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NASA NTRS1999

Cosmic Ray Telescope Experiment (CRT), Pioneer 10/11 Program

In May 1996 the electrical power on Pioneer 10 was no longer adequate to support the Cosmic Ray Telescope Experiment (CRT). In March 1997 ground based operations for the mission were terminated. The 25 years of Pioneer 10 were a remarkable voyage of discovery as it ventured into a vast new unexplored region of space. These observations by the Pioneer experiments led in the development of a new discipline of space science - heliospheric physics. For cosmic ray studies it was an incredible era, leading to the identification of new energetic particle populations and processes and initiating the study of the dynamics and large-scale structure and began the study of the dynamics and large-scale structure of the outer heliosphere. A summary of some of the principal scientific findings of the CRT experiment over this period is given in the next section. Even with the cessation of data from the Pioneer 10/11 mission there remained a great deal of scientific analysis and data archiving that required on the order of an additional three years of effort on the part of the CRT team. We have tried to select those tasks where the P10/11 CRT data have an important role to play. Special emphasis is placed on long-term synoptic studies that make use of the extended temporal and spatial coverage of the missions and the full capabilities of the CRT experiment. The major scientific objectives of this study are: (1) A phenomenological study of the modulation process in the heliosphere, thereby laying the foundation for developing a unified model of cosmic ray modulation over a complete 22 year heliomagnetic cycle; (2) These modulation studies and the temporal changes in the cosmic ray intensities also provide information on the large-scale structure and dynamics of the outer heliosphere; (3) use the galactic and anomalous cosmic ray data from Pioneer 10 to obtain a more accurate estimate of the distance to the modulation boundary and to the termination shock; (4) Use the results from (2) and from temporal variations to determine whether significant modulation occurs in the region of the heliosphere; (5)study the acceleration and transport of low energy solar interplanetary energetic particles and their relation to solar activity and interplanetary phenomena.

McDonald, Frank B.↗

NASA NTRS1974

Use of a diffuser for producing texture masks for image processing

The use of a diffuser in synthesizing binary texture-variance masks for applications in image processing is investigated. The binary texture-variance masks are used to separate various objects in an image on the basis of their spatial texture variance. The diffuser is required to reduce the speckling present in the mask. The reduction in speckling is described quantitatively as a reduction of the misclassification probability associated with the separation of the objects into several texture classes. General results are furnished for the statistics of the field scattered by the diffuser, and these are used to obtain expressions for the misclassification probabilities in the presence of a diffuser.

Stark, H.↗

NASA NTRS1975

A CCD image transducer and processor suitable for space flight

A satellite borne extreme ultraviolet solar telescope makes use of CCD area arrays for both image readout and onboard data processing. The instrument is designed to view the inner solar corona in the wavelength band 170 - 630 A, and the output video stream may be selected by ground command to present the coronal scene, or the time-rate-of-change of the scene. Details of the CCD application to onboard image processing are described, and a discussion of the processor's potential for telemetry bandwidth compression is included. Optical coupling methods, data storage requirements, spatial and temporal resolution, and nonsymmetry of resolution (pitch) in the CCD are discussed.

Michels, D. J.↗

NASA NTRS1975

An investigation of turbulent transport in the extreme lower atmosphere

A model in which the Lagrangian autocorrelation is expressed by a domain integral over a set of usual Eulerian autocorrelations acquired concurrently at all points within a turbulence box is proposed along with a method for ascertaining the statistical stationarity of turbulent velocity by creating an equivalent ensemble to investigate the flow in the extreme lower atmosphere. Simultaneous measurements of turbulent velocity on a turbulence line along the wake axis were carried out utilizing a longitudinal array of five hot-wire anemometers remotely operated. The stationarity test revealed that the turbulent velocity is approximated as a realization of a weakly self-stationary random process. Based on the Lagrangian autocorrelation it is found that: (1) large diffusion time predominated; (2) ratios of Lagrangian to Eulerian time and spatial scales were smaller than unity; and, (3) short and long diffusion time scales and diffusion spatial scales were constrained within their Eulerian counterparts.

Koper, C. A., Jr.↗

NASA NTRS1977

Digital image-rectification system

System removes spatial distortions from data and brings data into conformance with Universal Transverse Mercator map projection, produces digital output products suitable for further machine processing and analysis, and fills need for geometrically corrected Landsat multispectral scanner digital data in several remote sensing application areas.

Van Wie, P. H.↗

NASA NTRS1976

Age of Martian channels

The ages of large Martian channels have been studied by determining the relative abundances of craters superimposed on channels and adjacent terrains and by examining superposition relationships between channels and plains and mantle materials. The channels are extremely old, are spatially confined and temporally related to the ancient cratered terrain, and in many cases are related to the as yet poorly understood genetic processes of fretting and chaos formation. No evidence is found for recent channel activity.

