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1

RECENT IMPROVEMENTS IN VERTICAL ORBIT FEEDBACK AT THE DARESBURY SRS  

Microsoft Academic Search

A vertical orbit feedback system has been in routine operation at Daresbury since 1994 and plays an important role in providing stable beams for users. This system was based, until recently, on a local feedback scheme, which stabilised the vertical orbit at each line using a single photon monitor and a closed three magnet bump. This paper reports the improvements

S. L. Smith

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

Closed-orbit correction of the NSLS VUV ring  

SciTech Connect

We describe the results obtained from the orbit correction system in the NSLS VUV storage ring which consists of 24 PUE stations and 16 horizontal and vertical correction dipoles. The data were obtained by the PUEREAL module of the RING control program which provides automatic switching of the signal from individual electrodes of the PUE stations and provides a readout at harmonic of the rf frequency. The closed orbit is then calculated and corrected by measured displacements of the PUE's from the adjacent quadrupoles. The ORBIT module of the RING program was used to minimize the RMS orbit deviations choosing the most effective correctors and calculating their strengths. For the horizontal case, the correction was accomplished using 3 correctors in two iterations starting with RMS values X = 2.9 mm to X = 0.9 mm. Vertically three iterations and 6 correctors were required to correct the RMS value from Z = 6.8 nm to Z = 0.8 mm.

Bozoki, E.; Bittner, J.; Blumberg, L.; Dickinson, T.; Galayda, J.

1983-01-01

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 loop orbit trim using GPS  

NASA Technical Reports Server (NTRS)

This paper describes an onboard closed-loop navigation and control system capable of executing extremely precise orbit maneuvers. It uses information from the Global Positioning System (GPS) and an onboard controller to perform orbit adjustments. As a result, the system circumvents the need for extensive ground support. The particular application considered is an orbit injection system for NASA's Gravity Probe B (GP-B) spacecraft. Eccentricity adjustments of 0.0004 to 0.005, and inclination and node changes of 0.001 to 0.01 deg are demonstrated. The same technique can be adapted to other satellite missions.

Parkinson, B. W.; Axelrad, P.

1989-01-01

6

Resonant Tides in Close Orbiting Planets  

Microsoft Academic Search

The outer layers of a gas giant planet in a close orbit are isothermal because of heating by the star, and therefore these layers are convectively stable. A resonant tidal torque is exerted at the outer boundary of the interior convection zone. Tidal dissipation occurs through nonlinear damping. This process is similar to that previously considered for high-mass binary stars.

S. H. Lubow; C. A. Tout; M. Livio

1997-01-01

7

ERRATUM: Resonant Tides in Close Orbiting Planets  

Microsoft Academic Search

In the paper ``Resonant Tides in Close Orbiting Planets'' by S. H. Lubow, C. A. Tout, and M. Livio (ApJ, 484, 866 [1997]), there is a misprint in the abstract. The abstract states that ``the torque is exerted in a region where H\\/rp>>1....'' Instead, it should state that ``the torque is exerted in a region where H\\/rp<<1....''

S. H. Lubow; C. A. Tout; M. Livio

1999-01-01

8

Closed orbit feedback with digital signal processing  

SciTech Connect

The closed orbit feedback experiment conducted on the SPEAR using the singular value decomposition (SVD) technique and digital signal processing (DSP) is presented. The beam response matrix, defined as beam motion at beam position monitor (BPM) locations per unit kick by corrector magnets, was measured and then analyzed using SVD. Ten BPMs, sixteen correctors, and the eight largest SVD eigenvalues were used for closed orbit correction. The maximum sampling frequency for the closed loop feedback was measured at 37 Hz. Using the proportional and integral (PI) control algorithm with the gains Kp = 3 and K{sub I} = 0.05 and the open-loop bandwidth corresponding to 1% of the sampling frequency, a correction bandwidth ({minus}3 dB) of approximately 0.8 Hz was achieved. Time domain measurements showed that the response time of the closed loop feedback system for 1/e decay was approximately 0.25 second. This result implies {approximately} 100 Hz correction bandwidth for the planned beam position feedback system for the Advanced Photon Source storage ring with the projected 4-kHz sampling frequency.

Chung, Y.; Kirchman, J.; Lenkszus, F. [and others

1994-08-01

9

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

10

Tidal Decay of Close Planetary Orbits  

Microsoft Academic Search

The 4.2-day orbit of the newly discovered planet around 51~Pegasi is formally\\u000aunstable to tidal dissipation. However, the orbital decay time in this system\\u000ais longer than the main-sequence lifetime of the central star. Given our best\\u000acurrent understanding of tidal interactions, a planet of Jupiter's mass around\\u000aa solar-like star could have dynamically survived in an orbit with a

F. A. Rasio; C. A. Tout; S. H. Lubow; M. Livio

1996-01-01

11

February 1988 Tune Shifts Caused by Horizontal Closed. Orbit  

E-print Network

reduced and one is forced to add more sextupoles to eliminate harmful harmonic components. In the 7-Ge the linear horizontal- vertical coupling of betatron motion. Horizontal orbit deviations, on the other hand

Kemner, Ken

12

Dynamics of Orbits Close to Asteroid 4179 Toutatis  

NASA Technical Reports Server (NTRS)

We use a radar-derived physical model of 4179 Toutatis 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 have a wider application to orbit dynamics about bodies in a non-principal-axis rotation state.

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

1998-01-01

13

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

14

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

15

Close up oblique view aft, port side of the Orbiter ...  

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

Close up oblique view aft, port side of the Orbiter Discovery in the Vehicle Assembly Building at NASA's Kennedy Space Center. This view shows a close up of the elevons and underside of the port wing. On the aft fuselage in the approximate center rift of the image is the T-0 umbilical panels. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

16

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

17

Vertical orbit excursion fixed field alternating gradient accelerators  

NASA Astrophysics Data System (ADS)

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

Brooks, Stephen

2013-08-01

18

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

19

The hydrogen atom in an electric field: Closed-orbit theory with bifurcating orbits  

E-print Network

Closed-orbit theory provides a general approach to the semiclassical description of photo-absorption spectra of arbitrary atoms in external fields, the simplest of which is the hydrogen atom in an electric field. Yet, despite its apparent simplicity, a semiclassical quantization of this system by means of closed-orbit theory has not been achieved so far. It is the aim of this paper to close that gap. We first present a detailed analytic study of the closed classical orbits and their bifurcations. We then derive a simple form of the uniform semiclassical approximation for the bifurcations that is suitable for an inclusion into a closed-orbit summation. By means of a generalized version of the semiclassical quantization by harmonic inversion, we succeed in calculating high-quality semiclassical spectra for the hydrogen atom in an electric field.

T. Bartsch; J. Main; G. Wunner

2002-12-20

20

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

21

Spectroscopic Characterisation of Close Orbiting Extrasolar Giant Planets  

Microsoft Academic Search

A number of successful mid-infrared detections and studies of close orbiting extrasolar giant planetary atmospheres have been responsible for both driving and informing modelling efforts. Recent models have indicated that these planets may be subdivided into two groups, one with cooler atmospheres exhibiting solely absorption features, and a second comprising the most highly irradiated atmospheres which possess a temperature inversion

J. R. Barnes; Travis S. Barman; H. R. A. Jones; C. J. Leigh; A. Collier Cameron; Lisa Prato; R. Barber

2009-01-01

22

Dynamics of Orbits Close to Asteroid 4179 Toutatis  

NASA Astrophysics Data System (ADS)

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 that Toutatis has a homogeneous density distribution, and we assume a density of 2.5 g/cc. The asteroid's gravity field is computed using a truncated harmonic expansion when outside of its circumscribing sphere and a closed-form expression for the potential field of an arbitrary polyhedron when inside that sphere. The complete equations of motion are time-periodic in the Toutatis-fixed frame due to the complex rotation of the asteroid. The system is Hamiltonian and has all the characteristics of such a system, including conservation of phase volume, but there is no Jacobi constant of the motion and zero velocity surfaces cannot be used to analyze the system's behavior. We also examine some of the close-orbit dynamics with the Lagrange planetary form of the equations of motion. Families of quasi-periodic "frozen orbits" that show minimal variations in orbital elements are found to exist very close to the asteroid; some of them are stable and hence can hold natural or artificial satellites. A retrograde family of frozen orbits is especially robust and persists down to semi-major axes of about 2.5 km, comparable to half of Toutatis' longest dimension. We identify families of periodic orbits, which repeat in the Toutatis-fixed frame. Due to the time-periodic nature of the equations of motion, all periodic orbits about Toutatis in its body-fixed frame must be commensurate with the 5.42-day period associated with those equations. Exact calculations of both stable and unstable periodic orbits are made. The sum of surface forces acting on a particle on Toutatis is time-varying, so particles on and in the asteroid are being continually shaken with a period of 5.42 days, perhaps enhancing the uniformity of the regolith distribution. A global map of the gravitational slope reveals that it is surprisingly shallow for such an elongated, irregularly shaped object, averaging 16° globally and less than 35° over 96% of the surface. A global map of tangential accelerations shows no values larger than 0.5 mm/s 2, an average value of 0.2 mm/s 2, and less than 0.25 mm/s 2over 70% of the surface. A global map of the escape speed for launch normal to the surface shows that quantity to be between 1.2 and 1.8 m/s over most of the surface. Each of these mapped quantities has small periodic variations. We have found trajectories that leave the surface, persist in the region of phase space around a frozen orbit, and then impact the surface after a flight time of more than 100 days. Return orbit durations of years seem possible. Whereas a uniformly rotating asteroid preferentially accumulates non-escaping ejecta on its leading sides, Toutatis accumulates ejecta uniformly over its surface. We render a variety of close orbits in inertial and body-fixed frames.

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

1998-03-01

23

Orbital stability of systems of closely-spaced planets  

NASA Astrophysics Data System (ADS)

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

Smith, Andrew W.; Lissauer, Jack J.

2009-05-01

24

Stellar orbit evolution in close circumstellar disc encounters  

E-print Network

The formation and early evolution of circumstellar discs often occurs within dense, newborn stellar clusters. For the first time, we apply the moving-mesh code AREPO, to circumstellar discs in 3-D, focusing on disc-disc interactions that result from stellar fly-bys. Although a small fraction of stars are expected to undergo close approaches, the outcomes of the most violent encounters might leave an imprint on the discs and host stars that will influence both their orbits and their ability to form planets. We first construct well-behaved 3-D models of self-gravitating discs, and then create a suite of numerical experiments of parabolic encounters, exploring the effects of pericenter separation r_p, disc orientation and disc-star mass ratio (M_d/M_*) on the orbital evolution of the host stars. Close encounters (2r_porbital angular momentum extraction to induce stellar capture. We find that ...

Muñoz, Diego J; Vogelsberger, Mark; Hernquist, Lars; Springel, Volker

2014-01-01

25

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

26

Multiport well design for sampling of ground water at closely spaced vertical intervals  

Microsoft Academic Search

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

Geoffrey N. Delin; Matthew K. Landon

1996-01-01

27

Efficient Vertical Mining of Frequent Closed Itemsets and Generators  

E-print Network

/FG-mining. The proposed algorithm, Touch, deals with both tasks separately, i.e., uses a well-known vertical method, Charm]. An association miner typically proceeds in two steps: (i) extract all frequent patterns X of a database, and (ii-known FCI/FG-miners exclusively apply levelwise strategies, although the levelwise itemset miners

Boyer, Edmond

28

Photoabsorption spectra of the diamagnetic hydrogen atom in the transition regime to chaos: Closed orbit theory with bifurcating orbits  

E-print Network

With increasing energy the diamagnetic hydrogen atom undergoes a transition from regular to chaotic classical dynamics, and the closed orbits pass through various cascades of bifurcations. Closed orbit theory allows for the semiclassical calculation of photoabsorption spectra of the diamagnetic hydrogen atom. However, at the bifurcations the closed orbit contributions diverge. The singularities can be removed with the help of uniform semiclassical approximations which are constructed over a wide energy range for different types of codimension one and two catastrophes. Using the uniform approximations and applying the high-resolution harmonic inversion method we calculate fully resolved semiclassical photoabsorption spectra, i.e., individual eigenenergies and transition matrix elements at laboratory magnetic field strengths, and compare them with the results of exact quantum calculations.

T. Fabcic; J. Main; T. Bartsch; G. Wunner

2004-07-13

29

Orbital stability of systems of closely-spaced planets  

Microsoft Academic Search

An investigation of the stability of systems of 1 M? (Earth-mass) bodies orbiting a Sun-like star has been conducted for virtual times reaching 10 billion years. For the majority of the tests, a symplectic integrator with a fixed timestep of between 1 and 10 days was employed; however, smaller timesteps and a Bulirsch–Stoer integrator were also selectively utilized to increase

Andrew W. Smith; Jack J. Lissauer

2009-01-01

30

Closed orbit theory for the photoabsorption spectra of atoms in crossed electric and magnetic fields  

Microsoft Academic Search

The oscillations in the near-threshold spectrum of an atom in static external fields are known to be connected to classical closed orbits of the electron (orbits which start and end at the nucleus). Previous studies have derived formulas for computing this effect in the case of single fields or E allel B, for which cylindrical symmetry effectively limits the classical

Michael R. Haggerty; John B. Delos

1996-01-01

31

ORBITAL DISTRIBUTIONS OF CLOSE-IN PLANETS AND DISTANT PLANETS FORMED BY SCATTERING AND DYNAMICAL TIDES  

SciTech Connect

We investigated the formation of close-in planets (hot Jupiters) by a combination of mutual scattering, Kozai effect, and tidal circularization, through N-body simulations of three gas giant planets, and compared the results with discovered close-in planets. We found that in about 350 cases out of 1200 runs ({approx}30%), the eccentricity of one of the planets is excited highly enough for tidal circularization by mutual close scatterings followed by secular effects due to outer planets, such as the Kozai mechanism, and the planet becomes a close-in planet through the damping of eccentricity and semimajor axis. The formation probability of close-in planets by such scattering is not affected significantly by the effect of the general relativity and inclusion of inertial modes in addition to fundamental modes in the tides. Detailed orbital distributions of the formed close-in planets and their counterpart distant planets in our simulations were compared with observational data. We focused on the possibility for close-in planets to retain non-negligible eccentricities ({approx}> 0.1) on timescales of {approx}10{sup 9} yr and have high inclinations, because close-in planets in eccentric or highly inclined orbits have recently been discovered. In our simulations we found that as many as 29% of the close-in planets have retrograde orbits, and the retrograde planets tend to have small eccentricities. On the other hand, eccentric close-in planets tend to have orbits of small inclinations.

Nagasawa, M.; Ida, S., E-mail: nagasawa.m.ad@m.titech.ac.jp [Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

2011-12-01

32

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

33

Design considerations for the Shuttle/Orbiter closed-circuit television subsystem  

NASA Technical Reports Server (NTRS)

The Shuttle/Orbiter Program requirements relative to operational and performance parameters of the CCTV (closed circuit television) subsystem and their influence upon design considerations are presented. The anticipated use of the CCTV for rendezvous, docking, manipulator arm operation, satellite inspection and general orbiter operations is outlined to establish the performance requirements of each subsystem element. Typical physical characteristics, interface parameters, and remote-control design philosophy are briefly described.

Perry, W. E.

1974-01-01

34

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

35

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

Microsoft Academic Search

An experimental study was carried out to understand the nucleate boiling characteristics and the critical heat flux (CHF)\\u000a of water, the water based nanofluids and the water based nanoparticle-suspensions in vertical small heated tubes with a closed\\u000a bottom. Here, the nanofluids consisted of the base liquid, the CuO nanoparticles and the surfactant. The nanoparticle-suspensions\\u000a consisted of the base liquid and

Lv Lun-Chun; Liu Zhen-Hua

2008-01-01

36

A closed-form solution of vertical dipole antennas above a dielectric half-space  

Microsoft Academic Search

This paper derives a convenient closed-form expression for the input impedance of a vertical antenna above a dielectric half-space. The expression is obtained from the induced electromotive force (EMF) method using a complex-image spatial Green's function. It is found that the effect of the dielectric half-space can be modeled by a short image array of three to five complex image

R. M. Shubair; Y. L. Chow

1993-01-01

37

Orbital stability of systems of closely-spaced planets, II: configurations with coorbital planets  

NASA Astrophysics Data System (ADS)

We numerically investigate the stability of systems of 1 {M_{oplus}} planets orbiting a solar-mass star. The systems studied have either 2 or 42 planets per occupied semimajor axis, for a total of 6, 10, 126, or 210 planets, and the planets were started on coplanar, circular orbits with the semimajor axes of the innermost planets at 1 AU. For systems with two planets per occupied orbit, the longitudinal initial locations of planets on a given orbit were separated by either 60° (Trojan planets) or 180°. With 42 planets per semimajor axis, initial longitudes were uniformly spaced. The ratio of the semimajor axes of consecutive coorbital groups in each system was approximately uniform. The instability time for a system was taken to be the first time at which the orbits of two planets with different initial orbital distances crossed. Simulations spanned virtual times of up to 1 × 108, 5 × 105, and 2 × 105 years for the 6- and 10-planet, 126-planet, and 210-planet systems, respectively. Our results show that, for a given class of system (e.g., five pairs of Trojan planets orbiting in the same direction), the relationship between orbit crossing times and planetary spacing is well fit by the functional form log( t c / t 0) = b ? + c, where t c is the crossing time, t 0 = 1 year, ? is the separation in initial orbital semimajor axis (in terms of the mutual Hill radii of the planets), and b and c are fitting constants. The same functional form was observed in the previous studies of single planets on nested orbits (Smith and Lissauer 2009). Pairs of Trojan planets are more stable than pairs initially separated by 180°. Systems with retrograde planets (i.e., some planets orbiting in the opposite sense from others) can be packed substantially more closely than can systems with all planets orbiting in the same sense. To have the same characteristic lifetime, systems with 2 or 42 planets per orbit typically need to have about 1.5 or 2 times the orbital separation as orbits occupied by single planets, respectively.

Smith, Andrew W.; Lissauer, Jack J.

2010-08-01

38

HD179949b: a close orbiting extrasolar giant planet with a stratosphere?  

Microsoft Academic Search

We have carried out a search for the 2.14-mum spectroscopic signature of the close orbiting extrasolar giant planet, HD179949b. High-cadence time-series spectra were obtained with the Cryogenic high-resolution InfraRed Échelle Spectrograph at Very Large Telescope, Unit 1 on two closely separated nights. Deconvolution yielded spectroscopic profiles with mean signal-to-noise ratios of several thousand, enabling the near-infrared contrast ratios predicted for

J. R. Barnes; Travis S. Barman; H. R. A. Jones; C. J. Leigh; A. Collier Cameron; R. J. Barber; D. J. Pinfield

2008-01-01

39

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

40

Closed loop navigation and guidance for gravity probe B orbit insertion  

NASA Technical Reports Server (NTRS)

This paper addresses the problem of guiding the Gravity Probe B (GP-B) spacecraft from its location after initial insertion to a very precise low earth orbit. Specifically, the satellite orbit is required to be circular to within 0.001 eccentricity, polar to within 0.001 deg inclination, and aligned with the direction of the star Rigel to within 0.001 deg. Navigation data supplied by an on-board GPS receiver is used as feedback to a control algorithm designed to minimize the time to achieve the desired orbit. Translational control is provided by the proportional helium thrusters, which are used for drag-free and attitude control during the remainder of the science mission. Simulations of the guidance system are presented which give an indication of performance characteristics for several types of orbit injection errors. This research is the first reported effort to use GPS as a sensor for a closed loop space guidance system.

Axelrad, P.; Parkinson, B. W.

1989-01-01

41

The Formation of Close Binary Systems by Dynamical Interactions and Orbital Decay  

E-print Network

We present results from the first hydrodynamical star formation calculation to demonstrate that close binary stellar systems (separations $\\lsim 10$ AU) need not be formed directly by fragmentation. Instead, a high frequency of close binaries can be produced through a combination of dynamical interactions in unstable multiple systems and the orbital decay of initially wider binaries. Orbital decay may occur due to gas accretion and/or the interaction of a binary with its circumbinary disc. These three mechanisms avoid the problems associated with the fragmentation of optically-thick gas to form close systems directly. They also result in a preference for close binaries to have roughly equal-mass components because dynamical exchange interactions and the accretion of gas with high specific angular momentum drive mass ratios towards unity. Furthermore, due to the importance of dynamical interactions, we find that stars with greater masses ought to have a higher frequency of close companions, and that many close binaries ought to have wide companions. These properties are in good agreement with the results of observational surveys.

Matthew R. Bate; Ian A. Bonnell; Volker Bromm

2002-12-18

42

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

Microsoft Academic Search

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

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

1996-01-01

43

Near-infrared spectroscopic search for the close orbiting planet HD 75289b  

Microsoft Academic Search

We present a search for the near-infrared spectroscopic signature of the close orbiting extrasolar giant planet HD 75289b. We obtained ~230 spectra in the wavelength range 2.18-2.19 mum using the Phoenix spectrograph at Gemini South. By considering the direct spectrum, derived from irradiated model atmospheres, we search for the absorption profile signature present in the combined star and planet light.

J. R. Barnes; C. J. Leigh; H. R. A. Jones; Travis S. Barman; D. J. Pinfield; A. Collier Cameron; J. S. Jenkins

2007-01-01

44

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

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

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

SciTech Connect

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

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

1995-12-31

47

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

SciTech Connect

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

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

1995-10-20

48

Stability Orbits Close to 433 Eros Using a Shaped Polyhedral Source  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): A general characteristic of celestial minor planets as asteroids, objects of several recent studies, is the fact of having highly irregular shape. The recent observations and space probes that pass close to the asteroids with orbits near the Earth (NEOs) have shown the existence of binary and triple asteroid systems. The existence of these moons can be explained due to their irregular shape. One of the techniques used in the past decade to determine the shape with a good accuracy and estimate certain physical features (volume, mass, moments of inertia) of asteroids is the polyhedral model method. The aim of this study is to rebuild the shape and determine the physical characteristics of the asteroid 433 Eros using data from December 1998 observations of the probe NEAR-Shoemaker (Near Earth Asteroid Rendezvous). In our computations we use a code that avoids singularities from the line integrals of a homogeneous arbitrary shaped polyhedral source and is accurate. This code evaluates the gravitational potential function and its first and second order derivatives. Then, we find the location of the equilibrium points through the pseudo-potential energy and zero velocity curves. We also show the differences in the potential between our model and a point mass. Finally, taking the rotation of asteroid 433 Eros into consideration, we analyze the environment orbit dynamics compared with the analytical model.

Chanut, Thierry G.; Winter, O.

2013-05-01

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

Vertical Roughness of the Polar Regions of Mars from Mars Orbiter Laser Altimeter Pulse-Width Measurements  

NASA Technical Reports Server (NTRS)

The sub-kilometer scale vertical roughness of the martian surface in the polar regions can be investigated using calibrated, optical pulse width data provided by the Mars Orbiter Laser Altimeter (MOLA). Garvin and others have previously discussed initial observations of what we have called "total vertical roughness" or TVR, as derived from MOLA optical pulse width observations acquired during the pre-mapping phases of the Mars Global Surveyor (MGS) mission. Here we present the first assessment of the Mars polar region properties of the TVR parameter from more than nine months of continuous mapping by MOLA as part of the MGS mapping mission. Other than meter-scale surface properties directly inferred from Mars Orbiter Camera (MOC) images, MOLA measurements of footprint-scale TVR represent the only direct measurements of the local vertical structure of the martian surface at approx. 150 m length scales. These types of data have previously been shown to correlate with geologic process histories for terrestrial desert surfaces on the basis of Shuttle Laser Altimeter (SLA) observations. Additional information is obtained in the original extended abstract.

Garvin, J. B.; Frawley, J. J.; Sakimoto, S. E. H.

