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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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NASA NTRS1981

Airborne simultaneous spectroscopic detection of laser-induced water Raman backscatter and fluorescence from chlorophyll a and other naturally occurring pigments

The airborne laser-induced spectral emission bands obtained simultaneously from water Raman backscatter and the fluorescence of chlorophyll and other naturally occurring waterborne pigments are reported here for the first time. The importance of this type data lies not only in its single-shot multispectral character but also in the application of the Raman line for correction or calibration of the spatial variation of the laser penetration depth without the need for in situ water attenuation measurements. The entire laser-induced fluorescence and Raman scatter emissions resulting from each separate 532-nm 10-nsec laser pulse are collected and spectrally dispersed in a diffraction grating spectrometer having forty photomultiplier tube detectors. Results from field experiments conducted in the North Sea and the Chesapeake Bay/Potomac River are presented. Difficulties involving the multispectral resolution of the induced emissions are addressed, and feasible solutions are suggested together with new instrument configurations and future research directions.

Hoge, F. E.↗
NASA NTRS1988

Detection of parent molecules in the IR spectrum of P/Halley with the IKS-Vega spectrometer

The two spectroscopic channels of the IKS experiment on board the Vega probes were designed for the detection of emission bands of parent molecules and/or cometary dust, in the 2.5 to 5 micrometer range and the 6 to 12 micron range respectively. On Vega 1, the experiment worked successfully, and cometary spectra were recorded at distances from the comet nucleus ranging from about 250,000 to 40,000 km. The field of view was 1 deg and the spectral resolving power was about 50. On Vega 2, no result could be obtained due to a failure of the cryogenic system. The emission spectra obtained are briefly analyzed.

Encrenaz, Therese↗
NASA NTRS2016

JPSS-1 VIIRS Radiometric Characterization and Calibration Based on Pre-Launch Testing

The Visible Infrared Imaging Radiometer Suite (VIIRS) on-board the first Joint Polar Satellite System (JPSS) completed its sensor level testing on December 2014. The JPSS-1 (J1) mission is scheduled to launch in December 2016, and will be very similar to the Suomi-National Polar-orbiting Partnership (SNPP) mission. VIIRS instrument has 22 spectral bands covering the spectrum between 0.4 and 12.6 m. It is a cross-track scanning radiometer capable of providing global measurements twice daily, through observations at two spatial resolutions, 375 m and 750 m at nadir for the imaging and moderate bands, respectively. This paper will briefly describe J1 VIIRS characterization and calibration performance and methodologies executed during the pre-launch testing phases by the government independent team to generate the at-launch baseline radiometric performance and the metrics needed to populate the sensor data record (SDR) Look-Up-Tables (LUTs). This paper will also provide an assessment of the sensor pre-launch radiometric performance, such as the sensor signal to noise ratios (SNRs), radiance dynamic range, reflective and emissive bands calibration performance, polarization sensitivity, spectral performance, response-vs-scan (RVS), and scattered light response. A set of performance metrics generated during the pre-launch testing program will be compared to both the VIIRS sensor specification and the SNPP VIIRS pre-launch performance.

VIIRS↗
NASA NTRS1988

The solar wind control of Jupiter's broad-band kilometric radio emission

Observations of the solar wind close to Jupiter are compared with the broad-band kilometric radio emission (bKOM), using data recorded by Voyager 1 and Voyager 2 during 1979. The lower bKOM frequencies, less than about 300 kHz, are found to correlate with the solar wind density and pressure and with the interplanetary magnetic field (IMF) magnitude during periods when there is a well-defined magnetic sector structure. The results suggest that lower frequency bKOM events are most likely to occur after a sector boundary has passed Jupiter during the period when the solar wind density and the IMF magnitude are increasing towards the sector center. The average bKOM energy per Jovian rotation tends to have lower values soon after the sector center has passed. Higher-frequency/higher-energy bKOM emission may be contaminated by hectometric emission (HOM) and differently correlated with solar activity. The solar wind control may also be obscured by some stronger control. It is suggested that electron density fluctuations in the Io torus, where the source is believed to be located, may be responsible for variations in the beaming and hence variations in the observed emission.

