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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Thermal Emission Spectrometer Mosaics of Impact Craters: Progress on Shocked Plagioclase Detections

High shock pressures disorder the mineral lattice of plagioclase feldspars and cause weakening and shifts in thermal infrared absorption bands related to an increase in diaplectic glass content, particularly at shock pressures above ~20-25 GPa [1- 9]. We are continuing our investigation of spectral deconvolutions of TES mosaics and mosaics using standard TES orbits for eight impact crater areas. Using a combination of mineral laboratory spectra and spectra of experimentally shocked bytownite feldspars [5] to deconvolve the TES spectra, we find that locations of shocked feldspar detections are not restricted to ejecta near large craters.

Johnson, J. R.↗
NASA NTRS2012

The Radio Light Curve of the Gamma-Ray Nova in V407 CYG: Thermal Emission from the Ionized Symbiotic Envelope, Devoured from Within by the Nova Blast

We present multi-frequency radio observations of the 2010 nova event in the symbiotic binary V407 Cygni, obtained with the Karl G. Jansky Very Large Array (VLA) and spanning 1.45 GHz and 17.770 days following discovery. This nova.the first ever detected in gamma rays.shows a radio light curve dominated by the wind of the Mira giant companion, rather than the nova ejecta themselves. The radio luminosity grewas the wind became increasingly ionized by the nova outburst, and faded as the wind was violently heated from within by the nova shock. This study marks the first time that this physical mechanism has been shown to dominate the radio light curve of an astrophysical transient. We do not observe a thermal signature from the nova ejecta or synchrotron emission from the shock, due to the fact that these components were hidden behind the absorbing screen of the Mira wind. We estimate a mass-loss rate for the Mira wind of .Mw approximately equals 10(exp -6) Solar mass yr(exp -1). We also present the only radio detection of V407 Cyg before the 2010 nova, gleaned from unpublished 1993 archival VLA data, which shows that the radio luminosity of the Mira wind varies by a factor of 20 even in quiescence. Although V407 Cyg likely hosts a massive accreting white dwarf, making it a candidate progenitor system for a Type Ia supernova, the dense and radially continuous circumbinary material surrounding V407 Cyg is inconsistent with observational constraints on the environments of most Type Ia supernovae.

Chomiuk, Laura↗
NASA NTRS1988

Tersail - A numerical model for combined analysis of vegetation canopy bidirectional reflectance and thermal emissions

A modification of the Tergra model (Soer, 1977) is presented, which incorporates the scattering from arbitrarily inclined leaves canopy reflectance model (Verhoef and Bunnik, 1981) for the calculation of albedo and canopy resistance. The combined model, known as Tersail, is capable of simulating the relationship between the bidirectional reflectance and the thermal response of a canopy. The accuracy of the model is tested using data over wheat canopies in Phoenix, Arizona, showing that the model is a good simulator of canopy temperatures under a variety of conditions.

Hope, Allen S.↗
NASA NTRS2004

Thermal Emission Spectroscopy of Sulfates: Possible Hydrous Iron-Sulfate in the Soil at the MER-A Gusev Crater Landing Site

Sulfates are likely to be present on Mars as indicated by the sulfur abundances measured at the Viking and Pathfinder landing sites (approx. 5-10% by weight SO3) [1-3] and because of Mars strongly oxidizing environment. Telescopic observations of Mars tentatively identified weak sulfate bands in near infrared [4] and thermal infrared [5] data. The currently orbiting midinfrared instruments (TES, THEMIS) and the Mini-TES on the Mars Exploration Rover landers may enable a positive identification [6] and determination of the chemistry of the sulfates. Critically important to the identification of these minerals is the presence of their spectra in a spectral library. There exist approximately 370 sulfate-mineral species [7]. Sulfate minerals occur in volcanic, hydrothermal, evaporitic, and chemical-weathering environments.

