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Johnson, Mark S.

Publications and source records attributed to Johnson, Mark S..

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

ECOSTRESS: NASA's Next Generation Mission to Measure Evapotranspiration From the International Space Station

Abstract The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) was launched to the International Space Station on 29 June 2018 by the National Aeronautics and Space Administration (NASA). The primary science focus of ECOSTRESS is centered on evapotranspiration (ET), which is produced as Level‐3 (L3) latent heat flux ( LE ) data products. These data are generated from the Level‐2 land surface temperature and emissivity product (L2_LSTE), in conjunction with ancillary surface and atmospheric data. Here, we provide the first validation (Stage 1, preliminary) of the global ECOSTRESS clear‐sky ET product (L3_ET_PT‐JPL, Version 6.0) against LE measurements at 82 eddy covariance sites around the world. Overall, the ECOSTRESS ET product performs well against the site measurements (clear‐sky instantaneous/time of overpass: r 2 = 0.88; overall bias = 8%; normalized root‐mean‐square error, RMSE = 6%). ET uncertainty was generally consistent across climate zones, biome types, and times of day (ECOSTRESS samples the diurnal cycle), though temperate sites are overrepresented. The 70‐m‐high spatial resolution of ECOSTRESS improved correlations by 85%, and RMSE by 62%, relative to 1‐km pixels. This paper serves as a reference for the ECOSTRESS L3 ET accuracy and Stage 1 validation status for subsequent science that follows using these data.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Concept for maritime near-surface surveillance using water Raman scattering

Here, we discuss a maritime surveillance and detection concept based on Raman scattering of water molecules. Using a range-gated scanning lidar that detects Raman scattered photons from water, the absence or change of signal indicates the presence of a non-water object. With sufficient spatial resolution, a two-dimensional outline of the object can be generated by the scanning lidar. Because Raman scattering is an inelastic process with a relatively large wavelength shift for water, this concept avoids the often problematic elastic scattering for objects at or very close to the water surface or from the bottom surface for shallow waters. The maximum detection depth for this concept is limited by the attenuation of the excitation and return Raman light in water. If excitation in the UV is used, fluorescence can be used for discrimination between organic and non-organic objects. In this paper, we present a lidar model for this concept and discuss results of proof-of-concept measurements. Using published cross section values, the model and measurements are in reasonable agreement and show that a sufficient number of Raman photons can be generated for modest lidar parameters to make this concept useful for near-surface detection.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Building kit for metal cation binding sites in proteins

Starting with conformations of calcium-binding sites in parvalbumin and integrin (representative structures of EF-hand and calcium blade zones, respectively) we introduce four new different local Ca{sup 2+}-recognition units in proteins: a one-residue unit type I (ORI); a three-residue unit type I (TRI); a one-residue unit type II (ORII) and a three-residue unit type II (TRII). Based on the amount and nature of variable atoms, the type I and II units theoretically can have four and twelve variants, respectively. Analysis of known “Ca{sup 2+}-bound functional niches” in proteins revealed presence of almost all possible variants of Ca{sup 2+}-recognition units in actual structures. Parvalbumin, integrin alpha-IIb and sixteen other proteins with different Ca{sup 2+}-bound functional niches contain various consecutively joined combinations of OR(I/II) and TR(I/II) units. Such a OR(I/II)+TR(I/II) joint unit forms a tripeptide, which uses three main-chain atoms for metal binding: nitrogen{sub n} (Donor), oxygen{sub n} (Acceptor) and nitrogen{sub n+2} (Donor). Thus, taken together, the described ORI, TRI, ORII and TRII units can serve as elementary blocks to construct more complex calcium recognizing substructures in a variety of calcium binding sites of unrelated proteins.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Novel calcium recognition constructions in proteins: Calcium blade and EF-hand zone

Metal ions can regulate various cell processes being first, second or third messengers, and some of them, especially transition metal ions, take part in catalysis in many enzymes. As an intracellular ion, Ca{sup 2+} is involved in many cellular functions from fertilization and contraction, cell differentiation and proliferation, to apoptosis and cancer. Here, we have identified and described two novel calcium recognition environments in proteins: the calcium blade zone and the EF-hand zone, common to 12 and 8 different protein families, respectively. Each of the two environments contains three distinct structural elements: (a) the well-known characteristic Dx[DN]xDG motif; (b) an adjacent structurally identical segment, which binds metal ion in the same way between the calcium blade zone and the EF-hand zone; and (c) the following structurally variable segment, which distinguishes the calcium blade zone from the EF-hand zone. Both zones have sequence insertions between the last residue of the zone and calcium-binding residues in positions V or VI. The long insertion often connects the active and the calcium-binding sites in proteins. Using the structurally identical segments as an anchor, we were able to construct the classical calmodulin type EF-hand calcium-binding site out of two different calcium-binding motifs from two unrelated proteins.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Concept for Maritime Near-Surface Surveillance Using Water Raman Scattering

In this report we discuss a new maritime surveillance and detection concept based on Raman scattering of water molecules. Using a scanning lidar that detects Raman scattered photons from water, the absence or change of signal indicates the presence of a non-water object. With sufficient spatial resolution a negative two dimensional image of the object can be generated by the scanning lidar. Because Raman scattering is an inelastic process with a relatively large wavelength shift for water, this concept completely avoids the problematic elastic scattering for objects at or very close to the water surface. Elastic scattering makes it difficult to discriminate between water and dark objects at or near the water surface especially when automated detection is required. It is also difficult to deal with elastic scattering from the bottom surface for shallow waters. The maximum detection depth for this concept is limited by the attenuation of the excitation and return Raman light in water. If excitation in the UV is used, fluorescence can be used for discrimination between organic and non-organic objects. Range gating can be used for this concept for detection of objects below a specified depth. In this report we develop a lidar model for this concept to estimate the number of detected Raman photons for variable lidar parameters and depths in the presence of the solar background. We also report on the results of proof-of-concept measurements using the Sandia Ares lidar with excitation at 355 nm. The measurements show good agreement with the lidar model predictions. The detected number of photons for typical lidar parameter shows the concept is viable and applicable to a variety of day and nighttime detection scenarios. This concept has many potential applications including near-surface mine detection, swimmer detection for security purposes, wide area search, as well as other civilian applications.

47 OTHER INSTRUMENTATION↗
DOE OSTI2013

Aerosol characterization study using multi-spectrum remote sensing measurement techniques.

A unique aerosol flow chamber coupled with a bistatic LIDAR system was implemented to measure the optical scattering cross sections and depolarization ratio of common atmospheric particulates. Each of seven particle types (ammonium sulfate, ammonium nitrate, sodium chloride, potassium chloride, black carbon and Arizona road dust) was aged by three anthropogenically relevant mechanisms: 1. Sulfuric acid deposition, 2. Toluene ozonolysis reactions, and 3. m-Xylene ozonolysis reactions. The results of pure particle scattering properties were compared with their aged equivalents. Results show that as most particles age under industrial plume conditions, their scattering cross sections are similar to pure black carbon, which has significant impacts to our understanding of aerosol impacts on climate. In addition, evidence emerges that suggest chloride-containing aerosols are chemically altered during the organic aging process. Here we present the direct measured scattering cross section and depolarization ratios for pure and aged atmospheric particulates.

Glen, Crystal Chanea↗