Barrow, C. H.↗
NASA NTRS2004

A New Look at Stellar Outflows: Spitzer Observations of the HH 46/47 System

We present the Early Release Observations of the HH 46/47 system and HH 46 IRS 1 source, taken with the three instruments aboard the Spitzer Space Telescope. The optically invisible southwest lobe, driven by the HH 47C bow shock, is revealed in full detail by the Infrared Array Camera (IRAC) images and displays a 'loop'-like morphology. Both of the mid-infrared outflow lobes are narrower than those of CO flow. We believe that the combination of emission by H2 rotational lines [S(11)-S(4)] and some atomic lines, which fall within the IRAC passbands, are responsible for the bulk of the observed emission, although contributions from the 3.3, 6.2, and 7.7 micron polycyclic aromatic hydrocarbon emission bands cannot be ruled out. Weak spectral features corresponding to these emitters are present in the Infrared Spectrograph spectrum of the HH 47A bow shock. The spectrum of HH 46 IRS 1 shows remarkable similarities to those of high-mass protostars, which include the presence of H2O, CO2, CH4, and possibly NH3, CH3OH, and ices. The high ice abundances and the lack of signs of thermal processing indicate that these ices in the envelope are well shielded from the powerful outflow and its cavity. Emission from the Bok globule at 24 micron is detected and displays a similar structure to that observed at 8 micron.

Herbig-Haro objects↗
NASA NTRS2018

Terra and Aqua MODIS Intercomparison Using LEO-GEO Double Difference Method

The Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites havesuccessfully operated since their launch in 1999 and in 2002, providing more than 18 and 16 years ofcontinuous global observations, respectively. The inter-comparison between the two MODIS instruments can bevery supportive for the instrument calibration and uncertainty assessment. Aqua and Terra MODIS have almostidentical relative spectral response, spatial resolution, and dynamic range for each band. Therefore, a sitedependent correction for a sensor spectral band pair is not necessary for their comparison. However, Terra is inthe morning orbit with an equator crossing time of 10:30 am, and Aqua is in the afternoon orbit with equatorcrossing time of 1:30 pm. Consequently, there is a dearth of simultaneous nadir overpasses (SNOs)between the two satellites. Major challenges in cross-sensor comparison of instruments on different satellitesinclude differences in observation time, solar angle, and view angle over selected pseudo-invariant sites.In this work, the inter-comparisons of thermal emissive bands are performed over a pseudo-invariant target,using the observations from a sensor onboard a geostationary satellite as a bridge. Himawari8 was launched onOctober 7, 2014. The Advanced Himawari Imager (AHI) onboard Himawari8 can be used as a reference tobridge the comparison between Terra and Aqua MODIS. AHI has 16 channels; with spatial resolutions from 0.5km to 2 km at nadir and produces a full disk observations every 10 minutes. The band spectral coveragematchup, comparable spatial resolution and near-simultaneous observation between MODIS and AHI providefeasibility to implement a double difference method. This comparison method minimizes the impact of thedifference in observation time and solar angle. The comparison results will be used as an assessment for MODISinstrument calibration and will be helpful for future enhancement of the L1B product.

Himawari8↗
DOE OSTI2024

Evolution and persistence of SiO emission in nanosecond laser ablation plumes

Analyzing laser-produced plasmas in a controlled oxygen-containing environment provides insight into the formation and evolution of molecular species through gas-phase oxidation. This study explores the role of ambient pressure and oxygen availability in forming SiO molecular species in laser ablation plumes. The self-emission emanating during the reactive ablation of Si targets was characterized by optical emission spectroscopy and optical time-of-flight techniques. Our results showed that the SiO species formation was greatly influenced by both the ambient pressure and oxygen availability. The intensity and the persistence of SiO emission bands are lower at higher oxygen concentrations, indicating they are depopulated by the formation of more complex silicon oxides. The oxygen partial pressure effects on plume chemistry showed that SiO formation is favored even with a minimal oxygen concentration in the environment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2000

Advances in Fluorescence Sensing Systems for the Remote Assessment of Nitrogen Supply in Field Corn

