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The Federated Satellite System mission (FSSCat), winner of the 2017 Copernicus Masters Competition and the first ESA third-party mission based on CubeSats, aimed to provide coarse-resolution soil moisture estimations and sea ice concentration maps by means of the passive microwave measurements collected by the Flexible Microwave Payload-2 (FMPL-2). The mission was successfully launched on 3 September 2020. In addition to the primary scientific objectives, FMPL-2 data are used in this study to estimate sea surface salinity (SSS), correcting for the sea surface roughness using a wind speed estimate from the L-band microwave radiometer and GNSS-R data themselves. FMPL-2 was executed over the Arctic and Antarctic oceans on a weekly schedule. Different artificial neural network algorithms have been implemented, combining FMPL-2 data with the sea surface temperature, showing a root-mean-square error (RMSE) down to 1.68 m/s in the case of the wind speed (WS) retrieval algorithms, and RMSE down to 0.43 psu for the sea surface salinity algorithm in one single pass.
Joan Francesc Munoz-Martin; Adriano Camps. Sea Surface Salinity and Wind Speed Retrievals Using GNSS-R and L-Band Microwave Radiometry Data from FMPL-2 Onboard the FSSCat Mission. Remote Sensing 2021, 13, 3224 .
AMA StyleJoan Francesc Munoz-Martin, Adriano Camps. Sea Surface Salinity and Wind Speed Retrievals Using GNSS-R and L-Band Microwave Radiometry Data from FMPL-2 Onboard the FSSCat Mission. Remote Sensing. 2021; 13 (16):3224.
Chicago/Turabian StyleJoan Francesc Munoz-Martin; Adriano Camps. 2021. "Sea Surface Salinity and Wind Speed Retrievals Using GNSS-R and L-Band Microwave Radiometry Data from FMPL-2 Onboard the FSSCat Mission." Remote Sensing 13, no. 16: 3224.
The Institute of Electrical and Electronics Engineers (IEEE) Geoscience and Remote Sensing Society (GRSS) created the GRSS “Standards for Earth Observation Technical Committee” to advance the usability of remote sensing products by experts from academia, industry, and government through the creation and promotion of standards and best practices. In February 2019, a Project Authorization Request was approved by the IEEE Standards Association (IEEE-SA) with the title “Standard for Spaceborne Global Navigation Satellite Systems Reflectometry (GNSS-R) Data and Metadata Content.” At present, 4 GNSS constellations cover the Earth with their navigation signals: The United States of America (USA) Global Positioning System GPS with 31 Medium Earth Orbit (MEO) operational satellites, the Russian GLObal’naya NAvigatsionnaya Sputnikovaya Sistema GLONASS with 24 MEO operational satellites, the European Galileo with 24 MEO operational satellites, and the Chinese BeiDou-3 with 3 Inclined GeoSynchronous Orbit (IGSO), 24 MEO, and 2 Geosynchronous Equatorial Orbit (GEO) operational satellites. Additionally, several regional navigation constellations increase the number of available signals for remote sensing purposes: the Japanese Quasi-Zenith Satellite System QZSS with 1 GSO and 3 Tundra-type orbit operational satellites, and the Indian Regional Navigation Satellite System IRNSS with 3 GEO and 4 IGSO operational satellites. On the other hand, there are different GNSS-R processing techniques, instruments and spaceborne missions, and a wide variety of retrieval algorithms have been used. The heterogeneous nature of these signals of opportunity as well as the numerous working methodologies justify the need of a standard to further advance in the development of GNSS-R towards an operational Earth Observation technique. In particular, the scope of this working group is to develop a standard for data and metadata content arising from past, present, and future spaceborne missions such as the United Kingdom (UK) TechDemoSat-1 TDS-1, and the National Aeronautics and Space Administration (NASA) CYclone Global Navigation Satellite System CYGNSS constellation coordinated by the University of Michigan (UM). In this article we describe the scene study, including fundamental aspects, scientific applications, and historical milestones. The spaceborne standard is under development and it will be published in IEEE-SA.
Hugo Carreno-Luengo; Adriano Camps; Chris Ruf; Nicolas Floury; Manuel Martin-Neira; Tianlin Wang; Siri Jodha Khalsa; Maria Paola Clarizia; Jennifer Reynolds; Joel Johnson; Andrew O'Brien; Carmela Galdi; Maurizio Di Bisceglie; Andreas Dielacher; Philip Jales; Martin Unwin; Lucinda King; Giuseppe Foti; Rashmi Shah; Daniel Pascual; Bill Schreiner; Milad Asgarimehr; Jens Wickert; Serni Ribo; Estel Cardellach. The IEEE-SA Working Group on Spaceborne GNSS-R: Scene Study. IEEE Access 2021, 9, 89906 -89933.
AMA StyleHugo Carreno-Luengo, Adriano Camps, Chris Ruf, Nicolas Floury, Manuel Martin-Neira, Tianlin Wang, Siri Jodha Khalsa, Maria Paola Clarizia, Jennifer Reynolds, Joel Johnson, Andrew O'Brien, Carmela Galdi, Maurizio Di Bisceglie, Andreas Dielacher, Philip Jales, Martin Unwin, Lucinda King, Giuseppe Foti, Rashmi Shah, Daniel Pascual, Bill Schreiner, Milad Asgarimehr, Jens Wickert, Serni Ribo, Estel Cardellach. The IEEE-SA Working Group on Spaceborne GNSS-R: Scene Study. IEEE Access. 2021; 9 ():89906-89933.
