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1

Close Proximity and Landing Orbits at Asteroids  

NASA Technical Reports Server (NTRS)

This paper discusses and describes the dynamics and control of a spacecraft orbiting close to or landing on an asteroid or comet. The paper presents analytical and numerical results which illustrate the challenges facing near-asteroid orbiters.

Scheeres, D. J.

1996-01-01

2

Close up view of the Orbiter Discovery in the Orbiter ...  

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

Close up view of the Orbiter Discovery in the Orbiter Processing Facility at Kennedy Space Center. The view is a detail of the aft, starboard landing gear and a general view of the Thermal Protection System tiles around the landing-gear housing. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

3

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

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

Analytic closed orbit analysis for RHIC insertion  

SciTech Connect

Analytic closed orbit analysis is performed to evaluate the tolerance of quadrupole misalignment and dipole errors (b{sub 0},a{sub 0}) in the RHIC insertion. Sensitivity coefficients of these errors are tabulated for different {beta}{sup 0} values. Using these sensitivity tables, we found that the power supplies ripple of 10{sup {minus}4} can cause closed orbit motion of 0.05 mm at the IP in comparison with the rms beam size of 0.3 mm. It is desirable to have the power supply ripple less than 10{sup {minus}5}. 2 refs., 1 fig., 2 tabs.

Lee, S.Y. (Indiana Univ., Bloomington, IN (USA). Dept. of Physics); Tepikian, S. (Brookhaven National Lab., Upton, NY (USA))

1991-01-01

7

Closed orbits about a massive thin ring  

NASA Astrophysics Data System (ADS)

A study of the gravitational interaction of a unit point mass m, and a very thin ring of radius R and mass M (M Gt m) is presented. The point mass moves in a plane that is perpendicular to that containing the ring. The potential due to the ring is similar in geometry to that of the two-centre problem with two large point masses, if it were possible for the positions of such point masses to be fixed. The scope of the paper is restricted almost exclusively to closed orbits (trajectories), and these display a surprisingly wide range of patterns. A characterization plot, based on the initial conditions of the trajectories, is used to illustrate and aid in the categorization of the trajectories into 'families'. Figures showing an example member of 11 distinct families and one example trajectory in which the point mass is not restricted to motion in a plane are included. The period of a family of closed trajectories, roughly egg shaped and bound to a particular section of the ring, is found to depend almost linearly on the radius of the orbit, as expected.

Tobin, R. Wesley; West, J.

2006-03-01

8

Detail view of the vertical stabilizer of the Orbiter Discovery ...  

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

Detail view of the vertical stabilizer of the Orbiter Discovery as it sits at Launch Complex 39 A at Kennedy Space Center being prepared for its launch. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

9

Closed orbit related problems: Correction, feedback, and analysis  

SciTech Connect

Orbit correction - moving the orbit to a desired orbit, orbit stability - keeping the orbit on the desired orbit using feedback to filter out unwanted noise, and orbit analysis - to learn more about the model of the machine, are strongly interrelated. They are the three facets of the same problem. The better one knows the model of the machine, the better the predictions that can be made on the behavior of the machine (inverse modeling) and the more accurately one can control the machine. On the other hand, one of the tools to learn more about the machine (modeling) is to study and analyze the orbit response to {open_quotes}kicks.{close_quotes}

Bozoki, E.S.

1995-02-01

10

Detail view of the vertical stabilizer of the Orbiter Discovery ...  

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

Detail view of the vertical stabilizer of the Orbiter Discovery Discovery showing the thermal protection system components with the white Advanced Flexible Reusable Surface Insulation (AFSI) Blanket and the black High-temperature Reusable Surface Insulation (HRSI) tiles along the outer edges . The marks seen on the HRSI tiles are injection point marks and holes for the application of waterproofing material. This view also a good detailed view of the two-piece rudder which is used to control the yaw position of orbiter on approach and landing in earth's atmosphere and upon landing the two-piece rudder splays open to both sides of the stabilizer to act as an air brake to help slow the craft to a stop. This view was taken from a service platform in the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

11

Detail view of the vertical stabilizer of the Orbiter Discovery ...  

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

Detail view of the vertical stabilizer of the Orbiter Discovery looking at the two-piece rudder which is used to control the yaw position of orbiter on approach and landing in earth's atmosphere and upon landing the two-piece rudder splays open to both sides of the stabilizer to act as an air brake to help slow the craft to a stop. Note the thermal protection system components with the white Advanced Flexible Reusable Surface Insulation Blanket and the black High-temperature Reusable Surface Insulation tiles along the outer edges (HRSI tiles). The marks seen on the HRSI tiles are injection point marks and holes for the application of waterproofing material. This view was taken from a service platform in the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

12

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

13

Close up detail of the underside of the Orbiter Discovery ...  

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

Close up detail of the underside of the Orbiter Discovery in the Vehicle Assembly Building at NASA's Kennedy Space Center. This view is from underneath the aft section looking forward. It is a close-up view of the High-temperature Reusable Surface Insulation tiles showing the wear patterns from the heat of reentry, consequential replacement of worn and damaged tiles. The wear and replacement patters are unique to each Orbiter which can serve as their particular "fingerprint". - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

14

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

15

Close up view under the Orbiter Discovery in the Vehicle ...  

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

Close up view under the Orbiter Discovery in the Vehicle Assembly Building at NASA's Kennedy Space Center. The view is under the port wing looking forward toward the main fuselage showing a detail of the landing gear and landing gear door. This view also shows the patterns of worn and replaced High-temperature Reusable Surface Insulation tiles. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

16

A Simplified, Closed-Form Method for Screening Spacecraft Orbital Heating Variations  

NASA Technical Reports Server (NTRS)

A closed-form analytical technique has been developed to screen orbital average heating variations as a function of beta angle, altitude, surface area, and surface optical properties. Using planetary view factor equations for surfaces parallel-to and normal-to the local vertical, a cylindrical umbral shadow approximation, and a simplified albedo flux model, heating rate equations are formulated and then integrated to obtain orbital average heating. The results are compared to detailed analytical predictions using Monte Carlo integration and an assessment of error is presented.

Rickman, S. L.

2002-01-01

17

Influence of close encounters on the determination of cometary orbits  

Microsoft Academic Search

It has been shown that the precise determination of the motion of P\\/Shajn-Schaldach over a long time interval is practically impossible due to repeated close encounters with Jupiter, and that it would remain so even if the orbit of the comet were known with a much greater accuracy. An attempt is made to understand to what extent the possibility of

A. Carusi; E. Perozzi; G. B. Valsecchi; E. Pittich

1988-01-01

18

Orbital period modulation and magnetic cycles in close binaries  

NASA Astrophysics Data System (ADS)

We discuss the observed orbital period modulations in close binaries, and focus on the mechanism proposed by Applegate relating the changes of the stellar internal rotation associated with a magnetic activity cycle with the variation of the gravitational quadrupole moment of the active component; the variation of this quadrupole moment in turn forces the orbital motion of the binary stars to follow the activity level of the active star. We generalize this approach by considering the details of this interaction, and develop some illustrative examples in which the problem can be easily solved in analytical form. Starting from such results, we consider the interplay between rotation and magnetic field generation in the framework of different types of dynamo models, which have been proposed to explain solar and stellar activity. We show how the observed orbital period modulation in active binaries may provide new constraints for discriminating between such models. In particular, we study the case of the prototype active binary RS Canum Venaticorum, and suggest that torsional oscillations - driven by a stellar magnetic dynamo - may account for the observed behaviour of this star. Further possible applications of the relationship between magnetic activity and orbital period modulation, related to the recent discovery of binary systems containing a radio pulsar and a convecting upper main-sequence or a late-type low-mass companion, are discussed.

Lanza, A. F.; Rodono, M.; Rosner, R.

1998-06-01

19

Closed-eye orbital prosthesis: A clinical report.  

PubMed

One of the most challenging prostheses to fabricate is an acceptable orbital prosthesis. Successful reconstruction of the complex missing tissues, the globe, muscle, skin, and bony elements requires time and high levels of practical skill. A good match to the contralateral nondefect side will help mask the underlying defect and give the patient confidence to return to normal, routine life. The contralateral eye opening will commonly dictate the eye opening of such a prosthesis, but because of the expressive nature of the eye and its high levels of mobility, this can be difficult to achieve. This clinical report presents a patient who had an extended orbital exenteration and right maxillectomy to remove a maxillary squamous cell carcinoma. An alternative approach to constructing an orbital prosthesis was undertaken with the eye closed. Compared to the normal method of fabrication, this process was less complex and quicker, made the prosthesis less "staring," camouflaged the defect, and reduced the detection of the prosthesis because of movements in the remaining eye. The patient engaged in his routine daily life, which reinforced his self-esteem, confidence, and reintegration into the community. PMID:25449612

Hatamleh, Muhanad M; Watson, Jason; Srinivasan, Dilip

2015-03-01

20

Fast closed orbit control in the SLS storage ring  

Microsoft Academic Search

Concepts for a fast orbit feedback in the SLS storage ring are presented. The Singular Value Decomposition (SVD) based orbit correction scheme is supposed to fight orbit oscillations up to 100 Hz stabilizing the orbit to 1\\/10th of the beam sigma at the locations of the insertion devices. For an emittance ratio of 1%, this corresponds to 1 ?m tolerance

M. Boge; M. Dehler; T. Schilcher; V. Schlott; R. Ursic

1999-01-01

21

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

22

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

23

New method for inverting the closed-orbit distortion problem  

SciTech Connect

A certain class of magnet misalignments in storage rings and other accelerators produces closed-orbit distortions (CODs). Quite often the CODs are measured at a fewer number of locations (N) than the number of misalignment parameters (M). There is a linear relation between COD measurements, u(j), j=1, ..., N and the misalignment parameters e(k), k=1, ..., M. Hence the e(k)'s are underdetermined. If M < 2N, one can obtain an overdetermined set of equations by measuring the COD at two quadrupole settings. There are several ways of inverting the COD measurements to get the misalignment parameters that are fairly insensitive to errors in the measured CODs. A comptuer program called CODINV has been written to test some of these schemes. Two schemes give fairly good results when applied to the lattice of the Los Alamos Proton Storage Ring (PSR). The first scheme requires measurements at two nearby tunes and the use of singular-value decomposition methods. The second scheme requires measurements of the CODs in the FODO and DOFO cell arrangements but is easier mathematically.

Warren, J.L.; Channell, P.J.

1983-01-01

24

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

25

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

26

Numerical Prediction of Natural Convection in a Vertical Annulus Closed at Top and Opened at Bottom  

Microsoft Academic Search

A numerical prediction for natural convection flow in a vertical annulus closed at top and opened at bottom is presented. The outer cylindrical surface of the annulus is cooled to a low temperature, and a hot fluid is maintained below the open end temperature. The inner cylinder and the top wall of the annulus are insulated. The numerical technique used

S. Anil Lal; V. Arun Kumar

2013-01-01

27

Power Maximization of a Closed-orbit Kite Generator System Mariam Ahmed*  

E-print Network

Power Maximization of a Closed-orbit Kite Generator System Mariam Ahmed* Grenoble Electrical generated power T Orbit's period Kite's roll angle Fc,trc Tether's traction force PM Mean generated power. The third option is to use power kites as renewable energy generators such as the "Kite Wind Generator

Paris-Sud XI, Université de

28

Equilibrium, stability, and orbital evolution of close binary systems  

Microsoft Academic Search

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

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

1994-01-01

29

Multiport Well Design for Sampling of Ground Water at Closely Spaced Vertical Intervals  

USGS Publications Warehouse

Detailed vertical sampling is useful in aquifers where vertical mixing is limited and steep vertical gradients in chemical concentrations are expected. Samples can be collected at closely spaced vertical intervals from nested wells with short screened intervals. However, this approach may not be appropriate in all situations. An easy-to-construct and easy-to-install multiport sampling well to collect ground-water samples from closely spaced vertical intervals was developed and tested. The multiport sampling well was designed to sample ground water from surficial sand-and-gravel aquifers. The device consists of multiple stainless-steel tubes within a polyvinyl chloride (PVC) protective casing. The tubes protrude through the wall of the PVC casing at the desired sampling depths. A peristaltic pump is used to collect ground-water samples from the sampling ports. The difference in hydraulic head between any two sampling ports can be measured with a vacuum pump and a modified manometer. The usefulness and versatility of this multiport well design was demonstrated at an agricultural research site near Princeton, Minnesota where sampling ports were installed to a maximum depth of about 12 m below land surface. Tracer experiments were conducted using potassium bromide to document the degree to which short-circuiting occurred between sampling ports. Samples were successfully collected for analysis of major cations and anions, nutrients, selected herbicides, isotopes, dissolved gases, and chlorofluorcarbon concentrations.

Delin, G.N.; Landon, M.K.

1996-01-01

30

Closed-orbit prognosis, correction and manipulation for the PIMMS synchrotron  

E-print Network

Closed-orbit control is a basic ingredient for the efficient performance of any circular accelerator. The paper summarises the results of the simulations of the expected orbit distortions before and after correction for the PIMMS (Proton Ion Medical Machine Study) synchrotron. Different situations that lead to a deterioration of the orbit, such as broken position monitors and correctors, misalignment of the magnetic and diagnostic elements with time, have been examined. In particular, the consequences of lowering the injection energy of the space-charge-dominated proton beam have been investigated. The possibility of local orbit correction during extraction by applying closed bumps has been analysed. Finally, on the basis of the demands of both the global orbit correction and the local corrections at top energy, the corrector dipoles specifications have been evaluated.

Badano, L

1999-01-01

31

Importance of closely spaced vertical sampling in delineating chemical and microbiological gradients in groundwater studies  

USGS Publications Warehouse

Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, U.S.A. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume. A 27-fold change in bacterial abundance; a 35-fold change in frequency of dividing cells (FDC), an indicator of bacterial growth; a 23-fold change in 3H-glucose uptake, a measure of heterotrophic activity; and substantial changes in overall cell morphology were evident within a 9-m vertical interval at 250 m downgradient. The existence of these gradients argues for the need for closely spaced vertical sampling in groundwater studies because small differences in the vertical placement of a well screen can lead to incorrect conclusions about the chemical and microbiological processes within an aquifer.Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, USA. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume. A 27-fold change in bacterial abundance; a 35-fold change in frequency of dividing cells (FDC), an indicator of bacterial growth; a 23-fold change in 3H-glucose uptake, a measure of heterotrophic activity; and substantial changes in overall cell morphology were evident within a 9-m vertical interval at 250 m downgradient. The existence of these gradients argues for the need for closely spaced vertical sampling in ground-water studies because small differences in the vertical placement of a well screen can lead to incorrect conclusions about the chemical and microbiological processes within an aquifer.

Smith, R.L.; Harvey, R.W.; LeBlanc, D.R.

1991-01-01

32

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

NASA Astrophysics Data System (ADS)

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 component of the KS exchange-correlation (xc) potential vxc, the response potential vresp. Although -Ik will be a leading contribution to ?k, other Ij?k do enter through coupling terms which are determined by the overlaps between the densities of the KS orbitals as well as by overlaps between the KS and Dyson orbital densities. The orbital energies obtained with "exact" KS potentials are compared with the experimental VIPs of the molecules N2, CO, HF, and H2O. Very good agreement between the accurate -?k of the outer valence KS orbitals and the corresponding VIPs is established. The average difference, approaching 0.1 eV, is about an order of magnitude smaller than for HF orbital energies. The lower valence KS levels are a few eV higher than the corresponding -Ik, and the core levels some 20 eV, in agreement with the theoretically deduced upshift of the KS levels compared to -Ik by the response potential matrix elements. Calculations of 64 molecules are performed with the approximate vxc obtained with the statistical averaging of (model) orbitals potentials (SAOP) and the calculated ?k are compared with 406 experimental VIPs. Reasonable agreement between the SAOP -?k and the outer valence VIPs is found with an average deviation of about 0.4 eV.

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

2002-02-01

33

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

34

Effects and Correction of Closed Orbit Magnet Errors in the SNS Ring  

SciTech Connect

We consider the effect and correction of three types of orbit errors in SNS: quadrupole displacement errors, dipole displacement errors, and dipole field errors. Using the ORBIT beam dynamics code, we focus on orbit deflection of a standard pencil beam and on beam losses in a high intensity injection simulation. We study the correction of these orbit errors using the proposed system of 88 (44 horizontal and 44 vertical) ring beam position monitors (BPMs) and 52 (24 horizontal and 28 vertical) dipole corrector magnets. Correction is carried out numerically by adjusting the kick strengths of the dipole corrector magnets to minimize the sum of the squares of the BPM signals for the pencil beam. In addition to using the exact BPM signals as input to the correction algorithm, we also consider the effect of random BPM signal errors. For all three types of error and for perturbations of individual magnets, the correction algorithm always chooses the three-bump method to localize the orbit displacement to the region between the magnet and its adjacent correctors. The values of the BPM signals resulting from specified settings of the dipole corrector kick strengths can be used to set up the orbit response matrix, which can then be applied to the correction in the limit that the signals from the separate errors add linearly. When high intensity calculations are carried out to study beam losses, it is seen that the SNS orbit correction system, even with BPM uncertainties, is sufficient to correct losses to less than 10-4 in nearly all cases, even those for which uncorrected losses constitute a large portion of the beam.

Bunch, S.C.; Holmes, J.

2004-01-01

35

Three body resonances in close orbiting planetary systems: tidal dissipation and orbital evolution  

NASA Astrophysics Data System (ADS)

We study the orbital evolution of a three-planet system with masses in the super-Earth regime resulting from the action of tides on the planets induced by the central star which cause orbital circularization. We consider systems either in or near to a three-body commensurability for which adjacent pairs of planets are in a first-order commensurability. We develop a simple analytic solution, derived from a time averaged set of equations, that describes the expansion of the system away from strict commensurability as a function of time, once a state where relevant resonant angles undergo small amplitude librations has been attained. We perform numerical simulations that show the attainment of such resonant states focusing on the Kepler 60 system. The results of the simulations confirm many of the scalings predicted by the appropriate analytic solution. We go on to indicate how the results can be applied to put constraints on the amount of tidal dissipation that has occurred in the system. For example, if the system has been in a librating state since its formation, we find that its present period ratios imply an upper limit on the time average of 1/Q', With Q' being the tidal dissipation parameter. On the other hand if a librating state has not been attained, a lower upper bound applies.

Papaloizou, John C. B.

2015-04-01

36

Comparison of vertical-takeoff and horizontal-takeoff single-stage-to-orbit ascent performance  

NASA Astrophysics Data System (ADS)

A study was conducted to examine the ascent performance capability of the vertical-takeoff and horizontal-takeoff single-stage-to-orbit launchers. Both launchers, powered by Space Shuttle Main Engine rockets, were assumed to have a gross liftoff weight of 1,000,000 lb. The horizontal-takeoff launcher was assumed to be capable to take off from a conventional runway on its own power. The optimal ascent profile was designed to honor the dynamic pressure (900 psf), the axial load (3 g), and the normal load (1.25 g) constraints. Results of the study indicate that the vertical-takeoff performance with a burnout weight of 137,568 lb is not a strong function of the vehicle lift or wing area. The wing is required only for the reentry performance such as heating control, crossrange, and landing maneuvers. The horizontal-takeoff launcher has a burnout weight of 138,309 lb, but it will not have any payload capability if the ascent load is supported entirely by the vehicle landing gear at launch. Therefore, in order to make the horizontal-takeoff mode feasible, an undercarriage such as a trolley or a simple truss structure with wheels is required to alleviate the ascent load and, as a result, to reduce the landing gear weight. The horizontal-takeoff launcher, however, offers advantages over the winged vertical-takeoff launcher such as simpler launch preparedness and operation and a better launch abort capability.

Nguyen, Hai N.

1991-10-01

37

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

38

Orbital Angular Momentum (OAM) Vertical-Cavity Surface-Emitting Lasers  

E-print Network

Harnessing the Orbital Angular Momentum (OAM) of light is an appealing approach to developing photonic technologies for future applications in optical communications and high- dimensional Quantum Key Distributions (QKD). An outstanding challenge to the widespread uptake of the OAM resource is its efficient generation. We design a new device which can directly emit an OAM-carrying light beam. By fabricating micro-scale Spiral Phase Plates (SPPs) within the aperture of a Vertical-Cavity Surface-Emitting Laser (VCSELs), the linearly polarized Gaussian beam emitted by the VCSEL is converted into a beam carrying specific OAM modes and their superposition states with high efficiency and high beam quality. The innovative OAM emitter opens a new horizon in the field of OAM-based optical and quantum communications, especially for short reach data interconnects and Quantum Key Distribution (QKD).

Li, Huanlu; Wang, Xuyang; Ho, Daniel; Chen, Lifeng; Zhou, Xiaoqi; Zhu, Jiangbo; Yu, Siyuan; Cai, Xinlun

2015-01-01

39

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

40

Tidal interactions of a Maclaurin spheroid - II. Resonant excitation of modes by a close, misaligned orbit  

NASA Astrophysics Data System (ADS)

We model a tidally forced star or giant planet as a Maclaurin spheroid, decomposing the motion into the normal modes found by Bryan. We first describe the general prescription for this decomposition and the computation of the tidal power. Although this formalism is very general, forcing due to a companion on a misaligned, circular orbit is used to illustrate the theory. The tidal power is plotted for a variety of orbital radii, misalignment angles, and spheroid rotation rates. Our calculations are carried out including all modes of degree l ? 4, and the same degree of gravitational forcing. Remarkably, we find that for close orbits (a/R* ? 3) and rotational deformations that are typical of giant planets (e ? 0.4) the l = 4 component of the gravitational potential may significantly enhance the dissipation through resonance with surface gravity modes. There are also a large number of resonances with inertial modes, with the tidal power being locally enhanced by up to three orders of magnitude. For very close orbits (a/R* ? 3), the contribution to the power from the l = 4 modes is roughly the same magnitude as that due to the l = 3 modes.

Braviner, Harry J.; Ogilvie, Gordon I.

2015-02-01

41

Radial Velocity Detectability of Low Mass Extrasolar Planets in Close Orbits  

E-print Network

Detection of Jupiter mass companions to nearby solar type stars with precise radial velocity measurements is now routine, and Doppler surveys are moving towards lower velocity amplitudes. The detection of several Neptune-mass planets with orbital periods less than a week has been reported. The drive toward the search for close-in Earth-mass planets is on the agenda. Successful detection or meaningful upper limits will place important constraints on the process of planet formation. In this paper, we quantify the statistics of detection of low-mass planets in-close orbits, showing how the detection threshold depends on the number and timing of the observations. In particular, we consider the case of a low-mass planet close to but not on the 2:1 mean motion resonance with a hot jupiter. This scenario is a likely product of the core-accretion hypothesis for planet formation coupled with migration of jupiters in the protoplanetary disk. It is also advantageous for detection because the orbital period is well-constrained. Detection of few Earth mass rocky cores will require ~ 1 m/s velocity precision, and most importantly, a much better understanding of stellar radial velocity jitter.

Raman Narayan; Andrew Cumming; D. N. C. Lin

2004-09-30

42

Combined forced and buoyancy-induced convective heat transfer in a partially closed vertical channel  

SciTech Connect

This paper reports a numerical study of mixed convection flow over a horizontal surface in a partially closed adiabatic symmetric vertical channel. For low Rayleigh numbers, the forced flow enhances the buoyant convective heat transfer rates. For higher Rayleigh numbers, complex interactions arise between the buoyancy-dominated wall layer and the forced flow convection. The shearing between the buoyancy-dominated wall layer and the forced flow over it induces a stagnation region and a pair of weak recirculating cells in the middle of the channel above the horizontal surface. This effectively reduces heat transfer rates. Nusselt number data are presented for a wide range of Rayleigh and Reynolds numbers. Finally, the effect of the inlet height of forced flow on the transport is discussed.

Angirasa, D.; Mahajan, R.L. [Univ. of Colorado, Boulder, CO (United States). Dept. of Mechanical Engineering

1995-05-01

43

Boiling characteristics in small vertical tubes with closed bottom for nanofluids and nanoparticle-suspensions  

NASA Astrophysics Data System (ADS)

An experimental study was carried out to understand the nucleate boiling characteristics and the critical heat flux (CHF) of water, the water based nanofluids and the water based nanoparticle-suspensions in vertical small heated tubes with a closed bottom. Here, the nanofluids consisted of the base liquid, the CuO nanoparticles and the surfactant. The nanoparticle-suspensions consisted of the base liquid and CuO nanoparticles. The surfactant was sodium dodecyl benzene sulfate. The study focused on the influence of the nanoparticles and surfactant on the nucleate boiling characteristics and the CHF. The experimental results indicated that the nanoparticle concentrations of the nanofluids and nanoparticle-suspensions in the tubes do not change during the boiling processes; the nanoparticles in the evaporated liquid are totally carried away by the steam. The boiling heat transfer rates of nanofluids are poorer than that of the base liquid. However, the boiling heat transfer rates of nanoparticle-suspensions are better than that of the base liquid. Comparing with the base liquid, the CHF of the nanofluids and the nanoparticle-suspensions is higher. The CHF is only related to nanoparticle mass concentration when the tube length and the tube diameter are fixed. The experiment confirm that there is a thin nanoparticle coating layer on the heated surface after the nanofluids boiling test but there is no coating layer on the heated surface after the nanoparticle-suspensions boiling test. This coating layer is the main reason that deteriorates the boiling heat transfer rates of nanofluids. An empirical correlation was proposed for predicting the CHF of nanofluids boiling in the vertical tubes with closed bottom.

Lun-Chun, Lv; Zhen-Hua, Liu

2008-11-01

44

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

45

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

46

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

47

Hardware design and implementation of the closed-orbit feedback system at APS  

SciTech Connect

The Advanced Photon Source (APS) storage ring will utilize a closed-orbit feedback system in order to produce a more stable beam. The specified orbit measurement resolution is 25 microns for global feedback and 1 micron for local feedback. The system will sample at 4 kHz and provide a correction bandwidth of 100 Hz. At this bandwidth, standard rf BPMs will provide a resolution of 0.7 micron, while specialized miniature BPMs positioned on either side of the insertion devices for local feedback will provide a resolution of 0.2 micron (1). The measured BPM noise floor for standard BPMs is 0.06 micron per root hertz mA. Such a system has been designed, simulated, and tested on a small scale (2). This paper covers the actual hardware design and layout of the entire closed-loop system. This includes commercial hardware components, in addition to many components designed and built in-house. The paper will investigate the large-scale workings of all these devices, as well as an overall view of each piece of hardware used.

Barr, D.; Chung, Youngjoo

1996-10-01

48

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

49

Observation and analysis of time-dependent closed orbit motion in the LAMPF Proton Storage Ring  

SciTech Connect

When the stored beam is artificially offset in a section of the LAMPF Proton Storage Ring by changing selected ring dipole strengths, there is evidence for a small time dependence of the offset during the course of beam injection. A complete discussion of the time dependence of orbit offsets should take into account at least the following possibilities: (1) correlations between the injection timing pattern and ring dipole field ripple, (2) correlations between the injection timing pattern and changes of beam position monitor characteristics, and (3) growth of space-charge effects as the number of stored protons increases. Since there is no a priori reason to expect the correlations mentioned, we have analyzed the observed time dependence of the beam offset in terms of space-charge effects only, although the other possible causes cannot be ruled out. The buildup of circulating charge during proton injection leads to a shift of the betatron tune of individual protons because of space-charge forces; this shift can cause a change of the individual proton closed-orbit positions, and consequently a change in the position of the beam as a whole. At the end of a PSR injection cycle there are approximately 2.5 {times} 10{sup 13} protons stored in the ring. The observed time dependence of the beam offset indicates a horizontal-plane tune shift of {minus}0.03 {plus minus} 0.02; this is consistent with a theoretical estimate of a maximum expected space-charge tune shift of {minus}0.09 when 2.5 {times} 10{sup 13} protons are stored in the ring. 3 refs., 4 figs.

Hutson, R.L.; Fitzgerald, D.H.; Macek, R.J.

1991-01-01

50

Orbits  

NSDL National Science Digital Library

This Topic in Depth explores the Web's offerings on Orbits. The first site is offered by Northwestern University and asks: What is an orbit? (1 ). The site answers questions such as What causes an orbit to happen?, What is a satellite?, What travels in an orbit?, and Are there orbits within orbits?. A great starting site for this subject, visitors should come away with a broad and clear description of the topic. The second site, called Orbit Diagrams (2 ) is provided by the Harvard-Smithsonian Center for Astrophysics. The diagrams are "intended to aid in the visualization of the three-dimensional nature of the orbits and how they are orientated with respect to the orbit of the earth." Next, from the University of Wisconsin-Madison Department of Astronomy comes the Moon Phases (3 ) interactive Web site. Users are able to animate the moon's orbit in various phases and views as well as learn all the names of the phases. The fourth site is another virtual visualization tool provided by NASA's Near Earth Object Program called Orbits (4 ). The site lets users enter the designation or name of any asteroid or comet and then view the three-dimensional orbit of that object. The next site, maintained by the Conservation, Astronomy, Physics and Soaring Page, is called Satellite Orbits - Gravitational Assist from Planets (5 ). The site contains information on Kepler's Laws, which apply to elliptical orbits involving two bodies, hyperbolic orbits, relative motion, and the gravitational sphere of influence. The sixth site is an educational lesson provided by Dr. Richard L. Bowman of Bridgewater College called Planetary Orbit Exercise (6 ). Students are given information on Keplar's Laws of Planetary Motion, a list of definitions, links to outside sites for additional information, and then several questions to answer. The Planetary Physical Data (7 ) page is part of the larger Smithsonian Center for Earth and Planetary Studies Web site. Visitors will find a list of planets along with various information such as their relative sidereal period of orbit, mean orbital velocity, orbital eccentricity, and much more. The last site related to orbits is an educational activity provided by the Physics Classroom called Circular Motion and Planetary Motion (8 ). Four lessons are presented including Motion Characteristics for Circular Motion, Applications of Circular Motion, Universal Gravitation, and Planetary and Satellite Motion. Each contain clear and well written descriptions along with all the necessary information for successful completion.

Brieske, Joel A.

51

Closed form solutions for unsteady free convection flow of a second grade fluid over an oscillating vertical plate.  

PubMed

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. PMID:24551033

Ali, Farhad; Khan, Ilyas; Shafie, Sharidan

2014-01-01

52

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. PMID:24551033

Ali, Farhad; Khan, Ilyas; Shafie, Sharidan

2014-01-01

53

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

54

Spin-orbit coupling induced spin-transfer torque and current polarization in topological-insulator/ferromagnet vertical heterostructures.  

PubMed

We predict an unconventional spin-transfer torque (STT) acting on the magnetization of a free ferromagnetic (F) layer within N/TI/F vertical heterostructures, which originates from strong spin-orbit coupling on the surface of a three-dimensional topological insulator (TI), as well as from charge current becoming spin polarized in the direction of transport as it flows perpendicularly from the normal metal (N) across the bulk of the TI layer. The STT vector has both in-plane and perpendicular components that are comparable in magnitude to conventional torque in F'/I/F (where I stands for insulator) magnetic tunnel junctions, while not requiring additional spin-polarizing F' layer with fixed magnetization, which makes it advantageous for spintronics applications. Our principal formal result is a derivation of the nonequilibrium Green function-based formula and the corresponding gauge-invariant nonequilibrium density matrix, which makes it possible to analyze the components of the STT vector in the presence of arbitrary strong spin-orbit coupling either in the bulk or at the interface of the free F layer. PMID:23215105

Mahfouzi, Farzad; Nagaosa, Naoto; Nikoli?, Branislav K

2012-10-19

55

Some schemes for on-line correction of the closed orbit, dispersion and beta functions in PEP  

SciTech Connect

PEP has been operated successfully under computer control. It is necessary for colliding beam operation that the errors in closed orbits, dispersion and beta functions be corrected. The schemes in the PEP control program for on-line correction of these errors are described in this paper. The orbit control tasks in the PEP control system perform the functions of data gathering, data presentation (color display, printing), calculation and setting of corrector magnets. The tasks are generally small and modular, taking information from the database, processing it, then returning the results to the database. The PEP operator communicates with the tasks through touch panels monitored by the Director program. The display task, which displays orbit and corrector information on a TV color display, provides the main information required by the operator.

Donald, M.H.R.; Blocker, C.; Chao, A.W.; Hollebeek, R.J.; Lee, M.J.; Linstadt, J.E.; Siegrist, J.L.; Spencer, N.

