We describe modeling and simulation of long-range terrestrial laser communications links between static and mobile platforms. Atmospheric turbulence modeling, along with pointing, tracking and acquisition models are combined to provide an overall capability to estimate communications link performance.
During nearly a decade of remote sensing programs under the auspices of the U.S. Department of Energy (DOE), LLNL has developed a set of
performance modeling codes -- called APRS -- for both Active and
Passive Remote Sensing systems. These codes emphasize chemical detection sensitivity in the form of minimum detectable quantities with and without background spectral clutter and in the possible presence of other interfering chemicals. The codes have been benchmarked against data acquired in both active and passive remote
sensing programs at LLNL and Los Alamos National Laboratory (LANL).
The codes include, as an integral part of the performance modeling,
many of the data analysis techniques developed in the DOE's active and passive remote sensing programs (e.g., "band normalization" for an active system, principal component analysis for a passive system).
Application of a novel transform operator, the Sticklet transform, to the quantitative estimation of trace chemicals in industrial effluent plumes is reported. The sticklet transform si a superset of the well-known derivative operator and the Haar wavelet, and is characterized by independently adjustable lobe width and separation. Computer simulations demonstrate that we can make accurate and robust concentration estimates of multiple chemical species in industrial effluent plumes in the presence of strong clutter background, interferent chemicals and random noise. In this paper we address the application of the sticklet transform in estimating chemical concentrations in the effluent plumes in the presence of atmospheric transmission effects. We show that this transform retains the ability to yield accurate estimates using on-plume / off-plume measurements that represenst atmospheric differentials up to 10% of the full atmospheric attenuation.
KEYWORDS: Absorption, Chemical analysis, Fabry–Perot interferometers, Data analysis, Pulsed laser operation, Signal to noise ratio, Atmospheric sensing, Mid-IR, Solids, Chemical elements
Differential absorption LIDAR (DIAL) with multiple wavelengths provides capabilities for separately identifying and quantifying chemicals in mixtures that are impossible for conventional two-line DIAL. It also permits several choices about how to convert individual laser pulse returns into estimates of gas concentrations. These choices concern both averaging techniques and procedures for fitting averaged data to library spectra of possible gases. The purpose of this paper is to compare several analysis options using real data taken with 8 or 10 mid-wave IR wavelengths in field test. The options fall naturally into two groups, as implied above. The first group comprises ways to combine data averaging with ratioing. The second group comprises various maximum-likelihood estimators and least-squares fits of the averaged data. Several options arise in the second group because data is taken at multiple wavelengths; for two-line DIAL there would be only a single option in this second group. This paper compares the result of field data analysis for these two groups of options. The properties of the data acquired by the multi-line DIAL system are first described. Then the three averaging/ratioing techniques are discussed. The various options for extracting concentration estimates from averaged data are compared. Finally, the implications for remote sensing data analysis are discussed.
LLNL has utilized optical parametric oscillator technology to develop and field a rapidly-tunable mid-wave IR DIAL system. The system can be tuned at up to 1 KHz over the 3.3- 3.8 micron spectral region, where hydrogen-bond stretching modes provide spectroscopic signatures for a wide variety of chemicals. We have fielded the DIAL system on the LLNL site on range, turbulence, and receiver aperture size. In this paper we describe the interplay of turbulence and speckle to produce the observed nose fluctuations at short range.
This paper reports on recent progress made in developing rapidly tunable MWIR lidar system for the detection and identification of multiple trace atmospheric molecules. The lidar systems and multiline DIAL approach are described in detail. The unique advantages of the lidar system and multiline DIAL measurement technique are demonstrated with results from field measurements.
John Seeman, Karl Bane, R. Boyce, G. Loew, P. Morton, Heinz-Dieter Nuhn, J. Paterson, Piero Pianetta, T. Raubenheimer, Roman Tatchyn, V. Vylet, Herman Winick, Claudio Pellegrini, James Rosenzweig, Gil Travish, Donald Prosnitz, Ernst Scharlemann, Klaus Halbach, Kwang Kim, Ming Xie
We describe the possible use of the SLAC linac to drive a unique, powerful, short wavelength Linac Coherent Light Source. Using the FEL principle, lasing is achieved in a single pass of a high peak current electron beam through a long undulator by self-amplified-spontaneous- emission (SASE). The main components are a high-brightness electron RF gun with a photocathode, two electron bunch length compressors, the existing SLAC linac, beam diagnostics, and a long undulator combined with a FODO quadrupole focusing system. The RF gun, to be installed about 1 km from the end of the SLAC linac, would produce a single bunch of 6 X 109 electrons with an invariant emittance of about 3 mm-mrad and a bunch length of about 500 micrometers . That bunch is then accelerated to 100 MeV and compressed to a length of about 200 micrometers . The main SLAC linac accelerates the bunch to 2 GeV where a second bunch compressor reduces the length to 30 - 40 micrometers and produces a peak current of 2 - 3 kA. The bunch is then accelerated to 7 - 8 GeV and transported to a 50 - 70 m long undulator. Using electrons below 8 GeV, the undulator could operate at wavelengths down to 2 nm, producing about 10 GW peak power in sub-ps light pulses.
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