Chicago/Turabian StyleHugo Carreno-Luengo; Adriano Camps; Chris Ruf; Nicolas Floury; Manuel Martin-Neira; Tianlin Wang; Siri Jodha Khalsa; Maria Paola Clarizia; Jennifer Reynolds; Joel Johnson; Andrew O'Brien; Carmela Galdi; Maurizio Di Bisceglie; Andreas Dielacher; Philip Jales; Martin Unwin; Lucinda King; Giuseppe Foti; Rashmi Shah; Daniel Pascual; Bill Schreiner; Milad Asgarimehr; Jens Wickert; Serni Ribo; Estel Cardellach. 2021. "The IEEE-SA Working Group on Spaceborne GNSS-R: Scene Study." IEEE Access 9, no. : 89906-89933.
Weather forecast using GNSS-R relies, to a large extent, on data acquired by airborne and spaceborne platforms due to the extended coverage that can be achieved. GEO satellites can retrieve measurements over large areas, but with spatial resolutions on the order of thousands of meters per pixel. LEO satellites with polar orbits can provide measurements over the entire world, but they can not provide good spatial nor high temporal resolutions by themselves. LEO constellations of small satellites have the same coverage with improved spatial resolution and revisit times by using data fusion techniques. High-Altitude Pseudo-Satellites (HAPS) offer an excellent temporal and spatial resolution, but only over limited areas. In this work, the potential of using hosted GNSS-R payloads on commercial aircraft is explored as an alternative and cost-effective means to achieve a very high resolution and a very low revisit time for regional environmental applications. Finally, a case study of soil moisture monitoring over Europe is presented, including an analysis of the expected performance.
Adrian Perez-Portero; Joan Francesc Munoz-Martin; Hyuk Park; Adriano Camps. Airborne GNSS-R: A key enabling technology for environmental monitoring. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2021, PP, 1 -1.
AMA StyleAdrian Perez-Portero, Joan Francesc Munoz-Martin, Hyuk Park, Adriano Camps. Airborne GNSS-R: A key enabling technology for environmental monitoring. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 2021; PP (99):1-1.
Chicago/Turabian StyleAdrian Perez-Portero; Joan Francesc Munoz-Martin; Hyuk Park; Adriano Camps. 2021. "Airborne GNSS-R: A key enabling technology for environmental monitoring." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing PP, no. 99: 1-1.
CubeSats have revolutionized Earth Observation and space science, although their small size severely restricts satellite performance and payload. Antenna deployment from a stowed configuration in these small-satellites remains a great challenge. This paper presents the design, optimization, and testing of an L-band helix antenna deployment system for the 3 Cat-4, a 1U CubeSat developed at the NanoSat Lab (UPC). The 506-mm-long antenna is packed into a 26.8 mm gap together with a tip mass that provides a gravity gradient for nadir-pointing. The 3 Cat-4 Nadir Antenna Deployment Subsystem (NADS) melts dyneema strings to release the antenna in successive steps. PTFE coated fiberglass ensures the helix’s nominal diameter and pitch while a security locking mechanism serves as a redundant system for holding it in place before deploying. Our novel methodology optimizes the number and length of the NADS deployment steps. A slow-motion camera and image recognition software track the velocity and acceleration of the antenna sections by means of tracking dots. Kinematic analysis of the antenna resulted in a final design of four length steps: 90, 300, 420 and 506 mm. Our methodology for calculating these values can be widely applied for measuring many deployment system’s kinematic properties. The NADS performance is tested by characterizing antenna rigidity, analyzing helix behavior after one year in stowed configuration, and by testing the deployment mechanism in a thermal vacuum chamber at −35°C, the most critical temperature stress scenario. All test results are satisfactory. The final design of the NADS deployment mechanism is light, stable, reliable, affordable, highly scalable, and can be used in many antenna configurations and geometries. The 3 Cat-4 mission was selected by the ESA Academy to be launched in Q4 2021.
Miquel Sureda; Marco Sobrino; Oriol Millan; Andrea Aguilella; Arnau Solanellas; Marc Badia; Joan Francesc Munoz-Martin; Lara Fernandez; Joan A. Ruiz-De-Azua; Adriano Camps. Design and Testing of a Helix Antenna Deployment System for a 1U CubeSat. IEEE Access 2021, 9, 66103 -66114.
AMA StyleMiquel Sureda, Marco Sobrino, Oriol Millan, Andrea Aguilella, Arnau Solanellas, Marc Badia, Joan Francesc Munoz-Martin, Lara Fernandez, Joan A. Ruiz-De-Azua, Adriano Camps. Design and Testing of a Helix Antenna Deployment System for a 1U CubeSat. IEEE Access. 2021; 9 ():66103-66114.
Chicago/Turabian StyleMiquel Sureda; Marco Sobrino; Oriol Millan; Andrea Aguilella; Arnau Solanellas; Marc Badia; Joan Francesc Munoz-Martin; Lara Fernandez; Joan A. Ruiz-De-Azua; Adriano Camps. 2021. "Design and Testing of a Helix Antenna Deployment System for a 1U CubeSat." IEEE Access 9, no. : 66103-66114.
