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Fenimore, Edward E.

Publications and source records attributed to Fenimore, Edward E..

18 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Three New EMP Analysis Methods [Slides]

Three analysis techniques are presented. One is a new method of doing spectrograms that gives full time resolution and optimum frequency resolution. Another is a method that uses the phase of the Fourier transform of the signal rather than the magnitude of narrow band receivers. With one FFT, one can obtain 1000’s of TOA-frequency pairs to fit to that are unaffected by any magnetic field that the signal encounter during propagation. The third method dechirps the signal in a manner that identifies the STEC and VTOA that finds when the signal has both ionospheric modes equally.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Four-Dimensional Golden Search

The Golden search technique is a method to search a multiple-dimension space to find the minimum. It basically subdivides the possible ranges of parameters until it brackets, to within an arbitrarily small distance, the minimum. It has the advantages that (1) the function to be minimized can be non-linear, (2) it does not require derivatives of the function, (3) the convergence criterion does not depend on the magnitude of the function. Thus, if the function is a goodness of fit parameter such as chi-square, the convergence does not depend on the noise being correctly estimated or the function correctly following the chi-square statistic. And, (4) the convergence criterion does not depend on the shape of the function. Thus, long shallow surfaces can be searched without the problem of premature convergence. As with many methods, the Golden search technique can be confused by surfaces with multiple minima.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2014

How Common are Noise Sources on the Crash Arc of Malaysian Flight 370

Malaysian Flight 370 disappeared nearly without a trace. Besides some communication handshakes to the INMASAT satellite, the Comprehensive Test Ban Treaty monitoring system could have heard the aircraft crash into the southern Indian Ocean. One noise event from Cape Leeuwin has been suggested by Stead as the crash and occurs within the crash location suggested by Kunkle at el. We analyze the hydrophone data from Cape Leeuwin to understand how common such noise events are on the arc of possible locations where Malaysian Flight 370 might have crashed. Few other noise sources were found on the arc. The noise event found by Stead is the strongest. No noise events are seen within the Australian Transportation Safety Board (ATSB) new search location until the 10 th strongest event, an event which is very close to the noise level.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2014

From Pinholes to Black Holes

Pinhole photography has made major contributions to astrophysics through the use of “coded apertures”. Coded apertures were instrumental in locating gamma-ray bursts and proving that they originate in faraway galaxies, some from the birth of black holes from the first stars that formed just after the big bang.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The cause of outliers in electromagnetic pulse (EMP) locations

We present methods to calculate the location of EMP pulses when observed by 5 or more satellites. Simulations show that, even with a good initial guess and fitting a location to all of the data, there are sometime outlier results whose locations are much worse than most cases. By comparing simulations using different ionospheric transfer functions (ITFs), it appears that the outliers are caused by not including the additional path length due to refraction rather than being caused by not including higher order terms in the Appleton-Hartree equation. We suggest ways that the outliers can be corrected. These correction methods require one to use an electron density profile along the line of sight from the event to the satellite rather than using the total electron content (TEC) to characterize the ionosphere.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2014

Fifty-one years of Los Alamos Spacecraft

From 1963 to 2014, the Los Alamos National Laboratory was involved in at least 233 spacecraft. There are probably only one or two institutions in the world that have been involved in so many spacecraft. Los Alamos space exploration started with the Vela satellites for nuclear test detection, but soon expanded to ionospheric research (mostly barium releases), radioisotope thermoelectric generators, solar physics, solar wind, magnetospheres, astrophysics, national security, planetary physics, earth resources, radio propagation in the ionosphere, and cubesats. Here, we present a list of the spacecraft, their purpose, and their launch dates for use during RocketFest

99 GENERAL AND MISCELLANEOUS↗
NASA NTRS1997

Kinematic arguments against single relativistic shell models for GRBs

Two main types of models have been suggested to explain the long durations and multiple peaks of Gamma Ray Bursts (GRBs). In one, there is a very quick release of energy at a central site resulting in a single relativistic shell that produces peaks in the time history through its interactions with the ambient material. In the other, the central site sporadically releases energy over hundreds of seconds forming a peak with each burst of energy. The authors show that the average envelope of emission and the presence of gaps in GRBs are inconsistent with a single relativistic shell. They estimate that the maximum fraction of a single shell that can produce gamma-rays in a GRB with multiple peaks is 10(exp (minus)3), implying that single relativistic shells require 10(exp 3) times more energy than previously thought. They conclude that either the central site of a GRB must produce (approx)10(exp 51) erg/s(exp (minus)1) for hundreds of seconds, or the relativistic shell must have structure on a scales the order of (radical)(epsilon)(Gamma)(exp (minus)1), where (Gamma) is the bulk Lorentz factor ((approximately)10(exp 2) to 10(exp 3)) and (epsilon) is the efficiency.

Fenimore, Edward E.↗
NASA NTRS1995

Constraints on the gamma-ray burst luminosity function from Pioneer Venus Orbiter and BATSE observations

We examine the width of the gamma ray burst luminosity function through the distribution of Gamma Ray Burst (GRB) peak fluxes as detected by the Pioneer Venus Orbiter (PVO) and the Burst and Transient Source Experiment (BATSE). The strength of the analysis is greatly enhanced by using a merged catalog of peak fluxes from both instruments with good cross-calibration of their sensitivities. The range of peak fluxes is increased by approximately a factor of 20 relative to the BATSE catalog. Thus, more sensitive investigations of the log N - log P distribution are possible. We place constraints on the width of the luminosity function of gamma-ray bursts brighter than the BATSE completeness limit by comparing the intensity distribution in the merged catalog with those produced by a variety of spatial density and luminosity functions. For the models examined, 90% of the detectable bursts have peak luminosities within a range of 10, indicating that the peak luminosities of gamma-ray bursts span a markedly less wide range of values than many other of their measurable properties. We also discuss for which slopes of a power-law luminosity function the observed width is at the upper end of the constrained range. This is essential in determining the power-law slopes for which luminosity-duration correlations could be important.

Ulmer, Andrew↗
NASA NTRS1992

The high-energy transient experiment (HETE) - An international multiwavelength mission

The High Energy Transient Experiment (HETE), an international mission scheduled by NASA for launch on a Pegasus rocket in July 1994, is described. The prime objective of HETE is to carry out the first multiwavelength study of gamma-ray bursts with UV, X-ray, and gamma-ray instruments mounted on a single, compact spacecraft. A unique feature of the HETE mission is its capability to localize GRBs with about 10 arc second accuracy, in near real time aboard the spacecraft, and to transmit these positions directly to a network of receivers at existing ground-based observatories, enabling rapid, sensitive follow-up studies in the radio, IR, and optical bands.

Ricker, George R.↗
NASA NTRS1992

Cyclotron line strength variations in gamma-ray burst GB870303 - Possible evidence of neutron star rotation

An exhaustive search of the Ginga data on gamma-ray burst GB870303 reveals two separate time intervals during which statistically significant line features are evident. One interval shows a single prominent line feature at about 20 keV; a second, shows two line features at about 20 and 40 keV. From model fits to the data, we find that both sets of lines are well-described by cyclotron resonant scattering in a magnetic field B about 1.8 x 10 exp 12 G, and that the differences in the line strengths between the two intervals are significant. The variations are qualitatively similar to those produced by a change in the viewing angle theta relative to the magnetic field. We conjecture that the change in theta is due to rotation of the neutron star, and derive limits P = 45-180 sec on the rotation period P.

Graziani, Carlo↗