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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Satellite pattern classification using charge transfer devices

The potential uses of Charge Transfer Devices (CTDs) in pattern classification operations are explored. The needs for a hardware-based pattern classifier are established, and a matrix multiplication subsystem based upon a sum-of-products CTD is presented. Applications of the subsystem to the classification of multi-modal Gaussian distributions in general and to LANDSAT data processing in particular are discussed. Finally, the potential impact of this technology on satellite data processing methodologies is discussed.

Snyder, W. E.↗
NASA NTRS1979

Charge injection device as a candidate sensor for stellar tracking

Charge transfer devices (CTDs) are superior to the image dissector as stellar tracking sensors, considering their low voltage requirements, insensitivity to magnetic fields, good linearity, and low weight and power. An analysis of one type of CTD, called the charge injection device (CID), revealed an X-Y addressing capability which provides exceptional flexibility in array readout and results in enhanced S/N capability, a surface channel device which produces a larger dynamic range of operation, and exceptional and unique tolerance to optical overloads. A 128 row by 128 column CID array processed on silicon was evaluated in a cooled breadboard camera, and measured results indicate projected performance parameters of a large area CID array as follows: 20 micron square sensing site, noise not greater than 25 carriers per pixel, quantum yield of approximately 40% from 0.4 to 1.0 micron, and cooling requirements on the order of 0 degrees C.

Jones, C. S., Jr.↗
NASA NTRS1984

Breadboard stellar tracker system test report

BASD has, in the past, developed several unique position tracking algorithms for charge transfer device (CTD) sensors. These algorithms provide an interpixel transfer function with the following characteristics: (1) high linearity; (2) simplified track logic; (3) high gain; and (4) high noise rejection. A previous test program using the GE charge injection device (CID) showed that accuracy for BASD's breadboard was limited to approximately 2% of a pixel (1 sigma) whereas analysis and simulation indicated the limit should be less than 0.5% of a pixel, assuming the limit to be detector response and dark current noise. The test program was conducted under NASA contract No. NAS8-34263. The test approach for that program did not provide sufficient data to identify the sources of error and left open the amount of contribution from parameters such as image distribution, geometric distortion and system alignment errors.

Kollodge, J. C.↗
NASA NTRS1984

An upper ocean current jet and internal waves in a Gulf Stream warm core ring

On June 22, 1982, the R/V Endeavor, while participating in a multi-ship study of a warm core ring 82B, encountered a strong front in the core of the ring. The vessel was headed on a radial section outward from ring center while a CTD was repeatedly raised and lowered between 10 and 300 m. Current profiles in the upper 100 m were obtained continuously with a Doppler acoustic profiling system. Above the shallow 45 m seasonal thermocline, a current jet of 4 km width was encountered having a central core of relatively light water and a maximum current of 1.1 m/s. This jet was both highly nonlinear and totally unexpected. A high frequency packet of directional internal waves was acoustically observed in the seasonal thermocline at the outer edge of the jet. Vertical velocities were large enough (6 cm/s) as to be directly observable in the Doppler returns. The waves were propagating from the northeast, parallel to the ship track, and orthogonal to the jet toward the center of the warm core ring. While a nonlinear, centrifugal term was required for the force balance of the jet, the high-frequency internal wave packet could be explained with linear, gravest-mode wave dynamics.

Joyce, T. M.↗
NASA NTRS1985

Small-scale cyclones on the periphery of a Gulf Stream warm-core ring

Small-scale cyclones found around Gulf Stream warm-core ring 82B are investigated by using infrared satellite images and current information obtained with an acoustic-Doppler velocimeter. Currents in these cyclones reveal speeds ranging from 20 to 80 cm/s. One small cyclone or 'ringlet' found in June 1982 was studied extensively by removing the basic rotational velocities of 82B. The azimuthal velocity field for this ringlet was used with the gradient current equation to calculate the absolute dynamic topography at 100 dbar. It was found that the ringlet was 13 dyn-cm lower than its surroundings. In addition, neglect of the centrifugal term would have changed the dynamic topography of the ringlet by 30 percent. From a comparison with CTD data the absolute reference level was determined, and a vertical profile of horizontal currents was calculated for the ringlet. Other cyclones were found throughout the slope water region around warm-core ring 82B with observable lifetimes of 1 to 2 weeks. The northeast quadrant of 82B was a favored generation site for ringlets. Two cyclones were observed to form in this region and were advected anticyclonically around 82B. Typically, at any one time, six cyclones with diameters of approximately 40 to 50 km can be detected north of the Gulf Stream by using satellite images.

