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1

Estimating the tumble rates of galaxy halos  

SciTech Connect

It has previously been demonstrated that cold gas in a static spheroidal galaxy will damp to a preferred plane, in which the angular momentum vector of the gas is aligned with the symmetry axis of the potential, through dissipative processes. We show now that, if the same galaxy rigidly tumbles about a nonsymmetry axis, the preferred orientation of the gas can become a permanently and smoothly warped sheet, in which rings of gas at large radii may be fully orthogonal to those near the galaxy's core. Detailed numerical orbit calculations closely match an analytic prediction made previously for the structure of the warp. This structure depends primarily on the eccentricity, density profile, and tumble rate of the spheroid. We show that the tumble rate can now be determined for a galaxy containing a significantly warped disk. Ordinary observations used in conjunction with graphs such as those we present, yield at least firm lower limits to the tumble periods of these objects. We have applied this method to the two peculiar systems NGC 5128 and NGC 2685 and found that, if they are prolate systems supporting permanently warped gaseous disks, they must tumble with periods near 5 x 10/sup 9/ yr and 2 x 10/sup 9/ yr respectively. In a preliminary investigation, we also find that the massive, unseen halos surrounding spiral galaxies must tumble with periods longer than or on the same order as those of the elliptical galaxies.

Simonson, G.F.; Tohline, J.E.

1983-05-15

2

Study of effects of uncertainties of comet and asteroid encounter and contact guidance requirements. Part 2: Tumbling problem studies. [development of navigation and guidance techniques for space rendezvous  

NASA Technical Reports Server (NTRS)

The problem of determining the rotational motion of a tumbling celestial body of the asteroid type using spacecraft-acquired data is addressed. The rotational motion of the body is modeled by free-Eulerian motion of a triaxial, rigid body and its translational motion with respect, to a nonrotating, observing spacecraft, which is not thrusting, is assumed to be uniform during the time observations are made. The mathematical details which form the basis for a digital simulation of the motion and observations are presented. Two algorithms for determining the motion from observations for the special case of uniform rotational motion are given.

Cochran, J. E., Jr.

1974-01-01

3

Rendezvous guidance  

NASA Technical Reports Server (NTRS)

Viewgraphs on rendezvous guidance are presented. Topics covered include: rendezvous guidance; Lambert Targeting; Linear Quadratic Targeting; unmanned vehicles; rendezvous trajectory; and fuzzy logic control.

Mcguire, Andrew T.

1990-01-01

4

Tumbling of small axisymmetric particles in random and turbulent flows.  

PubMed

We analyze the tumbling of small nonspherical, axisymmetric particles in random and turbulent flows. We compute the orientational dynamics in terms of a perturbation expansion in the Kubo number, and obtain the tumbling rate in terms of Lagrangian correlation functions. These capture preferential sampling of the fluid gradients, which in turn can give rise to differences in the tumbling rates of disks and rods. We show that this is a weak effect in Gaussian random flows. But in turbulent flows persistent regions of high vorticity cause disks to tumble much faster than rods, as observed in direct numerical simulations [S. Parsa, E. Calzavarini, F. Toschi, and G.?A. Voth, Phys. Rev. Lett. 109, 134501 (2012)]. For larger particles (at finite Stokes numbers), rotational and translational inertia affects the tumbling rate and the angle at which particles collide, due to the formation of rotational caustics. PMID:24483903

Gustavsson, K; Einarsson, J; Mehlig, B

2014-01-10

5

Usage and User Experience of Communication before and during Rendezvous  

ERIC Educational Resources Information Center

This paper reports a field evaluation of the mobile phone as a "package" of device and services. The evaluation compares 44 university students' usage and user experience of communication before and during rendezvous. During a rendezvous (en route), students rated many aspects of the experience of phone use less favourably than before a rendezvous…

Colbert, Martin

2005-01-01

6

QUENCHING TUMBLING MILL TUMBLES CASTINGS OVER EACH OTHER TO REMOVE ...  

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

QUENCHING TUMBLING MILL TUMBLES CASTINGS OVER EACH OTHER TO REMOVE RUNNERS AND SPRUES WHILE QUICKLY COOLING THEM WITH WATER IN THE MALLEABLE ANNEALING BUILDING. THIS PROCESS ENSURES CASTINGS FORM WHITE IRON PRIOR TO BEING ASSEMBLED. - Stockham Pipe & Fittings Company, Malleable Annealing Building, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

7

Rough and Tumble Play 101  

ERIC Educational Resources Information Center

Many people fear that play-fighting or rough and tumble play is the same as real fighting. There is also a fear that this rough play will become real fighting if allowed to continue. Most of all, parents and teachers fear that during the course of rough and tumble play a child may be hurt. To provide for and allow children to play rough without…

Carlson, Frances

2009-01-01

8

Parametric study of predictor accuracy impact on OFT rendezvous targeting  

NASA Technical Reports Server (NTRS)

A parametric study was made to quantitatively define the effects of errors in the state vector predictor used by the Operational Flight Trainer (OFT) rendezvous targeting algorithms. The effect of the predictor accuracy on the OFT rendezvous profile is shown by the sensitivity of various critical rendezvous parameters with respect to downrange and radial predictor error rates. The effect of both inertial (same errors on both vehicles) and relative (differential errors on one vehicle with respect to the other) errors were considered. Relative radial error rates had the largest impact on the rendezvous followed by relative downrange errors, radial inertial errors and downrange inertial errors.

Glenn, S. W.

1976-01-01

9

Autonomous rendezvous and capture system design  

NASA Technical Reports Server (NTRS)

Marshall Space Flight Center has a long history of involvement in the design of Autonomous Rendezvous and Capture (AR&C) systems. The first extensive studies were begun in the late seventies, incrementally leading to the development of an assortment of Guidance, Navigation, and Control (GN&C) concepts and algorithms suitable for a variety of mission requirements and spacecraft capabilities, with a strong emphasis placed upon flexible system-level design. These efforts have led to the development of sophisticated algorithms for docking with tumbling targets, and simple but efficient algorithms for stabilized spacecraft; each has been tested and validated using dynamic system simulation, with hardware in the loop when practical. Recent investigations include the use of neural networks for video image interpretation, and fuzzy logic for control system implementation.

Dabney, Richard W.

1991-01-01

10

Rendezvous with Zarya  

NASA Technical Reports Server (NTRS)

Backdropped against a blanket of heavy cloud cover, the Russian-built FGB, also called Zarya, nears the Space Shuttle Endeavour and the U.S.-built Node 1, also called Unity (foreground). Inside Endeavour's cabin, the STS-88 crew readies the Remote Manipulator System (RMS) for Zarya capture as they await the carefully choreographed dance of the rendezvous.

1998-01-01

11

Kazakhstan's Currency Tumbles  

NSDL National Science Digital Library

This week's In the News follows economic conditions in the former Soviet Republic of Kazakhstan. The seven resources discussed provide news, government links, and background information on Kazakhstan and its currency. Following a Kazahk National Bank announcement ending government limitations on currency exchange, the tenge fell in value from 88.30 tenge to the dollar on April 2, 1999 to 150.00 tenge to the dollar on April 6, 1999. The decision allows Kazakhstan's currency to float freely on international exchange markets and has resulted in some criticism from the International Monetary Fund (IMF). According to the IMF's representative Paul Ross, the decision should stimulate economic growth in this once-industrial economy, but it may come at some social cost. Currently, Kazahk citizens may exchange their bank deposits at pre-fall rates to the dollar providing they do not withdraw their savings for nine months, and as the BBC reports, many shop keepers in the commercial capital of Almaty have already doubled their prices.

Waters, Megan.

1999-01-01

12

Rendezvous guidance with proportional navigation  

NASA Astrophysics Data System (ADS)

In this article, a new approach for rendezvous terminal guidance with proportional navigation is developed. Under this guidance scheme, the magnitude of commanded acceleration is programmed with modified proportional navigation and it is applied in a fixed direction with a bias angle to the normal direction of line-of-sight during rendezvous course. Then the solution of relative motion described in a polar coordinate can be easily obtained and the corresponding energy expenditure, which is related to propellant mass required for rendezvous in exoatmospheric flight, is also derived. From the result, we find that the rendezvous path is a form of spiral function and both commanded acceleration and relative velocity are maintained in fixed directions relative to line-of-sight during rendezvous course. Also, the energy expenditure required for exoatmospheric rendezvous is proportional to and greater than the initial relative velocity.

Yuan, Pin-Jar; Hsu, Shih-Che

1993-02-01

13

The tumbling spin state of (99942) Apophis  

NASA Astrophysics Data System (ADS)

Our photometric observations of Asteroid (99942) Apophis from December 2012 to April 2013 revealed it to be in a state of non-principal axis rotation (tumbling). We constructed its spin and shape model and found that it is in a moderately excited Short Axis Mode (SAM) state with a ratio of the rotational kinetic energy to the basic spin state energy E/E0=1.024±0.013. (All quoted uncertainties correspond to 3?.) The greatest and intermediate principal moments of inertia are nearly the same with I2/I3=0.965-0.015+0.009, but the smallest principal moment of inertia is substantially lower with I1/I3=0.61-0.08+0.11; the asteroid’s dynamically equivalent ellipsoid is close to a prolate ellipsoid. The precession and rotation periods are P?=27.38±0.07 h and P?=263±6 h, respectively; the strongest observed lightcurve amplitude for the SAM case is in the 2nd harmonic of P1=P=30.56±0.01 h. The rotation is retrograde with the angular momentum vector’s ecliptic longitude and latitude of 250° and -75° (the uncertainty area is approximately an ellipse with the major and minor semiaxes of 27° and 14°, respectively). An implication of the retrograde rotation is a somewhat increased probability of the Apophis’ impact in 2068, but it is still very small with the risk level on the Palermo Scale remaining well below zero. Apophis is a member of the population of slowly tumbling asteroids. Applying the theory of asteroid nutational damping by Breiter et al. (Breiter, S., Ro?ek, A., Vokrouhlický, D. [2012]. Mon. Not. R. Astron. Soc. 427, 755-769), we found that slowly tumbling asteroids predominate in the spin rate-size range where their estimated damping times are greater than about 0.2 Gyr. The appearance that the PA/NPA rotators transition line seems to follow a line of constant damping time may be because there are two or more asteroid spin evolution mechanisms in play, or the factor of ?Q (the elastic modulus times the quality factor) is not constant but it may decrease with decreasing asteroid size, which would oppose the trend due to decreasing collisional age or excitation time.

