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Search Publications by: John T. Woodward IV (Fed)

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Displaying 1 - 25 of 63

Measurements of Absolute, SI-traceable Lunar Irradiance with the Airborne LUnar Spectral Irradiance (air-LUSI) Instrument

May 5, 2022
Author(s)
John T. Woodward IV, Kevin Turpie, Thomas Stone, S. Andrew Gadsden, Andrew Newton, Stephen Maxwell, Steven Grantham, Thomas Larason, Steven W. Brown
The Airborne LUnar Spectral Irradiance (Air-LUSI) instrument is designed to make low uncertainty, hyperspectral measurements of the lunar spectral irradiance from an ER-2 aircraft from altitudes above 95 % to 99 % of the atmosphere. Measurements cover the

A pyroelectric detector-based method for low uncertainty spectral irradiance and radiance responsivity calibrations in the infrared using tunable lasers

April 4, 2022
Author(s)
Brian Alberding, John Woodward, Ping-Shine Shaw, Leonard Hanssen, Catherine Cooksey, Joseph P. Rice
The standard uncertainty of detector-based radiance and irradiance responsivity calibrations in the short-wave infrared (SWIR) traditionally has been limited to around 1 % or higher by the low spatial uniformity of detectors used to transfer the scale from

The Irradiance Instrument Subsystem (IRIS) on the Airborne-Lunar Spectral Irradiance (Air-LUSI) Instrument

March 23, 2022
Author(s)
Steven Grantham, Thomas C. Larason, Clarence Zarobila, Stephen Maxwell, John Woodward, Kevin Turpie, S. Andrew Gadsden
The objective of the airborne LUnar Spectral Irradiance (air-LUSI) project is to make low uncertainty, SI-traceable measurements of the lunar spectral irradiance in the visible to near-infrared (VNIR) region from an aircraft above most of the optically

Molecular-scale Structural and Functional Characterization of Sparsely Tethered Bilayer Membranes

October 12, 2021
Author(s)
Duncan McGillivray, Gintaras Valincius, David J. Vanderah, W Febo-Ayala, John T. Woodward IV, F Hienrich, John J. Kasianowicz, M Losche
Surface-tethered biomimetic bilayer membranes (tethered lipid bilayer membranes, tBLMs) have been formed on gold surfaces from phospholipids and a synthetic 1-thiahexa(ethy lene oxide) lipid, WC14. They have been characterized using electrochemical

Characterization and Absolute Calibration of an AERONET-OC Radiometer

April 15, 2021
Author(s)
B. Carol Johnson, Giuseppe Zibordi, Steven W. Brown, Michael Feinholz, Mikhail Sorokin, Ilya Slutsker, John T. Woodward IV, Howard Yoon
The Ocean Color component of the global Aerosol Robotic Network (AERONET-OC) utilizes CE-318 sun photometers modified for above-water radiometry from fixed structures such as oil rigs, lighthouses, and service platforms. Primarily, AERONET-OC measurements

Optical and Mechanical Design of a Telescope for Lunar Spectral Irradiance Measurements from a High-Altitude Aircraft

September 8, 2020
Author(s)
Clarence Zarobila, Steven Grantham, Steven W. Brown, John T. Woodward IV, Stephen Maxwell, Dana R. Defibaugh, Thomas Larason, Kevin Turpie
We have designed a non-imaging telescope for measurement of the spectral irradiance of the moon. The telescope was integrated into a wing pod of a NASA ER-2 research aircraft to measure lunar spectral irradiance during flight. The telescope and support

Invited Article: Advances in Tunable Laser-based Radiometric Calibration Applications at the National Institute of Standards and Technology, USA

September 26, 2018
Author(s)
John T. Woodward IV, Ping-Shine Shaw, Howard Yoon, Yuqin Zong, Steven W. Brown, Keith R. Lykke
Recent developments at the National Institute of Standards and Technology's facility for Spectral Irradiance and Radiance responsivity Calibrations using Uniform Sources (SIRCUS) are presented. The facility is predicated on the use of broadly tunable

CALIBRATION AND CHARACTERIZATION OF A SEAPRISM RADIOMETER FOR AERONET-OC

June 19, 2015
Author(s)
Bettye C. Johnson, Steven W. Brown, John T. Woodward IV, Keith R. Lykke, Giuseppe Zibordi
The global Aerosol Robotic Network for Ocean Color (AERONET-OC) program utilizes AERONET CE-318 sun photometers (termed “SeaPRISMs”) modified for in-air observations of ocean waters situated on oil drilling rigs, off-shore lighthouses, or other platforms

SI-Traceable Calibrations of Celestial Objects

May 14, 2015
Author(s)
Keith R. Lykke, Claire E. Cramer, John T. Woodward IV
Photometric calibration is currently the leading source of systematic uncertainty in supernova surveys that aim to determine the nature of dark energy. The bulk of this uncertainty is due to imperfect knowledge of the spectral energy distribution of stars

Precise Measurement of Lunar Spectral Irradiance at Visible Wavelengths

November 12, 2013
Author(s)
Keith R. Lykke, John T. Woodward IV, Allan W. Smith, Claire E. Cramer
We report a measurement of lunar spectral irradiance with an uncertainty below 1 % from 420 nm to 1000 nm. This measurement uncertainty meets the stability requirement for many climate data records derived from satellite images, including those for

