Climatology of oceanic zones suitable for in-flight calibration of space sensors

Fougnie, Bertrand; Llido, J.; Gross-Colzy, Lydwine; Henry, Patrice; Blumstein, Denis

doi:10.1117/12.859828

Cited by 15 publications

(11 citation statements)

References 1 publication

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“…Figure 1 shows the flowchart for the Rayleigh scattering method for VIIRS. The area of interests of this study are the six oceanic sites identified by Fougnie et al [11,12] that are suitable for radiometric calibration using the Rayleigh scattering method. These sits are spatially homogeneous, with low chlorophyll-a content, variability, and seasonality.…”

Section: Methodsmentioning

confidence: 99%

“…Chlorophyll-a climatology (mg/m3) minLat maxLat minLon maxLon Table 1 Oceanic sites for Rayleigh scattering vicarious calibration identified by Fougnie et al [11,12] and climatology of chlorophylla concentration for each site.…”

Section: Geolocation (Degree)mentioning

confidence: 99%

“…Fougnie et al [9] and Hagolle et al [10] absolutely calibrated the POLarization of Directionality of the Earth Reflectances (POLDER) visible bands over Rayleigh scattering. Fougnie et al [11,12] improved the method by identifying and characterizing stable and homogeneous oceanic sites using SeaWiFS ocean color products. Visible channels of the HRVIR and VEGETATION cameras aboard of SPOT4 were calibrated using the Rayleigh scattering method by [7].…”

Section: Introductionmentioning

confidence: 99%

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Monitoring the VIIRS ocean color band calibration using the Rayleigh scattering method

Wang¹,

Cao

2014

SPIE Proceedings

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Post-launch monitoring of radiometric accuracy and stability of VIIRS (Visible Infrared Imaging Radiometer Suite) Solar Reflective Bands (RSB) at high gain stage (HGS) is essential for ocean color applications. This study investigates the absolute radiometric calibration accuracy of VIIRS bands M1-M5 at HGS using selected clear-sky dark ocean surfaces where top of atmosphere (TOA) signal is dominated by Rayleigh scattering. Vicarious gains were estimated using ratios between satellite observed and radiative transfer model simulated TOA reflectance. VIIRS TOA reflectance was simulated using 6SV (Second Simulation of a Satellite Signal in the Solar Spectrum -Vector, version 1.1). Input parameters required by the 6SV, including atmospheric profiles, wind speed and direction, aerosol optical thickness, and chlorophyll-a concentration, were obtained from the NASA Modern-Era Retrospective Analysis for Research and Applications reanalysis products, VIIRS aerosol optical thickness product, and previous studies. The Rayleigh scattering method developed in this study was applied to June to August 2014 VIIRS observations over six oceanic sites. Preliminary results indicated that the 3-month averaged vicarious gain for bands M1, M2, and M5 are close to 1. Relatively larger vicarious gains were observed in the other two bands, especially in band M4. The Rayleigh scattering calibration results generally agree with results from the VIIRS deep convective clouds time series analysis.

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Section: Methodsmentioning

confidence: 99%

Section: Geolocation (Degree)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Monitoring the VIIRS ocean color band calibration using the Rayleigh scattering method

Wang¹,

Cao

2014

SPIE Proceedings

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“…From a statistical study based on analyzing several years of SeaWiFS and MODIS data, Fougnie et al (2002Fougnie et al ( , 2010 identified 6 major oceanic regions suitable for radiometric calibration using Rayleigh scattering. These regions, defined in Table 1, are located within the main subtropical gyres.…”

Section: Pre-defined Calibration Sitesmentioning

confidence: 99%

Operational in-flight calibration of S-NPP VIIRS in the visible using Rayleigh scattering