Kennelly, M. A.↗
NASA NTRS1988

Application of acoustic-Doppler current profiler and expendable bathythermograph measurements to the study of the velocity structure and transport of the Gulf Stream

The degree to which Acoustic-Doppler Current Profiler (ADCP) and expendable bathythermograph (XBT) data can provide quantitative measurements of the velocity structure and transport of the Gulf Stream is addressed. An algorithm is used to generate salinity from temperature and depth using an historical Temperature/Salinity relation for the NW Atlantic. Results have been simulated using CTD data and comparing real and pseudo salinity files. Errors are typically less than 2 dynamic cm for the upper 800 m out of a total signal of 80 cm (across the Gulf Stream). When combined with ADCP data for a near-surface reference velocity, transport errors in isopycnal layers are less than about 1 Sv (10 to the 6th power cu m/s), as is the difference in total transport for the upper 800 m between real and pseudo data. The method is capable of measuring the real variability of the Gulf Stream, and when combined with altimeter data, can provide estimates of the geoid slope with oceanic errors of a few parts in 10 to the 8th power over horizontal scales of 500 km.

Joyce, T. M.↗
NASA NTRS1993

Performances of a date dissemination code on telephone lines using commercial modems

A coded time/date information dissemination system (CTD), based on telephone lines and commercial modems, is now in its experimental phase in Italy at IEN. This service, born from a cooperation with other metrological laboratories (TUG, Austria, SNT, Sweden, VSL, The Netherlands), represents an attempt towards an European standardization. Some results of an experimental analysis in which a few modems were tested, both in laboratory conditions and connected to the telephone network, in order to evaluate the timing capability of the system are given. When the system is used in a one-way mode, in many practical cases the modems delay turns out to be the main factor which limits the accuracy, even more than the telephone line delays. If the two-way mode is used, the modems asymmetry, i.e., the delay difference between transmission and reception, is almost always the most important source of uncertainty, provided the link is not including a space segment. Comparing the widely used V.22 modems to the old V.21 ones, the latters turn out to be better both in delay time (30-100 ms V.22, and 7-15 ms V.21) and asymmetry (10-50 micro-s V.22, and 10 ms V.22). Time transfer accuracies of 10 micron-s (same turn) to 100 micro-s (long distance calls) were obtained in two-way mode with commercial V.21 modems.

Cordara, F.↗
NASA NTRS1994

An acoustic charge transport imager for high definition television applications

The primary goal of this research is to develop a solid-state television (HDTV) imager chip operating at a frame rate of about 170 frames/sec at 2 Megapixels/frame. This imager will offer an order of magnitude improvements in speed over CCD designs and will allow for monolithic imagers operating from the IR to UV. The technical approach of the project focuses on the development of the three basic components of the imager and their subsequent integration. The camera chip can be divided into three distinct functions: (1) image capture via an array of avalanche photodiodes (APD's); (2) charge collection, storage, and overflow control via a charge transfer transistor device (CTD); and (3) charge readout via an array of acoustic charge transport (ACT) channels. The use of APD's allows for front end gain at low noise and low operating voltages while the ACT readout enables concomitant high speed and high charge transfer efficiency. Currently work is progressing towards the optimization of each of these component devices. In addition to the development of each of the three distinct components, work towards their integration and manufacturability is also progressing. The component designs are considered not only to meet individual specifications but to provide overall system level performance suitable for HDTV operation upon integration. The ultimate manufacturability and reliability of the chip constrains the design as well. The progress made during this period is described in detail.

Hunt, W. D.↗
NASA NTRS1994

An acoustic charge transport imager for high definition television applications

The primary goal of this research is to develop a solid-state high definition television (HDTV) imager chip operating at a frame rate of about 170 frames/sec at 2 Megapixels per frame. This imager offers an order of magnitude improvement in speed over CCD designs and will allow for monolithic imagers operating from the IR to the UV. The technical approach of the project focuses on the development of the three basic components of the imager and their integration. The imager chip can be divided into three distinct components: (1) image capture via an array of avalanche photodiodes (APD's), (2) charge collection, storage and overflow control via a charge transfer transistor device (CTD), and (3) charge readout via an array of acoustic charge transport (ACT) channels. The use of APD's allows for front end gain at low noise and low operating voltages while the ACT readout enables concomitant high speed and high charge transfer efficiency. Currently work is progressing towards the development of manufacturable designs for each of these component devices. In addition to the development of each of the three distinct components, work towards their integration is also progressing. The component designs are considered not only to meet individual specifications but to provide overall system level performance suitable for HDTV operation upon integration. The ultimate manufacturability and reliability of the chip constrains the design as well. The progress made during this period is described in detail in Sections 2-4.