The studies described herein were conducted to better define changes in fluorescence properties of leaves from field grown corn (Zea mays L.) as they relate to varying levels of nitrogen (N) fertilization. This research was directed toward: 1) providing a remote non-destructive sensing technique to aid in the determination of optimal rates of N fertilization in corn crops and, 2) defining parameters for further development of fluorescence instrumentation to be operated remotely at field canopy levels. Fluorescence imaging bands centered in the blue (450 nm), green (525 nm), red (680 nm), and far-red (740 nm) and ratios of these bands were compared with the following plant parameters: rates of photosynthesis, N:C ratio, pigment concentrations, and grain yields. Both the fluorescence and physiological measures exhibited similar curvilinear responses to N fertilization level while significant linear correlations were obtained among fluorescence bands and band ratios to certain physiological measures of plant productivity. The red / blue, red / green, far-red / blue, far-red /green fluorescence ratios are well suited for remote observation and provided high correlations to grain yield, LAI, N:C, and chlorophyll contents. The results from this investigation indicate that fluorescence technology could aid in the determination of N fertilization requirements for corn. This discussion will also address design concepts and preliminary field trials of a mobile field-based Laser Induced Fluorescence Imaging System (LIFIS) capable of simultaneously acquiring images of four fluorescence emission bands from areas of plant canopies equaling 1 sq m and greater without interference of ambient solar radiation.

Corp, L. A.↗
NASA NTRS2007

Sensor On-orbit Calibration and Characterization Using Spacecraft Maneuvers

Spacecraft flight operations often require activities that involve different kinds of maneuvers for orbital adjustments (pitch, yaw, and roll). Different maneuvers, when properly planned and scheduled, can also be applied to support and/or to perform on-board sensor calibration and characterization. This paper uses MODIS (Moderate Resolution Imaging Spectroradiometer) as an example to illustrate applications of spacecraft maneuvers for Earth-observing sensors on-orbit calibration and characterization. MODIS is one of the key instruments for NASA's Earth Observing System (EOS) currently operated on-board the EOS Terra and Aqua spacecraft launched in December 1999 and May 2002, respectively. Since their launch, both Terra and Aqua spacecraft have made a number of maneuvers, specially the yaw and roll maneuvers, to support the MODIS on-orbit calibration and characterization. For both Terra and Aqua MODIS, near-monthly spacecraft roll maneuvers are executed for lunar observations. These maneuvers are carefully scheduled so that the lunar phase angles are nearly identical for each sensor's lunar observations. The lunar observations are used to track MODIS reflective solar bands (RSB) calibration stability and to inter-compare Terra and Aqua MODIS RSB calibration consistency. To date, two sets of yaw maneuvers (each consists of two series of 8 consecutive yaws) by the Terra spacecraft and one set by the Aqua spacecraft have been performed to validate MODIS solar diffuser (SD) bi-directional reflectance factor (BRF) and to derive SD screen transmission. Terra spacecraft pitch maneuvers, first made on March 26, 2003 and the second on April 14, 2003 (with the Moon in the spacecraft nadir view), have been applied to characterize MODIS thermal emissive bands (TEB) response versus scan angle (RVS). This is particularly important since the pre-launch TEB RSV measurements made by the sensor vendor were not successful. Terra MODIS TEB RVS obtained from pitch maneuvers have been used in the current LIB calibration algorithm. Lunq observations from pitch maneuvers also provided information to cross-calibrate MODIS with other sensors (MISR and ASTER) on the same platform. We will provide a summary of MODIS maneuver activities and their applications for MODIS calibration and characterization. The results and lessons learned discussed in this paper from MODIS maneuver activities will provide useful insights into future spacecraft and sensor operation.