Pravec, P.; Scheirich, P.; ?urech, J.; Pollock, J.; Kušnirák, P.; Hornoch, K.; Galád, A.; Vokrouhlický, D.; Harris, A. W.; Jehin, E.; Manfroid, J.; Opitom, C.; Gillon, M.; Colas, F.; Oey, J.; Vraštil, J.; Reichart, D.; Ivarsen, K.; Haislip, J.; LaCluyze, A.

2014-05-01

14

Cooperative control of UAV rendezvous  

Microsoft Academic Search

The cooperative control of timing and synchronization of tasks of multiple unmanned air vehicles (UAVs) represents a valuable capability for a wide range of potential multi-UAV missions. This research addresses the specific problem of cooperative rendezvous in which multiple UAVs are to arrive at their targets simultaneously. The development of a rendezvous manager state machine and a cooperative control decomposition

T. W. McLain; Phillip R. Chandler; Steven Rasmussen; Meir Pachter

2001-01-01

15

STS-135: Rendezvous Pitch Maneuver  

NASA Video Gallery

On July 10, 2011, space shuttle Atlantis performed the nine-minute Rendezvous Pitch Maneuver, or â??backflip.â? With Commander Chris Ferguson at the helm, Atlantis rotated 360 degrees backward to ...

16

STS-133: Rendezvous Pitch Maneuver  

NASA Video Gallery

At 1:15 p.m. EST Saturday, space shuttle Discovery began the nine-minute Rendezvous Pitch Maneuver, or "backflip." With Commander Steve Lindsey at the helm, Discovery rotated 360 degrees backward t...

17

STS-134: Rendezvous Pitch Maneuver  

NASA Video Gallery

On May 18, 2011, space shuttle Endeavour performed the Rendezvous Pitch Maneuver, or "backflip." With Commander Mark Kelly at the helm, Endeavour rotated 360 degrees backward to enable Internationa...

18

History of Space Shuttle Rendezvous  

NASA Technical Reports Server (NTRS)

This technical history is intended to provide a technical audience with an introduction to the rendezvous and proximity operations history of the Space Shuttle Program. It details the programmatic constraints and technical challenges encountered during shuttle development in the 1970s and over thirty years of shuttle missions. An overview of rendezvous and proximity operations on many shuttle missions is provided, as well as how some shuttle rendezvous and proximity operations systems and flight techniques evolved to meet new programmatic objectives. This revised edition provides additional information on Mercury, Gemini, Apollo, Skylab, and Apollo/Soyuz. Some chapters on the Space Shuttle have been updated and expanded. Four special focus chapters have been added to provide more detailed information on shuttle rendezvous. A chapter on the STS-39 mission of April/May 1991 describes the most complex deploy/retrieve mission flown by the shuttle. Another chapter focuses on the Hubble Space Telescope servicing missions. A third chapter gives the reader a detailed look at the February 2010 STS-130 mission to the International Space Station. The fourth chapter answers the question why rendezvous was not completely automated on the Gemini, Apollo, and Space Shuttle vehicles.

Goodman, John L.

2011-01-01

19

Optimal control during orbital rendezvous  

NASA Astrophysics Data System (ADS)

The paper examines the coplanar rendezvous of a maneuvering spacecraft with a passive spacecraft in a circular orbit. It is assumed that a control acceleration of limited magnitude is imposed on the active spacecraft, and that its direction changes in accordance with a fuel-optimal control law. An analytical solution is sought for the corresponding variational problem in a finite form, with specified constraints on the rendezvous time. An optimal relationship is obtained for changes of the tangent of the angle of the control-acceleration vector in the form of a fractional-linear function of time.

Iablonko, Iu. P.

1982-07-01

20

Tumbling For Seed Cleaning and Conditioning1  

Microsoft Academic Search

Small rock tumblers can be used to clean and condition seeds both in an aqueous and a dry mode. During the process, grit and gravel remove fruit pulp and abrade seed coats. Wet tumbling of seed aids imbibition, leaches water-soluble germination inhibitors, and may partially substitute for cold stratification for some shrub seed lots.

David Dreesen

21

Rendezvous maneuvers using Genetic Algorithm  

NASA Astrophysics Data System (ADS)

The present paper has the goal of studying orbital maneuvers of Rendezvous, that is an orbital transfer where a spacecraft has to change its orbit to meet with another spacecraft that is travelling in another orbit. This transfer will be accomplished by using a multi-impulsive control. A genetic algorithm is used to find the transfers that have minimum fuel consumption.

Souza dos Santos, Denílson Paulo; Rodrigo Barretto Teodoro, Anderson; Bertachini de Almeida Prado, Antônio F.

2013-10-01

22

Rendezvous lidar sensor system for terminal rendezvous, capture, and berthing to the International Space Station  

NASA Astrophysics Data System (ADS)

The Rendezvous Lidar System (RLS), a high-performance scanning time-of-flight lidar jointly developed by MDA and Optech, was employed successfully during the XSS-11 spacecraft's 23-month mission. Ongoing development of the RLS mission software has resulted in an integrated pose functionality suited to safety-critical applications, specifically the terminal rendezvous of a visiting vehicle with the International Space Station (ISS). This integrated pose capability extends the contribution of the lidar from long-range acquisition and tracking for terminal rendezvous through to final alignment for docking or berthing. Innovative aspects of the technology that were developed include: 1) efficacious algorithms to detect, recognize, and compute the pose of a client spacecraft from a single scan using an intelligent search of candidate solutions, 2) automatic scene evaluation and feature selection algorithms and software that assist mission planners in specifying accurate and robust scan scheduling, and 3) optimal pose tracking functionality using knowledge of the relative spacecraft states. The development process incorporated the concept of sensor system bandwidth to address the sometimes unclear or misleading specifications of update rate and measurement delay often cited for rendezvous sensors. Because relative navigation sensors provide the measured feedback to the spacecraft GN&C, we propose a new method of specifying the performance of these sensors to better enable a full assessment of a given sensor in the closed-loop control for any given vehicle. This approach, and the tools and methods enabling it, permitted a rapid and rigorous development and verification of the pose tracking functionality. The complete system was then integrated and demonstrated in the MDA space vision facility using the flight-representative engineering model RLS lidar sensor.

Allen, Andrew C. M.; Langley, Christopher; Mukherji, Raja; Taylor, Allen B.; Umasuthan, Manickam; Barfoot, Timothy D.

2008-05-01

23

Automated rendezvous and docking with video imagery  

NASA Technical Reports Server (NTRS)

For rendezvous and docking, assessing and tracking relative orientation is necessary within a minimum approach distance. Special target light patterns have previously been considered for use with video sensors for ease of determining relative orientation. A generalization of those approaches is addressed. At certain ranges, the entire structure of the target vehicle constitutes an acceptable target; at closer ranges, substructures will suffice. Acting on the same principle as the human intelligence, these structures can be compared with a memory model to assess the relative orientation and range. Models for comparison are constructed from a CAD facet model and current imagery. This approach requires fast image handling, projection, and comparison techniques which rely on rapidly developing parallel processing technology. Relative orientation and range assessment consists of successful comparison of the perceived target aspect with a known aspect. Generating a known projection from a model within required times, say subsecond times, is only now approaching feasibility. With this capability, rates of comparison used by the human brain can be approached and arbitrary known structures can be compared in reasonable times. Future space programs will have access to powerful computation devices which far exceed even this capability. For example, the possibility will exist to assess unknown structures and then control rendezvous and docking, all at very fast rates. The first step which has the current utility, namely applying this to known structures, is taken.

Rodgers, Mike; Kennedy, Larry Z.

1991-01-01

24

Hydra Rendezvous and Docking Sensor  

NASA Technical Reports Server (NTRS)

The U.S. technology to support a CEV AR&D activity is mature and was developed by NASA and supporting industry during an extensive research and development program conducted during the 1990's and early 2000 time frame at the Marshall Space Flight Center. Development and demonstration of a rendezvous/docking sensor was identified early in the AR&D Program as the critical enabling technology that allows automated proxinity operations and docking. A first generation rendezvous/docking sensor, the Video Guidance Sensor (VGS) was developed and successfully flown on STS 87 and again on STS 95, proving the concept of a video-based sensor. Advances in both video and signal processing technologies and the lessons learned from the two successful flight experiments provided a baseline for the development of a new generation of video based rendezvous/docking sensor. The Advanced Video Guidance Sensor (AVGS) has greatly increased performance and additional capability for longer-range operation. A Demonstration Automatic Rendezvous Technology (DART) flight experiment was flown in April 2005 using AVGS as the primary proximity operations sensor. Because of the absence of a docking mechanism on the target satellite, this mission did not demonstrate the ability of the sensor to coltrold ocking. Mission results indicate that the rendezvous sensor operated successfully in "spot mode" (2 km acquisition of the target, bearing data only) but was never commanded to "acquire and track" the docking target. Parts obsolescence issues prevent the construction of current design AVGS units to support the NASA Exploration initiative. This flight proven AR&D technology is being modularized and upgraded with additional capabilities through the Hydra project at the Marshall Space Flight Center. Hydra brings a unique engineering approach and sensor architecture to the table, to solve the continuing issues of parts obsolescence and multiple sensor integration. This paper presents an approach to sensor hardware trades, to address the needs of future vehicles that may rendezvous and dock with the International Space Station (ISS). It will also discuss approaches for upgrading AVGS to address parts obsolescence, and concepts for modularizing the sensor to provide configuration flexibility for multiple vehicle applications. Options for complementary sensors to be integrated into the multi-head Hydra system will also be presented. Complementary sensor options include ULTOR, a digital image correlator system that could provide relative six-degree-of-freedom information independently from AVGS, and time-of-flight sensors, which determine the range between vehicles by timing pulses that travel from the sensor to the target and back. Common targets and integrated targets, suitable for use with the multi-sensor options in Hydra, will also be addressed.