In the theoretical part of this work, a calibration strategy for both phase and amplitude calibration of rotating equispaced circular array based on redundant space calibration was introduced. It avoids the challenging implementation of conventional noise-injection networks, especially for a large-scale array, by using the strong self-consistency accomplished by array rotation. This study presents comprehensive simulation results of the proposed calibration strategy, where calibration residuals and image reconstruction errors are evaluated. The phase calibration shows outstanding performance, while the amplitude calibration is found to be biased due to the logarithms used to linearize the system of calibration equations, and the resulting image reconstruction bias is scene-dependent. A bias correction method is proposed accordingly, which requires an a priori regional brightness temperature within the observation scene. The performance of both phase and amplitude calibration take advantage of increasing the number of elements, which promises the system scalability for high spatial resolution applications.
Xi Guo; Adriano Camps; Hyuk Park; Hao Liu; Cheng Zhang; Ji Wu. Phase and Amplitude Calibration of Rotating Equispaced Circular Array for Geostationary Microwave Interferometric Radiometers--Simulation Results and Discussion. IEEE Transactions on Geoscience and Remote Sensing 2021, PP, 1 -19.
AMA StyleXi Guo, Adriano Camps, Hyuk Park, Hao Liu, Cheng Zhang, Ji Wu. Phase and Amplitude Calibration of Rotating Equispaced Circular Array for Geostationary Microwave Interferometric Radiometers--Simulation Results and Discussion. IEEE Transactions on Geoscience and Remote Sensing. 2021; PP (99):1-19.
Chicago/Turabian StyleXi Guo; Adriano Camps; Hyuk Park; Hao Liu; Cheng Zhang; Ji Wu. 2021. "Phase and Amplitude Calibration of Rotating Equispaced Circular Array for Geostationary Microwave Interferometric Radiometers--Simulation Results and Discussion." IEEE Transactions on Geoscience and Remote Sensing PP, no. 99: 1-19.
Several methods have been developed to provide polar maps of sea ice thickness (SIT) from L-band brightness temperature (T
Christoph Herbert; Joan Munoz-Martin; David Llaveria; Miriam Pablos; Adriano Camps. Sea Ice Thickness Estimation Based on Regression Neural Networks Using L-Band Microwave Radiometry Data from the FSSCat Mission. Remote Sensing 2021, 13, 1366 .
AMA StyleChristoph Herbert, Joan Munoz-Martin, David Llaveria, Miriam Pablos, Adriano Camps. Sea Ice Thickness Estimation Based on Regression Neural Networks Using L-Band Microwave Radiometry Data from the FSSCat Mission. Remote Sensing. 2021; 13 (7):1366.
Chicago/Turabian StyleChristoph Herbert; Joan Munoz-Martin; David Llaveria; Miriam Pablos; Adriano Camps. 2021. "Sea Ice Thickness Estimation Based on Regression Neural Networks Using L-Band Microwave Radiometry Data from the FSSCat Mission." Remote Sensing 13, no. 7: 1366.
Microwave radiometry at L‐band is sensitive to sea ice thickness (SIT) up to ∼ 60 cm. Current methods to infer SIT depend on ice‐physical properties and data provided by the ESA’s Soil Moisture and Ocean Salinity (SMOS) mission. However, retrieval accuracy is limited due to seasonally and regionally variable surface conditions during the formation and melting of sea ice. In this work, Arctic sea ice is segmented using a Bayesian unsupervised learning algorithm aiming to recognize spatial patterns by harnessing multi‐incidence angle brightness temperature observations. The approach considers both statistical characteristics and spatial correlations of the observations. The temporal stability and separability of classes are analyzed to distinguish ambiguous from well‐determined regions. Model uncertainty is quantified from class membership probabilities using information entropy. The presented approach opens up a new scope to improve current SIT retrieval algorithms, and can be particularly beneficial to investigate merged satellite products.
Christoph Herbert; Adriano Camps; Florian Wellmann; Mercedes Vall‐Llossera. Bayesian Unsupervised Machine Learning Approach to Segment Arctic Sea Ice Using SMOS Data. Geophysical Research Letters 2021, 48, 1 .
AMA StyleChristoph Herbert, Adriano Camps, Florian Wellmann, Mercedes Vall‐Llossera. Bayesian Unsupervised Machine Learning Approach to Segment Arctic Sea Ice Using SMOS Data. Geophysical Research Letters. 2021; 48 (6):1.
Chicago/Turabian StyleChristoph Herbert; Adriano Camps; Florian Wellmann; Mercedes Vall‐Llossera. 2021. "Bayesian Unsupervised Machine Learning Approach to Segment Arctic Sea Ice Using SMOS Data." Geophysical Research Letters 48, no. 6: 1.
The calibration strategy for synthetic aperture interferometric radiometers based on noise injection has been successfully demonstrated in the Microwave Imaging Radiometer with Aperture Synthesis (MIRAS) instrument onboard the Soil Moisture and Ocean Salinity (SMOS) mission of the European Space Agency (ESA). With the emerging demands of increasing both array size and frequency bands, the internal calibration hardware becomes more difficult to implement. Although several external calibration methods have been proposed, the so-called phase ambiguity problem was not carefully considered. In this article, a novel calibration strategy for both phase and amplitude calibrations based on redundant space calibration is proposed, which utilizes the unique structure of equispaced circular array and rotational sampling strategy. The original irregular phase ambiguity degenerates to the fixed π-ambiguity, where only two possible solutions to phases are introduced. Both phase and amplitude of visibility can be simultaneously calibrated by the proposed strategy, and no cooperative calibration target is needed.