Xiong, X.↗
NASA NTRS2015

JPSS-1 VIIRS Pre-Launch Radiometric Performance

The Visible Infrared Imaging Radiometer Suite (VIIRS) on-board the first Joint Polar Satellite System (JPSS) completed its sensor level testing on December 2014. The JPSS-1 (J1) mission is scheduled to launch in December 2016, and will be very similar to the Suomi-National Polar-orbiting Partnership (SNPP) mission. VIIRS instrument was designed to provide measurements of the globe twice daily. It is a wide-swath (3,040 kilometers) cross-track scanning radiometer with spatial resolutions of 370 and 740 meters at nadir for imaging and moderate bands, respectively. It covers the wavelength spectrum from reflective to long-wave infrared through 22 spectral bands [0.412 microns to 12.01 microns]. VIIRS observations are used to generate 22 environmental data products (EDRs). This paper will briefly describe J1 VIIRS characterization and calibration performance and methodologies executed during the pre-launch testing phases by the independent government team, to generate the at-launch baseline radiometric performance, and the metrics needed to populate the sensor data record (SDR) Look-Up-Tables (LUTs). This paper will also provide an assessment of the sensor pre-launch radiometric performance, such as the sensor signal to noise ratios (SNRs), dynamic range, reflective and emissive bands calibration performance, polarization sensitivity, bands spectral performance, response-vs-scan (RVS), near field and stray light responses. A set of performance metrics generated during the pre-launch testing program will be compared to the SNPP VIIRS pre-launch performance.

RSB↗
DOE OSTI2025

Strategic Lifetime Tuning of Visible-Light Absorbing Two-Coordinate Metal Complexes

This paper highlights how the singlet and triplet amide ligand centered ( 1,3 LC) and interligand charge transfer ( 1,3 ICT) states in (carbene)M(amide), M = Cu, Au (cMa) complexes influence the excited state properties when the triplet states are close in energy. To that end we prepared a set of five cMa complexes, in which the amide (i.e., 5H-benzo[b]carbazole, H-BnCz) was kept constant giving a 3 LC energy of ca. 2.15 eV. Four different carbene ligands were selected to develop M BnCz Carbene complexes which have energies for the ICT state that vary from being either markedly higher, lower, or close to the energy of the 3 LC state on the amide ligand. Steady-state and time-resolved spectroscopic studies show that the emission spectrum of the cMa complex mirrors the phosphorescence of the parent H-BnCz amide and has a luminescence decay lifetime in the millisecond regime when the lowest energy excited state is 3 LC. When the lowest energy states are 1,3 ICT in nature, the emission band is broad and featureless, giving a lifetime in the nanosecond regime. As the 3 LC and 1,3 ICT states have comparable energies, dynamic equilibrium between the states is observed with the luminescence consisting of a mixture of 3 LC and 1,3 ICT transitions. The measured lifetime of this equilibrating system is between 45 and 350 μs depending on the solvent, for both copper- and gold-based cMa complexes. Furthermore, these complexes demonstrate the ability to “park” the excited state population in the 3 LC state, allowing it to act as a reservoir for thermally activated emission, while still maintaining a very rapid equilibrium between LC and ICT states.

14 SOLAR ENERGY↗
NASA NTRS2000

Laboratory investigation of the contribution of complex aromatic/aliphatic polycyclic hybrid molecular structures to interstellar ultraviolet extinction and infrared emission

We have demonstrated by experiment that, in an energetic environment, a simple polycyclic aromatic hydrocarbon (PAH) such as naphthalene will undergo chemical reactions that produce a wide array of more complex species (an aggregate). For a stellar wind of a highly evolved star (post-asymptotic giant branch [post-AGB]), this process would be in addition to what is expected from reactions occurring under thermodynamic equilibrium. A surprising result of that work was that produced in substantial abundance are hydrogenated forms that are hybrids of polycyclic aromatic and polycyclic alkanes. Infrared spectroscopy described here reveals a spectral character for these materials that has much in common with that observed for the constituents of circumstellar clouds of post-AGB stars. It can be demonstrated that a methylene (-CH2-) substructure, as in cycloalkanes, is the likely carrier of the 6.9 microns band emission of dust that has recently been formed around IRAS 22272+5433, NGC 7027, and CPD -56 8032. Ultraviolet spectroscopy previously done with a lower limit of 190 nm had revealed that this molecular aggregate can contribute to the interstellar extinction feature at 2175 angstroms. We have now extended our UV spectroscopy of these materials to 110 nm by a vacuum ultraviolet technique. That work, described here, reveals new spectral characteristics and describes how material newly formed during the late stages of stellar evolution could have produced an extinction feature claimed to exist at 1700 angstroms in the spectrum of HD 145502 and also how the newly formed hydrocarbon material would be transformed/aged in the general interstellar environment. The contribution of this molecular aggregate to the rise in interstellar extinction at wavelengths below 1500 angstroms is also examined. The panspectral measurements of the materials produced in the laboratory, using plasmas of H, He, N, and O to convert the simple PAH naphthalene to an aggregate of complex species, provide insight into possible molecular structure details of newly formed hydrocarbon-rich interstellar dust and its transformation into aged material that becomes resident in the interstellar medium. Specifically the presence of naphthalene-like and butadiene-like conjugated structures as chromophores for the 2175 angstroms ultraviolet extinction feature is indicated.