Roe, Fred; Carrington, Connie

2007-01-01

25

Tank-treading, swinging, and tumbling of elastic capsules  

NASA Astrophysics Data System (ADS)

It is well known that deformable capsules, vesicles, and red blood cells undergo tank-treading or tumbling motion when freely suspended in shear flows. Recent experiments have shown the existence of a trembling or vacillating-breathing mode as well. Here we present three-dimensional simulations on the dynamics of elastic capsules in shear flow. Our objective is to investigate these different regimes of capsule dynamics, and the coupling between the shape deformation and orientation dynamics. By progressively increasing the viscosity ratio of the internal-to-external fluids at low shear rates, we predict the three distinct modes of motion: a swinging or oscillatory (OS) mode, a vacillating-breathing (VB) mode, and a pure tumbling mode (TU). We show how the coupling between the shape deformation and orientation dynamics influences the transition from the OS to VB to TU modes. At higher shear rates, we predict three new classes of transient motions during which the capsule switches from one mode to the other over time as (i) VB to OS, (ii) TU to VB to OS, and (iii) TU to VB. Phase diagrams showing various regimes are presented.

Bagchi, Prosenjit; Murthy Kalluri, R.

2009-11-01

26

STS-134 Re-Rendezvous Design History  

NASA Technical Reports Server (NTRS)

In preparation to provide the capability for the Orion spacecraft to rendezvous with the International Space Station (ISS), a new suite of relative navigation sensors are in development and will be tested on one of the final Space Shuttle missions to ISS. The National Aeronautics and Space Administration (NASA) commissioned a flight test of prototypes of the instruments on STS-134, in order to test their performance in the space environment during the nominal rendezvous and docking, as well as a re-rendezvous dedicated to testing the prototype sensors following the undocking of the Space Shuttle Orbiter at the end of the mission. Unlike the initial rendezvous and docking, the re-rendezvous profile would replicate the newly designed Orion coelliptic approach trajectory, something never before attempted with the Shuttle Orbiter. Therefore, there were a number of new parameters that needed to be conceived of, designed, and tested for this re-rendezvous to make the flight test successful. And all of this work had to be integrated with the normal operations of the ISS and Shuttle and had to conform to the constraints of the mission and vehicles. The result of this work is a separation and re-rendezvous trajectory design that will prove not only the design of the relative navigation sensors for the Orion vehicle, but also will serve as a proof of concept for the Orion rendezvous trajectory itself. This document presents the analysis and decision making process involved in attaining the final STS-134 re-rendezvous design.

Stuit, Timothy D.

2011-01-01

27

Unsteady aerodynamics of fluttering and tumbling plates  

NASA Astrophysics Data System (ADS)

We investigate the aerodynamics of freely falling plates in a quasi-two-dimensional flow at Reynolds number of 10(3) , which is typical for a leaf or business card falling in air. We quantify the trajectories experimentally using high-speed digital video at sufficient resolution to determine the instantaneous plate accelerations and thus to deduce the instantaneous fluid forces. We compare the measurements with direct numerical solutions of the two-dimensional Navier Stokes equation. Using inviscid theory as a guide, we decompose the fluid forces into contributions due to acceleration, translation, and rotation of the plate. For both fluttering and tumbling we find that the fluid circulation is dominated by a rotational term proportional to the angular velocity of the plate, as opposed to the translational velocity for a glider with fixed angle of attack. We find that the torque on a freely falling plate is small, i.e. the torque is one to two orders of magnitude smaller than the torque on a glider with fixed angle of attack. Based on these results we revise the existing ODE models of freely falling plates. We get access to different kinds of dynamics by exploring the phase diagram spanned by the Reynolds number, the dimensionless moment of inertia, and the thickness-to-width ratio. In agreement with previous experiments, we find fluttering, tumbling, and apparently chaotic motion. We further investigate the dependence on initial conditions and find brief transients followed by periodic fluttering described by simple harmonics and tumbling with a pronounced period-two structure. Near the cusp-like turning points, the plates elevate, a feature which would be absent if the lift depended on the translational velocity alone.

Andersen, A.; Pesavento, U.; Wang, Z. Jane

2005-10-01

28

Orbiter Servicer Rendezvous Simulation (ORSIM)  

NASA Astrophysics Data System (ADS)

Orbiter Servicer Rendezvous Simulation (ORSIM) is an automated tool that simulates sequential transfer maneuvers of an orbital maneuvering vehicle (OMV) transporting orbital replaceable units from a space-based depot, or logistics platform, to higher altitude SDI sdatellites. ORSIM calculates OMV energy expenditures (velocity changes) and event histories for various combinations of user-selected orbital transfer maneuvers. Additionally, ORSIM determines the optimal configuration/quantities of logistics platforms and OMVs which conform to the dynamics of differential nodal precession, given user-prescribed values of the scheduled maintenance cycle and required servicing times. ORSIM is coded in FORTRAN-77 and is resident on an IBM PC/AT.

Amato, Amiel; Hoffman, Mickie D.

29

The Comet Rendezvous Asteroid Flyby project  

NASA Technical Reports Server (NTRS)

The first Mariner Mark II (MMII) mission, the Comet Rendezvous Asteroid Flyby (CRAF), is described in detail. The comet Tempe 2 has been selected as the rendezvous target. The CRAF payload will include a cometary retarding ion mass spectrometer, a cometary ice and dust experiment, a penetrator/lander, a thermal IR radiometer, and a visual IR mapping spectrometer.

Draper, Ronald F.

1987-01-01

30

Boom Rendezvous Alternative Docking Approach  

NASA Technical Reports Server (NTRS)

Space rendezvous and docking has always been attempted with primarily one philosophic methodology. The slow matching of one vehicle's orbit by a second vehicle and then a final closing sequence that ends in matching the orbits with perfect precision and with near zero relative velocities. The task is time consuming, propellant intensive, risk inherent (plume impingement, collisions, fuel depletion, etc.) and requires substantial hardware mass. The historical background and rationale as to why this approach is used is discussed in terms of the path-not-taken and in light of an alternate methodology. Rendezvous and docking by boom extension is suggested to have inherent advantages that today s technology can readily exploit. Extension from the primary spacecraft, beyond its inherent large inertia, allows low inertia connections to be made rapidly and safely. Plume contamination issues are eliminated as well as the extra propellant mass and risk required for the final thruster (docking) operations. Space vehicle connection hardware can be significantly lightened. Also, docking sensors and controls require less fidelity; allowing them to be more robust and less sensitive. It is the potential safety advantage and mission risk reduction that makes this approach attractive, besides the prospect of nominal time and mass savings.

Bonometti, Joseph A.

2006-01-01

31

Rendezvous navigation for a two spacecraft stable orbit rendezvous in a small radius translunar halo orbit  

Microsoft Academic Search

A two-spacecraft terminal phase rendezvous navigation filter is examined for the circular restricted three-body problem. The relevant equations of motion are presented and the rendezvous navigation filter developed. The traditional passive target-active chaser vehicle relationship is used throughout this research. The rendezvous navigation filter is demonstrated using a small radius translunar halo orbit. Nonlinear simulation results validate the filter design

Brian L. Jones; Robert H. Bishop

1993-01-01

32

Red Blood Cells and Other Nonspherical Capsules in Shear Flow: Oscillatory Dynamics and the Tank-Treading-to-Tumbling Transition  

NASA Astrophysics Data System (ADS)

We consider the motion of red blood cells and other nonspherical microcapsules dilutely suspended in a simple shear flow. Our analysis indicates that depending on the viscosity, membrane elasticity, geometry, and shear rate, the particle exhibits either tumbling, tank-treading of the membrane about the viscous interior with periodic oscillations of the orientation angle, or intermittent behavior in which the two modes occur alternately. For red blood cells, we compute the complete phase diagram and identify a novel tank-treading-to-tumbling transition as the shear rate decreases. Observations of such motions coupled with our theoretical framework may provide a sensitive means of assessing capsule properties.

Skotheim, J. M.; Secomb, T. W.

2007-02-01

33

Hubble Space Telescope Servicing Mission 3A Rendezvous Operations  

NASA Technical Reports Server (NTRS)

The Hubble Space Telescope (HST) hardware complement includes six gas bearing, pulse rebalanced rate integrating gyros, any three of which are sufficient to conduct the science mission. After the loss of three gyros between April 1997 and April 1999 due to a known corrosion mechanism, NASA decided to split the third HST servicing mission into SM3A, accelerated to October 1999, and SM3B, scheduled for November 2001. SM3A was developed as a quick turnaround 'Launch on Need' mission to replace all six gyros. Loss of a fourth gyro in November 1999 caused HST to enter Zero Gyro Sunpoint (ZGSP) safemode, which uses sun sensors and magnetometers for attitude determination and momentum bias to maintain attitude stability during orbit night. Several instances of large attitude excursions during orbit night were observed, but ZGSP performance was adequate to provide power-positive sun pointing and to support low gain antenna communications. Body rates in ZGSP were estimated to exceed the nominal 0.1 deg/sec rendezvous limit, so rendezvous operations were restructured to utilize coarse, limited life, Retrieval Mode Gyros (RMGs) under Hardware Sunpoint (HWSP) safemode. Contingency procedures were developed to conduct the rendezvous in ZGSP in the event of RMGA or HWSP computer failure. Space Shuttle Mission STS-103 launched on December 19, 1999 after a series of weather and Shuttle-related delays. After successful rendezvous and grapple under HWSP/RMGA, the crew changed out all six gyros. Following deploy and systems checkout, HST returned to full science operations.

Lee, S.; Anandakrishnan, S.; Connor, C.; Moy, E.; Smith, D.; Myslinski, M.; Markley, L.; Vernacchio, A.

