Showing papers by "Computer Sciences Corporation published in 1975"
TL;DR: Performance in terms of meansquare reconstruction error versus bit rate can be shown to parallel the theoretical rate distortion function for the first-order Markov process by about 0.6 bits/sample at low bit rates.
Abstract: Predictive coders have been suggested for use as analog data compression devices. Exact expressions for reconstructed signal error have been rare in the literature. In fact most results reported in the literature are based on the assumption of Gaussian statistics for prediction error. Predictive coding of first-order Gaussian Markov sequences are considered in this paper. A numerical iteration technique is used to solve for the prediction error statistics expressed as an infinite series in terms of Hermite polynomials. Several interesting properties of predictive coding are thereby demonstrated. First, prediction error is in fact close to Gaussian, even for the binary quantizer. Sencond, quantizer levels may be optimized at each iteration according to the calculated density. Finally, the existence of correlation between successive quantizer outputs is shown. Using the series solutions described above, performance in terms of meansquare reconstruction error versus bit rate can be shown to parallel the theoretical rate distortion function for the first-order Markov process by about 0.6 bits/sample at low bit rates.
60 citations
TL;DR: In this paper, experimental results were reported on three energetic particle events with extremely high abundance of He-3, and it was shown that the abundance of protons relative to He nuclei were significantly low in these events.
Abstract: Experimental results are reported on three energetic particle events with extremely high abundance of He-3. The measurements were taken onboard the OGO-5 satellite. It was shown that the abundance of protons relative to He nuclei were significantly low in these events. Not more than four H-2 and three H-3 were detected during the entire period under study compared to 1110 H-3 nuclei. The limitations these observations place on theoretical models are discussed to explain He-3 flares.
50 citations
01 Jan 1975
TL;DR: In this paper, a standard kinematic model for aircraft simulation exists at NASA-Ames on a variety of computer systems, one of which is used to control the flight simulator for advanced aircraft (FSAA).
Abstract: A standard kinematic model for aircraft simulation exists at NASA-Ames on a variety of computer systems, one of which is used to control the flight simulator for advanced aircraft (FSAA). The derivation of the kinematic model is given and various mathematical relationships are presented as a guide. These include descriptions of standardized simulation subsystems such as the atmospheric turbulence model and the generalized six-degrees-of-freedom trim routine, as well as an introduction to the emulative batch-processing system which enables this facility to optimize its real-time environment.
47 citations
01 May 1975
TL;DR: In this paper, the flow field and surface response conditions for a planetary probe entering the atmosphere of Jupiter are described with a viscous-shock-layer analysis which includes mass injection, radiative transfer, diffusion, and viscous effects.
Abstract: This paper presents results that describe the flow field and surface response conditions for a planetary probe entering the atmosphere of Jupiter. The results are obtained with a viscous-shock-layer analysis which includes mass injection, radiative transfer, diffusion, and viscous effects. Radiative transfer is calculated with an existing nongray radiation model that accounts for molecular band, atomic line, and continuum transitions. Particular emphasis is given to the effect of mass injection on the stagnation and downstream flow. Results for both specified and coupled mass injection are obtained for a carbon heat shield.
46 citations
01 Jul 1975
TL;DR: In this paper, the motion of a satellite near a libration point collinear with the sun and the earth-moon barycenter is considered for a perturbed elliptic-restricted problem.
Abstract: Bounded motion about Lagrange collinear libration points is considered for a perturbed elliptic-restricted problem. A practical application is the motion of a satellite near a libration point collinear with the sun and the earth-moon barycenter. Such a system is treated here as an earth-sun-satellite elliptic restricted problem with lunar perturbations. The method of dual time scales is utilized to develop a uniformly valid three-dimensional analytical solution to the satellite's equations of motion. The analytical development applies somewhat generally to that class of four-body problems where the second primary mass is much greater than the first, and the third primary mass is much greater than the second.
41 citations
01 Oct 1975
TL;DR: An airborne laser depth sounding system was built and taken through a complete series of field tests Two green laser sources were tried: a pulsed neon laser at 540 nm and a frequency-doubled Nd:YAG transmitter at 532 nm as discussed by the authors.
