Articles de revistahttp://hdl.handle.net/2117/14432024-03-29T16:02:02Z2024-03-29T16:02:02ZImpact of incidence angle diversity on SMOS and sentinel-1 soil moisture retrievals at coarse and fine scalesPortal González, GerardVall-Llossera Ferran, Mercedes MagdalenaPiles Guillem, MaríaJagdhuber, ThomasCamps Carmona, Adriano JoséPablos Hernández, MiriamLópez Martínez, CarlosDas, NarendraEntekhabi, Darahttp://hdl.handle.net/2117/3872752024-03-10T14:33:08Z2023-05-10T15:30:30ZImpact of incidence angle diversity on SMOS and sentinel-1 soil moisture retrievals at coarse and fine scales
Portal González, Gerard; Vall-Llossera Ferran, Mercedes Magdalena; Piles Guillem, María; Jagdhuber, Thomas; Camps Carmona, Adriano José; Pablos Hernández, Miriam; López Martínez, Carlos; Das, Narendra; Entekhabi, Dara
Incidence angle diversity of space-borne radiometer and radar systems operating at low microwave frequencies needs to be taken into consideration to accurately estimate soil moisture (SM) across spatial scales. In this study, the single channel algorithm (SCA) is first applied to Soil Moisture and Ocean Salinity (SMOS) brightness temperatures at vertical polarization ( TBV ) to estimate SM at coarse resolution (25 km) and develop a land cover-specific and incidence angle (32.5°, 42.5°, and 52.5°)-adaptive calibration of single scattering albedo ( ¿ ) and soil roughness ( hs ) parameters. These effective parameters are used together with fine-scale multiangular Sentinel-1 backscatter in a single-pass active–passive downscaling approach to estimate TBV at fine scale (1 km) for each SMOS incidence angle. These TBVs are finally inverted to obtain the corresponding high-resolution SM maps. Results over the Iberian Peninsula for year 2018 show an increasing trend of ¿ and a decreasing trend of hs with SMOS incidence angle, with almost no variability of ¿ across land cover types. The active–passive covariation parameter is shown to increase with SMOS incidence angle and decrease with Sentinel-1 incidence angle. Coarse and fine TBV maps from the three SMOS incidence angles show similar distributions (mean differences below 0.38 K). Resulting high-resolution SM maps have maximum differences in mean and standard deviation of 0.016 and 0.015 m 3 /m 3 , respectively, and compare well with in situ measurements. Our results indicate that model-based microwave approaches to estimate SM can be adequately adapted to account for the incidence angle diversity of planned missions, such as Copernicus Microwave Imaging Radiometer (CIMR), Radar Observing System for Europe in L-band (ROSE-L), and Sentinel-1 next generation.
2023-05-10T15:30:30ZPortal González, GerardVall-Llossera Ferran, Mercedes MagdalenaPiles Guillem, MaríaJagdhuber, ThomasCamps Carmona, Adriano JoséPablos Hernández, MiriamLópez Martínez, CarlosDas, NarendraEntekhabi, DaraIncidence angle diversity of space-borne radiometer and radar systems operating at low microwave frequencies needs to be taken into consideration to accurately estimate soil moisture (SM) across spatial scales. In this study, the single channel algorithm (SCA) is first applied to Soil Moisture and Ocean Salinity (SMOS) brightness temperatures at vertical polarization ( TBV ) to estimate SM at coarse resolution (25 km) and develop a land cover-specific and incidence angle (32.5°, 42.5°, and 52.5°)-adaptive calibration of single scattering albedo ( ¿ ) and soil roughness ( hs ) parameters. These effective parameters are used together with fine-scale multiangular Sentinel-1 backscatter in a single-pass active–passive downscaling approach to estimate TBV at fine scale (1 km) for each SMOS incidence angle. These TBVs are finally inverted to obtain the corresponding high-resolution SM maps. Results over the Iberian Peninsula for year 2018 show an increasing trend of ¿ and a decreasing trend of hs with SMOS incidence angle, with almost no variability of ¿ across land cover types. The active–passive covariation parameter is shown to increase with SMOS incidence angle and decrease with Sentinel-1 incidence angle. Coarse and fine TBV maps from the three SMOS incidence angles show similar distributions (mean differences below 0.38 K). Resulting high-resolution SM maps have maximum differences in mean and standard deviation of 0.016 and 0.015 m 3 /m 3 , respectively, and compare well with in situ measurements. Our results indicate that model-based microwave approaches to estimate SM can be adequately adapted to account for the incidence angle diversity of planned missions, such as Copernicus Microwave Imaging Radiometer (CIMR), Radar Observing System for Europe in L-band (ROSE-L), and Sentinel-1 next generation.On the potential of empirical mode decomposition for RFI mitigation in microwave radiometryDíez García, RaúlCamps Carmona, Adriano JoséHyuk, Parkhttp://hdl.handle.net/2117/3745262023-10-29T06:14:33Z2022-10-18T07:26:51ZOn the potential of empirical mode decomposition for RFI mitigation in microwave radiometry
