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At least 1,729 records · Page 96

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.↗

Load-displacement measurement and work determination in three-point bend tests of notched or precracked specimens

Suggestions for testing of notched or cracked three-point bend specimens are presented that (1) correct displacement measurement errors resulting from misalignment between the load applicator and specimen; (2) account for coincidental strains not associated with the work of crack extension; (3) simplify record analysis and processing; and (4) extend displacement gage range without sacrifice of sensitivity or accuracy. These testing details are particularly applicable to procedures in which the crack extension force J(I) is determined from the work done on the specimen.

Buzzard, R. J.↗

An Evaluation of optional timing/synchronization features to support selection of an optimum design for the DCS digital communication network

The task was to evaluate the ability of a set of timing/synchronization subsystem features to provide a set of desirable characteristics for the evolving Defense Communications System digital communications network. The set of features related to the approaches by which timing/synchronization information could be disseminated throughout the network and the manner in which this information could be utilized to provide a synchronized network. These features, which could be utilized in a large number of different combinations, included mutual control, directed control, double ended reference links, independence of clock error measurement and correction, phase reference combining, and self organizing.

Bradley, D. B.↗

Effect of various features on the life cycle cost of the timing/synchronization subsystem of the DCS digital communications network

The effect on the life cycle cost of the timing subsystem was examined, when these optional features were included in various combinations. The features included mutual control, directed control, double-ended reference links, independence of clock error measurement and correction, phase reference combining, self-organization, smoothing for link and nodal dropouts, unequal reference weightings, and a master in a mutual control network. An overall design of a microprocessor-based timing subsystem was formulated. The microprocessor (8080) implements the digital filter portion of a digital phase locked loop, as well as other control functions such as organization of the network through communication with processors at neighboring nodes.

Kimsey, D. B.↗

Diurnal variations of the Martian surface layer meteorological parameters during the first 45 sols at two Viking Lander sites

Wind speed, ambient and surface temperatures from both Viking Landers have been used to compute bulk Richardson numbers and Monin-Obukhov lengths during the earliest phase of the Mars missions. These parameters are used to estimate drag and heat transfer coefficients, friction velocities and surface heat fluxes at the two sites. The principal uncertainty is in the specification of the roughness length. Maximum heat fluxes occur near local noon at both sites, and are estimated to be in the range 15-20 W/sq m at the Viking 1 site and 10-15 W/sq m at the Viking 2 site. Maximum values of friction velocity occur in late morning at Viking 1 and are estimated to be 0.4-0.6 m/s. They occur shortly after dawn at the Viking 2 site where peak values are estimated to be in the range 0.25-0.35 m/s. Extension of these calculations to later times during the mission will require allowance for dust opacity effects in the estimation of surface temperature and in the correction of radiation errors of the Viking 2 temperature sensor.

Sutton, J. L.↗

Quasi-optimal decoding of linear block codes using soft decision detection

A simple but effective decoding procedure, applicable to any (n,k) linear block code with symbols from GF(q), is described. The technique involves a transformation of the parity check equations which focuses the code's correction power on the soft symbol set while still retaining the capability to correct one symbol error from outside this set. The soft symbol set is defined to be the n-k least reliably detected code symbol positions whose parity check row-spaces are linearly independent. The process generates a number of error vector screening candidates, each a solution to the parity check equations, and the maximum-likelihood candidate is accepted.

Greene, E. P.↗

Subjective evaluation of the combined influence of satellite temperature sounding data and increased model resolution on numerical weather forecasting

The present evaluation is concerned with (1) the significance of prognostic differences resulting from the inclusion of satellite-derived temperature soundings, (2) how specific differences between the SAT and NOSAT prognoses evolve, and (3) comparison of two experiments using the Goddard Laboratory for Atmospheric Sciences general circulation model. The subjective evaluation indicates that the beneficial impact of sounding data is enhanced with increased resolution. It is suggested that satellite sounding data posses valuable information content which at times can correct gross analysis errors in data sparse regions.

Atlas, R.↗

DEKFIS user's guide: Discrete Extended Kalman Filter/Smoother program for aircraft and rotorcraft data consistency

The computer program DEKFIS (discrete extended Kalman filter/smoother), formulated for aircraft and helicopter state estimation and data consistency, is described. DEKFIS is set up to pre-process raw test data by removing biases, correcting scale factor errors and providing consistency with the aircraft inertial kinematic equations. The program implements an extended Kalman filter/smoother using the Friedland-Duffy formulation.

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Boresighting techniques for the Antenna Control Assembly (ACA)

Comparison of four scanning schemes including CONSCAN indicates that CONSCAN with signal cleanup and protection processes has the greatest merit in terms of accuracy, dependability and automatic unattended operation. Specific problem areas, error sources, and corrective measures are discussed.

Abichandani, K. P.↗

Comparison of wheat classification accuracy using different classifiers of the image-100 system

Classification results using single-cell and multi-cell signature acquisition options, a point-by-point Gaussian maximum-likelihood classifier, and K-means clustering of the Image-100 system are presented. Conclusions reached are that: a better indication of correct classification can be provided by using a test area which contains various cover types of the study area; classification accuracy should be evaluated considering both the percentages of correct classification and error of commission; supervised classification approaches are better than K-means clustering; Gaussian distribution maximum likelihood classifier is better than Single-cell and Multi-cell Signature Acquisition Options of the Image-100 system; and in order to obtain a high classification accuracy in a large and heterogeneous crop area, using Gaussian maximum-likelihood classifier, homogeneous spectral subclasses of the study crop should be created to derive training statistics.