Abstract: An airborne laser depth sounding system was built and taken through a complete series of field tests Two green laser sources were tried: a pulsed neon laser at 540 nm and a frequency-doubled Nd:YAG transmitter at 532 nm To obtain a depth resolution of better than 20 cm, the pulses had a duration of 5 to 7 nanoseconds and could be fired up to at rates of 50 pulses per second In the receiver, the signal was detected by a photomultiplier tube connected to a 28 cm diameter Cassegrainian telescope that was aimed vertically downward Oscilloscopic traces of the signal reflected from the sea surface and the ocean floor could either be recorded by a movie camera on 35 mm film or digitized into 500 discrete channels of information and stored on magnetic tape, from which depth information could be extracted An aerial color movie camera recorded the geographic footprint while a boat crew of oceanographers measured depth and other relevant water parameters About two hundred hours of flight time on the NASA C-54 airplane in the area of Chincoteague, Virginia, the Chesapeake Bay, and in Key West, Florida, have yielded information on the actual operating conditions of such a system and helped to optimize the design One can predict the maximum depth attainable in a mission by measuring the effective attenuation coefficient in flight This quantity is four times smaller than the usual narrow beam attenuation coefficient Several square miles of a varied underwater landscape were also mapped
24 citations
01 Aug 1975
TL;DR: In this paper, an analytical averaging technique was used to expand the disturbing potential in the equinoctial coordinate frame by considering third body harmonics and zonal functions harmonics, and general results were developed through applications of Legendre and associated Legendre polynomials and the Q sub nm functions for the gravitational potential.
Abstract: Analytical averaging techniques are used to expand the disturbing potential in the equinoctial coordinate frame by considering third body harmonics and zonal functions harmonics. General results are developed through applications of Legendre and associated Legendre polynomials and the Q sub nm functions for the gravitational potential.
23 citations
01 Jul 1975
TL;DR: In this article, the effect of operator variability and subjectivity in lineament mapping and methods to minimize or eliminate these problems by use of several machine preprocessing methods was studied and the results were compared statistically.
Abstract: The effect of operator variability and subjectivity in lineament mapping and methods to minimize or eliminate these problems by use of several machine preprocessing methods was studied. Mapped lineaments of a test landmass were used and the results were compared statistically. The total number of fractures mapped by the operators and their average lengths varied considerably, although comparison of lineament directions revealed some consensus. A summary map (785 linears) produced by overlaying the maps generated by the four operators shows that only 0.4 percent were recognized by all four operators, 4.7 percent by three, 17.8 percent by two, and 77 percent by one operator. Similar results were obtained in comparing these results with another independent group. This large amount of variability suggests a need for the standardization of mapping techniques, which might be accomplished by a machine aided procedure. Two methods of machine aided mapping were tested, both simulating directional filters.
20 citations
TL;DR: An approximate solution of the steady state two-dimensional diffusion equation, obtained by an integral method, is presented and can be used to predict dispersion of pollutants in the atmosphere over an area-source such as an urban area.
19 citations
01 Jan 1975
TL;DR: In this article, explicit expressions for the n-th term in the disturbing potential for three-body and zonal harmonics are derived for equinoxial elements and a recursive method for recursive computation of the disturbed potential and partial derivatives is proposed.
Abstract: Explicit expressions in equinoxial elements are derived for the n-th term in the disturbing potential for three-body and zonal harmonics. A method for recursive computation of the disturbing potential and the partial derivatives is proposed. Preliminary results for an arbitrary geopotential term are obtained.
17 citations
TL;DR: An algorithm for transposing large rectangular matrices using optimal partitioning and powers-of-2 partitioning is presented and it is found in the cases tested that a speed gain of up to 5.55 is obtained by optimizing the partition sizes.
Abstract: The purpose of this paper is to present an algorithm for transposing large rectangular matrices. This is basically a generalization of Eklundh's algorithm. Eklundh's method is designed to handle arrays in place of using powers-of-2 approach wherein partitions of the matrix have dimensions which are powers of 2. The algorithm presented here does not have this restriction. The choice of partitions is posed as an optimal control problem amenable to solution using Bellman's principle of optimality. The optimal partitioning of the matrix can be determined depending on the computer configuration (i.e., core size, whether moving-head or fixed-head disk drives are used, number of words per track, etc.) and the matrix dimensions. Simple modifications are noted for transposing complex/double precision and packed integer matrices. Experimental results are presented comparing the times needed for transposition using optimal partitioning and powers-of-2 partitioning. It is found in the cases tested that a speed gain of up to 5.55 is obtained by optimizing the partition sizes.