Díez García, Raúl; Camps Carmona, Adriano José; Hyuk, Park
Radio-frequency interference (RFI) is an increasing problem particularly for Earth observation using microwave radiometry. RFI has been observed, for example, at L-band by the European Space Agency’s (ESA’s) soil moisture and ocean salinity (SMOS) Earth Explorer and by National Aeronautics and Space Administration’s (NASA’s) soil moisture active passive (SMAP) and Aquarius missions, as well as at C-band by Advanced Microwave Scanning Radiometer (AMSR)-E and AMSR-2, and at 10.7 and 18.7 GHz by AMSR-E, AMSR-2, WindSat, and GPM Microwave Imager (GMI). Therefore, systems dedicated to interference detection and removal of contaminated measurements are nowadays a must in order to improve radiometric accuracy and reduce the loss of spatial coverage caused by interference. In this work, the feasibility of using the empirical mode decomposition (EMD) technique for RFI mitigation is explored. The EMD, also known as Hilbert–Huang transform (HHT), is an algorithm that decomposes the signal into intrinsic mode functions (IMFs). The achieved performance is analyzed, and the opportunities and caveats that this type of methods present are described. EMD is found to be a practical RFI mitigation method, albeit presenting some limitations and considerable complexity. Nevertheless, in some conditions, EMD exhibits a better performance than other commonly used methods (such as frequency binning). In particular, it has been found that EMD performs well for RFI affecting the <25% lower part of the intermediate frequency (IF) bandwidth.
2022-10-18T07:26:51ZDíez García, RaúlCamps Carmona, Adriano JoséHyuk, ParkRadio-frequency interference (RFI) is an increasing problem particularly for Earth observation using microwave radiometry. RFI has been observed, for example, at L-band by the European Space Agency’s (ESA’s) soil moisture and ocean salinity (SMOS) Earth Explorer and by National Aeronautics and Space Administration’s (NASA’s) soil moisture active passive (SMAP) and Aquarius missions, as well as at C-band by Advanced Microwave Scanning Radiometer (AMSR)-E and AMSR-2, and at 10.7 and 18.7 GHz by AMSR-E, AMSR-2, WindSat, and GPM Microwave Imager (GMI). Therefore, systems dedicated to interference detection and removal of contaminated measurements are nowadays a must in order to improve radiometric accuracy and reduce the loss of spatial coverage caused by interference. In this work, the feasibility of using the empirical mode decomposition (EMD) technique for RFI mitigation is explored. The EMD, also known as Hilbert–Huang transform (HHT), is an algorithm that decomposes the signal into intrinsic mode functions (IMFs). The achieved performance is analyzed, and the opportunities and caveats that this type of methods present are described. EMD is found to be a practical RFI mitigation method, albeit presenting some limitations and considerable complexity. Nevertheless, in some conditions, EMD exhibits a better performance than other commonly used methods (such as frequency binning). In particular, it has been found that EMD performs well for RFI affecting the <25% lower part of the intermediate frequency (IF) bandwidth.Parametric analysis of an L-band deployable offset reflector for CubeSatsMendez Soto, Mario AlbertoMarquez-Alperi, AdriánFernández Niño, ElenaCamps Carmona, Adriano Joséhttp://hdl.handle.net/2117/3744302023-10-15T10:39:47Z2022-10-14T07:29:59ZParametric analysis of an L-band deployable offset reflector for CubeSats
Mendez Soto, Mario Alberto; Marquez-Alperi, Adrián; Fernández Niño, Elena; Camps Carmona, Adriano José
Thanks to the advances in the miniaturization and improved power consumption efficiency of electronics, computers, cell phone technologies, etc., today’s spacecrafts and payloads are reducing their size and increasing their performance. However, not all systems can be reduced, as their dimensions are determined by the laws of physics. This study is focused on the design of an L-band reflector antenna for a CubeSat-based Earth observation mission devoted to measure the surface soil moisture. Two configurations of deployable parabolic reflector antennas and meshes are presented from the mechanical point of view. The electromagnetic analyses including the antenna feeder are also presented. It is found that the regular circular mesh performs slightly better than the irregular one, although requires a more careful manufacturing process.
