Tech Briefs

Pointing Reference Scheme for Free-Space Optical Communications Systems

A technique is proposed for referencing infrared transmit lasers with silicon detectors. NASA’s Jet Propulsion Laboratory, Pasadena, California A scheme is proposed for referencing the propagation direction of the transmit laser signal in pointing a free-space optical communications terminal. This recently developed scheme enables the use of low-cost, commercial silicon-based sensors for tracking the direction of the transmit laser, regardless of the transmit wavelength. Compared with previous methods, the scheme offers some advantages of less mechanical and optical complexity and avoids expensive and exotic sensor technologies.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Lasers, Optics, Sensors and actuators, Telecommunications


Single-Phase Rare-Earth Oxide/Aluminum Oxide Glasses

These glasses are suitable for advanced optical applications. Marshall Space Flight Center, Alabama Glasses that comprise rare-earth oxides and aluminum oxide plus, optionally, lesser amounts of other oxides, have been invented. The other oxide(s) can include SiO2, B2O3, GeO2, and/or any of a variety of glass-forming oxides that have been used heretofore in making a variety of common and specialty glasses. The glasses of the invention can be manufactured in bulk single-phase forms to ensure near uniformity in optical and mechanical characteristics, as needed for such devices as optical amplifiers, lasers, and optical waveguides (including optical fibers). These glasses can also be formulated to have high indices of refraction, as needed in some of such devices.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Molding, Composite materials, Glass, Refractory materials


Regulating Glucose and pH, and Monitoring Oxygen in a Bioreactor

Glucose and oxygen concentrations are monitored, and glucose concentration and pH are adjusted as needed.Figure 1 is a simplified schematic diagram of a system that automatically regulates the concentration of glucose or pH in a liquid culture medium that is circulated through a rotating-wall perfused bioreactor. Another system, shown in Figure 2, monitors the concentration of oxygen in the culture medium.

Posted in: Briefs, Bio-Medical, Medical, Biological sciences, Medical equipment and supplies, Test equipment and instrumentation


IMU/GPS System Provides Position and Attitude Data

A special navigation system is being developed to provide high-quality information on the position and attitude of a moving platform (an aircraft or spacecraft), for use in pointing and stabilization of a hyperspectral remote-sensing system carried aboard the platform. The system also serves to enable synchronization and interpretation of readouts of all onboard sensors. The heart of the system is a commercially available unit, small enough to be held in one hand, that contains an integral combination of an inertial measurement unit (IMU) of the microelectromechanical systems (MEMS) type, Global Positioning System (GPS) receivers, a differential GPS subsystem, and ancillary data-processing subsystems. The system utilizes GPS carrier-phase measurements to generate time data plus highly accurate and continuous data on the position, attitude, rotation, and acceleration of the platform. Relative to prior navigation systems based on IMU and GPS subsystems, this system is smaller, is less expensive, and performs better. Optionally, the system can easily be connected to a laptop computer for demonstration and evaluation. In addition to airborne and spaceborne remote-sensing applications, there are numerous potential terrestrial sensing, measurement, and navigation applications in diverse endeavors that include forestry, environmental monitoring, agriculture, mining, and robotics.

Posted in: Briefs, Electronics & Computers, Global positioning systems, Global positioning systems (GPS), Microelectromechanical devices, Remote sensing, Spacecraft guidance, Performance upgrades


Compact, Efficient Drive Circuit for a Piezoelectric Pump

Piezoelectric actuators are charged in a time much shorter than the pump cycle.Figure 1 depicts a switching circuit that drives a piezoelectric pump at a high voltage with a polarity that alternates at the desired mechanical pump frequency. This circuit offers advantages of (1) high energy efficiency relative to conventional direct-drive circuits and (2) compactness relative to conventional resonant drive circuits.

Posted in: Briefs, Electronics & Computers, Electrical systems, Pumps


Developing Signal Pattern Recognition Programs

Software system aids development of application programs that analyze signals.Pattern Interpretation and Recognition Application Toolkit Environment (PIRATE) is a block-oriented software system that aids the development of application programs that analyze signals in real time in order to recognize signal patterns that are indicative of conditions or events of interest. PIRATE was originally intended for use in writing application programs to recognize patterns in space-shuttle telemetry signals received at Johnson Space Center’s Mission Control Center: application programs were sought to (1) monitor electric currents on shuttle ac power busses to recognize activations of specific power-consuming devices, (2) monitor various pressures and infer the states of affected systems by applying a Kalman filter to the pressure signals, (3) determine fuel-leak rates from sensor data, (4) detect faults in gyroscopes through analysis of system measurements in the frequency domain, and (5) determine drift rates in inertial measurement units by regressing measurements against time. PIRATE can also be used to develop signal-pattern-recognition software for different purposes — for example, to monitor and control manufacturing processes.

Posted in: Briefs, Electronics & Computers, Architecture, Computer software and hardware, Telemetry, Manufacturing processes, Spacecraft


Mobile Robot for Exploring Cold Liquid/Solid Environments

This tethered robot could float, swim, crawl, and sample environmental materials. The Planetary Autonomous Amphibious Robotic Vehicle (PAARV), now at the prototype stage of development, was originally intended for use in acquiring and analyzing samples of solid, liquid, and gaseous materials in cold environments on the shores and surfaces, and at shallow depths below the surfaces, of lakes and oceans on remote planets. The PAARV also could be adapted for use on Earth in similar exploration of cold environments in and near Arctic and Antarctic oceans and glacial and sub-glacial lakes.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Cold weather, Autonomous vehicles, Off-highway vehicles and equipment, Spacecraft


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