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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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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Gray-Scale Processing For Tracking Of Welds

Digital analysis of video-image-processing system contributes to automation of weld-seam tracking. Makes no contact with seam. Small television camera views seam just ahead of point currently being welded. Arc provides illumination. Periodically frame grabber digitizes video image and stores in computer memory as gray-scale values. Seam located by analyzing Hough-transform arrays of derivatives of digitally-filtered image data. Information on location and orientation of seam used as feedback by welding robot to correct deviations of electrode from seam as welding continues.

Gutow, David A.↗
NASA NTRS1986

Orbit determination using synthetic aperture radar

The use of synthetic aperture radar (SAR) images to estimate orbital parameters is studied. The SAR image formation process which requires the ability to repeatedly transmit identical signals and accurately sense the return echoes from a region of terrain is described. The orbit determination capabilities of the SAR system's observables are investigated. Five SAR observations were collected from a simulated shuttle orbit, which was circular with a latitude of 220 km and along-track velocity of 7.7 km/sec, to obtain along-track and line-of-sight direction position measurements; the simulation reveals that only three SAR observations were required to determine the position of the spacecraft to within 100 m. A prototype SAR orbit determination system was developed. The system consists of a VAX 11/780 time-shared computer, a frame buffer, topographic maps, and software for line-pixel location of an object within a SAR image and for orbit determination. The prototype is applied to the processing of a single short arc of Shuttle Imaging-Radar-B (SIR-B) data. It is observed that the SAR data is useful as orbit determination or tracking data; however, the low SNRs in the SIR-B data made feature identification difficult.

Taber, W. L.↗
NASA NTRS1993

An improved gravity model for Mars: Goddard Mars Model-1 (GMM-1)

Doppler tracking data of three orbiting spacecraft have been reanalyzed to develop a new gravitational field model for the planet Mars, GMM-1 (Goddard Mars Model-1). This model employs nearly all available data, consisting of approximately 1100 days of S-bank tracking data collected by NASA's Deep Space Network from the Mariner 9, and Viking 1 and Viking 2 spacecraft, in seven different orbits, between 1971 and 1979. GMM-1 is complete to spherical harmonic degree and order 50, which corresponds to a half-wavelength spatial resolution of 200-300 km where the data permit. GMM-1 represents satellite orbits with considerably better accuracy than previous Mars gravity models and shows greater resolution of identifiable geological structures. The notable improvement in GMM-1 over previous models is a consequence of several factors: improved computational capabilities, the use of optimum weighting and least-squares collocation solution techniques which stabilized the behavior of the solution at high degree and order, and the use of longer satellite arcs than employed in previous solutions that were made possible by improved force and measurement models. The inclusion of X-band tracking data from the 379-km altitude, near-polar orbiting Mars Observer spacecraft should provide a significant improvement over GMM-1, particularly at high latitudes where current data poorly resolves the gravitational signature of the planet.

Smith, D. E.↗
NASA NTRS1975

Torque control system

System stabilizes aximuth of gondolas which are carried by high-altitude balloons as platforms for tracking telescopes. When telescopes must be constantly aimed at specific targets, control system stabilizes gondola to within 5 arc-seconds.

Studenick, D. K.↗
NASA NTRS2000

The Topography (and Ephemeris) of Phobos from MOLA Ranging

The MGS spacecraft experienced four close encounters with Phobos in the late summer of 1998. The last (and closest) of these, on September 12, 1998, had an encounter distance of 265 km, well within the maximum MOLA range of 780 km. The apparent motion of Phobos at encounter was 0.7 deg/sec (well in excess of the maximum MGS roll rate of 0.37 sec), which would have resulted in about 6 seconds on target for a fixed spacecraft orientation, or about 10 seconds using a spacecraft roll to partially compensate for the motion. A scheme was devised to maximize the ranging time on Phobos by overtaking the trailing limb with the MGS slew while at a distance (roughly 530 km) such that the apparent motion of Phobos was still less than 0.3 deg/sec. As the track crossed Phobos and the distance decreased, the increase in the apparent motion slowed and eventually reversed the track before the entire disk was traversed. The track then re-crossed the trailing limb at a range of about 350 km. This operation resulted in the first successful active spacecraft ranging to a small body, with nearly 70 seconds of time on target and 627 valid ranging measurements along two nearly coincident, but slightly offset tracks. These tracks cross the Mars-facing hemisphere from SE to NW, covering a length of about 120 deg of arc. At these ranges the laser footprint varied in size from 130 to 200 m and the footprint spacing ranged from less than 10 m near the reversal point to a few hundred meters near the limb. Successful returns were obtained at emission angles up to 80 deg.