2000-01-01

51

Secular orbital evolution of planetary systems and the dearth of close-in planets around fast rotators  

E-print Network

Recent analyses of Kepler space telescope data reveal that transiting planets with orbital periods shorter than about 2-3 days are generally observed around late-type stars with rotation periods longer than about 5-10 days. We investigate different explanations for this phenomenon and favor an interpretation based on secular perturbations in multi-planet systems on non-resonant orbits. In those systems, the orbital eccentricity of the innermost planet can reach values close to unity through a process of chaotic diffusion of its orbital elements in the phase space. When the eccentricity of the innermost orbit becomes so high that the periastron gets closer than about 0.05 AU, tides shrink and circularize the orbit producing a close-in planet on a timescale shorter than about 50 Myr. The probability of high eccentricity excitation and subsequent circularization is estimated and is found to increase with the age of the system. Thus, we are able to explain the observed statistical correlation between stellar rota...

Lanza, A F

2014-01-01

52

Feasibility of a responsive, hybrid propulsion augmented, Vertical-Takeoff-and-Landing, Single-Stage-to-Orbit launch system  

NASA Astrophysics Data System (ADS)

A novel, reusable, Vertical-Takeoff-and-Landing, Single-Stage-to-Orbit (VTOL/SSTO) launch system concept, named HYP-SSTO, is presented in this paper. This launch vehicle system concept uses a highly coupled, main high performance liquid oxygen/liquid hydrogen (LOX/LH2) propulsion system, that is used only for launch, with a hybrid auxiliary propulsion system which is used during final orbit insertion, major orbit maneuvering, and landing propulsive burn phases of flight. By using a hybrid propulsion system for major orbit maneuver burns and landing, this launch system concept has many advantages over conventional VTOL/SSTO concepts that use LOX/LH2 propulsion system(s) burns for all phases of flight. Because hybrid propulsion systems are relatively simple and inert by their nature, this concept has the potential to support short turnaround times between launches, be economical to develop, and be competitive in terms of overall system life-cycle cost. This paper provides a technical description of the novel, reusable HYP-SSTO launch system concept. Launch capability performance, as well as major design and operational system attributes, are identified and discussed.

Pelaccio, Dennis G.

1996-03-01

53

Ground-level ozone and ozone vertical profile measurements close to the foothills of the Guadarrama mountain range (Spain)  

Microsoft Academic Search

Continuous measurements of ozone vertical profiles, OVP, in the low troposphere (around 500–2400m) using an unattended commercial ozone profiler DIAL, were conducted during June–July 2004 in Segovia, SG, a small city in the upper plateau located close to the foothills of the Guadarrama mountain range, Guadarrama, in the Central Massif. The data obtained over almost 37 complete days have enabled

M. L. Sanchez; B. de Torre; M. A. García; I. Pérez

2007-01-01

54

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

Microsoft Academic Search

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 instaIled within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of

R. Smith; R HARVEY; D LEBLANC

1991-01-01

55

Vertical mixing processes in Intermittently Closed and Open Lakes and Lagoons, and the dissolved oxygen response  

Microsoft Academic Search

Intermittently Closed and Open Lakes and Lagoons (ICOLLs) are located on micro-tidal coasts (max. tidal range<2m) in temperate regions where the annual rainfall is non-seasonal. ICOLLs are generally shallow (<5m depth) and are closed to the ocean due to the formation of an entrance bar for the majority of the year, when rainfalls are low. After periods of heavy rainfall,

Emma Gale; Charitha Pattiaratchi; Roshanka Ranasinghe

2006-01-01

56

Single stage to orbit vertical takeoff and landing concept technology challenges  

NASA Astrophysics Data System (ADS)

General Dynamics has developed a VTOL concept for a single-stage-to-orbit under contract to the Strategic Defense Initiative Organization. This paper briefly describes the configuration and its basic operations. Two key advanced technolgy areas are then discussed: high-performance rocket propulsion employing a plug nozzle arrangement and integrated health management to facilitate very rapid turnaround between flights, more like an aircraft than today's rockets.

Heald, Daniel A.; Kessler, Thomas L.

1991-10-01

57

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

58

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

59

Orbital stability of systems of closely-spaced planets, II: configurations with coorbital planets  

Microsoft Academic Search

We numerically investigate the stability of systems of 1 $${{\\\\rm M}_{\\\\oplus}}$$ planets orbiting a solar-mass star. The systems studied have either 2 or 42 planets per occupied semimajor axis, for a total\\u000a of 6, 10, 126, or 210 planets, and the planets were started on coplanar, circular orbits with the semimajor axes of the innermost\\u000a planets at 1 AU. For

Andrew W. Smith; Jack J. Lissauer

2010-01-01

60

3D stability orbits close to 433 Eros using an effective polyhedral model method  

NASA Astrophysics Data System (ADS)

One of the techniques used in the past decade to determine the shape with a good accuracy and estimate certain physical features (volume, mass, moments of inertia) of asteroids is the polyhedral model method. We rebuild the shape of the asteroid 433 Eros using data from 1998 December observations of the probe Near-Earth-Asteroid-Rendezvous-Shoemaker. In our computations, we use a code that avoids singularities from the line integrals of a homogeneous arbitrary shaped polyhedral source. This code evaluates the gravitational potential function and its first- and second-order derivatives. Taking the rotation of asteroid 433 Eros into consideration, the aim of this work is to analyse the dynamics of numerical simulations of 3D initially equatorial orbits near the body. We find that the minimum radius for direct, equatorial circular orbits that cannot impact with the Eros surface is 36 km and the minimum radius for stable orbits is 31 km despite significant perturbations of its orbit. Moreover, as the orbits suffer less perturbations due to the irregular gravitational potential of Eros in the elliptic case, the most significant result of the analysis is that stable orbits exist at a periapsis radius of 29 km for initial eccentricities ei ? 0.2.

Chanut, T. G. G.; Winter, O. C.; Tsuchida, M.

2014-03-01

61

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

62

Limits on the 2.2-mum contrast ratio of the close-orbiting planet HD 189733b  

Microsoft Academic Search

We obtained 238 spectra of the close-orbiting extrasolar giant planet HD 189733b with resolution R ~ 15000 during one night of observations with the Near-Infrared High-Resolution Spectrograph (NIRSPEC), at the Keck II Telescope. We have searched for planetary absorption signatures in the 2.0-2.4mum region where H2O and CO are expected to be the dominant atmospheric opacities. We employ a phase-dependent

J. R. Barnes; Travis S. Barman; L. Prato; D. Segransan; H. R. A. Jones; C. J. Leigh; A. Collier Cameron; D. J. Pinfield

2007-01-01

63

Research Article Numerical and Analytical Study of Optimal Low-Thrust Limited-Power Transfers between Close Circular Coplanar Orbits  

Microsoft Academic Search

A numerical and analytical study of optimal low-thrust limited-power trajectories for simple transfer (no rendezvous) between close circular coplanar orbits in an inverse- square force field is presented. The numerical study is carried out by means of an indirect approach of the optimization problem in which the two-point boundary value problem, obtained from the set of necessary conditions describing the

Sandro da Silva Fernandes; Wander Almodovar Golfetto; Manoel Balthazar

64

Orbital Disturbance Analysis due to the Lunar Gravitational Potential and Deviation Minimization through the Trajectory Control in Closed Loop  

NASA Astrophysics Data System (ADS)

A study evaluating the influence due to the lunar gravitational potential, modeled by spherical harmonics, on the gravity acceleration is accomplished according to the model presented in Konopliv (2001). This model provides the components x, y and z for the gravity acceleration at each moment of time along the artificial satellite orbit and it enables to consider the spherical harmonic degree and order up to100. Through a comparison between the gravity acceleration from a central field and the gravity acceleration provided by Konopliv's model, it is obtained the disturbing velocity increment applied to the vehicle. Then, through the inverse problem, the Keplerian elements of perturbed orbit of the satellite are calculated allowing the orbital motion analysis. Transfer maneuvers and orbital correction of lunar satellites are simulated considering the disturbance due to non-uniform gravitational potential of the Moon, utilizing continuous thrust and trajectory control in closed loop. The simulations are performed using the Spacecraft Trajectory Simulator-STRS, Rocco (2008), which evaluate the behavior of the orbital elements, fuel consumption and thrust applied to the satellite over the time.

Gonçalves, L. D.; Rocco, E. M.; de Moraes, R. V.

2013-10-01

65

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

Microsoft Academic Search

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

S. F. Hill

66

Closed orbit correction using singular value decomposition of the response matrix  

SciTech Connect

A theory of global orbit correction using the technique of singular value decomposition (SVD) of the response matrix and simulation of its application to the Advanced Photon Source (APS) storage ring are presented. The response matrix relates beam motion at the beam position monitor (BPM) locations to changes in corrector magnet strengths. SVD reconfigures the BPMs and correctors into the same number of ``transformed`` BPMs (t-BPMs) and ``transformed`` correctors (t-correctors), each T-BPM being coupled to at most one t-corrector and vice versa with associated coupling strength which determines the efficiency of orbit correction. The coefficients of these linear transformations can be used to determine which BPMs and correctors are the most effective. Decoupling the weakly coupled pairs will enhance the overall correction efficiency at the expense of accuracy. The orbit errors at decoupled t-BPMs are conserved and the strengths of decoupled t-correctors can be adjusted appropriately to optimize the actual corrector strengths. This method allows for estimating the limitation on orbit correction with given sets of BPMs and correctors, as well as optimizing the connector strengths without overloading the corrector magnet power supplies.

Chung, Y.; Decker, G.; Evans, K. Jr.

1993-08-01

67

Towards the field binary population: influence of orbital decay on close binaries  

NASA Astrophysics Data System (ADS)

Context. Surveys of binary populations in the solar neighbourhood have discovered that the periods of G- and M-type stars are log-normally distributed in the range 0.1-1011 days. However, observations of young binary populations in various star-forming regions have instead inferred a log-uniform distribution. Some process(es) must clearly be responsible for this change in the period distribution over time. Most stars form in star clusters, so it is here that the(se) process(es) take place. Aims: In dense young clusters, two important dynamical processes occur: i) the gas-induced orbital decay of embedded binary systems and ii) the destruction of soft binaries in three-body interactions. The emphasis in this work is on orbital decay as its influence on the binary distribution in clustered environments has largely been neglected so far. Methods: We performed Monte Carlo simulations of binary populations to model the process of orbital decay due to friction between the gas and binary stars. In addition, the destruction of soft binaries in young dense star clusters was simulated using N-body modelling of binary populations. Results: It is known that the cluster dynamics destroy the number of wide binaries, but leave short-period binaries basically undisturbed. Here we demonstrate that this result is also valid for an initially log-uniform period binary distribution. In contrast, the process of orbital decay significantly reduces the number and changes the properties of short-period binaries, leaving wide binaries largely uneffected. Until now, it has been unclear whether the short period distribution of the field has remained unaltered since its formation. We show here, that if any alteration took place, then orbital decay is a prime candidate for this task. In combination, the dynamics of these two processes, convert even an initial log-uniform distribution into a log-normal period distribution. The probability is 94% that the evolved period distribution and the observed period distribution have been sampled from the same parent distribution. Conclusions: Our results provide a new picture for the development of the field binary population: binaries can be formed as a result of the star-formation process in star clusters with periods that are sampled from the log-uniform distribution. As the cluster evolves, short-period binaries merge to form single stars by means of gas-induced orbital decay, while the dynamical evolution in the cluster destroys wide binaries. The combination of these two equally important processes reshapes an initial log-uniform period distribution to the log-normal period distribution that is observed in the field.

Korntreff, C.; Kaczmarek, T.; Pfalzner, S.

2012-07-01

68

Near infrared spectroscopic search for the close orbiting planet HD 75289b  

Microsoft Academic Search

We present a search for the near infrared spectroscopic signature of the\\u000aclose orbiting extrasolar giant planet HD 75289b. We obtained ~230 spectra in\\u000athe wavelength range 2.18 - 2.19 microns using the Phoenix spectrograph at\\u000aGemini South. By considering the direct spectrum, derived from irradiated model\\u000aatmospheres, we search for the absorption profile signature present in the\\u000acombined star

J. R. Barnes; C. J. Leigh; H. R. A. Jones; Travis S. Barman; D. J. Pinfield; A. Collier Cameron; J. S. Jenkins

2007-01-01

69

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

70

Orbital Distributions of Close-in Planets and Distant Planets Formed by Scattering and Dynamical Tides  

Microsoft Academic Search

We investigated the formation of close-in planets (hot Jupiters) by a combination of mutual scattering, Kozai effect, and tidal circularization, through N-body simulations of three gas giant planets, and compared the results with discovered close-in planets. We found that in about 350 cases out of 1200 runs (~30%), the eccentricity of one of the planets is excited highly enough for

M. Nagasawa; S. Ida

2011-01-01

71

Orbital solutions of eight close sdB binaries and constraints on the nature of the unseen companions  

NASA Astrophysics Data System (ADS)

The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars (sdBs) with massive compact companions such as white dwarfs, neutron stars, or stellar-mass black holes. In a supplementary programme we obtained time-resolved spectroscopy of known hot subdwarf binary candidates. Here we present orbital solutions of eight close sdB binaries with orbital periods ranging from ~0.1 d to 10 d, which allow us to derive lower limits on the masses of their companions. Additionally, a dedicated photometric follow-up campaign was conducted to obtain light curves of the reflection-effect binary HS 2043+0615. We are able to constrain the most likely nature of the companions in all cases but one, making use of information derived from photometry and spectroscopy. Four sdBs have white dwarf companions, while another three are orbited by low-mass main sequence stars of spectral type M. Radial velocities are available in electronic form at http://www.aanda.org and at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A95

Geier, S.; Østensen, R. H.; Heber, U.; Kupfer, T.; Maxted, P. F. L.; Barlow, B. N.; Vu?kovi?, M.; Tillich, A.; Müller, S.; Edelmann, H.; Classen, L.; McLeod, A. F.

2014-02-01

72

Orbital solutions of eight close sdB binaries and constraints on the nature of the unseen companions  

E-print Network

The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars (sdBs) with massive compact companions such as white dwarfs, neutron stars, or stellar-mass black holes. In a supplementary programme we obtained time-resolved spectroscopy of known hot subdwarf binary candidates. Here we present orbital solutions of eight close sdB binaries with orbital periods ranging from 0.1 to 10 days, which allow us to derive lower limits on the masses of their companions. Additionally, a dedicated photometric follow-up campaign was conducted to obtain light curves of the reflection-effect binary HS 2043+0615. We are able to constrain the most likely nature of the companions in all cases but one, making use of information derived from photometry and spectroscopy. Four sdBs have white dwarf companions, while another three are orbited by low-mass main sequence stars of spectral type M.

Geier, S; Heber, U; Kupfer, T; Maxted, P F L; Barlow, B N; Vuckovic, M; Tillich, A; Mueller, S; Edelmann, H; Classen, L; McLeod, A F

2014-01-01

73

On the Stability of Extrasolar Planetary Systems and other Closely Orbiting Pairs  

E-print Network

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 $L_X$) 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 lit...

Adams, Fred C

2014-01-01

74

The impact of orbital sampling, monthly averaging and vertical resolution on climate chemistry model evaluation with satellite observations  

NASA Astrophysics Data System (ADS)

Ensemble climate model simulations used for the Intergovernmental Panel on Climate Change (IPCC) assessments have become important tools for exploring the response of the Earth System to changes in anthropogenic and natural forcings. The systematic evaluation of these models through global satellite observations is a critical step in assessing the uncertainty of climate change projections. This paper presents the technical steps required for using nadir sun-synchronous infrared satellite observations for multi-model evaluation and the uncertainties associated with each step. This is motivated by need to use satellite observations to evaluate climate models. We quantified the implications of the effect of satellite orbit and spatial coverage, the effect of variations in vertical sensitivity as quantified by the observation operator and the impact of averaging the operators for use with monthly-mean model output. We calculated these biases in ozone, carbon monoxide, atmospheric temperature and water vapour by using the output from two global chemistry climate models (ECHAM5-MOZ and GISS-PUCCINI) and the observations from the Tropospheric Emission Spectrometer (TES) satellite from January 2005 to December 2008. The results show that sampling and monthly averaging of the observation operators produce biases of less than ±3% for ozone and carbon monoxide throughout the entire troposphere in both models. Water vapour sampling biases were also within the insignificant range of ±3% (that is ±0.14 g kg-1) in both models. Sampling led to a temperature bias of ±0.3 K over the tropical and mid-latitudes in both models, and up to -1.4 K over the boundary layer in the higher latitudes. Using the monthly average of temperature and water vapour operators lead to large biases over the boundary layer in the southern-hemispheric higher latitudes and in the upper troposphere, respectively. Up to 8% bias was calculated in the upper troposphere water vapour due to monthly-mean operators, which may impact the detection of water vapour feedback in response to global warming. Our results reveal the importance of using the averaging kernel and the a priori profiles to account for the limited vertical resolution of a nadir observation during model application. Neglecting the observation operators resulted in large biases, which are more than 60% for ozone, ±30% for carbon monoxide, and range between -1.5 K and 5 K for atmospheric temperature, and between -60% and 100% for water vapour.

Aghedo, A. M.; Bowman, K. W.; Shindell, D. T.; Faluvegi, G.

2011-03-01

75

The impact of orbital sampling, monthly averaging and vertical resolution on climate chemistry model evaluation with satellite observations  

NASA Astrophysics Data System (ADS)

Ensemble climate model simulations used for the Intergovernmental Panel on Climate Change (IPCC) assessments have become important tools for exploring the response of the Earth System to changes in anthropogenic and natural forcings. The systematic evaluation of these models through global satellite observations is a critical step in assessing the uncertainty of climate change projections. This paper presents the technical steps required for using nadir sun-synchronous infrared satellite observations for multi-model evaluation and the uncertainties associated with each step. This is motivated by need to use satellite observations to evaluate climate models. We quantified the implications of the effect of satellite orbit and spatial coverage, the effect of variations in vertical sensitivity as quantified by the observation operator and the impact of averaging the operators for use with monthly-mean model output. We calculated these biases in ozone, carbon monoxide, atmospheric temperature and water vapour by using the output from two global chemistry climate models (ECHAM5-MOZ and GISS-PUCCINI) and the observations from the Tropospheric Emission Spectrometer (TES) instrument on board the NASA-Aura satellite from January 2005 to December 2008. The results show that sampling and monthly averaging of the observation operators produce zonal-mean biases of less than ±3 % for ozone and carbon monoxide throughout the entire troposphere in both models. Water vapour sampling zonal-mean biases were also within the insignificant range of ±3 % (that is ±0.14 g kg-1) in both models. Sampling led to a temperature zonal-mean bias of ±0.3 K over the tropical and mid-latitudes in both models, and up to -1.4 K over the boundary layer in the higher latitudes. Using the monthly average of temperature and water vapour operators lead to large biases over the boundary layer in the southern-hemispheric higher latitudes and in the upper troposphere, respectively. Up to 8 % bias was calculated in the upper troposphere water vapour due to monthly-mean operators, which may impact the detection of water vapour feedback in response to global warming. Our results reveal the importance of using the averaging kernel and the a priori profiles to account for the limited vertical resolution and clouds of a nadir observation during model application. Neglecting the observation operators resulted in large biases, which are more than 60 % for ozone, ±30 % for carbon monoxide, and range between -1.5 K and 5 K for atmospheric temperature, and between -60 % and 100 % for water vapour.

Aghedo, A. M.; Bowman, K. W.; Shindell, D. T.; Faluvegi, G.

2011-07-01

76

A vertically integrated snow/ice model over land/sea for climate models. I - Development. II - Impact on orbital change experiments  

NASA Technical Reports Server (NTRS)

A vertically integrated formulation (VIF) model for sea ice/snow and land snow is discussed which can simulate the nonlinear effects of heat storage and transfer through the layers of snow and ice. The VIF demonstates the accuracy of the multilayer formulation, while benefitting from the computational flexibility of linear formulations. In the second part, the model is implemented in a seasonal dynamic zonally averaged climate model. It is found that, in response to a change between extreme high and low summer insolation orbits, the winter orbital change dominates over the opposite summer change for sea ice. For snow over land the shorter but more pronounced summer orbital change is shown to dominate.

Neeman, Binyamin U.; Ohring, George; Joseph, Joachim H.

1988-01-01

77

Synthesis of high quality, closely packed vertically aligned carbon nanotube array and a quantitative study of the influence of packing density on the collective thermal conductivity  

Microsoft Academic Search

In this work, we present the effect of packing density of vertically aligned carbon nanotube (VACNT) array on its thermal conductivity, as a step closer to its application in thermal interface materials (TIMs). High quality, closely packed VACNT array is synthesized by chemical vapor deposition (CVD) method. Cyclic catalyst deposition is performed to increase the packing density of VACNT array.

Wentian Gu; Wei Lin; Yagang Yao; Chingping Wong

2011-01-01

78

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

79

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

80

Fast and accurate method-of-moment solution of vertical antennas in contiguous dielectric half-spaces using closed-form spatial Green's functions  

Microsoft Academic Search

This paper develops an efficient solution of vertical dipoles in contiguous dielectric half-spaces based on a mixed potential integral equation (MPIE) and moment method. Closed-form expressions for the spatial vector and scalar potential Green's functions are obtained using the simulated image technique (Y.L. Chow et al, Proc. IEEE Int. Symp. Antennas and Propag., vol. 2, pp. 818-821, 1995). This technique

R. M. Shubair

2003-01-01

81

Depth-explicit SOC assessments at high vertical resolution using closed-tube sampling and Vis-NIR spectroscopy  

NASA Astrophysics Data System (ADS)

We provide an alternative to standard Soil Organic Carbon (SOC) measurement methods combining percussion drilling with Visible and Near-Infrared reflectance spectroscopic analyses at a very high depth resolution on intact soil cores (151 soil profiles; 3 cm vertical resolution). Using a small but representative subset of the soil cores that we analyzed for SOC content with dry combustion, we developed chemometric models to predict SOC content for the entire dataset. We show that our approach allows producing accurate and repeatable measurements of SOC. It provides detailed SOC information at ~83% lower costs and reduces labor time by ~85% compared to a traditional approach at the same vertical resolution. The accuracy of spectroscopic predictions is comparable to standard soil analysis techniques and hence our approach can represent an operational alternative to reference methods of SOC analysis. However, the method is limited to soils with a low gravel content (<~5% gravel).

Dötterl, Sebastian; Stevens, Antoine; Van Oost, Kristof; Van Wesemael, Bas

2013-04-01

82

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

83

Atomic-Orbital Close-Coupling Calculations Of Electron Capture From Hydrogen Atoms Into Highly Excited Rydberg States Of Multiply Charged Ions  

SciTech Connect

Collisions of neutral hydrogen atoms with multiply charged ions have been studied in the past using the semi-classical atomic-orbital close-coupling method. We present total and state-resolved cross sections for charge exchange as well as ionization. The advent of supercomputers and parallel programming facilities now allow treatment of collision systems that have been out of reach before, because much larger basis sets involving high quantum numbers are now feasible.

Igenbergs, Katharina; Wallerberger, Markus; Aumayr, Friedrich [Institute of Applied Physics, Vienna University of Technology, Association OeAW-EURATOM, Wiedner Hauptstr.8-10/E134, 1040 Vienna (Austria); Schweinzer, Josef [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr.2, 85748 Garching (Germany)

2011-06-01

84

A tether tension control law for tethered subsatellites deployed along local vertical. [space shuttle orbiters - satellite control/towed bodies  

NASA Technical Reports Server (NTRS)

A tethered subsatellite deployed along the local vertical is in stable equilibrium. This applies equally to subsatellites deployed in the direction towards the earth from the main spacecraft or away from the earth. Momentary perturbations from this stable equilibrium will result in a swinging motion, which decays very slowly if passive means are relied upon to provide damping. A control law is described which actively damps the swinging motion by employing a reel, or other mechanism, to apply appropriate tension as a function of tetherline length, rate of change of length, and desired length. The same control law is shown to be useful for deployment and retrieval of tethered subsatellites in addition to damping to steady state.

Rupp, C. C.

1975-01-01

85

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

86

'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

87

Counter-Orbitals: Another Class of Co-Orbitals  

NASA Astrophysics Data System (ADS)

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

Dobrovolskis, Anthony R.

2012-10-01

88

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

NASA Technical Reports Server (NTRS)

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

Senent, Juan

2011-01-01

89

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

90

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

E-print Network

The requirement that a planet must orbit outside of its Roche limit gives a lower limit on the planet's mean density. The minimum density depends almost entirely on the orbital period and is immune to systematic errors in ...

