Note: This page contains sample records for the topic vertical closed orbit from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Orbits Close to Asteroid 4769 Castalia  

Microsoft Academic Search

We use a radar-derived physical model of 4769 Castalia (1989 PB) to investigate close orbit dynamics around that kilometer-sized, uniformly rotating asteroid. Our methods of analysis provide a basis for systematic studies of particle dynamics close to any uniformly rotating asteroid.We establish that a Jacobi integral exists for particles orbiting this asteroid, examine the attendant zero-velocity surfaces, find families of

D. J. Scheeres; S. J. Ostro; R. S. Hudson; R. A. Werner

1996-01-01

2

Orbits Close to Asteroid 4769 Castalia  

NASA Technical Reports Server (NTRS)

We use a radar-derived physical model of 4769 Castalia (1989 PB) to investigate close orbit dynamics around that kilometer- sized, uniformly rotating asteroid. Our methods of analysis provide a basis for systematic studies of particle dynamics close to any uniformly rotating asteroid. We establish that a Jacobi integral exists for particles orbiting this asteroid, examine the attendant zero-velocity surfaces, find families of periodic orbits, and determine their stability. All synchronous orbits and direct orbits within approx. 3 mean radii of Castalia are unstable and are subject to impact or escape from Castalia. Retrograde orbits are mostly stable and allow particles to orbit close to the asteroid surface. We derive a model which allows us to predict the escape conditions of a particle in orbit about Castalia and the (temporary) capture conditions for a hyperbolic interloper. Orbits within 1.5 km of Castalia are subject to immediate ejection from the system. Hyperbolic orbits with a V(sub infinity) less than 0.4 m/sec can potentially be captured by Castalia if their periapsis radius Is within approx. 2 km. For Castalia this capture region is small, but the results also apply to larger asteroids whose capture regions would also be larger. We determine bounds on ejecta speeds which either ensure ejecta escape or re-impact as functions of location on Castalia's surface. The speeds that ensure escape range from 0.28 to 0.84 m/sec and the speeds that ensure re-impact range from 0 to 0.18 m/sec. Speeds between these two bounds lead either to escape, re-impact, or potentially finite-time stable orbits. We develop a simple criterion which can establish whether a particle could have been ejected from the asteroid in the past and if it will impact the surface in the future.

Scheeres, D. J.; Ostro, S. J.; Hudson, R. S.; Werner, R. A.

1996-01-01

3

Orbits Close to Asteroid 4769 Castalia  

NASA Astrophysics Data System (ADS)

We use a radar-derived physical model of 4769 Castalia (1989 PB) to investigate close orbit dynamics around that kilometer-sized, uniformly rotating asteroid. Our methods of analysis provide a basis for systematic studies of particle dynamics close to any uniformly rotating asteroid. We establish that a Jacobi integral exists for particles orbiting this asteroid, examine the attendant zero-velocity surfaces, find families of periodic orbits, and determine their stability. All synchronous orbits and direct orbits within ˜3 mean radii of Castalia are unstable and are subject to impact or escape from Castalia. Retrograde orbits are mostly stable and allow particles to orbit close to the asteroid surface. We derive a model which allows us to predict the escape conditions of a particle in orbit about Castalia and the (temporary) capture conditions for a hyperbolic interloper. Orbits within 1.5 km of Castalia are subject to immediate ejection from the system. Hyperbolic orbits with a V?< 0.4 m/sec can potentially be captured by Castalia if their periapsis radius is within ˜2 km. For Castalia this capture region is small, but the results also apply to larger asteroids whose capture regions would also be larger. We determine bounds on ejecta speeds which either ensure ejecta escape or re-impact as functions of location on Castalia's surface. The speeds that ensure escape range from 0.28 to 0.84 m/sec and the speeds that ensure re-impact range from 0 to 0.18 m/sec. Speeds between these two bounds lead either to escape, re-impact, or potentially finite-time stable orbits. We develop a simple criterion which can establish whether a particle could have been ejected from the asteroid in the past and if it will impact the surface in the future.

Scheeres, D. J.; Ostro, S. J.; Hudson, R. S.; Werner, R. A.

1996-05-01

4

Closed Orbit Distortion and the Beam-Beam Interaction  

SciTech Connect

We study the applicability of beam-beam deflection techniques as a tuning tool for the SLAC/LBL/LLNL B factory, PEP-II. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, we calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the IP, provide distinct coordinate- or frequency-space signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed.

Furman, M.; Chin, Y.; Eden, J.; /LBL, Berkeley; Kozanecki, W.; /DAPNIA, Saclay /SLAC; Tennyson, J.L.; Ziemann, V.; /SLAC

2007-02-23

5

Closed orbit distortion and the beam-beam interaction  

SciTech Connect

We study the applicability of beam-beam deflection techniques as a tuning tool for the SLAC/LBL/LLNL B factory, PEP-II. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, we calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the IP, provide distinct coordinate- or frequency-space signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed.

Furman, M.; Chin, Y.H.; Eden, J. [Lawrence Berkeley Lab., CA (United States); Kozanecki, W. [CEA Centre d`Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)]|[Stanford Linear Accelerator Center, Menlo Park, CA (United States); Tennyson, J.; Ziemann, V. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

1992-06-01

6

Beam-Beam Diagnostics from Closed-Orbit Distortion  

SciTech Connect

The authors study the applicability of beam-beam deflection techniques as a tuning tool for asymmetric B factories, focusing on PEP-II as an example. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, they calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the interaction point (IP), provide distinct signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed. Because of their two-ring structure, asymmetric B factories are likely to require more diagnostics and feedback mechanisms than single-ring colliders in order to guarantee head-on collisions. In addition to the traditional techniques, however, the independence of the two beams allows one to envisage other kinds of beam diagnostics. In this article they investigate one such possibility, by looking at the closed orbit distortion produced by the beam-beam interaction when the beams do not collide exactly head-on. They base this investigation on an analytic model and strong-strong multiparticle simulations. Although the discussion uses the PEP-II design as an example, the conclusion is that this technique is quite a promising diagnostics tool for asymmetric colliders in general.

Furman, M.; Chin, Y.-H.; Eden, J.; Kozanecki, W.; Tennyson, J.; Ziemann, V.

1992-07-01

7

Dynamics of Orbits Close to Asteroid 4179 Toutatis  

Microsoft Academic Search

We use a radar-derived physical model of 4179 Toutatis (975870) to investigate close-orbit dynamics around that irregularly shaped, non-principal-axis rotator. The orbital dynamics about this body are markedly different than the dynamics about uniformly rotating asteroids. The results of this paper are generally applicable to orbit dynamics about bodies in a non-principal-axis rotation state. The radar results support the hypothesis

D. J. Scheeres; S. J. Ostro; R. S. Hudson; E. M. DeJong; S. Suzuki

1998-01-01

8

Influence of quantum defects on recurrence strengths of closed orbits  

SciTech Connect

Experimentally obtained Stark-recurrence spectra taken at low principal quantum numbers show unusual degrees of orbit profile asymmetry. To clearly illustrate the semiclassical mechanisms behind this behavior a numerical experiment is performed where orbit profiles (recurrence strength as a function of scaled energy) are found from computed Stark spectra. These spectra are generated for a wide range of quantum defects assuming a highly simplified excitation and core structure which represents a semiclassical system restricted to s-wave scattering. It is noted that at low quantum numbers, the expected dominant nonhydrogenic feature of recurrence spectra is scattered orbits whose scaled actions are unresolved from existing hydrogenic orbits. The semiclassical orbit profiles obtained from absorption spectra are compared with semiclassical closed-orbit theory. Closed-orbit theory successfully predicts the systematic shifting of recurrence strength as a function of quantum defect. In the limited parameter space investigated it is found that the distribution of recurrence strength is influenced primarily by interference with scattered combinations containing a primitive orbit repetition. The systematic shifting of recurrence strength as a function of quantum defect is attributed to a relative phase shift between the contributing orbits.

Keeler, M. L. [Physics Department, University of Minnesota, Morris, Minnesota 56267 (United States)

2007-11-15

9

Vertical orbit excursion fixed field alternating gradient accelerators  

NASA Astrophysics Data System (ADS)

Fixed field alternating gradient (FFAG) accelerators with vertical orbit excursion (VFFAGs) provide a promising alternative design for rings with fixed-field superconducting magnets. They have a vertical magnetic field component that increases with height in the vertical aperture, yielding a skew quadrupole focusing structure. Scaling-type VFFAGs are found with fixed tunes and no intrinsic limitation on momentum range. This paper presents the first multiparticle tracking of such machines. Proton driver rings to accelerate the 800 MeV beam from the ISIS synchrotron are presented, in terms of both magnet field geometry and longitudinal behavior during acceleration with space charge. The 12 GeV ring produces an output power of at least 2.18 MW. Possible applications of VFFAGs to waste transmutation, hadron therapy, and energy-recovery electron accelerators are also discussed.

Brooks, Stephen

2013-08-01

10

Orbital stability of systems of closely-spaced planets  

NASA Astrophysics Data System (ADS)

An investigation of the stability of systems of 1 M (Earth-mass) bodies orbiting a Sun-like star has been conducted for virtual times reaching 10 billion years. For the majority of the tests, a symplectic integrator with a fixed timestep of between 1 and 10 days was employed; however, smaller timesteps and a Bulirsch-Stoer integrator were also selectively utilized to increase confidence in the results. In most cases, the planets were started on initially coplanar, circular orbits, and the longitudinal initial positions of neighboring planets were widely separated. The ratio of the semimajor axes of consecutive planets in each system was approximately uniform (so the spacing between consecutive planets increased slowly in terms of distance from the star). The stability time for a system was taken to be the time at which the orbits of two or more planets crossed. Our results show that, for a given class of system (e.g., three 1 M planets), orbit crossing times vary with planetary spacing approximately as a power law over a wide range of separation in semimajor axis. Chaos tests indicate that deviations from this power law persist for changed initial longitudes and also for small but non-trivial changes in orbital spacing. We find that the stability time increases more rapidly at large initial orbital separations than the power-law dependence predicted from moderate initial orbital separations. Systems of five planets are less stable than systems of three planets for a specified semimajor axis spacing. Furthermore, systems of less massive planets can be packed more closely, being about as stable as 1 M planets when the radial separation between planets is scaled using the mutual Hill radius. Finally, systems with retrograde planets can be packed substantially more closely than prograde systems with equal numbers of planets.

Smith, Andrew W.; Lissauer, Jack J.

2009-05-01

11

Optimal transfer between close near-circular orbits  

NASA Technical Reports Server (NTRS)

A nonlinear analysis is carried out for the optimal transfer between close near-circular noncoplanar orbits with no limit on time. The degeneracy of the linear analyses of Marec and Edelbaum is, thereby, removed and with the aid of a generalized Jacobi test, it is established that the minimum-impulse transfer requires, at most, three impulses. A field of extremals is generated in an orbit element space starting with the initial state and anticipated adjoint variables and integrating these variables by using the optimal thrust control law that maximizes the variational Hamiltonian. The nonoptimality of any four-impulse strategy is determined numerically by observing the reflection of every extremal from either an envelope (conjugate point test) or a switching surface on or before the application of the fourth impulse. This test is carried out in Regions I, II, and III of Marec, as well as the special transition region of Breakwell near the boundary of Region III.

Kechichian, J.

1981-01-01

12

Equilibrium, stability, and orbital evolution of close binary systems  

NASA Technical Reports Server (NTRS)

We present a new analytic study of the equilibrium and stability properties of close binary systems containing polytropic components. Our method is based on the use of ellipsoidal trial functions in an energy variational principle. We consider both synchronized and nonsynchronized systems, constructing the compressible generalizations of the classical Darwin and Darwin-Riemann configurations. Our method can be applied to a wide variety of binary models where the stellar masses, radii, spins, entropies, and polytropic indices are all allowed to vary over wide ranges and independently for each component. We find that both secular and dynamical instabilities can develop before a Roche limit or contact is reached along a sequence of models with decreasing binary separation. High incompressibility always makes a given binary system more susceptible to these instabilities, but the dependence on the mass ratio is more complicated. As simple applications, we construct models of double degenerate systems and of low-mass main-sequence star binaries. We also discuss the orbital evoltuion of close binary systems under the combined influence of fluid viscosity and secular angular momentum losses from processes like gravitational radiation. We show that the existence of global fluid instabilities can have a profound effect on the terminal evolution of coalescing binaries. The validity of our analytic solutions is examined by means of detailed comparisons with the results of recent numerical fluid calculations in three dimensions.

Lai, Dong; Rasio, Frederic A.; Shapiro, Stuart L.

1994-01-01

13

Equilibrium, stability, and orbital evolution of close binary systems  

NASA Astrophysics Data System (ADS)

We present a new analytic study of the equilibrium and stability properties of close binary systems containing polytropic components. Our method is based on the use of ellipsoidal trial functions in an energy variational principle. We consider both synchronized and nonsynchronized systems, constructing the compressible generalizations of the classical Darwin and Darwin-Riemann configurations. Our method can be applied to a wide variety of binary models where the stellar masses, radii, spins, entropies, and polytropic indices are all allowed to vary over wide ranges and independently for each component. We find that both secular and dynamical instabilities can develop before a Roche limit or contact is reached along a sequence of models with decreasing binary separation. High incompressibility always makes a given binary system more susceptible to these instabilities, but the dependence on the mass ratio is more complicated. As simple applications, we construct models of double degenerate systems and of low-mass main-sequence star binaries. We also discuss the orbital evoltuion of close binary systems under the combined influence of fluid viscosity and secular angular momentum losses from processes like gravitational radiation. We show that the existence of global fluid instabilities can have a profound effect on the terminal evolution of coalescing binaries. The validity of our analytic solutions is examined by means of detailed comparisons with the results of recent numerical fluid calculations in three dimensions.

Lai, Dong; Rasio, Frederic A.; Shapiro, Stuart L.

1994-03-01

14

Kinematics of relative motion of two space bodies in close almost circular orbits  

NASA Astrophysics Data System (ADS)

The paper is dedicated to a qualitative investigation of relative motion and close convergences of two space bodies located in close almost circular orbits. This problem is topical due to the asteroid hazard originating from the NEA group asteroids located in the orbits close to that of the Earth. P.E. El’yasberg [1] considered similar problems in the 1960s in relation to Earth’s artificial satellites in close almost circular orbits.

Prokhorenko, V. I.

2010-06-01

15

Application of closed-orbit theory to the Rydberg hydrogen atom near a metal surface  

Microsoft Academic Search

Using closed-orbit theory, we study the classical motion and calculate the photoabsorption spectra and recurrence spectra of the Rydberg hydrogen atom near a metal surface. The results show that when the atom-surface distance is close to the critical value dc, the number of the closed orbits is the greatest. For d > dc, with the increase of the distance d,

Dehua Wang; M. L. Du; Shenglu Lin

2006-01-01

16

Weighted SVD algorithm for close-orbit correction and 10 Hz feedback in RHIC  

SciTech Connect

Measurements of the beam position along an accelerator are typically treated equally using standard SVD-based orbit correction algorithms so distributing the residual errors, modulo the local beta function, equally at the measurement locations. However, sometimes a more stable orbit at select locations is desirable. In this paper, we introduce an algorithm for weighting the beam position measurements to achieve a more stable local orbit. The results of its application to close-orbit correction and 10 Hz orbit feedback are presented.

Liu C.; Hulsart, R.; Marusic, A.; Michnoff, R.; Minty, M.; Ptitsyn, V.

2012-05-20

17

Observations of vertical motions in the troposphere and lower stratosphere using three closely spaced ST radars  

Microsoft Academic Search

Three closely spaced vertical clear-air radar sites were installed and operated in Southern France during the Alpex experiment. This United States-France cooperative effort was designed to determine atmospheric wave parameters in the troposphere and lower stratosphere. In this report we describe the experiment, give an overview of the data and present vertical wind speed power spectra. We also show spatial

W. L. Ecklund; B. B. Balsley; D. A. Carter; A. C. Riddle; M. Crochet; R. Garello

1985-01-01

18

Interpretation of the Kohn-Sham orbital energies as approximate vertical ionization potentials  

Microsoft Academic Search

Theoretical analysis and results of calculations are put forward to interpret the energies -?k of the occupied Kohn-Sham (KS) orbitals as approximate but rather accurate relaxed vertical ionization potentials (VIPs) Ik. Exact relations between ?k and Ik are established with a set of linear equations for the ?k, which are expressed through Ik and the matrix elements ?kresp of a

D. P. Chong; O. V. Gritsenko; E. J. Baerends

2002-01-01

19

Orbit determination of close binary systems using lucky imaging  

NASA Astrophysics Data System (ADS)

We present relative positions of visual binaries observed in 2009 with the FastCam 'lucky-imaging' camera mounted on the 1.5-m Carlos Sánchez Telescope at the Observatorio del Teide. We obtained 424 CCD observations (averaged in 198 mean relative positions) of 157 binaries with angular separations in the range 0.14-15.40 arcsec, with a median separation of 0.51 arcsec. For a given system, each CCD image represents the sum of the best 10-25 per cent images from 1000-5000 short-exposure frames. Derived internal errors were 7 mas in ? and 1?2 (9 mas) in ?. When comparing to systems with very well known orbits, we find that the rms deviation in ? residuals is 23 mas, while the rms deviation in ? residuals is 0?73/?. We confirmed 18 Hipparcos binaries and we report new companions to BVD 36 A and J 621 B. For binaries with preliminary orbital parameters, the relative radial velocity was estimated as well. We also present four new revised orbits computed for LDS 873, BU 627 A-BC, BU 628 and HO 197 AB. This work discusses the first results on visual binaries using the FastCam lucky-imaging camera.

Rica, F. M.; Barrena, R.; Vázquez, G.; Henríquez, J. A.; Hernández, F.

2012-01-01

20

A closed loop GPS-based orbit trim system for Gravity Probe B  

Microsoft Academic Search

An onboard closed loop navigation and control system capable of executing extremely precise orbit maneuvers is described. In particular, a system to adjust the orbit of the Gravity Probe B (GP-B) spacecraft is presented. This onboard system relies on the Global Positioning System (GPS) to provide navigation information directly to the vehicle, thus alleviating the need for ground support. GP-B

Penina Axelrad

1991-01-01

21

Constant covariance in local vertical coordinates for near-circular orbits  

NASA Technical Reports Server (NTRS)

A method is presented for devising a covariance matrix that either remains constant or grows in keeping with the presence of a period error in a rotating local-vertical coordinate system. The solution presented may prove useful in the initialization of simulation covariance matrices for near-circular-orbit problems. Use is made of the Clohessy-Wiltshire equations and the travelling-ellipse formulation.

Shepperd, Stanley W.

1991-01-01

22

Interpretation of the Kohn–Sham orbital energies as approximate vertical ionization potentials  

Microsoft Academic Search

Theoretical analysis and results of calculations are put forward to interpret the energies ?&egr;k of the occupied Kohn–Sham (KS) orbitals as approximate but rather accurate relaxed vertical ionization potentials (VIPs) Ik. Exact relations between &egr;k and Ik are established with a set of linear equations for the &egr;k, which are expressed through Ik and the matrix elements &egr;kresp of a

D. P. Chong; O. V. Gritsenko; E. J. Baerends

2002-01-01

23

Horocyclic Orbits on $\\\\Gamma(1)\\\\frontslash\\\\mathcal{H}$, \\\\ Closed and Otherwise  

Microsoft Academic Search

This paper studies certain horocyclic orbits on $\\\\Gamma(1)\\\\frontslash\\\\mathcal{H}$. In the first instance we examine horocycles defined using the pencil of circles whose common point (in the words of the Nielsen-Fenchel manuscript is $\\\\infty$. The orbits involved in this case are closed and long - judged by arc length between two points compared to the hyperbolic distance between them. We are

Marvin Knopp; Mark Sheingorn

2010-01-01

24

The effect of beam-cavity interaction on the closed orbit and the beam shape  

NASA Astrophysics Data System (ADS)

Analytic formulas for the closed orbit distortion (COD) and the beam shape distortion (BSD) due to the beam-cavity interaction are obtained with the cumulative, i.e., the multi-turn effect taken into account. The formulas are extended so that they are applicable to storage rings with many cavities and several counter-rotating bunches. In particular, the COD and the BSD of the bunches at the collision point are estimated for the case of TRISTAN. The effect of the COD and the BSD on the luminosity is found to be small. The beam-cavity interaction causes a difference between the closed orbits of the electron bunches and the positron bunches of almost 10% of the closed orbit due to magnet imperfections.

Hirata, Kohji; Suzuki, Toshio; Gluckstern, Robert L.

1984-12-01

25

Early Excitation of Spin-Orbit Misalignments in Close-in Planetary Systems  

NASA Astrophysics Data System (ADS)

Continued observational characterization of transiting planets that reside in close proximity to their host stars has shown that a substantial fraction of such objects possess orbits that are inclined with respect to the spin axes of their stars. Mounting evidence for the wide-spread nature of this phenomenon has challenged the conventional notion that large-scale orbital transport occurs during the early epochs of planet formation and is accomplished via planet-disk interactions. However, recent work has shown that the excitation of spin-orbit misalignment between protoplanetary nebulae and their host stars can naturally arise from gravitational perturbations in multi-stellar systems as well as magnetic disk-star coupling. In this work, we examine these processes in tandem. We begin with a thorough exploration of the gravitationally facilitated acquisition of spin-orbit misalignment and analytically show that the entire possible range of misalignments can be trivially reproduced. Moreover, we demonstrate that the observable spin-orbit misalignment only depends on the primordial disk-binary orbit inclination. Subsequently, we augment our treatment by accounting for magnetic torques and show that more exotic dynamical evolution is possible, provided favorable conditions for magnetic tilting. Cumulatively, our results suggest that observed spin-orbit misalignments are fully consistent with disk-driven migration as a dominant mechanism for the origin of close-in planets.

Spalding, Christopher; Batygin, Konstantin

2014-07-01

26

Determination of the operation range of a vertical two-phase closed thermosyphon  

NASA Astrophysics Data System (ADS)

A comprehensive model, proposed for a vertical two-phase closed thermosyphon (TPCT) by the present authors, is further developed by utilizing the criteria for dryout, flooding and boiling limits to investigate the effects of filling ratio on them together, while the available models can just consider one or two limits of them. A new concept named dryout ratio is proposed, which can be used for predicting dryout limit. The empirical correlation and the empirical value, provided by other researchers, are used for predicting flooding and boiling limit, respectively. The experiments with nitrogen as working fluid are performed, and compared with the calculations. The maximum filling ratio is introduced, beyond which the liquid could be carried to condenser and the heat transfer performance can be deteriorated. And then the closed operation range of a vertical TPCT is finally determined, which has not been reported before. The effects of operating pressure and geometries on the range are also analyzed.

Jiao, B.; Qiu, L. M.; Gan, Z. H.; Zhang, X. B.

2012-06-01

27

Behavior of nonclassical recurrence amplitudes near closed-orbit bifurcations in atoms  

SciTech Connect

We report an experimental and computational study of the energy dependence of nonclassical paths in atoms near bifurcations. The experiment employs scaled energy spectroscopy to measure the amplitudes of nonclassical orbits in helium singlet and triplet Stark Rydberg states (20close to bifurcations. We have also calculated this behavior for hydrogen. In both cases, the amplitude dependence on energy, just below a bifurcation, is consistent with an exponential function, in accord with theoretical predictions. Five different nonclassical paths have been studied and, in the case of helium but not hydrogen, the effect of interference between real and ghost orbits is found to produce oscillations in the exponential decay with closed orbit type. In the case of hydrogen, the n dependence of the decay exponent has been investigated and a linear relationship is found.

Keeler, M.L.; Flores-Rueda, Heric; Morgan, T. J.; Shaw, J. [Wesleyan University, Middletown, Connecticut 06457 (United States); Louisiana School of Math, Science and the Arts, 715 College Ave., Natchitoches, Louisiana 71457 (United States)

2004-01-01

28

Photoabsorption to Stark Rydberg States of Heavy Noble Gas Atoms: Testing Limits of Closed Orbit Theory  

Microsoft Academic Search

The selective dramatic effects of a dc electric field on the photoabsorption spectrum of Rydberg states and the associated recurrence strengths and closed orbits are studied in heavy noble gas atoms. Using collinear atom-laser beam spectroscopy, complex scaled-energy photoabsorption spectra are mapped experimentally in high resolution for pi and sigma transitions from the ns[3\\/2] and ns[1\\/2] metastable states, formed by

Heric Flores-Rueda; Matthew L. Keeler; David Wright; Thomas J. Morgan

2003-01-01

29

Digital closed orbit feedback system for the Advanced Photon Source storage ring  

Microsoft Academic Search

The Advanced Photon Source (APS) is a dedicated third-generation synchrotron light source with a nominal energy of 7 GeV and a circumference of 1104 m. The closed-orbit feedback system for the APS storage ring employs unified global and local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the

Y. Chung; D. Barr; G. Decker; J. Galayda; F. Lenkszus; A. Lumpkin; A. J. Votaw

1996-01-01

30

Measurement Variability of Vertical Scanning Interferometry Tool Used for Orbiter Window Defect Assessment  

NASA Technical Reports Server (NTRS)

The ability to sufficiently measure orbiter window defects to allow for window recertification has been an ongoing challenge for the orbiter vehicle program. The recent Columbia accident has forced even tighter constraints on the criteria that must be met in order to recertify windows for flight. As a result, new techniques are being investigated to improve the reliability, accuracy and resolution of the defect detection process. The methodology devised in this work, which is based on the utilization of a vertical scanning interferometric (VSI) tool, shows great promise for meeting the ever increasing requirements for defect detection. This methodology has the potential of a 10-100 fold greater resolution of the true defect depth than can be obtained from the currently employed micrometer based methodology. An added benefit is that it also produces a digital elevation map of the defect, thereby providing information about the defect morphology which can be utilized to ascertain the type of debris that induced the damage. However, in order to successfully implement such a tool, a greater understanding of the resolution capability and measurement repeatability must be obtained. This work focused on assessing the variability of the VSI-based measurement methodology and revealed that the VSI measurement tool was more repeatable and more precise than the current micrometer based approach, even in situations where operator variation could affect the measurement. The analysis also showed that the VSI technique was relatively insensitive to the hardware and software settings employed, making the technique extremely robust and desirable

Padula, Santo, II

2009-01-01

31

USING ORBITAL EFFECTS TO BREAK THE CLOSE/WIDE DEGENERACY IN BINARY-LENS MICROLENSING EVENTS  

SciTech Connect

Microlensing can provide an important tool to study binaries, especially those composed of faint or dark objects. However, accurate analysis of binary-lens light curves is often hampered by the well-known degeneracy between close (s < 1) and wide (s > 1) binaries, which can be very severe due to an intrinsic symmetry in the lens equation. Here, s is the normalized projected binary separation. In this paper, we propose a method that can resolve the close/wide degeneracy using the effect of a lens orbital motion on lensing light curves. The method is based on the fact that the orbital effect tends to be important for close binaries while it is negligible for wide binaries. We demonstrate the usefulness of the method by applying it to an actually observed binary-lens event MOA-2011-BLG-040/OGLE-2011-BLG-0001, which suffers from severe close/wide degeneracy. From this, we are able to uniquely specify that the lens is composed of K- and M-type dwarfs located {approx}3.5 kpc from the Earth.

Shin, I.-G.; Choi, J. Y.; Han, C. [Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of)] [Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of); Sumi, T. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan)] [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)] [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Gould, A. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)] [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Abe, F.; Furusawa, K.; Itow, Y.; Masuda, K.; Matsubara, Y.; Miyake, N. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan)] [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Bennett, D. P. [Department of Physics, University of Notre Damey, Notre Dame, IN 46556 (United States)] [Department of Physics, University of Notre Damey, Notre Dame, IN 46556 (United States); Bond, I. A.; Ling, C. H. [Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland (New Zealand)] [Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland (New Zealand); Botzler, C. S.; Freeman, M. [Department of Physics, University of Auckland, Private Bag 92019, Auckland (New Zealand)] [Department of Physics, University of Auckland, Private Bag 92019, Auckland (New Zealand); Chote, P.; Harris, P. [School of Chemical and Physical Sciences, Victoria University, Wellington (New Zealand)] [School of Chemical and Physical Sciences, Victoria University, Wellington (New Zealand); Fukui, A. [Okayama Astrophysical Observatory, National Astronomical Observatory, 3037-5 Honjo, Kamogata, Asakuchi, Okayama 719-0232 (Japan)] [Okayama Astrophysical Observatory, National Astronomical Observatory, 3037-5 Honjo, Kamogata, Asakuchi, Okayama 719-0232 (Japan); Collaboration: MOA Collaboration; OGLE Collaboration; and others

2013-02-10

32

Spacecraft formation-keeping using a closed-form orbit propagator and optimization technique  

NASA Astrophysics Data System (ADS)

In this paper, a simple method for modeling the relative orbital motion of multiple spacecraft and their formation-keeping control strategy is presented. Power series and trigonometric functions are used to express the relative orbital motion between the member spacecraft. Their coefficients are obtained using least square regression such that the difference between the exact numerically integrated position vector and the approximate vector obtained from the closed-form propagator is minimized. Then, this closed-form orbit propagator and optimization technique is used to plan a series of impulsive maneuvers which maintain the formation configuration within a specified limit. As an example, formation-keeping of four spacecraft is investigated. The motion projected onto the local horizontal plane (along- and cross-track plane) is a circle with the leader satellite located at its center and follower satellites positioned circumferentially. The radial distance between the leader and the followers, and the relative phase angles between the followers are controlled. Results from the nonlinear simulation are presented.

No, T. S.; Lee, J. G.; Cochran, J. E., Jr.

2009-08-01

33

Use of the Amplatzer ASD Occluder for Closing a Persistent Left Vertical Vein  

SciTech Connect

We report the case of a very large anomalous connection of the veins draining the upper lobe of the left lung to both the left-sided vertical vein and the left atrium, associated with mild rheumatic mitral valve stenosis, in which the atrial septum was intact and the remaining venous system, including the coronary sinus, was otherwise normal (a variant of Lutembacher's syndrome). In order to abolish the left-to-right shunting, a transcatheter approach to close this venous structure was successfully attempted using an Amplatzer ASD Occluder device. The technical aspects and the alternative options of performing a procedure with a device for a purpose outside the scope of its approved label are discussed.

Zanchetta, Mario, E-mail: emodinacit@ulss15.pd.it; Zennaro, Marco; Zecchel, Roberto; Mancuso, Daniela; Pedon, Luigi [Ospedale Civile, Dipartimento di Malattie Cardiovascolari (Italy)

2009-05-15

34

Effects of orbit squeezing on ion transport processes close to magnetic axis  

SciTech Connect

It is shown that ion thermal conductivity close to the magnetic axis in tokamaks is reduced by a factor of {vert_bar}S{vert_bar}{sup 5/3} if (M{sub i}/M{sub e}){sup 2/3}(T{sub e}/T{sub i}){sup 4/3}/{vert_bar}S{vert_bar}{sup 5/3} {much_gt} 1. Here, S is the orbit squeezing factor, M{sub i}(M{sub e}) is the ion (electron) mass, and T{sub i}(Te{sub e}) is the ion (electron) temperature. The reduction reflects both the increase of the fraction of trapped particles by a factor of {vert_bar}S{vert_bar}{sup 1/3}, and the decrease of the orbit size in units of the poloidal flux {psi} by a factor of {vert_bar}S{vert_bar}{sup 2/3}.

Shaing, K.C.; Hazeltine, R.D. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies; Zarnstorff, M.C. [Princeton Univ., NJ (United States). Plasma Physics Lab.

1997-01-01

35

Closed-shell coupled-cluster theory with spin-orbit coupling  

NASA Astrophysics Data System (ADS)

A two-component closed-shell coupled-cluster (CC) approach using relativistic effective core potentials with spin-orbit coupling included in the post-Hartree-Fock treatment is proposed and implemented at the CC singles and doubles (CCSD) level as well as at the CCSD level augmented by a perturbative treatment of triple excitations [CCSD(T)]. The latter invokes as an additional approximation the neglect of the occupied-occupied and virtual-virtual blocks of the spin-orbit coupling matrix in order to avoid the iterative N7 steps in the treatment of triple excitations. The computational effort of the implemented two-component CC methods is about 10-15 times that of its corresponding nonrelativistic counterpart, which needs to be compared to the by a factor of 32 higher cost for fully relativistic schemes and schemes with spin-orbit coupling included already at the Hartree-Fock self-consistent field (HF-SCF) level. This substantial computational saving is due to the use of real molecular orbitals and real two-electron integrals. Results on 5p-, 6p-, and 7p-block element compounds show that the bond lengths and harmonic frequencies obtained with the present two-component CCSD method agree well with those computed with the CCSD approach including spin-orbit coupling at the HF-SCF level even for the 7p-block element compounds. As for the CCSD(T) approach, high accuracy for 5p- and 6p-block element compounds is retained. However, the difference in bond lengths and harmonic frequencies becomes somewhat more pronounced for the 7p-block element compounds.

Wang, Fan; Gauss, Jürgen; van Wüllen, Christoph

2008-08-01

36

Closed-orbit theory of spatial density oscillations in finite fermion systems.  

PubMed

We investigate the particle and kinetic-energy densities for N noninteracting fermions confined in a local potential. Using Gutzwiller's semiclassical Green function, we describe the oscillating parts of the densities in terms of closed nonperiodic classical orbits. We derive universal relations between the oscillating parts of the densities for potentials with spherical symmetry in arbitrary dimensions and a "local virial theorem" valid also for arbitrary nonintegrable potentials. We give simple analytical formulas for the density oscillations in a one-dimensional potential. PMID:18518516

Roccia, Jérôme; Brack, Matthias

2008-05-23

37

Effect of the electron lenses on the RHIC proton beam closed orbit  

SciTech Connect

We are designing two electron lenses (E-lens) to compensate for the large beam-beam tune spread from proton-proton interactions at IP6 and IP8 in the Relativistic Heavy Ion Collider (RHIC). They will be installed at RHIC IR10. The transverse fields of the E-lenses bending solenoids and the fringe field of the main solenoids will shift the proton beam. We calculate the transverse kicks that the proton beam receives in the electron lens via Opera. Then, after incorporating the simplified E-lens lattice in the RHIC lattice, we obtain the closed orbit effect with the Simtrack Code.

Gu, X.; Luo, Y.; Pikin, A.; Okamura, M.; Fischer, W.; Montag, C.; Gupta, R.; Hock, J.; Jain, A.; Raparia, D.

2011-02-01

38

Strategic optimization of large-scale vertical closed-loop shallow geothermal systems  

NASA Astrophysics Data System (ADS)

Vertical closed-loop geothermal systems or ground source heat pump (GSHP) systems with multiple vertical borehole heat exchangers (BHEs) are attractive technologies that provide heating and cooling to large facilities such as hotels, schools, big office buildings or district heating systems. Currently, the worldwide number of installed systems shows a recurrent increase. By running arrays of multiple BHEs, the energy demand of a given facility is fulfilled by exchanging heat with the ground. Due to practical and technical reasons, square arrays of the BHEs are commonly used and the total energy extraction from the subsurface is accomplished by an equal operation of each BHE. Moreover, standard designing practices disregard the presence of groundwater flow. We present a simulation-optimization approach that is able to regulate the individual operation of multiple BHEs, depending on the given hydro-geothermal conditions. The developed approach optimizes the overall performance of the geothermal system while mitigating the environmental impact. As an example, a synthetic case with a geothermal system using 25 BHEs for supplying a seasonal heating energy demand is defined. The optimization approach is evaluated for finding optimal energy extractions for 15 scenarios with different specific constant groundwater flow velocities. Ground temperature development is simulated using the optimal energy extractions and contrasted against standard application. It is demonstrated that optimized systems always level the ground temperature distribution and generate smaller subsurface temperature changes than non-optimized ones. Mean underground temperature changes within the studied BHE field are between 13% and 24% smaller when the optimized system is used. By applying the optimized energy extraction patterns, the temperature of the heat carrier fluid in the BHE, which controls the overall performance of the system, can also be raised by more than 1 °C.

Hecht-Méndez, J.; de Paly, M.; Beck, M.; Blum, P.; Bayer, P.

2012-04-01

39

Digital closed orbit feedback system for the Advanced Photon Source storage ring  

SciTech Connect

Closed orbit feedback for the Advanced Photon Source (APS) storage ring employs unified global an local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the system will be described. In particular, we will discuss global and local orbit feedback algorithms, PID (proportional, integral, and derivative) control algorithm. application of digital signal processing to compensate for vacuum chamber eddy current effects, resolution of the interaction between global and local systems through decoupling, self-correction of the local bump closure error, user interface through the APS control system, and system performance in the frequency and time domains. The system hardware, including the DSPS, is distributed in 20 VNE crates around the ring, and the entire feedback system runs synchronously at 4-kHz sampling frequency in order to achieve a correction bandwidth exceeding 100 Hz. The required data sharing between the global and local feedback systems is facilitated via the use of fiber-optically-networked reflective memories.

Chung, Y.; Barr, D.; Decker, G.; Galayda, J.; Lenkszus, F.; Lumpkin, A.; Votaw, A.J.

1995-10-20

40

Digital closed orbit feedback system for the advanced photon source storage ring  

SciTech Connect

The Advanced Photon Source (APS) is a dedicated third-generation synchrotron light source with a nominal energy of 7 GeV and a circumference of 1104 m. The closed orbit feedback system for the APS storage ring employs unified global and local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the system will be described in this paper. In particular, we will discuss global and local orbit feedback algorithms, PID (proportional, integral, and derivative) control algorithm, application of digital signal processing to compensate for vacuum chamber eddy current effects, resolution of the interaction between global and local systems through decoupling, self-correction of the local bump closure error, user interface through the APS control system, and system performance in the frequency and time domains. The system hardware including the DSPs is distributed in 20 VME crates around the ring, and the entire feedback system runs synchronously at 4-kHz sampling frequency in order to achieve a correction bandwidth exceeding 100 Hz. The required data sharing between the global and local feedback systems is facilitated via the use of fiber-optically-networked reflective memories.

Chung, Y.; Barr, D.; Decker, G. [and others

1995-12-31

41

A General Closed-Form Solution for the Lunar Reconnaissance Orbiter (LRO) Antenna Pointing System  

NASA Technical Reports Server (NTRS)

The National Aeronautics and Space Administration s (NASA) Lunar Reconnaissance Orbiter (LRO) launched on June 18, 2009 from the Cape Canaveral Air Force Station aboard an Atlas V launch vehicle into a direct insertion trajectory to the Moon LRO, designed, built, and operated by the NASA Goddard Space Flight Center in Greenbelt, MD, is gathering crucial data on the lunar environment that will help astronauts prepare for long-duration lunar expeditions. During the mission s nominal life of one year its six instruments and one technology demonstrator will find safe landing site, locate potential resources, characterize the radiation environment and test new technology. To date, LRO has been operating well within the bounds of its requirements and has been collecting excellent science data images taken from the LRO Camera Narrow Angle Camera (LROC NAC) of the Apollo landing sites have appeared on cable news networks. A significant amount of information on LRO s science instruments is provided at the LRO mission webpage. LRO s Attitude Control System (ACS), in addition to controlling the orientation of the spacecraft is also responsible for pointing the High Gain Antenna (HGA). A dual-axis (or double-gimbaled) antenna, deployed on a meter-long boom, is required to point at a selected Earth ground station. Due to signal loss over the distance from the Moon to Earth, pointing precision for the antenna system is very tight. Since the HGA has to be deployed in spaceflight, its exact geometry relative to the spacecraft body is uncertain. In addition, thermal distortions and mechanical errors/tolerances must be characterized and removed to realize the greatest gain from the antenna system. These reasons necessitate the need for an in-flight calibration. Once in orbit around the moon, a series of attitude maneuvers was conducted to provide data needed to determine optimal parameters to load onboard, which would account for the environmental and mechanical errors at any antenna orientation. The nominal geometry for the HGA involves an outer gimbal axis that is exactly perpendicular to the inner gimbal axis, and a target direction that is exactly perpendicular to the outer gimbal axis. For this nominal geometry, closed-form solutions of the desired gimbal angles are simple to get for a desired target direction specified in the spacecraft body fame. If the gimbal axes and the antenna boresight are slightly misaligned, the nominal closed-form solution is not sufficiently accurate for computing the gimbal angles needed to point at a target. In this situation, either a general closed-form solution has to be developed for a mechanism with general geometries, or a correction scheme has to be applied to the nominal closed-form solutions. The latter has been adopted for Solar Dynamics Observatory (SDO) as can be seen in Reference 1, and the former has been used for LRO. The advantage of the general closed-form solution is the use of a small number of parameters for the correction of nominal solutions, especially in the regions near singularities. Singularities here refer to cases when the nominal closed-form solutions have two or more solutions. Algorithm complexity, however, is the disadvantage of the general closed-form solution.

Shah, Neerav; Chen, J. Roger; Hashmall, Joseph A.

2010-01-01

42

Orbit Uncertainty and Close-Approach Analysis Capabilities of the Horizons On-Line Ephemeris System  

NASA Astrophysics Data System (ADS)

The Horizons On-Line Ephemeris System was initially made available in 1996. It has since been used by 450000 people to generate 700000 high-precision solar system ephemerides and database search results relating to the planets, satellites, and a growing list of asteroids, comets and spacecraft. This database is presently in excess of 90000 objects. The system receives about 23000 requests per month via the three automated access methods (telnet, web and e-mail) described at http://ssd.jpl.nasa.gov/horizons.html. Horizons has recently been extended to perform linearized covariance mappings. This allows users to obtain orbital motion uncertainties of those asteroids and comets for which a covariance is available, as a function of time, in multiple coordinate systems such as the plane-of-sky. Also newly available is an on-line close-approach analysis capability. This provides efficient detection of asteroid and comet approaches to planets and the larger asteroids. For asteroids and comets with a computed covariance, approach quantities such as encounter timing uncertainty are computed. This allows convenient assessment of the quality of close-approach knowledge. Detailed Horizons documentation is available at ftp://ssd.jpl.nasa.gov/pub/ssd/Horizons_doc.ps

Giorgini, J. D.; Chodas, P. W.; Yeomans, D. K.

2001-12-01

43

Tidal perturbations of linear, isentropic oscillations in components of circular-orbit close binaries. I. Synchronously rotating components  

Microsoft Academic Search

The effects of the tidal force exerted by a companion on linear, isentropic oscillations of a uniformly rotating star that is a component of a circular-orbit close binary are studied. In contrast to an earlier perturbation method, which is almost only applicable to polytropic models, the procedure starts from an arbitrary physical model of a spherically symmetric equilibrium star. The

K. Reyniers; P. Smeyers

2003-01-01

44

Closed Form Solutions for Unsteady Free Convection Flow of a Second Grade Fluid over an Oscillating Vertical Plate  

PubMed Central

Closed form solutions for unsteady free convection flows of a second grade fluid near an isothermal vertical plate oscillating in its plane using the Laplace transform technique are established. Expressions for velocity and temperature are obtained and displayed graphically for different values of Prandtl number Pr, thermal Grashof number Gr, viscoelastic parameter ?, phase angle ?? and time ?. Numerical values of skin friction ?0 and Nusselt number Nu are shown in tables. Some well-known solutions in literature are reduced as the limiting cases of the present solutions.

Ali, Farhad; Khan, Ilyas; Shafie, Sharidan

2014-01-01

45

Applicability of orbital data obtained from ISON measurements for prediction and analysis of close encounters on GEO  

NASA Astrophysics Data System (ADS)

Large amount of data is collected within the framework of the ISON project in the KIAM database. The most part of the data is related to objects in GEO region, both operational and not functional. As of the end of 2009 there were 1467 GEO objects for which orbits were maintained on a routine basis. This number includes 892 spacecraft (including 391 under control), 250 upper stages and apogee kick motors (AKMs), 325 fragments and objects of undetermined type. Several new objects are discovering each month. It must be emphasized, that major part of already known non-operational objects in GEO (almost 66 The paper will present various quantity and quality characteristics of obtained measurements and constructed orbits from the point of view of their applicability for prediction and analysis of close encounters on GEO. It is well known that operators of the GEO spacecraft require high level of orbital data quality for making a decision on the need of an evasion manoeuvre in order to avoid unnecessary consumption of fuel. Usually it means that approaching object's orbit accuracy should be at the level of 2-3 km position error for in-track, better than 1-2 km for radial and 0.5-1 km for cross-track direction. The accuracy of measurements which ISON produce is enough to obtain such level of errors at orbit determination and propagation for the majority of GEO objects except the most complex cases of objects with not predictable area-to-mass variations or performing near-continuous, long duration or very frequent manoeuvres. But due to restricted observation time which optical sensors have to observe each individual GEO object it is not easy to keep this level of accuracy for all of objects all the time. So, it is important to understand whether it is feasible to collect some amount of measurements enough for construction of the initial pretty accurate orbit and then to maintain obtained orbit with less amount of measurements taking into account possible uncertainties (caused by varying acceleration due to solar radiation pressure for non operational spacecraft or by unknown orbital manoeuvres performing by the spacecraft under control). With those data we collected from the ISON network we were able to study this question not just theoretically but also practically for that specific observation network we have. We present examples of orbit determination and orbit accuracy estimation for different ob-jects, both under control and not operational. Also, we present results of analysis of several close encounters we discovered during routine work in KIAM. Statistics of close encounters de-pending of given distances and time perio will be presented for overall GEO population. This statistics represents an objective characteristic for the given objects population which do not depends neither of accuracy of orbits nor relation between real and estimated errors of orbit determination. This work is partially supported with RBFR 09-01-00566 and 09-01-13540 grants.

Agapov, Vladimir; Stepanyants, Victor; Khutorovsky, Zakhary; Molotov, Igor

46

Enhancing heat transfer rates from closed-sided, open-topped heat exchangers, each having vertical rectangular fins extending upwards from a horizontal base  

Microsoft Academic Search

The almost two-dimensional steady-state rates of heat loss from arrays of uniformly-spaced vertical rectangular fins, extending upwards--in otherwise stagnant air--from horizontal heated bases, have been measured. (The vertical air gaps between the fins were closed at their sides, by insulated vertical end-barriers.) The effects of various combinations of height, thickness and spacing of the fins, for different base temperatures (in

K. Jambunathan; S. D. Probert; M. J. Shilston

1984-01-01

47

Tidal decay and orbital circularization in close-in two-planet systems  

NASA Astrophysics Data System (ADS)

The motion of two planets around a Sun-like star under the combined effects of mutual interaction and tidal dissipation is investigated. The secular behaviour of the system is analysed using two different approaches. First, we solve the exact equations of motion through the numerical simulation of the system evolution. In addition to the orbital decay and circularization, we show that the final configuration of the system is affected by the shrinking of the inner orbit. Our second approach consists of the analysis of the stationary solutions of mean equations of motion based on a Hamiltonian formalism. We consider the case of a hot super-Earth planet with a more massive outer companion. As a real example, the CoRoT-7 system is analysed, solving the exact and mean equations of motion. The star-planet tidal interaction produces orbital decay and circularization of the orbit of CoRoT-7b. In addition, the long-term tidal evolution is such that the eccentricity of CoRoT-7c is also circularized and a pair of final circular orbits is obtained. A curve in the space of eccentricities can be constructed through the computation of stationary solutions of mean equations including dissipation. The application to the CoRoT-7 system shows that the stationary curve agrees with the result of numerical simulations of exact equations. A similar investigation performed in a super-Earth-Jupiter two-planet system shows that the doubly circular state is accelerated when there is a significant orbital migration of the inner planet, in comparison with previous results where migration is neglected.