2001-01-01

34

Rendezvous and Docking for Space Exploration  

NASA Technical Reports Server (NTRS)

To achieve the exploration goals, new approaches to exploration are being envisioned that include robotic networks, modular systems, pre-positioned propellants and in-space assembly in Earth orbit, Lunar orbit and other locations around the cosmos. A fundamental requirement for rendezvous and docking to accomplish in-space assembly exists in each of these locations. While existing systems and technologies can accomplish rendezvous and docking in low earth orbit, and rendezvous and docking with crewed systems has been successfully accomplished in low lunar orbit, our capability must extend toward autonomous rendezvous and docking. To meet the needs of the exploration vision in-space assembly requiring both crewed and uncrewed vehicles will be an integral part of the exploration architecture. This paper focuses on the intelligent application of autonomous rendezvous and docking technologies to meet the needs of that architecture. It also describes key technology investments that will increase the exploration program's ability to ensure mission success, regardless of whether the rendezvous are fully automated or have humans in the loop.

Machula, M. F.; Crain, T.; Sandhoo, G. S.

2005-01-01

35

The Rendezvous Monitoring Display Capabilities of the Rendezvous and Proximity Operations Program  

NASA Technical Reports Server (NTRS)

The Rendezvous and Proximity Operations Program (RPOP) is a laptop computer- based relative navigation tool and piloting aid that was developed during the Space Shuttle program. RPOP displays a graphical representation of the relative motion between the target and chaser vehicles in a rendezvous, proximity operations and capture scenario. After being used in over 60 Shuttle rendezvous missions, some of the RPOP display concepts have become recognized as a minimum standard for cockpit displays for monitoring the rendezvous task. To support International Space Station (ISS) based crews in monitoring incoming visiting vehicles, RPOP has been modified to allow crews to compare the Cygnus visiting vehicle s onboard navigated state to processed range measurements from an ISS-based, crew-operated Hand Held Lidar sensor. This paper will discuss the display concepts of RPOP that have proven useful in performing and monitoring rendezvous and proximity operations.

Brazzel, Jack; Spehar, Pete; Clark, Fred; Foster, Chris; Eldridge, Erin

2013-01-01

36

Rendezvous radar for the orbital maneuvering vehicle  

NASA Technical Reports Server (NTRS)

The Rendezvous Radar Set (RRS) was designed at Motorola's Strategic Electronics Division in Chandler, Arizona, to be a key subsystem aboard NASA's Orbital Maneuvering Vehicle (OMV). The unmanned OMV, which was under development at TRW's Federal Systems Division in Redondo Beach, California, was designed to supplement the Shuttle's satellite delivery, retrieval, and maneuvering activities. The RRS was to be used to locate and then provide the OMV with vectoring information to the target satellite (or Shuttle or Space Station) to aid the OMV in making a minimum fuel consumption approach and rendezvous. The OMV development program was halted by NASA in 1990 just as parts were being ordered for the RRS engineering model. The paper presented describes the RRS design and then discusses new technologies, either under development or planned for development at Motorola, that can be applied to radar or alternative sensor solutions for the Automated Rendezvous and Capture problem.

Locke, John W.; Olds, Keith A.; Quaid, Thomas

1991-01-01

37

Modeling E. coli Tumbles by Rotational Diffusion. Implications for Chemotaxis  

PubMed Central

The bacterium Escherichia coli in suspension in a liquid medium swims by a succession of runs and tumbles, effectively describing a random walk. The tumbles randomize incompletely, i.e. with a directional persistence, the orientation taken by the bacterium. Here, we model these tumbles by an active rotational diffusion process characterized by a diffusion coefficient and a diffusion time. In homogeneous media, this description accounts well for the experimental reorientations. In shallow gradients of nutrients, tumbles are still described by a unique rotational diffusion coefficient. Together with an increase in the run length, these tumbles significantly contribute to the net chemotactic drift via a modulation of their duration as a function of the direction of the preceding run. Finally, we discuss the limits of this model in propagating concentration waves characterized by steep gradients. In that case, the effective rotational diffusion coefficient itself varies with the direction of the preceding run. We propose that this effect is related to the number of flagella involved in the reorientation process.

Saragosti, Jonathan; Silberzan, Pascal; Buguin, Axel

2012-01-01

38

Artist's rendering of Lunar Ascent and Rendezvous  

NASA Technical Reports Server (NTRS)

Lunar Ascent and Rendezvous: After the asstronauts return to the spacecraft and rest for several hours, they fire the ascent engine to leave the Moon and rejoin the Command Module. The descent stage remains on the Moon and the ascent stage is ejected after docking and transfer back to the Command Module.

1969-01-01

39

Multiple NEO Rendezvous Using Solar Sail Propulsion  

NASA Technical Reports Server (NTRS)

The NASA Marshall Space Flight Center (MSFC) Advanced Concepts Office performed an assessment of the feasibility of using a near-term solar sail propulsion system to enable a single spacecraft to perform serial rendezvous operations at multiple Near Earth Objects (NEOs) within six years of launch on a small-to-moderate launch vehicle. The study baselined the use of the sail technology demonstrated in the mid-2000 s by the NASA In-Space Propulsion Technology Project and is scheduled to be demonstrated in space by 2014 as part of the NASA Technology Demonstration Mission Program. The study ground rules required that the solar sail be the only new technology on the flight; all other spacecraft systems and instruments must have had previous space test and qualification. The resulting mission concept uses an 80-m X 80-m 3-axis stabilized solar sail launched by an Athena-II rocket in 2017 to rendezvous with 1999 AO10, Apophis and 2001 QJ142. In each rendezvous, the spacecraft will perform proximity operations for approximately 30 days. The spacecraft science payload is simple and lightweight; it will consist of only the multispectral imager flown on the Near Earth Asteroid Rendezvous (NEAR) mission to 433 Eros and 253 Mathilde. Most non-sail spacecraft systems are based on the Messenger mission spacecraft. This paper will describe the objectives of the proposed mission, the solar sail technology to be employed, the spacecraft system and subsystems, as well as the overall mission profile.

Johnson, Les; Alexander, Leslie; Fabisinski, Leo; Heaton, Andy; Miernik, Janie; Stough, Rob; Wright, Roosevelt; Young, Roy

2012-01-01

40

Optical Signature Analysis of Tumbling Rocket Bodies via Laboratory Measurements  

NASA Technical Reports Server (NTRS)

The NASA Orbital Debris Program Office has acquired telescopic lightcurve data on massive intact objects, specifically spent rocket bodies, in order to ascertain tumble rates in support of the Active Debris Removal (ADR) task to help remediate the LEO environment. Rotation rates are needed to plan and develop proximity operations for potential future ADR operations. To better characterize and model optical data acquired from ground-based telescopes, the Optical Measurements Center (OMC) at NASA/JSC emulates illumination conditions in space using equipment and techniques that parallel telescopic observations and source-target-sensor orientations. The OMC employs a 75-watt Xenon arc lamp as a solar simulator, an SBIG CCD camera with standard Johnson/Bessel filters, and a robotic arm to simulate an object's position and rotation. The light source is mounted on a rotary arm, allowing access any phase angle between 0 -- 360 degrees. The OMC does not attempt to replicate the rotation rates, but focuses on how an object is rotating as seen from multiple phase angles. The two targets studied are scaled (1:48), SL-8 Cosmos 3M second stages. The first target is painted in the standard government "gray" scheme and the second target is primary white, as used for commercial missions. This paper summarizes results of the two scaled rocket bodies, each rotated about two primary axes: (a) a spin-stabilized rotation and (b) an end-over-end rotation. The two rotation states are being investigated as a basis for possible spin states of rocket bodies, beginning with simple spin states about the two primary axes. The data will be used to create a database of potential spin states for future works to convolve with more complex spin states. The optical signatures will be presented for specific phase angles for each rocket body and shown in conjunction with acquired optical data from multiple telescope sources.

Cowardin, H.; Lederer, S.; Liou, J.-C.

2012-01-01

41

76 FR 2076 - Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Tumbling Creek...  

Federal Register 2010, 2011, 2012, 2013

...DEPARTMENT OF THE INTERIOR Fish and Wildlife Service 50...Critical Habitat for Tumbling Creek Cavesnail AGENCY: Fish and Wildlife Service...SUMMARY: We, the U.S. Fish and Wildlife Service...habitat for the Tumbling Creek cavesnail (Antrobia...

2011-01-12

42

Aquapod: Prototype design of an amphibious tumbling robot  

Microsoft Academic Search

As mobile robots decrease in size so does their ability to traverse rough terrain. New forms of locomotion beyond the basic wheel are being explored to overcome this fault. This paper expands on the mechanical design of a previous robot with a high mobility-to-size ratio. To accomplish high mobility the robot uses tumbling as its form of locomotion. By actively

Andrew Carlson; Nikos Papanikolopoulos

2011-01-01

43

Designing the STS-134 Re-Rendezvous: A Preparation for Future Crewed Rendezvous Missions  

NASA Technical Reports Server (NTRS)

In preparation to provide the capability for the Orion spacecraft, also known as the Multi-Purpose Crew Vehicle (MPCV), to rendezvous with the International Space Station (ISS) and future spacecraft, a new suite of relative navigation sensors are in development and were tested on one of the final Space Shuttle missions to ISS. The National Aeronautics and Space Administration (NASA) commissioned a flight test of prototypes of the Orion relative navigation sensors on STS-134, in order to test their performance in the space environment during the nominal rendezvous and docking, as well as a re-rendezvous dedicated to testing the prototype sensors following the undocking of the Space Shuttle orbiter at the end of the mission. Unlike the rendezvous and docking at the beginning of the mission, the re-rendezvous profile replicates the newly designed Orion coelliptic approach trajectory, something never before attempted with the shuttle orbiter. Therefore, there were a number of new parameters that needed to be conceived of, designed, and tested for this rerendezvous to make the flight test successful. Additionally, all of this work had to be integrated with the normal operations of the ISS and shuttle and had to conform to the constraints of the mission and vehicles. The result of this work is a separation and rerendezvous trajectory design that would not only prove the design of the relative navigation sensors for the Orion vehicle, but also would serve as a proof of concept for the Orion rendezvous trajectory itself. This document presents the analysis and decision making process involved in attaining the final STS-134 re-rendezvous design.

