Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “retrievals”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Feasibility Study of the Superconducting Gravity Gradiometer (SGG) Flight Test on the European Retrievable Carrier (EURECA)

A study was performed to determine the feasibility of conducting a flight test of the Superconducting Gravity Gradiometer (SGG) Experiment Module on one of the reflights of the European Retrievable Carrier (EURECA). EURECA was developed expressly to accommodate space science experimentation, while providing a high quality microgravity environment. As a retrievable carrier, it offers the ability to recover science experiments after a nominal six months of operations in orbit. The study concluded that the SGG Experiment Module can be accommodated and operated in a EURECA reflight mission. It was determined that such a flight test would enable the verification of the SGG Instrument flight performance and validate the design and operation of the Experiment Module. It was also concluded that a limited amount of scientific data could be obtained on this mission.

Source record↗
NASA NTRS1989

Column atmospheric water vapor retrievals from airborne imaging spectrometer data

High-spatial-resolution column atmospheric water vapor amounts were derived from spectral data collected by the Airborne Visible Infrared Imaging Spectrometer (AVIRIS). The quantitative derivation is made by curve fitting observed spectra with calculated spectra in the 1.14- and 0.94-micron water-vapor band absorption regions with a nonlinear least-squares technique. The precision of the retrieved column water vapor is approximately 5 percent. The derived column water vapor amounts are independent of the absolute surface reflectance. Curve fitting of spectra near 1 micron from areas covered with vegetation indicates that both the amount of atmospheric water vapor and the moisture content of vegetation can be retrieved simultaneously. It should be possible to measure column water vapor over land areas from satellite altitude with the proposed high-resolution imaging spectrometer or even the moderate-resolution imaging spectrometer.

Gao, Bo-Cai↗
NASA NTRS1990

Radiative transfer based retrieval of reflectance from calibrated radiance imagery measured by an imaging spectrometer for lithological mapping of the Clark Mountains, California

Spectral radiance imagery measured by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) are reduced to reflectance through compensation for atmospheric scattering, water vapor absorption, absorption of the well mixed gases, solar irradiance and the solar zenith angle. The LOWTRAN 7 (Kneizys et al., 1989) radiative transfer code form the basis for this retrieal. LOWTRAN 7 is constrained with water vapor determinations from the AVIRIS radiance data through an algorithm operating on the 940 nm atmospheric water band for every spatial element. In situ measurements of atmospheric optical depths are used to constrain the LOWTRAN 7 aerosol models. Accuracy of the retrieved reflectance spectra is evaluated with respect to surface spectra measured at the time of the overflight. The mineral bastnaesite is identified in the analysis of the retrieved reflectance imagery. These reflectance data provide a means to map the subtle mineral gradients in the PreCambrian block of the Clark Mountain range in southeastern California for geological analysis.

Green, Robert O.↗
NASA NTRS1991

The 27-28 October 1986 FIRE Cirrus case study - Retrieval of cloud particle sizes and optical depths from comparative analyses of aircraft and satellite-based infrared measurements

Infrared radiance measurements were acquired from a narrow-field nadir-viewing radiometer based on the NASA ER-2 aircraft during a coincident Landsat 5 overpass on October 28, 1986 as part of the FIRE Cirrus IFO in the vicinity of Lake Michigan. The spectral bandpasses are 9.90-10.87 microns for the ER-2-based radiometer and 10.40-12.50 microns for the Landsat thematic mapper band. After adjusting for spatial and temporal differences, a comparative study using data from these two instruments is undertaken in order to retrieve cirrus cloud ice-crystal sizes and optical depths. Retrieval is achieved by analysis of measurement correlations between the two spectral bands and comparison to multistream radiative transfer model calculations. The results indicate that the equivalent sphere radii of the cirrus ice crystals were typically less than 30 microns. Such particles were too small to be measured by the available in situ instrumentation. Cloud optical depths at a reference wavelength of 11.4 microns ranged from 0.3 to 2.0 for this case study. Supplemental results in support of this study are described using radiation measurements from the King Air aircraft, which was also in near coincidence with the Landsat overpass.

Hammer, Philip D.↗
NASA NTRS1991

Automated information retrieval using CLIPS

Expert systems have considerable potential to assist computer users in managing the large volume of information available to them. One possible use of an expert system is to model the information retrieval interests of a human user and then make recommendations to the user as to articles of interest. At Cal Poly, a prototype expert system written in the C Language Integrated Production System (CLIPS) serves as an Automated Information Retrieval System (AIRS). AIRS monitors a user's reading preferences, develops a profile of the user, and then evaluates items returned from the information base. When prompted by the user, AIRS returns a list of items of interest to the user. In order to minimize the impact on system resources, AIRS is designed to run in the background during periods of light system use.