Rodríguez, A.; Ferraz-Mello, S.; Michtchenko, T. A.; Beaugé, C.; Miloni, O.

2011-08-01

48

Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets. II. A giant planet in a close-in orbit around the RGB star HIP 63242  

NASA Astrophysics Data System (ADS)

Context. More than 40 planets have been found around giant stars, revealing a lack of systems orbiting interior to ~0.6 AU. This observational fact contrasts with the planetary population around solar-type stars and has been interpreted as the result of the orbital evolution of planets through the interaction with the host star and/or because of a different formation/migration scenario of planets around more massive stars. Aims: We are conducting a radial velocity study of a sample of 166 giant stars aimed at studying the population of close-in planets orbiting post-main sequence stars. Methods: We computed precision radial velocities from multi-epoch spectroscopic data to search for planets around giant stars. Results: We present the discovery of a massive planet around the intermediate-mass giant star HIP 63242. The best Keplerian fit to the data leads to an orbital distance of 0.57 AU, an eccentricity of 0.23 and a projected mass of 9.2 MJ. HIP 63242 b is the innermost planet detected around any intermediate-mass giant star and also the first planet detected in our survey. Based on observations collected at La Silla - Paranal Observatory under programs ID's 085.C-0557, 087.C.0476, 089.C-0524, and 090.C-0345.

Jones, M. I.; Jenkins, J. S.; Rojo, P.; Melo, C. H. F.; Bluhm, P.

2013-08-01

49

AN IMPROVED CLOSED ORBIT SERVO FOR ENERGY RAMPS ON THE SRS AT DARESBURY  

Microsoft Academic Search

The SRS is a second generation synchrotron radiation source which ramps from its injection energy of 600 MeV to 2 GeV relatively slowly (~ 1 minute). Improvements in orbit control have been achieved using discrete corrector application at specific points during the ramp, but this requires regular dedicated beam studies time to re- optimise the stored steering files to match

S. F. Hill

50

Tidal decay and orbital circularization in close-in two-planet systems  

Microsoft Academic Search

The motion of two planets around a Sun-like star under the combined effects of mutual interaction and tidal dissipation is investigated. The secular behaviour of the system is analysed using two different approaches. First, we solve the exact equations of motion through the numerical simulation of the system evolution. In addition to the orbital decay and circularization, we show that

A. Rodríguez; S. Ferraz-Mello; T. A. Michtchenko; C. Beaugé; O. Miloni

2011-01-01

51

[Morphological, microscopic changes in the thyroid gland in the cases of hanging in vertical position with open and closed noose].  

PubMed

The aim of the morphological study was to search for traumatic changes in the thyroid in the cases of hanging in a vertical position with an open and closed noose. These changes would constitute an additional proof of intravital hanging and they would be useful in postmortem diagnosis of the hangings in which other commonly acknowledged features of intravitality are not discovered. In 33% of all cases, petechiae were observed in the thyroid gland. They appeared in 20% of the hangings with the closed noose, and in 13% of the hangings with the use of the open noose. The study showed that there was no difference between the open or closed, hard noose in terms of changes in the thyroid gland. There was also no correlation between the body position and the injury of the thyroid gland. In all the cases, hyperemia of the thyroid was observed and segmental expansion of blood vessels. The histopathological analysis showed that in one third of all the cases with negative macroscopic examination, it was discovered that microscopic changes indicated hanging alive. PMID:22715676

Ok?ota, Magdalena; Niemcunowicz-Janica, Anna; Dziecio?, Janusz; Ptaszy?ska-Sarosiek, Iwona; Klim, Beata; Sackiewicz, Adam; Za?uski, Janusz; Szeremeta, Micha?

2011-01-01

52

CYCLIC VARIATIONS OF ORBITAL PERIOD AND LONG-TERM LUMINOSITY IN CLOSE BINARY RT ANDROMEDAE  

SciTech Connect

Solutions of standard VR light curves for the eclipsing binary RT And were obtained using the PHOEBE program (ver. 0.3a). Absolute parameters of the stellar components were then determined, enabling them to be positioned on the mass-luminosity diagram. Times of minima data ({sup O} - C curve) were analyzed using the method of Kalimeris et al. A cyclic variation in the orbital period and brightness, with timescales of about 11.89 and 12.50 yr were found, respectively. This is associated with a magnetic activity cycle modulating the orbital period of RT And via the Applegate mechanism. To check the consistency of the Applegate model, we have estimated some related parameters of the RT And system. The calculated parameters were in accordance with those estimated by Applegate for other similar systems, except B, the subsurface magnetic field of which shows a rather high value for RT And.

Manzoori, Davood [Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil (Iran, Islamic Republic of)], E-mail: d.manzoori@uma.ac.ir

2009-12-15

53

Accretion as a function of Orbital Phase in Young Close Binaries  

NASA Astrophysics Data System (ADS)

Many planets are known to reside around binaries and the study of young binary systems is crucial to understand their formation. Young ($<10$ Myrs) low-mass binaries are generally surrounded by circumbinary disk with an inner gap. Gas from the disk must cross this gap for accretion to take place and here we present observations of this process as a function of orbital phase. We have obtained time-resolved FUV and NUV spectroscopy (1350 to 3000 A) of DQ Tau and UZ Tau E, using the Cosmic Origins Spectrograph on-board the Hubble Space Telescope. Each target was observed 2 to 4 times per binary orbit, over three or four consecutive orbits. For DQ Tau, we find some evidence that accretion occurs equally into both binary members, while for UZ Tau E this is not the case. H2 emission for DQ Tau most likely originates within the circumbinary gap, while for UZ Tau E no 1000 K gas is detected within the gap, although magnetospheric accretion does take place.

Ardila, David R.; Herczeg, G.; Johns-Krull, C. M.; Mathieu, R. D.; Vodniza, A.; Tofflemire, B. M.

2014-01-01

54

Outward electron orbit extending to inward part of closed helical magnetic surfaces surrounded by shifted negative space potential  

SciTech Connect

Outward electron orbits that extend to the inward part of a closed helical vacuum magnetic region are found in three-dimensional calculations, which take into account two experimental findings. The pitch angle of electrons in the stochastic magnetic region (SMR) is scattered considerably due to the presence of a shifted self-space potential phi{sub s}. Eventually, the electron becomes a helically trapped particle, and starts an inward movement along one of the |B{sub min}| contours. Once penetrating into the helical magnetic region, the electron is never lost to the chamber wall, because the negative phi{sub s} in the SMR acts as a potential barrier.

Himura, H.; Nakamura, K.; Masamune, S. [Department of Electronics, Kyoto Institute of Technology, Matsugasaki, Sakyo Ward, Kyoto 606-8585 (Japan); Isobe, M.; Shimizu, A. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)

2010-03-15

55

Closed-orbit theory of oscillations in atomic photoabsorption cross sections in a strong electric field. I. Comparison between theory and experiments on hydrogen and sodium above threshold  

SciTech Connect

Using a simple analytic formula from closed-orbit theory, we calculate photoabsorption cross sections of hydrogen and sodium in a strong electric field. The theoretical spectra show good agreement with experimental results. A scaled variable measurement is also suggested.

Gao, J.; Delos, J.B. (Physics Department, College of William and Mary, Williamsburg, Virginia 23187 (United States)); Baruch, M. (Physics Department, University of Virginia, Charlottesville, Virginia 22901 (United States))

1992-08-01

56

Stellar Wind Disruption by an Orbiting Neutron Star: Neutron Star Close-up  

NSDL National Science Digital Library

A tiny neutron star orbits incessantly around a massive star with a diameter a million times larger than its own. The high luminosity of the massive star drives a strong wind from its surface. The neutron star crashes through this wind at over 300 kilometers per second. The gravity and X-ray luminosity of the neutron star act to disrupt the wind, producing an extended wake of dense gas trailing behind the neutron star. The large scale structure seen in the accretion wake is powered by the release of gravitational potential energy near the surface of the neutron star. The numerical simulations depicted here were computed using the Cray X-MP 48 at the National Center for Supercomputing Applications, University of Illinois, Urbana-Champaign.

Mcconnell, Alan; Blondin, John; Stevens, Ian; Kallman, Tim; Fryxell, Bruce; Taam, Ron

1990-07-10

57

Asteroseismology in action: a test of spin-orbit synchronism in the close binary system Feige 48  

NASA Astrophysics Data System (ADS)

Aims: In this paper, we provide a test of spin-orbit synchronism in the close binary system Feige 48. This system is made of a rapidly pulsating subdwarf B (sdB) star with an unseen companion, most likely a white dwarf. The presence of nonradial oscillations offers the opportunity to infer the inner profile and period of rotation of the primary star through asteroseismology. This constitutes the key element for testing spin-orbit synchronism in depth, since stellar internal layers are inaccessible to traditional techniques. Methods: We carried out a new asteroseismic analysis of Feige 48 following the so-called “forward modeling” approach. This is done with our latest optimization algorithms, which have been updated to incorporate the effect of stellar rotation on pulsations, assuming various internal rotation laws. In this analysis, the simultaneous match of all the frequencies observed in Feige 48 leads objectively to the full identification of the pulsation modes through the determination of the indices k, ?, m. It also leads to determining the structural and rotational parameters of Feige 48. Results: Our optimal model, obtained with a solid-body rotation law, is characterized by a spin period of 9.028 ± 0.480 h. This value is remarkably similar to the system's orbital period of 9.024 ± 0.072 h, measured independently from radial velocity variations. We further demonstrate that the hypothesis of differential rotation of the core - including a fast rotating core - must be eliminated for Feige 48. Conclusions: These results strongly imply that Feige 48 rotates as a solid body in a tidally locked system. This constitutes the first explicit demonstration of spin-orbit synchronism in a binary star by asteroseismic means.

Van Grootel, V.; Charpinet, S.; Fontaine, G.; Brassard, P.

2008-06-01

58

Coupled thermal- and orbital-evolution of close-in super Earths with convective regulated tidal dissipation inside it  

NASA Astrophysics Data System (ADS)

With the rapid development of observational instruments and techniques, more than a dozen of "super Earths" (which is defined as a planet of which mass is less than 10M_E) have been detected already. Ongoing and oncoming space transit surveys (CoRoT, Kepler, TESS and JWST) will detect more and more planets of these sizes. The detection probability of transit method is proportional to inverse of semi-major axis of planet, and thus closer planets are more easily detected. In fact, most of detected super Earths is orbiting with relatively small semi-major axis around its host star. In this situation, the tidal interaction with host star is a very important heating mechanism for the planetary interior, while the situation is not the case of planets in our Solar system (except for the satellites of Jupiter and Saturn). Thus, the close-in super Earths are good targets to understand the mechanism of tidal dissipation inside rocky planets. In this context, we have simulated coupled thermal- and orbital-evolution of extra solar super Earths due to tidal dissipation inside them taking into account temperature- dependence of mantle rheology of rocky planets. The tidal dissipation affects the thermal state of planetary interior, whereas the tidal dissipation rate is highly affected by thermal state of planetary interior due to temperature dependence of mantle rheology. Especially, the viscosity of rocky mantle depends strongly on the temperature, which controls the dissipation rate. Therefore, the thermal evolution and orbital evolution is coupled through this tidal dissipation. Thus, we took into account such temperature dependencies of rock rheology and examined how it affects the evolution. We will show there are 2 regimes in the a-e plane where the thermal- and orbital-evolution is clearly changed. If the initial eccentricity is too high and/or semi-major axis is too low, the tidal dissipation occurs sufficiently to balance the mantle cooling rate due to convection. Thus the thermal evolution is regulated by temperature dependency of mantle rheology. On the other hand, if initial a and e are suitable, the tidal dissipation rate does not overcome the cooling rate and the mantle temperature is also monotonically decreased. This is because the higher the temperature is, the lower the dissipation rate is. According to the result, we would like to discuss about the observational constraints for tidal dissipation inside these super Earths.

Tachinami, C.; Yuen, D. A.

2010-12-01

59

Investigation on the effect of filling ratio on the steady-state heat transfer performance of a vertical two-phase closed thermosyphon  

Microsoft Academic Search

Filling ratio of the working fluid has a predominant effect on the heat transfer characteristics of a two-phase closed thermosyphon (TPCT). A comprehensive model is developed to investigate the effect of filling ratio on the steady-state heat transfer performance of a vertical TPCT. Three types of flow pattern and two types of transition, according to the distribution of liquid film

B. Jiao; L. M. Qiu; X. B. Zhang; Y. Zhang

2008-01-01

60

Effect of vertical-tail location on the aerodynamic characteristics at subsonic speeds of a close-coupled canard configuration  

NASA Technical Reports Server (NTRS)

The effects were studied of various vertical-tail configurations on the longitudinal and lateral directional-stability characteristics of a general research fighter model utilizing wing-body-canard. The study indicates that the addition of the high canard resulted in an increase in total lift at angles of attack above 4 deg with a maximum lift coefficient about twice as large as that for the wing-body configuration. For the wing-body (canard off) configuration, the center-line vertical tail indicates positive vertical-tail effectiveness throughout the test angle-of-attack range; however, for this configuration none of the wing-mounted vertical-tail locations tested resulted in a positive directional-stability increment at the higher angles of attack. For the wing-body-canard configuration several outboard locations of the wing-mounted vertical tails were found.

Huffman, J. K.

1975-01-01

61

Calculations of Low Energy Electron-Impact Excitation Cross Sections of Diatomic Molecules by the Close-Coupling R-Matrix and Polarized-Orbital Methods  

Microsoft Academic Search

Low energy electron-impact excitation cross sections of diatomic molecules are calculated by the close-coupling, R-matrix, and polarized-orbital methods. The standard close-coupling procedure is generalized to the excitation of the a('1)(PI)(,g) state of N(,2) in the energy range 12.5-50.0 eV. The target wave functions are calculated by the molecular self-consistent-field method using 10 s-type and 6 p-type Gaussian orbitals as basis

Thomas Kennedy Holley

1982-01-01

62

Single cell and neural process experimentation using laterally applied electrical fields between pairs of closely apposed microelectrodes with vertical sidewalls  

Microsoft Academic Search

As biomedical research has moved increasingly towards experimentation on single cells and subcellular structures, there has been a need for microscale devices that can perform manipulation and stimulation at a correspondingly small scale. We propose a microelectrode array (MEA) featuring thickened microelectrodes with vertical sidewalls (VSW) to focus electrical fields horizontally on targets positioned in between paired electrodes. These microelectrodes

Wesley C. Chang; David W. Sretavan

2009-01-01

63

Characterization of vertical electric fields and associated voltages induced on a overhead power line from close artificially initiated lightning  

NASA Technical Reports Server (NTRS)

Measurements were characterized of simultaneous vertical electric fields and voltages induced at both ends of a 448 m overhead power line by artificially initiated lightning return strokes. The lightning discharges struck ground about 20 m from one end of the line. The measured line voltages could be grouped into two categories: those in which multiple, similarly shaped, evenly spaced pulses were observed, which are called oscillatory; and those dominated by a principal pulse with subsidiary oscillations of much smaller amplitude, which are called impulsive. Voltage amplitudes range from tens of kilovolts for oscillatory voltages to hundreds of kilovolts for impulsive voltages.

Rubinstein, Marcos; Uman, Martin A.; Thomson, Ewen M.; Medelius, Pedro J.

1991-01-01

64

Single cell and neural process experimentation using laterally applied electrical fields between pairs of closely apposed microelectrodes with vertical sidewalls.  

PubMed

As biomedical research has moved increasingly towards experimentation on single cells and subcellular structures, there has been a need for microscale devices that can perform manipulation and stimulation at a correspondingly small scale. We propose a microelectrode array (MEA) featuring thickened microelectrodes with vertical sidewalls (VSW) to focus electrical fields horizontally on targets positioned in between paired electrodes. These microelectrodes were fabricated using gold electroplating that was molded by photolithographically patterned SU-8 photoresist. Finite element modeling showed that paired VSW electrodes produce more uniform electrical fields compared to conventional planar microelectrodes. Using paired microelectrodes, 3 microm thick and spaced 10 microm apart, we were able to perform local electroporation of individual axonal processes, as demonstrated by entry of EGTA to locally chelate intra-axonal calcium, quenching the fluorescence of a pre-loaded calcium indicator dye. The same electrode configuration was used to electroporate individual cells, resulting in the targeted transfection of a transgene expressing a cytoplasmically soluble green fluorescent protein (GFP). In addition to electroporation, our electrode configuration was also capable of precisely targeted field stimulation on individual neurons, resulting in action potentials that could be tracked by optical means. With its ability to deliver well-characterized electrical fields and its versatility, our configuration of paired VSW electrodes may provide the basis for a new tool for high-throughput and high-content experimentation in broad areas of neuroscience and biomedical research. PMID:19535240

Chang, Wesley C; Sretavan, David W

2009-08-15

65

Applicability of orbital data obtained from ISON measurements for prediction and analysis of close encounters on GEO  

Microsoft Academic Search

Large amount of data is collected within the framework of the ISON project in the KIAM database. The most part of the data is related to objects in GEO region, both operational and not functional. As of the end of 2009 there were 1467 GEO objects for which orbits were maintained on a routine basis. This number includes 892 spacecraft

Vladimir Agapov; Victor Stepanyants; Zakhary Khutorovsky; Igor Molotov

2010-01-01

66

Technical Note: One year of Raman-lidar measurements in Gual Pahari EUCAARI site close to New Delhi in India - Seasonal characteristics of the aerosol vertical structure  

NASA Astrophysics Data System (ADS)

One year of multi-wavelength (3 backscatter + 2 extinction + 1 depolarization) Raman lidar measurements at Gual Pahari, close to New Delhi, were analysed. The data was split into four seasons: spring (March-May), summer (June-August), autumn (September-November) and winter (December-February). The vertical profiles of backscatter, extinction, and lidar ratio and their variability during each season are presented. The measurements revealed that, on average, the aerosol layer was at its highest in spring (5.5 km). In summer, the vertically averaged (between 1-3 km) backscatter and extinction coefficients had the highest averages (3.3 Mm-1 sr-1 and 142 Mm-1 at 532 nm, respectively). Aerosol concentrations were slightly higher in summer compared to other seasons, and particles were larger in size. The autumn showed the highest lidar ratio and high extinction-related Ångström exponents (AEext), indicating the presence of smaller probably absorbing particles. The winter had the lowest backscatter and extinction coefficients, but AEext was the highest, suggesting still a large amount of small particles.

Komppula, M.; Mielonen, T.; Arola, A.; Korhonen, K.; Lihavainen, H.; Hyvärinen, A.-P.; Baars, H.; Engelmann, R.; Althausen, D.; Ansmann, A.; Müller, D.; Panwar, T. S.; Hooda, R. K.; Sharma, V. P.; Kerminen, V.-M.; Lehtinen, K. E. J.; Viisanen, Y.

2012-05-01

67

One year of Raman-lidar measurements in Gual Pahari EUCAARI site close to New Delhi in India: seasonal characteristics of the aerosol vertical structure  

NASA Astrophysics Data System (ADS)

One year of multi-wavelength (3+2) Raman lidar measurements at Gual Pahari, close to Delhi, were analysed. The data was split into four seasons: spring (March-May), summer (June-August), autumn (September-November) and winter (December-February). The vertical profiles of backscatter, extinction, and lidar ratio and their variability during each season are presented. The measurements revealed that, on average, the aerosol layer was at its highest in spring (5.5 km). In summer, the vertically averaged (between 1-3 km) backscatter and extinction coefficients had the highest averages (3.3 Mm-1 sr-1 and 142 Mm-1 at 532 nm, respectively). Aerosol concentrations were slightly higher in summer compared with other seasons, and particles were larger in size. The autumn showed the highest lidar ratio and high extinction-related Ångström exponents (AEext), indicating the presence of smaller probably absorbing particles. The winter had the lowest backscatter and extinction coefficients, but AEext was the highest, suggesting still a large amount of small particles.

Komppula, M.; Mielonen, T.; Arola, A.; Korhonen, K.; Lihavainen, H.; Hyvärinen, A.-P.; Baars, H.; Engelmann, R.; Althausen, D.; Ansmann, A.; Müller, D.; Panwar, T. S.; Hooda, R. K.; Sharma, V. P.; Kerminen, V.-M.; Lehtinen, K. E. J.; Viisanen, Y.

2010-12-01

68

A Fixed-Base-Simulator Study of the Ability of a Pilot to Establish Close Orbits Around the Moon  

NASA Technical Reports Server (NTRS)

A study was made on a six-degree-of-freedom fixed-base simulator of the ability of human pilots to modify ballistic trajectories of a 5 space vehicle approaching the moon to establish a circular orbit about 50 miles above the lunar surface. The unmodified ballistic trajectories had miss distances from the lunar surface of from 40 to 80 miles, and a velocity range of from 8,200 to 8,700 feet per second at closest approach. The pilot was given control of the thrust (along the vehicle longitudinal axis) and torques about all three body axes. The information display given to the pilot was a hodograph of the vehicle rate of descent and circumferential velocity, an altimeter, and vehicle attitude and rate meters.

Queijo, M. J.; Riley, Donald R.

1961-01-01

69

Counter-Orbitals: Another Class of Co-Orbitals  

NASA Astrophysics Data System (ADS)

Co-orbital companions share the same orbital period and semi-major axis about a primary (star or planet). Heretofore there have been three recognized classes of co-orbitals: (1) Trojans librate in tadpole-shaped orbits about the equilateral Lagrange points L4 and L5, 60 degrees ahead of or behind the secondary (planet or satellite). (2) Horse-shoe companions librate about both L4 and L5, as well as the L3 Lagrange point diametrically opposite the secondary. (3) ``Quasi-satellites'' appear to be in distant retrograde orbits about the secondary, but actually are in prograde orbits about the primary with the same period as the secondary. Quasi-satellite orbits lie outside the secondary's Hill sphere, and enclose both L1 and L2, and sometimes L4 and L5 as well. In addition, some asteroids and comets are found in hybrid orbits which alternate among the above three classes, or combine some of their features. New research now reveals a fourth class of co-orbitals, which does not appear to be known before, and may be called ``counter-orbitals''. Imagine reversing the inertial velocity of a distant quasi-satellite. Then it remains in orbit about the primary, with the same period, semi-major axis, eccentricity, and orbital plane, although retrograde. But instead of remaining relatively close to the secondary, now it passes the secondary twice per orbit, near periapsis and apoapsis. The attractive impulses at these conjunctions tend to stabilize this arrangement. Numerical simulations of the general three-body problem verify that counter-orbitals can persist for over 10,000 orbits, with small vertical excursions, but a wide range of eccentricities and mass ratios. For example, Charon can maintain counter-orbital companions at least up to 3 percent of its own mass, in eccentric orbits extending from about 7050 km out to 41700 km from the center of Pluto. This may present a collision hazard to the New Horizons spacecraft.

Dobrovolskis, Anthony R.

2012-10-01

70

Closed-Form and Numerically-Stable Solutions to Problems Related to the Optimal Two-Impulse Transfer Between Specified Terminal States of Keplerian Orbits  

NASA Technical Reports Server (NTRS)

The first part of the paper presents some closed-form solutions to the optimal two-impulse transfer between fixed position and velocity vectors on Keplerian orbits when some constraints are imposed on the magnitude of the initial and final impulses. Additionally, a numerically-stable gradient-free algorithm with guaranteed convergence is presented for the minimum delta-v two-impulse transfer. In the second part of the paper, cooperative bargaining theory is used to solve some two-impulse transfer problems when the initial and final impulses are carried by different vehicles or when the goal is to minimize the delta-v and the time-of-flight at the same time.

Senent, Juan

2011-01-01

71

Closed loop performance of a brushless dc motor powered electromechanical actuator for flight control applications. [computerized simulation for Shuttle Orbiter applications  

NASA Technical Reports Server (NTRS)

A comprehensive digital model for the analysis and possible optimization of the closed loop dynamic (instantaneous) performance of a power conditioner fed, brushless dc motor powered, electromechanical actuator system (EMA) is presented. This model was developed for the simulation of the dynamic performance of an actual prototype EMA built for NASA-JSC as a possible alternative to hydraulic actuators for consideration in Space Shuttle Orbiter applications. Excellent correlation was achieved between numerical model simulation and experimental test results obtained from the actual hardware. These results include: various current and voltage waveforms in the machine-power conditioner (MPC) unit, flap position as well as other control loop variables in response to step commands of change of flap position. These results with consequent conclusions are detailed in the paper.

Demerdash, N. A.; Nehl, T. W.

1980-01-01

72

Status of Digital Orbit Feedback for SPEAR  

SciTech Connect

The present global orbit feedback system for SPEAR can adjust the electron beam position with a cycle time of 5 s. In addition, 50 Hz analog local servos stabilize the vertical photon beam position at monitors situated in the ten SSRL beamlines. The global and local systems will soon be merged into a single unified system operating from a dedicated DSP board. The goal is to acquire orbits, process the data, and correct beam position in a 1-2 ms interval to achieve a 30-50 Hz closed-loop bandwidth.

Hettel, Robert

2003-05-30

73

Vertical mammaplasty.  

PubMed

Current criticisms regarding vertical mammaplasty include problems with poor immediate postoperative appearance, nipple-areola complex malposition, and excessive lower pole length. These problems can be avoided by proper patient selection, by utilizing correct concepts of skin design, and by observing correct glandular resection and closure concepts. Vertical mammaplasty also can result in other problems, such as hypertrophic circumareolar scars and lower pole deformities, including notching, boxy shape, infra-areolar depression, and flatness. These problems are also largely avoidable by using correct technique. Several basic concepts described previously have not proven necessary to achieve good results. Abandoning some of these principles has contributed to the ability to establish an aesthetically ideal breast shape intraoperatively as well as to a decrease in morbidity. This includes eliminating liposuction as a major integral component of the procedure, eliminating suturing the gland to the pectoralis muscle, not undermining the lower pole skin, and avoiding overly wide skin resection and tight wound closure that produces significant lower pole distortion in the early postoperative period. An important concept that has proven reliable is to use a "closed" design that does not predetermine the areolar opening whenever circumstances permit. When this is not possible, a modification that utilizes the smallest possible circumference as an open design is better than a large "mosque." These alternatives allow greater flexibility in determining final nipple position and also reduce the risk of hypertrophic circumareolar scars. Important glandular resection concepts include creating pillars that are attached to both the skin and the chest wall; making them of adequate dimension to avoid postoperative lower pole shape problems, such as flattening; resecting closer to the skin lateral to the pillars to avoid a boxy breast shape; and using a drain both to assist in accurately determining the endpoint of resection and to avoid postoperative seromas. Key closure concepts include approximation of the superior surfaces of the pillars at their base to maintain vertical height and thereby prevent lower pole flattening; approximation of the inferior surfaces of the pillars to the base of the breast to prevent notching; and proper management of the vertical incision by restricting the purse-string suture effect to only the inferior portion of the incision, where there may be skin excess present. Inclusion of these concepts leads to predictable and improved aesthetic results in vertical mammaplasty. This allows full realization of the purported advantages of vertical mammaplasty and allows this method to be utilized with a level of confidence similar to that seen with inverted-T techniques. PMID:15793463

Hidalgo, David A

2005-04-01

74

Orbital energies and negative electron affinities from density functional theory: Insight from the integer discontinuity  

Microsoft Academic Search

Orbital energies in Kohn-Sham density functional theory (DFT) are investigated, paying attention to the role of the integer discontinuity in the exact exchange-correlation potential. A series of closed-shell molecules are considered, comprising some that vertically bind an excess electron and others that do not. High-level ab initio electron densities are used to calculate accurate orbital energy differences, Delta?, between the

Andrew M. Teale; Frank de Proft; David J. Tozer

2008-01-01

75

Orbital energies and negative electron affinities from density functional theory: Insight from the integer discontinuity  

Microsoft Academic Search

Orbital energies in Kohn–Sham density functional theory (DFT) are investigated, paying attention to the role of the integer discontinuity in the exact exchange-correlation potential. A series of closed-shell molecules are considered, comprising some that vertically bind an excess electron and others that do not. High-level ab initio electron densities are used to calculate accurate orbital energy differences, ?&egr;, between the

Andrew M. Teale; Frank De Proft; David J. Tozer

2008-01-01

76

THE ROCHE LIMIT FOR CLOSE-ORBITING PLANETS: MINIMUM DENSITY, COMPOSITION CONSTRAINTS, AND APPLICATION TO THE 4.2 hr PLANET KOI 1843.03  

SciTech Connect

The requirement that a planet must orbit outside of its Roche limit gives a lower limit on the planet's mean density. The minimum density depends almost entirely on the orbital period and is immune to systematic errors in the stellar properties. We consider the implications of this density constraint for the newly identified class of small planets with periods shorter than half a day. When the planet's radius is accurately known, this lower limit to the density can be used to restrict the possible combinations of iron and rock within the planet. Applied to KOI 1843.03, a 0.6 R{sub Circled-Plus} planet with the shortest known orbital period of 4.245 hr, the planet's mean density must be {approx}> 7 g cm{sup -3}. By modeling the planetary interior subject to this constraint, we find that the composition of the planet must be mostly iron, with at most a modest fraction of silicates ({approx}< 30% by mass)

Rappaport, Saul; Sanchis-Ojeda, Roberto; Winn, Joshua N. [Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Rogers, Leslie A. [Department of Astronomy and Department of Planetary Science, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Levine, Alan, E-mail: rsanchis86@gmail.com, E-mail: sar@mit.edu, E-mail: jwinn@mit.edu, E-mail: larogers@caltech.edu, E-mail: aml@space.mit.edu [37-575 MIT Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139 (United States)

2013-08-10

77

Polar cloud structure as derived from the Pioneer Venus Orbiter  

NASA Technical Reports Server (NTRS)

Vertical absorption coefficient profiles of the Venus clouds in the north polar regions recorded by the Pioneer Venus Orbiter on orbits 9, 18, and 19 at the S band indicate dense cloud decks at the 1.5 to 4.7 bar levels in the Venus atmosphere. These cloud decks are at lower altitudes than the clouds detected by Mariner 10 and Pioneer Venus probes, and are uniform in absorption characteristics in the polar regions. The regions close to the polar hot spots have depressed the upper cloud heights and increased polar density; these areas are free of thermal inversions characteristic of the north polar regions away from the hot spots.

Cimino, J. B.; Elachi, C.; Kliore, A. J.; Mccleese, D. J.; Patel, I. R.

1980-01-01

78

The Torque at a Lindblad Vertical Resonance  

NASA Astrophysics Data System (ADS)

A fairly uniform, rapidly and differentially rotating disk of rarely colliding particles (when the frequency of interparticle collisions is much smaller than the local orbital frequency) in a planet-moon system is considered. A moon causes a number of orbital resonant effects in this continuous, viscous (through ordinary collisions) disk. In the frame of hydrodynamical theory, the gravitational torques exerted by an exterior moon on particles at an inner Lindblad horizontal resonance and corresponding vertical resonance are estimated. It is shown that the torques are negative at these resonances, so gaps in the disk near each resonance may be created. The latter result can be used to provide a viable clue to solving the puzzle of narrow, dense, and widely separated rings of Uranus. The model advocated suggests that the Uranian ring orbits have a close connection with the small moons of the planet that are interior to the orbit of Miranda, from Cordelia to Mab, discovered by Voyager 2 imaging observations in 1986.

Griv, Evgeny

2007-08-01

79

A COMPARISON OF SEVERAL LATTICE TOOLS FOR COMPUTATION OF ORBIT FUNCTIONS OF AN ACCELERATOR  

SciTech Connect

The values of orbit functions for accelerator lattices as computed with accelerator design programs may differ between different programs. For a simple lattice, consisting of identical constant-gradient bending magnets, the functions (horizontal and vertical betatron tunes, dispersions, closed orbit offsets, orbit lengths, chromaticities etc.) can be evaluated analytically. This lattice was studied with the accelerator physics tools SYNCH [1], COSY INFINITY [2], MAD [3], and TEAPOT [4]. It was found that while all the programs give identical results at the central design momentum, the results differ substantially among the various lattice tools for non-zero momentum deviations. Detailed results and comparisons are presented.

COURANT, E.DTRBOJEVIC,D.BERG,S.J.GARREN,A.A.TALMAN, R.

2003-05-12

80

Orbital pseudotumor  

MedlinePLUS

Orbital pseudotumor is a swelling of the tissues behind the eye in an area called the orbit. The ... and tissue that surround it. Unlike cancerous tumors, orbital pseudotumor does not spread to other tissues or places ...

81

Vertical Disintegration  

Microsoft Academic Search

With economies of scale, a vertically integrated firm can lower its upstream cost by supplying downstream competitors. The competitors may strategically choose not to purchase from the integrated firm, unless the latter's price for the intermediate good is sufficiently lower than those of alternative suppliers. In a simple model of dynamic scale economies through learning by doing, equilibrium vertical disintegration

Yongmin Chen

2005-01-01

82

Satellite services and orbital retrieval  

NASA Technical Reports Server (NTRS)

Within the capabilities of the Space Shuttle Orbiter, a broad range of services which can be made available to the satellite user community as summarized. Payload deployment, close proximity retrieval, and a number of other mission related functions are discussed. The focus here is on close proximity retrieval and retrieval of payloads in higher energy low Earth orbits.

Adornato, R. J.

1985-01-01

83

THE VERTICAL  

NASA Technical Reports Server (NTRS)

'THE VERTICAL' computer keyboard is designed to address critical factors which contribute to Repetitive Motion Injuries (RMI) (including Carpal Tunnel Syndrome) in association with computer keyboard usage. This keyboard splits the standard QWERTY design into two halves and positions each half 90 degrees from the desk. In order to access a computer correctly. 'THE VERTICAL' requires users to position their bodies in optimal alignment with the keyboard. The orthopaedically neutral forearm position (with hands palms-in and thumbs-up) reduces nerve compression in the forearm. The vertically arranged keypad halves ameliorate onset occurrence of keyboard-associated RMI. By utilizing visually-reference mirrored mylar surfaces adjustable to the user's eye, the user is able to readily reference any key indicia (reversed) just as they would on a conventional keyboard. Transverse adjustability substantially reduces cumulative musculoskeletal discomfort in the shoulders. 'THE VERTICAL' eliminates the need for an exterior mouse by offering a convenient finger-accessible curser control while the hands remain in the vertically neutral position. The potential commercial application for 'THE VERTICAL' is enormous since the product can effect every person who uses a computer anywhere in the world. Employers and their insurance carriers are spending hundreds of millions of dollars per year as a result of RMI. This keyboard will reduce the risk.

Albert, Stephen L.; Spencer, Jeffrey B.

1994-01-01

84

Kepler's Orbit  

NASA Video Gallery

Kepler does not orbit the Earth, rather it orbits the Sun in concert with the Earth, slowly drifting away from Earth. Every 61 Earth years, Kepler and Earth will pass by each other. Throughout the ...

85

Vertical partitioning algorithms for database design  

Microsoft Academic Search

This paper addresses the vertical partitioning of a set of logical records or a relation into fragments. The rationale behind vertical partitioning is to produce fragments, groups of attribute columns, that “closely match” the requirements of transactions.Vertical partitioning is applied in three contexts: a database stored on devices of a single type, a database stored in different memory levels, and

Shamkant B. Navathe; Stefano Ceri; Gio Wiederhold; Jinglie Dou

1984-01-01

86

Orbital pathology  

Microsoft Academic Search

This overview of orbital pathology deals with different kinds of tumors, inflammatory, vascular, and traumatic diseases, which may involve the orbit. Depending on the respective orbital compartment of the globe, the intrakonal, extrakonal and optic nerve the most important and most frequent lesions are presented with their specific clinical symptoms. Their specific presentation on CT- and MR-imaging is discussed in

W Müller-Forell; S Pitz

2004-01-01

87

[Vascular tumors of the orbit].  

PubMed

Vascular tumors of the orbit include capillary hemangioma, cavernous hemangioma, hemolymphangioma, hemangiopericytoma and a few rare tumors. Capillary hemangioma and hemolymphangioma, occurring mainly in children, are covered in the chapter devoted to childhood tumors. In this chapter, cavernous hemangioma and hemangiopericytoma are discussed as well as rare vascular tumors. Although orbital varix is not a tumor, it is also considered because of the diagnostic problems and the close correlation of orbital varix with a true tumor: hemolymphangioma. PMID:20303554

Cophignon, J; d'Hermies, F; Civit, T

2010-01-01

88

Origin of Pluto's Peculiar Orbit.  

National Technical Information Service (NTIS)

The origin of Pluto's unusual orbit - the most eccentric and inclined of all the planets - remains a mystery. The orbits of Pluto and Neptune overlap, but close approaches of these two planets are prevented by the existence of a resonance condition: Pluto...

R. Malhotra

1993-01-01

89

Orbital inflammation  

Microsoft Academic Search

Orbital inflammation is a common problem in adults and children, accounting for the majority of all orbital processes. The\\u000a presentation may be acute, subacute, or insidious. When the onset is acute, the process can be mistaken for orbital cellulitis.\\u000a In insidious cases, such as the sclerosing subtype of inflammation, the chronic painless course may prompt concerns about\\u000a a neoplastic infiltration

Kimberly P. Cockerham; Sang H. Hong; Ellen E. Browne

2003-01-01

90

Orbiting Earth  

NSDL National Science Digital Library

This Flash animation contrasts the geostationary versus polar orbits for satellites. For a geostationary orbit, the satellite remains directly above a fixed point at all times; in time with the Earth's rotation, the satellite circles the earth once every 24 hours, continually viewing the same part of Earth. For the polar orbit, the satellite circles over both poles in a constant plane while earth rotates beneath. Earth's rotation exposes different parts of the surface on each orbit. The animation is useful for a discussion on how remote sensing imagery and Global Positioning Systems (GPS) signals are derived. The animation can be paused and rewound to stress important points.

Loomis, Jennifer; Nasa; Earth, Exploring

91

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals Web site "was established as part of an (ongoing) project at Purdue University to develop 'visualization modules' for general chemistry students." Using the Chime plug-in, which allows unique and stunning visualizations, visitors can learn what an atomic orbital is; what the 1s, 2s, 3s, 2p, 3p, and 3d orbitals are; what hybrid orbitals are; and more. The combination of easy-to-read descriptions and educational graphics make the site a great learning resource for high school and even college level chemistry students.

1969-12-31

92

Orbiter door closure tools  

NASA Technical Reports Server (NTRS)

Safe reentry of the shuttle orbiter requires that the payload bay doors be closed and securely latched. Since a malfunction in the door drive or bulkhead latch systems could make safe reentry impossible, the requirement to provide tools to manually close and secure the doors was implemented. The tools would disconnect a disabled door or latch closure system and close and secure the doors if the normal system failed. The tools required to perform these tasks have evolved into a set that consists of a tubing cutter, a winch, a latching tool, and a bolt extractor. The design, fabrication, and performance tests of each tool are described.

Acres, W. R.

1980-01-01

93

Close encounters with PHOBOS  

NASA Astrophysics Data System (ADS)

Aspects of the Soviet mission to Phobos are examined, including the objectives of the mission, the spapcecraft, experiments, and landers. Past Mars research and unanswered questions concerning Mars and its satellites are discussed. The spacecraft is expected to reach Mars in early 1989 and to observe the planet from two orbits, coming as close as 500 km from the surface, before moving into a third path close to Phobos. After studying the Phobos terrain from above, the craft will jettison one or two small long-duration automated landers, which will perform surface experiments, including work on celestial mechanics, the history of the Phobos orbit, surface composition, and mechanical properties. In addition to studying Phobos and Mars, the craft will examine the interplanetary medium, make observations of the Sun, and possibly study Deimos.

Zakharov, A. V.

1988-07-01

94

Orbital Compass Model in a Checkerboard Lattice  

Microsoft Academic Search

The orbital compass model in a checkerboard lattice is studied. There is a competition between the interaction for the z component of the orbital pseudo-spin along the vertical\\/horizontal direction and the interaction for the x component along the diagonal direction in a checkerboard lattice. In a frustration point where the two interactions compete with each other, a macroscopic number of

Joji Nasu; Sumio Ishihara

2011-01-01

95

The Hot Orbit: Orbital Cellulitis  

PubMed Central

Orbital cellulitis is an uncommon condition previously associated with severe complications. If untreated, orbital cellulitis can be potentially sight and life threatening. It can affect both adults and children but has a greater tendency to occur in the pediatric age group. The infection most commonly originates from sinuses, eyelids or face, retained foreign bodies, or distant soources by hematogenous spread. It is characterized by eyelid edema, erythema, chemosis, proptosis, blurred vision, fever, headache, and double vision. A history of upper respiratory tract infection prior to the onset is very common especially in children. In the era prior to antibiotics, vision loss from orbital cellulitis was a dreaded complication. Currently, imaging studies for detection of orbital abcess, the use of antibiotics and early drainage have mitigated visual morbidity significantly. The purpose of this review is to describe current investigative strategies and management options in the treatment of orbital cellulitis, establish their effectiveness and possible complications due to late intervention.

Chaudhry, Imtiaz A.; Al-Rashed, Waleed; Arat, Yonca O.

2012-01-01

96

Orbital Decompression  

MedlinePLUS

... appearance. One of the most common indications is Graves’ disease, an autoimmune disorder that primarily affects the thyroid gland and the eye. If the eye is affected (Grave’s orbitopathy), there is an enlargement of the orbital ...

97

Orbital Motion  

NSDL National Science Digital Library

Authored by Eleanor Kopsian of Franklin Frazier, this is an activity intended to help students understand orbital motion and Kepler's Laws through a comparison of a circle and an ellipse and the application of Kepler's Law of Elliptical Orbits. The lesson contains objectives, vocabulary, needed materials, strategies, handouts, conclusions, evaluation questions and references. Although simple in design, this can still be a very useful resource for an instructor looking to enhance or create new curriculum.

Kopsian, Eleanor

2009-05-27

98

From Newton{close_quote}s moon to Einstein{close_quote}s moon  

SciTech Connect

Continuing the lunar orbit{close_quote}s 300-year role as gravity{close_quote}s testing ground, laser ranging to the Moon precisely confirms the foundations and structure of general relativity. {copyright} {ital 1996 American Institute of Physics.}

Nordtvedt, K.

1996-05-01

99

The origin of Pluto's peculiar orbit  

Microsoft Academic Search

THE origin of Pluto's unusual orbit---the most eccentric and inclined of all the planets---remains a mystery. The orbits of Pluto and Neptune overlap, but close approaches of these two planets are prevented by the existence of a resonance condition1: Pluto's orbital period is exactly 3\\/2 that of Neptune, which ensures that the conjunctions always occur near Pluto's aphelion. Long-term orbit

Renu Malhotra

1993-01-01

100

Study of Abnormal Vertical Emittance Growth in ATF Extraction Line  

SciTech Connect

Since several years, the vertical beam emittance measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, that will transport the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus beam line, is significantly larger than the emittance measured in the DR itself, and there are indications that it grows rapidly with increasing beam intensity. This longstanding problem has motivated studies of possible sources of this anomalous emittance growth. One possible contribution is non-linear magnetic fields in the extraction region experimented by the beam while passing off-axis through magnets of the DR during the extraction process. In this paper, simulations of the emittance growth are presented and compared to observations. These simulations include the effects of predicted non-linear field errors in the shared DR magnets and orbit displacements from the reference orbit in the extraction region. Results of recent measurements using closed orbit bumps to probe the relation between the extraction trajectory and the anomalous emittance growth are also presented.

Alabau, M.; Faus-Golfe, A.; /Valencia U., IFIC; Alabau, M.; Bambade, P.; Brossard, J.; Le Meur, G.; Rimbault, C.; Touze, F.; /Orsay, LAL; Angal-Kalinin, D.; Jones, J.K.; /Daresbury; Appleby, R.; Scarfe, A.; /Manchester U.; Kuroda, S.; /KEK, Tsukuba; White, G.R.; Woodley, M.; /SLAC; Zimmermann, F.; /CERN

2011-11-04

101

Autonomous orbital navigation using Kepler's equation  

NASA Technical Reports Server (NTRS)

A simple method of determining the six elements of elliptic satellite orbits has been developed for use aboard manned and unmanned spacecraft orbiting the earth, moon, or any planet. The system requires the use of a horizon sensor or other device for determining the local vertical, a precision clock or timing device, and Apollo-type navigation equipment including an inertial measurement unit (IMU), a digital computer, and a coupling data unit. The three elements defining the in-plane motion are obtained from simultaneous measurements of central angle traversed around the planet and elapsed flight time using a linearization of Kepler's equation about a reference orbit. It is shown how Kalman filter theory may also be used to determine the in-plane orbital elements. The three elements defining the orbit orientation are obtained from position angles in celestial coordinates derived from the IMU with the spacecraft vertically oriented after alignment of the IMU to a known inertial coordinate frame.

Boltz, F. W.

1974-01-01

102

Closing in on Close Reading  

ERIC Educational Resources Information Center

"A significant body of research links the close reading of complex text--whether the student is a struggling reader or advanced--to significant gains in reading proficiency and finds close reading to be a key component of college and career readiness" (Partnership for Assessment of Readiness for College and Careers, 2011, p. 7). When the author…

Boyles, Nancy

2013-01-01

103

Orbital YORP and asteroid orbit evolution, with application to Apophis  

NASA Astrophysics Data System (ADS)

Photon thrust from shape alone can produce quasi-secular changes in an asteroid's orbital elements. An asteroid in an elliptical orbit with a north-south shape asymmetry can steadily alter its elements over timescales longer than one orbital trip about the Sun. This thrust, called here orbital YORP (YORP = Yarkovsky-O'Keefe-Radzievskii-Paddack), operates even in the absence of thermal inertia, which the Yarkovsky effects require. However, unlike the Yarkovsky effects, which produce secular orbital changes over millions or billions of years, the change in an asteroid's orbital elements from orbital YORP operates only over the precession timescale of the orbit or of the asteroid's spin axis; this is generally only thousands or tens of thousands of years. Thus while the orbital YORP timescale is too short for an asteroid to secularly journey very far, it is long enough to warrant investigation with respect to 99942 Apophis, which might conceivably impact the Earth in 2036. A near-maximal orbital YORP effect is found by assuming Apophis is without thermal inertia and is shaped like a hemisphere, with its spin axis lying in the orbital plane. With these assumptions orbital YORP can change its along-track position by up to ±245 km, which is comparable to Yarkovsky effects. Though Apophis' shape, thermal properties, and spin axis orientation are currently unknown, the practical upper and lower limits are liable to be much less than the ±245 km extremes. Even so, the uncertainty in position is still likely to be much larger than the ˜0.5 km "keyhole" Apophis must pass through during its close approach in 2029 in order to strike the Earth in 2036.

