Improved optical lens system

Objective lens produces a backwardly curving image of a star field that matches the similarly curved surface of the photocathode of an image dissector tube. Lens eliminates the need for a fiber-optics translation between the flat plane image and curved photocathode

Finite Element Simulation of Light Propagation in Non-Periodic Mask Patterns

Rigorous electromagnetic field simulations are an essential part for scatterometry and mask pattern design. Today mainly periodic structures are considered in simulations. Non-periodic structures are typically modeled by large, artificially periodified computational domains. For systems with a large radius of influence this leads to very large computational domains to keep the error sufficiently small. In this paper we review recent advances in the rigorous simulation of isolated structures embedded into a surrounding media. We especially address the situation of a layered surrounding media (mask or wafer) with additional infinite inhomogeneities such as resist lines. Further we detail how to extract the far field information needed for the aerial image computation in the non-periodic setting.Comment: Proceedings SPIE conference Photomask Japan (2008

Mariner Mars 1969 sun sensor development

Photodetector and sun sensor development for Mariner Mars 1969 attitude control syste

Transient dynamics of a molecular quantum dot with a vibrational degree of freedom

We investigate the transient effects occurring in a molecular quantum dot described by an Anderson-Holstein Hamiltonian which is instantly coupled to two fermionic leads biased by a finite voltage. In the limit of weak electron-phonon interaction, we use perturbation theory to determine the time-dependence of the dot population and the average current. The limit of strong coupling is accessed by means of a self-consistent time-dependent mean-field approximation. These comple- mentary approaches allow us to investigate the dynamics of the inelastic effects occurring when the applied bias voltage exceeds the phonon frequency and the emergence of bistability.Comment: 7 pages, 4 figure

The stability of a zonally averaged thermohaline circulation model

A combination of analytical and numerical techniques are used to efficiently determine the qualitative and quantitative behaviour of a one-basin zonally averaged thermohaline circulation ocean model. In contrast to earlier studies which use time stepping to find the steady solutions, the steady state equations are first solved directly to obtain the multiple equilibria under identical mixed boundary conditions. This approach is based on the differentiability of the governing equations and especially the convection scheme. A linear stability analysis is then performed, in which the normal modes and corresponding eigenvalues are found for the various equilibrium states. Resonant periodic solutions superimposed on these states are predicted for various types of forcing. The results are used to gain insight into the solutions obtained by Mysak, Stocker and Huang in a previous numerical study in which the eddy diffusivities were varied in a randomly forced one-basin zonally averaged model. Resonant stable oscillations with century scale periods are predicted with structures that compare favorably with those found in the previous study. In cases with large horizontal diffusivities, the two-cell pattern is also stable, which parallels cases in the previous study where large vacillations were seen between the three stable steady states. Further, in cases with large horizontal {\it and} large vertical diffusivities, no one-cell pattern can be realised and the only asymptotic behaviour found is the two-cell pattern.Comment: 23 pages, plus 8 PostScript figures. Postscript version of full paper available at http://www.meteo.mcgill.ca/papers/gaslam.htm

Variable-beamwidth antenna without moving parts

Basic configuration consists of large parabolic dish reflector, smaller hyperboloidal subreflector, and two sets of monopulse feeds located in conjugate focal region on boresight axis of dish

Combined sun-acquisition and sun gate-sensor system for spacecraft attitude control

Arrangement combines acquisition and gate functions and reduces sensitivity so that attitude control is effective regardless of changes in solar intensity. There are five photoconductive detectors all electrically interconnected. Detectors are so positioned that, regardless of spacecraft orientation at any instant of interest, at least one detector is illuminated