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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Heterodyne Spectroscopy in the Thermal Infrared Region: A Window on Physics and Chemistry

The thermal infrared region contains molecular bands of many of the most important species in gaseous astronomical sources. True shapes and frequencies of emission and absorption spectral lines from these constituents of planetary and stellar atmospheres contain unique information on local temperature and abundance distribution, non-thermal effects, composition, local dynamics and winds. Heterodyne spectroscopy in the thermal infrared can remotely measure true line shapes in relatively cool and thin regions and enable the retrieval of detailed information about local physics and chemistry. The concept and techniques for heterodyne detection will be discussed including examples of thermal infrared photomixers and instrumentation used in studies of several astronomical sources. Use of heterodyne detection to study non-LTE phenomena, planetary aurora, minor planetary species and gas velocities (winds) will be discussed. A discussion of future technological developments and relation to space flight missions will be addressed.

Kostiuk, Theodor↗
NASA NTRS2007

An Investigation of the Characterization of Cloud Contamination in Hyperspectral Radiances

In regions lacking direct observations, the assimilation of radiances from infrared and microwave sounders is the primary method for characterizing the atmosphere in the analysis process. In recent years, technological advances have led to the launching of more advanced sounders, particularly in the thermal infrared spectrum. With the advent of these hyperspectral sounders, the amount of data available for the analysis process has and will continue to be dramatically increased. However, the utilization of infrared radiances in variational assimilation can be problematic in the presence of clouds; specifically the assessment of the presence of clouds in an instantaneous field of view (IFOV) and the contamination in the individual channels within the IFOV. Various techniques have been developed to determine if a channel is contaminated by clouds. The work presented in this paper and subsequent presentation will investigate traditional techniques and compare them to a new technique, the C02 sorting technique, which utilizes the high spectral resolution of the Atmospheric Infrared Sounder (AIRS) within the framework of the Gridpoint Statistical Interpolation (GSI) 3DVAR system. Ultimately, this work is done in preparation for the assessment of short-term forecast impacts with the regional assimilation of AIRS radiances within the analysis fields of the Weather Research and Forecast Nonhydrostatic Mesoscale Model (WRF-NMM) at the NASA Short-term Prediction Research and Transition (SPORT) Center.

McCarty, William↗
NASA NTRS1973

Chemical analysis of outgassing contaminants on spacecraft surfaces

Methods for analyzing and characterizing outgassing contaminants from such materials as RTV 501 potting compound and S 13 G paint are presented. Fractional distillation of a gross distillate from RTV 501 rubber was carried out and the distilled fractions examined as to their ultraviolet and infrared spectra by gas liquid chromatography. A sensitive technique for structural analysis and molecular identification was found to consist of a gas chromatography-mass spectroscopy system, which was determined to be economically unfeasible at present.

Mcnutt, R. C.↗
NASA NTRS1976

Soil water content and evaporation determined by thermal parameters obtained from ground-based and remote measurements

Soil water contents from both smooth and rough bare soil were estimated from remotely sensed surface soil and air temperatures. An inverse relationship between two thermal parameters and gravimetric soil water content was found for Avondale loam when its water content was between air-dry and field capacity. These parameters, daily maximum minus minimum surface soil temperature and daily maximum soil minus air temperature, appear to describe the relationship reasonably well. These two parameters also describe relative soil water evaporation (actual/potential). Surface soil temperatures showed good agreement among three measurement techniques: in situ thermocouples, a ground-based infrared radiation thermometer, and the thermal infrared band of an airborne multispectral scanner.

Reginato, R. J.↗
NASA NTRS1977

Electromagnetic power absorber

Device has reflection coefficient of order of few tenths of percent and is designed to maintain isothermal temperature distribution in high-power microwave and laser applications. Rigid tile functions over broad temperature range and serves as blackbody radiometric standard. Tile modules allow assembly of compact and economical custom-design configurations. Epoxy surface of tiles is insulated with styrofoam against environmental changes and is not subject to convective heat loss. Technique also prevents moisture accumulation and serves as infrared radiation shield.