Rubincam, David Parry

2007-12-01

104

Achieving Orbit  

NSDL National Science Digital Library

This is an engineering design challenge activity. Learners will use balloons to investigate how a multi-stage rocket, like that used to launch the Interstellar Boundary Explorer, or IBEX, spacecraft, can propel a satellite to a specific orbit. Learners will construct a two-stage balloon rocket that will be required to reach a particular location on the balloon track, simulating the proper orbit around Earth to be reached by the IBEX satellite. This activity complements other IBEX informal education materials. An instructional video explaining how to facilitate this activity is available: http://bit.ly/ZwlFf4.

105

Orbital Compass Model in a Checkerboard Lattice  

NASA Astrophysics Data System (ADS)

The orbital compass model in a checkerboard lattice is studied. There is a competition between the interaction for the z component of the orbital pseudo-spin along the vertical/horizontal direction and the interaction for the x component along the diagonal direction in a checkerboard lattice. In a frustration point where the two interactions compete with each other, a macroscopic number of the orbital pseudo-spin configurations are degenerated in the classical grounds state. This degeneracy is lifted by the thermal and quantum fluctuations and the z component long range order is realized. The tricritical point appears due to the coexistence of the orbital frustration and the geometrical frustration.

Nasu, Joji; Ishihara, Sumio

2011-09-01

106

Orbital Elements  

NSDL National Science Digital Library

Coordinates for tracking the International Space Station and the Mir Space Station are available here from NASA's Johnson Space Center Flight Design and Dynamics Division. The Orbital Elements page offers real-time data for use in ground track plotting programs. The site cautions the data are for ground track plotting programs only and "should not be used for precise applications or analysis!"

107

Elliptical Orbits  

NSDL National Science Digital Library

Although not inquiry, this activity is important for students to understand what an ellipse is and what a focus is, and to break misconceptions about Earth's orbit being highly elliptical. This is the perfect place to check to see if students have the mis

Horton, Michael

2009-05-30

108

Orbital Mechanics.  

ERIC Educational Resources Information Center

Three computer programs are presented that allow the high school student to explore and understand the physical forces involved in orbital flight at a greater depth than is usually possible. For each program, introductory material is given including the physics and mathematics involved. This is followed by the computer program in BASIC language.…

Dalton, Joel B.

109

Mars Orbit  

NSDL National Science Digital Library

This geometry lesson from Illuminations uses the model of the orbits of Mars and Earth relative to the sun to illustrate parametric equations. As an interdisciplinary learning activity, the material may be used in conjunction with astronomy lessons. An interactive applet and student questions are also included. The material is intended for grades 9-12 and should require 1 class period to complete.

2010-12-14

110

LISA Orbits  

Microsoft Academic Search

The LISA formation is composed of 3 spacecraft in an equilateral triangle formation. The baseline formation has a 5million km radius and lies in a heliocentric orbit 20deg away from the Earth. Earth's gravity induces a perturbation on the nominal Keplerian motion of the formation, generating a change in the relative ranges and thus a Doppler that can be very

Angelo Povoleri; Stephen Kemble

2006-01-01

111

Scattering outcomes of close-in planets  

NASA Astrophysics Data System (ADS)

Many exoplanets in close-in orbits are observed to have relatively high eccentricities and large stellar obliquities. We explore the possibility that these result from planet-planet scattering by studying the dynamical outcomes from a large number of orbit integrations in systems with two and three gas-giant planets in close-in orbits (0.05 AU< a <0.15 AU). We find that at these orbital separations, unstable systems generally lead to planet-planet collisions in which the collision product is a planet on a low-eccentricity, low-inclination orbit. This result is inconsistent with the observations. We conclude that eccentricity and inclination excitation from planet-planet scattering must precede migration of planets into short-period orbits.

Petrovich, Cristobal; Rafikov, Roman R

2014-05-01

112

Orbiting Hotel  

NSDL National Science Digital Library

It is the year 2025 and a large company, Z-Tech, wants to put a hotel in space having it orbit around one of the planets in our solar system. Our 9th grade class has been given a very important job. We have to search for the perfect location for the hotel. Our job is to report back to the company with the planet that is the best place for an orbiting hotel. The Task: You are to write a report recommending which planet should be chosen. Your report should include pictures of the planet you recommended. Here are the questions you should answer in order to report back to Z-Tech with your recommendation. * Which planet will be the ...

Hicken, Mrs.

2009-10-19

113

Motion of dust in a planetary magnetosphere - Orbit-averaged equations for oblateness, electromagnetic, and radiation forces with application to Saturn's E ring  

NASA Astrophysics Data System (ADS)

The orbital dynamics of micrometer-sized dust grains is explored numerically and analytically, treating the strongest perturbation forces acting on close circumplanetary dust grains: higher-order gravity, radiation pressure, and the electromagnetic force. The appropriate orbit-average equations are derived and applied to the E ring. Arguments are made for the existence of azimuthal and vertical asymmetries in the E ring. New understanding of the dynamics of E ring dust grains is applied to problems of the ring's breadth and height. The possibility for further ground-based and spacecraft observations is considered.

Hamilton, D. P.

1993-02-01

114

Motion of dust in a planetary magnetosphere - Orbit-averaged equations for oblateness, electromagnetic, and radiation forces with application to Saturn's E ring  

NASA Technical Reports Server (NTRS)

The orbital dynamics of micrometer-sized dust grains is explored numerically and analytically, treating the strongest perturbation forces acting on close circumplanetary dust grains: higher-order gravity, radiation pressure, and the electromagnetic force. The appropriate orbit-average equations are derived and applied to the E ring. Arguments are made for the existence of azimuthal and vertical asymmetries in the E ring. New understanding of the dynamics of E ring dust grains is applied to problems of the ring's breadth and height. The possibility for further ground-based and spacecraft observations is considered.

Hamilton, Douglas P.

1993-01-01

115

Theory of satellite orbit-orbit resonance  

Microsoft Academic Search

On the basis of the strong mathematical and physical parallels between orbit-orbit and spin-orbit resonances, the dynamics of mutual orbit perturbations between two satellites about a massive planet are examined, exploiting an approach previously adopted in the study of spin-orbit coupling. The satellites are assumed to have arbitrary mass ratio and to move in non-intersecting orbits of arbitrary size and

Leon Blitzer; John D. Anderson

1981-01-01

116

The vertical structure of the Daphnis wakes  

NASA Astrophysics Data System (ADS)

When Saturn approached its equinox in August 2009 the Sun cast long shadows onto the ring-plane. Many shadows are caused by local vertical perturbations of the otherwise thin disk. The shadows at the Keeler gap edge are, for example, caused by Daphnis' gravitational perturbations. It has been proposed that these large vertical structures (more than 1 km) are caused by the inclination of Daphnis' orbit [1]. Here we show the possibility that also the ring-moon Daphnis on a non-inclined orbit is able to produce these vertical structures. We performed N-body particle simulations and found that particle collisions in the wake crests can significantly increase the vertical dispersion velocity and therefore the height of the corresponding structures. In the case of the Keeler gap edges this can lead to vertical excursions of the ring particles larger than 1 km. We compare and discuss the importance of both processes (moon inclination and particle collisions) for the vertical structure of the Keeler gap edges.

Seiß, M.; Salo, H.; Hoffmann, H.; Spahn, F.; Schmidt, J.

2012-09-01

117

Vertical lid split approach for optic nerve sheath decompression  

PubMed Central

We describe a vertical lid split orbitotomy approach to perform optic nerve sheath fenestration which was done in a patient with idiopathic intracranial hypertension. A vertical lid split incision was used to enter the superomedial orbit and approach the optic nerve sheath. This approach resulted in a successful nerve sheath fenestration, with improvement in the patient's symptoms. The vertical lid split incision provides access to the optic nerve sheath with minimal morbidity and may be an option for optic nerve sheath decompression.

Prabhakaran, Venkatesh C; Selva, Dinesh

2009-01-01

118

Late-onset orbital hematoma secondary to alloplastic orbital implant mimicking transient ischemic attacks.  

PubMed

Alloplastic orbital implants are commonly used by surgeons in the repair of orbital wall defects. They are generally well tolerated, but they may cause late-onset complications. The authors present the case of a 65-year-old man with a history of left orbital floor fracture repair 25 years prior using a silicone orbital implant. He presented with a 1-year history of recurrent binocular vertical diplopia previously diagnosed as transient ischemic attacks. The patient subsequently presented with symptoms suggestive of orbital cellulitis, and after failure to respond to antibiotic therapy, he underwent surgical removal of the implant, revealing a large orbital hematoma. This case represents an unusual presentation of a known complication associated with orbital implant placement in a patient with previously diagnosed cerebrovascular disease as the cause of his neuroophthalmologic symptoms. PMID:20700069

Gupta, Shivani; Aakalu, Vinay K; Ahmad, Amjad Z

2011-01-01

119

Inflammation of the Orbit  

MedlinePLUS

... Socket Disorders 4 Inflammation of the Orbit (Inflammatory Orbital Pseudotumor) Any or all of the structures within the ... entire orbit and its contents is called inflammatory orbital pseudotumor (which is not really a tumor and is ...

120

Orbital energies and negative electron affinities from density functional theory: Insight from the integer discontinuity.  

PubMed

Orbital energies in Kohn-Sham density functional theory (DFT) are investigated, paying attention to the role of the integer discontinuity in the exact exchange-correlation potential. A series of closed-shell molecules are considered, comprising some that vertically bind an excess electron and others that do not. High-level ab initio electron densities are used to calculate accurate orbital energy differences, Deltavarepsilon, between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO), using the same potential for both. They are combined with accurate vertical ionization potentials, I(0), and electron affinities, A(0), to determine accurate "average" orbital energies. These are the orbital energies associated with an exchange-correlation potential that averages over a constant jump in the accurate potential, of magnitude Delta(XC)=(I(0)-A(0))-Deltavarepsilon, as given by the discontinuity analysis. Local functional HOMO energies are shown to be almost an order of magnitude closer to these average values than to -I(0), with typical discrepancies of just 0.02 a.u. For systems that do not bind an excess electron, this level of agreement is only achieved when A(0) is set equal to the negative experimental affinity from electron transmission spectroscopy (ETS); it degrades notably when the zero ground state affinity is instead used. Analogous observations are made for the local functional LUMO energies, although the need to use the ETS affinities is less pronounced for systems where the ETS values are very negative. The application of an asymptotic correction recovers the preference, leading to positive LUMO energies (but bound orbitals) for these systems, consistent with the behavior of the average energies. The asymptotically corrected LUMO energies typically agree with the average values to within 0.02 a.u., comparable to that observed with the HOMOs. The study provides numerical support for the view that local functionals exhibit a near-average behavior based on a constant jump of magnitude Delta(XC). It illustrates why a recently proposed DFT expression involving local functional frontier orbital energies and ionization potential yields reasonable estimates of negative ETS affinities and is consistent with earlier work on the failure of DFT for charge-transfer excited states. The near-average behavior of the exchange-correlation potential is explicitly illustrated for selected systems. The nature of hybrid functional orbital energies is also mentioned, and the results of the study are discussed in terms of the variation in electronic energy as a function of electron number. The nature of DFT orbital energies is of great importance in chemistry; this study contributes to the understanding of these quantities. PMID:18681637

Teale, Andrew M; De Proft, Frank; Tozer, David J

2008-07-28

121

Orbital energies and negative electron affinities from density functional theory: Insight from the integer discontinuity  

NASA Astrophysics Data System (ADS)

Orbital energies in Kohn-Sham density functional theory (DFT) are investigated, paying attention to the role of the integer discontinuity in the exact exchange-correlation potential. A series of closed-shell molecules are considered, comprising some that vertically bind an excess electron and others that do not. High-level ab initio electron densities are used to calculate accurate orbital energy differences, ??, between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO), using the same potential for both. They are combined with accurate vertical ionization potentials, I0, and electron affinities, A0, to determine accurate ``average'' orbital energies. These are the orbital energies associated with an exchange-correlation potential that averages over a constant jump in the accurate potential, of magnitude ?XC=(I0-A0)-??, as given by the discontinuity analysis. Local functional HOMO energies are shown to be almost an order of magnitude closer to these average values than to -I0, with typical discrepancies of just 0.02 a.u. For systems that do not bind an excess electron, this level of agreement is only achieved when A0 is set equal to the negative experimental affinity from electron transmission spectroscopy (ETS); it degrades notably when the zero ground state affinity is instead used. Analogous observations are made for the local functional LUMO energies, although the need to use the ETS affinities is less pronounced for systems where the ETS values are very negative. The application of an asymptotic correction recovers the preference, leading to positive LUMO energies (but bound orbitals) for these systems, consistent with the behavior of the average energies. The asymptotically corrected LUMO energies typically agree with the average values to within 0.02 a.u., comparable to that observed with the HOMOs. The study provides numerical support for the view that local functionals exhibit a near-average behavior based on a constant jump of magnitude ?XC. It illustrates why a recently proposed DFT expression involving local functional frontier orbital energies and ionization potential yields reasonable estimates of negative ETS affinities and is consistent with earlier work on the failure of DFT for charge-transfer excited states. The near-average behavior of the exchange-correlation potential is explicitly illustrated for selected systems. The nature of hybrid functional orbital energies is also mentioned, and the results of the study are discussed in terms of the variation in electronic energy as a function of electron number. The nature of DFT orbital energies is of great importance in chemistry; this study contributes to the understanding of these quantities.

Teale, Andrew M.; de Proft, Frank; Tozer, David J.

2008-07-01

122

Orbital insolation, ice volume, and greenhouse gases  

Microsoft Academic Search

The SPECMAP models of orbital-scale climate change (Imbrie et al., Paleoceanography 7 (1992) 701, Paleoceanography 8 (1993) 699) are the most comprehensive to date: all major climatic observations were analyzed within the framework of the three orbital signals. Subsequently, tuning of signals in Vostok ice to insolation forcing has fixed the timing of greenhouse-gas changes closely enough to permit an

William F. Ruddiman

2003-01-01

123

Small orbits  

NASA Astrophysics Data System (ADS)

We study both the large and small U-duality charge orbits of extremal black holes appearing in D=5 and D=4 Maxwell-Einstein supergravity theories with symmetric scalar manifolds. We exploit a formalism based on cubic Jordan algebras and their associated Freudenthal triple systems, in order to derive the minimal charge representatives, their stabilizers and the associated “moduli spaces.” After recalling N=8 maximal supergravity, we consider N=2 and N=4 theories coupled to an arbitrary number of vector multiplets, as well as N=2 magic, STU, ST2 and T3 models. While the STU model may be considered as part of the general N=2 sequence, albeit with an additional triality symmetry, the ST2 and T3 models demand a separate treatment, since their representative Jordan algebras are Euclidean or only admit nonzero elements of rank 3, respectively. Finally, we also consider minimally coupled N=2, matter-coupled N=3, and pure N=5 theories.

Borsten, L.; Duff, M. J.; Ferrara, S.; Marrani, A.; Rubens, W.

2012-04-01

124

Shuttle Orbiter Enterprise Transported Via Road at MSFC  

NASA Technical Reports Server (NTRS)

In this view looking northwest over the Marshall Space Flight Center (MSFC), the Shuttle Orbiter Enterprise is seen heading South on Rideout Road near the Redstone Arsenal Fire Station as it is being transported to MSFC's building 4755 for later Mated Vertical Ground Vibration tests (MVGVT) at MSFC's Dynamic Test Stand. The tests marked the first time ever that the entire shuttle complement (including Orbiter, external tank, and solid rocket boosters) were mated vertically.

1978-01-01

125

On vertical profile of ozone at Syowa  

NASA Technical Reports Server (NTRS)

The difference in the vertical ozone profile at Syowa between 1966-1981 and 1982-1988 is shown. The month-height cross section of the slope of the linear regressions between ozone partial pressure and 100-mb temperature is also shown. The vertically integrated values of the slopes are in close agreement with the slopes calculated by linear regression of Dobson total ozone on 100-mb temperature in the period of 1982-1988.

Chubachi, Shigeru

1994-01-01

126

Vertical bounce of two vertically aligned balls  

NASA Astrophysics Data System (ADS)

When a tennis ball rests on top of a basketball and both drop to the floor together, the tennis ball is projected vertically at high speed. A mass-spring model of the impact, as well as air track data, suggest that the tennis ball should be projected at relatively low speed. Measurements of the forces on each ball and the bounce of vertically aligned superballs are used to resolve the discrepancy.

Cross, Rod

2007-11-01

127

Enhanced Activity in Close T Tauri Binaries  

NASA Astrophysics Data System (ADS)

The number of confirmed and suspected close T Tauri binaries (period days) is increasing. We discuss some systems with enhanced emission line activity and periodic line profile changes. Non-axisymmetric flows of plasma in the region between the circumbinary disk and the stars can be generated through the influence of the secondary component. Such enhanced activity is found around binaries with eccentric as well as circular orbits. We discuss our observations of the T Tauri stars RW Aurigae A and RU Lupi, which may host very close brown dwarf companions. Model simulations indicate that non-axisymmetric flows are generated around close binaries with circumbinary disks, also in systems with circular orbits.

Gahm, Gösta

2006-08-01

128

Shapes of d Orbitals  

NSDL National Science Digital Library

Shapes of d Orbitals shows the d orbitals in an axis set. Running the mouse over an orbital reveals the "name" of that orbital. This is good practice for helping students link the name of an orbital to the orientation.Shapes of d Orbitals has a link to D Orbitals in an Octahedral Ligand Field. Here the user may click on the name of any one of the d orbitals to obtain a larger 3-dimensional image. The images are rotatable and scalable. Orbital phase is shown by the different colors.

129

Frequentist confidence intervals for orbits  

NASA Astrophysics Data System (ADS)

The problem of efficiently computing the orbital elements of a visual binary while still deriving confidence intervals with frequentist properties is treated. When formulated in terms of the Thiele-Innes elements, the known distribution of probability in Thiele-Innes space allows efficient grid-search plus Monte-Carlo-sampling schemes to be constructed for both the minimum-?2 and the Bayesian approaches to parameter estimation. Numerical experiments with 104 independent realizations of an observed orbit confirm that the 1 - and 2? confidence and credibility intervals have coverage fractions close to their frequentist values. Appendix is available in electronic form at http://www.aanda.org

Lucy, L. B.

2014-05-01

130

Vertical axis wind turbines  

DOEpatents

A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

Krivcov, Vladimir (Miass, RU) [Miass, RU; Krivospitski, Vladimir (Miass, RU) [Miass, RU; Maksimov, Vasili (Miass, RU) [Miass, RU; Halstead, Richard (Rohnert Park, CA) [Rohnert Park, CA; Grahov, Jurij (Miass, RU) [Miass, RU

2011-03-08

131

GOCE Gravity Gradients in an Orbital Aspect  

NASA Astrophysics Data System (ADS)

This work includes a study of the possibility of the Gravity Field and Steady-State Ocean Circulation Explorer Mission (GOCE) satellite orbit improvement using gravity gradient observations. The orbit improvement is performed by a dedicated software package, called Orbital Computation System (OCS), which is based on the classical least squares method. In an iterative process, the corrections to the initial state vector components of the satellite are estimated, using dynamical models describing gravitational perturbations. An important component implemented in the OCS package is the Cowell 8th order numerical integration procedure, which directly generates the satellite orbit. Taking into account the GOCE real and simulated gravity gradients, different variants of solution of the orbit improvement process were obtained. The improved orbits were compared to the GOCE reference orbits (Precise Science Orbits of the GOCE satellite delivered by the European Space Agency) using the root mean squares (RMS) of the differences between the satellite positions on the improved orbits and on the reference ones. The comparison between the improved orbits and the reference ones was performed with respect to the inertial reference frame (IRF) at J2000.0 epoch. RMS values for the solutions based on the real gravity gradients measurements are at a level of hundreds of kilometers and more. This means that the orbit improvement using the real gravity gradients is ineffective. However, all solutions using the simulated gravity gradients, have RMS values below the threshold determined by RMS values for the computed orbits (without the improvement). The most promising results have been achieved here in the case of improving of short orbital arcs with the lengths from a few to tens of minutes. For these short arcs, RMS values reach the level of centimeters, which is close to the accuracy of Precise Science Orbit of GOCE satellite. Additional research have provided requirements for the effective orbit improvement in terms of the accuracy and spectral content of measured gravity gradients.

Bobojc, Andrzej; Drozyner, Andrzej

2014-05-01

132

Orbital Propellant Depot  

NASA Technical Reports Server (NTRS)

In this artist's concept from 1971, an Earth-to orbit fuel tanker approaches the Orbital Propellant Depot. As envisioned by Marshall Space Flight Center Program Devlopment plarners, an orbital modular propellant storage depot, supplied periodically by the Space Shuttle or Earth-to-orbit fuel tankers would be critical in making available large amounts of fuel to various orbital vehicles and spacecraft.

1971-01-01

133

What is orbital pseudotumor?  

Microsoft Academic Search

We have reviewed the literature in order to delineate the clinicopathologic definition of orbital pseudotumor, also called idiopathic nonspecific orbital inflammation. The clinical picture of orbital pseudotumor varies widely, with signs of mass effect, inflammation and\\/or infiltration. On computed tomography, orbital pseudotumor presents as a unilateral focal or diffuse mass. The histopathologic hallmark of orbital pseudotumor is a mixed inflammatory

Ilse Mombaerts; Roel Goldschmeding; Reinier O. Schlingemann; Leo Koornneef

1996-01-01

134

Earth's Orbit  

NSDL National Science Digital Library

In this activity, learners draw a circle with a single focus, an ellipse with two foci close together, and an ellipse with two foci far apart, and compare the shapes. Learners then measure the Sun in four images each taken in a different season, comparing the apparent size of the Sun in each image to determine when Earth is closest to the Sun. This is the second activity in the SDO Secondary Learning Unit. The activity is reprinted with permission from the Great Explorations in Math and Science (GEMS).

135

MaRS: Mars Express Orbiter Radio Science  

Microsoft Academic Search

The Mars Express Orbiter Radio Science (MaRS) experiment will employ radio occultation to (I) sound the neutral martian atmosphere to derive vertical density, pressure and temperature profiles as functions of height to resolutions better than 100 m, (II) sound the ionosphere to derive vertical ionospheric electron density profiles and a description of the ionosphere through its diurnal and seasonal variations

M. Pätzold; F. M. Neubauer; L. Carone; A. Hagermann; C. Stanzel; B. Häusler; S. Remus; J. Selle; D. Hagl; D. P. Hinson; R. A. Simpson; G. L. Tyler; S. W. Asmar; W. I. Axford; T. Hagfors; J.-P. Barriot; J.-C. Cerisier; T. Imamura; K.-I. Oyama; P. Janle; G. Kirchengast; V. Dehant

2004-01-01

136

Geoscience Laser Altimeter System (GLAS) on the ICESat Mission: On-orbit measurement performance  

Microsoft Academic Search

The GLAS instrument on NASA's ICESat satellite has made over 904 million measurements of the Earth surface and atmosphere through June 2005. During its first seven operational campaigns it has vertically sampled the Earth's global surface and atmosphere on more than 3600 orbits with vertical resolutions approaching 3 cm. This paper summarizes the on-orbit measurement performance of GLAS to date.

James B. Abshire; Xiaoli Sun; Haris Riris; J. Marcos Sirota; Jan F. McGarry; Steve Palm; Donghui Yi; Peter Liiva

2005-01-01

137

RHIC BPM system average orbit calculations  

SciTech Connect

RHIC beam position monitor (BPM) system average orbit was originally calculated by averaging positions of 10000 consecutive turns for a single selected bunch. Known perturbations in RHIC particle trajectories, with multiple frequencies around 10 Hz, contribute to observed average orbit fluctuations. In 2006, the number of turns for average orbit calculations was made programmable; this was used to explore averaging over single periods near 10 Hz. Although this has provided an average orbit signal quality improvement, an average over many periods would further improve the accuracy of the measured closed orbit. A new continuous average orbit calculation was developed just prior to the 2009 RHIC run and was made operational in March 2009. This paper discusses the new algorithm and performance with beam.

Michnoff,R.; Cerniglia, P.; Degen, C.; Hulsart, R.; et al.

2009-05-04

138

Orbit Evolution in Common Envelopes  

NASA Astrophysics Data System (ADS)

We study how the inclination angle and eccentricity evolve during a common envelope phase. During a common envelope phase, a compact star is swallowed by its giant companion and spirals into a tighter orbit. A close binary results if the compact star releases enough energy to expel the envelope. We investigate possible fossil evidence of the common envelope phase on the inclination angle and the eccentricity. A convective common envelope leads to force component perpendicular to the orbital plane, and thus change the orbital inclination. This makes it harder to uniquely identify the signature of neutron star natal kicks. A common envelope is usually assumed to circularize orbits, but some eccentricity in fact arises both from the spiral-in process itself, and from random forces in the orbital plane. When the envelope is expelled, it might seem that the binary system would preserve whatever eccentricity had been established at the final stage of the inspiral. But tidal dissipation by the residual envelope can reduce the eccentricity. The final eccentricity depends on which of these effects wins or how they balance each other. We discuss applications and observational tests of these predictions.

Luan, Jing; Phinney, E. S.

2011-09-01

139

Statistical initial orbit determination  

Microsoft Academic Search

For the ballistic missile initial orbit determination problem in particular, the concept of 'launch folders' is extended. This allows to decouple the observational data from the initial orbit determination problem per se. The observational data is only used to select among the possible orbital element sets in the group of folders. Monte Carlo simulations using up to 7200 orbital element

L. G. Taff; B. Belkin; G. A. Schweiter; K. Sommar

1992-01-01

140

Vertical axis windmill  

SciTech Connect

A vertical axis windmill is described which involves a rotatable central vertical shaft having horizontal arms pivotally supporting three sails that are free to function in the wind like the main sail on a sail boat, and means for disabling the sails to allow the windmill to be stopped in a blowing wind.

Campbell, J.S.

1980-04-08

141

Vertical axis wind turbine  

Microsoft Academic Search

A Darrieus-type vertical axis wind turbine is disclosed which includes a vertically extending rotor tube mounted on a support structure with two or three rotor blades of troposkein configuration on the rotor tube for rotating the tube in response to wind energy and thereby drive a generator to produce electrical power. The turbine includes an erection hinge which permits assembly

Kutcher

1984-01-01

142

Real-time orbit feedback at the APS.  

SciTech Connect

A real-time orbit feedback system has been implemented at the Advanced Photon Source in order to meet the stringent orbit stability requirements. The system reduces global orbit motion below 30Hz by a factor of four to below 5{micro}m rms horizontally and 2{micro}m rms vertically. This paper focuses on dynamic orbit stability and describes the all-digital orbit feedback system that has been implemented at the APS. Implementation of the global orbit feedback system is described and its latest performance is presented. Ultimately, the system will provide local feedback at each x-ray source point using installed photon BPMs to measure x-ray beam position and angle directly. Technical challenges associated with local feedback and with dynamics of the associated corrector magnets are described. The unique diagnostic capabilities provided by the APS system are discussed with reference to their use in identifying sources of the underlying orbit motion.

Carwardine, J.

1998-06-18

143

Revised Orbits of Saturn's Small Inner Satellites  

NASA Technical Reports Server (NTRS)

We have updated the orbits of the small inner Saturnian satellites using additional Cassini imaging observations through 2007 March. Statistically significant changes from previously published values appear in the eccentricities and inclinations of Pan and Daphnis, but only small changes have been found in the estimated orbits of the other satellites. We have also improved our knowledge of the masses of Janus and Epimetheus as a result of their close encounter observed in early 2006.

Jacobson, R. A.; Spitale, J.; Porco, C. C.; Beurle, K.; Cooper, N. J.; Evans, M. W.; Murray, C. D.

2007-01-01

144

Multi-Body Orbit Architectures for Lunar South Pole Coverage  

NASA Technical Reports Server (NTRS)

A potential ground station at the lunar south pole has prompted studies of orbit architectures that ensure adequate coverage. Constant communications can be achieved with two spacecraft in different combinations of Earth-Moon libration point orbits. Halo and vertical families, as well as other orbits near L1 and L2 are considered. The investigation includes detailed results using nine different orbits with periods ranging from 7 to 16 days. Natural solutions are generated in a full ephemeris model, including solar perturbations. A preliminary station-keeping analysis is also completed.

Grebow, D. J.; Ozimek, M. T.; Howell, K. C.; Folta, D. C.

2006-01-01

145

Onset and melting of local orbital order  

NASA Astrophysics Data System (ADS)

The onset and melting of locally staggered charge/orbital correlations is investigated within a two-orbital correlated electron model with inter-orbital and inter-site Coulomb interactions. The CE-type orbital correlation exhibits a sharp onset close to the Curie temperature and rapid thermal melting thereafter, which provides quantitative understanding of the (?/2,?/2,0) feature observed in neutron scattering experiments on La0.7(CaySr1-y)0.3MnO3 single crystals. In the zig-zag AF state, the CE-type orbital correlations are found to be even more readily stabilized, but only within a narrow doping regime around x = 0.5.

Singh, Avinash; Singh, Dheeraj Kumar

2012-02-01

146

Onset and melting of local orbital order.  

PubMed

The onset and melting of locally staggered charge/orbital correlations is investigated within a two-orbital correlated electron model with inter-orbital and inter-site Coulomb interactions. The CE-type orbital correlation exhibits a sharp onset close to the Curie temperature and rapid thermal melting thereafter, which provides quantitative understanding of the (?/2,?/2,0) feature observed in neutron scattering experiments on La(0.7)(Ca(y)Sr(1-y))(0.3)MnO(3) single crystals. In the zig-zag AF state, the CE-type orbital correlations are found to be even more readily stabilized, but only within a narrow doping regime around x = 0.5. PMID:22277731

Singh, Avinash; Singh, Dheeraj Kumar

2012-02-29

147

Interactive Molecular Orbitals  

NSDL National Science Digital Library

The majority of Introductory Chemistry texts provide students with an adequate introduction to the visual aspects of the molecular orbital model for homonuclear diatomic molecules. The treatment of heteronuclear diatomic and polyatomic molecules is less uniform. Heteronuclear diatomics, when mentioned, are invariably treated as being derived from homonuclear diatomics. While the atomic orbital energy level differences in heteronuclear diatomics is sometimes pictured, the consequences of those differences for the resultant molecular orbitals are rarely discussed. The discussion of polyatomic molecular orbitals in these texts is limited to showing that parallel p-orbitals produce delocalized pi molecular orbitals. The molecules typically mentioned in this context are benzene, nitrate ion and carbonate ion. However, It is rarely pointed out that the six p-orbitals in benzene would form 6 pi molecular orbitals, and that only one of these orbitals would look like the picture in the text.These interactive modules are designed to clarify this subject.

148

Vertical Line Test  

NSDL National Science Digital Library

In this activity, students try to connect given points on a graph in a way that they will pass the vertical line test. If the points can't be made to pass the vertical line test, the student must adjust the points so they will pass the test. This activity allows students to explore the vertical line test for functions. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

2010-01-01

149

Linear Optics From Closed Orbits (LOCO): An Introduction  

SciTech Connect

The LOCO code is used to find and correct errors in the linear optics of storage rings. The original FORTRAN code was written to correct the optics of the NSLS X-Ray ring, and was applied soon thereafter to debug problems with the ALS optics. The ideas used in the code were developed from previous work at SLAC. Several years ago, LOCO was rewritten in MATLAB. As described in this newsletter, the MATLAB version includes a user-friendly interface, with many useful fitting and analysis options. LOCO has been used at many accelerators. Presently, a search for LOCO in the text of papers on the Joint Accelerator Conferences Website yields 107 papers. A comprehensive survey of applications will not be included here. Details of recent results at a few light sources are included in this newsletter. In the past, the quality of LOCO fitting results varied significantly, depending on the storage ring. In particular, the results were mixed for colliding beam facilities, where there tend to be fewer BPMs that in light sources. Fitting rings with less BPM data to constrain the fit optics parameters often led to unreasonably large fit quadrupole gradient variations. Recently, modifications have been made to the LOCO fitting algorithm which leads to much better results when the BPM data does not tightly constrain the fit parameters. The modifications are described in this newsletter, and an example of results with this new algorithm is included.

Safranek, James; /SLAC

2009-06-18

150

Fibrolipoma of the orbit.  

PubMed

A 47-year-old woman presented with a growing mass on the lateral rim of orbit. Orbital CT revealed a well-circumscribed soft tissue mass in the right lateral orbit, with focal hyperostosis of the adjacent zygomatic bone. MRI showed a lesion of mixed T1-signal intensity, which became hypointense after fat suppression. The lesion was excised, and the diagnosis of orbital fibrolipoma was made by histopathologic examination. There was no evidence of tumor after 12 months of follow-up. Orbital fibrolipoma is a rare variant of lipoma, with only 1 case described previously. It should be considered in the differential diagnosis of orbital mass. PMID:20700070

Kim, Myung Hun; Sa, Ho Seok; Woo, Kyung; Kim, Yoon-Duck

2011-01-01

151

Micromachined electrostatic vertical actuator  

DOEpatents

A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

Lee, Abraham P. (Walnut Creek, CA); Sommargren, Gary E. (Santa Cruz, CA); McConaghy, Charles F. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

1999-10-19

152

Paroxysmal Vertical Ocular Dyskinesia.  

National Technical Information Service (NTIS)

Paroxysmal vertical ocular dyskinesia of a previously undescribed nature is reported in a 42-year old woman with demyelinating disease, who was affected with a myelopathy, bilateral amblyopia, and a modified sylvian aqueduct syndrome. Electroencephalograp...

J. B. MacLean J. F. Sassin

1973-01-01

153

Variational definitions of orbital energies  

NASA Astrophysics Data System (ADS)

A formulation of Koopmans' theorem is derived for high-spin half-filled open shells in the restricted openshell Hartree-Fock (ROHF) method based on a variational treatment of both the initial (non-ionized) open-shell system X with spin S and the corresponding ions having a hole or an extra electron in the closed, open and virtual shells respectively. The six processes for forming ions with spin S+/-1/2 require two different definitions for canonical orbitals within each shell. These processes may be treated equivalently within a restricted CI using arbitrary non-canonical linear transforms of the ROHF orbitals optimal for the initial system. Canonical UHF orbitals also obey a variational principle for the ion energies, but they provide less appropriate estimates for actual states of the ion. Canonical spin-unrestricted Kohn-Sham orbitals with common exchange-correlation functionals suffer from all of the UHF problems and from selfinteraction error. They generally are not useful estimates for ion energies.

Davidson, Ernest R.

2012-12-01

154

'Columbia Hills' from Orbit  

NASA Technical Reports Server (NTRS)

This view of the 'Columbia Hills' in Gusev Crater was made by draping an image from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter (image E0300012 from that camera) over a digital elevation model that was derived from two Mars Orbiter Camera images (E0300012 and R0200357).

This unique view is helpful to the rover team members as they plan the journey of NASA's Mars Exploration Rover Spirit to the base of the Columbia Hills and beyond. Spirit successfully completed a three-month primary mission, and so far remains healthy in an extended mission of bonus exploration. As of sol 135 (on May 21, 2004), Spirit sits approximately 680 meters (0.4 miles) away from its first target at the western base of the hills, a spot informally called 'West Spur.' The team estimates that Spirit will reach West Spur by sol 146 (June 1, 2004). Spirit will most likely remain there for about a week to study the outcrops and rocks associated with this location.

When done there, Spirit will head approximately 620 meters (0.38 miles) to a higher-elevation location informally called 'Lookout Point.' Spirit might reach Lookout Point by around sol 165 (June 20, 2004). On the way, the rover will pass by and study ripple-shaped wind deposits that may reveal more information about wind processes on Mars.

Lookout Point will provide a great vantage point for scientists to remotely study the inner basin area of the Columbia Hills. This basin contains a broad range of interesting geological targets including the informally named 'Home Plate' and other possible layered outcrops. These features suggest that the hills contain rock layers. Spirit might investigate the layers to determine whether they are water-deposited sedimentary rock.

Once at Lookout Point, Spirit will acquire 360-degree panoramic images of the entire area to help define the rover's next steps. Assuming the rover stays healthy, Spirit will eventually drive down into the basin to get an up-close look at interesting features there.

2004-01-01

155

Orbital dynamics in galaxy mergers  

NASA Astrophysics Data System (ADS)

In the favored vacuum energy + cold dark matter (ACDM) cosmology, galaxies form through a hierarchical merging process. Mergers between comparable-mass sys tems are qualitatively different from the ongoing accretion of small objects by much larger ones, in that they can radically transform the nature of the merging objects, e.g. through violent relaxation of the stars and dark matter, triggered starbursts, and quasar activity. This thesis covers two phenomena unique to major galaxy mergers: the formation of supermassive black hole (SMBH) binary and triple systems, and the transformation of the stellar orbit structure through violent relaxation, triggered gas inflow, and star formation. In a major merger, the SMBHs can spiral in and form a bound binary in less than a Hubble time. If the binary lifetime exceeds the typical time between mergers, then triple black hole (BH) systems may form. We study the statistics of close triple-SMBH encounters in galactic nuclei by computing a series of three-body orbits with physically-motivated initial conditions appropriate for giant elliptical galaxies. Our simulations include a smooth background potential consisting of a stellar bulge plus a dark matter halo, drag forces due to gravitational radiation and dynamical friction on the stars and dark matter, and a simple model of the time evolution of the inner density profile under heating and mass ejection by the SMBHs. We find that the binary pair coalesces as a result of repeated close encounters in ~85% of our runs. In about 40% of the runs the lightest BH is left wandering through the galactic halo or escapes the galaxy altogether. The triple systems typically scour out cores with mass deficits ~1-2 times their total mass. The high coalescence rate and prevalence of very high-eccentricity orbits could provide interesting signals for the future Laser Interferometer Space Antenna (LISA). Our study of remnant orbit structure involved 42 disk-disk mergers at various gas fractions, and 10 re-mergers of the 40% gas remnants. All simulations were run using a version of GADGET-2 [173] that included subresolution models of radiative cooling, star formation, and supernova and AGN feedback. The potential was frozen at the last snapshot of each simulation and the orbits of ~50,000 randomly chosen stars were integrated for ~100 dynamical times, and classified based on their Fourier spectra using the algorithm of [30]. The 40% gas remnants were found to be dominated by minor-axis tube orbits in their inner regions, whereas box orbits were the dominant orbit family in the inner parts of the dissipationless disk-disk and remnant-remnant systems. The phase space available to minor-axis tube orbits in even the 5% gas remnants was much larger than that in the dissipationless remnants, but the 5% gas remnants are not fast rotators because these orbits tend to be isotropically distributed at low gas fractions. Some of the remnants show significant minor axis rotation, due to large orientation twists in their outer parts (in the 40% gas remnants) and asymmetrically rotating major-axis tube orbits throughout the remnants (in the re-mergers).

Hoffman, Loren

156

The Orbits of Saturn's Small Satellites  

NASA Astrophysics Data System (ADS)

We report on the orbits of the small, inner Saturnian satellites, either recovered or newly-discovered in recent Cassini imaging observations (excluding Helene, Telesto and Calypso, which will be discussed by another group). Using combined Cassini and Voyager observations, the mean motions of Pan and Atlas have been refined by several orders of magnitude. The Atlas orbit is based on a numerical integration perturbed by all of the massive Saturnian satellites including Prometheus, Pandora, Janus, and Epimetheus. We find that the dominant perturber is Prometheus. Cassini, Voyager, HST, and Earth-based data have been used to refine the orbits of Janus, Epimetheus, Prometheus and Pandora. The orbits of the co-orbitals, Janus and Epimetheus, remain stable; their orbital swap does not occur until Februrary, 2006. The orbits of Prometheus and Pandora remain close to recent values (Jacobson and French 2004, Icarus, 172, 382). Six new objects have been discovered to date -- three (S/2004 S3, S4, S6) in close proximity to the F ring, two (S/2004 S1(Methone), S/2004 S2(Pallene)) between the orbits of Mimas and Enceladus, and one (S/2004 S5(Polydeuces)) co-orbital with Dione, trailing by ˜60 deg (Porco et al., Science 307, 25 Feb 2005). One of the F-ring objects -- S/2004 S3 -- was seen over a 118-day interval, but none of those objects, including S/2004 S3, were subsequently recovered in an F-ring movie acquired on 15 November 2004 (29 days after the last sighting of S/2004 S3) with an image scale of 4 km/pixel, in which all were expected to appear. Consequently, we are confident only that Methone, Pallene and Polydeuces are solid satellites; S/2004 S3, S4 and S6 may be transient clumps. Our orbital fits, both precessing ellipse models and orbital integrations, suggest that Pallene is the same object as S/1981 S14, imaged by Voyager 2 on 23 August 1981, contrary to our initial reports (IAU circular 8389). The orbital inclination and eccentricity of Methone are considerably less excited than expected, given its proximity to Mimas (Porco et al., Science; in press), but orbital integrations spanning 4 years show that significant longitudinal perturbations from Mimas explain the observations. Polydeuces' orbit has been integrated over 5 years and is seen to librate about Saturn's L5 point with a period of about 792 days and an amplitude of about 25.8 deg.

Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M.; Charnoz, S.

2005-05-01

157

Lunar orbiting prospector  

NASA Technical Reports Server (NTRS)

One of the prime reasons for establishing a manned lunar presence is the possibility of using the potential lunar resources. The Lunar Orbital Prospector (LOP) is a lunar orbiting platform whose mission is to prospect and explore the Moon from orbit in support of early lunar colonization and exploitation efforts. The LOP mission is divided into three primary phases: transport from Earth to low lunar orbit (LLO), operation in lunar orbit, and platform servicing in lunar orbit. The platform alters its orbit to obtain the desired surface viewing, and the orbit can be changed periodically as needed. After completion of the inital remote sensing mission, more ambitious and/or complicated prospecting and exploration missions can be contemplated. A refueled propulsion module, updated instruments, or additional remote sensing packages can be flown up from the lunar base to the platform.

1988-01-01

158

Atomic Orbital Shapes  

NSDL National Science Digital Library

This applet shows 3-dimensional representations of hydrogenic orbital surfaces. Orbital phase is shown by the different colors. The images are rotatable and scalable. This applet will run very slowly on older, slower machines.

159

Harmonically Excited Orbital Variations.  

National Technical Information Service (NTIS)

Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In...

T. Morgan

1985-01-01

160

Orbiting Binary Stars  

NSDL National Science Digital Library

This simulation demonstrates the path of binary stars' orbit. The user is able to set the masses, orbital separation, orbital eccentricity, the inclination angle to our line of sight, and the angle of the nodes of two orbiting stars. The observed velocities of the two stars, and the Doppler shifted spectral lines are also shown in the upper right box. The site also includes definitions of terms used, instructions on how to use the simulation and a few examples.

Kolena, John

2007-12-11

161

Mars orbit selection  

NASA Technical Reports Server (NTRS)

Parking orbits for a manned Mars mission are examined for ease of access to the Martian moons. Delta V plots for a variety of burns versus elliptical orbit apoapsis are included. A high elliptical orbit (24 hour period, 500 km periapsis, 20 to 30 deg. inclination) minimizes delta V to the Martian moons and Mars orbit insertion (MOI) and trans-Earth injection (TEI) delta Vs.

Babb, Gus R.; Stump, William R.

1986-01-01

162

Pathologies of the Orbit  

Microsoft Academic Search

Pathologic lesions of the orbit continue to be a great challenge to the diagnostic radiologist. The complex anatomy of the\\u000a orbit on the one hand and the multitude of disease entities that may affect the orbit on the other hand demand a simple, well-structured\\u000a approach to diagnostic imaging. Subdividing the orbit into four (or five) distinct spaces, i.e., the eyeball,

Ullrich G. Mueller-Lisse; JuerGen Lutz

163

Arietid Meteor Orbits Measurements  

NASA Astrophysics Data System (ADS)

The Arietid meteor shower is one of the strongest of the year. The origin of this daytime shower is unknown; the orbit is therefore of great interest, since an accurate orbit distribution is needed to integrate the shower backward in time to test associations with comets or asteroids. The orbital parameters of the Arietid shower as a function of time, with errors, have been generated using 415 radar orbits gathered at the CMOR facility in Tavistock, Canada.

Campbell-Brown, M. D.

2004-12-01

164

A Review on Close Satellite Theory.  

National Technical Information Service (NTIS)

A review on close satellite theory is presented. A treatment is given on normal orbits in which case it is assumed that both the attracting and attracted masses are concentrated in points. Second, those factors are reviewed which deviate from these assump...

I. I. Mueller

1964-01-01

165

Terrestrial planet formation surrounding close binary stars  

Microsoft Academic Search

Most stars reside in binary\\/multiple star systems; however, previous models of planet formation have studied growth of bodies orbiting an isolated single star. Disk material has been observed around both components of some young close binary star systems. Additionally, it has been shown that if planets form at the right places within such disks, they can remain dynamically stable for

Elisa V. Quintana; Jack J. Lissauer

2006-01-01

166

Orbits of Photographic Meteors  

Microsoft Academic Search

New photographic observations of meterors in the brightness range-5 > Mp > -18 (?) and with a median value of M = -8.5 have yielded orbits with a precision of better than 1° in the angular elements and of about 0.05 in e and 1\\/a. A comparison of 100 of these fireball orbits with Super-Schmidt orbits shows: A. A class

R. E. McCrosky

1967-01-01

167

Orbital-Lifetime Program  

NASA Technical Reports Server (NTRS)

Orbital Lifetime Program (OL) analyzes long-term motion of Earthorbiting spacecraft at altitudes of up to 2,500 km. Models perturbations to orbit caused by solar-radiation pressure, atmospheric drag, and gravitational effects of Sun, Moon, and oblate Earth. Used to predict orbital lifetime and decay rate of satellites. OL written in FORTRAN 77.

Orr, L. H.

1986-01-01

168

SEASAT B orbit synthesis  

NASA Technical Reports Server (NTRS)

Addition were made to Battelle's Interactive Graphics Orbit Selection (IGOS) program; IGOS was exercised via telephone lines from JPL, and candidate SEASAT orbits were analyzed by Battelle. The additions to the program enable clear understanding of the implications of a specific orbit to the diverse desires of the SEASAT user community.

Rea, F. G.; Warmke, J. M.

1976-01-01

169

Statistical initial orbit determination  

Microsoft Academic Search

The computation of a meaningful initial orbital element set based on angles- only data is abandoned as a futile endeavor. Rather, for the ballistic missile initial orbit determination problem in particular, the concept of 'launch folders' is extended. This allows one to decouple the observational data from the initial orbit determination problem per se. The observational data is only used

Laurence G. Taff; Barry Belkin; G. A. Schweiter; K. Sommar

1991-01-01

170

Five Equivalent d Orbitals  

ERIC Educational Resources Information Center

Amplifies and clarifies a previous paper on pyramidal d orbitals. Discusses two sets of pyramid d orbitals with respect to their maximum bond strength and their symmetry. Authors described the oblate and prolate pentagonal antiprisms arising from the two sets of five equivalent d orbitals. (RR)

Pauling, Linus; McClure, Vance

1970-01-01

171

Idiopathic sclerosing orbital inflammation  

Microsoft Academic Search

Objective: To perform a multicenter review of the clinical features and treatment of 31 patients with idiopathic sclerosing orbital inflammation. Methods: We included all patients with histologically confirmed idiopathic sclerosing orbital inflammation from 5 regional orbital centers. We reviewed the case notes to determine the clinical presentation, diagnostic features, and response to treatment. The main outcome measures were duration and

James D. Hsuan; Dinesh Selva; Alan A. McNab; Timothy J. Sullivan; Peerooz Saeed; Brett A. O'Donnell

2006-01-01

172

Orbital cavernous hemangiomas  

Microsoft Academic Search

Cavernous hemangiomas are the most frequently found primary tumors in the orbital region. They normally appear in adults. Diagnostic features in the majority of cases include protrusio bulbi and orbital enlargement. B-Scan and computed tomography\\/MRI are the prime diagnostic aids. We recommend surgical removal of these tumors, at least in cases with marked orbital protrusion or significant optic nerve compression.

