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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Automatic Digital Noise Checker determines the noise content of the many analog imputs of a data acquisition system and whether the Electronic Calibrations /EC/ on some data channels are operating properly.
An experimental airborne remote sensing system includes a remotely controlled, lightweight, solar-powered airplane (see figure) that carries two digital-output electronic cameras and communicates with a nearby ground control and monitoring station via a wireless local-area network (WLAN). The speed of the airplane -- typically <50 km/h -- is low enough to enable loitering over farm fields, disaster scenes, or other areas of interest to collect high-resolution digital imagery that could be delivered to end users (e.g., farm managers or disaster-relief coordinators) in nearly real time.
Two algorithms for processing the digitized readings of electronic noses, and computer programs to implement the algorithms, have been devised in a continuing effort to increase the utility of electronic noses as means of identifying airborne compounds and measuring their concentrations. One algorithm identifies the two vapors in a two-vapor mixture and estimates the concentration of each vapor (in principle, this algorithm could be extended to more than two vapors). The other algorithm identifies a single vapor and estimates its concentration.
High Intensity Radiated Fields (HIRF) are the result of a multitude of intentional and nonintentional electromagnetic sources that currently exists in the world. Many of today's digital systems are susceptible to electronic upset if subjected to certain electromagnetic environments (EME). Modern aerospace designers and manufacturers increasingly rely on sophisticated digital electronic systems to provide critical flight control in both military, commercial, and general aviation aircraft. In an effort to understand and emulate the undesired environment that high energy RF provides modern electronics, the Electromagnetics Research Branch (ERB) of the Flight Electronics and Technology Division (FETD) conducts research on RF and microwave measurement methods related to the understanding of HIRF. In the High Intensity Radiated Fields Laboratory, the effects of high energy radiating electromagnetic fields on avionics and electronic systems are tested and studied.
Parameters in analog /dc/ and digital /single electron pulse count/ modes of processing data from photomultiplier tubes
Consideration is given to the following types of high energy physics instrumentation: drift chambers, multiwire proportional chambers, calorimeters, optical detectors, ionization and scintillation detectors, solid state detectors, and electronic and digital subsystems. Attention is also paid to reactor instrumentation, nuclear medicine instrumentation, data acquisition systems for nuclear instrumentation, microprocessor applications in nuclear science, environmental instrumentation, control and instrumentation of nuclear power generating stations, and radiation monitoring. Papers are also presented on instrumentation for the High Energy Astronomy Observatory.
Satellite communication is by far the most advanced of all commercial applications of space technology. The past, present, and some future possibilities for the field of public communications are considered. Some serious concerns that are becoming apparent to the user of this technology are examined. Among the specific topics mentioned are digital television, electronic mail, cable television, and systems security.
The radiometric calibration accuracy of the Shuttle Imaging Radar (SIR-C) sensor is discussed. The analysis includes the antenna, RF electronics, the digital data handling system, the platform attitude control, attitude determination accuracy, and orbit effects. The radiometric distortion of the image products by the ground processing system used for the image formation is also considered. Since the SIR-C system is a dual-frequency quad-polarized system (i.e., 8 channels), the amplitude and phase error is considered over all possible operating modes and environments for absolute and relative (long-term and short-term) calibration within a channel and across channels.
Hughes Aircraft Company developed qualified and integrated flight, a flight test Ion Auxiliary Propulsion System (IAPS), on an Air Force technology satellite. The IAPS Flight Package consists of two identical Thruster Subsystems and a Diagnostic Subsystem. Each thruster subsystem (TSS) is comprised of an 8-cm ion Thruster-Gimbal-Beam Shield Unit (TGBSU); Power Electronics Unit; Digital Controller and Interface Unit (DCIU); and Propellant Tank, Valve and Feed Unit (PTVFU) plus the requisite cables. The Diagnostic Subsystem (DSS) includes four types of sensors for measuring the effect of the ion thrusters on the spacecraft and the surrounding plasma. Flight qualifications of IAPS, prior to installation on the spacecraft, consisted of performance, vibration and thermal-vacuum testing at the unit level, and thermal-vacuum testing at the subsystem level. Mutual compatibility between IAPS and the host spacecraft was demonstrated during a series of performance and environmental tests after the IAPS Flight Package was installed on the spacecraft. After a spacecraft acoustic test, performance of the ion thrusters was reverified by removing the TGBSUs for a thorough performance test at Hughes Research Laboratories (HRL). The TGBSUs were then reinstalled on the spacecraft. The IAPS Flight Package is ready for flight testing when Shuttle flights are resumed.