NASA Discipline Exobiology↗
NASA NTRS1997

Land Surface Temperature Measurements from EOS MODIS Data

We applied the multi-method strategy of land-surface temperature (LST) and emissivity measurements in two field campaigns this year for validating the MODIS LST algorithm. The first field campaign was conducted in Death Valley, CA, on March 3rd and the second one in Railroad Valley, NV, on June 23-27. ER2 MODIS Airborne Simulator (MAS) data were acquired in morning and evening for these two field campaigns. TIR spectrometer, radiometer, and thermistor data were also collected in the field campaigns. The LST values retrieved from MAS data with the day/night LST algorithm agree with those obtained from ground-based measurements within 1 C and show close correlations with topographic maps. The band emissivities retrieved from MAS data show close correlations with geological maps in the Death Valley field campaign. The comparison of measurement data in the latest Railroad Valley field campaign indicates that we are approaching the goals of the LST validation: LST uncertainty less than 0.5 C, and emissivity uncertainty less than 0.005 in the 10-13 spectral range. Measurement data show that the spatial variation in LST is the major uncertainty in the LST validation. In order to reduce this uncertainty, a new component of the multi-method strategy has been identified.

Wan, Zhengming↗
NASA NTRS1975

Auroral electrons and the optical emissions of nitrogen

Simultaneous rocket measurements of the auroral electron flux and the optical emissions of N2 give a consistent picture of electron impact excitation in an aurora. The electron data show that the incident auroral electrons are nearly monoenergetic with energy about 25 keV. The overall shape of the observed low-energy electron spectrum is in good agreement with other recent observations and also with recent theoretical models, although there is some disagreement with the models in the value of the power law slope above 20 eV. A discussion of the secondary electron spectrum obtained near apogee shows that a single power law cannot accurately describe the secondary electron spectrum in the energy range from 3 to 85 eV. About 40% of the N2(+) 1NG (0,0) band emission at 3914 A is excited by electrons with energy below 85 eV.

Feldman, P. D.↗
NASA NTRS1994

Land surface temperature measurements from EOS MODIS data

A generalized split-window method for retrieving land-surface temperature (LST) from AVHRR and MODIS data has been developed. Accurate radiative transfer simulations show that the coefficients in the split-window algorithm for LST must depend on the viewing angle, if we are to achieve a LST accuracy of about 1 K for the whole scan swath range (+/-55.4 deg and +/-55 deg from nadir for AVHRR and MODIS, respectively) and for the ranges of surface temperature and atmospheric conditions over land, which are much wider than those over oceans. We obtain these coefficients from regression analysis of radiative transfer simulations, and we analyze sensitivity and error by using results from systematic radiative transfer simulations over wide ranges of surface temperatures and emissivities, and atmospheric water vapor abundance and temperatures. Simulations indicated that as atmospheric column water vapor increases and viewing angle is larger than 45 deg it is necessary to optimize the split-window method by separating the ranges of the atmospheric column water vapor and lower boundary temperature, and the surface temperature into tractable sub-ranges. The atmospheric lower boundary temperature and (vertical) column water vapor values retrieved from HIRS/2 or MODIS atmospheric sounding channels can be used to determine the range where the optimum coefficients of the split-window method are given. This new LST algorithm not only retrieves LST more accurately but also is less sensitive than viewing-angle independent LST algorithms to the uncertainty in the band emissivities of the land-surface in the split-window and to the instrument noise.

