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Davis, R.

Publications and source records attributed to Davis, R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

The cold land processes experiment (CLPX) local scale observatin site (LSOS)

The Local Scale Observation Site (LSOS) is the smallest study site of the Cold LandProcesses Experiment (CLPX) and is located within the Fraser Meso-cell Study Area (MSA), near the Fraser Experimental Forest Headquarters Facility, in Fraser, CO USA.The 100-m x 100-m site consists of a small open field, a managed dense canopy and an open, mixed age canopy. Unlike the other components of the experiment, which focus on spatial distributions at relatively brief snapshots in time, measurements at the local scale site focused on the temporal domain.

cold land processes ground-based remote sensing va↗
NASA NTRS1994

Discovery of Shell-Like Radio-Structure in SN 1993J

The radio-luminous supernova SN 1993J in M81 offers an unprecedented opportunity to study with high linear resolution the details of the growth of a supernova radio structure by means of the VLBI technique.

radio-luminous supernova supernova gas speeds↗
NASA NTRS1991

SPROC: A multiple-processor DSP IC

A large, single-chip, multiple-processor, digital signal processing (DSP) integrated circuit (IC) fabricated in HP-Cmos34 is presented. The innovative architecture is best suited for analog and real-time systems characterized by both parallel signal data flows and concurrent logic processing. The IC is supported by a powerful development system that transforms graphical signal flow graphs into production-ready systems in minutes. Automatic compiler partitioning of tasks among four on-chip processors gives the IC the signal processing power of several conventional DSP chips.

Davis, R.↗
NASA NTRS1989

Flight support system servicing aid tool

The Space Shuttle EVA on-orbit satellite servicing time is a scare commodity which has been limited for each mission to two 6-hour work periods with an intervening 40-hour rest period. New complex missions being planned require more servicing than two EVA's can accommodate. The GSFC (Goddard Space Flight Center) Satellite Servicing Project has been working for several years to develop a Serving Aid Tool to effectively extend this on-orbit servicing capability by IVA to the point that use of a master-slave bilateral force reflecting manipulator is now planned. This will be controlled from the Shuttle aft flight deck by the RMS mission specialist using a miniature hand controller while outfitted with a physical restraint system. This development is being done on a low cost basis using demonstrated state-of-the-art commercial teleoperated system hardware and software upgraded for space flight use.

Davis, R.↗
NASA NTRS1987

In-orbit and laboratory exchange of ORUs designed/not designed for servicing

The practicality of employing a combination of automated and extravehicular activity forms of servicing in-orbit was demonstrated with the STS 41-C Solar Maximum Repair Mission. This shows that modular Orbital Replacement Units (ORUs) designed for servicing can be readily accommodated. Successful replacement of an experiment ORU, not designed for replacement, was performed following extensive preparations. In a laboratory, spacecraft ORUs were replaced using a completely preplanned automated approach. This was later done using a completely unstructured teleoperations mode including the complicated exchange of the instrument ORU. As a result of this effort and work on powered tools, an approach for combining these techniques is underway to produce a flight support system servicing aid to increase the STS astronauts' effective in-orbit servicing capability by several fold.

Davis, R.↗
NASA NTRS1985

Air Force satellite position management

The Space Act of 1958 identified the Department of Defense as responsible for conducting military operations in space. Subsequently, the United States Air Force was assigned to act as the DOD's executive agent for space. In addition, the Air Force is responsible for acquisition and launch of DOD space systems. Within the Air Force, space related roles and activities have been delegated to several subordinate organizations and agencies. The roles and responsibilities of agencies are still evolving. The Air Force has designated the Air Force System Command's Space Division as its office of primary responsibility for satellite position management. Spacecraft program offices at Space Division are required by regulation to include position management planning in both prelaunch and orbital phases of spacecraft development and operation.

Davis, R.↗
NASA NTRS1983

The rotational velocities of a sample of Herbig Ae/Be stars

Rotational velocity estimates are presented for 15 Herbig Ae/Be stars. Those objects with nominal optical spectral types between B5 and A0 show a frequency distribution of v sin i values significantly different from that of normal Be stars in this spectral type range; the Herbig emission stars must have significantly smaller intrinsic rotational velocities. Herbig emission stars of types B0-B5 cannot be distinguished from normal Be stars on the basis of rotational velocity alone.

Davis, R.↗
NASA NTRS1983

Constraints on the inclination and masses of the HDE 226868/Cygnus X-1 system from the observations

Analyses of two high-dispersions IUE spectra of HDE 226868 (the optical counterpart of Cygnus X-1) are combined with studies of low-dispersion IUE spectra to provide a more accurate determination of the variation of C IV stellar wind absorption as a function of orbital phase. By incorporating these observational results into an analysis of the structure of the X-ray ionization cavity in the stellar wind, it is found that the orbital inclination must lie between 36 and 67 deg, leading to a mass for the compact object between 5.7 and 11.2 solar masses.

