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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Influence of a fat layer on the near infrared spectra of human muscle: quantitative analysis based on two-layered Monte Carlo simulations and phantom experiments

The influence of fat thickness on the diffuse reflectance spectra of muscle in the near infrared (NIR) region is studied by Monte Carlo simulations of a two-layer structure and with phantom experiments. A polynomial relationship was established between the fat thickness and the detected diffuse reflectance. The influence of a range of optical coefficients (absorption and reduced scattering) for fat and muscle over the known range of human physiological values was also investigated. Subject-to-subject variation in the fat optical coefficients and thickness can be ignored if the fat thickness is less than 5 mm. A method was proposed to correct the fat thickness influence. c2005 Optical Society of America.

NASA Discipline Life Sciences Technologies↗
DOE OSTI2025

An accurate measurement of the spectral resolution of the JWST Near Infrared Spectrograph

The spectral resolution (R ≡ λ/Δλ) of spectroscopic data is crucial information for accurate kinematic measurements. In this letter we present a robust measurement of the spectral resolution of the JWST Near Infrared Spectrograph (NIRSpec) in fixed slit (FS) and integral field spectroscopy (IFS) modes. Due to the similarity of the utilized slit dimension in the FS mode to that of the shutters in the multi-object spectroscopy (MOS) mode, our resolution measurements in the FS mode can also be used for the MOS mode in principle. We modeled H and He lines of the planetary nebula SMP LMC 58 using a Gaussian line spread function (LSF) to estimate the wavelength-dependent resolution for multiple disperser and filter combinations. We corrected for the intrinsic width of the planetary nebula’s H and He lines due to its expansion velocity by measuring it from a higher-resolution X-shooter spectrum. We find that NIRSpec’s in-flight spectral resolutions exceed the pre-launch estimates provided in the JWST User Documentation by 11–53% in the FS mode and by 1–24% in the IFS mode across the covered wavelengths. We recover the expected trend that the resolution increases with the wavelength within a configuration. The robust and accurate LSFs presented in this letter will enable high-accuracy kinematic measurements using NIRSpec for applications in cosmology and galaxy evolution.

methods: data analysis↗
NASA NTRS1985

A two-dimensional near-infrared tracking system

Video tracking systems face the problem of discriminating between a target in space and the earth in the background. The visual tracking system described in this paper uses the near-infrared to take advantage of differences in spectral reflectance between the target and the earth in the background to enhance amplitude differences, simplifying the detection process. The real-time visual tracking system is microprocessor controlled, light weight, and low-power.

Walton, D. P.↗
NASA NTRS1993

Galileo/NIMS near-infrared thermal imagery of the surface of Venus

Numerous highland and lowland features on the surface of Venus are observed in multispectral imagery acquired at approximately 50 km spatial resolution by the Near-Infrared Mapping Spectrometer (NIMS) on board the Galileo spacecraft in Feb. 1990. Specifically, such features are observed at 1.18 microns, a wavelength particularly sensitive to thermal emission from the hot, lower atmosphere (less than 10 km) and surface, and show up particularly well when this image is 'de-clouded' using a simultaneously-acquired 2.3-microns image of the upper, cloudy atmosphere. Due to the steep atmospheric temperature gradient (approximately 8 degrees per kilometer), hot lowland areas appear relatively bright, while cooler, highland areas appear dark (due to the steep atmospheric temperature gradient - approximately 8 degrees per kilometer - surface temperatures span approximately 100 K over the 13 kilometer range of surface altitudes observed in this image). Prominent highland features include Maxwell Montes (approximately 12 km altitude), Alpha Regio (2.5 km), Eistla Regio (approximately 2.0 km), Bell Regio (2-3 km), and the western edge of Aphrodite Terra (2-2.5 km). Low-lying regions include Sedna Planitia (-1.0 km), Tinatin Planitia (-0.5 km), and the Bereghinya Planitia (0 km). From correlations with radar altimetry maps, such imagery may place useful constraints on surface emissivity and temperature variations, as well as on the nature of continuum opacity of CO2 in the 1-micron region.

