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NASA NTRS1993

The origin of Venusian channels: Modelling of thermal erosion by lava

Magellan imagery has revealed that channels, apparently volcanic in origin, are abundant on the surface of Venus. There has been much debate about the origin of these channels. Are they the result of erosional (either thermal or mechanical) or constructional processes? A common characteristic of the simple sinuous channels is that they show evidence of erosion near their source and then become purely constructional, forming levees and in some cases roofing over completely. One method of showing that thermal erosion is capable of producing the type of channels seen is to use computer modeling incorporating the physical conditions on Venus and the physical characteristics of the different types of lava that may have been erupted. It is possible to calculate, relatively easily, two channel parameters. The first is the erosion rate, which combined with eruption duration, gives depth. The second is for how long after leaving the source the erupted lava will continue to be capable of thermal erosion before constructional processes dominate. Making assumptions about the rheology of the lava (e.g., assume it behaves as a Bingham plastic) along with the slope angle yields a flow velocity and therefore a distance over which thermal erosion will take place. Due to the resolution (both vertical and horizontal) of the Magellan altimetric data, the distance from the source that the channel is erosional can be much more accurately measured than the depth of the channel. This will remain the case until stereo imagery becomes available for large areas of the planet.

Bussey, D. B. J.↗
NASA NTRS1993

Polarimetric thermal emission from periodic water surfaces

Experimental results and theoretical calculations are presented to study the polarimetric emission from water surfaces with directional features. For our ground-based Ku-band radiometer measurements, a water pool was constructed on the roof of a building in the Jet Propulsion Laboratory, and a fiberglass surface with periodic corrugations in one direction was impressed on the top of the water surface to create a stationary water surface underneath it. It is observed that the measured Stokes parameters of corrugated fiberglass-covered water surfaces are functions of azimuth angles and agree very well with the theoretical calculations. The theory, after being verified by the experimental data, was then used to calculate the Stokes parameters of periodic surfaces without fiberglass surface layer and with rms height of the order of wind-generated water ripples. The magnitudes of the azimuthal variation of the calculated emissivities at horizontal and vertical polarizations corresponding to the first two Stokes parameters are found to be comparable to the values measured by airborne radiometers and SSM/I. In addition, the third Stokes parameter not shown in the literature is seen to have approximately twice the magnitude of the azimuth variation of either T(sub h) or T(sub v), which may make it more sensitive to the row direction, while less susceptive to noises because the atmospheric and system noises tend to be unpolarized and are expected to be cancelled out when the third Stokes parameter is derived as the difference of two or three power measurements, as indicated by another experiment carried out at a swimming pool with complicated surroundings. The results indicate that passive polarimetry is a potential technology in the remote sensing of ocean wind vector which is a crucial component in the understanding of global climate change. Issues related to the application of microwave passive polarimetry to ocean wind are also discussed.

Yueh, S. H.↗
NASA NTRS1993

Sculpting in cyberspace: Parallel processing the development of new software

Stimulating creativity in problem solving, particularly where software development is involved, is applicable to many disciplines. Metaphorical thinking keeps the problem in focus but in a different light, jarring people out of their mental ruts and sparking fresh insights. It forces the mind to stretch to find patterns between dissimilar concepts, in the hope of discovering unusual ideas in odd associations (Technology Review January 1993, p. 37). With a background in Engineering and Visual Design from MIT, I have for the past 30 years pursued a career as a sculptor of interdisciplinary monumental artworks that bridge the fields of science, engineering and art. Since 1979, I have pioneered the application of computer simulation to solve the complex problems associated with these projects. A recent project for the roof of the Carnegie Science Center in Pittsburgh made particular use of the metaphoric creativity technique described above. The problem-solving process led to the creation of hybrid software combining scientific, architectural and engineering visualization techniques. David Steich, a Doctoral Candidate in Electrical Engineering at Penn State, was commissioned to develop special software that enabled me to create innovative free-form sculpture. This paper explores the process of inventing the software through a detailed analysis of the interaction between an artist and a computer programmer.

