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How to Maximize Temperature Measurement Accuracy

Thermocouples are the most versatile and widely used devices for temperature measurements. Most test engineers are aware of the measurement errors caused by thermocouples but not always about the errors caused by the measurement system itself. This technical note will focus on the lesser known and important aspect called "Self-Calibration" and how it can be used to overcome errors in temperature measurement.

Posted in: Test & Measurement, White Papers

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A High-Cross-Polarization-Isolation, Multi-Frequency Antenna for Cloud and Precipitation Research

Goddard Space Flight Center, Greenbelt, Maryland The Global Precipitation Mission (GPM) has an immediate need for a matched-beam Ku-band/Ka-band antenna system that can be used as a component of a ground validation radar. Retrieval techniques based on both polarization and differential absorption at the two wavelengths can be used to provide additional insight into precipitation type and particle size distribution over a 10- to 40-km spatial domain. These measurements can then be compared with long range radar, such as the WSR-88D, and in situ sensors to provide a comprehensive dataset for evaluating and improving satellite-based precipitation estimates.

Posted in: Physical Sciences, Briefs, TSP

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External Magnetic Field Reduction Technique for Advanced Stirling Radioisotope Generator

New generators can be configured for very low magnetic emissions so as not to interfere with sensitive instrumentation. John H. Glenn Research Center, Cleveland, Ohio Linear alternators coupled to Stirling power converters are promising candidates for high-efficiency heat-to-electricity power conversion in space. Presently, the external magnetic field emissions of such converters may exceed the allowed emission limits for use with certain sensitive scientific instrumentation. This invention, based on concepts of magnetic moment balancing, can reduce such field emissions sufficiently to enable use of the space power Stirling converters in sensitive instrumentation missions.

Posted in: Physical Sciences, Briefs

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Advanced P-Band Spaceborne Radar System

A new imaging approach can overcome the fundamental limitations of conventional radar systems. Goddard Space Flight Center, Greenbelt, Maryland Low-cost, flexible spaceborne radar architectures are needed to provide critical data for Earth and science applications. An instrument concept was developed for an advanced spaceborne radar system that can measure terrestrial biomass (woody mass per unit area), ecosystem structure (height and density), and extent on a global scale. The PNTB band polarimetric radar architecture employs advanced techniques to increase the science value of the measurements while achieving it at a lower cost. The spaceborne radar concept leverages the existing airborne L-band digital beamforming synthetic aperture radar (DBSAR) and the new P-band digital beamforming (DBF) polarimetric and interferometric EcoSAR (ESTO IIP) architectures that employ DBF and reconfigurable hardware to provide advanced radar capabilities not possible with conventional radar instruments.

Posted in: Physical Sciences, Briefs, TSP

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Global Fire Detection Constellation

Small satellites could monitor and process images to track fires from space. NASA’s Jet Propulsion Laboratory, Pasadena, California Wildfires that start in backcountry areas sometimes burn for hours before being detected and reported. Satellites offer a vantage point from which infrared sensors can detect fires. Individual satellites in low Earth orbit (LEO) offer infrequent overpasses, making the delay from ignition to detection unacceptably long. Geostationary satellites offer a platform from which to maintain a round-the-clock vigil, but lack geographic precision, and cannot detect a rather small fire within a large pixel definitively above noise.

Posted in: Physical Sciences, Briefs, TSP

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Compact Solid-State Entangled Photon Source

John H. Glenn Research Center, Cleveland, Ohio In the fields of quantum information, quantum optics, quantum cryptography, and quantum communications, there is a need to generate entangled photon pairs. The entangled photon pairs are described by an inseparable wave equation such that if a measurement is performed on one photon, its twin’s photon state is completely determined. The problem up to now is that these sources of entangled photons require large, expensive, and power-intensive Ar-ion lasers to generate light in the UV to pump a nonlinear crystal to produce spontaneous parametric down conversion (SPDC). The SPDC process generates a pair of photons (the signal and the idler) whose momentum and energy sum up to equal the initial pump photon.

Posted in: Physical Sciences, Briefs, TSP

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Interface Validation for Distributed Software Systems

Goddard Space Flight Center, Greenbelt, Maryland As a result of performing IV&V (Independent Verification and Validation) on Space Station software, a number of interface faults were found during integrated testing or actual software deployment. Faults found at this late phase of the software development lifecycle are very expensive to fix. Other research indicates that significant cost savings can be realized if these types of faults can be discovered at earlier software development lifecycle phases, such as specification or coding. A need was determined for processes, procedures, and tools that will reliably identify interface faults during these earlier software development lifecycle phases. The ability to perform interface validation during earlier phases will reduce costly fixes due to interface faults discovered during later software development phases.

Posted in: Information Sciences, Electronics & Computers, Briefs, TSP

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