Characterizing Ionospheric Effects on GNSS Reflectometry at Grazing Angles from Space
Coherent observations in GNSS reflectometry are prominent in regions with smooth reflecting surfaces and at grazing elevation angles. However, within these lower elevation ranges, GNSS signals traverse a more extensive atmospheric path, and increased ionospheric effects (e.g., delay biases) are expe...
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| Format: | Article |
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MDPI AG
2023-10-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/15/20/5049 |
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| author | Mario Moreno Maximilian Semmling Georges Stienne Mainul Hoque Jens Wickert |
| author_facet | Mario Moreno Maximilian Semmling Georges Stienne Mainul Hoque Jens Wickert |
| author_sort | Mario Moreno |
| collection | DOAJ |
| description | Coherent observations in GNSS reflectometry are prominent in regions with smooth reflecting surfaces and at grazing elevation angles. However, within these lower elevation ranges, GNSS signals traverse a more extensive atmospheric path, and increased ionospheric effects (e.g., delay biases) are expected. These biases can be mitigated by employing dual-frequency receivers or models tailored for single-frequency receivers. In preparation for the single-frequency GNSS-R ESA “PRETTY” mission, this study aims to characterize ionospheric effects under variable parameter conditions: elevation angles in the grazing range (5° to 30°), latitude-dependent regions (north, tropic, south) and diurnal changes (day and nighttime). The investigation employs simulations using orbit data from Spire Global Inc.’s Lemur-2 CubeSat constellation at the solar minimum (F10.7 index at 75) on March, 2021. Changes towards higher solar activity are accounted for with an additional scenario (F10.7 index at 180) on March, 2023. The electron density associated with each reflection event is determined using the Neustrelitz Electron Density Model (NEDM2020) and the NeQuick 2 model. The results from periods of low solar activity reveal fluctuations of up to approximately 300 TECUs in slant total electron content, 19 m in relative ionospheric delay for the GPS L1 frequency, 2 Hz in Doppler shifts, and variations in the peak electron density height ranging from 215 to 330 km. Sea surface height uncertainty associated with ionospheric model-based corrections in group delay altimetric inversion can reach a standard deviation at the meter level. |
| first_indexed | 2024-03-10T20:55:51Z |
| format | Article |
| id | doaj.art-9b7d1940747f4b9680875556dce2801f |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T20:55:51Z |
| publishDate | 2023-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-9b7d1940747f4b9680875556dce2801f2023-11-19T18:00:11ZengMDPI AGRemote Sensing2072-42922023-10-011520504910.3390/rs15205049Characterizing Ionospheric Effects on GNSS Reflectometry at Grazing Angles from SpaceMario Moreno0Maximilian Semmling1Georges Stienne2Mainul Hoque3Jens Wickert4Deutsches Zentrum für Luft-und Raumfahrt, Institut für Solar-Terrestrische Physik (DLR-SO), Kalkhorstweg 53, 17235 Neustrelitz, GermanyDeutsches Zentrum für Luft-und Raumfahrt, Institut für Solar-Terrestrische Physik (DLR-SO), Kalkhorstweg 53, 17235 Neustrelitz, GermanyLaboratoire d’Informatique, Signal et Image de la Côte d’Opale (LISIC), Université Littoral Côte d’Opale (ULCO), 50 rue Ferdinand Buisson, 62228 Calais, FranceDeutsches Zentrum für Luft-und Raumfahrt, Institut für Solar-Terrestrische Physik (DLR-SO), Kalkhorstweg 53, 17235 Neustrelitz, GermanyInstitute of Geodesy and Geoinformation Science, Department of GNSS Remote Sensing, Navigation and Positioning, Technische Universität Berlin (TUB), Str. des 17. Juni 135, 10623 Berlin, GermanyCoherent observations in GNSS reflectometry are prominent in regions with smooth reflecting surfaces and at grazing elevation angles. However, within these lower elevation ranges, GNSS signals traverse a more extensive atmospheric path, and increased ionospheric effects (e.g., delay biases) are expected. These biases can be mitigated by employing dual-frequency receivers or models tailored for single-frequency receivers. In preparation for the single-frequency GNSS-R ESA “PRETTY” mission, this study aims to characterize ionospheric effects under variable parameter conditions: elevation angles in the grazing range (5° to 30°), latitude-dependent regions (north, tropic, south) and diurnal changes (day and nighttime). The investigation employs simulations using orbit data from Spire Global Inc.’s Lemur-2 CubeSat constellation at the solar minimum (F10.7 index at 75) on March, 2021. Changes towards higher solar activity are accounted for with an additional scenario (F10.7 index at 180) on March, 2023. The electron density associated with each reflection event is determined using the Neustrelitz Electron Density Model (NEDM2020) and the NeQuick 2 model. The results from periods of low solar activity reveal fluctuations of up to approximately 300 TECUs in slant total electron content, 19 m in relative ionospheric delay for the GPS L1 frequency, 2 Hz in Doppler shifts, and variations in the peak electron density height ranging from 215 to 330 km. Sea surface height uncertainty associated with ionospheric model-based corrections in group delay altimetric inversion can reach a standard deviation at the meter level.https://www.mdpi.com/2072-4292/15/20/5049GNSS reflectometrygrazing anglesionospheric delayionospheric Doppler shiftNEDM2020 modelNeQuick model |
| spellingShingle | Mario Moreno Maximilian Semmling Georges Stienne Mainul Hoque Jens Wickert Characterizing Ionospheric Effects on GNSS Reflectometry at Grazing Angles from Space Remote Sensing GNSS reflectometry grazing angles ionospheric delay ionospheric Doppler shift NEDM2020 model NeQuick model |
| title | Characterizing Ionospheric Effects on GNSS Reflectometry at Grazing Angles from Space |
| title_full | Characterizing Ionospheric Effects on GNSS Reflectometry at Grazing Angles from Space |
| title_fullStr | Characterizing Ionospheric Effects on GNSS Reflectometry at Grazing Angles from Space |
| title_full_unstemmed | Characterizing Ionospheric Effects on GNSS Reflectometry at Grazing Angles from Space |
| title_short | Characterizing Ionospheric Effects on GNSS Reflectometry at Grazing Angles from Space |
| title_sort | characterizing ionospheric effects on gnss reflectometry at grazing angles from space |
| topic | GNSS reflectometry grazing angles ionospheric delay ionospheric Doppler shift NEDM2020 model NeQuick model |
| url | https://www.mdpi.com/2072-4292/15/20/5049 |
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