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Where is GIOVE-A exactly? Using microwaves and laser ranging for precise orbit determination / Erik Schönemann in GPS world, vol 20 n° 7 (July 2009)

Public [article]  inGPS world > vol 20 n° 7 (July 2009) . - pp 42 - 50 Titre : Where is GIOVE-A exactly? Using microwaves and laser ranging for precise orbit determination Type de document : Article/Communication Auteurs : Erik Schönemann, Auteur ; Tim A. Springer, Auteur ; R. Langley, Auteur ; et al., Auteur Année de publication : 2009 Article en page(s) : pp 42 - 50 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] constellation Galileo [Termes IGN] GIOVE (satellite) [Termes IGN] orbitographie [Termes IGN] télémétrie laser sur satellite Résumé : (Auteur) We use them for listening to music, for routine surgeries, for making a point in a presentation, and even for hanging pictures straight. Of course, I'm talking about lasers. Invented in 1960, the laser (an acronym for light amplification by the stimulated emission of radiation) has become ubiquitous in modem society. Every CD and DVD player has one. Many printers use them. But lasers are also used in a wide range of industrial and scientific applications including determining the orbits of satellites through satellite laser ranging (SLR). In the SLR technique, pulses of laser light from a ground reference station are directed at satellites equipped with an array of coner-cube retroreflectors, which direct the pulses back towards a collocated receiving, telescope. By accurately measuring the two-way travel times of the pulses and knowing location of the station and other operating parameters, the positions of the satellites can be determined. A network of SLR reference stations around the globe is used to monitor the orbits of satellites over time and their variations have been used by scientists to improve our knowledge of the Earth's gravity field ; to study the long term dynamics of the solid Earth, oceans, and atmosphere; and even to verify predictions of the General Theory of Relativity. The first SLR measurements were obtained from the Beacon Explorer-B satellite which launched in october 1964. Since then, dozens of satellite equipped with corner-cube retroreflectors have been launched including a number of radio-navigation satellites. Every GLONASS satellite is equipped with retroreflectors and two GPS satellite have been equipped - SVN35/PRN05 and SVN36/PNR06. The COMPASS-M1 satellite in medium earth orbit carries retroreflectors, as do both GIOVE-A and -B, the Galileo test satellites. Precise orbit determination of radio-navigation satellites using SLR has the advantage of being unaffected by any onboard satellite electronics and associated signal biases. Radiometric observations of a satellite's microwave signals, on the other hand, are influenced by the satellite's clock, for example, and its effect must be estimated to obtain precise (and accurate) satellite orbits for navigation and positioning. Therefore, a comparison of SLR-and microwave derived orbits can be very useful for studying the performance of the data measurement and orbit-determination processes of both techniques. In this month's column, we take a look at some work being carried out to precisely determine the orbit of the GIOVE-A test satellite using SLR and microwave observations. This preliminary investigation will benefit the procedures to be implemented for the future Galileo constellation. Copyright Questex Media Group Numéro de notice : A2009-282 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29912 [article]

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