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Geoscience and Remote Sensing, IEEE Transactions on

Issue 4 • Date Jul 1999

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Displaying Results 1 - 25 of 35
  • Tests of sequential data assimilation for retrieving profile soil moisture and temperature from observed L-band radiobrightness

    Page(s): 1860 - 1870
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    Sequential data assimilation (Kalman filter optimal estimation) techniques are applied to the problem of retrieving near-surface soil moisture and temperature state from periodic terrestrial radiobrightness observations that update soil heat and moisture diffusion models. The retrieval procedure uses a time-explicit numerical model to continuously propagate the soil state profile, its error of estimation, and its interdepth covariances through time. The model's coupled soil moisture and heat fluxes are constrained by micrometeorology boundary conditions drawn from observations or atmospheric modeling. When radiometer data are available, the Kalman filter updates the state profile estimate by weighing the propagated state, error, and covariance estimates against an a priori estimate of radiometric measurement error. The Kalman filter compares predicted and observed radiobrightnesses directly, so no inverse algorithm relating brightness to physical parameters is required. The authors demonstrate Kalman filter model effectiveness using field observations and a simulation study. An observed 1 m soil state profile is recovered over an eight-day period from daily L-band observations following an intentionally poor initial state estimate. In a four-month simulation study, they gauge the longer term behavior of the soil state retrieval and Kalman gain through multiple rain events, soil dry-downs, and updates from radiobrightnesses View full abstract»

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  • Development of an innovative, two-processor data processing unit for the magnetospheric imaging instrument onboard the Cassini mission to Saturn. I. Hardware architecture

    Page(s): 1980 - 1996
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    This paper presents an innovative two-processor computer architecture, developed for the data processing unit (DPU) of the Magnetospheric IMaging Instrument (MIMI), on-board the Cassini spacecraft mission to Saturn. The main advantages of this architecture are its high performance and reliability, and its intelligence. The high performance is justified by the following: 1) optimum combination of two powerful Harris RTX 2010 processors; 2) adoption of two independent main bus structures used for the communication of the processors with the various instrument interfaces and subsystems; 3) adoption of two additional local buses on each processor board used to speed the on-board operations of the processors; 4) high speed interprocessor communication port. The high reliability is justified by the following: 1) simplicity of hardware/software structures; 2) fault tolerance capabilities; 3) capability for on-flight hardware/software reconfiguration by ground command. Moreover, the on-board intelligence is justified by the following: 1) sophisticated fault protection, data handling, and instrument control software; 2) intelligent interfaces [implemented using held programmable gate arrays (FPGAs)]; 3) capability for autonomous on-flight hardware/software reconfiguration in case of an unrecoverable failure in one processor. The advantages of this architecture make it the best choice for the DPU of the complex, sophisticated scientific MIMI instrument, compared to the traditional master-slave (low reliability-single point failure) and common shared bus (low performance, hardware and software complexity) architectures View full abstract»

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  • Determination of the ScaRaB FM1 broadband channel point spread functions

    Page(s): 2004 - 2010
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    An analytical expression for the dynamic point spread functions (PSFs) of the scanner for radiation budget (ScaRaB) FM1 broadband radiometer is derived. The calculated PSFs are validated by comparing ScaRaB broadband radiances with high-resolution METEOSAT 5 broadband radiance estimations. The derived, PSFs reduce the relative rms difference between the radiances with 54% for the shortwave radiances and with 8% for the longwave radiances View full abstract»

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  • Observations of forests using a helicopter-borne nadir-looking radar: a new method for morphometric purposes

    Page(s): 2080 - 2091
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    The authors present an original pattern recognition method for the observation of forests using a nadir-looking ranging scatterometer. The radar configuration provides vertical profiles of the vegetation. Radar data were not processed in a classical way, i.e., the calculation of a radar cross section, but through pattern recognition methods applied to the raw data. The aim of the study was to search for typical patterns related to three types of forests. A small subsample of the data was determined for methodology validation purposes. Some results are also reported for a much larger data set. Morphodecomposition, a new methodology presented for the first time in these types of applications, is able to recognize the main features of the data, not only the types of forests involved, but also subtle morphological patterns of the signals. Morphodecomposition provides a morphometric methodology applicable to other geophysical univariate sampled signals View full abstract»