2022-10-14T07:29:59ZMendez Soto, Mario AlbertoMarquez-Alperi, AdriánFernández Niño, ElenaCamps Carmona, Adriano JoséThanks to the advances in the miniaturization and improved power consumption efficiency of electronics, computers, cell phone technologies, etc., today’s spacecrafts and payloads are reducing their size and increasing their performance. However, not all systems can be reduced, as their dimensions are determined by the laws of physics. This study is focused on the design of an L-band reflector antenna for a CubeSat-based Earth observation mission devoted to measure the surface soil moisture. Two configurations of deployable parabolic reflector antennas and meshes are presented from the mechanical point of view. The electromagnetic analyses including the antenna feeder are also presented. It is found that the regular circular mesh performs slightly better than the irregular one, although requires a more careful manufacturing process.Measurement report: Spectral and statistical analysis of aerosol hygroscopic growth from multi-wavelength lidar measurements in Barcelona, SpainSicard, MichaëlOliveira, Daniel Camilo Fortunato dos SantosMuñoz Porcar, ConstantinoGil Díaz, CristinaComerón Tejero, AdolfoRodríguez Gómez, Alejandro AntonioDios Otín, Víctor Federicohttp://hdl.handle.net/2117/3732982022-12-11T02:18:17Z2022-09-22T11:06:48ZMeasurement report: Spectral and statistical analysis of aerosol hygroscopic growth from multi-wavelength lidar measurements in Barcelona, Spain
Sicard, Michaël; Oliveira, Daniel Camilo Fortunato dos Santos; Muñoz Porcar, Constantino; Gil Díaz, Cristina; Comerón Tejero, Adolfo; Rodríguez Gómez, Alejandro Antonio; Dios Otín, Víctor Federico
This paper presents the estimation of the hygroscopic growth parameter of atmospheric aerosols retrieved with a multi-wavelength lidar, a micro-pulse lidar (MPL) and daily radiosoundings in the coastal region ofBarcelona, Spain. The hygroscopic growth parameter, γ , parameterizes the magnitude of the scattering enhancement in terms of the backscatter coefficient following Hänel parameterization. After searching for time-colocated lidar and radiosounding measurements (performed twice a day, all year round at 00:00 and 12:00 UTC), a strict criterion-based procedure (limiting the variations of magnitudes such as water vapor mixing ratio (WMVR), potential temperature, wind speed and direction) is applied to select only cases of aerosol hygroscopic growth. A spectral analysis (at the wavelengths of 355, 532 and 1064 nm) is performed with the multi-wavelength lidar, and a climatological one, at the wavelength of 532 nm, with the database of both lidars. The spectral analysis shows that below 2 km the regime of local pollution and sea salt γ decreases with increasing wavelengths. Sincethe 355 nm wavelength is sensitive to smaller aerosols, this behavior could indicate slightly more hygroscopic aerosols present at smaller size ranges. Above 2 km (the regime of regional pollution and residual sea salt) the values of γ at 532 nm are nearly the same as those below 2 km, and its spectral behavior is flat. This analysis and others from the literature are put together in a table presenting, for the first time, a spectral analysis of the hygroscopic growth parameter of a large variety of atmospheric aerosol hygroscopicities ranging from low (pure mineral dust, γ <0.2) to high (pure sea salt, γ > 1.0) hygroscopicity. The climatological analysis shows that, at 532 nm, γ is rather constant all year round and has a large monthly standard deviation, suggesting the presence of aerosols with different hygroscopic properties all year round. The annual γ is 0.55 ± 0.23. The height of the layer where hygroscopic growth was calculated shows an annual cycle with a maximum in summer and a minimum in winter. Former works describing the presence of recirculation layers of pollutants injected at various heights above the planetary boundary layer (PBL) may explain why γ , unlike the height of the layer where hygroscopic growth was calculated, is not season-dependent. The subcategorization of the whole database into No cloud and Below-cloud cases reveals a large difference of γ in autumn between both categories (0.71 and 0.33, respectively), possibly attributed to a depletion of inorganics at the point of activation into cloud condensation nuclei (CCN) in the Below-cloud cases. Our work calls for more in situ measurements to synergetically complete such studies based on remote sensing.
2022-09-22T11:06:48ZSicard, MichaëlOliveira, Daniel Camilo Fortunato dos SantosMuñoz Porcar, ConstantinoGil Díaz, CristinaComerón Tejero, AdolfoRodríguez Gómez, Alejandro AntonioDios Otín, Víctor FedericoThis paper presents the estimation of the hygroscopic growth parameter of atmospheric aerosols retrieved with a multi-wavelength lidar, a micro-pulse lidar (MPL) and daily radiosoundings in the coastal region ofBarcelona, Spain. The hygroscopic growth parameter, γ , parameterizes the magnitude of the scattering enhancement in terms of the backscatter coefficient following Hänel parameterization. After searching for time-colocated lidar and radiosounding measurements (performed twice a day, all year round at 00:00 and 12:00 UTC), a strict criterion-based procedure (limiting the variations of magnitudes such as water vapor mixing ratio (WMVR), potential temperature, wind speed and direction) is applied to select only cases of aerosol hygroscopic growth. A spectral analysis (at the wavelengths of 355, 532 and 1064 nm) is performed with the multi-wavelength lidar, and a climatological one, at the wavelength of 532 nm, with the database of both lidars. The spectral analysis shows that below 2 km the regime of local pollution and sea salt γ decreases with increasing wavelengths. Sincethe 