Iwasaki, R.↗
NASA NTRS1978

The potential for astrometry in the infrared

Infrared interferometry promises to be a useful astrometric technique. Preliminary measurements of the star alpha Orionis made with a heterodyne interferometer exhibit phase coherence over a period of at least 1000 seconds. The measurements were equivalent to a positional determination of 60 milliarcsecond accuracy every 5 seconds of integration.

Storey, J. W. V.↗
NASA NTRS1981

Four band differential radiometer for monitoring LNG vapors

The development by JPL of a four band differential radiometer (FBDR) which is capable of providing a fast rate of response, accurate measurements of methane, ethane, and propane concentrations on the periphery of a dispersing LNG cloud. The FBDR is a small, low power, lightweight, portable instrument system that uses differential absorption of near infrared radiation by the LNG cloud as a technique for the determination of concentration of the three gases as the LNG cloud passes the instrument position. Instrument design and data analysis approaches are described. The data obtained from the FBDR prototype instrument system deployed in an instrument array during two 40 cubic meter spill tests are discussed.

Simmonds, J. J.↗
NASA NTRS1982

Aircraft measurement of sea surface temperature during the West Coast Experiment

During the West Coast Experiment in March 1977, a test was conducted to ascertain the effectiveness of using remote sensing techniques to estimate sea surface temperature (SST) from infrared (IR) emissions of the sea surface. Aircraft flights were made over three buoys moored in southern California coastal waters, and data was collected of sea surface emissions at thermal IR wavelengths (7.95-13.5 micrometers). SST obtained from the remote sensing measurements were compared with in situ SST measured with thermistors mounted on the buoys. The remotely determined SST were from 1.4-2.9 C lower than the in situ measurements. Several factors are discussed that could account for the differences.

Schieldge, J. P.↗
NASA NTRS1981

Application of remote sensing to land and water resource planning: The Pocomoke River Basin, Maryland

Because of the size of the Pocomoke River Basin, the inaccessibility of certain areas, and study time constraints, several remote sensing techniques were used to collect base information on the river corridor, (a 23.2 km channel) and on a 1.2 km wooded floodplain. This information provided an adequate understanding of the environment and its resources, thus enabling effective management options to be designed. The remote sensing techniques used for assessment included manual analysis of high altitude color-infrared photography, computer-assisted analysis of LANDSAT-2 imagery, and the application of airborne oceanographic Lidar for topographic mapping. Results show that each techniques was valuable in providing the needed base data necessary for resource planning.

Wildesen, S. E.↗
NASA NTRS1985

Synoptic cryosphere-atmosphere interactions in the Northern Hemisphere from DMSP image analysis

A climatology of Northern Hemisphere cyclonic cloud vortices is developed from high-resolution Defense Meteorological Satellite Program (DMSP) infrared imagery for mid-season months. The technique which is described involves pattern recognition using a detailed vortex classification system. Variations in hemispheric frequencies of successive vortex types are dominantly seasonal rather than latitudinal and imply a close association with surface (mainly cryosphere) variations. More extensive sea ice or snow cover in April and January is associated with increased cyclogenesis, indicating enhanced surface-atmosphere feedback. A significant relationship exists between cloud-vortex variations and the sea ice boundary, but not with the continental snowline.

Carleton, A. M.↗
NASA NTRS1985

Tentative identification of the 780/cm nu-4 band Q branch of chlorine nitrate in high-resolution solar absorption spectra of the stratosphere

According to models of the photochemistry of the stratosphere, chlorine nitrate (ClONO2) is an important temporary reservoir of stratospheric chlorine. At night, ClO is believed to combine in a three-body reaction with NO2 to form chlorine nitrate. During daylight, chlorine nitrate is destroyed by photolysis to form free chlorine and NO3. Infrared spectroscopy has the potential to provide a technique for conducting important quantitative measurements of stratospheric chlorine nitrate. The present paper reports a detailed study of spectra in the 780/cm region. This study has led to the tentative identification of the nu-4 band Q branch of ClONO2 as a significant contributor to the observed stratospheric absorption near 780.21 per cm.