Banerdt, W. B.↗
NASA NTRS2015

SOAREX-8 Suborbital Experiments 2015 - A New Paradigm for Small Spacecraft Communication

In 2015 NASA plans to launch a payload to 280 Km altitude on a sounding rocket from the Wallops Flight Facility. This payload will contain several novel technologies that work together to demonstrate methodologies for space sample return missions and for nanosatellite communications in general. The payload will deploy and test an Exo-Brake, which slows the payload aerodynamically, providing eventual de-orbit and recovery of future ISS samples through a Small Payload Quick Return project. In addition, this flight addresses future Mars mission entry technology, space-to-space communications using the Iridium Short Messaging Service (SMS), GPS tracking, and wireless sensors using the ZigBee protocol. SOAREX-8 is being assembled and tested at Ames Research Center (ARC) and the NASA Engineering and Safety Center (NESC) is funding sensor and communications work. Open source Arduino technology and software are used for system control. The ZigBee modules used are XBee units that connect analog sensors for temperature, air pressure and acceleration measurement wirelessly to the payload telemetry system. Our team is developing methods for power distribution and module mounting, along with software for sensor integration, data assembly and downlink. We have demonstrated relaying telemetry to the ground using the Iridium satellite constellation on a previous flight, but the upcoming flight will be the first time we integrate useful flight test data from a ZigBee wireless sensor network. Wireless sensor data will measure the aerodynamic efficacy of the Exo-Brake permitting further on orbit flight tests of improved designs. The Exo-Brake is 5 sq m in area and will be stored in a container and deployed during ascent once the payload is jettisoned from the launch vehicle. We intend to further refine the hardware and continue testing on balloon launches, future sounding rocket flights and on nanosatellite missions. The use of standards-based and open source hardware/software has allowed for this project to be completed with a very modest budget and a challenging schedule. There is a wealth of hardware and software available for both the Arduino platform and the XBee, all low-cost or open-source. Along with the Exo-Brake hardware and deployment discussion, this paper will describe in detail the system architecture emphasizing the successful use of open source hardware and software to minimize effort and cost. Testing procedures, radio frequency interference (RFI) mitigation, success criteria and expected results will also be discussed. The use of Iridium short messaging capability for space-to-space links, standards-based wireless sensor networks, and other innovative communications technology are also presented.

aerobrake↗
NASA NTRS2019

Multi-Arc Filtering During the Navigation Campaign of the OSIRIS-REx Mission

The Navigation Campaign of the OSIRIS-REx mission consisted of three phases: Approach, Preliminary Survey and Orbital-A. These phases were designed to optimize the initial characterization of Bennu's mass, shape and spin-state to support a safe orbit insertion and a quick transition to landmark-based optical navigation tracking. The standard orbit determination filtering techniques used to navigate the spacecraft were unable to fit data from these three phases simultaneously due to numerical issues associated with the nonlinear dynamics and the long arc length. Consequently, a multi-arc filtering algorithm was implemented in order to combine the information from each of these arcs. Multi-arc solutions for Bennu's spin state and gravity field are presented here.

French, Andrew S.↗
NASA NTRS1996

Tracking Motions Of Manually Controlled Welding Torches

Techniques for measuring motions of manually controlled welding torches undergoing development. Positions, orientations, and velocities determined in real time during manual arc welding. Makes possible to treat manual welding processes more systematically so manual welds made more predictable, especially in cases in which mechanical strengths and other properties of welded parts highly sensitive to heat inputs and thus to velocities and orientations of welding torches.

