The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Alexander Timofeevsky - One of the best experts on this subject based on the ideXlab platform.
-
THz Photometers for solar flare observations from space
Experimental Astronomy, 2014Co-Authors: Pierre Kaufmann, Rogério Marcon, André Abrantes, Emilio C. Bortolucci, Luis Olavo T. Fernandes, Grigory I. Kropotov, Amauri S. Kudaka, Adolfo Marun, Valery Nikolaev, Claudemir S. da Silva, Alexandre Silva, Nelson Machado, Alexander TimofeevskyAbstract:The search for the still unrevealed spectral shape of the mysterious THz solar flare emissions is one of the current most challenging research issues. The concept, fabrication and performance of a double THz photometer system, named SOLAR-T, is presented. Its innovative optical setup allows observations of the full solar disk and the detection of small burst transients at the same time. The detecting system was constructed to observe solar flare THz emissions on board of stratospheric balloons. The system has been integrated to data acquisition and telemetry modules for this application. SOLAR-T uses two Golay cell detectors preceded by low-pass filters made of rough surface primary mirrors and membranes, 3 and 7 THz band-pass filters, and choppers. Its Photometers can detect small solar bursts (tens of solar flux units) with sub second time resolution. Tests have been conducted to confirm the entire system performance, on ambient and low pressure and temperature conditions. An artificial Sun setup was developed to simulate performance on actual observations. The experiment is planned to be on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014–2016.
-
the performance of thz Photometers for solar flare observations from space
SBMO MTT-S International Microwave and Optoelectronics Conference, 2013Co-Authors: Pierre Kaufmann, Rogério Marcon, André Abrantes, Emilio C. Bortolucci, Luis Olavo T. Fernandes, Amauri S. Kudaka, Nelio Machado, C M Da Silva, V Nicolaev, Alexander TimofeevskyAbstract:The performance of the double THz Photometers system is presented. It is the first detection device conceived to observed solar flare THz emissions on board of stratospheric balloons. The system, named SOLAR-T, has been built, integrated to data acquisition and telemetry modules developed for this application, and tested. It utilizes two Golay cell detectors preceded by low-pass filters, 3 and 7 THz band-pass filters, and choppers. SOLAR-T Photometers can detect relative temperature variations smaller than 1 K with sub second time resolution. It is intended to determine the still unrevealed spectral shape of the mysterious THz solar flares emissions. The experiment is planned to fly on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014-2016.
C. Deroo - One of the best experts on this subject based on the ideXlab platform.
-
Detection and characterization of volcanic ash plumes over Lille during the Eyjafjallajökull eruption
Atmospheric Chemistry and Physics, 2013Co-Authors: Anneleen Mortier, T. Podvin, C. Deroo, N. Ajtai, Alan Chaikovsky, Luc Blarel, Philippe Goloub, Didier Tanré, Y. DerimianAbstract:Routine sun-photometer and micro-lidar measure-ments were performed in Lille, northern France, in April and May 2010 during the Eyjafjallajökull volcanic erup-tion. The impact of such an eruption emphasized significance of hazards for human activities and importance of observa-tions of the volcanic aerosol particles. This paper presents the main results of a joint micro-lidar/sun-photometer anal-ysis performed in Lille, where volcanic ash plumes were observed during at least 22 days, whenever weather condi-tions permitted. Aerosol properties retrieved from automatic sun-photometer measurements (AERONET) were strongly changed during the volcanic aerosol plumes transport over Lille. In most cases, the aerosol optical depth (AOD) in-creased, wherea Angström exponent decreased, thus indi-cating coarse-mode dominance in the volume size distri-bution. Moreover, the non-spherical fraction retrieved by AERONET significantly increased. The real part of the com-plex refractive index was up to 1.55 at 440 nm during the eruption, compared to background data of about 1.46 be-fore the eruption. Collocated lidar data revealed that several aerosol layers were present between 2 and 5 km, all origi-nating from the Iceland region as confirmed by backward trajectories. The volcanic ash AOD was derived from lidar extinction profiles and sun-photometer AOD, and its maxi-mum was estimated around 0.37 at 532 nm on 18 April 2010. This value was observed at an altitude of 1700 m and corre-sponds to an ash mass concentration (AMC) slightly higher than 1000 µg m −3 (±50 %). An effective lidar ratio of ash particles of 48 sr was retrieved at 532 nm for 17 April dur-ing the early stages of the eruption, a value which agrees with several other studies carried out on this topic. Even though the accuracy of the retrievals is not as high as that obtained from reference multiwavelength lidar systems, this study demonstrates the opportunity of micro-lidar and sun-photometer joint data processing for deriving volcanic AMC. It also outlines the fact that a network of combined micro-lidars and sun Photometers can be a powerful tool for routine monitoring of aerosols, especially in the case of such haz-ardous volcanic events.
