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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Assessment of MSS spectral indexes for monitoring arid rangeland

The utility of MSS spectral indexes for monitoring arid rangeland vegetation was tested by determining correlations between spectral indexes and vegetation parameters and by examining retrospective MSS data to determine if vegetation change could be detected and measured using spectral indexes. MSS Band 5, albedo, and the Kauth-Thomas Brightness component appear to be useful for monitoring total vegetation cover. Multiseasonal green vegetation indexes could be used to estimate changes in the shrub/grass ratio. In retrospective monitoring, spectral index change appeared to be offset from true change, indicating that the methods used to standardize data sets for differences in solar elevation and sensor radiometric response were not completely successful.

Musick, H. B.↗
NASA NTRS1986

The response function of modulated grid Faraday cup plasma instruments

Modulated grid Faraday cup plasma analyzers are a very useful tool for making in situ measurements of space plasmas. One of their great attributes is that their simplicity permits their angular response function to be calculated theoretically. An expression is derived for this response function by computing the trajectories of the charged particles inside the cup. The Voyager Plasma Science (PLS) experiment is used as a specific example. Two approximations to the rigorous response function useful for data analysis are discussed. The theoretical formulas were tested by multi-sensor analysis of solar wind data. The tests indicate that the formulas represent the true cup response function for all angles of incidence with a maximum error of only a few percent.

Barnett, A.↗
NASA NTRS1986

Results from the Balloon Ozone Intercomparison Campaign (BOIC)

Data from the BOIC which consisted of three balloon missions conducted in Palestine, Texas from June 1983 to March 1984 are presented. The BOIC was to assess the ability to perform ozone measurements from balloon platforms. The accuracy and precision of the various ozone measurement systems, which were composed of a photometer, a mass spectrometer, and solar UV absorption sensors, are evaluated. The ozone observations obtained with the instruments on the three flight missions are analyzed and intercompared. The flight in situ data are also compared to the National Bureau of Standards reference photometer, satellite measurements, and under simulated stratospheric pressure and ozone concentrations.

Hilsenrath, E.↗
NASA NTRS1989

Modeling directional thermal radiance from a forest canopy

The thermal vegetation canopy radiance model of Smith et al. (1981) is extended to account for the geometrically rough structure of a forest canopy. Fourier series expansion of a canopy height profile is used to calculate improved view facts which partially account for directional variations in canopy thermal radiance transfers. Predictions from the Smith model and the modified model are compared with experimental data obtained over a deciduous forest site in Tennessee. The results show that thermal radiance from a forest canopy depends on sensor viewing angle, solar position, and the degree of geometric roughness of the canopy surface. The maximum off-nadir angle variation in the original model was 1.6 deg C, compared with 4.4 C for the modified model.

Mcguire, M. J.↗
NASA NTRS1995

Extinction coefficient (1 micrometer) properties of high-altitude clouds from solar occultation measurements (1985-1990): Evidence of volcanic aerosol effect

The properties of the 1-micrometer volume extinction coefficient of two geographically different high-altitude cloud systems have been examined for the posteruption period (1985-1990) of the April 1982 El Chichon volcanic event with emphasis on the effect of volcanic aerosols on clouds. These two high-altitude cloud systems are the tropical clouds in the tropopause region observed by the Stratospheric Aerosol and Gas Experiment (SAGE) 2 and the polar stratospheric clouds (PSCs) sighted by the Stratospheric Aerosol Measurement (SAM) 2. The results indicate that volcanic aerosols alter the frequency distributions of these high-altitude clouds in such a manner that the occurrence of clouds having high extinction coefficients (6 x 10(exp -3) - 2 x 10(exp -2)/km) is suppressed, while that of clouds having low extinction coefficients (2 x 10(exp -3) - 6 x 10(exp -2)/km) is enhanced. This influence of the volcanic aerosols appears to be opposite to the increase in the extinction coefficient of optically thick clouds observed by the Earth Radiation Budget Experiment (ERBE) during the initial posteruption period of the June 1991 Pinatubo eruption. A plausible explanation of this difference, based on the Mie theory, is presented. As a consequence of the Mie theory, the effective radius of most, if not all, of the high-altitude clouds, measured by the SAGE series of satellite instruments must be less than about 0.8 micrometers. This mean cloud particle size implied by the satellite extinction-coefficient data at a single wavelength (1 micrometer) is further substantiated by the particle size analysis based on cloud extinction coefficient at two wavelengths (0.525 and 1.02 micrometers) obtained by the SAGE 2 observations. Most of the radiation measured by ERBE is reflected by cloud systems comprised of particles having effective radii much greater than 1 micrometer. A reduction in the effective radius of these clouds due to volcanic aerosols is expected to increase their extinction-coefficient values, opposite the effect observed by SAGE 2 and SAM 2. This work further illustrates the capability of the solar occultation satellite sensor to provide particulate extinction-coefficient measurements important to the study of the aerosol-cloud interactions. It is important to examine the variations of the extinction coefficient of these two high-altitude cloud systems for the posteruption years of the Pinatubo volcanic event for further evidence of the impact of volcanic aerosols on high-altitude clouds.