Thomas Herter; Harald Bennefeld; Matthias Brandt

1988-01-01

173

Mean value coordinates for closed triangular meshes  

Microsoft Academic Search

Constructing a function that interpolates a set of values defined at vertices of a mesh is a fundamental operation in computer graphics. Such an interpolant has many uses in applications such as shading, parameterization and deformation. For closed polygons, mean value coordinates have been proven to be an excellent method for constructing such an interpolant. In this paper, we generalize

Tao Ju; Scott Schaefer; Joe D. Warren

2005-01-01

174

Tidal evolution of close binary asteroid systems  

NASA Astrophysics Data System (ADS)

We provide a generalized discussion of tidal evolution to arbitrary order in the expansion of the gravitational potential between two spherical bodies of any mass ratio. To accurately reproduce the tidal evolution of a system at separations less than 5 times the radius of the larger primary component, the tidal potential due to the presence of a smaller secondary component is expanded in terms of Legendre polynomials to arbitrary order rather than truncated at leading order as is typically done in studies of well-separated system like the Earth and Moon. The equations of tidal evolution including tidal torques, the changes in spin rates of the components, and the change in semimajor axis (orbital separation) are then derived for binary asteroid systems with circular and equatorial mutual orbits. Accounting for higher-order terms in the tidal potential serves to speed up the tidal evolution of the system leading to underestimates in the time rates of change of the spin rates, semimajor axis, and mean motion in the mutual orbit if such corrections are ignored. Special attention is given to the effect of close orbits on the calculation of material properties of the components, in terms of the rigidity and tidal dissipation function, based on the tidal evolution of the system. It is found that accurate determinations of the physical parameters of the system, e.g., densities, sizes, and current separation, are typically more important than accounting for higher-order terms in the potential when calculating material properties. In the scope of the long-term tidal evolution of the semimajor axis and the component spin rates, correcting for close orbits is a small effect, but for an instantaneous rate of change in spin rate, semimajor axis, or mean motion, the close-orbit correction can be on the order of tens of percent. This work has possible implications for the determination of the Roche limit and for spin-state alteration during close flybys.

Taylor, Patrick A.; Margot, Jean-Luc

2010-12-01

175

Verticality in hydroelectric machines  

SciTech Connect

Everyone who erects a vertical hydroelectric machine makes an effort to put the machine together so that its elements are vertical. A plumb line (or its optical equivalent) is a practical starting point for aligning the stationary parts of the machine - the generator stator, turbine case, and bearings. This does not mean, though, that the machine parts must be in near-perfect vertical orientation for the machine to perform well. Verticality is sometimes over-emphasized when procedures are undertaken to achieve good machine alignment. If the generator rotor, the connecting shaft, and the turbine runner are centered in stationary parts that are well-aligned along the same axis angle, this angle can depart from true vertical by a significant amount without ill effect. Mechanical balance does not often play a large part in determining how well a generator rotor is centered in the air gap. Magnetic forces are much more important. This is why it is desirable to maintain air gap variations around the machine to less than 5 percent from the average. However, this is sometimes difficult, especially if bearing clearances are large.

O'Kelly, F.

1991-12-01

176

Microorbitalism: a technique for orbital rim expansion.  

PubMed

A simple technique for orbital aperture expansion to facilitate placement of ocular prostheses is described. Both superolateral and inferolateral orbital margins are released by means of a single burr hole craniectomy of the frontosphenoid bone behind the orbital process of the frontal bone. Vertical and horizontal marginal lengthenings are performed by a rotatory displacement of one bone segment alongside the other. The expanded osseous aperture is secured with wire and plate-and-screw fixation following a supraorbital rim craniectomy to allow an adequate fit. The result provides for easier access of ocular prostheses and tissue expanders. The method has been applied to a series of patients with microorbitalism due to unilateral or bilateral congenital anophthalmia over the past 3 years without complication and with excellent results. Three-dimensional re-formatted CT reconstructions of the craniofacial skeleton are shown preoperatively and postoperatively. PMID:1896532

Elisevich, K; Bite, U; Colcleugh, R

1991-10-01

177

Dynamical Effects of Mass Exchange in Close Binary Systems.  

National Technical Information Service (NTIS)

The problem of mass exchange in a close binary system is studied from the point of view of the evolution of the orbital elements. It is assumed that the original orbit is nearly circular and one of the components has expanded and fills the area inside the...

J. D. Hadjidemetriou

1968-01-01

178

The mass-period distribution of close-in exoplanets  

Microsoft Academic Search

Context. The lower limit to the distribution of orbital periods P for the current population of close-in exoplanets shows a distinctive discontinuity located at approximately one Jovian mass. Most smaller planets have orbital periods longer than P ~ 2.5 days, while higher masses are found down to P ~ 1 day. Aims: We analyze whether this observed mass-period distribution could

P. Benítez-Llambay; F. Masset; C. Beaugé

2011-01-01

179

Orbit Software Suite  

NASA Technical Reports Server (NTRS)

Orbit Software Suite is used to support a variety of NASA/DM (Dependable Multiprocessor) mission planning and analysis activities on the IPS (Intrusion Prevention System) platform. The suite of Orbit software tools (Orbit Design and Orbit Dynamics) resides on IPS/Linux workstations, and is used to perform mission design and analysis tasks corresponding to trajectory/ launch window, rendezvous, and proximity operations flight segments. A list of tools in Orbit Software Suite represents tool versions established during/after the Equipment Rehost-3 Project.

Osgood, Cathy; Williams, Kevin; Gentry, Philip; Brownfield, Dana; Hallstrom, John; Stuit, Tim

2012-01-01

180

Superior orbital fissure syndrome  

PubMed Central

A patient is described with features of a superior orbital fissure (Tolosa Hunt) syndrome and a coexistent intraorbital lesion. There was radiological evidence both of narrowing of the carotid artery and of an intraorbital obstruction of venous return from the orbit. The diagnostic value of orbital venography and carotid angiography in the investigation of granulomata in the region of the orbit is stressed. The condition described here is responsive to corticosteroids and it is also inferred that there may be a clinicopathological spectrum encompassing both the Tolosa Hunt syndrome and pseudotumour of the orbit. Images

Hallpike, J. F.

1973-01-01

181

Orbit correction in an orbit separated cyclotron  

NASA Astrophysics Data System (ADS)

The orbit separated proton cyclotron (OSC) described in [1] differs in concept from that of a separated orbit cyclotron (SOC) [2]. Synchronous acceleration in an OSC is based on harmonic number jumps and orbit length adjustments via reverse bending. Four-turn acceleration in the OSC enables it to have four times fewer cryogenic-cavity systems than in a superconducting linac of the same high beam power and energy range. Initial OSC studies identified a progressive distortion of the spiral beam orbits by the off-axis, transverse deflecting fields in its accelerating cavities. Compensation of the effects of these fields involves the repeated use of a cavity field map, in a 3-D linac tracking code, to determine the modified arc bends required for the OSC ring. Subsequent tracking studies confirm the compensation scheme and show low emittance growth in acceleration.

Plostinar, C.; Rees, G. H.

2014-04-01

182

16. Perspective view of bascule span in closed position and ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

16. Perspective view of bascule span in closed position and vertical left span in open position, facing northeast - Sault Ste. Marie International Railroad Bridge, Spanning Soo Locks at St. Marys Falls Canal, Sault Ste. Marie, Chippewa County, MI

183

Painless orbital myositis.  

PubMed

Idiopathic orbital inflammation is the third most common orbital disease, following Graves orbitopathy and lymphoproliferative diseases. We present a 11 year old girl with 15 days history of painless diplopia. There was no history of fluctuation of symptoms, drooping of eye lids or diminished vision. She had near total restricted extra-ocular movements and mild proptosis of the right eye. There was no conjunctival injection, chemosis, or bulb pain. There was no eyelid retraction or lid lag. Rest of the neurological examination was unremarkable.Erythrocyte sedimentation rate was raised with eosinophilia. Antinuclear antibodies were positive. Liver, renal and thyroid functions were normal. Antithyroid, double stranded deoxyribonucleic acid and acetylcholine receptor antibodies were negative. Repetitive nerve stimulation was negative. Magnetic resonance imaging (MRI) of the orbit was typical of orbital myositis. The patient responded to oral steroids. Orbital myositis can present as painless diplopia. MRI of orbit is diagnostic in orbital myositis. PMID:22919201

Chakor, Rahul T; Santhosh, N S

2012-07-01

184

Glow experiment documentation of OMS/RCS pods and vertical stabilizer  

NASA Technical Reports Server (NTRS)

Glow experiment documentation of orbital maneuvering system (OMS) reaction control system (RCS) pods and vertical stabilizer shows chemoluminescent effect resulting from atomic oxygen impacting the spacecraft and building to the point that the atomic oxygen atoms combine to form molecules of oxygen. Image intensifier on NIKON 35mm camera used to record glow on vertical tail and OMS pods.

1982-01-01

185

Glow experiment documentation of OMS/RCS pods and vertical stabilizer  

NASA Technical Reports Server (NTRS)

Glow experiment documentation of orbital maneuvering system (OMS) reaction control system (RCS) pods and vertical stabilizer shows chemo-luminescent effect resulting from atomic oxygen impacting the spacecraft and building to the point that the atomic oxygen atoms combine to form molecules of oxygen. Image intensifier on NIKON 35mm camera was used to record glow on vertical tail and OMS pods.

1982-01-01

186

Vertical emitting aperture nanoantennas.  

PubMed

Herein we propose, theoretically investigate, and numerically demonstrate a compact design for a vertical emitter at a wavelength of 1.5 ?m based on nanophotonic aperture antennas coupled to a dielectric waveguide. The structure utilizes a plasmonic antenna placed above a Si3N4 waveguide with a ground plane for breaking the up-down symmetry and increasing the emission efficiency. Three-dimensional (3-D) finite-difference time-domain (FDTD) simulations reveal that up to 60% vertical emission efficiency is possible in a structure only four wavelengths long with a 3 dB bandwidth of over 300 nm. PMID:22555702

Yaacobi, Ami; Timurdogan, Erman; Watts, Michael R

2012-05-01

187

Vertical breast reduction.  

PubMed

The vertical approach to breast reduction surgery has achieved increasing popularity. The learning curve can be a problem for surgeons starting to incorporate vertical techniques into their practices; the medial pedicle approach is outlined in detail. Designing and creating the medial pedicle is straightforward and rotating it into position is easy. An elegant curve to the lower pole of the reduced breast can thus be created. Current concepts related to the skin brassiere, breast sutures, and the longevity of results are reviewed. It is important for the surgeon to understand that the skin resection pattern and the pedicle design are separate issues when discussing breast reduction surgery. PMID:20574477

Hall-Findlay, Elizabeth J

2004-08-01

188

GOCE Satellite Orbit in a Computational Aspect  

NASA Astrophysics Data System (ADS)

The presented work plays an important role in research of possibility of the Gravity Field and Steady-State Ocean Circulation Explorer Mission (GOCE) satellite orbit improvement using a combination of satellite to satellite tracking high-low (SST- hl) observations and gravity gradient tensor (GGT) measurements. The orbit improvement process will be started from a computed orbit, which should be close to a reference ("true") orbit as much as possible. To realize this objective, various variants of GOCE orbit were generated by means of the Torun Orbit Processor (TOP) software package. The TOP software is based on the Cowell 8th order numerical integration method. This package computes a satellite orbit in the field of gravitational and non-gravitational forces (including the relativistic and empirical accelerations). The three sets of 1-day orbital arcs were computed using selected geopotential models and additional accelerations generated by the Moon, the Sun, the planets, the Earth and ocean tides, the relativity effects. Selected gravity field models include, among other things, the recent models from the GOCE mission and the models such as EIGEN-6S, EIGEN-5S, EIGEN-51C, ITG-GRACE2010S, EGM2008, EGM96. Each set of 1-day orbital arcs corresponds to the GOCE orbit for arbitrary chosen date. The obtained orbits were compared to the GOCE reference orbits (Precise Science Orbits of the GOCE satellite delivered by the European Space Agency) using the root mean squares (RMS) of the differences between the satellite positions in the computed orbits and in the reference ones. These RMS values are a measure of performance of selected geopotential models in terms of GOCE orbit computation. The RMS values are given for the truncated and whole geopotential models. For the three variants with the best fit to the reference orbits, the empirical acceleration models were added to the satellite motion model. It allowed for further improving the fitting of computed orbits to the reference orbits. A linear and non-linear model of empirical accelerations was used. After using the non-linear model, the RMS values were reduced by the factor from about 2 to 3 compared with the linear model. A general form of the non-linear model of empirical accelerations is shown in this work. This model can be scaled to a given set of dynamical data for orbit determination by estimating of 192 parameters. The comparison between the computed orbits and the reference ones was performed with respect to the inertial reference frame (IRF) at J2000.0 epoch. Thus, the given GOCE reference orbits were transformed from ITRF2005 reference frame into IRF frame. It is shown that the velocity components of GOCE reference orbits must be transformed into IRF frame using the full rotation vector of the Earth. In such a case RMS values reach a level of meters.

Bobojc, Andrzej; Drozyner, Andrzej

2013-04-01

189

Chaos in orbits due to disk crossings.  

PubMed

We study orbits of halo stars in simple models of galaxies with disks and halos to see if the cumulative effects of the sudden changes in acceleration that occur at disk crossings can induce chaos. We find that they can, although not in all orbits and not in all potentials. Most of the orbits that become chaotic stay relatively close to the disk and range widely in the radial direction. Heavier disks and increased halo flattening both enhance the extent of the chaos. A limited range of experiments with a three-component model of the Milky Way with an added central bulge finds that many chaotic disk-crossing orbits can be expected in the central regions, and that prolateness of the halo is much more effective than oblateness in generating chaos. PMID:15980309

Hunter, C

2005-06-01

190

A radar orbit search for meteors from comet Lexell  

Microsoft Academic Search

In this paper the 3759 radar meteor orbits determined from Adelaide, South Australia, in the 1960's are analysed using a new and powerful stream-search technique. Although there is some evidence for Lexell-related showers, this is not unambiguous due to the presence in the sporadic background of many orbits with similar orbital characteristics (very low inclinations, aphelia close to Jupiter), so

D. I. Olsson-Steel

1988-01-01

191

Orbits and Interiors of Planets  

NASA Astrophysics Data System (ADS)

The focus of this thesis is a collection of problems of timely interest in orbital dynamics and interior structure of planetary bodies. The first three chapters are dedicated to understanding the interior structure of close-in, gaseous extrasolar planets (hot Jupiters). In order to resolve a long-standing problem of anomalously large hot Jupiter radii, we proposed a novel magnetohydrodynamic mechanism responsible for inflation. The mechanism relies on the electro-magnetic interactions between fast atmospheric flows and the planetary magnetic field in a thermally ionized atmosphere, to induce electrical currents that flow throughout the planet. The resulting Ohmic dissipation acts to maintain the interior entropies, and by extension the radii of hot Jupiters at an enhanced level. Using self-consistent calculations of thermal evolution of hot Jupiters under Ohmic dissipation, we demonstrated a clear tendency towards inflated radii for effective temperatures that give rise to significant ionization of K and Na in the atmosphere, a trend fully consistent with the observational data. Furthermore, we found that in absence of massive cores, low-mass hot Jupiters can over-flow their Roche-lobes and evaporate on Gyr time-scales, possibly leaving behind small rocky cores. Chapters four through six focus on the improvement and implications of a model for orbital evolution of the solar system, driven by dynamical instability (termed the "Nice" model). Hydrodynamical studies of the orbital evolution of planets embedded in protoplanetary disks suggest that giant planets have a tendency to assemble into multi-resonant configurations. Following this argument, we used analytical methods as well as self-consistent numerical N-body simulations to identify fully-resonant primordial states of the outer solar system, whose dynamical evolutions give rise to orbital architectures that resemble the current solar system. We found a total of only eight such initial conditions, providing independent constraints for the solar system's birth environment. Next, we addressed a significant drawback of the original Nice model, namely its inability to create the physically unique, cold classical population of the Kuiper Belt. Specifically, we showed that a locally-formed cold belt can survive the transient instability, and its relatively calm dynamical structure can be reproduced. The last four chapters of this thesis address various aspects and consequences of dynamical relaxation of planetary orbits through dissipative effects as well as the formation of planets in binary stellar systems. Using octopole-order secular perturbation theory, we demonstrated that in multi-planet systems, tidal dissipation often drives orbits onto dynamical "fixed points," characterized by apsidal alignment and lack of periodic variations in eccentricities. We applied this formalism towards investigating the possibility that the large orbital eccentricity of the transiting Neptune-mass planet Gliese 436b is maintained in the face of tidal dissipation by a second planet in the system and computed a locus of possible orbits for the putative perturber. Following up along similar lines, we used various permutations of secular theory to show that when applied specifically to close-in low-mass planetary systems, various terms in the perturbation equations become separable, and the true masses of the planets can be solved for algebraically. In practice, this means that precise knowledge of the system's orbital state can resolve the sin( i) degeneracy inherent to non-transiting planets. Subsequently, we investigated the onset of chaotic motion in dissipative planetary systems. We worked in the context of classical secular perturbation theory, and showed that planetary systems approach chaos via the so-called period-doubling route. Furthermore, we demonstrated that chaotic strange attractors can exist in mildly damped systems, such as photo-evaporating nebulae that host multiple planets. Finally, we considered planetary formation in highly inclined binary systems,

Batygin, Konstantin

2012-05-01

192

Vertical Fluxes of Potential Vorticity and the Structure of the Thermocline  

Microsoft Academic Search

A new framework for understanding the vertical structure of ocean gyres is developed based on vertical fluxes of potential vorticity. The key ingredient is an integral constraint that in a steady state prohibits a net flux of potential vorticity through any closed contour of Bernoulli potential or density. Applied to an ocean gyre, the vertical fluxes of potential vorticity associated

DAVID P. M ARSHALL

2000-01-01

193

The atomic orbitals of the topological atom.  

PubMed

The effective atomic orbitals have been realized in the framework of Bader's atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These correspond to atomic hybrids that closely resemble the core and valence shells of the atom. The occupation numbers of the remaining effective orbitals are almost negligible, except for atoms with hypervalent character. In addition, the molecular orbitals of a calculation can be exactly expressed as a linear combination of this orthonormalized set of numerical atomic orbitals, and the Mulliken population analysis carried out on this basis set exactly reproduces the original QTAIM atomic populations of the atoms. Approximate expansion of the molecular orbitals over a much reduced set of orthogonal atomic basis functions can also be accomplished to a very good accuracy with a singular value decomposition procedure. PMID:23758358

Ramos-Cordoba, Eloy; Salvador, Pedro; Mayer, István

2013-06-01

194

Vertical axis windmill  

SciTech Connect

A vertical axis windmill has a blade pivotally connected to a rotatable support structure on an axis passing through its center of gravity which is arranged to lie forward of its aerodynamic center whereby the blade automatically swings outwardly and inwardly when moving on the windward and leeward sides respectively of the axis of rotation of said support means.

Zheug, Y.K.

1984-03-06

195

Vertical shaft windmill  

SciTech Connect

A vertical shaft has several equally spaced blades mounted thereon. Each blade consists of an inboard section and an outboard section skew hinged to the inboard section. The inboard sections automatically adjust their positions with respect to the fixed inboard sections with changes in velocity of the wind. This windmill design automatically governs the maximum rotational speed of shaft.

Grana, D.C.; Inge, S.V. Jr.

1983-11-15

196

Vertical shaft windmill  

NASA Technical Reports Server (NTRS)

A vertical shaft has several equally spaced blades mounted. Each blade consists of an inboard section and an outboard section skew hinged to the inboard section. The inboard sections automatically adjust their positions with respect to the fixed inboard sections with changes in velocity of the wind. This windmill design automatically governs the maximum rotational speed of shaft.

Grana, D. C.; Inge, S. V., Jr. (inventors)

1983-01-01

197

Improved vertical scanning interferometry  

Microsoft Academic Search

Vertical scanning interferometers are routinely used for the measurement of optical fiber connectors. There are increasing needs for measurements of such items as machined surfaces, contact lenses, paint texture, cell structure, and integrated circuit devices, to name a few. These structures have too much depth, or are too rough, to measure with standard interferometry methods. Phase- measurement interferometry methods are

Akiko Harasaki; Joanna Schmidt; James C. Wyant

2000-01-01

198

Developing Vertical File Resources.  

ERIC Educational Resources Information Center

Describes how to develop vertical file resources for school libraries. Discusses the importance of having primary sources that are not available in other formats; sources for obtaining materials, including the Internet and printed sources; how to organize the materials; providing access; and promoting the collection. (LRW)

Smallwood, Carol

1998-01-01

199

Aiding Vertical Guidance Understanding  

NASA Technical Reports Server (NTRS)

A two-part study was conducted to evaluate modern flight deck automation and interfaces. In the first part, a survey was performed to validate the existence of automation surprises with current pilots. Results indicated that pilots were often surprised by the behavior of the automation. There were several surprises that were reported more frequently than others. An experimental study was then performed to evaluate (1) the reduction of automation surprises through training specifically for the vertical guidance logic, and (2) a new display that describes the flight guidance in terms of aircraft behaviors instead of control modes. The study was performed in a simulator that was used to run a complete flight with actual airline pilots. Three groups were used to evaluate the guidance display and training. In the training, condition, participants went through a training program for vertical guidance before flying the simulation. In the display condition, participants ran through the same training program and then flew the experimental scenario with the new Guidance-Flight Mode Annunciator (G-FMA). Results showed improved pilot performance when given training specifically for the vertical guidance logic and greater improvements when given the training and the new G-FMA. Using actual behavior of the avionics to design pilot training and FMA is feasible, and when the automated vertical guidance mode of the Flight Management System is engaged, the display of the guidance mode and targets yields improved pilot performance.

Feary, Michael; McCrobie, Daniel; Alkin, Martin; Sherry, Lance; Polson, Peter; Palmer, Everett; McQuinn, Noreen

1998-01-01

200

Orbital tube flaring system produces tubing connectors with zero leakage  

NASA Technical Reports Server (NTRS)

An orbital tube flaring system produces tubing connectors with a zero-leak potential needed in high pressure hydraulic and pneumatic systems. The flaring system incorporates a rolling cone and rolling die to closely control flare characteristics.

Williams, J. R.

1967-01-01

201

Orbital Evolution and Chaos Among the Inner Moons of Uranus  

Microsoft Academic Search

Uranus has a family of thirteen satellites orbiting interior to the innermost classical moon, Miranda. Nine of these comprise the Portia group, a closely-packed dynamical system that has recently been found to show significant orbital variations over time scales of 1-2 decades. This result supports inferences that the system is chaotic, with collisions expected over time scales of less than

Mark Showalter

2006-01-01

202

Global Orbit Patterns for Dynamical Systems On Finite Sets  

Microsoft Academic Search

In this paper, the study of the global orbit pattern (gop) formed by all the periodic orbits of discrete dynamical systems on a finite set X allows us to describe precisely the behaviour of such systems. We can predict by means of closed formulas, the number of gop of the set of all the function from X to itself. We

René Lozi; Clarisse Fiol

2009-01-01

203

Design of a Formation of Earth Orbiting Satellites: The Auroral Lites Mission  

NASA Technical Reports Server (NTRS)

The National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) has proposed a set of spacecraft flying in close formation around the Earth in order to measure the behavior of the auroras. The mission, named Auroral Lites, consists of four spacecraft configured to start at the vertices of a tetrahedron, flying over three mission phases. During the first phase, the distance between any two spacecraft in the formation is targeted at 10 kilometers (km). The second mission phase is much tighter, requiring satellite interrange spacing targeted at 500 meters. During the final phase of the mission, the formation opens to a nominal 100-km interrange spacing. In this paper, we present the strategy employed to initialize and model such a close formation during each of these phases. The analysis performed to date provides the design and characteristics of the reference orbit, the evolution of the formation during Phases I and II, and an estimate of the total mission delta-V budget. AI Solutions' mission design tool, FreeFlyer(R), was used to generate each of these analysis elements. The tool contains full force models, including both impulsive and finite duration maneuvers. Orbital maintenance can be fully modeled in the system using a flexible, natural scripting language built into the system. In addition, AI Solutions is in the process of adding formation extensions to the system facilitating mission analysis for formations like Auroral Lites. We will discuss how FreeFlyer(R) is used for these analyses.

Hametz, Mark E.; Conway, Darrel J.; Richon, Karen

1999-01-01

204

Neonatal orbital abscess  

PubMed Central

Orbital complications due to ethmoiditis are rare in neonates. A case of orbital abscess due to acute ethmoiditis in a 28-day-old girl is presented. A Successful outcome was achieved following antimicrobial therapy alone; spontaneous drainage of the abscess occurred from the lower lid without the need for surgery. From this case report, we intend to emphasize on eyelid retraction as a sign of neonatal orbital abscess, and to review all the available literature of similar cases.

Al-Salem, Khalil M; Alsarayra, Fawaz A; Somkawar, Areej R

2014-01-01

205

Orbital Debris: A Chronology  

NASA Technical Reports Server (NTRS)

This chronology covers the 37-year history of orbital debris concerns. It tracks orbital debris hazard creation, research, observation, experimentation, management, mitigation, protection, and policy. Included are debris-producing, events; U.N. orbital debris treaties, Space Shuttle and space station orbital debris issues; ASAT tests; milestones in theory and modeling; uncontrolled reentries; detection system development; shielding development; geosynchronous debris issues, including reboost policies: returned surfaces studies, seminar papers reports, conferences, and studies; the increasing effect of space activities on astronomy; and growing international awareness of the near-Earth environment.

Portree, Davis S. F. (Editor); Loftus, Joseph P., Jr. (Editor)

1999-01-01

206

Ghost orbit spectroscopy  

NASA Astrophysics Data System (ADS)

Direct periodic-orbit expansions of individual spectral eigenvalues is a new direction in quantum mechanics. Using a unitary S -matrix theory, we present exact, convergent, integral-free ghost orbit expansions of spectral eigenvalues for a step potential in the tunneling regime. We suggest an experiment to extract ghost orbit information from measured spectra in the tunneling regime (ghost orbit spectroscopy). We contrast our unitary, convergent theory with a recently published nonunitary, divergent theory [Yu. Dabaghian and R. Jensen, Eur. J. Phys. 26, 423 (2005)].

Bhullar, A. S.; Blümel, R.; Koch, P. M.

2006-01-01

207

Magnetospheric Multiscale (MMS) Orbit  

NASA Video Gallery

This animation shows the orbits of Magnetospheric Multiscale (MMS) mission, a Solar-Terrestrial Probe mission comprising of four identically instrumented spacecraft that will study the Earth's magn...

208

Family of Orbiters  

NASA Technical Reports Server (NTRS)

This image shows the paths of three spacecraft currently in orbit around Mars, as well as the path by which NASA's Phoenix Mars Lander will approach and land on the planet. The t-shaped crosses show where the orbiters will be when Phoenix enters the atmosphere, while the x-shaped crosses show their location at landing time.

All three orbiters, NASA's Mars Reconnaissance Orbiter, NASA's Mars Odyssey and the European Space Agency's Mars Express, will be monitoring Phoenix during the final steps of its journey to the Red Planet.

Phoenix will land just south of Mars's north polar ice cap.

2008-01-01

209

Optimization of the Helical Orbits in the Tevatron  

SciTech Connect

To avoid multiple head-on collisions the proton and antiproton beams in the Tevatron move along separate helical orbits created by 7 horizontal and 8 vertical electrostatic separators. Still the residual long-range beam-beam interactions can adversely affect particle motion at all stages from injection to collision. With increased intensity of the beams it became necessary to modify the orbits in order to mitigate the beam-beam effect on both antiprotons and protons. This report summarizes the work done on optimization of the Tevatron helical orbits, outlines the applied criteria and presents the achieved results.

Alexahin, Y.; /Fermilab

2007-06-01

210

Orbital Evolution of Jupiter-family Comets  

NASA Astrophysics Data System (ADS)

The orbital evolution of more than 25,000 Jupiter-family comets (JFCs) under the gravitational influence of planets was studied. After 40 Myr one considered object (with initial orbit close to that of Comet 88P) got aphelion distance Q<3.5 AU, and it moved in orbits with semi-major axis a=2.60-2.61 AU, perihelion distance 1.7orbit close to that of Comet 94P) moved in orbits with a=1.95-2.1 AU, q>1.4 AU, Q<2.6 AU, e=0.2-0.3, and i=9-33 deg for 8 Myr (and it had Q<3 AU for 100 Myr). So JFCs can rarely get typical asteroid orbits and move in them for Myrs. In our opinion, it can be possible that Comet 133P (Elst--Pizarro) moving in a typical asteroidal orbit was earlier a JFC and it circulated its orbit also due to non-gravitational forces. JFCs got near-Earth object (NEO) orbits more often than typical asteroidal orbits. A few JFCs got Earth-crossing orbits with a<2 AU and Q<4.2 AU and moved in such orbits for more than 1 Myr (up to tens or even hundreds of Myrs). Three considered former JFCs even got inner-Earth orbits (with Q<0.983 AU) or Aten orbits for Myrs. The probability of a collision of one of such objects, which move for millions of years inside Jupiter's orbit, with a terrestrial planet can be greater than analogous total probability for thousands other objects. Results obtained by the Bulirsch-Stoer method and by a symplectic method were mainly similar (except for probabilities of close encounters with the Sun when they were high). Our results show that the trans-Neptunian belt can provide a significant portion of NEOs, or the number of trans-Neptunian objects migrating inside solar system could be smaller than it was earlier considered, or most of 1-km former trans-Neptunian objects that had got NEO orbits disintegrated into mini-comets and dust during a smaller part of their dynamical lifetimes if these lifetimes are not small. The obtained results show that during the accumulation of the giant planets the total mass of icy bodies delivered to the Earth could be about the mass of water in Earth's oceans. Several our papers on this problem were put in http://arXiv.org/format/astro-ph/ (e.g., 0305519, 0308448). This work was supported by NASA (NAG5-10776) and INTAS (00-240).

Ipatov, S. I.; Mather, J. C.

2004-05-01

211

Titan Orbiter with Aerorover Mission (TOAM)  

NASA Technical Reports Server (NTRS)

We propose to develop a new mission to Titan called Titan Orbiter with Aerorover Mission (TOAM). This mission is motivated by the recent discoveries of Titan, its atmosphere and its surface by the Huygens Probe, and a combination of in situ, remote sensing and radar mapping measurements of Titan by the Cassini orbiter. Titan is a body for which Astrobiology (i.e., prebiotic chemistry) will be the primary science goal of any future missions to it. TOAM is planned to use an orbiter and balloon technology (i.e., aerorover). Aerobraking will be used to put payload into orbit around Titan. One could also use aerobraking to put spacecraft into orbit around Saturn first for an Enceladus phase of the mission and then later use aerocapture to put spacecraft into orbit around Titan. The Aerorover will probably use a hot air balloon concept using the waste heat from the MMRTG approx. 1000 watts. Orbiter support for the Aerorover is unique to our approach for Titan. Our strategy to use an orbiter is contrary to some studies using just a single probe with balloon. Autonomous operation and navigation of the Aerorover around Titan will be required, which will include descent near to the surface to collect surface samples for analysis (i.e., touch and go technique). The orbiter can provide both relay station and GPS roles for the Aerorover. The Aerorover will have all the instruments needed to sample Titan's atmosphere, surface, possible methane lakes-rivers, use multi-spectral imagers for surface reconnaissance; to take close up surface images; take core samples and deploy seismometers during landing phase. Both active and passive broadband remote sensing techniques will be used for surface topography, winds and composition measurements.

Sittler, E. C., Jr.; Cooper, J. F.; Mahaffy, P.; Esper, J.; Fairbrother, D.; Farley, R.; Pitman, J.; Kojiro, D. R.; Acuna, M.; Allen, M.; Bjoraker, G.; Brasunas, J.; Farrell, W.; Burchell, M. J.; Burger, M.; Chin, G.; Coates, A. J.; Farrell, W.; Flasar, M.; Gerlach, B.; Gorevan, S.; Hartle, R. E.; Im, Eastwood; Jennings, D.; Johnson, R. E.

2007-01-01

212

Kalman Orbit Optimized Loop Tracking  

NASA Technical Reports Server (NTRS)

Under certain conditions of low signal power and/or high noise, there is insufficient signal to noise ratio (SNR) to close tracking loops with individual signals on orbiting Global Navigation Satellite System (GNSS) receivers. In addition, the processing power available from flight computers is not great enough to implement a conventional ultra-tight coupling tracking loop. This work provides a method to track GNSS signals at very low SNR without the penalty of requiring very high processor throughput to calculate the loop parameters. The Kalman Orbit-Optimized Loop (KOOL) tracking approach constitutes a filter with a dynamic model and using the aggregate of information from all tracked GNSS signals to close the tracking loop for each signal. For applications where there is not a good dynamic model, such as very low orbits where atmospheric drag models may not be adequate to achieve the required accuracy, aiding from an IMU (inertial measurement unit) or other sensor will be added. The KOOL approach is based on research JPL has done to allow signal recovery from weak and scintillating signals observed during the use of GPS signals for limb sounding of the Earth s atmosphere. That approach uses the onboard PVT (position, velocity, time) solution to generate predictions for the range, range rate, and acceleration of the low-SNR signal. The low- SNR signal data are captured by a directed open loop. KOOL builds on the previous open loop tracking by including feedback and observable generation from the weak-signal channels so that the MSR receiver will continue to track and provide PVT, range, and Doppler data, even when all channels have low SNR.

Young, Lawrence E.; Meehan, Thomas K.

2011-01-01

213

Comet Odyssey: Comet Nucleus Orbiter  

NASA Astrophysics Data System (ADS)

Comet Odyssey is a comet nucleus orbiter mission, proposed to NASA's Discovery program in 2004. The goal of the mission is to completely characterize a cometary nucleus, both physically and compositionally, as can only be done during an extended rendezvous and not with a fast flyby. Comet Odyssey will launch in October 2009 on a Delta II 7925 and use a solar-electric powered spacecraft to effect a rendezvous with periodic comet 46P/Wirtanen in October 2013. Arrival is 96 days after perihelion at a heliocentric distance of 1.61 AU. Comet Odyssey's science payload includes narrow- and wide-angle CCD cameras, an infrared thermal imager, a gas chromatograph/mass spectrometer, an XRD/XRF dust compositional analyzer, and a dust counter and accumulation sensors. The Comet Odyssey spacecraft implementation uses a high heritage approach of flight proven and redundant hardware. The 3-engine ion propulsion subsystem is derived from that on Dawn but includes the capability for multi-engine thrusting. Comet Odyssey will approach the Wirtanen nucleus and make repeated slow flybys through the active cometary coma for a period of three months. It will then be placed in a ˜100-km radius orbit around the nucleus, with a plan to eventually orbit at 40-km altitude or less. From that altitude the narrow-angle camera will map the entire nucleus surface at 1 meter/pixel and the thermal imager will map at 19 meter/pixel. The orbital portion of the nominal mission will last 4.5 months, following the comet outward from the Sun to 3.3 AU as the comet evolves from an active to a quiescent state. En route to P/Wirtanen, the Comet Odyssey spacecraft will perform a close flyby of the 200-km diameter, G-type, main belt asteroid 19 Fortuna in January 2012 and make appropriate remote sensing observations.

Weissman, P. R.; Smythe, W. D.; Spitz, S. J.; Bernard, D. E.; Bailey, R. W.

2004-11-01

214

THE FATE OF MOONS OF CLOSE-IN GIANT EXOPLANETS  

SciTech Connect

We show that the fate of moons of a close-in giant planet is mainly determined by the migration history of the planet in the protoplanetary disk. As the planet migrates in the disk from beyond the snow line toward a multi-day period orbit, the formed and forming moons become unstable as the planet's sphere of influence shrinks. Disk-driven migration is faster than the moons' tidal orbital evolution. Moons are eventually ejected from around close-in exoplanets or forced into collision with them before tides from the planet affect their orbits. If moons are detected around close-in exoplanets, they are unlikely to have been formed in situ, instead they were captured from the protoplanetary disk on retrograde orbits around the planets.

Namouni, Fathi, E-mail: namouni@obs-nice.f [Universite de Nice, CNRS, Observatoire de la Cote d'Azur, BP 4229, 06304 Nice (France)

2010-08-20

215

The Galactic Orbits of Nearby UV Ceti Stars  

NASA Astrophysics Data System (ADS)

The galactic orbits of 93 UV Ceti stars of the solar neighborhood have been numerically integrated. The UV Ceti stars studied are those of the working list for which Poveda et al. (1996a) determined kinematic properties and ages. All stars are contained within 25 pc of the Sun (? ? 0.04''), and values for their distances, proper motions and radial velocities are available for them (Gliese & Jahreiss 1991). The galactic potential model of Allen & Santillán (1991) was used, and the orbits were integrated for times similar to the age of the old disk. The galactic orbital parameters are obtained. The orbits are all regular, and the values found for the orbital parameters are similar to those characteristic of the classic young thin disk. The vertical scale height found for the whole sample is 115 pc. However, the orbital parameters found for the 7 objects with extreme kinematic characteristics recognized in Poveda et al. are markedly different from those of the rest of the flare stars; in particular, their orbital eccentricities are larger than 0.3. The vertical scale height of the sample excluding the anomalous objects is just 103 pc. Consequently, we propose that the anomalous objects belong to the thick disk, which may be characterized by either e? 0.3 or | zmax | > 400 pc.

Allen, C.; Herrera, M. A.

1998-04-01

216

The galactic orbits of nearby UV Ceti stars  

NASA Astrophysics Data System (ADS)

The galactic orbits of 93 UV Ceti stars of the solar neighborhood have been numerically integrated. The UV Ceti stars studied are those of the working list for which Poveda et al. (1996) determined kinematic properties and ages. All stars are contained within 25 pc of the sun, and values for their distances, proper motions and radial velocities are available for them (Gliese & Jahreiss 1991). The galactic potential model of Allen & Santillan (1991) was used, and the orbits were integrated for times similar to the age of the old disk. The galactic orbital parameters are obtained. The orbits are all regular, and the values found for the orbital parameters are similar to those characteristic of the classic young thin disk. The vertical scale height found for the whole sample is 115 pc. However, the orbital parameters found for the 7 objects with extreme kinematic characteristics recognized in Poveda et al. are markedly different from those of the rest of the flare stars; in particular, their orbital eccentricities are larger than 0.3. The vertical scale height of the sample excluding the anomalous objects is just 103 pc. Consequently, we propose that the anomalous objects belong to the thick disk, which may be characterized by either e >= 0.3 or |z max| > 400 pc.

Allen, C.; Herrera, M. A.

1998-11-01

217

Vertical vector face lift.  

PubMed

Facial rejuvenation using local anesthesia has evolved in the past decade as a safer option for patients seeking fewer complications and minimal downtime. Mini- and short-scar face lifts using more conservative incision lengths and extent of undermining can be effective in the younger patient with lower face laxity and minimal loose, elastotic neck skin. By incorporating both an anterior and posterior approach and using an incision length between the mini and more traditional face lift, the Vertical Vector Face Lift can achieve longer-lasting and natural results with lesser cost and risk. Submentoplasty and liposuction of the neck and jawline, fundamental components of the vertical vector face lift, act synergistically with superficial musculoaponeurotic system plication to reestablish a more youthful, sculpted cervicomental angle, even in patients with prominent jowls. Dramatic results can be achieved in the right patient by combining with other procedures such as injectable fillers, chin implants, laser resurfacing, or upper and lower blepharoplasties. PMID:21276163

Somoano, Brian; Chan, Joanna; Morganroth, Greg

2011-01-01

218

Closed-loop nominal and abort atmospheric ascent guidance for rocket-powered launch vehicles  

NASA Astrophysics Data System (ADS)

An advanced ascent guidance algorithm for rocket-powered launch vehicles is developed. The ascent guidance function is responsible for commanding attitude, throttle and setting during the powered ascent phase of flight so that the vehicle attains target cutoff conditions in a near optimal manner while satisfying path constraints such as maximum allowed bending moment and maximum allowed axial acceleration. This algorithm cyclically solves the calculus-of-variations two-point boundary-value problem starting at vertical rise completion through orbit insertion. This is different from traditional ascent guidance algorithms which operate in an open-loop mode until the high dynamic pressure portion of the trajectory is over, at which time there is a switch to a closed loop guidance mode that operates under the assumption of negligible aerodynamic forces. The main contribution of this research is an algorithm of the predictor-corrector type wherein the state/costate system is propagated with known (navigated) initial state and guessed initial costate to predict the state/costate at engine cutoff. The initial costate guess is corrected, using a multi-dimensional Newton's method, based on errors in the terminal state constraints and the transversality conditions. Path constraints are enforced within the propagation process. A modified multiple shooting method is shown to be a very effective numerical technique for this application. Results for a single stage to orbit launch vehicle are given. In addition, the formulation for the free final time multi-arc trajectory optimization problem is given. Results for a two-stage launch vehicle burn-coast-burn ascent to orbit in a closed-loop guidance mode are shown. An abort to landing site formulation of the algorithm and numerical results are presented. A technique for numerically treating the transversality conditions is discussed that eliminates part of the analytical and coding burden associated with optimal control theory.

Dukeman, Greg A.

219

Self-interaction-free density-functional theoretical study of the electronic structure of spherical and vertical quantum dots  

NASA Astrophysics Data System (ADS)

We study the electronic structure and shell-filling effects of both spherical and vertical quantum dots by means of the density functional theory (DFT) with optimized effective potential (OEP) and self-interaction-correction (SIC) recently developed. The OEP/SIC procedure allows the elimination of the spurious self-interaction energy and the construction of accurate single-particle local potential with proper long-range Coulombic behavior. The OEP/SIC equations are discretized and solved accurately and efficiently by the generalized pseudospectral (GPS) method. The highest occupied orbital energy of N-electron quantum dots provides a direct measure of the electron affinity or chemical potential. We apply the OEP/SIC method to the study of the capacitive energy of N-electron spherical dots for N up to 70. The results show the shell and subshell structure pattern and the electron filling pattern follows closely the Hund's rule. We also consider the effect of including the vertical dimension in the quantum dot study. We perform a detailed study of the shell-filling effect and the angular and radial density distributions of vertical quantum dots. The calculated capacitive energy spectrum is in good agreement with the recent experimental results, providing physical insights regarding the origin of electron shells and the role of electron-electron interaction in quantum dots.

Jiang, T. F.; Tong, Xiao-Min; Chu, Shih-I.

2001-01-01

220

Mars Geoscience Orbiter and Lunar Geoscience Orbiter.  

National Technical Information Service (NTIS)

The feasibility of using the AE/DE Earth orbiting spacecraft design for the LGO and/or MGO missions was determined. Configurations were developed and subsystems analysis was carried out to optimize the suitability of the spacecraft to the missions. The pr...

W. V. Fuldner P. F. Kaskiewicz

1983-01-01

221

Satellite orbit determination  

Microsoft Academic Search

Statistical methods for determining satellite trajectories after being put into orbit, after changes in the trajectory and at regular intervals during orbital lifetime are outlined. The least squares method, a differential Gauss-Newton correction algorithm, and interpretation of the results are introduced.

P. Legendre

1984-01-01

222

Saturn Orbiter Mission Study.  

National Technical Information Service (NTIS)

A preliminary analysis of the important aspects of missions orbiting the planet Saturn is provided. Orbital missions to Saturn is given serious consideration for the 1980's, or after flybys by Pioneer 10/G and Mariner Jupiter-Saturn 1977. An attempt is ma...

W. C. Wells R. J. Sullivan

1973-01-01

223

MRI of orbital schwannomas.  

PubMed

The literature on MRI of orbital schwannomas is limited. The appearances in three patients with an orbital schwannoma were reviewed. A superior orbitotomy through a subfrontal craniotomy revealed a schwannoma in all cases. MRI characteristics of very low signal on T1-weighted images and homogeneous postcontrast enhancement may be helpful for differentiating schwannomas from other intraconal masses. PMID:10929312

Abe, T; Kawamura, N; Homma, H; Sasaki, K; Izumiyama, H; Matsumoto, K

2000-06-01

224

Noninteger Slater orbital calculations  

Microsoft Academic Search

In order to calculate the one- and two-electron, two-center integrals over non-integer n Slater type orbitals, use is made of elliptical coordinates for the monoelectronic, hybrid, and Coulomb integrals. For the exchange integrals, the atomic orbitals are translated to a common center. The final integration is performed by Gaussian quadrature.

Alain Allouche

1976-01-01

225

Orbital trapdoor fractures  

PubMed Central

Orbital trapdoor fractures are commonly encountered in children. Awareness of trapdoor fractures is of particular importance. This is because early recognition and treatment are necessary to prevent permanent motility abnormities. In this article, we will provide a brief overview of orbital fractures. The clinical and radiographic features of trapdoor fractures will then be reviewed, followed by a discussion on their proper management.

Phan, Laura T.; Jordan Piluek, W.; McCulley, Timothy J.

2012-01-01

226

Topex orbit sustenance maneuver design. [Ocean Topography Experiment spacecraft  

NASA Technical Reports Server (NTRS)

A trade-off analysis between maneuver period, execution errors, and orbit determination uncertainties is carried out for the Ocean Topography Experiment spacecraft for a given nodal equatorial constraint. Semimajor axis and eccentricity are controlled with minimum impulse using the linear theory of optimal transfer between close coplanar near-circular orbits. Ellipses of equal minimum and average maneuver periods are presented in the (3 execution error, 3 orbit determination uncertainty) space for different nodal equatorial constraints enabling the determination of the appropriate combination of execution errors and orbit determination uncertainties that guarantees a mission required minimum maneuver period for a given nodal deadband.

Kechichian, J. A.

1982-01-01

227

Orbital Debris Mitigation  

NASA Technical Reports Server (NTRS)

Policies on limiting orbital debris are found throughout the US Government, many foreign space agencies, and as adopted guidelines in the United Nations. The underlying purpose of these policies is to ensure the environment remains safe for the operation of robotic and human spacecraft in near- Earth orbit. For this reason, it is important to consider orbital debris mitigation during the design of all space vehicles. Documenting compliance with the debris mitigation guidelines occurs after the vehicle has already been designed and fabricated for many CubeSats, whereas larger satellites are evaluated throughout the design process. This paper will provide a brief explanation of the US Government Orbital Debris Mitigation Standard Practices, a discussion of international guidelines, as well as NASA's process for compliance evaluation. In addition, it will discuss the educational value of considering orbital debris mitigation requirements as a part of student built satellite design.

