Fiber-Optic Sensor for Aircraft and Structure Lightning Measurement

Langley Research Center, Hampton, Virginia An optical-fiber sensor based on Faraday Effect was developed for measuring total lightning current. Designed for aircraft installation, it is lightweight, non-conducting, structure conforming, and is immune to electromagnetic interference, hysteresis, and saturation. It can also be used on windmills, lightning towers, and can help validate lightning detection network measurements.

Posted in: Briefs, TSP, Tech Briefs, Photonics


Shock-Sensing Apparatus

This apparatus enables easy and reliable shock detection and localization in high-speed inlets of aerospace vehicles. John H. Glenn Research Center, Cleveland, Ohio Acompact shock-sensing device, which employs an innovative light sheet generator, has been created. The device may be used either as a solo aerodynamic shock detector or in combination with a scanning mode shock sensor. This permits easy detection and tracking of unstable and traveling shocks in supersonic inlets.

Posted in: Briefs, TSP, Lasers & Laser Systems, Detectors, Sensors


Low Er-Doped Yttrium Gallium Garnet (YGG) as Active Media for Solid-State Lasers at 1651 nm

This technology could serve applications in the bio-medical areas such as nerve stimulation and dentistry. Goddard Space Flight Center, Greenbelt, Maryland The typical approach for producing laser output at the 1651-nm wavelength is via nonlinear frequency conversion. Lasers based on nonlinear conversion are complex, and it is very difficult to provide stability over time and over a wide range of operating temperatures. The efficiency of such optical sources is also low. A much more promising approach is the use of active media that allows for the development of solid-state lasers (SSL) with spectral emission at 1651 nm. An important requirement for this active medium is the ability to support in-band pumping with a low quantum defect since this approach leads to significant improvement in efficiency of SSLs and excellent beam characteristics due to low thermal stress of the active media.

Posted in: Briefs, TSP, Lasers & Laser Systems


Dual-Cavity Rayleigh Scattering Measurement System

A method and apparatus were developed for simultaneous measurement of velocity, density, temperature, and their spatial and temporal derivatives in gas flow. Langley Research Center, Hampton, Virginia Molecular-based optical diagnostics techniques capable of obtaining simultaneous measurements of multiple fluid properties are critically important for characterizing hypersonic air-breathing engines, such as scramjet engines and scramjet-rocket combined cycle engines. Correlations between those properties lead to a more detailed understanding of complex flow behavior, and aid in the development of multiparameter turbulence models required for supersonic combustion engine flow path predictions.

Posted in: Briefs, TSP, Optics, Measuring Instruments


Miniature Laser Magnetometer

This conceptual design includes three key innovations future space science requires while minimizing size, mass, and power. Goddard Space Flight Center, Greenbelt, Maryland Space missions using magnetometers have been very successful. However, science missions now require higher levels of accuracy and stability in order to refine existing understanding and improve modeling. In most space missions that require high-accuracy vector measurement of magnetic fields, a separate scalar magnetometer must also be included in order to calibrate the vector measurements. The miniature laser magnetometer (MLM) addresses the need for a single, high-stability magnetometer instrument that provides both scalar and vector measurements for future space science needs while minimizing size, mass, and power.

Posted in: Briefs, TSP, Lasers & Laser Systems, Measuring Instruments


Nonlinear Swept Frequency Technique for CO2 Measurements Using a CW Laser System

The measurements would be used to significantly reduce the uncertainties in global estimates of CO2, improve climate models, and close the carbon budget for improved forecasting and policy decisions. Langley Research Center, Hampton, Virginia The U.S. National Research Council recently identified the need for a near-term space mission of Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS). The primary objective of the ASCENDS mission is to make CO2 column measurements across the troposphere during the day and night over all latitudes and all seasons, and in the presence of scattered clouds. These measurements would be used to significantly reduce the uncertainties in global estimates of CO2 sources and sinks, provide an increased understanding of the connection between climate and CO2 exchange, improve climate models, and close the carbon budget for improved forecasting and policy decisions.

Posted in: Briefs, TSP, Greenhouse Gases, Lasers & Laser Systems


Algorithm for Estimating PRC Wavefront Errors from Shack-Hartmann Camera Images

Phase retrieval is used for the calibration and the fine-alignment of an optical system. NASA’s Jet Propulsion Laboratory, Pasadena, California Phase retrieval (PR) and Shack-Hartmann Sensor (SHS) are the two preferred methods of image-based wavefront sensing widely used in various optical testbeds, adaptive optical systems, and ground- and space-based telescopes. They are used to recover the phase information of an optical system from defocused point source images (PR) and focused point source or extended scene images (SHS). For example, the Terrestrial Planet Finder Coronagraph’s (TPF-C’s) High-Contrast Imaging Testbed (HCIT) uses a PR camera (PRC) to estimate, and subsequently correct, the phase error at the exit pupil of this optical system. Several other test-beds at JPL were, and will be, equipped with both a PRC and a Shack-Hartmann camera (SHC).

Posted in: Briefs, TSP, Cameras, Optics, Sensors