355 nm wavelength is sensitive to smaller aerosols, this behavior could indicate slightly more hygroscopic aerosols present at smaller size ranges. Above 2 km (the regime of regional pollution and residual sea salt) the values of γ at 532 nm are nearly the same as those below 2 km, and its spectral behavior is flat. This analysis and others from the literature are put together in a table presenting, for the first time, a spectral analysis of the hygroscopic growth parameter of a large variety of atmospheric aerosol hygroscopicities ranging from low (pure mineral dust, γ <0.2) to high (pure sea salt, γ > 1.0) hygroscopicity. The climatological analysis shows that, at 532 nm, γ is rather constant all year round and has a large monthly standard deviation, suggesting the presence of aerosols with different hygroscopic properties all year round. The annual γ is 0.55 ± 0.23. The height of the layer where hygroscopic growth was calculated shows an annual cycle with a maximum in summer and a minimum in winter. Former works describing the presence of recirculation layers of pollutants injected at various heights above the planetary boundary layer (PBL) may explain why γ , unlike the height of the layer where hygroscopic growth was calculated, is not season-dependent. The subcategorization of the whole database into No cloud and Below-cloud cases reveals a large difference of γ in autumn between both categories (0.71 and 0.33, respectively), possibly attributed to a depletion of inorganics at the point of activation into cloud condensation nuclei (CCN) in the Below-cloud cases. Our work calls for more in situ measurements to synergetically complete such studies based on remote sensing.Design of a deployable helix antenna at L-Band for a 1-Unit CubeSat: from theoretical analysis to flight model resultsFernandez Capon, Lara PilarSobrino Hidalgo, MarcoRuiz de Azua, Joan AdriaCalveras Augé, Anna M.Camps Carmona, Adriano Joséhttp://hdl.handle.net/2117/3703152023-12-22T14:25:06Z2022-07-18T09:36:23ZDesign of a deployable helix antenna at L-Band for a 1-Unit CubeSat: from theoretical analysis to flight model results
Fernandez Capon, Lara Pilar; Sobrino Hidalgo, Marco; Ruiz de Azua, Joan Adria; Calveras Augé, Anna M.; Camps Carmona, Adriano José
The 3Cat-4 mission aims at demonstrating the capabilities of a CubeSat to perform Earth Observation (EO) by integrating a combined GNSS-R and Microwave Radiometer payload into a 1-Unit CubeSat. One of the greatest challenges is the design of an antenna that respects the 1-Unit CubeSat envelope while operating at the different frequency bands: Global Positioning System (GPS) L1 and Galileo E1 band (1575 MHz), GPS L2 band (1227 MHz), and the microwave radiometry band (1400–1427 MHz). Moreover, it requires between 8 and 12 dB of directivity depending on the band whilst providing at least 10 dB of front-to-back lobe ratio in L1 and L2 GPS bands. After a trade-off analysis on the type of antenna that could be used, a helix antenna was found to be the most suitable option to comply with the requirements, since it can be stowed during launch and deployed once in orbit. This article presents the antenna design from a radiation performance point of view starting with a theoretical analysis, then presenting the numerical simulations, the measurements in an Engineering Model (EM), and finally the final design and performance of the Flight Model (FM)
2022-07-18T09:36:23ZFernandez Capon, Lara PilarSobrino Hidalgo, MarcoRuiz de Azua, Joan AdriaCalveras Augé, Anna M.Camps Carmona, Adriano JoséThe 3Cat-4 mission aims at demonstrating the capabilities of a CubeSat to perform Earth Observation (EO) by integrating a combined GNSS-R and Microwave Radiometer payload into a 1-Unit CubeSat. One of the greatest challenges is the design of an antenna that respects the 1-Unit CubeSat envelope while operating at the different frequency bands: Global Positioning System (GPS) L1 and Galileo E1 band (1575 MHz), GPS L2 band (1227 MHz), and the microwave radiometry band (1400–1427 MHz). Moreover, it requires between 8 and 12 dB of directivity depending on the band whilst providing at least 10 dB of front-to-back lobe ratio in L1 and L2 GPS bands. After a trade-off analysis on the type of antenna that could be used, a helix antenna was found to be the most suitable option to comply with the requirements, since it can be stowed during launch and deployed once in orbit. This article presents the antenna design from a radiation performance point of view starting with a theoretical analysis, then presenting the numerical simulations, the measurements in an Engineering Model (EM), and finally the final design and performance of the Flight Model (FM)Volcanic eruption of Cumbre Vieja, La Palma, Spain: A first insight to the particulate matter injected in the troposphereSicard, MichaëlCordoba Jabonero, CarmenBarreto Velasco, ÁfricaWelton, Ellsworth J.Gil Díaz, CristinaCarvajal Pérez, Clara VioletaComerón Tejero, AdolfoGarcía Rodríguez, OmairaMuñoz Porcar, ConstantinoRodríguez Gómez, Alejandro Antoniohttp://hdl.handle.net/2117/3693342023-11-12T16:40:38Z2022-06-30T07:12:11ZVolcanic eruption of Cumbre Vieja, La Palma, Spain: A first insight to the particulate matter injected in the troposphere
Sicard, Michaël; Cordoba Jabonero, Carmen; Barreto Velasco, África; Welton, Ellsworth J.; Gil Díaz, Cristina; Carvajal Pérez, Clara Violeta; Comerón Tejero, Adolfo; García Rodríguez, Omaira; Muñoz Porcar, Constantino; Rodríguez Gómez, Alejandro Antonio
