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Brown, S. T.

Publications and source records attributed to Brown, S. T..

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

EGS Collab SIGMA-V Project: Stimulation Investigations for Geothermal Modeling Analysis and Validation Phase 1 Report. For the period February 2017 – March 2019

The EGS Collab project was initiated in March 2017 to enable the subsurface modelling and research community to establish validations against controlled, small-scale, in-situ experiments focused on rock fracture behavior and permeability enhancement. The EGS Collab project is to provide the opportunity for reservoir model prediction and validation, in coordination with in depth analysis of geophysical and other fracture characterization data with an ultimate goal of further elucidating the basic relationship between stress, seismicity and permeability enhancement. In addition, the project is to identify and quantify other key governing parameters that impact permeability as well as understanding how these parameters change throughout the three EGS development phases (identify/characterize site, create reservoir, operate power plant). The project is to use comprehensive instrumentation and data collection effort to inform baseline, predictive, and post stimulation reservoir modeling is essential. This report describes the activities performed in Phase 1 of the project. The work done to date is extensive, and a large number of participants have contributed significant effort to enable project success. From planning to execution, we have stayed on track to address the objectives established by the Department of Energy in the paragraph above.

15 GEOTHERMAL ENERGY↗
DOE OSTI2019

Thermodynamic controls on redox-driven kinetic stable isotope fractionation

Stable isotope fractionation arising from redox reactions has the potential to illuminate the oxygenation of Earth's interior, oceans, and atmosphere. However, reconstruction of past and present redox conditions from stable isotope signatures is complicated by variable fractionations associated with different reduction pathways. Here we demonstrate a linear relationship between redox-driven kinetic fractionation and the standard free energy of reaction for aqueous chromium(VI) reduction by iron(II) species. We also show that the intrinsic kinetic fractionation factor is log-linearly correlated with the rate constant of reaction, which is in turn a function of the free energy of reaction. The linear free energy relationship for kinetic fractionation describes both our experimental results and previous observations of chromium isotope fractionation and allows the magnitude of fractionation to be directly linked to environmental conditions such as pH and oxygen levels. By demonstrating that the magnitude of kinetic fractionation can be thermodynamically controlled, this study systematically explains the large variability in chromium(VI) isotope fractionation and provides a conceptual framework that is likely applicable to other isotope systems.

58 GEOSCIENCES↗
NASA NTRS2010

Assessment of the Jason-2 Extension to the TOPEX/Poseidon, Jason-l Sea-Surface Height Time Series for Global Mean Sea Level Monitoring

The Jason-2 (OSTM) follow-on mission to Jason-I provides for the continuation of global and regional mean sea level estimates along the ground-track of the initial phase of the TOPEX/Poseidon mission. During the first several months, Jason-I and Jason-2 flew in formation separated by only 55 seconds, enabling the isolation of intermission instrument biases through direct collinear differencing of near simultaneous observations. The Jason-2 Ku-band range bias with respect to Jason-I is estimated to be -84 +/- 9 mm, based on the orbit altitudes provided on the Geophysical Data Records. Modest improved agreement is achieved with the GSFC replacement orbits, which further enables the isolation of subtle 1 cm) instrument-dependent range correction biases. Inter-mission bias estimates are confirmed with an independent assessment from comparisons to a 64-station tide-gauge network, also providing an estimate of the stability of the 17-year time series to be less than 0.1 mm/yr +/- 0.4 mm/yr. The global mean sea level derived from the multi-mission altimeter sea-surface height record from January 1993 through September 2009 is 3.3 +/- 0.4 mm/yr. Recent trends over the period from 2004 through 2008 are smaller and estimated to be 2.0 +/- 0.4 mm/yr.

Beckley, B. D.↗
NASA NTRS2007

Geo-STAR: A Geostationary Microwave Sounder for the Future

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new Earth remote sensing instrument concept that has been under development at the Jet Propulsion Laboratory. First conceived in 1998 as a NASA New Millennium Program mission and subsequently developed in 2003-2006 as a proof-of-concept prototype under the NASA Instrument Incubator Program, it is intended to fill a serious gap in our Earth remote sensing capabilities - namely the lack of a microwave atmospheric sounder in geostationary orbit. The importance of such observations have been recognized by the National Academy of Sciences National Research Council, which recently released its report on a 'Decadal Survey' of NASA Earth Science activities1. One of the recommended missions for the next decade is a geostationary microwave sounder. GeoSTAR is well positioned to meet the requirements of such a mission, and because of the substantial investment NASA has already made in GeoSTAR technology development, this concept is fast approaching the necessary maturity for implementation in the next decade. NOAA is also keenly interested in GeoSTAR as a potential payload on its next series of geostationary weather satellites, the GOES-R series. GeoSTAR, with its ability to map out the three-dimensional structure of temperature, water vapor, clouds, precipitation and convective parameters on a continual basis, will significantly enhance our ability to observe hurricanes and other severe storms. In addition, with performance matching that of current and next generation of low-earth-orbiting microwave sounders, GeoSTAR will also provide observations important to the study of the hydrologic cycle, atmospheric processes and climate variability and trends. In particular, with GeoSTAR it will be possible to fully resolve the diurnal cycle. We discuss the GeoSTAR concept and basic design, the performance of the prototype, and a number of science applications that will be possible with GeoSTAR. The work reported on here was performed at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration.

Geostationary Synthetic Thinned Aperture Radiomete↗
NASA NTRS2006

Initial Results of the Geosynchronous Synthetic Thinned Array Radiometer (GeoSTAR)

An error budget is presented to meet 1 Kelvin radiometric accuracy in a geostationary atmospheric sounder with 50 km spatial resolution on the earth. The gain and phase errors are weighted by the magnitude of visibility versus antenna separation, and requirements range between approx.0.5% and 0.3 degrees of amplitude and phase, respectively, for the closest spacings at the center of the array, and about 5% and 3 degrees for the majority of the array. The latter requirement is met by our design without any special testing or stabilizations by reference signals. The former is met using an internal noise diode reference and by measuring the detailed antenna patterns on the antenna range. Biases and other additive errors in the raw visibility samples must be below about 2 mK on average, and this requirement is met by a phase shifting scheme applied to the local oscillator distribution. An outline of the data processing is presented, along with the first images from this system.

Synthetic Thinned Aperture Radiometer (STAR)↗
NASA NTRS2005

Progress in developing GeoSTAR - Microwave Sounder for GOES-R

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR)is a new concept for a microwave sounder, intended to be deployed at the Jet Propulsion Laboratory under NASA Instrument Incubator Program sponsorship, and is currently undergoing tests and performance characterization.

aperture synthesis↗
NASA NTRS2005

A GeoSTAR progress report

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new concept for a microwave sounder, intended to be deployed on NOAA's next generation of geostationary weather satellites, GOES-R. A ground based prototype has been developed at the Jet Propulsion Laboratory, under NASA Instrument Incubator Program sponsorship, and is now undergoing tests and performance characterization. With the aperture synthesis approach used by GeoSTAR it is possible to achieve very high spatial resolutions even in the crucial 50-GHz temperature sounding band without having to deploy the impractically large parabolic reflector antenna that is required with the conventional approach. The technology and system design required for GeoSTAR are rapidly maturing, and it is expected that a space demonstration mission can be developed before the first GOES-R launch. GeoSTAR will be ready for operational deployment 2-3 years after that. The prototype developed under IIP implements a small version of the temperature sounding component of GeoSTAR, is fully functional as a sounder and has all of the features and capabilities of an operational system with the exception of spatial resolution. It therefore represents a complete proof of concept as well as significant risk reduction for a space implementation.

microwaves↗