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  • The KidSat project flight system

    Page(s): 1768 - 1774
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    This paper was written to discuss the technical aspects of granting students in classrooms the ability to explore and study Earth sciences from a unique view of our planet. A high-resolution digital imaging system mounted in the space shuttle cabin window made it possible, in part, to provide real-time student interaction with the space program. This access provided an individual ownership of research and interest in our environment and Earth sciences. The other project technical elements, also key to the program success and real-time student interaction, were the University of California, San Diego (UCSD) web-based mission operations system and the Jet Propulsion Laboratory (JPL) ground data system View full abstract»

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  • Mapping surface mineralogy and scattering behavior using backscattered reflectance from a hyperspectral midinfrared airborne CO 2 laser system (MIRACO2LAS)

    Page(s): 2019 - 2034
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    Airborne, high-spectral resolution, thermal-infrared (TIR) MIRACO 2LAS reflectance data were evaluated for mapping surface mineralogy and scattering behavior for a variety of semi-arid, geological test sites in Australia. MIRACO2LAS is a rapidly tuned, airborne CO2 laser system that measures backscattered (bidirectional) reflectance at 100 wavelengths between 9.1 and 11.2 μm for 2-m footprints in line profile mode. An operational methodology is described that permits reduction of the raw airborne signal-to-ground reflectance. This ground reflectance has two major properties, namely, wavelength-dependent mineralogical variations and reflection albedo variations related to surface roughness. Comparisons between the airborne MIRACO2LAS spectra and laboratory directional hemispherical reflectance (DHR) spectra show the same spectral shapes, though differences in average reflectance (albedo) occur for some types of rocks. The minerals identified using MIRACO2LAS include silicates (for example, quartz, microcline, plagiodase, almandine, spessartine, talc, tremolite, and kaolinite) and carbonates (dolomite and magnesite) as well as vegetation (dry and green). Many of the diagnostic spectral features that allow identification of these materials are narrow (<0.2 μm), making them difficult to detect with broadband TIR systems, like the airborne TIMS and satelliteborne ASTER. Based on an empirical relationship between the minimum and maximum reflectance established using laboratory DHR spectra, a method is proposed that allows the use of MIRACO2 LAS data to identify surfaces that are characterized by Lambertian or specular scattering. The MIRACO2LAS results show that Lambertian-type scatterers include soils and many types of isotropic rocks View full abstract»

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  • Relief reconstruction from SAR stereo pairs: the “optimal gradient” matching method

    Page(s): 2099 - 2107
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    The authors present a method for improving relief reconstruction from SAR stereo images, relying on preprocessing of input data with an optimal filter. This filter strongly reduces speckle noise and enhances relief structures, leading to better matching results. The method was tested using X-SAR data of a mountainous site whose DEM was available for control View full abstract»

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  • Measurements of sea surface temperature and wind vector by nadir airborne microwave instruments in Joint United States/Russia Internal Waves Remote Sensing Experiment JUSREX'92

    Page(s): 1907 - 1915
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    The results of the Joint United States/Russia Internal Waves Remote Sensing Experiment (JUSREX'92) are presented. A Russian research aircraft, TU-134, equipped with both optical and microwave instruments participated in the experiment. In situ data were obtained from the “Akademik Ioffe;” a research vessel equipped with contact and remote sensing instruments. To determine surface wind speed and direction by means of passive microwave polarimetry, airborne Ka-band radiometer-polarimeter was used. Sea surface temperature was measured by means of the S-band radiometer. Surface temperature and wind vector data were related to true surface data. Special attention was paid to the factors affecting the accuracy of surface parameters retrieval. Wind and temperature fields retrieved from radiometer data were compared with side-looking radar images. The combined analysis of passive and active microwave instrument data has proved important for furthering our understanding of the ocean-atmosphere interaction View full abstract»

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  • Combination of low- and high-resolution SAR images for differential interferometry