Kelley, R. L.; Jarkey, D. R.; Stansbery, G.

2014-01-01

228

Mars Climate Orbiter  

NASA Technical Reports Server (NTRS)

The purpose of this mission is to study the climate history and the water distribution of Mars. Beautiful panoramic views of the shuttle on the launch pad, engine ignition, Rocket launch, and the separation and burnout of the Solid Rocket Boosters are shown. The footage also includes an animation of the mission. Detailed views of the path that the Orbiter traversed were shown. Once the Orbiter lands on the surface of Mars, it will dig a six to eight inch hole and collect samples from the planets' surface. The animation also included the prospective return of the Orbiter to Earth over the desert of Utah. The remote sensor on the Orbiter helps in finding the exact location of the Orbiter so that scientists may collect the sample and analyze it.

1998-01-01

229

Fibrolipoma of the orbit.  

PubMed

Herein we present a retrospective case report of a very rare fibrolipoma originating in the orbit. Lipomas and related variants presenting in the orbit are very rare. Only 2 documented orbital fibrolipomas were noted in our review of literature. A 26-year-old woman presented with a growing mass below the left eyebrow 4 years after suffering facial trauma after being kicked in the face by a horse. CT demonstrated a hypodense nodule adherent to the orbital portion of the left frontal bone that was not encapsulated. An elective left anterior orbitotomy with excisional biopsy was performed, and fibrolipoma was confirmed on histopathologic examination. There was no evidence of tumor after 2-year follow up. The presence of a fibrolipoma in the periosteum of the orbital rim is very rare and might be a result of inflammatory transformation following facial trauma. PMID:23392312

Ali, Sana F; Farber, Martha; Meyer, Dale R

2013-01-01

230

Orbital endoscopic surgery  

PubMed Central

Minimally invasive ?keyhole? surgery performed using endoscopic visualization is increasing in popularity and is being used by almost all surgical subspecialties. Within ophthalmology, however, endoscopic surgery is not commonly performed and there is little literature on the use of the endoscope in orbital surgery. Transorbital use of the endoscope can greatly aid in visualizing orbital roof lesions and minimizing the need for bone removal. The endoscope is also useful during decompression procedures and as a teaching aid to train orbital surgeons. In this article, we review the history of endoscopic orbital surgery and provide an overview of the technique and describe situations where the endoscope can act as a useful adjunct to orbital surgery.

Selva, Dinesh

2008-01-01

231

Planet-C: Venus Climate Orbiter mission of Japan  

Microsoft Academic Search

The Venus Climate Orbiter mission (PLANET-C), one of the future planetary missions of Japan, aims at understanding the atmospheric circulation of Venus. Meteorological information will be obtained by globally mapping clouds and minor constituents successively with four cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing the vertical structure of the atmosphere with radio science

Masato Nakamura; Takeshi Imamura; Munetaka Ueno; Naomoto Iwagami; Takehiko Satoh; Shigeto Watanabe; Makoto Taguchi; Yukihiro Takahashi; Makoto Suzuki; Takumi Abe; George L. Hashimoto; Takeshi Sakanoi; Shoichi Okano; Yasumasa Kasaba; Jun Yoshida; Manabu Yamada; Nobuaki Ishii; Takahiro Yamada; Kazunori Uemizu; Tetsuya Fukuhara; Koh-Ichiro Oyama

2007-01-01

232

Artists's Conception of Cassini Saturn Orbit Insertion  

NASA Technical Reports Server (NTRS)

This is an artists concept of Cassini during the Saturn Orbit Insertion (SOI) maneuver, just after the main engine has begun firing. The spacecraft is moving out of the plane of the page and to the right (firing to reduce its spacecraft velocity with respect to Saturn) and has just crossed the ring plane.

The SOI maneuver, which is approximately 90 minutes long, will allow Cassini to be captured by Saturn's gravity into a five-month orbit.Cassini's close proximity to the planet after the maneuver offers a unique opportunity to observe Saturn and its rings at extremely high resolution.

2002-01-01

233

Orbital Evolution of Jupiter-Family Comets  

NASA Technical Reports Server (NTRS)

We investigated the evolution for periods of at least 5-10 Myr of 2500 Jupiter-crossing objects (JCOs) under the gravitational influence of all planets, except for Mercury and Pluto (without dissipative factors). In the first series we considered N=2000 orbits near the orbits of 30 real Jupiter-family comets with period less than 10 yr, and in the second series we took 500 orbits close to the orbit of Comet 10P Tempel 2. We calculated the probabilities of collisions of objects with the terrestrial planets, using orbital elements obtained with a step equal to 500 yr and then summarized the results for all time intervals and all bodies, obtaining the total probability P(sub sigma) of collisions with a planet and the total time interval T(sub sigma) during which perihelion distance of bodies was less than a semimajor axis of the planet. The values of P = 10(exp 6)P(sub sigma)/N and T = T(sub sigma)/1000 yr are presented in Table together with the ratio r of the total time interval when orbits were of Apollo type (at e less than 0.999) to that of Amor type.

Ipatov, S. I.; Mather, J. S.; Oegerle, William R. (Technical Monitor)

2002-01-01

234

Design of Vertically Stacked Waveguide Filters in LTCC  

Microsoft Academic Search

This paper proposes four-pole quasi-elliptic function bandpass waveguide filters using multilayer low-temperature co-fired ceramic technology. The vertical metal walls of the waveguide resonators are realized by closely spaced metallic vias. Adjacent cavities are coupled by a narrow slot at the edge of the common broad wall or an inductive window on the sidewall. Two types of vertical coupling structures are

Tze-Min Shen; Chi-Feng Chen; Ting-Yi Huang; Ruey-Beei Wu

2007-01-01

235

Project Plan for Vertical Lift Machine  

SciTech Connect

This document describes the Project Plan for the development and manufacture of a Vertical Lift Machine. It is assumed by this project plan that the Vertical Lift Machine will be developed, designed, manufactured, and tested by a qualified vendor. LLNL will retain review and approval authority for each step given in this project plan. The Vertical Lift Machine is a single linear axis positioning device capable of lifting objects vertically at controlled rates and positioning them repeatedly at predetermined heights, in relation to other objects suspended from above, for high neutron multiplication experiments. Operation of the machine during the experiments is done remotely. The lift mechanism shall accommodate various platforms (tables) that support the objects to be raised. A frame will support additional subassemblies from above such that the lower subassembly can be raised close to and/or interface with those above. The structure must be stiff and motion of the table linear such that radial alignment is maintained (e.g. concentricity). The safe position for the Vertical Lift Machine is the lift mechanism fully retracted with the subassemblies fully separated. The machine shall reside in this position when not in use. It must return to this safe condition from any position upon failure of power sources, open safety interlocks, or operator initiated SCRAM. The Vertical Lift Machine shall have the capability of return to the safe position with no externally applied power. The Vertical Lift Machine shall have dual operator interfaces, one near the machine and another located in a remote control room. Conventional single key, key-lock switching shall be implemented to lock out the control interface not in use. The interface at the machine will be used for testing and ''dry running'' experimental setup(s) with inert subassemblies (i.e. Setup Mode). The remote interface shall provide full control and data recording capability (i.e. Assembly Mode). The control system will be a combination of Programmable Logic Controller (PLC), or equivalent, and relay logic. The operator shall have the ability to adjust lift/lower velocity and position of the table. All measurements will be made as close to, and in line with, the axis of motion as practical. Measurement data, system parameter information, and interlock status shall be displayed.

Ellsworth, G F

2002-08-05

236

Closed loop electrostatic levitation system  

NASA Technical Reports Server (NTRS)

An electrostatic levitation system is described, which can closely control the position of objects of appreciable size. A plurality of electrodes surround the desired position of an electrostatically charged object, the position of the objects is monitored, and the voltages applied to the electrodes are varied to hold the object at a desired position. In one system, the object is suspended above a plate-like electrode which has a concave upper face to urge the object toward the vertical axis of the curved plate. An upper electrode that is also curved can be positioned above the object, to assure curvature of the field at any height above the lower plate. In another system, four spherical electrodes are positioned at the points of a tetrahedron, and the voltages applied to the electrodes are varied in accordance with the object position as detected by two sensors.

Rhim, W. K.; Saffren, M. M.; Elleman, D. D. (inventors)

1985-01-01

237

Vertical transport processes in unconfined aquifers  

NASA Astrophysics Data System (ADS)

We derive simple two-dimensional mathematical models describing the unsteady transport of conservative contaminants through an unconfined aquifer with a gently sloping aquiclude subject to advection, recharge, and vertical dispersion. The inclusion of vertical transport terms permits the proper nonreactive analysis of closed and open chemical systems, with the latter allowing dispersion of volatile constituents across the water table. These systems exhibit conservative and pseudoreactive behavior respectively when the pollution is analyzed on a depth-integrated basis, as is common in present one-dimensional models of groundwater contamination. Vertical and longitudinal chloride and total inorganic carbon observations at the well-documented Babylon, Long Island sanitary landfill plume are used to calibrate and test the analyses with a modest level of accuracy, using the vertical dispersivity as a calibration factor in this testing process. The parameter is important in the determination of reaeration rates across the water table and nutrient mixing from below in the related problem of biological transformations near the free surface.

Ostendorf, David W.; Reckhow, David A.; Popielarczyk, David J.

1989-02-01

238

Vertically integrated silicon-germanium nanowire field-effect transistor  

NASA Astrophysics Data System (ADS)

We demonstrate in this paper the possibility to vertically integrate SiGe nanowires in order to use them as vertical channel for field-effect transistors (FETs). We report a threshold voltage close to 3.9 V, an ION/IOFF ratio of 104. The subthreshold slope was estimated to be around 0.9 V/decade and explained by a high traps density at the nanowire core/oxide shell interface with an estimated density of interface traps Dit ~ 1.2 × 1013 cm-2 eV-1. Comparisons are made with both vertical Si and horizontal SiGe FETs performances.

Rosaz, G.; Salem, B.; Pauc, N.; Potié, A.; Gentile, P.; Baron, T.

2011-11-01

239

Plasma vertical stability and feedback control for TPX  

SciTech Connect

The n=0 axisymmetric vertical stability and vertical position control have been examined for the Tokamak Physics Experiment. The passive stabilization is accomplished by using stabilizer plates close to the plasma. The present configuration is found to provide robust stability over wide range of plasma parameters. The active feed-back control of the plasma vertical position is done using coils located inside the vacuum vessel. These are required to control random disturbances leading to {le} 1.0 cm RMS displacements from the midplane, and acceptable coil currents and voltages are found.

Kessel, C.E; Jardin, S.C.; Neilson, G.H.

1993-11-01

240

School Closings in Philadelphia  

ERIC Educational Resources Information Center

In 2012, the School District of Philadelphia closed six schools. In 2013, it closed 24. The closure of 30 schools has occurred amid a financial crisis, headlined by the district's $1.35 billion deficit. School closures are one piece of the district's plan to cut expenditures and close its budget gap. The closures are also intended to…

Jack, James; Sludden, John

2013-01-01

241

Nonlinear station-keeping control of unstable orbits near collinear libration points  

Microsoft Academic Search

A new nonlinear optimal tracking control method is proposed and analyzed which stabilizes a class of unstable periodic orbits near collinear libration points. Since such libration point orbits are, in general, unstable, spacecraft moving on these orbits must use some form of trajectory control to remain close to their nominal paths. In this study, the control law based on optimal

Zhiqin Cai; Jun Zhao; Haijun Peng; Zhaohui Qi

2010-01-01

242

The 'halo' family of 3-dimensional periodic orbits in the restricted 3-body problem  

Microsoft Academic Search

A study of quasi-periodic orbits about the translunar libration point conducted by Farquhar and Kamel (1973) is considered. In the analysis position is measured in a rotating frame with origin at the earth-moon barycenter. An instability of the orbits close to the libration point diminishes as the orbits grow nearer to the moon and shorter in period. The parameeters for

J. V. Breakwell; J. V. Brown

1976-01-01

243

Vertical blind assembly  

US Patent & Trademark Office Database

A vertical blind assembly includes an elongate header casing and two sets of louvers movably supported in adjacent channels within the header casing, including a first set of plain louvers structured to be moved horizontally along the length of the first channel, and a second set of louvers which are molded and configured in a decorative, three-dimensional pattern and structured to be moved horizontally along the length of the second channel so that they are positioned in front of the first set of louvers.

1997-01-28

244

'Endurance' Untouched (vertical)  

NASA Technical Reports Server (NTRS)

This navigation camera mosaic, created from images taken by NASA's Mars Exploration Rover Opportunity on sols 115 and 116 (May 21 and 22, 2004) provides a dramatic view of 'Endurance Crater.' The rover engineering team carefully plotted the safest path into the football field-sized crater, eventually easing the rover down the slopes around sol 130 (June 12, 2004). To the upper left of the crater sits the rover's protective heatshield, which sheltered Opportunity as it passed through the martian atmosphere. The 360-degree view is presented in a vertical projection, with geometric and radiometric seam correction.

2004-01-01

245

Vertical Motion Simulator  

NSDL National Science Digital Library

The Vertical Motion Simulator (VMS), at the NASA Ames Research Center, is an advanced flight simulation facility. This Web site provides thorough descriptions of all of the VMS systems. The VMS is a full immersion environment, complete with customizable cockpit, controls, and instrumentation to give the appearance of any aerospace vehicle. One of its most intriguing characteristics is "out-the-window graphics." This allows the pilot to see computer generated imagery of real locations, so virtually everything is identical to the actual flying experience. Even aircraft that are still in the design stage can be simulated on the VMS.

246

Visualization of atom's orbits.  

PubMed

High-resolution imaging techniques have been used to obtain views of internal shapes of single atoms or columns of atoms. This review article focuses on the visualization of internal atomic structures such as the configurations of electron orbits confined to atoms. This is accomplished by applying visualization techniques to the reported images of atoms or molecules as well as static and dynamic ions in a plasma. It was found that the photon and electron energies provide macroscopic and microscopic views of the orbit structures of atoms, respectively. The laser-imaged atoms showed a rugged orbit structure, containing alternating dark and bright orbits believed to be the pathways for an externally supplied laser energy and internally excited electron energy, respectively. By contrast, the atoms taken by the electron microscopy provided a structure of fine electron orbits, systematically formed in increasing order of grayscale representing the energy state of an orbit. This structure was identical to those of the plasma ions. The visualized electronic structures played a critical role in clarifying vague postulates made in the Bohr model. Main features proposed in the atomic model are the dynamic orbits absorbing an externally supplied electromagnetic energy, electron emission from them while accompanying light radiation, and frequency of electron waves not light. The light-accompanying electrons and ionic speckles induced by laser light signify that light is composed of electrons and ions. PMID:24749452

Kim, Byungwhan

2014-02-01

247

OL- ORBITAL LIFETIME PROGRAM  

NASA Technical Reports Server (NTRS)

The Orbital Lifetime (OL) program analyzes the long-term motion of Earth-orbiting spacecraft at altitudes of up to 2500 kilometers. It models perturbations to the orbit caused by solar radiation pressure, atmospheric drag, and gravitational effects due to the sun, the moon, and Earth oblateness. OL can be used to predict the orbital lifetime and decay rate of a satellite. The atmospheric density models used in OL are the U.S. Standard Atmosphere for altitudes below 90 km and the Jacchia model for altitudes above 90 km. The Jacchia model requires solar flux and geomagnetic index for the date of orbit. An input file containing these values for 1984 to 1998 is supplied with the OL package. The solar radiation pressure calculations in OL will predict the amount of time a spacecraft is subjected to the Earth's shadow. Input to OL includes spacecraft physical characteristics, initial orbit parameters, and launch date/time. OL calculates time histories of the orbital elements, total lifetime, and decay rates. A spacecraft is considered 'down' at an altitude of 64 km. OL also generates a file of plot data which can be input to a user-supplied graphics program for lifetime plots of altitude against time. OL is written in FORTRAN 77 for interactive or batch execution and has been implemented on a DEC VAX series computer operating under VMS. This program was developed in 1985.

Orr, L. H.

1994-01-01

248

[Orbital fractures in children].  

PubMed

The aim of this article is to review data concerning paediatric orbital fractures. These fractures exhibit strong specificities because they occur in a growing face. Due to the craniofacial growing pattern and the peumatization of paranasal sinuses, there are differences in the anatomical location of orbital fracture with the age: before the age of seven they are mostly orbital roof and after seven they involve the orbital floor. The clinical diagnosis is confirmed with a computed tomography scan (CT scan), gold standard for the imaging in the orbital fractures. The magnetic resonance imaging (MRI) offers a better soft-tissue depiction and is useful when clinical data are not consistent with CT scan findings. The orbital fractures in children are rarely operated. In emergency the main surgical indications are the trap-door fracture involving the ocular muscles and the compressive haematomas. We hypothesize that the periosteum more likely than the bony structure is involved in the responsible trap-door fractures: the thickness and the elasticity of the periosteum leads to reposition the floor or the medial wall of the orbit to its initial position. PMID:21420194

Guyot, L; Lari, N; Benso-Layoun, C; Denis, D; Chossegros, C; Thiery, G

2011-04-01

249

Orbit Stabilization of Nanosat  

SciTech Connect

An algorithm is developed to control a pulsed {Delta}V thruster on a small satellite to allow it to fly in formation with a host satellite undergoing time dependent atmospheric drag deceleration. The algorithm uses four short thrusts per orbit to correct for differences in the average radii of the satellites due to differences in drag and one thrust to symmetrize the orbits. The radial difference between the orbits is the only input to the algorithm. The algorithm automatically stabilizes the orbits after ejection and includes provisions to allow azimuthal positional changes by modifying the drag compensation pulses. The algorithm gives radial and azimuthal deadbands of 50 cm and 3 m for a radial measurement accuracy of {+-} 5 cm and {+-} 60% period variation in the drag coefficient of the host. Approaches to further reduce the deadbands are described. The methodology of establishing a stable orbit after ejection is illustrated in an appendix. The results show the optimum ejection angle to minimize stabilization thrust is upward at 86{sup o} from the orbital velocity. At this angle the stabilization velocity that must be supplied by the thruster is half the ejection velocity. An ejection velocity of 0.02 m/sat 86{sup o} gives an azimuthal separation after ejection and orbit stabilization of 187 m. A description of liquid based gas thrusters suitable for the satellite control is included in an appendix.

JOHNSON,DAVID J.

1999-12-01

250

The Solar Orbiter mission  

NASA Astrophysics Data System (ADS)

Approved in October 2000 by ESA's Science Programme Committee as a flexi-mission, the Solar Orbiter will studythe Sun and unexplored regions of the inner heliosphere from a unique orbit that brings the probe to within 45 solar radii (0.21 AU) of our star, and to solar latitudes as high as 38°. This orbit will allow the Solar Orbiter to make fundamental contributions to our understanding of the acceleration and propagation of energetic particles in the extended solar atmosphere. During quasi-heliosynchronous phases of the orbit, Solar Orbiter will track a given region of the solar surface for several days, making possible unprecedented studies of the sources of impulsive and CME-related particle events. The scientific payload to be carried by the probe will include a sophisticated remote-sensing package, as well as state-of-the-art in-situ instruments. The multi-wavelength, multi-disciplinary approach of Solar Orbiter, combined with its novel location, represents a powerful tool for studies of energetic particle phenomena.

Marsden, R. G.; Fleck, B.

251

The Solar Orbiter mission  

NASA Astrophysics Data System (ADS)

Approved in October 2000 by ESA's Science Programme Committee as a flexi mission, the Solar Orbiter will study the Sun and unexplored regions of the inner heliosphere from a unique orbit that brings the probe to within 45 solar radii (0.21 AU) of our star, and to solar latitudes as high as 38° This orbit will allow the Solar Orbiter to make fundamental contributions to our understanding of the acceleration and propagation of energetic particles in the extended solar atmosphere. During the quasi-heliosynchronous phases of the orbit, Solar Orbiter will track a given region of the solar surface for several days, making possible unprecedented studies of the sources of impulsive and CME-related particle events. The scientific payload to be carried by the probe will include a sophisticated remote-sensing package, as well as state-of-the-art in-situ instruments. The multi-wavelength, multi-disciplinary approach of Solar Orbiter, combined with its novel location, represents a powerful tool for studies of energetic particle phenomena.

Marsden, R.; Fleck, B.

252

Harmonically excited orbital variations  

SciTech Connect

Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.

Morgan, T.

1985-08-06

253

Disruption of co-orbital (1:1) planetary resonances during gas-driven orbital migration  

NASA Astrophysics Data System (ADS)

Planets close to their stars are thought to form farther out and migrate inwards due to angular momentum exchange with gaseous protoplanetary discs. This process can produce systems of planets in co-orbital (Trojan or 1:1) resonance, in which two planets share the same orbit, usually separated by 60 deg. Co-orbital systems are detectable among the planetary systems found by the Kepler mission either directly or by transit timing variations. However, no co-orbital systems have been found within the thousands of Kepler planets and candidates. Here, we study the orbital evolution of co-orbital planets embedded in a protoplanetary disc using a grid-based hydrodynamics code. We show that pairs of similar-mass planets in co-orbital resonance are disrupted during large-scale orbital migration. Destabilization occurs when one or both planets are near the critical mass needed to open a gap in the gaseous disc. A confined gap is opened that spans the 60 deg azimuthal separation between planets. This alters the torques imparted by the disc on each planet - pushing the leading planet outwards and the trailing planet inwards - and disrupts the resonance. The mechanism applies to systems in which the two planets' masses differ by a factor of 2 or less. In a simple flared disc model, the critical mass for gap opening varies from a few Earth masses at the inner edge of the disc to 1 Saturn mass at 5 au. A pair of co-orbital planets with masses in this range that migrates will enter a region where the planets are at the gap-opening limit. At that point, the resonance is disrupted. We therefore predict an absence of planets on co-orbital configurations with masses in the super-Earth to Saturn mass range with similar masses.

Pierens, A.; Raymond, S. N.

2014-08-01

254

Mars Reconnaissance Orbiter Accelerometer Experiment Results  

NASA Astrophysics Data System (ADS)

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005, designed for aerobraking, achieved Mars Orbital Insertion (MOI), March 10, 2006. Atmospheric density decreases exponentially with increasing height. By small propulsive adjustments of the apoapsis orbital velocity, periapsis altitude is fine tuned to the density surface that safely used the atmosphere of Mars to aerobrake over 400 orbits. MRO periapsis precessed from the South Pole at 6pm LST to near the equator at 3am LST. Meanwhile, apoapsis was brought dramatically from 40,000km at MOI to 460 km at aerobraking completion (ABX) August 30, 2006. After ABX, a few small propulsive maneuvers established the Primary Science Orbit (PSO), which without aerobraking would have required an additional 400 kg of fuel. Each of the 400 plus aerobraking orbits provided a vertical structure and distribution of density, scale heights, and temperatures, along the orbital path, providing key in situ insight into various upper atmosphere (greater than 100 km) processes. One of the major questions for scientists studying Mars is: "Where did the water go?" Honeywell's substantially improved electronics package for its IMU (QA-2000 accelerometer, gyro, electronics) maximized accelerometer sensitivities at the requests of The George Washington University, JPL, and Lockheed Martin. The improved accelerometer sensitivities allowed density measurements to exceed 200km, at least 40 km higher than with Mars Odyssey (MO). This extended vertical structures from MRO into the neutral lower exosphere, a region where various processes may allow atmospheric gasses to escape. Over the eons, water may have been lost in both near the surface and in the upper atmosphere. Thus the water balance throughout the entire atmosphere from subsurface to exosphere may both be critical. Comparisons of data from Mars Global Surveyor (MGS), MO and MRO help characterize key temporal and spatial cycles including: winter polar warming, planetary scale gravity waves, latitudinal, seasonal, and diurnal variations, and variations from perihelion to aphelion. This will validate and constrain both upper atmospheric circulation models used to understand the nature of high-altitude variability and transport processes, and engineering models used to plan future missions.

Keating, G. M.; Bougher, S. W.; Theriot, M. E.; Zurek, R. W.; Blanchard, R. C.; Tolson, R. H.; Murphy, J. R.

2007-05-01

255

The orbital record in stratigraphy  

NASA Technical Reports Server (NTRS)

Orbital signals are being discovered in pre-Pleistocene sediments. Due to their hierarchical nature these cycle patterns are complex, and the imprecision of geochronology generally makes the assignment of stratigraphic cycles to specific orbital cycles uncertain, but in sequences such as the limnic Newark Group under study by Olsen and pelagic Cretaceous sequence worked on by our Italo-American group the relative frequencies yield a definitive match to the Milankovitch hierarchy. Due to the multiple ways in which climate impinges on depositional systems, the orbital signals are recorded in a multiplicity of parameters, and affect different sedimentary facies in different ways. In platform carbonates, for example, the chief effect is via sea-level variations (possibly tied to fluctuating ice volume), resulting in cycles of emergence and submergence. In limnic systems it finds its most dramatic expression in alternations of lake and playa conditions. Biogenic pelagic oozes such as chalks and the limestones derived from them display variations in the carbonate supplied by planktonic organisms such as coccolithophores and foraminifera, and also record variations in the aeration of bottom waters. Whereas early studies of stratigraphic cyclicity relied mainly on bedding variations visible in the field, present studies are supplementing these with instrumental scans of geochemical, paleontological, and geophysical parameters which yield quantitative curves amenable to time-series analysis; such analysis is, however, limited by problems of distorted time-scales. My own work has been largely concentrated on pelagic systems. In these, the sensitivity of pelagic organisms to climatic-oceanic changes, combined with the sensitivity of botton life to changes in oxygen availability (commonly much more restricted in the Past than now) has left cyclic patterns related to orbital forcing. These systems are further attractive because (1) they tend to offer depositional continuity, and (2) presence of abundant microfossils yields close ties to geochronology. A tantalizing possibility that stratigraphy may yield a record of orbital signals unrelated to climate has turned up in magnetic studies of our Cretaceous core. Magnetic secular variations here carry a strong 39 ka periodicity, corresponding to the theoretical obliquity period of that time - Does the obliquity cycle perhaps have some direct influence on the magnetic field?

Fischer, Alfred G.

1992-01-01

256

External Resource: What is orbit?  

NSDL National Science Digital Library

A 5-8 NASA Education reference answering the question, " What is orbit?" Topics include: satellite, ecliptic plane, perigee, apogee, escape velocity, geosynchronous, polar orbits, and low Earth orbit.

1900-01-01

257

Space Shuttle Orbiter  

NSDL National Science Digital Library

Students learn how orbits are created by a force pulling toward the center in this Moveable Museum unit, in which they build a paper model of a Space Shuttle. This activity simulates an object in orbit. A paper Space Shuttle is swung in a circle on a string. The string provides a pull toward the center of the orbit, simulating the force of gravity. The four-page PDF guide includes suggested background readings for educators, activity notes, and step-by-step directions with suggested discussion questions for older students.

258

Nontraumatic orbital hemorrhage.  

PubMed

Nontraumatic orbital hemorrhage (NTOH) is uncommon. I summarize the published reports of NTOH and offer a classification based on anatomic and etiologic factors. Anatomic patterns of NTOH include diffuse intraorbital hemorrhage, "encysted" hemorrhage (hematic cyst), subperiosteal hemorrhage, hemorrhage in relation to extraocular muscles, and hemorrhage in relation to orbital floor implants. Etiologic factors include vascular malformations and lesions, increased venous pressure, bleeding disorders, infection and inflammation, and neoplastic and nonneoplastic orbital lesions. The majority of NTOH patients can be managed conservatively, but some will have visual compromise and may require operative intervention. Some will suffer permanent visual loss, but a large majority have a good visual outcome. PMID:24359805

McNab, Alan A

2014-01-01

259

Cassini orbit determination performance during the first eight orbits of the Saturn satellite tour  

NASA Technical Reports Server (NTRS)

From June 2004 through July 2005, the Cassini/Huygens spacecraft has executed nine successful close-targeted encounters by three major satellites of the Saturnian system. Current results show that orbit determination has met design requirements for targeting encounters, Hugens descent, and predicting science instrument pointing for targetd satellite encounters. This paper compares actual target dispersion against, the predicte tour covariance analyses.

Antreasian, P. G.; Bordi, J. J.; Criddle, K. E.; Ionasescu, R.; Jacobson, R. A.; Jones, J. B.; MacKenzie, R. A.; Meek, M. C.; Pelletier, F. J.; Roth, D. C.; Roundhill, I. M.; Stauch, J.

2005-01-01

260

Clustering of Periodic Orbits and Ensembles of Truncated Unitary Matrices  

NASA Astrophysics Data System (ADS)

In present article we consider a combinatorial problem of counting and classification of periodic orbits in dynamical systems on an example of the baker's map. Periodic orbits of a chaotic system can be organized into a set of clusters, where orbits from a given cluster traverse approximately the same points of the phase space but in a different time-order. We show that counting of cluster sizes in the baker's map can be turned into a spectral problem for matrices from truncated unitary ensemble (TrUE). We formulate a conjecture of universality of the spectral edge in the eigenvalues distribution of TrUE and utilize it to derive asymptotics of the second moment of cluster distribution in the regime when both the orbit lengths and the parameter controlling closeness of the orbit actions tend to infinity. The result obtained allows to estimate the size of average cluster for various numbers of encounters in periodic orbit.

Gutkin, Boris; Osipov, Vladimir

2013-12-01

261

B-52 Flight Mission Symbology - Close up  

NASA Technical Reports Server (NTRS)

A close-up view of some of the mission markings that tell the story of the NASA B-52 mothership's colorful history. These particular markings denote some of the experiments the bomber conducted to develop parachute recovery systems for the solid rocket boosters used by the Space Shuttle. NASA B-52, Tail Number 008, is an air launch carrier aircraft, 'mothership,' as well as a research aircraft platform that has been used on a variety of research projects. The aircraft, a 'B' model built in 1952 and first flown on June 11, 1955, is the oldest B-52 in flying status and has been used on some of the most significant research projects in aerospace history. Some of the significant projects supported by B-52 008 include the X-15, the lifting bodies, HiMAT (highly maneuverable aircraft technology), Pegasus, validation of parachute systems developed for the space shuttle program (solid-rocket-booster recovery system and the orbiter drag chute system), and the X-38. The B-52 served as the launch vehicle on 106 X-15 flights and flew a total of 159 captive-carry and launch missions in support of that program from June 1959 to October 1968. Information gained from the highly successful X-15 program contributed to the Mercury, Gemini, and Apollo human spaceflight programs as well as space shuttle development. Between 1966 and 1975, the B-52 served as the launch aircraft for 127 of the 144 wingless lifting body flights. In the 1970s and 1980s, the B-52 was the launch aircraft for several aircraft at what is now the Dryden Flight Research Center, Edwards, California, to study spin-stall, high-angle-of attack, and maneuvering characteristics. These included the 3/8-scale F-15/spin research vehicle (SRV), the HiMAT (Highly Maneuverable Aircraft Technology) research vehicle, and the DAST (drones for aerodynamic and structural testing). The aircraft supported the development of parachute recovery systems used to recover the space shuttle solid rocket booster casings. It also supported eight orbiter (space shuttle) drag chute tests in 1990. In addition, the B-52 served as the air launch platform for the first six Pegasus space boosters. During its many years of service, the B-52 has undergone several modifications. The first major modification was made by North American Aviation (now part of Boeing) in support of the X-15 program. This involved creating a launch-panel-operator station for monitoring the status of the test vehicle being carried, cutting a large notch in the right inboard wing flap to accommodate the vertical tail of the X-15 aircraft, and installing a wing pylon that enables the B-52 to carry research vehicles and test articles to be air-launched/dropped. Located on the right wing, between the inboard engine pylon and the fuselage, this wing pylon was subjected to extensive testing prior to its use. For each test vehicle the B-52 carried, minor changes were made to the launch-panel operator's station. Built originally by the Boeing Company, the NASA B-52 is powered by eight Pratt & Whitney J57-19 turbojet engines, each of which produce 12,000 pounds of thrust. The aircraft's normal launch speed has been Mach 0.8 (about 530 miles per hour) and its normal drop altitude has been 40,000 to 45,000 feet.. It is 156 feet long and has a wing span of 185 feet. The heaviest load it has carried was the No. 2 X-15 aircraft at 53,100 pounds. Project manager for the aircraft is Roy Bryant.

1993-01-01

262

FAST DIGITAL ORBIT FEEDBACK SYSTEMS AT NSLS.  

SciTech Connect

We are implementing digital orbit feedback systems to replace the analog ones in both the VUV and the X-ray rings. We developed an original VME-based design which is run by a powerful Motorola 2305 CPU and consists entirely of off-the-shelf VME boards. This makes the system inexpensive and easy to configure, and allows for high digitizing rates. The new 5 kHz digital global feedback system is currently operational in the VUV ring, and the X-ray system is in the commissioning phase. Some of the parameters achieved include vertical correction bandwidth of 200 Hz (at DC gain of 100) and typical orbit drift over a fill of <3% of the rms beam size. In this paper we discuss the system architecture, implementation and performance.

PODOBEDOV,B.; KUSHNER,B.; RAMAMOORTHY,S.; TANG,Y.; ZITVOGEL,E.

2001-06-18

263

Europa Planetary Protection for Juno Jupiter Orbiter  

NASA Astrophysics Data System (ADS)

NASA's Juno mission will launch in 2011 and explore the Jupiter system starting in 2016. Juno's suite of instruments is designed to investigate the gravitational fields, magnetic fields, and auroral regions and its low perijove polar orbit will allow it to explore portions of the Jovian environment never before visited. While the Juno mission is not orbiting or flying close to Europa or the other Galilean satellites, planetary protection requirements for avoiding the contamination of Europa have been taken into account in the Juno mission design. The science mission is concluded with a deorbit burn that disposes of the spacecraft in Jupiter's atmosphere. Compliance with planetary protection requirements is verified through a set of analyses including analysis of initial bioburden, analysis of the effect of bioburden reduction due to the space and Jovian radiation environments, probabilistic risk assessment of successful deorbit, Monte-Carlo orbit propagation, and bioburden reduction due to impact into an icy body.

Bernard, Douglas; Abelson, Robert; Johannesen, Jennie; Lam, Try; McAlpine, William; Newlin, Laura

264

Europa Planetary Protection for Juno Jupiter Orbiter  

NASA Technical Reports Server (NTRS)

NASA's Juno mission launched in 2011 and will explore the Jupiter system starting in 2016. Juno's suite of instruments is designed to investigate the atmosphere, gravitational fields, magnetic fields, and auroral regions. Its low perijove polar orbit will allow it to explore portions of the Jovian environment never before visited. While the Juno mission is not orbiting or flying close to Europa or the other Galilean satellites, planetary protection requirements for avoiding the contamination of Europa have been taken into account in the Juno mission design.The science mission is designed to conclude with a deorbit burn that disposes of the spacecraft in Jupiter's atmosphere. Compliance with planetary protection requirements is verified through a set of analyses including analysis of initial bioburden, analysis of the effect of bioburden reduction due to the space and Jovian radiation environments, probabilistic risk assessment of successful deorbit, Monte-Carlo orbit propagation, and bioburden reduction in the event of impact with an icy body.

Bernard, Douglas E.; Abelson, Robert D.; Johannesen, Jennie R.; Lam, Try; McAlpine, William J.; Newlin, Laura E.

2010-01-01

265

Altimetry, Orbits and Tides  

NASA Technical Reports Server (NTRS)

The nature of the orbit error and its effect on the sea surface heights calculated with satellite altimetry are explained. The elementary concepts of celestial mechanics required to follow a general discussion of the problem are included. Consideration of errors in the orbits of satellites with precisely repeating ground tracks (SEASAT, TOPEX, ERS-1, POSEIDON, amongst past and future altimeter satellites) are detailed. The theoretical conclusions are illustrated with the numerical results of computer simulations. The nature of the errors in this type of orbits is such that this error can be filtered out by using height differences along repeating (overlapping) passes. This makes them particularly valuable for the study and monitoring of changes in the sea surface, such as tides. Elements of tidal theory, showing how these principles can be combined with those pertinent to the orbit error to make direct maps of the tides using altimetry are presented.

Colombo, O. L.

1984-01-01

266

Space: Orbiting the Earth  

NSDL National Science Digital Library

In this activity, students solve various problems related to John Glenn's first ride into space, and complete calculations involving velocity, distance and time. Then they calculate the height a satellite would need to be to keep to a geosynchronous orbit.

2010-01-01

267

Spiral Orbit Tribometry, 2.  

National Technical Information Service (NTIS)

The coefficients of friction and relative degradation rates of three lubricants run in the boundary regime in vacuum are evaluated in a Spiral Orbit Tribometer. This tribometer subjected the lubricants to rolling contact conditions similar to those found ...

S. V. Pepper E. P. Kingsbury

2002-01-01

268

Orbiter thermal protection system  

NASA Technical Reports Server (NTRS)

The major material and design challenges associated with the orbiter thermal protection system (TPS), the various TPS materials that are used, the different design approaches associated with each of the materials, and the performance during the flight test program are described. The first five flights of the Orbiter Columbia and the initial flight of the Orbiter Challenger provided the data necessary to verify the TPS thermal performance, structural integrity, and reusability. The flight performance characteristics of each TPS material are discussed, based on postflight inspections and postflight interpretation of the flight instrumentation data. Flights to date indicate that the thermal and structural design requirements for the orbiter TPS are met and that the overall performance is outstanding.

Dotts, R. L.; Curry, D. M.; Tillian, D. J.

1985-01-01

269

Report on orbital debris  

NASA Technical Reports Server (NTRS)

The success of space endeavors depends upon a space environment sufficiently free of debris to enable the safe and dependable operation of spacecraft. An environment overly cluttered with debris would threaten the ability to utilize space for a wide variety of scientific, technological, military, and commercial purposes. Man made space debris (orbital debris) differs from natural meteoroids because it remains in earth orbit during its lifetime and is not transient through the space around the Earth. The orbital debris environment is considered. The space environment is described along with sources of orbital debris. The current national space policy is examined, along with ways to minimize debris generation and ways to survive the debris environment. International efforts, legal issues and commercial regulations are also examined.

1989-01-01

270

Tethered orbital refueling study  

NASA Technical Reports Server (NTRS)

One of the major applications of the space station will be to act as a refueling depot for cryogenic-fueled space-based orbital transfer vehicles (OTV), Earth-storable fueled orbit maneuvering vehicles, and refurbishable satellite spacecraft using hydrazine. One alternative for fuel storage at the space station is a tethered orbital refueling facility (TORF), separated from the space station by a sufficient distance to induce a gravity gradient force that settles the stored fuels. The technical feasibility was examined with the primary focus on the refueling of LO2/LH2 orbital transfer vehicles. Also examined was the tethered facility on the space station. It was compared to a zero-gravity facility. A tethered refueling facility should be considered as a viable alternative to a zero-gravity facility if the zero-gravity fluid transfer technology, such as the propellant management device and no vent fill, proves to be difficult to develop with the required performance.

Fester, Dale A.; Rudolph, L. Kevin; Kiefel, Erlinda R.; Abbott, Peter W.; Grossrode, Pat

1986-01-01

271

Habitability study shuttle orbiter  

NASA Technical Reports Server (NTRS)

Studies of the habitability of the space shuttle orbiter are briefly summarized. Selected illustrations and descriptions are presented for: crew compartment, hygiene facilities, food system and galley, and storage systems.

1972-01-01

272

Spectrophotovoltaic Orbital Power Generation.  

National Technical Information Service (NTIS)

The feasibilty of a spectrophotovoltaic orbital power generation system that optically concentrates solar energy is demonstrated. A dichroic beam-splitting mirror is used to divide the solar spectrum into two wavebands. Absorption of these wavebands by Ga...

J. R. Onffroy

1980-01-01

273

Subjective Visual Vertical and Postural Performance in Healthy Children  

PubMed Central

Introduction Verticality is essential in our life, especially for postural stability. Subjective vertical as well as postural stability depends on different sensorial information: visual, vestibular and somesthesic. They help to build the spatial referentials and create a central representation of verticality. Children are more visuo-dependant than adults; however, we did not find any study focusing on how children develop their sense of verticality. Methods We studied two groups of subjects: 10 children (from 6 to 8 years) and 12 young adults. We recorded postural stability with a Techno Concept plateform and perception of subjective visual vertical in the following conditions: while adjusting the vertical in the dark or with visual perturbation, while fixating the vertical bar, and with eyes closed. Results Children are more instable than adults in terms of postural parameters, and also while performing a double task, especially when no visual references are present. They also present a higher variability and lower accuracy than adults in reporting their perception of true vertical reference. Discussion Children might have limited attentional resources, and focus their attention on the more demanding task, corresponding to the U-shaped non-linear model.

Gaertner, Chrystal; Bucci, Maria Pia; Obeid, Rima; Wiener-Vacher, Sylvette

2013-01-01

274

Satellites Orbiting Earth  

NSDL National Science Digital Library

In recent years, there has been a push to better understand how Earth works as a system- how land, oceans, air, and life all interact. Satellites in orbit around Earth are a fast and efficient way of gathering remotely sensed data about the planet as a whole. This animated video shows the orbital paths of the satellites in the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS), a collection of satellites that work together to study Earth on a wide scale.

275

A tapestry of orbits  

SciTech Connect

In this book, the author describes how orbital research developed to yield a rich harvest of knowledge about the earth and its atmosphere. King-Hele relates a personal account of this research based on analysis of satellite orbits between 1957 and 1990 conducted from the Royal Aircraft Establishment in Farnborough England. The early research methods used before the launch of Sputnik in 1957 are discussed.

King-Hele, D.

1992-01-01

276

Two Body Orbits Model  

NSDL National Science Digital Library

The Two Body Orbits model for teachers shows the motion of two objects (binary star or moon-planet system) interacting via Newton's law of universal gravitation. It is designed to teach physics, Earth science, and environmental science topics by showing the spatial path of objects around their common center of mass (barycenter). An optional 3D view shows the celestial sphere and and the orbital plane (ecliptic). Default units are chosen for Earth obit about our Sun so that the distance unit is one astronomical unit and the time unit is one year.   An important feature of the ready-to-run Two Body Orbits simulation is that it can be customized by teachers to meet various learning objectives. The teacher sets the ratio of the two masses, their initial positions and velocities, and various visualization and scale parameters. Documentation, such as an exercise or lesson, can be added to the simulation by entering a filename into the Customization dialog. Selecting the âstudentâ checkbox creates a ready-to-run package with the new configuration without the Customization dialog. The Two Body Orbits model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run Java archive. Double clicking the ejs_mech_orbits_TwoBodyOrbits.jar file will run the program if Java is installed. EJS is a part of the Open Source Physics Project and is available in the OSP Collection.

Christian, Wolfgang

2012-07-18

277

Centropages behaviour: Swimming and vertical migration  

NASA Astrophysics Data System (ADS)

The evolutionary success of any species living in a variable environment depends on its capacity to enhance the probability of finding food and mates, and escaping predators. In the case of copepods of the genus Centropages, as in all planktonic copepods, their swimming behaviour is closely tied to these vital aspects, and shows a high degree of plasticity and adaptive capacity. Swimming mechanisms of Centropages change radically during development, mainly in the transition between naupliar stages to the 1st copepodite; nauplii do not produce feeding currents, whereas copepodites do. Adults and late developmental stages of C. typicus, C. hamatus and C. velificatus spend most of the time in slow swimming and resting breaks, with occasional and brief fast swimming (escape reactions) and grooming events. Slow swimming is closely related to the creation of feeding currents, and results from the beating of the cephalic appendages in a “fling and clap” manner. The proportion of time allocated to the different swimming activities depends on sensory cues like type and concentration of food, presence of potential mates, light intensity, hydrodynamic flow, etc. The responses of Centropages to changes in flow velocity fluctuations (small-scale turbulence) are similar to the escape responses (fast swimming) triggered by the presence of potential predators. Centropages generally have standard nocturnal vertical migration patterns involving considerable vertical displacements. This behaviour is closely related to the narrow spectral sensitivity and the low intensity threshold of the genus, and has important consequences for the active vertical transport of matter and energy. The variety of responses of Centropages to environmental changes, and in general all the aspects related to its swimming behaviour seem to be controlled by the trade-off between energetic gains (food intake), losses (swimming energy expenditure), and predation risk. Behavioural plasticity and adaptation appear to be the most relevant characteristics for the success of the genus in a wide range of marine environments.

Alcaraz, Miguel; Saiz, Enric; Calbet, Albert

2007-02-01

278

Perturbations in orbital elements of a low earth orbiting satellite  

Microsoft Academic Search

The main point of this paper is to evaluate the perturbations in orbital elements of a low Earth orbiting satellite. The outcome of a numerical orbit integration process is the position and velocity vectors of satellite in an inertial coordinate system. The velocity and position vectors are converted into the corresponding orbital elements. Perturbations in a satellite motion affect the

Najafi Alamdari; Nasir Toosi

279

Orbital YORP and asteroid orbit evolution, with application to Apophis  

Microsoft Academic Search

Photon thrust from shape alone can produce quasi-secular changes in an asteroid's orbital elements. An asteroid in an elliptical orbit with a north south shape asymmetry can steadily alter its elements over timescales longer than one orbital trip about the Sun. This thrust, called here orbital YORP (YORP = Yarkovsky O'Keefe Radzievskii Paddack), operates even in the absence of thermal

David Parry Rubincam

2007-01-01

280

Regional Elevations in the Southern Hemisphere of Mars From the Mars Orbiter Laser Altimeter  

NASA Technical Reports Server (NTRS)

The Mars Orbiter Laser Altimeter (MOLA) is an instrument on the Mars Global Surveyor (MGS) spacecraft that is currently providing the first high vertical and spatial resolution topographic measurements of surface elevations on Mars. The shot size in the mapping orbit is about 100 m and the shot-to-shot spacing is 330 m. The instrument has a vertical precision of 37.5 cm and a vertical accuracy that depends on the radial accuracy of the MGS orbit that is currently in the range 5-30 km. The initial focus on observations in the nominal mapping mission will be on the southern hemisphere, which was not sampled during the MGS aerobraking hiatus and Science Phasing orbits. During the first several weeks of global mapping there will be emphasis on producing a digital terrain model (DTM) of the Mars '98 landing site.

Smith, D. E.; Zuber, M. T.; Frey, H. V.; Garvin, J. B.; Head, J. W.; Muhleman, D. O.; Neumann, G. A.; Pettengill, G. H.; Phillips, R. J.; Solomon, S. C.

