35,106 research outputs found
Analysis and applications of a general boresight algorithm for the DSS-13 beam waveguide antenna
A general antenna beam boresight algorithm is presented. Equations for axial pointing error, peak received signal level, and antenna half-power beamwidth are given. A pointing error variance equation is derived that illustrates the dependence of the measurement estimation performance on the various algorithm inputs, including RF signal level uncertainty. Plots showing pointing error uncertainty as function of algorithm inputs are presented. Insight gained from the performance analysis is discussed in terms of its application to the areas of antenna controller and receiver interfacing, pointing error compensation, and antenna calibrations. Current and planned applications of the boresight algorithm, including its role in the upcoming Ka-band downlink experiment (KABLE), are highlighted
An analysis of the least-squares problem for the DSN systematic pointing error model
A systematic pointing error model is used to calibrate antennas in the Deep Space Network. The least squares problem is described and analyzed along with the solution methods used to determine the model's parameters. Specifically studied are the rank degeneracy problems resulting from beam pointing error measurement sets that incorporate inadequate sky coverage. A least squares parameter subset selection method is described and its applicability to the systematic error modeling process is demonstrated on Voyager 2 measurement distribution
Application of optimal control theory to the design of the NASA/JPL 70-meter antenna servos
The application of Linear Quadratic Gaussian (LQG) techniques to the design of the 70-m axis servos is described. Linear quadratic optimal control and Kalman filter theory are reviewed, and model development and verification are discussed. Families of optimal controller and Kalman filter gain vectors were generated by varying weight parameters. Performance specifications were used to select final gain vectors
Organizing on the edge: Heading to Mount Everest
The paper analyzes complexity in organizations facing threatening environments. Such contexts are characterized by very high levels of risk and uncertainty that challenge organizational survival: fire-fighting, aerospace projects, high-tech research programs, etc. A paradox of these contexts is that although they remain stable, organizations operating within them are often transitory, single-project and with a high variety of skills and knowledge. These organizations show a peculiar way of organizing complexity, that deserves special attention. This paper is built upon a longitudinal case study based on successive attempts to climb Mount Everest by Chilean expeditions. After three failed attempts (1984, 1986, 1989) the summit was finally reached in 1992 through one of the hardest routes. Each expedition was an independent organization, and structural arrangements as well as participants were different, except for a small permanent coreComplexity in organizations; environment;
Charged current neutrino induced coherent pion production
We analyze the neutrino induced charged current coherent pion production at
the energies of interest for recent experiments like K2K and MiniBooNE. Medium
effects in the production mechanism and the distortion of the pion wave
function, obtained solving the Klein Gordon equation with a microscopic optical
potential, are included in the calculation. We find a strong reduction of the
cross section due to these effects and also substantial modifications of the
energy distributions of the final lepton and pion.Comment: 11 pages, 6 figures. Some details and new references added; results
unchanged. Accepted in PR
Atmospheric refraction correction for Ka-band blind pointing on the DSS-13 beam waveguide antenna
An analysis of the atmospheric refraction corrections at the DSS-13 34-m diameter beam waveguide (BWG) antenna for the period Jul. - Dec. 1990 is presented. The current Deep Space Network (DSN) atmospheric refraction model and its sensitivity with respect to sensor accuracy are reviewed. Refraction corrections based on actual atmospheric parameters are compared with the DSS-13 station default corrections for the six-month period. Average blind-pointing improvement during the worst month would have amounted to 5 mdeg at 10 deg elevation using actual surface weather values. This would have resulted in an average gain improvement of 1.1 dB
Direct T-violation measurements and T-odd effects in decay experiments
Motivated by the recent experimental announcements for direct measurements of
time-reversal non-invariance in the neutral kaon system, we make a comparative
discussion of the CPLEAR and KTeV measurements. The most suitable way to
consistently incorporate the mixing, the time evolution and the decays of
kaons, is to describe the neutral kaon system as a system with a non-Hermitean
Hamiltonian. In this framework, the physical (decaying) incoming and outgoing
states are distinct and belong to dual spaces. Moreover, since they are
eigenstates of the full Hamiltonian, they never oscillate. This is directly
manifest in the orthogonality conditions of the physical states, which entirely
determine the evolution of the kaon system. Along these lines we conclude:
CPLEAR studies K0-bar{K0} oscillations, a process where initial and final
states can be reversed, the CPLEAR asymmetry being an effect directly related
to the definition of time-reversal. Conclusively, CPLEAR provides a direct
measurement of T-violation without any assumption either on unitarity or on
CPT-invariance. The KTeV experiment studies in particular the process KL -> pi+
pi- e+ e- where they measure a T-odd effect. However, using unitarity together
with estimates of the final state interactions, it should be possible to
determine whether this effect can be identified with a genuine T-reversal
violation.Comment: 11 pages, no figures. Presented at the 34th Rencontres de Moriond on
Electroweak Interactions and Unified Theories, Les Arcs, 13-20 March, 199
Space-time noncommutativity and (1+1) Higgs Model
We compare the classical scattering of kinks in (1+1) Higgs model with its
analogous noncommutative counterpart. While at a classical level we are able to
solve the scattering at all orders finding a smooth solution, at a
noncommutative level we present only perturbative results, suggesting the
existence of a smooth solution also in this case.Comment: 18 pages, 2 figure
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