1981-02-01

56

Closed orbit control in 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 in about 1 minute. Some orbit control during energy ramping has taken place on the SRS for the last two years, to overcome problems encountered with large uncorrected orbit drifts and allow high currents (>300 mA) to be ramped

S. F. Hill; S. L. Smith

1996-01-01

57

Estimation of Vertical Deflections in Concrete Beams Through Digital Close Range Photogrammetry  

NASA Astrophysics Data System (ADS)

Deformation monitoring, and in general structural health monitoring, of civil infrastructure systems is important in terms of both safety and serviceability. Traditionally, large structures have been monitored using surveying techniques, while fine-scale monitoring of structural components has been done with geotechnical instrumentation. This paper reviews the advantages and disadvantages of using remote sensing methods, such as terrestrial laser scanning and digital close range photogrammetry, for the purposes of precise 3D reconstruction and the estimation of deflections in structural materials. It is also shown how a low-cost setup of multiple digital cameras and projectors can be used for the monitoring of concrete beams subjected to different loading conditions by a hydraulic actuator. The photogrammetric system used does not require any physical targets other than for the purposes of establishing the relative orientation between the involved cameras. The setup was tested in two experiments, and the beam deflections resulted from the photogrammetric system were compared to the ones from a set of one-dimensional laser transducers and a terrestrial laser scanner. The experiments proved that it was possible to detect sub-millimetre level deformations given the used equipment and the geometry of the setup.

Detchev, I.; Habib, A.; El-Badry, M.

2011-09-01

58

Analytic second derivatives in closed-shell coupled-cluster theory with spin-orbit coupling  

Microsoft Academic Search

The theory for geometrical second derivatives of the energy is outlined for the recently suggested two-component coupled-cluster approach using relativistic effective core potentials with spin-orbit coupling included in the post-Hartree-Fock treatment [F. Wang, J. Gauss, and C. van Wüllen, J. Chem. Phys. 129, 064113 (2008)], and an implementation is reported at the coupled-cluster singles and doubles (CCSD) level as well

Fan Wang; Jürgen Gauss

2009-01-01

59

Imaging Comet C/2013 A1 {Siding Spring} to Support Risk Assessment for Mars Orbiters during the Close Mars Encounter  

NASA Astrophysics Data System (ADS)

Newly discovered comet C/Siding Spring passes Mars on October 19, 2014 at a distance of only 134,000 km. Such a close encounter of a dynamically new comet is extremely rare, providing an opportunity for instruments on Mars to observe it around close approach and for studying the interactions between the coma and the Martian atmosphere. However, comet dust also poses a potential risk to NASA's Mars-orbiting spacecraft. We request four HST DD orbits to observe C/Siding Spring in three epochs between October 2013 and March 2014, to characterize the comet's environment. Our goals are to measure the dust activity and its temporal evolution, characterize the coma and tail morphology and colors {to constrain the dust particle size distribution}, investigate features or jets near the nucleus, and determine the nucleus' size and rotation state. The proposed studies will provide valuable information about this dynamically new comet and will help in planning future observations {from both Mars- and Earth-based facilities}. These studies will provide critical input for assessing the hazards to Mars orbiters. DD time is requested because the potential risks from the dust coma were not fully recognized until after the normal Cycle 21 GO proposal deadlines {when the comet's orbit determination accurately predicted the Mars encounter}, and waiting until the normal Cycle 22 will be too late to obtain the necessary data. HST's high angular resolution is essential for the proposed observations as C/Siding Spring is still 5 AU from the Sun, with a coma only a few arcsec in size.

Li, Jian-Yang

2013-10-01

60

On the stability of extrasolar planetary systems and other closely orbiting pairs  

NASA Astrophysics Data System (ADS)

This paper considers the stability of tidal equilibria for planetary systems in which stellar rotation provides a significant contribution to the angular momentum budget. We begin by applying classic stability considerations for two bodies to planetary systems - where one mass is much smaller than the other. The application of these stability criteria to a subset of the Kepler sample indicates that the majority of the systems are not in a stable equilibrium state. Motivated by this finding, we generalize the stability calculation to include the quadrupole moment for the host star. In general, a stable equilibrium requires that the total system angular momentum exceeds a minimum value (denoted here as LX) and that the orbital angular momentum of the planet exceeds a minimum fraction of the total. Most, but not all, of the observed planetary systems in the sample have enough total angular momentum to allow an equilibrium state. Even with the generalizations of this paper, however, most systems have too little orbital angular momentum (relative to the total) and are not in an equilibrium configuration. Finally, we consider the time evolution of these planetary systems; the results constrain the tidal quality factor of the stars and suggest that 106 ? Q* ? 107.

Adams, Fred C.; Bloch, Anthony M.

2015-02-01

61

Break-up of suspension drops settling under gravity in a viscous fluid close to a vertical wall  

E-print Network

The evolution of suspension drops sedimenting under gravity in a viscous fluid close to a vertical wall was studied experimentally and numerically with the use of the point-force model, in the Stokes flow regime. The fluid inside and outside the drop was identical. The initial distribution of the suspended solid heavy particles was uniform inside a spherical volume. In the experiments and in the simulations, the suspension drops evolved qualitatively in the same way as in an unbounded fluid. However, it was observed, both experimentally and numerically that, on the average, the destabilization time T and the distance L traveled by the drop until break-up were smaller for a closer distance h of the drop center from the wall, with approximately linear dependence of T and L on D/h, for h larger or comparable to the drop diameter D. Destabilization times and lengths of individual drops with different random configurations of the particles were shown to differ significantly from each other, owing to the chaotic nature of the particle dynamics.

Anna Mylyk; Walter Meile; Gunter Brenn; Maria L. Ekiel-Jezewska

2011-02-24

62

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.

Alan McConnell

1990-07-10

63

Tidal forces and stability of circular and near-circular orbits of massive close-in planets: the CoRoT example  

NASA Astrophysics Data System (ADS)

The ensemble of CoRoT planets is studied with regard to tidal interactions and orbital decay. Four simple principles are formulated for a first order estimate of orbital stability under tidal forces: i) present orbit within the virtual synchronous orbit with regard to stellar rotation, ii) the Doodson constant, iii) the property factor and iv) the critical orbit radius depending on remaining stellar life time and the dissipation Q*/k2*. Tidal forces are driving the planetary rotation synchronous with the orbital revolution within a few hundred million years if the planetary orbit is within 0.1 AU. From the 22 studied CoRoT planets, 15 are massive close-in hot Jupiters. Three of them are around G-stars and another three are around F-stars within 0.033 AU and 0.044 AU, respectively. Those will reach the Roche zone of their stars within the remaining stellar life time for Q*/k2*?107. Scenarios of extremely small Q*/k2* are considered unrealistic because the planets would migrate into the stellar Roche zones in extremely short time scales and would spin up strongly the stellar rotation. A special class of fast rotating old sun-like stars is, to our knowledge, not observed. Tidal forces may drive the stellar rotation and the planetary orbit into double synchronous rotation. This state may eventually be achieved but is considered as unstable. The slow-down of the stellar rotation by magnetic braking (strong with G-stars, weak with F-stars) will drive the synchronous orbit outward and out of the double synchronous state which leaves the planetary orbit within the synchronous orbit.

Pätzold, M.; Carone, L.

2013-09-01

64

WASP-24 b: A NEW TRANSITING CLOSE-IN HOT JUPITER ORBITING A LATE F-STAR  

SciTech Connect

We report the discovery of a new transiting close-in giant planet, WASP-24 b, in a 2.341 day orbit, 0.037 AU from its F8-9 type host star. By matching the star's spectrum with theoretical models, we infer an effective temperature T{sub eff} = 6075 {+-} 100 K and a surface gravity of log g = 4.15 {+-} 0.10. A comparison of these parameters with theoretical isochrones and evolutionary mass tracks places only weak constraints on the age of the host star, which we estimate to be 3.8{sup +1.3}{sub -1.2} Gyr. The planetary nature of the companion was confirmed by radial velocity measurements and additional photometric observations. These data were fit simultaneously in order to determine the most probable parameter set for the system, from which we infer a planetary mass of 1.071{sup +0.036}{sub -0.038} M {sub Jup} and radius 1.3{sup +0.039}{sub -0.037} R{sub Jup}.

Street, R. A.; Lister, T. A.; Depagne, E. [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Simpson, E.; Barros, S. C. C.; Pollacco, D.; Joshi, Y.; Todd, I. [Astrophysics Research Centre, Physics Building, Queen's University, Belfast, County Antrim, BT7 1NN (United Kingdom); Collier Cameron, A.; Enoch, B.; Parley, N. [SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Stempels, E. [Department of Physics and Astronomy, P.O. Box 516, SE-751 20 Uppsala (Sweden); Hebb, L. [Physics and Astronomy Department, Vanderbilt University, 1807 Station B, Nashville, TN 37235 (United States); Triaud, A. H. M. J.; Queloz, D.; Segransan, D.; Pepe, F.; Udry, S. [Observatoire Astronomique de l'Universite de Geneve, 51 Chemin des Maillettes, 1290 Sauverny (Switzerland); West, R. G. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom); Norton, A. J. [Department of Physics and Astronomy, The Open University, N2041, Venables Building, Milton Keynes, MK7 6AA (United Kingdom)

2010-09-01

65

Evolution of rotationally and tidally distorted low-mass, close binary systems - Implications for the minimum orbital period of cataclysmic variables  

Microsoft Academic Search

A (1 + 0.4) solar mass close binary system consisting of a compact primary and a red dwarf secondary has been evolved numerically. Such a binary system should effectively model cataclysmic variables for which a minimum orbital period cutoff of about 81 minutes has been observed. The influence of gravitational radiation losses which drive Roche lobe overflow has been studied,

L. A. Nelson; W. Y. Chau; A. Rosenblum

1985-01-01

66

Evolution of rotationally and tidally distorted low-mass, close binary systems - implications for the minimum orbital period of cataclysmic variables  

Microsoft Academic Search

A (1 + 0.4) solar mass close binary system consisting of a compact primary and a red dwarf secondary has been evolved numerically. Such a binary system should effectively model cataclysmic variables for which a minimum orbital period cutoff of about 81 minutes has been observed. The influence of gravitational radiation losses which drive Roche lobe overflow has been studied,

L. A. Nelson; W. Y. Chau; A. Rosenblum

1985-01-01

67

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

68

Vertical stratification of ° 13 C values in closed natural and plantation forests in the Luquillo mountains, Puerto Rico  

Microsoft Academic Search

The variability of d13C values was measured in leaf, stem and root tissues of several tree species growing in closed natural and plantation forests in the Luquillo mountains of Puerto Rico. Results confirm a significant decrease of d13C values from the tree canopy to the forest floor. The values measured in understory plants growing in gaps were not significantly different

Ernesto Medina; Leonel Sternberg; Elvira Cuevas

1991-01-01

69

Evolution of rotationally and tidally distorted low-mass, close binary systems - Implications for the minimum orbital period of cataclysmic variables  

NASA Technical Reports Server (NTRS)

A (1 + 0.4) solar mass close binary system consisting of a compact primary and a red dwarf secondary has been evolved numerically. Such a binary system should effectively model cataclysmic variables for which a minimum orbital period cutoff of about 81 minutes has been observed. The influence of gravitational radiation losses which drive Roche lobe overflow has been studied, and the effects of rotational and tidal distortion have also been incorporated in the calculation. The evolution of the He-3 abundance, which has been suggested as a possible explanation for the upper limit of the apparent orbital period gap exhibited by cataclysmic variables, is also considered. It is found that both the distortional effects and the He-3 chemical profile can play an important role in determining the subsequent evolution of these systems. Specifically, when distortion is included, the theoretical minimum orbital period is increased by about 10 percent, yielding better agreement with observations.

Nelson, L. A.; Chau, W. Y.; Rosenblum, A.

1985-01-01

70

Atomic-orbital close-coupling calculations for collisions involving fusion relevant highly charged impurity ions using very large basis sets  

SciTech Connect

The atomic-orbital close-coupling formalism is a well-known method for the semiclassical treatment of ion-atom collisions. Cross sections for these kinds of collisions are mainly needed in the analysis of certain spectroscopic data from nuclear fusion experiments as well as astrophysical data. We shall outline how the computational implementation can be improved in such a way that collisions involving heavy, highly charged impurity ions, such as Ar{sup 18+} can be treated. Furthermore we show and discuss exemplary results.

Igenbergs, Katharina; Wallerberger, Markus; Schweinzer, Josef; Aumayr, Friedrich [Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstr.8-10/134, A-1040 Vienna (Austria); Max-Planck-Institute of Plasma Physics, Boltzmannstr.2, D-85748 Garching (Germany); Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstr.8-10/134, A-1040 Vienna (Austria)

2012-05-25

71

'Night' scene of the STS-5 Columbia in orbit over the earth  

NASA Technical Reports Server (NTRS)

'Night' scene of the STS-5 Columbia in orbit over the earth's glowing horizon. The aft section of the cargo bay contains two closed protective shields for satellites which were deployed on the flight. The nearest shield hoses the Satellite Business System's (SBS-3) satellite. The vertical stabilizer, illuminated by the sun, is flanked by two orbital maneuvering system (OMS) pods.

1982-01-01

72

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

73

Atmosphere Expansion and Mass Loss of Close-orbit Giant Exoplanets Heated by Stellar XUV. I. Modeling of Hydrodynamic Escape of Upper Atmospheric Material  

NASA Astrophysics Data System (ADS)

In the present series of papers we propose a consistent description of the mass loss process. To study in a comprehensive way the effects of the intrinsic magnetic field of a close-orbit giant exoplanet (a so-called hot Jupiter) on atmospheric material escape and the formation of a planetary inner magnetosphere, we start with a hydrodynamic model of an upper atmosphere expansion in this paper. While considering a simple hydrogen atmosphere model, we focus on the self-consistent inclusion of the effects of radiative heating and ionization of the atmospheric gas with its consequent expansion in the outer space. Primary attention is paid to an investigation of the role of the specific conditions at the inner and outer boundaries of the simulation domain, under which different regimes of material escape (free and restricted flow) are formed. A comparative study is performed of different processes, such as X-ray and ultraviolet (XUV) heating, material ionization and recombination, H_3^ + cooling, adiabatic and Ly? cooling, and Ly? reabsorption. We confirm the basic consistency of the outcomes of our modeling with the results of other hydrodynamic models of expanding planetary atmospheres. In particular, we determine that, under the typical conditions of an orbital distance of 0.05 AU around a Sun-type star, a hot Jupiter plasma envelope may reach maximum temperatures up to ~9000 K with a hydrodynamic escape speed of ~9 km s-1, resulting in mass loss rates of ~(4-7) · 1010 g s-1. In the range of the considered stellar-planetary parameters and XUV fluxes, that is close to the mass loss in the energy-limited case. The inclusion of planetary intrinsic magnetic fields in the model is a subject of the follow-up paper (Paper II).

Shaikhislamov, I. F.; Khodachenko, M. L.; Sasunov, Yu. L.; Lammer, H.; Kislyakova, K. G.; Erkaev, N. V.

2014-11-01

74

Closeup view of the Orbiter Discovery as it is suspended ...  

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

Close-up view of the Orbiter Discovery as it is suspended vertically by the hoist in the transfer aisle of the Vehicle Assembly Building at Kennedy Space Center. This view is a detail of the starboard wing of the orbiter. Note the Reinforced Carbon-Carbon panels on the leading edge of the wing, the elevons and the elevon seal panels on the wing's trailing edge. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

75

Effects of vertical girder realignment in the Argonne APS storage ring.  

SciTech Connect

The effects of vertical girder misalignments on the vertical orbit of the Advanced Photon Source (APS) storage ring are studied. Partial sector-realignment is prioritized in terms of the closed-orbit distortions due to misalignments of the corresponding girders in the sectors. A virtual girder-displacement (VGD) method is developed that allows the effects of a girder realignment to be tested prior to physically moving the girder. The method can also be used to anticipate the corrector strengths needed to restore the beam orbit after a realignment. Simulation results are compared to experimental results and found to reproduce the latter quite closely. Predicted corrector strengths are also found to be close to the actual local corrector strengths after a proof-of-principle two-sector realignment was performed.

Lessner, E.

1999-04-14

76

Orbit design concepts for Jupiter orbiter missions  

NASA Technical Reports Server (NTRS)

Advanced mission and orbit planning efforts are currently in progress for a Mariner-class Jupiter orbiter. Baseline spacecraft and orbit design criteria are the goals of a NASA effort to define such a mission. Orbit design concepts that have been discovered during the early stages of mission planning are both challenging and exciting. A description is given of several such concepts that may greatly increase the flexibility and scientific return of orbiters designed for close study of the Galilean satellites and exploration of the Jovian system. Some new jargon is introduced in discussions to describe the exploitation of gravity-assist trajectories using the giant satellites for orbit control. Orbit 'pumping' and 'cranking' and 'resonance hopping' are defined and shown to be dynamically feasible means of controlling the orbit and, thus, the scientific return. A candidate encounter sequence is presented for an equatorial tour of the Galilean moons.

Uphoff, C.; Roberts, P. H.; Friedman, L. D.

1974-01-01

77

Gravity and Orbits: Orbits  

NSDL National Science Digital Library

This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:? 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)

2006-11-01

78

Interaction of Close-in Planets with the Magnetosphere of Their Host Stars. II. Super-Earths as Unipolar Inductors and Their Orbital Evolution  

NASA Astrophysics Data System (ADS)

Planets with several Earth masses and orbital periods of a few days have been discovered through radial velocity and transit surveys. Regardless of their formation mechanism, an important evolution issue is the efficiency of their retention in the proximity of their host stars. If these "super-Earths" attained their present-day orbits during or shortly after the T Tauri phase of their host stars, a large fraction of these planets would have encountered an intense stellar magnetic field. These rocky planets have a higher conductivity than the atmosphere of their host stars and, therefore, the magnetic flux tube connecting them would slip though the envelope of the host stars faster than across the planets. The induced electromotive force across the planet's diameter leads to a potential drop which propagates along a flux tube away from the planet with an Alfvén speed. The foot of the flux tube would sweep across the stellar surface and the potential drop across the field lines drives a DC current analogous to that proposed for the electrodynamics of the Io-Jupiter system. The ohmic dissipation of this current produces potentially observable hot spots in the star envelope. It also heats the planet and leads to a torque which drives the planet's orbit to evolve toward both circularization and a state of synchronization with the spin of the star. The net effect is the damping of the planet's orbital eccentricity. Around slowly (or rapidly) spinning stars, this process also causes rocky planets with periods less than a few days to undergo orbital decay (or expansion/stagnation) within a few Myr. In principle, this effect can determine the retention efficiency of short-period hot Earths. We also estimate the ohmic dissipation interior to these planets and show that it can lead to severe structure evolution and potential loss of volatile material in them. However, these effects may be significantly weakened by the reconnection of the induced field.

Laine, Randy O.; Lin, Douglas N. C.

2012-01-01

79

INTERACTION OF CLOSE-IN PLANETS WITH THE MAGNETOSPHERE OF THEIR HOST STARS. II. SUPER-EARTHS AS UNIPOLAR INDUCTORS AND THEIR ORBITAL EVOLUTION  

SciTech Connect

Planets with several Earth masses and orbital periods of a few days have been discovered through radial velocity and transit surveys. Regardless of their formation mechanism, an important evolution issue is the efficiency of their retention in the proximity of their host stars. If these 'super-Earths' attained their present-day orbits during or shortly after the T Tauri phase of their host stars, a large fraction of these planets would have encountered an intense stellar magnetic field. These rocky planets have a higher conductivity than the atmosphere of their host stars and, therefore, the magnetic flux tube connecting them would slip though the envelope of the host stars faster than across the planets. The induced electromotive force across the planet's diameter leads to a potential drop which propagates along a flux tube away from the planet with an Alfven speed. The foot of the flux tube would sweep across the stellar surface and the potential drop across the field lines drives a DC current analogous to that proposed for the electrodynamics of the Io-Jupiter system. The ohmic dissipation of this current produces potentially observable hot spots in the star envelope. It also heats the planet and leads to a torque which drives the planet's orbit to evolve toward both circularization and a state of synchronization with the spin of the star. The net effect is the damping of the planet's orbital eccentricity. Around slowly (or rapidly) spinning stars, this process also causes rocky planets with periods less than a few days to undergo orbital decay (or expansion/stagnation) within a few Myr. In principle, this effect can determine the retention efficiency of short-period hot Earths. We also estimate the ohmic dissipation interior to these planets and show that it can lead to severe structure evolution and potential loss of volatile material in them. However, these effects may be significantly weakened by the reconnection of the induced field.

Laine, Randy O. [Ecole Normale Superieure, Paris (France); Lin, Douglas N. C., E-mail: laine@ens.fr, E-mail: randy.laine@normalesup.org, E-mail: lin@ucolick.org [Department of Astronomy and Astrophysics University of California, Santa Cruz, CA 95064 (United States)

2012-01-20

80

Random Matrix Theory for Closed Quantum Dots with Weak Spin-Orbit Coupling K. Held,* E. Eisenberg, and B. L. Altshuler  

E-print Network

~nn=212; ~aak 1 6 ~rr~nnz 12 x11 1 x22 2 ; i denote the Pauli matrices and B is the magnetic field that spin-orbit scattering has a significant effect in the presence of an in-plane magnetic field [3 at relatively low magnetic fields. The term ~aak is responsible for spin flips, but it is of higher order

Eisenberg, Eli

81

Vertical close pack rod arraying system  

SciTech Connect

A rod arraying system is described comprising: (a) a rigid support structure; (b) a canister positioned in and supported by the support structure; (c) a mounting base slidably attached to the support structure on an incline; (d) a guide assembly attached to the mounting base for positioning rods inside the canister. The system consists of: (i) an upper guide plate mounted on the mounting base; (ii) a lower guide plate slidably mounted on the upper guide plate; (iii) means for causing forward and backward cycling of the lower guide plate relative to the upper guide plate; and e. the canister having a window for receiving the guide assembly.

Attix, D.J.; Kelly, M.J.; Mason, F.L.; Stinnett, C.E.

1989-06-27

82

Vertical close pack rod arraying system  

Microsoft Academic Search

A rod arraying system is described comprising: (a) a rigid support structure; (b) a canister positioned in and supported by the support structure; (c) a mounting base slidably attached to the support structure on an incline; (d) a guide assembly attached to the mounting base for positioning rods inside the canister. The system consists of: (i) an upper guide plate

D. J. Attix; M. J. Kelly; F. L. Mason; C. E. Stinnett

1989-01-01

83

Observable Properties of Orbits in Exact Bumpy Spacetimes  

E-print Network

We explore the properties of test-particle orbits in "bumpy" spacetimes - stationary, reflection-symmetric, asymptotically flat solutions of Einstein equations that have a non-Kerr (anomalous) higher-order multipole-moment structure but can be tuned arbitrarily close to the Kerr metric. Future detectors should observe gravitational waves generated during inspirals of compact objects into supermassive central bodies. If the central body deviates from the Kerr metric, this will manifest itself in the emitted waves. Here, we explore some of the features of orbits in non-Kerr spacetimes that might lead to observable signatures. As a basis for this analysis, we use a family of exact solutions proposed by Manko & Novikov which deviate from the Kerr metric in the quadrupole and higher moments, but we also compare our results to other work in the literature. We examine isolating integrals of the orbits and find that the majority of geodesic orbits have an approximate fourth constant of the motion (in addition to the energy, angular momentum and rest mass) and the resulting orbits are tri-periodic to high precision. We also find that this fourth integral can be lost for certain orbits in some oblately deformed Manko-Novikov spacetimes. However, compact objects will probably not end up on these chaotic orbits in nature. We compute the location of the innermost stable circular orbit (ISCO) and find that the behavior of orbtis near the ISCO can be qualitatively different depending on whether the ISCO is determined by the onset of an instability in the radial or vertical direction. Finally, we compute periapsis and orbital-plane precessions for nearly circular and nearly equatorial orbits in both the strong and weak field, and discuss weak-field precessions for eccentric equatorial orbits.

Jonathan R Gair; Chao Li; Ilya Mandel

2008-01-11

84

Digital orbit feedback control for SPEAR  

Microsoft Academic Search

A digital orbit feedback system is being developed for SPEAR to improve electron beam stability at photon beam sourcepoints. The first phase implementation of this system operates at 1 minute intervals and stabilizes the horizontal and vertical orbit position to 50 ?m RMS at beam position monitors. The vertical global system works in tandem with local 50 Hz analog photon

R. Hettel; J. Corbett; D. Keeley; I. Linscott; D. Mostowfi; J. Sebek; C. Wermelskirchen

1995-01-01

85

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

86

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 ...

87

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

88

Model Calibration and Optics Correction Using Orbit Response Matrix in the Fermilab Booster  

SciTech Connect

We have calibrated the lattice model and measured the beta and dispersion functions in Fermilab's fast-ramping Booster synchrotron using the Linear Optics from Closed Orbit (LOCO) method. We used the calibrated model to implement ramped coupling, dispersion, and beta-beating corrections throughout the acceleration cycle, reducing horizontal beta beating from its initial magnitude of {approx}30% to {approx}10%, and essentially eliminating vertical beta-beating and transverse coupling.

Lebedev, V.A.; Prebys, E.; /Fermilab; Petrenko, A.V.; /Novosibirsk, IYF; Kopp, S.E.; McAteer, M.J.; /Texas U.

2012-05-01

89

Vertical Farm  

NSDL National Science Digital Library

With the continued growth of the human population of the Earth, there is increasing concern with the planet's ability to provide sustenance for all of its inhabitants. This compelling website by Dickson Despommier and his colleagues at Columbia University provides a worthy alternative to other forms of agriculture: the vertical farm. As Dr. Despommier notes on the site, "..they offer the promise of urban renewal, sustainable production of a safe and varied food supply (year-round crop production), and the eventual repair of ecosystems that have been sacrificed for horizontal farming." The site offers a great deal of information about these vertical farms, a detailed essay on the importance of such farms, a number of potential designs, and a discussion forum. Finally, there are a number of plans that indicate how this type of farm might be effectively created and sustained.

90

Examination of trajectories between low planetary orbits and circulation orbits  

NASA Astrophysics Data System (ADS)

Circulating orbits have been investigated to provide regular periodic transfers between the Earth and Mars. The circulating orbits pass close enough to each planet to be considered hyperbolic in planetocentric frame. The large spacecraft (CASTLE) in the circulating orbit is resupplied by a smaller 'Taxi' spacecraft leaving a low planetary orbit. The Taxi follows an optimal three-impulse patched-conic trajectory to travel from its spaceport to the large spacecraft following a hyperbolic fly-by. Examining the parameters of the situation produces a Delta V profile for each planetary fly-by of the circulating orbit.

Knoedler, Andrew J.

91

The Orbital Acceleration Research Experiment  

NASA Technical Reports Server (NTRS)

The hardware and software of NASA's proposed Orbital Acceleration Research Experiment (OARE) are described. The OARE is to provide aerodynamic acceleration measurements along the Orbiter's principal axis in the free-molecular flow-flight regime at orbital attitude and in the transition regime during reentry. Models considering the effects of electromagnetic effects, solar radiation pressure, orbiter mass attraction, gravity gradient, orbital centripetal acceleration, out-of-orbital-plane effects, orbiter angular velocity, structural noise, mass expulsion signal sources, crew motion, and bias on acceleration are examined. The experiment contains an electrostatically balanced cylindrical proofmass accelerometer sensor with three orthogonal sensing axis outputs. The components and functions of the experimental calibration system and signal processor and control subsystem are analyzed. The development of the OARE software is discussed. The experimental equipment will be enclosed in a cover assembly that will be mounted in the Orbiter close to the center of gravity.

Blanchard, R. C.; Hendrix, M. K.; Fox, J. C.; Thomas, D. J.; Nicholson, J.

1986-01-01

92

Adaptation of vertical eye alignment in relation to head tilt  

Microsoft Academic Search

Binocular visual feedback is used to continually calibrate binocular eye alignment so that the retinal images of the two eyes remain in correspondence. Past experiments have shown that vertical eye alignment (measured as vertical phoria) can be altered by training to disparities that vary as a function of orbital eye position. The present experiments demonstrate that vertical eye alignment can

James S. Maxwell; Clifton M. Schor

1996-01-01

93

Orbital Decompression  

MedlinePLUS

INTRODUCTION Orbital decompression is a surgical procedure which has been in existence for well over 100 years to treat a variety ... optic nerve) and fat). The goal of orbital decompression is to remove some of the bony walls ...

94

Congenital orbital encephalocele, orbital dystopia, and exophthalmos.  

PubMed

We present here an exceedingly rare variant of a nonmidline basal encephalocele of the spheno-orbital type, and this was accompanied with orbital dystopia in a 56-year-old man. On examination, his left eye was located more inferolaterally than his right eye, and the patient said this had been this way since his birth. The protrusion of his left eye was aggravated when he is tired. His naked visual acuity was 0.7/0.3, and the ocular pressure was 14/12 mm Hg. The exophthalmometry was 10/14 to 16 mm. His eyeball motion was not restricted, yet diplopia was present in all directions. The distance from the midline to the medial canthus was 20/15 mm. The distance from the midline to the midpupillary line was 35/22 mm. The vertical dimension of the palpebral fissure was 12/9 mm. The height difference of the upper eyelid margin was 11 mm, and the height difference of the lower eyelid margin was 8 mm. Facial computed tomography and magnetic resonance imaging showed left sphenoid wing hypoplasia and herniation of the left anterior temporal pole and dura mater into the orbit, and this resulted into left exophthalmos and encephalomalacia in the left anterior temporal pole. To the best of our knowledge, our case is the second case of basal encephalocele and orbital dystopia. PMID:22801176

Hwang, Kun; Kim, Han Joon

2012-07-01

95

Hyperbolic Orbits in the EDMOND  

NASA Astrophysics Data System (ADS)

The present work is based on an analysis of 83369 meteor orbits collected in the European video meteor network database - EDMOND (Kornoš et al. 2013a), 5.7% of which have orbits determined as hyperbolic. Among them, we searched for gravitationally accelerated meteoroids. The investigation showed that only 8 meteoroids from all 4712 hyperbolic orbits had close encounters with one of the major planets, giving a proportion of only 0.0017 of all hyperbolic orbits. However, for none of these 8 meteoroids did the integration procedure show significant changes in their orbits; thus, the close encounters did not cause their hyperbolicity. Indeed, our analysis showed that erroneous determinations of the heliocentric velocity is responsible for the vast majority of hyperbolic orbits among the detected meteors in the EDMOND.

Hajduková, M., Jr.; Kornoš, L.; Tóth, J.

2014-07-01

96

Examination of a constrained three-impulse trajectory between low planetary orbits and circulating orbits  

Microsoft Academic Search

Circulating orbits have been investigated to provide regular periodic transfers between the Earth and Mars. The circulating orbits pass close enough to each planet to be considered hyperbolic in planetocentric frame. The large spacecraft in the circulating orbit is resupplied by a smaller 'Taxi' spacecraft leaving a low planetary orbit. The Taxi follows a three-impulse patched-conic trajectory to travel from

Andrew J. Knoedler

1992-01-01

97

Dexterous and expedient approach strategies considering non-zero eccentricity orbits and J2 perturbations  

NASA Astrophysics Data System (ADS)

Recently bio-inspired rendezvous strategies have been investigated for applications in space situation awareness. Particularly, closed-loop solutions have been developed for the cases that the target object is in a circular orbit without considering any orbital perturbations. In this paper, the minimum-fuel consumption bio-inspired motions are further studied. The follow cases considering the J2 perturbation, the non-zero eccentricities, and different boundary conditions are analyzed: (1) the target object is at the local vertical local horizontal coordinate origin; (2) the target is moving in the local vertical local horizontal coordinate; (3) the rendezvous object approaches the target object from the R-bar, V-bar, and Z-bar directions, respectively. Fast solutions can be obtained for the rendezvous object to approach the target object with minimum energy consumption.

Remeikas, Charles; Xu, Yunjun; Pham, Khanh; Chen, Genshe; Jia, Bin; Shen, Dan

2014-06-01

98

[Orbital inflammation].  

