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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 163 records · Page 9

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NASA NTRS1978

A flight evaluation of a trailing anemometer for low-speed calibrations of airspeed systems on research aircraft

Research airspeed systems on three low-speed general aviation airplanes were calibrated by the trailing anemometer method. Each airplane was fitted with an NASA pitot-static pressure tube mounted on either a nose or wing boom. The uncalibrated airspeed systems contained residual static-pressure position errors which were too large for high-accuracy flight research applications. The trailing anemometer calibration was in agreement with the tower flyby calibration for the one aircraft for which the comparison was made. The continuous deceleration technique for the trailing anemometer method offers reduced test time with no appreciable loss of accuracy for airspeed systems with pitot-static system lag characteristics similar to those described.

Fisher, B. D.↗

NASA NTRS1977

Maps of Jovian radio emission

Observations were made of Jupiter with the Westerbork telescope at all three frequencies available: 610 MHz, 1415 MHz, and 4995 MHz. The raw measurements were corrected for position errors, atmospheric extinction, Faraday rotation, clock, frequency, and baseline errors, and errors due to a shadowing effect. The data was then converted into brightness distribution of the sky by Fourier transformation. Maps of both thermal and nonthermal radiation were developed. Results indicate that the thermal disk of Jupiter measured at a wavelength of 6 cm has a temperature of 236 + or - 15 K. The radiation belts have an overall structure governed by the trapping of electrons in the dipolar field of the planet with significant beaming of the synchrotron radiation into the plane of the magnetic equator.

Depater, I.↗

NASA NTRS1977

Airborne navigation system performance during RNAV/MLS transition

Aircraft position error sensitivity to sensor errors and flight path geometry is analyzed during RNAV/MLS transition using a digital computer simulation. The avionics sensitivity data provides information necessary to establish requirements for additional guidance law design and to establish airspace requirements for maneuvering to null out any residual RNAV errors upon MLS transition. The data base is also beneficial as planning information for subsequent flight testing. The parameters varied during the generation of the data base include flight profile, error source content and magnitude, ground facility location, runway/flight path orientation and navigation mode. The avionics, autopilots and aircraft dynamics correspond to the existing NASA Terminal Configured Vehicle. Significant transients were observed during MLS transition, primarily in the vertical channel. These transients have a significant impact on airspace requirements and operational procedures in the RNAV/MLS environment.

Heine, W.↗

NASA NTRS1978

Positions of galactic X-ray sources - At longitudes /l-II/ of 55-320 deg

Rotating modulation collimeter detectors on the SAS-3 X-ray observatory were used to supply precise (20-40 sec) positional data on 10 galactic X-ray sources in the l super II region between 55 and 320 deg. It is noted that the position for 2S0114+650 has led to the discovery of an optical counterpart. Attention is given to the temperature dependence of the experiments, and it is found that position measurements made at low temperatures are consistent with those obtained at normal (0 C) temperatures. Positions, error radii, and intensities (2-11 keV) are listed for each of the ten sources.

Dower, R. G.↗

NASA NTRS1979

X-ray observations of H1908+050 /=SS 433/

The X-ray source H1908+050 (=4U 1908+05 = A1909+04) was observed for three 6 day periods in 1977 and 1978 with the HEAO A-2 experiment. Because of the positional error box and variability of the source, the unusual emission-line object and variable radio source SS 433 has been suggested as the optical counterpart. The X-ray luminosity of the source varied by a factor of about 2 on a time scale of 6 months, and the spectrum of the object is consistent with either a power law of photon index of 2.1 or with 14.3 KeV thermal bremsstrahlung emission with an about 575 eV equivalent-width iron line. These X-ray characteristics argue against the source being extragalactic, but do not uniquely identify the type of source. The measurements are consistent with emission from a white dwarf with 100 million gauss magnetic field, but are also similar to the X-ray emission sometimes seen from Cir X-1. A search has been made for X-ray emission from similar radio sources, but no new X-ray sources were detected. A previously known source, A1850+00, is a possible counterpart for one of these radio sources.

