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Search Publications by: B. Carol Johnson (Fed)

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Displaying 51 - 75 of 178

Hyperspectral Image Projector for Advanced Sensor Characterization

December 4, 2006
Author(s)
Steven W. Brown, Joseph P. Rice, Jorge E. Neira, Bettye C. Johnson
In this work, we describe radiometric platforms able to produce realistic spectral distributions and spatial scenes for the development of application-specific metrics to quantify the performance of sensors and systems. Using these platforms, sensor and

Spectrally Tunable Sources for Advanced Radiometric Applications

October 1, 2006
Author(s)
Steven W. Brown, Joseph P. Rice, J D. Jackson, Jorge E. Neira, Bettye C. Johnson
A common radiometric platform for the development of application-specific metrics to quantify the performance of sensors and systems is described. Using this platform, systems may be quantified in terms of the accuracy of measurements of standardized sets

Hyperspectral Image Projectors for Radiometric Applications

March 23, 2006
Author(s)
Joseph P. Rice, Steven W. Brown, Bettye C. Johnson, Jorge E. Neira
We describe a new type of Calibrated Hyperspectral Image Projector (CHIP) intended for radiometric testing of instruments ranging from complex hyperspectral or multispectral imagers to simple filter radiometers. The CHIP, based on the same digital mirror

Simple Spectral Stray Light Correction Method for Array Spectroradiometers

February 20, 2006
Author(s)
Yuqin Zong, Steven W. Brown, Bettye C. Johnson, Keith R. Lykke, Yoshihiro Ohno
In many applications, the measurement accuracy of spectroradiometers, particularly instruments with a single dispersive element, is limited by the presence of stray radiation within the instrument. A simple, practical method has been developed to correct a

Correction of Stray Light in Spectrographs: Implications for Remote Sensing

August 22, 2005
Author(s)
Yuqin Zong, Steven W. Brown, Bettye C. Johnson, Keith R. Lykke, Yoshihiro Ohno
Spectrographs are used in a variety of applications in the field of remote sensing for radiometric measurements due to the benefits of measurement speed, sensitivity, and portability. However, spectrographs are single grating instruments that are

Advances in Radiometry for Ocean Color

November 10, 2003
Author(s)
Steven W. Brown, D K. Clark, Bettye C. Johnson, Howard W. Yoon, Keith R. Lykke, S Flora, M Feinholz, N Souaidia, C Pietras, Thomas C. Stone, M Yarbrough, Y S. Kim, R Barnes, J Mueller
Organic materials in the oceans have spectral signatures based on their light-scattering properties. These optical properties are related to bio-physical and bio-chemical data products, such as the concentration of phytoplankton chlorophyll-α, through bio

Calibration and Characterization of Trap Detector Filter Radiometers

November 1, 2003
Author(s)
David W. Allen, George P. Eppeldauer, Steven W. Brown, E A. Early, Bettye C. Johnson, Keith R. Lykke
We describe the development of a mechanically simple, radiometrically stable transfer radiometer designed for both radiance and irradiance measurements. The filter radiometer consists of a six-element Si trap detector, a temperature stabilized filter wheel

Comparison of Laser-Based and Conventional Calibrations of Sun Photometers

November 1, 2003
Author(s)
N Souaidia, C Pietras, G Fargion, R Barnes, R Frouin, Keith R. Lykke, Bettye C. Johnson, Steven W. Brown
Sun photometers are used to characterize the radiative properties of the atmosphere. They measure both the incident solar irradiance as well as the sky radiance (from scattered incident flux). Global networks of sun photometers provide data products such

Temperature Scales Using Radiation Thermometers Calibratied From Absolute Irradiance and Radiance Responsivity

August 21, 2003
Author(s)
Howard W. Yoon, David W. Allen, Charles E. Gibson, Robert D. Saunders, Bettye C. Johnson, Steven W. Brown, Keith R. Lykke
In the International Temperature Scale of 1990 (ITS-90), temperatures above the freezing temperature of silver are defined with radiation thermometers calibrated using spectral radiance ratios to one of the silver-, gold- or copper-freezing temperature

New Technologies for Radiometry: Impact on Ocean Color Research

August 1, 2003
Author(s)
Bettye C. Johnson, Steven W. Brown, N Souaidia, M Feinholz, M Yarbrough, S Flora, D K. Clark
Ocean color satellites provide global determinations of chlorophyll a by measurements of the spectral radiance of the oceans. This is a difficult measurement because the at-satellite radiance is dominated by the atmospheric contribution, and pre-flight

MOBY, A Radiometric Buoy for Performance Monitoring and Vicarious Calibration of Satellite Ocean Color Sensors: Measurement and Data Analysis Protocols

June 1, 2003
Author(s)
D K. Clark, Marilyn Y. Murphy, M Yarbrough, M Feinholz, S Flora, W Broenkow, B. Carol Johnson, Steven W. Brown, Y S. Kim, J Mueller
The Marine Optical Buoy (MOBY) (Clark et al. 1997) is the centerpiece of the primary ocean measurement site for calibration of satellite ocean color sensors based on independent in situ measurements. Since late 1996, the time series of normalized water

Stray-Light Correction of the Marine Optical Buoy

June 1, 2003
Author(s)
Steven W. Brown, Bettye C. Johnson, S Flora, M Feinholz, M Yarbrough, R Barnes, Y S. Kim, Keith R. Lykke, D K. Clark
In ocean-color remote sensing, approximately 90% of the flux at the sensor originates from atmospheric scattering, with the water-leaving radiance contribution the remaining 10 % of the total flux. Consequently, errors in the measured top-of-the atmosphere

Radiometric Measurement Comparison on the Integrating Sphere Source Used to Calibrate the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Landsat 7 Enhanced Thematic Mapper Plus (ETM+)

May 1, 2003
Author(s)
James J. Butler, Steven W. Brown, Robert D. Saunders, B. Carol Johnson, S F. Biggar, E F. Zalewski, B L. Markham, P N. Gracey, J B. Young, R Barnes
As part of a continuing effort to validate the radiometric scales assigned to integrating spheresources used in the calibration of Earth Observing System (EOS) instruments, a radiometric measurement comparison was held in May 1998 at Raytheon/Santa Barbara

Uncertainty Budgets For Realisation of Scales By Radiation Thermometry

March 1, 2003
Author(s)
J Fischer, M Battuello, M Sadli, M Ballico, S N. Park, P Saunders, Y Zundong, B. Carol Johnson, E Van der Ham, W Li, F Sakuma, Graham Machin, N Fox, S Ugur, M Matveyev
Some recent international comparisons and the preliminary results of the key comparison CCT-K5 evidenced that the realisation of theITS-90 above the freezing point of silver and its dissemination with tungsten strip lamps may be less straightforward than

Comparison of Cryogenic Radiometry and Thermal Radiometry Calibrations at NIST Using Multichannel Filter Raidometers

February 7, 2003
Author(s)
Bettye C. Johnson, Steven W. Brown, Keith R. Lykke, Charles E. Gibson, G Fargion, G Meister, S B. Hooker, B L. Markham, James J. Butler
Comparison of independent measurement results allows an assessment of the accuracy of the underlying methods. In this work, four multichannel filter radiometers were calibrated using tunable laser-illuminated and lamp-illuminated integrating sphere sources