01 Jul 1975
TL;DR: In this paper, an edge image correlation algorithm is presented, which performs rapid automatic registration of the edge images and, consequently, the grey level images, by detecting the edges of features in a particular spectral band of a digital satellite image.
Abstract: An algorithm is described which will form an edge image by detecting the edges of features in a particular spectral band of a digital satellite image. It is capable also of forming composite multispectral edge images. In addition, an edge image correlation algorithm is presented which performs rapid automatic registration of the edge images and, consequently, the grey level images.
TL;DR: This paper describes the maintenance and enhancement of the Computer Sciences Teleprocessing System (CSTS) and its component processors and the design and documentation of test programs and the organization of test sets.
Abstract: This paper describes the maintenance and enhancement of the Computer Sciences Teleprocessing System (CSTS) and its component processors. CSTS is the system offered by the INFONET Division of Computer Sciences Corporation to provide nationwide conversational and batch teleprocessing service. In the first section, the organization of the project personnel and major activities of project departments are described. The second section describes the process by which functional enhancements and error corrections are implemented. The final section describes testing techniques and procedures used during implementation.The project staff is organized into implementation departments and service departments. Implementation departments develop new features of the system, corrections to errors, and improvements in system operation, especially in reduction of software overhead. Implementation departments are organized by system software functions such as operating system (device control, task management, and file management), language processors and data management systems, communications software, and applications. The service departments are system integration, performance analysis, product management and system test. The functions performed by these departments are described. Also described are the system evolution conferences and the periodic review of enhancements by a Change Advisory Board.During the development of a new version of the system, effective tracking of the status of changed modules is essential. The data base and process used to track new features, error corrections and changed component modules are described. The flow of implemented changes through system integration and system test is delineated, as is the development and verification of change documentation for users, administrators and operations personnel.The final section of the paper describes the design and documentation of test programs and the organization of test sets. Effective test operations are achieved by using self-checking tests as well as automated test operation and verification. Tests for compliance with functional specifications and for conformity to internal design are described.
TL;DR: A method for the analysis of expected system response is developed and applied to a typical spacecraft digital control system design.
01 Jul 1975
TL;DR: A low-cost multi-comet intercept mission with a launch in March 1985 is proposed in this paper, where two cometary spacecraft of identical design will be placed into a low earth parking orbit using a single Shuttle launch vehicle Solid kick stages will then be used to boost each spacecraft into its required interplanetary trajectory.
Abstract: A low-cost multi-comet intercept mission with a launch in March 1985 is proposed Two cometary spacecraft of identical design will be placed into a low earth parking orbit using a single Shuttle launch vehicle Solid kick stages will then be used to boost each spacecraft into its required interplanetary trajectory It is planned to have one spacecraft intercept comet Giacobini-Zinner in September 1985 and then go on to comet Borrelly with an encounter in December 1987 Earth swingby maneuvers will be used to achieve the double cometary intercept The other spacecraft will be targeted for a pre-perihelion encounter with Halley's comet in December 1985
01 Jan 1975
TL;DR: This paper describes the maintenance and enhancement of the Computer Sciences Teleprocessing System (CSTS) and its component processors and the design and documentation of test programs and the organization of test sets.