Stuit, Timothy D.

2011-01-01

44

Concept definition study for recovery of tumbling satellites. Volume 2: Supporting research and technology report  

NASA Technical Reports Server (NTRS)

A number of areas of research and laboratory experiments were identified which could lead to development of a cost efficient remote, disable satellite recovery system. Estimates were planned of disabled satellite motion. A concept is defined as a Tumbling Satellite Recovery kit which includes a modular system, composed of a number of subsystem mechanisms that can be readily integrated into varying combinations. This would enable the user to quickly configure a tailored remote, disabled satellite recovery kit to meet a broad spectrum of potential scenarios. The capability was determined of U.S. Earth based satellite tracking facilities to adequately determine the orientation and motion rates of disabled satellites.

Cable, D. A.; Derocher, W. L., Jr.; Cathcart, J. A.; Keeley, M. G.; Madayev, L.; Nguyen, T. K.; Preese, J. R.

1986-01-01

45

Laser space rendezvous and docking tradeoff  

NASA Technical Reports Server (NTRS)

A spaceborne laser radar (LADAR) was configured to meet the requirements for rendezvous and docking with a cooperative object in synchronous orbit. The LADAR, configurated using existing pulsed CO2 laser technology and a 1980 system technology baseline, is well suited for the envisioned space tug missions. The performance of a family of candidate LADARS was analyzed. Tradeoff studies as a function of size, weight, and power consumption were carried out for maximum ranges of 50, 100, 200, and 300 nautical miles. The investigation supports the original contention that a rendezvous and docking LADAR can be constructed to offer a cost effective and reliable solution to the envisioned space missions. In fact, the CO2 ladar system offers distinct advantages over other candidate systems.

Adelman, S.; Levinson, S.; Raber, P.; Weindling, F.

1974-01-01

46

Simulation models for autonomous rendezvous and capture  

Microsoft Academic Search

Autonomous rendezvous and capture (AR&C) is a critical space technology with significant application to a variety of missions. Martin Marietta Astronautics Group (MMAG) has been developing AR&C technical capability in support of several recent NASA contracts. The use of AR&C for the Mars Rover\\/Sample Return (MRSR) mission was studied through a contract with JSC. Incorporation of AR&C in the Space

Nick G. Smith; Jim A. McKinnis; Sid M. Early

1991-01-01

47

Simulations of the tumbling and tank treading motions of cells immersed in fluid flow  

NASA Astrophysics Data System (ADS)

We describe the development of computational techniques to study the deformation of cells modeled as liquid capsules enclosed by thin shells suspended in fluid flow. Computations are performed for cells with spherical, ellipsoidal and biconcave unstressed shapes over a wide range of the dimensionless shear rate and for a broad range of the ratio of the internal to surrounding fluid viscosities. Results for small deformations of initially spherical capsules are in quantitative agreement with analytic predictions. Under large deformations, the results show that spherical capsules deform to stationary configurations and the membranes undergo steady tank-treading motion. For capsules of ellipsoidal and biconcave unstressed shapes, the capsules exhibit either tumbling, tank-treading of the membrane about the viscous interior with periodic oscillations of the orientation angle, or intermittent behaviour in which the two modes occur alternately depending on the viscosity, membrane elasticity and shear rate. Our method provides an efficient way to study the tank-treading-to-tumbling transition of red blood cells in shear flows as the shear rate decreases. Observations of such motions may provide a sensitive mean of assessing cell membrane properties. Finally, we also describe simulations of the long-time behavior of a dense suspension of red-blood cells in a micro-channel to illustrate the efficiency of the method.

Chiam, Keng-Hwee; Le, Duc Vinh

2009-11-01

48

Rendezvous radar requirements analysis for mission 3B  

NASA Technical Reports Server (NTRS)

Data are presented verifying the compatibility of currently proposed rendezvous radar measurement accuracies with Mission 3B rendezvous requirements. In addition, data presented indicate a potential for increasing the acceptable time lag between termination of thrusting and availability of accurate measurement data. Additional investigation is recommended to define any acceptable time lag above the current proposed value. Finally, Mission 3B rendezvous performance is shown to be sensitive to variations in the relative downrange position dispersions at insertion. It is therefore recommended that insertion relative state dispersions used in studies of 3B rendezvous be reviewed when results of 3B ascent dispersion studies are available.

Hutchison, W. L.; Jones, A. K.

1975-01-01

49

KU-Band rendezvous radar performance computer simulation model  

NASA Technical Reports Server (NTRS)

The preparation of a real time computer simulation model of the KU band rendezvous radar to be integrated into the shuttle mission simulator (SMS), the shuttle engineering simulator (SES), and the shuttle avionics integration laboratory (SAIL) simulator is described. To meet crew training requirements a radar tracking performance model, and a target modeling method were developed. The parent simulation/radar simulation interface requirements, and the method selected to model target scattering properties, including an application of this method to the SPAS spacecraft are described. The radar search and acquisition mode performance model and the radar track mode signal processor model are examined and analyzed. The angle, angle rate, range, and range rate tracking loops are also discussed.

Griffin, J. W.

1980-01-01

50

Coping with perturbations to a layout somersault in tumbling.  

PubMed

Tumbling is a dynamic movement requiring control of the linear and angular momenta generated during the approach and takeoff phases. Both of these phases are subject to some variability even when the gymnast is trying to perform a given movement repeatedly. This paper used a simulation model of tumbling takeoff to establish how well gymnasts can cope with perturbations of the approach and takeoff phases. A five segment planar simulation model with torque generators at each joint was developed to simulate tumbling takeoffs. The model was customised to an elite gymnast by determining subject specific inertia and torque parameters and a simulation was produced which closely matched a performance of a layout somersault by the gymnast. The performance of a layout somersault was found to be sensitive to the approach characteristics and the activation timings but relatively insensitive to the elasticity of the track and maximum muscle strength. Appropriate variation of the activation timings used during the takeoff phase was capable of coping with moderate perturbations of the approach characteristics. A model of aerial movement established that variation of body configuration in the flight phase was capable of adjusting for takeoff perturbations that would lead to rotation errors of up to 8%. Providing the errors in perceiving approach characteristics are less than 5% or 5 degrees and the errors in timing activations are less than 7ms, perturbations in the approach can be accommodated using adjustments during takeoff and flight. PMID:12757800

King, M A; Yeadon, M R

2003-07-01

51

Autonomous Rendezvous and Docking Conference, volume 2  

NASA Technical Reports Server (NTRS)

Autonomous Rendezvous and Docking (ARD) will be a requirement for future space programs. Clear examples include satellite servicing, repair, recovery, and reboost in the near term, and the longer range lunar and planetary exploration programs. ARD will permit more aggressive unmanned space activities, while providing a valuable operational capability for manned missions. The purpose of the conference is to identify the technologies required for an on-orbit demonstration of ARD, assess the maturity of those technologies, and provide the necessary insight for a quality assessment of programmatic management, technical, schedule, and cost risks.

1990-01-01

52

Rendezvous Planning in Wireless Sensor Networks with Mobile Elements  

Microsoft Academic Search

Recent research shows that significant energy saving can be achieved in wireless sensor networks by using mobile elements (MEs) capable of carrying data mechanically. However, the low movement speed of MEs hinders their use in data-intensive sensing applications with temporal constraints. To address this issue, we propose a rendezvous-based approach in which a subset of nodes serves as the rendezvous

Guoliang Xing; Tian Wang; Zhihui Xie; Weijia Jia

2008-01-01

53

Radar Performance Improvement. Angle Tracking Modification to Fire Control Radar System for Space Shuttle Rendezvous  

NASA Technical Reports Server (NTRS)

The AN/APQ-153 fire control radar modified to provide angle tracking was evaluated for improved performance. The frequency agile modifications are discussed along with the range-rate improvement modifications, and the radar to computer interface. A parametric design and comparison of noncoherent and coherent radar systems are presented. It is shown that the shuttle rendezvous range and range-rate requirements can be made by a Ku-Band noncoherent pulse radar.

Little, G. R.

1976-01-01

54

Development of Ku-band rendezvous radar tracking and acquisition simulation programs  

NASA Technical Reports Server (NTRS)

The fidelity of the Space Shuttle Radar tracking simulation model was improved. The data from the Shuttle Orbiter Radar Test and Evaluation (SORTE) program experiments performed at the White Sands Missile Range (WSMR) were reviewed and analyzed. The selected flight rendezvous radar data was evaluated. Problems with the Inertial Line-of-Sight (ILOS) angle rate tracker were evaluated using the improved fidelity angle rate tracker simulation model.

1986-01-01

55

Role of methionine in bacterial chemotaxis: requirement for tumbling and involvement in information processing.  

PubMed

Chemotactic responses are mediated by modulation of the frequency of tumbling. Studies with methionine auxotrophs of wild-type Escherichia coli and four mutants which tumble continuously show that methionine or one of its metabolites is involved in the tumbling process. Following removal of methionine, the wild type and two mutants, after various periods of time, became unable to tumble. The presence of constant levels of chemical attractants considerably shortened these periods in the three strains and eliminated tumbling in another mutant. This effect of attractants considerably shortened these periods in the three strains and eliminated tumbling in another mutant. This effect of attractants implies that methionine or some derivative of methionine is also involved in transducing chemical stimuli to bacterial responses. PMID:1105586

Springer, M S; Kort, E N; Larsen, S H; Ordal, G W; Reader, R W; Adler, J

1975-11-01

56

Concept definition study for recovery of tumbling satellites. Volume 1: Executive summary, study results  

NASA Technical Reports Server (NTRS)

The first assessment is made of the design requirements and conceptual definition of a front end kit to be transported on the currently defined Orbital Maneuvering Vehicle (OMV) and the Space Transportation System Shuttle Orbiter, to conduct remote, teleoperated recovery of disabled and noncontrollable, tumbling satellites. Previous studies did not quantify the dynamic characteristics of a tumbling satellite, nor did they appear to address the full spectrum of Tumbling Satellite Recovery systems requirements. Both of these aspects are investigated with useful results.

