S6

iag-comm4-2022
SC43: Atmospheric Remote Sensing: GNSS-Reflectometry
Convener: Milad Asgarimehr | Co-convener: Michael Schmidt
Orals
| Tue, 06 Sep, 13:40–14:30 (CEST)|Wissenschaftsetage Potsdam

Orals: Tue, 06 Sep | Wissenschaftsetage Potsdam

13:40–14:10
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iag-comm4-2022-54
|
invited
Milad Asgarimehr, Tianqi Xiao, Minfeng Song, Caroline Arnold, Mina Rahmani, and Jens Wickert

The exploitation of Global Navigation Satellite System (GNSS) signals after reflection from the Earth’s surface, called GNSS Reflectometry (GNSS-R), is a novel technique for the remote sensing of a variety of geophysical parameters. The demonstration mission, UK TechDemoSat-1 (TDS-1) launched in 2014, carried a spaceborne GNSS-R receiver showing the capabilities of the technique to monitor ocean, land, and the cryosphere. The GNSS-R small satellites need to carry only the low-cost, low-mass, and low-power receivers, which leads to the cost-effective development of multi-satellite constellations. This along with the capability of GNSS-R receivers to track multiple reflected GNSS signals at the same time offer an unprecedented sampling rate and potentially knowledge of the Earth system and the climate beyond those derived from conventional sensors. NASA Cyclone GNSS (CYGNSS), launched in late 2016, is one of the operational constellations with eight microsatellites tracking up to four GPS reflected signals. More missions are in orbit, e.g., constellations launched by Spire (commercial) and Chinese FENGYUN-3E mission. GNSS-R satellites with different objectives will be launched, e.g., ESA Passive REflecTomeTry and dosimetry (PRETTY) CubeSat and ESA HydroGNSS, whose data will be available in 2022 and 2024 respectively.

In this presentation, an overview of selected recent GNSS-R studies at the German Research Centre for Geosciences GFZ will be given. After a brief history of the technique, the principles of the measurements and important GNSS-R missions will be introduced. The ocean surface and wind speed monitoring, from the first products of TDS-1 to recent deep learning-based CYGNSS wind speeds with an RMSE and 1.4 m/s, will be presented. Rain splash alters ocean surface, based on which, rain over calm ocean can be detected. Experiments for precipitation monitoring are carried out. The capabilities of GNSS-R for inland water body detection, land surface, and aridity monitoring in forests is studied.

How to cite: Asgarimehr, M., Xiao, T., Song, M., Arnold, C., Rahmani, M., and Wickert, J.: GNSS Reflectometry: Novel Remote Sensing of the Earth, 2nd Symposium of IAG Commission 4 “Positioning and Applications”, Potsdam, Germany, 5–8 Sep 2022, iag-comm4-2022-54, https://doi.org/10.5194/iag-comm4-2022-54, 2022.

14:10–14:30
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iag-comm4-2022-24
Ole Roggenbuck, Axel Rülke, Elke Kühmstedt, and Christian Plötz

Multi-year sea level estimation at O´Higgins station using GNSS interferometric reflectometry

Ole Roggenbuck, Axel Rülke, Elke Kühmstedt, Christian Plötz

Bundesamt für Kartographie und Geodäsie, Richard-Strauss-Allee 11, 60598 Frankfurt am Main

Precise knowledge of the local ocean tides is important to correct space geodetic observations for ocean tide loading displacements. In remote areas as Antarctica ocean tide models still suffer from limited coverage of satellite altimetry observations in high latitudes and especially in coastal areas. The coverage of tide gauges is poor in this region and their continues operation is still a challenge due to harsh environmental conditions.

The GNSS interferometric reflectometry (GNSS-R) is a promising method for continues observations of the sea surface heights (SSH) near the coast. In GNSS-R the signal to noise ratio (SNR) is analyzed to obtain the height difference between the GNSS antenna phase center and the reflecting sea surface. The method determines the sea surface height directly in the global reference system.

The German Antarctic Receiving Station (GARS) O’Higgins is located at the northern tip of the Antarctic Peninsula and jointly operated by the German Aerospace Center (DLR) and the German Federal Agency for Cartography and Geodesy (BKG). The radio telescope is used for VLBI observations within the International VLBI Service.

In this study we analysed 1 Hz GNSS observation data from the GNSS marker OHI3 at O’Higgins in order to determine SSH. We analysed several years of data using an inverse modelling approach. We introduce the method and assess their error budget. The GNSS-R results are compared to simultaneous campaign-wise tide gauge observations. The multi-year solution is used to estimate a set of tidal harmonics which is compared to existing ocean tide models.

How to cite: Roggenbuck, O., Rülke, A., Kühmstedt, E., and Plötz, C.: Multi-year sea level estimation at O´Higgins station using GNSS interferometric reflectometry, 2nd Symposium of IAG Commission 4 “Positioning and Applications”, Potsdam, Germany, 5–8 Sep 2022, iag-comm4-2022-24, https://doi.org/10.5194/iag-comm4-2022-24, 2022.