Russell, Carolyn↗
DOE OSTI2026

Simulations of grain growth in tungsten armor materials under ARC plasma edge operation conditions using an integrated plasma-edge/materials model

An integrated model of grain growth deuterium-exposed tungsten polycrystals, consisting of a two-dimensional vertex dynamics model fitted to atomistic data, has been developed to assess the grain growth kinetics of deuterium-exposed polycrystalline tungsten (W). The model tracks the motion of grain boundaries under the effect of driving forces stemming from grain boundary curvature and differential deuterium concentration accumulation. Here, we apply the model to experimentally synthesized tungsten polycrystals under deuterium-saturated conditions relevant to the ARC concept design. The results indicate rapid grain growth kinetics in the near-surface region adjacent to the plasma, where the temperature reaches 1400 K, whereas the microstructure remains stable deeper in the material with the lower temperature of 1000 K. The combined modeling and analysis further reveal that monolithic tungsten produced via conventional fabrication routes is highly susceptible to grain coarsening at temperatures exceeding 1000 K, largely independent of the magnitude of the applied driving force. Moreover, the accumulation of deuterium near grain boundaries has a pronounced inhibitory effect on grain boundary migration. High-angle grain boundaries ( > 50°) contribute more significantly to the overall grain growth process.

36 MATERIALS SCIENCE↗
NASA NTRS1976

The preliminary design of an orbiting observatory - The Space Telescope

The systems and subsystems of the Space Telescope proposed for an orbiting observatory to be launched by the Space Shuttle in the 1980s are described. The structural design is simple and based on existing technologies for high reliability. Provisions are made for on-orbit servicing and maintenance. All deployable appendages are designed for manual override to insure retrieval and return of the Space Telescope to earth for major refurbishing, which should occur at intervals of not less than six years. Low performance risk, passive techniques are used in the thermal control subsystem to provide a cold-biased design with thermostatically controlled heaters to adjust temperature. The electrical power system utilizes NASA Standard Hardware - 50 ampere hour nickel-cadmium battery cells, a standard power regulator unit, and a flight-proven flexible rollup solar array with high-efficiency (12.5 per cent) silicon solar cells. The communication subsystem is designed for compatibility with the Tracking and Data Relay Satellite System. The pointing control system will have a maximum line of sight variation of 0.007 arc seconds. The telescope optics are a Ritchey-Chretien version of the Cassegrain configuration.

Timmons, K. P.↗
NASA NTRS1990

The application of Encke's method to long arc orbit determination solutions

The Laser Geodynamics Satellite (LAGEOS) was launched on May 4, 1976 to provide geophysical measurements by means of laser ranging techniques. To date, over twelve years of laser range measurements have been collected from various tracking stations located around the world. Laser range measurements to LAGEOS have contributed to studies of earth rotation, plate tectonics, global baseline, and the gravity field as well as many other areas. Some of these studies are based upon the determination of a single, continuous orbit for LAGEOS for time spans on the order of several years. Current studies at the University of Texas Center for Space Research include the precision orbit determination of LAGEOS for arc lengths of up to 12.8 years which represents over 31,000 orbital revolutions. These long arc studies have led to the implementation of Encke's method to improve the convergence of the batch filter while reducing numerical integration errors. While the technique has been successfully applied to arc lengths of up to 12.8 years, the results presented focus on the solution of a six-year arc.

