Kenneth J. Voss

• Ph.D. Physics, Texas A&M, 1984
• Professor Emeritus at University of Miami

System Vicarious Calibration (SVC) enhances the accuracy of satellite ocean color radiometric data products by removing the bias due to the intrinsic inaccuracies affecting both the responsivity of the space sensor and the correction for the atmospheric and sea surface contributions to the measured signal. Various SVC procedures have been implement...

PixPol is an in-water multi-spectral polarized upwelling radiance distribution fisheye camera system. Its imaging sensors utilize a pixel-level polarizer structure allowing for polarimetric retrieval from one image capture, offering an advantage compared to other in-water polarimetric fisheye camera systems that require information from multiple im...

The effect of a linear polarizer is conventionally well defined when viewed along the axis normal to its face. However, even for ideal linear polarizers, the non-normal viewing geometries attainable with wide-angle lenses require further considerations. A method to describe the polarization state of light passed through a linear polarizer and obser...

The effect of a linear polarizer is conventionally well defined when viewed along the axis normal to its face. However, even for ideal linear polarizers, the non-normal viewing geometries attainable with wide-angle lenses require further considerations. A method to describe the polarization state of light passed through a linear polarizer and obser...

The effect of a linear polarizer is conventionally well defined when viewed along the axis normal to its face. However, even for ideal linear polarizers, the non-normal viewing geometries attainable with wide-angle lenses require further considerations. A method to describe the polarization state of light passed through a linear polarizer and obser...

The collection of independent in situ field measurements of ocean and atmospheric parameters is a crucial element of passive environmental satellite calibration and validation (hereafter cal/val). Despite multigenerational efforts by scientists, engineers, and the crew aboard research and commercial vessels (see Chapter 11), it remains a daunting c...

A global in situ data set for validation of ocean colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI) is presented. This version of the compilation, starting in 1997, now extends to 2021, which is important for the validation of the most recent satellite optical sensors such as Sentinel 3B OLCI and NOAA-20 VIIRS. The data s...

Ocean color satellites measure the color of the ocean, allowing for the retrieval of optical, biological, and biogeochemical properties of waters. However, satellite ocean color products must be validated with field measurements to ensure their fidelity and suitability for environmental and climate applications. This work details satellite ocean co...

A global in-situ data set for validation of ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI) is presented. This version of the compilation, starting in 1997, now extends to 2021, which is important for the validation of the most recent satellite optical sensors such as Sentinel 3B OLCI and NOAA-20 VIIRS. The data s...

A 3-D instrument self-shading correction has been developed for the MOBY upwelling radiance measurements. This correction was tested using the 23 year time series of MOBY measurements, at the Lanai, Hawaii site. The correction is small (less than 2%) except when the sun and collectors are aligned within 20° azimuth on opposite sides of the main MOB...

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...

A methodology is developed for deriving consistent ocean biological and biogeochemical products from multiple satellite ocean color sensors that have slightly different sensor spectral characteristics. Specifically, the required coefficients for algorithm modifications are obtained using the hyperspectral in situ optical measurements from the Marin...

Ocean colour is recognised as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS); and spectrally-resolved water-leaving radiances (or remote-sensing reflectances) in the visible domain, and chlorophyll-a concentration are identified as required ECV products. Time series of the products at the global scale and at high...

This paper reviews the state of the art of protocols for measurement of waterleaving radiance in the context of fiducial reference measurements (FRM) of water reflectance for satellite validation. Measurement of water reflectance requires the measurement of waterleaving radiance and downwelling irradiance just above water. For the former there are...

This paper reviews the state of the art of protocols for the measurement of downwelling irradiance in the context of Fiducial Reference Measurements (FRM) of water reflectance for satellite validation. The measurement of water reflectance requires the measurement of water-leaving radiance and downwelling irradiance just above water. For the latter,...

A global compilation of in situ data is useful to evaluate the quality of ocean-colour satellite data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (including, inter alia, MOBY, BOUSSOLE, AERONET-OC...

Global downwelling plane irradiance is a necessary variable to normalize water-leaving radiance measurements, reducing the magnitude and spectral variabilities introduced by the incident light field. As a result, the normalized measurements, known as remote sensing reflectance, have higher correlation with the inherent optical properties of the wat...

A global compilation of in situ data is useful to evaluate the quality of ocean-colour satellite data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (including, inter alia, MOBY, BOUSSOLE, AERONET-OC...