Marshall, F. E.↗

NASA NTRS1979

Map characteristics of Landsat mosaics

Map characteristics of the Landsat mosaics developed at JPL are considered. Procedures for digital mosaicking of Landsat frames to standard map projections were used to mosaic at full resolution ten scenes over the California desert region and twenty-one scenes over Arizona. The procedures are analyzed for horizontal positioning error (global and local) and the potential for classification error associated with the adjustment of brightness of Z values between frames; the use of this technology for the mapping of extensive features is discussed. Mosaicking facilities, techniques, mapping accuracy, and thematic mapping characteristics are described. A comparative analysis of Landsat mosaicking technology developed at Goddard Space Flight Center, IBM Gaithersburg, and USGS Flagstaff is made, and suggestions are given for algorithm development to improve systems capacity and ability to handle a variety of cases.

Zobrist, A. L.↗

NASA NTRS1981

An analysis of the adaptability of Loran-C to air navigation

The sources of position errors characteristics of the Loran-C navigation system were identified. Particular emphasis was given to their point on entry as well as their elimination. It is shown that the ratio of realized accuracy to theoretical accuracy of the Loran-C is highly receiver dependent.

Littlefield, J. A.↗

NASA NTRS1980

Search and rescue emergency locating transmitter detection/location procedure via TIROS satellite

A procedure is described which works effectively to detect and locate emergency locating transmitters (ELTs) and emergency position indicating radio beacons (EPIRBs) in a multisignal environment. Using data generated from several manufactured ELTs with diverse superimposed Doppler curves, as many as 9 simultaneous ELTs can be detected and located at a variety of signal strengths. It is noted that average position errors of 10 km are attainable today at signal power to noise spectral density ratios as low as 17 dB-Hz.

Wren, P. E.↗

NASA NTRS1981

The effect of abnormal cell proportion on specimen classifier performance

An analysis is presented of the results obtained from a cell classifier which is confronted with an abnormal/normal cell ratio which is different from the ratio assumed in the calibration of the classifier. False negative and false positive error rates are determined in advance for classifier operation, along with the necessary sample size in order to validate the predicted distributions. Changes are demonstrated to happen only regarding the false negative rate, where reductions in the abnormal cell rate below the expected rates would cause totally unreliable data. Substantial overproduction of abnormal cells would be quickly noticeable, while production rates beyond, but close to, the expected rates would only require more extensive sampling. Classifier systems for 10% proportions of abnormal cells are concluded to be possible, but difficulties are present with much lower rates

Castleman, K. R.↗

NASA NTRS1983

Electrostatic Levitator With Feedback Control

Sample position automatically maintained. Object levitated by electrostatic field between two electrodes. Because of particular curved electrode shape, levitation field has stable horizontal position on vertical axis of symmetry. Vertical position of object sensed and compared with preset value. When position error is detected, amplitude of levitating field is increased or decreased to restore zero error. System offers options well to containerless processing.

Rhim, W. K.↗

NASA NTRS1984

A review of recent developments in flight test techniques at the Ames Research Center, Dryden Flight Research Facility

New flight test techniques in use at Ames Dryden are reviewed. The use of the pilot in combination with ground and airborne computational capabilities to maximize data return is discussed, including the remotely piloted research vehicle technique for high-risk testing, the remotely augmented vehicle technique for handling qualities research, and use of ground computed flight director information to fly unique profiles such as constant Reynolds number profiles through the transonic flight regime. Techniques used for checkout and design verification of systems-oriented aircraft are discussed, including descriptions of the various simulations, iron bird setups, and vehicle tests. Some newly developed techniques to support the aeronautical research disciplines are discussed, including a new approach to position-error determination, and the use of a large skin friction balance for the measurement of drag caused by various excrescencies.

Layton, G. P.↗

NASA NTRS1984

Registratiom of TM data to digital elevation models

Several problems arise when attempting to register LANDSAT thematic mapper data to U.S. B Geological Survey digital elevation models (DEMs). The TM data are currently available only in a rotated variant of the Space Oblique Mercator (SOM) map projection. Geometric transforms are thus; required to access TM data in the geodetic coordinates used by the DEMs. Due to positional errors in the TM data, these transforms require some sort of external control. The spatial resolution of TM data exceeds that of the most commonly DEM data. Oversampling DEM data to TM resolution introduces systematic noise. Common terrain processing algorithms (e.g., close computation) compound this problem by acting as high-pass filters.

