Ionospheric effects in GNS-reflectometry from space
Global navigation satellite systems-reflectometry (GNSS-R) is an emerging technique that uses navigation opportunistic signals as a multistatic radar. Most GNSS systems operate at L-band, which is affected by the ionosphere. At present, there is only a GNSS-R space-borne scatterometer on board the U...
| Autores: | , , , |
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| Formato: | artículo |
| Fecha de publicación: | 2016 |
| País: | España |
| Recursos: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/102729 |
| Acesso em linha: | https://hdl.handle.net/2117/102729 https://dx.doi.org/10.1109/JSTARS.2016.2612542 |
| Access Level: | acceso abierto |
| Palavra-chave: | Global Positioning System Altimetry Global navigation satellite systems reflectometry (GNSS-R) Ionosphere Scatterometry Scintillations Signal-to-noise ratio Sistema de posicionament global Àrees temàtiques de la UPC::Enginyeria de la telecomunicació::Radiocomunicació i exploració electromagnètica::Teledetecció |
| Resumo: | Global navigation satellite systems-reflectometry (GNSS-R) is an emerging technique that uses navigation opportunistic signals as a multistatic radar. Most GNSS systems operate at L-band, which is affected by the ionosphere. At present, there is only a GNSS-R space-borne scatterometer on board the UK TechDemoSat-1, but in late 2016, NASA will launch the CYGNSS constellation, and in 2019, ESA will carry out the GEROS experiment on board the International Space Station. In GNSS-R, reflected signals are typically processed in open loop using a short coherent integration time (~1 ms), followed by long incoherent averaging (~1000 times, ~1 s) to increase the signal-to-noise ratio. In this study, the global ionospheric scintillation model is first used to evaluate the total electron content and the scintillation index S4 . The ionospheric scintillation impact is then evaluated as a degradation of the signal-to-noise ratio, which can be used to assess the altimetry and scatterometry performance degradation in a generic GNSS-R mission. Since ionospheric scintillations are mostly produced by a layer of electron density irregularities at ~350 km height, underneath most LEO satellites, but closer to them than to the Earth’s surface, intensity scintillations occur especially in theGNSS transmitter-to-ground transect, therefore, the impact is very similar in conventional and interferometric GNSS-R. Using UK TechDemoSat-1 data, signal-to-noise ratio fluctuations are computed and geo-located, finding that they occur in the open ocean along ~±20° from the geomagnetic equator where S4 exhibits a maximum, and in low wind speed regions, where reflected signals contain a non-negligible coherent component. |
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