Xi Guo; Adriano Camps; Hyuk Park; Hao Liu; Cheng Zhang; Ji Wu. Phase and Amplitude Calibrations of Rotating Equispaced Circular Array for Geostationary Microwave Interferometric Radiometers--Theory and Methods. IEEE Transactions on Geoscience and Remote Sensing 2021, PP, 1 -15.
AMA StyleXi Guo, Adriano Camps, Hyuk Park, Hao Liu, Cheng Zhang, Ji Wu. Phase and Amplitude Calibrations of Rotating Equispaced Circular Array for Geostationary Microwave Interferometric Radiometers--Theory and Methods. IEEE Transactions on Geoscience and Remote Sensing. 2021; PP (99):1-15.
Chicago/Turabian StyleXi Guo; Adriano Camps; Hyuk Park; Hao Liu; Cheng Zhang; Ji Wu. 2021. "Phase and Amplitude Calibrations of Rotating Equispaced Circular Array for Geostationary Microwave Interferometric Radiometers--Theory and Methods." IEEE Transactions on Geoscience and Remote Sensing PP, no. 99: 1-15.
For the first time, rain effects on the polarimetric observations of the global navigation satellite system reflectometry (GNSS-R) are investigated. The physical feasibility of tracking the modifications in the surface roughness by rain splash and the surface salinity by the accumulation of freshwater is theoretically discussed. An empirical analysis is carried out using measurements of a coastal GNSS-R station with two side-looking antennas in right- and left-handed circular polarizations (RHCP and LHCP). Discernible drops in RHCP and LHCP powers are observed during rain over a calm sea. The power drop becomes larger at higher elevation angles. The average LHCP power drops by ≈ 5 dB at an elevation angle of 45°. The amplitude of the correlation sum shows a dampening, responding to rain rate systematically. The LHCP observations show higher sensitivity to rainfall compared to RHCP observations. The retrieved standard deviation of surface heights shows a steady increase with the rain rate. The derived surface salinity shows a decrease at rains higher than 10 mm/h. This study confirms the potential under environmental conditions of the GNSS-R ground-based station, e.g., with salinity mostly lower than 30 psu, over a calm sea, being a starting point for future investigations.
Milad Asgarimehr; Mostafa Hoseini; Maximilian Semmling; Markus Ramatschi; Adriano Camps; Hossein Nahavandchi; Rudiger Haas; Jens Wickert. Remote Sensing of Precipitation Using Reflected GNSS Signals: Response Analysis of Polarimetric Observations. IEEE Transactions on Geoscience and Remote Sensing 2021, PP, 1 -12.
AMA StyleMilad Asgarimehr, Mostafa Hoseini, Maximilian Semmling, Markus Ramatschi, Adriano Camps, Hossein Nahavandchi, Rudiger Haas, Jens Wickert. Remote Sensing of Precipitation Using Reflected GNSS Signals: Response Analysis of Polarimetric Observations. IEEE Transactions on Geoscience and Remote Sensing. 2021; PP (99):1-12.
Chicago/Turabian StyleMilad Asgarimehr; Mostafa Hoseini; Maximilian Semmling; Markus Ramatschi; Adriano Camps; Hossein Nahavandchi; Rudiger Haas; Jens Wickert. 2021. "Remote Sensing of Precipitation Using Reflected GNSS Signals: Response Analysis of Polarimetric Observations." IEEE Transactions on Geoscience and Remote Sensing PP, no. 99: 1-12.
CubeSat-based Earth Observation missions have emerged in recent times, achieving scientifically valuable data at a moderate cost. FSSCat is a two 6U CubeSats mission, winner of the ESA S3 challenge and overall winner of the 2017 Copernicus Masters Competition, that was launched in September 2020. The first satellite, 3Cat-5/A, carries the FMPL-2 instrument, an L-band microwave radiometer and a GNSS-Reflectometer. This work presents a neural network approach for retrieving sea ice concentration and sea ice extent maps on the Arctic and the Antarctic oceans using FMPL-2 data. The results from the first months of operations are presented and analyzed, and the quality of the retrieved maps is assessed by comparing them with other existing sea ice concentration maps. As compared to OSI SAF products, the overall accuracy for the sea ice extent maps is greater than 97% using MWR data, and up to 99% when using combined GNSS-R and MWR data. In the case of Sea ice concentration, the absolute errors are lower than 5%, with MWR and lower than 3% combining it with the GNSS-R. The total extent area computed using this methodology is close, with 2.5% difference, to those computed by other well consolidated algorithms, such as OSI SAF or NSIDC. The approach presented for estimating sea ice extent and concentration maps is a cost-effective alternative, and using a constellation of CubeSats, it can be further improved.
David Llaveria; Juan Munoz-Martin; Christoph Herbert; Miriam Pablos; Hyuk Park; Adriano Camps. Sea Ice Concentration and Sea Ice Extent Mapping with L-Band Microwave Radiometry and GNSS-R Data from the FFSCat Mission Using Neural Networks. Remote Sensing 2021, 13, 1139 .