Cable, D. A.; Derocher, W. L., Jr.; Cathcart, J. A.; Keeley, M. G.; Madayev, L.; Nguyen, T. K.; Preese, J. R.

1986-01-01

57

Rendezvous radar for the orbital maneuvering vehicle  

NASA Technical Reports Server (NTRS)

This paper describes the development of the Rendezvous Radar Set (RRS) for the Orbital Maneuvering Vehicle (OMV) for the National Aeronautics and Space Administration (NASA). The RRS was to be used to locate, and then provide vectoring information to, target satellites (or Shuttle or Space Station) to aid the OMV in making a minimum-fuel-consumption approach and rendezvous. The RRS design is that of an X-Band, all solid-state, monopulse tracking, frequency hopping, pulse-Doppler radar system. The development of the radar was terminated when the OMV prime contract to TRW was terminated by NASA. At the time of the termination, the development was in the circuit design stage. The system design was virtually completed, the PDR had been held. The RRS design was based on Motorola's experiences, both in the design and production of radar systems for the US Army and in the design and production of hi-rel communications systems for NASA space programs. Experience in these fields was combined with the latest digital signal processor and micro-processor technology to design a light-weight, low-power, spaceborne radar. The antenna and antenna positioner (gimbals) technology developed for the RRS is now being used in the satellite-to-satellite communication link design for Motorola's Iridium telecommunications system.

Locke, John W.; Olds, Keith; Parks, Howard

1991-01-01

58

Demonstration of Autonomous Rendezvous Technology (DART) Project Summary  

NASA Technical Reports Server (NTRS)

Since the 1960's, NASA has performed numerous rendezvous and docking missions. The common element of all US rendezvous and docking is that the spacecraft has always been piloted by astronauts. Only the Russian Space Program has developed and demonstrated an autonomous capability. The Demonstration of Autonomous Rendezvous Technology (DART) project currently funded under NASA's Space Launch Initiative (SLI) Cycle I, provides a key step in establishing an autonomous rendezvous capability for the United States. DART's objective is to demonstrate, in space, the hardware and software necessary for autonomous rendezvous. Orbital Sciences Corporation intends to integrate an Advanced Video Guidance Sensor and Autonomous Rendezvous and Proximity Operations algorithms into a Pegasus upper stage in order to demonstrate the capability to autonomously rendezvous with a target currently in orbit. The DART mission will occur in April 2004. The launch site will be Vandenburg AFB and the launch vehicle will be a Pegasus XL equipped with a Hydrazine Auxiliary Propulsion System 4th stage. All mission objectives will be completed within a 24 hour period. The paper provides a summary of mission objectives, mission overview and a discussion on the design features of the chase and target vehicles.

Rumford, TImothy E.

2003-01-01

59

Autonomous rendezvous and capture development infrastructure  

NASA Technical Reports Server (NTRS)

In the development of the technology for autonomous rendezvous and docking, key infrastructure capabilities must be used for effective and economical development. This involves facility capabilities, both equipment and personnel, to devise, develop, qualify, and integrate ARD elements and subsystems into flight programs. One effective way of reducing technical risks in developing ARD technology is the use of the ultimate test facility, using a Shuttle-based reusable free-flying testbed to perform a Technology Demonstration Test Flight which can be structured to include a variety of additional sensors, control schemes, and operational approaches. This conceptual testbed and flight demonstration will be used to illustrate how technologies and facilities at MSFC can be used to develop and prove an ARD system.

Bryan, Thomas C.; Roe, Fred; Coker, Cindy; Nelson, Pam; Johnson, B.

1991-01-01

60

TALON and CRADLE: Systems for the rescue of tumbling spacecraft and astronauts  

NASA Technical Reports Server (NTRS)

Advanced pressure suit and tool designs are beginning to allow extravehicular astronauts to repair space vehicles and so increase mission life and system reliability. A common spacecraft failure that is a severe challenge to the rescue mission planner is loss of attitude control resulting in tumbling motion. If an extravehicular astronaut flying the Manned Maneuvering Unit (MMU) 'falls' into a tumble, the result could be loss of life. TALON (Tumble Arresting Large Oscillation Nullifier) is a device capable of capturing a target in an uncontrolled three-axis tumble. CRADLE (Concentric Rotating Astronaut Detumble Lifesaving Equipment) is a similar device sized to rescue a suited astronaut. The two rescue vehicles work on the same basic principle. They are structural shells with articulated limbs which can surround a tumbling target and thus align both the chaser and target centers of mass (CM).

Idle, Dunning, V

1991-01-01

61

Method for detecting a tumble flow in a cylinder chamber of an internal combustion engine  

US Patent & Trademark Office Database

For the purpose of detecting a tumble flow in a cylinder chamber of an internal combustion engine, with a characteristic tumble value being determined as a quotient from an angular velocity .omega..sub.FK of the tumble movement and an angular velocity .omega..sub.Mot of the internal combustion engine, a method is proposed in which the asymmetry of a flow field w.sub.LDA in the cylinder chamber is detected for a predetermined number of measuring points i with a differential measuring method on a flow test stand and the characteristic tumble value is determined as a result of the asymmetry of the flow field w.sub.LDA. Characteristic tumble values can thus be determined in a simple and practical manner.

2002-05-07

62

Apollo experience report: Lunar module landing radar and rendezvous radar  

NASA Technical Reports Server (NTRS)

A developmental history of the Apollo lunar module landing and rendezvous radar subsystems is presented. The Apollo radar subsystems are discussed from initial concept planning to flight configuration testing. The major radar subsystem accomplishments and problems are discussed.

Rozas, P.; Cunningham, A. R.

1972-01-01

63

Supervised autonomous rendezvous and docking systems technology evaluations  

NASA Technical Reports Server (NTRS)

The Jet Propulsion Laboratory, employing the technology assessment that resulted from the Autonomous Rendezvous and Docking Conference held at the Lyndon B. Johnson Space Center on 15-16 Aug. 1990 as the basis undertook a literature search and contacts with major national and international aerospace companies to perform an assessment of the existing technologies and those that are needed to accomplish supervised autonomous rendezvous and docking in space. The following five issues are covered: (1) lessons learned; (2) technology assessment for navigation and guidance sensors for Autonomous Rendezvous and Docking (AR&D); (3) technology assessment of Guidance, Navigation and Controls (GN&C), techniques for rendezvous and docking; (4) docking mechanisms; and (5) space and ground operations.

Marzwell, Neville I.

1991-01-01

64

Effect of location-awareness on rendezvous behaviour  

Microsoft Academic Search

This paper presents an exploratory field study investigating the behavioral effects of mobile location-aware computing on rendezvousing. Participants took part in one of three mobile device conditions (a mobile phone, a location-aware handheld or both a mobile phone and a location-aware handheld) and completed different rendezvousing scenarios. We present one of the scenarios in depth and discuss the effect of

David Dearman; Kirstie Hawkey; Kori M. Inkpen

2005-01-01

65

Effects of Location-Aware Computing On Rendezvous Behaviour  

Microsoft Academic Search

This paper presents a field study investigating the behavioral effects of mobile location-aware computing on rendezvousing. Participants took part in one of three mobile device conditions (a mobile phone, a location-aware handheld, or both a mobile phone and a location-aware handheld) and completed rendezvousing scenarios. The results reveal key differences in communication patterns between the mediums, and in the type

David Dearman; Kirstie Hawkey; Kori M. Inkpen

66

Shuttle on-orbit rendezvous targeting: Circular orbits  

NASA Technical Reports Server (NTRS)

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

Bentley, E. L.

1972-01-01

67

Low Earth Orbit Rendezvous Strategy for Lunar Missions  

NASA Technical Reports Server (NTRS)

On January 14, 2004 President George W. Bush announced a new Vision for Space Exploration calling for NASA to return humans to the moon. In 2005 NASA decided to use a Low Earth Orbit (LEO) rendezvous strategy for the lunar missions. A Discrete Event Simulation (DES) based model of this strategy was constructed. Results of the model were then used for subsequent analysis to explore the ramifications of the LEO rendezvous strategy.

Cates, Grant R.; Cirillo, William M.; Stromgren, Chel

2006-01-01

68

Robot Acting on Moving Bodies (RAMBO): Interaction with tumbling objects  

NASA Technical Reports Server (NTRS)

Interaction with tumbling objects will become more common as human activities in space expand. Attempting to interact with a large complex object translating and rotating in space, a human operator using only his visual and mental capacities may not be able to estimate the object motion, plan actions or control those actions. A robot system (RAMBO) equipped with a camera, which, given a sequence of simple tasks, can perform these tasks on a tumbling object, is being developed. RAMBO is given a complete geometric model of the object. A low level vision module extracts and groups characteristic features in images of the object. The positions of the object are determined in a sequence of images, and a motion estimate of the object is obtained. This motion estimate is used to plan trajectories of the robot tool to relative locations rearby the object sufficient for achieving the tasks. More specifically, low level vision uses parallel algorithms for image enhancement by symmetric nearest neighbor filtering, edge detection by local gradient operators, and corner extraction by sector filtering. The object pose estimation is a Hough transform method accumulating position hypotheses obtained by matching triples of image features (corners) to triples of model features. To maximize computing speed, the estimate of the position in space of a triple of features is obtained by decomposing its perspective view into a product of rotations and a scaled orthographic projection. This allows use of 2-D lookup tables at each stage of the decomposition. The position hypotheses for each possible match of model feature triples and image feature triples are calculated in parallel. Trajectory planning combines heuristic and dynamic programming techniques. Then trajectories are created using dynamic interpolations between initial and goal trajectories. All the parallel algorithms run on a Connection Machine CM-2 with 16K processors.