Hunt, W. D.↗
NASA NTRS1995

Halocline water formation in the Barents Sea

Hydrographic data from the first phase of the Coordinated Eastern Arctic Experiment (CEAREX) are analyzed. The data consist of temperature and salinity measurements made by a ship-based conductivity-temperature-depth (CTD) instrument and by a drifting SALARGOS buoy. These data were collected in the autumn and early winter of 1988-1989 in the northern Barents Sea, mostly in ice-covered conditions and then across the marginal ice zone (MIZ). The data show that relatively warm, salty water of Atlantic origin is modified by air cooling and ice melting to produce lighter water that has properties identical to (lower) halocline water found in the Arctic Ocean. This occurs mostly at the MIZ and to a lesser degree within the ice pack itself. At the MIZ the halocline water subjects underneath the lighter meltwater that resides directly under the ice pack; geostrophic velocity calculations indicate that it then turns eastward and flows toward the Kara Sea, in keeping with previous chemical tracer analyses. A rough calculation reveals that the amount of halocline water formed in this way in the Barents Sea and Fram Strait is 30-50% of that formed by ice growth in eastern Arctic polynyas.

Steele, Michael↗
NASA NTRS1996

Properties of Two Carbon Composite Materials Using LTM25 Epoxy Resin

In this report, the properties of two carbon-epoxy prepreg materials are presented. The epoxy resin used in these two materials can yield lower manufacturing costs due to its low initial cure temperature, and the capability of being cured using vacuum pressure only. The two materials selected for this study are MR50/LTM25, and CFS003/LTM25 with Amoco T300 fiber; both prepregs are manufactured by The Advanced Composites Group. MR50/LTM25 is a unidirectional prepreg tape using Mitsubishi MR50 carbon fiber impregnated with LTM25 epoxy resin. CRS003/LTM25 is a 2 by 2 twill fabric using Amoco T300 fiber and impregnated with LTM25 epoxy resin. Among the properties presented in this report are strength, stiffness, bolt bearing, and damage tolerance. Many of these properties were obtained at three environmental conditions: cold temperature/dry (CTD), room temperature/dry (RTD), and elevated temperature/wet (ETW). A few properties were obtained at room temperature/wet (RTW), and elevated temperature/dry (ETD). The cold and elevated temperatures used for testing were -125 F and 180 F, respectively. In addition, several properties related to processing are presented.

Cruz, Juan R.↗
NASA NTRS1997

Satellite Analysis of Ocean Biogeochemistry and Mesoscale Variability in the Sargasso Sea

The objective of this study was to analyze the impact of spatial variability on the time-series of biogeochemical measurements made at the U.S. JGOFS Bermuda Atlantic Time-series Study (BATS) site. Originally the study was planned to use SeaWiFS as well as AVHRR high-resolution data. Despite the SeaWiFS delays we were able to make progress on the following fronts: (1) Operational acquisition, processing, and archive of HRPT data from a ground station located in Bermuda; (2) Validation of AVHRR SST data using BATS time-series and spatial validation cruise CTD data; (3) Use of AVHRR sea surface temperature imagery and ancillary data to assess the impact of mesoscale spatial variability on P(CO2) and carbon flux in the Sargasso Sea; (4) Spatial and temporal extent of tropical cyclone induced surface modifications; and (5) Assessment of eddy variability using TOPEX/Poseidon data.

Siegel, D. A.↗
NASA NTRS1999

Assimilation of Satellite Altimeter Data With a Four Dimensional Model of the Japan Sea

