Time-of-arrival observations of eleven pulsars
Pulsars pulse arrival time measured using cesium clock during weekly observations
Downs, G. S.↗
SEARCH · Search NASA
Results for “Arrivals”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Quasi-sinusoidal oscillation in arrival times of pulses from NP 0532
Crab Nebula pulsar NP 0532, describing quasi- sinusoidal oscillation in arrival times of radio pulses
Counselman, C. C., III↗
Crab Nebula pulsar radio pulse arrival times at Arecibo Observatory
Tables of Crab Nebula pulsar radio pulse arrival times at Arecibo observatory
Counselman, C. C., III↗
Investigations of acoustic-seismic effects at long range - Early-arriving seismic waves from Apollo 16
A reasonably comprehensive technical effort is described dealing with the investigations of acoustically generated seismic waves of Apollo 16 and Apollo 17 origin along the eastern seabord of the United States. This expanded effort is a continuation of earlier, rather successful detections of rocket-generated seismic disturbances on Skidaway Island, Georgia. The more recent effort has yielded few positive results other than a recording of an early-arriving seismic wave from Apollo 16 that was detected in Jacksonville. Evaluation of the negative results obtained in the Fort Monmouth area, with earlier studies of infrasound, local weather conditions, and geology, could be advantageous in the process of trying to gain a better insight into the acoustic-seismic resonance mechanism requiring phase-velocity matching at the atmosphere-ground interface.
Dalins, I.↗
Techniques for measuring arrival times of pulsar signals 1: DSN observations from 1968 to 1980
Techniques used in the ground based observations of pulsars are described, many of them applicable in a navigation scheme. The arrival times of the pulses intercepting Earth are measured at time intervals from a few days to a few months. Low noise, wide band receivers, amplify signals intercepted by 26 m, 34, and 64 m antennas. Digital recordings of total received signal power versus time are cross correlated with the appropriate pulse template.
Downs, G. S.↗
The CTS 11.7 GHz angle of arrival experiment
The objective of the experiment was to determine the statistical behavior of attenuation and angle of arrival on an Earth-space propagation path using the CTS 11.7 GHz beacon. Measurements performed from 1976 to 1978 form the data base for analysis. The statistics of the signal attenuation and phase variations due to atmospheric disturbances are presented. Rainfall rate distributions are also included to provide a link between the above effects on wave propagation and meteorological conditions.
Kwan, B. W.↗
Equations for the angles of arrival and departure for multivariable root loci using frequency-domain methods
Frequency domain methods are used to study the angles of arrival and departure for multivariable root loci. Explicit equations are obtained. For a special class of poles and zeros, some simpler equations that are generalizations of the single input/single output equations are presented.
Yagle, A. E.↗
Practical solutions to the aircraft minimum fuel, fixed-range, fixed time-of-arrival trajectory optimization problem
A practical scheme is presented for generating fixed range, minimum fuel vertical flight profiles that also satisfy time-of-arrival constraints. The resulting algorithm is suitable for incorporation into an on-board flight management system. Example results show that such a capability can save up to 6% of fuel burned in flights subject to delays because of terminal area congestion.
Sorensen, J. A.↗
The cost of noise reduction for departure and arrival operations of commercial tilt rotor aircraft
The relationship between direct operating cost (DOC) and noise annoyance due to a departure and an arrival operation was developed for commercial tilt rotor aircraft. This was accomplished by generating a series of tilt rotor aircraft designs to meet various noise goals at minimum DOC. These vehicles ranged across the spectrum of possible noise levels from completely unconstrained to the quietest vehicles that could be designed within the study ground rules. Optimization parameters were varied to find the minimum DOC. This basic variation was then extended to different aircraft sizes and technology time frames.
Faulkner, H. B.↗
Equations for the angles of arrival and departure for multivariable root loci using frequency-domain methods
Frequency domain methods are developed to obtain explicit equations for the angles of arrival and departure for multivariable root loci. The techniques involve an evaluation of polynomials formulated within the transfer function matrix. The equations defined require simpler computations than the state-space results of Shaked (1976). A class of higher order poles and zeros is formulated in terms of simpler equations than Shaked's, and the equations are shown to be generalizations of the single-input-single-output root locus equations.
Yagle, A. E.↗
Energy spectrum and arrival direction of primary cosmic rays of energy above 10 to the 18th power eV
The observation of ultra high energy cosmic rays with 20 sq km array has started at Akeno. The preliminary results on energy spectrum and arrival direction of energies above 10 to the 18th eV are prsented with data accumulated for four years with the 1 sq km array, for two years with the 4 sq km array and for a half year with the new array. The energy spectrum is consistent with the previous experiments showing the flattening above 10 to the 18.5 eV.