1999-01-01

281

Real-time Sub-cm Differential Orbit Determination of two Low-Earth Orbiters with GPS Bias Fixing  

NASA Technical Reports Server (NTRS)

An effective technique for real-time differential orbit determination with GPS bias fixing is formulated. With this technique, only real-time GPS orbits and clocks are needed (available from the NASA Global Differential GPS System with 10-20 cm accuracy). The onboard, realtime orbital states of user satellites (few meters in accuracy) are used for orbit initialization and integration. An extended Kalman filter is constructed for the estimation of the differential orbit between the two satellites as well as a reference orbit, together with their associating dynamics parameters. Due to close proximity of the two satellites and of similar body shapes, the differential dynamics are highly common and can be tightly constrained which, in turn, strengthens the orbit estimation. Without explicit differencing of GPS data, double-differenced phase biases are formed by a transformation matrix. Integer-valued fixing of these biases are then performed which greatly strengthens the orbit estimation. A 9-day demonstration between GRACE orbits with baselines of approx.200 km indicates that approx.80% of the double-differenced phase biases can successfully be fixed and the differential orbit can be determined to approx.7 mm as compared to the results of onboard K-band ranging.

Wu, Sien-Chong; Bar-Sever, Yoaz E.

2006-01-01

282

Extravehicular activity at geosynchronous earth orbit  

NASA Technical Reports Server (NTRS)

The basic contract to define the system requirements to support the Advanced Extravehicular Activity (EVA) has three phases: EVA in geosynchronous Earth orbit; EVA in lunar base operations; and EVA in manned Mars surface exploration. The three key areas to be addressed in each phase are: environmental/biomedical requirements; crew and mission requirements; and hardware requirements. The structure of the technical tasks closely follows the structure of the Advanced EVA studies for the Space Station completed in 1986.

Shields, Nicholas, Jr.; Schulze, Arthur E.; Carr, Gerald P.; Pogue, William

1988-01-01

283

Visualization of A-Train vertical profiles using Google Earth  

NASA Astrophysics Data System (ADS)

Online tools, such as those pioneered by Google Earth (GE), are changing the way in which scientists and the general public interact with three-dimensional geospatial data in a virtual environment. However, while GE provides a number of features to facilitate geospatial data visualization, there is currently no readily available method for rendering vertical geospatial data derived from Earth—viewing remote sensing satellites as an orbit curtain seen from above. Here, a solution (one of many possible) is demonstrated to render vertical profiles of atmospheric data from the A-Train satellite formation in GE, using as a proof-of-concept data from one of the instruments—the NASA CloudSat satellite. CloudSat carries a nadir-viewing Cloud Profiling Radar that produces data revealing the vertical distribution of cloud characteristics along the satellite track. These data are first rendered into a long vertical image for a user-selected spatial range through the NASA Goddard Interactive Online Visualization ANd aNalysis Infrastructure (G IOVANNI) system ( http://giovanni.gsfc.nasa.gov/). The vertical image is then chopped into small slices representing 15 s of satellite time (˜103 km long ground distance). Each small piece, as a texture, is fed into a generalized COLLAborative Design Activity (COLLADA) three-dimensional (3-D) model. Using the satellite orbit coordinates, the repeated 15 s "3-D model slices" are spliced together to form a vertical "curtain" image in Keyhole Markup Language (KML) format. Each model slice is geolocated along the CloudSat orbit path based on its size, scale and angle with the longitude line that are precisely calculated on the fly. The resulting vertical cloud data can be viewed in GE, either transparently or opaquely, superimposed above the Earth's surface with an exaggerated vertical scale. Since CloudSat is just a part of the A-Train formation, the full utility of this tool can be explored within the context of the A-Train Data Depot (ATDD, http://disc.gsfc.nasa.gov/atdd/) and the corresponding Giovanni instance ( http://disc1.sci.gsfc.nasa.gov/daac-bin/G3/gui.cgi?instance_id=atrain). The latter portal allows scientists and the general public to access and visualize complex A-Train datasets without having to delve into data formats specific to a given mission.

Chen, Aijun; Leptoukh, Gregory; Kempler, Steven; Lynnes, Christopher; Savtchenko, Andery; Nadeau, Denis; Farley, John

2009-02-01

284

Orbital Evolution and Chaos Among the Inner Moons of Uranus  

NASA Astrophysics Data System (ADS)

Uranus has a family of thirteen satellites orbiting interior to the innermost classical moon, Miranda. Nine of these comprise the Portia group, a closely-packed dynamical system that has recently been found to show significant orbital variations over time scales of 1-2 decades. This result supports inferences that the system is chaotic, with collisions expected over time scales of less than one million years. No analogous orbital system has been seen elsewhere in the Solar System. With these new results, it becomes much more important to understand the orbital history of the inner moons of Uranus. The HST archive contains numerous detections of these moons, from WFPC2, NICMOS and ACS, that have never been used for orbital determinations. Many observations fill a gap between 1994 and 2003, during which the orbits have never been measured. This is a proposal to use all the available data from the HST archive to derive the orbital variations of the larger moons in the Portia group from 1994 to 2005. This investigation will provide unique new information about the time scales over which the variations occur and the nature of the hypothesized chaos. For example, this study will enable us to test the prediction that the two adjacent moons Cressida and Desdemona have closely coupled variations, and it may reveal whether the surprisingly large orbital deviations of Belinda are related to its resonance with the nearby, but much smaller moon Perdita.

Showalter, Mark

2006-07-01

285

Mars Geoscience Orbiter and Lunar Geoscience Orbiter  

NASA Technical Reports Server (NTRS)

The feasibility of using the AE/DE Earth orbiting spacecraft design for the LGO and/or MGO missions was determined. Configurations were developed and subsystems analysis was carried out to optimize the suitability of the spacecraft to the missions. The primary conclusion is that the basic AE/DE spacecraft can readily be applied to the LGO mission with relatively minor, low risk modifications. The MGO mission poses a somewhat more complex problem, primarily due to the overall maneuvering hydrazine budget and power requirements of the sensors and their desired duty cycle. These considerations dictate a modification (scaling up) of the structure to support mission requirements.

Fuldner, W. V.; Kaskiewicz, P. F.

1983-01-01

286

Titan Orbiter with Aerorover Mission (TOAM)  

NASA Technical Reports Server (NTRS)

We propose to develop a new mission to Titan called Titan Orbiter with Aerorover Mission (TOAM). This mission is motivated by the recent discoveries of Titan, its atmosphere and its surface by the Huygens Probe, and a combination of in situ, remote sensing and radar mapping measurements of Titan by the Cassini orbiter. Titan is a body for which Astrobiology (i.e., prebiotic chemistry) will be the primary science goal of any future missions to it. TOAM is planned to use an orbiter and balloon technology (i.e., aerorover). Aerobraking will be used to put payload into orbit around Titan. The Aerorover will probably use a hot air balloon concept using the waste heat from the MMRTG approx. 500 watts. Orbiter support for the Aerorover is unique to our approach for Titan. Our strategy to use an orbiter is contrary to some studies using just a single probe with balloon. Autonomous operation and navigation of the Aerorover around Titan will be required, which will include descent near to the surface to collect surface samples for analysis (i.e., touch and go technique). The orbiter can provide both relay station and GPS roles for the Aerorover. The Aerorover will have all the instruments needed to sample Titan's atmosphere, surface, possible methane lakes-rivers, use multi-spectral imagers for surface reconnaissance; to take close up surface images; take core samples and deploy seismometers during landing phase. Both active and passive broadband remote sensing techniques will be used for surface topography, winds and composition measurements.

Sittler, Edward C.; Cooper, J. F.; Mahaffey, P; Esper, J.; Fairbrother, D.; Farley, R.; Pitman, J.; Kojiro, D. R.

2006-01-01

287

GPS orbit accuracy and its influence on large network solutions  

NASA Astrophysics Data System (ADS)

Geodetic networks belong still to the most important tools of applied geodesy, surveying and mapping. Required accuracy is of the order of millimetres and the vertical component is of particular importance for geodynamics and sea level change research. In combination with classical levelling the network offers excellent information about the shape of the geoid. Modern geodetic networks are established almost exclusively with GPS. In the solution of the network the orbital data is used provided by the IGS service and by regional analysing centres like CODE. In the paper authors discuss the quality of GPS orbits published by different sources and analyse the differences in solution caused by differences in orbital elements. It is proved that in some cases the longitudinal deformation or the tilt of the network is caused by orbital errors but in general the solution is not very sensitive if the error is in the range of two decimetres.

Zieli?ski, J. B.; Zdunek, R.

1999-01-01

288

Vertical Dimension in Complete Dentures.  

National Technical Information Service (NTIS)

The video demonstrates proportional and functional methods to establish a tentative vertical dimension for the edentulous patient. It emphasizes the correlation of this dimension with the centric relation.

1994-01-01

289

Study Close-Out  

Cancer.gov

Step 4: Closing Out a Cancer Prevention Clinical Trial These documents are intended for the use of DCP Consorta staff conducting cancer chemoprevention studies under contract with NCI/DCP. SOP #2: Study Close-Out Responsibilities (SOP) (doc, 48kb) Lists

290

Close Formation Flight Control.  

National Technical Information Service (NTIS)

In this research the close formation flight control problem is addressed. The formation consists of a lead and wing aircraft, where the wing flies in close formation with the lead, such that the lead's vortices produce aerodynamic coupling effects, and a ...

A. W. Proud

1999-01-01

291

Orbital Density Reconstruction for Molecules  

NASA Astrophysics Data System (ADS)

The experimental imaging of electronic orbitals has allowed one to gain a fascinating picture of quantum effects. We here show that the energetically high-lying orbitals that are accessible to experimental visualization in general differ, depending on which approach is used to calculate the orbitals. Therefore, orbital imaging faces the fundamental question of which orbitals are the ones that are visualized. Combining angular-resolved photoemission experiments with first-principles calculations, we show that the orbitals from self-interaction-free Kohn-Sham density functional theory are the ones best suited for the orbital-based interpretation of photoemission.

Dauth, M.; Körzdörfer, T.; Kümmel, S.; Ziroff, J.; Wiessner, M.; Schöll, A.; Reinert, F.; Arita, M.; Shimada, K.

2011-11-01

292

ICESat Precision Orbit Determination  

NASA Astrophysics Data System (ADS)

Following the successful launch of the Ice, Cloud and land Elevation Satellite (ICESat) on January 13, 2003, 00:45 UTC, the GPS receiver on ICESat was turned on successfully on Jan. 17, 2003. High quality GPS data were collected since then to support Precision Orbit Determination (POD) activities. ICESat carries Geoscience Laser Altimeter System (GLAS) to measure ice-sheet topography and associated temporal changes, as well as cloud and atmospheric properties. To accomplish the ICESat science objectives, the position of the GLAS instrument in space should be determined with an accuracy of 5 cm and 20 cm in radial and horizontal components, respectively. This knowledge is acquired by the POD activities using the data collected by the GPS receiver on ICESat and the ground-based satellite laser ranging (SLR) data. It has been shown from pre-launch POD studies that the gravity model error is the dominant source of ICESat orbit errors. The predicted radial orbit errors at the ICESat orbit (600 km altitude) based on pre-launch gravity models, such as TEG-4 and EGM-96, are 7-15 cm. Performance of these gravity models and the recent gravity models from GRACE on ICESat POD were evaluated. The radial orbit accuracy is approaching 1-2 cm level with the GRACE gravity model. This paper also summarizes POD activities at Center for Space Research (CSR), which is responsible to generate ICESat POD products.

Rim, H.; Yoon, S.; Webb, C. E.; Kim, Y.; Schutz, B. E.

2003-12-01

293

Vertical quantum dot with a vertically coupled charge detector  

Microsoft Academic Search

We fabricated a vertical quantum dot equipped with a charge detector. The dot current flows vertically between the top and bottom contacts. The charge detector is formed at the bottom contact layer with a current channel constricted to the region just under the dot. This channel current is reduced by addition of an extra electron onto the dot due to

Koichiro Zaitsu; Yosuke Kitamura; Keiji Ono; Seigo Tarucha

2008-01-01

294

Exomoon habitability constrained by energy flux and orbital stability  

NASA Astrophysics Data System (ADS)

Context. Detecting massive satellites that orbit extrasolar planets has now become feasible, which led naturally to questions about the habitability of exomoons. In a previous study we presented constraints on the habitability of moons from stellar and planetary illumination as well as from tidal heating. Aims: Here I refine our model by including the effect of eclipses on the orbit-averaged illumination. I then apply an analytic approximation for the Hill stability of a satellite to identify the range of stellar and planetary masses in which moons can be habitable. Moons in low-mass stellar systems must orbit their planet very closely to remain bounded, which puts them at risk of strong tidal heating. Methods: I first describe the effect of eclipses on the stellar illumination of satellites. Then I calculate the orbit-averaged energy flux, which includes illumination from the planet and tidal heating to parametrize exomoon habitability as a function of stellar mass, planetary mass, and planet-moon orbital eccentricity. The habitability limit is defined by a scaling relation at which a moon loses its water by the runaway greenhouse process. As a working hypothesis, orbital stability is assumed if the moon's orbital period is less than 1/9 of the planet's orbital period. Results: Due to eclipses, a satellite in a close orbit can experience a reduction in orbit-averaged stellar flux by up to about 6%. The smaller the semi-major axis and the lower the inclination of the moon's orbit, the stronger the reduction. I find a lower mass limit of ? 0.2 M? for exomoon host stars that allows a moon to receive an orbit-averaged stellar flux comparable to the Earth's, with which it can also avoid the runaway greenhouse effect. Precise estimates depend on the satellite's orbital eccentricity. Deleterious effects on exomoon habitability may occur up to ? 0.5 M? if the satellite's eccentricity is ? 0.05. Conclusions: Although the traditional habitable zone lies close to low-mass stars, which allows for many transits of planet-moon binaries within a given observation cycle, resources should not be spent to trace habitable satellites around them. Gravitational perturbations by the close star, another planet, or another satellite induce eccentricities that likely make any moon uninhabitable. Estimates for individual systems require dynamical simulations that include perturbations among all bodies and tidal heating in the satellite.

Heller, R.

2012-09-01

295

Tidal evolution in close binary systems.  

NASA Technical Reports Server (NTRS)

Mathematical outline of the theory of tidal evolution in close binary systems of secularly constant total momentum. Following a general outline of the problem the basic expressions for the energy and momenta of close binaries consisting of components of arbitrary internal structure are established, and the maximum and minimum values of the energy (kinetic and potential) which such systems can attain for a given amount of total momentum are investigated. These results are compared with the actual facts encountered in binaries with components whose internal structure (and, therefore, rotational momenta) are known from evidence furnished by the observed rates of apsidal advance. The results show that all such systems whether of detached or semidetached type - disclose that more than 99% of their total momenta are stored in the orbital momentum. The sum of the rotational momenta of the constituent components amounts to less than 1% of the total -a situation characteristic of a state close to the minimum energy for given total momentum.

Kopal, Z.

1972-01-01

296

Nonmalignant Tumors of the Orbit  

Microsoft Academic Search

\\u000a Most orbital tumors are nonmalignant. Nonmalignant orbital tumors can arise from any of the structures within the orbit, including\\u000a blood vessels, fat, nerves, lacrimal gland, and connective tissue. Nonmalignant orbital tumors can be grouped into cystic\\u000a lesions, vascular tumors, lymphoproliferative lesions, inflammatory lesions, mesenchymal tumors, neurogenic tumors, and lacrimal\\u000a gland tumors. Although most orbital tumors are benign, their location may

Eric M. Hink; Vikram Durairaj

297

Natural convection in vertical Bridgman configurations  

NASA Astrophysics Data System (ADS)

Buoyancy driven convection in closed vertical cylinders heated from below and crystal growth in corresponding configurations (vertical Bridgman technique with top seeding) have been studied experimentally and theoretically. The hydrodynamic state in such configurations is described by three dimensionless numbers, the Rayleigh number Ra, the aspect ratio (height h/diameter d) and the Prandtl number Pr. Two different types of melts have been investigated, H 2O (Pr = 6.7), and Ga and GaSb melts (Pr ? 2 × 10 -2) for various aspect ratios (0.5 ? h/ d ? 5) and Rayleigh numbers up to 10 8. Both experimental results and numerical analysis for the onset of convection (critical Rayleigh number Ra c1) and the state of convective flow are presented. The values of Ra c1 for 0.5 ? h/ d ? 5 and the symmetries of the basic flow (axial symmetry for h/ d = 0.5 and non-axial symmetry for 1 ? h/ d ? 5) are in good agreement with the theoretical predictions of Charlson and Sani [1]. Te-doped GaSb crystals have been grown by using the vertical Bridgman technique with top seeding. Temperatures have been measured in the GaSb melt during growth and compared with the results of our flow investigations in Ga melts. It shows clearly, that the occurrence of doping striations in the GaSb crystals can be very well correlated to the unsteady flow regimes.

Müller, G.; Neumann, G.; Weber, W.

1984-12-01

298

Mars Reconnaissance Orbiter Navigation  

NASA Technical Reports Server (NTRS)

Mars Reconnaissance Orbiter will launch in August 2005 at Cape Canaveral Air Force Station. The heavyweight spacecraft will use a Lockheed-Martin Atlas V-401 launch vehicle. It will be the first mission in a low Mars Orbit to characterize the surface, subsurface, and atmospheric properties. The intensive science operation imposes a great challenge for Navigation to satisfy the stringent requirements. This paper describes navigation key requirements, major challenges, and the sophisticated dynamic modeling. It also details navigation strategy and processes for various mission phases. Mars Reconnaissance Orbiter will return significant amount of scientific data in support of the objectives set by the Mars Exploration Program. A robust and precise navigation is the key to the success of this mission.

You, Tung-Han; Halsell, Allen; Highsmith, Dolan; Moriba, Jah; Demcak, Stuart; Higa, Earl; Long, Stacia; Bhaskaran, Shyam

2004-01-01

299

Ballistics and Orbits Model  

NSDL National Science Digital Library

The EJS Ballistics and Orbits model displays ballistic trajectories near the Earth. The model shows the trajectory with respect to the inertial coordinate system and the trajectory as seen from a point of view that is co-rotating with the Earth. You can examine and modify this simulation if you have EJS installed by right-clicking within the plot and selecting âOpen EJS Modelâ from the pop-up menu item. The Ballistics and Orbits model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_nl_teunissen_ballistics_and_orbits.jar file will run the program if Java is installed. Additional information about this model can be found by visiting the authorâs web site: http://www.cleonis.nl/index.htm.

Teunissen, Cleon

2009-11-03

300

Natural convection in a vertical enclosure with internal permeable screen  

Microsoft Academic Search

This paper documents the thermal insulation effect of a screen installed inside a vertical rectangular enclosure (e.g., double-glazed window). The screen is a venetian blind system made out of horizontal strips that can be rotated. The focus is on the closed position, where the strips almost touch. The effect of this permeable screen on the temperature field, the flow field,

Z. Zhang; A. Bejan; J. L. Lage

1991-01-01

301

Scattering Layers and Vertical Distribution of Oceanic Animals off Oregon.  

National Technical Information Service (NTIS)

The paper reviews some of the distributional features of vertically migrating micronekton off Oregon; describes a new, conducting-cable, midwater-trawl system using an eight-net, opening-closing cod-end unit; and gives some preliminary results on trawl ca...

W. G. Pearcy R. S. Mesecar

1974-01-01

302

Spiral Orbit Tribometer  

NASA Technical Reports Server (NTRS)

The spiral orbit tribometer (SOT) bridges the gap between full-scale life testing and typically unrealistic accelerated life testing of ball-bearing lubricants in conjunction with bearing ball and race materials. The SOT operates under realistic conditions and quickly produces results, thereby providing information that can guide the selection of lubricant, ball, and race materials early in a design process. The SOT is based upon a simplified, retainerless thrust bearing comprising one ball between flat races (see figure). The SOT measures lubricant consumption and degradation rates and friction coefficients in boundary lubricated rolling and pivoting contacts. The ball is pressed between the lower and upper races with a controlled force and the lower plate is rotated. The combination of load and rotation causes the ball to move in a nearly circular orbit that is, more precisely, an opening spiral. The spiral s pitch is directly related to the friction coefficient. At the end of the orbit, the ball contacts the guide plate, restoring the orbit to its original radius. The orbit is repeatable throughout the entire test. A force transducer, mounted in-line with the guide plate, measures the force between the ball and the guide plate, which directly relates to the friction coefficient. The SOT, shown in the figure, can operate in under ultra-high vacuum (10(exp -9) Torr) or in a variety of gases at atmospheric pressure. The load force can be adjusted between 45 and 450 N. By varying the load force and ball diameter, mean Hertzian stresses between 0.5 and 5.0 GPa can be obtained. The ball s orbital speed range is between 1 and 100 rpm.

Pepper, Stephen V.; Jones, William R., Jr.; Kingsbury, Edward; Jansen, Mark J.

2007-01-01

303

Satellite orbit predictor  

NASA Technical Reports Server (NTRS)

An analog aid to determine satellite coverage of Emergency Locator Transmitters Emergency Position Indicating Radio Beacon (ELT/EPIRB) distress incidence is discussed. The satellite orbit predictor is a graphical aid for determining the relationship between the satellite orbit, antenna coverage of the spacecraft and coverage of the Local User Terminal. The predictor allows the user to quickly visualize if a selected position will probably be detected and is composed of a base map and a satellite track overlay for each satellite.A table of equator crossings for each satellite is included.

Friedman, Morton l.; Garrett, James, Major

304

[Orbital arteriovenous anastomoses].  

PubMed

Separate angiography of the channels of a. carotis externa and a. carotis interna revealed two cases with orbital arteriovenous anastomoses between the branches of a. maxillaris interna and v. ophthalmica inferior. In one of these cases the fistule was additionally supplied with blood by branches of a. ophthalmica. The clinical picture of arteriovenous anastomoses of the orbit resembles that of carotid-cavernous fistules. Surgical management consisted in embolization of the channel of a. maxillaris interna on the side of the anastomosis with muscular emboli. The vascular murmur and exophthalmos disappeared after the operation. PMID:716744

Serbinenko, F A; Padalko, P I

1978-01-01

305

Gravity and Orbits  

NSDL National Science Digital Library

The Gravity and Orbits SciPack explores concepts related to Earth's universal gravitation and how gravity affects the universe around us. The focus is on Standards and Benchmarks related to universal gravitation including variables that influence the amount of gravitational force and how gravity governs the motion of the solar system.In addition to comprehensive inquiry-based learning materials tied to Science Education Standards and Benchmarks, the SciPack includes the following additional components:� Pedagogical Implications section addressing common misconceptions, teaching resources and strand maps linking grade band appropriate content to standards. � Access to one-on-one support via e-mail to content "Wizards".� Final Assessment which can be used to certify mastery of the concepts.Learning Outcomes:Gravity and Orbits: Universal Gravitation� Identify gravity as an attractive force associated with all objects, including less intuitive examples (such as soda cans and pencils).� Recognize some examples of phenomena that are the result of Earth's gravity and objects and structures in the universe in general.� Reject the idea that Earth's gravity is an effect of air pushing down toward the surface.� Recognize that gravitational force does not require air (or any other substance) as a medium to act.� Describe gravitational force as a mutual attraction, rather than as one object pulling on another.Gravity and Orbits: Gravitational Force� Identify variables that affect the strength of the gravitational force acting between any two objects.� Provide a quantitative description of the relationship between the mass of two object and the gravitational force between them.� Provide a qualitative description of the relationship between the mass of two objects and the gravitational force between them.� Provide a quantitative description of the relationship between distance and gravitational force. � Provide a qualitative description of the inverse square relationship.� Recognize the effect of air resistance on object falling near Earth's surface, and thus be able to explain why two objects with different masses, at the same distance from Earth's surface, will have equal accelerations if air resistance is ignored. Gravity and Orbits: Orbits� Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.� Explain how an object orbits a planet in terms of trajectories and free fall.� Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2007-03-21

306

Trajectories and Orbits  

NSDL National Science Digital Library

Materials presented here outline some basic concepts associated with space flight. Users can read about orbits and the difference between an orbit and a trajectory, escape velocities for Earth and some planets, launch velocities and transit times for interplanetary flights, and the effects of time dilation for astronauts travelling at near-light speeds. This is part of the famous Rand corporation study that was commissioned by Congress in 1958 after the Soviet Union stunned the world by launching Sputnik, the world's first artificial satellite.

307

Vertical velocity estimates in the North Pacific using Argo floats  

NASA Astrophysics Data System (ADS)

Vertical velocity in the oceans is critical for maintenance of the structure of the main thermoclines and the transport of nutrients from deepwater towards the surface and thus is an important variable for understanding the dynamics of the ocean and the transport of scalar variables. In the mid 1970s the author was engaged in discussions with Tom Rossby about how SOFAR floats might be used to observe the vertical component of velocity. This paper in some sense follows on from those discussions almost 40 years later. In this paper the Argo array is used to compute the horizontal volume divergence in a control volume in the North Pacific. Divergence is found and this must be related to a volume flux through the base of the control volume. The implied vertical velocity is large and various tests are proposed to determine whether or not the estimate is plausible. The first test shows that a vertical velocity this large is necessary to close the salt budget. The second test shows that the vertical velocity balances about half of the observed heat divergence, the remainder is then accounted for by heat flux at the sea surface. Finally the time variable vertical velocity is computed and used to compute the evolution of the salt content in the control volume. Thus though the estimated vertical velocity is surprisingly large, it passes plausibility tests.

Freeland, Howard J.

2013-01-01

308

Orbit-orbit interaction and photonic orbital Hall effect in reflection of a light beam  

NASA Astrophysics Data System (ADS)

We examine the orbit—orbit interaction when a paraxial beam with intrinsic orbital angular momentum (IOAM) reflects at an air—glass interface. The orbital-dependent splitting of the beam intensity distribution arises due to the interaction between IOAM and extrinsic orbital angular momentum (EOAM). In addition, we find that the beam centroid shows an orbital-dependent rotation when seen along the propagation axis. However, the motion of the beam centroid related to the orbit—orbit interaction undergoes a straight line trajectory with a small angle inclining from the propagation axis. Similar to a previously developed spin-dependent splitting in the photonic spin Hall effect, the orbital-dependent splitting could lead to the photonic orbital Hall effect.

Zhang, Jin; Zhou, Xin-Xing; Ling, Xiao-Hui; Chen, Shi-Zhen; Luo, Hai-Lu; Wen, Shuang-Chun

2014-06-01

309

Requirements report for SSTO vertical take-off and horizontal landing vehicle  

NASA Technical Reports Server (NTRS)

This document describes the detailed design requirements and design criteria to support Structures/TPS Technology development for SSTO winged vehicle configurations that use vertical take-off and horizontal landing and delivers 25,000 lb payloads to a 220 nm circular orbit at an inclination of 51.6 degrees or 40,000 lb payloads to a 150 nm circular orbit at a 28.5 degree inclination.

Greenberg, H. S.

1994-01-01

310

Measuring Growth with Vertical Scales  

ERIC Educational Resources Information Center

A vertical score scale is needed to measure growth across multiple tests in terms of absolute changes in magnitude. Since the warrant for subsequent growth interpretations depends upon the assumption that the scale has interval properties, the validation of a vertical scale would seem to require methods for distinguishing interval scales from…

Briggs, Derek C.

2013-01-01

311

Vertical strabismus in monofixation syndrome  

Microsoft Academic Search

Purpose: The manifest angle of the horizontal deviation in monofixation syndrome (MFS) has been reported to reach a maximum of 8 to 10 PD. Review of the literature, however, revealed no studies about the vertical deviation associated with MFS. The purpose of this study is to evaluate the range of the angle of the vertical deviation in MFS. Methods: Forty

Dong Gyu Choi; Sherwin J. Isenberg

2001-01-01

312

Functions and Vertical Line Test  

NSDL National Science Digital Library

This lesson is designed to introduce students to the vertical line test for functions as well as practice plotting points and drawing simple functions. The lesson provides links to discussions and activities related to the vertical line test and functions as well as suggested ways to integrate them into the lesson.

2010-01-01

313

The Gains from Vertical Scaling  

ERIC Educational Resources Information Center

It is often assumed that a vertical scale is necessary when value-added models depend upon the gain scores of students across two or more points in time. This article examines the conditions under which the scale transformations associated with the vertical scaling process would be expected to have a significant impact on normative interpretations…

Briggs, Derek C.; Domingue, Ben

2013-01-01

314

The relativistic factor in the orbital dynamics of point masses  

Microsoft Academic Search

There is a growing population of relativistically relevant minor bodies in the Solar System and a growing population of massive\\u000a extrasolar planets with orbits very close to the central star where relativistic effects should have some signature. Our purpose\\u000a is to review how general relativity affects the orbital dynamics of the planetary systems and to define a suitable relativistic\\u000a correction

Federico Benitez; Tabaré Gallardo

2008-01-01

315

The impact orbits of the dangerous asteroid (99942) Apophis  

Microsoft Academic Search

The impact solutions of the dangerous asteroid (99942) Apophis were obtained from computations performed with the use of the OrbFit software. For all the computations the OrbFit Software, Package 3.3.2, was used. Precise impact orbits for all impact solutions of Apophis predicted for the 2007 epoch and three impact orbits for epochs close to the impact dates in 2036, 2037

I. Wlodarczyk

2008-01-01

316

Orbital-independent superconducting gaps in iron pnictides.  

PubMed

The origin of superconductivity in the iron pnictides has been attributed to antiferromagnetic spin ordering that occurs in close combination with a structural transition, but there are also proposals that link superconductivity to orbital ordering. We used bulk-sensitive laser angle-resolved photoemission spectroscopy on BaFe(2)(As(0.65)P(0.35))(2) and Ba(0.6)K(0.4)Fe(2)As(2) to elucidate the role of orbital degrees of freedom on the electron-pairing mechanism. In strong contrast to previous studies, an orbital-independent superconducting gap magnitude was found for the hole Fermi surfaces. Our result is not expected from the superconductivity associated with spin fluctuations and nesting, but it could be better explained invoking magnetism-induced interorbital pairing, orbital fluctuations, or a combination of orbital and spin fluctuations. Regardless of the interpretation, our results impose severe constraints on theories of iron pnictides. PMID:21474714

Shimojima, T; Sakaguchi, F; Ishizaka, K; Ishida, Y; Kiss, T; Okawa, M; Togashi, T; Chen, C-T; Watanabe, S; Arita, M; Shimada, K; Namatame, H; Taniguchi, M; Ohgushi, K; Kasahara, S; Terashima, T; Shibauchi, T; Matsuda, Y; Chainani, A; Shin, S

2011-04-29

317

Method of resolving radio phase ambiguity in satellite orbit determination  

NASA Technical Reports Server (NTRS)

For satellite orbit determination, the most accurate observable available today is microwave radio phase, which can be differenced between observing stations and between satellites to cancel both transmitter- and receiver-related errors. For maximum accuracy, the integer cycle ambiguities of the doubly differenced observations must be resolved. To perform this ambiguity resolution, a bootstrapping strategy is proposed. This strategy requires the tracking stations to have a wide ranging progression of spacings. By conventional 'integrated Doppler' processing of the observations from the most widely spaced stations, the orbits are determined well enough to permit resolution of the ambiguities for the most closely spaced stations. The resolution of these ambiguities reduces the uncertainty of the orbit determination enough to enable ambiguity resolution for more widely spaced stations, which further reduces the orbital uncertainty. In a test of this strategy with six tracking stations, both the formal and the true errors of determining Global Positioning System satellite orbits were reduced by a factor of 2.

Councelman, Charles C., III; Abbot, Richard I.

1989-01-01

318

The diffusion of chaotic orbits in 3D barred spiral galaxies  

NASA Astrophysics Data System (ADS)

We study the way in which the 3D chaotic orbits, initially belonging to the bar of an N-body model simulating a barred spiral galaxy, are getting diffused outwards. An important percentage of these orbits stay trapped for very long time inside the corotation radius and behave as regular orbits. In the 4D phase space these orbits seem to be trapped close to rotational tori of stable periodic orbits, or close to simply unstable periodic orbits, supporting the shape of the bar. After they get diffused outwards, they get trapped along the asymptotic manifolds of the simply unstable periodic orbits of the region outside corotation and support the shape of the spiral structure for approximately 100 half mass crossing times of the system (Thmct), before escape from it. This phenomenon of diffusion through the 3rd dimension is known as "Arnold Diffusion".

Harsoula, M.

2013-09-01

319

MASSIVE SATELLITES OF CLOSE-IN GAS GIANT EXOPLANETS  

SciTech Connect

We study the orbits, tidal heating and mass loss from satellites around close-in gas giant exoplanets. The focus is on large satellites which are potentially observable by their transit signature. We argue that even Earth-size satellites around hot Jupiters can be immune to destruction by orbital decay; detection of such a massive satellite would strongly constrain theories of tidal dissipation in gas giants, in a manner complementary to orbital circularization. The star's gravity induces significant periodic eccentricity in the satellite's orbit. The resulting tidal heating rates, per unit mass, are far in excess of Io's and dominate radioactive heating out to planet orbital periods of months for reasonable satellite tidal Q. Inside planet orbital periods of about a week, tidal heating can completely melt the satellite. Lastly, we compute an upper limit to the satellite mass loss rate due to thermal evaporation from the surface, valid if the satellite's atmosphere is thin and vapor pressure is negligible. Using this upper limit, we find that although rocky satellites around hot Jupiters with orbital periods less than a few days can be significantly evaporated in their lifetimes, detectable satellites suffer negligible mass loss at longer orbital periods.

Cassidy, Timothy A.; Johnson, Robert E. [Engineering Physics Program, University of Virginia, Charlottesville, VA 22904-4325 (United States); Mendez, Rolando; Arras, Phil; Skrutskie, Michael F., E-mail: tac2z@virginia.ed, E-mail: rem5d@cms.mail.virginia.ed, E-mail: arras@virginia.ed, E-mail: rej@virginia.ed, E-mail: mfs4n@virginia.ed [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)

2009-10-20

320

Closed Small Cell Clouds  

article title:  Closed Small Cell Clouds in the South Pacific     ... they are bright and abundant, and reflect a large amount of solar energy toward space. They are difficult to represent in climate models ...

2013-04-19

321

Orbital myositis: diagnosis and management.  

PubMed

Orbital myositis is an inflammatory process that primarily involves the extraocular muscles and most commonly affects young adults in the third decade of life, with a female predilection. Clinical characteristics of orbital myositis include orbital and periorbital pain, ocular movement impairment, diplopia, proptosis, swollen eyelids, and conjunctival hyperemia. The most common presentation is acute and unilateral, which initially responds to systemic corticosteroid therapy. However, chronic and recurrent cases may involve both orbits. Many inflammatory, vascular, neoplastic, and infectious conditions that affect the extraocular muscles and other orbital tissue can mimic orbital myositis. The most important differential diagnoses include thyroid-related eye disease, other orbital inflammatory processes (unspecific idiopathic inflammation, vasculitis, and sarcoidosis), orbital cellulitis, and orbital tumors. In refractory, chronic, or recurrent cases, steroid-sparing agents, inmmunosuppressants, or radiation therapy may be indicated. PMID:19656480

Costa, Roberta M S; Dumitrascu, Oana M; Gordon, Lynn K

2009-07-01

322

Closed anisotropic cosmological models.  

NASA Technical Reports Server (NTRS)

Derivation of a new exact solution to Einstein's equations representing homogeneous nonisotropic cosmological models of a closed universe containing electromagnetic and scalar fields. This solution reduces to a generalization of Brill's electromagnetic universe when the scalar field vanishes, and to the Taub-NUT-M space when both these fields vanish. The solutions also satisfy the scalar tensor equations and represent a universe containing electromagnetic fields and a source-free solution to the scalar-tensor equations representing a closed universe.

Batakis, N.; Cohen, J. M.

1972-01-01

323

Close It Up  

NSDL National Science Digital Library

As learners play this challenging strategy game, they build understanding of area and perimeter. On each turn, a player draws a line between two dots next to each other on the grid. When you close a shape, mark it as yours. You can make any shapes, as long as theyâre closed. Keep taking turns until there is no more room. The player with the most area wins. Includes easier and harder variations. Available as a downloadable pdf and in Spanish.

Terc

2010-01-01

324

Mars Climate Orbiter  

NASA Technical Reports Server (NTRS)

The Mars Surveyor '98 Climate Orbiter is shown here during acoustic tests that simulate launch conditions. The orbiter was to conduct a two year primary mission to profile the Martian atmosphere and map the surface. To carry out these scientific objectives, the spacecraft carried a rebuilt version of the pressure modulated infrared radiometer, lost with the Mars Observer spacecraft, and a miniaturized dual camera system the size of a pair of binoculars, provided by Malin Space Science Systems, Inc., San Diego, California. During its primary mission, the orbiter was to monitor Mars atmosphere and surface globally on a daily basis for one Martian year (two Earth years), observing the appearance and movement of atmospheric dust and water vapor, as well as characterizing seasonal changes of the planet's surface. Imaging of the surface morphology would also provide important clues about the planet's climate in its early history. The mission was part of NASA's Mars Surveyor program, a sustained program of robotic exploration of the red planet, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, DC. Lockheed Martin Astronautics was NASA's industrial partner in the mission. Unfortunately, Mars Climate Orbiter burned up in the Martian atmosphere on September 23, 1999, due to a metric conversion error that caused the spacecraft to be off course.

1998-01-01

325

Satellite orbits: Plot routines  

NASA Astrophysics Data System (ADS)

Routines for plotting satellite orbits for the Waves in Space Plasmas shuttle-borne experiment are presented. The principles of virtual device coordinate text are outlined. The programs are written in C language on the HP-UX operating system and the Starbase graphics package.

Olsson, Pelle

1987-02-01

326

Global orbit corrections  

SciTech Connect

There are various reasons for preferring local (e.g., three bump) orbit correction methods to global corrections. One is the difficulty of solving the mN equations for the required mN correcting bumps, where N is the number of superperiods and m is the number of bumps per superperiod. The latter is not a valid reason for avoiding global corrections, since, we can take advantage of the superperiod symmetry to reduce the mN simultaneous equations to N separate problems, each involving only m simultaneous equations. Previously, I have shown how to solve the general problem when the machine contains unknown magnet errors of known probability distribution; we made measurements of known precision of the orbit displacements at a set of points, and we wish to apply correcting bumps to minimize the weighted rms orbit deviations. In this report, we will consider two simpler problems, using similar methods. We consider the case when we make M beam position measurements per superperiod, and we wish to apply an equal number M of orbit correcting bumps to reduce the measured position errors to zero. We also consider the problem when the number of correcting bumps is less than the number of measurements, and we wish to minimize the weighted rms position errors. We will see that the latter problem involves solving equations of a different form, but involving the same matrices as the former problem.

Symon, K.

1987-11-01

327

Orbital physics in RIXS  

NASA Astrophysics Data System (ADS)

In contrast to magnetism, phenomena associated with the orbital degrees of freedom in transition metal oxides had always been considered to be very difficult to observe. However, recently resonant inelastic x-ray scattering (RIXS) has established itself as a perfect probe of the orbital excitations [1] and orbital order [2] in transition metal oxides. Here we give a brief overview of these recent theoretical and experimental advances which have inter alia led to the observation of the separation of the spin and orbital degree of freedom of an electron [1, 3].[4pt] [1] J. Schlappa, K. Wohlfeld, K. J. Zhou, M. Mourigal, M. W. Haverkort, V. N. Strocov, L. Hozoi, C. Monney, S. Nishimoto, S. Singh, A. Revcolevschi, J.-S. Caux, L. Patthey, H. M. Rønnow, J. van den Brink, T. Schmitt, Nature 485, 82 (2012).[0pt] [2] P. Marra, K. Wohlfeld, J. van den Brink, Phys. Rev. Lett. 109, 117401 (2012).[0pt] [3] K. Wohlfeld, M. Daghofer, S. Nishimoto, G. Khaliullin, J. van den Brink, Phys. Rev. Lett. 107, 147201 (2011).

Wohlfeld, Krzysztof; Marra, Pasquale; Grueninger, Markus; Schmitt, Thorsten; van den Brink, Jeroen

2013-03-01

328

Orbital Forces: Teacher Page  

NSDL National Science Digital Library

This activity demonstates orbital motions and forces using a tennis ball swung by a ribbon (this activity should be done outside). The Teacher Page contains background information, tennis ball preparation instructions, and wrap up information. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

329

Orbital Forces: Student Page  

NSDL National Science Digital Library

This activity teaches students about orbital motions and forces using a tennis ball swung by a ribbon. Students answer the question "What happens when you let the ball go?" Background information, activity procedures, and key words are provided. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

330

Orbit determination: Statistical methods  

Microsoft Academic Search

The problem of finding a satellite trajectory from position and\\/or velocity measurements taken at a given instant in time is examined. A trajectory evolution model including a random vector which represents measurement error is presented. Assuming an iterative approach, the problem is linearized using a previous orbital position estimation. The least squares method is considered in terms of the linear

P. Legendre

1980-01-01

331

Lunar Orbit Anomaly  

NASA Astrophysics Data System (ADS)

Independent experiments show a large anomaly in measurements of lunar orbital evolution, with applications to cosmology and the speed of light. The Moon has long been known to be slowly drifting farther from Earth due to tidal forces. The Lunar Laser Ranging Experiment (LLRE) indicates the Moon's semimajor axis increasing at 3.82 ± .07 cm/yr, anomalously high. If the Moon were today gaining angular momentum at this rate, it would have coincided with Earth less than 2 Gyr ago. Study of tidal rhythmites indicates a rate of 2.9 ± 0.6 cm/yr. Historical eclipse observations independently measure a recession rate of 2.82 ± .08 cm/yr. Detailed numerical simulation of lunar orbital evolution predicts 2.91 cm/yr. LLRE differs from three independent experiments by over12 sigma. A cosmology where speed of light c is related to time t by GM=tc^3 has been suggested to predict the redshifts of Type Ia supernovae, and a 4.507034% proportion of baryonic matter. If c were changing in the amount predicted, lunar orbital distance would appear to increase by an additional 0.935 cm/yr. An anomaly in the lunar orbit may be precisely calculated, shedding light on puzzles of 'dark energy'. In Planck units this cosmology may be summarized as M=R=t.Lunar Recession Rate;

Riofrio, L.

2012-12-01

332

On-orbit refueling  

NASA Technical Reports Server (NTRS)

During the past decade, both NASA and the DOD have conducted numerous space servicing studies. These studies have shown that fluid resupply of on-orbit spacecraft is feasible and would allow for extended spacecraft utilization. In order to prove that the studies have validity, an on-orbit flight demonstration of automatic fluid resupply is required. To embark on this flight demonstration, the system concepts, operational procedures, and conceptual service and target vehicles must be identified. Hernandez Engineering, Inc. (HEI), under the direction of the Space Servicing System Project Office of the NASA/JSC New Initiatives Office, has conducted a systems engineering and integration study. The study objective was to develop preliminary concepts for a flight demonstration of automatic rendezvous, proximity operations, capture, and fluid transfer utilizing servicer and target vehicles. The results show that a servicer vehicle/target kit can be launched to orbit with an ELV and automatically rendezvous and dock with the explorer platform (EP). The servicer vehicle can then separate from the EP/kit, perform proximity maneuvers, redock with the EP/kit, and perform fluid transfer operations. After the on-orbit flight demonstration is completed, the servicer/kit can be separated from the EP and be deorbited into the Earth's atmosphere.

Moore, James S.; Owens, Shelby L.

1993-01-01

333

On-orbit refueling  

NASA Astrophysics Data System (ADS)

During the past decade, both NASA and the DOD have conducted numerous space servicing studies. These studies have shown that fluid resupply of on-orbit spacecraft is feasible and would allow for extended spacecraft utilization. In order to prove that the studies have validity, an on-orbit flight demonstration of automatic fluid resupply is required. To embark on this flight demonstration, the system concepts, operational procedures, and conceptual service and target vehicles must be identified. Hernandez Engineering, Inc. (HEI), under the direction of the Space Servicing System Project Office of the NASA/JSC New Initiatives Office, has conducted a systems engineering and integration study. The study objective was to develop preliminary concepts for a flight demonstration of automatic rendezvous, proximity operations, capture, and fluid transfer utilizing servicer and target vehicles. The results show that a servicer vehicle/target kit can be launched to orbit with an ELV and automatically rendezvous and dock with the explorer platform (EP). The servicer vehicle can then separate from the EP/kit, perform proximity maneuvers, redock with the EP/kit, and perform fluid transfer operations. After the on-orbit flight demonstration is completed, the servicer/kit can be separated from the EP and be deorbited into the Earth's atmosphere.

Moore, James S.; Owens, Shelby L.

1993-02-01

334

A Neptune Orbiter Mission  

NASA Technical Reports Server (NTRS)

This paper describes the results of new analyses and mission/system designs for a low cost Neptune Orbiter mission. Science and measurement objectives, instrumentation, and mission/system design options are described and reflect an aggressive approach to the application of new advanced technologies expected to be available and developed over the next five to ten years.

Wallace, R. A.; Spilker, T. R.

1998-01-01

335

Orbital sonography in children  

Microsoft Academic Search

Orbital sonography with color-flow Doppler imaging is a relatively new technology with significant application in the pediatric patient. This review stresses the primary indications for pediatric ophthalmic ultrasound and also discusses those instances where the use of ultrasound supplements other imaging studies.

F. G. Ramji; T. L. Slovis; J. D. Baker

1996-01-01

336

Space Station: Orbiter Berthing.  

National Technical Information Service (NTIS)

The berthing/docking maneuver is important for the construction and assembly of the Space Station Freedom (SSF). Berthing has a direct effect on the SSF assembly build up and SSF/Orbiter operations. The dynamics associated with the berthing activities pot...

J. Mapar Y. C. Lin M. Kilby

1992-01-01

337

On-orbit refueling  

NASA Astrophysics Data System (ADS)

The goal of this program is to increase operational availability of space assets by refueling with an expendable launch vehicle (not the Shuttle) in LEO or GEO. Information is drawn from the on-orbit refueling model, COSEMS model, COMA study, and information provided from the San Antonio Air Logistics Center.

Pospisil

1993-02-01

338

Apollo Project - Lunar Orbiter  

NASA Technical Reports Server (NTRS)

Lunar Orbiter press conference at the Jet Propulsion Laboratory. A mockup of the solar-powered spacecraft (called the 'Two-Eyed Robot') is shown on the right. It was built by Boeing for the NASA Langley Research Center. From Edgar M. Cortright, 'Scouting the Moon' in Apollo Expeditions to the Moon: 'It was in its photo system that Orbiter was most unconventional. Other spacecraft took TV images and sent them back to Earth as electrical signals. Orbiter took photographs, developed them on board, and then scanned them with a special photoelectric system--a method that, for all its complications and limitations, could produce images of exceptional quality. One Orbiter camera could resolve details as small as 3 feet from an altitude of 30 nautical miles. A sample complication exacted by this performance: because slow film had to be used (because of risk of radiation fogging), slow shutter speeds were also needed. This meant that, to prevent blurring from spacecraft motion, a velocity-height sensor had to insure that the film was moved a tiny, precise, and compensatory amount during the instant of exposure.' Published in Edgar M. Cortright, 'Scouting the Moon, ' in Apollo Expeditions to the Moon, ed. Edgar M. Cortright, (Washington: NASA SP-350, 1975), p. 93.