Rogers, Leslie A.

91

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

92

Numerical modelling the unsteady process of closed rectangular area radiant heating in conjugate formulation with accounting energy distribution along horizontal and vertical enclosure structures  

NASA Astrophysics Data System (ADS)

Mathematical modelling of unsteady convective-conductive heat exchange in premises, heated by infrared radiant heater is passed. Heat flux density from infrared radiant heater was calculated accounting energy distribution along horizontal and vertical building envelope. Comparison between zonal method and Lambert's law radiant energy distribution was done.

Nee, A. E.

2014-08-01

93

The Roche Limit for Close-orbiting Planets: Minimum Density, Composition Constraints, and Application to the 4.2 hr Planet KOI 1843.03  

NASA Astrophysics Data System (ADS)

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

Rappaport, Saul; Sanchis-Ojeda, Roberto; Rogers, Leslie A.; Levine, Alan; Winn, Joshua N.

2013-08-01

94

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

95

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

96

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

SciTech Connect

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

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

2013-08-10

97

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

98

Superdeep vertical seismic profiling at the KTB deep drill hole (Germany): Seismic close-up view of a major thrust zone down to 8.5 km depth  

NASA Astrophysics Data System (ADS)

The lowermost section of the continental superdeep drill hole German Continental Deep Drilling Program (KTB) (south Germany) has been investigated for the first time by vertical seismic profiling (VSP). The new VSP samples the still accessible range of 6-8.5 km depth. Between 7 and 8.5 km depth, the drill hole intersects a major cataclastic fault zone which can be traced back to the Earth's surface where it forms a lineament of regional importance, the Franconian line. To determine the seismic properties of the crust in situ, in particular within and around this deep fault zone, was one of the major goals of the VSP. For the measurements a newly developed high-pressure/high-temperature borehole geophone was used that was capable of withstanding temperatures and pressures up to 260°C and 140 MPa, respectively. The velocity-depth profiles and reflection images resulting from the VSP are of high spatial resolution due to a small geophone spacing of 12.5 m and a broad seismic signal spectrum. Compared to the upper part of the borehole, we found more than 10% decrease of the P wave velocity in the deep, fractured metamorphic rock formations. P wave velocity is ˜5.5 km/s at 8.5 km depth compared to 6.0-6.5 km/s at more shallow levels above 7 km. In addition, seismic anisotropy was observed to increase significantly within the deep fracture zone showing more than 10% shear wave splitting and azimuthal variation of S wave polarization. In order to quantify the effect of fractures on the seismic velocity in situ we compared lithologically identical rock units at shallow and large depths: Combining seismic velocity and structural logs, we could determine the elastic tensors for three gneiss sections. The analysis of these tensors showed that we need fracture porosity in the percent range in order to explain seismic velocity and anisotropy observed within the fault zone. The opening of significant pore space around 8 km depth can only be maintained by differential tectonic stress combined with intense macroscopic fracturing. VSP reflection imaging based on PP and PS converted reflected waves showed that the major fault system at the KTB site is wider and more complex than previously known. The so-called SE1 reflection previously found in two- and three-dimensional surface seismic surveys corresponds to the top of an ˜1 km wide fault system. Its lower portion was not illuminated by surface seismic acquisition geometry. VSP imaging shows that the fault zone comprises two major and a number of smaller SE dipping fault planes and several conjugate fracture planes. The previously recognized upper fault plane is not associated with a strong velocity anomaly but indicates the depth below which the dramatic velocity decrease starts. Regarding the complexly faulted crustal section of the KTB site as a whole, we found that fluctuation spectra of rock composition and seismic velocity show similar patterns. We could verify that a significant amount of P wave energy is continuously converted into shear energy by forward scattering and that multipathing plays an important role in signal formation. The media behaves effectively smoothly only at wavelength larger than 150 m. It was shown by moving source profiling that the media is orthorhombic on a regional scale. The tilt of the symmetry axes of anisotropy varies with depth following the dip of the geological structure.

Rabbel, W.; Beilecke, T.; Bohlen, T.; Fischer, D.; Frank, A.; Hasenclever, J.; Borm, G.; Kück, J.; Bram, K.; Druivenga, G.; Lüschen, E.; Gebrande, H.; Pujol, J.; Smithson, S.

2004-09-01

99

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

E-print Network

Planets with several Earth masses and a few day orbital periods have been discovered through radial velocity and transit surveys. Regardless of their formation mechanism, a key evolution issue is the efficiency of their retention near their host stars. If these planets attained their present-day orbits during or shortly after the T Tauri phase of their host stars, a large fraction would have encountered intense stellar magnetic field. Since these planets have a higher conductivity than the atmosphere of their stars, the magnetic flux tube connecting the planet and host star would slip though the envelope of the star faster than across the planet. The induced electro-motive 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 sweeps across the stellar surface and the potential drop drives a DC current analogous to that proposed for the Io-Jupiter electrodynamic interaction. The ohmic dissipation of t...

Laine, Randy O; 10.1088/0004-637X/745/1/2

2012-01-01

100

Periodic orbits and stability  

Microsoft Academic Search

A review is presented of periodic orbits which are of interest to dynamical astronomy, and their relation to actual systems is considered. In particular, the paper reviews periodic orbits in planetary systems with two or more planets, in the asteroid system, in stellar systems, and in the motion of a star in various types of galaxies. Most systems are close

John D. Hadjidemetriou

1988-01-01

101

An orbit fit program for localizing errors in RHIC  

SciTech Connect

Many errors in an accelerator are evidenced as transverse kicks to the beam which distort the beam trajectory. Therefore, the information of the errors are imprinted in the distorted orbits, which are different from what would be predicted by the optics model. In this note, we introduce an algorithm for fitting the orbit based on an on-line optics model. By comparing the measured and fitted orbits, we first present results validating the algorithm. We then apply the algorithm and localize the location of the elusive source of vertical diurnal variations observed in RHIC. The difference of two trajectories (linear accelerator) or closed orbits (storage ring) should match exactly a betatron oscillation, which is predictable by the optics model, in an ideal machine. However, in the presence of errors, the measured trajectory deviates from prediction since the model is imperfect. Comparison of measurement to model can be used to detect such errors. To do so the initial conditions (phase space parameters at any point) must be determined which can be done by comparing the difference orbit to prediction using only a few beam position monitors (BPMs). The fitted orbit can be propagated along the beam line based on the optics model. Measurement and model will agree up to the point of an error. The error source can be better localized by additionally fitting the difference orbit using downstream BPMs and back-propagating the solution. If one dominating error source exist in the machine, the fitted orbit will deviate from the difference orbit at the same point.

Liu, C.; Minty, M.; Ptitsyn, V.

2011-11-01

102

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

103

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

104

Kepler's Orbit  

NASA Video Gallery

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

105

Orbit Program  

NSDL National Science Digital Library

The Orbit program displays the dynamics of multiple massive objects interacting gravitationally. The default scenario shows the figure-eight orbit of three particles first discovered by Montgomery. Additional particles and their initial positions and velocities can be specified using the Display | Switch GUI menu item. Orbit is an Open Source Physics program written for the teaching of classical orbits. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the mech_orbit.jar file will run the program if Java is installed. Other classical mechanics programs are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or mechanics.

Christian, Wolfgang

2008-05-20

106

Closed FCC cyclone system  

Microsoft Academic Search

An apparatus is described for the fluid catalytic cracking of a hydrocarbon feed in a closed cyclone system. The apparatus consists of: a reactor vessel; a riser conversion zone defined by a vertically disposed elongated tubular conduit means having an upstream end and a downstream end, the downstream end terminating within the reactor vessel; the riser conversion zone having a

A. Y. Kam; F. J. Krambeck; K. L. Schatz

1986-01-01

107

Localized control of the orbit in the RHIC insertions  

SciTech Connect

It is proposed here that, for RHIC92 insertions, we remove the corrector from Ql and the beam position monitor (BPM) from Q2 in order to alleviate difficulties associated with the physical layout of the quadrupole triplet (Ql-Q2-Q3). Furthermore, it is suggested that there should be both (horizontal and vertical) types of BPMs at each end of the free space between Q3 and Q4 and between Q7 and Q8 so that one can measure the direction of the closed orbit. With this model, a localized control of the beam position and angle at the interaction point (IP) with either four or six correctors has been investigated. Similarly, a control of the orbit within an insertion for minimizing the orbit displacements at seven (or eight) BPM locations with nine (or ten) correctors in each transverse direction has been studied. Examples are given for the beta at IP = 2m, 10m, 20m, and 200m. It is shown that the design value of the integrated field strength of 0.3 T-m for each corrector should be sufficient for the tasks considered here except for some cases with extreme parameter values. At the same time, it is emphasized that the overall correction of the closed orbit for the entire ring (arcs and insertions) should be re-examined for RHIC92 lattice with the proposed arrangement of correctors and BPMS.

Ohnuma, S.

1992-08-01

108

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.

2004-01-01

109

Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities  

E-print Network

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 ...

Deck, Katherine M.

110

Atomic Orbitals  

NSDL National Science Digital Library

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

1969-12-31

111

Orbiter door closure tools  

NASA Technical Reports Server (NTRS)

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

Acres, W. R.

1980-01-01

112

Orbit selection for a Mars geoscience/climatology orbiter  

NASA Technical Reports Server (NTRS)

This paper is a presentation of recent work to provide orbit design and selection criteria for a close, nearly polar, nearly circular orbit of Mars. The main aspects of the work are the evaluation of atmospheric drag for altitude selection, the orbit evolution for variations in periapsis altitude, and the interactions of those factors with the science objectives of the MGCO mission. A dynamic model of the Mars atmosphere is available from parallel efforts and the latest estimates of the upper atmospheric density and its time history are incorporated into the analysis to provide a final orbit that satisfies planetary quarantine requirements.

Uphoff, C.

1984-01-01

113

The vertical distribution of Radiolaria in the waters surrounding Japan  

Microsoft Academic Search

Geographic and vertical distribution patterns of living Radiolaria are closely related to the characters of the water column. We studied living Radiolaria in samples collected at closely spaced depth intervals in the waters surrounding Japan in order to understand their vertical distribution and its controlling factors. Such information is needed to reconstruct past vertical water mass structure. The Japanese Islands

Yoshiyuki Ishitani; Kozo Takahashi

2007-01-01

114

Orbital imaging.  

PubMed

Appropriate axial or coronal computed x-ray tomography is the most inexpensive method to reliably supply detail in orbital disease. Magnetic resonance imaging can provide additional information and may be characteristic in some conditions. Magnetic resonance imaging is imperative for detailed imaging of disease at the orbital apex, optic canal, or chiasm. Color-coded Doppler ultrasonography allows examination of physiological blood flow within orbital vasculature and recent reports have reported the changes of flow in various orbital diseases. Limited results with computed tomographic or video-radiographic investigation of lacrimal outflow obstruction have been presented in several articles, although it remains doubtful whether these techniques are superior to the cheaper, more readily available, conventional macrodacryocystography. Endoscopy of the lacrimal drainage system is proving to be an interesting research tool, but is of uncertain applicability in the treatment of disease. PMID:10146487

Rose, G E

1993-11-01

115

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

116

Orbital YORP and asteroid orbit evolution, with application to Apophis  

NASA Astrophysics Data System (ADS)

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

Rubincam, David Parry

2007-12-01

117

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

118

Irregular Satellites: Orbits and Origins  

Microsoft Academic Search

Each of the giant planets has irregular satellites, moons that occupy large orbits of significant eccentricity e and\\/or inclination i. Since 1997, when only 10 irregular satellites were known, 29 new ones have been discovered, allowing the dynamical structure of these systems to be discerned. The irregulars often lie close to the orbital stability limit, about 1\\/2-1\\/3 of the way

J. A. Burns; B. J. Gladman; P. D. Nicholson; R. A. Jacobson; V. Carruba; M. J. Holman; JJ Kavelaars

2001-01-01

119

Orbit extrapolation  

Microsoft Academic Search

Orbit extrapolation problems are considered for the following examples: the ARGOS satellite, the SPOT satellite, the D2B and Signe 3 satellites, the Laser satellites, the Transit satellites, and Skylab atmospheric entry. Various extrapolation methods are then described, including analytical (integration and transformation) methods, numerical integration methods (e.g., the Adams-Moulton, Cowell method), and the centering method.

N. Borderies

1980-01-01

120

Mars Orbit  

NSDL National Science Digital Library

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

2010-12-14

121

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!"

122

Elliptical Orbits  

NSDL National Science Digital Library

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

Horton, Michael

2009-05-30

123

Asteroid-Asteroid Close Approaches  

NASA Astrophysics Data System (ADS)

Using selected asteroids from JPL's asteroid and comet database and Lowell Observatory's asteroid database (Courtesy E. Bowell), a search for significant asteroid-asteroid close approaches was performed. Initial osculating elements for more than 20,000 asteroids were integrated from 1800 to 2100 using a fully perturbed (i.e. 9 planets and the moon [DE-0405] and Ceres, Pallas, Vesta) N-body model including relativistic effects. Estimated orbital uncertainties for each asteroid orbit were considered in the calculation of all close approach parameters. A significant close approach is loosely defined for this study as one in which the smaller of the two asteroids is measurably perturbed. Using methods similar to those of Hilton et al. (1996), this work examines more than 20,000 asteroids and their orbital uncertainties. Consideration of these uncertainties in the resulting ephemerides allows for significant close approaches where nominal orbits could miss such possibilities. Results show the details of all significant close approaches and identify those for which masses may possibly be determined. Reference: Hilton, J.L., Seidelmann, P.K., and Middour, J. 1996. ``Prospects for Determining Asteroid Masses'', AJ 112:2139-2329.

Chamberlin, A. B.

1998-09-01

124

Closing in on Close Reading  

ERIC Educational Resources Information Center

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

Boyles, Nancy

2013-01-01

125

Double lunar swing-by orbits revisited  

NASA Astrophysics Data System (ADS)

The double lunar swing-by orbits are a special kind of orbits in the Earth-Moon system. These orbits repeatedly pass through the vicinity of the Moon and change their shapes due to the Moon's gravity. In the synodic frame of the circular restricted three-body problem consisting of the Earth and the Moon, these orbits are periodic, with two close approaches to the Moon in every orbit period. In this paper, these orbits are revisited. It is found that these orbits belong to the symmetric horseshoe periodic families which bifurcate from the planar Lyapunov family around the collinear libration point L3. Usually, the double lunar swing-by orbits have k= i+ j loops, where i is the number of the inner loops and j is the number of outer loops. The genealogy of these orbits with different i and j is studied in this paper. That is, how these double lunar swing-by orbits are organized in the symmetric horseshoe periodic families is explored. In addition, the 2 n lunar swing-by orbits ( n?2) with 2 n close approaches to the Moon in one orbit period are also studied.

Hou, XiYun; Liu, Lin

2014-04-01

126

Newton's hypothetical orbits independently derived.  

NASA Astrophysics Data System (ADS)

The mathematical results of four hypothetical orbital problems from the Principia are confirmed by an independent physical method. Each orbital problem that Newton posed and solved is characterized as follows. Given the shape of the orbit and the position of the force center, find the functional form of the central attractive force that will keep a body moving around the orbit. None of Newton's hypothetical orbital problems has so far found any apparent practical application, whereas the Kepler problem, also solved by Newton in the Principia, is of great importance to physics. The Kepler problem too can be derived easily by the present method. Newton used primarily geometrical constructions and logical deductions to arrive at his force functions. In contrast to this, the present (inverse) approach is based on a force balance: as a body moves along a curved path the outward centrifugal force always balances the component of the inward attractive force that is perpendicular to the orbit. Taking the functional form for the central force derived by Newton and inserting it into the force balance, the orbital shape can be derived by solving an ordinary second-order differential equation-the forced harmonic oscillator equation. Two of Newton's four force functions examined in this way lead to (different) fully nonlinear differential equations, which, surprisingly, can both be solved analytically and in closed form by means of the elementary functions that describe the shapes of the orbits.

Kenyon, K. E.

127

Eye and orbit ultrasound  

MedlinePLUS

Echography - eye orbit; Ultrasound - eye orbit; Ocular ultrasonography; Orbital ultrasonography ... ophthalmology department of a hospital or clinic. Your eye is numbed with medicine (anesthetic drops). The ultrasound ...

128

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

129

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

130

Overview of Venus orbiter, Akatsuki  

NASA Astrophysics Data System (ADS)

The Akatsuki spacecraft of Japan was launched on May 21, 2010. The spacecraft planned to enter a Venus-encircling near-equatorial orbit in December 7, 2010; however, the Venus orbit insertion maneuver has failed, and at present the spacecraft is orbiting the Sun. There is a possibility of conducting an orbit insertion maneuver again several years later. The main goal of the mission is to understand the Venusian atmospheric dynamics and cloud physics, with the explorations of the ground surface and the interplanetary dust also being the themes. The angular motion of the spacecraft is roughly synchronized with the zonal flow near the cloud base for roughly 20 hours centered at the apoapsis. Seen from this portion of the orbit, cloud features below the spacecraft continue to be observed over 20 hours, and thus the precise determination of atmospheric motions is possible. The onboard science instruments sense multiple height levels of the atmosphere to model the three-dimensional structure and dynamics. The lower clouds, the lower atmosphere and the surface are imaged by utilizing near-infrared windows. The cloud top structure is mapped by using scattered ultraviolet radiation and thermal infrared radiation. Lightning discharge is searched for by high speed sampling of lightning flashes. Night airglow is observed at visible wavelengths. Radio occultation complements the imaging observations principally by determining the vertical temperature structure.

Nakamura, M.; Imamura, T.; Ishii, N.; Abe, T.; Satoh, T.; Suzuki, M.; Ueno, M.; Yamazaki, A.; Iwagami, N.; Watanabe, S.; Taguchi, M.; Fukuhara, T.; Takahashi, Y.; Yamada, M.; Hoshino, N.; Ohtsuki, S.; Uemizu, K.; Hashimoto, G. L.; Takagi, M.; Matsuda, Y.; Ogohara, K.; Sato, N.; Kasaba, Y.; Kouyama, T.; Hirata, N.; Nakamura, R.; Yamamoto, Y.; Okada, N.; Horinouchi, T.; Yamamoto, M.; Hayashi, Y.

2011-05-01

131

Optical Observations and Orbital Parameters of the Close DA plus dMe Binaries BPM 71214, EUVE J0720-31.7, BPM 6502, and EC 13471-1258  

NASA Astrophysics Data System (ADS)

We have obtained photometric and spectroscopic observations of the close DA plus dMe binaries BPM 6502 and EC 13471-1258, and spectroscopic observations of the close binaries BPM 71214 and EUVE J0720-31.7. We have updated the ephemerides of BPM 6502 and EUVE J0720-31.7 with the spectroscopic measurements and obtained periods of 0.20162 and 0.15074 days for BPM 71214 and EC 13471-1258, respectively, by measuring the shift in H? emission. Photometric variations in R and I due to reprocessing of incoming radiation from the hot white dwarf were observed in BPM 6502. We have also observed eclipses and ellipsoidal variations in B and R for EC 13471-1258, suggesting that the secondary is nearly filling its Roche lobe.

Kawka, Adela; Vennes, Stéphane; Koch, Rolf; Williams, Andrew

2002-11-01

132

Comparing Gaseous and Stellar Orbits in a Spiral Potential  

NASA Astrophysics Data System (ADS)

It is generally assumed that gas in a galactic disk follows closely non self-intersecting periodic stellar orbits. In order to test this common assumption, we have performed MHD simulations of a galactic-like disk under the influence of a spiral galactic potential. We also have calculated the actual orbit of a gas parcel and compared it to stable periodic stellar orbits in the same galactic potential and position. We found that the gaseous orbits approach periodic stellar orbits far from the major orbital resonances only. Gas orbits initialized at a given galactocentric distance but at different azimuths can be different, and scattering is conspicuous at certain galactocentric radii. Also, in contrast to the stellar behavior, near the 4:1 (or higher order) resonance the gas follows nearly circular orbits, with much shorter radial excursions than the stars. Also, since the gas does not settle into a steady state, the gaseous orbits do not necessarily close on themselves.

Gómez, G. C.; Pichardo, B.; Martos, M. A.

2014-03-01

133

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

134

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.

135

GOCE Gravity Gradients in an Orbital Aspect  

NASA Astrophysics Data System (ADS)

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

Bobojc, Andrzej; Drozyner, Andrzej

2014-05-01

136

Early orbit determination  

Microsoft Academic Search

Orbit determination for near real time monitoring of satellite movement based on limited observations is discussed. For geostationary satellites this early orbit determination requirement arises after injection into geostationary transfer orbit, apogee motor firing, and larger orbit maneuvers during the on-station phase. Early orbit determination is hampered by the limited amount of data caused by nonavailability of the tracking system.

S. Pallaschke

1986-01-01

137

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

138

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

139

Enhanced Activity in Close T Tauri Binaries  

NASA Astrophysics Data System (ADS)

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

Gahm, Gösta

2006-08-01

140

RHIC BPM system average orbit calculations  

SciTech Connect

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

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

2009-05-04

141

LISA Orbits  

NASA Astrophysics Data System (ADS)

The LISA formation is composed of 3 spacecraft in an equilateral triangle formation. The baseline formation has a 5million km radius and lies in a heliocentric orbit 20deg away from the Earth. Earth's gravity induces a perturbation on the nominal Keplerian motion of the formation, generating a change in the relative ranges and thus a Doppler that can be very harmful for the scientific goals of the mission. Zero station keeping options are preferred, so alternative passive solutions have to be found. This paper presents results obtained by optimising the formation design, particularly the orientation of the eccentricity vectors. Formation design optimisation proves to be an effective strategy, succeeding in keeping the relative range rate between any two spacecraft below 13m/s. Another possible source of perturbation arises from the self-acceleration induced on the formation by the imperfect mass distribution on each spacecraft. The effect of this perturbing acceleration on the motion of the formation has been studied, and the formation design has been re-optimised assuming several levels of perturbation. This approach has shown the result that such effect can be even beneficial on the formation stability, provided that the acceleration doesn't exceed 1e-8m/s2. The transfer to the optimal stability formation has then been optimised, assuming a launch window throughout the year. Mission ?v to a specific target is quite sensitive to the launch date: trailing formations are most effectively reached if the launch occurs at Earth's apohelion (summer), while the opposite applies to leading formations. A strategy where leading and trailing formations are alternatively targeted according to the launch date has proved to be the most effective in keeping the ?v as low as possible.

Povoleri, Angelo; Kemble, Stephen

2006-11-01

142

ERS orbit control  

NASA Astrophysics Data System (ADS)

The European remote sensing mission orbit control is addressed. For the commissioning phase, the orbit is defined by the following requirements: Sun synchronous, local time of descending node 10:30; three days repeat cycle with 43 orbital revolutions; overhead Venice tower (12.508206 deg east, 45.314222 deg north). The launch, maneuvers for the initial acquisition of the operational orbit, orbit maintenance maneuvers, evaluation of the orbit control, and the drift of the inclination are summarized.

Rosengren, Mats

1991-12-01

143

TIDAL EVOLUTION OF CLOSE-IN PLANETS  

SciTech Connect

Recent discoveries of several transiting planets with clearly non-zero eccentricities and some large obliquities started changing the simple picture of close-in planets having circular and well-aligned orbits. The two major scenarios that form such close-in planets are planet migration in a disk and planet-planet interactions combined with tidal dissipation. The former scenario can naturally produce a circular and low-obliquity orbit, while the latter implicitly assumes an initially highly eccentric and possibly high-obliquity orbit, which are then circularized and aligned via tidal dissipation. Most of these close-in planets experience orbital decay all the way to the Roche limit as previous studies showed. We investigate the tidal evolution of transiting planets on eccentric orbits, and find that there are two characteristic evolution paths for them, depending on the relative efficiency of tidal dissipation inside the star and the planet. Our study shows that each of these paths may correspond to migration and scattering scenarios. We further point out that the current observations may be consistent with the scattering scenario, where the circularization of an initially eccentric orbit occurs before the orbital decay primarily due to tidal dissipation in the planet, while the alignment of the stellar spin and orbit normal occurs on a similar timescale to the orbital decay largely due to dissipation in the star. We also find that even when the stellar spin-orbit misalignment is observed to be small at present, some systems could have had a highly misaligned orbit in the past, if their evolution is dominated by tidal dissipation in the star. Finally, we also re-examine the recent claim by Levrard et al. that all orbital and spin parameters, including eccentricity and stellar obliquity, evolve on a similar timescale to orbital decay. This counterintuitive result turns out to have been caused by a typo in their numerical code. Solving the correct set of tidal equations, we find that the eccentricity behaves as expected, with orbits usually circularizing rapidly compared to the orbital decay rate.