Davis, Larry S.; Dementhon, Daniel; Bestul, Thor; Ziavras, Sotirios; Srinivasan, H. V.; Siddalingaiah, Madhu; Harwood, David

1989-01-01

69

Advanced multipurpose rendezvous tracking system study  

NASA Technical Reports Server (NTRS)

Rendezvous and docking (R&D) sensors needed to support Earth orbital operations of vehicles were investigated to determine the form they should take. An R&D sensor must enable an interceptor vehicle to determine both the relative position and the relative attitude of a target vehicle. Relative position determination is fairly straightforward and places few constraints on the sensor. Relative attitude determination, however, is more difficult. The attitude is calculated based on relative position measurements of several reflectors placed in a known arrangement on the target vehicle. The constraints imposed on the sensor by the attitude determination method are severe. Narrow beamwidth, wide field of view (fov), high range accuracy, and fast random scan capability are all required to determine attitude by this method. A consideration of these constraints as well as others imposed by expected operating conditions and the available technology led to the conclusion that the sensor should be a cw optical radar employing a semiconductor laser transmitter and an image dissector receiver.

Laurie, R. J.; Sterzer, F.

1982-01-01

70

Automated Rendezvous and Capture System Development and Simulation for NASA  

NASA Technical Reports Server (NTRS)

The United States does not have an Automated Rendezvous and Capture/Docking (AR and C) capability and is reliant on manned control for rendezvous and docking of orbiting spacecraft. This reliance on the labor intensive manned interface for control of rendezvous and docking vehicles has a significant impact on the cost of the operation of the International Space Station (ISS) and precludes the use of any U.S. expendable launch capabilities for Space Station resupply. The Soviets have the capability to autonomously dock in space, but their system produces a hard docking with excessive force and contact velocity. Automated Rendezvous and Capture/Docking has been identified as a key enabling technology for the Space Launch Initiative (SLI) Program, DARPA Orbital Express and other DOD Programs. The development and implementation of an AR&C capability can significantly enhance system flexibility, improve safety, and lower the cost of maintaining, supplying, and operating the International Space Station. The Marshall Space Flight Center (MSFC) has conducted pioneering research in the development of an automated rendezvous and capture (or docking) (AR and C) system for U.S. space vehicles. This AR&C system was tested extensively using hardware-in-the-loop simulations in the Flight Robotics Laboratory, and a rendezvous sensor, the Video Guidance Sensor was developed and successfully flown on the Space Shuttle on flights STS-87 and STS-95, proving the concept of a video- based sensor. Further developments in sensor technology and vehicle and target configuration have lead to continued improvements and changes in AR&C system development and simulation. A new Advanced Video Guidance Sensor (AVGS) with target will be utilized on the Demonstration of Autonomous Rendezvous Technologies (DART) flight experiment in 2004.

Roe, Fred D.; Howard, Richard T.; Murphy, Leslie

2004-01-01

71

Tank-treading and tumbling frequencies of capsules and red blood cells.  

PubMed

This study is motivated in part by the discrepancy that exists in the literature with regard to the dependence of the tank-treading frequency of red blood cells on the shear rate and suspending medium viscosity. Here we consider three-dimensional numerical simulations of deformable capsules of initially spherical and oblate spheroidal shapes and biconcave discoid representing the red blood cell resting shape. By considering a much broader range of the viscosity ratio (ratio of capsule or cell interior to suspending fluid viscosity), shear rate, and aspect ratio (ratio of minor to major axes) than that considered in the previous experiments, we find several new characteristics of the tank-treading and tumbling frequencies that have not been reported earlier. These new characteristics are the result of the large shape deformation and the coupling between shape and angular oscillations of the capsules or cells. For the spherical and oblate spheroidal capsules, the tank-treading frequency shows a nonmonotonic trend that is characterized by an initial decrease leading to a minimum followed by an increase with increasing viscosity ratio. For red blood cells, we find two regimes of the viscosity dependence of the tank-treading frequency: an exponential regime in which the tank-treading frequency decreases at a slower rate with increasing viscosity ratio, and a logarithmic range in which it decreases at a much faster rate. While this trend agrees well with different theoretical models of shape-preserving capsules, it was not evident in previous experimental results. When the shear rate dependence is considered, the tank-treading frequency of red blood cells and capsules of highly elongated initial shapes exhibits a nonmonotonic trend that is characterized by an initial increase leading to a maximum followed by a sharp decrease with decreasing shear rate. This anomalous behavior of the tank-treading frequency is shown to be due to a breathing-like dynamics of the capsule or cell that is characterized by a repeated emergence and absence of deep, crater-like dimples, and a large swinging motion. We further observe that the tumbling frequency exhibits a decreasing trend with increasing viscosity ratio that is in contrast to the theoretical result for the shape-preserving capsules and is due to the periodic deformation and preferential alignment of the capsules in the extensional quadrant of the flow. PMID:21599293

Yazdani, Alireza Z K; Kalluri, R Murthy; Bagchi, Prosenjit

2011-04-01

72

Spacecraft rendezvous operational considerations affecting vehicle systems design and configuration  

NASA Technical Reports Server (NTRS)

One lesson learned from Orbiting Maneuvering Vehicle (OMV) program experience is that Design Reference Missions must include an appropriate balance of operations and performance inputs to effectively drive vehicle systems design and configuration. Rendezvous trajectory design is based on vehicle characteristics (e.g., mass, propellant tank size, and mission duration capability) and operational requirements, which have evolved through the Gemini, Apollo, and STS programs. Operational constraints affecting the rendezvous final approach are summarized. The two major objectives of operational rendezvous design are vehicle/crew safety and mission success. Operational requirements on the final approach which support these objectives include: tracking/targeting/communications; trajectory dispersion and navigation uncertainty handling; contingency protection; favorable sunlight conditions; acceptable relative state for proximity operations handover; and compliance with target vehicle constraints. A discussion of the ways each of these requirements may constrain the rendezvous trajectory follows. Although the constraints discussed apply to all rendezvous, the trajectory presented in 'Cargo Transfer Vehicle Preliminary Reference Definition' (MSFC, May 1991) was used as the basis for the comments below.

Prust, Ellen E.

1991-01-01

73

Rendezvous and Proximity Operations of the Space Shuttle  

NASA Technical Reports Server (NTRS)

Space Shuttle rendezvous missions present unique challenges that were not fully recognized when the Shuttle was designed. Rendezvous targets could be passive (i.e., no lights or transponders), and not designed to facilitate Shuttle rendezvous, proximity operations, and retrieval. Shuttle reaction control system jet plume impingement on target spacecraft presented induced dynamics, structural loading, and contamination concerns. These issues, along with limited reaction control system propellant in the Shuttle nose, drove a change from the legacy Gemini/Apollo coelliptic profile to a stable orbit profile, and the development of new proximity operations techniques. Multiple scientific and on-orbit servicing missions, and crew exchange, assembly and replenishment flights to Mir and to the International Space Station drove further profile and piloting technique changes. These changes included new proximity operations, relative navigation sensors, and new computer generated piloting cues. However, the Shuttle's baseline rendezvous navigation system has not required modification to place the Shuttle at the proximity operations initiation point for all rendezvous missions flown.

Goodman, John L.

2005-01-01

74

Unsteady aerodynamic forces and torques on falling parallelograms in coupled tumbling-helical motions  

NASA Astrophysics Data System (ADS)

Falling parallelograms exhibit coupled motion of autogyration and tumbling, similar to the motion of falling tulip seeds, unlike maple seeds which autogyrate but do not tumble, or rectangular cards which tumble but do not gyrate. This coupled tumbling and autogyrating motion are robust, when card parameters, such as aspect ratio, internal angle, and mass density, are varied. We measure the three-dimensional (3D) falling kinematics of the parallelograms and quantify their descending speed, azimuthal rotation, tumbling rotation, and cone angle in each falling. The cone angle is insensitive to the variation of the card parameters, and the card tumbling axis does not overlap with but is close to the diagonal axis. In addition to this connection to the dynamics of falling seeds, these trajectories provide an ideal set of data to analyze 3D aerodynamic force and torque at an intermediate range of Reynolds numbers, and the results will be useful for constructing 3D aerodynamic force and torque models. Tracking these free falling trajectories gives us a nonintrusive method for deducing instantaneous aerodynamic forces. We determine the 3D aerodynamic forces and torques based on Newton-Euler equations. The dynamical analysis reveals that, although the angle of attack changes dramatically during tumbling, the aerodynamic forces have a weak dependence on the angle of attack. The aerodynamic lift is dominated by the coupling of translational and rotational velocities. The aerodynamic torque has an unexpectedly large component perpendicular to the card. The analysis of the Euler equation suggests that this large torque is related to the deviation of the tumbling axis from the principle axis of the card.

Varshney, Kapil; Chang, Song; Wang, Z. Jane

2013-05-01

75

Rendezvous missions: From ISS to lunar space station  

NASA Astrophysics Data System (ADS)

There was a lot of experience gained in the rendezvous of different vehicles in the LEO during the years of human space exploration. In the framework of the Apollo program when the astronauts landed on the surface of the Moon, the docking of the Lunar Module launched from the Moon?s surface to the Apollo Command Module was successfully implemented in the near-Moon orbit. Presently many space agencies are considering a return to the Moon. It is necessary to solve the new task of docking the vehicle launched from the Earth to the long-term near-Moon orbital station taking into account specific constraints. Based on the ISS experience the author proposes a number of ballistic rendezvous strategies that provide for docking to the near-Moon orbital station with minimum propellant consumption. The trade-off analysis of the given rendezvous strategies is presented.