Fisher, Rob↗
NASA NTRS1994

Radial microstrip slotline feed network for circular mobile communications array

In mobile and satellite communications there is a need for low cost and low profile antennas which have a toroidal pattern. Antennas that have been developed for mobile communications include a L-Band electronically steered stripline phased array, a Ka-Band mechanically steered elliptical reflector antenna and a Ka-Band printed dipole. In addition, a L-Band mechanically steered microstrip array, a L-Band microstrip phased array tracking antenna for mounting on a car roof and an X-Band radial line slotted waveguide antenna have been demonstrated. In the above electronically scanned printed arrays, the individual element radiates normally to the plane of the array and hence require a phase shifter to scan the beam towards the horizon. Scanning in the azimuth is by mechanical or electronic steering. An alternate approach is to mount microstrip patch radiators on the surface of a cone to achieve the required elevation angle. The array then scans in the azimuth by beam switching.

Simons, Rainee N.↗
NASA NTRS1994

A Supersonic Tunnel for Laser and Flow-Seeding Techniques

A supersonic wind tunnel with flow conditions of 3 lbm/s (1.5 kg/s) at a free-stream Mach number of 2.5 was designed and tested to provide an arena for future development work on laser measurement and flow-seeding techniques. The hybrid supersonic nozzle design that was used incorporated the rapid expansion method of propulsive nozzles while it maintained the uniform, disturbance-free flow required in supersonic wind tunnels. A viscous analysis was performed on the tunnel to determine the boundary layer growth characteristics along the flowpath. Appropriate corrections were then made to the contour of the nozzle. Axial pressure distributions were measured and Mach number distributions were calculated based on three independent data reduction methods. A complete uncertainty analysis was performed on the precision error of each method. Complex shock-wave patterns were generated in the flow field by wedges mounted near the roof and floor of the tunnel. The most stable shock structure was determined experimentally by the use of a focusing schlieren system and a novel, laser based dynamic shock position sensor. Three potential measurement regions for future laser and flow-seeding studies were created in the shock structure: deceleration through an oblique shock wave of 50 degrees, strong deceleration through a normal shock wave, and acceleration through a supersonic expansion fan containing 25 degrees of flow turning.

Bruckner, Robert J.↗
NASA NTRS1994

Long path monitoring of tropospheric O3, NO2, H2CO and SO2

Concentrations of tropospheric O3, NO2, H2CO, and SO2 have been measured on the Campus of the 'Universite Libre de Bruxelles' on a routine basis since October 1990. The long path system consists of a source lamp, a first 30 cm f/8 Cassegrain type telescope which collimates the light onto a slightly parabolic mirror placed on the roof of a building situated 394 m away from the laboratory. The light is sent back into a second 30 cm Cassegrain telescope. This telescope has been modified so that the output beam is a 5 cm diameter parallel beam. This beam is then focused onto the entrance aperture of the BRUKER IFS120HR fourier transform spectrometer. The two telescopes are mounted on alignment devices and the external mirror is equipped with a driving system operated from the laboratory. The choice of the light source (either a 1000 W high pressure 'ozone free' xenon lamp or a 250 W tungsten filament) and of the detector (either a solar blind UV-diode or a silicon diode) depended on the spectral region studied. These regions lie respectively from 26,000 cm(exp -1) to 30,000 cm(exp -1) (260-380 nm) and from 14,000 cm(exp -1) to 30,000 cm(exp -1) (330-700 nm). The spectra have been recorded at the resolution of 16 cm(exp -1) and with a dispersion of 7.7 cm(exp -1). They have been measured during the forward and the backward movements of the mobile mirror, in double sided mode; each spectrum is an average of 2000 scans. The time required to record a spectrum is about 45 minutes. The shape of the raw spectra in the two investigated regions are represented.