    Page(s): 2035 - 2049
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    The authors propose a combination of low-resolution (LR) and full-resolution (FR) SAR images for differential SAR interferometry. The principal problem in such a combination is the volume scattering decorrelation that limits the useful baseline of the interferometric pair to very small, impractical values. A technique has been introduced to remove this decorrelation by exploiting a digital elevation model (DEM) of the area imaged. The resulting interferogram has the quality (in terms of coherence or phase noise standard deviation) of a conventional FR interferogram, but reduced geometric resolution. The technique is suited to those differential interferometry applications where the resolution of the “differential” phase field to be monitored is much coarser than that of local topography. As a possible application, they propose a system that exploits the wide swath imaged by low-resolution ScanSAR modes for frequent monitoring of hazardous areas View full abstract»

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  • The far field of a borehole radar and its reflection at a planar interface

    Page(s): 1940 - 1950
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    The far held of an electric Hertzian dipole located in a borehole is expressed as the product of a transmission coefficient and the far field of a dipole in a homogeneous region. The derivation uses the method of steepest descent, and gives physical insight into the wave phenomena that are important for borehole radar. The received field inside the borehole due to a planar interface located in the vicinity of the borehole is calculated using geometrical optics and the principle of reciprocity. The resulting expression is validated by numerically comparing it with a finite-difference time-domain solution. In an idealized situation, the reflection from the oil-mater boundary in a horizontal well can be detected with a borehole radar View full abstract»

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  • Seasonal comparison of HUTSCAT ranging scatterometer and ERS-1 SAR microwave signatures of boreal forest zone

    Page(s): 2068 - 2079
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    A set of ERS-1 SAR images along with airborne non-imaging ranging scatterometer (HUTSCAT) measurements and in situ surveys has been obtained from the Sodankyla test site (center latitude=67.41°N, center longitude=26.58°E) in Northern Finland. A total of five measurement campaigns were organized during 1991-1993. Nineteen test lines have been selected from the test site to represent different land-use categories. The land-use in the test area consists of open areas (agricultural fields, bogs, and clear-cut areas) and sparsely forested areas (mires, pine, and mixed forests). Microwave signatures representing the test lines have been extracted from ERS-1 SAR images and HUTSCAT measurements. The behavior of these signatures has been compared with each other and with their boreal forest semiempirical backscattering model. A set of extensive field measurements (snow depth, density, wetness, coverage, and snow water equivalent) made on the test lines are used in the various analyzes. The results indicate that the behavior of ERS-1 SAR microwave signatures is similar to that of HUTSCAT even in the presence of forest canopies. Also, the deviations of microwave signatures for various land-use classes behave similarly. This allows the authors to use the boreal forest semiempirical backscattering model based on HUTSCAT data to divide the ERS-1 backscattering signal into two contributions: 1) backscattering contribution from the top layer of vegetation canopy and 2) backscattering contribution from the canopy, ground, and ground-canopy reflections. By using the boreal forest semiempirical model, the behavior of these contributions is also observed in various soil conditions. These results explain some aspects of the boreal forest backscattering mechanism in the presence of snow cover and wet soil, which have not been experimentally investigated before View full abstract»

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  • Covariance estimation with limited training samples

    Page(s): 2113 - 2118
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    This paper describes a covariance estimator formulated under an empirical Bayesian setting to mitigate the problem of limited training samples in the Gaussian maximum likelihood (ML) classification for remote sensing. The most suitable covariance mixture is selected by maximizing the average leave-one-out log likelihood. Experimental results using AVIRIS data are presented View full abstract»

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  • The KidSat Student Mission Operations Center-SMOC

    Page(s): 1775 - 1784
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1788 KB)  

