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Communicating Underground



Posted in: Blog

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Measuring Positions of Objects Using Two or More Cameras

This method could determine the causes of accidents. An improved method of computing positions of objects from digitized images acquired by two or more cameras (see figure) has been developed for use in tracking debris shed by a spacecraft during and shortly after launch. The method is also readily adaptable to such applications as (1) tracking moving and possibly interacting objects in other settings in order to determine causes of accidents and (2) measuring positions of stationary objects, as in surveying. Images acquired by cameras fixed to the ground and/or cameras mounted on tracking telescopes can be used in this method.

Posted in: Briefs, TSP

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Magnetic Compensation for Second-Order Doppler Shift in LITS

Fractional frequency stability could be the lowest ever achieved. The uncertainty in the frequency of a linear- ion-trap frequency standard (LITS) can be reduced substantially by use of a very small magnetic inhomogeneity tailored to compensate for the residual second-order Doppler shift. An effect associated with the relativistic time dilatation, one cause of the second-order Doppler shift, is ion motion that is attributable to the trapping radio- frequency (RF)electromagnetic field used to trap ions. The second- order Doppler shift is reduced by using a muli-pole trap; however it is still the largest source of systematic frequency shift in the latest generation of LITSs, which are among the most stable clocks in the world. The present compensation scheme reduces the frequency instability of the affected LITS to about a tenth of its previous value.

Posted in: Briefs

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Polarization/Spatial Combining of Laser-Diode Pump Beams

Four beams are combined into two, which are then combined into one. The figure depicts a breadboard version of an optical beam combiner that makes it possible to use the outputs of any or all of four multimode laser diodes to pump a non-planar ring oscillator (NPRO) laser. This apparatus could be an alternative to the one described in the immediately preceding article. Whereas that one utilizes spatial (beam-shaping) beam- combining techniques, this one utilizes a combination of polarization and spatial beam-combining techniques. In both that case and this one, the combined multiple laser-diode pump beams are coupled into an optical fiber for delivery to the NPRO pump optics.

Posted in: Photonics, Briefs

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NCAR's New Supercomputer



Posted in: Blog

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Focusing on Ultrashort Laser Pulses



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Satellites Allow View Into Ancient Past



Posted in: Blog

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