Abstract: This paper describes the maintenance and enhancement of the Computer Sciences Teleprocessing System (CSTS) and its component processors. CSTS is the system offered by the INFONET Division of Computer Sciences Corporation to provide nationwide conversational and batch teleprocessing service. In the first section, the organization of the project personnel and major activities of project departments are described. The second section describes the process by which functional enhancements and error corrections are implemented. The final section describes testing techniques and procedures used during implementation.The project staff is organized into implementation departments and service departments. Implementation departments develop new features of the system, corrections to errors, and improvements in system operation, especially in reduction of software overhead. Implementation departments are organized by system software functions such as operating system (device control, task management, and file management), language processors and data management systems, communications software, and applications. The service departments are system integration, performance analysis, product management and system test. The functions performed by these departments are described. Also described are the system evolution conferences and the periodic review of enhancements by a Change Advisory Board.During the development of a new version of the system, effective tracking of the status of changed modules is essential. The data base and process used to track new features, error corrections and changed component modules are described. The flow of implemented changes through system integration and system test is delineated, as is the development and verification of change documentation for users, administrators and operations personnel.The final section of the paper describes the design and documentation of test programs and the organization of test sets. Effective test operations are achieved by using self-checking tests as well as automated test operation and verification. Tests for compliance with functional specifications and for conformity to internal design are described.
TL;DR: Using a smog-chamber-validated computer model for the photochemical kinetics of C 3 H 6 NO x systems, it is shown that by proper choice of reactant concentrations and light intensities, the reaction rates can be sufficiently accelerated to yield ozone formation times of 30 s or less.
TL;DR: Computer simulations of the Mr,k, model in the context of feature selection in an unsupervised environment has demonstrated the superiority of the model over similar models without this multi-state-choice innovation.
01 Jun 1975
TL;DR: In this paper, computer enhanced imagery developed by color compositing stretched MSS ratio data was constructed for a test site in northwestern Saudi Arabia and initial results indicate that several igneous and sedimentary rock types can be discriminated.
Abstract: Various computer enhancement and data extraction systems using LANDSAT data were assessed and used to complement a continuing geologic mapping program. Interactive digital classification techniques using both the maximum-likelihood and thresholding statistical approaches achieve very limited success in areas of highly dissected terrain. Computer enhanced imagery developed by color compositing stretched MSS ratio data was constructed for a test site in northwestern Saudi Arabia. Initial results indicate that several igneous and sedimentary rock-types can be discriminated.
TL;DR: In this article, the equivalence between a class of non-linear non-autonomous systems of second order and a linear model of lower order is established through a differential transformation relation.
01 Jul 1975
TL;DR: In this paper, the adaptive trajectory flexibility of the mission is discussed and procedures used to handle low perigee maneuver operations (to 130 km), for achieving ground track control and orbit phasing, for making a transition from elliptical to circular orbits, and for circular orbit restoration and maintenance are summarized.
Abstract: The preflight mission design and in-flight execution are presented to illustrate the actual utilization of the adaptive nature of this mission. Spacecraft systems (propulsion, attitude, accelerometer) and software (maneuver program) features which contribute to the adaptive trajectory flexibility are discussed. Descriptions of procedures used to handle low perigee maneuver operations (to 130 km), for achieving ground track control and orbit phasing, for making a transition from elliptical to circular orbits, and for circular orbit restoration and maintenance are presented in detail. The 85 maneuvers made during the first 17 months of the mission are summarized.
TL;DR: A new flexible multiplier design using r.o.m.s in a cellular array is presented, which operates at high speed without loss of accuracy, even when the number of bits increases, say, to 48 × 48 bits.
Abstract: A new flexible multiplier design using r.o.m.s in a cellular array is presented. This economical multiplier operates at high speed without loss of accuracy, even when the number of bits increases, say, to 48 × 48 bits.
01 Jul 1975
TL;DR: In this article, the determinability of spacecraft attitude and bias parameters is predicted using a set of simple geometrical rules for the Synchronous Meteorological Satellite-2 (SMS-2).
Abstract: Geometrical procedures are presented for predicting the determinability of spacecraft attitude and bias parameters An analysis is presented on three common attitude measurements: sun angle, nadir angle, and sun-to-earth mid-scan rotation angle First, the geometry of these measurements is considered for an arbitrary fixed location of the spacecraft; then the effect of orbital motion is analyzed The results are summarized in a set of simple geometrical rules The application of these rules to the Synchronous Meteorological Satellite-2 (SMS-2) is discussed As a result of this geometrical analysis, modifications were made to the SMS-2 bias determination schedule which substantially enhanced the determinability of attitude sensor biases
01 Aug 1975
TL;DR: In order to obtain information on radioactive background induced in the Apollo 15 and 16 gamma-ray spectrometers (7 cm x 7 cm NaI) by particle irradiation during spaceflight, an identical detector was flown and returned to earth on the Apollo 17 mission.