1966-01-01

339

Interactive Molecular Orbital Diagrams  

NSDL National Science Digital Library

Here is an application for constructing the molecular orbital electron configurations of heteronuclear diatomic molecules. Energy level diagrams are given for the two different cases encountered in heteronuclear diatomics of the first short period (Li2 - Ne2). This is a useful tool for having students explore questions of bond order, magnetic properties and numbers of unpaired electrons.

340

Vertical quantum dot with a vertically coupled charge detector  

NASA Astrophysics Data System (ADS)

We fabricated a vertical quantum dot equipped with a charge detector. The dot current flows vertically between the top and bottom contacts. The charge detector is formed at the bottom contact layer with a current channel constricted to the region just under the dot. This channel current is reduced by addition of an extra electron onto the dot due to the electrostatic coupling to the dot. The charge state of the vertical dot was detected, starting from zero electrons. The sensitivity of the charge detector was comparable to that previously reported for lateral dots with nearby quantum point contacts.

Zaitsu, Koichiro; Kitamura, Yosuke; Ono, Keiji; Tarucha, Seigo

2008-01-01

341

The impact orbits of the dangerous asteroid (99942) Apophis  

NASA Astrophysics Data System (ADS)

The impact solutions of the dangerous asteroid (99942) Apophis were obtained from computations performed with the use of the OrbFit software. For all the computations the OrbFit Software, Package 3.3.2, was used. Precise impact orbits for all impact solutions of Apophis predicted for the 2007 epoch and three impact orbits for epochs close to the impact dates in 2036, 2037 and 2054 were computed. The computations of impact orbits were made according to Sitarski (2006) using the OrbFit package and the interpolation method. Moreover, we found out additional dates of impacts of Apophis, especially in 2038.

W?odarczyk, I.

2008-02-01

342

Classical and modern orbit determination for asteroids  

NASA Astrophysics Data System (ADS)

With the substantial improvements in observational techniques we have to deal with very big databases, consisting of a few positions of an object over a short time span; this is often not enough to compute a preliminary orbit with traditional tools. In this paper we first review a classical method by C.F. Gauss to compute a preliminary orbit for asteroids. This method, followed by a least squares fit to improve the orbit, still today gives successful results when we have at least three separate observations. Then we introduce the basics of a very recent orbit determination theory, that has been thought just to be used with modern sets of data. These data allow us in many cases to know the angular position and velocity of an asteroid at a given time, even though the radial distance and velocity (r,dot r), needed to compute its full orbit, are unknown. The variables (r,dot r) can be constrained to a compact set, that we call the admissible region(AR), whose definition requires that the body belongs to the Solar System, that it is not a satellite of the Earth, and that it is not a "shooting star" (i.e. very close and very small). We provide a mathematical description of the AR: its topological properties are surprisingly simple, in fact it turns out that the AR cannot have more than two connected components. A sampling of the AR can be performed by means of a Delaunay triangulation; a finite number of six-parameter sets of initial conditions are thus defined, with each node of the triangulation representing a possible orbit (a virtual asteroid).

Gronchi, Giovanni F.

2005-04-01

343

Accessibility, stabilizability, and feedback control of continuous orbital transfer.  

PubMed

This paper investigates the problem of low-thrust orbital transfer using orbital element feedback from a control-theoretic standpoint, concepts of controllability, feedback stabilizability, and their interaction. The Gauss variational equations (GVEs) are used to model the state-space dynamics. First, the notion of accessibility, a weaker form of controllability, is presented. It is then shown that the GVEs are globally accessible. Based on the accessibility result, a nonlinear feedback controller is derived that asymptotically steers a vehicle from an initial elliptic Keplerian orbit to any given elliptic Keplerian orbit. The performance of the new controller is illustrated by simulating an orbital transfer between two geosynchronous Earth orbits. It is shown that the low-thrust controller requires less fuel than an impulsive maneuver for the same transfer time. Closed-form, analytic expressions for the new orbital transfer controller are given. Finally, it is proved, based on a topological nonlinear stabilizability test, that there does not exist a continuous closed-loop controller that can transfer a spacecraft to a parabolic escape trajectory. PMID:15220148

Gurfil, Pini

2004-05-01

344

Technology requirements for advanced earth-orbital transportation systems: Summary report. [single stage to orbit vehicles  

NASA Technical Reports Server (NTRS)

Areas of advanced technology that are either critical or offer significant benefits to the development of future Earth-orbit transportation systems were identified. Technology assessment was based on the application of these technologies to fully reusable, single-state-to-orbit (SSTO) vehicle concepts with horizontal landing capability. Study guidelines included mission requirements similar to space shuttle, an operational capability beginning in 1995, and main propulsion to be advanced hydrogen-fueled rocket engines. The technical and economic feasibility of this class of SSTO concepts were evaluated as well as the comparative features of three operational take-off modes, which were vertical boost, horizontal sled launch, and horizontal take-off with subsequent inflight fueling. Projections of both normal and accelerated technology growth were made. Figures of merit were derived to provide relative rankings of technology areas. The influence of selected accelerated areas on vehicle design and program costs was analyzed by developing near-optimum point designs.

Haefeli, R. C.; Littler, E. G.; Hurley, J. B.; Winter, M. G.

1977-01-01

345

Forming Close-in Earth-like Planets Via a Collision-merger Mechanism in Late-stage Planet Formation  

Microsoft Academic Search

The large number of exoplanets found to orbit their host stars in very close orbits have significantly advanced our understanding of the planetary formation process. It is now widely accepted that such short-period planets cannot have formed in situ, but rather must have migrated to their current orbits from a formation location much farther from their host star. In the

Jianghui Ji; Sheng Jin; C. G. Tinney

2011-01-01

346

Retinoblastoma associated orbital cellulitis  

PubMed Central

AIM—Preseptal and orbital cellulitis are rare presenting features of intraocular retinoblastoma. The objectives of this study were to determine the frequency of retinoblastoma associated cellulitis, as well as to review its clinical and histopathological features.?METHODS—The medical records of 292 retinoblastoma patients in the King Khaled Eye Specialist Hospital in Riyadh, Saudi Arabia were reviewed. Those indicating a history of, or presenting with, cellulitis were retrieved and their clinical, radiological, and histopathological variables were assessed. Patients with definite extraocular tumour extension on clinical or radiological examination were excluded.?RESULTS—14 patients were found to have retinoblastoma associated cellulitis (4.8%); nine had bilateral and five had unilateral retinoblastoma. Conjunctival and blood cultures were performed in 10 cases and were negative. 10 children were treated with intravenous steroids, often in conjunction with antibiotics, resulting in a prompt decrease in inflammation. Three other children were treated with antibiotics alone and one received no treatment. Computed tomographic scanning depicted large intraocular tumours occupying between 80% and 100% of the globe in each case. In eight patients, periocular inflammation was radiologically interpreted as possible extraocular extension. In one patient serial computed tomographic scanning showed a reduction in intraocular calcification over time which occurred in the presence of cellulitis. 12 patients underwent enucleation and histopathological examination revealed large necrotic, poorly differentiated tumours associated with uveal involvement and early optic nerve invasion. Focal perilimbal destruction was seen in one patient, and in another peripapillary extrascleral extension was present. 12 patients are alive with a mean follow up of 56.4 months.?CONCLUSIONS—Radiological evaluation of scleral integrity may be hindered by periocular inflammatory changes. The orbital cellulitis correlated well with the presence of advanced intraocular retinoblastoma with massive necrosis and anterior chamber involvement. In the majority of patients, cellulitis was not indicative of an extension of retinoblastoma into the orbit. Intravenous steroid treatment reduced orbital inflammation, facilitating examination and subsequent enucleation.?? Keywords: retinoblastoma; orbital cellulitis

Mullaney, P.; Karcioglu, Z.; Huaman, A.; Al-Mesfer, S.

1998-01-01

347

CO-ORBITAL OLIGARCHY  

SciTech Connect

We present a systematic examination of the changes in semimajor axis of a protoplanet as it interacts with other protoplanets in the presence of eccentricity dissipation. For parameters relevant to the oligarchic stage of planet formation, dynamical friction keeps the typical eccentricities small and prevents orbit crossing. Interactions at impact parameters greater than several Hill radii cause the protoplanets to repel each other; if the impact parameter is instead much less than the Hill radius, the protoplanets shift slightly in semimajor axis but remain otherwise unperturbed. If the orbits of two or more protoplanets are separated by less than a Hill radius, they are each pushed toward an equilibrium spacing between their neighbors and can exist as a stable co-orbital system. In the shear-dominated oligarchic phase of planet formation, we show that the feeding zones contain several oligarchs instead of only one. Growth of the protoplanets in the oligarchic phase drives the disk to an equilibrium configuration that depends on the mass ratio of protoplanets to planetesimals, {sigma}/{sigma}. Early in the oligarchic phase, when {sigma}/{sigma} is low, the spacing between rows of co-orbital oligarchs are about 5 Hill radii wide, rather than the 10 Hill radii cited in the literature. It is likely that at the end of oligarchy, the average number of co-orbital oligarchs is greater than unity. In the outer solar system, this raises the disk mass required to form the ice giants. In the inner solar system, this lowers the mass of the final oligarchs and requires more giant impacts than previously estimated. This result provides additional evidence that Mars is not an untouched leftover from the oligarchic phase, but must be composed of several oligarchs assembled through giant impacts.

Collins, Benjamin F.; Sari, Re'em [California Institute of Technology, MC 130-33, Pasadena, CA 91125 (United States)], E-mail: bfc@tapir.caltech.edu

2009-04-15

348

Orbital Fluid Transfer System  

NASA Technical Reports Server (NTRS)

An automated fluid and power interface system needs to be developed for future space missions which require on orbit consumable replenishment. Current method of fluid transfer require manned vehicles and extravehicular activity. Currently the US does not have an automated capability for consumable transfer on-orbit. This technology would benefit both Space Station and long duration satellites. In order to provide this technology the Automated Fluid Interface System (AFIS) was developed. The AFIS project was an advanced development program aimed at developing a prototype satellite servicer for future space operations. This mechanism could transfer propellants, cryogens, fluids, gasses, electrical power, and communications from a tanker unit to the orbiting satellite. The development of this unit was a cooperative effort between Marshall Space Flight Center in Huntsville, Alabama, and Moog, Inc. in East Aurora, New York. An engineering model was built and underwent substantial development testing at Marshall Space Flight Center (MSFC). While the AFIS is not suitable for spaceflight, testing and evaluation of the AFIS provided significant experience which would be beneficial in building a flight unit. The lessons learned from testing the AFIS provided the foundation for the next generation fluid transfer mechanism, the Orbital Fluid Transfer System (OFTS). The OFTS project was a study contract with MSFC and Moog, Inc. The OFTS was designed for the International Space Station (ISS), but its flexible design could used for long duration satellite missions and other applications. The OFTS was designed to be used after docking. The primary function was to transfer bipropellants and high pressure gases. The other items addressed by this task included propellant storage, hardware integration, safety and control system issues. A new concept for high pressure couplings was also developed. The results of the AFIS testing provided an excellent basis for the OFTS design. The OFTS meet the servicing requirements for ISS and could also provide the automated fluid and power interface system needed for on orbit consumable resupply of spacecraft into the new century.

Johnston, A. S., (Nick); Ryder, Mel; Tyler, Tony R.

1998-01-01

349

Single Frequency GPS Orbit Determination for Low Earth Orbiters  

NASA Technical Reports Server (NTRS)

A number of missions in the future are planning to use GPS for precision orbit determination. Cost considerations and receiver availability make single frequency GPS receivers attractive if the orbit accuracy requirements can be met.

Bertiger, Willy; Wu, Sien-Chong

1996-01-01

350

Wind tunnel blockage corrections: Review and application to Savonius vertical-axis wind turbines  

Microsoft Academic Search

An investigation into wake and solid blockage effects of vertical axis wind turbines (VAWTs) in closed test-section wind tunnel testing is described. Static wall pressures have been used to derive velocity increments along wind tunnel test section which in turn are applied to provide evidence of wake interference characteristics of rotating bodies interacting within this spatially restricted domain. Vertical-axis wind

Ian Ross; Aaron Altman

2011-01-01

351

Shuttle on-orbit rendezvous targeting: Circular orbits  

NASA Technical Reports Server (NTRS)

The strategy and logic used in a space shuttle on-orbit rendezvous targeting program are described. The program generates ascent targeting conditions for boost to insertion into an intermediate parking orbit, and generates on-orbit targeting and timeline bases for each maneuver to effect rendezvous with a space station. Time of launch is determined so as to eliminate any plane change, and all work was performed for a near-circular space station orbit.

Bentley, E. L.

1972-01-01

352

Unusual Sclerosing Orbital Pseudotumor Infiltrating Orbits and Maxillofacial Regions  

PubMed Central

Idiopathic orbital pseudotumor (IOP) is a benign inflammatory condition of the orbit without identifiable local or systemic causes. Bilateral massive orbital involvement and extraorbital extension of the IOP is very rare. We present an unusual case of IOP with bilateral massive orbital infiltration extending into maxillofacial regions and discuss its distinctive magnetic resonance imaging (MRI) features that help to exclude other entities during differential diagnoses.

Toprak, Huseyin; Aralasmak, Ayse; Y?lmaz, Temel Fatih; Ozdemir, Huseyin

2014-01-01

353

Orbital YORP and asteroid orbit evolution, with application to Apophis  

Microsoft Academic Search

Photon thrust from shape alone can produce quasi-secular changes in an asteroid's orbital elements. An asteroid in an elliptical orbit with a north–south shape asymmetry can steadily alter its elements over timescales longer than one orbital trip about the Sun. This thrust, called here orbital YORP (YORP = Yarkovsky–O'Keefe–Radzievskii–Paddack), operates even in the absence of thermal inertia, which the Yarkovsky

David Parry Rubincam

2007-01-01

354

DISCOVERING HABITABLE EARTHS, HOT JUPITERS, AND OTHER CLOSE PLANETS WITH MICROLENSING  

SciTech Connect

Searches for planets via gravitational lensing have focused on cases in which the projected separation, a, between planet and star is comparable to the Einstein radius, R{sub E} . This paper considers smaller orbital separations and demonstrates that evidence of close-orbit planets can be found in the low-magnification portion of the light curves generated by the central star. We develop a protocol for discovering hot Jupiters as well as Neptune-mass and Earth-mass planets in the stellar habitable zone. When planets are not discovered, our method can be used to quantify the probability that the lens star does not have planets within specified ranges of the orbital separation and mass ratio. Nearby close-orbit planets discovered by lensing can be subject to follow-up observations to study the newly discovered planets or to discover other planets orbiting the same star. Careful study of the low-magnification portions of lensing light curves should produce, in addition to the discoveries of close-orbit planets, definite detections of wide-orbit planets through the discovery of 'repeating' lensing events. We show that events exhibiting extremely high magnification can effectively be probed for planets in close, intermediate, and wide distance regimes simply by adding several-time-per-night monitoring in the low-magnification wings, possibly leading to gravitational lensing discoveries of multiple planets occupying a broad range of orbits, from close to wide, in a single planetary system.

Di Stefano, R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2012-06-20

355

Very Precise Orbits of 1998 Leonid Meteors  

NASA Technical Reports Server (NTRS)

Seventy-five orbits of Leonid meteors obtained during the 1998 outburst are presented. Thirty-eight are precise enough to recognize significant dispersion in orbital elements. Results from the nights of 1998 November 16/17 and 17/18 differ, in agreement with the dominant presence of different dust components. The shower rate profile of 1998 November 16/17 was dominated by a broad component, rich in bright meteors. The radiant distribution is compact. The semimajor axis is confined to values close to that of the parent comet, whereas the distribution of inclination has a central condensation in a narrow range. On the other hand, 1998 November 17/18 was dominated by dust responsible for a more narrow secondary peak in the flux curve. The declination of the radiant and the inclination of the orbit are more widely dispersed. The argument of perihelion, inclination, and the perihelion distance are displaced. These data substantiate the hypothesis that trapping in orbital resonances is important for the dynamical evolution of the broad component.

Betlem, Hans; Jenniskens, Peter; vantLeven, Jaap; terKuile, Casper; Johannink, Carl; Zhao, Hai-Bin; Lei, Chen-Ming; Li, Guan-You; Zhu, Jin; Evans, Steve; DeVincenzi, Donald L. (Technical Monitor)

1999-01-01

356

New determination of the orbit of Miranda  

NASA Astrophysics Data System (ADS)

Determinations of the orbital elements of Miranda, the innermost satellite of Uranus, which were made subsequent to the determinations of Whitaker and Greenberg (1973) are reported. The present determination is based on observations made during the 1975 and 1977 oppositions with the 155-cm astrometric reflector at Flagstaff Observatory, and during the successive oppositions of 1977, 1978 and 1979 with the Pic-du-Midi 1-m reflector. Comparison of the observed position angles with those predicted from the orbit of Whitaker and Greenberg reveals a discrepancy increasing with time until 1978, indicating the need for an orbital revision. Calculations of a sinusoidal approximation of the residuals in longitude observed in 1948-49 and since 1972 results in a period close to the circulation period of near commensurability between Ariel, Umbriel and Miranda, which may also be interpreted as the gravitational effect of Ariel and Umbriel on Miranda. Determinations of the orbit of Miranda taking into account these gravitational perturbations confirm the previously determined irregularities in inclination and eccentricity. A mass product of Ariel and Umbriel of 1.10 plus or minus 0.25 x 10 to the -10th is also derived. It is noted that observations are continuing to improve the accuracy of the present results.

Veillet, C.

1981-05-01

357

THEMIS Orbits and Data at SPDF  

NASA Astrophysics Data System (ADS)

The Space Physics Data Facility (SPDF) within Goddard's Heliospheric Physics Laboratory has worked closely with the THEMIS team to adapt SPDF's orbit and data tools/services to the special needs of the THEMIS mission. We will explain and demonstrate these systems that now include Level-2 data from the THEMIS ground and space instruments and the latest orbits and orbit predictions. CDAWeb now serves current FluxGate Magnetometer (FGM), ElectroStatic Analyzer (ESA), Solid-State Telescope (SST), Electric Field Instrument (EFI) and Search Coil Magnetometer (SCM) data from all 5 THEMIS spacecraft and magnetometer data from 20+ THEMIS ground stations. CDAWeb displays include line plots and spectrograms and outputs are now also available in PDF and Postscript. The latest version of the 3-D interactive orbit viewer now includes the capability to follow the magnetic ground tracks of the THEMIS satellites and their relation to the THEMIS ground stations making it an excellent tool for the coordinated analysis of THEMIS space and ground data. The SSCWeb system allows complex queries involving magnetic conjunctions between satellites and between satellites and ground stations, and region occupancy. Several THEMIS-specific queries were set up and saved and are now available for easy (one click) usage. THEMIS is utilizing the Common Data Format (CDF) for its data products, a format developed and maintained by SPDF and the backbone of the CDAWeb system. A number of CDF routines were customized for most efficient use by the THEMIS team.

Bilitza, D.; McGuire, R. E.; Candey, R. M.; Chimiak, R. A.; Harris, B. T.; Han, D. B.; Kovalick, T. J.; Johnson, R. C.; Leckner, H. A.; Angelopoulos, V.

2007-12-01

358

Orbit Insertion by Mars Reconnaissance Orbiter (Artist's Concept)  

NASA Technical Reports Server (NTRS)

This is an artist's concept of NASA's Mars Reconnaissance Orbiter during the critical process of Mars orbit insertion. In order to be captured into orbit around Mars, the spacecraft must conduct a 25-minute rocket burn when it is just shy of reaching the planet. As pictured, it will pass under the red planet's southern hemisphere as it begins the insertion burn.

2005-01-01

359

A dynamics and control algorithm for low Earth orbit precision formation flying satellites  

NASA Astrophysics Data System (ADS)

An innovative dynamics and control algorithm is developed for a dual-nanosatellite formation flying mission. The principal function of this algorithm is to use regular GPS state measurements to determine the controlled satellite's tracking error from a set of reference trajectories in the local-vertical/local-horizontal reference frame. A linear state-feedback control law---designed using a linear quadratic regulator method---calculates the optimal thrusts necessary to correct this error and communicates the thrust directions to the attitude control system and the thrust durations to the propulsion system. The control system is developed to minimize the conflicting metrics of tracking error and DeltaV requirements. To reconfigure the formation, an optimization algorithm is designed using the analytical solution to the state-space equation and the Hill-Clohessy-Wiltshire state transition matrix to solve for dual-thrust reconfiguration maneuvers. The resulting trajectories require low DeltaV, use finite-time thrusts and are accurate in a fully nonlinear orbital environment. This algorithm will be used to control the CanX-4&5 formation flying demonstration mission. In addition, an iterative method which numerically generates quasi periodic trajectories for a satellite formation is presented. This novel technique utilizes a shooting approach to the Newton method to close the relative deputy trajectory over a specific number of orbits, then fits the actual perturbed motion of the deputy with a Fourier series to enforce periodicity. This process is applied to two well-known satellite formations: a projected circular orbit and a J2-invariant formation. Compared to conventional formations, these resulting quasi-periodic trajectories require a dramatically lower control effort to maintain and could therefore be used to extend DeltaV-limited formation flying missions. Finally, an analytical study of the stability of the formation flying algorithm is conducted. To facilitate the proof, the control algorithm is converted into a discrete-time linear time-varying system. Stability of the system is determined via discrete Floquet theory. This analysis is applied to the CanX-4&5 control laws for tracking along-track orbits, projected circular orbits, and quasi J2-invariant formations.

Eyer, Jesse Koovik

360

Surgical treatment of orbital cavernomas  

Microsoft Academic Search

BackgroundThere are numerous descriptions for the operative techniques applied in orbital lesions. We present a systematic overview of the surgical approaches, as determined by the location and extension of orbital cavernomas.

Uta Schick; Uwe Dott; Werner Hassler

2003-01-01

361

Sleeping with an Elephant: Asteroids that Share a Planet's Orbit  

NASA Astrophysics Data System (ADS)

Under special circumstances, relatively small asteroids are able to safely share the orbit of a much larger planet. The best known examples of such "co-orbital" bodies are the Trojan asteroids of Jupiter, over 1700 of which are known to travel either 60 degrees ahead of or behind this giant planet in its orbit. The stability of such configurations might be thought to depend on the asteroid giving the planet a wide berth. In reality, co-orbital asteroids may approach their planet relatively closely, to within a few times its Hill sphere (which is five times the distance to the Moon in the case of the Earth). For many co-orbital bodies such approaches occur rarely or not at all, but recently examples of co-orbital states that become trapped near their planet have been found. Such "quasi-satellites" may remain near their much larger partner for thousands of years, though in actuality they are not true satellites and continue to orbit the Sun. Here we discuss the behaviour of some recently discovered co-orbital asteroids with emphasis on 2004 GU9, recently found to have a long-lived quasi-satellite state relative to the Earth.

Wiegert, Paul; Connors, Martin; Brasser, Ramon; Mikkola, Seppo; Stacey, Greg; Innanen, Kimmo

2005-08-01

362

Practical aspects of transfer from GTO to lunar orbit  

NASA Technical Reports Server (NTRS)

This paper is a presentation of some practical aspects of orbital transfer from Geosynchronous Transfer Orbit (GTO) to close, near-circular orbits of the Moon. The intent is to identify the important parameters affecting the problem and to bound (approximately) the range of required delta V for a spacecraft that has been placed in GTO. The basic geometric relationships are described and the dynamics are simulated by use of the Zero-Sphere-of Influence Patched Conic method. It is found that the inclination of the transfer orbit to the Earth-Moon plane is relatively unimportant while the position of the line of apsides with respect to the Moon's orbit is the main geometric parameter of interest. It is shown that this parameter can be controlled by selecting the time of day for launch and that two launch windows of approximately 45 minutes duration are available each day of the year if use is made of the recommended phasing orbit transfer. The phasing orbit transfer not only provides twice-daily launch windows, but also provides a mechanism for efficacious correction of GTO injection errors. Delta V penalties for out-of-plane transfer and for late launch are evaluated and the method is recommended for use as an affordable means of achieving lunar orbit.

Uphoff, Chauncey

1993-01-01

363

Measurement of Orbital Volume after Enucleation and Orbital Implantation  

PubMed Central

Introduction This article reports experience relating to the measurement of orbital volume by means of cone beam computed tomography (CBCT) and Cranioviewer program software in patients who have undergone enucleation and orbital implantation. Patients and Methods CBCT scans were made in 30 cases, 10 of which were later excluded because of various technical problems. The study group therefore consisted of 20 patients (8 men and 12 women). The longest follow-up time was 7 years, and the shortest was 1 year. In all 20 cases, the orbital volume was measured with Cranioviewer orbital program software. Slices were made in the ventrodorsal direction at 4.8 mm intervals in the frontal plane, in both bony orbits (both that containing the orbital implant and the healthy one). Similar measurements were made in 20 patients with various dental problems. CBCT scans were recorded for the facial region of the skull, containing the orbital region. The Cranioviewer program can colour the area of the slices red, and it automatically measures the area in mm. Results In 5 of the 20 cases, the first 4 or all 5 slices revealed that the volume of the operated orbit was significantly smaller than that of the healthy orbit, in 12 cases only from 1 to 3 of the slices indicated such a significant difference, and in 3 cases no differences were observed between the orbits. In the control group of patients with various dental problems, there was no significant difference between the two healthy orbits. The accuracy of the volume measurements was assessed statistically by means of the paired samples t-test. Summary To date, no appropriate method is avaliable for exact measurement of the bony orbital volume, which would be of particular importance in orbital injury reconstruction. However, the use of CBCT scans and Cranioviewer orbital program software appears to offer a reliable method for the measurement of changes in orbital volume.

Lukats, Olga; Vizkelety, Tamas; Markella, Zsolt; Maka, Erika; Kiss, Maria; Dobai, Adrienn; Bujtar, Peter; Szucs, Attila; Barabas, Jozsef

2012-01-01

364

Orbital velocities induced by surface waves  

NASA Technical Reports Server (NTRS)

During the third intensive observational period of the Surface Wave Dynamics Experiment (SWADE), an aircraft-based experiment was conducted on 5 March 1991 by deploying slow-fall airborne expendable current profilers (AXCPs) and airborne expendable bathythermographs (AXBTs) during a scanning radar altimeter (SRA) flight on the NASA NP-3A research aircraft. As the Gulf Stream (GS) moved into the SWADE domain in late February, maximum upper-layer currents of 1.98 m/s were observed in the core of the baroclinic jet where the vertical current shears were O(10(exp -2)/s). The SRA concurrently measured the sea surface topography, which was transformed into two-dimensional directional wave spectra at 5-6-km intervals along the flight tracks. The wave spectra indicated a local wave field with wavelengths of 40-60 m propagating southward between 120 deg and 180 deg, and a northward-moving swell field from 300 deg to 70 deg associated with significant wave heights of 2-4 m. As the AXCP descended through the upper ocean, the profiler sensed orbital velocity amplitudes of 0.2-0.5 m/s due to low-frequency surface waves. These orbital velocities were isolated by fitting the observed current profiles to the three-layer model based on a monochromatic surface wave, including the steady and current shear terms within each layer. The depth-integrated differences between the observed and modeled velocity profiles were typically less than 3 cm/s. For 17 of the 21 AXCP drop sites, the rms orbital velocity amplitudes, estimated by integrating the wave spectra over direction and frequency, were correlated at a level of 0.61 with those derived from the current profiles. The direction of wave propagation inferred from the AXCP-derived orbital velocities was in the same direction observed by the SRA. These mean wave directions were highly correlated (0.87) and differed only by about 5 deg.

Shay, Lynn K.; Walsh, Edward J.; Zhang, Pen Chen

1994-01-01

365

A Third Exoplanetary System with Misaligned Orbital and Stellar Spin Axes  

NASA Technical Reports Server (NTRS)

We presented evidence that the WASP-14 exoplanetary system has misaligned orbital and stellar-rotational axes, with an angle of 33.1 plus or minus 7.4 degrees between their sky projections. At the time of this publication, WASP-14 was the third system known to have a significant spin-orbit misalignment, and all three systems had super- Jupiter planets and eccentric orbits. Therefore we hypothesized that the migration and subsequent orbital evolution of massive, eccentric exoplanets is somehow different from that of less massive close-in Jupiters, the majority of which have well-aligned orbits.

Johnosn, John A.; Winn, Joshua N.; Albrecht, Simon; Howard, Andrew W.; Marcy, Geoffrey W.; Gazak, J. Zachary

2009-01-01

366

Orbital order in vanadium spinels  

Microsoft Academic Search

Motivated by recent theoretical and experimental controversy, we present a theoretical study to clarify the orbital symmetry of the ground state of vanadium spinel oxides AV2O4 ( A=Zn , Mg, Cd). The study is based on an effective Hamiltonian with spin-orbital superexchange interaction and a local spin-orbit coupling term. We construct a classical phase diagram and prove the complex orbital

S. di Matteo; G. Jackeli; N. B. Perkins

2005-01-01

367

Plotting Orbital Trajectories For Maneuvers  

NASA Technical Reports Server (NTRS)

Interactive Orbital Trajectory Planning Tool (EIVAN) computer program is forward-looking interactive orbit-trajectory-plotting software tool for use with proximity operations (operations occurring within 1-km sphere of space station) and other maneuvers. Developed to plot resulting trajectories, to provide better comprehension of effects of orbital mechanics, and to help user develop heuristics for planning missions on orbit. Program runs with Microsoft's Excel for execution on MacIntosh computer running MacIntosh OS.

Brody, Adam R.

1991-01-01

368

Mercury orbiter transport study  

NASA Technical Reports Server (NTRS)

A data base and comparative performance analyses of alternative flight mode options for delivering a range of payload masses to Mercury orbit are provided. Launch opportunities over the period 1980-2000 are considered. Extensive data trades are developed for the ballistic flight mode option utilizing one or more swingbys of Venus. Advanced transport options studied include solar electric propulsion and solar sailing. Results show the significant performance tradeoffs among such key parameters as trip time, payload mass, propulsion system mass, orbit size, launch year sensitivity and relative cost-effectiveness. Handbook-type presentation formats, particularly in the case of ballistic mode data, provide planetary program planners with an easily used source of reference information essential in the preliminary steps of mission selection and planning.

Friedlander, A. L.; Feingold, H.

1977-01-01

369

Uprated orbital maneuvering engine  

NASA Technical Reports Server (NTRS)

The baseline orbital maneuvering system (OMS) of the Space Shuttle has the potential for significant performance uprating, leading to increased Shuttle payload capability. The baseline OMS, its requirements, and its operational characteristics are described. Potential uprating approaches are discussed and the logic for selection of a higher performance engine is presented. It is shown that a higher performance engine essentially means an engine operating at higher pressures and that a pump-fed engine is necessary for the higher pressure operation. A description of the uprated OMS engine, including requirements, baseline engine characteristics, and significant engine issues, is presented. Discussion of the program underway at the NASA Lyndon B. Johnson Space Center to attain additional insight into these issues, through the performance of a component demonstration program, includes the technical objectives, approach, and program schedule. The plans for further development are presented, culminating in the plans for integration with the Orbiter and the Shuttle system.

Hooper, J. C.

1984-01-01

370

Orbital and intraocular myofibroblastoma.  

PubMed

Abstract A 66-year-old woman presented with a blind, painful, hypertensive, and proptotic left eye. Computed tomographic imaging revealed a well-circumscribed mass involving the left orbit and globe. Metastatic work-up failed to reveal extraorbital lesions and the tumor was removed in toto via an evisceration approach orbitotomy. Histopathology and immunohistochemistry were most consistent with mammary-type myofibroblastoma with fascicles of bland, uniform spindle cells that stained positive for desmin and CD34. We are not aware of previous reports of orbital or ocular myofibroblastoma. This neoplasm has not been shown to recur, undergo malignant transformation, or metastasize. Familiarity with its clinical, histopathologic, and immunohistochemical features may improve diagnostic accuracy and treatment decisions for patients presenting with similar findings. PMID:24410721

Costin, Bryan R; Plesec, Thomas P; Rubinstein, Tal J; Medina, Carlos A; Singh, Arun D; Goldblum, John R; Perry, Julian D

2014-06-01

371

Lunar Reconnaissance Orbiter  

NSDL National Science Digital Library

Humans have been to the moon numerous times, but the United States is gearing up to do so again with the creation of the Lunar Reconnaissance Orbiter (LRO) mission. With a launch date of October 31, 2008, the goal of the LRO is to obtain "data that will facilitate returning humans safely to the Moon and enable extended stays.ïÿý On this site, visitors can learn all of the excellent details about the mission. The site includes a timeline of scheduled events, the particulars about the spacecraft and its instruments, and a wide range of multimedia files and images. In keeping with NASA's high video standards, there are a number of rather remarkable short films here, including one that shows the LRO orbiting the moon.

372

Horizontal and Vertical Line Designs.  

ERIC Educational Resources Information Center

Presents an art lesson in which students learn about the artist Piet Mondrian and create their own abstract artworks. Focuses on geometric shapes using horizontal and vertical lines. Includes background information about the artist. (CMK)

Johns, Pat

2003-01-01

373

Vertical Electromagnetic Pulse (VEMP) Testing.  

National Technical Information Service (NTIS)

This TOP provides methods for planning, providing instrumentation, and execution of testing of Army/DOD Materiel to determine the effects of Vertical Component High Altitude Electromagnetic Pulse (VHEMP) Environment on the safety and/or reliability of the...

2009-01-01

374

Vertical axis wind turbine airfoil  

DOEpatents

A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

2012-12-18

375

Vertical Reactor Coolant Pump Instabilities.  

National Technical Information Service (NTIS)

This paper describes the investigation conducted at the Tennessee Valley Authority's Sequoyah Nuclear Power Plant to determine and correct increasing vibrations in the vertical reactor coolant pumps. Diagnostic procedures to determine the vibration causes...

1985-01-01

376

Families of three-dimensional axisymmetric periodic orbits in the restricted three-body problem - Sun-Jupiter case  

Microsoft Academic Search

Families of three-dimensional axisymmetric periodic orbits are determined numerically in the sun-Jupiter case of the restricted three-body problem. These families bifurcate from the 'vertical-critical' orbits of the 'basic' plane families i and l. Further, the predictor-corrector procedure employed to reveal these families has been described, and interesting numerical results have been pointed out. Also, computer plots of the orbits of

P. G. Kazantzis

1979-01-01

377

Research Study to Identify Technology Requirements for Advanced Earth-Orbital Transportation Systems, Dual-Mode Propulsion  

NASA Technical Reports Server (NTRS)

The results of a study of dual mode propulsion concepts applied to advanced earth orbital transportation systems using reuseable single stage to orbit vehicle concepts were summarized. Both series burn and parallel burn modes of propulsion were analyzed for vertical takeoff, horizontal landing vehicles based on accelerated technology goals. A major study objective was to assess the merits of dual mode main propulsion concepts compared to single mode concepts for carrying payloads of Space Shuttle type to orbit.

1977-01-01

378

Solitary orbital cysticercosis  

Microsoft Academic Search

Isolated orbital cysticercosis is rare. A 54-year-old woman had unilateral, painful, axial, and downward proptosis; palpable,\\u000a superomedial mass; blepharoptosis; and painful ocular movements. Findings of ultrasonography and computed tomography corroborated\\u000a the clinical diagnosis of pseudotumor. However, failure of medical therapy prompted us to order magnetic resonance imaging\\u000a (MRI), which outlined a cyst with cysticercus features. Death of the parasite was

Usha Yadava; Punita Kumari Sodhi

2000-01-01

379

Developing Lunar Orbiter  

Microsoft Academic Search

In January 1961 the Hughes Aircraft Company was selected to build the Surveyor spacecraft. With a planned mass of about 1,125\\u000a kg at translunar injection, it would require the Atlas-Centaur. The plan was for the orbital version to provide wide-area\\u000a mapping and reconnaissance of potential landing sites for the surface Surveyors and, later, for Apollo. The mass at touchdown\\u000a was

David M. Harland

380

Solar sail orbit operations  

Microsoft Academic Search

The inherent capabilities of solar sails and the fact that they need no onboard supplies of fuel for propulsion make them well suited for use in long-term, multiple-objective missions. They are especially well suited for the exploration of asteroids. In this dissertation, both hovering points and orbiting trajectories about point-mass asteroids using equations of motion for a perfectly reflecting solar

Esther Marie Morrow

2002-01-01

381

Spectrophotovoltaic orbital power generation  

NASA Technical Reports Server (NTRS)

The feasibilty of a spectrophotovoltaic orbital power generation system that optically concentrates solar energy is demonstrated. A dichroic beam-splitting mirror is used to divide the solar spectrum into two wavebands. Absorption of these wavebands by GaAs and Si solar cell arrays with matched energy bandgaps increases the cell efficiency while decreasing the amount of heat that must be rejected. The projected cost per peak watt if this system is $2.50/W sub p.

Onffroy, J. R.

1980-01-01

382

Small Mercury Relativity Orbiter  

NASA Technical Reports Server (NTRS)

The accuracy of solar system tests of gravitational theory could be very much improved by range and Doppler measurements to a Small Mercury Relativity Orbiter. A nearly circular orbit at roughly 2400 km altitude is assumed in order to minimize problems with orbit determination and thermal radiation from the surface. The spacecraft is spin-stabilized and has a 30 cm diameter de-spun antenna. With K-band and X-band ranging systems using a 50 MHz offset sidetone at K-band, a range accuracy of 3 cm appears to be realistically achievable. The estimated spacecraft mass is 50 kg. A consider-covariance analysis was performed to determine how well the Earth-Mercury distance as a function of time could be determined with such a Relativity Orbiter. The minimum data set is assumed to be 40 independent 8-hour arcs of tracking data at selected times during a two year period. The gravity field of Mercury up through degree and order 10 is solved for, along with the initial conditions for each arc and the Earth-Mercury distance at the center of each arc. The considered parameters include the gravity field parameters of degree 11 and 12 plus the tracking station coordinates, the tropospheric delay, and two parameters in a crude radiation pressure model. The conclusion is that the Earth-Mercury distance can be determined to 6 cm accuracy or better. From a modified worst-case analysis, this would lead to roughly 2 orders of magnitude improvement in the knowledge of the precession of perihelion, the relativistic time delay, and the possible change in the gravitational constant with time.

Bender, Peter L.; Vincent, Mark A.

1989-01-01

383

[Echinococcosis of the orbit].  

PubMed

A 5 year old girl with an echinococcuscyst in the right orbit is reported. The final diagnosis was made by removal of the cyst. A second cyst was found in the liver. The epidemiology, clinical and diagnostic problems of echinococcosis are reviewed. Radical surgery is still the only reliable treatment. For inoperable cases chemotherapy with Mebendazol seems promising. Many problems of chemotherapy remain to be solved and Mebendazol therapy is still in an experimental stage. PMID:4077595

Staindl, O; Krenkel, C

1985-09-01

384

Interplanetary orbit determination  

NASA Technical Reports Server (NTRS)

The logistical aspects of orbit determination (OD) in the interplanetary phase of the Mariner Mars 1971 mission are described and the working arrangements for the OD personnel, both within the Navigation Team and with outside groups are given. Various types of data used in the OD process are presented along with sources of the data. Functional descriptions of the individual elements of the OD software and brief sketches of their modes of operation are provided.

Zielenbach, J. W.; Acton, C. H.; Born, G. H.; Breckenridge, W. G.; Chao, C. C.; Duxbury, T. C.; Green, D. W.; Jerath, N.; Jordan, J. F.; Mottinger, N. A.

1973-01-01

385

An Orbit Plan toward AKATSUKI Venus Reencounter and Orbit Injection  

NASA Technical Reports Server (NTRS)

On December 7, 2010, AKATSUKI, the Japanese Venus explorer reached its destination and tried to inject itself into Venus orbit. However, due to a malfunction of the propulsion system, the maneuver was interrupted and AKATSUKI again escaped out from the Venus into an interplanetary orbit. Telemetry data from AKATSUKI suggests the possibility to perform orbit maneuvers to reencounter the Venus and retry Venus orbit injection. Reported in this paper is an orbit plan investigated under this situation. The latest results reflecting the maneuvers conducted in the autumn 2011 is introduced as well.

Kawakatsu, Yasuhiro; Campagnola, Stefano; Hirose, Chikako; Ishii, Nobuaki

2012-01-01

386

Horizontal Inequity and Vertical Redistribution  

Microsoft Academic Search

Inequality of post-tax income among pre-tax equals is evaluated andaggregated to form a global index of horizontal inequity in the income tax.The vertical action of the tax is captured by its inequality effect on averagebetween groups of pre-tax equals. Putting the two together, horizontalinequity measures loss of vertical performance. The identification problem,which has previously been thought insuperable, is addressed by

Peter J. Lambert; Xavier Ramos

1997-01-01

387

Exenteration for benign orbital disease  

Microsoft Academic Search

Exenteration, or removal of the globe with part or all of the surrounding orbital contents, is generally reserved for malignancy. The procedure may, however, be of value in the management of some benign orbital diseases. The indications for exenteration in management of benign orbital disease are threefold. Firstly, patients in whom diffuse disease, such as idiopathic inflammation, has resulted in

G E Rose; J E Wright

1994-01-01

388

Orbital order driven quantum criticality  

Microsoft Academic Search

Charge, spin, and orbital degrees of freedom underlie the physics of transition metal compounds. Much work has revealed quantum critical points associated with spin and charge degrees of freedom in many of these systems. Here we illustrate that the simplest models that embody the orbital degrees of freedom ---the two- and three-dimensional quantum orbital compass models--- exhibit an exact quantum

Zohar Nussinov; Gerardo Ortiz

2008-01-01

389

Heteronuclear Diatomic Molecular Orbital Formation  

NSDL National Science Digital Library

Here is a set of movies that demonstrates heteronuclear diatomic molecular orbital formation. The orbitals start at a distance where there is little or no interatomic interaction and move to the appropriate bond distance. Orbital phase is shown by the different colors.

390

Verification of the naval oceanic vertical aerosol model during FIRE  

NASA Technical Reports Server (NTRS)

The value of Naval Oceanic Vertical Aerosol Model (NOVAM) is illustrated for estimating the non-uniform and non-logarithmic extinction profiles, based on a severe test involving conditions close to and beyond the limits of applicability of NOVAM. A more comprehensive evaluation of NOVAM from the FIRE data is presented, which includes a clear-air case. For further evaluation more data are required on the vertical structure of the extinction in the marine atmospheric boundary layer (MABL), preferably for different meteorological conditions and in different geographic areas (e.g., ASTEX).

Davidson, K. L.; Deleeuw, G.; Gathman, S. G.; Jensen, D. R.

1990-01-01

391

Orbiter Autoland reliability analysis  

NASA Technical Reports Server (NTRS)

The Space Shuttle Orbiter is the only space reentry vehicle in which the crew is seated upright. This position presents some physiological effects requiring countermeasures to prevent a crewmember from becoming incapacitated. This also introduces a potential need for automated vehicle landing capability. Autoland is a primary procedure that was identified as a requirement for landing following and extended duration orbiter mission. This report documents the results of the reliability analysis performed on the hardware required for an automated landing. A reliability block diagram was used to evaluate system reliability. The analysis considers the manual and automated landing modes currently available on the Orbiter. (Autoland is presently a backup system only.) Results of this study indicate a +/- 36 percent probability of successfully extending a nominal mission to 30 days. Enough variations were evaluated to verify that the reliability could be altered with missions planning and procedures. If the crew is modeled as being fully capable after 30 days, the probability of a successful manual landing is comparable to that of Autoland because much of the hardware is used for both manual and automated landing modes. The analysis indicates that the reliability for the manual mode is limited by the hardware and depends greatly on crew capability. Crew capability for a successful landing after 30 days has not been determined yet.

Welch, D. Phillip

1993-01-01

392

Europa planetary protection for Juno Jupiter Orbiter  

NASA Astrophysics Data System (ADS)

NASA's Juno mission launched in 2011 and will explore Jupiter and its near environment starting in 2016. Planetary protection requirements for avoiding the contamination of Europa have been taken into account in the Juno mission design. In particular Juno's polar orbit, which enables scientific investigations of parts of Jupiter's environment never before visited, also greatly assist avoiding close flybys of Europa and the other Galilean satellites. The science mission is designed to conclude with a deorbit burn that disposes of the spacecraft in Jupiter's atmosphere. Compliance with planetary protection requirements is verified through a set of analyses including analysis of initial bioburden, analysis of the effect of bioburden reduction due to the space and Jovian radiation environments, probabilistic risk assessment of successful deorbit, Monte-Carlo orbit propagation, and bioburden reduction in the event of impact with an icy body.

Bernard, Douglas E.; Abelson, Robert D.; Johannesen, Jennie R.; Lam, Try; McAlpine, William J.; Newlin, Laura E.

2013-08-01

393

Ultra low vertical emittance at SLS through systematic and random optimization  

NASA Astrophysics Data System (ADS)

A new vertical emittance record of 0.9±0.4 pm rad was established in the storage ring of the Swiss Light Source (SLS) at 2.4 GeV by the application of a sequence of methods: Magnet girders were remotely vertically realigned in order to suppress the dipolar fields that produce the spurious dispersion in the vertical plane. A systematic optimization was then performed by measuring and correcting the betatron coupling and the vertical dispersion by means of 36 skew quadrupole correctors. The correction is performed until a limit is reached from the orbit response matrix (ORM) measurement errors and residual model deficiencies. At this point, the method of random optimization (RO), a multi-variable optimization procedure, was invoked. In the present experiment, the vertical beam size is the target function while the skew quadrupole currents act as the correction variables. The methodology of RO and the systematic correction scheme are described.

Aiba, M.; Böge, M.; Milas, N.; Streun, A.

2012-12-01

394

Christinitas. (Video) (Closed Captioned).  

National Technical Information Service (NTIS)

Discuses that some people think that only creative people are artists and writers, but that is a myth. This myth prevents people from recognizing the potential for creativity within each of us. It closes their eyes to the examples of imaginative thinking ...

1978-01-01

395

Closed Captioning on Television  

MedlinePLUS

... not regulate captioning of home videos, DVDs or video games.) FCC Regulatory Background on Closed Captioning Beginning in ... captioning quality and providing much-needed guidance to video programming ... new rules go into effect are announced.) The new rules apply to all ...