PubMed

Orbital inflammation is a generic term encompassing inflammatory pathologies affecting all structures within the orbit : anterior (involvement up to the posterior aspect of the globe), diffuse (involvement of intra- and/or extraconal fat), apical (involvement of the posterior orbit), myositis (involvement of only the extraocular muscles), dacryoadenitis (involvement of the lacrimal gland). We distinguish between specific inflammation and non-specific inflammation, commonly referred to as idiopathic inflammation. Specific orbital inflammation corresponds to a secondary localization of a "generalized" disease (systemic or auto-immune). Idiopathic orbital inflammation corresponds to uniquely orbital inflammation without generalized disease, and thus an unknown etiology. At the top of the differential diagnosis for specific or idiopathic orbital inflammation are malignant tumors, represented most commonly in the adult by lympho-proliferative syndromes and metastases. Treatment of specific orbital inflammation begins with treatment of the underlying disease. For idiopathic orbital inflammation, treatment (most often corticosteroids) is indicated above all in cases of visual loss due to optic neuropathy, in the presence of pain or oculomotor palsy. PMID:25455557

Mouriaux, F; Coffin-Pichonnet, S; Robert, P-Y; Abad, S; Martin-Silva, N

2014-12-01

99

Elliptical Orbits  

NSDL National Science Digital Library

This resource provides a textual explanation as well as animated illustration of elliptical orbits with different eccentricities. It also shows how the Sun is at the focus of an ellipse, and some of the math behind elliptical orbits. Beginner, intermediate and advanced versions of the content are available.

Roberta Johnson

2000-07-01

100

Orbital dynamics of three-dimensional bars - IV. Boxy isophotes in face-on views  

Microsoft Academic Search

We study the conditions that favour boxiness of isodensities in the face-on views of orbital 3D models for barred galaxies. Using orbital weighted profiles we show that boxiness is in general a composite effect that appears when one considers stable orbits belonging to several families of periodic orbits. 3D orbits that are introduced due to vertical instabilities play a crucial

P. A. Patsis; Ch. Skokos; E. Athanassoula

2003-01-01

101

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

102

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. PMID:22346113

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

2012-01-01

103

Orbital Myiasis  

PubMed Central

Purpose To present a case of massive orbital myiasis. Case Report An 87-year-old debilitated woman suffering from left ocular pain of four days’ duration presented with a severely necrotized left orbit and several attached live larvae. The upper and lower eyelids and the eyeball were completely destroyed. She had history of eyelid surgery in the same eye due to a skin lesion, apparently some type of skin cancer, 15 years before. The larvae were identified as Chrysomya bezziana (Diptera: Calliphoridae) or old world screwworm fly. Conclusion Infestation of ocular and orbital tissues by fly larvae (ophthalmomyiasis) progresses rapidly and can completely destroy orbital tissues within days, especially in patients with poor general health. Treatment consists of removal of the larvae and surgical debridement. PMID:22454736

Khataminia, Gholamreza; Aghajanzadeh, Roja; Vazirianzadeh, Babak; Rahdar, Mahmoud

2011-01-01

104

Head-position-dependent Adaptation of Nonconcomitant Vertical Skew  

Microsoft Academic Search

Vertical phoria can be trained to vary with either head position or orbital eye position. The present experiments show that subjects can simultaneously adapt their eye-position-specific (nonconcomi- tant) vertical phorias in different directions at different head positions. Eye-position-dependent and head-position-dependent adaptive pathways, therefore, are not independent. Rather, the adaptation of vertical skew takes into account both eye and head position.

JAMES S. MAXWELL; CLIFTON M. SCHOR

105

Head-position-dependent Adaptation of Nonconcomitant Vertical Skew  

Microsoft Academic Search

Vertical phoria can be trained to vary with either head position or orbital eye position. The present experiments show that subjects can simultaneously adapt their eye-position-specific (nonconcomitant) vertical phorias in different directions at different head positions. Eye-position-dependent and head-position-dependent adaptive pathways, therefore, are not independent. Rather, the adaptation of vertical skew takes into account both eye and head position. In

JAMES S MAXWELL; CLIFTON M SCHOR

1997-01-01

106

Orbital Debris  

NASA Technical Reports Server (NTRS)

Earth orbital debris issues and recommended future activities are discussed. The workshop addressed the areas of environment definition, hazards to spacecraft, and space object management. It concluded that orbital debris is a potential problem for future space operations. However, before recommending any major efforts to control the environment, more data are required. The most significant required data are on the population of debris smaller than 4 cm in diameter. New damage criteria are also required. When these data are obtained, they can be combined with hypervelocity data to evaluate the hazards to future spacecraft. After these hazards are understood, then techniques to control the environment can be evaluated.

Kessler, D. J. (compiler); Su, S. Y. (compiler)

1985-01-01

107

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

108

Configuration interaction singles natural orbitals: an orbital basis for an efficient and size intensive multireference description of electronic excited states.  

PubMed

Multireference quantum chemical methods, such as the complete active space self-consistent field (CASSCF) method, have long been the state of the art for computing regions of potential energy surfaces (PESs) where complex, multiconfigurational wavefunctions are required, such as near conical intersections. Herein, we present a computationally efficient alternative to the widely used CASSCF method based on a complete active space configuration interaction (CASCI) expansion built from the state-averaged natural orbitals of configuration interaction singles calculations (CISNOs). This CISNO-CASCI approach is shown to predict vertical excitation energies of molecules with closed-shell ground states similar to those predicted by state averaged (SA)-CASSCF in many cases and to provide an excellent reference for a perturbative treatment of dynamic electron correlation. Absolute energies computed at the CISNO-CASCI level are found to be variationally superior, on average, to other CASCI methods. Unlike SA-CASSCF, CISNO-CASCI provides vertical excitation energies which are both size intensive and size consistent, thus suggesting that CISNO-CASCI would be preferable to SA-CASSCF for the study of systems with multiple excitable centers. The fact that SA-CASSCF and some other CASCI methods do not provide a size intensive/consistent description of excited states is attributed to changes in the orbitals that occur upon introduction of non-interacting subsystems. Finally, CISNO-CASCI is found to provide a suitable description of the PES surrounding a biradicaloid conical intersection in ethylene. PMID:25591333

Shu, Yinan; Hohenstein, Edward G; Levine, Benjamin G

2015-01-14

109

Configuration interaction singles natural orbitals: An orbital basis for an efficient and size intensive multireference description of electronic excited states  

NASA Astrophysics Data System (ADS)

Multireference quantum chemical methods, such as the complete active space self-consistent field (CASSCF) method, have long been the state of the art for computing regions of potential energy surfaces (PESs) where complex, multiconfigurational wavefunctions are required, such as near conical intersections. Herein, we present a computationally efficient alternative to the widely used CASSCF method based on a complete active space configuration interaction (CASCI) expansion built from the state-averaged natural orbitals of configuration interaction singles calculations (CISNOs). This CISNO-CASCI approach is shown to predict vertical excitation energies of molecules with closed-shell ground states similar to those predicted by state averaged (SA)-CASSCF in many cases and to provide an excellent reference for a perturbative treatment of dynamic electron correlation. Absolute energies computed at the CISNO-CASCI level are found to be variationally superior, on average, to other CASCI methods. Unlike SA-CASSCF, CISNO-CASCI provides vertical excitation energies which are both size intensive and size consistent, thus suggesting that CISNO-CASCI would be preferable to SA-CASSCF for the study of systems with multiple excitable centers. The fact that SA-CASSCF and some other CASCI methods do not provide a size intensive/consistent description of excited states is attributed to changes in the orbitals that occur upon introduction of non-interacting subsystems. Finally, CISNO-CASCI is found to provide a suitable description of the PES surrounding a biradicaloid conical intersection in ethylene.

Shu, Yinan; Hohenstein, Edward G.; Levine, Benjamin G.

2015-01-01

110

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

Michael Horton

2009-05-30

111

Orbital Surgery  

MedlinePLUS

The orbit is the boney socket in your skull that contains and houses the eye and all the associated structures that support the function of the eye ... variety of problems can occur in the eye socket that effect the function of the eye. These ...

112

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!"

113

Analysis of KEK-ATF optics and coupling using orbit response matrix analysis  

SciTech Connect

LOCO is a code for analysis of the linear optics in a storage ring based on the closed orbit response to steering magnets. The analysis provides information on focusing errors, BPM gain and rotation errors, and local coupling. Here, we report the results of an application of LOCO to the KEK-ATF. Although the analysis appears to have provided useful information on the optics of the machine, it appears that one of the main aims of the study--to reduce the vertical emittance by correcting the local coupling--was not successful, and we discuss some possible reasons for this.

Wolski, A.; /LBL, Berkeley; Nelson, J.; Ross, M.; Woodley, M.; /SLAC; Mishra, S.; /Fermilab

2004-01-01

114

Analysis of KEK-ATF Optics And Coupling Using Orbit Response Matrix Analysis  

SciTech Connect

LOCO is a code for analysis of the linear optics in a storage ring based on the closed orbit response to steering magnets. The analysis provides information on focusing errors, BPM gain and rotation errors, and local coupling. Here, we report the results of an application of LOCO to the KEK-ATF. Although the analysis appears to have provided useful information on the optics of the machine, it appears that one of the main aims of the study--to reduce the vertical emittance by correcting the local coupling--was not successful, and we discuss some possible reasons for this.

Wolski, A.; /LBL, Berkeley; Nelson, J.; Ross, M.; Woodley, M.; /SLAC; Mishra, S.; /Fermilab

2006-10-13

115

Orbit Correction for the Newly Developed Polarization-Switching Undulator  

SciTech Connect

A new scheme of undulator magnet arrangements has been proposed and developed as a polarization-switching radiation source, and its test-stand was installed in the 2.5-GeV Photon Factory storage ring (PF ring) in order to investigate the effects on the beam orbit. The closed orbit distortion (COD) over 200 {mu}m was produced in a vertical direction when we switched the polarization of the radiation from the test-stand. In a horizontal direction, the COD was less than 50{mu}m. The results agreed well with the predictions from the magnetic-field measurement on the bench. In order to suppress the CODs and realize a stable operation of the ring with the polarization-switching, we developed an orbit correction system which consists of an encoder to detect motion of magnets, a pair of beam position monitors (BPMs), signal processing parts, and a pair of steering magnets. We succeeded in suppressing the CODs to the level below 3{mu}m using the system even when we switch the polarization at a maximum frequency of 0.8 Hz.

Obina, Takashi; Honda, Tohru; Shioya, Tatsuro; Kobayashi, Yukinori; Tsuchiya, Kimichika [Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Yamamoto, Shigeru [Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Department of Photoscience, Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa 240-0193 (Japan)

2007-01-19

116

Eye and orbit ultrasound  

MedlinePLUS

Echography - eye orbit; Ultrasound - eye orbit; Ocular ultrasonography; Orbital ultrasonography ... eye is numbed with medicine (anesthetic drops). The ultrasound wand (transducer) is placed against the front surface ...

117

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 ...

Mrs. Hicken

2009-10-19

118

Achieving Orbit  

NSDL National Science Digital Library

In this Engineering Design Challenge activity, participants use balloons to investigate how a two-stage rocket, like that used in the IBEX mission, can propel a satellite to a specific orbit. Participants will construct a two-stage balloon that will be required to reach a particular location on the balloon track, simulating the proper orbit to be reached by the IBEX satellite. This activity is adapted from the NASA Rockets Educators Guide (EG-2003-01-108-HQ) and the NASA Glenn Research Center’s online Learning Technologies Project for facilitation with an informal museum audience. Each short activity/product helps to build awareness and engagement in the science and engineering aspects of the mission that is reinforced as visitors choose to participate in more activities, including viewing the planetarium show and mission Web site.

Michelle Nichols

2008-01-15

119

Vertical Map Storage.  

ERIC Educational Resources Information Center

Discusses the superiority of vertical filing of maps in compressor-style vertical units over horizontal filing in drawers, emphasizing such factors as physical protection of the collection, ease of filing and retrieval, and efficient use of space. Disadvantages of vertical filing are also reviewed. (Author/JL)

Perry, Joanne M.

1982-01-01

120

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

121

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 ...

122

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

2011-03-08

123

Artist's Concept of Mars Reconnaissance Orbiter  

NASA Technical Reports Server (NTRS)

NASA's Mars Reconnaissance Orbiter, depicted above Mars in this artist's concept illustration, is scheduled for launch in 2005. The orbiter will carry cameras to zoom in for extreme close-up photography of the martian surface, use a sounder to find subsurface water and look for safe and scientifically worthy landing sites for future exploration.

2003-01-01

124

Orbital Analysis for Near-Earth Objects  

NASA Technical Reports Server (NTRS)

For recently discovered Near-Earth Objects (NEO) two body computations can be used to determine the minimum distance between the object's orbit and that of the Earth. Determinations can then be made for potential near-term threats to the Earth. This preliminary orbit analysis must be followed with planetary perturbation computations of the object's future motion to predict actual close Earth approaches.

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

1995-01-01

125

Orbit analysis  

SciTech Connect

The past fifteen years have witnessed a remarkable development of methods for analyzing single particle orbit dynamics in accelerators. Unlike their more classic counterparts, which act upon differential equations, these methods proceed by manipulating Poincare maps directly. This attribute makes them well matched for studying accelerators whose physics is most naturally modelled in terms of maps, an observation that has been championed most vigorously by Forest. In the following sections the author sketchs a little background, explains some of the physics underlying these techniques, and discusses the best computing strategy for implementing them in conjunction with modeling accelerators.

Michelotti, L.

1995-01-01

126

Everything in OrbitEverything in Orbit Orbital VelocityOrbital Velocity  

E-print Network

is the speed at which a planetary body moves in Orbital velocity is the speed at which a planetary body moves Escape velocity = "speed required to project a body completely Escape velocity = "speed requiredEverything in OrbitEverything in Orbit #12;Orbital VelocityOrbital Velocity Orbital velocity

Herrick, Robert R.

127

Rock-Around Orbits  

E-print Network

; !). Using these parameters, one can create an orbit that will surround the target orbit allowing the satellite in the Rock-Around Orbit (RAO) orbit to have a 360 degree view of RSOs in the target orbit. The RAO orbit can be applied to any circular...

Bourgeois, Scott K.

2010-07-14

128

Pioneer probe mission with orbiter option  

NASA Technical Reports Server (NTRS)

A spacecraft is described which is based on Pioneer 10 and 11, and existing propulsion technology; it can transport and release a probe for entry into Jupiter's atmosphere, and subsequently maneuver to place the spacecraft in orbit about Jupiter. Orbital operations last 3 years and include maneuvers to provide multiple close satellite encounters which allow the orbit to be significantly changed to explore different parts of the magnetosphere. A mission summary, a guide to related documents, and background information about Jupiter are presented along with mission analysis over the complete mission profile. Other topics discussed include the launch, interplanetary flight, probe release and orbit deflection, probe entry, orbit selection, orbit insertion, periapsis raising, spacecraft description, and the effects of Jupiter's radiation belt on both orbiter and the probe.

1975-01-01

129

Venus Orbital Imaging Radar mission analysis  

NASA Technical Reports Server (NTRS)

Mission objectives for the Venus Orbital Imaging Radar (VOIR) project are outlined with attention to its scientific instrumentation. Design parameters of the SAR (Synthetic Aperture Radar) are described, including a high resolution capability of 200 m from a circular orbit of 375 km, which will be able to map the entire surface of the planet. Nineteen atmospheric experiments are foreseen, among them: CO2 stability assays, measurements of vertical mass transfer rates, observations of cloud circulation and composition, and an evaluation of solar wind effects on atmospheric dynamics. Navigation and orbital injection plans are reviewed, noting that the 1983 launch window (using STS) is optimum.

Nock, K. T.; Bender, D. F.

1977-01-01

130

Vertical and horizontal transport of the Australian Black Saturday bushfire plume in the stratosphere (Invited)  

NASA Astrophysics Data System (ADS)

The Australian Black Saturday bushfire on February 7, 2009 resulted in the injection of a significant amount of plume material into the stratosphere. We study the vertical and horizontal transport of this bushfire plume at altitudes above 14 km with the Optical Spectrograph and Infrared Imager System (OSIRIS) instrument on the polar orbiting Odin satellite. OSIRIS measures the limb-scattered solar radiance in the wavelength range 280-810 nm with the spectral resolution of about 1 nm. As Odin makes 15 orbits per day and typically covers the latitude range from 82.2 N to 82.2 S, the global daily maps of limb-scattered spectral radiances at various altitudes can be created. The OSIRIS radiances around 800 nm (a spectral region of the highest Rayleigh-aerosol scattering contrast) measured with nearly 2 km vertical step are used to infer the location and strength of the bushfire plume with respect to the background radiances. According to our analysis, the plume has reached the altitudes of 14-16 km on February 11th, gradually moved upwards to 19-23 km in the next 10 days, and remained closely confined at these altitudes until at least the end of March. The plume density, proportional to the measured intensity of the limb-scattered radiance at its peak, remained at nearly same level during February and did not decrease significantly during March. After reaching New Zealand on February 11-12th, the plume has moved westward and almost circled the Earth by the end of March, being confined to latitudes of 10-30 degrees S. Interestingly, the vertical distribution of the plume material did not exceed 4-5 km at any time during the February 11 - March 26 period. Using the radiance measurements at various OSIRIS wavelengths, we retrieve the Angström exponent at the plume peak and estimate the vertical distribution and time evolution of aerosol particles sizes inside the plume.

Petelina, S. V.; Siddaway, J. M.

2009-12-01

131

General view of the mid deck of the Orbiter Discovery ...  

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

General view of the mid deck of the Orbiter Discovery during pre-launch preparations. Note the payload and mission specialists seats. The seats are removed packed and stowed during on-orbit activities. Also not the black panels in the right of the image, they are protective panels used for preparation of the orbiter and astronaut ingress while the orbiter is in its vertical launch position. This image was taken at Kenney Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

132

Offset vertical radar profiling  

USGS Publications Warehouse

Diffraction tomography imaging was applied to VRP data acquired by vertically moving a receiving antenna in a number of wells. This procedure simulated a vertical downhole receiver array. Similarly, a transmitting antenna was sequentially moved along a series of radial lines extending outward from the receiver wells. This provided a sequence of multistatic data sets and, from each data set, a two-dimensional vertical cross-sectional image of spatial variations in wave speed was reconstructed.

Witten, A.; Lane, J.

2003-01-01

133

Orbital evolution modeling of Damocloides  

NASA Astrophysics Data System (ADS)

In this paper we performed the task of orbital evolution modeling for 93 currently known Damocloids, 1 Gyr backward and forward in time, using the integration package SWIFTER. The package includes seven integration technics. We choosed the SyMBA integrator (Symplectic Massive Body Algorithm), which allows to handle close approaches between test particles and planets. We included the Sun, the eight planets, and Pluto as massive bodies in our simulation. The initial state vectors for test particles and planets were taken from HORIZONS JPL service. The timestep of integration was 7.305 days. The calculations were stopped when the particle reached heliocentric distance 5000 AU. The value is close to the inner boundary of the Oort cloud. It is shown, that dynamical lifetime of the population is about 1-10 myr. We present the Damocloids orbital parameters distributions and discuss the results of the simulation for Damocloids inclinations changes with time. Our results show that the dynamic lifetime of Damocloids population is about 106-107 years. Population of Damocloids retains highly inclined orbits during the integration time into the past and into the future. Thus, the population of Damocloids may indeed represent the dynamical relationship of comets on inclined orbits (Halley-type comets) with a hypothetical spherical Oort Cloud. Some of evolutionary tracks allow transition from retrograde motion to direct and vice versa (e.g.Dioretsa asteroid (20461)). However, for large periods of time, due to close encounters with the giant planets, the simulation results should be considered only statistically.

Guliyev, Rustam; Churyumov, Klim; Kovalenko, Nataliya

134

General view of the "bottom" side of the Orbiter Discovery ...  

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

General view of the "bottom" side of the Orbiter Discovery as it is being hoisted in a vertical position in the transfer aisle of the Vehicle Assembly Building at Kennedy Space Center - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

135

General view of the "top" side of the Orbiter Discovery ...  

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

General view of the "top" side of the Orbiter Discovery as it is being hoisted in a vertical position in the transfer aisle of the Vehicle Assembly Building at Kennedy Space Center - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

136

Orbital and epicyclic frequencies of Maclaurin spheroids  

NASA Astrophysics Data System (ADS)

We present analytical formulae for the orbital and epicyclic frequencies in orbits around Maclaurin spheroids in Newtonian gravity. The Laplace equation for the gravitational potential implies that the orbital frequency squared is the arithmetic mean of the squares of the epicyclic frequencies, ? _r^2 + ? _z^2 = 2? _o^2. The radial epicyclic frequency has a maximum at radius r=?{2}ae for spheroid ellipticities e>1/?{2}, while for e = 0.834 583 18 it vanishes at the stellar equator (at r = a). For still larger ellipticities the innermost stable circular orbit (ISCO) is separated from the surface of the spheroid by a gap and has radius rms = 1.198 203 ae. The vertical epicyclic frequency is always larger than the orbital one, and always by a factor of ?{2} in the marginally stable orbit. The presence of periastron motion, nodal precession (whose sense is the same as in retrograde orbits in the Kerr metric) and of the ISCO makes the properties of orbital motion around Maclaurin spheroids analogous to those in the Kerr metric. We find that the condition for the existence of circular orbits in test-particle motion is ? _r^2 + ? _z^2 >0, equally for the Maclaurin spheroid and for the Kerr metric.

Klu?niak, W.; Rosi?ska, D.

2013-10-01

137

A Simple Vertical Slab Gel Electrophoresis Apparatus.  

ERIC Educational Resources Information Center

Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

Carter, J. B.; And Others

1983-01-01

138

Stability analysis of the orbits of control systems  

Microsoft Academic Search

Extensive research in nonlinear system theory in recent years has shown that a number of system theoretic questions are closely related to the behaviour of the (controllability) orbits of the system. Thus orbit minimality, namely the property of the system having its state space identical to one orbit, arises naturally when dealing with controllability questions. This paper is concerned with

N. Kalouptsidis; D. L. Elliott

1981-01-01

139

ACM99 SPECIAL ISSUE Asteroid Close Encounters with Earth  

E-print Network

ACM99 SPECIAL ISSUE Asteroid Close Encounters with Earth: Risk Assessment Andrea Milani, Steven R. Chesley \\Lambda and Giovanni B. Valsecchi y Abstract When an asteroid with an orbit close to the Earth. The first approach could change the orbital period in such a way that the asteroid is injected into a reso

Milani, Andrea

140

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.

141

ISAL experiment documentation of vertical tail and OMS pods  

NASA Technical Reports Server (NTRS)

Investigation of Space Transportation System (STS) Atmospheric Luminosities (ISAL) experiment documentation includes vertical tail and orbital maneuvering system (OMS) pods with surface glow against the blackness of space. This glowing scene was provided by a long duration exposure with a 35mm camera aimed toward the tail of the Earth-orbiting Challenger, Orbiter Vehicle (OV) 099. OV-099 was maneuvered to a 120-nautical-mile altitude and flown with open payload bay (PLB) in the velocity vector for the conducting of a test titled, 'Evaluation of Oxygen Interaction with Materials (EOIM)'. Atomic oxygen within the low orbital environment is known to be extremely reactive when in contact with solid surfaces. In the darkened area between the camera and the glowing OMS pods and vertical stabilizer are two trays of test materials.

1983-01-01

142

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).

143

Orbital resonances in exoplanetary systems  

NASA Astrophysics Data System (ADS)

At present, more than 700 exoplanetary systems are known to have been discovered. They incorporate more than 130 multiplanet systems, i.e. those hosting two or more planets. The orbital resonance and near-resonance phenomena are ubiquitous in them. We present a statistical and dynamical analysis of the resonance structure of the multiplanet systems and planetary systems of binary stars. We have built distributions of the orbital period ratios, separately considering the cases of inner and outer location of the massive perturber. The histograms reveal apparent peaks close to the first order orbital resonances 2/1 and 3/2 in both cases; this confirms previous findings. We have performed analytical modelling of the histograms, and obtained exact positions of the peaks. Moreover, we have built the "period ratio – eccentricity" diagrams, with collision curves superimposed, so that to find anomalous systems.

Popova, E. A.; Shevchenko, I. I.

2014-12-01

144

Orbital tumors: operative and therapeutic strategies.  

PubMed

The term "orbital tumors" includes diverse benign or malignant space-occupying lesions of the orbit, often leading to dystopia of the eyeball, motility disturbances, diplopia, visual field defects, and sometimes a complete loss of vision. Removing these tumors in a limited surgical field is challenging. Therefore, the preservation of function is a primary concern. We retrospectively reviewed 671 patients with orbital tumors from October 1999 to June 2014. Diagnosis on referral, presenting symptoms, radiological records, histology of the primary tumor or orbital metastasis, and treatment choice were analyzed. Among the 671 orbital tumors, 40% were accessed anteriorly, 36% via an orbitotomy with temporary osteotomy, and 23.9% underwent an orbital exenteration. As an illustration of the operative strategies with subsequent reconstructions, a distinction was made among the main indication groups: (1) function-preserving therapy for retrobulbar tumors, (2) malignant tumors of the conjunctiva and the eyelids, (3) exenteration of the orbit and subsequent reconstruction, and (4) operative and therapeutic strategy for orbital metastases. Adequate preoperative use of modern imaging techniques and thorough planning of the operation are crucial. Accurate histopathological diagnosis is crucial for planning appropriate therapeutic and surgical interventions. New innovative treatment concepts and surgical techniques arise from the close cooperation of related disciplines such as ophthalmology and neurosurgery. Although an orbital exenteration in patients with eyelid and conjunctival carcinomas can now often be avoided, eye-preserving treatment for locally advanced carcinomas of the conjunctiva and eyelid must be attempted. For extensive orbital malignancies, orbital exenteration is curative. In this context, primary closure of the orbit can improve the patient's quality of life and avoid subsequent complications. Concerning orbital metastasis, early diagnosis can preserve function and fulfil the esthetic demands of the patients. In palliative tumor disease, operative procedures such as orbital decompression or tumor debulking can reduce patient complaints and contribute to improved quality of life. PMID:25397713

Pförtner, R; Mohr, C; Daamen, J; Metz, A

2014-10-01

145

Orbital evolution. [of large natural satellite  

NASA Technical Reports Server (NTRS)

The orbital evolution of a large satellite is governed primarily by tidal interactions between the satellite and the planet it orbits. Tides raised on a planet by a satellite transfer energy and angular momentum to the satellite orbit; this changes the semimajor axes of satellite orbits, increasing the size of those orbits where the satellite mean motion is smaller than the planetary angular velocity, and decreasing those where the opposite is true. Substantial changes caused by such tides for satellites of the terrestrial planets may explain the absence of satellites about Mercury and Venus. For Jovian and Saturnian satellites, such tides probably are only important in bringing about some of the observed orbital resonances. Tides raised on satellites generally cause decreasing orbital eccentricities, indicating why close satellites always have nearly circular orbits. Different processes of orbital evolution dominate for small bodies; their effects probably are critical in positioning material in the primordial dust cloud so that satellite coagulation may occur. A qualitative description is given of the orbital results of gas drag, radiation pressure, Poynting-Robertson drag and electromagnetic forces.

Burns, J. A.

1977-01-01

146

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.

2011-05-24

147

A vertical microfluidic probe.  

PubMed

Performing localized chemical events on surfaces is critical for numerous applications. We earlier invented the microfluidic probe (MFP), which circumvented the need to process samples in closed microchannels by hydrodynamically confining liquids that performed chemistries on surfaces (Juncker et al. Nat. Mater. 2005, 4, 622-628). Here we present a new and versatile probe, the vertical MFP (vMFP), which operates in the scanning mode while overcoming earlier challenges that limited the practical implementation of the MFP technology. The key component of the vMFP is the head, a microfluidic device (?1 cm(2) in area) consisting of glass and Si and having microfluidic features fabricated in-plane in the Si layer. The base configuration of the head has two micrometer-size channels that inject/aspirate liquids and terminate at the apex which is ?1 mm(2). In scanning mode, the head is oriented vertically with the apex parallel to the surface with typical spacing of 1-30 ?m. Such length scales and using flow rates from nanoliters/second to microliters/second allow chemical events to be performed on surfaces with tens of picoliter quantities of reagents. Before scanning, the head is clipped on a holder for leak-free, low dead volume interface assembly, providing a simple world-to-chip interface. Surfaces are scanned by mounting the holder on a computer-controlled stage having ?0.1 ?m resolution in positioning. We present detailed steps to fabricate vMFP heads having channels with dimensions from 1 ?m × 1 ?m to 50 ?m × 50 ?m for liquid localization over areas of 10-10,000 ?m(2). Additionally, advanced design strategies are described to achieve high yield in fabrication and to support a broad range of applications. These include particulate filters, redundant aperture architectures, inclined flow-paths that service apertures, and multiple channels to enable symmetric flow confinement. We also present a method to characterize flow confinement and estimate the distance between the head and the surface by monitoring the evolution of a solution of fluorescently labeled antibody on an activated glass surface. This flow characterization reveals regimes of operation suitable for different surface topographies. We further integrate the dispensing of immersion liquid to the vMFP head for processing surfaces for extended periods of time (?60 min). The versatility of the vMFP is exemplified by patterning fluorescently labeled proteins, inactivation of cells using sodium hypochlorite, and staining living NIH fibroblasts with Cellomics. These applications are enabled by the compact design of the head, which provides easy access to the surface, simplifies alignment, and enables processing surfaces having dimensions from the micrometer to the centimeter scale and with large topographical variations. We therefore believe that ease-of-operation, reconfigurability, and conservative use of chemicals by the vMFP will lead to its widespread use by microtechnologists and the chemical and biomedical communities. PMID:21476506

Kaigala, G V; Lovchik, R D; Drechsler, U; Delamarche, E

2011-05-01

148

Mars Orbiter Most Likely Lost  

NSDL National Science Digital Library

In an embarrassing setback to NASA, the Mars Climate Orbiter is believed lost. In the early hours of September 23, the orbiter fired its main engine to go in orbit around Mars and passed behind the planet, losing radio contact as planned. However, due to what was most likely a navigation error, the spacecraft did not resume contact and may have flown too close to the atmosphere and broken apart or burned up. The relatively inexpensive ($125 million) Climate Orbiter was launched in December 1998 to become the first interplanetary weather satellite, studying Martian weather for one Mars year (about two Earth years). It was also to serve as a relay station for five years, relaying information to and from the Mars Polar Lander, due to land on December 3, 1999. NASA, however, insists that the Polar Lander's mission can be accomplished independently and "the science return of that mission won't be affected." The sites listed provide information about Mars Climate Orbiter and its possible loss.

de Nie, Michael Willem.

149

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

150

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

151

PROTOTYPING LHC ORBIT CONTROL  

Microsoft Academic Search

Orbit correction consists in varying the strengths of the corrector magnets to make the measured beam position match a predefined reference. In the two LHC rings, this involves around 1000 beam position monitors and over 500 orbit correctors in each plane. The orbit control loop of the LHC must be able to compensate orbit drifts at frequencies between 10?2 and

J. Wenninger; T. Wijnands; B. Srinivasan

2002-01-01

152

Orbital dystopia due to orbital roof defect.  

PubMed

We performed a retrospective review of patients who presented with delayed dystopia as a consequence of an orbital roof defect due to fractures and nontraumatic causes to search for a correlation between orbital roof defect size and surgical indications for the treatment thereof. Retrospective analyses were performed in 7 patients, all of whom presented with delayed dystopia due to orbital roof defects, between January 2001 and June 2011. The causes of orbital roof defects were displaced orbital roof fractures (5 cases), tumor (1 case), and congenital sphenoid dysplasia (1 case). All 7 patients had initially been treated conservatively and later presented with significant dystopia. The sizes of the defects were calculated on computed tomographic scans. Among the 7 patients, aspiration of cerebrospinal fluid, which caused ocular symptoms, in 1 patient with minimal displaced orbital roof and reconstruction with calvarial bone, titanium micromesh, or Medpor in 6 other patients were performed. The minimal size of the orbital roof in patients who underwent orbital roof reconstruction was 1.2 cm (defect height) x 1.0 cm (defect length), 0.94 cm(2). For all patients with orbital dystopia, displacement of the globe was corrected without any complications, regardless of whether the patient was evaluated grossly or by radiology. In this retrospective study, continuous monitoring of clinical signs and active surgical management should be considered for cases in which an orbital roof defect is detected, even if no definite symptoms are noted, to prevent delayed sequelae. PMID:24163861

Rha, Eun Young; Joo, Hong Sil; Byeon, Jun Hee

2013-01-01

153

Stable low-altitude orbits around Ganymede considering a disturbing body in a circular orbit  

NASA Astrophysics Data System (ADS)

Some missions are being planned to visit Ganymede like the Europa Jupiter System Mission that is a cooperation between NASA and ESA to insert the spacecraft JGO (Jupiter Ganymede Orbiter) into Ganymedes orbit. This comprehension of the dynamics of these orbits around this planetary satellite is essential for the success of this type of mission. Thus, this work aims to perform a search for low-altitude orbits around Ganymede. An emphasis is given in polar orbits and it can be useful in the planning of space missions to be conducted around, with respect to the stability of orbits of artificial satellites. The study considers orbits of artificial satellites around Ganymede under the influence of the third-body (Jupiter's gravitational attraction) and the polygenic perturbations like those due to non-uniform distribution of mass (J_2 and J_3) of the main body. A simplified dynamic model for these perturbations is used. The Lagrange planetary equations are used to describe the orbital motion of the artificial satellite. The equations of motion are developed in closed form to avoid expansions in eccentricity and inclination. The results show the argument of pericenter circulating. However, low-altitude (100 and 150 km) polar orbits are stable. Another orbital elements behaved variating with small amplitudes. Thus, such orbits are convenient to be applied to future space missions to Ganymede. Acknowledgments: FAPESP (processes n° 2011/05671-5, 2012/12539-9 and 2012/21023-6).