Wang, Pi-Huan↗
NASA NTRS2006

A New Empirical Thermospheric Density Model JB2006 using New Solar Indices

A new empirical atmospheric density model is developed using the CIRA72 (Jacchia 71) model as the basis for the diffusion equations. New solar indices based on orbit based sensor data are used for the solar irradiances in the extreme and far ultraviolet wavelengths. New exospheric temperature and semiannual density equations are employed to represent the major thermospheric density variations. Temperature correction equations are also developed for diurnal and latitudinal effects, and finally density correction factors are used for model corrections required at high altitude (1500-4000 km). The new model, Jacchia-Bowman 2006, is validated through comparisons of accurate daily density drag data previously computed for numerous satellite. For 400 km altitude the standard deviation of 16% for the standard Jacchia model is reduced to 10% for the new JB2006 model for periods of low geomagnetic storm activity.

Bowman, Bruce R.↗
NASA NTRS2007

Probabilistic Thermal Analysis During Mars Reconnaissance Orbiter Aerobraking

A method for performing a probabilistic thermal analysis during aerobraking has been developed. The analysis is performed on the Mars Reconnaissance Orbiter solar array during aerobraking. The methodology makes use of a response surface model derived from a more complex finite element thermal model of the solar array. The response surface is a quadratic equation which calculates the peak temperature for a given orbit drag pass at a specific location on the solar panel. Five different response surface equations are used, one of which predicts the overall maximum solar panel temperature, and the remaining four predict the temperatures of the solar panel thermal sensors. The variables used to define the response surface can be characterized as either environmental, material property, or modeling variables. Response surface variables are statistically varied in a Monte Carlo simulation. The Monte Carlo simulation produces mean temperatures and 3 sigma bounds as well as the probability of exceeding the designated flight allowable temperature for a given orbit. Response surface temperature predictions are compared with the Mars Reconnaissance Orbiter flight temperature data.

Dec, John A.↗
NASA NTRS2001

Propulsion Instruments for Small Hall Thruster Integration

Planning and development are underway for the propulsion instrumentation necessary for the next AFRL electric propulsion flight project, which includes both a small Hall thruster and a micro-PPT. These instruments characterize the environment induced by the thruster and the associated data constitute part of a 'user's manual' for these thrusters. Several instruments probe the back-flow region of the thruster plume, and the data are intended for comparison with detailed numerical models in this region. Specifically, an ion probe is under development to determine the energy and species distributions, and a Langmuir probe will be employed to characterize the electron density and temperature. Other instruments directly measure the effects of thruster operation on spacecraft thermal control surfaces, optical surfaces, and solar arrays. Specifically, radiometric, photometric, and solar-cell-based sensors are under development. Prototype test data for most sensors should be available, together with details of the instrumentation subsystem and spacecraft interface.

ion probes↗
NASA NTRS2017

Importance of Calibration/Validation Traceability for Multi-Sensor Imaging Spectrometry Applications