-
Impact of the mixing boundary layer on the relationship between PM2.5 and aerosol optical thickness
Atmospheric Environment, 2010Co-Authors: Neda Boyouk, Jean-françois Leon, T. Podvin, Hervé Delbarre, C. DerooAbstract:The purpose of this paper is to study the relationship between columnar aerosol optical thickness and ground-level aerosol mass. A set of Sun photometer, elastic backscattering lidar and TEOM measurements were acquired during April 2007 in Lille, France. The PM2.5 in the mixed boundary layer is estimated using the lidar signal, aerosol optical thickness, or columnar integrated Sun photometer size distribution and compared to the ground-level station measurements. The lidar signal recorded in the lowest level (240 m) is well correlated to the PM2.5 (R2 = 0.84). We also show that the correlation between AOT-derived and measured PM2.5 is significantly improved when considering the mixed boundary layer height derived from the lidar. The use of the Sun photometer aerosol fine fraction volume does not improve the correlation. © 2009 Elsevier Ltd. All rights reserved.
T. Podvin - One of the best experts on this subject based on the ideXlab platform.
-
measurements on pointing error and field of view of cimel 318 sun Photometers in the scope of aeronet
Atmospheric Measurement Techniques, 2013Co-Authors: Benjamin Torres, Philippe Goloub, Alberto Berjon, C Toledano, V E Cachorro, David Fuertes, V Molina, Ramiro Gonzalez, Marius Canini, T. PodvinAbstract:Abstract. Sensitivity studies indicate that among the diverse error sources of ground-based sky radiometer observations, the pointing error plays an important role in the correct retrieval of aerosol properties. The accurate pointing is specially critical for the characterization of desert dust aerosol. The present work relies on the analysis of two new measurement procedures (cross and matrix) specifically designed for the evaluation of the pointing error in the standard instrument of the Aerosol Robotic Network (AERONET), the Cimel CE-318 Sun photometer. The first part of the analysis contains a preliminary study whose results conclude on the need of a Sun movement correction for an accurate evaluation of the pointing error from both new measurements. Once this correction is applied, both measurements show equivalent results with differences under 0.01° in the pointing error estimations. The second part of the analysis includes the incorporation of the cross procedure in the AERONET routine measurement protocol in order to monitor the pointing error in field instruments. The pointing error was evaluated using the data collected for more than a year, in 7 Sun Photometers belonging to AERONET sites. The registered pointing error values were generally smaller than 0.1°, though in some instruments values up to 0.3° have been observed. Moreover, the pointing error analysis shows that this measurement can be useful to detect mechanical problems in the robots or dirtiness in the 4-quadrant detector used to track the Sun. Specifically, these mechanical faults can be detected due to the stable behavior of the values over time and vs. the solar zenith angle. Finally, the matrix procedure can be used to derive the value of the solid view angle of the instruments. The methodology has been implemented and applied for the characterization of 5 Sun Photometers. To validate the method, a comparison with solid angles obtained from the vicarious calibration method was developed. The differences between both techniques are below 3%.
-
characterization of temperature sensitivity of sun Photometers by field comparison with a reference instrument
Journal of Aerosol Science, 2013Co-Authors: Alberto Berjon, T. Podvin, Luc Blarel, Philippe Goloub, Benjamin Torres, C Toledano, N Prats, V E CachorroAbstract:Abstract The temperature sensitivity of sun Photometers is mainly caused by the temperature dependency of detectors and filters. For the 1020 nm channel of the photometer CIMEL-318 the relative change in signal due to temperature is about 2.50E−3 °C −1 . For other channels, this dependency is significantly lower. However, the uncertainty of the temperature coefficient, about 5.0E−4 °C −1 , is a limitation to the improvement of the data quality. So as to get a better data quality, AERONET has begun to thermally characterize the response of each photometer by means of laboratory measurements in a thermally controlled chamber. In this work, we study the possibility of carrying out the thermal characterization of Photometers, by comparison with a previously characterized sun photometer. Our goal is to develop a temperature correction method for checking temperature dependency of field Photometers with no additional cost, using the measurements already performed during the radiometric calibration process. Furthermore, this method could be also used to obtain the temperature coefficients for archived data, for example, on Photometers that were physically modified (filter or detector replaced).