A novel apparatus to measure reflected sunlight from the Moon

September 19, 2013
Author(s)
Claire E. Cramer, Gerald T. Fraser, Keith R. Lykke, John T. Woodward IV, Alan W. Smith
We describe a new apparatus for measuring the spectral irradiance of the Moon at visible wavelengths. Our effort builds upon the United States Geological Survey’s highly successful Robotic Lunar Observatory (ROLO), which determined a precise model for the

New Instruments to Calibrate Atmospheric Transmission

September 17, 2012
Author(s)
Claire E. Cramer, Keith R. Lykke, John T. Woodward IV, Peter Zimmer, John T. McGraw, Daniel C. Zirzow
Changing atmospheric transmission accounts for the largest systematic errors limiting photometric measurement precision and accuracy for ground-based telescopes. While considerable resources have been devoted to correcting the effects of the atmosphere on

Near-field Calibration of an Objective Spectrophotometer to NIST Radiometric Standards for the Creation and Maintenance of Standard Stars for Ground- and Space-Based Applications

September 13, 2012
Author(s)
John T. Woodward IV, Keith R. Lykke, Claire E. Cramer, John T. McGraw, Peter Zimmer, Daniel C. Zirzow, Susana Deustua, Dean Hines
NIST-calibrated detectors will be used by the ground-based 100mm diameter Astronomical Extinction Spectrophotometer (AESoP) to calibrate the spectral energy distributions of bright stars to sub-1% per 1nm spectral resolution element accuracy. AESoP will

Tunable Laser Techniques for Improving the Precision of Optical Astronomy

September 13, 2012
Author(s)
Keith R. Lykke, Claire E. Cramer, John T. Woodward IV, Steven W. Brown, Ping-Shine Shaw
Improving the precision of optical astronomy requires not only new telescopes and instrumentation, but also advances in observing protocols, calibrations and data analysis. The Laser Applications Group at the National Institute of Standards and Technology

Precise Throughput Determination of the PanSTARRS Telescope and the Gigapixel Imager using a Calibrated Silicon Photodiode and a Tunable Laser: Initial Results

December 2, 2010
Author(s)
Christopher W. Stubbs, Peter Doherty, Claire Cramer, Gautham Narayan, Yorke Brown, Ned Henry, Keith R. Lykke, John T. Woodward IV, John L. Tinry
We have used a precision calibrated photodiode as the fundamental metrology reference in order to determine the relative throughput of the PanSTARRS telescope and the Gigapixel imager, from 400 nm to 1050 nm. Our technique uses a tunable laser as a source

Ground-based observatory operations optimized and enhanced by direct atmospheric measurements

July 22, 2010
Author(s)
John T. McGraw, Peter C. Zimmer, Azzam Mansour, Dean C. Hines, Anthony B. Hull, Lisa Rossmann, Daniel C. Zirzow, Steven W. Brown, Gerald T. Fraser, Keith R. Lykke, Allan W. Smith, John T. Woodward IV, Christopher W. Stubbs
Earth's atmosphere represents a turbulent, turbid refractive element for every ground-based telescope. We describe the significantly enhanced and optimized operation of observatories supported by the combination of a lidar and spectrophotometer that allows

Spectroradiometric Calibration of Telescopes using Laser Illumination of Flat Field Screens

July 15, 2010
Author(s)
Steven W. Brown, Claire E. Cramer, Keith R. Lykke, Allan W. Smith, John T. Woodward IV, Peter Doherty, Emilio Falco, Christopher W. Stubbs
It is standard practice at many telescopes to take a series of flat field images prior to an observation run. Typically the flat field consists of a screen mounted inside the telescope dome that is uniformly illuminated with a broadband light source. These

Space-based photometric precision from ground-based telescopes

July 1, 2010
Author(s)
Peter C. Zimmer, John T. McGraw, Anthony B. Hull, Daniel C. Zirzow, Steven W. Brown, Claire E. Cramer, Gerald T. Fraser, Keith R. Lykke, Allan W. Smith, John T. Woodward IV, Christopher W. Stubbs, Mark R. Ackermann, Dean C. Hines
Ground-based telescopes supported by lidar and spectrophotometric auxiliary instrumentation can attain space-based precision for all-sky photometry, with uncertainties dominated by fundamental photon counting statistics. Earth‟s atmosphere is a wavelength-

Internal quantum efficiency modeling of silicon photodiodes

April 1, 2010
Author(s)
Thomas R. Gentile, Steven W. Brown, Keith R. Lykke, Ping-Shine Shaw, John T. Woodward IV
Results are presented for modeling of the internal quantum efficiency (IQE) of silicon photodiodes in the 400 nm to 900 nm wavelength range. The IQE data are based on measurements of the external quantum efficiencies of three transmission trap detectors

Hyperspectral Imager Characterization and Calibration

December 1, 2009
Author(s)
John T. Woodward IV, Steven W. Brown, Allan W. Smith, Keith R. Lykke
Current radiometric calibration standards, specifically blackbody and lamp-based optical radiation sources, produce spatially, spectrally, and temporally simple scenes. Hyperspectral imaging instruments, which in-practice view spatially, spectrally, and