AMA StyleDavid Llaveria, Juan Munoz-Martin, Christoph Herbert, Miriam Pablos, Hyuk Park, Adriano Camps. Sea Ice Concentration and Sea Ice Extent Mapping with L-Band Microwave Radiometry and GNSS-R Data from the FFSCat Mission Using Neural Networks. Remote Sensing. 2021; 13 (6):1139.
Chicago/Turabian StyleDavid Llaveria; Juan Munoz-Martin; Christoph Herbert; Miriam Pablos; Hyuk Park; Adriano Camps. 2021. "Sea Ice Concentration and Sea Ice Extent Mapping with L-Band Microwave Radiometry and GNSS-R Data from the FFSCat Mission Using Neural Networks." Remote Sensing 13, no. 6: 1139.
Presently, the Earth Observation community is demanding applications that provide low latency and high downlink capabilities. An increase in downlink contacts becomes essential to meet these new requirements. The Federated Satellite Systems concept addresses this demand by promoting satellite collaborations to share unused downlink opportunities. These collaborations are established opportunistically and temporarily, posing multiple technology challenges to be implemented in-orbit. This work contributes to the definition of the Federation Deployment Control Protocol which formalizes a mechanism to fairly establish and manage these collaborations by employing a negotiation process between the satellites. Moreover, this manuscript presents the results of a validation campaign of this protocol with three stratospheric balloons. In summary, more than 27 federations with 63.0% of throughput were established during the field campaign. Some of these federations were used to download data to the ground, and others were established to balance data storage between balloons. These federations allowed also the extension of the coverage of a ground station with a federation that relayed data through a balloon, and the achievement of a hybrid scenario with one balloon forwarding data from a ground device. The results demonstrate that the proposed protocol is functional and ready to be embedded in a CubeSat mission.
Joan Ruiz-De-Azua; Nicola Garzaniti; Alessandro Golkar; Anna Calveras; Adriano Camps. Towards Federated Satellite Systems and Internet of Satellites: The Federation Deployment Control Protocol. Remote Sensing 2021, 13, 982 .
AMA StyleJoan Ruiz-De-Azua, Nicola Garzaniti, Alessandro Golkar, Anna Calveras, Adriano Camps. Towards Federated Satellite Systems and Internet of Satellites: The Federation Deployment Control Protocol. Remote Sensing. 2021; 13 (5):982.
Chicago/Turabian StyleJoan Ruiz-De-Azua; Nicola Garzaniti; Alessandro Golkar; Anna Calveras; Adriano Camps. 2021. "Towards Federated Satellite Systems and Internet of Satellites: The Federation Deployment Control Protocol." Remote Sensing 13, no. 5: 982.
The Federated Satellite System mission (FSSCat) was the winner of the 2017 Copernicus Masters Competition and the first Copernicus third-party mission based on CubeSats. One of FSSCat’s objectives is to provide coarse Soil Moisture (SM) estimations by means of passive microwave measurements collected by Flexible Microwave Payload-2 (FMPL-2). This payload is a novel CubeSat based instrument combining an L1/E1 Global Navigation Satellite Systems-Reflectometer (GNSS-R) and an L-band Microwave Radiometer (MWR) using software-defined radio. This work presents the first results over land of the first two months of operations after the commissioning phase, from 1 October to 4 December 2020. Four neural network algorithms are implemented and analyzed in terms of different sets of input features to yield maps of SM content over the Northern Hemisphere (latitudes above 45° N). The first algorithm uses the surface skin temperature from the European Centre of Medium-Range Weather Forecast (ECMWF) in conjunction with the 16 day averaged Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) to estimate SM and to use it as a comparison dataset for evaluating the additional models. A second approach is implemented to retrieve SM, which complements the first model using FMPL-2 L-band MWR antenna temperature measurements, showing a better performance than in the first case. The error standard deviation of this model referred to the Soil Moisture and Ocean Salinity (SMOS) SM product gridded at 36 km is 0.074 m
Joan Munoz-Martin; David Llaveria; Christoph Herbert; Miriam Pablos; Hyuk Park; Adriano Camps. Soil Moisture Estimation Synergy Using GNSS-R and L-Band Microwave Radiometry Data from FSSCat/FMPL-2. Remote Sensing 2021, 13, 994 .
AMA StyleJoan Munoz-Martin, David Llaveria, Christoph Herbert, Miriam Pablos, Hyuk Park, Adriano Camps. Soil Moisture Estimation Synergy Using GNSS-R and L-Band Microwave Radiometry Data from FSSCat/FMPL-2. Remote Sensing. 2021; 13 (5):994.
Chicago/Turabian StyleJoan Munoz-Martin; David Llaveria; Christoph Herbert; Miriam Pablos; Hyuk Park; Adriano Camps. 2021. "Soil Moisture Estimation Synergy Using GNSS-R and L-Band Microwave Radiometry Data from FSSCat/FMPL-2." Remote Sensing 13, no. 5: 994.