The volcanic eruption of Cumbre Vieja (La Palma Island, Spain), started on 19 September 2021 and was declared terminated on 25 December 2021. A complete set of aerosol measurements were deployed around the volcano within the first month of the eruptive activity. This paper describes the results of the observations made at Tazacorte on the west bank of the island where a polarized micro-pulse lidar was deployed. The analyzed two-and-a-half months (16 October–31 December) reveal that the peak height of the lowermost and strongest volcanic plume did not exceed 3 km (the mean of the hourly values is 1.43 ± 0.45 km over the whole period) and was highly variable. The peak height of the lowermost volcanic plume steadily increased until week 11 after the eruption started (and 3 weeks before its end) and started decreasing afterward. The ash mass concentration was assessed with a method based on the polarization capability of the instrument. Two days with a high ash load were selected: The ash backscatter coefficient, aerosol optical depth, and the volume and particle depolarization ratios were, respectively, 3.6 (2.4) Mm−1sr−1, 0.52 (0.19), 0.13 (0.07) and 0.23 (0.13) on 18 October (15 November). Considering the limitation of current remote sensing techniques to detect large-to-giant particles, the ash mass concentration on the day with the highest ash load (18 October) was estimated to have peaked in the range of 800–3200 μg m−3 in the lowermost layer below 2.5 km.
2022-06-30T07:12:11ZSicard, MichaëlCordoba Jabonero, CarmenBarreto Velasco, ÁfricaWelton, Ellsworth J.Gil Díaz, CristinaCarvajal Pérez, Clara VioletaComerón Tejero, AdolfoGarcía Rodríguez, OmairaMuñoz Porcar, ConstantinoRodríguez Gómez, Alejandro AntonioThe volcanic eruption of Cumbre Vieja (La Palma Island, Spain), started on 19 September 2021 and was declared terminated on 25 December 2021. A complete set of aerosol measurements were deployed around the volcano within the first month of the eruptive activity. This paper describes the results of the observations made at Tazacorte on the west bank of the island where a polarized micro-pulse lidar was deployed. The analyzed two-and-a-half months (16 October–31 December) reveal that the peak height of the lowermost and strongest volcanic plume did not exceed 3 km (the mean of the hourly values is 1.43 ± 0.45 km over the whole period) and was highly variable. The peak height of the lowermost volcanic plume steadily increased until week 11 after the eruption started (and 3 weeks before its end) and started decreasing afterward. The ash mass concentration was assessed with a method based on the polarization capability of the instrument. Two days with a high ash load were selected: The ash backscatter coefficient, aerosol optical depth, and the volume and particle depolarization ratios were, respectively, 3.6 (2.4) Mm−1sr−1, 0.52 (0.19), 0.13 (0.07) and 0.23 (0.13) on 18 October (15 November). Considering the limitation of current remote sensing techniques to detect large-to-giant particles, the ash mass concentration on the day with the highest ash load (18 October) was estimated to have peaked in the range of 800–3200 μg m−3 in the lowermost layer below 2.5 km.Overview: On the transport and transformation of pollutants in the outflow of major population centres – observational data from the EMeRGe European intensive operational period in summer 2017Andrés Hernández, Maria DoloresHilboll, AndreasZiereis, HelmutFörster, EricKrüger, Ovid O.Kaiser, KatharinaSchneider, JohannesBarnaba, FrancescaVrekoussis, MSicard, Michaëlhttp://hdl.handle.net/2117/3686402022-12-11T02:37:50Z2022-06-17T11:19:20ZOverview: On the transport and transformation of pollutants in the outflow of major population centres – observational data from the EMeRGe European intensive operational period in summer 2017
Andrés Hernández, Maria Dolores; Hilboll, Andreas; Ziereis, Helmut; Förster, Eric; Krüger, Ovid O.; Kaiser, Katharina; Schneider, Johannes; Barnaba, Francesca; Vrekoussis, M; Sicard, Michaël
Megacities and other major population centres (MPCs) worldwide are major sources of air pollution, both locally as well as downwind. The overall assessment and prediction of the impact of MPC pollution on tropospheric chemistry are challenging. The present work provides an overview of the highlights of a major new contribution to the understanding of this issue based on the data and analysis of the EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) international project. EMeRGe focuses on atmospheric chemistry, dynamics, and transport of local and regional pollution originating in MPCs. Airborne measurements, taking advantage of the long range capabilities of the High Altitude and LOng Range Research Aircraft (HALO, https://www.halo-spp.de, last access: 22 March 2022), are a central part of the project. The synergistic use and consistent interpretation of observational data sets of different spatial and temporal resolution (e.g. from ground-based networks, airborne campaigns, and satellite measurements) supported by modelling within EMeRGe provide unique insight to test the current understanding of MPC pollution outflows. In order to obtain an adequate set of measurements at different spatial scales, two field experiments were positioned in time and space to contrast situations when the photochemical transformation of plumes emerging from MPCs is large. These experiments were conducted in summer 2017 over Europe and in the inter-monsoon period over Asia in spring 2018. The intensive observational periods (IOPs) involved HALO airborne measurements of ozone and its precursors, volatile organic compounds, aerosol particles, and related species as well as coordinated ground-based ancillary observations at different sites. Perfluorocarbon (PFC) tracer releases and model forecasts supported the flight planning, the identification of pollution plumes, and the analysis of chemical transformations during transport. This paper describes the experimental deployment and scientific questions of the IOP in Europe. The MPC