The upwelling spectral radiance distribution is polarized, and this polarization varies with the optical properties of the water body. Knowledge of the polarized, upwelling, bidirectional radiance distribution function (BRDF) is important for generating consistent, long-term data records for ocean color because the satellite sensors from which the...

The optical depths and sizes of optically thin passive shallow cumuli are characterized with a micropulse lidar. The measurements are from a coastal south Florida location spanning a 10-week synoptically suppressed winter time period with almost no upper-level clouds present. Clouds are distinguished from aerosol through visual comparison to zenith...

We present the uncertainty budget for the plaque method on the estimation of downwelling plane irradiance for normalization of the water-leaving radiance (remote sensing reflectance). The error sources are: BRDF effects, shadow effects and tilt effects. Field comparisons with irradiance sensors are also presented.

We challenge a recent paper in this journal suggesting that the well-established formula governing the transmittance of radiance across a refracting interface needs revision [Optics Express, 25(22) 27086 (2017)]. We provide a simple example of radiative transfer across an interface showing that the accepted formula is correct.

The spectral resolution requirements for in situ remote sensing reflectance measurements aiming at supporting satellite ocean color validation and System Vicarious Calibration (SVC) were investigated. The study, conducted using sample hyperspectral from different water types, focused on the visible spectral bands of the ocean land color imager (OLC...

The immersion coefficient accounts for the difference in responsivity for a radiometer placed in the air versus water or another medium. In this study, the immersion coefficients for the radiance collectors on the Marine Optical Buoy (MOBY) were modeled and measured. The experiment showed that the immersion coefficient for the MOBY radiance collect...

The transmission coefficient TL commonly used to propagate the upwelling nadir radiance from just below the ocean surface to above the surface has been assumed to be a constant value of 0.543 in seawater. Because the index of refraction of seawater varies with wavelength, salinity, and temperature, the variation of TL with these parameters should b...

The upwelling radiance attenuation coefficient KLu in the upper 10 m of the water column can be significantly influenced by inelastic scattering processes and thus will vary even with homogeneous water properties. The Marine Optical Buoy (MOBY), the primary vicarious calibration site for many ocean color sensors, makes measurements of the upwelling...

The standard method to convert the measured water-leaving radiances from the observation direction to the nadir direction developed by Morel and coworkers requires knowledge of the chlorophyll concentration (CHL). Also, the standard method was developed for open ocean water, which makes it unsuitable for turbid coastal waters. We introduce a neural...

Optical closure is assessed between measured and simulated remote-sensing reflectance () using Hydrolight radiative transfer code for five data sets that included a broad range of both Case I and Case II water types. Model-input inherent optical properties (IOPs) were the absorption coefficient determined with a WET Labs ac9 and the volume scatteri...

The polarization of the irradiance from several 1000 W FEL lamps was measured between 450 and 900 nm. These lamps are universally used as irradiance calibration standards in radiometric laboratories. The irradiance was polarized between 2.3% and 3.2%, with the polarization axis aligned with the coiled filament, nearly perpendicular to the lamp axis...

The near-infrared (NIR) and shortwave infrared (SWIR)-based atmospheric correction algorithms are used in satellite ocean color data processing, with the SWIR-based algorithm particularly useful for turbid coastal and inland waters. In this study, we describe the NIR- and two SWIR-based on-orbit vicarious calibration approaches for satellite ocean...

A compiled set of in situ data is important to evaluate the quality of ocean-colour satellite-data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (MOBY, BOUSSOLE, AERONET-OC, SeaBASS, NOMAD, MERMAID,...

A compiled set of in situ data is important to evaluate the quality of ocean-olour satellite data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (MOBY, BOUSSOLE, AERONET-OC, SeaBASS, NOMAD, MERMAID,...

Ocean color algorithms that rely on “atmospherically corrected” nadir water-leaving radiances to infer information about marine constituents such as the chlorophyll concentration depend on a reliable method to convert the angle-dependent measured radiances from the observation direction to the nadir direction. It is also important to convert the me...

A technique for monitoring and evaluating the performance of on-orbit calibration for satellite ocean color sensors has been developed. The method is based on the sensor on-orbit vicarious calibration approach using in situ ocean optics measurements and radiative transfer simulations to predict (calculate) sensor-measured top-of-atmosphere spectral...

System Vicarious Calibration (SVC) ensures a relative radiometric calibration to satellite ocean color sensors that minimizes uncertainties in the water-leaving radiance Lw derived from the top of atmosphere radiance LT. This is achieved through the application of gain-factors, g-factors, to pre-launch absolute radiometric calibration coefficients...