Rinsland, C. P.↗
NASA NTRS1986

Brewster-Plate Spoiler for Laser Spectrometer

Oscillating Brewster plate reduces effects of unwanted interference fringes on absorption-spectroscopic measurements obtained with tuned diode lasers. Plate modulates optical-path length past several resonance peaks causing interference fringes to pass by rapidly and become blurred. Thus, fringe effects averaged out over time. Technique used at other wavelengths from ultraviolet to infrared and in spectrometers with short or long optical paths, including those with retroreflectors or multipass cells.

Webster, C. R.↗
NASA NTRS1987

Mechanisms of polymer degradation using an oxygen plasma generator

An RF oxygen plasma generator was used to produce polymer degradation which appears to be similar to that which has been observed in low Earth orbit. Mechanisms of this type of degradation were studied by collecting the reaction products in a cryogenic trap and identifying the molecular species using infrared, mass spectral, and X-ray diffraction techniques. No structurally dependent species were found from Kapton, Teflon, or Saran polymers. However, very reactive free radical entities are produced during the polymer degradation, as well as carbon dioxide and water. Reactions of the free radicals with the glass reaction vessel, with copper metal in the cold trap, and with a triphenyl phosphate scavenger in the cold trap, demonstrated the reactivity of the primary products.

Colony, Joe A.↗
NASA NTRS1989

Effect of metal stress on the thermal infrared emission of soybeans: A greenhouse experiment - Possible utility in remote sensing

Manganese-sensitive forest and manganese-tolerant lee soybean cultivars were subjected to differential manganese stress in loring soil in a greenhouse experiment. Leaf temperature measurements were made using thermistors for forest and lee. Manganese-stressed plants had higher leaf temperatures than control plants in both forest and lee. Results of this experiment have potential applications in metal stress detection using remote sensing thermal infrared data over large areas of vegetation. This technique can be useful in reconnaissance mineral exploration in densely-vegetated regions where conventional ground-based methods are of little help.

Suresh, R.↗
NASA NTRS1989

Low temperature measurement of the vapor pressures of planetary molecules

Interpretation of planetary observations and proper modeling of planetary atmospheres are critically upon accurate laboratory data for the chemical and physical properties of the constitutes of the atmospheres. It is important that these data are taken over the appropriate range of parameters such as temperature, pressure, and composition. Availability of accurate, laboratory data for vapor pressures and equilibrium constants of condensed species at low temperatures is essential for photochemical and cloud models of the atmospheres of the outer planets. In the absence of such data, modelers have no choice but to assume values based on an educated guess. In those cases where higher temperature data are available, a standard procedure is to extrapolate these points to the lower temperatures using the Clausius-Clapeyron equation. Last summer the vapor pressures of acetylene (C2H2) hydrogen cyanide (HCN), and cyanoacetylene (HC3N) was measured using two different methods. At the higher temperatures 1 torr and 10 torr capacitance manometers were used. To measure very low pressures, a technique was used which is based on the infrared absorption of thin film (TFIR). This summer the vapor pressure of acetylene was measured the TFIR method. The vapor pressure of hydrogen sulfide (H2S) was measured using capacitance manometers. Results for H2O agree with literature data over the common range of temperature. At the lower temperatures the data lie slightly below the values predicted by extrapolation of the Clausius-Clapeyron equation. Thin film infrared (TFIR) data for acetylene lie significantly below the values predicted by extrapolation. It is hoped to bridge the gap between the low end of the CM data and the upper end of the TFIR data in the future using a new spinning rotor gauge.

Kraus, George F.↗
NASA NTRS1993

The Mars Aerial Platform (MAP) mission

The Mars Aerial Platform (MAP) mission is a conceptual design for a low-cost, Discovery-class mission whose purpose would be to generate tens of thousands of very-high-resolution (20 cm/pixel) pictures of the martian surface, map the global circulation of the martian atmosphere, and examine the surface and subsurface with ground-penetrating radar, infrared spectroscopy, neutron spectroscopy, and other remote sensing techniques. The data would be acquired by instruments that are carried by balloons flying at a nominal altitude of about 7 km over the martian surface. Because new balloon and microspacecraft technology is now available, the balloon probes could be quite long-lived, lasting hundreds or even thousands of days, producing an immense science harvest in the process. Together with the Mars Environmental Survey (MESUR) surface network science mission, MAP would revolutionize our knowledge of the Red Planet.

Zubrin, R.↗