Lundberg, J. B.↗
NASA NTRS2016

High Precision Sunphotometer using Wide Dynamic Range (WDR) Camera Tracking

The NASA Ames Sun-photometer-Satellite Group, DOE, PNNL Atmospheric Sciences and Global Change Division, and NASA Goddards AERONET (AErosol RObotic NETwork) team recently collaborated on the development of a new airborne sunphotometry instrument that provides information on gases and aerosols extending far beyond what can be derived from discrete-channel direct-beam measurements, while preserving or enhancing many of the desirable AATS features (e.g., compactness, versatility, automation, reliability). The enhanced instrument combines the sun-tracking ability of the current 14-Channel NASA Ames AATS-14 with the sky-scanning ability of the ground-based AERONET Sunsky photometers, while extending both AATS-14 and AERONET capabilities by providing full spectral information from the UV (350 nm) to the SWIR (1,700 nm). Strengths of this measurement approach include many more wavelengths (isolated from gas absorption features) that may be used to characterize aerosols and detailed (oversampled) measurements of the absorption features of specific gas constituents. The Sky Scanning Sun Tracking Airborne Radiometer (3STAR) replicates the radiometer functionality of the AATS14 instrument but incorporates modern COTS technologies for all instruments subsystems. A 19-channel radiometer bundle design is borrowed from a commercial water column radiance instrument manufactured by Biospherical Instruments of San Diego California (ref, Morrow and Hooker)) and developed using NASA funds under the Small Business Innovative Research (SBIR) program. The 3STAR design also incorporates the latest in robotic motor technology embodied in Rotary actuators from Oriental motor Corp. having better than 15 arc seconds of positioning accuracy. Control system was designed, tested and simulated using a Hybrid-Dynamical modeling methodology. The design also replaces the classic quadrant detector tracking sensor with a wide dynamic range camera that provides a high precision solar position tracking signal as well as an image of the sky in the 45 field of view around the solar axis, which can be of great assistance in flagging data for cloud effects or other factors that might impact data quality.

aerosols↗
NASA NTRS1979

Estimation of the ocean geoid near the Blake Escarpment using GEOS-3 satellite altimetry

The accuracy with which the local ocean geoid structure could be determined using satellite altimetry data was investigated. The undulation and along-track component of the vertical deflection for selected passes of GEOS-3 near the Blake Escarpment were estimated and compared with independent analogous estimates based on U. S. Navy surface gravimetric survey data. The results of these comparisons show agreement in the geoid undulation values generally to within one or two meters. The nature of the discrepancy in the undulation values was primarily that of a bias error believed to be due essentially to radial orbit uncertainties. The agreement between the vertical deflection estimates was not significantly affected by orbit uncertainties over the track lengths considered in this study (100 - 1500 km), and the comparisons show typical rms differences of between one and two arc secs. In addition, the capability of the altimeter to resolve short wavelength features of the geoid was determined. This analysis involved spectrum and cross spectrum analysis of sets of closely spaced parallel subtracks to determine statistically significant short wavelength geoid resolution capability. The results of this analysis show that resolution can be achieved down to wavelengths as short as 30 km - 80 km depending on regional geoid variations.

Brammer, R. F.↗
NASA NTRS1995

Results of an Automated GPS Tracking System in Support of Topex/Poseidon and GPSMet

A fully automated near real-time GPS tracking system has been developed around JPL's GIPSY/OASIS II software. The system produces <25 cm (3D rms) GPS orbits and one-half nanosecond (15 cm) clock estimates. The process starts automatically when a favorable global distribution of ground data from the IGS network (International GPS Service for Geodynamics) becomes available. Ionospherically corrected phase and pseudorange data are optimally combined to remove satellite and ground receiver clock errors, including selective availability. After the GPS orbits are determined within the data arc, they are then propagated with empirically determined dynamic force models. Real-time <2 meter (3D rms) GPS orbits are always available. As a by-product of this process, other calibration estimates such as station clocks, troposphere estimates, and Earth orientation parameters are also produced. For daily arc fits, the process requires 7-8 hours of CPU time on an HP9000/735 workstation.