Cardoso dos Santos, J.; Carvalho, J. P. S.; Vilhena de Moraes, R.

2014-10-01

154

Working With Orbits  

NSDL National Science Digital Library

This site offers two programs to illustrate how orbits work. The Orbital Elements calculator contains animations to see how the appearance of an orbit depends on the values of the orbital elements which include distance from the Sun, eccentricity, pericenter location and anomaly. This is available in two or three dimensions. The Solar System allows users to watch several planets in our Solar System simultaneously orbit the Sun. An additional object (asteroid or comet) is present and users change the orbital parameters to see what types of orbits are possible for this object.

Douglas Hamilton

155

Impact on Spin Tune From Horizontal Orbital Angle Between Snakes and Orbital Angle Between Spin Rotators  

SciTech Connect

To keep the spin tune in the spin depolarizing resonance free region is required for accelerating polarized protons to high energy. In RHIC, two snakes are located at the opposite side of each accelerator. They are configured to yield a spin tune of 1/2. Two pairs of spin rotators are located at either side of two detectors in each ring in RHIC to provide longitudinal polarization for the experiments. Since the spin rotation from vertical to longitudinal is localized between the two rotators, the spin rotators do not change the spin tune. However, due to the imperfection of the orbits around the snakes and rotators, the spin tune can be shifted. This note presents the impact of the horizontal orbital angle between the two snakes on the spin tune, as well as the effect of the vertical orbital angle between two rotators at either side of the collision point on the spin tune.

Bai,M.; Ptitsyn, V.; Roser, T.

2008-10-01

156

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

157

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

158

Orbital fractures: a review  

PubMed Central

This review of orbital fractures has three goals: 1) to understand the clinically relevant orbital anatomy with regard to periorbital trauma and orbital fractures, 2) to explain how to assess and examine a patient after periorbital trauma, and 3) to understand the medical and surgical management of orbital fractures. The article aims to summarize the evaluation and management of commonly encountered orbital fractures from the ophthalmologic perspective and to provide an overview for all practicing ophthalmologists and ophthalmologists in training. PMID:21339801

Joseph, Jeffrey M; Glavas, Ioannis P

2011-01-01

159

Closed-drift thruster investigations  

NASA Technical Reports Server (NTRS)

Recent data obtained from a second generation closed-drift thruster design, employing Hall current acceleration is outlined. This type device is emphasized for electric propulsion for geocentric mission applications. Because geocentric mission profiles are best achieved with a specific impulse range of 1000 to 2000 s, closed-drift thrusters are well suited for this application, permitting time payload compromises intermediate of those possible with either electrothermal or electrostatic devices. A discussion is presented of the potential advantages of using a 1000 to 2000 s device for one way orbit raising of nonpower payloads. Because closed-drift thruster operation is not space charge limited, and requires only one power circuit for steady state operation, their application is technically advantageous. Beam, plasma and thrust characteristics are detailed for a range of operating conditions.

Robinson, Raymond S.; Schemmel, Terry D.; Patterson, Michael J.

1986-01-01

160

Mars Observer trajectory and orbit control  

NASA Technical Reports Server (NTRS)

The Mars Observer mission will study Mars from a low-altitude orbit. During interplanetary cruise, propulsive maneuvers are required to ensure capture, with a secondary constraint to satisfy limits on the probability of impact with Mars. After capture, the spacecraft will be brought to a near-circular mapping orbit through a series of maneuvers. Mapping orbit maneuvers will be performed in order to follow a predetermined set of ground tracks and to maintain orbit altitude. This will allow accurate spacecraft command sequence generation and aid science planning throughout the mapping phase. Specific orbit control plans for the open and close of the launch period have been developed to meet these needs. This paper describes the control capabilities and the associated expected velocity changes for the mission.

Halsell, C. A.; Bollman, W. E.

1991-01-01

161

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

Results from operational OD produced by the NASA Goddard Flight Dynamics Facility for the LRO nominal and extended mission are presented. During the LRO nominal mission, when LRO flew in a low circular orbit, orbit determination requirements were met nearly 100% of the time. When the extended mission began, LRO returned to a more elliptical frozen orbit where gravity and other modeling errors caused numerous violations of mission accuracy requirements. Prediction accuracy is particularly challenged during periods when LRO is in full-Sun. A series of improvements to LRO orbit determination are presented, including implementation of new lunar gravity models, improved spacecraft solar radiation pressure modeling using a dynamic multi-plate area model, a shorter orbit determination arc length, and a constrained plane method for estimation. The analysis presented in this paper shows that updated lunar gravity models improved accuracy in the frozen orbit, and a multiplate dynamic area model improves prediction accuracy during full-Sun orbit periods. Implementation of a 36-hour tracking data arc and plane constraints during edge-on orbit geometry also provide benefits. A comparison of the operational solutions to precision orbit determination solutions shows agreement on a 100- to 250-meter level in definitive accuracy.

Slojkowski, Steven E.

2014-01-01

162

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.

163

W-reps, nilp orbits, orbit method  

E-print Network

W reps nilp orbits W reps Explaining the arrows Remembrance of things past Weyl group Institute of Technology Lie groups: structure, actions and representations In honor of Joe Wolf, on his 75th of things past Outline What is representation theory about? Nilpotent orbits from G reps W reps from G reps

Vogan, David

164

Efficient orbit integration by orbital longitude methods  

NASA Astrophysics Data System (ADS)

Recently we developed a new formulation of numerical integration of orbital motion named manifold correction methods. The main trick is to keep rigorously the consistency of some physical relations such as that of the orbital energy, of the orbital angular momentum, or of the Laplace integral of a binary subsystem. This maintenance is done by applying a sort of correction to the integrated variables at every integration step. Typical methods of correction are certain geometric transformation such as the spatial scaling and the spatial rotation, which are commonly used in the comparison of reference frames, or mathematically-reasonable operations such as the modularization of angle variables into the standard domain [-?, ?). The finally-evolved form of the manifold correction methods is the orbital longitude methods, which enable us to conduct an extremely precise integration of orbital motions. In the unperturbed orbits, the integration errors are suppressed at the machine epsilon level for an infinitely long period. In the perturbed cases, on the other hand, the errors initially grow in proportion to the square root of time and then increase more rapidly, the onset time of which depends on the type and the magnitude of perturbations. This feature is also realized for highly eccentric orbits by applying the same idea to the KS-regularization. Expecially the introduction of time element greatly enhances the performance of numerical integration of KS-regularized orbits whether the scaling is applied or not.

Fukushima, Toshio

165

Simple, Accurate, Approximate Orbits in the Logarithmic and a Range of Power-Law Galactic Potentials  

E-print Network

Curves in a family derived from powers of the polar coordinate formula for ellipses are found to provide good fits to bound orbits in a range of power-law potentials. This range includes the well-known $1/r$ (Keplerian) and logarithmic potentials. These approximate orbits, called p-ellipses, retain some of the basic geometric properties of ellipses. They satisfy and generalize Newton's apsidal precession formula, which is one of the reasons for their surprising accuracy. Because of their simplicity the p-ellipses make very useful tools for studying trends among power-law potentials, and especially the occurence of closed orbits. The occurence of closed or nearly closed orbits in different potentials highlights the possibility of period resonances between precessing, eccentric orbits and circular orbits, or between the precession period of multi-lobed closed orbits and satellite periods. These orbits and their resonances promise to help illuminate a number of problems in galaxy and accretion disk dynamics.

Curtis Struck

2005-12-09

166

Near Action-Degenerate Periodic-Orbit Bunches:. a Skeleton of Chaos  

NASA Astrophysics Data System (ADS)

Long periodic orbits of hyperbolic dynamics do not exist as independent individuals but rather come in closely packed bunches. Under weak resolution a bunch looks like a single orbit in configuration space, but close inspection reveals topological orbit-to-orbit differences. The construction principle of bunches involves close self-"encounters" of an orbit wherein two or more stretches stay close. A certain duality of encounters and the intervening "links" reveals an infinite hierarchical structure of orbit bunches. -- The orbit-to-orbit action differences ?S within a bunch can be arbitrarily small. Bunches with ?S of the order of Planck's constant have constructively interfering Feynman amplitudes for quantum observables, and this is why the classical bunching phenomenon could yield the semiclassical explanation of universal fluctuations in quantum spectra and transport.

Altland, A.; Braun, P.; Haake, F.; Heusler, S.; Knieper, G.; Müller, S.

2008-11-01

167

'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

168

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

169

Vertical Integration and Communication  

Microsoft Academic Search

Among the many possible motives for vertical integration, the one emphasized here is uncertainty in the supply of the upstream good and the consequent need for information by downstream firms. The basic conclusion is that, even when the initial conditions are of the type usually thought of as competitive, the upshot will be a tendency to imperfect competition.

Kenneth J. Arrow

1975-01-01

170

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

171

Relative Orbit Determination For Autonomous Close Formation Flying Spacecraft  

Microsoft Academic Search

Formation flying of multiple spacecrafts is an enabling technology for many future space missions. It allows a few small cost-effective satellites to offer capabilities that are only achievable with a much more expensive single satellite. While spacecraft formation flying provides many operational and performance advantages, it also poses many significant challenges in navigation, guidance, and control. One of the key

Ramin Tavvafi

2010-01-01

172

Dynamics on the cone: Closed orbits and superintegrability  

SciTech Connect

The generalization of Bertrand’s theorem to the case of the motion of point particle on the surface of a cone is presented. The superintegrability of such models is discussed. The additional integrals of motion are analysed for the case of Kepler and harmonic oscillator potentials. -- Highlights: •Bertrand’s theorem is generalized to the case of the motion on a cone. •The superintegrability of the dynamics on a cone is discussed. •The W-algebra of integrals of motion for Kepler and harmonic oscillator problems on a cone is derived.

Brihaye, Y. [Department of Theoretical and Mathematical Physics, University of Mons, 20, Place du Parc, B7000 Mons (Belgium); Kosi?ski, P., E-mail: pkosinsk@uni.lodz.pl [Department of Theoretical Physics and Computer Science, University of ?ód?, Pomorska 149/153, 90-236 ?ód? (Poland); Ma?lanka, P., E-mail: pmaslan@uni.lodz.pl [Department of Theoretical Physics and Computer Science, University of ?ód?, Pomorska 149/153, 90-236 ?ód? (Poland)

2014-05-15

173

Magnetically controlled mass loss from extrasolar planets in close orbits  

E-print Network

We consider the role magnetic fields play in guiding and controlling mass-loss via evaporative outflows from exoplanets that experience UV irradiation. First we present analytic results that account for planetary and stellar magnetic fields, along with mass-loss from both the star and planet. We then conduct series of numerical simulations for gas giant planets, and vary the planetary field strength, background stellar field strength, UV heating flux, and planet mass. These simulations show that the flow is magnetically controlled for moderate field strengths and even the highest UV fluxes, i.e., planetary surface fields $B_P\\gtrsim 0.3$ gauss and fluxes $F_{UV}\\sim10^{6}$ erg s$^{-1}$. We thus conclude that outflows from all hot Jupiters with moderate surface fields are magnetically controlled. The inclusion of magnetic fields highly suppresses outflow from the night-side of the planet. Only the magnetic field lines near the pole are open and allow outflow to occur. The fraction of open field lines depends s...

Owen, James E

2014-01-01

174

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.

175

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

176

THE RHIC ORBIT CONTROL  

Microsoft Academic Search

The paper describes the methods used at RHIC collider for both global orbit correction over the whole ring and lo- cal orbit control in particular regions. Most routinely used tools of the local orbit control include the beam separa- tion, to avoid beam-beam effects at the acceleration, and the beam steering for collisions. The correction on the ramp uses feed-forward

V. Ptitsyn; T. Satogata

177

Mars Reconnaissance Orbiter  

NSDL National Science Digital Library

This is the mission web site for the Mars Reconnaissance Orbiter, which went into orbit around Mars on March 10, 2006. The site provides links to updates and information about the project. The site features links to Mars Reconnaissance Orbiter images, animations, and datasets. Science operations commence in November, 2006.

Jet Propulsion Laboratory

178

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

179

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

180

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

181

Relativistic Hydrodynamics in Close Neutron Star Binaries  

Microsoft Academic Search

We discuss several new physical processes which occur in close neutron star binaries. These processes are purely relativistic effects which can be directly traced to terms in our formulation of general relativistic hydrodynamics. In addition to the well known orbit instability, we show that these systems may also be subject to relativistically induced compression, heating and collapse. The neutrino emission

G. J. Mathews; P. Marronetti; J. R. Wilson

1997-01-01

182

Tidal friction in close-in planets  

Microsoft Academic Search

We use Darwin's theory (Darwin, 1880) to derive the main results on the orbital and rotational evolution of a close-in companion (exoplanet or planetary satellite) due to tidal friction. The given results do not depend on any assumption linking the tidal lags to the frequencies of the corresponding tide harmonics (except that equal frequency harmonics are assumed to span equal

Adrián Rodríguez; Sylvio Ferraz-Mello; Hauke Hussmann

2008-01-01

183

Circular orbits in Einstein-Gauss-Bonnet gravity  

SciTech Connect

The stability under radial and vertical perturbations of circular orbits associated to particles orbiting a spherically symmetric center of attraction is studied in the context of the n-dimensional: the Newtonian theory of gravitation, Einstein's general relativity, and the Einstein-Gauss-Bonnet theory of gravitation. The presence of a cosmological constant is also considered. We find that this constant as well as the Gauss-Bonnet coupling constant are crucial to have stability for n>4.

Rosa, Valeria M.; Letelier, Patricio S. [Departamento de Matematica, Universidade Federal de Vicosa, 36570-000 Vicosa, M.G. (Brazil); Departamento de Matematica Aplicada-IMECC, Universidade Estadual de Campinas, 13083-970 Campinas, S.P. (Brazil)

2008-10-15

184

On leading spiral arms in close pairs of galaxies  

NASA Technical Reports Server (NTRS)

It is explained why one can observe a leading spiral pattern in close pairs of galaxies where the direction of the orbital momentum of the satellite is opposite to the direction of the spin of the spiral galaxy.

Fridman, A. M.

1990-01-01

185

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

186

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, 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 is used for these analyses.

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

1999-01-01

187

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

188

OTV orbital tanking systems  

NASA Technical Reports Server (NTRS)

Orbital transfer of cryogenic propellants could benefit spacecraft and Orbital Transfer Vehicle (OTV) missions in the 1980s by supplying main propulsion, attitude control, or other fluid systems. The Space Shuttle can operate as a tanker when equipped with cryogenic propellant storage and orbital transfer systems. The key technologies are multilayer insulation, capillary propellant acquisition, zero-g gaging, orbital chilldown, and possibly large flight weight dewars. The technologies and operations could be realistically demonstrated using a Centaur that has been integrated with the Shuttle. Orbital refueling capability can enhance the usefulness of the whole Shuttle program

Heald, D. A.; Merino, F.

1979-01-01

189

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

LRO definitive and predictive accuracy requirements were easily met in the nominal mission orbit, using the LP150Q lunar gravity model. center dot Accuracy of the LP150Q model is poorer in the extended mission elliptical orbit. center dot Later lunar gravity models, in particular GSFC-GRAIL-270, improve OD accuracy in the extended mission. center dot Implementation of a constrained plane when the orbit is within 45 degrees of the Earth-Moon line improves cross-track accuracy. center dot Prediction accuracy is still challenged during full-Sun periods due to coarse spacecraft area modeling - Implementation of a multi-plate area model with definitive attitude input can eliminate prediction violations. - The FDF is evaluating using analytic and predicted attitude modeling to improve full-Sun prediction accuracy. center dot Comparison of FDF ephemeris file to high-precision ephemeris files provides gross confirmation that overlap compares properly assess orbit accuracy.

Slojkowski, Steven E.

2014-01-01

190

Compound orbits break-up in constituents: an algorithm  

E-print Network

In this paper decomposition of periodic orbits in bifurcation diagrams are derived in unidimensional dynamics system $x_{n+1}=f(x_{n};r)$, being $f$ an unimodal function. We proof a theorem which states the necessary and sufficient conditions for the break-up of compound orbits in their simpler constituents. A corollary to this theorem provides an algorithm for the computation of those orbits. This process closes the theoretical framework initiated in (Physica D, 239:1135--1146, 2010).

Jesús San Martín; A. González Gómez; Ma José Moscoso; Daniel Rodríguez-Pérez

2014-02-24

191

On the tidal evolution of Hot Jupiters on inclined orbits  

Microsoft Academic Search

Tidal friction is thought to be important in determining the long-term spin-orbit evolution of short-period extrasolar planetary systems. Using a simple model of the orbit-averaged effects of tidal friction, we study the evolution of close-in planets on inclined orbits, due to tides. We analyse the effects of the inclusion of stellar magnetic braking by performing a phase-plane analysis of a

Adrian J. Barker; Gordon I. Ogilvie

2009-01-01

192

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

193

Controlling the NGST Orbit  

NASA Astrophysics Data System (ADS)

NGST will likely be placed in an elliptical orbit around the external collinear Lagrange point L2. However, the orbit is dynamically unstable and on-board thrusters must be used to make corrections to the orbit over time. The limited fuel available for such corrections may well limit the mission lifetime. Due to its large (200 m2) heat shield, NGST will be subject to significant perturbations by solar radiation pressure. We present an analysis for controlling the orbit against various perturbations, including solar radiation pressure. Ignoring effects of nonlinearity, we obtain an analytic description of the orbital evolution subject to arbitrary time-dependent perturbations. Orbital instability can be controlled by minimizing the effects of secular growing terms. Several control strategies are described. These strategies include the optimal use of thrusters and the selection of an appropriate orbit which compensates for perturbations.

Lubow, S. H.

2001-11-01

194

ORBITS AROUND BLACK HOLES IN TRIAXIAL NUCLEI  

SciTech Connect

We discuss the properties of orbits within the influence sphere of a supermassive black hole (BH), in the case that the surrounding star cluster is non-axisymmetric. There are four major orbit families; one of these, the pyramid orbits, have the interesting property that they can approach arbitrarily closely to the BH. We derive the orbit-averaged equations of motion and show that in the limit of weak triaxiality, the pyramid orbits are integrable: the motion consists of a two-dimensional libration of the major axis of the orbit about the short axis of the triaxial figure, with eccentricity varying as a function of the two orientation angles and reaching unity at the corners. Because pyramid orbits occupy the lowest angular momentum regions of phase space, they compete with collisional loss cone repopulation and with resonant relaxation (RR) in supplying matter to BHs. General relativistic advance of the periapse dominates the precession for sufficiently eccentric orbits, and we show that relativity imposes an upper limit to the eccentricity: roughly the value at which the relativistic precession time is equal to the time for torques to change the angular momentum. We argue that this upper limit to the eccentricity should also apply to evolution driven by RR, with potentially important consequences for the rate of extreme-mass-ratio inspirals in low-luminosity galaxies. In giant galaxies, we show that capture of stars on pyramid orbits can dominate the feeding of BHs, at least until such a time as the pyramid orbits are depleted; however this time can be of order a Hubble time.

Merritt, David [Department of Physics and Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623 (United States); Vasiliev, Eugene, E-mail: merritt@astro.rit.edu, E-mail: eugvas@lpi.ru [Lebedev Physical Institute, Leninsky prospekt 53, Moscow (Russian Federation)

2011-01-10

195

Efficient orbit integration by orbital longitude methods  

NASA Astrophysics Data System (ADS)

Triggered by the desire to investigate numerically the planetary precession through a long-term numerical integration of the solar system, we developed a new formulation of numerical integration of orbital motion named manifold correction methods. The main trick is to keep rigorously the consistency of some physical relations such as that of the orbital energy, of the orbital angular momentum, or of the Laplace integral of a binary subsystem. This maintenance is done by applying a sort of correction to the integrated variables at every integration step. Typical methods of correction are certain geometric transformation such as the spatial scaling and the spatial rotation, which are commonly used in the comparison of reference frames, or mathematically-reasonable operations such as the modularization of angle variables into the standard domain [-?,?). The finally-evolved form of the manifold correction methods is the orbital longitude methods, which enable us to conduct an extremely precise integration of orbital motions. In the unperturbed orbits, the integration errors are suppressed at the machine epsilon level for an infinitely long period. In the perturbed cases, on the other hand, the errors initially grow in proportion to the square root of time and then increase more rapidly, the onset time of which depends on the type and the magnitude of perturbations. This feature is also realized for highly eccentric orbits by applying the same idea to the KS-regularization. Especially the introduction of time element greatly enhances the performance of numerical integration of KS-regularized orbits whether the scaling is applied or not.

Fukushima, T.

2005-09-01

196

Examination of a constrained three-impulse trajectory between low planetary orbits and circulating orbits  

NASA Astrophysics Data System (ADS)

Circulating orbits have been investigated to provide regular periodic transfers between the Earth and Mars. The circulating orbits pass close enough to each planet to be considered hyperbolic in planetocentric frame. The large spacecraft in the circulating orbit is resupplied by a smaller 'Taxi' spacecraft leaving a low planetary orbit. The Taxi follows a three-impulse patched-conic trajectory to travel from its spaceport to the large spacecraft following a hyperbolic fly-by resulting in a Delta V profile for each encounter. When the location of the first impulse of the trajectory is constrained to an arbitrary value then launch windows for each orbit of the spaceport can be determined. The length of the windows depend primarily upon the Delta V capability of the Taxi.

Knoedler, Andrew J.

197

Closeup view of the aft flight deck of the Orbiter ...  

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

Close-up view of the aft flight deck of the Orbiter Discovery looking at the aft center control panels A6, A7, A8, A12, A13, A14, A16 and A17. This View was taken at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

198

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

199

Lunar Prospector mapping-phase orbit determination  

NASA Astrophysics Data System (ADS)

This paper details the model method and results for lunar satellite orbit determination OD with the newly developed OD software PASAX Lunar Prospector LP one-week S-band two-way doppler and range observations during the norminal mission will be used for the OD Prior to the OD LP orbital variation during this week will be analysed During the OD the accuracy for the OD and the orbit prediction will be investigated in great details Orbit determination comparison with different gravity field different planetary ephemeredes and different strategies will be examined The OD results on two extreme geometries i e when the orbit plane is perpendicular or parallel to the Earth-Moon line will be discussed Comparing the orbit on the overlap period indicates that the OD accuracy is on meters level The range rate O-C residual is about 0 5mm s close to the actual measurement noise The position difference of orbit solutions produced by PASAX and GEODYN softwares is within 2m 1-Sigma

Wang, J. S.; Chen, J. R.; Ma, P. B.; Wang, Y. R.; Li, J. S.; Chen, C. G.; Jiang, J. C.

200

Nonlinear Analysis of Unbalanced Mass of Vertical Conveyer-Elevator  

NASA Astrophysics Data System (ADS)

The Vertical conveyers have a cylindrical casing, a helical open trough or closed pipe is attached at the outside or at the inside of the vertical tubular casing, along which the load can be transported from the bottom upwards. A vibration-exciting drive is mounted at the top or bottom of the casing to impart to the latter directed vibrations along and around the vertical axis, which cause the load to move upwards along the helix. In this work, nonlinear analysis for the change of the parameters of the motion, stability condition, and the jump phenomena has been shown graphically.

Bay?ro?lu, Hüseyin

2011-12-01

201

Exploration of Titan using Vertical Lift Aerial Vehicles  

NASA Technical Reports Server (NTRS)

Autonomous vertical lift aerial vehicles (such as rotorcraft or powered-lift vehicles) hold considerable potential for supporting planetary science and exploration missions. Vertical lift aerial vehicles would have the following advantages/attributes for planetary exploration: low-speed and low-altitude detailed aerial surveys; remote-site sample return to lander platforms; precision placement of scientific probes; soft landing capability for vehicle reuse (multiple flights) and remote-site monitoring; greater range, speed, and access to hazardous terrain than a surface rover; greater resolution of surface details than an orbiter or balloons. Exploration of Titan presents an excellent opportunity for the development and usage of such vehicles.

Young, L. A.

2001-01-01

202

Jupiter orbiter lifetime: The hazard of Galilean satellite collision  

NASA Technical Reports Server (NTRS)

The four Galilean satellites of Jupiter present a long-term collision hazard to an uncontrolled orbiting spacecraft that repeatedly enters the spatial region occupied by the satellites. Satellite close encounters and the likelihood of collision over a wide range of initial orbit conditions were analyzed. The effect of orbit inclination was of key interest. The scope of the analysis was restricted to orbital dynamic considerations alone, i.e. the question of biological contamination given the event of collision was not considered. A quarantine or orbiter lifetime of 50 years was assumed. This time period begins at spacecraft shutdown following completion of the mission objectives. A numerical approach was adopted wherein each initial orbit is propagated for 50 years, and satellite closest encounter distances recorded on every revolution. The computer program includes approximations of the three major perturbation effects on the long-term motion of the orbiter: (1) Jupiter oblateness, (2) solar gravity, and (3) satellite gravity.

Friedlander, A. L.

1975-01-01

203

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

204

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.

205

Vertical solar louver project  

NASA Astrophysics Data System (ADS)

The thermal network analysis computer program MICROPAS was used to analyze Vertical Solar Louvers and other reference solar designs in eight selected climates. The results have been used to generate a set of correlation coefficients for use in performance predictions by the Solar Load Ratio method. At low mass VSL were shown to be superior to ordinary direct gain and equal to the trombe wall systems in energy savings. The energy savings advantage of VSL over direct gain disappears in comparable systems of high mass. Identical solar water tanks of oval cross section were compared in the water wall and VSL configurations.

Bier, C. J.

1984-09-01

206

'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

207

Hydrodynamic Stability Criteria for Vertically Stratified Protoplanetary Disks  

NASA Astrophysics Data System (ADS)

Whenever a vertically stratified circumstellar disk has a radial entropy gradient, the balance of forces in the radial and vertical directions implies that the unperturbed orbit frequency is a function of both radius and height above the midplane of the disk. This vertical shear in the orbit frequency can produce baroclinic instabilities that result in slanted convection in the r-z plane, vertical corrugations of the disk midplane, and outward angular momentum transport with an effective alpha of 0.001 (Nelson et al., MNRAS 435, 2610-2632, (2013)). It is difficult to derive a rigorous dispersion relation for this instability due to the inseparable nature of the r and z-dependence of the problem. Previously published stability criteria are limited to small vertical scales because they assume the vertical component of the star’s gravity to be independent of z. This limitation can be overcome if one assumes that the vertical structure near the disk midplane is nearly adiabatic, so that the anelastic approximation is valid. For this case, the problem can be reduced to a set of three evolution equations for the z-component of the angular momentum, the potential temperature, and the component of vorticity due to motions in the r-z plane. This reduced dynamical system has a Hamiltonian structure that allows one to readily derive a Liapunov functional that governs the linear and nonlinear stability of the problem. The stability criterion reduces to a statement about the relative slopes in the r-z plane of the surfaces of constant angular momentum and constant potential temperature in the unperturbed disk. This stability condition is analogous to the criterion for symmetric baroclinic instabilities in planetary atmospheres. Support from NASA’s Origins of Solar Systems program is gratefully acknowledged.

Stewart, Glen R.

2014-11-01

208

Orbit Determination of the Lunar Reconnaissance Orbiter  

NASA Technical Reports Server (NTRS)

We present the results on precision orbit determination from the radio science investigation of the Lunar Reconnaissance Orbiter (LRO) spacecraft. We describe the data, modeling and methods used to achieve position knowledge several times better than the required 50-100m (in total position), over the period from 13 July 2009 to 31 January 2011. In addition to the near-continuous radiometric tracking data, we include altimetric data from the Lunar Orbiter Laser Altimeter (LOLA) in the form of crossover measurements, and show that they strongly improve the accuracy of the orbit reconstruction (total position overlap differences decrease from approx.70m to approx.23 m). To refine the spacecraft trajectory further, we develop a lunar gravity field by combining the newly acquired LRO data with the historical data. The reprocessing of the spacecraft trajectory with that model shows significantly increased accuracy (approx.20m with only the radiometric data, and approx.14m with the addition of the altimetric crossovers). LOLA topographic maps and calibration data from the Lunar Reconnaissance Orbiter Camera were used to supplement the results of the overlap analysis and demonstrate the trajectory accuracy.

Mazarico, Erwan; Rowlands, D. D.; Neumann, G. A.; Smith, D. E.; Torrence, M. H.; Lemoine, F. G.; Zuber, M. T.

2011-01-01

209

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.

2005-07-01

210

48The Grail and LRO Spacecraft Encounters in Lunar Orbit On May 31, 2012 the Grail `Ebb'  

E-print Network

' of light as it passes by. Note: Explore the encounter by using NASA's Eyes on the Solar System orbit48The Grail and LRO Spacecraft Encounters in Lunar Orbit On May 31, 2012 the Grail `Ebb' spacecraft and the Lunar Reconnissance Orbiter (LRO) will come very close to each other in their orbits around the moon

Christian, Eric

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

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

214

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

215

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

216

Closeup view looking forward along the centerline of the Orbiter ...  

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

Close-up view looking forward along the centerline of the Orbiter Discovery looking into the payload bay. This view is a close-up view of the external airlock and the beam-truss attach structure supporting it and attaching it to the payload bay sill longerons. Also note the protective covering over the docking mechanism on top of the airlock assembly. This external airlock configuration was for mating to the International Space Station. This photograph was taken in the Orbiter Processing Facility at Kennedy Space Cente - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

217

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

218

Orbital Evolution of Planetesimals due to the Galactic Tide: Formation of the Comet Cloud  

Microsoft Academic Search

We have investigated the orbital evolution of planetesimals perturbed by the Galactic tide using analytical expressions. We consider the vertical component of the tidal force from the Galactic disk. The Galactic tide increases or decreases the perihelia and randomizes the inclination of planetesimals with large aphelion distances. We applied the analytical solutions to the orbital evolution of planetesimals that form

A. Higuchi; E. Kokubo; H. Kinoshita; T. Mukai

2007-01-01

219

View of 41-D mission payloads after loading aboard the orbiter  

NASA Technical Reports Server (NTRS)

View of 41-D mission payloads after loading into the orbiter payload bay. The orbiter is in its on-pad vertical mode. The payloads are, top to bottom, OAST-1, SBS-D, Telstar 3-C and Syncom IV-2. The Kennedy Space Center alternative photo number is 108-KSC-84PC-551.