Wan, Zhengming↗
DOE OSTI2020

Point defects in Ga 2 O 3

In the field of high-power electronics, gallium oxide (Ga 2 O 3 ) is attracting attention due to its wide band gap and ability to be doped n-type. Point defects, including vacancies, impurities, and dopants, play important roles in optimizing device performance. This tutorial discusses the fundamental properties of point defects in monoclinic β-Ga 2 O 3 and the methods employed to study them. Oxygen vacancies are deep donors that do not cause n-type conductivity but may compensate acceptors. Gallium vacancies are deep acceptors that can be partially passivated by hydrogen. Substitutional magnesium is a promising acceptor that produces semi-insulating material and also forms a complex with hydrogen. Calcium and iron also have deep acceptor levels. Iridium deep donors are introduced into crystals grown from a melt in an Ir crucible. Here, other defects are introduced by irradiation with energetic particles such as neutrons or protons. In addition to altering the electronic properties, defects give rise to UV/visible emission bands in photoluminescence and cathodoluminescence spectra.

36 MATERIALS SCIENCE↗
NASA NTRS2006

Results and Lessons from MODIS Reflective Solar Bands Calibration: Pre-launch to On-orbit

MODIS is a major instrument for the NASA EOS Terra (1aunched in December 1999) and Aqua (launched in May 2002) missions. It was designed and built to enhance and extend its heritage sensors' measurements and data records with applications covering a wide range of studies of the Earth's land, oceans, and atmosphere. MODIS has 36 spectral bands (0.41 - 14.4 micrometers) located on four focal plane assemblies (FPAs). It makes measurements at three nadir spatial resolutions: 250m (bands 1-2), 500m (bands 3-7), and lkm (bands 8-36). Because of instrument design complexity and stringent calibration requirements, extensive calibration and characterization activities were conducted pre-launch by the sensor vendor (Raytheon / Santa Barbara Remote Sensing) for both Tesa and Aqua MODIS. For the 20 reflective solar bands (RSB), these activities include measurements for the detectors noise characterization and radiometric performance, system level response versus scan-angle (RVS), polarization sensitivity, and relative spectral response (RSR). Key radiometric performance was evaluated using thermal vacuum observations. On-orbit MODIS RSB calibration is performed using a solar diffuser (SD) and solar diffuser stability monitor (SDSM) system. The SD bi-directional reflectance factor (BRF) was characterized pre-launch by the sensor vendor with reference samples traceable to NIST reflectance standards. This paper provides a summary of Terra and Aqua MODIS RSB pre-launch and on-orbit calibration and characterization activities and results with focus on the detectors' noise characterization and radiometric performance. Challenging and concerning issues and lessons learned from RSB pre-launch calibration and their impact on post launch performance are also presented. A similar summary for MODIS thermal emissive bands (TEB) is reported in a separate paper in these proceedings.

Xiong, X.↗
NASA NTRS2016

Spiral Structure and Differential Dust Size Distribution in the LkH(alpha) 330 Disk

Dust trapping accelerates the coagulation of dust particles, and, thus, it represents an initial step toward the formation of planetesimals. We report H-band (1.6 microns) linear polarimetric observations and 0.87 mm interferometric continuum observations toward a transitional disk around LkH(alpha) 330. As a result, a pair of spiral arms were detected in the H-band emission, and an asymmetric (potentially arm-like) structure was detected in the 0.87 mm continuum emission. We discuss the origin of the spiral arm and the asymmetric structure and suggest that a massive unseen planet is the most plausible explanation. The possibility of dust trapping and grain growth causing the asymmetric structure was also investigated through the opacity index (beta) by plotting the observed spectral energy distribution slope between 0.87 mm from our Submillimeter Array observation and1.3 mm from literature. The results imply that grains are indistinguishable from interstellar medium-like dust in the east side (beta = 2.0 +/- 0.5) but are much smaller in the west side beta = 0.7+0.5 -0.4, indicating differential dust size distribution between the two sides of the disk. Combining the results of near-infrared and submillimeter observations, we conjecture that the spiral arms exist at the upper surface and an asymmetric structure resides in the disk interior. Future observations at centimeter wavelengths and differential polarization imaging in other bands (Y-K) with extreme AO imagers are required to understand how large dust grains form and to further explore the dust distribution in the disk.

polarimetric observations↗