Matsumura, Soko; Rasio, Frederic A. [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Peale, Stanton J., E-mail: soko@astro.umd.ed [Physics Department, University of California, Santa Barbara, CA 93106 (United States)

2010-12-20

144

Atmosphere and orbital stability of exosolar planets orbiting gamma Cephei  

Microsoft Academic Search

The recently discovered Jupiter-like planet (m sin i= 1.76 M_jup) in the binary system gamma Cephei moves in a so-called S-type orbit around its host-star with a distance of about 2.15 AU. It is the first planet that have been found in a close binary and is from the dynamical point of view a very stable configuration. Numerical computations in

H. Lammer; R. Dvorak; E. Pilat-Lohinger; B. Funk; F. Freistetter; I. Ribas; F. Selsis; E. F. Guinan; W. W. Weiss; S. J. Bauer

2003-01-01

145

Closeup view of the reinforced carboncarbon nose of the Orbiter ...  

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

Close-up view of the reinforced carbon-carbon nose of the Orbiter Discovery from the service platform in the Orbiter Processing Facility at Kennedy Space Center. Note the clear protective shield around the nose cap, and the reflective insulation protecting the Crew Compartment bulkhead and orbiter structure in the void created by the removal of the Forward Reaction Control Module. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

146

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

147

A feedback linearization approach to orbital maneuvers  

NASA Astrophysics Data System (ADS)

New methods for obtaining optimal orbital maneuvers of a space vehicle in total velocity change are described and applied. The elegance of Lambert's Theorem is combined with feedback linearization and linear optimal control to obtain solutions to nonlinear orbital maneuver problems. In particular, geocentric orbital maneuvers with finite-thrust acceleration are studied. The full nonlinear equations of motion are transformed exactly into a controllable linear set in Brunovsky canonical form by using feedback linearization and choosing the position vector as the fully observable output vector. These equations are used to pose a linear optimal tracking problem with a solution to the Lambert's impulsive-thrust two-point boundary-value problem as the reference orbit. The same procedure is used to force the space vehicle to follow a linear analytical solution to the continuous low-thrust orbital maneuver problem between neighboring orbits. Limits on thrust magnitudes are enforced by adjusting the weights on the states in the performance index, which is chosen to be the sum of integrals of the square sum of new control variables and the square sum of state variable errors from the reference trajectory. For comparison purpose, the feedback linearized equations are used to obtain a simple closed-form solution to an orbital maneuver problem without the use of a reference trajectory. In this case, the performance index was chosen as the integral of the square sum of new control variables only. Three different examples, coplanar rendezvous between neighboring orbits, large coplanar orbit transfer, and non-coplanar orbit transfer, are used to show the advantages of using the new methods introduced in this dissertation. The minimum-eccentricity orbit, Hohmann transfer orbit, and minimum energy orbit were used in turn as the reference trajectories. The principal problems encountered in using the new methods are the choices of the proper reference trajectory, a suitable time-dependent scalar weighting function, and appropriate constant weighting matrices.

Lee, Sanguk

148

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.

Hamilton, Douglas

149

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

150

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

151

Simulation Studies on the Vertical Emittance Growth in the ATF Extraction Beamline  

SciTech Connect

Significant dependence of the vertical emittance growth on the beam intensity was experimentally observed at the ATF/KEK extraction beamline. This technical note describes the simulations of possible vertical emittance growth sources, particularly in the extraction channel, where the magnets are shared by both the ATF extraction beamline and its damping ring. The vertical emittance growth is observed in the simulations by changing the beam orbit in the extraction channel even with all optics corrections. The possible reasons for the experimentally observed dependence of the vertical emittance growth on the beam intensity are discussed. An experiment to measure the emittance vs beam orbit at the existing ATF extraction beamline is proposed.

Zhou, F.; Amann, J.; Selestiky, S.; Seryi, A.; Spencer, C.; Woodley, M.; /SLAC

2007-12-18

152

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

153

Secular Orbital Evolution of Compact Planet Systems Ke Zhang, Douglas P. Hamilton, and Soko Matsumura  

E-print Network

Secular Orbital Evolution of Compact Planet Systems Ke Zhang, Douglas P. Hamilton, and Soko 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 #12;­ 2 ­ elliptical orbit is apsidally-locked to a more distant

Hamilton, Douglas P.

154

APPROXIMATING THE PATH OF A CELESTIAL BODY WITH A CIRCULAR ORBIT FROM TWO  

E-print Network

. At this time, no asteroids were known, but the search for an unknown "planet" between the orbits of Mars1 APPROXIMATING THE PATH OF A CELESTIAL BODY WITH A CIRCULAR ORBIT FROM TWO CLOSE OBSERVATIONS elliptical orbit. Using ecliptic longitudes from only two close observations, we try to compute a circle

Osler, Thomas

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

DCI Closed: A Fast and Memory Efficient Algorithm to Mine Frequent Closed Itemsets  

Microsoft Academic Search

One of the main problems raising up in the frequent closeditemsetsminingproblemistheduplicatedetection. In this paper we propose a general technique for promptly detecting and discarding duplicate closed itemsets, with- out the need of keeping in the main memory the whole set of closed patterns. Our approach can be exploited with substantial perfor- mance benefits by any algorithm that adopts a vertical

Claudio Lucchese; Salvatore Orlando; Raffaele Perego

2004-01-01

157

The Sudden Discontinuity in the Orbital Period of Sputnik 4 Satellite  

Microsoft Academic Search

THE orbit of the fourth Russian Earth satellite soon after its late launching on May 14, 1960, was similar to the orbits of the previous Sputniks, as may be seen from the orbital elements shown in Table 1. A Tass News Agency report of May 17 indicated that there were two objects close together in orbit-the composite satellite itself, consisting

B. R. May; D. E. Smith

1960-01-01

158

Periodic orbits around areostationary points in the Martian gravity field  

NASA Astrophysics Data System (ADS)

This study investigates the problem of areostationary orbits around Mars in three-dimensional space. Areostationary orbits are expected to be used to establish a future telecommunication network for the exploration of Mars. However, no artificial satellites have been placed in these orbits thus far. The characteristics of the Martian gravity field are presented, and areostationary points and their linear stability are calculated. By taking linearized solutions in the planar case as the initial guesses and utilizing the Levenberg-Marquardt method, families of periodic orbits around areostationary points are shown to exist. Short-period orbits and long-period orbits are found around linearly stable areostationary points, but only short-period orbits are found around unstable areostationary points. Vertical periodic orbits around both linearly stable and unstable areostationary points are also examined. Satellites in these periodic orbits could depart from areostationary points by a few degrees in longitude, which would facilitate observation of the Martian topography. Based on the eigenvalues of the monodromy matrix, the evolution of the stability index of periodic orbits is determined. Finally, heteroclinic orbits connecting the two unstable areostationary points are found, providing the possibility for orbital transfer with minimal energy consumption.

Liu, Xiao-Dong; Baoyin, Hexi; Ma, Xing-Rui

2012-05-01

159

Factorization of cubic vertices involving three different higher spin fields  

NASA Astrophysics Data System (ADS)

We derive a class of cubic interaction vertices for three higher spin fields, with integer spins ?1, ?2, ?3, by closing commutators of the Poincaré algebra in four-dimensional flat spacetime. We find that these vertices exhibit an interesting factorization property which allows us to identify off-shell perturbative relations between them.

Akshay, Y. S.; Ananth, Sudarshan

2014-10-01

160

Pure orbital blowout fracture: new concepts and importance of medial orbital blowout fracture.  

PubMed

Pure orbital blowout fracture first occurs at the weakest point of the orbital wall. Although the medial orbital wall theoretically should be involved more frequently than the orbital floor, the orbital floor has been reported as the most common site of pure orbital blowout fractures. A total of 82 orbits in 76 patients with pure orbital blowout fracture were evaluated with computed tomographic scans taken on all patients with any suspicious clinical evidence, including nasal fracture. Isolated medial wall fracture was most common (55 percent), followed by medial and inferior wall fracture (27 percent). The most common facial fracture associated with medial wall fracture was nasal fracture (51 percent), not inferior wall fracture (33 percent). This finding suggests that the force causing nasal fracture is an important causative factor of pure medial wall fracture as the buckling force from the medial orbital rim. Of patients with medial wall fractures, 25 percent had diplopia and 40 percent had enophthalmos. On plain radiographs, diagnostic signs were found in 79 percent of medial wall fractures and in 95 percent of inferior wall fractures. On computed tomographic scans, late enophthalmos was expected in 76 percent of medial wall fractures. Therefore, the medial orbital blowout fracture may be an important cause of late enophthalmos, because it has a high incidence of occurrence, a low diagnostic rate, and a high severity of defect. Among the causes of limitation of ocular motility, muscle traction of the connective septa and direct muscle injury were found frequently, but true incarceration of the muscle was extremely rare in all fractures. The medial and inferior orbital walls are clearly demarcated by the bony buttress, which is an important structure supporting these orbital walls. Its buttress was closely correlated with the fracture of these orbital walls. Most orbital blowout fractures without collapse of the bony buttress had a trapdoor fracture with or without small fragments of punched-out fracture. PMID:10359243

Burm, J S; Chung, C H; Oh, S J

1999-06-01

161

Fibrolipoma of the orbit.  

PubMed

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

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

2011-01-01

162

Vertical Line Test  

NSDL National Science Digital Library

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

2010-01-01

163

Vertical lid split approach for optic nerve sheath decompression  

PubMed Central

We describe a vertical lid split orbitotomy approach to perform optic nerve sheath fenestration which was done in a patient with idiopathic intracranial hypertension. A vertical lid split incision was used to enter the superomedial orbit and approach the optic nerve sheath. This approach resulted in a successful nerve sheath fenestration, with improvement in the patient's symptoms. The vertical lid split incision provides access to the optic nerve sheath with minimal morbidity and may be an option for optic nerve sheath decompression. PMID:19574700

Prabhakaran, Venkatesh C; Selva, Dinesh

2009-01-01

164

Transneptunian Orbit Computation  

NASA Astrophysics Data System (ADS)

We review the orbit computation problem for the transneptunian population. For these distant objects, the problem is characterized by their short observed orbital arcs, which are known to be coupled with large uncertainties in orbital elements. Currently, the observations of even the best observed objects, such as the first-ever transneptunian object (TNO), Pluto, cover only a fraction of their revolution. Furthermore, of the some 1200 objects discovered since 1992, roughly half have observations from only one opposition. To ensure realistic analyses of the population, e.g., in the derivation of unbiased orbital distributions or correlations between orbital and physical properties, realistic estimation of orbital uncertainties is important. We describe the inverse problem of orbit computation, emphasizing the short-arc problem and its statistical treatment. The complete solution to the problem can be given in terms of the orbital-element probability density function (p.d.f.), which then serves as a starting point for any further analysis, where knowledge of orbital uncertainties is required. We give an overview of the variety of computational techniques developed for TNO orbital uncertainty estimation in the recent years. After presenting the current orbital distribution, we demonstrate their application to several prediction problems, such as classification, ephemeris prediction, and dynamical analysis of objects. We conclude with some future prospects for TNO orbit computation concerning the forthcoming next-generation surveys, including the anticipated evolution of TNO orbital uncertainties over the coming decades.

Virtanen, J.; Tancredi, G.; Bernstein, G. M.; Spahr, T.; Muinonen, K.

165

Detail view of the lower portion of the vertical stabilizer ...  

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

Detail view of the lower portion of the vertical stabilizer of the Orbiter Discovery. The section below the rudder, often referred to as the "stinger", is used to house the orbiter drag chute assembly. The system consisted of a mortar deployed pilot chute, the main drag chute, a controller assembly and an attach/jettison mechanism. This system was a modification to the original design of the Orbiter Discovery to safely reduce the roll to stop distance without adversely affecting the vehicle handling qualities. 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

166

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

167

Micromachined electrostatic vertical actuator  

SciTech Connect

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, A.P.; Sommargren, G.E.; McConaghy, C.F.; Krulevitch, P.A.

1999-10-19

168

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

169

An Orbit And Dispersion Correction Scheme for the PEP II  

SciTech Connect

To achieve optimum luminosity in a storage ring it is vital to control the residual vertical dispersion. In the original PEP storage ring, a scheme to control the residual dispersion function was implemented using the ring orbit as the controlling element. The 'best' orbit not necessarily giving the lowest vertical dispersion. A similar scheme has been implemented in both the on-line control code and in the simulation code LEGO. The method involves finding the response matrices (sensitivity of orbit/dispersion at each Beam-Position-Monitor (BPM) to each orbit corrector) and solving in a least squares sense for minimum orbit, dispersion function or both. The optimum solution is usually a subset of the full least squares solution. A scheme of simultaneously correcting the orbits and dispersion has been implemented in the simulation code and on-line control system for PEP-II. The scheme is based on the eigenvector decomposition method. An important ingredient of the scheme is to choose the optimum eigenvectors that minimize the orbit, dispersion and corrector strength. Simulations indicate this to be a very effective way to control the vertical residual dispersion.

Cai, Y.; Donald, M.; Shoaee, H.; White, G.; Yasukawa, L.A.; /SLAC

2011-09-01

170

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

171

Rock-Around Orbits  

E-print Network

. . . . . . . . . . . . . 8 D. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 E. Minimum Distance . . . . . . . . . . . . . . . . . . . . . . 15 III ELLIPTICAL TARGET ORBITS : : : : : : : : : : : : : : : : : 18 A. Acceptable and Compatible Orbits... . . . . . . . . . . . . . 18 B. Eccentricity and Inclination Bounds . . . . . . . . . . . . . 19 C. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 D. Minimum Distance . . . . . . . . . . . . . . . . . . . . . . 26 IV J2 PERTURBATIONS...

Bourgeois, Scott K.

2010-07-14

172

Orbit CT scan  

MedlinePLUS

Massoud TF, Cross JJ. The orbit. In: Adam A, Dixon A, eds. Grainger and Allison's Diagnostic Radiology. 5th ed. Philadelphia, Pa: Elsevier Saunders; 2008:chap 61. Szatmary G. Imaging of the orbit. Neurol Clin . 2008;27:251-284.

173

Preliminary orbital parallax catalog  

NASA Technical Reports Server (NTRS)

The study is undertaken to calibrate the more reliable parallaxes derived from a comparison of visual and spectroscopic orbits and to encourage observational studies of other promising binaries. The methodological techniques used in computing orbital parallaxes are analyzed. Tables summarizing orbital data and derived system properties are then given. Also given is a series of detailed discussions of the 71 individual systems included in the tables. Data are listed for 57 other systems which are considered promising candidates for eventual orbital parallax determination.

Halliwell, M.

1981-01-01

174

Cosmetic orbital surgery  

Microsoft Academic Search

PurposeCurrent indications for orbital surgery primarily aimed at improving cosmesis are considered in the context of subspecialist orbital practice by an ophthalmologist.ScopeThyroid eye disease, orbital vascular anomalies, and dermolipomas are common orbital diseases in which the symptoms can be purely cosmetic. Accurate anatomical awareness, preoperative scanning, control of medical factors including smoking and thyroid status, and endoscopic techniques have all

2006-01-01

175

Mars orbit selection  

NASA Technical Reports Server (NTRS)

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

Babb, Gus R.; Stump, William R.

1986-01-01

176

Orbiting Binary Stars  

NSDL National Science Digital Library

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

Kolena, John

2007-12-11

177

Near action-degenerate periodic-orbit bunches: A skeleton of chaos  

E-print Network

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 $\\Delta S$ within a bunch can be arbitrarily small. Bunches with $\\Delta S$ 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.

Alexander Altland; Petr Braun; Fritz Haake; Stefan Heusler; Gerhard Knieper; Sebastian Müller

2009-06-26

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

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.

Laboratory, Jet P.; Administration, National A.

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

The vertical structure of limb hazes in the Martian atmosphere  

Microsoft Academic Search

Vertical distribution and reflectance properties of aerosols in the Martian atmosphere are presented, based on Viking Orbiter images containing the planetary limb. Profiles of scattered light above the limb are used to constrain the temporal and spatial behavior of the aerosols. The data cover a wide range of seasons, locations, and viewing geometries. The typical atmospheric column contains one or

Fred Jaquin; Peter Gierasch; Ralph Kahn

1986-01-01

182

Radically new design of SAR satellite: short vertical antenna approach  

Microsoft Academic Search

The idea of this work is the use of a vertical antenna (antenna placed in the orbit plane) for a spaceborne radar. This surprising geometry is proven to work properly and to simplify the design of the instrument, particularly when it is associated with a short antenna length (<5 m, along speed vector). The number of antenna control points is

JEAN-PAUL AGUTTES

2001-01-01

183

Close approaches of asteroid 1999 AN10: resonant and non-resonant returns  

Microsoft Academic Search

The Earth passes very close to the orbit of the asteroid 1999 AN10 twice per year, but whether or not this asteroid can have a close approach depends upon the timing of its passage across the ecliptic plane. Among the possible orbits there are some with a close approach in 2027. The period of the asteroid may be perturbed in

Andrea Milani; Steven R. Chesley; Giovanni B. Valsecchi

1999-01-01

184

Vertical instability and inclination excitation during planetary migration  

NASA Astrophysics Data System (ADS)

We consider a two-planet system migrating under the influence of dissipative forces that mimic the effects of gas-driven (Type II) migration. It has been shown that, in the planar case, migration leads to resonant capture after an evolution that forces the system to follow families of periodic orbits. Starting with planets that differ slightly from a coplanar configuration, capture can, also, occur and, additionally, excitation of planetary inclinations has been observed in some cases. We show that excitation of inclinations occurs, when the planar families of periodic orbits, which are followed during the initial stages of planetary migration, become vertically unstable. At these points, vertical critical orbits may give rise to generating stable families of periodic orbits, which drive the evolution of the migrating planets to non-coplanar motion. We have computed and present here the vertical critical orbits of the and resonances, for various values of the planetary mass ratio. Moreover, we determine the limiting values of eccentricity for which the "inclination resonance" occurs.

Voyatzis, G.; Antoniadou, K. I.; Tsiganis, K.

2014-08-01

185

Vertical instability and inclination excitation during planetary migration  

E-print Network

We consider a two-planet system, which migrates under the influence of dissipative forces that mimic the effects of gas-driven (Type II) migration. It has been shown that, in the planar case, migration leads to resonant capture after an evolution that forces the system to follow families of periodic orbits. Starting with planets that differ slightly from a coplanar configuration, capture can, also, occur and, additionally, excitation of planetary inclinations has been observed in some cases. We show that excitation of inclinations occurs, when the planar families of periodic orbits, which are followed during the initial stages of planetary migration, become vertically unstable. At these points, {\\em vertical critical orbits} may give rise to generating stable families of $3D$ periodic orbits, which drive the evolution of the migrating planets to non-coplanar motion. We have computed and present here the vertical critical orbits of the $2/1$ and $3/1$ resonances, for various values of the planetary mass ratio....

Voyatzis, G; Tsiganis, K

2014-01-01

186

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

187

Orbital evolution around irregular bodies  

NASA Astrophysics Data System (ADS)

The new profiles of the space missions aimed at asteroids and comets, moving from fly-bys to rendezvous and orbiting, call for new spaceflight dynamics tools capable of propagating orbits in an accurate way around these small irregular objects. Moreover, interesting celestial mechanics and planetary science problems, requiring the same sophisticated tools, have been raised by the first images of asteroids (Ida/Dactyl, Gaspra and Mathilde) taken by the Galileo and NEAR probes, and by the discovery that several near-Earth asteroids are probably binary. We have now developed two independent codes which can integrate numerically the orbits of test particles around irregularly shaped primary bodies. One is based on a representation of the central body in terms of "mascons" (discrete spherical masses), while the other one models the central body as a polyhedron with a variable number of triangular faces. To check the reliability and performances of these two codes we have performed a series of tests and compared their results. First we have used the two algorithms to calculate the gravitational potential around non-spherical bodies, and have checked that the results are similar to each other and to those of other, more common, approaches; the polyhedron model appears to be somewhat more accurate in representing the potential very close to the body's surface. Then we have run a series of orbit propagation tests, integrating several different trajectories of a test particle around a sample ellipsoid. Again the two codes give results in fair agreement with each other. By comparing these numerical results to those predicted by classical perturbation formulae, we have noted that when the orbit of the test particle gets close to the surface of the primary, the analytical approximations break down and the corresponding predictions do not match the results of the numerical integrations. This is confirmed by the fact that the agreement gets better and better for orbits farther away from the primary. Finally, we have found that in terms of CPU time requirements, the performances of the two codes are quite similar, and that the optimal choice probably depends on the specific problem under study.

Rossi, A.; Marzari, F.; Farinella, P.

1999-11-01

188

Terrestrial planet formation surrounding close binary stars  

Microsoft Academic Search

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

Elisa V. Quintana; Jack J. Lissauer

2006-01-01

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

Chemguide: Atomic Orbitals  

NSDL National Science Digital Library

This web page explains what atomic orbitals are in a way that makes it appropriate for pre-college introductory chemistry or physics courses. It goes into detail on s and p orbitals, including their shapes and energies, while devoting less discussion to d and f orbitals. The author uses an analogy comparing an atom to a multi-story house -- with the nucleus on the ground floor and then various rooms (orbitals) on the higher floors occupied by the electrons. A full page debunks the misconception that "orbitals" are like "orbits" (common among beginning students). Beyond this foundation, the tutorial explores how electrons fill orbitals (from low-to-high energy). It concludes with a set of questions, with answers provided, for self-gauging understanding. This page is part of Chemguide, an informational website developed by a veteran high school teacher to promote deeper understanding of concepts in introductory and intermediate-level chemistry.

Clark, Jim

2013-02-20

191

On The Origins Of Eccentric Close-in Planets  

E-print Network

Strong tidal interaction with the central star can circularize the orbits of close-in planets. With the standard tidal quality factor Q of our solar system, estimated circularization times for close-in extrasolar planets are typically shorter than the ages of the host stars. While most extrasolar planets with orbital radii a orbits, some close-in planets with substantial orbital eccentricities have recently been discovered. This new class of eccentric close-in planets implies that either their tidal Q factor is considerably higher, or circularization is prevented by an external perturbation. Here we constrain the tidal Q factor for transiting extrasolar planets by comparing their circularization times with accurately determined stellar ages. Using estimated secular perturbation timescales, we also provide constraints on the properties of hypothetical second planets exterior to the known ones.

Soko Matsumura; Genya Takeda; Fred Rasio

2008-08-27

192

GOCE Satellite Orbit in a Computational Aspect  

NASA Astrophysics Data System (ADS)

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

Bobojc, Andrzej; Drozyner, Andrzej

2013-04-01

193

Orbits and Interiors of Planets  

NASA Astrophysics Data System (ADS)

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

Batygin, Konstantin

2012-05-01

194

Vertical emitting aperture nanoantennas.  