1984-01-01

220

Evolution of close binaries  

NASA Astrophysics Data System (ADS)

The evolution of a star depends primarily on its mass, chemical composition, so it is important to know the distribution of stellar masses when the stars are born. Stars can be born as singles, in pairs, or in multiple systems. A large fraction of the stars belongs to binary systems. Hence it is essential to know how stellar masses are distributed at birth, how many stars are formed, not only as singles, but also what fraction originates as binary systems, and what is then the mass ratio and orbital period distribution of these binaries. Since massive stars are intrinsically the brightest ones, it is interesting to try to discover their properties in distant stellar groups. Until now observations of massive stars are reasonably complete for a restricted portion of our own Galaxy, within a sphere with a radius of about 3 kpc from the Sun. Conclusions from these observations are then extended to the whole Galaxy. Before starting the study of evolution of close binary systems, we examine first the evolution of single stars. So we begin to deal with the stellar structure processes, stellar evolution in general, we investigate how evolution occurs differently for stars of low, intermediate and large mass. Comparison of evolutionary computations with observations allows restricting a number of uncertainties of the value of parameters in the equations of stellar structure and evolution. The evolution of close binaries differs from the evolution of single stars, since the presence of a companion sets limits on the stellar expansion during its evolution. We examine the processes that have to be added to the stellar structure equations to compute the structure of the components of binary systems, and to calculate their evolution. Here also we study in detail the uncertainties and their effects on the results of the computations. An overview is presented of the existing evolutionary computations for various masses, with various assumptions on the processes, stellar wind mass losses for massive components, convection criteria, the behaviour of semiconvection, the accretion process, standard accretion models, full mixing models, the formation of common envelope systems, the formation of discs. Comparison of computations with observations of binaries that are representative for a given class allows to draw general conclusions and to discard a number of uncertainties. The combination of the results of massive single stars and massive binaries allows predictions concerning the evolution of certain stellar populations (Wolf-Rayet stars, luminous blue variables, X-ray binaries, ...), i.e. predictions on their progenitors, and their evolutionary history. We investigate uncertainties in binary statistics (frequency, mass ratio and period distribution) and try to determine how these uncertainties affect the results. Observations of massive single stars and of massive close binaries, allow to present a consistent evolutionary model for both, that is able to explain the stellar content and the overall stellar properties for the solar neighbourhood.

de Loore, Bert C.

221

Closeup oblique view of the aft fuselage of the Orbiter ...  

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

Close-up oblique view of the aft fuselage of the Orbiter Discovery looking forward and port with the Space Shuttle Main Engines (SSME) and Orbiter Maneuvering System/Reaction Control System pods still in place. However. the heat shields have been removed from the SSMEs providing a good view toward the interior of the aft fuselage. This image was taken inside the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

222

Closeup oblique view of the aft fuselage of the Orbiter ...  

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

Close-up oblique view of the aft fuselage of the Orbiter Discovery looking forward and starboard with the Space Shuttle Main Engines (SSME) and Orbiter Maneuvering System/Reaction Control System pods still in place. However. the heat shields have been removed from the SSMEs providing a good view toward the interior of the aft fuselage. This image was taken inside the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

223

Closeup oblique view of the aft fuselage of the Orbiter ...  

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

Close-up oblique view of the aft fuselage of the Orbiter Discovery looking forward and starboard with the Space Shuttle Main Engines (SSME) and Orbiter Maneuvering System/Reaction Control System pods removed. The openings for the SSMEs have been covered with a flexible barrier to create a positive pressure envelope inside of the aft fuselage. This image was taken inside the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

224

Heating of near-Earth objects and meteoroids due to close approaches to the Sun  

Microsoft Academic Search

It is known that near-Earth objects (NEOs) during their orbital evolution may often undergo close approaches to the Sun. Indeed it is estimated that up to ~70 per cent of them end their orbital evolution colliding with the Sun. Starting from the present orbital properties, it is possible to compute the most likely past evolution for every NEO, and to

S. Marchi; M. Delbo; A. Morbidelli; P. Paolicchi; M. Lazzarin

2009-01-01

225

Orbit stability and feedback control in synchrotron radiation rings  

SciTech Connect

Stability of the electron orbit is essential for the utilization of a low emittance storage ring as a high brightness radiation source. We discuss the development of the measurement and feedback control of the closed orbit, with emphasis on the activities as the National Synchrotron Light Source of BNL. We discuss the performance of the beam position detectors in use and under development: the PUE rf detector, split ion chamber detector, photo-emission detector, solid state detector, and the graphite detector. Depending on the specific experiments, different beamlines require different tolerances on the orbit motion. Corresponding to these different requirements, we discuss two approaches to closed orbit feedback: the global and local feedback systems. Then we describe a new scheme for the real time global feedback by implementing a feedback system based upon a harmonic analysis of both the orbit movements and the correction magnetic fields. 14 refs., 6 figs., 2 tabs.

Yu, L.H.

1989-01-01

226

Pioneer Venus orbiter electron temperature probe  

NASA Technical Reports Server (NTRS)

This document lists the scientific accomplishments of the Orbiter Electron Temperature Probe (OETP) group. The OETP instrument was fabricated in 1976, integrated into the PVO spacecraft in 1977, and placed in orbit about Venus in December 1978. The instrument operated flawlessly for nearly 14 years until PVO was lost as it entered the Venusian atmosphere in October 1992. The OETP group worked closely with other PVO investigators to examine the Venus ionosphere and its interactions with the solar wind. After the mission was completed we continued to work with the scientist selected for the Venus Data Analysis Program (VDAP), and this is currently leading to additional publications.

Brace, Larry H.

1994-01-01

227

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

228

Measurement of ultralow vertical emittance using a calibrated vertical undulator  

NASA Astrophysics Data System (ADS)

Very few experimental techniques are useful for the direct observation of ultralow vertical emittance in electron storage rings. In this work, quantitative measurements of ultralow (pm rad) electron beam vertical emittance using a vertical undulator are presented. An undulator radiation model was developed using the measured magnetic field of the APPLE-II type undulator. Using calibrated experimental apparatus, a geometric vertical emittance of ?y=0.9 ±0.3 pm rad has been observed. These measurements could also inform modeling of the angular distribution of undulator radiation at high harmonics, for proposed diffraction-limited storage ring light sources.

Wootton, K. P.; Boland, M. J.; Rassool, R. P.

2014-11-01

229

Observation of Picometer Vertical Emittance with a Vertical Undulator  

NASA Astrophysics Data System (ADS)

Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic.

Wootton, K. P.; Boland, M. J.; Dowd, R.; Tan, Y.-R. E.; Cowie, B. C. C.; Papaphilippou, Y.; Taylor, G. N.; Rassool, R. P.

2012-11-01

230

Astrometric orbits of SB9 stars  

E-print Network

Hipparcos Intermediate Astrometric Data (IAD) have been used to derive astrometric orbital elements for spectroscopic binaries from the newly released Ninth Catalogue of Spectroscopic Binary Orbits (SB9). Among the 1374 binaries from SB9 which have an HIP entry, 282 have detectable orbital astrometric motion (at the 5% significance level). Among those, only 70 have astrometric orbital elements that are reliably determined (according to specific statistical tests discussed in the paper), and for the first time for 20 systems, representing a 10% increase relative to the 235 DMSA/O systems already present in the Hipparcos Double and Multiple Systems Annex. The detection of the astrometric orbital motion when the Hipparcos IAD are supplemented by the spectroscopic orbital elements is close to 100% for binaries with only one visible component, provided that the period is in the 50 - 1000 d range and the parallax is larger than 5 mas. This result is an interesting testbed to guide the choice of algorithms and stati...

Jancart, S; Babusiaux, C; Pourbaix, D

2005-01-01

231

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

232

Planetary Orbit Simulator  

NSDL National Science Digital Library

This web page from the University of Nebraska contains a simulation of a planetary orbit. The visitor can control the size of the orbit and the eccentricity. The simulation shows velocity and acceleration factors continually. Each of Kepler's three laws has a separate section, with different display options to illustrate each law.

233

Titan Orbiter Aerorover Mission  

NASA Technical Reports Server (NTRS)

We propose a combined Titan orbiter and Titan Aerorover mission with an emphasis on both in situ and remote sensing measurements of Titan's surface, atmosphere, ionosphere, and magnetospheric interaction. The biological aspect of the Titan environment will be emphasized by the mission (i.e., search for organic materials which may include simple organics to 'amono' analogues of amino acids and possibly more complex, lightening detection and infrared, ultraviolet, and charged particle interactions with Titan's surface and atmosphere). An international mission is assumed to control costs. NASA will provide the orbiter, launch vehicle, DSN coverage and operations, while international partners will provide the Aerorover and up to 30% of the cost for the scientific instruments through collaborative efforts. To further reduce costs we propose a single PI for orbiter science instruments and a single PI for Aerorover science instruments. This approach will provide single command/data and power interface between spacecraft and orbiter instruments that will have redundant central DPU and power converter for their instruments. A similar approach could be used for the Aerorover. The mission profile will be constructed to minimize conflicts between Aerorover science, orbiter radar science, orbiter radio science, orbiter imaging science, and orbiter fields and particles (FP) science. Additional information is contained in the original extended abstract.

Sittler Jr., E. C.; Acuna, M.; Burchell, M. J.; Coates, A.; Farrell, W.; Flasar, M.; Goldstein, B. E.; Gorevan, S.; Hartle, R. E.; Johnson, W. T. K.

2001-01-01

234

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. PMID:23961006

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

2012-01-01

235

Focus on Orbital Physics  

Microsoft Academic Search

The quest for a microscopic understanding of the physical properties of transition metal oxides with orbital degeneracy (`orbital physics') is currently at the forefront of solid-state physics. The field was kicked off nearly 50 years ago by a remarkable pair of papers. In the first, Wollan and Koehler reported using the newly developed technique of neutron scattering to elucidate the

Bernhard Keimer; Andrzej M Oles

2004-01-01

236

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

237

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

238

STS-46 Atlantis', OV-104's, vertical tail and OMS pods lit up by RCS jet firing  

NASA Technical Reports Server (NTRS)

STS-46 Atlantis', Orbiter Vehicle (OV) 104's, vertical tail and orbital maneuvering system (OMS) pods are highlighted by the glow of the reaction control system (RCS) jet firings. OV-104 was at an altitude of 128 nautical miles. The remote manipulator system (RMS) arm is partially visible stowed along the port side sill longeron.

1992-01-01

239

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

240

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

241

Kepler-36: a pair of planets with neighboring orbits and dissimilar densities.  

PubMed

In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets' orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky "super-Earth," whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system. PMID:22722249

Carter, Joshua A; Agol, Eric; Chaplin, William J; Basu, Sarbani; Bedding, Timothy R; Buchhave, Lars A; Christensen-Dalsgaard, Jørgen; Deck, Katherine M; Elsworth, Yvonne; Fabrycky, Daniel C; Ford, Eric B; Fortney, Jonathan J; Hale, Steven J; Handberg, Rasmus; Hekker, Saskia; Holman, Matthew J; Huber, Daniel; Karoff, Christopher; Kawaler, Steven D; Kjeldsen, Hans; Lissauer, Jack J; Lopez, Eric D; Lund, Mikkel N; Lundkvist, Mia; Metcalfe, Travis S; Miglio, Andrea; Rogers, Leslie A; Stello, Dennis; Borucki, William J; Bryson, Steve; Christiansen, Jessie L; Cochran, William D; Geary, John C; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer; Howard, Andrew W; Jenkins, Jon M; Klaus, Todd; Koch, David G; Latham, David W; MacQueen, Phillip J; Sasselov, Dimitar; Steffen, Jason H; Twicken, Joseph D; Winn, Joshua N

2012-08-01

242

Hydrogen atom in a magnetic field: Ghost orbits, catastrophes, and uniform semiclassical approximations  

SciTech Connect

Applying closed-orbit theory to the recurrence spectra of the hydrogen atom in a magnetic field, one can interpret most, but not all, structures semiclassically in terms of closed classical orbits. In particular, conventional closed-orbit theory fails near bifurcations of orbits where semiclassical amplitudes exhibit unphysical divergences. Here we analyze the role of ghost orbits living in complex phase space. The ghosts can explain resonance structures in the spectra of the hydrogen atom in a magnetic field at positions where no real orbits exist. For three different types of catastrophes, viz. fold, cusp, and butterfly catastrophes, we construct uniform semiclassical approximations and demonstrate that these solutions are completely determined by classical parameters of the real orbits and complex ghosts. {copyright} {ital 1997} {ital The American Physical Society}

Main, J.; Wunner, G. [Institut fuer Theoretische Physik I, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)] [Institut fuer Theoretische Physik I, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

1997-03-01

243

Astrometric orbits of SB9 stars  

E-print Network

Hipparcos Intermediate Astrometric Data (IAD) have been used to derive astrometric orbital elements for spectroscopic binaries from the newly released Ninth Catalogue of Spectroscopic Binary Orbits (SB9). Among the 1374 binaries from SB9 which have an HIP entry, 282 have detectable orbital astrometric motion (at the 5% significance level). Among those, only 70 have astrometric orbital elements that are reliably determined (according to specific statistical tests discussed in the paper), and for the first time for 20 systems, representing a 10% increase relative to the 235 DMSA/O systems already present in the Hipparcos Double and Multiple Systems Annex. The detection of the astrometric orbital motion when the Hipparcos IAD are supplemented by the spectroscopic orbital elements is close to 100% for binaries with only one visible component, provided that the period is in the 50 - 1000 d range and the parallax is larger than 5 mas. This result is an interesting testbed to guide the choice of algorithms and statistical tests to be used in the search for astrometric binaries during the forthcoming ESA Gaia mission. Finally, orbital inclinations provided by the present analysis have been used to derive several astrophysical quantities. For instance, 29 among the 70 systems with reliable astrometric orbital elements involve main sequence stars for which the companion mass could be derived. Some interesting conclusions may be drawn from this new set of stellar masses, like the enigmatic nature of the companion to the Hyades F dwarf HIP 20935. This system has a mass ratio of 0.98 but the companion remains elusive.

S. Jancart; A. Jorissen; C. Babusiaux; D. Pourbaix

2005-07-29

244

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

245

Reconstruction of the Orbit With a Temporalis Muscle Flap After Orbital Exenteration  

PubMed Central

Objectives This study presents the role of the temporalis muscle flap in primary reconstruction after orbital exenteration. Methods A retrospective nonrandomized study of orbital exenterations performed between 1990 and 2010 for malignant tumors of the skin, paranasal sinus, and nasal cavity is presented. Results The study included 13 patients (nine men, four women; age range, 30-82 years) with paranasal sinus, nasal cavity, or skin carcinomas. Primary reconstruction of the cavity was performed in all patients after orbital exenteration. No visible defects in the muscle flap donor site were present. Local recurrences were readily followed up with nasal endoscopy, whereas radiology helped to diagnose intracranial involvement in three patients. Two patients died of systemic metastases and five died for other reasons Conclusion The temporalis muscle flap is readily used to close the defect after orbital exenteration, and does not prevent the detection of recurrence. PMID:25729496

Uyar, Yavuz; Y?ld?r?m, Güven; Kuzdere, Mustafa; Arba?, Hamdi; Jorayev, Chary; K?l?ç, Mehmet Vefa; Gümrükçü, Said Serdar

2015-01-01

246

Spin-Orbit Couplings in X-ray Binaries  

E-print Network

We discuss the influence of tidal spin-orbit interactions on the orbital dynamics of close intermediate-mass X-ray binaries. In particular we consider here a process in which spin angular momentum of a contracting RLO donor star, in a synchronous orbit, is converted into orbital angular momentum and thus helps to stabilize the mass transfer by widening the orbit. Binaries which would otherwise suffer from dynamically unstable mass transfer (leading to the formation of a common envelope and spiral-in evolution) are thus shown to survive a phase of extreme mass transfer on a sub-thermal timescale. Furthermore, we discuss the orbital evolution prior to RLO in X-ray binaries with low-mass donors, caused by the competing effects of wind mass loss and tidal effects due to expansion of the (sub)giant.

T. M. Tauris; G. J. Savonije

2000-01-03

247

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

248

4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe ...  

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

4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe (VTL). Machining the fixture for GE Turboshroud. G.S. O'Brien, operator. - Juniata Shops, Machine Shop No. 1, East of Fourth Avenue at Third Street, Altoona, Blair County, PA

249

DISTANCES BETWEEN PAIRS OF VERTICES AND VERTICAL PROFILE IN CONDITIONED  

E-print Network

DISTANCES BETWEEN PAIRS OF VERTICES AND VERTICAL PROFILE IN CONDITIONED GALTON­WATSON TREES LUC DEVROYE AND SVANTE JANSON Abstract. We consider a conditioned Galton­Watson tree and prove an estimate of a randomly labelled conditioned Galton­Watson tree converges in distribution, after suitable normalization

Janson, Svante

250

DISTANCES BETWEEN PAIRS OF VERTICES AND VERTICAL PROFILE IN CONDITIONED  

E-print Network

DISTANCES BETWEEN PAIRS OF VERTICES AND VERTICAL PROFILE IN CONDITIONED GALTON--WATSON TREES LUC DEVROYE AND SVANTE JANSON Abstract. We consider a conditioned Galton--Watson tree and prove an estimate of a randomly labelled conditioned Galton--Watson tree converges in distribution, after suitable normalization

Janson, Svante

251

Close encounters of three black holes  

SciTech Connect

We present the first fully relativistic long-term numerical evolutions of three equal-mass black holes in a system consisting of a third black hole in a close orbit about a black-hole binary. These close-three-black-hole systems have very different merger dynamics from black-hole binaries; displaying complex trajectories, a redistribution of energy that can impart substantial kicks to one of the holes, distinctive waveforms, and suppression of the emitted gravitational radiation. In one configuration the binary is quickly disrupted and the individual holes follow complicated trajectories and merge with the third hole in rapid succession, while in another, the binary completes a half-orbit before the initial merger of one of the members with the third black hole, and the resulting two-black-hole system forms a highly elliptical, well separated binary that shows no significant inspiral for (at least) the first t{approx}1000M of evolution.

Campanelli, Manuela; Lousto, Carlos O.; Zlochower, Yosef [Center for Computational Relativity and Gravitation, School of Mathematical Sciences, Rochester Institute of Technology, 78 Lomb Memorial Drive, Rochester, New York 14623 (United States)

2008-05-15

252

The orbital record in stratigraphy  

NASA Astrophysics Data System (ADS)

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.

1992-12-01

253

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

254

Subjective Visual Vertical and Postural Capability in Children Born Prematurely  

PubMed Central

Purpose We compared postural stability and subjective visual vertical performance in a group of very preterm-born children aged 3-4 years and in a group of age-matched full-term children. Materials and Methods A platform (from TechnoConcept) was used to measure postural control in children. Perception of subjective visual vertical was also recorded with posture while the child had to adjust the vertical in the dark or with visual perturbation. Two other conditions (control conditions) were also recorded while the child was on the platform: for a fixation of the vertical bar, and in eyes closed condition. Results Postural performance was poor in preterm-born children compared to that of age-matched full-term children: the surface area, the length in medio-lateral direction and the mean speed of the center of pressure (CoP) were significantly larger in the preterm-born children group (p < 0.04, p < 0.01, and p < 0.04, respectively). Dual task in both groups of children significantly affected postural control. The subjective visual vertical (SVV) values were more variable and less precise in preterm-born children. Discussion-Conclusions We suggest that poor postural control as well as perception of verticality observed in preterm-born children could be due to immaturity of the cortical processes involved in the motor control and in the treatment of perception and orientation of verticality. PMID:25790327

Bucci, Maria Pia; Wiener-Vacher, Sylvette; Trousson, Clémence; Baud, Olivier; Biran, Valerie

2015-01-01

255

Orbital metastatic osteosarcoma.  

PubMed

At an estimated incidence of 2 cases per million persons per year, osteosarcoma is the most common primary malignant bone tumor in children and adults, excluding hematopoietic intraosseous tumors. Orbital metastases of osteosarcoma are very rare. Only 5 cases of orbital metastasis of osteosarcoma previously reported in the literature. We report the case of a 19-year-old man with known history of osteosarcoma of right distal femur who presented with acute visual loss and progressive protrusion of his left eye. Orbital CT scan and MRI revealed orbital mass eroding orbital walls and intracranial invasion. He underwent superotemporal orbitotomy for debulking of orbital mass. Histopathological examination (HPE) of the specimen was reported as metastatic osteosarcoma with extensive tumor necrosis. Then he underwent adjuvant chemotherapy and palliative radiotherapy. Although orbital metastasis of osteosarcoma is a rare event, it seems it has had an increasing trend recently. so, making efforts to palliate the patient's symptoms by multidisciplinary teamwork and proper interaction among ophthalmologist, orthopedic surgeons and oncologists is necessary. PMID:25644802

Rajabi, Mohammad Taher; Saeedi-Anari, Ghasem; Ramezani, Farshid; Tabatabaie, Seyed-Ziaeddin; Rajabi, Mohammad Bagher; Asadi Amoli, Fahimeh

2015-02-01

256

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

257

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

258

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

259

Spaceport aurora: An orbiting transportation node  

NASA Technical Reports Server (NTRS)

With recent announcements of the development of permanently staffed facilities on the Moon and Mars, the national space plan is in need of an infrastructure system for transportation and maintenance. A project team at the University of Houston College of Architecture and the Sasakawa International Center for Space Architecture, recently examined components for a low Earth orbit (LEO) transportation node that supports a lunar build-up scenario. Areas of investigation included identifying transportation node functions, identifying existing space systems and subsystems, analyzing variable orbits, determining logistics strategies for maintenance, and investigating assured crew return systems. The information resulted in a requirements definition document, from which the team then addressed conceptual designs for a LEO transportation node. The primary design drivers included: orbital stability, maximizing human performance and safety, vehicle maintainability, and modularity within existing space infrastructure. For orbital stability, the power tower configuration provides a gravity gradient stabilized facility and serves as the backbone for the various facility components. To maximize human performance, human comfort is stressed through zoning of living and working activities, maintaining a consistent local vertical orientation, providing crew interaction and viewing areas and providing crew return vehicles. Vehicle maintainability is accomplished through dual hangars, dual work cupolas, work modules, telerobotics and a fuel depot. Modularity is incorporated using Space Station Freedom module diameter, Space Station Freedom standard racks, and interchangeable interior partitions. It is intended that the final design be flexible and adaptable to provide a facility prototype that can service multiple mission profiles using modular space systems.

1990-01-01

260

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

261

Orbital Debris Environment Monitor (ODEM)  

NASA Technical Reports Server (NTRS)

Viewgraphs on orbital debris environmental monitor (ODEM) are presented. Topics covered include: Long Duration Exposure Facility (LDEF); interplanetary dust experiment; orbital debris clouds; mapping and modeling of orbital debris clouds; and solar maximum mission spacecraft.

Oliver, John P.

1992-01-01

262

Working in orbit and beyond  

SciTech Connect

This book contains papers presented at a conference on the challenges for space medicine. Topics covered include radiation hazards in low earth orbit, polar orbit, geosynchronous orbit, and deep space.

Lorr, D.B. (Space Medicine Systems, Inc. (US)); Garshnek, V. (George Washington Univ., Washington, DC (US)); Cadoux, C. (Union Memorial Hospital, Baltimore, MD (US))

1989-01-01

263

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

264

Prototyping LHC Orbit Control  

E-print Network

Orbit correction consists in adjusting the strengths of the corrector magnets to make the measured beam position match a predefined reference. In the LHC, this involves around 2000 sensors and more than 1000 actuators that are distributed along both rings. The orbit correction scheme should be able to compensate for very slow orbit drifts in the range of a 10-2 Hz but also for fast motions (vibrations) up to 1 Hz. In this paper we investigate correction schemes that could be used in either case. The choice of design formalisms is based on the experience we gained with the SPS and the LEP.

Wijnands, Thijs; Srinivasan, B

2002-01-01

265

Removal of orbital debris  

NASA Technical Reports Server (NTRS)

The several methods presently identified for the reduction of orbital debris populations are broadly classifiable as either preventive or remedial, and fall within distinctive operational regimes. For all particles, (1) in the 250-2000-km altitude band, intelligent sweepers may be used; (2) for large objects, in the 80-250-km altitude band, orbital decay renders removal impractical; (3) for the 250-750-km altitude band, deorbit devices should be used; (4) for 750-2500-km altitude, OMV rendezvous for propulsive deorbit package attachment is foreseeable; and beyond 2500 km, (5) propulsive escape from earth orbit is required.

Petro, Andrew J.; Talent, David L.

1989-01-01

266

SECULAR ORBITAL EVOLUTION OF COMPACT PLANET SYSTEMS  

SciTech Connect

Recent observations have shown that at least some close-in exoplanets maintain eccentric orbits despite tidal circularization timescales that are typically much shorter than stellar ages. We explore gravitational interactions with a more distant planetary companion as a possible cause of these unexpected non-zero eccentricities. For simplicity, we focus on the evolution of a planar two-planet system subject to slow eccentricity damping and provide an intuitive interpretation of the resulting long-term orbital evolution. We show that dissipation shifts the two normal eigenmode frequencies and eccentricity ratios of the standard secular theory slightly, and we confirm that each mode decays at its own rate. Tidal damping of the eccentricities drives orbits to transition relatively quickly between periods of pericenter circulation and libration, and the planetary system settles into a locked state in which the pericenters are nearly aligned or nearly anti-aligned. Once in the locked state, the eccentricities of the two orbits decrease very slowly because of tides rather than at the much more rapid single-planet rate, and thus eccentric orbits, even for close-in planets, can often survive much longer than the age of the system. Assuming that an observed close-in planet on an elliptical orbit is apsidally locked to a more distant, and perhaps unseen companion, we provide a constraint on the mass, semi-major axis, and eccentricity of the companion. We find that the observed two-planet system HAT-P-13 might be in just such an apsidally locked state, with parameters that obey our constraint reasonably well. We also survey close-in single planets, some with and some without an indication of an outer companion. None of the dozen systems that we investigate provides compelling evidence for unseen companions. Instead, we suspect that (1) orbits are in fact circular, (2) tidal damping rates are much slower than we have assumed, or (3) a recent event has excited these eccentricities. Our method should prove useful for interpreting the results of both current and future planet searches.

Zhang, Ke; Hamilton, Douglas P.; Matsumura, Soko, E-mail: dphamil@umd.edu, E-mail: soko@astro.umd.edu [Department of Astronomy, University of Maryland College Park, MD 20742 (United States)

2013-11-20

267

Distant retrograde orbits for the Moon's exploration  

NASA Astrophysics Data System (ADS)

We discuss the properties of the distant retrograde orbits (which are called quasi-satellite orbits also) around Moon. For the first time the distant retrograde orbits were described by J.Jackson in studies on restricted three body problem at the beginning of 20th century [1]. In the synodic (rotating) reference frame distant retrograde orbit looks like an ellipse whose center is slowly drifting in the vicinity of minor primary body while in the inertial reference frame the third body is orbiting the major primary body. Although being away the Hill sphere the third body permanently stays close enough to the minor primary. Due to this reason the distant retrograde orbits are called “quasi-satellite” orbits (QS-orbits) too. Several asteroids in solar system are in a QS-orbit with respect to one of the planet. As an example we can mention the asteroid 2002VE68 which circumnavigates Venus [2]. Attention of specialists in space flight mechanics was attracted to QS-orbits after the publications of NASA technical reports devoted to periodic moon orbits [3,4]. Moving in QS-orbit the SC remains permanently (or at least for long enough time) in the vicinity of small celestial body even in the case when the Hill sphere lies beneath the surface of the body. The properties of the QS-orbit can be studied using the averaging of the motion equations [5,6,7]. From the theoretical point of view it is a specific case of 1:1 mean motion resonance. The integrals of the averaged equations become the parameters defining the secular evolution of the QS-orbit. If the trajectory is robust enough to small perturbations in the simplified problem (i.e., restricted three body problem) it may correspond to long-term stability of the real-world orbit. Our investigations demonstrate that under the proper choice of the initial conditions the QS-orbits don’t escape from Moon or don’t impact Moon for long enough time. These orbits can be recommended as a convenient technique for the large scale browsing of the Moon’s environment. [1] Jackson, J. (1913) MNRAS, 74, 62-82. [2] Mikkola, S., Brasser, R., Wiegert, P., Innanen, K. (2004) MNRAS, 351, L63-L65. [3] Broucke, R.A. (1968) NASA Technical Report 32-1168, JPL. [4] Broucke, R.A. (1969) NASA Technical Report 32-1360, JPL. [5] Kogan, A.I. (1989) Cosmic Research, 26, 705-710. [6] Namouni, F. (1999) Icarus, 6, 293-314. [7] Sidorenko, V.V., Neishtadt, A.I., Artemyev, A.V., Zelenyi, L.M. (2013) Doklady Physics, 58, 207-211.

Sidorenko, Vladislav

268

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

269

Astrometric orbits of SB^9 stars  

NASA Astrophysics Data System (ADS)

Hipparcos Intermediate Astrometric Data (IAD) have been used to derive astrometric orbital elements for spectroscopic binaries from the newly released Ninth Catalogue of Spectroscopic Binary Orbits (SB^9). This endeavour is justified by the fact that (i) the astrometric orbital motion is often difficult to detect without the prior knowledge of the spectroscopic orbital elements, and (ii) such knowledge was not available at the time of the construction of the Hipparcos Catalogue for the spectroscopic binaries which were recently added to the SB^9 catalogue. Among the 1374 binaries from SB^9 which have an HIP entry (excluding binaries with visual companions, or DMSA/C in the Double and Multiple Stars Annex), 282 have detectable orbital astrometric motion (at the 5% significance level). Among those, only 70 have astrometric orbital elements that are reliably determined (according to specific statistical tests), and for the first time for 20 systems. This represents a 8.5% increase of the number of astrometric systems with known orbital elements (The Double and Multiple Systems Annex contains 235 of those DMSA/O systems). The detection of the astrometric orbital motion when the Hipparcos IAD are supplemented by the spectroscopic orbital elements is close to 100% for binaries with only one visible component, provided that the period is in the 50-1000 d range and the parallax is >5 mas. This result is an interesting testbed to guide the choice of algorithms and statistical tests to be used in the search for astrometric binaries during the forthcoming ESA Gaia mission. Finally, orbital inclinations provided by the present analysis have been used to derive several astrophysical quantities. For instance, 29 among the 70 systems with reliable astrometric orbital elements involve main sequence stars for which the companion mass could be derived. Some interesting conclusions may be drawn from this new set of stellar masses, like the enigmatic nature of the companion to the Hyades F dwarf HIP 20935. This system has a mass ratio of 0.98 but the companion remains elusive.

Jancart, S.; Jorissen, A.; Babusiaux, C.; Pourbaix, D.

2005-10-01

270

Vertically reciprocating auger  

NASA Technical Reports Server (NTRS)

The mathematical model and test results developed for the Vertically Reciprocating Auger (VRA) are summarized. The VRA is a device capable of transporting cuttings that result from below surface drilling. It was developed chiefly for the lunar surface, where conventional fluid flushing while drilling would not be practical. The VRA uses only reciprocating motion and transports material through reflections with the surface above. Particles are reflected forward and land ahead of radially placed fences, which prevent the particles from rolling back down the auger. Three input wave forms are considered to drive the auger. A modified sawtooth wave form was chosen for testing, over a modified square wave or sine wave, due to its simplicity and effectiveness. The three-dimensional mathematical model predicted a sand throughput rate of 0.2667 pounds/stroke, while the actual test setup transported 0.075 pounds/stroke. Based on this result, a correction factor of 0.281 is suggested for a modified sawtooth input.

Etheridge, Mark; Morgan, Scott; Fain, Robert; Pearson, Jonathan; Weldi, Kevin; Woodrough, Stephen B., Jr.

1988-01-01

271

Orbit Determination Issues for Libration Point Orbits  

NASA Technical Reports Server (NTRS)

Libration point mission designers require knowledge of orbital accuracy for a variety of analyses including station keeping control strategies, transfer trajectory design, and formation and constellation control. Past publications have detailed orbit determination (OD) results from individual libration point missions. This paper collects both published and unpublished results from four previous libration point missions (ISEE (International Sun-Earth Explorer) -3, SOHO (Solar and Heliospheric Observatory), ACE (Advanced Composition Explorer) and MAP (Microwave Anisotropy Probe)) supported by Goddard Space Flight Center's Guidance, Navigation & Control Center. The results of those missions are presented along with OD issues specific to each mission. All past missions have been limited to ground based tracking through NASA ground sites using standard range and Doppler measurement types. Advanced technology is enabling other OD options including onboard navigation using seaboard attitude sensors and the use of the Very Long Baseline Interferometry (VLBI) measurement Delta Differenced One-Way Range (DDOR). Both options potentially enable missions to reduce coherent dedicated tracking passes while maintaining orbital accuracy. With the increased projected loading of the DSN (Deep Space Network), missions must find alternatives to the standard OD scenario.

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

272

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

273

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

274

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.