Carlson, R. W.↗
DOE OSTI2025

Sensitivity of Simulated Polar Climate to Improved Partitioning of Spectral Solar Irradiance Between Visible and Near‐Infrared Bands

The solar radiative processes that contribute to Earth's surface and atmospheric energy budgets are strongly dependent on wavelength. For example, snow and water vapor become more absorptive as incident radiation shifts from visible (VIS) to near-infrared (NIR) wavelengths. Some earth system models (ESMs) aggregate solar radiation into just two bands (VIS and NIR) partitioned at 0.7 μm for transmission between the atmospheric and surface components. In the widely used radiative transfer model RRTMG_SW this partition is near the center of the overlap spectral band spanning 0.625–0.778 μm, whose flux is often approximated as being evenly divided between the VIS and NIR surface bands. Using a hyperspectral radiative transfer model, we show that the fractional downwelling surface flux within the overlap band is usually distributed about 55.5%:44.5% VIS:NIR. This improved approximation shifts as much as 4.27 W m −2 from the NIR to the VIS band, leading to an instantaneous decrease in surface absorption of up to 0.91 W m −2 over snow-covered surfaces. Century-long fully coupled ESM simulations show surface absorption over snow decreases by over 1.6 W m −2 . The coupled response in sea ice regions amplifies the initial forcing ten-fold, and increases seasonal sea ice area by up to 4.9%. These results highlight the importance of accurately representing the spectral distribution of solar radiation in the cryosphere.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Imaging of dark line defect growth in high-power diode laser cavities using broadband near infrared light emission from the laser cavity

An in situ and nondestructive technique is developed to image the formation and evolution of dark line defects in the cavity of a high-power diode laser. Here, the technique uses broadband near infrared emission that originates in the laser's core layers and enables defects to be imaged with high spatial resolution through the substrate. In particular, it enables defect imaging through the substrate of shorter wavelength lasers, even when the substrate is opaque near the lasing wavelength. The evolution of dark line defects during aging is studied in several devices, with correlations established between the observed characteristics of defect growth and changes in device parameters such as optical power, operating wavelength, threshold current, and slope efficiency. Gradual degradation is found to be associated with dark line defects that slowly propagate from dark spots that are present in the device interior in its fresh (unaged) condition, rather than propagating from spots that are formed during aging, suggesting a strategy to screen fresh devices for expected reliability. This defect growth phenomenon is found to be particularly evident in the dark spots near the output facet.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

A near-infrared optical nanosensor for measuring aerobic respiration in microbial systems

We developed a ratiometric oxygen-sensitive nanosensor and demonstrated application in monitoring metabolic oxygen consumption in microbial samples over time. Based on a near-infrared (NIR) emitting oxygen-quenched luminophore, platinum(II) octaethylporphine ketone (PtOEPK), along with a stable dioctadecyl dicarbocyanine reference dye (DiD), this nanosensor system provides an advantageous approach for overcoming imaging issues in biological systems, such as autofluorescence and optical scattering in the visible wavelength region. The dyes are encapsulated within a polymer-based nanoparticle matrix to maintain them at a constant ratio in biological samples, precluding the need for complex synthetic approaches. With this constant ratio of the two dyes, the nanosensor response can be measured as a ratio of their two signals, accounting for nanosensor concentration artifacts in measurements. The nanosensors are reversible, which enabled us to temporally monitor systems in which dissolved oxygen concentrations both increase and decrease. These sensors were applied for the monitoring of oxygen in samples of Saccharomyces cerevisiae (brewing yeast) in a 96-well optical fluorescence plate reader format over 60 h. By mixing the nanosensors directly into the sample well with the yeast, we were able to dynamically track metabolic activity changes over time due to varying cell concentration and exposure to an antimicrobial agent. As a result, this system could be a potential platform for high-throughput screening of various species or variants of microbes with unknown metabolic rates in response to external stimuli (antimicrobials, metabolites, etc.).