targets – London (United Kingdom; UK), the Benelux/Ruhr area (Belgium, the Netherlands, Luxembourg and Germany), Paris (France), Rome and the Po Valley (Italy), and Madrid and Barcelona (Spain) – were investigated during seven HALO research flights with an aircraft base in Germany for a total of 53 flight hours. An in-flight comparison of HALO with the collaborating UK-airborne platform Facility for Airborne Atmospheric Measurements (FAAM) took place to assure accuracy and comparability of the instrumentation on board. Overall, EMeRGe unites measurements of near- and far-field emissions and hence deals with complex air masses of local and distant sources. Regional transport of several European MPC outflows was successfully identified and measured. Chemical processing of the MPC emissions was inferred from airborne observations of primary and secondary pollutants and the ratios between species having different chemical lifetimes. Photochemical processing of aerosol and secondary formation or organic acids was evident during the transport of MPC plumes. Urban plumes mix efficiently with natural sources as mineral dust and with biomass burning emissions from vegetation and forest fires. This confirms the importance of wildland fire emissions in Europe and indicates an important but discontinuous contribution to the European emission budget that might be of relevance in the design of efficient mitigation strategies. The present work provides an overview of the most salient results in the European context, with these being addressed in more detail within additional dedicated EMeRGe studies. The deployment and results obtained in Asia will be the subject of separate publications.
2022-06-17T11:19:20ZAndrés Hernández, Maria DoloresHilboll, AndreasZiereis, HelmutFörster, EricKrüger, Ovid O.Kaiser, KatharinaSchneider, JohannesBarnaba, FrancescaVrekoussis, MSicard, MichaëlMegacities and other major population centres (MPCs) worldwide are major sources of air pollution, both locally as well as downwind. The overall assessment and prediction of the impact of MPC pollution on tropospheric chemistry are challenging. The present work provides an overview of the highlights of a major new contribution to the understanding of this issue based on the data and analysis of the EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) international project. EMeRGe focuses on atmospheric chemistry, dynamics, and transport of local and regional pollution originating in MPCs. Airborne measurements, taking advantage of the long range capabilities of the High Altitude and LOng Range Research Aircraft (HALO, https://www.halo-spp.de, last access: 22 March 2022), are a central part of the project. The synergistic use and consistent interpretation of observational data sets of different spatial and temporal resolution (e.g. from ground-based networks, airborne campaigns, and satellite measurements) supported by modelling within EMeRGe provide unique insight to test the current understanding of MPC pollution outflows. In order to obtain an adequate set of measurements at different spatial scales, two field experiments were positioned in time and space to contrast situations when the photochemical transformation of plumes emerging from MPCs is large. These experiments were conducted in summer 2017 over Europe and in the inter-monsoon period over Asia in spring 2018. The intensive observational periods (IOPs) involved HALO airborne measurements of ozone and its precursors, volatile organic compounds, aerosol particles, and related species as well as coordinated ground-based ancillary observations at different sites. Perfluorocarbon (PFC) tracer releases and model forecasts supported the flight planning, the identification of pollution plumes, and the analysis of chemical transformations during transport. This paper describes the experimental deployment and scientific questions of the IOP in Europe. The MPC targets – London (United Kingdom; UK), the Benelux/Ruhr area (Belgium, the Netherlands, Luxembourg and Germany), Paris (France), Rome and the Po Valley (Italy), and Madrid and Barcelona (Spain) – were investigated during seven HALO research flights with an aircraft base in Germany for a total of 53 flight hours. An in-flight comparison of HALO with the collaborating UK-airborne platform Facility for Airborne Atmospheric Measurements (FAAM) took place to assure accuracy and comparability of the instrumentation on board. Overall, EMeRGe unites measurements of near- and far-field emissions and hence deals with complex air masses of local and distant sources. Regional transport of several European MPC outflows was successfully identified and measured. Chemical processing of the MPC emissions was inferred from airborne observations of primary and secondary pollutants and the ratios between species having different chemical lifetimes. Photochemical processing of aerosol and secondary formation or organic acids was evident during the transport of MPC plumes. Urban plumes mix efficiently with natural sources as mineral dust and with biomass burning emissions from vegetation and forest fires. This confirms the importance of wildland fire emissions in Europe and indicates an important but discontinuous contribution to the European emission budget that might be of relevance in the design of efficient mitigation strategies. The present work provides an overview of the most salient results in the European context, with these being addressed in more detail within additional dedicated EMeRGe studies. The deployment and results obtained in Asia will be the subject of separate publications.Architectures and synchronization techniques for distributed satellite systems: a surveyMartínez Marrero, LizMerlano-Duncan, Juan CarlosQuerol Borràs, JorgeKumar, SumitKrivochiza, JevgenijKrishna Sharma, ShreeChatzinotas, SymeonCamps Carmona, Adriano JoséOttersten, Björnhttp://hdl.handle.net/2117/3682112022-06-12T15:46:10Z2022-06-09T12:05:01ZArchitectures and synchronization techniques for distributed satellite systems: a survey