PubMed

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

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

2012-05-01

195

Potential of elliptic orbits for theatre observation  

NASA Astrophysics Data System (ADS)

The intuitive interest of elliptic orbit is to enable low altitude flight with much less orbit decay constraints since the atmospheric drag occurs during the limited duration of perigee, and therefore to enable higher resolution capabilities within a given instrument and satellite format. A factor greater than 2 can be foreseen with respect to the lowest usual circular orbits. The working restriction to perigee leads to coverage limitation within a latitude window of 30°. This is not a fundamental obstacle since there are (will be) in the world several regional concentrations of needs for high-resolution civilian or military surveillance. For the only goal of high resolution near the vertical of the satellite, the elliptic has no equivalent, but under given coverage and revisit constraint the circular orbit reduces the need for off-nadir steering and the resulting degradation of (optical) resolution with respect to vertical. Therefore, the purpose of this preliminary study is, through comparison of elliptical and circular orbit at an unusually low altitude, to identify more precisely the application domain of elliptical. This is based on existing formats of satellite designed to fly above the usual altitude floor (500 km) and therefore according to limited mass extension (˜10%) to accommodate the extra ? V and propulsion needs for flying lower than usual. Emphasis is given to the microsatellite format. Electrical and chemical solutions are compared as well as different satellite configurations with respect to the matter of solar array drag. It comes up that the elliptic orbits can be very efficient solutions when the needs are geographically concentrated ( 1000 km circle) permanently or for several weeks or months, what corresponds to the usual definition of theatre with military, civilian (e.g.: catastrophe) understanding. This needs to select an orbit cycle of one day locked on the theatre. The theatre location can be moved to any longitude within one or few weeks (depending on propulsion choices). One can imagine scenarios with constellations of satellites on circular orbits giving the global coverage, plus one or few extra satellites able through some modifications/adaptations and placement on elliptical orbits to drastically upgrade both the resolution and the revisit on one or several theatres with tuneable locations within a fixed 30° latitude zone.

Aguttes, J.-P.; Fernandez, N.; Foliard, J.

2004-08-01

196

Analytic orbit plane targeting for orbit transfers about an oblate planet  

NASA Technical Reports Server (NTRS)

This paper develops closed-form expressions which accurately model variations in orbital inclination and longitude of the ascending node due to the influence of the J2 oblateness perturbation. These analytic expressions are particularly useful in defining perturbed orbit transfer planes which naturally regress into the target intercept position for Lambert-type transfers and in compensating for differential nodal regression between two orbiting vehicles in rendezvous targeting problems. Results of example problems for each of these scenarios demonstrate that they accurately compensate for these oblateness effects.

Mchenry, R. L.

1992-01-01

197

Twist number and order properties of periodic orbits  

NASA Astrophysics Data System (ADS)

A less studied numerical characteristic of periodic orbits of area preserving twist maps of the annulus is the twist or torsion number, called initially the amount of rotation Mather (1984) [2]. It measures the average rotation of tangent vectors under the action of the derivative of the map along that orbit, and characterizes the degree of complexity of the dynamics. The aim of this paper is to give new insights into the definition and properties of the twist number and to relate its range to the order properties of periodic orbits. We derive an algorithm to deduce the exact value or a demi-unit interval containing the exact value of the twist number. We prove that at a period-doubling bifurcation threshold of a mini-maximizing periodic orbit, the new born doubly periodic orbit has the absolute twist number larger than the absolute twist of the original orbit after bifurcation. We give examples of periodic orbits having large absolute twist number, that are badly ordered, and illustrate how characterization of these orbits only by their residue can lead to incorrect results. In connection to the study of the twist number of periodic orbits of standard-like maps we introduce a new tool, called 1-cone function. We prove that the location of minima of this function with respect to the vertical symmetry lines of a standard-like map encodes a valuable information on the symmetric periodic orbits and their twist number.

Petrisor, Emilia

2013-11-01

198

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

199

Error growth of the KS regularized orbital motion  

Microsoft Academic Search

Long term integrations of highly eccentric orbits are necessary to study the orbital evolution of comets and some minor planets. We discovered that the KS regularization is effective not only in the sense the magnitude of local error is reduced in the close approach but in the sense it dramatically reduces the positional error growth. In fact, it is in

H. Arakida; T. Fukushima

2000-01-01

200

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

201

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

202

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

203

Orbital Resonance and Solar Cycles  

E-print Network

We present an analysis of planetary moves, encoded in DE406 ephemerides. We show resonance cycles between most planets in Solar System, of differing quality. The most precise resonance - between Earth and Venus, which not only stabilizes orbits of both planets, locks planet Venus rotation in tidal locking, but also affects the Sun: This resonance group (E+V) also influences Sunspot cycles - the position of syzygy between Earth and Venus, when the barycenter of the resonance group most closely approaches the Sun and stops for some time, relative to Jupiter planet, well matches the Sunspot cycle of 11 years, not only for the last 400 years of measured Sunspot cycles, but also in 1000 years of historical record of "severe winters". We show, how cycles in angular momentum of Earth and Venus planets match with the Sunspot cycle and how the main cycle in angular momentum of the whole Solar system (854-year cycle of Jupiter/Saturn) matches with climatologic data, assumed to show connection with Solar output power and insolation. We show the possible connections between E+V events and Solar global p-Mode frequency changes. We futher show angular momentum tables and charts for individual planets, as encoded in DE405 and DE406 ephemerides. We show, that inner planets orbit on heliocentric trajectories whereas outer planets orbit on barycentric trajectories.

P. A. Semi

2009-03-29

204

Curvature in orbital dynamics  

NASA Astrophysics Data System (ADS)

The physical basis and the geometrical significance of the equation for the orbit of a particle moving under the action of external forces is exhibited by deriving this equation in a coordinate-independent representation in terms of the radius of curvature of the orbit. Although this formulation appeared in Newton's Principia, it has been ignored in contemporary classical mechanics textbooks. For small eccentricities, the orbit equation is used to obtain approximate solutions that illustrate the role of curvature. It is shown that this approach leads to a simple graphical method for determining the orbits for central forces. This method is similar to one attributed to Newton, who applied it to a constant central force, and sent a diagram of the orbit to Hooke in 1679. The result is compared to the corresponding orbit of a ball revolving inside an inverted cone which Hooke described in his response to Newton.

Nauenberg, Michael

2005-04-01

205

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

206

Secondary star magnetic fields in close binaries  

NASA Astrophysics Data System (ADS)

In this paper an attempt is made to use magnetic braking to constrain the surface polar field strengths of the secondary stars in close binaries with orbital periods between Porb ~ 3 and 7 h. By using a standard Mestel & Spruit model, assuming field saturation, a linear relation was obtained between the mass transfer and orbital period, for the period range under consideration, which allows constraining the surface polar field between B?,2 ~ 2900 and 3300 G. It has been shown that the predicted mass-transfer rates correlate with the Verbunt & Zwaan empirical mass transfer versus orbital period relation. Furthermore, it has been shown that the closed field lines, that is, the so-called dead zone, of the secondary star envelopes a substantial fraction of the binary, including the white dwarf, for all orbital periods under consideration. It has been shown that the interaction of the white dwarf field with the surrounding envelope can result in the intermediate polars entering the period gap being magnetically synchronized over time-scales ?syn <= 107yr. This mechanism may then play a significant role in the orbital evolution of the intermediate polars into the polars. Furthermore, surface magnetic field structures in the L1 region may play a significant role in the fragmentation of the mass flow near the L1 region, which may explain the inferred fragmented mass transfer, that is, the blobby mass flow, in magnetic cataclysmic variables.

Meintjes, P. J.; Jurua, E.

2006-11-01

207

Ghost orbit spectroscopy  

SciTech Connect

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

Bhullar, A. S.; Bluemel, R. [Department of Physics, Wesleyan University, Middletown, Connecticut 06459-0155 (United States); Koch, P. M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800 (United States)

2006-01-15

208

Magnetospheric Multiscale (MMS) Orbit  

NASA Video Gallery

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

209

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

210

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

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

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

E-print Network

Planets close to their stars are thought to form farther out and migrate inward due to angular momentum exchange with gaseous protoplanetary disks. This process can produce systems of planets in co-orbital (Trojan or 1:1) resonance, in which two planets share the same orbit, usually separated by 60 degrees. Co-orbital systems are detectable among the planetary systems found by the Kepler mission either directly or by transit timing variations. However, no co-orbital systems have been found within the thousands of Kepler planets and candidates. Here we study the orbital evolution of co-orbital planets embedded in a protoplanetary disk using a grid-based hydrodynamics code. We show that pairs of similar-mass planets in co-orbital resonance are disrupted during large-scale orbital migration. Destabilization occurs when one or both planets is near the critical mass needed to open a gap in the gaseous disk. A confined gap is opened that spans the 60 degree azimuthal separation between planets. This alters the torq...

Pierens, Arnaud

2014-01-01

213

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

214

Jamming in Vertical Channels  

NASA Astrophysics Data System (ADS)

We study jamming of low aspect-ratio cylindrical Delrin grains in a vertical channel. Grain heights are less than their diameter so the grains resemble antacid tablets, coins, or poker chips. These grains are allowed to fall through a vertical channel with a square cross section where the channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. Grains are sometimes observed to form jams, stable structures supported by the channel walls with no support beneath them. The probability of jam occurrence and the strength or robustness of a jam is effected by grain and channel sizes. We will present experimental measurements of the jamming probability and jam strength in this system and discuss the relationship of these results to other experiments and theories.

Baxter, G. William; Steel, Fiona

2011-03-01

215

Jamming in Vertical Channels  

NASA Astrophysics Data System (ADS)

We experimentally study jamming of cylindrical grains in a vertical channel. The grains have a low aspect-ratio (height/diameter < 1) so their shape is like antacid tablets or poker chips. They are allowed to fall through a vertical channel with a square cross section. The channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. It is observed that grains sometimes jam in this apparatus. In a jam, grains form a stable structure from one side of the channel to the other with nothing beneath them. Jams may be strong enough to support additional grains above. The probability of a jam occurring is a function of the grain height and diameter. We will present experimental measurements of the jamming probability in this system and discuss the relationship of these results to other experiments and theories.

Baxter, G. William; McCausland, Jeffrey; Steel, Fiona

2010-03-01

216

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

217

Extrapolation of orbits  

Microsoft Academic Search

The use of analytic theory, numerical integration, or a mixed method in the extrapolation of a spacecraft orbit is shown to depend on mission requirements. Parameters to be extrapolated for the ARGOS satellite system, for SPOT satellite, DZB satellite, and for geostationary satellites are among examples cited. Orbit extrapolation for SKYLAB reentry is also covered. Analytic methods include integration of

N. Borderies

1980-01-01

218

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

219

Constraint Orbital Branching  

E-print Network

a group of strong constraints on which to base the orbital branching .... that maps each feasible solution onto a feasible solution of the same value. ... For a point z ? Z, the orbit of z under the action of the group ? is the set of all elements of Z to

2008-01-01

220

Orbital Shape Representations.  

ERIC Educational Resources Information Center

Discusses the use of orbital shapes for instructional purposes, emphasizing that differences between polar, contour, and three-dimensional plots must be made clear to students or misconceptions will occur. Also presents three-dimensional contour surfaces for the seven 4f atomic orbitals of hydrogen and discusses their computer generation. (JN)

Kikuchi, Osamu; Suzuki, Keizo

1985-01-01

221

Analyzing Shuttle Orbiter Trajectories  

NASA Technical Reports Server (NTRS)

LRBET4 program best-estimated-of-trajectory (BET) calculation for post-flight trajectory analysis of Shuttle orbiter. Produces estimated measurements for comparing predicted and actual trajectory of Earth-orbiting spacecraft. Kalman filter and smoothing filter applied to input data to estimate state vector, reduce noise, and produce BET. LRBET4 written in FORTRAN IV for batch execution.

Lear, W. M.

1986-01-01

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 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

223

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

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

Close-up view of the aft fuselage of the Orbiter Discovery on the starboard side looking forward. This view is of the attach surface for the Orbiter Maneuvering System/Reaction Control System (OMS/RCS) Pod. The OMS/RCS pods are removed for processing and reconditioning at another facility. 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

224

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

225

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

226

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

227

Fibrolipoma of the orbit.  

PubMed

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

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

2013-01-01

228

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

229

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

230

Stability of Frozen Orbits Around Europa  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): A planetary satellite of interest at the present moment for the scientific community is Europa, one of the four largest moons of Jupiter. There are some missions planned to visit Europa in the next years, for example, Jupiter Europa Orbiter (JEO, NASA) and Jupiter IcyMoon Explorer (JUICE, ESA). In this work we are formulating theories and constructing computer programs to be used in the design of aerospace tasks as regards the stability of artificial satellite orbits around planetary satellites. The studies are related to translational motion of orbits around planetary satellites considering polygenic perturbations due to forces, such as the nonspherical shape of the central body and the perturbation of the third body. The equations of motion will be developed in closed form to avoid expansions in eccentricity and inclination. For a description of canonical formalism are used the Delaunay canonical variables. The canonical set of equations, which are nonlinear differential equations, will be used to study the stability of orbits around Europa. We will use a simplified dynamic model, which considers the effects caused by non-uniform distribution of mass of Europa (J2, J3 and C22) and the gravitational attraction of Jupiter. Emphasis will be given to the case of frozen orbits, defined as having almost constant values of eccentricity, inclination, and argument of pericentre. An approach will be used to search for frozen orbits around planetary satellites and study their stability by applying a process of normalization of Hamiltonian. Acknowledges: FAPESP

Cardoso Dos Santos, Josué; Vilhena de Moraes, R.; Carvalho, J. S.

2013-05-01

231

Granular cell tumor of the orbit: a case report.  

PubMed

A 42-year-old woman had vertical diplopia secondary to a palpable mass located in the left inferior orbit. At surgery, the mass was adherent to the globe, encapsulated, and seemed to arise from the inferior rectus muscle. Frozen section diagnosis was granular cell tumor. The tumor was removed in toto. No recurrence was apparent six years after surgery. PMID:6318639

Singleton, E M; Nettleship, M B

1983-09-01

232

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

233

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

234

Stable Orbits of Planets of a Binary Star System in the Three-Dimensional Restricted Problem  

Microsoft Academic Search

The present research was motivated by the recent discovery of planets around binary stars. Our initial intention was thus to investigate the 3-dimensional nearly circular periodic orbits of the circular restricted problem of three bodies; more precisely Stromgren's class L, (direct) and class m, (retrograde). We started by extending several of Hénon's vertical critical orbits of these 2 classes to

Roger A. Broucke

2001-01-01

235

Flight Mechanics of Manned SubOrbital Reusable Launch Vehicles with Recommendations for Launch and Recovery  

Microsoft Academic Search

An overview of every significant method of launch and recovery for manned sub-orbital Reusable Launch Vehicles (RLV) is presented here. We have categorized launch methods as vertical takeoff, horizontal takeoff, and air launch. Recovery methods are categorized as wings, aerodynamic decelerators, rockets, and rotors. We conclude that both vertical takeoff and some air launch methods are viable means of attaining

Marti Sarigul-Klijn; Nesrin Sarigul-Klijn

236

The stellar perturbations of orbital elements of long-period comets  

Microsoft Academic Search

Perturbations in orbital elements of comets with large heliocentric distances that are caused by nearby stars are calculated by the impulse approximation and by accurate numerical integration using Cowell's method. It is shown that the agreement is sufficiently close for elliptic orbits but rather poor for parabolic orbits. The perturbation of inclination is a few tens of degrees while that

S. Yabushita; I. Hasegawa; K. Kobayashi

1982-01-01

237

Origin, Dynamics and Stability of the Mutually Inclined Orbits of the upsilo Andromedae Planetary System  

Microsoft Academic Search

The planetary system of upsilo Andromedae is the first to display evidence for mutually inclined orbits around a main sequence star (McArthur et al. 2010). Moreover, the planets upsilo And c and d have orbital elements that oscillate with large amplitudes and lie very close to the limits of stability. The substantial mutual inclination, as well as its other orbital

Rory Barnes; R. Greenberg; T. R. Quinn; B. McArthur; A. Antonsen; G. F. Benedict

2011-01-01

238

Project Plan for Vertical Lift Machine  

SciTech Connect

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

Ellsworth, G F

2002-08-05

239

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

240

Fast phase recovery from a single closed-fringe pattern  

Microsoft Academic Search

A new framework for phase recovering from a single fringe pattern with closed fringes is proposed. Our algorithm constructs an un- wrapped phase from previously computed phases with a simple open fringes analysis algorithm; twice applied for analyzing horizontal and vertical oriented fringes, respectively. That reduces the closed fringe analysis problem to chose the better phase between the two oriented

Oscar S. Dalmau-Cedeño; Mariano Rivera; Ricardo Legarda-Saenz

2008-01-01

241

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

242

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

243

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

244

Nontraumatic orbital hemorrhage.  

PubMed

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

McNab, Alan A

2014-01-01

245

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

246

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

247

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

248

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.

249

'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

250

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

251

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 notation point missions. This paper collects both published and unpublished results from four previous notation point missions (ISEE-3, SOHO, ACE and MAP) 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 marine and Doppler measurement types. Advanced technology is enabling other OD options including onboard navigation using onboard 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, missions must find alternatives to the standard OD scenario.

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

252

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

253

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

254

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

255

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

256

Energy Level Diagrams for Black Hole Orbits  

E-print Network

A spinning black hole with a much smaller black hole companion forms a fundamental gravitational system, like a colossal classical analog to an atom. In an appealing if imperfect analogy to atomic physics, this gravitational atom can be understood through a discrete spectrum of periodic orbits. Exploiting a correspondence between the set of periodic orbits and the set of rational numbers, we are able to construct periodic tables of orbits and energy level diagrams of the accessible states around black holes. We also present a closed form expression for the rational q, thereby quantifying zoom-whirl behavior in terms of spin, energy, and angular momentum. The black hole atom is not just a theoretical construct, but corresponds to extant astrophysical systems detectable by future gravitational wave observatories.

Janna Levin

2009-07-29

257

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

258

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

259

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

260

Orbiter entry aerothermodynamics  

NASA Technical Reports Server (NTRS)

The challenge in the definition of the entry aerothermodynamic environment arising from the challenge of a reliable and reusable Orbiter is reviewed in light of the existing technology. Select problems pertinent to the orbiter development are discussed with reference to comprehensive treatments. These problems include boundary layer transition, leeward-side heating, shock/shock interaction scaling, tile gap heating, and nonequilibrium effects such as surface catalysis. Sample measurements obtained from test flights of the Orbiter are presented with comparison to preflight expectations. Numerical and wind tunnel simulations gave efficient information for defining the entry environment and an adequate level of preflight confidence. The high quality flight data provide an opportunity to refine the operational capability of the orbiter and serve as a benchmark both for the development of aerothermodynamic technology and for use in meeting future entry heating challenges.

Ried, R. C.

1985-01-01

261

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

262

Mars parking orbit selection  

NASA Technical Reports Server (NTRS)

For a Mars mission, the selection of a parking orbit is greatly influenced by the precession caused by the oblateness of the planet. This affects the departure condition for earth return, and therefore, the mass required in LEO for a Mars mission. In this investigation, minimum LEO mass penalties were observed for parking orbits characterized by having near-equatorial inclinations, high eccentricities, and requiring a three-dimensional departure burn. However, because near-equatorial inclination orbits have poor planetary coverage characteristics, they are not desirable from a science viewpoint. To enhance these science requirements along with landing-site accessibility, a penalty in initial LEO mass is required. This study shows that this initial LEO mass penalty is reduced for orbits characterized with low to moderate eccentricities, nonequatorial inclinations, and a tangential periapsis arrival and departure burn.

Desai, Prasun N.; Braun, Robert D.

1990-01-01

263

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

264

Altimetry, Orbits and Tides  

NASA Technical Reports Server (NTRS)

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

Colombo, O. L.

1984-01-01

265

ARTEMIS Orbits Magnetic Moon  

NASA Video Gallery

NASA's THEMIS spacecraft have completed their mission and are still working perfectly, so NASA is re-directing the outermost two spacecraft to special orbits around the Moon. Now called ARTEMIS, th...

266

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

267

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

268

NASA A-Train Vertical Data (Curtains) in Google Earth  

NASA Astrophysics Data System (ADS)

Google Earth combines satellite imagery, aerial photography, map data, and human-social data to make a real 3D interactive template of the world. It is revolutionizing the way that general public recognize our planet and professional scientists discover, add, and share information about different geographic-related subjects in the world. NASA Goddard Earth Science (GES) Data and Information Service Center (DISC) has done innovative work integrating NASA imagery in Google Earth in order to facilitate scientific research and releasing of geospatial- related public information. The NASA imagery includes two dimensional (2D) flat data and three dimensional (3D) vertical data. Here, a new solution is introduced to integrate the vertical data from the A-Train constellation satellites CloudSat, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation), and Aqua (mainly MODIS and AIRS products) into Google Earth to vividly expose cloud, aerosol, and H2O characteristics and atmospheric temperature profile in the form of curtain along the satellite orbit. All kinds of vertical data are first processed by GIOVANNI (GES-DISC Interactive Online Visualization ANd aNalysis Infrastructure) A-Train system based on user-selected spatial/temporal range and physical parameters. The resultant image is processed into transparent small image slices with each image slice representing the fixed temporal internal orbit range. A generalized COLLADA (COLLAborative Design Activity) 3D model is designed to render the image slices in the form of 3D. Based on the designed COLLADA models and satellite orbit coordinates, an orbit model is designed and implemented in KML (Keyhole Markup Language) format. The resultant orbit curtain makes vertical data viewable, transparently or opaquely, in Google Earth. Thus, three- dimensional science research data can be made available to scientists and the general public in a popular venue. Also, simultaneous visualization and efficient exploration of the relationships among quantitative geospatial data (e.g. comparing the vertical data profiles with MODIS, AIRS data and TRMM precipitation data) becomes possible. This method allows combining vertical data together with other geospatial data for scientific research and allows better understanding of our planet. A key capability of the system is the ability to visualize and compare diverse, simultaneous data from different providers, revealing new information and knowledge that would otherwise be hidden.

Chen, A.; Leptoukh, G.; di, L.; Lynnes, C.; Kempler, S.; Nadeau, D.

2007-12-01

269

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

270

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.

271

Orbital Dirofilariasis: MR Findings  

Microsoft Academic Search

Summary: Dirofilariasis is a helminthic zoonosis occurring in many parts of the world. We report the findings in a 61- year-old woman who had painless right exophthalmos caused by orbital dirofilariasis. A vivid worm was embed- ded inside an inflammatory nodule in the right orbit. On T1-weighted MR images, the parasite was visible as a dis- crete, low-intensity, tubular signal

Reinhard Groell; Gerhard Ranner; Martin M. Uggowitzer; Hannes Braun

272

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

273

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

274

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

275

Two Body Orbits Model  

NSDL National Science Digital Library

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

Christian, Wolfgang

2012-07-18

276

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

277

Overall view of the Orbiter Servicing Structure within the Orbiter ...  

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

Overall view of the Orbiter Servicing Structure within the Orbiter Processing Facility at Kennedy Space Center. Can you see any hint of the Orbiter Discovery? It is in there. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

278

Electron vortex orbits and merger  

SciTech Connect

Pure electron plasma columns are contained inside hollow conducting cylinders in an axial magnetic field. In the 2D {ital E}{bold {times}}{ital B} drift approximation, an electron column is a vortex evolving in ({ital r},{theta}) according to the Euler equation. First the center-of-mass orbits of two vortices sufficiently well-separated to be stable to merger are characterized. Equilibria are observed in which the vortices orbit about the center of the cylinder, with either oscillations about stable equilibria or exponential divergence away from unstable equilibria. The equilibrium positions, oscillation frequencies, and instability rates for these spatially extended vortices agree well with the predictions of point vortex theory, apparently because surface waves and shape distortions do not couple significantly to the center-of-mass motion. Next, the merger of two vortices with unequal radii is quantified. Merger is accompanied by the formation of filamentary arms, and results ultimately in an axisymmetric central core surrounded by a lower density halo. The self-energy of the merged core is found to be roughly the sum of the self-energy of the merging vortices. The fraction of the total circulation entrained into the core varies from 70{percent} to 90{percent} as the ratio of the initial vortex radii is varied from 1:1 to 2:1. The point-like vortex dynamics and the circulation loss with merger are both consistent with the {open_quote}{open_quote}punctuated Hamiltonian{close_quote}{close_quote} models of decaying turbulence. {copyright} {ital 1996 American Institute of Physics.}

Mitchell, T.B. [Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States); Driscoll, C.F. [Department of Physics 0319, University of California at San Diego, La Jolla, California 92093-0319 (United States)] [Department of Physics 0319, University of California at San Diego, La Jolla, California 92093-0319 (United States)

1996-07-01

279

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

280

Titan Orbiter with Aerorover Mission (TOAM)  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

281

Orbit Determination in the Pluto System  

NASA Astrophysics Data System (ADS)

The once simple binary system of Pluto and Charon has, until now, eluded a precise description of its orbital motion. The most important component that makes this system so difficult is a consequence of its fully relaxed spin-orbit state. The surface of Pluto has a highly variable albedo that also changes with time. These albedo variations lead to a shift of the photocenter relative to the center of the body. The synchronicity of the rotation of Pluto and the orbit of Charon couples the albedo pattern to the astrometry and lead, if uncorrected, to erroneous values for the orbital elements. In this presentation we will show results based on astrometry with the Hubble Space Telescope that now span nearly 20 years. We use two-body Keplerian orbit fits to describe the motions of all satellites as a tool to understand and remove the astrometric effects of the albedo pattern. The most immediate result of this work is a demonstration that the orbit of Charon is very close to circular (1-sigma limit is 3 km out of round). We also present an analysis of the degree to which albedo effects (spatial and temporal) impact the astrometry the resulting orbit determinations. These considerations show the value and necessity of combining photometric and astrometric data to further improve the dynamical description of this system. This work is a necessary precursor to upcoming New Horizons encounter with Pluto as well as our on-going work to determine the masses of the outer satellites. This work was supported by grants from NASA Planetary Astronomy and from the Space Telescope Science Institute.