Malin, M. C.↗

NASA NTRS1981

Basic research planning in mathematical pattern recognition and image analysis

Fundamental problems encountered while attempting to develop automated techniques for applications of remote sensing are discussed under the following categories: (1) geometric and radiometric preprocessing; (2) spatial, spectral, temporal, syntactic, and ancillary digital image representation; (3) image partitioning, proportion estimation, and error models in object scene interference; (4) parallel processing and image data structures; and (5) continuing studies in polarization; computer architectures and parallel processing; and the applicability of "expert systems" to interactive analysis.

Bryant, J.↗

NASA NTRS1982

Dissipation of ionospheric irregularities by wave-particle and collisional interactions

The nonlinear dissipation of plasma irregularities aligned parallel to an ambient magnetic field is studied numerically using a model which employs both wave-particle and collisional diffusion. A wave-particle diffusion coefficient derived from a local theory of the universal drift instability is used. This coefficient is effective in regions of nonzero plasma gradients and produces triangular-shaped irregularities with spectra which vary as f to the -4th, where f is the spatial frequency. Collisional diffusion acts rapidly on the vertices of the irregularities to reduce their amplitude. The simultaneous action of the two dissipative processes is more efficient than collisions acting alone. In this model, wave-particle diffusion mimics the forward cascade process of wave-wave coupling.

Bernhardt, P. A.↗

NASA NTRS1983

Quantitative measurement of density and velocity in compressible flows using laser-induced iodine fluorescence

A nonintrusive optical technique for the quantitative measurement of molecular density and velocity at a point or in an entire cross-sectional plane of a compressible flowfield is reported. Iodine molecules, seeded into the flowfield reservoir, are excited by a tunable narrow-bandwidth laser and the resulting spatially-resolved fluorescence is collected by a single- or multiple-element detector. A theoretical model for the iodine laser-induced fluorescence process is essential for quantitative measurements and is developed using a rate-equation approach. Density measurements using laser-induced fluorescence are normally complicated by collisional quenching; however, the theory predicts that the off-resonant fluorescent signal is directly proportional to density. Velocity is directly related to the Doppler shift of the iodine absorption line, determined by monitoring the broadband fluorescent signal as the laser is tuned in frequency. Experiments in a steady supersonic flowfield are compared with numerical calculations to demonstrate the accuracy of the approach for density and velocity measurement and the lack of perturbation to the flowfield by the iodine seeding. Extensions of the current approach to density and velocity measurement in lower Mach number flows, to the measurement of pressure and temperature, and to temporally-resolved measurements are discussed.

Mcdaniel, J. C.↗

NASA NTRS1984

Prescription of land-surface boundary conditions in GISS GCM 2: A simple method based on high-resolution vegetation data bases

A simple method was developed for improved prescription of seasonal surface characteristics and parameterization of land-surface processes in climate models. This method, developed for the Goddard Institute for Space Studies General Circulation Model II (GISS GCM II), maintains the spatial variability of fine-resolution land-cover data while restricting to 8 the number of vegetation types handled in the model. This was achieved by: redefining the large number of vegetation classes in the 1 deg x 1 deg resolution Matthews (1983) vegetation data base as percentages of 8 simple types; deriving roughness length, field capacity, masking depth and seasonal, spectral reflectivity for the 8 types; and aggregating these surface features from the 1 deg x 1 deg resolution to coarser model resolutions, e.g., 8 deg latitude x 10 deg longitude or 4 deg latitude x 5 deg longitude.

Matthews, E.↗

NASA NTRS1984

Evidence for an infrared disk in the core of the extraordinary planetary nebula Abell 30

High spatial resolution infrared maps of the core of the evolved planetary nebula Abell 30, which has been shown to be composed of heavily processed material, are presented. These maps reveal an elongated, disklike structure that is not evident on optical pictures. Multicolor photometry at several positions in this disk shows that this emission is due to dust, some of which is near the evaporation temperature of graphite. Lyman-alpha trapping is shown to be inadequate as a heating source for these grains, but direct absorption of stellar photons is sufficient. In view of the unusual chemical composition, A30 represents a late stage in the evolution of a planetary nebula progenitor. The observed infrared structure may provide clues to the ejection mechanism at this stage of development.

Lester, D. F.↗

NASA NTRS1986

Solar calibration results from two earth radiation budget experiment nonscanner instruments

The Earth Radiation Budget Experiment (ERBE) makes use of three sets of two independent, but complementary, flight instruments. The two instruments in each set include a three-channel narrow field-of-view scanning instrument (scanner) and a five-channel wide field-of-view staring instrument (nonscanner). The ERBE nonscanner instruments are designed for the conduction of broad spectral and spatial measurements of the earth's reflected solar and emitted radiation and the determination of the incident solar flux. The nonscanner solar calibration process is considered along with the solar calibration results. A description of the data processing algorithms is also provided, taking into account the earth viewing channels and the solar monitor.