Hyperspectral (every 5 nm) absorption coefficients of “pure” seawater in the range of 350–550 nm are derived from remote sensing reflectance measured in oligotrophic oceans. The absorption spectrum is reduced by for the 350–400-nm range and for the 510–530-nm range compared with the commonly adopted standard for ocean color processing and shows dif...

Comprehensive field measurement programs supporting satellite ocean color missions are essential for the generation of data products with the traceability, accuracy, and consistency required for climate-change investigations. Within such a context, in situ optical radiometry plays a fundamental role in system vicarious calibration, validation of da...

Satellite ocean color missions devoted to climate change investigations require in situ optical radiometry data of exceptional traceability, accuracy, long-term stability and cross-site consistency for the vicarious calibration of the space system, the assessment of the satellite derived water-leaving radiance, and the development of algorithms for...

Light scattering by size-resolved aerosols in near-surface air at Tudor Hill, Bermuda, was measured between January and June 2009. Vertical distributions of aerosol backscattering and column-averaged aerosol optical properties were characterized in parallel with a micro-pulse lidar (MPL) and an automated sun–sky radiometer. Comparisons were made be...

Two reflectance techniques, based on Kubelka-Munk (K-M) theory and on the Beer-Lambert (B-L) law, were used to measure the absorption coefficient of aerosol particles collected on a filter. The two methods agreed, with the B-L technique being higher than the K-M method by a factor of 1.10, but with a correlation, r(2), between the two methods of 0....

Dichotomous aerosols (nominal super- and sub-μm-diameter size fractions) in sectored on-shore flow were sampled daily from July 2006 through June 2009, at the Tudor Hill Atmospheric Observatory (THAO) on the western coast of Bermuda (32.27° N, 64.87° W) and analyzed for major chemical and physical properties. FLEXPART retroplumes were calculated fo...

Light scattering and spectral absorption by size-resolved aerosols in near-surface air at Tudor Hill, Bermuda were measured continuously between January and June 2009. Vertical distributions of aerosol backscattering and column-averaged aerosol optical properties were characterized in parallel with a Micro-pulse lidar (MPL) and an automated sun-sky...

of the primary goals for the Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi National Polar-orbiting Partnership is to provide the science and user communities with the data continuity of the Environmental Data Records (EDR) (or Level-2 products) over global oceanic waters for various research and applications, including assess...

Dichotomous aerosols (nominal super- and sub-μm-diameter size fractions) in sectored on-shore flow were sampled daily from July 2006 through June 2009, at the Tudor Hill Atmospheric Observatory (THAO) on the western coast of Bermuda (32.27° N, 64.87° W) and analyzed for major chemical and physical properties. Flexpart retroplumes were calculated fo...

A new instrument for measuring the full radiance distribution in the ocean interior is introduced. The system is based on CMOS technology to achieve intra-scene dynamic range of 6 decades and system dynamic range of more than 9 decades. The spatial resolution is nominally 0.5 degrees with a temporal frame rate between 1 and 15 frames per second. Th...

Optical variability occurs in the near-surface and upper ocean on very short time and space scales (e.g., milliseconds and millimeters and less) as well as greater scales. This variability is caused by solar, meteorological, and other physical forcing as well as biological and chemical processes that affect optical properties and their distribution...

Simulated bidirectional reflectance distribution functions (BRDF) were compared with measurements made just beneath the water’s surface. In Case I water, the set of simulations that varied the particle scattering phase function depending on chlorophyll concentration agreed more closely with the data than other models. In Case II water, however, the...

The uncertainties associated with MERIS remote sensing reflectance (RRS) data derived from the SeaWiFS Data Analysis System (SeaDAS) are assessed with field observations. In agreement with the strategy applied for other sensors, a vicarious calibration is conducted using in situ data from the Marine Optical BuoY offshore Hawaii, and leads to vicari...

Substantial effort has been invested by NASA to create and maintain a long-term, consistent, and calibrated time series of ocean color radiometry over multiple missions and satellite sensors. This is a very difficult measurement problem because the water-leaving radiance is a small fraction of the total radiance measured by the satellite sensor. As...

As part of the Radiance in a Dynamic Ocean (RaDyO) program, we have developed a numerical model for efficiently simulating the polarized light field under highly dynamic ocean surfaces. Combining the advantages of the three-dimensional Monte Carlo and matrix operator methods, this hybrid model has proven to be computationally effective for simulati...

We have built a new camera system to measure the downwelling polarized radiance distribution in the ocean. This system uses 4 fisheye lenses and coherent fiber bundles behind each image to transmit all 4 fisheye images onto a single camera image. This allows simultaneous images to be collected with 4 unique polarization states, and thus the full St...