The LITE electronics system consists of the following seven subsystems: Laser Transmitter Module (LTM), Boresight Assembly (BA), Aft-Optics Electronics (AOE), Digital Data Handling Unit (DDHU), Engineering Data System (EDS), Instrument Controller (IC), and the Ground Support Equipment (GSE). Each of these subsystems is discussed.
Two reports present numerical study of performance of feedforward neural network trained by back-propagation algorithm in learning continuous-valued mappings from data corrupted by noise. Two types of noise considered: plant noise which affects dynamics of controlled process and data-processing noise, which occurs during analog processing and digital sampling of signals. Study performed with view toward use of neural networks as neurocontrollers to substitute for, or enhance, performances of human experts in controlling mechanical devices in presence of sensor and actuator noise and to enhance performances of more-conventional digital feedback electronic process controllers in noisy environments.
The design and analysis of the electromechanical actuator (EMA) being developed for the NASA/Marshall Space Flight Center as part of the National Launch System (NLS) Propellant Control Effector Advanced Development Program (ADP) are addressed. The EMA design uses several proven technologies combined into a single modular package which includes single stage high ratio gear reduction, redundant electric motors mounted on a common drive shaft, redundant drive and control electronics, and digital technology for performing the closed loop position feedback, communication, and health monitoring functions. Results of tests aimed at evaluating both component characteristics and overall system performance demonstrated that the goal of low cost, reliable control in a cryogenic environment is feasible.
We have developed techniques to use digitized scanning electron micrographs and computer image analysis programs to measure track densities in lunar soil grains. Tracks were formed by highly ionizing solar energetic particles and cosmic rays during near surface exposure on the Moon. The track densities are related to the exposure conditions (depth and time). Distributions of the number of grains as a function of their track densities can reveal the modality of soil maturation. We used a sample that had already been etched in 6 N NaOH at 118 C for 15 h to reveal tracks. We determined that back-scattered electron images taken at 50 percent contrast and approximately 49.8 percent brightness produced suitable high contrast images for analysis. We ascertained gray-scale thresholds of interest: 0-230 for tracks, 231 for masked regions, and 232-255 for background. We found no need to set an upper size limit for distinguishing tracks. We did use lower limits to exclude noise: 16 pixels at 15000x, 4 pixels at 10000x, 2 pixels at 6800x, and 0 pixels at 4600x. We used computer counting and measurement of area to obtain track densities. We found an excellent correlation with manual measurements for track densities below 1x10(exp 8) sq cm. For track densities between 1x10(exp 8) sq cm to 1x10(exp 9) sq cm, we found that a regression formula using the percentage area covered by tracks gave good agreement with manual measurements. Finally we used these new techniques to obtain a track density distribution that gave more detail and was more rapidly obtained than using manual techniques 15 years ago.
We have used digitized scanning electron micrographs and computer image analysis programs to measure track densities in lunar soil grains. Tracks were formed by highly ionizing solar energetic particles and cosmic rays. Back-scattered electron images produced suitable high contrast images for analysis. We used computer counting and measurement of area to obtain track densities. We found an excellent correlation with manual measurements for track densities below 1x10(exp 8) cm(exp -2). For track densities between 1x10(exp 8) to 1x10(exp 9) cm(exp -2) we found that a regression formula using the percentage area covered by tracks gave good agreement with manual measurements. Measurement of tract densities in lunar samples has been a very rewarding technique for measuring exposure ages and soil maturation processes. We have shown that we can reliably measure track densities in lunar grains using image analysis techniques. Automating track counting may allow application of this technique to important problems in regolith dynamics including the ratio of radiation exposure to reworking in various surface and core samples and in regolith breccias.