Davis, R.↗
NASA NTRS1979

Chromospheres of the active dwarf binaries EQ Pegasi and Xi Bootis

Ultraviolet spectroscopic measurements of the M dwarf binary EQ Peg and the G8 V star Xi Boo A have been made with the International Ultraviolet Explorer satellite. High-temperature emission lines (N V, C IV, Si IV) are present with similar strengths in both stars. The surface fluxes of chromospheric and transition-region lines are enhanced relative to those of normal main-sequence stars and are comparable to those observed in solar active regions. If inhomogeneities are present, the surface fluxes may be markedly higher than the derived values. It is likely that the emission observed from EQ Peg was not the result of major flare activity; however, the quiescent radiative losses observed in the ultraviolet are comparable to the time-averaged optical flare losses. The similarity of the line emissions of active dwarfs of diverse spectral types suggests that the character of the transition region is independent of the stellar effective temperature.

Hartmann, L.↗
NASA NTRS1979

Chromospheres and coronae of late-type stars

IUE short wavelength (1150-2000 A) spectra of late-type dwarfs, giant, and supergiant stars show a variety of emission features varying in excitation from about 10,000 K to about 3 x 10 to the 5th K. High excitation species are found most strongly in main sequence stars. Dwarf stars with active chromospheres (e.g., Xi Boo) and flare stars (EQ Peg) show enhancement of surface flux as compared to the quiet sun; binary systems of W UMa and RS CVn types show even larger surface fluxes. The enhancement increases with temperature of formation much like a solar active region. The presence of high excitation species in the giant and supergiant stars suggests that parameters other than effective temperature and luminosity are important in establishing a transition region and corona.

Dupree, A. K.↗
NASA NTRS1978

Remote sensing applications to hydrologic modeling in the southern Sierra Nevada and portions of the San Joaquin Valley, volume 1

The author has identified the following significant results. Characteristics of LANDSAT MSS imagery present problems in using satellite radiation measurements to estimate the shortwave albedo of an alpine snow cover. Every 15 minute USGS quadrangle contains over 100,000 pixels which poses a computation problem if each pixel is to be evaluated individually. The sampling interval may be sufficiently great to mask some effects of terrain and vegetation on reflectance. Three frames of LANDSAT imagery are needed for complete coverage of the study area, yet less than one third of the area coverage from each frame covers an area of interest. Because of distortions inherent in the imagery, information regarding spacecraft altitude, attitude, and position must be statistically derived with respect to ground control points in the image whose geodetic locations are known. An inspection of shade points indicates that up to one third of the most heavily snow covered areas may saturate in bands 4 through 6. LANDSAT's 9 day repeat cycle is not optimum for snow cover reflectance modeling because the most pronounced changes in albedo occur most nearly following a new snowfall. Such a snowfall, occurring between overpasses, is inadequately represented by extrapolation from the previous overpasses.

Dozier, J.↗
NASA NTRS1977

Remote sensing applications to hydrologic modeling

An energy balance snowmelt model for rugged terrain was devised and coupled to a flow model. A literature review of remote sensing applications to hydrologic modeling was included along with a software development outline.

Dozier, J.↗
NASA NTRS1977

Bending and torsional vibrations of open tube booms on spinning spacecraft

The mathematical formulation is presented of the coupled bending and twisting equations of motion for open tube booms in spinning spacecraft. The equations are applicable to a general class of open tube booms whose shear center does not coincide with the centroid of the cross section. The emphasis in this paper is on the treatment of the coupled bending and twisting motions. The equations of motion of the center of mass are provided in other references. The results of a simulation of the bending and twisting motion of a circular cross-section boom having a small longitudinal slot on a spinning spacecraft is provided. The simulation demonstrates that the centrifugal forces will induce twisting motion due to offset shear center.

Juang, J. N.↗
NASA NTRS1975

Ambient Atmospheric Hydrocarbon Content as Determined by Gas Chromatographic Techniques from Rural Tidewater Virginia in Late Spring 1974

In an attempt to ascertain the naturally generated hydrocarbon contribution to the air quality of the Hampton Roads region of Tidewater Virginia, a series of 27 air samples was obtained in two rural locations during late spring of 1974. These samples were analyzed for their hydrocarbon content (carbon number range C5 to C10) using gas chromatographic techniques. The thirty different hydrocarbon species were identified and monitored in the experiment. Preliminary analysis of the data indicates an average concentration of 397 parts per billion by weight (carbon) for the total non-methane hydrocarbon loading for C5 to C10 during the experiment. This value exceeds the National Primary Air Quality Standards as set by the Environmental Protection Agency.

Copeland, G. E.↗
NASA NTRS1975

AST-6/CSM training console operations manual

The ATS-6/Command Service Module Training Console houses, controls, and cools telecommunication subsystems during support of ASTP test programs. The function of each switch on the power control and mode control panels is described along with the input functions on the stimulus input panel. The switch settings for each mode of operation are presented.

Davis, R.↗