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Sea state-dependent Doppler spread as a limit of coherent GNSS reflectometry from an airborne platform

Moreno, Mario and Semmling, Maximilian and Stienne, Georges and Dalil, Wafa and Hoque, Mohammed Mainul and Wickert, Jens and Reboul, Serge (2022) Sea state-dependent Doppler spread as a limit of coherent GNSS reflectometry from an airborne platform. In: ESA Living Planet Symposium 2022. ESA Living Planet Symposium 2022, 23–27 May 2022, Bonn.

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Sea level rise and sea state variability due to climate change and global warming are major research topics in the scientific community. Ocean weather conditions considerably impact coastal areas, and wind speed (WS) and significant wave height (SWH) are usable parameters to monitor the sea state threats on the coasts. GNSS reflectometry (GNSS-R) has shown considerable promise as a remote sensing technique for ocean parameters estimation. Multiple studies have been conducted successfully in the recent two decades by using GNSS-R ground-based, airborne and spaceborne data to retrieve geophysical properties of the ocean surface. The focus of this study is to investigate the Doppler shift of the reflected signal as observable to estimate the Doppler spread (DS) and determine its correlation with sea state changes employing GNSS-R airborne data in coastal areas. An additional aim is to study the possibility of using the Doppler spread as a metric for coherent GNSS reflectometry for applications such as precise altimetry and precise total electron content (TEC) estimates. An experiment was conducted from the 12th to the 19th of July 2019 along Opal Coast, between the cities of Calais and Boulogne-sur-Mer, France. The experiment consisted of multiple flights at an altitude of ~780m (a.m.s.l), and the direct and reflected signals were received by dual-polarized (Right-Handed and Left-Handed Circular Polarizations) antenna mounted on a gyrocopter. A software receiver is used to process the direct and reflected signals from the right-hand channel. The resulting in-phase (I) and quadrature (Q) components (at 50 Hz rate) of the reflected signals are analyzed in the spectral domain every ten seconds to obtain the relative Doppler shift and power estimates. The coherence is established by analyzing the phase observations obtained from I and Q. The sensitivity of the reflected signal parameters and the sea state is determined by the correlation between the Doppler Spread with wind speed and significant wave height. The latter two were obtained from the atmospheric, land and oceanic climate model, ERA5, provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). Initial results have shown promising performance at a calm sea (WS: 2.9 m/s and SWH: 0.26 m) and grazing angles. Satellites with low elevations (E < 10°) present a Doppler Spread of 0.3 Hz and its Pearson correlations with respect to WS and SHW are 0.89 and 0.75, respectively. The performance is relatively poor for high-elevation events (E > 30°). The DS increases up to 2.1 Hz and the correlation decrease to 0.55 and 0.42 respectively. Coherence conditions are still under study; however, preliminary phase analysis reveals coherent observations at events with elevations below 15° and sea state with a significant wave height of 0.26 m.

Item URL in elib:https://elib.dlr.de/188812/
Document Type:Conference or Workshop Item (Poster)
Title:Sea state-dependent Doppler spread as a limit of coherent GNSS reflectometry from an airborne platform
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Semmling, MaximilianUNSPECIFIEDhttps://orcid.org/0000-0002-5228-8072UNSPECIFIED
Date:23 May 2022
Journal or Publication Title:ESA Living Planet Symposium 2022
Refereed publication:No
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
Keywords:GNSS Reflectometry, sea state, Doppler spreading.
Event Title:ESA Living Planet Symposium 2022
Event Location:Bonn
Event Type:international Conference
Event Dates:23–27 May 2022
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Communication, Navigation, Quantum Technology
DLR - Research area:Raumfahrt
DLR - Program:R KNQ - Communication, Navigation, Quantum Technology
DLR - Research theme (Project):R - Ionosphere
Location: Neustrelitz
Institutes and Institutions:Institute for Solar-Terrestrial Physics > Space Weather Observation
Deposited By: Moreno Bulla, Mario Andres
Deposited On:14 Oct 2022 12:15
Last Modified:29 Mar 2023 00:52

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