Bandwidth and spectral stray light effects in the NASA GSFC Radiometric Calibration Facility primary transfer radiometer

Barnes, Robert A.; Cooper, J.; Marketon, John; Brown, Steven W.; Johnson, B. Carol; Butler, James J.

doi:10.1117/12.679493

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…We have chosen to derive a nominal ORCA slit function based on existing single-grating spectrometers 27,28 , rather than to use a simple mathematical shape such as a Gaussian curve. A Gaussian curve can represent the specular reflectance from a grating at the grating's scattering angle, but it cannot represent the haze of imperfectly scattered light from the grating at the same angle 28 .…”

Section: Wavelength Calibration Using Atmospheric Absorption Featuresmentioning

confidence: 99%

“…It is the function for one of the regular pixels in the ORCA red spectrometer. It is based on a slit function from the NASA GSFC Radiometric Calibration Facility (RCF) primary transfer radiometer 27 , which has a FWHM of 10 nm. The FWHM for the RCF slit function was converted to 5.6 nm by modifying the wavelength spacing of the function in Fig.…”

Section: Wavelength Calibration Using Atmospheric Absorption Featuresmentioning

confidence: 99%

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Modeling spectral effects in Earth-observing satellite instruments

Barnes

Butler

2007

SPIE Proceedings

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We present a simple, spreadsheet-based model to examine the effects of the spectral response functions of individual instrument bands on their measurements of top-of-the-atmosphere radiances. The model uses spectral radiances at 1 nm resolution from the near ultraviolet to the shortwave infrared at wavelengths from 300 nm to 2500 nm, convolving them with the spectral responses of the bands to calculate band-average spectral radiances. For on-orbit calibration purposes, the model uses nominal solar irradiance and lunar albedo spectra to provide saturation, diffuser, and lunar radiances for the bands. For prelaunch calibration purposes, the model uses a 2850K Planck function, normalized to a maximum value of unity, to approximate the spectral shape from a laboratory integrating sphere source. For Earth-exiting radiances, the model uses nominal radiance spectra over a blue ocean, a desert, and a grassland. These spectra are provided with the effects of atmospheric trace gas absorption removed. In addition, the model includes a trace gas transmittance spectrum that can be modified as a function of airmass. Currently, a spectrum with an airmass of 2.4 is used. In the model, this transmittance spectrum is combined with the three Earth-exiting radiance spectra to provide top-of-theatmosphere radiance spectra both with and without trace gas absorption features.Here we use the model to investigate three types of spectral response features. The first study involves the out-of-band response from one of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) bands. Using the model, we demonstrate a technique to correct for the effect of that response on measurements of Earth-exiting radiances. The second study shows the effect of in-band spectral differences in an instrument band with multiple detectors. In this example, the effects are small, but differ with the type of Earth scene and with the amount of atmospheric trace gas absorption. On-orbit corrections for portions these detector-to-detector spectral differences are possible. However, at some level these differences will cause a residual striping in the band's measurements that cannot be removed. The final study examines measurements by a proposed multispectral grating-based spectrometer of the wavelength region near 760 nm, where there is a substantial absorption feature from atmospheric oxygen. Based on the bandwidth and wavelength spacing of the instrument's bands, we investigate the use of the absorption feature to provide a wavelength calibration for the instrument.This model provides a tool for use in the design of new satellite instruments. In addition, it is possible to use the model to help mitigate the effects of actual spectral response features in instrument bands after those features are revealed during prelaunch characterization.

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Section: Wavelength Calibration Using Atmospheric Absorption Featuresmentioning

confidence: 99%

Section: Wavelength Calibration Using Atmospheric Absorption Featuresmentioning

confidence: 99%

Modeling spectral effects in Earth-observing satellite instruments

Barnes

Butler

2007

SPIE Proceedings

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GSFC Calibration Laboratory capabilities and future plans overview

Kelley,

McCorkel,

Wanzek

et al. 2023

Earth Observing Systems XXVIII

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The NASA GSFC Code 618 Calibration Laboratory maintains instruments and National Institute of Standards and Technology (NIST) traceable calibrated sources and detectors to calibrate, characterize, and monitor remote sensing instrumentation throughout NASA and the larger scientific community. Under the Calibration Laboratory umbrella, we operate the Radiometric Calibration Lab (RCL) focused on calibrating instrument radiometers, the Diffuser Calibration Lab (DCL) specializing in NIST traceable calibration of reflective and transmissive space diffusers.The RCL uses broadband sources as well as an array of options for monochromatic spectral calibration to provide regular NIST traceable calibration services to ground, flight, and remote sensing missions at NASA GSFC. The DCL uses scatterometers to measure the Bidirectional Reflectance and Transmittance Distribution Functions (BRDF & BTDF) of flight diffusers and witness samples.As we look to the future, the Calibration Laboratory will be automating routine processes throughout the facility and updating our online data collection and distribution capabilities. We are adding monitoring radiometers to our Grande calibration sphere to improve NIST traceability. Hardware updates to our scatterometers will keep us aligned with the diffuser calibration capabilities being developed at NIST.

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Bandwidth and spectral stray light effects in the NASA GSFC Radiometric Calibration Facility primary transfer radiometer

Cited by 2 publications

References 5 publications

Modeling spectral effects in Earth-observing satellite instruments

Modeling spectral effects in Earth-observing satellite instruments

GSFC Calibration Laboratory capabilities and future plans overview

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