Vandaele, A. C.↗
NASA NTRS1996

The 27-28 October 1986 FIRE IFO Cirrus Case Study: Cloud Optical Properties Determined by High Spectral Resolution Lidar

During the First ISCCP Region Experiment (FIRE) cirrus intensive field observation (IFO) the High Spectral Resolution Lidar was operated from a roof top site on the University of Wisconsin-Madison campus. Because the HSRL technique separately measures the molecular and cloud particle backscatter components of the lidar return, the optical thickness is determined independent of particle backscatter. This is accomplished by comparing the known molecular density distribution to the observed decrease in molecular backscatter signal with altitude. The particle to molecular backscatter ratio yields calibrated measurements of backscatter cross sections that can be plotted ro reveal cloud morphology without distortion due to attenuation. Changes in cloud particle size, shape, and phase affect the backscatter to extinction ratio (backscatter-phase function). The HSRL independently measures cloud particle backscatter phase function. This paper presents a quantitative analysis of the HSRL cirrus cloud data acquired over an approximate 33 hour period of continuous near zenith observations. Correlations between small scale wind structure and cirrus cloud morphology have been observed. These correlations can bias the range averaging inherent in wind profiling lidars of modest vertical resolution, leading to increased measurement errors at cirrus altitudes. Extended periods of low intensity backscatter were noted between more strongly organized cirrus cloud activity. Optical thicknesses ranging from 0.01-1.4, backscatter phase functions between 0.02-0.065 sr (exp -1) and backscatter cross sections spanning 4 orders of magnitude were observed. the altitude relationship between cloud top and bottom boundaries and the cloud optical center altitude was dependent on the type of formation observed Cirrus features were observed with characteristic wind drift estimated horizontal sizes of 5-400 km. The clouds frequently exhibited cellular structure with vertical to horizontal dimension ratios of 1:5-1:1.

Grund, C. J.↗
NASA NTRS1996

Fade Measurements into Buildings from 500 to 3000 MHz

Slant-path fade measurements from 500 to 3000 MHz were made into six different buildings employing a vector network analyzer, a tower-mounted transmitting antenna and an automatically positioned receiving antenna. The objective of the measurements was to provide information for satellite audio broadcasting and personal communications satellite design on the correlation of fading inside buildings. Fades were measured with 5 cm spatial separation and every 0.2 percent of the frequency. Median fades ranged from 10 to 20 dB in woodframe houses with metal roofs and walls without and with an aluminum heat shield, respectively. The median decorrelation distance was from 0.5 to 1.1. m and was independent of frequency. The attenuation into the buildings increased only moderately with frequency in most of the buildings with a median slope of about 1 to 3 db/GHz, but increased fastest in the least attenuating building with a slope of 5 dB/GHz. The median decorrelation bandwidth ranged from 1.2 to 3.8 percent of frequency in five of the buildings, and was largest in the least attenuating building, with 20.2 percent of frequency.

