New Radcalnet Site at Gobabeb, Namibia: Installation of the Instrumentation and First Satellite Calibration Results

Marcq, Sébastien; Meygret, Aimé; Bouvet, Marc; Fox, Nigel; Greenwell, Claire; Scott, Barry; Berthelot, Béatrice; Besson, B.; Guilleminot, Nicolas; Damiri, Bahaiddin

doi:10.1109/igarss.2018.8517716

Cited by 16 publications

(10 citation statements)

References 4 publications

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“…The surface reflectance in the viewing direction of Sentinel-2 acquisition is estimated using ROSAS acquisitions for the whole day and the TOA reflectance is simulated with a radiative transfer code (6S) with the atmospheric parameters measured simultaneously with the satellite overpass. More recently, ESA and CNES have set up a system equivalent to ROSAS in Gobabeb, Namibia, presented in Marcq et al (2018). Use is made of both sites in this work.…”

Section: Calibration Based On Instrumented Sitesmentioning

confidence: 99%

Sentinel-2A and 2B absolute calibration monitoring

Revel

Lonjou

Marcq

et al. 2019

European Journal of Remote Sensing

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As part of the Copernicus program, Sentinel-2 is the optical imaging mission designed for the operational monitoring of land and coastal areas. It offers a unique combination of global coverage with a wide field of view, a high revisit capability (5 days with two satellites), a high resolution and multi-spectral imagery.CNES, the French Space Agency, was involved in the commissioning of both Sentinel-2 satellites and is currently working in collaboration with ESA on their long-term monitoring. This paper reviews all the techniques used to ensure an absolute calibration of the 13 spectral bands to better than 5% (the target is 3%) at TOA level. After a brief description of the mission and its related radiometric calibration scheme, we show how standard vicarious calibration methods based on acquisitions over natural targets (oceans, deserts, and Antarctica during winter) are used to check and improve the accuracy of the absolute calibration coefficients. Finally, the verification scheme, exploiting photometer in-situ measurements over the La Crau plain in France and Gobabeb in Namibia, is described. The paper concludes with a summary that includes spectral coherence, agreement between the results obtained with various calibration methods and temporal evolution. ARTICLE HISTORY

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Section: Calibration Based On Instrumented Sitesmentioning

confidence: 99%

Sentinel-2A and 2B absolute calibration monitoring

Revel

Lonjou

Marcq

et al. 2019

European Journal of Remote Sensing

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“…The modeled nadir TOA hyperspectral reflectances are simulated using the moderate-resolution atmospheric transmission (MODTRAN-5) RTM and, after spectral resampling considering the sensors' RSRFs, these serve as a direct "REF" to compare the satellite-measured TOA signal with. It is important to highlight here that although BRDF measurements are performed at the sites, the RadCalNet portal only gives access to the nadir surface reflectance measurements and the corresponding nadir TOA reflectance simulations [21].…”

Section: Radcalnetmentioning

confidence: 99%

Radiometric Top-of-Atmosphere Reflectance Consistency Assessment for Landsat 8/OLI, Sentinel-2/MSI, PROBA-V, and DEIMOS-1 over Libya-4 and RadCalNet Calibration Sites

Sterckx

Wolters

2019

Remote Sensing

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There is a clear trend toward the use of higher spatial resolution satellite sensors. Due to the low revisit time of these sensors and frequent cloud coverage, many applications require data from different sensors to be combined in order to have more frequent observations. This raises concerns regarding data interoperability and consistency. The initial pre-requisite is that there are no radiometric differences in top-of-atmosphere (TOA) observations. This paper aims to quantitatively assess differences in the TOA signal provided by PROBA-V, Sentinel-2A and Sentinel-2B, Landsat-8, and Deimos-1 by using observations over both the Libya-4 desert calibration site and the RadCalNet sites. The results obtained over the Libya-4 site indicate that for all sensors investigated, the inter-sensor deviations are negligible, i.e., within ±2% for comparable spectral bands, with the exception of the Deimos-1 Green band. Clear BRDF (bi-directional reflectance distribution function) effects were observed over the RadCalNet sites, thereby preventing consistent conclusions on inter-sensor deviations from being made. In order to fully explore the potential of the RadCalNet sites, it is recommended that BRDF characterizations be additionally incorporated into the RadCalNet simulations and made publicly available through the distribution portal.

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“…• cross-calibration with other sensors such as MERIS or Sentinel-2 with acquisitions over desert sites [10]; • cross-calibration with Sentinel-2 using Simultaneous Nadir Observations (SNO) [8,9]; • absolute calibration and temporal monitoring thanks to Moon images [9,11]; • absolute calibration with instrumented sites (Gobabeb in Namibia) [12]; • absolute calibration based on the Rayleigh scattering and ocean acquisitions [13].…”

Section: • Absolute Calibrationmentioning

confidence: 99%

VENμS: Mission Characteristics, Final Evaluation of the First Phase and Data Production

et al. 2022

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VENμS (Vegetation and Environment New micro (μ) Satellite) is a micro satellite launched in 2017 by the Israeli Space Agency (ISA) and the French Centre National d’Etudes Spatiales (CNES). VENμS is a research satellite containing two very different devices: an electric Hall effect thruster and a multispectral optical camera. This paper focuses on the multispectral camera. The camera provides images at a resolution of 5 m, with a field of view of 27 km, and the orbit of the satellite was chosen to allow us to revisit of each observed site with constant angles every second day. In November 2020, VENμS ended the first phase of its mission. This phase, called VM01, allowed us to provide about 150 accurate time series over selected scientific sites over almost three years. Extensive work was conducted to calibrate the camera and assess the quality of the products. Not everything worked as planned before launch and a large amount of work was necessary to correct some defects of the camera or to improve the geometric registration of images. This article establishes the image quality VM01 final assessment including the presentation of radiometric and geometric calibration methods, the estimation of instrument performances and their associated temporal stabilities and the monitoring activities. In addition, it highlights the whole mechanism of data programming, reception and production. The end of VM01 phase is not the end of the VENμS mission, and a new phase started on a one-day repeat orbit.

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New Radcalnet Site at Gobabeb, Namibia: Installation of the Instrumentation and First Satellite Calibration Results

Cited by 16 publications

References 4 publications

Sentinel-2A and 2B absolute calibration monitoring

Sentinel-2A and 2B absolute calibration monitoring

Radiometric Top-of-Atmosphere Reflectance Consistency Assessment for Landsat 8/OLI, Sentinel-2/MSI, PROBA-V, and DEIMOS-1 over Libya-4 and RadCalNet Calibration Sites

VENμS: Mission Characteristics, Final Evaluation of the First Phase and Data Production

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