    KidSat was a NASA pilot project wherein middle school students investigated their world with images of the Earth using a digital camera onboard the space shuttle. Students requested and retrieved Earth images in Student Mission Operations Centers (SMOCs) located in their schools using the Internet as their communications link while the shuttle was in orbit. In the SMOCs, students selected specific geographic sites around the world, determined the map coordinates for each site, and relayed the site data to a KidSat computer on the shuttle via a KidSat Mission Control Gateway (MCG). The computer then activated the KidSat digital camera mounted in the window of the shuttle, and the images were downloaded to the KidSat data system and posted on a web page for the middle schools students. The SMOC was a miniature mission control center modeled after NASA's Mission Control Center in Houston, TX, but with a very specific purpose: to image the Earth with the KidSat camera. The SMOCs had one primary task: target and verify images of the Earth to meet the objectives of their school's investigation themes. Students were organized into teams that planned investigations and associated locations to image, monitored orbit paths and flight timelines, checked weather conditions at the targeted sites, and provided public information to the local media. The SMOCs made the KidSat program unique and exciting as students actually used NASA technology in combination with school equipment to actively participate in a shuttle mission. Prior to launch, students gathered information, asked questions, hypothesized outcomes, and planned ways to test their hypotheses using the Earth images. From their studies, they were able to draw conclusions, for example, about the relationship between man and the environment. In a school setting, the application of knowledge is too often restricted to controlled science lab experiments in which the outcome is already known. KidSat opened a world of possibilities, allowing students to investigate issues using images to determine actual conditions. KidSat successfully adapted NASA technology for use in the middle school curriculum, expanding the horizons of those who were involved View full abstract»

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  • Antireflection coated, wedged, single-crystal silicon aircraft window for the far-infrared

    Page(s): 1997 - 2003
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    Operating far-infrared remote-sensing instruments from inside a pressurized cabin of an aircraft requires a window with high transmittance. Furthermore, the radiometric properties of the window, such as the transmittance and the emitted radiation (i.e., temperature distribution), have to be known. The design of a wedged, antireflection coated single-crystal silicon aircraft window, its modeled transmittance spectrum, and the applied coating technique are presented. Measurements of the window transmittance with the 2.5 THz heterodyne spectrometer TeraHertz OH-Measurement Airborne Sounder (THOMAS) and a Fourier-transform spectrometer are presented, showing a transmittance of about 90% around 84 cm-1. The window was designed and built for the 2.5 THz OH-Sensor THOMAS, operated on the DLR research aircraft FALCON. The transmittance of 90% means a substantial improvement compared to the window used previously. With this new window, systematic errors in the measured atmospheric radiance could be lowered, making the retrieval of atmospheric parameters easier. Several successful flights with the new window up to an altitude of 43000 ft have already been performed View full abstract»

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  • Analysis and applications of backscattered frequency correlation function

    Page(s): 1895 - 1906
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    The application of the radar backscatter frequency correlation for classification and inversion of physical parameters of terrestrial targets is investigated. Traditionally, in radar remote sensing, the backscattering coefficients and the backscatter phase difference statistics of a distributed target are considered for estimating the biophysical parameters of interest. Because of the complex nature of random media scattering problems, however, target classification and parameter inversion algorithms are very convoluted. One obvious way of enhancing the success and accuracy of an inversion algorithm is to expand the dimension of the input vector space. Depending on the radar parameters, such as footprint (pixel) size, incidence angle, and the target attributes (physical parameters), the backscatter signal decorrelates as function of frequency. In this paper, analytical and experimental procedures are developed to establish a relationship between the complex frequency correlation function (FCF) of the backscatter and the radar and target attributes. Specifically, two classes of distributed targets are considered: 1) rough surfaces and 2) random media. Analytical expressions for the frequency correlation function are derived and it is shown that the effect of radar parameters can be expressed explicitly and thus removed from the measured correlation functions. The University of Michigan wideband polarimetric scatterometer systems are used to verify the theoretical models and inversion algorithms developed in this study View full abstract»

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  • The integration of science explorations through the use of Earth images in middle school curriculum

    Page(s): 1801 - 1817
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2328 KB)  

    KidSat was a pilot project dedicated to bringing students to the center of the learning process. In this unique pilot program. KidSat created a dynamic collaboration among middle school, high school, and university students with scientists, engineers, teachers, and educational theorists to create a program that tied “real-time” science exploration and discovery to learning in the classroom. This project, supported by NASA, the National Science Foundation (NSF), Johnson Space Center (JSC), and corporate and individual donors, inspired and motivated young people to expand their knowledge base through the use of Earth images. Middle school students from across the country controlled a student-designed, digital camera mounted onboard three space shuttle missions. Images from this instrument were incorporated into the teaching process and demonstrated the importance of using real data to excite and motivate young people. By providing students the opportunity to learn through analysis of self-chosen images of the Earth taken from the space shuttle, the acquisition of knowledge became more relevant and applicable to all subject areas. This initiative changed the expectations of many participants as to what students can learn and accomplish when provided with exciting content, well-trained teachers, and access to real data View full abstract»

