A5085396591- Geophysics and Gravity Measurements
- Ocean Waves and Remote Sensing
- Oceanographic and Atmospheric Processes
- Atmospheric and Environmental Gas Dynamics
- Cryospheric studies and observations
- Underwater Acoustics Research
- GNSS positioning and interference
- Radar Systems and Signal Processing
- Spacecraft Design and Technology
- Ionosphere and magnetosphere dynamics
- Radio Wave Propagation Studies
- Soil Moisture and Remote Sensing
- Distributed and Parallel Computing Systems
- Remote Sensing and LiDAR Applications
- Planetary Science and Exploration
- Inertial Sensor and Navigation
- Atmospheric aerosols and clouds
- Calibration and Measurement Techniques
- Winter Sports Injuries and Performance
- Arctic and Antarctic ice dynamics
- Meteorological Phenomena and Simulations
- Image Processing and 3D Reconstruction
- Scientific Computing and Data Management
- Space exploration and regulation
- Reservoir Engineering and Simulation Methods
Goddard Space Flight Center
2002-2022
National Aeronautics and Space Administration
2021
Science Systems and Applications (United States)
2021
Wallops Flight Facility
1993-2019
Sigma Space (United States)
2011-2012
IBM (United States)
1993
United States Naval Research Laboratory
1982
The Geoscience Laser Altimeter System (GLAS) on the NASA Ice, Cloud and land Elevation Satellite (ICESat) has provided a view of Earth in three dimensions with unprecedented accuracy. Although primary objectives focus polar ice sheet mass balance, GLAS measurements, distributed 15 science data products, have interdisciplinary application to topography, hydrology, vegetation canopy heights, cloud heights atmospheric aerosol distributions. Early laser life issues been mitigated adoption 33‐day...
Abstract Comparison of satellite altimetry against a high‐quality network tide gauges suggests that sea‐surface heights from the TOPEX altimeter may be biased by ±5 mm, in an approximate piecewise linear, or U‐shaped, drift. This has been previously reported at least two other studies. The bias is probably caused use internal calibration‐mode range correction, included “net instrument” which suspect owing to changes altimeter's point target response. Removal this correction appears mitigate...
Abstract We present the first winter season of surface height and sea ice freeboards Arctic Ocean from new Ice, Cloud, Land Elevation Satellite (ICESat‐2; IS‐2) mission. The Advanced Topographic Laser Altimeter System onboard has six photon‐counting beams for profiling with a 10‐kHz pulse rate (interpulse distance ~0.7 m) footprints ~17 m. Geolocated heights assigned to individual photons scattered allow significant flexibility in construction distributions used finding. For IS‐2 products,...
To remain competitive, software development organizations must reduce cycle time and cost, while at the same adding function improving quality. One potential solution lies in reuse. Because reuse is not free, we weigh benefits against expenditures of resources required to identify integrate reusable into products. We first introduce concepts examine cost-benefit trade-offs investments. then provide a set metrics used by IBM accurately reflect effort saved define that distinguish savings from...
The Surface Contour Radar is a 36-GHz computer-controlled airborne radar which generates false-color coded elevation map of the sea surface below aircraft in real-time, and can routinely produce ocean directional wave spectra with post-flight data processing has much higher angular resolution than pitch-and-roll buoys. When compared waveriders XERB EDECO buoys, there good agreement among nondirectional spectra. There also angles associated a1, b1, a2, b2 Fourier coefficients spreading...
The Surface Contour Radar (SCR) is a 36-GHz computer-controlled airborne system, which produces ocean directional wave spectra with much higher angular resolution than pitch-and-roll buoys. SCR observations of the evolution fetch-limited spectrum are presented indicate existence fully-developed sea state. JONSWAP growth model for energy and frequency was in best agreement measurements. Donelan et al. correctly predicted propagation direction waves asymmetrical fetch situation nearshore....
The TOPEX/POSEIDON Project is a joint US and French mission to develop operate an Earth-orbiting satellite with sensors capable of making accurate measurements sea level. NASA radar altimeter (NRA), fifth-generation Altimeter, will provide the primary measurement for altimetric mission. authors present requirements, fundamentals, design description, integration test program, elements ground processing, assessment dual-frequency altimeter.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Abstract The sole instrument on the upcoming Ice, Cloud, and Land Elevation Satellite ( ICESat-2 ) altimetry mission is a micropulse lidar that measures time of flight individual photons from laser pulses transmitted at 532 nm. Prior to launch, Multiple Altimeter Beam Experimental Lidar (MABEL) serves as an airborne implementation for testing development. This paper provides first examination MABEL data acquired two flights over sea ice in April 2012: one north Arctic coast Greenland other...
The TOPEX/Poseidon radar altimeter satellite applies advances in remote sensing instrumentation to reduce long wavelength measurement errors dramatically lower levels. TOPEX measures the range ocean surface with 2-cm precision and accuracy through use of both Ku- C-band radars, a high pulse repetition frequency, an agile tracker, absolute internal height calibration. Dual bandwidths for frequencies make it possible quickly acquire begin tracking after crossing land/ocean boundary....