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Near-infrared noise in intense electron beams

Requirements for the noise in electron beams (NEB) have recently approached the Shot-noise level in some new applications. The density fluctuations of intense beams in the near-infrared (NIR) region are being measured at the Fermilab Accelerator Science and Technology (FAST) facility. The main goal of the experiment is to accurately compare the Shot-noise model with the observations of optical transition radiation (OTR) generated by the gamma=63 electron beam transiting an Al metal surface. In addition, evidence for longitudinal-space-charge-induced microbunching for the chicane-compressed beam was obtained with coherent enhancements up to 100 in the various bandwidth-filtered NIR OTR photodiode signals. With micropulse charges up to 1 nC, the beam parameters are close to those proposed for a stage in an Electron-Ion Collider (EIC) with coherent electron cooling (CEC). In this paper we present the current progress of the NEB project and compare the low electron energy measurements with ImpactX simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Near-Infrared Noise in Intense Electron Beams

Requirements for the noise in electron beams (NEB) have recently approached the Shot-noise level in some new applications. The density fluctuations of intense beams in the near-infrared (NIR) region are being measured at the Fermilab Accelerator Science and Technology (FAST) facility. The main goal of the experiment is to accurately compare the Shot-noise model with the observations of optical transition radiation (OTR) generated by a relativistic electron beam ($\gamma \approx 63$), transiting an Aluminium metal surface. In addition, some evidence for longitudinal space-charge-induced microbunching for the chicane-compressed beam was obtained with coherent enhancements up to 100 in the various bandwidth-filtered NIR OTR photodiode signals. With micropulse charges up to 1 nC, the beam parameters are close to those proposed for a stage in an Electron-Ion Collider (EIC) with coherent electron cooling (CEC). In this paper we present the current progress of the NEB project and compare the low electron energy measurements with ImpactX simulations.

43 PARTICLE ACCELERATORS↗
NASA NTRS2005

Visible-Near Infrared Imaging Spectrometer Data of Explosion Craters

In a continuing study to capture a realistic terrain applicable to studies of cratering processes and landing hazards on Mars, we have obtained new high resolution visible-near infrared images of several explosion craters at the Nevada Test Site. We used the Airborne Visible-Infrared Imaging Spectrometer (AVIRIS) to obtain images in 224 spectral bands from 0.4-2.5 microns [1]. The main craters that were imaged were Sedan, Scooter, Schooner, Buggy, and Danny Boy [2]. The 390 m diameter Sedan crater, located on Yucca Flat, is the largest and freshest explosion crater on Earth that was formed under conditions similar to hypervelocity impact cratering. As such, it is effectively pristine, having been formed in 1962 as a result of the detonation of a 104 kiloton thermonuclear device, buried at the appropriate equivalent depth of burst required to make a "simple" crater [2]. Sedan was formed in alluvium of mixed lithology [3] and subsequently studied using a variety of field-based methods. Nearby secondary craters were also formed at the time and were also imaged by AVIRIS. Adjacent to Sedan and also in alluvium is Scooter, about 90 m in diameter and formed by a high-explosive event. Schooner (240 m) and Danny Boy (80 m, Fig. 1) craters were also important targets for AVIRIS as they were excavated in hard welded tuff and basaltic andesite, respectively [3, 4]. This variation in targets will allow the study of ejecta patterns, compositional modifications due to the explosions, and the role of craters as subsurface probes.