Buie, Marc W.; Grundy, W. M.; Tholen, D. J.

2012-05-01

282

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

283

Observation of picometer vertical emittance with a vertical undulator.  

PubMed

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. PMID:23215388

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

284

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

285

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

286

Mars Reconnaissance Orbiter Aerobraking  

NASA Technical Reports Server (NTRS)

December 10, 2003

NASA's Mars Reconnaissance Orbiter dips into the thin martian atmosphere to adjust its orbit in this artist's concept illustration.

NASA plans to launch this multipurpose spacecraft in August 2005 for arrival at Mars in March 2006. The plans call for controlled use of atmospheric friction in a process called aerobraking for about six months after arrival to change the initial, very elongated orbit into a rounder shape optimal for science operations.

Mars Reconnaissance Orbiter is designed to advance our understanding of Mars through detailed observation, to examine potential landing sites for future surface missions and to provide a high-data-rate communications relay for those missions.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter Project for the NASA Office of Space Science, Washington. JPL's main industrial partner in the project, Lockheed Martin Space Systems, Denver, Colo., is building the spacecraft.

2003-01-01

287

Primary orbital extraskeletal osteosarcoma.  

PubMed

The authors describe a case of orbital extraskeletal osteosarcoma. A 78-year-old man with a history of rheumatoid arthritis on long-term corticosteroids had a left medial canthal basal cell carcinoma excision followed by adjuvant radiotherapy. Twelve months later, he re-presented with a large rapidly-growing calcified mass involving his left medial canthus and orbit. An incisional biopsy demonstrated an infiltrate of atypical cells exhibiting mitotic activity with a rosette arrangement around partially calcified necrotic tissue. The patient underwent orbital exenteration and a partial maxillectomy. Histopathology demonstrated an extraskeletal osteosarcoma. It is extremely rare for this tumor to occur in the orbit. Immunosuppression and adjuvant radiotherapy were possible predisposing factors in the development of this tumor. Extraskeletal osteosarcoma (ESOS) is a malignant tumour that produces osteoid. It develops in soft tissue without continuity to bone or periosteum. It is rare and comprises fewer than 5% of all osteosarcomas. Extraskeletal osteosarcoma primarily affects patients above 50 years of age and has a poor prognosis. In this report, we describe the clinical, radiologic, and pathologic records of a rare case of primary ESOS of the orbit. PMID:22132847

Fan, Jennifer C; Lamont, Duncan L; Greenbaum, Adam R; Ng, Stephen G J

2011-12-01

288

Helioseismology with Solar Orbiter  

E-print Network

The Solar Orbiter mission, to be launched in July 2017, will carry a suite of remote sensing and in-situ instruments, including the Polarimetric and Helioseismic Imager (PHI). PHI will deliver high-cadence images of the Sun in intensity and Doppler velocity suitable for carrying out novel helioseismic studies. The orbit of the Solar Orbiter spacecraft will reach a solar latitude of up to 21 deg (up to 34 deg by the end of the extended mission) and thus will enable the first local helioseismology studies of the polar regions. Here we consider an array of science objectives to be addressed by helioseismology within the baseline telemetry allocation (51 Gbit per orbit, current baseline) and within the science observing windows (baseline 3 x 10 days per orbit). A particularly important objective is the measurement of large-scale flows at high latitudes (rotation and meridional flow), which are largely unknown but play an important role in flux transport dynamos. The full range of Earth-Sun-spacecraft angles provi...

Löptien, Björn; Gizon, Laurent; Schou, Jesper; Appourchaux, Thierry; Rodríguez, Julián Blanco; Cally, Paul S; Dominguez-Tagle, Carlos; Gandorfer, Achim; Hill, Frank; Hirzberger, Johann; Scherrer, Philip H; Solanki, Sami K

2014-01-01

289

ICESat Precision Orbit Determination  

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

290

Orbital maneuvers around irregular shaped bodies  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): In the solar system there are many small bodies called asteroids. The large majority of these bodies are located in the asteroid belt, between the orbits of the planets Mars and Jupiter. The Near- Earth Objects, or NEOs, are objects with perihelion below 1.3AU, which include comets and asteroids. The NEOs are considered to have orbits passing close to the Earth’s orbit and, in the case of asteroids, are called Near-Earth Asteroids (NEAs). Among the NEAs there are bodies considered potentially hazardous asteroids (PHAs), whose minimum orbit intersection distance with Earth is 0.05AU and that have absolute magnitude (H) of 22, which would mean an asteroid of at least 110-240 meters, depending on its albedo. One of the major characteristic of the asteroids is the irregular shape, causing the dynamics of orbits around these bodies to be different from a spherical shaped one. The fact that an object is not spherical generates a perturbation on the gravitational field. The disturbing force can be determined considering the shape of the specific body. A satellite orbiting this body would suffer the effects of this perturbation, but knowing the disturbing force, it’s possible to correct and control the orbit according to the desired mission. The polyhedron method is a traditional way to model an asteroid by dividing the object into smaller parts. The data used on this work are composed by a combination of triangular faces. The total disturbing force is a sum of the force on each piece of the model. Therefore, after the simulations are obtained, it’s possible to apply the desired corrections of the perturbation using continuous low thrust in closed loop, making it possible to perform maneuvers near these bodies. One of the important applications of the study shown above is in the ASTER mission, that is under study by INPE and several other Brazilian academic institutions, which goal is to send a spacecraft to an asteroid and then to remain in orbit around it.

Venditti, Flaviane; Rocco, E. M.; Almeida Prado, A. B.

2013-05-01

291

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

292

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

293

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

294

Simulation Studies On The Vertical Emittance Growth At The Existing ATF Extraction Beamline  

SciTech Connect

Significant beam intensity-dependence of the vertical emittance growth was experimentally observed at the Accelerator Test Facility (ATF) at KEK extraction beamline. This paper presents the simulations of possible vertical emittance growth sources, particularly in the extraction channel, where the magnets are shared by both the ATF extraction beamline and its damping ring. The vertical emittance growth is observed in the simulations by changing the beam orbit in the extraction channel, even with all optics corrections. The possible reasons for the experimentally observed dependence of the vertical emittance growth on the beam intensity are also discussed. An experiment to measure the emittance versus beam orbit at the existing ATF extraction beamline is on-going led by the European colleagues.

Zhou, F.; Amann, J.; Seletskiy, S.; Seryi, A.; Spencer, C.M.; Woodley, M.D.

2008-06-27

295

Congenital orbital teratoma.  

PubMed

Congenital orbital teratoma though rare is available in this environment. This is a case report of a baby with a protruding orbital mass in the left eye with all classical clinical features of teratoma. Though the histopathological report fell short of confirming the diagnosis the clinical features and outcome of management strongly suggest that the lesion is a teratoma. Multidisciplinary approach to the management not only saved the life of the baby in question but also enhanced the outcome of treatment. Good and compliant follow up for six months was experienced. Cytological test is mandatory for any suspected cases ofteratoma. PMID:20857798

Onyekwe, L O; Onwuegbuna, A N; Emejulu, J K C

2010-09-01

296

[A Roman orbital implant?].  

PubMed

During an excavation in Regensburg/Germany the skeleton of an approximately 20-year-old Roman man was found who was buried in the 3rd/4th century after Christ. A "stone" was found which fitted into the left orbit precisely. After a thorough investigation of the "stone" and with the ophthalmohistorical literature in mind an orbital "implant" as well as a petrified medical paste ("Kollyrium") could be ruled out almost with certainty. Possibly the "stone" served another medical purpose or was used for protection of the eye. PMID:23011607

Rohrbach, J M; Harbeck, M; Holzhauser, P; Tekeva-Rohrbach, C I; Mach, M; Codreanu-Windauer, S

2012-11-01

297

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

298

The impact orbits of the dangerous asteroid (99942) Apophis  

Microsoft Academic Search

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

I. Wlodarczyk

2008-01-01

299

Acoustics evaluation of vertical greenery systems for building walls  

Microsoft Academic Search

After decades of fast growth, the scarcity of land in cities causes many buildings to be constructed very close to expressways, exposing occupants to serious noise pollution. In recent years, sustainable cities have found that greenery is a key element in addressing this noise pollution, giving rise to the popularity of vertical greenery systems (VGS). This research has two objectives.

Nyuk Hien Wong; Alex Yong Kwang Tan; Puay Yok Tan; Kelly Chiang; Ngian Chung Wong

2010-01-01

300

Incidence of incisional hernia following vertical banded gastroplasty  

Microsoft Academic Search

Background: Our aim was to determine which patient-related factors influence the incidence of incisional hernia after vertical banded gastroplasty for morbid obesity. Methods: We reviewed the medical records of 80 morbidly obese patients operated on between 1986 and 1993. All the operations were performed by only one surgeon, and the midline laparotomy was closed by means of continuous polyglactin 910

D. Arribas; M. Elía; C. Artigas; A. Jiménez; V. Aguilella; M. Martínez

2004-01-01

301

The Effect of Availability of Vertical Space on Personal Space  

Microsoft Academic Search

The horizontal personal space requirements of 48 adult S s were examined under two conditions of vertical space. S s were matched by height and sex and assigned to a high or low ceiling height. S s told an approaching stranger to stop when the approacher's closeness made them feel uncomfortable. A significant result was that, as the distance between

C. D. Cochran; Sally Urbanczyk

1982-01-01

302

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

NASA Technical Reports Server (NTRS)

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

Greenberg, H. S.

1994-01-01

303

Functions and Vertical Line Test  

NSDL National Science Digital Library

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

2010-01-01

304

Precipitation Sensing in GEO Orbit with High Resolution  

NASA Astrophysics Data System (ADS)

Now casting of precipitation in geostationary orbit is a strongly requirements , two of difficults are antenna and radiometer receiver,it should satisfies high spatial and time resolution, this paper present two satellites with large scale feed array cofiguration get over 600 spot beams cove 3.5% China area, work in 118GHz for atmospheric temperature vertical profille and 183GHz for humidity vertical profille, two satellites consists of interferometric synthetic aperture it can satisfies weather nowcasting both spatial and time resolution in suspect zone for now casting requirements.

You, Rui

2012-07-01

305

The impact orbits of the dangerous asteroid (99942) Apophis  

NASA Astrophysics Data System (ADS)

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

W?odarczyk, I.

2008-02-01

306

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

307

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.

308

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.

309

Interactive Molecular Orbital Diagrams  

NSDL National Science Digital Library

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

310

Goddard Brouwer Orbit Bulletin  

NASA Technical Reports Server (NTRS)

The bulletin provides operational support for earth space research and technological missions by producing a tape containing pertinent spacecraft orbital information which is provided to a number of cities around the world in support of individual missions. A program description of the main and associated subroutines, and a complete description of the input, output and requirements of the bulletin program are presented.

Morgan, D. B.; Gordon, R. A.

1971-01-01

311

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

312

Orbit Stabilization of Nanosat  

Microsoft Academic Search

An algorithm is developed to control a pulsed ÎV 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

DAVID J

1999-01-01

313

The Mercury Orbiter mission  

Microsoft Academic Search

A Mercury Orbiter is considered by the European Space Agency as one of the cornerstones of its Horizons 2000 programme. The scientific objectives of this mission are both planetary and magnetospheric. The spacecraft and mission concepts which resulted from the ESA assessment study and an outline of the forthcoming activities are presented.

R. Grard

1997-01-01

314

Orbits of colliding galaxies  

Microsoft Academic Search

A simple, semi-analytic method is developed for obtaining the orbits of galaxies undergoing fast collisions in which the galaxies are represented by Plummer models. The results are found to agree fairly well with those of N-body simulations.

M. Narasimha Rao; Saleh Mohamed Alladin; K. S. V. S. Narasimhan

1994-01-01

315

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

316

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

317

Lessons Learned from Natural Space Debris in Heliocentric Orbit: An Analogue for Hazardous Debris in Earth Orbit  

NASA Astrophysics Data System (ADS)

Interplanetary Field Enhancements (IFEs) were discovered almost 30 years ago in the PVO magnetic-field records. Our current understanding is that IFEs result from interactions between solar wind and clouds of nanometer-scale charged dust released in interplanetary collisions. These charged dust clouds are then accelerated by the solar wind and moving away from the Sun at near solar wind speed and detected by spacecraft in heliocentric orbit. The dynamics of the debris in heliocentric orbit is analogous to that mankind has placed into Earth orbit. There are lessons here that are worth exploring. The IFE formation hypothesis was supported by the discovery of co-orbiting materials associated with asteroid 2201 Oljato: IFE rate peaked when Oljato was close and IFE occurrence clustered in the longitudes near which the orbit of Oljato intersects the orbital plane of Venus. A followed up study with Venus Express observations suggested that the co-orbiting materials dissipated in 30 years. An important aspect of this evolution is that at collisional speeds of 20 km/s, a small body can destroy one 106 times more massive. This destruction of large debris by small debris could also be important in the evolution of the terrestrial debris. At 1AU, based on ACE and Wind observations, IFEs have a significant cluster in the longitude range between 195° and 225°. Thus we use the same IFE technique to identify the ‘parent’ Near-Earth Objects of co-orbiting materials which should be responsible for those IFEs. There are more than 5000 JPL documented NEOs whose ecliptic plane crossings are near to or inside the Earth’s orbit and whose orbital periods are less than five years. By comparing their trajectories, we find that the asteroid 138175 is a good candidate for the ‘parent’ body. This asteroid orbits the Sun in a 5.24° inclined elliptical orbit with a period of 367.96 days. Its descending node is at about 206°, where the IFE occurrence rate peaks. We also find that there is a spread of the IFE rate around the descending node, indicating that the co-orbiting materials have significant dispersion about the asteroid’s orbit. In summary, orbiting debris in orbits intersecting at high speeds can destroy itself quite efficiently, but with a long timescale. In deep space, this process is a step on the path between the asteroidal source population and the creation of solar system dust. This may be true for Earth-orbiting debris as well.

Russell, C. T.; Wei, Hanying; Connors, Martin; Lai, Hairong; Delzanno, Gian Luca

318

Precision Orbit Determination for the Lunar Reconnaissance Orbiter  

Microsoft Academic Search

The Lunar Reconnaissance Orbiter (LRO) spacecraft was launched on June 18, 2009. In mid-September 2009, the spacecraft orbit was changed from its commissioning orbit (30 x 216 km polar) to a quasi-frozen polar orbit with an average altitude of 50km (+-15km). One of the goals of the LRO mission is to develop a new lunar reference frame to facilitate future

F. G. Lemoine; E. Mazarico; D. D. Rowlands; M. H. Torrence; J. F. McGarry; G. A. Neumann; D. Mao; D. E. Smith; M. T. Zuber

2010-01-01

319

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

2014-01-01

320

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

321

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

322

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

323

Five Special Types of Orbits Around Mars  

Microsoft Academic Search

The abstract is additional with repect to the paper published in JGCD. Ordinary Earth satellites are usually placed into five categories of special orbits: sun-synchronous orbits, orbits at the critical inclination, frozen orbits, repeating ground track orbits, and geostationary orbits. This paper investigates their counterparts around Mars and examines the basic nature of these orbits, which are of special interest

Xiaodong Liu; Hexi Baoyin; Xingrui Ma

2011-01-01

324

SPECS: Orbital debris removal  

NASA Technical Reports Server (NTRS)

The debris problem has reached a stage at which the risk to satellites and spacecraft has become substantial in low Earth orbit (LEO). This research discovered that small particles posed little threat to spacecraft because shielding can effectively prevent these particles from damaging the spacecraft. The research also showed that, even though collision with a large piece of debris could destroy the spacecraft, the large pieces of debris pose little danger because they can be tracked and the spacecraft can be maneuvered away from these pieces. Additionally, there are many current designs to capture and remove large debris particles from the space environment. From this analysis, it was decided to concentrate on the removal of medium-sized orbital debris, that is, those pieces ranging from 1 cm to 50 cm in size. The current design incorporates a transfer vehicle and a netting vehicle to capture the medium-sized debris. The system is based near an operational space station located at 28.5 deg inclination and 400 km altitude. The system uses ground-based tracking to determine the location of a satellite breakup or debris cloud. These data are uploaded to the transfer vehicle, which proceeds to rendezvous with the debris at a lower altitude parking orbit. Next, the netting vehicle is deployed, tracks the targeted debris, and captures it. After expending the available nets, the netting vehicle returns to the transfer vehicle for a new netting module and continues to capture more debris in the target area. Once all the netting modules are expended, the transfer vehicle returns to the space station's orbit where it is resupplied with new netting modules from a space shuttle load. The new modules are launched by the shuttle from the ground and the expended modules are taken back to Earth for removal of the captured debris, refueling, and repacking of the nets. Once the netting modules are refurbished, they are taken back into orbit for reuse. In a typical mission, the system has the ability to capture 50 pieces of orbital debris. One mission will take approximately six months and the system is designed to allow for a 30 deg inclination change on the outgoing and incoming trips of the transfer vehicle.

1991-01-01

325

Closed Large Cell Clouds  

article title:  Closed Large Cell Clouds in the South Pacific     ... unperturbed by cyclonic or frontal activity. When the cell centers are cloudy and the main sinking motion is concentrated at cell ...

2013-04-19

326

Closed Captioning on Television  

MedlinePLUS

... cable operators, broadcasters, satellite distributors and other multi-channel video programming distributors) to close caption their television ... or TTY number or email address The television channel number, call sign and network The name of ...

327

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

328

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

SciTech Connect

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

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

2012-06-20

329

Periodic Orbit Theory Revisited in the Anisotropic Kepler Problem  

E-print Network

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

Kazuhiro Kubo; Tokuzo Shimada

2013-11-07

330

Autonomous Aerobraking for Mars Orbiters  

NASA Astrophysics Data System (ADS)

Autonomous Aerobraking is a developing technology that will reduce cost and increase flexibility of an aerobraking orbiter around Mars. Currently in its second phase of development, autonomous aerobraking could be implemented for a 2018 Mars orbiter.

Prince, J. L.

2012-06-01

331

Early History & Fiction! Orbital Motion!  

E-print Network

! (1777-1855)! �! German mathematician who contributed to many fields" �! Determination of conic section-Body Orbits are Conic Sections " #12;Orbits 102" (2-Body Problem)! �! e.g., " �! Sun and Earth or" �! Earth

Stengel, Robert F.

332

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

333

LRO Enters Lunar Orbit (Highlights)  

NASA Video Gallery

After a four and a half day journey from the Earth, the Lunar Reconnaissance Orbiter, or LRO, successfully entered orbit around the moon. Engineers at NASA's Goddard Space Flight Center in Greenbel...

334

A Third Exoplanetary System with Misaligned Orbital and Stellar Spin Axes  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

335

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.

336

Martian satellite orbits and ephemerides  

NASA Astrophysics Data System (ADS)

We discuss the general characteristics of the orbits of the Martian satellites, Phobos and Deimos. We provide a concise review of the various descriptions of the orbits by both analytical theories and direct numerical integrations of their equations of motion. After summarizing the observational data used to determine the orbits, we discuss the results of our latest orbits obtained from a least squares fit to the data.

Jacobson, R. A.; Lainey, V.

2014-11-01

337

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

338

Orbital rhabdomyosarcomas: A review  

PubMed Central

Rhabdomyosarcoma (RMS) is a highly malignant tumor and is one of the few life-threatening diseases that present first to the ophthalmologist. It is the most common soft-tissue sarcoma of the head and neck in childhood with 10% of all cases occurring in the orbit. RMS has been reported from birth to the seventh decade, with the majority of cases presenting in early childhood. Survival has changed drastically over the years, from 30% in the 1960’s to 90% presently, with the advent of new diagnostic and therapeutic modalities. The purpose of this review is to provide a general overview of primary orbital RMS derived from a literature search of material published over the last 10 years, as well as to present two representative cases of patients that have been managed at our institute. PMID:24227982

Jurdy, Lama; Merks, Johanus H.M.; Pieters, Bradly R.; Mourits, Maarten P.; Kloos, Roel J.H.M.; Strackee, Simone D.; Saeed, Peerooz

2013-01-01

339

Tethered orbital propellant depot  

NASA Technical Reports Server (NTRS)

A planned function of the Space Station is to refurbish and refuel an advanced space-based LO2/LH2 orbit transfer vehicle. An alternative to propellant storage at the station is to use a remote facility tied to the station with a log tether. Preliminary design of such a facility is described with emphasis on fluid transfer and storage requirements. Using tether lengths of at least 300 ft, gravity gradient forces will dominate surface tension in such a system. Although gravity given transfer is difficult because of line pressure drops, fluid settling over the tank outlet greatly alleviates acquisition concerns and will facilitate vented tank fills. The major concern with a tethered orbital refueling facility is its considerable operational complexity including transport of the OTV to and from the facility.

Fester, D. A.; Rudolph, L. K.; Kiefel, E. R.

1985-01-01

340

Orbiter based construction equipment  

NASA Technical Reports Server (NTRS)

Many orbiter based activities need equipment to hold a payload steady while it is being worked on. This work may be construction, updating, repair, services, check out, or refueling operations in preparation for return to Earth. The Handling and Positioning Aid (HPA) is intended for use as general purpose equipment. The HPA provides a wide choice of work station positions, both immediately above the orbiter cargo bay and beyond. It can act in a primary docking role and, if required, can assist actively in the berthing process. From an analysis of ten reference missions, it was determined that two types of HPA mobility are needed; a tilt table, which simply swings out of the cargo bay, pivoting about an athwartships y axis, and an articulated arm. Illustration of the aid are provided.

Goodwin, C. J.

1982-01-01

341

Three orbital transfer vehicles  

NASA Technical Reports Server (NTRS)

Aerospace engineering students at the Virginia Polytechnic Institute and State University undertook three design projects under the sponsorship of the NASA/USRA Advanced Space Design Program. All three projects addressed cargo and/or crew transportation between low Earth orbit and geosynchronous Earth orbit. Project SPARC presents a preliminary design of a fully reusable, chemically powered aeroassisted vehicle for a transfer of a crew of five and a 6000 to 20000 pound payload. The ASTV project outlines a chemically powered aeroassisted configuration that uses disposable tanks and a relatively small aerobrake to realize propellant savings. The third project, LOCOST, involves a reusable, hybrid laser/chemical vehicle designed for large cargo (up to 88,200 pounds) transportation.

1990-01-01

342

Mercury orbiter transport study  

NASA Technical Reports Server (NTRS)

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

Friedlander, A. L.; Feingold, H.

1977-01-01

343

On-orbit coldwelding  

NASA Technical Reports Server (NTRS)

Spacecraft mechanisms are required to operate in the space environment for extended periods of time. A significant concern to the spacecraft designer is the possibility of metal to metal coldwelding or significant increases in friction. Coldwelding can occur between atomically clean metal surfaces when carefully prepared in a vacuum chamber on earth. The question is whether coldwelding occurs in orbit service conditions. The results of the System Special Investigation Group's (SIG's) investigation into whether coldwelding had occurred on any Long Duration Exposure Facility (LDEF) hardware are presented. The results of a literature search into previous ground based anomalies is also presented. Results show that even though there have been no documented on-orbit coldwelding related failures, precautions should be taken to ensure that coldwelding does not occur in the space environment and that seizure does not occur in the prelaunch or launch environment.