Within the Radiance in a Dynamic Ocean (RaDyO) program, we have created and deployed a high dynamic range camera that can resolve the full spherical radiance distribution at the ocean surface and at depth. We present here the first results from deployments of the camera in near-surface water in eutrophic, mesotropic, and oligotropic environments. T...

The spectral polarized radiance distribution provides the most complete description of the light field that can be measured. However, this is a very difficult parameter to measure, particularly near the surface, because of its large dynamic range, changes in the skylight illumination, and waves at the air-sea interface. To measure the Stokes vector...

We study the polarization properties of the light field under a dynamic ocean surface using realistic linear and nonlinear ocean surface waves. The three-dimensional polarized radiative transfer of the dynamic ocean-atmosphere system is considered using a Monte Carlo vector radiative transfer simulation for arbitrary depth. The program is validated...

Remote-sensing reflectance ( R rs ), which is defined as the ratio of water-leaving radiance ( L w ) to downwelling irradiance just above the surface ( E d ( 0 + ) ), varies with both water constituents (including bottom properties of optically-shallow waters) and angular geometry. L w is commonly measured in the field or by satellite sensors at co...

Light drives the physics, chemistry, and biology of the ocean. Without light in the ocean, life on Earth could not exist, nor would there be fuel for the heat engine that drives the ocean's currents and the atmosphere's circulation. Furthermore, light and sound are the two primary means available for probing the ocean. (See the article by Tom Sanfo...

The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. Over 80 cruises were completed through early 2010 with deployments continuing. Measurement areas included various parts of the Atlantic Ocean, the Northern and Southern Pacific Ocean, the South Indian Ocean, the Southern Ocean, the Arctic Ocean and inla...

The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. Over 80 cruises were completed through early 2010 with deployments continuing. Measurements areas included various parts of the Atlantic Ocean, the Northern and Southern Pacific Ocean, the South Indian Ocean, the Southern Ocean, the Arctic Ocean and inl...

Neutral points are specific directions in the light field where the three Stokes parameters Q, U, V, and thus the degree of polarization simultaneously go to zero. We have made the first measurement of non-principal-plane neutral points in the upwelling light field in natural waters. These neutral points are located at approximately 40°- 80° nadir...

We demonstrate that the diffraction removal procedure outlined by Hapke et al. [Icarus, 199, 210 (2009)] contains an error. By following their intended scheme we found that the Hapke model is not anisotropic enough to describe the reflectance patterns.

The spectral polarized radiance distribution provides the most complete description of the light field that can be measured. However, this is a very difficult parameter to measure near the surface because of its large dynamic range, changes in the sky, and waves at the air-sea interface. To measure the Stokes vector of the light field, which descri...

Vicarious calibration of ocean color satellites involves the use of accurate surface measurements of waterleaving radiance to update and improve the system calibration of ocean color satellite sensors. An experiment was performed to compare a free-fall technique with the established Marine Optical Buoy (MOBY) measurement. It was found in the labora...

While the upwelling radiance distribution in the ocean can be highly polarized, there are few measurements of this parameter in the open ocean. To obtain the polarized in-water upwelling spectral radiance distribution data we have developed the POLRADS instrument. This instrument is based on the NuRADS radiance distribution camera systems in which...

Since the early 1980s, with the onset of missions for global mapping of marine biomass, accurate in-situ radiometric data has become a pressing need to support satellite ocean color applications. This work presents a brief introduction to in-situ marine optical radiometry through an overview of absolute calibration, measurement methods, uncertainti...

A spectral matching algorithm (SMA) that allows atmospheric correction in the presence of dust aerosols is applied to SeaWiFS imagery in the northwest Mediterranean Sea. The goal is to find criteria that could be used to identify SMA target pixels and to gain insights into the method's accuracy relative to the standard SeaWiFS processing scheme (ST...

We made continuous measurements of size segregated aerosol light scattering (with a nephelometer and absorption (using filterpad absorption) at the surface at Tudor Hill, Bermuda between January and June 2009. Along with these measurements we have a Micro-pulse lidar (MPL, operated by MPLnet) and a CIMEL automated sun-sky radiometer, operated by AE...

A methodology is proposed to infer the altitude of aerosol plumes over the ocean from reflectance ratio measurements in the O2 absorption A-band (759 to 770 nm). The reflectance ratio is defined as the ratio of the reflectance in a first spectral band, strongly attenuated by O2 absorption, and the reflectance in a second spectral band, minimally at...