-
Detection and characterization of volcanic ash plumes over Lille during the Eyjafjallajökull eruption
Atmospheric Chemistry and Physics, 2013Co-Authors: Anneleen Mortier, T. Podvin, C. Deroo, N. Ajtai, Alan Chaikovsky, Luc Blarel, Philippe Goloub, Didier Tanré, Y. DerimianAbstract:Routine sun-photometer and micro-lidar measure-ments were performed in Lille, northern France, in April and May 2010 during the Eyjafjallajökull volcanic erup-tion. The impact of such an eruption emphasized significance of hazards for human activities and importance of observa-tions of the volcanic aerosol particles. This paper presents the main results of a joint micro-lidar/sun-photometer anal-ysis performed in Lille, where volcanic ash plumes were observed during at least 22 days, whenever weather condi-tions permitted. Aerosol properties retrieved from automatic sun-photometer measurements (AERONET) were strongly changed during the volcanic aerosol plumes transport over Lille. In most cases, the aerosol optical depth (AOD) in-creased, wherea Angström exponent decreased, thus indi-cating coarse-mode dominance in the volume size distri-bution. Moreover, the non-spherical fraction retrieved by AERONET significantly increased. The real part of the com-plex refractive index was up to 1.55 at 440 nm during the eruption, compared to background data of about 1.46 be-fore the eruption. Collocated lidar data revealed that several aerosol layers were present between 2 and 5 km, all origi-nating from the Iceland region as confirmed by backward trajectories. The volcanic ash AOD was derived from lidar extinction profiles and sun-photometer AOD, and its maxi-mum was estimated around 0.37 at 532 nm on 18 April 2010. This value was observed at an altitude of 1700 m and corre-sponds to an ash mass concentration (AMC) slightly higher than 1000 µg m −3 (±50 %). An effective lidar ratio of ash particles of 48 sr was retrieved at 532 nm for 17 April dur-ing the early stages of the eruption, a value which agrees with several other studies carried out on this topic. Even though the accuracy of the retrievals is not as high as that obtained from reference multiwavelength lidar systems, this study demonstrates the opportunity of micro-lidar and sun-photometer joint data processing for deriving volcanic AMC. It also outlines the fact that a network of combined micro-lidars and sun Photometers can be a powerful tool for routine monitoring of aerosols, especially in the case of such haz-ardous volcanic events.
-
Impact of the mixing boundary layer on the relationship between PM2.5 and aerosol optical thickness
Atmospheric Environment, 2010Co-Authors: Neda Boyouk, Jean-françois Leon, T. Podvin, Hervé Delbarre, C. DerooAbstract:The purpose of this paper is to study the relationship between columnar aerosol optical thickness and ground-level aerosol mass. A set of Sun photometer, elastic backscattering lidar and TEOM measurements were acquired during April 2007 in Lille, France. The PM2.5 in the mixed boundary layer is estimated using the lidar signal, aerosol optical thickness, or columnar integrated Sun photometer size distribution and compared to the ground-level station measurements. The lidar signal recorded in the lowest level (240 m) is well correlated to the PM2.5 (R2 = 0.84). We also show that the correlation between AOT-derived and measured PM2.5 is significantly improved when considering the mixed boundary layer height derived from the lidar. The use of the Sun photometer aerosol fine fraction volume does not improve the correlation. © 2009 Elsevier Ltd. All rights reserved.
Pierre Kaufmann - One of the best experts on this subject based on the ideXlab platform.