GPS↗
NASA NTRS1993

The star identification, pointing and tracking system of UVSTAR, an attached payload instrument system for the Shuttle Hitchhiker-M platform

We describe an algorithm for star identification and pointing/tracking of a spaceborne electro-optical system and simulation analyses to test the algorithm. The algorithm will be implemented in the guiding system of UVSTAR, a spectrographic telescope for observations of astronomical and planetary sources operating in the 500-1250 A waveband at approximately 1 A resolution. The experiment is an attached payload and will fly as a Hitchhiker-M payload on the Shuttle. UVSTAR includes capabilities for independent target acquisition and tracking. The spectrograph package has internal gimbals that allow angular movement of plus or minus 3 deg from the central position. Rotation about the azimuth axis (parallel to the Shuttle z axis) and elevation axis (parallel to the Shuttle x axis) will actively position the field of view to center the target of interest in the fields of the spectrographs. The algorithm is based on an on-board catalog of stars. To identify star fields, the algorithm compares the positions of stars recorded by the guiding imager to positions computed from the on-board catalog. When the field has been identified, its position within the guiding imager field of view can be used to compute the pointing corrections necessary to point to a target of interest. In tracking mode, the software uses the past history to predict the quasi-periodic attitude control motions of the shuttle and sends pointing commands to cancel the motion and stabilize UVSTAR on the target. The guiding imager (guider) will have an 80-mm focal length and f/1.4 optics giving a field of view of 6 deg x 4.5 deg using a 385 x 288 pixel intensified CCD. It will be capable of providing high accuracy (better than 2 arc-sec) attitude determination from coarse (6 deg x 4.5 deg) initial knowledge of the pointing direction; and of pointing toward the target. It will also be capable of tracking at the same high accuracy with a processing time of less than a few hundredths of a second.

Decarlo, Francesco↗
DOE OSTI2025

Advancing Temperature Monitoring of the Bottom Anode in a Direct Current Electric Arc Furnace Operations with Distributed Optical Fiber Sensors.

The bottom anode in the Direct Current Electric Arc Furnace (DC EAF) is critical for completing the electrical circuit necessary for sustaining the arc within the furnace. For pin-type bottom anodes, monitoring of the temperature of select pins instrumented with thermocouples is performed to track bottom wear in the EAF and inform the operator when the furnace should be removed from service. Furthermore, this work presents the results from a plant trial using distributed temperature monitoring of bottom anode pins in a 165-ton DC EAF over a two-month service period utilizing two optical fiber sensing techniques: fiber Bragg grating (FBG) and Rayleigh backscattering (RBS). The early detection of temperature anomalies along the length of the anode pin through distributed sensing enhances operational safety, providing a robust alternative to traditional thermocouples.

42 ENGINEERING↗
NASA NTRS1971

The relation of the European Datum to a geocentric reference system

Over 31,000 precision reduced optical observations of GEOS-1 and 2 in 70 two-day orbital arcs were used at Goddard Space Flight Center (GSFC) in a dynamical solution to determine center-of-mass coordinates for 15 tracking stations on the European Datum. Comparisons with the results obtained at Centre National d'Etudes Spatiales (CNES) give agreement of about 1.5 ppm for chord lengths. After considering a scale correction to the European Datum (ED) of 1950 to account for the absence of geoid heights at the time of its reduction, agreement to a few ppm between the CNES/GSFC and the ED chords is obtained. However, a small systematic difference between survey and satellite results remains for stations in southeastern France and Switzerland.

Marsh, J. G.↗
NASA NTRS1988

Topex orbit determination and gravity recovery using GPS data from repeat orbits

A covariance analysis is presented for a differential GPS-based technique for satellite tracking and gravity recovery to be demonstrated on Topex in the early 1990's. The technique employs data from an ensemble of repeat ground tracks to recover a unique satellite epoch state for each track and a set of invariant local gravity parameters common to all tracks. For satellites above about 800 km altitude, where gravity modeling is the dominant systematic error, averaging of random error over many arcs and adjustment of the gravity model reduces the final satellite position error. The local gravity parameters can then be used to produce a refined global gravity model. The analysis indicates that errors ranging from 5 to 8 cm in Topex altitude and 0.05 to 0.2 mgal for the gravity field can be achieved, depending on the number of repeat arcs used.

Wu, Jiun-Tsong↗