Global Navigation Satellite System—Reflectometry (GNSS-R) has already proven its potential for retrieving a number of geophysical parameters, including soil moisture. However, single-pass GNSS-R soil moisture retrieval is still a challenge. This study presents a comparison of two different data sets acquired with the Microwave Interferometer Reflectometer (MIR), an airborne-based dual-band (L1/E1 and L5/E5a), multiconstellation (GPS and Galileo) GNSS-R instrument with two 19-element antenna arrays with four electronically steered beams each. The instrument was flown twice over the OzNet soil moisture monitoring network in southern New South Wales (Australia): the first flight was performed after a long period without rain, and the second one just after a rain event. In this work, the impact of surface roughness and vegetation attenuation in the reflectivity of the GNSS-R signal is assessed at both L1 and L5 bands. The work analyzes the reflectivity at different integration times, and finally, an artificial neural network is used to retrieve soil moisture from the reflectivity values. The algorithm is trained and compared to a 20-m resolution downscaled soil moisture estimate derived from SMOS soil moisture, Sentinel-2 normalized difference vegetation index (NDVI) data, and ECMWF Land Surface Temperature.
Joan Munoz-Martin; Raul Onrubia; Daniel Pascual; Hyuk Park; Miriam Pablos; Adriano Camps; Christoph Rüdiger; Jeffrey Walker; Alessandra Monerris. Single-Pass Soil Moisture Retrieval Using GNSS-R at L1 and L5 Bands: Results from Airborne Experiment. Remote Sensing 2021, 13, 797 .
AMA StyleJoan Munoz-Martin, Raul Onrubia, Daniel Pascual, Hyuk Park, Miriam Pablos, Adriano Camps, Christoph Rüdiger, Jeffrey Walker, Alessandra Monerris. Single-Pass Soil Moisture Retrieval Using GNSS-R at L1 and L5 Bands: Results from Airborne Experiment. Remote Sensing. 2021; 13 (4):797.
Chicago/Turabian StyleJoan Munoz-Martin; Raul Onrubia; Daniel Pascual; Hyuk Park; Miriam Pablos; Adriano Camps; Christoph Rüdiger; Jeffrey Walker; Alessandra Monerris. 2021. "Single-Pass Soil Moisture Retrieval Using GNSS-R at L1 and L5 Bands: Results from Airborne Experiment." Remote Sensing 13, no. 4: 797.
Note: In lieu of an abstract, this is an excerpt from the first page. This paper
Changjiang Hu; Craig Benson; Hyuk Park; Adriano Camps; Li Qiao; Chris Rizos. Addendum: Hu, C.; et al. Detecting Targets above the Earth’s Surface Using GNSS-R Delay Doppler Maps: Results from TDS-1. Remote Sens. 2019, 11, 2327. Remote Sensing 2021, 13, 715 .
AMA StyleChangjiang Hu, Craig Benson, Hyuk Park, Adriano Camps, Li Qiao, Chris Rizos. Addendum: Hu, C.; et al. Detecting Targets above the Earth’s Surface Using GNSS-R Delay Doppler Maps: Results from TDS-1. Remote Sens. 2019, 11, 2327. Remote Sensing. 2021; 13 (4):715.
Chicago/Turabian StyleChangjiang Hu; Craig Benson; Hyuk Park; Adriano Camps; Li Qiao; Chris Rizos. 2021. "Addendum: Hu, C.; et al. Detecting Targets above the Earth’s Surface Using GNSS-R Delay Doppler Maps: Results from TDS-1. Remote Sens. 2019, 11, 2327." Remote Sensing 13, no. 4: 715.
Radio frequency interference (RFI) is an increasing problem in microwave radiometry, particularly for Earth observation, because the antennas are pointing toward the Earth. RFI has been observed at the L-band in European Space Agency's (ESA's) Soil Moisture and Ocean Salinity (SMOS) Earth Explorer mission, National Aeronautics and Space Administration's (NASA's) Soil Moisture Active and Passive (SMAP) and Aquarius missions, and Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) and WindSat missions at 10.7 and 18.7 GHz (Misra and de Matthaeis, 2014). Therefore, dedicated onboard systems are, nowadays, a must to detect and remove contaminated measurements, improving radiometric accuracy and increasing the spatial coverage. In this work, a novel detection technique, specially tailored for synthetic aperture interferometric radiometers (SAIRs), is proposed and its performance analyzed. It is based on the change of the shape of the cross correlation function at lags different from zero under the presence of RFI. The performance of the proposed technique is compared to other common RFI detection algorithms, and its limitations and advantages are discussed. Postcorrelation detection performance is found to outperform other commonly used algorithms, such as kurtosis. In addition, it presents some convenient properties for its practical application in correlation and real aperture radiometers.
Raul Diez-Garcia; Adriano Camps. A Novel RFI Detection Method for Microwave Radiometers Using Multilag Correlators. IEEE Transactions on Geoscience and Remote Sensing 2021, PP, 1 -12.
AMA StyleRaul Diez-Garcia, Adriano Camps. A Novel RFI Detection Method for Microwave Radiometers Using Multilag Correlators. IEEE Transactions on Geoscience and Remote Sensing. 2021; PP (99):1-12.
Chicago/Turabian StyleRaul Diez-Garcia; Adriano Camps. 2021. "A Novel RFI Detection Method for Microwave Radiometers Using Multilag Correlators." IEEE Transactions on Geoscience and Remote Sensing PP, no. 99: 1-12.