Vogel, Wolfhard J.↗
NASA NTRS1997

Threatened and Endangered Species Survey for Patrick Air Force Base, Florida

A review of previous environmental work conducted at Patrick Air Force Base (PAFB) indicated that several threatened, endangered, or species of special concern occurred or had the potential to occur there. This study was implemented to collect more information on protected species at PAFB. A map of landcover types was prepared for PAFB using aerial photography, groundtruthing, and a geographic information system (GIS). Herbaceous vegetation was the most common vegetation type. The second most abundant vegetation type was disturbed shrubs/exotics. The beach and associated dune vegetation comprised 3.2% of the land area, but was the most extensive natural community within PAFB. A few isolated mangrove communities exist along the Banana River. Seventy-seven species of vascular plants occurred on the dunes, including four species listed by state agencies: spider lily (Hymenocallis latifolia), prickly pear cactus (Opuntia stricta), beach star (Remirea maritima), and inkberry (Scaevola plumien). Surveys of other habitats revealed eighty-four species of vascular plants including two state-listed species: spider lily and prickly pear cactus. Many of these areas are dominated by invasive, exotic species, particularly Brazilian pepper (Schinus terebinthifolius) and Australian pine (Casuarina equisetifolia), and native species of open or disturbed sites such as camphorweed (Heterotheca subaxillaris) and beardgrass (Andropogon spp.). Due to the isolation of PAFB from other natural areas, most exotic plant populations on the base are not an immediate threat to intact native plant communities. Dune habitat was surveyed for the southeastem beach mouse (Peromyscus polionotus niveiventris) by quarterly trapping along eight 100 m transects. No beach mice were found. The limited extent of dune habitat, its fragmented condition, and the isolation of PAFB from extant populations of the beach mouse probably accounts for its absence. Surveys of birds on PAFB found an avifauna characteristic of species that occur in the Indian River Lagoon system. Twenty-five species of waterbirds were observed during quarterly surveys on PAFB, including five species listed as species of special concern by the state of Florida: Snowy Egret (Egretta thula), Little Blue Heron (Egretta caerulea), Tricolored Heron (Egretta tricolo4, White Ibis (Eudocimus albus), and Brown Pelican (Pelecanus occidentalis). The Golf Course was used extensively by almost all species of waterbirds on PAFB. Twenty-two species of shorebirds were observed on PAFB. Although no listed species were observed, the potential exists for several protected species of shorebirds to use the beach at PAFB during some parts of the year. The Airfield runways and associated grass areas were important sites at PAFB for loafing and feeding for some shorebirds. Surveys of rooftop nesting by Least Terns (Stema antillarum) on PAFB found a large colony on a rooftop in the PAFB Industrial Area. This colony produced some independent young. Two rooftop Least Tern colonies reported from previous years were inactive during 1996. A small number of Black Skimmers (Rhynchops nigee attempted to nest at the Least Ten colony but were unsuccessful. Surveys for the gopher tortoise (Gopherus polyphemus) revealed burrows and tortoises only at the Waste Study Site; five burrows and three tortoises were observed. No Florida scrub lizards (Sceloporus woodi), eastern indigo snakes (Drymarchon corais couperl), or diamondback terrapins (Malademys terrapin terrapin) were observed. American alligators (Alligator mississippiensis) were observed on the Golf Course and using ditches, ponds, and areas along the Banana River. The amount of dune habitat could be expanded by not mowing areas adjacent to the dunes to allow dune species to colonize and expand. Planting dune species as part of the beach renourishment project will also increase this habitat. Exotic plants dominate several areas on the base and are used by threatened, endangered, and species of special concern. However, the use of native vegetation in landscaping projects throughout the base would improve habitat for wildlife, and invasive, exotic plants should not be used in any horticultural plantings. Water quality of ponds, ditches, and canals is important for waterbirds; it should be maintained and protected from contamination. Nesting Least Terns are sensitive to disturbance; rooftops used for nesting should be protected from disturbance. Monitoring of Least Tern and Black Skimmer nesting should be continued to determine what roofs are being used and whether nesting is successful. Furthermore, based on the large numbers of waterbirds observed on PAFB, continued monitoring of them is recommended.

Oddy, Donna M.↗
NASA NTRS1996

First Two Years of Observations NASA ACTS Propagation Experiment Central Oklahoma Site

Continuous observations from December 1, 1993 through November 30, 1995 were made at the ACTS Propagation Terminal on the roof of the Sarkeys Energy Center at the University of Oklahoma in Norman, Oklahoma. Beacon and radiometer observations were combined to calibrate the beacon system for the estimation of total attenuation (attenuation relative to free space) and attenuation relative to clear sky (gaseous absorption component removed). Empirical cumulative distributions (edf's) were compiled for each month of observation and for each year. The annual edf's are displayed in the figures, the monthly and annual edf's are listed in the tables. The tables are organized by blocks and pages within a block. The blocks correspond to the headings in the edf files generated by the ACTS Preprocessing (actspp) software and contained in the fourth disk in the set of ACTS Propagation Experiment CD-ROMs generated by the University of Texas.