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  • The use of KidSat images in the further pursuit of the frankincense roads to Ubar

    Page(s): 1841 - 1847
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    A small team of middle and high school students used space shuttle images from the KidSat camera to conduct remote archaeology in an attempt to find indications of ancient “lost” cities, structures, or caravan routes in the Arabian desert. Working with scientists from NASA's Jet Propulsion Laboratory in Pasadena, CA, archaeologists from Southwest Missouri State University in Springfield, MO, and geographers from Humboldt State University in Arcata, CA, students utilized a variety of data and resources, including images taken from the space shuttle, Landsat images, Tactical Pilotage Charts (TPCs), Operational Navigation Charts (ONCs), archaeological maps, primary historical accounts, image processing tools, and secondary text and internet sources to hypothesize the many possible trade routes. In this research, the student team encountered and applied unique features of the KidSat images to this investigation View full abstract»

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  • The potential of C- and L-band SAR in estimating vegetation biomass: the ERS-1 and JERS-1 experiments

    Page(s): 2107 - 2110
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    The sensitivity of backscattering coefficient, measured by ERS-1 and JERS-1 radars, to vegetation biomass is discussed and compared with the best results achieved using multifrequency polarimetric JPL-AIRSAR data. Experimental results show that measurements with JERS-1/L-band and ERS-1/C-band SAR provide the means for detecting vegetation growth. In particular, the C-band signal of ERS radar was found to be very well correlated to forest woody volume View full abstract»

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  • Analysis of radiowave propagation in a four-layered anisotropic forest environment

    Page(s): 1967 - 1979
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    Propagation of electromagnetic waves in forest environments is examined in which both the transmitting and receiving points are located in the trunk layer of a four-layered anisotropic forest model. This propagation model considers the forest as a horizontally stratified, anisotropic media of canopy and trunk, bounded by ground below and air above. The electromagnetic fields are obtained using dyadic Green's functions in their eigenfunction expansion forms for an anisotropic four-layered geometry. Analytical results are found for the fields, which consist primarily of three wave modes: a direct wave, multiply reflected waves, and lateral waves. These field constituents are compared, and their domains of preponderance are calculated; it is found that the lateral wave plays a major role in communication at large distances. Radio losses for typical forest are calculated to illustrate numerical application of the forest model View full abstract»

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  • Radar backscatter from breaking waves in Gulf Stream current convergence fronts

    Page(s): 1951 - 1966
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    Bright linear features have been observed in radar imagery taken near the Gulf Stream (GS) boundary on two separate occasions. In each case, these have been observed directly over strong current convergences. Progress has been made in understanding the origin of these signatures through simulations that incorporate environmental forcing from the winds and currents. These simulations significantly underestimate the backscatter unless wave-breaking (WB) effects are included at least approximately. Using a new, quasistatistical procedure that generalizes and quantifies earlier procedures for including WB effects, the authors have been able to successfully simulate the magnitude and behavior of these signatures. The approach combines the statistically based, composite model of radar backscatter with a deterministic feature model that relates backscatter from breaking waves to a particular geometrical model of a spilling breaker. This is accomplished using localized criteria, defined by local wave crest acceleration, to determine the probability of breaking, and by extending the feature model so that its unknown parameters may be evaluated directly from wave-current interaction calculations. The new approach provides an estimate of the critical crest acceleration of a potentially breaking wave, as a function of wind speed, that agrees with independent measurements View full abstract»

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  • The center-of-mass correction of the geodetic satellite AJISAI for single-photon laser ranging

    Page(s): 2011 - 2018
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    Detection timing of laser pulse returned from the satellite AJISAI is modeled for a single-photon laser ranging system. The average distribution of ten thousand return pulses simulated under their model agrees well with the distribution of residuals of full-rate range data taken from Herstmonceux station that uses the single-photon detection concept. Their model indicates that the center-of-mass correction for AJISAI will differ by 28 mm between multiphoton detection and single-photon detection. The ranging data of AJISAI and LAGEOS satellites from 1995-1996 was analyzed to estimate the range bias for each laser station, and Herstmonceux station was found to have a 26 mm difference between AJISAI and LAGEOS. The other multiphoton stations have smaller differences. The results show that the difference between the multiphoton system and the single-photon system is detected and close to that predicted by our AJISAI model View full abstract»