2011-01-17

275

Latitude and longitude vertical disparity  

PubMed Central

The literature on vertical disparity is complicated by the fact that several different definitions of the term “vertical disparity” are in common use, often without a clear statement about which is intended or a widespread appreciation of the properties of the different definitions. Here, we examine two definitions of retinal vertical disparity: elevation-latitude and elevation-longitude disparity. Near the fixation point, these definitions become equivalent, but in general, they have quite different dependences on object distance and binocular eye posture, which have not previously been spelt out. We present analytical approximations for each type of vertical disparity, valid for more general conditions than previous derivations in the literature: we do not restrict ourselves to objects near the fixation point or near the plane of regard, and we allow for non-zero torsion, cyclovergence and vertical misalignments of the eyes. We use these expressions to derive estimates of the latitude and longitude vertical disparity expected at each point in the visual field, averaged over all natural viewing. Finally, we present analytical expressions showing how binocular eye position – gaze direction, convergence, torsion, cyclovergence, and vertical misalignment – can be derived from the vertical disparity field and its derivatives at the fovea. PMID:20055544

Read, Jenny C. A.; Phillipson, Graeme P.; Glennerster, Andrew

2010-01-01

276

Fast vertical mining using diffsets  

Microsoft Academic Search

A number of vertical mining algorithms have been proposed recently for association mining, which have shown to be very effective and usually outperform horizontal approaches. The main advantage of the vertical format is support for fast frequency counting via intersection operations on transaction ids (tids) and automatic pruning of irrelevant data. The main problem with these approaches is when intermediate

Mohammed Javeed Zaki; Karam Gouda

2003-01-01

277

Vertical Mergers and Market Foreclosure  

Microsoft Academic Search

The model in this paper illustrates three effects of vertical mergers when both stages are oligopolistic and vertically integrated and unintegrated producers coexist. First, the merging firm increases its final good output. Second, the resulting backward shift in the residual demand curve facing unintegrated final good producers lowers their demand for the intermediate good. Third, the merged firm withdraws from

Michael A Salinger

1988-01-01

278

The past orbital evolution of periodic comets Shajn-Schaldach and Whipple  

Microsoft Academic Search

Improved orbital elements of the comets P\\/Shajn-Schaldach and P\\/Whipple are used to integrate their orbital evolution for the last 250 years. The numerical investigation lends no support to a common origin of the two comets, and the present similarity of their orbits is shown to be a result of recent close encounters with Jupiter. The evolution of the individual orbital

E. M. Pittich

1981-01-01

279

Spectroscopic Orbits for Kepler FOV Eclipsing Binaries  

NASA Astrophysics Data System (ADS)

We are working on a program of precise photometry with the NASA Kepler Observatory to search for variations in minimum light timing for intermediate mass eclipsing binaries. Such periodic variations will reveal the reflex motion caused by any distant, low mass object that orbits the close binary. Kepler's unprecedented accuracy and continuous observations provide a unique opportunity to detect the low mass companions that are predicted to result from the angular momentum of the natal cloud. We need to determine the masses of the central binary to help estimate the companion mass. The goal of this proposal is to obtain blue spectra of these targets, derive radial velocities, and produce a double-lined spectroscopic orbit. Combined with the Kepler light curve, we will determine very accurate masses, radii, and effective temperatures for the members of the close binary, and this will yield M sin i for any companions detected by light travel time effects.

Williams, Stephen J.; Gies, Douglas R.; Matson, Rachel A.

2010-08-01

280

Spectroscopic Orbits for Kepler FOV Eclipsing Binaries  

NASA Astrophysics Data System (ADS)

A program of precise eclipsing binary photometry with the NASA Kepler Observatory is now in progress. Our goal is to search for variations in minimum light timing for intermediate mass eclipsing binaries. Such periodic variations will reveal the reflex motion caused by any distant, low mass object that orbits the close binary. Kepler's unprecedented accuracy and continuous observations provide a unique opportunity to detect the low mass companions that are predicted to result from the angular momentum of the natal cloud. We need to determine the masses of the central binary to help estimate the companion mass. The goal of this proposal is to obtain blue spectra of these targets, derive radial velocities, and produce a double-lined spectroscopic orbit. Combined with the Kepler light curve, we will determine very accurate masses, radii, and effective temperatures for the members of the close binary, and this will yield M sin i for any companions detected by light travel time effects.

Williams, Stephen J.; Gies, Douglas R.; Matson, Rachel A.

2011-02-01

281

Spectroscopic Orbits for Kepler FOV Eclipsing Binaries  

NASA Astrophysics Data System (ADS)

A three year program of precise eclipsing binary photometry with the NASA Kepler Observatory is now in progress. Our goal is to search for variations in minimum light timing for intermediate mass eclipsing binaries. Such periodic variations will reveal the reflex motion caused by any distant, low mass object that orbits the close binary. Kepler's unprecedented accuracy and continuous observations provide a unique opportunity to detect the low mass companions that are predicted to result from the angular momentum of the natal cloud. We need to determine the masses of the central binary to help estimate the companion mass. The goal of this proposal is to obtain blue spectra of these targets, derive radial velocities, and produce a double-lined spectroscopic orbit. Combined with the Kepler light curve, we will determine very accurate masses, radii, and effective temperatures for the members of the close binary, and this will yield M sin i for any companions detected by light travel time effects.

Williams, Stephen J.; Gies, Douglas R.; Matson, Rachel A.; Guo, Zhao

2011-08-01

282

Light's Orbital Angular Momentum  

Microsoft Academic Search

The realization that light beams can have quantized orbital angular momentum in addition to spin angular momentum has led, in recent years, to novel experiments in quantum mechanics and new methods for manipulating microparticles.

Miles Padgett; Johannes Courtial; Les Allen

2004-01-01

283

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

284

orbit.ps  

E-print Network

consist of an arbitrary number of troughs are found numerically. The bifurca- ... Key words: water wave, Boussinesq system, traveling wave, homoclinic orbit,. multi-pulsed solution ... But to the best of my knowledge, there is no result regarding.

285

Imaging in orbital trauma  

PubMed Central

Orbital trauma is one of the most common reasons for ophthalmology specialty consultation in the emergency department setting. We survey the literature from 1990 to present to describe the role of computed tomography (CT), magnetic resonance imaging (MRI) and their associated angiography in some of the most commonly encountered orbital trauma conditions. CT orbit can often detect certain types of foreign bodies, lens dislocation, ruptured globe, choroidal or retinal detachments, or cavernous sinus thrombosis and thus complement a bedside ophthalmic exam that can sometimes be limited in the setting of trauma. CT remains the workhorse for acute orbital trauma owing to its rapidity and ability to delineate bony abnormalities; however MRI remains an important modality in special circumstances such as soft tissue assessment or with organic foreign bodies. PMID:23961028

Lin, Ken Y.; Ngai, Philip; Echegoyen, Julio C.; Tao, Jeremiah P.

2012-01-01

286

Aerobraking orbital transfer vehicle  

NASA Technical Reports Server (NTRS)

An aerobraking orbital transfer vehicle which includes an aerobraking device which also serves as a heat shield in the shape of a raked-off elliptic or circular cone with a circular or elliptical base, and with an ellipsoid or other blunt shape nose. The aerobraking device is fitted with a toroid-like skirt and is integral with the support structure of the propulsion system and other systems of the space vehicle. The vehicle is intended to be transported in components to a space station in lower earth orbit where it is assembled for use as a transportation system from low earth orbit to geosynchronous earth orbit and return. Conventional guidance means are included for autonomous flight.

Scott, Carl D. (Inventor); Nagy, Kornel (Inventor); Roberts, Barney B. (Inventor); Ried, Robert C. (Inventor); Kroll, Kenneth R. (Inventor); Gamble, Joe (Inventor)

1989-01-01

287

Optical lattices: Orbital dance  

NASA Astrophysics Data System (ADS)

Emulating condensed-matter physics with ground-state atoms trapped in optical lattices has come a long way. But excite the atoms into higher orbital states, and a whole new world of exotic states appears.

Lewenstein, Maciej; Liu, W. Vincent

2011-02-01

288

Indian Mars Orbiter Mission  

NASA Astrophysics Data System (ADS)

The Mars Orbiter Mission (MOM) is the first interplanetary mission of India launched by Indian Polar Satellite Launch Vehicle (PSLV-XL) on 5 November 2013. It departed from Earth's orbit on Dec. 1, 2013, on its 300-days journey to Mars. MOM will reach Mars on Sept. 24, 2014. The orbit of MOM around Mars is highly elliptical with periapsis ~370 km and apoapsis ~80000 km, inclination 151 degree, and orbital period 3.15 sols. The spacecraft mass is 1350 kg, with dry mass of 500 kg and science payload mass of 14 kg. The spacecraft carries five science payloads, namely: Methane Sensor for Mars (MSM), Mars Colour Camera (MCC), Lyman Alpha Photometer (LAP), Mars Exospheric Neutral Composition Analyzer (MENCA), TIR Imaging Spectrometer (TIS). This paper will present the details of the instruments, observation plan, and expected science.

Bhardwaj, Anil

289

Optical orbital debris spotter  

NASA Astrophysics Data System (ADS)

The number of man-made debris objects orbiting the Earth, or orbital debris, is alarmingly increasing, resulting in the increased probability of degradation, damage, or destruction of operating spacecraft. In part, small objects (<10 cm) in Low Earth Orbit (LEO) are of concern because they are abundant and difficult to track or even to detect on a routine basis. Due to the increasing debris population it is reasonable to assume that improved capabilities for on-orbit damage attribution, in addition to increased capabilities to detect and track small objects are needed. Here we present a sensor concept to detect small debris with sizes between approximately 1.0 and 0.01 cm in the vicinity of a host spacecraft for near real time damage attribution and characterization of dense debris fields and potentially to provide additional data to existing debris models.

Englert, Christoph R.; Bays, J. Timothy; Marr, Kenneth D.; Brown, Charles M.; Nicholas, Andrew C.; Finne, Theodore T.

2014-11-01

290

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

291

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

292

Vertical distribution of small pelagic fish eggs and larvae on the eastern Agulhas Bank, South Africa  

Microsoft Academic Search

Vertical distributions of anchovy Engraulis encrasicolus and sardine Sardinops sagax eggs and larvae within the upper 50 m of the water column on the eastern Agulhas Bank, South Africa, were examined using discrete depth samples collected with a multiple, opening\\/closing plankton net. Eggs and larvae of sardine and anchovy had significantly different vertical distributions with eggs closer to the surface

W Osman; C L Moloney; C D van der Lingen

2010-01-01

293

The perception of body verticality (subjective postural vertical) in peripheral and central vestibular disorders.  

PubMed

The perception of body verticality (subjective postural vertical, SPV) was assessed in normal subjects and in patients with peripheral and central vestibular lesions and the data were compared with conventional neuro-otological assessments. Subjects were seated with eyes closed in a motorized gimbal which executed cycles of tilt at low constant speed (1.5 degrees s-1), both in the frontal (roll) and sagittal (pitch) planes. Subjects indicated with a joystick when they entered and left verticality, thus defining a sector of subjective uprightness in each plane. The mean angle of tilt (identifying a bias of the SPV) and the width of the sector (defining sensitivity of the SPV) were then determined. In normal subjects, the angle of the "verticality' sector was 5.9 degrees for pitch and roll. Patients with bilateral absence of vestibular function, patients with vertigo, i.e. acute unilateral lesions, benign paroxysmal positional vertigo (BPPV) and Ménière's disease, and patients with positionally modulated up-/downbeat nystagmus all had enlarged sectors (i.e. loss in sensitivity). Mean sector angle in these groups ranged from 7.8 to 11 degrees and the abnormality was present both in pitch and roll, regardless of the direction of nystagmus or body sway. Patients with chronic unilateral peripheral vestibular lesions and those with position-independent vertical nystagmus had normal sensitivities. No significant bias of the SPV was found in any patient group, not even those with acute unilateral vestibular lesions who had marked tilts of the subjective visual vertical (SVV). Complementary experiments in normal subjects tested under galvanic vestibular or roll-plane optokinetic stimulation also failed to show biases of the SPV. In contrast, a significant bias in the SPV could be induced in normal subjects by asymmetric cycles of gimbals tilt, presumably by proprioceptive adaptation. The following conclusions can be drawn. (i) The perception of body verticality whilst seated is mainly dependent on proprioceptive/contact cues but these are susceptible to tilt-mediated adaptation. (ii) Vestibular input improves the sensitivity of the SPV, even in vestibular disorders, as long as the abnormality is stable. (iii) There can be marked dissociation between vestibulo-motor (ocular and postural) phenomena and the perception of body verticality, and between the SPV and SVV. (iv) The postural sway asymmetries in patients with peripheral and central vestibular lesions, like those induced by galvanic or optokinetic stimulation in normal subjects, are not consequences of changes of the SPV. PMID:8931577

Bisdorff, A R; Wolsley, C J; Anastasopoulos, D; Bronstein, A M; Gresty, M A

1996-10-01

294

Orientation and shape-control of an orbiting flexible beam under the influence of solar radiation pressure  

NASA Technical Reports Server (NTRS)

In this paper, the uncontrolled and controlled dynamics of a thin flexible beam in orbit and in the presence of solar radiation disturbance are analyzed. A beam nominally oriented along (i) the local horizontal and carrying a gimballed rigid dumbbell for gravity stabilization, and (ii) a beam nominally oriented along the local vertical are considered. The uncontrolled dynamics of the beam in the presence of the solar radiation pressure disturbance shows the excitation of the rigid pitch mode. The control laws previously designed for the case where the environmental effects were neglected, are found to be inadequate to control the shape and orientation of very flexible beams that are exposed to solar radiation disturbances. The control laws and the gain parameters are reevaluated for both cases of nominal beam orientations; this results, in general, in increased robustness of the closed-loop system. Methods of obtaining a robust control system in the presence of environmental perturbations are discussed.

Krishna, R.; Bainum, P. M.

1984-01-01

295

Pediatric Orbital Fractures  

PubMed Central

It is wise to recall the dictum “children are not small adults” when managing pediatric orbital fractures. In a child, the craniofacial skeleton undergoes significant changes in size, shape, and proportion as it grows into maturity. Accordingly, the craniomaxillofacial surgeon must select an appropriate treatment strategy that considers both the nature of the injury and the child's stage of growth. The following review will discuss the management of pediatric orbital fractures, with an emphasis on clinically oriented anatomy and development. PMID:24436730

Oppenheimer, Adam J.; Monson, Laura A.; Buchman, Steven R.

2013-01-01

296

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.

297

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

298

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

299

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

300

Numerical simulation of orbiting black holes  

E-print Network

We present numerical simulations of binary black hole systems which for the first time last for about one orbital period for close but still separate black holes as indicated by the absence of a common apparent horizon. An important part of the method is the construction of comoving coordinates, in which both the angular and radial motion is minimized through a dynamically adjusted shift condition. We use fixed mesh refinement for computational efficiency.

Bernd Bruegmann; Wolfgang Tichy; Nina Jansen

2004-05-12

301

Exomoon habitability constrained by energy flux and orbital stability  

E-print Network

Detecting massive satellites of extrasolar planets has now become feasible, which led naturally to questions about their habitability. In a previous study we presented constraints on the habitability of moons from stellar and planetary illumination as well as from tidal heating. Here I refine our model by including the effect of eclipses on the orbit-averaged illumination. Moons in low-mass stellar systems must orbit their planet very closely to remain bound, which puts them at risk of strong tidal heating. I first describe the effect of eclipses on stellar illumination of satellites. Then I calculate the orbit-averaged energy flux including illumination from the planet and tidal heating. Habitability 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. Due to eclipses, a satellite in a close orbit can experience a reduction in orbit...

Heller, René

2012-01-01

302

The Lunar Orbital Prospector  

NASA Technical Reports Server (NTRS)

The establishment of lunar bases will not end the need for remote sensing of the lunar surface by orbiting platforms. Human and robotic surface exploration will necessarily be limited to some proximate distance from the support base. Near real-time, high-resolution, global characterization of the lunar surface by orbiting sensing systems will continue to be essential to the understanding of the Moon's geophysical structure and the location of exploitable minerals and deposits of raw materials. The Lunar Orbital Prospector (LOP) is an orbiting sensing platform capable of supporting a variety of modular sensing packages. Serviced by a lunar-based shuttle, the LOP will permit the exchange of instrument packages to meet evolving mission needs. The ability to recover, modify, and rotate sensing packages allows their reuse in varying combinations. Combining this flexibility with robust orbit modification capabilities and near real-time telemetry links provides considerable system responsiveness. Maintenance and modification of the LOP orbit are accomplished through use of an onboard propulsion system that burns lunar-supplied oxygen and aluminum. The relatively low performance of such a system is more than compensated for by the elimination of the need for Earth-supplied propellants. The LOP concept envisions a continuous expansion of capability through the incorporation of new instrument technologies and the addition of platforms.

Redd, Frank J.; Cantrell, James N.; Mccurdy, Greg

1992-01-01

303

General view of the flight deck of the Orbiter Discovery ...  

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

General view of the flight deck of the Orbiter Discovery looking forward along the approximate center line of the orbiter at the center console. The Multifunction Electronic Display System (MEDS) is evident in the mid-ground center of this image, this system was a major upgrade from the previous analog display system. The commander's station is on the port side or left in this view and the pilot's station is on the starboard side or right tin this view. Not the grab bar in the upper center of the image which was primarily used for commander and pilot ingress with the orbiter in a vertical position on the launch pad. Also note that the forward observation windows have protective covers over them. This image was taken at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

304

GREEK HOUSE CLOSING INFORMATION _________________________________ will be closing and securing the _____________________________  

E-print Network

GREEK HOUSE CLOSING INFORMATION _________________________________ will be closing and securing the _____________________________ NAME HOUSE HOUSE On _____________________________________________________________________________________. DATE

Bogaerts, Steven

305

Uncertainties in MARS Meteor Orbit Radar Data  

NASA Astrophysics Data System (ADS)

The uncertainties in meteor radar data and the problem of hyperbolic meteors are interconnected. Meteor orbital data, obtained by the Meteor Automatic Radar System (MARS) at the Kharkiv Institute of Radio Electronics, Ukraine, was used to develop the algorithm to determine the uncertainties of the orbital elements obtained by radar systems such as MARS. We have constructed the empirical model of the distribution of uncertainties in the orbital elements of meteor radar data. MARS had a high effective sensitivity (the limiting magnitude of observed meteors was close to 12 ^ M) and was capable to carry out comprehensive geophysical and astronomical studies of meteors. When we register meteor numbers, radiants, meteoroid velocities, we can talk about astronomical observations. The main objective of meteor astronomy research is to determine the orbit of the meteoroid, in other words, to study a meteoroid as an astronomical object of the Solar System. Sometimes meteoroids may have an interstellar origin. Such meteoroids usually have hyperbolic orbits (i.e. with eccentricities e>1). However, hyperbolic orbits of meteoroids may have another origin, e.g. arise due to errors of observations (primarily due to the errors of eccentricities - ?e). To correctly interpret the astronomical data, it is necessary to know how the errors are calculated. In this paper, we estimated the uncertainties in the Kharkiv meteor radar data (the average ?e ~0.2) and discussed their connection to the problem of hyperbolic meteors. We obtained ~0.8% of total number of meteoroid orbits in 1975, which we named "real" hyperboles, i.e. with eccentricities more or equal 1+2?e.

Kolomiyets, S. V.

2015-03-01

306

[Orbital complications of sinusitis].  

PubMed

Orbital complications categorised by Chandler are emergency. They need early diagnosis and agresive treatment. Stage and origin of orbital complications are identified by rhinoendoscopy, ophtalmologic examination and CT of orbite and paranasal sinuses. Periorbital cellulitis and early stage of orbital cellulitis can be treated conservatively with i. v. antibiotics. Monitoring of laboratory parameters and ophtalmologic symptoms is mandatory. Lack of improvement or worsening of symptoms within 24-48 hours and advanced stages of orbital complications are indicated for surgery. The purpose of the study is to evaluate epidemiology, clinical features and management of sinogenic orbital complications. Retrospective data of 8 patients with suspicion of orbital complication admited to hospital from 2008 to 2013 were evaluated. Patients were analyzed in terms of gender, age, CT findings, microbiology, clinical features, stage and treatment. Male and female were afected in rate 1,66:1. Most of patients were young adult in 3rd. and 4th. decade of life (62,5 %). Acute and chronic sinusitis were cause of orbital complication in the same rate. The most common origin of orbital complication was ethmoiditis (62,5 %), than maxillary (25 %) and frontal (12,5 %) sinusitis. Polysinusitis with affection of ethmoidal, maxillary and frontal sinuses (75 %) was usual CT finding. Staphylococcus epidermidis and Staphylococcus aureus were etiological agens in half of cases. Periorbital oedema (100 %), proptosis, chemosis (50 %), diplopia and glaucoma (12,5 %) were observed. Based on examinations, diagnosis of periorbital oedema/preseptal cellulitis was made in 3 (37,5 %), orbital cellulitis in 3 (37,5 %) and subperiosteal abscess in 2 cases (25 %). All patients underwent combined therapy - i. v. antibiotics and surgery within 24 hours. Eradication of disease from ostiomeatal complex (OMC), drainage of affected sinuses and drainage of subperiosteal abscess were done via fuctional endonasal endoscopic surgery (FEES). In case of superior subperiosteal abscess, combined endonasal and external approach (external orbitotomy) was needed. Combined therapy facilitated quick improvement of local and systematic symptoms. Average time of hospitalisation was 7 days. Early diagnosis and agresive combined therapy prevent loss of vision and life threatening complications. PMID:25640234

Šucha?, M; Hor?ák, M; Kaliarik, L; Krempaská, S; Koštialová, T; Kova?, J

2014-12-01

307

Laser, GPS and absolute gravimetry vertical positioning time series comparison at the OCA observatory, France  

NASA Astrophysics Data System (ADS)

Time-dependent displacements of stations usually have magnitude close to the accuracy of each individual technique, and it still remains difficult to separate the true geophysical motion from possible artifacts inherent to each space geodetic technique. The Observatoire de la C“te d'Azur (OCA), located at Grasse, France benefits from the collocation of several geodetic instruments and techniques (3 laser ranging stations, and a permanent GPS) what allows us to do a direct comparison of the time series. Moreover, absolute gravimetry measurement campaigns have also been regularly performed since 1997, first by the "Ecole et Observatoire des Sciences de la Terre (EOST) of Strasbourg, France, and more recently by the Royal Observatory of Belgium. This study presents a comparison between the positioning time series of the vertical component derived from the SLR and GPS analysis with the gravimetric results from 1997 to 2003. The laser station coordinates are based on a LAGEOS -1 and -2 combined solution using reference 10-day arc orbits, the ITRF2000 reference frame, and the IERS96 conventions. Different GPS weekly global solutions provided from several IGS are combined and compared to the SLR results. The absolute gravimetry measurements are converted into vertical displacements with a classical gradient. The laser time series indicate a strong annual signal at the level of about 3-4 cm peak to peak amplitude on the vertical component. Absolute gravimetry data agrees with the SLR results. GPS positioning solutions also indicate a significant annual term, but with a magnitude of only 50% of the one shown by the SLR solution and by the gravimetry measurements. Similar annual terms are also observed on other SLR sites we processed, but usually with! lower and various amplitudes. These annual signals are also compared to vertical positioning variations corresponding to an atmospheric loading model. We present the level of agreement between the different techniques and we discuss possible explanations for the discrepancy noted between the signals. At last, we expose explanations for the large annual term at Grasse: These annual variations could be partly due to an hydrological loading effect on the karstic massif on which the observatory is located.

Nicolas, J.; Nocquet, J.; van Camp, M.; Coulot, D.

2003-12-01

308

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

309

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

310

The effect of top and bottom lids on natural convection inside a vertical cylinder  

Microsoft Academic Search

Natural convection experiments inside a vertical cylindrical cavity were performed for Rayleigh numbers of 1.08×1010–2.11×1013 and for four different geometrical arrangements: both-open (pipe-shape), bottom-closed (cup-shape), top-closed (cap), and both-closed (cavity) cylinders. A copper electroplating system was employed for the measurements of heat transfer rates using analogy concept. The lids used to close top or bottom were adiabatic; i.e. inactive surfaces

Bum-Jin Chung; Jeong-Hwan Heo; Min-Hwan Kim; Gyeong-Uk Kang

2011-01-01

311

LAGEOS orbit and solar eclipses  

Microsoft Academic Search

The objective was to assess the importance of solar eclipses on Lageos' orbit. Solar radiation pressure perturbs the orbit of the Lageos satellite. The GEODYN orbit determination computer program includes solar radiation pressure as one of the forces operating on the satellite as it integrates the orbit. GEODYN also takes into account the extinction of sunlight when Lageos moves into

D. P. Rubincam

1984-01-01

312

Core scattering of quadratic Zeeman orbits in barium  

SciTech Connect

We report a method to uncover the peaks due to scattering of quadratic Zeeman orbits by the atomic core of a many-electron atom. The method is experimental, and consists in identifying the supernumerary peaks in the scaled-energy spectra by comparing them with the corresponding hydrogenic calculations using closed-orbit theory. The scaled actions of the observed additional peaks correspond to combining the scaled actions of individual closed orbits, except for a small blueshift, which is explainable as a core-induced interaction, depending on the penetration of the orbits. Our method is related to earlier theoretical studies of helium, but can be applied to any experimentally accessible atom, including those with large cores. We show that, for barium, core-scattering processes do indeed occur, and that they are confined to a specific portion of the scaled-energy spectrum.

Liu Hongping; Zhan Mingsheng [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Center for Cold Atom Physics, Chinese Academy of Sciences, Wuhan 430071 (China); Quan Wei; Shen Li [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Center for Cold Atom Physics, Chinese Academy of Sciences, Wuhan 430071 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Connerade, Jean-Patrick [Quantum Optics and Laser Science Group, Blackett Laboratory, Imperial College, London SW7 2BW (United Kingdom); State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China)

2007-07-15

313

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

314

Mars Telecommunications Orbiter, Artist's Concept  

NASA Technical Reports Server (NTRS)

This illustration depicts a concept for NASA's Mars Telecommunications Orbiter in flight around Mars. The orbiter is in development to be the first spacecraft with a primary function of providing communication links while orbiting a foreign planet. The project's plans call for launch in September 2009, arrival at Mars in August 2010 and a mission of six to 10 years while in orbit. Mars Telecommunication Orbiter would serve as the Mars hub for an interplanetery Internet, greatly increasing the information payoff from other future Mars missions. The mission is designed to orbit Mars more than 10 times farther from the planet than orbiters dedicated primarily to science. The high-orbit design minimizes the time that Mars itself blocks the orbiter from communicating with Earth and maximizes the time that the orbiter is above the horizon -- thus capable of communications relay -- for rovers and stationary landers on Mars' surface.

2005-01-01

315

Sedna Orbit Comparisons  

NASA Technical Reports Server (NTRS)

These four panels show the location of the newly discovered planet-like object, dubbed 'Sedna,' which lies in the farthest reaches of our solar system. Each panel, moving counterclockwise from the upper left, successively zooms out to place Sedna in context. The first panel shows the orbits of the inner planets, including Earth, and the asteroid belt that lies between Mars and Jupiter. In the second panel, Sedna is shown well outside the orbits of the outer planets and the more distant Kuiper Belt objects. Sedna's full orbit is illustrated in the third panel along with the object's current location. Sedna is nearing its closest approach to the Sun; its 10,000 year orbit typically takes it to far greater distances. The final panel zooms out much farther, showing that even this large elliptical orbit falls inside what was previously thought to be the inner edge of the Oort cloud. The Oort cloud is a spherical distribution of cold, icy bodies lying at the limits of the Sun's gravitational pull. Sedna's presence suggests that this Oort cloud is much closer than scientists believed.

2004-01-01

316

Periodic orbit theory revisited in the anisotropic Kepler problem  

NASA Astrophysics Data System (ADS)

Gutzwiller's trace formula for the anisotropic Kepler problem (AKP) is Fourier transformed with a convenient variable u=1/?{-2E}, which takes care of the scaling property of the AKP action S(E). The proper symmetrization procedure (Gutzwiller's prescription) is used by the introduction of half orbits that close under symmetry transformations, so that the 2D semiclassical formulas correctly match the quantum subsectors m^? =0^+ and m^? =0^-. Response functions constructed from half orbits in the periodic orbit theory (POT) side are explicitly given. In particular, the response function g_X from the X-symmetric half orbit has an amplitude where the root of the monodromy determinant is inverse hyperbolic. The resultant weighted densities of periodic orbits D^{m=0}_e(?) and D^{m=0}_o(?) from both quantum subsectors show peaks at the actions of the periodic orbits with correct peak heights and widths corresponding to their Lyapunov exponents. The formulation takes care of the cut-off of the energy levels, and the agreement between the D(?)s of the quantum mechanical (QM) and POT sides is observed to be independent of the choice of cut-off. The systematics appearing in the densities of the periodic orbits is explained in terms of features of the periodic orbits. It is shown that, from quantum energy levels, one can extract information on AKP periodic orbits, even the Lyapunov exponents-the success of inverse quantum chaology in AKP.

Kubo, Kazuhiro; Shimada, Tokuzo

2014-02-01

317

Close up view of the Commander's Seat on the Flight ...  

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

Close up view of the Commander's Seat on the Flight Deck of the Orbiter Discovery. It appears the Orbiter is in the roll out / launch pad configuration. A protective cover is over the Rotational Hand Controller to protect it during the commander's ingress. Most notable in this view are the Speed Brake/Thrust Controller in the center right in this view and the Translational Hand Controller in the center top of the view. This image was taken at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

318

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

319

Core scattering of quadratic Zeeman orbits in barium  

Microsoft Academic Search

We report a method to uncover the peaks due to scattering of quadratic Zeeman orbits by the atomic core of a many-electron atom. The method is experimental, and consists in identifying the supernumerary peaks in the scaled-energy spectra by comparing them with the corresponding hydrogenic calculations using closed-orbit theory. The scaled actions of the observed additional peaks correspond to combining

Zhan Mingsheng; Liu Hongping; Shen Li; Jean-Patrick Connerade

2007-01-01

320

Supermassive black hole binaries in gaseous and stellar circumnuclear discs: orbital dynamics and gas accretion  

E-print Network

The dynamics of two massive black holes in a rotationally supported nuclear disc of 10^8 solar masses is explored using N-Body/SPH simulations. Gas and star particles are co-present in the disc. Described by a Mestel profile, the disc has a vertical support provided by turbulence of the gas, and by stellar velocity dispersion. A primary black hole of 4 million solar masses is placed at the centre of the disc, while a secondary black hole is set initially on an eccentric co-rotating orbit in the disc plane. Its mass is in a 1 to 1, 1 to 4, and 1 to 10 ratio, relative to the primary. With this choice, we mimic the dynamics of black hole pairs released in the nuclear region at the end of a gas-rich galaxy merger. It is found that, under the action of dynamical friction, the two black holes form a close binary in ~10 Myrs. The inspiral process is insensitive to the mass fraction in stars and gas present in the disc and is accompanied by the circularization of the orbit. We detail the gaseous mass profile bound to each black hole that can lead to the formation of two small Keplerian discs, weighing ~2 % of the black hole mass, and of size ~0.01 pc. The mass of the tightly (loosely) bound particles increases (decreases) with time as the black holes spiral into closer and closer orbits. Double AGN activity is expected to occur on an estimated timescale of ~10 Myrs, comparable to the inspiral timescale. The double nuclear point-like sources that may appear during dynamical evolution have typical separations of ~10 pc.

M. Dotti; M. Colpi; F. Haardt; L. Mayer

2007-06-12

321

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

322

Indentities Relating Spin-Spin and Orbit-Orbit to Spin-Orbit Interactions  

Microsoft Academic Search

We derive indentities that express spin-spin and orbit-orbit interactions in terms of two-electron spin-orbit matrix elements. They can reduce, in effect, any study of the two-electron Breit-Pauli Hamiltonian for atoms or molecules to one of determining the spin-orbit integrals, thereby considerably unifying and simplifying the whole analysis.

R. L. Matcha; C. W. Kern

1970-01-01

323

Radiation therapy: orbital tumors.  