Teshima, M.↗
Longitudinal development of muons in large air showers studies from the arrival time distributions measured at 900m above sea level
The arrival time distributions of muons with energies above 1.0GeV and 0.5GeV have been measured in the Akeno air-shower array to study the longitudinal development of muons in air showers with primary energies in the range 10 to the 17th power to 10 to the 18th power ev. The average rise times of muons with energies above 1.0GeV at large core distances are consistent with those expected from very high multiplicity models and, on the contrary, with those expected from the low multiplicity models at small core distances. This implies that the longitudinal development at atmospheric depth smaller than 500 cm square is very fast and that at larger atmospheric depths is rather slow.
Kakimoto, F.↗
A note on some statistical properties of rise time parameters used in muon arrival time measurements
Most investigations of the muon arrival time distribution in EAS during the past decade made use of parameters which can collectively be called rise time parameters. The rise time parameter T sub A/B is defined as the time taken for the integrated pulse from a detector to rise from A% to B% of its full amplitude. The use of these parameters are usually restricted to the determination of the radial dependence thereof. This radial dependence of the rise time parameters are usually taken as a signature of the particle interaction characteristics in the shower. As these parameters have a stochastic nature, it seems reasonable that one should also take notice of this aspect of the rise time parameters. A statistical approach to rise time parameters is presented.
Vanderwalt, D. J.↗
Time-resolved speckle effects on the estimation of laser-pulse arrival times
A maximum-likelihood (ML) estimator of the pulse arrival in laser ranging and altimetry is derived for the case of a pulse distorted by shot noise and time-resolved speckle. The performance of the estimator is evaluated for pulse reflections from flat diffuse targets and compared with the performance of a suboptimal centroid estimator and a suboptimal Bar-David ML estimator derived under the assumption of no speckle. In the large-signal limit the accuracy of the estimator was found to improve as the width of the receiver observational interval increases. The timing performance of the estimator is expected to be highly sensitive to background noise when the received pulse energy is high and the receiver observational interval is large. Finally, in the speckle-limited regime the ML estimator performs considerably better than the suboptimal estimators.
Tsai, B.-M.↗
Air traffic controller aids for planning of arrival traffic - An AI approach
Air traffic management is considered as an AI problem, and planning concepts are developed for incorporation into an automation aid for enroute arrival controllers being developed by NASA. An Assumption-Based Truth Maintenance System is modified to include the nonmonotonicities inherent in the Air Traffic Control (ATC) domain, and it is noted under what circumstances the advantages of the ATMS in standard problem-solving domains carry over to planning. The noninteracting actions of the conceptualization are contrasted with the interacting actions of other domains. It is shown that the noninteracting nature of the ATC domain makes it possible to provide an efficient planner that avoids the frame problem.
Chrisley, Ron↗
Computer Scheduling Of Airplane Arrivals
Prototype computer-based system developed to assist air-traffic controllers in scheduling arrivals of many airplanes at airport and at designated points along approaches to airport. Designed to follow as many as 100 airplanes within radius of 150 nautical miles. Software written in Symbolics Zetalisp language.
Tobias, L.↗
GPS/Loran-C interoperability for time and frequency applications: A survey of the times of arrival of Loran-C transmissions via GPS common mode/common view satellite observations
The results from this survey clearly indicate that the Global Positioning System (GPS) time transfer capability is superior to that of the Loran-C system for absolute timing accuracy, and that even with the most careful calibration of the Loran-C receiver delay and propagation path, inexplicable time of arrival (TOA) biases remain which are larger than the variations across all of the transmitters. Much more data covering years would be needed to show that these biases were stable enough to be removed with a one time site calibration. The synchronization of the transmissions is excellent, all showing low parts in 10(exp 13) offsets versus the United States Naval Observatory (USNO) master clock. With the exception of the Searchlight transmitter, all of the transmissions exhibit timing stabilities over the entire period of less than 300 ns RMS which is at the observed levels of GPS under selective availability (SA). The Loran-C phase instabilities take place over a much greater time interval than those being forced onto the GPS signals under SA, providing for better medium to short term frequency stability. Data show that all but the most distant transmitters offer better than three parts in 10(exp 11) stability at this averaging time. It is in the frequency control area where GPS/Loran-C interoperation will offer some synergistic advantages over GPS alone under SA.
Penrod, Bruce↗
The effect of the Earth's oblate spheroid shape on the accuracy of a time-of-arrival lightning ground strike locating system
The algorithm used in previous technology time-of-arrival lightning mapping systems was based on the assumption that the earth is a perfect spheroid. These systems yield highly-accurate lightning locations, which is their major strength. However, extensive analysis of tower strike data has revealed occasionally significant (one to two kilometer) systematic offset errors which are not explained by the usual error sources. It was determined that these systematic errors reduce dramatically (in some cases) when the oblate shape of the earth is taken into account. The oblate spheroid correction algorithm and a case example is presented.
Casper, Paul W.↗