A data assimilation is carried out to detect the variability of the Japan Sea circulation in the range from a few days to several years and from eddy to basin scale. The model applied in this study is the same 1/6 degree GFDL MOM1 as Kim and Yoon (1999) but is driven by ECMWF daily wind stress, heat and fresh water fluxes. The satellite altimeter data of TOPEX/POSEIDON, ERS-1 (phase C and G) and -2 are assimilated by an approximate Kalman filter (Fukumori and M.Rizzoli, 1995). The approximation is made by seeking an asymptotic steady error covariance matrix (Fukumori et al., 1993) and by introducing a coarser grid model for the innovation (data-model misfit). The coarse grid model is defined on 1/2 degree horizontal resolution and consists of the barotropic stream function, first baroclinic displacement and velocity amplitudes. The assimilated estimates explain about 6cm sea level variability of the data (approximately 12cm in the southern part), which is much larger than the previous reduced-gravity model and TOPEX/POSEIDON altimeter data assimilation (Hirose et al., 1999). The impacts of the T/P and ERS data on the filtered estimates are comparable. The result also shows high correlation to subsurface water temperatures measured by CTD. Many of the mesoscale eddies/disturbances travel east-northeastward with the advection speed of 1-3cm/s though most of them generated in the western region can not pass over the Oki Spur. The quasi-biennial variability found by Hirose and Ostrovskii (1999) did not show clear propagation pattern. The shallow Oki Spur may work as a "western boundary" to this signal. This is more plausible estimation than by the R-G model which has no bottom topography.

Hirose, Naoki↗
NASA NTRS2002

Nonlinear Internal Waves in the South China Sea During ASIAEX

Internal wave distribution maps have been compiled from more than one hundred ERS-1/2, RADARSAT and Space Shuttle SAR images in the South China Sea (SCS) from 1993 to 2000. Based on these distribution maps, most of internal waves in the northeast part of SCS were propagating westward. The wave crest can be as long as 200 km with amplitude of 100 m, due to strong current from the Kuroshio branching out into the SCS. In recent Asian Seas International Acoustics Experiment (ASIAEX), moorings have been deployed in April 2000 and May 2001. Simultaneous RADARSAT ScanSAR images have been collected during the field test to integrate with the model and the in-situ measurements in the SCS. During ASIAEX in May 2001, many large internal waves were observed at the test area and were the major features for acoustic volume interaction. The environmental parameters have been calculated based on extensive CTD castings and mooring data. Nonlinear internal wave models have been applied to simulate the wave evolution on the continental shelf and the results compare reasonably with mooring measurements. The evolution and dissipation of huge internal waves on the shelf break, mode-two waves, elevation waves, and wave-wave interaction are very important issues for acoustic propagation. The implication of internal wave effects on acoustic propagation will also be discussed.

ACOUSTIC PROPAGATION↗
NASA NTRS2003

Variability in Ocean Color Associated with Phytoplankton and Terrigenous Matter: Time Series Measurements and Algorithm Development at the FRONT Site on the New England Continental Shelf

Fronts in the coastal ocean describe areas of strong horizontal gradients in both physical and biological properties associated with tidal mixing and freshwater estuarine output (e.g. Simpson, 1981 and O Donnell, 1993). Related gradients in optically important constituents mean that fronts can be observed from space as changes in ocean color as well as sea surface temperature (e.g., Dupouy et al., 1986). This research program is designed to determine which processes and optically important constituents must be considered to explain ocean color variations associated with coastal fronts on the New England continental shelf, in particular the National Ocean Partnership Program (NOPP) Front Resolving Observational Network with Telemetry (FRONT) site. This site is located at the mouth of Long Island sound and was selected after the analysis of 12 years of AVHRR data showed the region to be an area of strong frontal activity (Ullman and Cornillon, 1999). FRONT consists of a network of modem nodes that link bottom mounted Acoustic Doppler Current Profilers (ADCPs) and profiling arrays. At the center of the network is the Autonomous Vertically Profiling Plankton Observatory (AVPPO) (Thwaites et al. 1998). The AVPPO consists of buoyant sampling vehicle and a trawl-resistant bottom-mounted enclosure, which holds a winch, the vehicle (when not sampling), batteries, and controller. Three sampling systems are present on the vehicle, a video plankton recorder, a CTD with accessory sensors, and a suite of bio-optical sensors including Satlantic OCI-200 and OCR-200 spectral radiometers and a WetLabs ac-9 dual path absorption and attenuation meter. At preprogrammed times the vehicle is released, floats to the surface, and is then winched back into the enclosure with power and data connection maintained through the winch cable. Communication to shore is possible through a bottom cable and nearby surface telemetry buoy, equipped with a mobile modem, giving the capability for near-real time data transmission and interactive sampling control.