Dursch, Harry; Spear, Steve

1991-01-01

344

Interplanetary orbit determination  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

345

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

346

'Spider' in Earth Orbit  

NASA Technical Reports Server (NTRS)

View of the Apollo 9 Lunar Module 'Spider' in a lunar landing configuration photographed by Command Module pilot David Scott inside the Command/Service Module 'Gumdrop' on the fifth day of the Apollo 9 earth-orbital mission. The landing gear on 'Spider' has been deployed. lunar surface probes (sensors) extend out from the landing gear foot pads. Inside the 'Spider' were astronauts James A. McDivitt, Apollo 9 Commander; and Russell L. Schweickart, Lunar Module pilot.

1969-01-01

347

Orbits of colliding galaxies  

Microsoft Academic Search

A simple, semi-analytic method is developed for obtaining the orbits of galaxies undergoing fast collisions in which the galaxies are represented by Plummer models. The results are found to agree fairly well with those of N-body simulations. A simple formula for obtaining the angle of deflection is deduced. The maximum angle of deflection is 180 deg for Vp\\/Vesc(p) = 1.00,

M. Narasimha Rao; Saleh Mohamed Alladin; K. S. V. S. Narasimhan

1994-01-01

348

Radiation Propulsion For Maintaining Orbits  

NASA Technical Reports Server (NTRS)

Brief report proposes radiative propulsion systems for maintaining precise orbits of spacecraft. Radiation from electrical heaters directed outward by paraboloidal reflectors to produce small forces to oppose uncontrolled drag and solar-radiative forces perturbing orbits. Minimizes or eliminates need to fire rocket thrusters to correct orbits.

Richter, Robert

1995-01-01

349

Voyager orbit determination at Jupiter  

Microsoft Academic Search

This paper summarizes the Voyager 1 and Voyager 2 orbit determination activity extending from encounter minus 60 days to the Jupiter encounter, and includes quantitative results and conclusions derived from mission experiences. The major topics covered include an identification and quantification of the major orbit determination error sources and a review of salient orbit determination results from encounter, with emphasis

J. K. Campbell; S. P. Synnott; G. J. Bierman

1983-01-01

350

Voyager orbit determination at Jupiter  

Microsoft Academic Search

This paper summarizes the Voyager 1 and Voyager 2 orbit determination activity extending from encounter minus 60 days to the Jupiter encounter, and includes quantitative results and conclusions derived from mission experience. The major topics covered include an identifica- tion and quantification of the major orbit determination error sources and a review of salient orbit determination results from encounter, with

JAMES K. CAMPBELL; STEPHEN P. SYNNOTT; GERALD J. BIERMAN

1983-01-01

351

Transverse halo orbits about Mars?  

Microsoft Academic Search

We predict a new family of charged dust rings about Mars, transverse to the ecliptic plane. These orbits are stable to the perturbations of planetary oblateness, Mars' orbital motion, and the solar wind. Lifetimes of individual orbits are limited primarily by the Lorentz force and Poynting-Robertson drag, and may exceed 1000 years. They may be populated via collisions of micrometeoroids

J. E. Howard; A. V. Krivov; F. Spahn

2003-01-01

352

Heteronuclear Diatomic Molecular Orbital Formation  

NSDL National Science Digital Library

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

353

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

354

Ejs Keplerian Orbit Model  

NSDL National Science Digital Library

The Ejs Keplerian Orbit model displays the dynamics of a mass orbiting a much larger mass subject to Newtonian gravity. The simulation displays the motion of the smaller mass and the effective potential energy diagram. The initial energy of the system can be changed via textbox and the initial conditions can also be changed by dragging the mass or dragging the black circle in the effect potential energy diagram. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Keplerian Orbit model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_central_forces_kepler.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-18

355

Frozen Orbital Plane Solutions for Satellites in Nearly Circular Orbit  

NASA Astrophysics Data System (ADS)

This paper deals with the determination of the initial conditions (right ascension of the ascending node and inclination) that minimize the orbital plane variation for nearly circular orbits with a semimajor axis between 3 and 10 Earth radii. An analysis of two-line elements over the last 40 years for mid-, geostationary-, and high-Earth orbits has shown, for initially quasi-circular orbits, low eccentricity variations up to the geostationary altitude. This result makes the application of mathematical models based on satellite circular orbits advantageous for a fast prediction of long-term temporal evolution of the orbital plane. To this purpose, a previous model considering the combined effect due to the Earth's oblateness, moon, and sun (both in circular orbit) has been improved in terms of required computational time and accuracy. The eccentricity of the sun and moon and the equinoctial precession have been taken into account. Resonance phenomena with the lunar plane motion have been found in mid-Earth orbit. Dynamical properties concerning the precession motions of the orbital pole have been investigated, and frozen solutions for geosynchronous and navigation satellites have been proposed. Finally, an accurate model validation has also been carried out by comparing the obtained results with two-line elements of abandoned geostationary-Earth orbit and mid-Earth orbit satellites.

Ulivieri, Carlo; Circi, Christian; Ortore, Emiliano; Bunkheila, Federico; Todino, Francesco

2013-08-01

356

Vertically scanned laser sheet microscopy.  

PubMed

Laser sheet microscopy is a widely used imaging technique for imaging the three-dimensional distribution of a fluorescence signal in fixed tissue or small organisms. In laser sheet microscopy, the stripe artifacts caused by high absorption or high scattering structures are very common, greatly affecting image quality. To solve this problem, we report here a two-step procedure which consists of continuously acquiring laser sheet images while vertically displacing the sample, and then using the variational stationary noise remover (VSNR) method to further reduce the remaining stripes. Images from a cleared murine colon acquired with a vertical scan are compared with common stitching procedures demonstrating that vertically scanned light sheet microscopy greatly improves the performance of current light sheet microscopy approaches without the need for complex changes to the imaging setup and allows imaging of elongated samples, extending the field of view in the vertical direction. PMID:25271539

Dong, Di; Arranz, Alicia; Zhu, Shouping; Yang, Yujie; Shi, Liangliang; Wang, Jun; Shen, Chen; Tian, Jie; Ripoll, Jorge

2014-10-01

357

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 50°. 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

2014-07-01

358

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

359

Ozone vertical profiles in the upper troposphere and stratosphere from the OMPS limb sensor  

NASA Astrophysics Data System (ADS)

Scheduled for launch in October 2011, the NPOESS Preparatory Project (NPP) mission includes the Ozone Mapping and Profiler Suite (OMPS) which is composed of two Nadir looking sensors and an Earth-limb viewing sensor. This paper is concerned with the OMPS limb sensor, the primary product of which is an ozone vertical profile with a 1.5 km vertical resolution, a vertical range of cloud top to 60 km and an along-track spacing of 125 km. Secondary products include stratospheric aerosol vertical distribution, cloud top height and NO2 vertical profiles. The paper describes the OMPS mission (sensor specifications, orbital characteristics, timeline), reviews the heritage in space-based ozone measurements, illustrates the limb sensor expected performance (accuracy and precision), describes the planned product validation effort (comparison with ground and space instruments) and defines the data release procedure (content, format and release schedule).

Fleig, Albert; Rault, Didier F.

2011-11-01

360

Orbital Anomalies FLORIN DIACU  

E-print Network

planet. After passing the asteroid belt and surviving intense radiation, in December 1973 it came close on an Atlas-Centaur rocket. NASA had invested great hopes in this mission, whose objec- tives were to study missions fulfilled their objec

Diacu, Florin

361

46 CFR 108.160 - Vertical ladders.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Vertical ladders. 108.160 Section 108.160 Shipping COAST GUARD, DEPARTMENT OF HOMELAND... Construction and Arrangement Means of Escape § 108.160 Vertical ladders. (a) Each vertical...

2010-10-01

362

Voyager orbit determination at Jupiter  

NASA Technical Reports Server (NTRS)

This paper summarizes the Voyager 1 and Voyager 2 orbit determination activity extending from encounter minus 60 days to the Jupiter encounter, and includes quantitative results and conclusions derived from mission experiences. The major topics covered include an identification and quantification of the major orbit determination error sources and a review of salient orbit determination results from encounter, with emphasis on the Jupiter approach phase orbit determination. Special attention is paid to the use of combined spacecraft-based optical observations and earth-based radiometric observations to achieve accurate orbit determination during the Jupiter encounter approach phase.

Campbell, J. K.; Synnott, S. P.; Bierman, G. J.

1983-01-01

363

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

364

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

365

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

366

The parallax and astrometric orbit of Mu Cassiopeiae  

NASA Technical Reports Server (NTRS)

A total of 371 photographic plates were made of the binary Mu Cassiopeia (Mu Cas) region with a 76 cm refractor. An astrometric orbit of nearly 22.09 yr was calculated, accompanied by an eccentricity of close to 0.58 and a semimajor axis close to 0.19 arcsec. The absolute magnitude was approximately 5.83 and the radial velocity 164 km/sec.

Russell, J. L.; Gatewood, G. D.

1984-01-01

367

Applicability of the control configured design approach to advanced earth orbital transportation systems  

NASA Technical Reports Server (NTRS)

The applicability of the control configured design approach (CCV) to advanced earth orbital transportation systems was studied. The baseline system investigated was fully reusable vertical take-off/horizontal landing single-stage-to-orbit vehicle and had mission requirements similar to the space shuttle orbiter. Technical analyses were made to determine aerodynamic, flight control and subsystem design characteristics. Figures of merit were assessed on vehicle dry weight and orbital payload. The results indicated that the major parameters for CCV designs are hypersonic trim, aft center of gravity, and control surface heating. Optimized CCV designs can be controllable and provide substantial payload gains over conventional non-CCV design vertical take-off vehicles.

Hepler, A. K.; Zeck, H.; Walker, W. H.; Shafer, D. E.

1978-01-01

368

Exact closed-form geolocation for SAR interferometry  

Microsoft Academic Search

Exact closed-form algorithms for InSAR-derived digital elevation model (DEM) geolocation are described. They are based on the knowledge of orbit parameters and time\\/Doppler frequency coordinates of each SAR image, as well as of their interferometric phase. The proposed scheme gives a simple framework for deriving the geolocation accuracy

Giovanni Nico

2002-01-01

369

Orbit synthesis for target satellites  

NASA Astrophysics Data System (ADS)

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

Wilkinson, Charles K.

370

Orbital Phase Environments and Stereoselectivities  

NASA Astrophysics Data System (ADS)

Facial selections are reviewed to propose a new theory, orbital phase environment, for stereoselectivities of organic reactions. The orbital phase environment is a generalized idea of the secondary orbital interaction between the non-reacting centers and the unsymmetrization of the orbitals at the reacting centers arising from in-phase and out-of-phase overlapping with those at the neighboring non-reacting sites. In this context, the nucleophilic addition preferentially occurs on the face of the carbonyl functionality opposite to the better electron-donating orbital at the ? position. In a similar manner to the carbonyl cases, the preferred reaction faces of olefins in electrophilic addition reactions are opposite to the better electron-donating orbitals at the ? positions. The orbital phase environments in Diels-Alder reactions are also reviewed.

Ohwada, Tomohiko

371

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

372

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

373

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

374

The vertical structure of limb hazes in the Martian atmosphere  

NASA Technical Reports Server (NTRS)

Vertical distribution and reflectance properties of aerosols in the Martian atmosphere are presented, based on Viking Orbiter images containing the planetary limb. Profiles of scattered light above the limb are used to constrain the temporal and spatial behavior of the aerosols. The data cover a wide range of seasons, locations, and viewing geometries. The typical atmospheric column contains one or more discrete, optically thin, ice-like haze layers between 30 and 90 km elevation, depending on the season, whose composition is inferred to be water ice. Below the detached hazes there is a continuous haze extending to the surface. The continuous haze is rarely above 50 km and is much redder in color than the detached hazes above, implying a composition that has a strong dust component. The aerosol distribution exhibits solid seasonal control inferred to be driven by the variable solar flux around the orbit of Mars.

Jaquin, Fred; Gierasch, Peter; Kahn, Ralph

1986-01-01

375

Alien Visitations Close Encounters  

E-print Network

Alien Visitations #12;#12;Close Encounters · I: Visual sighting of aerial object (UFO) · II damage · III: Direct observation of extraterrestrials · IV: Abduction #12;UFOs What is a UFO? ·All Sheaffer: http://www.debunker.com/ufo.html #12;#12;#12;Extraordinary Claims Require Extraordinary Evidence

Walter, Frederick M.

376

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

377

Closed Captioning: Students' Responses.  

ERIC Educational Resources Information Center

A study investigated the attitudes of adult university students of English as a Second Language (ESL) toward use of closed captioned television (CCTV) as an instructional tool. Students at the intermediate (n=51) and advanced (n=55) levels of ESL study in classes using CCTV were administered a questionnaire concerning their perceptions of the…

Weasenforth, Donald L.

378

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

379

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.

380

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.

381

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

382

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

383

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

384

Solid Earth and ocean tides estimated from satellite orbit analyses  

Microsoft Academic Search

The earth's tidal deformations cause perturbations in the motions of close earth satellites, observations of which give estimates of the Love number k2 and phase lag ?. The contribution of the ocean tides has generally been considered unimportant, but this is not so. These ocean tides cause the same spectrum of orbital perturbations as the solid tide, and a complete

Kurt Lambeck; Anny Cazenave; Georges Balmino

1974-01-01

385

Nilpotent orbits in bad characteristic and the Springer correspondence  

E-print Network

Let G be a connected reductive algebraic group over an algebraically closed field of characteristic p, g the Lie algebra of G and g* the dual vector space of g. This thesis is concerned with nilpotent orbits in g and g* ...

Xue, Ting, Ph. D. Massachusetts Institute of Technology

2010-01-01

386

Hydrodynamic capture of microswimmers into sphere-bound orbits  

E-print Network

in their speed, into close orbits around solid spheres resting on or near a horizontal plane. We show length, and for a variety of sphere materials. We consider a simple model, based on lubrication theory near a solid surface. The model demonstrates capture, or movement towards the surface, and yields

Shelley, Michael

387

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

388

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

389

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

390

The orbital dynamics and long-term stability of planetary systems  

E-print Network

A large population of low-mass exoplanets with short orbital periods has been discovered using the transit method. At least 40% of these planets are actually part of compact systems with more than one planet. The closeness ...

Deck, Katherine Michele

2014-01-01

391

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

NASA Astrophysics Data System (ADS)

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

Yang, Yong; Wang, Xiaojun; Tang, Yihua

2002-01-01

392

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

393

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

394

The orbital surgeon.  

PubMed Central

While the number of orbital surgeons is limited, it is hoped these can be recognized and patients referred to them by ophthalmologists not interested or trained in that specialty. Let the orbital surgeon determine whether he can handle the problem in 1 to 2 days, or whether a neurosurgeon should do the procedure or make it a joint effort. It may well involve other specialty team effort approaches. It is essential to have an understanding of x-rays, CT, angiography, and MRI techniques and films. Sit with these specialists to learn more and help to avoid negative, misdiagnosis reports in the interest of the patient. Use judgement in helping the patient decide on ophthalmic or the more extensive neurosurgical approach after careful study and what is in their best interest. The team approach is used in well established medical centers with the ophthalmologist and neurosurgeon (or other specialist) working together in the best interest of the patient. This is more interesting and keeps the ophthalmologist in the mainstream of medicine. Images FIGURE 1 A FIGURE 1 B FIGURE 1 C FIGURE 2 FIGURE 3 A FIGURE 3 B FIGURE 3 C FIGURE 3 D FIGURE 4 A FIGURE 4 B FIGURE 5 A FIGURE 5 B FIGURE 6 A FIGURE 6 B FIGURE 7 A FIGURE 7 B FIGURE 7 C FIGURE 8 A FIGURE 8 B FIGURE 9 PMID:2979017

Kennedy, R E

1988-01-01

395

Multiple Poincaré sections method for finding the quasiperiodic orbits of the restricted three body problem  

NASA Astrophysics Data System (ADS)

A new fully numerical method is presented which employs multiple Poincaré sections to find quasiperiodic orbits of the Restricted Three-Body Problem (RTBP). The main advantages of this method are the small overhead cost of programming and very fast execution times, robust behavior near chaotic regions that leads to full convergence for given family of quasiperiodic orbits and the minimal memory required to store these orbits. This method reduces the calculations required for searching two-dimensional invariant tori to a search for closed orbits, which are the intersection of the invariant tori with the Poincaré sections. Truncated Fourier series are employed to represent these closed orbits. The flow of the differential equation on the invariant tori is reduced to maps between the consecutive Poincaré maps. A Newton iteration scheme utilizes the invariance of the circles of the maps on these Poincaré sections in order to find the Fourier coefficients that define the circles to any given accuracy. A continuation procedure that uses the incremental behavior of the Fourier coefficients between close quasiperiodic orbits is utilized to extend the results from a single orbit to a family of orbits. Quasi-halo and Lissajous families of the Sun-Earth RTBP around the L2 libration point are obtained via this method. Results are compared with the existing literature. A numerical method to transform these orbits from the RTBP model to the real ephemeris model of the Solar System is introduced and applied.

Kolemen, Egemen; Kasdin, N. Jeremy; Gurfil, Pini

2012-01-01

396

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

397

Orbital Structure and Asymptotic Orbits in Barred-Spiral Galaxies  

NASA Astrophysics Data System (ADS)

Using frequency analysis we find the orbital structure of a self-consistent N-body configuration simulating a rotating barred-spiral galaxy. We detect the main families of the regular orbits and of the chaotic ones, separately. Chaotic orbits play a major role in supporting the outer envelope of the bar as well as the ring and the spiral arms. The explanation is given by studying the unstable asymptotic curves of the main unstable periodic orbits of the system. A new type of stickiness phenomenon near the main unstable asymptotic curves on the phase space seems to be responsible for the galaxy’s shape outside corotation.

Harsoula, M.; Kalapotharakos, C.; Contopoulos, G.

2010-07-01

398

The Orbital Workshop Trash Disposal Airlock  

NASA Technical Reports Server (NTRS)

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

1972-01-01

399

Radiation absorption properties of orbital implants.  

PubMed

PURPOSE: To determine the radiation absorption properties (RAP) of three commonly used orbital implant materials, namely, methylmethacrylate (MM), hydroxyapatite (HA), and porous polyethylene (PP). METHODS: Eighteen (18)-mm spheres of MM, HA and PP were tested with 1.25 MV gamma-rays from cobalt-60, 6 MV X-rays, and 9 MeV, 12 MeV, and 16 MeV electron beams. The implants were immersed in a water phantom, and the measurements were obtained on X-omat V(R) film; the scanning was done with a computerized laser densitometer, CADSCAN(R). RESULTS: The RAP of all three materials appeared to be very close to those of water. The density of the MM implant was calculated to be the closest to that of water at all photon and electron energies. PP had a higher transmission than water at all electron energies (9, 12 and 16 MeV); the transmission through HA, however, was lower than through water. CONCLUSION: When postoperative radiation is indicated for an orbit containing an implant, the RAP of the allograft material play a significant role in the planning of the radiation treatment. Our study indicated that MM implants have RAP equivalent to those of water when treatment of orbital tumors is undertaken at the commonly used photon and electron energies. The RAP of the other allografts were either higher or lower, which may lead to unreliability in irradiation planning. PMID:12048723

Karcioglu, Zeynel A.; Al-Ghamdi, Hassan; Al-Bateri, Abdulkarim; Rostem, Assem

1998-09-01

400

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

401

Mars Observer orbit determination analysis  

NASA Technical Reports Server (NTRS)

Results are presented of a simulated orbit determination analysis for three phases of the Mars Observer mission (interplanetary cruise, orbit insertion, and mapping), together with a summary of orbital accuracies throughout the Mars Observer mission. The plan for achieving the navigation objectives of the Mars Observer mission is described. These objectives are to navigate the Mars Observer spacecraft to Mars and achieve accurate targeting at Mars; to propulsively maneuver the spacecraft into a 3-day period, capture orbit; to navigate the spacecraft into a 1.96-hr period low-altitude, nearly circular mapping orbit; and to maintain Mars Observer in the mapping orbit throughout the 687 days devoted for scientific data acquisition. Factors that will affect the spacecraft during each of the three phases are discussed.

Esposito, Pasquale; Roth, Duane; Demcak, Stuart

1991-01-01

402

Mars Observer orbit determination analysis  

NASA Astrophysics Data System (ADS)

Results are presented of a simulated orbit determination analysis for three phases of the Mars Observer mission (interplanetary cruise, orbit insertion, and mapping), together with a summary of orbital accuracies throughout the Mars Observer mission. The plan for achieving the navigation objectives of the Mars Observer mission is described. These objectives are to navigate the Mars Observer spacecraft to Mars and achieve accurate targeting at Mars; to propulsively maneuver the spacecraft into a 3-day period, capture orbit; to navigate the spacecraft into a 1.96-hr period low-altitude, nearly circular mapping orbit; and to maintain Mars Observer in the mapping orbit throughout the 687 days devoted for scientific data acquisition. Factors that will affect the spacecraft during each of the three phases are discussed.

Esposito, Pasquale; Roth, Duane; Demcak, Stuart

1991-10-01

403

Geostationary Earth Orbit Satellite Model  

NSDL National Science Digital Library

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

Wee, Loo K.

2012-04-08

404

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.

Farland, Donna

2008-02-01

405

Analysis of geometries with closed timelike curves  

NASA Astrophysics Data System (ADS)

This work deals with the analysis of cylindrically symmetric and stationary space-times mathcal{C}_{t} with closed timelike curves. The equation of motion describing the evolution of a massive scalar field in a mathcal{C}_{t} space-time is obtained. A class of space-times with closed timelike curves describing cosmic strings and cylinders is studied in detail. In such space-times, both massive particles as well as photons can reach the non-causal region. Geodesics and closed timelike curves are calculated and investigated. We have observed that massive particles and photons describe, essentially, two kinds of trajectories: confined orbits and scattering states. The analysis of the light cones show us clearly the intersection between future and past inside the non-causal region. Exact solutions for the equation of motion of massive scalar field propagating in cosmic strings and cylinder space-times are presented. Quasinormal modes for the scalar field have been calculated in static and rotating cosmic cylinders. We found unstable modes in the rotating cases. Rotating as well as static cosmic strings, i.e., without regular interior solutions, do not display quasinormal modes for the scalar field. We conclude presenting a conjecture relating closed timelike curves and space-time instability.

Pavan, A. B.

2010-05-01

406

Irreducible, incarcerated vertical dislocation of patella into a Hoffa fracture.  

PubMed

Rotational dislocations of patella, which involve rotation of the patella around a horizontal or vertical axis are rare. These rotational dislocations of patella are difficult to reduce by close methods. These dislocations can have associated osteochondral and retinacular injury. We report a case of a 20-year-old male who presented with swelling and pain in the right knee following a motor cycle accident. Radiological evaluation using the computed tomography revealed a patellar dislocation with a concomitant Hoffa fracture. Patella was rotated around the vertical axis and was incarcerated into the Hoffa fracture. This is a very rare injury and first of its kind to be reported. The difficulties in diagnosis, mechanism of injury and management have been discussed. We feel closed reduction of such an injury is likely to fail and open reduction is recommended. PMID:25298564

Soraganvi, Prasad C; Narayan Gowda, Bs; Rajagopalakrishnan, Ramakanth; Gavaskar, Ashok S

2014-09-01

407

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

408

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

409

Waves, circulation and vertical dependence  

NASA Astrophysics Data System (ADS)

Longuet-Higgins and Stewart (J Fluid Mech 13:481-504, 1962; Deep-Sea Res 11:529-562, 1964) and later Phillips (1977) introduced the problem of waves incident on a beach, from deep to shallow water. From the wave energy equation and the vertically integrated continuity equation, they inferred velocities to be Stokes drift plus a return current so that the vertical integral of the combined velocities was nil. As a consequence, it can be shown that velocities of the order of Stokes drift rendered the advective term in the momentum equation negligible resulting in a simple balance between the horizontal gradients of the vertically integrated elevation and wave radiation stress terms; the latter was first derived by Longuet-Higgins and Stewart. Mellor (J Phys Oceanogr 33:1978-1989, 2003a), noting that vertically integrated continuity and momentum equations were not able to deal with three-dimensional numerical or analytical ocean models, derived a vertically dependent theory of wave-circulation interaction. It has since been partially revised and the revisions are reviewed here. The theory is comprised of the conventional, three-dimensional, continuity and momentum equations plus a vertically distributed, wave radiation stress term. When applied to the problem of waves incident on a beach with essentially zero turbulence momentum mixing, velocities are very large and the simple balance between elevation and radiation stress gradients no longer prevails. However, when turbulence mixing is reinstated, the vertically dependent radiation stresses produce vertical velocity gradients which then produce turbulent mixing; as a consequence, velocities are reduced, but are still larger by an order of magnitude compared to Stokes drift. Nevertheless, the velocity reduction is sufficient so that elevation set-down obtained from a balance between elevation gradient and radiation stress gradients is nearly coincident with that obtained by the aforementioned papers. This paper includes four appendices. The first appendix demonstrates the numerical process by which Stokes drift is excluded from the turbulence stress parameterization in the momentum equation. A second appendix determines a bottom slope criterion for the application of linear wave relations to the derivation of the wave radiation stress. The third appendix explores the possibility of generalizing results by non-dimensionalization. The final appendix applies the basic theory to a problem introduced by Bennis and Ardhuin (J Phys Oceanogr 41:2008-2012, 2011).

