• Beginning calibration planning in the early stages of sensor design: Promotes an optimum sensor calibration approach Reduces costs and expenditures Minimizes uncertainty for the intended application • Experienced calibration personnel must be involved throughout the sensor’s development phase to optimize calibration e orts • Planning should address calibration throughout the lifetime of the sensor Data management and analysis should be considered in the planning process · Today’s sensors produce large amounts of data

/pdf/guidelines-for-radiometric-calibration-of-electro-optical-25zsr20xdt.pdf

Guidelines for Radiometric Calibration of Electro-Optical Instruments for Remote Sensing

Analysis of visible remote sensing data research requires removing atmospheric effects by conversion from radiance to at-surface reflectance. This conversion can be achieved through theoretical radiative transfer models, which yield good results when well constrained by field observations, although these measurements are often lacking. Additionally, radiative transfer models often perform poorly in marine or lacustrine settings or when complex air masses with variable aerosols are present. The empirical line method (ELM) measures reference targets of known reflectance in the scene. ELM methods require minimal environmental observations and are conceptually simple. However, calibration coefficients are unique to the image containing the reflectance reference. Here we compare the conversion of hyperspectral radiance observations obtained with the NASA Glenn Research Center Hyperspectral Imager to at-surface reflectance factor using two reflectance reference targets. The first target employs spherical convex mirrors, deployed on the water surface to reflect ambient direct solar and hemispherical sky irradiance to the sensor. We calculate the mirror gain using near concurrent at-sensor reflectance, integrated mirror radiance, and in situ water reflectance. The second target is the Lambertian-like blacktop surface at Maumee Bay State Park, Oregon, OH, where reflectance was measured concurrently by a downward looking, spectroradiometer on the ground, the aerial hyperspectral imager and an upward looking spectroradiometer on the aircraft. These methods allows us to produce an independently calibrated at-surface water reflectance spectrum, when atmospheric conditions are consistent. We compare the mirror and blacktop-corrected spectra to the in situ water reflectance, and find good agreement between methods. The blacktop method can be applied to all scenes, while the mirror calibration method, based on direct observation of the light illuminating the scene validates the results. The two methods are complementary and a powerful evaluation of the quality of atmospheric correction over extended areas. We decompose the resulting spectra using varimax-rotated, principal component analysis, yielding information about the underlying color producing agents that contribute to the observed reflectance factor scene, identifying several spectrally and spatially distinct mixtures of algae, cyanobacteria, illite, haematite and goethite. These results have implications for future hyperspectral remote sensing missions, such as PACE, HyspIRI, and GeoCAPE.

/pdf/intercomparison-of-approaches-to-the-empirical-line-method-2zznte6qtk.pdf

Intercomparison of Approaches to the Empirical Line Method for Vicarious Hyperspectral Reflectance Calibration

A method and a system for vicarious characterization of a remote sensing sensor are described. The system includes a plurality of reflective mirrors configured and arranged to reflect radiation from a source of radiation onto a remotely located radiation sensor. The plurality of mirrors are spaced apart so as to obtain a plurality of distinct spot images on the remotely located radiation sensor. The system further includes a processor configured to analyze the plurality of spot images by fitting the images to obtain a point spread function of the remote sensing sensor.

Method and system for vicarious spatial characterization of a remote image sensor

This paper describes a design concept for a Landsat-class imaging spectrometer. The challenge is to match the
Landsat data parameters, including a 185 Km swath and a 30 meter ground sample distance (GSD) from a 705 Km
sun-synchronous orbit with a sensor that has contiguous spectral coverage of the solar reflected spectrum (400 to
2500 nm). The result is a remote sensing satellite that provides global access imaging spectrometer data at moderate
spatial resolution. Key design trades exist for the spectrometer, focal plane array, dispersive element, and calibrator.
Recent developments in large format imaging spectrometers at Raytheon are presented in support of a monolithic
spectrometer approach. Features of the design include (1) high signal-to-noise ratio, (2) well-corrected spectral
fidelity across a 6,000 pixel push-broom field-of-view, (3) straightforward calibration of the data to units of absolute
spectral radiance, and (4) real-time simulation of Thematic Mapper bands, vegetation indices, and water vapor maps
for direct continuous downlink.