396

Trust in Close Relationships  

Microsoft Academic Search

A theoretical model describing interpersonal trust in close relationships is presented. Three dimensions of trust are identified, based on the type of attributions drawn about a partner's motives. These dimensions are also characterized by a developmental progression in the relationship. The validity of this theoretical perspective was examined through evidence obtained from a survey of a heterogeneous sample of established

John K. Rempel; John G. Holmes; Mark P. Zanna

1985-01-01

397

Solar Sails at Asteroids: Close Proximity Operations for Scientific Missions  

Microsoft Academic Search

The inherent capabilities of solar sails and the fact that they need no onboard supplies of fuel for propulsion make them well suited for use in long-term, multiple-objective missions. They are especially well suited for the exploration of asteroids, where one spacecraft can rendezvous with a number of asteroids in succession. The orbital mechanics of solar sail operations in close

E. Morrow; D. J. Scheeres; C. R. McInnes; D. Lubin

2000-01-01

398

Midcourse Space Experiment closed-loop image and track processing  

Microsoft Academic Search

The Midcourse Space Experiment (MSX) satellite is a DoD sponsored spacecraft currently under development that will collect phenomenology in a variety of wavebands. MSX is required to perform on-orbit closed loop tracking of various objects of interest including not only dedicated targets but also targets of opportunity and atmospheric phenomena such as stars, auroral surges, and cloud structures. The onboard

Gene A. Heyler; Patricia K. Murphy

1994-01-01

399

Topological analysis of chaotic orbits: Revisiting Hyperion  

NASA Technical Reports Server (NTRS)

There is emerging interest in the possibility of chaotic evolution in astrophysical systems. To mention just one example, recent well-sampled ground-based observations of the Saturian satellite Hyperion strongly suggest that it is exhibiting chaotic behavior. We present a general technique, the method of close returns, for the analysis of data from astronomical objects believed to be exhibiting chaotic motion. The method is based on the extraction of pieces of the evolution that exhibit nearly periodic behavior-episodes during which the object stays near in phase space to some unstable periodic orbit. Such orbits generally act as skeletal features, tracing the topological organization of the manifold on which the chaotic dynamics takes place. This method does not require data sets as lengthy as other nonlinear analysis techniques do and is therefore well suited to many astronomical observing programs. Well sampled data covering between twenty and forty characteristic periods of the system have been found to be sufficient for the application of this technique. Additional strengths of this method are its robustness in the presence of noise and the ability for a user to clearly distinguish between periodic, random, and chaotic behavior by inspection of the resulting two-dimensional image. As an example of its power, we analyze close returns in a numerically generated data set, based on a model for Hyperion extensively studied in the literature, corresponding to nightly observations of the satellite. We show that with a small data set, embedded unstable periodic orbits can be extracted and that these orbits can be responsible for nearly periodic behavior lasting a substantial fraction of the observing run.

Boyd, Patricia T.; Mindlin, Gabriel B.; Gilmore, Robert; Solari, Hernan G.

1994-01-01

400

Glow experiment documentation of OMS/RCS pod and vertical stabilizer  

NASA Technical Reports Server (NTRS)

Glow experiment documentation of one of the orbital maneuvering system (OMS) reaction control system (RCS) pods and a portion of the vertical stabilizer shows chemoluminescent effectresulting from atomic oxygen impacting the spacecraft and building to the point that the atomic oxygen atoms combine to form molecules of oxygen. The Image Intensifier on NIKON 35mm camera was used to record the glow.

1982-01-01

401

Near vertical view of Birmingham, Alabama as seen from Apollo 9  

NASA Technical Reports Server (NTRS)

Near vertical view of the Birmingham, Alabama area extending to Gadeden, as photographed from the Apollo 9 spacecraft during its earth-orbital mission. The city spreads out between ridges of the folded southern Appalachien Mountains. The major stream in the picture is the Coosa River.

1969-01-01

402

The buried vertical mattress: a simplified technique for eyelid margin repair.  

PubMed

We describe a new approach for the closure of eyelid margin defects. We conducted a prospective evaluation of patients undergoing the buried vertical mattress technique for full-thickness eyelid margin repair and found that 90 patients (follow-up, 3 to 18 months; average, 6 months) had eyelid margin defects closed with the use of a buried vertical mattress technique. There were no cases of dehiscence, and only 5 (5.5%) patients had minor notch formation. We conclude that the buried vertical mattress suture technique can be a safe and effective method to close eyelid margin defects while saving postoperative time and the cost of multiple sutures. PMID:12878884

Burroughs, John R; Soparkar, Charles N S; Patrinely, James R

2003-07-01

403

Global Orbit Feedback in RHIC  

SciTech Connect

For improved reproducibility of good operating conditions and ramp commissioning efficiency, new dual-plane slow orbit feedback during the energy ramp was implemented during run-10 in the Relativistic Heavy Ion Collider (RHIC). The orbit feedback is based on steering the measured orbit, after subtraction of the dispersive component, to either a design orbit or to a previously saved reference orbit. Using multiple correctors and beam position monitors, an SVD-based algorithm is used for determination of the applied corrections. The online model is used as a basis for matrix computations. In this report we describe the feedback design, review the changes made to realize its implementation, and assess system performance.

Minty, M.; Hulsart, R.; Marusic, A.; Michnoff, R.; Ptitsyn, V.; Robert-Demolaize, G.; Satogata, T.

2010-05-23

404

Formation of giant planets and brown dwarfs on wide orbits  

NASA Astrophysics Data System (ADS)

Aims: We numerically studied the formation of giant planet (GP) and brown dwarf (BD) embryos in gravitationally unstable protostellar disks and compared our findings with the directly imaged, wide-orbit (?50 AU) companions that are known to-date. The viability of the disk fragmentation scenario for the formation of wide-orbit companions in protostellar disks around (sub-)solar mass stars was investigated. We focused on the likelihood of survival of GP/BD embryos formed via disk gravitational fragmentation. Methods: We used numerical hydrodynamics simulations of disk formation and evolution with an accurate treatment of disk thermodynamics. Using the thin-disk limit allowed us to probe the long-term evolution of protostellar disks, starting from the gravitational collapse of a pre-stellar core and ending in the T Tauri phase after at least 1.0 Myr of disk evolution. We focused on models that produced wide-orbit GP/BD embryos that opened a gap in the disk and showed radial migration timescales similar to or longer than the typical disk lifetime. Results: While most models showed disk fragmentation, only 6 models out of 60 revealed the formation of quasi-stable, wide-orbit GP/BD embryos. The low probability for the fragment survival is caused by efficient inward migration/ejection/dispersal mechanisms that operate in the embedded phase of star formation. We found that only massive and extended protostellar disks (?0.2 M?), which experience gravitational fragmentation not only in the embedded but also in the T Tauri phases of star formation, can form wide-orbit companions. Disk fragmentation produced GP/BD embryos with masses in the 3.5-43 MJ range, covering the whole mass spectrum of directly imaged, wide-orbit companions to (sub-)solar mass stars. On the other hand, our modeling failed to produce embryos on orbital distances ?170 AU, whereas several directly imaged companions were found at smaller orbits down to a few AU. Disk fragmentation also failed to produce wide-orbit companions around stars with mass ?0.7 M?, in disagreement with observations. Conclusions: Disk fragmentation is unlikely to explain the whole observed spectrum of wide-orbit companions to (sub-)solar-mass stars and other formation mechanisms, for instance, dynamical scattering of closely packed companions onto wide orbits, should be invoked to account for companions at orbital distance from a few tens to ?150 AU and wide-orbit companions with masses of the host star ? 0.7 M?. Definite measurements of orbit eccentricities and a wider sample of numerical models are needed to distinguish between the formation scenarios of GP/BD on wide orbits.

Vorobyov, E. I.

2013-04-01

405

Behavior of Jupiter Non-Trojan Co-Orbitals  

NASA Astrophysics Data System (ADS)

Searching for the non-Trojan Jupiter co-orbitals we have numerically integrated orbits of 3160 asteroids and 24 comets discovered by October 2010 and situated within and close to the planet co-orbital region. Using this sample we have been able to select eight asteroids and three comets and analyze their orbital behavior in a great detail. Among them we have identified five new Jupiter co-orbitals: (241944) 2002 CU147, 2006 SA387, 2006 QL39, 2007 GH6, and 200P/Larsen, as well as we have analyzed six previously identified co-orbitals: (118624) 2000 HR24, 2006 UG185, 2001 QQ199, 2004 AE9, P/2003 WC7 LINEAR-CATALINA and P/2002 AR2 LINEAR. (241944) 2002 CU147 is currently on a quasi-satellite orbit with repeatable transitions into the tadpole state. Similar behavior shows 2007 GH6 which additionally librates in a compound tadpole-quasi-satellite orbit. 2006 QL39 and 2000P/Larsen are the co-orbitals of Jupiter which are temporarily moving in a horseshoe orbit occasionally interrupted by a quasi-satellite behavior. 2006 SA387 is moving in a pure horseshoe orbit. Orbits of the latter three objects are unstable and according to our calculations, these objects will leave the horseshoe state in a few hundred years. Two asteroids, 2001 QQ199 and 2004 AE9, are long-lived quasi-satellites of Jupiter. They will remain in this state for a few thousand years at least. The comets P/2002 AR2 LINEAR and P/2003 WC7 LINEAR-CATALINA are also quasi-satellites of Jupiter. However, the non-gravitational effects may be significant in the motion of these comets. We have shown that P/2003 WC7 is moving in a quasi-satellite orbit and will stay in this regime to at least 2500 year. Asteroid (118624) 2000 HR24 will be temporarily captured in a quasi-satellite orbit near 2050 and we have identified another one object which shows similar behavior - the asteroid 2006 UG185, although, its guiding center encloses the origin, it is not a quasi-satellite. The orbits of these two objects can be accurately calculated for a few hundred years forward and backward.

Wajer, P.; Królikowska, M.

2012-03-01

406

Terrestrial Planet Formation Around Close Binary Stars  

NASA Technical Reports Server (NTRS)

Most stars reside in multiple star systems; however, virtually all models of planetary growth have assumed an isolated single star. Numerical simulations of the collapse of molecular cloud cores to form binary stars suggest that disks will form within such systems. Observations indirectly suggest disk material around one or both components within young binary star systems. If planets form at the right places within such circumstellar disks, they can remain in stable orbits within the binary star systems for eons. We are simulating the late stages of growth of terrestrial planets around close binary stars, using a new, ultrafast, symplectic integrator that we have developed for this purpose. The sum of the masses of the two stars is one solar mass, and the initial disk of planetary embryos is the same as that used for simulating the late stages of terrestrial planet growth within our Solar System and in the Alpha Centauri wide binary star system. Giant planets &are included in the simulations, as they are in most simulations of the late stages of terrestrial planet accumulation in our Solar System. When the stars travel on a circular orbit with semimajor axis of up to 0.1 AU about their mutual center of mass, the planetary embryos grow into a system of terrestrial planets that is statistically identical to those formed about single stars, but a larger semimajor axis and/or a significantly eccentric binary orbit can lead to significantly more dynamically hot terrestrial planet systems.

Lissauer, Jack J.; Quintana, Elisa V.

2003-01-01

407

Lunar Prospector Orbit Determination Results  

NASA Technical Reports Server (NTRS)

The orbit support for Lunar Prospector (LP) consists of three main areas: (1) cislunar orbit determination, (2) rapid maneuver assessment using Doppler residuals, and (3) routine mapping orbit determination. The cislunar phase consisted of two trajectory correction maneuvers during the translunar cruise followed by three lunar orbit insertion burns. This paper will detail the cislunar orbit determination accuracy and the real-time assessment of the cislunar trajectory correction and lunar orbit insertion maneuvers. The non-spherical gravity model of the Moon is the primary influence on the mapping orbit determination accuracy. During the first two months of the mission, the GLGM-2 lunar potential model was used. After one month in the mapping orbit, a new potential model was developed that incorporated LP Doppler data. This paper will compare and contrast the mapping orbit determination accuracy using these two models. LP orbit support also includes a new enhancement - a web page to disseminate all definitive and predictive trajectory and mission planning information. The web site provides definitive mapping orbit ephemerides including moon latitude and longitude, and four week predictive products including: ephemeris, moon latitude/longitude, earth shadow, moon shadow, and ground station view periods. This paper will discuss the specifics of this web site.

Beckman, Mark; Concha, Marco

1998-01-01

408

Warner Prize Lecture: A New View on Planetary Orbital Dynamics  

NASA Astrophysics Data System (ADS)

Prior to the discovery of exoplanets, astronomers fine tuned theories of planet formation to explain detailed properties of the solar system. Doppler planet searches revealed that many giant planets orbit close to their host star or in highly eccentric orbits. These and subsequent observations inspired new theories of planet formation that invoke strong mutual gravitation interactions in multiple planet systems to explain the excitation of orbital eccentricities and even short-period giant planets. NASA's Kepler mission has identified over 300 systems with multiple transiting planet candidates, including many potentially rocky planets. Most of these systems include multiple planets with sizes between Earth and Neptune and closely-spaced orbits. These systems represent another new and unexpected class of planetary systems and provide an opportunity to test the theories developed to explain the properties of giant exoplanets. I will describe how transit timing observations by Kepler are characterizing the gravitational effects of mutual planetary perturbations for hundreds of planets and providing precise (but complex) constraints on planetary masses, densities and orbits, even for planetary systems with faint host stars. I will discuss early efforts to translate these observations into new constraints on the formation and orbital evolution of planetary systems with low-mass planets.

Ford, Eric B.

2013-01-01

409

Orbital Debris: A Policy Perspective  

NASA Technical Reports Server (NTRS)

A viewgraph presentation describing orbital debris from a policy perspective is shown. The contents include: 1) Voyage through near-Earth Space-animation; 2) What is Orbital Debris?; 3) Orbital Debris Detectors and Damage Potential; 4) Hubble Space Telescope; 5) Mir Space Station Solar Array; 6) International Space Station; 7) Space Shuttle; 8) Satellite Explosions; 9) Satellite Collisions; 10) NASA Orbital Debris Mitigation Guidelines; 11) International Space Station Jettison Policy; 12) Controlled/Uncontrolled Satellite Reentries; 13) Return of Space Objects; 14) Orbital Debris and U.S. National Space Policy; 15) U.S Government Policy Strategy; 16) Bankruptcy of the Iridium Satellite System; 17) Inter-Agency Space Debris Coordination Committee (IADC); 18) Orbital Debris at the United Nations; 19) Chinese Anti-satellite System; 20) Future Evolution of Satellite Population; and 21) Challenge of Orbital Debris

Johnson, Nicholas L.

2007-01-01

410

Orbit synthesis for target satellites  

NASA Astrophysics Data System (ADS)

The purpose of the study is to illustrate the orbit synthesis process for a hypothetical test of a direct-ascent-based kinetic energy weapon (KEW) against an instrumented test vehicle. Test arena and communications considerations for a ground-based directed energy weapon and a direct-ascent-based KEW are outlined, along with launch vehicle constraints, algorithms for off-nominal orbits, and thermal-control and orbit lifetime considerations. Focus is placed on altitude and illumination cycles, general-test and detailed-test constraints, and methodologies for assessing orbit performance. The orbit synthesis is demonstratedd, with emphasis on the test opportunity influence on orbit inclination, test window concept, selection of apogee altitude, orbit inclination, perigee altitude, launch window, and the effect of the launch date.

Wilkinson, Charles K.

411

Optimal control strategies for constrained relative orbits  

NASA Astrophysics Data System (ADS)

The US Air Force's ability to protect space assets is enhanced by a proficiency in satellite proximity operations and Space Situational Awareness (SSA). In pursuit of that proficiency, this research develops a key capability of interest to mission planners; the ability of a deputy satellite to "hover" within a defined volume fixed in the vicinity of a chief satellite for an extended period of time. Previous research has developed initial methodologies for maintaining restricted teardrop hover orbits that exist in a plane fixed within the chief's local reference frame. These methods use the natural drift of the deputy satellite in the relative frame and impulsive thrust to keep the deputy in a bounded volume relative to the chief, but do not address fuel-optimality. This research extends and enhances that work by finding optimal trajectories, produced with discrete-thrusts, that minimize fuel spent per unit time and stay within the user-defined volume, thus providing a practical hover capability in the vicinity of the chief. The work assumes the Clohessy-Wiltshire closeness assumption between the deputy and chief is valid, however, elliptical chief orbits are allowed. Using the new methodology developed in this work, feasible closed and non-closed relative orbits are found and evaluated based on a fuel criterion and compared to an easily calculated continuous-thrust baseline. It is shown that in certain scenarios the discrete-thrust solution provides the lowest overall fuel cost. These scenarios are generally constrained to a smaller total time-of-flight. A simple check is proposed that enables the mission planner to make the correct strategy choice.

Irvin, David Jonathan, Jr.

412

Orbital dynamics of the gravitational field in Bardeen space-time  

NASA Astrophysics Data System (ADS)

In this paper, the orbital dynamics of the gravitational field in Bardeen space-time are investigated. The equations of the particle's orbital motion are given by solving the Lagrangian equation, and the stability and types of orbits are studied by means of analysing the effective potential of particles. Also, with the help of phase-plane method, the closed and non-closed orbits of test particle are analysed. We find that the stability and types of orbits in the Bardeen space-time are determined not only by the particles' energy but also by the angular momentum. And for q=0.5 M and b<3.3731 M, absorbed by the black hole is the only fate of the test particle. We also find that the position of the innermost stable circular orbit of Bardeen black hole occurs at r min =5.5722 M.

Zhang, Yu; Li, EnKun; Geng, JinLing

2014-06-01

413

Application of a tip-fin controller to the Shuttle Orbiter for improved yaw control  

NASA Technical Reports Server (NTRS)

Aerodynamic and flight control analyses have shown that the application of the tip-fin controller and removal of the centerline vertical tail does not produce improved flyability of the Shuttle Orbiter in the supersonic speed regime. Preliminary design studies show that removal of the centerline vertical tail and the installation of tip-fin controllers could result in savings up to 900 kg. It is also shown that the reaction control system could be deactivated much sooner than it is possible with the present nominal orbiter configuration.

Powell, R. W.; Freeman, D. C., Jr.

1981-01-01

414

Tidal Evolution of Close Binary Asteroid Systems  

NASA Astrophysics Data System (ADS)

Roughly 75% of near-Earth, Mars-crossing, and small main-belt binary asteroids (those with primaries under 10 km in diameter) have inter-component separations of less than five primary radii where the traditional assumption of a well-separated system breaks down. We expand the tidal potential between the two components in terms of Legendre polynomials to arbitrary order, rather than truncating at leading order as is typically done, to allow for accurate reproduction of the tidal evolution at separations within five primary radii. Accounting for higher order terms in the tidal potential serves to speed up the tidal evolution of the system leading to underestimates if such corrections are ignored. Special attention is given to the effect of close orbits on the calculation of material properties of the components, in terms of the rigidity and tidal dissipation function, based on the tidal evolution of the system, though it is found that accurate determinations of the physical parameters of the system, e.g., densities, sizes, and current separation, are typically more important. In the scope of long-term tidal evolution, the correction for close orbits is small, but for an instantaneous rate of change in spin rate, semimajor axis, or mean motion, the effect can be on the order of tens of percent.

Taylor, Patrick A.; Margot, J. L.

2010-05-01

415

Commission 42: Close Binaries  

NASA Astrophysics Data System (ADS)

The triennial report from Commission 42 covers various topics like massive binaries, contact systems, cataclysmic variables and low-mass binary stars. We try in a number of sections to provide an update on the current status of the main research areas in the field of close binaries. It is not a formal review, even complete or comprehensive, but an attempt to bring the main topics on recent research to astronomers working in other fields. References are also not comprehensive and simply added to the text to help the reader looking for deeper information on the subject. For this reason, we have chosen to include references (sometimes incomplete for ongoing work) not in a list at the end but integrated with the main text body. Complete references and additional sources can be easily obtained through web access of ADS or SIMBAD. Furthermore, the summary of papers on close-binary research contained in the Bibliography of Close Binaries (BCB) can be accessed from the web site of Commission 42. I would like to express the gratitude of the commission for the careful work of Colin Scarfe as Editor-in-Chief of BCB and Andras Holl and Attila Sragli for maintaining the web pages of the Commission within the structure of Division V. Finally, K. Olah and J. Jurcsik are gratefully acknowledged for their continued support as editors of the Information Bulletin on Variable Stars (IBVS), also accessible through the commission web page.

Giménez, Alvaro; Rucinski, Slavek; Szkody, P.; Gies, D.; Kang, Y.-W.; Linsky, J.; Livio, M.; Morrell, N.; Hilditch, R.; Nordström, B.; Ribas, I.; Sion, E.; Vrielman, S.

2007-03-01

416

Quasi-satellite Orbits in the Context of Coorbital Dynamics  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): The investigations on long-term evolution of asteroid’s orbits are crucial to understanding the route through which the present configuration of the Solar system came to be. The so-called coorbiting asteroids (which share their orbits with major planets) attract the special attention in this connection: are they the primordial remnants of the building blocks of the corresponding major planet or are they the "migrants" from the other parts of the Solar system? The most well known examples of co-orbits in natural objects are provided by Trojan groups of asteroids and by asteroids moving in horseshoe orbits. These asteroids are precluded from having relatively close encounters with their host planets. However, there exists another class of coorbiting objects in which the opposite is true: they remain very near to the host planet eternally or, at least, for long enough time. Since typically they never enter the planet’s Hill sphere, they cannot be considered as satellites in the usual sense of the word. In order to emphasize this specific they are called quasi-satellites (QS). We explore the properties of QS-orbits under the scope of the restricted spatial circular three-body problem. Via double numerical averaging, we construct evolutionary equations which describe the long-term behaviour of the orbital elements of an asteroid. Special attention is paid at possible transitions between the motion in a QS-orbit and that in another type of orbit available in the 1:1 mean motion resonance. To illustrate the typical rates of the orbital elements's secular evolution, the dynamics of the near-Earth asteroid 2004GU9 was studied. This asteroid will keep describing a QS-orbit for the next several hundreds of years. This work was supported by the grant of the Russian Academy of Sciences Presidium Program 22: "Fundamental problems of research and exploration of the Solar system".

Sidorenko, Vladislav; Artemyev, A.; Neishtadt, A.; Zelenyi, L.

2013-05-01

417

Weather Satellite and Orbits  

NSDL National Science Digital Library

In this interactive, online module, students learn about satellite orbits (geostationary and polar), remote-sensing satellite instruments (radiometers and sounders), satellite images, and the math and physics behind satellite technology. The module is part of an online course for grades 7-12 in satellite meteorology, which includes 10 interactive modules. The site also includes lesson plans developed by teachers and links to related resources. Each module is designed to serve as a stand-alone lesson, however, a sequential approach is recommended. Designed to challenge students through the end of 12th grade, middle school teachers and students may choose to skim or skip a few sections.

418

[Porous orbital implants].  

PubMed

Since the introduction of the first coralline hydroxyapatite porous orbital implant as eye replacement in the early 1980s, numerous other modified porous implants have been developed. Due to the different design of the existing studies concerning long-term safety with, in some cases, relatively short follow-up, a comparison is difficult and none of the implant types can be clearly identified as being superior. Factors affecting the exposure rate of the implant seem to be the implant coating, the surgical technique and the condition of the patient's tissue at the beginning of surgery. PMID:24942122

Cleres, B; Meyer-Rüsenberg, H W

2014-06-01

419

Cryogen acquisition in orbit  

NASA Technical Reports Server (NTRS)

Orbital cryogen acquisition is a definite requirement for engine restart and/or propellant transfer on all major future missions. The most promising methods, especially for large scale vehicles, are acquisition by linear acceleration and acquisition by capillary systems. Intermittent acceleration and propellant settling requires some state-of-the-art extension since it has not been attempted on a large scale cryogen vehicle. Capillary acquisition systems offer the advantages of reusability, passiveness, low weight, and mission flexibility. The major disadvantage is that of an undeveloped technology. The method does not lend itself to verification through ground testing.

Hastings, L. J.

1971-01-01

420

The Earth's Orbit  

NSDL National Science Digital Library

These eleven activities relate to the results of the motion and position of the Earth in its orbit, investigating both the causes and the effects of changing seasons. It starts simply by trying to quantify the observation that it is colder in the winter and ends by measuring the tilt of the Earth. This is chapter two of the online book Eyes on the Sky, Feet on the Ground, containing explorations into astronomy as a classroom tool for learning how to theorize, experiment, and analyze data. The activities are fully illustrated and contain detailed, step-by-step instructions as well as suggested discussion topics.

2007-12-12

421

Lunar Exploration Orbiter (LEO)  

NASA Astrophysics Data System (ADS)

The Moon is an integral part of the Earth-Moon system, it is a witness to more than 4.5 b. y. of solar system history, and it is the only planetary body except Earth for which we have samples from known locations. The Moon is our closest companion and can easily be reached from Earth at any time, even with a relatively modest financial budget. Consequently, the Moon was the first logical step in the exploration of our solar system before we pursued more distant targets such as Mars and beyond. The vast amount of knowledge gained from the Apollo and other lunar missions of the late 1960's and early 1970's demonstrates how valuable the Moon is for the understanding of our planetary system. Even today, the Moon remains an extremely interesting target scientifically and technologically, as ever since, new data have helped to address some of our questions about the Earth-Moon system, many questions remained. Therefore, returning to the Moon is the critical stepping-stone to further exploring our immediate planetary neighborhood. In this concept study, we present scientific and technological arguments for a national German lunar mission, the Lunar Explorations Orbiter (LEO). Numerous space-faring nations have realized and identified the unique opportunities related to lunar exploration and have planned missions to the Moon within the next few years. Among these missions, LEO will be unique, because it will globally explore the Moon in unprecedented spatial and spectral resolution. LEO will significantly improve our understanding of the lunar surface composition, surface ages, mineralogy, physical properties, interior, thermal history, gravity field, regolith structure, and magnetic field. The Lunar Explorations Orbiter will carry an entire suite of innovative, complementary technologies, including high-resolution camera systems, several spectrometers that cover previously unexplored parts of the electromagnetic spectrum over a broad range of wavelengths, microwave and radar experiments, a very sensitive magnetometer and gradiometer, a subsatellite, and a state-of-the-art optical communication system. The Lunar Explorations Orbiter concept is technologically challenging but feasible, and will gather unique, integrated, interdisciplinary data sets that are of high scientific interest and will provide an unprecedented new context for all other international lunar missions. In fact, the Lunar Explorations Orbiter will further establish Germany as a leader among space-faring nations and will demonstrate expertise and technological know-how, which is "Made in Germany". With its high visibility, LEO will foster the growing acceptance of space exploration in Germany and will capture the imagination of the general public.

Jaumann, R.; Spohn, T.; Hiesinger, H.; Jessberger, E. K.; Neukum, G.; Oberst, J.; Helbert, J.; Christensen, U.; Keller, H. U.; Mall, U.; Böhnhardt, H.; Hartogh, P.; Glassmeier, K.-H.; Auster, H.-U.; Moreira, A.; Werner, M.; Pätzold, M.; Palme, H.; Wimmer-Schweingruber, R.; Mandea, M.; Lesur, V.; Häusler, B.; Hördt, A.; Eichentopf, K.; Hauber, E.; Hoffmann, H.; Köhler, U.; Kührt, E.; Michaelis, H.; Pauer, M.; Sohl, F.; Denk, T.; van Gasselt, S.

2007-08-01

422

A MULTIRATE STOeRMER ALGORITHM FOR CLOSE ENCOUNTERS  

SciTech Connect

We present, analyze, and test a multirate Stoermer-based algorithm for integrating close encounters when performing N-body simulations of the Sun, planets, and a large number of test particles. The algorithm is intended primarily for accurate simulations of the outer solar system. The algorithm uses stepsizes H and h{sub i} , i = 1, ..., N{sub p} , where h{sub i} << H and N{sub p} is the number of planets. The stepsize H is used for the integration of the orbital motion of the Sun and planets at all times. H is also used as the stepsize for the integration of the orbital motion of test particles when they are not undergoing a close encounter. The stepsize h{sub i} is used to integrate the orbital motion of test particles during a close encounter with the ith planet. The position of the Sun and planets during a close encounter is calculated using Hermite interpolation. We tested the algorithm on two contrasting problems, and compared its performance with the existing method which uses the same stepsize for all bodies (this stepsize must be significantly smaller than H to ensure the close encounters are integrated accurately). Our tests show that the integration error for the new and existing methods are comparable when the stepsizes are chosen to minimize the error, and that for this choice of stepsizes the new method requires considerably less CPU time than the existing method.

Grazier, K. R. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Newman, W. I. [University of California, Los Angeles (United States); Sharp, P. W., E-mail: kevin_grazier@yahoo.com, E-mail: win@ucla.edu, E-mail: sharp@math.auckland.ac.nz [Department of Mathematics, University of Auckland, Private Bag 92019, Auckland (New Zealand)

2013-04-15

423

Spontaneous symmetry breaking in a generalized orbital compass model  

NASA Astrophysics Data System (ADS)

We introduce a generalized two-dimensional orbital compass model, which interpolates continuously from the classical Ising model to the orbital compass model with frustrated quantum interactions, and investigate it using the multiscale entanglement renormalization ansatz (MERA). The results demonstrate that increasing frustration of exchange interactions triggers a second-order quantum phase transition to a degenerate symmetry broken state which minimizes one of the interactions in the orbital compass model. Using boson expansion within the spin-wave theory we unravel the physical mechanism of the symmetry-breaking transition as promoted by weak quantum fluctuations and explain why this transition occurs only surprisingly close to the maximally frustrated interactions of the orbital compass model. The spin waves remain gapful at the critical point, and both the boson expansion and MERA do not find any algebraically decaying spin-spin correlations in the critical ground state.

Cincio, Lukasz; Dziarmaga, Jacek; Ole?, Andrzej M.

2010-09-01

424

Relative Navigation In Elliptical Orbits Using An Iterative Nonlinear Filter  

Microsoft Academic Search

The two step filter is applied to process intersate llite radar measurements to determine the motion of one satelli te relative to another in close elliptical orbits. Thi s filter breaks a nonlinear estimation problem into two stat e vectors. The \\

James L. Garrison

1997-01-01

425

Secular love and tidal numbers of synchronously orbiting satellites  

Microsoft Academic Search

The secular Love and the secular tidal numbers have been computed for eight synchronously orbiting satellites in the solar system for which the triaxiality parameters and satellite-centric gravitational constant are available. Excepting Deimos the total mass of which should be first refined, the secular Love and tidal numbers are rather close to unity, as a rule. That is why, the

M. Bursa

1988-01-01

426

The Lunar Orbiter Laser Altimeter (LOLA) laser transmitter  

Microsoft Academic Search

We present the final configuration of the space flight laser transmitter as delivered to the Lunar Orbiter Laser Altimeter (LOLA) instrument. The instrument was launched in 2009 and has been in operation for close to two years and accumulated over 1.3 billion laser shots in space.

Anthony W. Yu; George B. Shaw; Anne Marie Novo-Gradac; Steven X. Li; Luis Ramos-Izquierdo; Jeffrey Guzek; Alberto Rosanova; John Cavanaugh; Alan Lukemire; Glenn Unger; Danny Krebs

2011-01-01

427

Periodic orbits for three and four co-orbital bodies  

NASA Astrophysics Data System (ADS)

We investigate the natural families of periodic orbits associated with the equilibrium configurations of the planar-restricted 1 + n-body problem for the case 2 ? n ? 4 equal-mass satellites. Such periodic orbits can be used to model both trojan exoplanetary systems and parking orbits for captured asteroids within the Solar system. For n = 2, there are two families of periodic orbits associated with the equilibria of the system: the well-known horseshoe and tadpole orbits. For n = 3, there are three families that emanate from the equilibrium configurations of the satellites, while for n = 4, there are six such families as well as numerous additional connecting families. The families of periodic orbits are all of the horseshoe or tadpole type, and several have regions of neutral linear stability.

Verrier, P. E.; McInnes, C. R.

2014-08-01

428

Microdebrider use in orbital surgery.  

PubMed

Abstract Purpose: To report the novel use of a sinus microdebrider for the removal of tissue during orbital surgery. Methods: This retrospective study reviewed the logs of 3 surgeons to identify patients who required orbital surgery during which the surgeon chose to use a sinus microdebrider with an open sky technique as a means of removing portions of the orbital tissue. Collected data included patient demographics, clinical examinations, pathologic diagnoses, radiologic studies, operative reports and, when available, photographs and intra-operative video. Results: Three patients were identified as having undergone orbital surgery assisted by the use of a sinus microdebrider. The first patient had an extensive, recurrent left orbital myxoid tumor. Debulking of this gelatinous, infiltrative mass was aided by the combined suction and cutting action of the microdebrider. Two cases involved orbital exenteration for infiltrative sino-orbital fungus infection resulting in a blind eye and frozen globe. Removal of orbital apical tissue during exenteration surgery was facilitated with the microdebrider. Conclusions: The characteristics of the sinus microdebrider make it a useful adjunct for orbital surgery, particularly in situations where tissue may be difficult to grasp and excise. Caution should be exercised whenever using this electrically powered tool due to its potential for rapid tissue destruction. Therefore, the microdebrider should only be used in cases in which there is little risk of damage to essential orbital structures. PMID:24678870

Freitag, Suzanne K; Yoon, Michael K; Callahan, Alison B; Lee, N Grace; Lefebvre, Daniel R

2014-06-01

429

Simple control laws for low-thrust orbit transfers  

NASA Technical Reports Server (NTRS)

Two methods are presented by which to determine both a thrust direction and when to apply thrust to effect specified changes in any of the orbit elements except for true anomaly, which is assumed free. The central body is assumed to be a point mass, and the initial and final orbits are assumed closed. Thrust, when on, is of a constant value, and specific impulse is constant. The thrust profiles derived from the two methods are not propellant-optimal, but are based firstly on the optimal thrust directions and location on the osculating orbit for changing each of the orbit elements and secondly on the desired changes in the orbit elements. Two examples of transfers are presented, one in semimajor axis and inclination, and one in semimajor axis and eccentricity. The latter compares favourably with a propellant-optimized transfer between the same orbits. The control laws have few input parameters, but can still capture the complexity of a wide variety of orbit transfers.

Petropoulos, Anastassios E.

2003-01-01

430

Orbital debris issues  

NASA Astrophysics Data System (ADS)

Orbital debris issues fall into three major topics: Environment Definition, Spacecraft Hazard, and Space Object Management. The major issue under Environment Definition is defining the debris flux for sizes smaller (10 cm in diameter) than those tracked by the North American Aerospace Defense Command (NORAD). Sources for this size debris are fragmentation of larger objects, either by explosion or collision, and solid rocket motor products. Modeling of these sources can predict fluxes in low Earth orbit which are greater than the meteoroid environment. Techniques to measure the environment in the size interval between 1 mm and 10 cm are being developed, including the use of telescopes and radar both on the ground and in space. Some impact sensors designed to detect meteoroids may have detected solid rocket motor products. Once the environment is defined, it can be combined with hypervelocity impact data and damage criteria to evaluate the Spacecraft Hazard. Shielding may be required to obtain an acceptable damage level. Space Object Management includes techniques to control the environment and the desired policy to effectively minimize the hazard to spacecraft. One control technique - reducing the likelihood of future explosions in space - has already been implemented by NASA. The effectiveness of other techniques has yet to be evaluated.

Kessler, D. J.

431

Observed Orbital Eccentricities  

NASA Astrophysics Data System (ADS)

For binaries with periods of more than a few weeks, nearly all eccentricities from zero (circular) to nearly one (highly elliptical) are possible. What are the average characteristics and limiting values? I considered the 1169 spectroscopic and visual systems with known orbital elements and B0-M5 dwarf primaries. The average eccentricities as a function of orbital period show a very systematic behavior. For systems with periods greater than about 1000 days, all eccentricities are equally probable, showing that in the process of binary formation, no specific eccentricities are favored. It is well known that for periods of a few days, all systems have been circularized by tidal interactions. For periods between a few days and 1000 days, the mean eccentricities increase from zero to a mean asymptotic value of 0.5. The upper limiting eccentricities are 0.8 for periods of months, 0.7 for periods of weeks, and 0.3 for periods around one week. Double-lined binaries tend to have higher mean eccentricities than single-lined ones of the same periods in accord with Kepler's third law because they have greater total masses and hence larger separations. Systems with giant primaries have the same behavior except they are circularized for periods less than about 70 days.

Abt, Helmut A.

2007-08-01

432

Orbital construction demonstration study  

NASA Technical Reports Server (NTRS)

A conceptual design and program plan for an Orbital Construction Demonstration Article (OCDA) was developed that can be used for evaluating and establishing practical large structural assembly operations. A flight plan for initial placement and continued utility is presented as a basic for an entirely new shuttle payload line-item having great future potential benefit for space applications. The OCDA is a three-axis stabilized platform in low-earth orbit with many structural nodals for mounting large construction and fabrication equipments. This equipment would be used to explore methods for constructing the large structures for future missions. The OCDA would be supported at regular intervals by the shuttle. Construction experiments and consumables resupply are performed during shuttle visit periods. A 250 kw solar array provides sufficient power to support the shuttle while attached to the OCDA and to run construction experiments at the same time. Wide band communications with a Telemetry and Data Relay Satellite compatible high gain antenna can be used between shuttle revisits to perform remote controlled, TV assisted construction experiments.

1976-01-01

433

Finite thrust orbital transfers  

NASA Astrophysics Data System (ADS)

The finite thrust optimal transfer in the presence of the Earth?s shadow and oblate planet perturbations is a problem of strong interest in modern telecommunication satellite design with plasmic propulsion. The Maximum Principle cannot be used in its standard form to deal with the Earth?s shadow. In this paper, using a regularization of the Hamiltonian which expands the Maximum Principle application domain, we provide for the first time, the necessary conditions in a very general context for the finite thrust optimal transfer with limited power around an oblate planet. The costate in such problems is generally discontinuous. To obtain fast numerical solutions, the averaging of the Hamiltonian is introduced. Two classes of boundary conditions are analyzed and numerically solved: the minimum time and the minimum fuel at a fixed time. These two problems are the basic tools for designing the orbit raising of a satellite after the launcher injection into its separation orbit. Numerical solutions have been calculated for the more important applications of LEO to GEO/MEO missions and the results have been reported and discussed.

Mazzini, Leonardo

2014-07-01

434

The orbital surgeon.  

PubMed Central

While the number of orbital surgeons is limited, it is hoped these can be recognized and patients referred to them by ophthalmologists not interested or trained in that specialty. Let the orbital surgeon determine whether he can handle the problem in 1 to 2 days, or whether a neurosurgeon should do the procedure or make it a joint effort. It may well involve other specialty team effort approaches. It is essential to have an understanding of x-rays, CT, angiography, and MRI techniques and films. Sit with these specialists to learn more and help to avoid negative, misdiagnosis reports in the interest of the patient. Use judgement in helping the patient decide on ophthalmic or the more extensive neurosurgical approach after careful study and what is in their best interest. The team approach is used in well established medical centers with the ophthalmologist and neurosurgeon (or other specialist) working together in the best interest of the patient. This is more interesting and keeps the ophthalmologist in the mainstream of medicine. Images FIGURE 1 A FIGURE 1 B FIGURE 1 C FIGURE 2 FIGURE 3 A FIGURE 3 B FIGURE 3 C FIGURE 3 D FIGURE 4 A FIGURE 4 B FIGURE 5 A FIGURE 5 B FIGURE 6 A FIGURE 6 B FIGURE 7 A FIGURE 7 B FIGURE 7 C FIGURE 8 A FIGURE 8 B FIGURE 9

Kennedy, R E

1988-01-01

435

A Concept of Two-Stage-To-Orbit Reusable Launch Vehicle  

NASA Astrophysics Data System (ADS)

Reusable Launch Vehicle (RLV) has a capability of delivering a wide rang of payload to earth orbit with greater reliability, lower cost, more flexibility and operability than any of today's launch vehicles. It is the goal of future space transportation systems. Past experience on single stage to orbit (SSTO) RLVs, such as NASA's NASP project, which aims at developing an rocket-based combined-cycle (RBCC) airplane and X-33, which aims at developing a rocket RLV, indicates that SSTO RLV can not be realized in the next few years based on the state-of-the-art technologies. This paper presents a concept of all rocket two-stage-to-orbit (TSTO) reusable launch vehicle. The TSTO RLV comprises an orbiter and a booster stage. The orbiter is mounted on the top of the booster stage. The TSTO RLV takes off vertically. At the altitude about 50km the booster stage is separated from the orbiter, returns and lands by parachutes and airbags, or lands horizontally by means of its own propulsion system. The orbiter continues its ascent flight and delivers the payload into LEO orbit. After completing orbit mission, the orbiter will reenter into the atmosphere, automatically fly to the ground base and finally horizontally land on the runway. TSTO RLV has less technology difficulties and risk than SSTO, and maybe the practical approach to the RLV in the near future.

Yang, Yong; Wang, Xiaojun; Tang, Yihua

2002-01-01

436

Vertical motion simulator familiarization guide  

NASA Technical Reports Server (NTRS)

The Vertical Motion Simulator Familiarization Guide provides a synoptic description of the Vertical Motion Simulator (VMS) and descriptions of the various simulation components and systems. The intended audience is the community of scientists and engineers who employ the VMS for research and development. The concept of a research simulator system is introduced and the building block nature of the VMS is emphasized. Individual sections describe all the hardware elements in terms of general properties and capabilities. Also included are an example of a typical VMS simulation which graphically illustrates the composition of the system and shows the signal flow among the elements and a glossary of specialized terms, abbreviations, and acronyms.

Danek, George L.

1993-01-01

437

Convection in vertical Bridgman configurations  

NASA Technical Reports Server (NTRS)

We are interested in tracing the convective profiles of vertical Bridgman growth in two configurations, the pure Rayleigh convective mode and the combined Rayleigh-Marangoni mode. In order to do so, we conducted a numerical investigation that involved a finite volume calculation. The governing equations were integrated about a cell volume, using the Gauss Theorem and the volume variables like temperature and velocity were related to the surface variables. In order to solve for the pressure field, we employed the continuity equation and the residuals resulted in a Poisson equation. Results and comments for the Rayleigh and Marangoni problems in a vertical cylinder or Bridgman configuration are given.

Narayanan, Ranga

1991-01-01

438

Up Close to Mimas  

NASA Technical Reports Server (NTRS)

During its approach to Mimas on Aug. 2, 2005, the Cassini spacecraft narrow-angle camera obtained multi-spectral views of the moon from a range of 228,000 kilometers (142,500 miles).

This image is a narrow angle clear-filter image which was processed to enhance the contrast in brightness and sharpness of visible features.

Herschel crater, a 140-kilometer-wide (88-mile) impact feature with a prominent central peak, is visible in the upper right of this image.

This image was obtained when the Cassini spacecraft was above 25 degrees south, 134 degrees west latitude and longitude. The Sun-Mimas-spacecraft angle was 45 degrees and north is at the top.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

2005-01-01

439

Investigation of Factors Affecting Vertical Drain Behavior  

Microsoft Academic Search

Some influencing factors on vertical drain behavior were investigated by laboratory tests as well as by back-analyses of test embankments on vertical drain improved subsoil at Saga Airport, Saga, Japan. Based on the results from this study, suggestions are made on determining the design parameters for vertical drain improvement. For the discharge capacity test of a prefabricated vertical drain, confining

Jun-Chun Chai; Norihiko Miura

1999-01-01

440

The Orbital Workshop Trash Disposal Airlock  

NASA Technical Reports Server (NTRS)

This is a close-up photograph of the Orbital Workshop (OWS) trash disposal airlock located on the floor of the lower level of the OWS. It provided a means of passing trash from the pressurized habitable area into the unpressurized waste tank. The crewman opened a valve which brought the airlock to the same pressure as that within the workshop. He then opened the lid, placed the bagged trash inside, closed the lid and locked it. By turning the valve handle, he reduced the pressure within the airlock until it reached the vacuum of the waste tank. The crewman then operated an ejector handle that caused a scissors-type mechanism to push the bagged trash from the airlock into the tank.

1972-01-01

441

Geostationary Earth Orbit Satellite Model  

NSDL National Science Digital Library

The Geostationary Earth Orbit Satellite Model is a simple angular velocity model that uses Java3D for a realistic visualization of satellites in geostationary orbits. Students can view and explore the behavior of geostationary orbits, non-geostationary orbits, and non-physical orbits. This model tests the Java 3D implementation of the EJS 3D library. A warning message will appear if the Java 3D library is not available. The Geostationary Earth Orbit Satellite Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Wee, Loo K.

2012-04-08

442

Design of ASTROD-GW Orbit  

NASA Astrophysics Data System (ADS)

The ASTROD-GW (ASTROD [Astrodynamical Space Test of Relativity Using Optical Devices] Optimized for Gravitation Wave Detection), the mission of the laser astrodynamical gravitational wave detection, is the scheme of optimality of the gravitational wave detection on which the ASTROD is concentrated. Its spacecraft orbits form a triangular array close to an equilateral triangle in the vicinity of the solar-terrestrial Lagrangian points L 3, L 4 and L 5. The length of the interference arm is about 2.6 × 10 8 km and the detectable wavelength of the gravitational wave is 52 times larger than that detected by the LISA (Laser Interferometer Space Antenna). In this article, the design and optimization method of the ASTROD-GW orbit are summarized. After the orbit is optimized, the variation in the arm length difference (which can be called the interference difference in laser interferometry) within 10 years is in the order of magnitude of 10 -4 AU. The Doppler velocities in the three arm length directions are smaller than 4 m/s, and all of them are less than that required by the LISA. Therefore the laser ranging techniques developed by the LISA can be applied to the ASTROD-GW.

Men, Jin-rui; Ni, Wei-tou; Wang, Gang

2010-10-01

443

High-frequency vertical current observations in stratified seas  

Microsoft Academic Search

Although large-scale tidal and inertial motions dominate the kinetic energy and vertical current shear in shelf seas and ocean, short-scale internal waves at higher frequencies close to the local buoyancy frequency are of some interest for studying internal wave breaking and associated diapycnal mixing. Such waves near the upper limit of the inertio-gravity wave band are thought to have relatively

Hans van Haren

2009-01-01

444

On halo orbits spacecraft stabilization  

Microsoft Academic Search

The paper deals with the application of recent non-linear control techniques to the problem of tracking and maintaining a given satellite on prescribed orbits around the so-called translunar libration point L2. Such orbits, known in literature as Halo Orbits, have the property of ensuring visibility both from the dark side of the Moon and from Earth at any time. Their

P. Di Giamberardino; S. Monaco

1996-01-01

445

Orbital myositis: Diagnosis and management  

Microsoft Academic Search

Orbital myositis is an inflammatory process that primarily involves the extraocular muscles and most commonly affects young\\u000a adults in the third decade of life, with a female predilection. Clinical characteristics of orbital myositis include orbital\\u000a and periorbital pain, ocular movement impairment, diplopia, proptosis, swollen eyelids, and conjunctival hyperemia. The most\\u000a common presentation is acute and unilateral, which initially responds to

Roberta M. S. Costa; Oana M. Dumitrascu; Lynn K. Gordon

2009-01-01

446

Vascular tumors of the orbit  

Microsoft Academic Search

Eighty-five vascular lesions of the orbit examined and treated between 1963–1993 were reviewed retrospectively to reveal the types of vascular tumors, age and sex distribution, clinical characteristics, treatment options and prognosis. Capillary hemangioma was the most frequent orbital vascular tumor accounting for 37 of 85 cases making up 43.5% of the entire orbital masses. Cavernous hemangioma accounted for 35 cases

Ilhan Günalp; Kaan Gündüz

1995-01-01

447

Orbit synthesis for target satellites  

Microsoft Academic Search

The purpose of the study is to illustrate the orbit synthesis process for a hypothetical test of a direct-ascent-based kinetic energy weapon (KEW) against an instrumented test vehicle. Test arena and communications considerations for a ground-based directed energy weapon and a direct-ascent-based KEW are outlined, along with launch vehicle constraints, algorithms for off-nominal orbits, and thermal-control and orbit lifetime considerations.

Charles K. Wilkinson