Farr, T. G.↗
NASA NTRS1993

Simulations of Deep Optical and Near Infrared Extragalactic Counts

Monte-Carlo simulations of three dimensional galaxy distributions are performed, following the prescription of Chokshi and Wright(1988), to study the photometric properties of evolving galaxy populations in the optical and near infrared bands to high redshifts.

faint galaxies galaxy evolution↗
NASA NTRS2003

Laboratory Characterization and Modeling of a Near-Infrared Enhanced Photomultiplier Tube

The photon-starved channel for optical communications from deep space requires the development of detector technology that can achieve photon-counting sensitivities with high bandwidth. In this article, a near-infrared enhanced photomultiplier tube (PMT) with a quantum e.ciency of 0.08 at a 1.06- m wavelength is characterized in the laboratory. A Polya distribution model is used to compute the probability distribution function of the emitted secondary photoelectrons from the PMT. The model is compared with measured pulse-height distributions with reasonable agreement. The model accounts for realistic device parameters, such as the individual dynode stage gains and a shape parameter that is representative of the spatial uniformity of response across the photocathode and dynodes. Bit-error rate (BER) measurements also are presented for 4- and 8-pulse-position modulation (PPM) modulation schemes with data rates of 20 to 30 Mb/s. A BER of 10-2 is obtained for a mean of 8 detected photons.

Biswas, A.↗
DOE OSTI2023

The DEHVILS survey overview and initial data release: high-quality near-infrared Type Ia supernova light curves at low redshift

ABSTRACT While the sample of optical Type Ia supernova (SN Ia) light curves (LCs) usable for cosmological parameter measurements surpasses 2000, the sample of published, cosmologically viable near-infrared (NIR) SN Ia LCs, which have been shown to be good ‘standard candles,’ is still ≲ 200. Here, we present high-quality NIR LCs for 83 SNe Ia ranging from 0.002 < z < 0.09 as a part of the Dark Energy, H0, and peculiar Velocities using Infrared Light from Supernovae (DEHVILS) survey. Observations are taken using UKIRT’s WFCAM, where the median depth of the images is 20.7, 20.1, and 19.3 mag (Vega) for Y, J, and H-bands, respectively. The median number of epochs per SN Ia is 18 for all three bands (Y,J, and H) combined and 6 for each band individually. We fit 47 SN Ia LCs that pass strict quality cuts using three LC models, SALT3, snoopy, and B ayeSN and find scatter on the Hubble diagram to be comparable to or better than scatter from optical-only fits in the literature. Fitting NIR-only LCs, we obtain standard deviations ranging from 0.128 to 0.135 mag. Additionally, we present a refined calibration method for transforming 2MASS magnitudes to WFCAM magnitudes using HST CALSPEC stars that results in a 0.03 mag shift in the WFCAM Y-band magnitudes.

Astronomy & Astrophysics↗
NASA NTRS2003

A Near-Infrared (NIR) Global Multispectral Map of the Moon from Clementine

In May and June of 1994, the NASA/DoD Clementine Mission acquired global, 11- band, multispectral observations of the lunar surface using the ultraviolet-visible (UVVIS) and near-infrared (NIR) camera systems. The global 5-band UVVIS Digital Image Model (DIM) of the Moon at 100 m/pixel was released to the Planetary Data System (PDS) in 2000. The corresponding NIR DIM has been compiled by the U.S. Geological Survey for distribution to the lunar science community. The recently released NIR DIM has six spectral bands (1100, 1250, 1500, 2000, 2600, and 2780 nm) and is delivered in 996 quads at 100 m/pixel (303 pixels/degree). The NIR data were radiometrically corrected, geometrically controlled, and photometrically normalized to form seamless, uniformly illuminated mosaics of the lunar surface.

Eliason, E. M.↗
NASA NTRS1972

A near-infrared view of the Uranus system.

An image intensifying tube placed at the f/10 Cassegrain focus of an 88-in. reflector telescope was used together with a narrow filter centered at the 8870-A methane band to obtain near-infrared photographs of Uranus and its satellites. Good images of Uranus were obtained with a 1-min exposure, while the faintest satellite Miranda was well recorded in about one hour. The short-exposure photograph of Uranus shows that the limb is brighter than the center of the disk and brightest at the south pole. The explanation for the brightening of the limb and pole seems to be haze in the planet's upper atmosphere.