Frouin

Sei

Hauss³

et al. 2014

SPIE Proceedings

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The Rayleigh scattering approach to absolute radiometric calibration of satellite optical sensors is investigated for S-NPP VIIRS. The vicarious calibration coefficients are obtained by comparing measured and predicted top-ofatmosphere (TOA) reflectance sampled under "favorable" scene conditions, i.e., oceanic areas with stable water optical properties, where situations of clear sky, low wind speed, and low aerosol content are frequent. In such situations, and under suitable geometry, the dominant contribution to the satellite signal in the visible is due to molecular (Rayleigh) scattering, which can be computed accurately. A sensitivity study performed for suitable calibration sites indicates that, using thresholds of 7 m/s for wind speed, 0.1 for aerosol optical thickness, 0.0005 for Sun glint reflectance, and 60 o for Sun and view zenith angles, the error on the TOA reflectance is 2.3% at 410.5 nm (M1), increasing to 4.5% at 671.4 nm (M5). The error budget is dominated by the effect of uncertainty on aerosol optical thickness at the longer wavelengths and on marine reflectance at the shorter wavelengths. Two methods are developed to compute the VIIRS reflectance. The first method (Method 1) consists in using for the region of interest environmental conditions obtained from ancillary data or climatology. The second method (Method 2) addresses the uncertainty in aerosol model and optical thickness by accounting for the aerosol content of the scene. Application of Method 1 to VIIRS data yields calibration coefficients that are site and air mass dependent, which is not satisfactory. This results from using climatology data to specify aerosol parameters. Method 2, which utilizes the measured VIIRS reflectance in the near infrared to estimate the aerosol reflectance, reduces substantially the site and angular geometry dependence of the calibration coefficients. Accuracy can be improved by better specifying the marine reflectance, estimating the aerosol model, and further stratifying the calibration data. The large number of realizations allows for absolute calibration of individual detectors, studies of angular dependence, linearity, and polarization sensitivity, which is not possible using vicarious techniques based on (too few) in situ measurements.

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“…The images for Rayleigh scattering calibration should follow the conditions [17] including: (a) case I waters for reducing the total reflection of seawater; (b) clean atmosphere for reducing aerosol scattering; and (c) large solar zenith angle for enhancing atmospheric molecules scattering. According to these conditions, we chose the case I water, which contains little chlorophyll in both spatial and temporal dimensions [32,33]. Figure 3 shows the September-October 2015 mean global distribution map of oceanic chlorophyll.…”

Section: Principles and Proceduresmentioning

confidence: 99%

In-Flight Calibration of GF-1/WFV Visible Channels Using Rayleigh Scattering

et al. 2017

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Abstract:China is planning to launch more and more optical remote-sensing satellites with high spatial resolution and multistep gains. Field calibration, the current operational method of satellite in-flight radiometric calibration, still does not have enough capacity to meet these demands. Gaofen-1 (GF-1), as the first satellite of the Chinese High-resolution Earth Observation System, has been specially arranged to obtain 22 images over clean ocean areas using the Wide Field Viewing camera. Following this, Rayleigh scattering calibration was carried out for the visible channels with these images after the appropriate data processing steps. To guarantee a high calibration precision, uncertainty was analyzed in advance taking into account ozone, aerosol optical depth (AOD), seawater salinity, chlorophyll concentration, wind speed and solar zenith angle. AOD and wind speed were found to be the biggest error sources, which were also closely coupled to the solar zenith angle. Therefore, the best sample data for Rayleigh scattering calibration were selected at the following solar zenith angle of 19-22 • and wind speed of 5-13 m/s to reduce the reflection contributed by the water surface. The total Rayleigh scattering calibration uncertainties of visible bands are 2.44% (blue), 3.86% (green), and 4.63% (red) respectively. Compared with the recent field calibration results, the errors are −1.69% (blue), 1.83% (green), and −0.79% (red). Therefore, the Rayleigh scattering calibration can become an operational in-flight calibration method for the high spatial resolution satellites.

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Climatology of oceanic zones suitable for in-flight calibration of space sensors

Cited by 15 publications

References 1 publication

Monitoring the VIIRS ocean color band calibration using the Rayleigh scattering method

Monitoring the VIIRS ocean color band calibration using the Rayleigh scattering method

Operational in-flight calibration of S-NPP VIIRS in the visible using Rayleigh scattering

In-Flight Calibration of GF-1/WFV Visible Channels Using Rayleigh Scattering

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