Knowledge of calibration traceability is essential for ensuring the quality of data products relying on multiple sensors and especially true for imaging spectrometers. The current work discusses the expected impact that imaging spectrometers have in ensuring radiometric traceability for both multispectral and hyperspectral products. The Climate Absolute Radiance and Refractivity Observatory Pathfinder mission is used to show the role that high-accuracy imaging spectrometers can play in understanding test sites used for vicarious calibration of sensors. The associated Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer calibration demonstration system is used to illustrate recent advances in laboratory radiometric calibration approaches that will allow both the use of imaging spectrometers as calibration standards as well as to ensure the consistency of the multiple imaging spectrometers expected to be on orbit in the next decade.

imagin↗
NASA NTRSDate not supplied

TPSAS-NF1676L-20735-DND

Higher than normal accuracy is required to rigorously observe decadal climate change. But what level is needed? How can this be quantified? This presentation will summarize a new more rigorous and quantitative approach to determining the required accuracy for climate change observations (Wielicki et al., 2013, BAMS). Most current global satellite observations cannot meet this accuracy level. A proposed new satellite mission to resolve this challenge is CLARREO (Climate Absolute Radiance and Refractivity Observatory). CLARREO is designed to achieve advances of a factor of 10 for reflected solar spectra and a factor of 3 to 5 for thermal infrared spectra (Wielicki et al., Oct. 2013 BAMS). The CLARREO spectrometers are designed to serve as SI traceable benchmarks for the Global Satellite Intercalibration System (GSICS) and to greatly improve the utility of a wide range of LEO and GEO infrared and reflected solar passive satellite sensors for climate change observations (e.g. CERES, MODIS, VIIIRS, CrIS, IASI, Landsat, SPOT, etc). Providing more accurate decadal change trends can in turn lead to more rapid narrowing of key climate science uncertainties such as cloud feedback and climate sensitivity. A study has been carried out to quantify the economic benefits of such an advance as part of a rigorous and complete climate observing system. The study concludes that the economic value is ~ $12 Trillion U.S. dollars in Net Present Value for a nominal discount rate of 3% (Cooke et al. 2013, J. Env. Sys. Dec.). A brief summary of these two studies and their implications for the future of climate science will be presented.

Bruce Wielicki↗
NASA NTRS2022

A Radiative Transfer Simulator for PACE: Theory and Applications

A radiative transfer simulator was developed to compute the synthetic data of all three instruments onboard NASA’s Plankton Aerosol, Cloud, ocean Ecosystem (PACE) observatory, at the top of the atmosphere (TOA). The instrument suite includes the ocean color instrument (OCI), the HyperAngular Rainbow Polarimeter 2 (HARP2), and the Spectro-Polarimeter for Planetary Exploration 1 (SPEXone). The PACE simulator is wrapped around a monochromatic radiative transfer model based on the successive order of scattering (RTSOS), which accounts for atmosphere and ocean coupling, polarization, and gas absorption. Inelastic scattering, including Raman scattering from pure ocean water, fluorescence due to chlorophyll, and colored dissolved organic matter (CDOM), is also simulated. This PACE simulator can be used to explore the sensitivity of the hyperspectral and polarized reflectance of the Earth system with tunable atmosphere and ocean parameters, which include aerosol and cloud number concentration, refractive indices, and size distribution, ocean particle microphysical parameters, and solar and sensor-viewing geometry. The PACE simulator is used to study two important case studies. One is the impact of the significant uncertainty in pure ocean water absorption coefficient to the radiance field in the ultraviolet (UV) spectral region, which can be as much as 6%. The other is the influence of different amounts of brown carbon aerosols and CDOM on the polarized radiance field at TOA. The percentage variation of the radiance field due to CDOM is mostly for wavelengths smaller than 600 nm, while brown aerosols affect the whole spectrum from 350 to 890 nm, primarily due to covaried soot aerosols. Both case studies are important for aerosol and ocean color remote sensing and have not been previously reported in the literature.