The Flexible Microwave Payload-2 is the GNSS-R and L-band Microwave Radiometer Payload on board 3Cat-5/A, one of the two 6-unit CubeSats of the FSSCat mission, which were successfully launched on 3 September 2020 on Vega flight VV16. The instrument occupies nearly a single unit of the CubeSat, and its goal is to provide sea-ice extension and thickness over the poles, and soil moisture maps at low-moderate resolution over land, which will be downscaled using data from Cosine Hyperscout-2 on board 3Cat-5/B. The spacecrafts are in a 97.5∘ inclination Sun-synchronous orbit, and both the reflectometer and the radiometer have been successfully executed and validated over both the North and the South poles. This manuscript presents the results and validation of the first data sets collected by the instrument during the first two months of the mission. The results of the validation are showing a radiometric accuracy better than 2 K, and a sensitivity lower than the Kelvin. For the reflectometer, the results are showing that the sea-ice transition can be estimated even at short integration times (40 ms). The presented results shows the potential for Earth Observation missions based on CubeSats, which temporal and spatial resolution can be further increased by means of CubeSat constellations.
Joan Munoz-Martin; Lara Fernandez; Adrian Perez; Joan Ruiz-De-Azua; Hyuk Park; Adriano Camps; Bernardo Carnicero Domínguez; Massimiliano Pastena. In-Orbit Validation of the FMPL-2 Instrument—The GNSS-R and L-Band Microwave Radiometer Payload of the FSSCat Mission. Remote Sensing 2020, 13, 121 .
AMA StyleJoan Munoz-Martin, Lara Fernandez, Adrian Perez, Joan Ruiz-De-Azua, Hyuk Park, Adriano Camps, Bernardo Carnicero Domínguez, Massimiliano Pastena. In-Orbit Validation of the FMPL-2 Instrument—The GNSS-R and L-Band Microwave Radiometer Payload of the FSSCat Mission. Remote Sensing. 2020; 13 (1):121.
Chicago/Turabian StyleJoan Munoz-Martin; Lara Fernandez; Adrian Perez; Joan Ruiz-De-Azua; Hyuk Park; Adriano Camps; Bernardo Carnicero Domínguez; Massimiliano Pastena. 2020. "In-Orbit Validation of the FMPL-2 Instrument—The GNSS-R and L-Band Microwave Radiometer Payload of the FSSCat Mission." Remote Sensing 13, no. 1: 121.
Phase, frequency, and time synchronization are crucial requirements for many applications, such as multi-static remote sensing and communication systems. Moreover, the synchronization solution becomes even more challenging when the nodes are orbiting or flying on airborne or spaceborne platforms. This paper compares the available technologies used for the synchronization and coordination of nodes in distributed remote sensing applications. Additionally, this paper proposes a general system model and identifies preliminary guidelines and critical elements for implementing the synchronization mechanisms exploiting the inter-satellite communication link. The distributed phase synchronization loop introduced in this work deals with the self-interference in a full-duplex point to point scenario by transmitting two carriers at each node. All carriers appear with different frequency offsets around a central frequency, called the application central-frequency or the beamforming frequency. This work includes a detailed analysis of the proposed algorithm and the required simulations to verify its performance for different phase noise, AWGN, and Doppler shift scenarios.
Juan Carlos Merlano-Duncan; Liz Martinez-Marrero; Jorge Querol; Sumit Kumar; Adriano Camps; Symeon Chatzinotas; Bjorn Ottersten. A Remote Carrier Synchronization Technique for Coherent Distributed Remote Sensing Systems. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2020, 14, 1909 -1922.
AMA StyleJuan Carlos Merlano-Duncan, Liz Martinez-Marrero, Jorge Querol, Sumit Kumar, Adriano Camps, Symeon Chatzinotas, Bjorn Ottersten. A Remote Carrier Synchronization Technique for Coherent Distributed Remote Sensing Systems. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 2020; 14 (99):1909-1922.
Chicago/Turabian StyleJuan Carlos Merlano-Duncan; Liz Martinez-Marrero; Jorge Querol; Sumit Kumar; Adriano Camps; Symeon Chatzinotas; Bjorn Ottersten. 2020. "A Remote Carrier Synchronization Technique for Coherent Distributed Remote Sensing Systems." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 14, no. 99: 1909-1922.
The FSSCat mission was the 2017 ESA Sentinel Small Satellite (S⌃3) Challenge winner and the Copernicus Masters competition overall winner. It was successfully launched on 3 September 2020 onboard the VEGA SSMS PoC (VV16). FSSCat aims to provide coarse and downscaled soil moisture data and over polar regions, sea ice cover, and coarse resolution ice thickness using a combined L-band microwave radiometer and GNSS-Reflectometry payload. As part of the calibration and validation activities of FSSCat, a GNSS-R instrument was deployed as part of the MOSAiC polar expedition. The Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition was an international one-year-long field experiment led by the Alfred Wegener Institute to study the climate system and the impact of climate change in the Arctic Ocean. This paper presents the first results of the PYCARO-2 instrument, focused on the GNSS-R techniques used to measure snow and ice thickness of an ice floe. The Interference Pattern produced by the combination of the GNSS direct and reflected signals over the sea-ice has been modeled using a four-layer model. The different thicknesses of the substrate layers (i.e., snow and ice) are linked to the position of the fringes of the interference pattern. Data collected by MOSAiC GNSS-R instrument between December 2019 and January 2020 for different GNSS constellations and frequencies are presented and analyzed, showing that under general conditions, sea ice and snow thickness can be retrieved using multiangular and multifrequency data.