Dejesusparada, N.↗

Visible infrared spin-scan radiometers (VISSR) for the Geostationary Operational Environmental Satellite (GOES) B and C application

Two visible infrared spin scan radiometer (VISSR) instruments provided for the Geostationary Operational Environmental Satellite B and C (GOES B and C) spacecrafts are described. The instruments are identical to those supplied previously are summarized. A significant number of changes primarily involving corrections of drawing errors and omissions were also performed. All electrical changes were breadboarded (where complexity required this), were incorporated into the test module, and subjected to verification of proper operation throughout fall instrument temperature range. Evaluation of the changes also included design operating safety margins to account for component variations and life.

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The resonance line of B II in IUE spectra of chemically peculiar stars

A description is presented of high-dispersion spectroscopic observations of eight chemically peculiar stars including Kappa Cnc and Mu Lep, and of one normal comparison star, Nu Cap, in the vicinity of 1362 A. The reported data were obtained with the International Ultraviolet Explorer during the first 15 months of its operation. The initial reduction of the data, which were originally described in a qualitative summary by Leckrone (1980), was affected by a serious error in the calibration of the instrument's intensity transfer function. This error has been corrected in the currently presented data. The results of spectrum syntheses of the 1362 A feature are also described for several of the stars.

Leckrone, D. S.↗

Automatic weld torch guidance control system

A highly reliable, fully digital, closed circuit television optical, type automatic weld seam tracking control system was developed. This automatic tracking equipment is used to reduce weld tooling costs and increase overall automatic welding reliability. The system utilizes a charge injection device digital camera which as 60,512 inidividual pixels as the light sensing elements. Through conventional scanning means, each pixel in the focal plane is sequentially scanned, the light level signal digitized, and an 8-bit word transmitted to scratch pad memory. From memory, the microprocessor performs an analysis of the digital signal and computes the tracking error. Lastly, the corrective signal is transmitted to a cross seam actuator digital drive motor controller to complete the closed loop, feedback, tracking system. This weld seam tracking control system is capable of a tracking accuracy of + or - 0.2 mm, or better. As configured, the system is applicable to square butt, V-groove, and lap joint weldments.

Smaith, H. E.↗

Documentation for the machine-readable version of the Uppsala general catalogue of galaxies

The machine-readable version of the catalog containing descriptions of galaxies, their surrounding areas, and position angles for flattened galaxies is described. In addition to the correction of several errors discovered in a previous computerized version, a few duplicate records were removed and the record structure was revised slightly to accommodate a large data value and to remove superfluous blanks.

Warren, W. H., Jr.↗

Optical alignment measurements at Goddard Space Flight Center

The significant changes that have been made in the Optical Alignment Facility at the Goddard Space Flight Center since it was last described (Appler and Howell, 1968) are discussed. The changes are reflected in both the hardware and the software involved in making alignment measurements. The data analysis procedures can now be done on a desktop computer with turn-around times of approximately 4 h. Arbitrary coordinate transformations and corrections for facility errors are also feasible while retaining absolute accuracies of less than 6 sec of arc.

Eichhorn, W. L.↗

Active wavefront correction in large telescopes

Astronomical progress with the MMT telescope, which attains high-resolution imaging by partial compensation for atmospheric distortion, is discussed. The small tertiary and beam combiner mirrors at the MMT bring six images to a common focus, where there is a TV system for acquisition and guiding. Individual image positions can be controlled by stepper motors driving actuators on the secondaries, each step moving an image 0.05 arc seconds in the focal plane. The instrument's correction for image jiggle due to atmospheric turbulence and drift of the relative positions of the images due to gravitational and thermal effects on the structure are described. A scheme for correcting residual structural errors is discussed. It appears that the telescope can work to about the 17th visual magnitude. For faint sky limited objects comparable performance would require a perfectly rigid single mirror of the same aperture to have 50 percent more collecting area and cost at least 1.5 times more.

Angel, J. R. P.↗

The PDS for space telescope guide star selection system: Status and improvements

Pointing the ST (Space Telescope) requires that the onboard guidance system be provided with the coordinates and magnitudes of at least two guide stars for each observation region. The accuracy and limitations of the model 2020G PDS microdensitometer are assessed in view of the guide star requirements of the space telescope. Modifications of the PDS to correct for measuring errors are reviewed.

Kinsey, J. H.↗

Analysis of experimental shaft seal data for high-performance turbomachines, as for Space Shuttle main engines

High-pressure, high-temperature seal flow (leakage) data for nonrotating and rotating Raleigh-step and convergent-tapered-bore seals were characterized in terms of a normalized flow coefficient. The data for normalized Rayleigh-steip and nonrotating tapered-bore seals were in reasonable agreement with theory, but data for the rotating tapered-bore seals were not. The tapered-bore-seal operational clearances estimated from the flow data were significantly larger than calculated. Although clearances are influenced by wear from conical to cylindrical geometry and errors in clearance corrections, the problem was isolated to the shaft temperature - rotational speed clearance correction. The geometric changes support the use of some conical convergence in any seal. Under these conditions rotation reduced the normalized flow coefficiently by nearly 10 percent.

Hendricks, R. C.↗