The three fine guidance sensors (FGSs) on board the HST have been operated extensively since the observatory was launched in April, 1990. The FGSs, each capable of measuring angles as small as 0.003 arcsec, provide required fine pointing information to the HST's pointing control system and are intended to serve as astrometry instruments. On-orbit data have shown that the acquisition, pointing and tracking performance of the FGSs in most cases meets, and of these sometimes exceeds, requirements. The versatility of the FGS digital control electronics to adapt to the unexpected conditions imposed on the sensors by the telescope spherical aberration and by solar panel jitter is discussed. There is encouragement from both on-orbit tests and analytical studies that the FGSs can accommodate the current telescope characteristics. Improvements to guide star acquisitions within the FGSs and to target acquisitions within science instruments have been accomplished with the internal distortion calibration of each FGS and with the alignment calibration between sensors. Techniques used in the calibration process and the resulting improvements in acquisitions are presented.
We have developed techniques to use digitized scanning electron micrographs and computer image analysis programs to measure track densities in lunar soil grains and plastic dosimeters. Tracks in lunar samples are formed by highly ionizing solar energetic particles and cosmic rays during near surface exposure on the Moon. The track densities are related to the exposure conditions (depth and time). Distributions of the number of grains as a function of their track densities can reveal the modality of soil maturation. We worked on two samples identified for a consortium study of lunar weathering effects, 61221 and 67701. They were prepared by the lunar curator's staff as polished grain mounts that were etched in boiling 1 N NaOH for 6 h to reveal tracks. We determined that backscattered electron images taken at 10 percent contrast and approximately 50 percent brightness produced suitable high contrast images for analysis. We used the NIH Image program to cut out areas that were unsuitable for measurement such as edges, cracks, etc. We ascertained a gray-scale threshold of 25 to separate tracks from background. We used the computer to count everything that was two pixels or greater in size and to measure the area to obtain track densities. We found an excellent correlation with manual measurements for track densities below 1 x 10(exp 8) cm(exp -2). For track densities between 1 x 10(exp 8) cm(exp -2) to 1 x 10(exp 9) cm(exp -2) we found that a regression formula using the percentage area covered by tracks gave good agreement with manual measurements. We determined the track density distributions for 61221 and 67701. Sample 61221 is an immature sample, but not pristine. Sample 67701 is a submature sample that is very close to being fully mature. Because only 10 percent of the grains have track densities less than 10(exp 9) cm(exp -2), it is difficulty to determine whether the sample matured in situ or is a mixture of a mature and a submature soil. Although our analysis of plastic dosimeters is at an early stage of development, results are encouraging. The dosimeter was etched in 6.25 N NaOH at 70 deg C for 16 h. We took 200x secondary electron images of the sample and used the NIH Image software to count and measure major and minor diameters of the etched tracks. We calculated the relative track etch rate from a formula that relates it to the major and minor diameters. We made a histogram of the number of tracks versus their relative etch rate. The relative track etching rate is proportional to the linear energy transfer of the particle. With appropriate calibration experiments, the histogram could be used to calculate the radiation dose.
Charge Coupled Devices (CCDs) are high technology silicon chips that connect light directly into electronic or digital images, which can be manipulated or enhanced by computers. When Goddard Space Flight Center (GSFC) scientists realized that existing CCD technology could not meet scientific requirements for the Hubble Space Telescope Imagining Spectrograph, GSFC contracted with Scientific Imaging Technologies, Inc. (SITe) to develop an advanced CCD. SITe then applied many of the NASA-driven enhancements to the manufacture of CCDs for digital mammography. The resulting device images breast tissue more clearly and efficiently. The LORAD Stereo Guide Breast Biopsy system incorporates SITe's CCD as part of a digital camera system that is replacing surgical biopsy in many cases. Known as stereotactic needle biopsy, it is performed under local anesthesia with a needle and saves women time, pain, scarring, radiation exposure and money.
An examination of how mass is used in spacecraft design indicates that technology efforts directed only to reduce the mass of electronics, both digital and analog will not significantly reduce the mass of a spacecraft, regardless of how much success those efforts achieve.