Morrison, John R.↗
NASA NTRS2004

Contrasting Inherent Optical Properties and Carbon Metabolism Between Five Northeastern (USA) Estuary-plume Systems

We have recently developed the ability to rapidly assess Surface inherent optical properties (IOP), oxygen concentration and pCO2 in estuarine-plume systems using flow-through instrumentation. During the summer of 2004, several estuarine-plume systems were surveyed which include the Pleasant (ME), Penobscot (ME), Kennebec-Androscoggin (ME), Merrimack (NH-MA) and Hudson (NY). Continuous measurements of surface chlorophyll and colored dissolved organic carbon (CDOM) fluorescence, beam attenuation, temperature, salinity, oxygen and pC02 were taken at each system along a salinity gradient from fresh water to near oceanic endmembers. CTD and IOP profiles were also taken at predetermined surface salinity intervals. These were accompanied by discrete determinations of chlorophyll (HPLC and fluorometric), total suspended solids (TSS), dissolved organic carbon (DOC) and alkalinity. IOP data were calibrated using chlorophyll, DOC and TSS data to enable the retrieval of these constituents from IOP data. Considerable differences in the data sets were observed between systems. These ranged from the DOC-enriched, strongly heterotrophic Pleasant River System to the high-chlorophyll autotrophic Merrimack River System. Using pCO2 and oxygen saturation measurements as proxies for water column metabolism, distinct relationships were found between trophic status and inherent optical properties. The nature of these relationships varies between systems and is likely a function of watershed and estuarine attributes including carbon and nutrient loading, in-situ production and related autochthonous inputs of DOC and alkalinity. Our results suggest that IOP data may contain significant information about the trophic status of estuarine and plume systems.

Vandemark, Doug↗
NASA NTRS2005

Long Term Surface Salinity Measurements

Our long-term goal is to establish a reliable system for monitoring surface salinity around the global ocean. Salinity is a strong indicator of the freshwater cycle and has a great influence on upper ocean stratification. Global salinity measurements have potential to improve climate forecasts if an observation system can be developed. This project is developing a new internal field conductivity cell that can be protected from biological fouling for two years. Combined with a temperature sensor, this foul-proof cell can be deployed widely on surface drifters. A reliable in-situ network of surface salinity sensors will be an important adjunct to the salinity sensing satellite AQUARIUS to be deployed by NASA in 2009. A new internal-field conductivity cell has been developed by N Brown, along with new electronics. This sensor system has been combined with a temperature sensor to make a conductivity - temperature (UT) sensor suitable for deployment on drifters. The basic sensor concepts have been proven on a high resolution CTD. A simpler (lower cost) circuit has been built for this application. A protection mechanism for the conductivity cell that includes antifouling protection has also been designed and built. Mr. A.Walsh of our commercial partner E-Paint has designed and delivered time-release formulations of antifoulants for our application. Mr. G. Williams of partner Clearwater Instrumentation advised on power and communication issues and supplied surface drifters for testing.

Schmitt, Raymond W.↗
NASA NTRS2010

Airspace Systems Program: Next Generation Air Transportation System Concepts and Technology Development FY2010 Project Plan Version 3.0

This document describes the FY2010 plan for the management and execution of the Next Generation Air Transportation System (NextGen) Concepts and Technology Development (CTD) Project. The document was developed in response to guidance from the Airspace Systems Program (ASP), as approved by the Associate Administrator of the Aeronautics Research Mission Directorate (ARMD), and from guidelines in the Airspace Systems Program Plan. Congress established the multi-agency Joint Planning and Development Office (JPDO) in 2003 to develop a vision for the 2025 Next Generation Air Transportation System (NextGen) and to define the research required to enable it. NASA is one of seven agency partners contributing to the effort. Accordingly, NASA's ARMD realigned the Airspace Systems Program in 2007 to "directly address the fundamental research needs of the Next Generation Air Transportation System...in partnership with the member agencies of the JPDO." The Program subsequently established two new projects to meet this objective: the NextGen-Airspace Project and the NextGen-Airportal Project. Together, the projects will also focus NASA s technical expertise and world-class facilities to address the question of where, when, how and the extent to which automation can be applied to moving aircraft safely and efficiently through the NAS and technologies that address optimal allocation of ground and air technologies necessary for NextGen. Additionally, the roles and responsibilities of humans and automation influence in the NAS will be addressed by both projects. Foundational concept and technology research and development begun under the NextGen-Airspace and NextGen-Airportal projects will continue. There will be no change in NASA Research Announcement (NRA) strategy, nor will there be any change to NASA interfaces with the JPDO, Federal Aviation Administration (FAA), Research Transition Teams (RTTs), or other stakeholders

Kopardekar, Parimal H.↗