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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Process-Hardened, Multi-Analyte Sensor for Characterizing Multiple Rocket Plume Constituents in a Test Environment

A multi-analyte measurement capability is integrated into a single sensor. Stennis Space Center, Mississippi Stennis Space Center (SSC) is one of three government-operated rocket engine test facilities in the United States and is the primary center for testing and flight-certifying rocket propulsion systems for future space vehicles. Safety is a top priority at NASA-SSC. To safely test and certify rocket engines, monitoring technologies for rocket test stands, which (1) verify compliance with federal, state, and local government guidelines; (2) ensure a safe work environment for its personnel at ground testing facilities; as well as (3) monitor environmental impacts, are all required. Additionally, NASA has a need to monitor engine combustion efficiencies and engine health of a variety of launch vehicle configurations utilizing liquid oxygen, liquid hydrogen, isopropanol, and kerosene. Multi-analyte measurement technology is essential for a safe and effective working environment. Therefore, for the advancement in multi-analyte technology in the rocket testing industry, a device was created that integrates multi-analyte measurements into a single sensor unit.

Posted in: Articles, Briefs, Sensors, Monitoring

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Automated Table Lookup Solution Algorithm of the Optimal Powered Descent Guidance for Planetary Landing

NASA’s Jet Propulsion Laboratory, Pasadena, California A novel automated table lookup method is developed to compute the near-fuel-optimal powered descent guidance trajectories, in real-time, for planetary soft landing. The main advantage of this algorithm is that it can be executed autonomously in milliseconds without performing iterative numerical computations to obtain the solution of the optimization problem. The key enabling idea behind this approach is to store, in a lookup table, a number of optimal trajectories that have been computed on the ground for a systematically chosen set of initial conditions. In flight, a near-fuel-optimal trajectory is computed for the actual initial condition by interpolating between these pre-computed trajectories. The lookup method requires only a small, predetermined number of basic algebraic operations. Moreover, this method guarantees that the interpolated solutions are in a prescribed neighborhood of the true optimal solutions.

Posted in: Articles, Briefs, Aviation

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