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  • Rediscovering the meaning of the world: using space shuttle images to inspire poetry

    Page(s): 1834 - 1840
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    Places of height and elevation have always been significant factors in the development of religion and science. Throughout history, the accomplishments of both have been articulated in the form of poetry. While the contemporary accomplishment of space-originated imagery plays an important role in the sciences, the celebration of our technological wisdom has yet to be articulated in modern poetry. A poetry writing workshop held at a science symposium for junior and high school students used space shuttle images to inspire verse. The results demonstrate that poetry is still a vital form of expression that reconnects us to our experience and allows us to fit ourselves into the story of the universe View full abstract»

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  • Airborne retrievals of snow and ice surface emissivity at millimeter wavelengths

    Page(s): 1871 - 1879
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    Passive microwave radiometers (24-157 GHz) have been flown over Baltic Sea ice and snow sites in April 1995 and on March 15, 1997. Data from these instruments are analyzed with reference to ground measurements of snow and ice conditions, and emissivity spectra are presented for 12 classifications of surface type. A simple model based on dielectric permittivity can accurately represent the microwave spectra of sea ice, but cannot be extended to the behavior of dry snow above 100 GHz without the addition of an extra term to represent volume scattering. The parameterization presented is intended to provide a background for temperature and humidity retrievals from satellite sounders, but the results will be of interest to the snow and ice remote-sensing communities View full abstract»

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  • The KidSat project

    Page(s): 1753 - 1767
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    Imagine viewing our world from space; a world astronauts have described as “bright and vivid” with “no borders or boundaries”. Then consider how much can be learned by studying Earth from this unique vantage point. The National Aeronautics and Space Administration (NASA) began a three-year pilot program in 1995 designed by a team of scientists, educators, engineers, and high school and college students to share astronauts' unique view of Earth with middle school students. This pilot program was called KidSat. KidSat's primary objective was to merge real-time professional space flight with middle school education by providing students with equal access and direct contribution to the United States space program for the exploration of the Earth. KidSat's long-term intent was to produce higher student achievement and increased competence in science, math, technology, and geography, and to promote an interactive understanding of Earth as an integrated system. Similar to the regular duties of astronauts, scientists, and engineers, students around the nation planned observations and captured images to study Earth's dynamic, fragile environment, using a remotely operated high-resolution color digital camera onboard the Space Shuttle, custom flight software, the Internet, NASA's infrastructure, and a mission operations infrastructure that linked middle schools to the Shuttle through a student-built mission Control Gateway. Using accompanying curriculum, students determined which areas of Earth they wanted to explore and photograph along the Shuttle's flight path. Orbiting communications satellites and the Internet transmitted commands, telemetry and images to and from the classrooms. Via the Shuttle cargo bay video camera. NASA TV carried video of the mission and the Earth for simultaneous viewing in classrooms. The KidSat pilot program was conceived in November 1993 and ended in December 1997. This paper summarizes the results of this program View full abstract»

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  • KidSat views 1997 Indonesia fires

    Page(s): 1827 - 1833
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    In 1997, El Nino-related fires raged across the Indonesian archipelago, and smoke from the fires covered Southeast Asia. Images of this disaster were captured by the KidSat camera. The KidSat Project was a NASA pilot program designed to allow students to view and study the Earth from space using a shuttle-mounted camera. A series of 15 images was taken by the camera of the Indonesian fires as they began to rage out of control. Using various techniques to analyze these images, the KidSat Exploration Team comprised a report detailing the social and scientific significance of the Indonesian fires View full abstract»

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Aims & Scope

 

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING (TGRS) is a monthly publication that focuses on the theory, concepts, and techniques of science and engineering as applied to sensing the land, oceans, atmosphere, and space; and the processing, interpretation, and dissemination of this information.

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Antonio J. Plaza
University of Extremadura