PACE↗
DOE OSTI2021

Meteodrone data

The University of Nebraska-Lincoln (UNL) Meteodrone (model SSE MM-641) is a small (1.1 kg GTOW, ~40 cm across) hexcopter UAS manufactured by Meteomatics. Maximum endurance is approximately 30 min and estimated maximum operating altitude of 1500 m. Profiles can be executed at ascent/descent rates up to 10 m/s. The Meteodrone is capable of measuring temperature, relative humidity, wind velocity and GPS position time-stamped with GPS time. Temperature and dual relative humidity sensors are shielded from solar exposure by a housing with a vertically oriented air intake and hoirizontal exhaust. Sensor aspiration is driven by rotorwash across the horizontal exhaust. In its current configuration data are recorded only when executing vertical profiles. Attitude and position are updated at a data rate of 20 Hz while meteorological observations are updated at 10 Hz.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1981

A summary of results from solar monitoring rocket flights

Three rocket flights to measure the solar constant and provide calibration data for sensors aboard Nimbus 6, 7, and Solar Maximum Mission (SMM) spacecraft were accomplished. The values obtained by the rocket instruments for the solar constant in SI units are: 1367 w/sq m on 29 June 1976; 1372 w/sq m on 16 November 1978; and 1374 w/sq m on 22 May 1980. The uncertainty of the rocket measurements is + or - 0.5%. The values obtained by the Hickey-Frieden sensor on Nimbus 7 during the second and third flights was 1376 w/sq m. The value obtained by the Active Cavity Radiometer Model IV (ACR IV) on SMM during the flight was 1368 w/sq m.

Duncan, C. H.↗
NASA NTRS1987

The Giotto three-dimensional positive ion analyser

An instrument to measure the three-dimensional energy distribution of positive ions in order to study the interaction between the solar wind and ionized Halley cometary particles was designed. Two sensors measure the distribution from 10 eV to 20 keV once per spacecraft spin and the distribution from 90 eV to 90 keV, with coarse mass discrimination, once every 32 spins. The instrument was turned on September 8, 1985. The performance throughout all testing was nominal. The spacecraft was greater than 10 million km from the earth in the solar wind. The only population identified is the solar wind. The Fast Ion Sensor follows solar wind variations with its autoranging capability. The Implanted Ion Sensor identifies higher mass ions such as O(6+) and O(5+) in the solar wind.

Johnstone, A. D.↗
NASA NTRS1975

Haze and sun angle effects on automatic classification of satellite data-simulation and correction

Variations in sun angle and haze level change the spectral signatures collected by multispectral scanners (MSS). This paper describes methods and computer programs that have been developed to simulate the effect of such variations and to correct for them. A basic program, Prediction of the Response of Earth Pointed Sensors (PREPS), is used to calculate the response of the sensor as a function of solar angle, atmospheric haze level, and target reflectance. It is then simply a matter of interpolating these results to simulate changes in haze level or solar angle. In principle, this can be done for any sensor, although at the present time it has been completed for only one - the ERTS-1 MSS.

Potter, J. F.↗
NASA NTRSDate not supplied

Leveraging ­ CPF Spectral Information for Effective Angular Corrections in Sensor Inter-calibration Studies

The Climate Absolute Radiance and Refractivity Observatory Pathfinder (CPF) mission will provide a high-accuracy (0.3% radiometric uncertainty at k=1) SI-traceable on-orbit calibration reference for sensor intercalibration in reflective solar spectral region. CPF inter-calibration algorithms have been developed to address various sampling differences between CPF and target sensors, particularly in spectral, angular, spatial and temporal domains. CPF provides unique hyper-spectral measurements that allow the utilization of rich spectral information for critical inter-calibration procedures including angular correction and spectral-gap filling. The angular correction scheme of CPF mission has been constructed based on the spectral correlation relationship between CPF observed spectra and the spectra to be measured at the viewing/sun geometry angles of target sensors. The angular correction relationship is both angular and scene dependent. The scene variability issue can impose undesired uncertainties that complicates the correction for those errors. We have demonstrated that hyper-spectral radiance information can be well utilized to identify different scene types associated with CPF observations. Using spectral radiances-based scene clustering analysis can greatly reduce the uncertainty associated with the angular correction algorithm. Additionally, a reliable quality control scheme has been established, utilizing spectral similarity and regression-prediction error analyses, to ensure the successful and efficient implementation of the angular correction method.