Lane, Melissa D.↗
DOE OSTI2024

Non-thermal emission in gap-mode plasmon photoluminescence

Abstract Photoluminescence from spatially inhomogeneous plasmonic nanostructures exhibits fascinating wavelength-dependent nonlinear behaviors due to the intraband recombination of hot electrons excited into the conduction band of the metal. The properties of the excited carrier distribution and the role of localized plasmonic modes are subjects of debate. In this work, we use plasmonic gap-mode resonators with precise nanometer-scale confinement to show that the nonlinear photoluminescence behavior can become dominated by non-thermal contributions produced by the excited carrier population that strongly deviates from the Fermi-Dirac distribution due to the confinement-induced large-momentum free carrier absorption beyond the dipole approximation. These findings open new pathways for controllable light conversion using nonequilibrium electron states at the nanoscale.

Science & Technology - Other Topics↗
NASA NTRS2018

Thermal Emission From Saturn's Polar Cyclones

We have used data from the Cassini Composite Infrared Spectrometer to map the temperatures in Saturn's polar cyclones at the highest spatial resolution obtained during the Cassini mission. We find temperature contrasts of 7 K in the upper troposphere within 1.4° of both poles, roughly 50 percent larger than earlier measurements at lower spatial resolution. The polar hot spots weaken with depth, disappearing near 500 mbar. In the stratosphere, the polar hot spot becomes broader, extending 4° from the poles, and weakens with altitude disappearing near 1 mbar. A thermal relaxation model shows that the tropospheric hot spot is consistent with adiabatic heating from subsidence with a vertical velocity of about −0.05 mm/s above 500 mbar. The observed temperature gradients imply that the winds in the polar cyclone decay with increasing altitude over roughly three pressure scale heights above the 200‐mbar level.

Polar↗
DOE OSTI2023

Assessment of Mechanical Draft Cooling Tower Thermal Emissions from Visual Images of Plumes

Using a one-dimensional code, we computed the power (enthalpy discharge rate) of a twelve-cell mechanical draft cooling tower (MDCT) using over two hundred visible condensed water vapor plume volume measurements derived from images, weather data, and tower operating conditions. The plume images were simultaneously captured by multiple stationary digital cameras surrounding the cooling tower. An analysis technique combining structure from motion (SfM), a neural-network-based image segmentation algorithm, and space carving was used to quantify the volumes. Afterwards, the power output was computed using novel techniques in the one-dimensional code that included cooling tower exhaust plume adjacency effects implemented with a modified version of the entrainment function, weather data averaged from eleven stations, and fan operations at the times when plume volumes were measured. The model was then compared with the averaged observed power output, and it validated well with an average error ranging from 6 to 12%, depending on the meteorological data used in the simulations. This methodology can possibly determine power plant fuel consumption rates by applying visible imagery.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Simulating the Multi-epoch Direct Detection Technique to Isolate the Thermal Emission of the Non-transiting Hot Jupiter HD187123b

We report the 6.5σ detection of water from the hot Jupiter HD187123b with a Keplerian orbital velocity K {sub p} of 53 ± 13 km s{sup −1}. This high-confidence detection is made using a multi-epoch, high-resolution, cross-correlation technique, and corresponds to a planetary mass of 1.4{sub −0.3}{sup +0.5} M {sub J} and an orbital inclination of 21° ± 5°. The technique works by treating the planet/star system as a spectroscopic binary and obtaining high signal-to-noise, high-resolution observations at multiple points across the planet’s orbit to constrain the system’s binary dynamical motion. All together, seven epochs of Keck/NIRSPEC L-band observations were obtained, with five before the instrument upgrade and two after. Using high-resolution SCARLET planetary and PHOENIX stellar spectral models, we were able to drastically increase the confidence of the detection by running simulations that could reproduce, and thus remove, the nonrandom structured noise in the final likelihood space well. The ability to predict multi-epoch results will be extremely useful for furthering the technique. Here, we use these simulations to compare three different approaches to combining the cross correlations of high-resolution spectra and find that the Zucker log(L) approach is least affected by unwanted planet/star correlation for our HD187123 data set. Furthermore, we find that the same total signal-to-noise ratio (S/N) spread across an orbit in many, lower S/N epochs rather than fewer, higher S/N epochs could provide a more efficient detection. This work provides a necessary validation of multi-epoch simulations, which can be used to guide future observations and will be key to studying the atmospheres of farther separated, non-transiting exoplanets.

79 ASTRONOMY AND ASTROPHYSICS↗