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MACOS Version 3.31

Version 3.31 of Modeling and Analysis for Controlled Optical Systems (MACOS) has been released. MACOS is an easy-to-use computer program for modeling and analyzing the behaviors of a variety of optical systems, including systems that have large, segmented apertures and are aligned with the technology of wavefront sensing and control. Two previous versions were described in “Improved Software for Modeling Controlled Optical Systems” (NPO-19841) NASA Tech Briefs, Vol. 21, No. 12 (December 1997), page 42 and “Optics Program Modified for Multithreaded Parallel Computing” (NPO-40572) NASA Tech Briefs, Vol. 30, No. 1 (January 2006) page 13a. The present version incorporates the following enhancements over prior versions:

Posted in: Photonics, Briefs

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Simulated Models Test Design of Space Shuttles and Rocket Engines

Finite element modeling and analysis Dynamic Concepts Huntsville, AL 256-922-9888 www.dynamic-concepts.com NASA tasked Dynamic Concepts (DCI) with assessing the structural dynamics of the rollout process, whereby the space shuttle orbiter, external tank, and solid rocket booster assembly is moved via a crawler transporter from the Vertical Assembly Building to the launch pad. DCI used Femap finiteelement modeling software from Siemens PLM Software (Plano, TX) to create an integrated model of all the shuttle components, and used Siemens’ NX Nastran to analyze the simulated vibration environment. The analysis helped NASA resolve issues with support structures and determine target rollout speeds that minimized potentially damaging vibration.

Posted in: Application Briefs

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Advanced Position Sensors to Aid NASA in Future Spaceflight

Silicon carbide-based position sensors INPROX Technology Corp. Boston, MA 617-573-5158 www.inproxtechnology.com INPROX Technology Corp. (ITC) has entered into a Space Act Agreement (SAA) with NASA’s John H. Glenn Research Center in Ohio to develop advanced silicon carbide (SiC)- based position sensors aimed at potential uses in future spaceflight, turbine engine controls, and automotive engine applications. Under this SAA, high-temperature SiC electronics from NASA will be prototyped into ITC’s proprietary linear position sensor technology platform.

Posted in: Application Briefs

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Performance of 1mm2 Silicon Photomultipliers

A silicon photomultiplier (SPM) is a new type of semiconductor detector that has the potential to replace the photo- multiplier tube (PMT) detector in many applications. In common with a PMT detector, the output of an SPM is an easily detectable current pulse for each detected photon and can be used in both photon counting mode and as an analogue (photocurrent) detector. However, the SPM also has a distinct advantage over PMT detectors. The photon-induced current pulse from a PMT varies greatly from photon to photon, due to the statistics of the PMT multiplication process (excess noise). In contrast, the current pulse from an SPM is identical from photon to photon. This gives the SPM a distinct advantage in photon counting applications as it allows the associated electronics to be greatly simplified. Identical pulses also mean that the SPM can resolve the number of photons in weak optical pulses, so-called photon number resolution. This is critical in a number of applications including linear-optics quantum computing.

Posted in: Articles

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Attitude and Translation Control of a Solar Sail Vehicle

A report discusses the ability to control the attitude and translation degrees-of-freedom of a solar sail vehicle by changing its center of gravity. A movement of the spacecraft’s center of mass causes solar- pressure force to apply a torque to the vehicle. At the compact core of the solar-sail vehicle lies the spacecraft bus which is a large fraction of the total vehicle mass. In this concept, the bus is attached to the spacecraft by two single degree-of-freedom linear tracks. This allows relative movement of the bus in the sail plane. At the null position, the resulting solar pressure applies no torque to the vehicle. But any deviation of the bus from the null creates an offset between the spacecraft center of mass and center of solar radiation pressure, resulting in a solar-pressure torque on the vehicle which changes the vehicle attitude. Two of the three vehicle degrees of freedom can be actively controlled in this manner. The third, the roll about the sun-line, requires a low-authority vane/propulsive subsystem.

Posted in: Briefs, TSP

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Efficient Coupler for a Bessel Beam Dispersive Element

A document discusses overcoming efficient optical coupling to high orbital momentum modes by slightly bending the taper dispersive element. This little shape distortion is not enough to scramble the modes, but it allows the use of regular, free-beam prism coupling, fiber coupling, or planar fiber on-chip coupling with, ultimately, 100 percent efficiency.

Posted in: Briefs, TSP

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Symmetric Phase-Only Filtering in Particle-Image Velocimetry

Performance is enhanced significantly with little increase in computation time. Symmetrical phase-only filtering (SPOF) can be exploited to obtain substantial improvements in the results of data processing in particle- image velocimetry (PIV). In comparison with traditional PIV data processing, SPOF PIV data processing yields narrower and larger amplitude correlation peaks, thereby providing more-accurate velocity estimates. The higher signal-to-noise ratios associated with the higher amplitude correlation peaks afford greater robustness and reliability of processing. SPOF also affords superior performance in the presence of surface flare light and/or background light. SPOF algorithms can readily be incorporated into pre-existing algorithms used to process digitized image data in PIV, without significantly increasing processing times.

Posted in: Briefs

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