Large format imaging spectrometers for future hyperspectral Landsat mission

A method and a system for spectral calibration of a remote sensing sensor and a synthetic target having a tunable spectral composition are described. The system or synthetic target includes a plurality of reflective mirrors arranged to reflect radiation from a source of radiation onto a remotely located radiation sensor. A first mirror in the plurality of mirrors is configured to reflect a first portion of the radiation in a first wavelength toward the remotely located radiation sensor. A second mirror in the plurality of mirrors is configured to reflect a second portion of the radiation in a second wavelength different from the first wavelength toward the remotely located radiation sensor. The first portion of the radiation and the second portion of the radiation can be selected to calibrate the remotely located radiation sensor so as to provide a quantitative spectral relationship between the radiation detected at the remotely located sensor and the radiation reflected by the plurality of mirrors.

Method and system for spectral calibration of a remote sensing sensor and a synthetic target having a tunable spectral composition

Physics-based exploitation of image data from Earth observing sensors requires knowledge of the accuracy, stability and
repeatability of a sensor's radiometric response within its in-flight environment. Vicarious radiometric calibration
techniques, using terrestrial targets, provide an effective approach to obtaining this knowledge by measuring system
performance under actual operational conditions. This paper introduces a new capability for performing the vicarious
radiometric calibration of high spatial resolution sensors. The SPecular Array Radiometric Calibration (SPARC) method
employs convex mirrors to create two arrays of calibration targets for deriving absolute calibration coefficients of Earth
remote sensing systems in the solar reflective spectrum. The first is an array of single mirrors used to oversample the
sensor's point spread function (PSF) providing necessary spatial quality information needed to perform the radiometric
calibration of a sensor when viewing small targets. The second is a set of panels consisting of multiple mirrors designed
to stimulate detector response with known at-sensor irradiance traceable to the exo-atmospheric solar spectral constant.
The outcome is improved radiometric performance knowledge compared to other in-flight vicarious techniques through
reduced uncertainties in target reflectance, atmospheric effects, and temporal variability. The only ground truth needed is
the measurement of atmospheric transmittance. In addition, the simplification of calibration targets and ground truth
collection in the SPARC method makes the deployment more cost effective and portable, thus creating the opportunity
to imbed spectral, spatial and radiometric targets at a study site providing references that improve a sensor's interactivity
as a phenomenological tool. A demonstration of the SPARC method is presented based on data collected with the
IKONOS satellite operated by GeoEye. A SPARC measurement of absolute calibration coefficients for the IKONOS
multispectral bands is compared to coefficients derived from the established reflectance-based vicarious calibration
method.

The Specular Array Radiometric Calibration (SPARC) method: a new approach for absolute vicarious calibration in the solar reflective spectrum

On-Orbit Calibration and Focus of Responsive Space Remote Sensing Payloads

/pdf/comprehensive-vicarious-calibration-and-characterization-of-j3b3udb3cs.pdf

Comprehensive Vicarious Calibration and Characterization of a Small Satellite Constellation Using the Specular Array Radiometric Calibration (SPARC) Method

https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1255&context=calcon

Using Vicarious Calibration to Evaluate Small Target Radiometry

/pdf/the-specular-array-radiometric-calibration-sparc-technique-p3btx6ed55.pdf

Stephen Schiller

Papers

The Specular Array Radiometric Calibration (SPARC) method: a new approach for absolute vicarious calibration in the solar reflective spectrum

On-Orbit Calibration and Focus of Responsive Space Remote Sensing Payloads

Comprehensive Vicarious Calibration and Characterization of a Small Satellite Constellation Using the Specular Array Radiometric Calibration (SPARC) Method

Using Vicarious Calibration to Evaluate Small Target Radiometry

The Specular Array Radiometric Calibration (SPARC) Technique As A Vicarious Methodology For Accurate Inter-Sensor Calibration