Source record↗

NASA NTRS1984

Predictions of Cockpit Simulator Experimental Outcome Using System Models

This study involved predicting the outcome of a cockpit simulator experiment where pilots used cockpit displays of traffic information (CDTI) to establish and maintain in-trail spacing behind a lead aircraft during approach. The experiments were run on the NASA Ames Research Center multicab cockpit simulator facility. Prior to the experiments, a mathematical model of the pilot/aircraft/CDTI flight system was developed which included relative in-trail and vertical dynamics between aircraft in the approach string. This model was used to construct a digital simulation of the string dynamics including response to initial position errors. The model was then used to predict the outcome of the in-trail following cockpit simulator experiments. Outcome included performance and sensitivity to different separation criteria. The experimental results were then used to evaluate the model and its prediction accuracy. Lessons learned in this modeling and prediction study are noted.

Sorensen, J. A.↗

NASA NTRS1983

High dynamic, low volume GPS receiver

A new GPS receiver concept and design are presented to meet the high dynamic and low volume requirements for range applications in missiles and drones. The receiver has the potential to satisfy all range requirements with one basic receiver, which has significant potential economic benefit over the alternate approach of using a family of receivers, each tailored for specific applications. The main new concept is to use approximate maximum likelihood estimates of pseudo range and range-rate, rather than tracking with carrier phase locked loops and code delay locked loops. Preliminary analysis indicates that receivers accelerating at 50 g or more can track with position errors due to acceleration of approximately 0.2 m/g, or 10 m at 50 g. Implementation is almost entirely digital to meet the low volume requirements.

Hurd, W. J.↗

NASA NTRS1985

Coupled translations of the 64-meter antenna subreflector supports

The Tricone subreflector assembly of the 64-m diameter antenna is supported from the apex of the quadripod by six flexure rods. The subreflector can be translated in the three orthogonal axes by jackscrews at the ends of each rod. The arrangement of the six rods is described and analysis of the position errors introduced by coupled translation is presented. The results indicate that negligible RF gain losses caused by axis-coupled translations (less than 0.05 dB) are possible at X-band (8.45 GHz) operation.

Katow, M. S.↗

NASA NTRS1986

High precision GPS orbit determination using March 1985 demonstration data

Preliminary orbit determination for satellites in the U.S. Department of Defense's Global Positioning System has been performed using GPS carrier phase data collected in March-April 1985 at 10 sites in the continental United States. The data were analyzed using a new data processing software package called GIPSY (GPS Inferred Positioning SYstem) and with existing covariance analysis software. Data from one day have been processed with average formal position errors of 1.4 to 3.6 meters. The true errors are probably somewhat larger. Covariance results are presented which suggest that the orbits can be obtained with formal errors under 2 meters after certain software issues are resolved.

Bertiger, W.↗

NASA NTRS1986

Fast transients - A search in X-rays for short flares, bursts, and related phenomena

The HEAO 1 A-2 database on fast high energy X-ray transients was examined for any discernible regularities. The data were taken over the interval 1977-79 with six collimated multiwire, multilayer, proportional counters that had a sensitivity sufficient for detecting events lasting 1-5 sec at energies as low as 8-120 keV. The entire sky was surveyed completely three times in the observational period. Best-fit position, error box corners, mean transient flux and quiescent flux data are provided for all six of the type 3 events that were found. All the sources were within the Galaxy. The duration of the events ranged from 60-2000 sec. The limited number of events observed leads to estimates of 10,000-200,000 events per year. It is suggested that all the events originate from hard flares occurring at a rate of 20,000/yr on dMe/dKe stars.

Connors, A.↗

NASA NTRS1986

Airborne spectroradiometry: The application of AIS data to detecting subtle mineral absorption features

Analysis of Airborne Imaging Spectrometer (AIS) data acquired in Australia has revealed a number of operational problems. Horizontal striping in AIS imagery and spectral distortions due to order overlap were investigated. Horizontal striping, caused by grating position errors can be removed with little or no effect on spectral details. Order overlap remains a problem that seriously compromises identification of subtle mineral absorption features within AIS spectra. A spectrometric model of the AIS was developed to assist in identifying spurious spectral features, and will be used in efforts to restore the spectral integrity of the data.

Cocks, T. D.↗