Martínez Marrero, Liz; Merlano-Duncan, Juan Carlos; Querol Borràs, Jorge; Kumar, Sumit; Krivochiza, Jevgenij; Krishna Sharma, Shree; Chatzinotas, Symeon; Camps Carmona, Adriano José; Ottersten, Björn
Cohesive Distributed Satellite Systems (CDSSs) is a key enabling technology for the future of remote sensing and communication missions. However, they have to meet strict synchronization requirements before their use is generalized. When clock or local oscillator signals are generated locally at each of the distributed nodes, achieving exact synchronization in absolute phase, frequency, and time is a complex problem. In addition, satellite systems have significant resource constraints, especially for small satellites, which are envisioned to be part of the future CDSSs. Thus, the development of precise, robust, and resource-efficient synchronization techniques is essential for the advancement of future CDSSs. In this context, this survey aims to summarize and categorize the most relevant results on synchronization techniques for Distributed Satellite Systems (DSSs). First, some important architecture and system concepts are defined. Then, the synchronization methods reported in the literature are reviewed and categorized. This article also provides an extensive list of applications and examples of synchronization techniques for DSSs in addition to the most significant advances in other operations closely related to synchronization, such as inter-satellite ranging and relative position. The survey also provides a discussion on emerging data-driven synchronization techniques based on Machine Learning (ML). Finally, a compilation of current research activities and potential research topics is proposed, identifying problems and open challenges that can be useful for researchers in the field.
2022-06-09T12:05:01ZMartínez Marrero, LizMerlano-Duncan, Juan CarlosQuerol Borràs, JorgeKumar, SumitKrivochiza, JevgenijKrishna Sharma, ShreeChatzinotas, SymeonCamps Carmona, Adriano JoséOttersten, BjörnCohesive Distributed Satellite Systems (CDSSs) is a key enabling technology for the future of remote sensing and communication missions. However, they have to meet strict synchronization requirements before their use is generalized. When clock or local oscillator signals are generated locally at each of the distributed nodes, achieving exact synchronization in absolute phase, frequency, and time is a complex problem. In addition, satellite systems have significant resource constraints, especially for small satellites, which are envisioned to be part of the future CDSSs. Thus, the development of precise, robust, and resource-efficient synchronization techniques is essential for the advancement of future CDSSs. In this context, this survey aims to summarize and categorize the most relevant results on synchronization techniques for Distributed Satellite Systems (DSSs). First, some important architecture and system concepts are defined. Then, the synchronization methods reported in the literature are reviewed and categorized. This article also provides an extensive list of applications and examples of synchronization techniques for DSSs in addition to the most significant advances in other operations closely related to synchronization, such as inter-satellite ranging and relative position. The survey also provides a discussion on emerging data-driven synchronization techniques based on Machine Learning (ML). Finally, a compilation of current research activities and potential research topics is proposed, identifying problems and open challenges that can be useful for researchers in the field.DNN-based PolSAR image classification on noisy labelsNi, JunXiang, DeliangLin, ZhiyuanLópez Martínez, CarlosHu, WeiZhang, Fanhttp://hdl.handle.net/2117/3682032022-06-12T15:46:52Z2022-06-09T10:03:59ZDNN-based PolSAR image classification on noisy labels
Ni, Jun; Xiang, Deliang; Lin, Zhiyuan; López Martínez, Carlos; Hu, Wei; Zhang, Fan
Deep neural networks (DNNs) appear to be a solution for the classification of polarimetric synthetic aperture radar (PolSAR) data in that they outperform classical supervised classifiers under the condition of sufficient training samples. The design of a classifier is challenging because DNNs can easily overfit due to limited remote sensing training samples and unavoidable noisy labels. In this article, a softmax loss strategy with antinoise capability, namely, the probability-aware sample grading strategy (PASGS), is developed to overcome this limitation. Combined with the proposed softmax loss strategy, two classical DNN-based classifiers are implemented to perform PolSAR image classification to demonstrate its effectiveness. In this framework, the difference distribution implicitly reflects the probability that a training sample is clean, and clean labels can be distinguished from noisy labels according to the method of probability statistics. Then, this probability is employed to reweight the corresponding loss of each training sample during the training process to locate the noisy data and to prevent participation in the loss calculation of the neural network. As the number of training iterations increases, the condition of the probability statistics of the noisy labels will be constantly adjusted without supervision, and the clean labels will eventually be identified to train the neural network. Experiments on three PolSAR datasets with two DNN-based methods also demonstrate that the proposed method is superior to state-of-the-art methods.
