Physical Sciences

Uplink/Downlink Spacecraft Radio Occultation Measurements

A report proposes a method to increase the accuracy of Doppler measurements made at the beginnings and endings of Earth/spacecraft radio occultations. Such measurements can reveal structural details of occulting objects in outer space. Heretofore, one-way measurements have been used, and have been subject to degradation of accuracy by frequency fluctuations of an onboard oscillator.

Posted in: Briefs, TSP, Physical Sciences, Measurements, Radar, Performance upgrades, Spacecraft


Integrated Environmental Monitoring Instrument

This is a semiautonomous reference instrument with radio-communication and networking capability. A miniature, battery-powered, semiautonomous environmental monitoring instrument contains advanced meteorological sensors, a Global Positioning System (GPS) receiver for determining its position, radio-communication circuitry, and a controller that performs measurement, control, and data-communication interface functions. The instrument could serve as a high-accuracy radiosonde, though its intended use is in providing reference measurements for calibration and comparison of ordinary radiosondes.

Posted in: Briefs, TSP, Physical Sciences, Measurements, Sensors and actuators, Test equipment and instrumentation


Molten-Carbonate Electrolyzers for Making CO and O2

Molten-carbonate fuel cells would be operated in reverse. Electrochemical cells in which molten carbonates would serve as electrolytes have been proposed for use in electrolyzing CO2. The proposal was made in an effort to implement a concept of in situ resource utilization (ISRU) for the exploration of Mars; the basic idea is to generate CO (if needed as a fuel) and O2 (for oxidizing fuel and/or for breathing) by electrolysis of CO2 from the Martian atmosphere. On Earth, molten-carbonate electrolyzers could be used to make breathable O2 for medical use, pure O2 for oxidizing surfaces of semiconductor chips, and CO as a feedstock for synthesis of alcohols and hydrocarbons. In both terrestrial and spacecraft life-support systems, the electrolyzers could be used to regenerate breathable O2 from CO2.

Posted in: Briefs, TSP, Physical Sciences, Carbon dioxide, Carbon monoxide, Oxygen


Improved Spherical Energy Analyzer

An improved spherical energy analyzer (a type of electrostatic mass spectrometer) is under development for use in analyzing a beam of ions generated by a Hall thruster. The major improvement, relative to a commercial spherical energy analyzer, is the addition of a quadrupole stage (with refocusing electron optics) for separating ions of different charge states. The development work also includes efforts to make the instrument smaller and lighter than the commercial version in order to make it possible to translate and rotate the instrument through the ion beam inside a vacuum chamber that contains the Hall thruster.

Posted in: Briefs, TSP, Physical Sciences, Test equipment and instrumentation


Redundant Oxygen-Deficiency Monitoring System

An oxygen-deficiency monitoring system (ODMS) has been developed for a ten-room facility in which the use of large amounts of nitrogen and helium could cause an oxygen deficiency severe enough to be hazardous to personnel. The ODMS comprises three subsystems, of which two monitor three rooms each, and one monitors four rooms. The ODMS generates alarms when the oxygen content of the air in a room falls below 19.5 mole percent. Each subsystem includes transport pumps that draw air continuously from each room through two tubes. Each subsystem includes two oxygen analyzers equipped with sampling pumps, plus two programmable-logic controllers (PLCs) and associated hardware that control electrically actuated valves that admit small fractions of the transport flows to the oxygen analyzers. The PLCs cause the valves to connect the two oxygen analyzers to two different sampling tubes, and then to switch the connections to a different pair of sampling tubes after an interval of about 10 seconds, and so forth until the air from all sampling points has been monitored, and then the sequence repeats. If one sampling tube, oxygen analyzer, pump, or PLC fails, it can be repaired while the system continues to operate, albeit at a reduced rate.

Posted in: Briefs, TSP, Physical Sciences, Oxygen, Test equipment and instrumentation


Report on User's Guidefor Monthly Vector Wind Profile Model

A report briefly describes a user's guide for a computer program that constructs vector wind profiles on the basis of a statistical model. The monthly vector wind profiles are meant to be used (1) to estimate wind-dispersion-related dispersions of critical aerodynamic loads and corresponding aerospace-ascent-vehicle design parameters and (2) to analyze effects of monthly wind-profile dispersions on ascent trajectories and to design ascent autopilot systems to correct for these effects. The user's guide is also said to list output data to aid the user in the verification of test output.

Posted in: Briefs, TSP, Physical Sciences, Statistical analysis, Wind power, Aerodynamics


Sizes of Surface and Capped InxGa1-xAs/GaAs Quantum Dots

A report describes an experimental study of the sizes and concentrations of capped (buried) and surface In0.6Ga0.4As/GaAs quantum dots that were grown by metal-organic vapor deposition under the same conditions except for the inclusion or exclusion of capping. [InxGa1-xAs/GaAs quantum dots are lens-shaped islands (typically a few nanometers thick and tens of nanometers in diameter) of InxGa1-xAs grown on a GaAs substrate. As used here, "capping" signifies the growth of a layer of GaAs over the InxGa1-xAs islands.] In the experiments, the sizes of the capped In0.6Ga0.4As/GaAs islands were measured by transmission electron microscopy (TEM).

Posted in: Briefs, TSP, Physical Sciences, Microscopy, Nanotechnology


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