Abstract: In order to obtain information on radioactive background induced in the Apollo 15 and 16 gamma-ray spectrometers (7 cm x 7 cm NaI) by particle irradiation during spaceflight, and identical detector was flown and returned to earth on the Apollo 17 mission. The induced radioactivity was monitored both internally and externally from one and a half hours after splashdown. When used in conjunction with a computation scheme for estimating induced activation from calculated trapped proton and cosmic-ray fluences, these results show an important contribution resulting from both thermal and energetic neutrons produced in the heavy spacecraft by cosmic-ray interactions.
Journal Article•
15 Apr 1975
TL;DR: A high speed digital video image system was utilized to digitize the analog video signal, place the information directly into computer-type memory, and record data on digital magnetic tape for permanent storage and subsequent analysis.
Abstract: A 25-mm vidicon camera was previously modified to allow operation in an integration mode for low-light-level astronomical work. The camera was then mated to a low-dispersion spectrograph for obtaining spectral information in the 400 to 750 nm range. A high speed digital video image system was utilized to digitize the analog video signal, place the information directly into computer-type memory, and record data on digital magnetic tape for permanent storage and subsequent analysis.
01 Jul 1975
TL;DR: A description is given of a digital computer program which prepares contour plots of three dimensional data using a triangulation procedure, which can handle essentially unlimited amounts of data.
Abstract: A description is given of a digital computer program which prepares contour plots of three dimensional data. The contouring technique uses a triangulation procedure. As presently configured, the program can accept up to 56,000 randomly spaced data points, although the required computer resources may be prohibitive. However, with relatively minor internal modifications, the program can handle essentially unlimited amounts of data. Up to 20 contouring intervals can be selected and contoured with either polygonal lines or smooth curves. Sample cases are illustrated. A general description of the main program and primary level subroutines is included to permit simple modifications of the program.
01 Dec 1975
TL;DR: In this paper, a numerical integration procedure is described which numerically integrates the equations of motion of an unguided rocket through the final burnout; and then, through impact, only three translational motions are considered.
Abstract: A computational procedure is described which numerically integrates the equations of motion of an unguided rocket. Three translational and two angular (roll discarded) degrees of freedom are integrated through the final burnout; and then, through impact, only three translational motions are considered. Input to the routine is: initial time, altitude and velocity, vehicle characteristics, and other defined options. Input format has a wide range of flexibility for special calculations. Output is geared mainly to the wind-weighting procedure, and includes summary of trajectory at burnout, apogee and impact, summary of spent-stage trajectories, detailed position and vehicle data, unit-wind effects for head, tail and cross winds, coriolis deflections, range derivative, and the sensitivity curves (the so called F(Z) and DF(Z) curves). The numerical integration procedure is a fourth-order, modified Adams-Bashforth Predictor-Corrector method. This method is supplemented by a fourth-order Runge-Kutta method to start the integration at t=0 and whenever error criteria demand a change in step size.
01 Apr 1975
TL;DR: In this article, a program of large area scanning of the waning Moon is described, where procedures for atmospheric attenuation correction and data reduction to temperature by relative radiometry are outlined.
Abstract: A program of lunar infrared radiometry which uses large area scanning is described. Procedures for atmospheric attenuation correction and data reduction to temperature by relative radiometry are outlined. The scan data of the waning Moon taken during ten evenings in the 10- to 12-µm window are presented as isothermal contour maps of the lunar disc. More than 160 areas of anomalous thermal emission have been found in the lunar darkside data. These are tabulated and are also shown on an accompanying map. An error analysis, derived from accuracy estimates of the independent parameters, is included.
01 Jul 1975
TL;DR: In this article, a mathematical formulation of CNTRLF, the maneuver control program for the Applications Technology Satellite-F (ATS-F), is presented, and the purpose is to specify the mathematical models that are included in the design.
Abstract: The mathematical formulation is presented of CNTRLF, the maneuver control program for the Applications Technology Satellite-F (ATS-F). The purpose is to specify the mathematical models that are included in the design of CNTRLF.