Test & Measurement

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

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JWST IV&V Simulation and Test (JIST) RT Logic T501 Emulator

Emulator using only software implements the behavior of a processor. Goddard Space Flight Center, Greenbelt, Maryland In order to develop a software-only test environment for the James Webb Space Telescope (JWST) mission, a solution was needed to send commands and receive telemetry between the TCTS (Telemetry and Command Test Set) and CMM-S card. The as-is solution requires the utilization of commercial off-the-shelf hardware (RT Logic Telemetrix T501 processor) and custom CMM-S hardware.

Posted in: Articles, Briefs, TSP, Electronics & Computers

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Cooling Test Samples With a Combined Convective and Conductive System to Rapidly Reach 77 K

This innovation enables rapid cooling to 77 K of James Webb Space Telescope shields, which enables hypervelocity impact testing with micro-particle spheres. Lyndon B. Johnson Space Center, Houston, Texas In this innovation, a team successfully developed and implemented a combined convective and conductive cooling system that permits rapid cooling. Using a spray system, liquid nitrogen (LN2) was injected into a test article enclosure located in the target tank that was evacuated to a lower pressure than the surrounding ambient pressure of the White Sands Test Facility (WSTF). According to the saturation curve for nitrogen, temperatures lower than 77 K can be achieved by using the evaporative process as long as the pressure remains above the triple point where nitrogen ice is formed.

Posted in: Articles, Briefs, TSP

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Guarded Two-Dimensional Flat Plate Insulation Test Calorimeter with Attach Points

Consistent test results are obtained in a cost-effective, safe, reliable, and practical manner. John F. Kennedy Space Center, Florida Insulation systems usually do not operate on their own; they must work together with a structural system that is designed to support the article being insulated. Typically this structure penetrates the insulation, degrading it in some manner, and gives a pathway for the conduction of unwanted heat. High-performance insulation systems that use reflective foils are highly anisotropic (the heat flows more easily in one direction than the others), so disturbing the temperature gradients through the material can cause much greater effects than are due to the disturbances alone.

Posted in: Articles, Briefs, TSP, Data Acquisition, Sensors

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Test, Calibration, and Training Target for a Microwave Sensor

NASA’s Jet Propulsion Laboratory, Pasadena, California Human subjects are unsuitable for objective performance testing of victim detection radar because their heart and respiration rates are not controllable or repeatable. There are limitations on human targets from a safety standpoint as well. It is difficult to relate the ground truth to the measured data for a human target without needing additional equipment that must be attached to the human subject. Artificial targets using pneumatics do not provide sufficient fidelity of the radar return for development of identification algorithms.

Posted in: Articles, Briefs, TSP, Sensors

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Test it Like da Vinci

Timeless wisdom and new technologies are revolutionizing the world of testing, and bringing us from vision to finished product faster. Do you see product testing and checking as a necessary evil? Then take some time to change your mind. In the long process from vision to reality of a product, intelligent and efficient testing is indispensable. The latest metrological instruments help to begin developing a product when it only exists in our minds.

Posted in: Articles

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The Touch Screen Revolution

Touch screens are slowly but surely creeping into every aspect of our day-to-day lives. It’s not unlikely that you wake up to a cellphone alarm, adjust the room temperature on a thermostat, change the radio station in the car, and even start the washing machine using only a touch screen. A decade ago, we wouldn’t have used a touch screen for any of these tasks, but today it’s commonplace. To understand the impact of touch screens on test and measurement, you must first know the difference between resistive and capacitive touch screens, and the impact smartphones have had on touch screen implementations.

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