Crane, Robert K.↗
NASA NTRS1996

Fade Measurements into Buildings from 500 to 3000 MHz

Slant-path fade measurements from 500 to 3000 MHz were made into six different buildings employing a vector network analyzer, a tower-mounted transmitting antenna and an automatically positioned receiving antenna. The objective of the measurements was to provide information for satellite audio broadcasting and personal communications satellite design on the correlation of fading inside buildings. Fades were measured with 5 cm spatial separation and every 0.2% of the frequency. Median fades ranged from 10 to 20 dB in woodframe houses with metal roofs and walls without and with an aluminum heatshield, respectively. The median decorrelation distance was from 0.5 to 1.1 m and was independent of frequency. The attenuation into the buildings increased only moderately with frequency in most of the buildings with a median slope of about 1 to 3 dB/GHz, but increased fastest in the least attenuating building with a slope of 5 dB/GHz. The median decorrelation bandwidth ranged from 1.2 to 3.8% of frequency in five of the buildings, and was largest in the least attenuating building, with 20.2% of frequency.

Vogel, Wolfhard J.↗
NASA NTRS1998

User's Manual for FEMOM3DR

FEMoM3DR is a computer code written in FORTRAN 77 to compute radiation characteristics of antennas on 3D body using combined Finite Element Method (FEM)/Method of Moments (MoM) technique. The code is written to handle different feeding structures like coaxial line, rectangular waveguide, and circular waveguide. This code uses the tetrahedral elements, with vector edge basis functions for FEM and triangular elements with roof-top basis functions for MoM. By virtue of FEM, this code can handle any arbitrary shaped three dimensional bodies with inhomogeneous lossy materials; and due to MoM the computational domain can be terminated in any arbitrary shape. The User's Manual is written to make the user acquainted with the operation of the code. The user is assumed to be familiar with the FORTRAN 77 language and the operating environment of the computers on which the code is intended to run.

Reddy, C. J.↗
NASA NTRS1999

Icehouse Effect: A Polar Autumn and Winter Cooling Trend

The icehouse effect is a hypothesized polar climate trend toward cooling (or lack of warming) in response to greenhouse warming of adjacent lower latitudes. When greenhouse warmed air from lower latitudes moves over ice and snow, it generates a stronger, more stable, cappino, inversion than in a parallel case without greenhouse warming. Because the degree of decoupling between vertically adjacent air masses is directly dependent on the strength of the inversion, the capping inversion acts somewhat analogously to the walls and roof of the icehouse of generations past. What is inside the icehouse, namely the cold polar atmospheric boundary layer (ABL) air, is preserved by the "insulation" or decoupling, provided by the warm air aloft. Observations over the Arctic Ocean have shown an unexpected lack of any detectable surface warming trend over the past 40 years. This finding strongly contradicts climate model predictions that polar regions should show the strongest effect of greenhouse warming. It also stands in contrast to the consensus reached by the Intergovernmental Panel on Climate Change (IPCC), that human caused greenhouse warming is now detectable globally. One might ask: Are these Arctic observations wrong? Or, if right, is there a plausible physical explanation for them? The published observations mentioned above used about 50,000 soundings over the Arctic Ocean. Here I present a novel analysis of ALL available Arctic rawinsonde data north of 65N--a total of more than 1.1 million soundings. The analysis confirms the previously published result: There is indeed a slight climate-cooling trend in the vast majority of the data. Importantly, there are also select conditions (very strong and very weak stability of the ABL) which show a consistent, strong Arctic warming trend. It is the juxtaposition of these warming and cooling trends which defines a unique "icehouse signature" for which an explanation can be sought.

