Calibration of a three‐component angular distribution model of sky radiance

Coombes, Charles A.; Harrison, A. W.

doi:10.1080/07055900.1988.9649298

Cited by 5 publications

(3 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…No values were provided by the manufacturer in this study, but these values are typical for manufacturers (e.g., Sea-Bird Scientific HyperOCR radiometer [37]). The isotropic sky is a simplification and clear-sky radiance distributions are not isotropic and normally show larger radiances for large zenith angles (e.g., [38]) and band circumsolar brightening (aureole) [39]. For measurements presented here with SZA approximatetly 24 • the aureole effect is minimised by the small errors in cosine response of the diffuser for small incidence angles (see Figure 8).…”

Section: Stray Light Correction (C Stray )mentioning

confidence: 95%

Example of Monte Carlo Method Uncertainty Evaluation for Above-Water Ocean Colour Radiometry

et al. 2020

View full text Add to dashboard Cite

We describe a method to evaluate an uncertainly budget for the in situ Ocean Colour Radiometric measurements. A Monte Carlo approach is chosen to propagate the measurement uncertainty inputs through the measurements model. The measurement model is designed to address instrument characteristics and uncertainty associated with them. We present the results for a particular example when the radiometers were fully characterised and then use the same data to show a case when such characterisation is missing. This, depending on the measurement and the wavelength, can increase the uncertainty value significantly; for example, the downwelling irradiance at 442.5 nm with fully characterised instruments can reach uncertainty values of 1%, but for the instruments without such characterisation, that value could increase to almost 7%. The uncertainty values presented in this paper are not final, as some of the environmental contributors were not fully evaluated. The main conclusion of this work are the significance of thoughtful instrument characterisation and correction for the most significant uncertainty contributions in order to achieve a lower measurements uncertainty value.Remote Sens. 2020, 12, 780 2 of 28 of hyperspectral sensors in situ, some aspects of this work need to be repeated. Particularly since significant differences (up to 25%) are found when compared to theoretical modelling and conventional multispectral instruments [15]. It seems that the well known and well characterised multispectral instruments that are described in the NASA protocols are not utilised as much nowadays, as the world focuses on hyperspectal instruments, which provide greater spectral information. However, generally, they are less well characterised but require a wider array of characterisation tests (e.g., spectral stray light). Similarly with the new generation of Ocean Colour sensors like the Sentinel 3 series [16] and planned PACE [17] mission there is a need for even better quality measurements. The old Ocean Colour accuracy requirements, set at 5%, are now being pushed to achieve a level of 3%. In order to achieve this very ambitious target we need to better understand the individual uncertainty components that effect ocean colour measurements as well as their contribution to the final products.The Fiducial Reference Measurements for Satellite Ocean Colour (FRM4SOC) project, with funding from ESA, aimed to provide support for evaluating and improving the state of the art in satellite ocean colour validation through a series of comparisons under the auspices of the Committee on Earth Observation Satellites (CEOS). The project makes a fundamental contribution to the European system for monitoring the Earth (Copernicus) by ensuring high quality ground-based Fiducial Reference Measurements (FRM) for ocean colour radiometry for use in validation of ocean colour products from missions like Sentinel-3 Ocean Colour and Land Imager (OLCI) [16] and Sentinel-2 Multi Spectral Imager (MSI) [18]. The main aim of FRM4SOC is to establish and mainta...

show abstract

Section: Stray Light Correction (C Stray )mentioning

confidence: 95%

Example of Monte Carlo Method Uncertainty Evaluation for Above-Water Ocean Colour Radiometry

et al. 2020

View full text Add to dashboard Cite

show abstract

“…The value of z btm has been varied between 50 and 200 m. The value adopted for z sns is 14 m, which corresponds to the depth of the sensor that is mostly affected by bottom reflectance. The Harrison-Coombes model has been employed for the sky radiance [46,47]. The values of total irradiance and the diffuse-to-direct irradiance ratio have been determined according to [48].…”

Section: Existing Infrastructuresmentioning

confidence: 99%

“…Raman scattering [33] has been neglected because it only accounts for a second-order contribution. Examples of optical profiles for a black and sandy bottom are presented in Figure 6 for water depths of 50 m and 200 m. The Harrison-Coombes model has been employed for the sky radiance [46,47]. The values of total irradiance and the diffuse-to-direct irradiance ratio have been determined according to [48].…”

Section: Existing Infrastructuresmentioning

confidence: 99%

European Radiometry Buoy and Infrastructure (EURYBIA): A Contribution to the Design of the European Copernicus Infrastructure for Ocean Colour System Vicarious Calibration

Liberti

D’Alimonte²,

Sarra

et al. 2020

Remote Sensing

View full text Add to dashboard Cite

In the context of the Copernicus Program, EUMETSAT prioritizes the creation of an ocean color infrastructure for system vicarious calibration (OC-SVC). This work aims to reply to this need by proposing the European Radiometry Buoy and Infrastructure (EURYBIA). EURYBIA is designed as an autonomous European infrastructure operating within the Marine Optical Network (MarONet) established by University of Miami (Miami, FL, USA) based on the Marine Optical Buoy (MOBY) experience and NASA support. MarONet addresses SVC requirements in different sites, consistently and in a traceable way. The selected EURYBIA installation is close to the Lampedusa Island in the central Mediterranean Sea. This area is widely studied and hosts an Atmospheric and Oceanographic Observatory for long-term climate monitoring. The EURYBIA field segment comprises off-shore and on-shore infrastructures to manage the observation system and perform routine sensors calibrations. The ground segment includes the telemetry center for data communication and the processing center to compute data products and uncertainty budgets. The study shows that the overall uncertainty of EURYBIA SVC gains computed for the Sentinel-3 OLCI mission under EUMETSAT protocols is of about 0.05% in the blue-green wavelengths after a decade of measurements, similar to that of the reference site in Hawaii and in compliance with requirements for climate studies.

show abstract