Raines, Rodney Doyle, III↗
NASA NTRS1991

A vector-product information retrieval system adapted to heterogeneous, distributed computing environments

Vector-product information retrieval (IR) systems produce retrieval results superior to all other searching methods but presently have no commercial implementations beyond the personal computer environment. The NASA Electronic Library Systems (NELS) provides a ranked list of the most likely relevant objects in collections in response to a natural language query. Additionally, the system is constructed using standards and tools (Unix, X-Windows, Notif, and TCP/IP) that permit its operation in organizations that possess many different hosts, workstations, and platforms. There are no known commercial equivalents to this product at this time. The product has applications in all corporate management environments, particularly those that are information intensive, such as finance, manufacturing, biotechnology, and research and development.

Rorvig, Mark E.↗
NASA NTRS1992

Retrievable payload carrier: Next generation Long Duration Exposure Facility

This paper describes the Retrievable Payload Carrier (RPC), which is a multi-experiment, free flyer spacecraft being privately developed to make in-space experimentation more accessible and economically feasible for research and development organizations. The carrier concept was derived from NASA's highly successful and flight proven Long Duration Exposure Facility (LDEF). The LDEF capabilities have been enhanced to meet new customer requirements. This reusable payload carrier is planned for launch and retrieval by the space shuttle on a regular basis. The RPC's flexible design will facilitate manifesting of the shuttle cargo bay space. The vehicle is designed so that either the entire vehicle or only individual experiments can be removed and replaced. A fully operational RPC program consists of: (1) a carrier spacecraft; (2) a ground control station; (3) a ground processing facility; and (4) the personnel required to support both the development and operational phases of the program.

Perry, Arthur T.↗
NASA NTRS1992

Retrievable payload carrier. Next generation Long Duration Exposure Facility: Update 1992

Access to space and cost have been two major inhibitors of low Earth orbit research. The Retrievable Payload Carrier (RPC) Program is a commercial space program which strives to overcome these two barriers in space experimentation. The RPC Program's fleet of spacecraft, ground communications station, payload processing facility, and experienced integration and operations team will provide a convenient 'one stop shop' for investigators seeking to use the unique vantage point and environment of low Earth orbit for research. The RPC is a regularly launched and retrieved, free-flying spacecraft providing resources adequate to meet modest payload/experiment requirements, and presenting ample surface area, volume, mass, and growth capacity for investigator usage. Mission lengths of 6-18 months are envisioned. Presented here is an update on progress made on the RPC Program's development since the November 1991 LDEF Materials Workshop.

Perry, A. T.↗
NASA NTRS1991

Theoretical computation of trace gases retrieval random error from measurements of high spectral resolution infrared sounder

The purpose of this paper is to demonstrate the trace gas profiling capabilities of future passive high spectral resolution (1 cm(exp -1) or better) infrared (600 to 2700 cm(exp -1)) satellite tropospheric sounders. These sounders, such as the grating spectrometer, Atmospheric InfRared Sounders (AIRS) (Chahine et al., 1990) and the interferometer, GOES High Resolution Interferometer Sounder (GHIS), (Smith et al., 1991) can provide these unique infrared spectra which enable us to conduct this analysis. In this calculation only the total random retrieval error component is presented. The systematic error components contributed by the forward and inverse model error are not considered (subject of further studies). The total random errors, which are composed of null space error (vertical resolution component error) and measurement error (instrument noise component error), are computed by assuming one wavenumber spectral resolution with wavenumber span from 1100 cm(exp -1) to 2300 cm(exp -1) (the band 600 cm(exp -1) to 1100 cm(exp -1) is not used since there is no major absorption of our three gases here) and measurement noise of 0.25 degree at reference temperature of 260 degree K. Temperature, water vapor, ozone and mixing ratio profiles of nitrous oxide, carbon monoxide and methane are taken from 1976 US Standard Atmosphere conditions (a FASCODE model). Covariance matrices of the gases are 'subjectively' generated by assuming 50 percent standard deviation of gaussian perturbation with respect to their US Standard model profiles. Minimum information and maximum likelihood retrieval solutions are used.