Wetzel, Peter J.↗
NASA NTRS1997

America's Urban Forests: Keeping Our Cities Cool

The additional heating of the air over the city is the result of the replacement of naturally vegetated surfaces with those composed of asphalt, concrete, rooftops and other man-made materials. The temperatures of these artificial surfaces can be 20 to 40 C higher than vegetated surfaces. Materials such as asphalt store much of the sun's energy and remains hot long after sunset. This produces a dome of elevated air temperatures 5 to 8 C greater over the city, compared to the air temperatures over adjacent rural areas. This effect is called the "urban heat island". Tree canopies can reduce the urban heat island effect by dissipating the solar energy received by transpiring water from leaf surfaces which cools the air by taking "heat" from the air to evaporate the water and by shading surfaces like asphalt, roofs, and concrete parking lots which prevents initial heating and storage of heat. It is difficult to take enough temperature measurements over a large city area to characterize the surface temperature variability and quantify the temperature reduction effects of tree canopies. However, the use of remotely sensed thermal data from airborne scanners are ideal for the task. In a study funded by NASA, a series of flights over Huntsville AL were performed in September 1994 and over Atlanta in May 1997. In this article we will examine the techniques of analyzing remotely sensed data for measuring the effect of tree canopies in reducing the urban heat island effect.

Luvall, Jeffrey C.↗
NASA NTRS1999

Using Remote Sensing Data and Research Results for Urban Heat Island Mitigation

This paper provides information on the characteristics of the urban heat island, research designed to provide the data needed to develop effective urban heat island reduction strategies, and the development of local working groups to develop implementation plans. As background, an overview of research results on the urban heat island phenomenon and the resultant effect on energy usage and air quality will be explored. The use of more reflective roofing materials, paving materials, tree planting, and other initiatives will be explored as a basis for strategies to mitigate urban heat islands and improve the urban environment. Current efforts to use aircraft remote sensing data in Atlanta, Baton Rouge, Sacramento, and Salt Lake City and our work with non-profit organizations designated to lead public education and strategic development efforts will be presented. Efforts to organize working groups comprised of key stakeholders, the process followed in communicating research results, and methodology for soliciting feedback and incorporating ideas into local plans, policies and decision-making will be discussed. Challenges in developing and transferring data products and research results to stakeholders will be presented. It is our ultimate goal that such efforts be integrated into plans and/or decision models that encourage sustainable development.

Estes, Maury↗
NASA NTRS1985

STS-51B/Challenger - Isolated Launch View

Live footage of various isolated launch views is seen. Views of the Space Shuttle Challenger are shown from different camera sites such as the VAB (Vehicle Assembly Building) Roof, Pad Perimeter, Helicopter, Convoy, and Midfield. Also shown from different cameras is the re-entry and landing of the shuttle at Kennedy Space Center (KSC). Footage also includes the ground recovery crew as they travel to the spacecraft. Challengers crew, Commander Robert F. Overmyer, Pilot Frederick D. Gregory, Mission Specialists Don L. Lind, Norman E. Thagard, and William E. Thornton, and Payload Specialists Lodewijk van den Berg, and Taylor G. Wang are also seen leaving the craft.

Source record↗
NASA NTRS1998

Monitoring of Volcanogenic CO2-Induced Tree Kills with AVIRIS Image Data at Mammoth Mountain, California