PubMed

Orbital tumors are rare overall, comprising 0.1% of all tumors and less than 20% of all orbital diseases. Tumors may be benign, locally aggressive, or malignant. Of the malignant tumors, lymphomas and metastases are the most common and are primarily seen in the elderly population. While surgery and chemotherapeutic agents are often employed in the management of these lesions, not all patients are candidates for these therapies. Radiation therapy offers a noninvasive, well-tolerated primary treatment modality, whereby vision-sparing is feasible in many cases. In this chapter, we review an array of non-neoplastic entities and orbital tumors, for which there exists a role for radiation, and the radiotherapeutic techniques and applications in their management. PMID:23989130

Marwaha, Gaurav; Macklis, Roger; Singh, Arun D

2013-01-01

324

Observed and real orbital dispersion within meteoroid streams  

NASA Astrophysics Data System (ADS)

The present paper, based on a statistical analysis of orbits obtained from video meteors, shows the orbits' distribution within the meteoroid streams with heliocentric velocities close to the parabolic limit. The high proportion of hyperbolic orbits among the corresponding meteor showers was used to deduce the contribution of the real orbital dispersion within the stream, because an excess of a heliocentric velocity of a stream meteoroid over the parabolic value can be regarded entirely as the result of measuring errors. Four meteor showers, April Lyrids, Perseids, Orionids, and Leonids, were selected for this analysis. The orbital dispersion within the investigated meteoroid streams, based on the distribution of their reciprocal semimajor axes, obtained from different catalogues, were compared. It was shown that the major part of the observed differences in the semimajor axes within meteoroid streams from the European Video Meteor Network data is indeed due to measuring errors.

Hajduková, Mária

2014-01-01

325

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

326

Orbit maintenance for low altitude near-circular lunar orbits  

NASA Technical Reports Server (NTRS)

The behavior of low altitude near-circular lunar orbits is a key design issue for some missions in the proposed Space Exploration Initiative. The lunar gravity field strongly perturbs low altitude orbits, so an effective orbit maintenance strategy is needed. This strategy must contend with the long term orbit evolution due to the zonal gravity field. Two possible orbit control scenarios are passive control using a frozen orbit and active orbit control using maneuvers. A maneuver strategy can be designed which optimizes the propellant required for long term orbit sustenance. The long term requirements dominate the total propellant required for orbit control. Additional propellant may be required to offset the impact of medium period gravity field effects. Careful selection of maneuver times and directions, however, can eliminate any medium period penalty.

Cook, Richard A.; Sweetser, Theodore H.

1992-01-01

327

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

328

Using DORIS measurements for modeling the vertical total electron content of the Earth's ionosphere  

NASA Astrophysics Data System (ADS)

The Doppler orbitography and radiopositioning integrated by satellite (DORIS) system was originally developed for precise orbit determination of low Earth orbiting (LEO) satellites. Beyond that, it is highly qualified for modeling the distribution of electrons within the Earth's ionosphere. It measures with two frequencies in L-band with a relative frequency ratio close to 5. Since the terrestrial ground beacons are distributed quite homogeneously and several LEOs are equipped with modern receivers, a good applicability for global vertical total electron content (VTEC) modeling can be expected. This paper investigates the capability of DORIS dual-frequency phase observations for deriving VTEC and the contribution of these data to global VTEC modeling. The DORIS preprocessing is performed similar to commonly used global navigation satellite systems (GNSS) preprocessing. However, the absolute DORIS VTEC level is taken from global ionospheric maps (GIM) provided by the International GNSS Service (IGS) as the DORIS data contain no absolute information. DORIS-derived VTEC values show good consistency with IGS GIMs with a RMS between 2 and 3 total electron content units (TECU) depending on solar activity which can be reduced to less than 2 TECU when using only observations with elevation angles higher than . The combination of DORIS VTEC with data from other space-geodetic measurement techniques improves the accuracy of global VTEC models significantly. If DORIS VTEC data is used to update IGS GIMs, an improvement of up to 12 % can be achieved. The accuracy directly beneath the DORIS satellites' ground-tracks ranges between 1.5 and 3.5 TECU assuming a precision of 2.5 TECU for altimeter-derived VTEC values which have been used for validation purposes.

Dettmering, Denise; Limberger, Marco; Schmidt, Michael

2014-12-01

329

Notes to Saturn satellites Ijiraq and Kiviuq mutual close encounters  

E-print Network

The problem of origin of outer irregular satellites of large planets is considered. The capture way of their origin most probable, however there is not detail theory. There are a number of irregular satellites, discovered in recent time. It gives an ability to investigate the statistics of orbital interaction and try to reconstruct real collision history of these objects We restrict this consideration by pair of orbits with close elements: Kiviuq and Ijiraq and determine period of close encounters between this satellites. It may be considered as a first step on road to the construction of theory of origin of the abundant class of irregular satellites.

A. E. Rosaev

2006-02-01

330

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.

331

Passive orbital disconnect strut  

NASA Technical Reports Server (NTRS)

The design and test results with a third generation passive orbital disconnect strut (PODS) for space-based cryogenic He dewars are presented. Three pairs of PODS struts support a tank and change lengths in response to gas and temperature changes. A thin wall fiberglass tube is used on the cold disconnect end, which can be operated on the ground or in space. Tests were performed to characterize heat flows across the cold end to a liquid He sink and subsequent vacuum pressure within the He tank. Heat transfer was lower than predicted, suggesting that longer dewar in-orbit lifetimes can be expected with the new PODS.

Parmley, R. T.; Kittel, P.

1984-01-01

332

Can agents close contracts?  

Microsoft Academic Search

One of the tasks of software agents on the Internet will be to close contracts on behalf of their owner. The closing of a contract is subject to liabilities. In this, there is no distinction between the real world and the virtual world. Like in the real world, within the virtual world a distinction has to be made between the

Frances Brazier; Anja Oskamp; Maurice Schellekens; Niek Wijngaards

2003-01-01

333

Surviving a School Closing  

ERIC Educational Resources Information Center

When a beloved school closes, community emotions run high. De Witt and Moccia, administrators in the Averill Park School District in upstate New York, describe how their district navigated through parents' anger and practical matters in closing a small neighborhood elementary school and transferring all its students to another school. With a group…

De Witt, Peter M.; Moccia, Josephine

2011-01-01

334

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

335

The forecast of predictability for computed orbits in galactic models  

NASA Astrophysics Data System (ADS)

The predictability of a system indicates how much time a computed orbit is close to an actual orbit of the system, independent of its stability or chaotic nature. We derive a predictability index from the distributions of finite-time Lyapunov exponents of several prototypical orbits, both regular and irregular, in a variety of galactic potentials. In addition, by analysing the evolution of the shapes of the distributions with the finite-time intervals sizes, we get an insight into the time-scales of the model when the flow dynamics evolve from the local to the global regime.

Vallejo, J. C.; Sanjuán, M. A. F.

2015-03-01

336

The challenge of reusable, single stage to orbit propulsion  

NASA Astrophysics Data System (ADS)

Single stage to orbit (SSTO) applications will require high performance of the main propulsion system (whether rocket or airbreathing) throughout launch-to-orbit to achieve any meaningful payload capability. The challenge of true reusability dictates fail safe operation, high reliability and low maintenance actions to achieve turnaround similar to that achieved thousands of times each day in the commercial and military aircraft industry. This paper discusses the relative merits of candidate SSTO rocket propulsion systems and defines a reusable near-term expander cycle configuration for a vertical take-off/vertical landing vehicle with high performance and attractive operability characteristics. This engine could be available for a flight test program within four years of the start of development.

Holloway, J. F.; Limerick, C. D.

1993-02-01

337

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

338

Sedna Orbit Animation  

NASA Technical Reports Server (NTRS)

This animation shows the location of the newly discovered planet-like object, dubbed 'Sedna,' in relation to the rest of the solar system. Starting at the inner solar system, which includes the orbits of Mercury, Venus, Earth, and Mars (all in yellow), the view pulls away through the asteroid belt and the orbits of the outer planets beyond (green). Pluto and the distant Kuiper Belt objects are seen next until finally Sedna comes into view. As the field widens the full orbit of Sedna can be seen along with its current location. Sedna is nearing its closest approach to the Sun; its 10,000 year orbit typically takes it to far greater distances. Moving past Sedna, what was previously thought to be the inner edge of the Oort cloud appears. The Oort cloud is a spherical distribution of cold, icy bodies lying at the limits of the Sun's gravitational pull. Sedna's presence suggests that this Oort cloud is much closer than scientists believed.

2004-01-01

339

Magellan orbits Venus  

NASA Technical Reports Server (NTRS)

Various events surrounding Magellan's orbit of Venus are recounted. Significant events include the successful firing of a solid rocket motor while the spacecraft was behind Venus to transfer it from a solar-centered trajectory to an orbit around the planet. The spacecraft orbits Venus every 3.26 hours at a maximum altitude of 8500 km and minimum altitude of 291 km in an elliptical orbit. The successful August 16 test of the synthetic-aperture radar system is discussed, noting that it produced two strips, each about 20 km x 16,000 km, revealing details as small as 120 m. Two anomalies causing a delay in the start of mapping operations and subsequent breaks in the communication link with earth for 14.5 hours and 17.7 hours are discussed. Protective measures directed from the spacecraft's ROM during breach of contact are listed, and possible causes of the anomalies are suggested, such as solar activity or hardware or software elements, although the actual cause is not yet known.

Mclaughlin, W. I.

1990-01-01

340

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.

341

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.

342

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

343

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

344

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

345

KBO orbits for occultations  

NASA Astrophysics Data System (ADS)

The orbits and physical properties of Kuiper Belt Objects (KBOs) provide valuable constraints on the dynamical and environmental evolution of the outer Solar System. Much progress has been made in the past two decades of KBO observations but we still have limited information on physical sizes of these objects. Thermal observations work well (with Spitzer and Herschel) but the dynamically cold classical KBOs (low inclination, low eccentricity near 45 AU) have proven especially challenging with radiometric techniques. This particular class of object is arguably the most primitive (least disturbed) and are a critical component for study. Stellar occultations can provide the missing sizes but to do so we need more objects with better orbits to make these observations feasible. The cold classical objects are also the most likely to have satellites. Getting an occultation diameter on binary objects will permit getting accurate densities since the system mass is known from the satellite orbit. These proposed observations will collect critical astrometry needed to improve the orbits of under- observed KBOs that are candidates for stellar occultation observations. Where possible, known binaries will be given preference for astrometry. This work is part of a NSF-funded pilot project to secure occultation diameters of KBOs.

Buie, Marc

2013-08-01

346

PKUPs Around Orbit Test  

NASA Astrophysics Data System (ADS)

This program is designed to test the idea of multiple PKUPs per viewing interval using the MDRS aperture. The same target will be scheduled in several different patterns with respect to the orbital Day/Night boundary to assess the best method of MDRS operations to get SiC coverage of D/H and other targets.

Blair, William

347

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

348

CLOSE APPROACHES OF ASTEROID 1999 AN 10 : RESONANT AND NONRESONANT RETURNS  

E-print Network

CLOSE APPROACHES OF ASTEROID 1999 AN 10 : RESONANT AND NON­RESONANT RETURNS Andrea Milani, Steven R to the orbit of the asteroid 1999 AN 10 twice per year, but whether or not this asteroid can have a close there are some with a close approach in 2027. The period of the asteroid may be perturbed in such a way

Milani, Andrea

349

Advanced technologies for rocket single-stage-to-orbit vehicles  

Microsoft Academic Search

A single-stage-to-orbit vertical takeoff\\/horizontal landing rocket vehicle was studied to determine the benefits of advanced technology. Advanced technologies that were included in the study were variable mixture ratio oxygen\\/hydrogen rocket engines and materials, structures, and subsystem technologies currently being developed in the National Aero-Space Plane Program. The application of advanced technology results in an 85 percent reduction in vehicle dry

Alan W. Wilhite; Lance B. Bush; Christopher I. Cruz; Roger A. Lepsch; W. Douglas Morris; Douglas O. Stanley; Kathryn E. Wurster

1991-01-01

350

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

351

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

352

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

353

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

354

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

355

Vertical saccades in dyslexic children.  

PubMed

Vertical saccades have never been studied in dyslexic children. We examined vertical visually guided saccades in fifty-six dyslexic children (mean age: 10.5±2.56 years old) and fifty-six age matched non dyslexic children (mean age: 10.3±1.74 years old). Binocular eye movements were recorded using an infrared video-oculography system (mobileEBT®, e(ye)BRAIN). Dyslexic children showed significantly longer latency than the non dyslexic group, also the occurrence of anticipatory and express saccades was more important in dyslexic than in non dyslexic children. The gain and the mean velocity values were significantly smaller in dyslexic than in non dyslexic children. Finally, the up-down asymmetry reported in normal population for the gain and the velocity of vertical saccades was observed in dyslexic children and interestingly, dyslexic children also reported an up-down asymmetry for the mean latency. Taken together all these findings suggested impairment in cortical areas responsible of vertical saccades performance and also at peripheral level of the extra-ocular oblique muscles; moreover, a visuo-attentionnal bias could explain the up-down asymmetry reported for the vertical saccade triggering. PMID:25151607

Tiadi, Aimé; Seassau, Magali; Bui-Quoc, Emmanuel; Gerard, Christophe-Loïc; Bucci, Maria Pia

2014-11-01

356

Amplatzer vascular plug for transcatheter closure of persistent unligated vertical vein after repair of infracardiac total anomalous pulmonary venous connection.  

PubMed

Repair of total anomalous pulmonary venous connection (TAPVC) involves anastomosing the pulmonary venous confluence with the left atrium and ligating the vertical vein. Sometimes, the vertical vein needs to be left open as a pop off with the idea that it will close over time. Infrequently an unligated vertical vein may remain patent after repair of infaracardiac TAPVC leading to hemodynamic instability. We report an infant in whom an unligated vertical vein remained patent after the repair of infracardiac TAPVC and caused hemodynamically significant left-to-right shunting. A successful transcatheter closure of persistent patent unligated vertical vein was performed using the Amplatzer Vascular Plug-I device. PMID:22422595

Kobayashi, Daisuke; Forbes, Thomas J; Delius, Ralph E; Aggarwal, Sanjeev

2012-08-01

357

Gravitational radiation from close double white dwarfs  

NASA Astrophysics Data System (ADS)

We use recent population synthesis models for the production of close double white dwarfs [1] to calculate their gravitational wave spectrum. The properties of that spectrum are nearly independent of the assumptions involved in that model, depending in normalization only on the frequency of primordial binaries of intermediate mass, orbital periods of a few years, and mass ratios near unity. The gravitational wave energy density at lower frequencies in the LISA window will provide a robust measure of the galactic type Ia supernova rate. Roughly 3600 individual close white dwarf binaries should be resolvable at frequencies above the confusion limit at 3.6 mHz, with 90 percent of these systems showing detectable orbital evolution due to gravitational radiation within a 5-year mission lifetime. For these binaries, distances and chirp masses can be obtained independently, making it possible to study their intrinsic and spatial distributions separately. In an exceptional one or two cases, it should be possible to detect v? within a 5-year mission, providing an important probe into tidal heating processes preceding a merger. The probability of observing an actual merger within a 5-year mission is small (about 15%), but not negligible. Only a small fraction of mergers can produce supernovae. However, it will be possible to identify supernova progenitors from the general population of close double white dwarfs, and to predict their outburst dates with uncertainties as small as a century, or even a few years in the most favorable of cases.

Webbink, Ronald F.; Han, Zhanwen

1998-12-01

358

Horseshoe Asteroids and Quasi-satellites in Earth-like Orbits  

NASA Technical Reports Server (NTRS)

Newly found asteroid 2003 YN107 is the first and only known current quasi-satellite (QS) of the Earth. Asteroid 2002 AA29 is in a horseshoe orbit (HS) but has periods of QS behavior. Both asteroids closely follow Earth s orbit. 2002 AA29 has inclination i is approximately 11 degrees while for 2003 YN107 i<5 degrees, making the most Earth-like orbit known. 2003 YN107, 2002 AA29, and other Earth-resonant objects in less Earthlike orbits, form an important new class of co-orbital bodies with interesting dynamics and are the best targets for sample return missions to asteroids.

Connors, M.; Veillet, C.; Brasser, R.; Wiegert, P.; Chodas, P. W.; Mikkola, S.; Innanen, K.

2004-01-01

359

Unusual sclerosing orbital pseudotumor infiltrating orbits and maxillofacial regions.  

PubMed

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. PMID:24991481

Toprak, Huseyin; Arala?mak, Ay?e; Y?lmaz, Temel Fatih; Ozdemir, Huseyin

2014-01-01

360

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. PMID:24991481

Toprak, Huseyin; Arala?mak, Ay?e; Y?lmaz, Temel Fatih; Ozdemir, Huseyin

2014-01-01

361

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

362

Enceladus' Influence on the Vertical Structure of Saturn's E Ring  

NASA Astrophysics Data System (ADS)

Within ~+/- 20,000 km of Enceladus' orbit, Saturn's tenuous E ring has a double-banded appearance, with the number of particles depleted by a few percent within +/- 1000 km of the planet’s equatorial plane (Hedman et al. 2012). We wish to understand this vertical structure, to learn if it might indicate launch speeds or a sweeping effect of Enceladus. We have combined order-of-magnitude analytical estimates and numerical simulations that include Enceladus and Saturn's gravity up to J6 in short-term (1-2 days) and longer-term 200-yr) integrations. Because most particles emanating from the surface geysers will fall back on the moon, the E ring must be dominated by particles that barely escaped. Hence we follow the orbits of many hundreds of particles launched near Enceladus' southern pole with speeds between ~ 0.8 to 2 times the nominal escape speed (i.e., that from an isolated sphere). We illustrate some contorted trajectories within the three-body problem for such launch conditions. Typically, gravitational deceleration after launch followed by a few gravitational kicks from the moon induce many particles to attain orbital inclinations corresponding to a maximum height of ~4rE (rE = radius of Enceladus = 250 km), or about one Hill radius for Enceladus. The vertical epicyclic motions of such inclined orbits account the observed two-banded structure. Simultaneous gravitational interactions will scatter particles to produce a two-banded, radially extended (+/-10,000km) Gaussian core on either side of Enceladus, as observed. In our simple model, particles are lost by collisions into Enceladus in ~ 100 yrs; mutual impacts are ignored. Since gravity alone can generate in short order the most prominent features in the observed structures, non-gravitational forces (cf. Kempf et al. 2010) mostly affect other aspects of the E ring structure and evolution.

Burns, Joseph A.; Agarwal, M.; Hedman, M. M.; Tiscareno, M. S.

2013-10-01

363

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 they’re 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.

2012-06-26

364

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

365

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

366

Options for human {open_quote}{open_quote}return to the moon{close_quote}{close_quote} using tomorrow{close_quote}s SSTO, ISRU, and LOX-augmented NTR technologies  

Microsoft Academic Search

The feasibility of conducting human missions to the Moon is examined assuming the use of three {open_quote}{open_quote}high leverage{close_quote}{close_quote} technologies: (1) a single-stage-to-orbit (SSTO) launch vehicle, (2) {open_quote}{open_quote}{ital in}-{ital situ}{close_quote}{close_quote} {ital resource} {ital utilization} (ISRU)specifically {open_quote}{open_quote}lunar-derived{close_quote}{close_quote} liquid oxygen (LUNOX), and (3) LOX-augmented nuclear thermal rocket (LANTR) propulsion. Lunar transportation system elements consisting of a LANTR-powered lunar transfer vehicle (LTV) and a

Borowski

1996-01-01

367

Free convection over a vertical porous plate with transpiration  

NASA Technical Reports Server (NTRS)

The problem of free convection over an isothermal vertical porous plate with transpiration is studied both numerically and experimentally. Numerical solutions to the variable-property transpired free-convection boundary layer equations have been obtained using the finite difference procedure of Patankar and Spalding (1967). The effects of uniform transpiration on heat transfer and on temperature and velocity profiles are predicted. Interferometrically measured nondimensional temperature profiles for the uniform wall temperature and transpiration case agreed closely with these numerical predictions.

Parikh, P. G.; Moffat, R. J.; Kays, W. M.; Bershader, D.

1974-01-01

368

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

369

Measurements of vertical bar Vcb vertical bar and vertical bar Vub vertical bar at BaBar  

SciTech Connect

We report results from the BABAR Collaboration on the semileptonic B decays, highlighting the measurements of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix elements Vub and Vcb. We describe the techniques used to obtain the matrix element |Vcb| using the measurement of the inclusive B {yields} Xclv process and a large sample of exclusive B {yields} D*lv decays. The vertical bar Vub vertical bar matrix elements has been measured studying different kinematic variables of the B {yields} Xulv process, and also with the exclusive reconstruction of B {yields} {pi}({rho})lv decays.

Rotondo, M. [Dipartimento di Fisica Galileo Galilei, Via Marzolo 8, Padova 35131 (Italy)

2005-10-12

370

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

371

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

372

Orbital Motions in Binary Protostellar Systems  

NASA Astrophysics Data System (ADS)

Using high-resolution ( ˜ 0to z @. hss ''1), multi-epoch Very Large Array observations, we have detected orbital motions in several low-luminosity protobinary systems in the Taurus and ? Ophiuchus molecular complexes. The masses obtained from Kepler's third law are of the order of 0.5 to 2 M?, as expected for such low-mass protostars. The relatively large bolometric luminosities of these young systems corroborates the notion that protostars obtain most of their luminosity from accretion and not from nuclear reactions. In addition, in one of the sources studied (a multiple system in Taurus), a low-mass young star has shown a drastic change in its orbit after a close approach with another component of the system, presumed to be a double star. The large proper motion achieved by this low mass protostar (20 km s-1), suggests an ejection from the system.

Rodríguez, L. F.

2004-08-01

373

Condensation heat transfer in two-phase co-current closed thermosyphon  

NASA Astrophysics Data System (ADS)

This paper presents a theoretical analysis and experimental results of condensation heat transfer in the vertical two-phase cocurrent closed thermosyphon. The effects of the relative importance of two kinds of shear stresses are considered in the theoretical prediction.

Wei, Hong; Ma, Tongze

1991-05-01

374

Subjective postural vertical in peripheral and central vestibular disorders.  

PubMed

The perception of subjective postural vertical was assessed in normals and patients with peripheral and central vestibular disorders and spasmodic torticollis. The subjects were seated in a motorized gimbal with the head and torso restrained and their eyes closed. The gimbal executed 7-10 cycles of tilt around the vertical at 1.5 degrees/s in either pitch or roll. Subjects indicated when they began to feel upright and again when they began to feel tilted by an analogous 3-position joystick. Normal subjects felt upright within a sector of 5-6 degrees around vertical in pitch and roll. Five patients with absent vestibular function, 25 torticollis patients and 3 patients with acute unilateral peripheral vestibular lesions showed a significant increase of the sector in pitch and roll, but only the latter had a mild directional bias. Two patients with long standing complete unilateral vestibular deficit and 8 patients with up or downbeat nystagmus in the vicinity of upright had abnormally large sectors within which they felt to be upright. The results suggest that vestibular function is important for the accurate perception of the postural vertical and that a directional asymmetry in vestibulo-ocular function or a head tilt does not necessarily correlate with a directional bias of subjective verticality. PMID:8749084

Bisdorff, A R; Anastasopoulos, D; Bronstein, A M; Gresty, M A

1995-01-01

375

Flight Paths of Orbiting Satellites  

NSDL National Science Digital Library

This is an activity to help students visualize the relationship of motion, time and space as it relates to objects orbiting the earth. They will be able to track the path of an orbiting object on a globe, plot the path of an orbiting object on a flat world map, and explain that an object orbiting earth on a plane will produce a flight path which appears as wavy lines on the earths surface.

376

Multidisciplinary Management of Orbital Rhabdomyosarcoma  

Microsoft Academic Search

\\u000a Rhabdomyosarcoma (RMS) is the most common orbital malignancy in childhood. Embryonal RMS and alveolar RMS are the two most\\u000a common histologic subtypes of RMS, and embryonal RMS is the most common subtype of orbital RMS. The clinical presentation\\u000a of orbital RMS depends on the tumor location in the orbit. Diagnosis is chiefly made through open biopsy, and complete initial\\u000a tumor

Winston W. Huh; Anita Mahajan

377

Orbiter Servicer Rendezvous Simulation (ORSIM)  

Microsoft Academic Search

Orbiter Servicer Rendezvous Simulation (ORSIM) is an automated tool that simulates sequential transfer maneuvers of an orbital maneuvering vehicle (OMV) transporting orbital replaceable units from a space-based depot, or logistics platform, to higher altitude SDI sdatellites. ORSIM calculates OMV energy expenditures (velocity changes) and event histories for various combinations of user-selected orbital transfer maneuvers. Additionally, ORSIM determines the optimal configuration\\/quantities

Amiel Amato; Mickie D. Hoffman

1987-01-01

378

Orbital myxoma: a case report.  

PubMed

Orbital myxomas are extremely rare tumors. We describe a 75-year old male patient with lower eyelid ectropion and 8-mm of left non-axial proptosis. Orbital CT and MRI revealed a well-demarcated lesion in the lateral quadrant of the orbit. After complete surgical excision, histopathological examination led to the diagnosis of orbital myxoma. The patient was followed-up for 1 year without recurrence. PMID:23560550

Tawfik, Hatem A; Elraey, Haidy Z

2013-06-01

379

Stability of orbits around planetary satellites considering a disturbing body in an elliptical orbit: Applications to Europa and Ganymede  

NASA Astrophysics Data System (ADS)

Europa and Ganymede are two of the four Jupiter’s moons which compose the Galilean satellite. These ones are planetary satellites of greater interest at the present moment among the scientific community. There are some missions being planned to visit them and and the Jovian system. One of them is the cooperation between NASA and ESA for the Europa Jupiter System Mission (EJSM). In this mission are planned the insertion of the spacecrafts JEO (Jupiter Europa Orbiter) and JGO (Jupiter Ganymede Orbiter) into Europa and Ganymede’s orbit. Thus, there is a great necessity for having a better comprehension of the dynamics of the orbits around this planetary satellite. This comprehension is essential for the success of this type of mission. In this context, this work aims to perform a search for low-altitude orbits around these planetary satellites. An emphasis is given in polar orbits. These orbits can be useful in the planning of aerospace activities to be conducted around this planetary satellite, with respect to the stability of orbits of artificial satellites. The study considers orbits of an artificial satellite around Europa and Ganymede under the influence of the third-body perturbation (the gravitational attraction of Jupiter) and the polygenic perturbations. These last ones occur due to forces such as the non-uniform distribution of mass (J2 and J3) of the main (central) body. A simplified dynamic model for polygenic perturbations is used. A new model for the third-body disturbance is presented considering it in an elliptical orbit. The Lagrange planetary equations, which compose a system of nonlinear differential equations, are used to describe the orbital motion of the artificial satellite around Ganymede. The equations showed here are developed in closed form to avoid expansions in inclination and eccentricity.

Cardoso dos Santos, Josué; Carvalho, Jean Paulo; Vilhena de Moraes, Rodolpho

380

Orbit Spaces in Superconductivity  

E-print Network

In the framework of Landau theory of phase transitions one is interested to describe all the possible low symmetry ``superconducting'' phases allowed for a given superconductor crystal and to determine the conditions under which this crystal undergoes a phase transition. These problems are best described and analyzed in the orbit space of the high symmetry group of the ``normal, non-superconducting'' phase of the crystal. In this article it is worked out a simple example concerning superconductivity, that shows the P-matrix method to determine the equations and inequalities defining the orbit space and its stratification. This approach is of general validity and can be used in all physical problems that make use of invariant functions, as long as the symmetry group is compact.

Vittorino Talamini

2006-07-30

381

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.� 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.

382

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

383

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

384

Orbiter KU-band transmitter  

NASA Technical Reports Server (NTRS)

The design, build, and test of an engineering breadboard Ku band quadraphase shift keyed and wideband frequency modulated transmitter are described. This orbiter Ku band transmitter drawer is to simulate the orbiter transmitter and meet the functional requirements of the orbiter communication link.

Halterman, R.

1976-01-01

385

Orbiter OMS and RCS technology  

NASA Technical Reports Server (NTRS)

Orbiter Orbital Maneuver Subsystem (OMS) and Reaction Control Subsystem (RCS) tankage has proved to be highly successful in shuttle flights on-orbit propellant transfer tests were done. Tank qualification tests along with flight demonstrations were carried out future uses of storable propellants are cited.

Boudreaux, R. A.

1982-01-01

386

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

387

Orbital Debris Modeling  

NASA Technical Reports Server (NTRS)

Presentation outlne: (1) The NASA Orbital Debris (OD) Engineering Model -- A mathematical model capable of predicting OD impact risks for the ISS and other critical space assets (2) The NASA OD Evolutionary Model -- A physical model capable of predicting future debris environment based on user-specified scenarios (3) The NASA Standard Satellite Breakup Model -- A model describing the outcome of a satellite breakup (explosion or collision)

Liou, J. C.

2012-01-01

388

Backtrack Orbit Search Algorithm  

Microsoft Academic Search

A Mathematical Solution to a Mathematical Problem. With the dramatic increase in satellite-born sensor resolution traditional methods of spatially searching for orbital data have become inadequate. As data volumes increase end-users of the data have become increasingly intolerant of false positives. And, as computing power rapidly increases end-users have come to expect equally rapid search speeds. Meanwhile data archives have

K. Knowles; R. Swick

2002-01-01

389

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

390

[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

391

Orbital spacecraft consumables resupply  

NASA Technical Reports Server (NTRS)

The capability to replenish spacecraft, satellites, and laboratories on-orbit with consumable fluids provides significant increases in their cost and operational effectiveness. Tanker systems to perform on-orbit fluid resupply must be flexible enough to operate from the Space Transportation System (STS), Space Station, or the Orbital Maneuvering Vehicle (OMV), and to accommodate launch from both the Shuttle and Expendable Launch Vehicles (ELV's). Resupply systems for storable monopropellant hydrazine and bipropellants, and water have been developed. These studies have concluded that designing tankers capable of launch on both the Shuttle and ELV's was feasible and desirable. Design modifications and interfaces for an ELV launch of the tanker systems were identified. Additionally, it was determined that modularization of the tanker subsystems was necessary to provide the most versatile tanker and most efficient approach for use at the Space Station. The need to develop an automatic umbilical mating mechanism, capable of performing both docking and coupler mating functions was identified. Preliminary requirements for such a mechanism were defined. The study resulted in a modular tanker capable of resupplying monopropellants, bipropellants, and water with a single design.

Dominick, Sam M.; Eberhardt, Ralph N.; Tracey, Thomas R.

1988-01-01

392

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

393

Close up view of the center console on the flight ...  

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

Close up view of the center console on the flight deck of the Orbiter Discovery showing the console's instrumentation and controls. The commanders station is located to the left in this view and the pilot's station is to the right in the view. The handle and lever located on the right side of the center console and towards its front is one of a pair, the commander has one on the left of his seat in his station, of Speed Brake/Thrust Controllers. These are dual purpose controllers. During ascent the controller can be use to throttle the main engines and during entry the controllers can be used to control aerodynamic drag by opening or closing the orbiter's speed brake. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

394

General Relativistic Hydrodynamic Processes in Close Neutron Star Binaries  

Microsoft Academic Search

We discuss several new physical processes which occur in close neutron star binaries. These processes are purely relativistic effects which can be directly traced to terms in our formulation of general relativistic hydrodynamics. In addition to the well known orbit instability, we show that these systems are also subject to relativistically induced compression, heating and collapse. The neutrino emission associated

Grant J. Mathews; Pedro Marronetti; James R. Wilson

1997-01-01

395

STS-46 Atlantis, Orbiter Vehicle (OV) 104, lands at KSC SLF Runway 33  

NASA Technical Reports Server (NTRS)

STS-46 Atlantis, Orbiter Vehicle (OV) 104, lands on Runway 33 at the Kennedy Space Center (KSC) Shuttle Landing Facility (SLF) at 9:11:50 am (Eastern Daylight Time (EDT)). As OV-104 rides along the runway via its main landing gear (MLG), three space shuttle main engines (SSMEs), the orbital maneuvering system (OMS) pods, the vertical stabilizer (tail), and the deployed rudder / speedbrake are visible. The nose landing gear (NLG) glides above the runway before wheel stop.

1992-01-01

396

Recent Progress with Vertical Transistors  

Microsoft Academic Search

Vertical MOS transistors are a promising approach for channel lengths in the range of 100 to 25nm without the need for extreme fine line lithography. These devices provide high satura­ tion currents due to the short channel length and small lateral size due to the 3D-geometry. The channel is defined by epitaxy which can be grown with very good layer

Lothar Risch; Thomas Aeugle; Wolfgang Rosner

1997-01-01

397

Quantum well vertical cavity laser  

SciTech Connect

This patent describes an apparatus which comprises: quantum well laser vertical cavity structure for lasing in a direction non-parallel to the major dimensions of a quantum well, such laser consisting essentially of an active element containing one or two quantum wells and a cavity dependent upon reflectance as between two distributed feedback mirrors.