Mellor, George

2013-04-01

410

Orbital myositis: Diagnosis and management  

Microsoft Academic Search

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

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

2009-01-01

411

Orbit synthesis for target satellites  

Microsoft Academic Search

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

Charles K. Wilkinson

1990-01-01

412

Ancient schwannoma of the orbit.  

PubMed

Schwannoma, also referred to as neurilemmoma or peripheral neurinoma, is an unusual orbital benign tumour that may pose diagnostic challenges. Awareness of the clinical features that may be associated with the tumour and prompt surgical excision with histopathologic examination enable correct diagnosis. The authors describe a progressively increasing inferolateral orbital mass in a 32-year-old patient that was demonstrated to be an orbital ancient schwannoma. PMID:23316621

Pecorella, I; Toth, J; Lukats, O

2012-08-01

413

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

414

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

E-print Network

If accretion disc contains weak frozen-in entangled magnetic fields, their dynamical effect may be important inside the last stable orbit because of the 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 show the vertical structure is more complicated. In particular, 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

2014-01-01

415

Aerobraked orbital transfer vehicle definition  

NASA Technical Reports Server (NTRS)

A new technique has been developed to enhance the use of upper atmosphere aerobraking for increased performance from orbital transfer vehicles. This technique utilizes a pressure supported drag brake and the orbital transfer vehicle main engine to modulate aerodynamic drag and also to alleviate the aerodynamic heating during a grazing pass through the atmosphere. Performance analyses of vehicles utilizing all-propulsive or aerobraking during round trip missions from low earth orbit (LEO) to geo-synchronous earth orbit (GEO) and back shows that aerobraking allows a given vehicle to deliver approximately twice as much payload to GEO and return. Aerobraking also provides more than twice the round trip payload.

Andrews, D. G.; Bloetscher, F.

1981-01-01

416

Numerical Simulations of Vertical Oscillations of a Curved Coronal Loop  

NASA Astrophysics Data System (ADS)

We consider an impulsively-started, vertical excitation of a solar coronal loop that is embedded into a potential arcade. The two-dimensional numerical model we implement includes the effects of line curvature and allows us to explore the effect of varying the initial pulse position. The results of the numerical simulations reveal kink mode oscillations with waveperiods that are reasonably close to the observational findings of Wang and Solanki (2004).

Murawski, K.; Selwa, M.; Rossmanith, J. A.

2005-09-01

417

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

418

Skylab Orbiter Workshop Illustration  

NASA Technical Reports Server (NTRS)

This cutaway illustration shows the characteristics and basic elements of the Skylab Orbiter Workshop (OWS). The OWS was divided into two major compartments. The lower level provided crew accommodations for sleeping, food preparation and consumption, hygiene, waste processing and disposal, and performance of certain experiments. The upper level consisted of a large work area and housed water storage tanks, a food freezer, storage vaults for film, scientific airlocks, mobility and stability experiment equipment, and other experimental equipment. The compartment below the crew quarters was a container for liquid and solid waste and trash accumulated throughout the mission. A solar array, consisting of two wings covered on one side with solar cells, was mounted outside the workshop to generate electrical power to augment the power generated by another solar array mounted on the solar observatory. Thrusters were provided at one end of the workshop for short-term control of the attitude of the space station.

1972-01-01

419

Orbiting Carbon Observatory  

NASA Technical Reports Server (NTRS)

Human impact on the environment has produced measurable changes in the geological record since the late 1700s. Anthropogenic emissions of CO2 today may cause the global climate to depart for its natural behavior for many millenia. CO2 is the primary anthropogenic driver of climate change. The Orbiting Carbon Observatory goals are to help collect measurements of atmospheric CO2, answering questions such as why the atmospheric CO2 buildup varies annually, the roles of the oceans and land ecosystems in absorbing CO2, the roles of North American and Eurasian sinks and how these carbon sinks respond to climate change. The present carbon cycle, CO2 variability, and climate uncertainties due atmospheric CO2 uncertainties are highlighted in this presentation.

Miller, Charles E.

2005-01-01

420

Orbital science's 'Bermuda Triangle'  

NASA Astrophysics Data System (ADS)

The effects of a part of the inner Van Allen belt lying closest to the earth, known as the South Atlantic Anomaly (SAA) upon spacecraft including the Hubble Space Telescope (HST), are discussed. The area consists of positively charged ions and electrons from the Van Allen Belt which become trapped in the earth's dipole field. Contor maps representing the number of protons per square centimeter per second having energies greater than 10 million electron volts are presented. It is noted that the HST orbit causes it to spend about 15 percent of its time in the SAA, but that, unlike the experience with earlier spacecraft, the satellite's skin, internal structure, and normal electronic's packaging provides sufficient protection against eletrons, although some higher energy protons still get through. Various charged particle effects which can arise within scientific instruments including fluorescence, Cerenkov radiation, and induced radioactivity are described.

Sherrill, Thomas J.

1991-02-01

421

TOPEX orbital radiation study  

NASA Technical Reports Server (NTRS)

The space radiation environment of the TOPEX spacecraft is investigated. A single trajectory was considered. The external (surface incident) charged particle radiation, predicted for the satellite, is determined by orbital flux integration for the specified trajectory. The latest standard models of the environment are used in the calculations. The evaluation is performed for solar maximum conditions. The spacecraft exposure to cosmic rays of galactic origin is evaluated over its flight path through the magnetosphere in terms of geomagnetic shielding effects, both for surface incident heavy ions and for particles emerging behind different material thickness. Limited shielding and dose evaluations are performed for simple infinite slab and spherical geometries. Results, given in graphical and tabular form, are analyzed, explained, and discussed. Conclusions are presented and commented on.

Stassinopoulos, E. G.; Barth, J. M.

1984-01-01

422

Orbital magnetic ratchet effect  

NASA Astrophysics Data System (ADS)

Magnetic ratchets—two-dimensional systems with superimposed noncentrosymmetric ferromagnetic gratings—are considered theoretically. It is demonstrated that excitation by radiation results in a directed motion of two-dimensional carriers due to the pure orbital effect of the periodic magnetic field. Magnetic ratchets based on various two-dimensional systems such as topological insulators, graphene, and semiconductor heterostructures are investigated. The mechanisms of the electric current generation caused by both radiation-induced heating of carriers and by acceleration in the radiation electric field in the presence of a space-oscillating Lorentz force are studied in detail. The electric currents sensitive to the linear polarization plane orientation as well as to the radiation helicity are calculated. It is demonstrated that the frequency dependence of the magnetic ratchet currents is determined by the dominant elastic-scattering mechanism of two-dimensional carriers and differs for the systems with linear and parabolic energy dispersions.

Budkin, G. V.; Golub, L. E.

2014-09-01

423

Geology orbiter comparison study  

NASA Technical Reports Server (NTRS)

Instrument requirements of planetary geology orbiters were examined with the objective of determining the feasibility of applying standard instrument designs to a host of terrestrial targets. Within the basic discipline area of geochemistry, gamma-ray, X-ray fluorescence, and atomic spectroscopy remote sensing techniques were considered. Within the discipline area of geophysics, the complementary techniques of gravimetry and radar were studied. Experiments using these techniques were analyzed for comparison at the Moon, Mercury, Mars and the Galilean satellites. On the basis of these comparative assessments, the adaptability of each sensing technique was judged as a basic technique for many targets, as a single instrument applied to many targets, as a single instrument used in different mission modes, and as an instrument capability for nongeoscience objectives.

Cutts, J. A. J.; Blasius, K. R.; Davis, D. R.; Pang, K. D.; Shreve, D. C.

1977-01-01

424

Hypervelocity orbital intercept guidance  

NASA Astrophysics Data System (ADS)

Terminal guidance of a hypervelocity exo-atmospheric orbital interceptor with free end-time is examined. The pursuer is constrained to lateral thrusting with the evader modeled as an ICBM in its final boost phase. Proportional navigation, optimal control using certainty equivalence, dual control, and control with optimum thrust spacing are all examined. Also, a new approach called certainty control is developed for this problem. This algorithm constrains the final state to a function of projected estimate error to reduce control energy expenditure. All methods model the trajectories using splines and employ eight state Extended Kalman Filters with line-of-sight and range updates. The relative effectiveness of these control strategies is illustrated by applying them to various intercept problems.

Alfano, Salvatore

1988-04-01

425

Exploratory orbit analysis  

SciTech Connect

Unlike the other documents in these proceedings, this paper is neither a scientific nor a technical report. It is, rather, a short personal essay which attempts to describe an Exploratory Orbit Analysis (EOA) environment. Analyzing the behavior of a four or six dimensional nonlinear dynamical system is at least as difficult as analyzing events in high-energy collisions; the consequences of doing it badly, or slowly, would be at least as devastating; and yet the level of effort and expenditure invested in the latter, the very attention paid to it by physicists at large, must be two orders of magnitude greater than that given to the former. It is difficult to choose the model which best explains the behavior of a physical device if one does not first understand the behavior of the available models. The time is ripe for the development of a functioning EOA environment, which I will try to describe in this paper to help us achieve this goal.

Michelotti, L.

1989-03-01

426

Observations of orbital debris and satellites in Slovak Republic  

NASA Astrophysics Data System (ADS)

There are many accidental optically tracked artificial objects during observations at Astronom-ical and Geophysical Observatory FMPI CU, Modra, Slovak Republic (AGO). Those objects are usually orbital debris or satellites. A tool to identify such a type of objects was necessary to create. Our software is called SatEph and is used to identify tracked artificial objects and to compute their orbital elements. SatEph is based on analytic propagation model SGP4 and TLE data. Program is still under development and in the near future it will be a part of software for automated search telescope for small near Earth asteroids at AGO. We present orbital debris observation simulation for the new optical searching system. Unlike other aster-oids searching systems (Catalina Sky Survey, LINEAR, Spacewatch etc.) our system should be capable to detect small asteroids in close vicinity of the Earth (smaller then Lunar distance) with high angular speed. The limiting magnitude of observable objects is about +16 magnitude and the pixel scale is 4,6 arcsec/px. This allows us to detect man made objects as well. We studied how many satellites and orbital debris with known orbital elements are able to track per given observing night. We also studied frequency detection of tracked object during one night. The searching system field of view will be 4.4 x 4.4 square degrees and the system will search more then 2000 square degrees per night. Exposure time for every single CCD shot is set to 30 seconds. We found out, there is possible to track from 250 to 450 objects (mostly with geosynchronous orbits) per one night in dependence on given day of the year. More then 200 objects have at least 3 astrometric positions per one night, which can be useful for orbit determination process. The tracked objects are mostly satellites and rocket bodies, which have different orbits, from low Earth orbit to geosynchronous Earth orbit. Data of orbital debris astrometric positions will be offered for national space agencies and used for our own orbit determination. Those data could be useful for orbital elements updating of catalogue, or non catalogue artificial objects.

Silha, Jiri; Toth, Juraj

427

Cornering characteristics of the main-gear tire of the space shuttle orbiter  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted at the NASA Langley Research Center to study the effects of various vertical load and yaw angle conditions on the cornering behavior of the Space Shuttle Orbiter main gear tire. Measured parameters included side and drag force, side and drag force coefficients, aligning torque, and overturning torque. Side force coefficient was found to increase as yaw angle was increased, but decreased as the vertical load was increased. Drag force was found to increase as vertical load was increased at constant yaw angles. Aligning torque measurements indicated that the tire is stable in yaw.

Daugherty, Robert H.; Stubbs, Sandy M.; Robinson, Martha P.

1988-01-01

428

Evolution of asteroid orbits that are orbitally commensurable with Mars  

Microsoft Academic Search

The statistical properties of the distribution of asteroids that have first-order orbital commensurability with Mars are qualitatively interpreted within the framework of the exterior version of the circular restricted three-body problem. Numerical parameters are derived for the orbital evolution of some resonant asteroids.

I. A. Gerasimov; B. R. Mushailov

1992-01-01

429

Optimal transfers from an Earth orbit to a Mars orbit  

Microsoft Academic Search

This paper deals with the optimal transfer of a spacecraft from a low Earth orbit (LEO) to a low Mars orbit (LMO). The transfer problem is formulated via a restricted four-body model in that the spacecraft is considered subject to the gravitational fields of Earth, Mars, and Sun along the entire trajectory. This is done to achieve increased accuracy with

A. Miele; T. Wang

1999-01-01

430

7, 1275112779, 2007 Vertical distribution  

E-print Network

boundary layer and vertical distribution of pollutants are discussed in terms15 of the energy balance. In an urban area there are many buildings, which cause large inhomogeneities in the energy and wind profiles Center for the Energy and the Environment (MCE2), La Jolla, CA, USA 2 Department of Earth, Atmospheric

Boyer, Edmond

431

Wideband Fractal Vertical Patch Antenna  

Microsoft Academic Search

A wideband vertical patch antenna (VPA) is depicted, which is devised from fractal antenna technology. By using a dual-Koch loop structure, a wideband VPA with 42% bandwidth and 8 dBi gain at the center frequency is designed and tested. Symmetrical broadside patterns are obtained at the passband.

T. P. Wong; Carmen K. L. Lau; Kwai-Man Luk; Kai-Fong Lee

2007-01-01

432

Insulated vertical antennas above ground  

Microsoft Academic Search

A fast efficient method is proposed to solve the problem of a vertical dielectric-coated antenna located in free space above ground. The solution is a moment method solution. The influence of lossy ground is taken into account via equivalent images due to Popovic, and the currents of images are expressed by the source current. The dielectric coating is modeled by

Xianshan Li; Khalil El Khamlichi Drissi; Françoise Paladian

2004-01-01

433

6, 72077233, 2006 Vertical distribution  

E-print Network

cloud sides. Inversion of measurements from the cloud sides requires rigorous understanding of10 the 3 cloud fields generated by a simple stochastic cloud model with the prescribed vertically resolved values of the droplet effective radius. The retrieval algorithm is based on the Bayesian theorem that com

Paris-Sud XI, Université de

434

Vertical axis wind turbine development  

Microsoft Academic Search

Theoretical and experimental research accomplished in evaluating an innovative concept for vertical axis wind turbines (VAWT) is described. The concept is that of using straight blades composed of circulation controlled airfoil sections. The theoretical analysis was developed to determine the unsteady lift and moment characteristics of multiple-blade cross-flow wind turbines. To determine the drag data needed as input to the

R. E. Walters; J. B. Fanucci; P. W. Hill; P. G. Migliore

1979-01-01

435

Unsteady aerodynamic flow field analysis of the space shuttle configuration. Part 4: 747/orbiter aeroelastic stability  

NASA Technical Reports Server (NTRS)

A quasi-steady analysis of the aeroelastic stability of the lateral (antisymmetric) modes of the 747/orbiter vehicle was accomplished. The interference effect of the orbiter wake on the 747 tail furnishes an aerodynamic undamping contribution to the elastic modes. Likewise, the upstream influence of the 747 tail and aft fuselage on the orbiter beaver-tail rail fairing also is undamping. Fortunately these undamping effects cannot overpower the large damping contribution of the 747 tail and the modes are damped for the configurations analyzed. However, significant interference effects of the orbiter on the 747 tail have been observed in the pitch plane. The high response of the 747 vertical tail in the orbiter wave was also considered. Wind tunnel data points to flapping of the OMS pod wakes as the source of the wake resonance phenomenon.

Reding, J. P.; Ericsson, L. E.

1976-01-01

436

Orbiter-orbiter and orbiter-lander tracking using same-beam interferometry  

NASA Technical Reports Server (NTRS)

Two spacecraft orbiting Mars will subtend a small angle as viewed from Earth. This angle will usually be smaller than the beam width of a single radio antenna. Thus the two spacecraft may be tracked simultaneously by a single Earth-based antenna. The same-beam interferometry (SBI) technique involves using two widely separated antennas, each observing the two spacecraft, to produce a measurement of the angular separation of the two spacecraft in the plane of the sky. The information content of SBI data is thus complementary to the line-of-sight information provided by conventional Doppler data. The inclusion of SBI data with the Doppler data in a joint orbit estimation procedure can desensitize the solution to gravity mismodeling and result in improved orbit determination accuracy. This article presents an overview of the SBI technique, a measurement error analysis, and an error covariance analysis of some examples of the application of SBI to orbit determination. For hypothetical scenarios involving the Mars Observer and the Russian Mars '94 spacecraft, orbit determination accuracy improvements of up to an order of magnitude are predicted, relative to the accuracy that can be obtained by using only Doppler data acquired separately from each spacecraft. Relative tracking between a Mars orbiter and a lander fixed on the surface of Mars is also studied. Results indicate that the lander location may be determined to a few meters, while the orbiter ephemeris may be determined with accuracy similar to the orbiter-orbiter case.

Folkner, William M.; Border, J. S.

1992-01-01

437

Orbits of subsystem stabilizers  

Microsoft Academic Search

Let ? be a reduced irreducible root system. We consider pairs (S, X (S)), where S is a closed set of roots, X(S) is its stabilizer\\u000a in the Weyl group W(?). We are interested in such pairs maximal with respect to the following order: (S1, X (S1)) ? (S2, X (S2)) if S1 ? S2 and X(S1) ? X(S2). The

N. A. Vavilov; N. P. Kharchev

2007-01-01

438

Artificial frozen orbits around Mercury  

NASA Astrophysics Data System (ADS)

Orbits around Mercury are influenced by the strong elliptic third-body perturbation, especially for high eccentricity orbits, the periapsis altitude changes dramatically. Frozen orbits whose mean eccentricity and argument of perigee remain constants are obviously a good choice for space missions, but the forming conditions are too harsh to meet practical needs. To deal with this problem, a continuous control method that combines analytical theory and parameter optimization is proposed to build an artificial frozen orbit. The artificial frozen orbits are investigated on the basis of double averaged Hamiltonian, of which the second and third zonal harmonics and the perturbation of elliptic third-body gravity are considered. In this paper, coefficients of perturbations which satisfy the conditions of frozen orbits are involved as control parameters, and the relevant artificial perturbations are compensated by the control strategy. So probes around Mercury can be kept on frozen orbit under the influence of continuous control force. Then complex method of optimization is used to search for the energy optimized artificial frozen orbits. The choosing of optimal parameters, the objective function setting and other issues are also discussed in the study. Evolution of optimal control parameters are given in large ranges of semi-major axis and eccentricity, through the variation of these curves, the fuel efficiency is discussed. The result shows that the control method proposed in this paper can effectively maintain the eccentricity and argument of perigee frozen.

Ma, Xue; Li, Junfeng

2013-12-01

439

Constraint Orbital Branching JAMES OSTROWSKI  

E-print Network

Constraint Orbital Branching JAMES OSTROWSKI Department of Industrial and Systems Engineering@di.univaq.it · smriglio@di.univaq.it November 15, 2007 Abstract Orbital branching is a method for branching on variables in integer programming that reduces the likelihood of evaluating redundant, isomorphic nodes in the branch

Linderoth, Jeffrey T.

440

Orbital evolution around irregular bodies  

Microsoft Academic Search

The new profiles of the space missions aimed at asteroids and comets, moving from fly-bys to rendezvous and orbiting, call for new spaceflight dynamics tools capable of propagating orbits in an accurate way around these small irregular objects. Moreover, interesting celestial mechanics and planetary science problems, requiring the same sophisticated tools, have been raised by the first images of asteroids

A. Rossi; F. Marzari; P. Farinella

1999-01-01

441

What is a MISR orbit?  

... during one half of the complete orbit or a bit less. Of course, the Earth itself keeps turning around its own axis while Terra proceeds ... to 9 days (Equator), depending on its latitude, but of course under a variety of angular conditions. An Orbit/Date Conversion ...

2013-03-05

442

Performance capability of laser-powered launch vehicles using vertical ascent trajectories  

NASA Technical Reports Server (NTRS)

The use of a ground-based high-power laser source to power a vertically launched rocket vehicle is investigated. By using a vertical ascent trajectory, only a single laser source is required. The vertical ascent mode is not applicable to earth orbit destinations but is applicable to missions beyond earth escape. Performance and trajectory characteristics are examined for vertical trajectories to earth escape and solar escape (which may be of interest in the future for radioactive waste disposal). Specific impulse values from 2000 to 5000 seconds are considered. With these values, a single-stage vehicle can deliver payloads to earth escape and beyond, but extremely high power sources (gigawatts) are required.

Spurlock, O. F.

1974-01-01

443

Shuttle orbiter - IUS/DSP satellite interface contamination study  

NASA Technical Reports Server (NTRS)

The results of a contamination analysis on the Defense Support Program (DSP) satellite during launch and deployment by the Space Transportation System (STS) are presented. Predicted contaminant deposition was also included on critical DSP surfaces during the period soon after launch when the DSP is in the shuttle orbiter bay with the doors closed, the bay doors open, and during initial deployment. Additionally, a six sided box was placed at the spacecraft position to obtain directional contaminant flux information for a general payload while in the bay and during deployment. The analysis included contamination sources from the shuttle orbiter, IUS and cradle, the DSP sensor and the DSP support package.

Rantanen, R. O.; Strange, D. A.

1978-01-01

444

Local reactivity descriptors from degenerate frontier molecular orbitals  

NASA Astrophysics Data System (ADS)

Conceptual Density Functional Theory (DFT) has proposed a set of local descriptors to measure the reactivity on specific sites of a molecule, as an example dual descriptor has been successfully used in analyzing interesting systems to understand their local reactivity, however under the frozen orbital approximation (FOA), it is defined from non-degenerate frontier molecular orbitals (FMOs). In this work, the degeneration is taken into account to propose approximated expressions to obtain the dual descriptor, nucleophilic and electrophilic Fukui functions in closed-shell systems. The proposed expressions have been tested on molecules presenting degenerate FMOs.

Martínez, Jorge

2009-08-01

445

Solar Orbiter—Heat shield and system technology  

NASA Astrophysics Data System (ADS)

Solar Orbiter will enhance our knowledge of the Sun by observations and in situ measurements as close as 0.22 AU from our star. Placed on an orbit with a period two-thirds the one of Venus, Solar Orbiter will use the many encounters with the planet to gradually incline its orbit and gain view on the Sun's poles. The permanent in situ observations will be associated to remote-sensing observations over large parts of the orbits. ESA Science Directorate has awarded in parallel two Solar Orbiter Heat Shield and System Technology contracts to industry. This paper presents the achievements of Thales Alenia Space thanks to one of these two ESA contracts. It shows how the main technical challenge brought by the heat flux of 20 solar constants has been addressed by the system and heat shield design. The design and manufacturing of a breadboard of the heat shield in view of thermal test verification is then reported. The main technological developments and residual risks are assessed, paving the way for the definition phase of the program.

Poncy, J.; Jubineau, F.; D'Angelo, F.; Perotto, V.; Juillet, J. J.

2009-10-01

446

The final status of Japanese Venus Climate Orbiter (PLANET-C) in the integration test  

Microsoft Academic Search

The Venus Climate Orbiter mission (PLANET-C), one of the future planetary missions of Japan, aims at