Huang, Hung-Lung↗
NASA NTRS1991

Retrievals of surface reflectances from AVIRIS data

A method for retrieving surface reflectances from spectral data collected by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) is being developed. In this method, the integrated water vapor amount on a pixel by pixel basis is derived from the 0.94- and 1.14-micron water vapor features. The water vapor, carbon dioxide (CO2), oxygen (O2) and methane (CH4) transmission spectrum in the 0.4-2.5 micron region is calculated. The derived water vapor value and the solar and observational geometry are used in the calculation. The AVIRIS spectrum is ratioed against the transmission spectrum to obtain the surface reflectance spectrum. Major mineral absorption features near 2.2 microns in retrieved reflectance spectra can be identified. Different vegetation absorption characteristics are observed. At present, the method is most useful for deriving surface reflectances from AVIRIS data measured on clear days with high visibilities.

Gao, Bo-Cai↗
NASA NTRS1992

Aerosol retrieval over land from AVHRR data - Application for atmospheric correction

Two retrieval mechanisms previously developed for Landsat are presently modified for the NOAA satellites' AVHRR. While the first of these methods retrieves aerosols on the basis of atmospheric effects on the path radiance, the second employs the change in contrast for several scenes to ascertain the change in optical thickness between the scenes. The two methods are presently discussed with reference to other methods, as well as with a view to their implications for global-scale aerosol monitoring and atmospheric correction.

Holben, Brent N.↗
NASA NTRS1992

National Space Science Data Center data archive and distribution service (NDADS) automated retrieval mail system user's guide

The National Space Science Data Center (NSSDC) has developed an automated data retrieval request service utilizing our Data Archive and Distribution Service (NDADS) computer system. NDADS currently has selected project data written to optical disk platters with the disks residing in a robotic 'jukebox' near-line environment. This allows for rapid and automated access to the data with no staff intervention required. There are also automated help information and user services available that can be accessed. The request system permits an average-size data request to be completed within minutes of the request being sent to NSSDC. A mail message, in the format described in this document, retrieves the data and can send it to a remote site. Also listed in this document are the data currently available.

Perry, Charleen M.↗
NASA NTRS1993

An integrated information retrieval and document management system

This paper describes the requirements and prototype development for an intelligent document management and information retrieval system that will be capable of handling millions of pages of text or other data. Technologies for scanning, Optical Character Recognition (OCR), magneto-optical storage, and multiplatform retrieval using a Standard Query Language (SQL) will be discussed. The semantic ambiguity inherent in the English language is somewhat compensated-for through the use of coefficients or weighting factors for partial synonyms. Such coefficients are used both for defining structured query trees for routine queries and for establishing long-term interest profiles that can be used on a regular basis to alert individual users to the presence of relevant documents that may have just arrived from an external source, such as a news wire service. Although this attempt at evidential reasoning is limited in comparison with the latest developments in AI Expert Systems technology, it has the advantage of being commercially available.

Coles, L. Stephen↗
NASA NTRS1993

Coordinating Council. Tenth Meeting: Information retrieval: The role of controlled vocabularies

The theme of this NASA Scientific and Technical Information Program Coordinating Council meeting was the role of controlled vocabularies (thesauri) in information retrieval. Included are summaries of the presentations and the accompanying visuals. Dr. Raya Fidel addressed 'Retrieval: Free Text, Full Text, and Controlled Vocabularies.' Dr. Bella Hass Weinberg spoke on 'Controlled Vocabularies and Thesaurus Standards.' The presentations were followed by a panel discussion with participation from NASA, the National Library of Medicine, the Defense Technical Information Center, and the Department of Energy; this discussion, however, is not summarized in any detail in this document.

Source record↗
NASA NTRS1992

Aerosol optical depth retrievals over the Konza Prairie

The aerosol optical depth over the Konza Prairie, near Manhattan, Kansas, was recorded at various locations by five separate teams. These measurements were made in support of the First ISLSCP Field Experiment (FIFE) and used to correct imagery from a variety of satellite and aircraft sensors for the effects of atmospheric scattering and absorption. The results from one instrument are reported here for 26 days in 1987 and for 7 in 1989. Daily averages span a range of 0.05 to 0.28 in the midvisible wavelengths. In addition, diurnal variations are noted in which the afternoon optical depths are greater than those of the morning by as much as 0.07. A comparison between instruments and processing techniques used to determine these aerosol optical depths is provided. The first comparisons are made using summer 1987 data. Differences of as much as 0.05 (midvisible) are observed. Although these data allow reasonable surface reflectance retrievals, they do not agree to within the performance limits typically associated with these types of instruments. With an accuracy goal of 0.02 a preseason calibration/comparison experiment was conducted at a mountain site prior to the final field campaign in 1989. Good calibration data were obtained, and good agreement (0.01, midvisible) was observed in the retrieved optical depth acquired over the Konza. By comparing data from the surface instruments at different locations, spatial inhomogeneities are determined. Then, data from the airborne tracking sunphotometer allow one to determine variations as a function of altitude. Finally, a technique is proposed for using the in situ data to establish an instrument calibration.