-
THz Photometers for solar flare observations from space
Experimental Astronomy, 2014Co-Authors: Pierre Kaufmann, Rogério Marcon, André Abrantes, Emilio C. Bortolucci, Luis Olavo T. Fernandes, Grigory I. Kropotov, Amauri S. Kudaka, Adolfo Marun, Valery Nikolaev, Claudemir S. da Silva, Alexandre Silva, Nelson Machado, Alexander TimofeevskyAbstract:The search for the still unrevealed spectral shape of the mysterious THz solar flare emissions is one of the current most challenging research issues. The concept, fabrication and performance of a double THz photometer system, named SOLAR-T, is presented. Its innovative optical setup allows observations of the full solar disk and the detection of small burst transients at the same time. The detecting system was constructed to observe solar flare THz emissions on board of stratospheric balloons. The system has been integrated to data acquisition and telemetry modules for this application. SOLAR-T uses two Golay cell detectors preceded by low-pass filters made of rough surface primary mirrors and membranes, 3 and 7 THz band-pass filters, and choppers. Its Photometers can detect small solar bursts (tens of solar flux units) with sub second time resolution. Tests have been conducted to confirm the entire system performance, on ambient and low pressure and temperature conditions. An artificial Sun setup was developed to simulate performance on actual observations. The experiment is planned to be on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014–2016.
-
the performance of thz Photometers for solar flare observations from space
SBMO MTT-S International Microwave and Optoelectronics Conference, 2013Co-Authors: Pierre Kaufmann, Rogério Marcon, André Abrantes, Emilio C. Bortolucci, Luis Olavo T. Fernandes, Amauri S. Kudaka, Nelio Machado, C M Da Silva, V Nicolaev, Alexander TimofeevskyAbstract:The performance of the double THz Photometers system is presented. It is the first detection device conceived to observed solar flare THz emissions on board of stratospheric balloons. The system, named SOLAR-T, has been built, integrated to data acquisition and telemetry modules developed for this application, and tested. It utilizes two Golay cell detectors preceded by low-pass filters, 3 and 7 THz band-pass filters, and choppers. SOLAR-T Photometers can detect relative temperature variations smaller than 1 K with sub second time resolution. It is intended to determine the still unrevealed spectral shape of the mysterious THz solar flares emissions. The experiment is planned to fly on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014-2016.
André Abrantes - One of the best experts on this subject based on the ideXlab platform.
-
THz Photometers for solar flare observations from space
Experimental Astronomy, 2014Co-Authors: Pierre Kaufmann, Rogério Marcon, André Abrantes, Emilio C. Bortolucci, Luis Olavo T. Fernandes, Grigory I. Kropotov, Amauri S. Kudaka, Adolfo Marun, Valery Nikolaev, Claudemir S. da Silva, Alexandre Silva, Nelson Machado, Alexander TimofeevskyAbstract:The search for the still unrevealed spectral shape of the mysterious THz solar flare emissions is one of the current most challenging research issues. The concept, fabrication and performance of a double THz photometer system, named SOLAR-T, is presented. Its innovative optical setup allows observations of the full solar disk and the detection of small burst transients at the same time. The detecting system was constructed to observe solar flare THz emissions on board of stratospheric balloons. The system has been integrated to data acquisition and telemetry modules for this application. SOLAR-T uses two Golay cell detectors preceded by low-pass filters made of rough surface primary mirrors and membranes, 3 and 7 THz band-pass filters, and choppers. Its Photometers can detect small solar bursts (tens of solar flux units) with sub second time resolution. Tests have been conducted to confirm the entire system performance, on ambient and low pressure and temperature conditions. An artificial Sun setup was developed to simulate performance on actual observations. The experiment is planned to be on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014–2016.
-
the performance of thz Photometers for solar flare observations from space
SBMO MTT-S International Microwave and Optoelectronics Conference, 2013Co-Authors: Pierre Kaufmann, Rogério Marcon, André Abrantes, Emilio C. Bortolucci, Luis Olavo T. Fernandes, Amauri S. Kudaka, Nelio Machado, C M Da Silva, V Nicolaev, Alexander TimofeevskyAbstract:The performance of the double THz Photometers system is presented. It is the first detection device conceived to observed solar flare THz emissions on board of stratospheric balloons. The system, named SOLAR-T, has been built, integrated to data acquisition and telemetry modules developed for this application, and tested. It utilizes two Golay cell detectors preceded by low-pass filters, 3 and 7 THz band-pass filters, and choppers. SOLAR-T Photometers can detect relative temperature variations smaller than 1 K with sub second time resolution. It is intended to determine the still unrevealed spectral shape of the mysterious THz solar flares emissions. The experiment is planned to fly on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014-2016.
