		Many of these constellations are described in a tutorial introducing satellite constellations given to the International Space University.
		Satellite coverage (which defaults to yellow/red) is intended to give an idea of the number of satellites visible from a point, or available diversity.
		Satellites selected in the main window will be shown in the coverage panel as purple, rather than green, as will their groundtracks.
	savi.cvs.sourceforge.net /checkout/savi/savi-dev/manual/index.html (2069 words)

	SaVi: Satellite constellation Visualization software
		I've created and run simulations of satellite constellations using SaVi, the Satellite Visualization software that was originally written at the Geometry Center.
		The SaVi 1.3 releases include the constellation simulation scripts I've written, as well as enhanced resizeable coverage and fisheye displays.
		Satellite constellations are introduced in a tutorial using SaVi.
	www.ee.surrey.ac.uk /Personal/L.Wood/software/SaVi (207 words)

	Lloyd's satellite constellations - Introduction
		You won't gain a complete picture of what any proposed constellation is capable of, or really in-depth technical details, but you will gain an idea of what the developments in this area are, where the industry and technology is headed - and you will pick up background knowledge of satellites along the way.
		This is not intended to be a guide to individual satellites in geostationary orbit.
		some serious and dull academic material on satellite constellations.
	www.ee.surrey.ac.uk /Personal/L.Wood/constellations (342 words)

	SC Modeler - Satellite Constellation Design and Analysis Software
		Constellation Design modules implement highly optimized search algorithms capable of producing an efficient constellation design for global or zonal continuous coverage, in a matter of seconds.
		The Constellation Design/Circular Orbits module allows you to consider symmetric constellations (known as "Walker delta" constellations) and "streets of coverage" constellations with polar or inclined orbits.
		Constellation Design modules can help you to minimize the number of satellites required by the constellation if orbital inclination and altitude are specified (see examples).
	www.avmdynamics.com /software1.htm (1596 words)

	NASA - NASA Technology Spawns Weather, Climate Satellite Constellation
		A globe-spanning constellation of six weather and climate research satellites based on a novel application of NASA-developed technology is set to launch from Vandenberg Air Force Base, Calif., Friday, April 14, at 5:10 p.m.
		The Constellation Observing System for Meteorology, Ionosphere and Climate network, known as Cosmic in the United States and Formosat-3 in Taiwan, is expected to improve weather forecasts, monitor climate change and enhance space weather research.
		The satellites are also expected to improve analysis and forecasting of space weather -- the geomagnetic storms that can interrupt sensitive satellite and communications systems and affect power grids.
	www.nasa.gov /centers/jpl/news/cosmic-20060413.html (646 words)

	GPS_sat_constellation
		The Block I satellites are not identical to the Block II/IIA/IIR satellites (HOFMANN-WELLENHOF et al., 1998), however the most important difference is that they have been launched into orbits of different inclination: 63 degrees for the Block I satellites, 55 degrees for the Block II/IIA/IIR satellites.
		The satellite availability is expressed in the form of satellite visibility graphs, and "skyplots" showing the satellite tracks on a polar projection relative to a site's zenith.
		Note, however, that although a satellite may be "unhealthy" for navigation purposes, it may still be suitable for phase tracking and post-processing in the GPS survey mode.
	www.gmat.unsw.edu.au /snap/gps/gps_survey/chap2/222sats.htm (1124 words)

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