Wan Wu↗
NASA NTRS2003

MOBY, A Radiometric Buoy for Performance Monitoring and Vicarious Calibration of Satellite Ocean Color Sensors: Measurement and Data Analysis Protocols

The Marine Optical Buoy (MOBY) is the centerpiece of the primary ocean measurement site for calibration of satellite ocean color sensors based on independent in situ measurements. Since late 1996, the time series of normalized water-leaving radiances L(sub WN)(lambda) determined from the array of radiometric sensors attached to MOBY are the primary basis for the on-orbit calibrations of the USA Sea-viewing Wide Field-of-view Sensor (SeaWiFS), the Japanese Ocean Color and Temperature Sensor (OCTS), the French Polarization Detection Environmental Radiometer (POLDER), the German Modular Optoelectronic Scanner on the Indian Research Satellite (IRS1-MOS), and the USA Moderate Resolution Imaging Spectrometer (MODIS). The MOBY vicarious calibration L(sub WN)(lambda) reference is an essential element in the international effort to develop a global, multi-year time series of consistently calibrated ocean color products using data from a wide variety of independent satellite sensors. A longstanding goal of the SeaWiFS and MODIS (Ocean) Science Teams is to determine satellite-derived L(sub WN)(labda) with a relative combined standard uncertainty of 5 %. Other satellite ocean color projects and the Sensor Intercomparison for Marine Biology and Interdisciplinary Oceanic Studies (SIMBIOS) project have also adopted this goal, at least implicitly. Because water-leaving radiance contributes at most 10 % of the total radiance measured by a satellite sensor above the atmosphere, a 5 % uncertainty in L(sub WN)(lambda) implies a 0.5 % uncertainty in the above-atmosphere radiance measurements. This level of uncertainty can only be approached using vicarious-calibration approaches as described below. In practice, this means that the satellite radiance responsivity is adjusted to achieve the best agreement, in a least-squares sense, for the L(sub WN)(lambda) results determined using the satellite and the independent optical sensors (e.g. MOBY). The end result of this approach is to implicitly absorb unquantified, but systematic, errors in the atmospheric correction, incident solar flux, and satellite sensor calibration into a single correction factor to produce consistency with the in situ data.

Clark, Dennis K.↗
NASA NTRS2016

Assessment of MODIS On-Orbit Calibration Using a Deep Convective Cloud Technique

The MODerate Resolution Imaging Spectroradiometer (MODIS) sensors onboard Terra and Aqua satellites are calibrated on-orbit with a solar diffuser (SD) for the reflective solar bands (RSB). The MODIS sensors are operating beyond their designed lifetime and hence present a major challenge to maintain the calibration accuracy. The degradation of the onboard SD is tracked by a solar diffuser stability monitor (SDSM) over a wavelength range from 0.41 to 0.94 micrometers. Therefore, any degradation of the SD beyond 0.94 micrometers cannot be captured by the SDSM. The uncharacterized degradation at wavelengths beyond this limit could adversely affect the Level 1B (L1B) product. To reduce the calibration uncertainties caused by the SD degradation, invariant Earth-scene targets are used to monitor and calibrate the MODIS L1B product. The use of deep convective clouds (DCCs) is one such method and particularly significant for the short-wave infrared (SWIR) bands in assessing their long-term calibration stability. In this study, we use the DCC technique to assess the performance of the Terra and Aqua MODIS Collection-6 L1B for RSB 1 3- 7, and 26, with spectral coverage from 0.47 to 2.13 micrometers. Results show relatively stable trends in Terra and Aqua MODIS reflectance for most bands. Careful attention needs to be paid to Aqua band 1, Terra bands 3 and 26 as their trends are larger than 1% during the study time period. We check the feasibility of using the DCC technique to assess the stability in MODIS bands 17-19. The assessment test on response versus scan angle (RVS) calibration shows substantial trend difference for Aqua band 1between different angles of incidence (AOIs). The DCC technique can be used to improve the RVS calibration in the future.

Mu, Qiaozhen↗