Bruegge, Carol J.↗
NASA NTRS1992

Water vapor column abundance retrievals during FIFE

A variation of the modified Langley plot algorithm is reported here and applied to the retrieval of atmospheric water column abundance from a filtered sunphotometer. In this new methodology an absorption data base (LOWTRAN 7) is used to compute a water abundance versus transmittance curve of growth, rather than the square-root dependence previously assumed. Validation of the technique is provided from an uncertainty analysis, and plans to further validate using Fourier transform spectrometers are detailed. The new sunphotometer technique is used to report local column water vapor during the First ISLSCP Field Experiment (FIFE), and comparisons are made with abundances retrieved via FIFE radiosonde observations. The sunphotometer data can best be utilized, however, to in turn validate data from airborne or in-orbit measurements of water vapor. With these flight sensors, horizontal and topographic variability within the scene can be viewed. An example of the airborne data set is given using an image from the airborne visible infrared imaging spectrometer, as acquired on August 31, 1990.

Bruegge, Carol J.↗
NASA NTRS1992

Surface reflectance retrieval from satellite and aircraft sensors - Results of sensors and algorithm comparisons during FIFE

Visible to shortwave infrared radiometric data collected by a number of remote sensing instruments on aircraft and satellite platforms were compared over common areas in the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) site on August 4, 1989, to assess their radiometric consistency and the adequacy of atmospheric correction algorithms. The instruments in the study included the Landsat 5 Thematic Mapper (TM), the SPOT 1 high-resolution visible (HRV) 1 sensor, the NS001 Thematic Mapper simulator, and the modular multispectral radiometers (MMRs). Atmospheric correction routines analyzed were an algorithm developed for FIFE, LOWTRAN 7, and 5S. A comparison between corresponding bands of the SPOT 1 HRV 1 and the Landsat 5 TM sensors indicated that the two instruments were radiometrically consistent to within about 5 percent. Retrieved surface reflectance factors using the FIFE algorithm over one site under clear atmospheric conditions indicated a capability to determine near-nadir surface reflectance factors to within about 0.01 at a reflectance of 0.06 in the visible (0.4-0.7 microns) and about 0.30 in the near infrared (0.7-1.2 microns) for all but the NS001 sensor. All three atmospheric correction procedures produced absolute reflectances to within 0.005 in the visible and near infrared. In the shortwave infrared (1.2-2.5 microns) region the three algorithms differed in the retrieved surface reflectances primarily owing to differences in predicted gaseous absorption. Although uncertainties in the measured surface reflectance in the shortwave infrared precluded definitive results, the 5S code appeared to predict gaseous transmission marginally more accurately than LOWTRAN 7.

Markham, B. L.↗
NASA NTRS1992

Analysis of the upper atmosphere CO2(nu-2) vibrational temperatures retrieved from ATMOS/Spacelab 3 observations

An analysis of the upper atmospheric (80-116 km) CO2(nu-2) vibrational temperatures retrieved from atmospheric trace molecule spectroscopy (ATMOS) experiment Spacelab 3 spectra by using a nonlocal thermodynamic equilibrium (non-LTE) radiative transfer model is presented. Thermal collisions with atmospheric atomic oxygen keep this vibrational state very close to LTE up to around 100 km. Above this height, the different deviations from LTE retrieved from ATMOS/Spacelab 3 spectra for the Northern and the Southern Hemispheres are explained in terms of this collisional process and in terms of the different kinetic temperature profiles measured at those locations. From these simultaneous observations of the kinetic and CO2(nu-2) vibrational temperatures, a deactivation rate of CO2(nu-2) by O(3P) has been derived which leads to a rate coefficient value between 3 and 6 x 10 exp -12 cu cm/s and favors an independent or negative temperature dependence rate constant for the atmospheric temperature range. Cooling rates induced by the CO2 15-micron fundamental band in the upper mesosphere and lower thermosphere were derived from the simultaneous kinetic temperature, CO2(nu-2) vibrational temperature, and CO2 concentration, as measured by ATMOS/Spacelab 3, and found to be a factor of between 5 and 10 times larger than those generally accepted until very recently.

Lopez-Puertas, M.↗