Sinton, W. M.↗
NASA NTRS1995

Near-Infrared Monitoring of Model Chronic Compartment Syndrome In Exercising Skeletal Muscle

Chronic compartment syndrome (CCS) is characterized by muscle ischemia, usually in the anterior oompartment of the leg, caused by high intramuscular pressure during exercise. Dual-wave near-infrared (NIR) spectroscopy is an optical technique that allows noninvasive tracking of variations in muscle tissue oxygenation (Chance et al., 1988). We hypothesized that with a model CCS, muscle tissue oxygenation will show a greater decline during exercise and a slower recovery post-exercise than under normal conditions.

Hargens, Alan R.↗
NASA NTRS2005

Near-Infrared Single-Photon-Counting Detectors for Laser Instrument Applications at NASA Goddard Space Flight Center

We discuss single-photon-counting detectors requirements for NASA remote sensing and communications systems. We present experimental measurements on several different near-infrared single-photon-counting detectors including InGaAs/InP and InGaAs/InAlAs avalanche photodiodes (APD), an InGaAsP photocathode hybrid photomultiplier (PMT) and an InGaAs photomultiplier. We present the experimental performance of prototype instruments for laser ranging, communication, and trace-gas detection that use these detectors.

Krainak, Michael A.↗
NASA NTRS2008

Near-Infrared Spectroscopic Measurements of Calf Muscle during Walking at Simulated Reduced Gravity - Preliminary Results

Consideration for lunar and planetary exploration space suit design can be enhanced by investigating the physiologic responses of individual muscles during locomotion in reduced gravity. Near-infrared spectroscopy (NIRS) provides a non-invasive method to study the physiology of individual muscles in ambulatory subjects during reduced gravity simulations. PURPOSE: To investigate calf muscle oxygen saturation (SmO2) and pH during reduced gravity walking at varying treadmill inclines and added mass conditions using NIRS. METHODS: Four male subjects aged 42.3 +/- 1.7 years (mean +/- SE) and weighing 77.9 +/- 2.4 kg walked at a moderate speed (3.2 +/- 0.2 km/h) on a treadmill at inclines of 0, 10, 20, and 30%. Unsuited subjects were attached to a partial gravity simulator which unloaded the subject to simulate body weight plus the additional weight of a space suit (121 kg) in lunar gravity (0.17G). Masses of 0, 11, 23, and 34 kg were added to the subject and then unloaded to maintain constant weight. Spectra were collected from the lateral gastrocnemius (LG), and SmO2 and pH were calculated using previously published methods (Yang et al. 2007 Optics Express ; Soller et al. 2008 J Appl Physiol). The effects of incline and added mass on SmO2 and pH were analyzed through repeated measures ANOVA. RESULTS: SmO2 and pH were both unchanged by added mass (p>0.05), so data from trials at the same incline were averaged. LG SmO2 decreased significantly with increasing incline (p=0.003) from 61.1 +/- 2.0% at 0% incline to 48.7 +/- 2.6% at 30% incline, while pH was unchanged by incline (p=0.12). CONCLUSION: Increasing the incline (and thus work performed) during walking causes the LG to extract more oxygen from the blood supply, presumably to support the increased metabolic cost of uphill walking. The lack of an effect of incline on pH may indicate that, while the intensity of exercise has increased, the LG has not reached a level of work above the anaerobic threshold. In these preliminary studies, 30% incline walking at reduced gravity may not require anaerobic LG activity due to the low exercise intensity (42.8 +/- 1.6% of VO(sub 2max)). It is also possible that at reduced gravity additional work is being done by muscle groups other than the calf.

Ellerby, Gwenn E. C.↗