Luther, M. R.↗

NASA NTRS1986

International Halley Watch: Discipline specialists for near-nucleus studies

The purpose of the Near-Nucleus Studies Net is to study the processes taking place in the near-nucleus environment as they relate to the nature of nucleus. This is accomplisghed by measuring the spatial and temporal distribution of dust, gases and ions in the coma on high resolution images taken from many observatories around the world. By modeling the motions of discrete dust features in Comet Halley, it is often possible to determine the locations of the emission sources on the surface and learn about the nucleus structure. In addition to the general goals shared by all IHW nets, the scientific goals of the net has been to determine (1)the gross surface structure of the nucleus, (2)the nucleus spin vector, (3)the distribution and evolution of jet sources and (4)the interrelationships between the gas, dust and ion components of the coma. An additional Comet Giacobini-Zinner watch was carried out by the NNSN in support of the NASA International Cometary Explorer flyby.

Larson, S.↗

NASA NTRS1988

Numerical simulation of morphological development during Ostwald ripening

The morphological evolution of a small number of particles undergoing Ostwald ripening in two dimensions was investigated using a boundary integral technique. The numerical calculations show that, in many cases, interparticle diffusional interactions do not induce large distortions in particle morphology from a circle, due to the strong local interaction between regions of different curvature on the same particle. Particle migration due to interparticle diffusional interactions was observed, with the migration distance larger than the initial radius of a particle, which is linked to the particle spatial arrangement. As diffusion is the mechanism for the migration, it is expected that particle movement is a generic aspect of the coarsening process at high volume fractions of coarsening phase and, possibly, at low volume fractions. The calculations support unambiguously the Ostwald ripening mechanism for flat formation during liquid-phase sintering. As such, the appearance or regions of low interfacial curvature is a dynamic phenomenon dependent on interparticle diffusion.

Voorhees, P. W.↗

NASA NTRS1988

EIT: Solar corona synoptic observations from SOHO with an Extreme-ultraviolet Imaging Telescope

The Extreme-ultraviolet Imaging Telescope (EIT) of SOHO (solar and heliospheric observatory) will provide full disk images in emission lines formed at temperatures that map solar structures ranging from the chromospheric network to the hot magnetically confined plasma in the corona. Images in four narrow bandpasses will be obtained using normal incidence multilayered optics deposited on quadrants of a Ritchey-Chretien telescope. The EIT is capable of providing a uniform one arc second resolution over its entire 50 by 50 arc min field of view. Data from the EIT will be extremely valuable for identifying and interpreting the spatial and temperature fine structures of the solar atmosphere. Temporal analysis will provide information on the stability of these structures and identify dynamical processes. EIT images, issued daily, will provide the global corona context for aid in unifying the investigations and in forming the observing plans for SOHO coronal instruments.

Delaboudiniere, J. P.↗

NASA NTRS1990

Preliminary simulations of the large-scale environment during the FIRE cirrus IFO

Large scale forcing (scales greater than 500 km) is the dominant factor in the generation, maintenance, and dissipation of cirrus cloud systems. However, the analyses of data acquired during the first Cirrus IFO have highlighted the importance of mesoscale processes (scales of 20 to 500 km) to the development of cirrus cloud systems. Unfortunately, Starr and Wylie found that the temporal and spatial resolution of the standard and supplemental rawinsonde data were insufficient to allow an explanation of all of the mesoscale cloud features that were present on the 27 to 28 Oct. 1986. It is described how dynamic initialization, or 4-D data assimilation (FDDA) can provide a method to address this problem. The first steps towards application of FDDA to FIRE are also described.

Westphal, Douglas L.↗

NASA NTRS1990

Application of beamform to sound propagation in the atmosphere

The feasibility of applying beam-former technology (i.e., the technique that uses the combined signal from an array of sensors as a spatial filter to locate sound sources) in atmospheric acoustics is examined. Special attention is given to the microphone array, data collection, and signal processing technology as well as to an array processing algorithm. It is shown that this algorithm, which incorporates the maximum-likelihood method, is operational. Also discussed is a postprocessing algorithm for eliminating the ghosting sidelobes that arise from the moving sources.

Gerhold, Carl H.↗

NASA NTRS1991

Photonics

Optoelectronic materials and devices are examined. Optoelectronic devices, which generate, detect, modulate, or switch electromagnetic radiation are being developed for a variety of space applications. The program includes spatial light modulators, solid state lasers, optoelectronic integrated circuits, nonlinear optical materials and devices, fiber optics, and optical networking photovoltaic technology and optical processing.

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