Huang, R.F.; Jewell, J.L.; McCall, S.L. Jr.; Tai, K.

1991-03-12

398

Vertical two chamber reaction furnace  

Microsoft Academic Search

A vertical two chamber reaction furnace is disclosed. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the

Blaugher

1999-01-01

399

Vertical two chamber reaction furnace  

Microsoft Academic Search

A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber.

Blaugher; Richard D

1999-01-01

400

Equilibrium structures in vertical oligopoly  

Microsoft Academic Search

The central purpose of this paper is to examine vertical integration as an equilibrium phenomenon. We model it as integration between Cournot oligopolists in both the upstream and the downstream stages. We consider the issue of private profitability versus collective profitability and show that under several situations the equilibrium outcomes may result in a Prisoner's dilemma. The analysis is extended

Masahiro Abiru; Babu Nahata; Subhashis Raychaudhuri; Michael Waterson

1998-01-01

401

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

402

Close up view of the Commander's Seat on the Flight ...  

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

Close up view of the Commander's Seat on the Flight Deck of the Orbiter Discovery. Toward the right of the view and in front of te seat is the commander's Rotational Hand Controller. The pilot station has an identical controller. These control the acceleration in the roll pitch and yaw directions via the reaction control system and/or the orbiter maneuvering system while outside of Earth's atmosphere or via the orbiter's aerosurfaces wile in Earth's atmosphere when the atmospheric density permits the surfaces to be effective. There are a number of switches on the controller, most notably a trigger switch which is a push-to-talk switch for voice communication and a large button on top of the controller which is a switch to engage the backup flight system. This view was taken at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

403

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.

404

A vertical resonance heating model for X- or peanut-shaped galactic bulges  

NASA Astrophysics Data System (ADS)

We explore a second-order Hamiltonian vertical resonance model for X-shaped or peanut-shaped galactic bulges. The X- or peanut-shape is caused by the 2:1 vertical Lindblad resonance with the bar, with two vertical oscillation periods per orbital period in the bar frame. We examine N-body simulations and find that due to the bar slowing down and disc thickening during bar buckling, the resonance and associated peanut-shape moves outward. The peanut-shape is consistent with the location of the 2:1 vertical resonance, independent of whether the bar buckled or not. We estimate the resonance width from the potential m = 4 Fourier component and find that the resonance is narrow, affecting orbits over a narrow range in the angular momentum distribution, dL/L ˜ 0.05. As the resonance moves outward, stars originally in the mid-plane are forced out of the mid-plane and into orbits just within the resonance separatrix. The height of the separatrix orbits, estimated from the Hamiltonian model, is approximately consistent with the peanut-shape height. The peanut- or X-shape is comprised of stars in the vicinity of the resonance separatrix. The velocity distributions from the simulations illustrate that low-inclination orbits are depleted within resonance. Within resonance, the vertical velocity distribution is broad, consistent with resonant heating caused by the passage of the resonance through the disc. In the Milky Way bulge, we relate the azimuthally averaged mid-plane mass density near the vertical resonance to the rotation curve and bar pattern speed. At an estimated vertical resonance galactocentric radius of ˜1.3 kpc, we confirm a mid-plane density of ˜5 × 108 M? kpc-3, consistent with recently estimated mass distributions. We find that the rotation curve, bar pattern speed, 2:1 vertical resonance location, X-shaped tips and mid-plane mass density, are all self-consistent in the Milky Way galaxy bulge.

Quillen, Alice C.; Minchev, Ivan; Sharma, Sanjib; Qin, Yu-Jing; Di Matteo, Paola

2014-01-01

405

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

406

Closing the Health Gap  

NSDL National Science Digital Library

The US Department of Health and Human Services (HHS) and ABC Radio Networks are working together to help African-Americans gain access to the best possible information regarding health issues. HHS reports that life expectancies for African-Americans lag five years behind expectancies for White Americans. The new Website Closing the Health Gap has links to information on health conditions such as diabetes and cancer as well as consumer health resources that relate to African-Americans' particular needs. Each page offers links, publications, and any news related to the subject, all in an effort to close "the health gap."

2001-01-01

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

The thickness of a weakly magnetized accretion flow inside the last stable orbit of a Kerr black hole  

NASA Astrophysics Data System (ADS)

If an accretion disc contains weak frozen-in entangled magnetic fields, their dynamical effect may be important inside the last stable orbit because of decompression near the sonic point. Here, I consider the radial and vertical structure of a nearly free-falling flow inside the last stable orbit of a thin disc around a Kerr black hole. The thickness of such a flow is determined primarily by the vertical stress created by radial and azimuthal magnetic fields. The thickness is predicted to oscillate vertically around its equilibrium value, determined by the magnetic field balance with gravity. For thin discs, this thickness is much larger than that of the accretion disc itself. Numerical simulations with HARM2D (High Accuracy Relativistic Magnetohydrodynamics) show that the vertical structure is more complicated. In particular, a magnetically supported disc seems to be unstable to segregation of matter into thinner streams, with the vertical scale determined by thermal pressure or other processes.

Abolmasov, P.

2014-12-01

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

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

411

SPECKLE INTERFEROMETRY AND ORBITS OF 'FAST' VISUAL BINARIES  

SciTech Connect

Results of speckle observations at the 4.1 m SOAR telescope in 2012 (158 measures of 121 systems, 27 non-resolutions) are reported. The aim is to follow fast orbital motion of recently discovered or neglected close binaries and sub-systems. Here, eight previously known orbits are defined better, two more are completely revised, and five orbits are computed for the first time. Using differential photometry from Hipparcos or speckle and the standard relation between mass and absolute magnitude, the component's masses and dynamical parallaxes are estimated for all 15 systems with new or updated orbits. Two astrometric binaries HIP 54214 and 56245 are resolved here for the first time, another eight are measured. We highlight several unresolved pairs that may actually be single despite multiple historic measures, such as 104 Tau and f Pup AB. Continued monitoring is needed to understand those enigmatic cases.

Tokovinin, Andrei, E-mail: atokovinin@ctio.noao.edu [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile)

2012-08-15

412

Closeup oblique view of the aft fuselage of the Orbiter ...  

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

Close-up oblique view of the aft fuselage of the Orbiter Discovery looking forward and port as the last Space Shuttle Main Engine is being removed, it can be seen on the left side of the image frame. Note that one of the Orbiter Maneuvering System/ Reaction Control System has been removed while one of them remains. Also note that the body flap, below the engine positions has a protective covering to prevent damage to the High-temperature Reusable Surface Insulation tiles. This image was taken inside the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

413

Closeup oblique view of the aft fuselage of the Orbiter ...  

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

Close-up oblique view of the aft fuselage of the Orbiter Discovery looking forward and starboard as the last Space Shuttle Main Engine is being removed, it can be seen on the right side of the image frame. Note that one of the Orbiter Maneuvering System/ Reaction Control System has been removed while one of them remains. Also note that the body flap, below the engine positions has a protective covering to prevent damage to the High-temperature Reusable Surface Insulation tiles. This image was taken inside the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

414

Vertical leakage and vertically averaged vertical conductance for Karst Lakes in Florida  

Microsoft Academic Search

In the karst lake district in peninsular Florida in the southeastern United States, as many as 70% of the lakes lack surface outlets, and groundwater outflow is an important part of the water budgets of these lakes. For 11 karst lakes in the Central Lake District, vertical leakage from the lakes to the upper Floridan aquifer averages 0.12 to 4.27

L. H. Motz

1998-01-01

415

Closing the Loop Sampler.  

ERIC Educational Resources Information Center

Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

California Integrated Waste Management Board, Sacramento.

416

Closing the Assessment Loop  

ERIC Educational Resources Information Center

Accreditors, speakers at assessment conferences, and campus leaders all decry the fact that too few faculty are closing the loop--that is, studying assessment findings to see what improvements might be suggested and taking the appropriate steps to make them. This is difficult enough with locally developed measures; adding the need to interpret…

Banta, Trudy W.; Blaich, Charles

2011-01-01

417

Alien Visitations Close Encounters  

E-print Network

Alien Visitations #12;#12;Close Encounters · I: Visual sighting of aerial object (UFO) · II are indeed unidentified. ·Most are Venus. ·Almost certainly none are alien spacecraft Picture from Robert do aliens think? #12;How to Serve Man #12;#12;

Walter, Frederick M.

418

Closed Small Cell Clouds  

Atmospheric Science Data Center

... (right)   The structure of tightly packed "closed cells" in a layer of marine stratocumulus over the southeastern Pacific Ocean ... into interesting structures such as those shown here. These cells are notably small, with diameters ranging from 10-15 kilometers, instead ...

2013-04-19

419

Close Window Position Information  

E-print Network

of the new Center for Invasive Species Eradication (CISE). Coordination and facilitation of applied research and outreach.Collecting and organizing biological data. Application of aquatic herbicides. Occasional Duties, Horticulture, Wildlife and Fisheries Science, Environmental Sciences Aquatic Weed Science or closely related

Behmer, Spencer T.

420

Closing the Performance Gap.  

ERIC Educational Resources Information Center

Describes how the principal of a K-2, 400-student suburban elementary school near Flint, Michigan, worked with her staff and superintendent to develop and implement a strategic plan to close the student achievement gap. Reports significant improvement in reading and math scores after 1 year. (PKP)

Riggins, Cheryl G.

2002-01-01

421

Mars orbits with daily repeating ground traces  

NASA Technical Reports Server (NTRS)

This paper derives orbits at Mars with ground traces that repeat at the same times every solar day (sol). A relay orbiter in such an orbit would pass over insitu probes at the same times every sol, ensuring consistent coverage and simplifying mission design and operations. 42 orbits in five classes are characteried: 14 cicular equatorial prograde orbits; 14 circular equatorial retrograde orbits; 11 circular sun synchrounous orbits; 2 eccentroc equatorial orbits; 1 eccentric critcally inclined orbit. the paper reports on the performance of a relay orbiter in some of the orbits.

Noreen, Gary K.; Kerridge, Stuart; Diehl, Roger; neelon, Joseph; Ely, Todd; Turner, Andrew

2003-01-01

422

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

423

Natural bond orbitals in multiconfigurational expansions: Local treatment of electron correlation in molecules  

Microsoft Academic Search

We describe a localized treatment of electron correlation in terms of complete active-space wave functions derived from natural bond orbitals, closely related to the localized transferable units of molecular structure. We find that in many cases the procedure leads to solutions which retain the essentially localized character of their ‘‘parent’’ orbitals. Such localized solutions lead to an extremely selective treatment

A. V. Nemukhin; F. Weinhold

1992-01-01

424

A quantitative analysis of the Eutherian orbit: correlations with masticatory apparatus  

Microsoft Academic Search

The mammalian orbit, or eye-socket, is a highly plastic region of the skull. It comprises between seven and nine bones, all of which vary widely in their contribution to this region among the different mammalian orders and families. It is hypothesised that the structure of the mammalian orbit is principally influenced by the forces generated by the jaw-closing musculature. In

Philip G. Cox

2008-01-01

425

Long term behavior of a hypothetical planet in a highly eccentric orbit  

E-print Network

For a hypothetical planet on a highly eccentric orbit, we have calculated the osculating orbital parameters and its closest approaches to Earth and Moon over a period of 750 kyr. The approaches which are close enough to influence the climate of the Earth form a pattern comparable to that of the past climatic changes, as recorded in deep sea sediments and polar ice cores.

R. Nufer; W. Baltensperger; W. Woelfli

1999-09-28

426

Heteroclinic connections between periodic orbits and resonance transitions in celestial mechanics  

E-print Network

heliocentric orbit is typi- cally close to the 3:2 resonance three revolutions around the Sun in two Jupiter periods while the exterior heliocentric orbit is near the 2:3 resonance two revolutions around the Sun in three Jupiter periods . An important feature of the dynamics of these comets is that during

Ross, Shane

427

Neptune Orbiter Mission Scenario Based on Nuclear Electric Propulsion and Aerocapture Orbital Insertion  

NASA Astrophysics Data System (ADS)

insertion of spacecraft into elliptical orbit around target planet is proposed for Neptune orbiter mission. The primary goal of combining nuclear electric propulsion (NEP) and aerocapture orbital insertion is a reduction of a trip time comparing to that of similar mission, which would use nuclear electric propulsion only. One of the limitations of the all NEP orbiter is that at the planetary approach it must match its arrival velocity with Neptune's orbital speed in order to initiate slow capture into the desired orbit using low thrust electric propulsion. Use of aerocapture for insertion into closed elliptical orbit around Neptune through a single aerodynamically controlled atmospheric pass gives advantage of having higher entry velocities than it would be possible in case of all NEP scenario, thus reducing trip time required for interplanetary transfer. propulsion and thermal protection systems. Moreover, because faster interplanetary trip times for combined NEP/Aerocapture orbiter result in a higher entry velocities into the Neptune's atmosphere, they will also drive the increase in aerobrake mass fraction. In addition, aerocapture at Neptune also presents a challenge for aerobrake's guidance system which must target vehicle to the desired atmospheric exit conditions in the presence of significant uncertainties in Neptune's atmospheric density. Hence, there is a need to design a robust nominal aerocapture trajectory capable of accommodating density dispersions and also optimized for minimum thermal protection mass, thus contributing to overall reduction of aerobrake mass fraction. determine the optimal combination between reduction of the trip time and increase in aerobrake mass fraction was undertaken. The initial assumptions on aerobrake thermal protection materials and NEP system characteristics were based on near term state of the art technology, corresponding to 2007-2010 time frame, when such a mission to Neptune could be launched. interplanetary trajectory simulation including capture into orbit around Neptune. In these low thrust trajectory simulations the trust level and the specific impulse of a single electric rocket engine were fixed, thus allowing to optimize number of engines and their thrust time history for a rapid transfer to Neptune. Therefore, for combined NEP/Aerocapture mission use of this approach made possible to determine the change in NEP mass fraction, comparing to that one of all NEP mission scenario where spacecraft velocity at its arrival would have to be matched with Neptune's orbital speed. atmosphere, where vehicle was captured into a highly elliptical orbit, which insures periodical close fly-by of the biggest Neptune's moon Triton, thus allowing its scientific observation. Nominal trajectories found in the process of aerocapture simulations were optimized for minimum mass of aerobrake's thermal protection system and were also shown to withstand significant density variations which are likely to be encountered in Neptune's atmosphere. These nominal trajectories were used to determine sensitivity of aerobrake's thermal protection system mass fraction to the variation of atmospheric entry velocity resulted from shorter trip times to Neptune. that for the same initial mass at the low earth orbit, all NEP mission flight time is 11-12 years, when as for the mission scenario which combines NEP and aerocapture flight time can be reduced to 5-6 years. Such a reduction in mission flight time represents much faster scientific return and it also translates into a higher chance of mission success and significant operational cost savings due to much shorter mission time.

Jits, R.

2002-01-01

428

PSEUDO-NEWTONIAN POTENTIALS FOR NEARLY PARABOLIC ORBITS  

SciTech Connect

We describe a pseudo-Newtonian potential which, to within 1% error at all angular momenta, reproduces the precession due to general relativity of particles whose specific orbital energy is small compared to c{sup 2} in the Schwarzschild metric. For bound orbits, the constraint of low energy is equivalent to requiring the apoapsis of a particle to be large compared to the Schwarzschild radius. Such low-energy orbits are ubiquitous close to supermassive black holes in galactic nuclei, but the potential is relevant in any context containing particles on low-energy orbits. Like the more complex post-Newtonian expressions, the potential correctly reproduces the precession in the far field, but also correctly reproduces the position and magnitude of the logarithmic divergence in precession for low angular momentum orbits. An additional advantage lies in its simplicity, both in computation and implementation. We also provide two simpler, but less accurate potentials, for cases where orbits always remain at large angular momenta, or when the extra accuracy is not needed. In all of the presented cases, the accuracy in precession in low-energy orbits exceeds that of the well-known potential of Paczynski and Wiita, which has {approx}30% error in the precession at all angular momenta.

Wegg, Christopher, E-mail: wegg@tapir.caltech.edu [Theoretical Astrophysics, California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)

2012-04-20

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

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

431

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

432

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

433

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.

434

Vertically Integrated Circuits at Fermilab  

SciTech Connect

The exploration of the vertically integrated circuits, also commonly known as 3D-IC technology, for applications in radiation detection started at Fermilab in 2006. This paper examines the opportunities that vertical integration offers by looking at various 3D designs that have been completed by Fermilab. The emphasis is on opportunities that are presented by through silicon vias (TSV), wafer and circuit thinning and finally fusion bonding techniques to replace conventional bump bonding. Early work by Fermilab has led to an international consortium for the development of 3D-IC circuits for High Energy Physics. The consortium has submitted over 25 different designs for the Fermilab organized MPW run organized for the first time.

Deptuch, Grzegorz; Demarteau, Marcel; Hoff, James; Lipton, Ronald; Shenai, Alpana; Trimpl, Marcel; Yarema, Raymond; Zimmerman, Tom; /Fermilab

2009-01-01

435

Global Vertical Rates from VLBl  

NASA Technical Reports Server (NTRS)

The analysis of global VLBI observations provides vertical rates for 50 sites with formal errors less than 2 mm/yr and median formal error of 0.4 mm/yr. These sites are largely in Europe and North America with a few others in east Asia, Australia, South America and South Africa. The time interval of observations is up to 20 years. The error of the velocity reference frame is less than 0.5 mm/yr, but results from several sites with observations from more than one antenna suggest that the estimated vertical rates may have temporal variations or non-geophysical components. Comparisons with GPS rates and corresponding site position time series will be discussed.

Ma, Chopo; MacMillan, D.; Petrov, L.

2003-01-01

436

Kinematic Fitting of Detached Vertices  

SciTech Connect

The eg3 experiment at the Jefferson Lab CLAS detector aims to determine the existence of the $\\Xi_{5}$ pentaquarks and investigate the excited $\\Xi$ states. Specifically, the exotic $\\Xi_{5}^{--}$ pentaquark will be sought by first reconstructing the $\\Xi^{-}$ particle through its weak decays, $\\Xi^{-}\\to\\pi^{-}\\Lambda$ and $\\Lambda\\to\\pi^{-}$. A kinematic fitting routine was developed to reconstruct the detached vertices of these decays, where confidence level cuts on the fits are used to remove background events. Prior to fitting these decays, the exclusive reaction $\\gamma D\\rightarrow pp\\pi^{-}$ was studied in order to correct the track measurements and covariance matrices of the charged particles. The $\\Lambda\\rightarrow p\\pi^{-}$ and $\\Xi^{-}\\to\\pi^{-}\\Lambda$ decays were then investigated to demonstrate that the kinematic fitting routine reconstructs the decaying particles and their detached vertices correctly.

Paul Mattione

2007-05-01

437

[Endoscopic approaches to the orbit].  

PubMed

During the last decade, the use of endoscopic endonasal approaches to the pituitary has increased considerably. The endoscopic endonasal and transantral approaches offer a minimally invasive alternative to the classic transcranial or transconjunctival approaches to the medial aspect of the orbit. The medial wall of the orbit, the orbital apex, and the optic canal can be exposed through a middle meatal antrostomy, an anterior and posterior ethmoidectomy, and a sphenoidotomy. The inferomedial wall of the orbit can be also perfectly visualized through a sublabial antrostomy or an inferior meatal antrostomy. Several reports have described the use of an endoscopic approach for the resection or the biopsy of lesions located on the medial extraconal aspect of the orbit and orbital apex. However, the resection of intraconal lesions is still limited by inadequate instrumentation. Other indications for the endoscopic approach to the orbit are the decompression of the orbit for Graves' ophthalmopathy and traumatic optic neuropathy. However, the optimal management of traumatic optic neuropathy remains very controversial. Endoscopic endonasal decompression of the optic nerve in case of tumor compression could be a more valid indication in combination with radiation therapy. Finally, the endoscopic transantral treatment of blowout fracture of the floor of the orbit is an interesting option that avoids the eyelid or conjunctive incision of traditional approaches. The collaboration between the neurosurgeon and the ENT surgeon is mandatory and reduces the morbidity of the approach. Progress in instrumentation and optical devices will certainly make this approach promising for intraconal tumor of the orbit. PMID:20347457

Cebula, H; Lahlou, A; De Battista, J C; Debry, C; Froelich, S

2010-01-01

438

STS-45 ATLAS-1 in Atlantis, Orbiter Vehicle (OV) 104, payload bay (PLB)  

NASA Technical Reports Server (NTRS)

STS-45 Atmospheric Laboratory for Applications and Science 1 (ATLAS-1) pallet mounted instruments are documented in the payload bay (PLB) of the Earth-orbiting Atlantis, Orbiter Vehicle (OV) 104. The forward portion of the ATLAS-1 payload package is visible and includes the spacelab (SL) igloo (with U.S. flag, NASA, ATLAS, and European Space Agency (ESA) insignias), the Space Experiments with Particle Accelerators (SEPAC) spheres, and the Millimeter-Wave Atmospheric Sounder (MAS) (near center top). In the background against the blackness of space are the vertical tail and the orbital maneuvering system (OMS) pods.

1992-01-01

439

NASA-Ames vertical gun  

NASA Technical Reports Server (NTRS)

A national facility, the NASA-Ames vertical gun range (AVGR) has an excellent reputation for revealing fundamental aspects of impact cratering that provide important constraints for planetary processes. The current logistics in accessing the AVGR, some of the past and ongoing experimental programs and their relevance, and the future role of this facility in planetary studies are reviewed. Publications resulting from experiments with the gun (1979 to 1984) are listed as well as the researchers and subjects studied.

Schultz, P. H.

1984-01-01

440

Vertical Structure of the Atmosphere  

NSDL National Science Digital Library

Earth is surrounded by a protective atmosphere, composed of nitrogen, oxygen, and argon, and trace amounts of other gases, that protects Earth's surface from damaging solar radiation and plays a major role in water and energy transport. This interactive feature shows the vertical structure of the atmosphere. Viewers can see the regions of the atmosphere, some of the objects (natural and man-made) found at various altitudes, as well as the variations in air temperature and pressure with altitude.

441

Vertical integration, collusion, and tariffs  

Microsoft Academic Search

This article presents a link between tariff rates and industry structure in a dynamic setting. We examine the role of tariffs\\u000a on final-goods in a firm’s decision to integrate and collude in the presence of competitive imports. It is shown that, under\\u000a some conditions, the upstream firm has an incentive to engage in vertical integration to introduce profitably a wholesale

Pedro Mendi; Rafael Moner-Colonques; José J. Sempere-Monerris

2011-01-01

442

Vertical Height of the Atmosphere  

NSDL National Science Digital Library

This is a lesson about the vertical dimension of the atmosphere and includes four activities. Activity 1 Introduces concepts related to distance, including length and height and units of measurement. Students are asked to make comparisons of distances. In activity 2, students learn about the vertical profile of the atmosphere. They work with a graph and plot the heights of objects and the layers of the atmosphere: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. In activity 3, students learn about other forms of visual displays using satellite imagery. They compare images of the same weather feature, a hurricane, using two different images from MODIS and CALIPSO. One image is looking down on the hurricane from space, the other looks through the hurricane to display a profile of the hurricane. Activity 4 reinforces the concept of the vertical nature of the atmosphere. Students will take a CALIPSO satellite image that shows a profile of the atmosphere and use this information to plot mountains and clouds on their own graph of the atmosphere. The recommended order for the activities is to complete the first two activities on day one, and the second two activities on day two. Each day will require approximately 1 to 1.5 hours.

2012-08-03

443

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

444

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

445

General view of the Orbiter Discovery in the Orbiter Processing ...  

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

General view of the Orbiter Discovery in the Orbiter Processing Facility at Kennedy Space Center showing the payload bay doors open exposing the heat-dissipating radiator panels located on the inside of the payload bay doors. Also in the view is the boom portion of the boom sensor system deployed as part of the return to flight procedures after STS-107 to inspect the orbiter's thermal protection system. The Remote Manipulator System, the "Canadarm", and the airlock are seen in the background of the image. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

446

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

447

LSST: Comprehensive NEO detection, characterization, and orbits  

NASA Astrophysics Data System (ADS)

The Large Synoptic Survey Telescope (LSST) has Solar System mapping as one of its four key scientific design drivers, with emphasis on efficient Near-Earth Object (NEO) and Potentially Hazardous Asteroid (PHA) detection, orbit determination, and characterization. The baseline design satisfies strong constraints on the cadence of observations mandated by PHAs such as closely spaced pairs of observations to link different detections and short exposures to avoid trailing losses. Due to frequent repeat visits LSST will effectively provide its own follow-up to derive orbits for detected moving objects. We will describe detailed modeling of LSST operations, incorporating real historical weather and seeing data from Cerro Pachon in Chile, the LSST site, which shows that LSST using its baseline design cadence could find 90% of the PHAs with diameters larger than 250 m, and 75% of those greater than 140 m within ten years. However, simulations also show that LSST can reach the completeness of 90% of PHAs larger than 140m by optimizing observing cadence andextending the survey lifetime to 12 years. In addition to detecting and determining orbits for these PHAs, LSST will also provide valuable data on their physical characteristics through accurate color and variability measurements, which can be used to determine approximate taxonomical types, better size estimates by constraining albedos, rotation periods, and shape characteristics; thus constraining PHA properties relevant for risk mitigation strategies.

Ivezic, Zeljko; Jones, Lynne

2014-11-01

448

Lunar Topography: Results from the Lunar Orbiter Laser Altimeter  

NASA Technical Reports Server (NTRS)

The Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter (LRO) has been operating nearly continuously since July 2009, accumulating over 6 billion measurements from more than 2 billion in-orbit laser shots. LRO's near-polar orbit results in very high data density in the immediate vicinity of the lunar poles, with full coverage at the equator from more than 12000 orbital tracks averaging less than 1 km in spacing at the equator. LRO has obtained a global geodetic model of the lunar topography with 50-meter horizontal and 1-m radial accuracy in a lunar center-of-mass coordinate system, with profiles of topography at 20-m horizontal resolution, and 0.1-m vertical precision. LOLA also provides measurements of reflectivity and surface roughness down to its 5-m laser spot size. With these data LOLA has measured the shape of all lunar craters 20 km and larger. In the proposed extended mission commencing late in 2012, LOLA will concentrate observations in the Southern Hemisphere, improving the density of the polar coverage to nearly 10-m pixel resolution and accuracy to better than 20 m total position error. Uses for these data include mission planning and targeting, illumination studies, geodetic control of images, as well as lunar geology and geophysics. Further improvements in geodetic accuracy are anticipated from the use of re ned gravity fields after the successful completion of the Gravity Recovery and Interior Laboratory (GRAIL) mission in 2012.

Neumann, Gregory; Smith, David E.; Zuber, Maria T.; Mazarico, Erwan

2012-01-01

449

Unique Non-Keplerian Orbit Vantage Locations for Sun-Earth Connection and Earth Science Vision Roadmaps  

NASA Technical Reports Server (NTRS)

The purpose of this investigation is to determine the feasibility of attaining and maintaining unique non-Keplerian orbit vantage locations in the Earth/Moon environment in order to obtain continuous scientific measurements. The principal difficulty associated with obtaining continuous measurements is the temporal nature of astrodynamics, i.e., classical orbits. This investigation demonstrates advanced trajectory designs to meet demanding science requirements which cannot be met following traditional orbital mechanic logic. Examples of continuous observer missions addressed include Earth pole-sitters and unique vertical libration orbits that address Sun-Earth Connection and Earth Science Vision roadmaps.

Folta, David; Young, Corissa; Ross, Adam

2001-01-01

450

Close, Closer, Closest  

NSDL National Science Digital Library

As educators, we are always deciding what experiences we want to give students in order to achieve our goals of developing science process skills. One of the best ways of teaching about observation is described here. Using a hand lens and an illuminated pocket microscope, students observe an object at three different levels of magnification--"Close, Closer, Closest." You may be amazed at how surprisingly simple and effective this experience is for teaching young learners to be keen observers.

Donna Farland

2008-02-01

451

Moessbauer Close-Up  

NASA Technical Reports Server (NTRS)

This close-up image of the Mars Exploration Rover Spirit's instrument deployment device, or 'arm,' shows the donut-shaped plate on the Moessbauer spectrometer. This image makes it easy to recognize the imprint left by the instrument in the martian soil at a location called 'Peak' on sol 43 (February 16, 2004). This image was taken by the rover's panoramic camera on sol 39 (February 11, 2004).

2004-01-01

452

Vertical silicon nanowire arrays for gas sensing  

E-print Network

The goal of this research was to fabricate and characterize vertically aligned silicon nanowire gas sensors. Silicon nanowires are very attractive for gas sensing applications and vertically aligned silicon nanowires are ...

Zhao, Hangbo

2014-01-01

453

Vertical Integration and Technology: Theory and Evidence  

E-print Network

We study the determinants of vertical integration. We first derive a number of predictions regarding the relationship between technology intensity and vertical integration from a simple incomplete contracts model. Then, ...

Acemoglu, Daron

454

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

455

Neutrino mass hierarchy, vacuum oscillations, and vanishing vertical bar U{sub e3} vertical bar  

SciTech Connect

Is the relatively isolated member of the neutrino mass spectrum heavier or lighter than the two closely-spaced members? This question--the character of the neutrino mass hierarchy--is of great theoretical interest. All previously identified experiments for addressing it via neutrino oscillations require that the currently unknown size of the U{sub e3} element of the leptonic mixing matrix (parameterized by the unknown {theta}{sub 13} mixing angle) be sufficiently large, and will utterly fail in the limit {theta}{sub 13}{yields}0. For this reason, we explore alternative oscillation approaches that would still succeed even if {theta}{sub 13} vanishes. We identify several alternatives that require neither a nonzero vertical bar U{sub e3} vertical bar nor the presence of significant matter effects (even if the latter are unavoidable in the case of long-baseline, Earth-based experiments). All include multiple percent-level neutrino oscillation measurements, usually involving muon-neutrino (or antineutrino) disappearance and very long baselines. We comment on the degree of promise that these alternative approaches show.

Gouvea, Andre de; Jenkins, James; Kayser, Boris [Northwestern University, Department of Physics and Astronomy, 2145 Sheridan Road, Evanston, Illinois 60208 (United States); Theoretical Physics Department, Fermilab, PO Box 500, Batavia, Illinois 60510-0500 (United States); Northwestern University, Department of Physics and Astronomy, 2145 Sheridan Road, Evanston, Illinois 60208 (United States); Theoretical Physics Department, Fermilab, PO Box 500, Batavia, Illinois 60510-0500 (United States)

2005-06-01

456

Vertical constituent transport in the mesosphere  

Microsoft Academic Search

Ground-based microwave spectroscopy measurements of mesospheric CO and H2O vertical mixing ratio profiles are used to infer vertical mixing rates in the upper mesosphere. The CO and H2O data consistently imply vertical eddy diffusion coefficients in the 70- to 85-km region of 100,000-200,000 sq cm\\/s during spring through summer at midlatidues. Although chemical acceleration of vertical transport is substantial for

Darrell F. Strobel; Michael E. Summers; Richard M. Bevilacqua; Matthew T. Deland; Mark Allen

1987-01-01

457

Spectroscopic Orbits for Kepler FOV Eclipsing Binaries  

NASA Astrophysics Data System (ADS)

We are currently involved in a four year program of precise eclipsing binary photometry with the NASA Kepler Observatory. Our goal is to search for variations in minimum light timing for intermediate mass eclipsing binaries. Such periodic variations will reveal the reflex motion caused by any distant, low mass object that orbits the close binary. it Kepler's unprecedented accuracy and continuous observations provide a unique opportunity to detect the low mass companions that are predicted to result from the angular momentum of the natal cloud. The goal of this proposal is to obtain blue spectra of short period (0.9-6d) eclipsing binaries, derive radial velocities, and produce a double-lined spectroscopic orbit (as well as estimates of the stellar effective temperatures, gravities, and metallicities). Combined with the it Kepler light curve, we will determine very accurate masses and radii for the members of the close binary, which will yield the mass-inclination product M_3 sin i for any companions detected by light travel time or other effects. An extended sample of eclipsing binaries with longer periods (up to 50d) is now being investigated to test whether the presence of a tertiary companion declines with increasing period. We propose to obtain a single spectrum at quadrature for the brightest 48 stars in this expanded sample to characterize the effective temperatures and total mass contained in these systems.

Matson, Rachel A.; Gies, Douglas R.; Williams, Stephen J.; Guo, Zhao

2013-02-01