Abstract The Advanced Topographic Laser Altimeter System (ATLAS) was launched aboard the Ice Cloud and land‐Elevation Satellite‐2 (ICESat‐2) satellite in September 2018. ATLAS is a single wavelength (532 nm) lidar system designed to acquire high resolution measurements of earth's surface while also obtaining atmospheric backscatter from molecules, clouds, aerosols. Because optimized for altimetry, data acquired unique many respects requires non‐standard analysis techniques. For example,...
Abstract Tenuous atmospheric layers, such as high, thin cirrus clouds and blowing snow over Antarctica, play an important role in the climate system, affecting energy fluxes between Earth atmosphere. Our knowledge of structure atmosphere is largely derived from satellite measurements. Yet tenuous layers can be hard to detect lidar data, especially daylight data characterized by high solar background. In this study, we introduce approach measurements NASA's ICESat‐2. The density‐dimension...
The routine ground processing of data from the NASA radar altimeter TOPEX/POSEIDON includes instrument corrections for effects significant wave height and attitude angle changes on altimeter's estimates range, backscattered power, height. This paper describes how these were generated they are applied. Detailed waveform fitting to telemetered samples is used assess effectiveness corrections. There several hardware‐caused small departures model waveforms departures, designated “features,”...
Directional ocean wave spectra derived from Shuttle Imaging Radar-B (SIR-B) L-band imagery collected off the coast of southern Chile on 11 and 12 October 1984 were compared with independent spectral estimates two airborne scanning radars. In sea states significant heights ranging 3 to 5 meters, SIR-B-derived at 18 degrees 25 nadir yielded reasonable wavelengths, directions, shapes for all systems encountered, including a purely azimuth-traveling system. A SIR-B image intensity variance...
Data from satellite altimeters are often degraded by the occurrence of unrealistically high radar return cross sections, which indicate a breakdown rough surface scattering model used to interpret these measurements in terms sea height ranges. The TOPEX altimetric data examined and nearly 200 000 such events during 7-yr period, 1993–99, inclusive, identified. primary purpose this paper is make comprehensive description where when occur, important because many communities that use generally...
Abstract Electromagnetic (EM) bias is caused by the tendency for troughs of ocean waves to be better reflectors than crests. This results in centroid returned power a radar altimeter being shifted away from mean sea level (MSL) toward waves. Being able model and predict magnitude EM critical satellite missions such as TOPEX, where determination MSL few centimeters required. By measuring both return elevation high accuracy, 36‐GHz surface contour (SCR) can determine various states how...
Range estimates from a radar altimeter have biases which are function of the significant wave height (SWH) and satellite attitude angle. Based on results pre‐launch Geosat modeling simulation by Johns Hopkins Applied Physics Laboratory, correction for SWH was already applied to sea surface Geosat's production data processing. By fitting detailed model return waveform sampler data, we can provide an independent estimate bias due The also produces has been carried out 10‐s averages over wide...
Abstract NASA's ICESat‐2 mission measures Earth's elevation with the Advanced Topographic Laser Altimeter System (ATLAS), a 6‐beam photon‐counting laser altimeter. The Global Geolocated Photon data product (ATL03) is primary source of photon information used by surface‐type‐specific higher‐level products, along Atmospheric Layer Characteristics (ATL09). ATL03 provides time‐tagged, geolocated heights referenced to ellipsoid and parameter providing an initial classification events as signal or...
The Seasat altimeter is designed to measure three parameters important oceanography: height of the spacecraft above ocean surface ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</tex> ), significant wave xmlns:xlink="http://www.w3.org/1999/xlink">H_{1/3}</tex> and backscatter coefficient xmlns:xlink="http://www.w3.org/1999/xlink">\sigma\deg</tex> ) from which winds may be inferred. Since measurement process indirect, environment complicated...
The presence of land within a radar altimeter's footprint may contaminate the tracking performance and perturb nadir oceanographic signal. An altimeter tracker tends to move towards brighter, more specular reflections in return waveforms. Researchers unintentionally include data over small mid‐ocean islands their sets. If goal is obtain sea surface height (SSH) information at subdecimeter level, such inclusion inappropriate because can locally affect SSH by than ±4 m. Altimeter signal...
The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) measures ocean surface heights using a pulsed, photon-counting laser altimeter. data from ICESat-2 ATL03 consist of point cloud returned photon at typical rates over the one to four measured per meter. Our primary processing for ATL12 Ocean Surface Height product consists finding deconvolution instrument impulse response yield height histograms with their first moments segment lengths few hundred meters 7 km. also includes spatial...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTArgon: A New Constituent of the Atmosphere.David HancockCite this: J. Am. Chem. Soc. 1895, 17, 3, 219–243Publication Date (Print):March 1, 1895Publication History Published online1 May 2002Published inissue 1 March 1895https://pubs.acs.org/doi/10.1021/ja02158a008https://doi.org/10.1021/ja02158a008research-articleACS PublicationsRequest reuse permissionsArticle Views85Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are COUNTER-compliant...
The Geodetic Satellite (Geosat) Follow-On (GFO), Ocean Topography Experiment (TOPEX), and Poseidon altimeter white-noise levels have been evaluated using a technique based on high-pass filtering of 1-Hz sea surface height time series. High-pass removes the geoid oceanography signals while revealing random noise. This is simpler to use than repeat-track method, gives essentially same results, makes it easier analyze much larger amounts data investigate subtle variations in noise levels. new...