Cloud detection by lidar extinction calculations

A new lidar method of measuring cloud ceiling height using the Klett solution to the lidar equation was developed. This simple technique will find cloud ceiling height for clouds that rangefinder-like lidars cannot theoretically detect. In addition, the noise signals that do not correspond to clouds removed by using the convergence of the Klett solution to discriminate between signal changes and broader signal changes due to clouds. Clouds above rain or light fog can be detected without error, and it is possible to discriminate against haze layers by the magnitude of their maximum extinction

A Proposal to Detect Dark Matter Using Axionic Topological Antiferromagnets

Antiferromagnetically doped topological insulators (A-TI) are among the candidates to host dynamical axion fields and axion-polaritons; weakly interacting quasiparticles that are analogous to the dark axion, a long sought after candidate dark matter particle. Here we demonstrate that using the axion quasiparticle antiferromagnetic resonance in A-TI's in conjunction with low-noise methods of detecting THz photons presents a viable route to detect axion dark matter with mass 0.7 to 3.5 meV, a range currently inaccessible to other dark matter detection experiments and proposals. The benefits of this method at high frequency are the tunability of the resonance with applied magnetic field, and the use of A-TI samples with volumes much larger than 1 mm$^3$.Comment: 6 pages, 4 figures. v2 accepted for publication in Physical Review Letters. Many points clarified, some parameter estimates revise

Image display and background analysis with the Naval Postgraduate School infrared search and target designation system

Characterization, Propagation, and Simulation of Sources and Backgrounds, (1 July 1991)The article of record as published may be found at http://dx.doi.org/10.1117/12.45772Commercial frame grabber technology in IBM PC compatible computers has been adapted to allow direct digital input of InfraRed Search and Track data at rates of up to 10 megabytes per second, permitting realtime processing and display of false color thermal images. Examples of single frame displays and background suppression by frame subtraction are shown. On-board processed fourier spectra and fourier power spectra of selected frame lines are shown. Curve-fitted representations are compared for clear air, cloud and land clutter, and a commercial aircraft at close range.Naval Sea Systems CommandNaval Postgraduate SchoolPMS-42