Test & Measurement

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, Medical, Lasers & Laser Systems, Instrumentation, Test & Measurement, Medical, health, and wellness

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, Instrumentation, Measuring Instruments, Test & Measurement, Optics, Diagnostics, Test equipment and instrumentation

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, Aerospace, Lasers & Laser Systems, Instrumentation, Measuring Instruments, Test & Measurement, Test equipment and instrumentation

Cryogenic Slosh Apparatus

John F. Kennedy Space Center, Florida

Commercially available components are integrated into an assembly that can be used to measure the slosh dynamics of cryogenic liquids. The apparatus consists of a linear motion table that is properly instrumented to record highfidelity position, force, and acceleration measurements of all linear and rotation responses of the cryogenic liquid.

Posted in: Briefs, Instrumentation, Measuring Instruments, Test & Measurement, Test equipment and instrumentation

Negative-Ion Time Projection Chamber Polarimeter for Measuring Polarization of Bright Transient Astrophysical Sources

Goddard Space Flight Center, Greenbelt, Maryland

A negative ion time projection chamber (NI-TPC) was developed that is suitable for measuring the polarization of bright transient events. The polarization of the astrophysical source is determined by imaging photoelectron tracks created by incident x-rays interacting in a gas. The tracks drift through the gas under a uniform electric field to the readout electronics. The initial photoelectron direction is correlated with the polarization of the incident x-ray, and therefore by imaging many tracks, one can determine the polarization magnitude and direction of the incident x-rays.

Posted in: Briefs, TSP, Instrumentation, Measuring Instruments, Test & Measurement, Imaging and visualization, Test equipment and instrumentation, Test facilities

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.

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, Green Design & Manufacturing, Greenhouse Gases, Lasers & Laser Systems, Test & Measurement, Carbon dioxide, Spacecraft

Advanced Rolling Mechanics Analysis (AROMA) 1.0

Lyndon B. Johnson Space Center, Houston, Texas

AROMA uses a boundary-element formulation to calculate normal and shear pressure distributions and sub-surface stresses for elastic bodies in contact. In addition to handling static normal and sheer loading, it also solves the contact problem for rolling elements such as bearings, traction drives, and wheel-to-rail interfaces. AROMA is a powerful and flexible tool for studying the tractive forces that arise during rolling in combination with kinematic effects, such as creepage and spin that are related to rolling element alignment. This GUI-based tool was developed in MATLAB, and can run within the MATLAB environment or as a standalone application.

Posted in: Briefs, Motion Control, Software, Measuring Instruments, Analysis methodologies

Nozzle Heat Flux Gauge

Marshall Space Flight Center, Alabama

This innovation is a tungsten-rhenium gauge that can be placed into an aft exit cone of a rocket motor. It will measure heat flux with time for the full duration of the RSRM (reusable solid rocket motor) nozzle environment with equal response time.

Posted in: Briefs, Mechanical Components, Measuring Instruments, Nozzles, Rocket engines, Thermal testing

Magnetic Sensitivity of a Ka-Band Isolator Measured Using the GRAIL Testbed

NASA’s Jet Propulsion Laboratory, Pasadena, California

The magnetic sensitivity of a Ka-band isolator’s output phase is measured at 7 × 10–4 deg/G level. This high degree of precision is enabled by the sensitive phase measuring capabilities of a testbed built to mimic NASA’s Gravity Recovery and Interior Laboratory (GRAIL) spacecraft. Its ground-based testbed was used to measure the magnetic sensitivity of a flight-spare Ka-band isolator, and the authors found it to be 0.0052 ±0.0007 deg/G along its most sensitive axis. The GRAIL mission was able to incorporate microwave isolators into its instrumentation because the spacecraft orbited the Moon and, thus, did not travel through a permanent magnetic field as it would in a mission around Earth. Understanding this magnetic sensitivity is key to evaluating the impact an isolator would have on data quality for future gravity missions such as GRACE-FO (Gravity Recover and Climate Experiment — Follow On), a scheduled follow-on mission to GRACE, which has been mapping out Earth’s gravity for over a decade.

Posted in: Briefs, Electronics & Computers, Information Sciences, Software, Measuring Instruments, Test & Measurement, Computer simulation, Test equipment and instrumentation, Test procedures, Spacecraft

Method for Performing GPS L1 C/A Measurements in Wideband Jamming and Interference

John F. Kennedy Space Center, Florida

For effective range safety, global positioning system (GPS) metric tracking must be robust to interference with, and jamming of, GPS signals. The conventional approach to mitigating interference and jamming is to use a Controlled Reception Pattern Antenna (CRPA). These few-element phased arrays are used to steer nulls in the directions of interference sources, and/or to point beams in the directions of GPS satellites. The use of CRPAs is limited by their cost and size, as well as the difficulties of integrating the array into a platform. The problems are compounded for a launch vehicle, which must acquire and track GPS signals at high speed and acceleration, and undergo vibration and temperature conditions not common to CRPA use.

Posted in: Articles, Briefs, TSP, Communications, Test & Measurement, Antennas, Global positioning systems, Global positioning systems (GPS), Satellites

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