Joan Munoz-Martin; Adrian Perez; Adriano Camps; Serni Ribó; Estel Cardellach; Julienne Stroeve; Vishnu Nandan; Polona Itkin; Rasmus Tonboe; Stefan Hendricks; Marcus Huntemann; Gunnar Spreen; Massimiliano Pastena. Snow and Ice Thickness Retrievals Using GNSS-R: Preliminary Results of the MOSAiC Experiment. Remote Sensing 2020, 12, 4038 .
AMA StyleJoan Munoz-Martin, Adrian Perez, Adriano Camps, Serni Ribó, Estel Cardellach, Julienne Stroeve, Vishnu Nandan, Polona Itkin, Rasmus Tonboe, Stefan Hendricks, Marcus Huntemann, Gunnar Spreen, Massimiliano Pastena. Snow and Ice Thickness Retrievals Using GNSS-R: Preliminary Results of the MOSAiC Experiment. Remote Sensing. 2020; 12 (24):4038.
Chicago/Turabian StyleJoan Munoz-Martin; Adrian Perez; Adriano Camps; Serni Ribó; Estel Cardellach; Julienne Stroeve; Vishnu Nandan; Polona Itkin; Rasmus Tonboe; Stefan Hendricks; Marcus Huntemann; Gunnar Spreen; Massimiliano Pastena. 2020. "Snow and Ice Thickness Retrievals Using GNSS-R: Preliminary Results of the MOSAiC Experiment." Remote Sensing 12, no. 24: 4038.
Global navigation satellite systems reflectometry (GNSS-R) is a relatively novel remote sensing technique, but it can be understood as a multi-static radar using satellite navigation signals as signals of opportunity. The scattered signals over sea ice, flooded areas, and even under dense vegetation show a detectable coherent component that can be separated from the incoherent component and processed accordingly. This work derives an analytical formulation of the response of a GNSS-R instrument to a step function in the reflectivity using well-known principles of electromagnetic theory. The evaluation of the spatial resolution then requires a numerical evaluation of the proposed equations, as the width of the transition depends on the reflectivity values of two regions. However, it is found that results are fairly constant over a wide range of reflectivities, and they only vary faster for very high or very low reflectivity gradients. The predicted step response is then satisfactorily compared to airborne experimental results at L1 (1575.42 MHz) and L5 (1176.45 MHz) bands, acquired over a water reservoir south of Melbourne, in terms of width and ringing, and several examples are provided when the transition occurs from land to a rough ocean surface, where the coherent scattering component is no longer dominant.
Adriano Camps; Joan Munoz-Martin. Analytical Computation of the Spatial Resolution in GNSS-R and Experimental Validation at L1 and L5. Remote Sensing 2020, 12, 3910 .
AMA StyleAdriano Camps, Joan Munoz-Martin. Analytical Computation of the Spatial Resolution in GNSS-R and Experimental Validation at L1 and L5. Remote Sensing. 2020; 12 (23):3910.
Chicago/Turabian StyleAdriano Camps; Joan Munoz-Martin. 2020. "Analytical Computation of the Spatial Resolution in GNSS-R and Experimental Validation at L1 and L5." Remote Sensing 12, no. 23: 3910.
At some frequencies, Earth’s ionosphere may significantly impact satellite communications, Global Navigation Satellite Systems (GNSS) positioning, and Earth Observation measurements. Due to the temporal and spatial variations in the Total Electron Content (TEC) and the ionosphere dynamics (i.e., fluctuations in the electron content density), electromagnetic waves suffer from signal delay, polarization change (i.e., Faraday rotation), direction of arrival, and fluctuations in signal intensity and phase (i.e., scintillation). Although there are previous studies proposing GNSS Reflectometry (GNSS-R) to study the ionospheric scintillation using, for example TechDemoSat-1, the amount of data is limited. In this study, data from NASA CYGNSS constellation have been used to explore a new source of data for ionospheric activity, and in particular, for travelling equatorial plasma depletions (EPBs). Using data from GNSS ground stations, previous studies detected and characterized their presence at equatorial latitudes. This work presents, for the first time to authors’ knowledge, the evidence of ionospheric bubbles detection in ocean regions using GNSS-R data, where there are no ground stations available. The results of the study show that bubbles can be detected and, in addition to measure their dimensions and duration, the increased intensity scintillation (S4) occurring in the bubbles can be estimated. The bubbles detected here reached S4 values of around 0.3–0.4 lasting for some seconds to few minutes. Furthermore, a comparison with data from ESA Swarm mission is presented, showing certain correlation in regions where there is S4 peaks detected by CYGNSS and fluctuations in the plasma density as measured by Swarm.
Carlos Molina; Adriano Camps. First Evidences of Ionospheric Plasma Depletions Observations Using GNSS-R Data from CYGNSS. Remote Sensing 2020, 12, 3782 .
AMA StyleCarlos Molina, Adriano Camps. First Evidences of Ionospheric Plasma Depletions Observations Using GNSS-R Data from CYGNSS. Remote Sensing. 2020; 12 (22):3782.
Chicago/Turabian StyleCarlos Molina; Adriano Camps. 2020. "First Evidences of Ionospheric Plasma Depletions Observations Using GNSS-R Data from CYGNSS." Remote Sensing 12, no. 22: 3782.