2022-06-09T10:03:59ZNi, JunXiang, DeliangLin, ZhiyuanLópez Martínez, CarlosHu, WeiZhang, FanDeep neural networks (DNNs) appear to be a solution for the classification of polarimetric synthetic aperture radar (PolSAR) data in that they outperform classical supervised classifiers under the condition of sufficient training samples. The design of a classifier is challenging because DNNs can easily overfit due to limited remote sensing training samples and unavoidable noisy labels. In this article, a softmax loss strategy with antinoise capability, namely, the probability-aware sample grading strategy (PASGS), is developed to overcome this limitation. Combined with the proposed softmax loss strategy, two classical DNN-based classifiers are implemented to perform PolSAR image classification to demonstrate its effectiveness. In this framework, the difference distribution implicitly reflects the probability that a training sample is clean, and clean labels can be distinguished from noisy labels according to the method of probability statistics. Then, this probability is employed to reweight the corresponding loss of each training sample during the training process to locate the noisy data and to prevent participation in the loss calculation of the neural network. As the number of training iterations increases, the condition of the probability statistics of the noisy labels will be constantly adjusted without supervision, and the clean labels will eventually be identified to train the neural network. Experiments on three PolSAR datasets with two DNN-based methods also demonstrate that the proposed method is superior to state-of-the-art methods.A preliminary study on ionospheric scintillation anomalies detected using GNSS-R data from NASA CYGNSS mission as possible earthquake precursorsMolina Ordóñez, CarlosBoudriki Semlali, Badr EddineHyuk, ParkCamps Carmona, Adriano Joséhttp://hdl.handle.net/2117/3682012023-10-29T03:09:05Z2022-06-09T09:23:06ZA preliminary study on ionospheric scintillation anomalies detected using GNSS-R data from NASA CYGNSS mission as possible earthquake precursors
Molina Ordóñez, Carlos; Boudriki Semlali, Badr Eddine; Hyuk, Park; Camps Carmona, Adriano José
Ionospheric perturbations affect the propagation of electromagnetic waves. These perturbations, besides being a problem for space communications, satellite navigation, and Earth observation techniques, could also be used as another Earth observation tool. Several recent studies showed correlations with earthquakes with ionospheric anomalies, but almost all of them use ground stations to measure the Total Electron Content (TEC) variations, and, in particular, the ones occurring after an earthquake. Here, a preliminary study is presented on how the ionospheric scintillation measured with GNSS-R instruments over oceanic regions shows a small, but detectable correlation with the occurrence of earthquakes, which in some cases occurs before the earthquakes. This study uses GNSS-R data from NASA CYGNSS Mission to measure the ionospheric amplitude scintillation (S4) for 6 months from March 2019 to August 2019, applying a statistical analysis based on confusion matrixes, and the Receiver Operating Characteristic (ROC) curves to correlate S4 anomalous variations to earthquakes. A small positive correlation is found between the ionospheric scintillation and the earthquakes during the six previous days. However, the study has some weakness because (a) a small number (~45) of large (M > 6) earthquakes over oceanic regions are studied, (b) the region studied is close to the geomagnetic equator, where ionospheric scintillations are usual, and (c) the overall correlation is small.
2022-06-09T09:23:06ZMolina Ordóñez, CarlosBoudriki Semlali, Badr EddineHyuk, ParkCamps Carmona, Adriano JoséIonospheric perturbations affect the propagation of electromagnetic waves. These perturbations, besides being a problem for space communications, satellite navigation, and Earth observation techniques, could also be used as another Earth observation tool. Several recent studies showed correlations with earthquakes with ionospheric anomalies, but almost all of them use ground stations to measure the Total Electron Content (TEC) variations, and, in particular, the ones occurring after an earthquake. Here, a preliminary study is presented on how the ionospheric scintillation measured with GNSS-R instruments over oceanic regions shows a small, but detectable correlation with the occurrence of earthquakes, which in some cases occurs before the earthquakes. This study uses GNSS-R data from NASA CYGNSS Mission to measure the ionospheric amplitude scintillation (S4) for 6 months from March 2019 to August 2019, applying a statistical analysis based on confusion matrixes, and the Receiver Operating Characteristic (ROC) curves to correlate S4 anomalous variations to earthquakes. A small positive correlation is found between the ionospheric scintillation and the earthquakes during the six previous days. However, the study has some weakness because (a) a small number (~45) of large (M > 6) earthquakes over oceanic regions are studied, (b) the region studied is close to the geomagnetic equator, where ionospheric scintillations are usual, and (c) the overall correlation is small.