Elevated cold CO2 emissions from the flank of Mammoth Mountain volcano on the southwest rim of the Long Valley Caldera, eastern California, have been the cause of over 100 acres of dead trees in that area since 1990. The source of the CO2 gas is thought to be from one or more magmatic intrusion(s) beneath Mammoth Mountain and is probably related to a period of seismic unrest that began in 1989. The gas rises to the surface probably from depths of a few kilometers, along faults and fracture zones. The gas is at ambient temperature and diffuses from the soil rather than discharging from distinct vents. Typically, soil gas concentrations in tree-kill areas range from 10% to over 90% CO2 by volume, as compared to normal background of < 1% in healthy forest. The gas composition is predominantly CO2 mixed with air (sulfur gases are not elevated), and C and He isotopic ratios are consistent with a magmatic origin for the gas. The total CO2 emission has been estimated at 1200 tons/day, comparable to the emissions at Kilauea. Some of the dead trees are as old as 250 years, suggesting that similar anomalous gas discharge has not occurred over the previous few hundred years. The delta C-13/12 ratio in the Mammoth Mountain CO2 emission averages about -4.5 (PDB standard). This is consistent with a mantle source for the carbon. However, the large volume of the emission suggests that not all of the CO2 is necessarily being generated from the 1989 intrusion. The voluminous gas could be leaking from a vapor-rich zone, capped by an impermeable layer, that was supplied CO2 from degassing of many small magma bodies that intruded beneath the mountain over a period of decades or centuries. Earthquakes in 1989 could have fractured the capping layer and provided pathways for the escape Of CO2 to the surface. Alternatively, some of the CO2 could be derived from contact metamorphism of carbonate rocks intruded by magma. Carbonate-bearing Paleozoic roof pendents crop out in close proximity to Mammoth Mountain. It is possible that similar rocks could occur at depth beneath Mammoth Mountain, and could have contributed CO2 from thermal decomposition caused from recent intrusions. We hope to determine the C-13/12 ratio of a suite of samples to demonstrate if the carbonate rocks could be the source of at least part of the 1990-97 CO2 emission. To better understand the behavior of the CO2 gas, we have used hyperspectral imagery data of Mammoth Mountain acquired from the Airborne Visual/Infrared Imaging Spectrometer (AVIRIS) to map out areas of dead trees. The areas of tree kill have increased in size from about 50 acres in 1994 to about 100 acres in 1997. Tree kill is the major surface manifestation of the carbon dioxide flux at Mammoth Mountain, is widely dispersed, and has been cursorily mapped by regular field mapping techniques in the area. Initial investigations using airborne digital imagery from the Thematic Mapper Simulator (NS001) and AVIRIS instruments have shown extremely encouraging results for complete delineation of the vegetation anomalies. The most successful maps (when compared with ground truth) were developed using AVIRIS data with spectral angle mapper and matched filter algorithms with a data set that was reduced to maximum variance via the minimum noise fraction transformation. The result of this work is a series of maps that show the tree kill areas occurring in an halo-pattern surrounding the base of Mammoth Mountain. We are applying these same techniques to earlier AVIRIS images of Mammoth Mountain to examine the progression of the tree kill areas over time. Temporal maps of the tree kill areas may assist in constructing a picture of the structure beneath Mammoth Mountain.

Hausback, Brian P.↗
NASA NTRS2000

GLOW: The Goddard Lidar Observatory for Winds

GLOW (Goddard Lidar Observatory for Winds) is a mobile Doppler lidar system which uses direct detection Doppler lidar techniques to measure wind profiles from the surface into the lower stratosphere. The system is contained in a modified van to allow deployment in field operations. The lidar system uses a Nd:YAG laser transmitter to measure winds using either aerosol backscatter at 1064 nm or molecular backscatter at 355 nm. The receiver telescope is a 45 cm Dall-Kirkham which is fiber coupled to separate Doppler receivers, one optimized for the aerosol backscatter wind measurement and another optimized for the molecular backscatter wind measurement. The receivers are implementations of the 'double edge' technique and use high spectral resolution Fabry-Perot etalons to measure the Doppler shift. A 45 cm aperture azimuth-over-elevation scanner is mounted on the roof of the van to allow full sky access and a variety of scanning options. GLOW is intended to be used as a deployable field system for studying atmospheric dynamics and transport and can also serve as a testbed to evaluate candidate technologies developed for use in future spaceborne systems. In addition, it can be used for calibration/validation activities following launch of spaceborne wind lidar systems. A description of the mobile system is presented along with the examples of lidar wind profiles obtained with the system.

Gentry, Bruce M.↗