Hyperspectral profiles of downwelling irradiance and upwelling radiance in natural waters (oligotrophic and mesotrophic) are combined with inverse radiative transfer to obtain high resolution spectra of the absorption coefficient (a) and the backscattering coefficient (bb ) of the water and its constituents. The absorption coefficient at the mesotr...

Laboratory bidirectional reflectance and polarization measurements were carried out on packed layers of both natural sediments and manufactured spherical particles. The results indicate that among the natural sediments showing a strong backscattering peak (“hotspot”), the rough platelets are the only sediments with a branch of negative polarization...

Coastal waters (Case 2) are generally more optically complex than oceanic waters and contain much higher quantities of colored detrital matter (CDM, a combination of dissolved organic matter and detrital particulates) as well as suspended sediment. Exclusion of CDM in the retrieval can lead to an overestimation of chlorophyll a concentration (C). W...

My work involves experimentally investigating the interrelationships and variability of optical properties in the ocean and atmosphere. My goal is to define the variability of the optical properties, particularly those dealing with light scattering, and to improve the prediction capabilities of image and radiative transfer models used in the ocean....

Many long term records of atmospheric optical and chemical properties are based on near-surface measurements. Interpreting and extending climatologies of near-surface observations in the context of column-averaged properties such as aerosol optical depth (e.g., the AERONET network) requires information concerning the structure and distribution of a...

The optical properties of aerosols have a large influence on the radiation balance, particularly over low reflectance surfaces such as the ocean. Understanding the absorption characteristics of the aerosols is also important for atmospheric correction of ocean color satellites. Islands, such as Bermuda, provide useful platforms from which to measur...

The physiochemical processing and radiative influences of aerosols over the western North Atlantic Ocean (NAO) during spring 2007 were evaluated based on an integrated analysis of in-situ and remotely sensed aerosol characteristics and modeled transport. Super- and sub-μm-diameter size fractions were sampled daily at Bermuda and analyzed for elemen...

One of the most general ways to quantify the surface reflectance of a medium is by use of the bi-directional reflectance distribution function (BRDF) (Hapke, 1993). The BRDF gives the reflectance of a surface as a function of illumination geometry and viewing geometry and is required in many scientific and engineering disciplines. For example, in s...

We are investigating the measurable features in the BRDF (Bi-directional Reflectance Distribution Function) of benthic surfaces made of natural sediments and how that is influenced by the morphology of the sediment grain composition. If the measured BRDF shows features which can be numerically derived from the physical properties such as size and s...

Data from recent campaigns conducted in the tropical Atlantic and Indian Oceans provide thorough testbeds for determining the contribution of clouds, aerosols, and water vapor to surface radiative forcing, with particular focus on areas of extreme SST gradients. Oceanographic cruises conducted during the African Monsoon Multidisciplinary Analysis i...

Survey protocols for monitoring the composition and status of coral reef benthic communities vary in the level of detail acquired, but fundamentally follow one of two approaches: 1) a diver identifies organisms in the field, 2) an analyst identifies organisms from underwater imagery (photos or video). Both methods are highly labor intensive and req...

Determination of the water-leaving spectral radiance using in-water instrumentation requires measurements of the upwelling spectral radiance (Lu) at several depths. If these measurements are separated in time, changes in the measurement conditions result in increased variance in the results. A prototype simultaneous multi-track system was developed...

The Visible/Infrared Imager/Radiometer Suite (VIIRS) collects visible/infrared imagery and radiometric data. The radiometric requirements are such that the instrument's polarization sensitivity must be very well understood. This paper presents the ZEMAX and FORTRAN polarization ray trace models of the instrument's visible light path. This will incl...

We have made bi-directional reflectance distribution function (BRDF) measurements on particulate layers wetted by absorbing liquids. The measurement results indicate that the BRDF tends to become more Lambertian as the interstitial pore liquid becomes more absorbing. The directional hemispherical reflectance, or albedo, of such a layer decreases no...

The radiance viewed from the ocean depends on the illumination and viewing geometry along with the water properties, and this variation is called the bidirectional effect. This bidirectional effect depends on the inherent optical properties of the water, including the volume scattering function, and is important when comparing data from different s...

We performed extensive bidirectional reflectance measurements on dry, wet, and submerged particulate layers with various albedos to investigate the darkening effect caused by wetting with fluids. It was found that, in addition to the reduction of the refractive index contrast when there is a pore liquid (wetted), the concentration of translucent gr...