Murtazin, Rafail

2014-08-01

76

Endoscopic retrograde cholangiopancreatography with rendezvous cannulation reduces pancreatic injury  

PubMed Central

AIM: To examine whether rendezvous endoscopic retrograde cholangiopancreatography (ERCP) is associated with less pancreatic damage, measured as leakage of proenzymes, than conventional ERCP. METHODS: Patients (n = 122) with symptomatic gallstone disease, intact papilla and no ongoing inflammation, were prospectively enrolled in this case-control designed study. Eighty-one patients were subjected to laparoscopic cholecystectomy and if intraoperative cholangiography suggested common bile duct stones (CBDS), rendezvous ERCP was performed intraoperatively (n = 40). Patients with a negative cholangiogram constituted the control group (n = 41). Another 41 patients with CBDS, not subjected to surgery, underwent conventional ERCP. Pancreatic proenzymes, procarboxypeptidase B and trypsinogen-2 levels in plasma, were analysed at 0, 4, 8 and 24 h. The proenzymes were determined in-house with a double-antibody enzyme linked immunosorbent assay. Pancreatic amylase was measured by an enzymatic colourimetric modular analyser with the manufacturer’s reagents. All samples were blinded at analysis. RESULTS: Post ERCP pancreatitis (PEP) occurred in 3/41 (7%) of the patients cannulated with conventional ERCP and none in the rendezvous group. Increased serum levels indicating pancreatic leakage were significantly higher in the conventional ERCP group compared with the rendezvous ERCP group regarding pancreatic amylase levels in the 4- and 8-h samples (P = 0.0015; P = 0.03), procarboxypeptidase B in the 4- and 8-h samples (P < 0.0001; P < 0.0001) and trypsinogen-2 in the 24-hour samples (P = 0.03). No differences in these markers were observed in patients treated with rendezvous cannulation technique compared with patients that underwent cholecystectomy alone (control group). Post procedural concentrations of pancreatic amylase and procarboxypeptidase B were significantly correlated with pancreatic duct cannulation and opacification. CONCLUSION: Rendezvous ERCP reduces pancreatic enzyme leakage compared with conventional ERCP cannulation technique. Thus, laparo-endoscopic technique can be recommended with the ambition to minimise the risk for post ERCP pancreatitis.

Swahn, Fredrik; Regner, Sara; Enochsson, Lars; Lundell, Lars; Permert, Johan; Nilsson, Magnus; Thorlacius, Henrik; Arnelo, Urban

2013-01-01

77

MultiSensor Testing for Automated Rendezvous and Docking Sensor Testing at the Flight Robotics Lab  

Microsoft Academic Search

The exploration systems architecture defines missions that require rendezvous, proximity operations, and docking (RPOD) of two spacecraft both in low earth orbit (LEO) and in low lunar orbit (LLO). Uncrewed spacecraft must perform automated and\\/or autonomous rendezvous, proximity operations and docking operations (commonly known as AR&D). The crewed missions may also perform rendezvous and docking operations and may require different

Linda L. Brewster; Richard T. Howard; A. S. Johnston; C. Carrington; J. D. Mitchell; S. P. Cryan

2008-01-01

78

Trajectory options for the Comet Rendezvous Asteroid Flyby mission  

NASA Technical Reports Server (NTRS)

The Comet Rendezvous Asteroid Flyby mission is strongly supported by the scientific community. Two major events during the past year have forced a re-analysis of the mission options, with the goal of selecting a baseline mission for launch in 1993. Venus and earth gravity assists can be used to allow rendezvous with comet Tempel 2 in 1996; the scientific potential of the resulting mission is excellent. Although backup mission opportunities have been identified, the significantly longer flight times weaken the scientific appeal of these missions.

Miller, S. L.; Bender, D. F.; Stetson, D. S.; Myers, M. R.

1987-01-01

79

Stable orbit rendezvous for a small radius translunar halo orbit  

Microsoft Academic Search

A two spacecraft terminal phase rendezvous targeting law, which is valid for the three-body problem, is given. The relevant equations of motion are derived and the targeting law developed assuming the traditional target\\/chaser vehicle relationship. The targeting law is demonstrated using a small radius translunar halo orbit. Nonlinear simulation results verify that acceptable performance is obtained. Using these results, the

Brian L. Jones; Robert H. Bishop

1993-01-01

80

Optimal analytic rendezvous using Clohessy-Wiltshire equations  

NASA Technical Reports Server (NTRS)

The optimal solution time that minimizes the sum of the two applied impulses necessary to rendezvous is obtained analytically for the Clohessy-Wiltshire equations with a linear gravity model assumption. A plume impingement inequality constraint on the solution is examined, and an optimal policy is developed. Numerical tests are conducted to verify the analysis and to illustrate the optimal solution algorithm.

Jezewski, D. J.; Donaldson, J. D.

1978-01-01

81

Comet Rendezvous Asteroid Flyby Mission: A Status Report (Abstract Only).  

National Technical Information Service (NTIS)

The Comet Rendezvous Asteroid Flyby (CRAF) mission received a new start in fiscal year 1990. CRAF will match orbits with an active short-period comet and follow it around the Sun, making scientific measurements of the nucleus, coma, and tail. The Imaging ...

P. R. Weissman M. Neugebauer

1991-01-01

82

Autonomous rendezvous and docking for Space Station Freedom  

NASA Technical Reports Server (NTRS)

Viewgraphs on autonomous rendezvous and docking (AR&D) for Space Station Freedom are presented. Topics covered include: requirements for AR&D experience; Comet spacecraft performance; AR&D mission profile; analytical models for approach trajectory, loosely coupled configuration, and contact dynamics; and application to space infrastructure.

Garrison, James L., Jr.; Katzberg, Stephen J.

1993-01-01

83

Test Results for the Automated Rendezvous and Capture System  

NASA Technical Reports Server (NTRS)

The Automated Rendezvous and Capture (AR&C) system was designed and tested at NASA's Marshall Space Flight Center (MSFC) to demonstrate technologies and mission strategies for automated rendezvous and docking of spacecraft in Earth orbit, The system incorporates some of the latest innovations in Global Positioning, System space navigation, laser sensor technologies and automated mission sequencing algorithms. The system's initial design and integration was completed in 1998 and has undergone testing at MSFC. This paper describes the major components of the AR&C system and presents results from the official system tests performed in MSFC's Flight Robotics Laboratory with digital simulations and hardware in the loop tests. The results show that the AR&C system can safely and reliably perform automated rendezvous and docking missions in the absence of system failures with 100 percent success. When system failures are included, the system uses its automated collision avoidance maneuver logic to recover in a safe manner. The primary objective of the AR&C project is to prove that by designing a safe and robust automated system, mission operations cost can be reduced by decreasing the personnel required for mission design, preflight planning and training required for crewed rendezvous and docking missions.

Cruzen, Craig; Dabney, Richard; Lomas, James

1999-01-01

84

Optimal Rendezvous Problem in a Central gravity Field with Drag.  

NASA Astrophysics Data System (ADS)

The work aims at solving the optimal feedback rendezvous problem for a spacecraft moving in a central field of gravity in addition experiencing air drag. We will use the generating function techneque to solve the Hamilton-Jacobi-Bellman equation and compute the optimal control.We will discuss both the hard and soft boundary conditions.

Owis, Ashraf H.

2006-06-01

85

Dynamical properties of nematic liquid crystals subjected to shear flow and magnetic fields: Tumbling instability and nonequilibrium fluctuations  

NASA Astrophysics Data System (ADS)

We investigate the dynamical properties of monodomain nematic liquid crystals under shear flow and magnetic fields on the basis of the Ericksen-Leslie theory. Stable and unstable states appear depending on the magnetic field and the shear rate. The trajectory of the unstable state shows tumbling motion. The phase diagram of these states is plotted as a function of the three components of the magnetic field at a constant shear rate. The phase diagram changes depending on the viscous properties of different types of nematic liquid crystals. In this nonequilibrium steady state, we calculate the correlation function of director fluctuations and the response function, and discuss the nonequilibrium fluctuations and the modified fluctuation-dissipation relation in connection with nonconservative forces due to shear flow.

Fatriansyah, Jaka Fajar; Orihara, Hiroshi

2013-07-01

86

Enchanted rendezvous: John C. Houbolt and the genesis of the lunar-orbit rendezvous concept  

NASA Technical Reports Server (NTRS)

This is the fourth publication of the 'Monographs in Aerospace History' series, prepared by the NASA History Office. These publications are intended to be tightly focused in terms of subject, relatively short in length, and reproduced to allow timely and broad dissemination to researchers in aerospace history. This publication details the arguments of John C. Houbolt, an engineer at the Langley Research Center in Hampton, Virginia, in his 1961-1962 campaign to support the lunar-orbit rendezvous (LOR). The LOR was eventually selected during Project Apollo as the method of flying to the Moon, landing on the surface, and returning to Earth. The LOR opted to send the entire lunar spacecraft up in one launch, enter into the lunar orbit, and dispatch a small lander to the lunar surface. It was the simplest of the various methods, both in terms of development and operational costs, but it was risky. There was no room for error or the crew could not get home; and the more difficult maneuvers had to be done when the spacecraft was committed to a circumlunar flight. Houbolt was one of the most vocal people supporting the LOR.

Hansen, James R.

1995-01-01

87

Abrasion in pyroclastic density currents: Insights from tumbling experiments  

NASA Astrophysics Data System (ADS)

During granular mass movements of any kind, particles may interact with one another. The degree of interaction is a function of several variables including; grain-size distribution, particle concentration, density stratification and degree of fluidisation. The impact of particle interaction is additionally influenced by the relative speed, impact angle and clast temperature. Thus, both source conditions and transport-related processes are expected to influence the flow dynamics of pyroclastic density currents and their subsequent deposition. Here, we use tumbling experiments to shed light on the susceptibility of porous clasts to abrasion. We investigated the abrasion of unaltered volcanic rocks (5.7-80 vol.% porosity) from Unzen (Japan), Bezymianny (Russia) and Santorini (Greece) volcanoes as well as one synthetic analogue material, an insulating material with the trade name Foamglas® (95 vol.% porosity). Each experiment started with angular fragments generated in a jaw crusher from larger clasts. Two experimental series were performed; on samples with narrow and broader grain-size distributions, respectively. The dry samples were subject to rotational movement at constant speed and ambient temperature in a gum rotational tumbler for durations of 15, 30, 45, 60 and 120 min. The amount of volcanic ash (particles <2 mm) generated was evaluated as a function of experimental duration and sample porosity. We term “abrasion” as the ash fraction generated during the experiments. The observed increase of “abrasion” with increasing sample porosity and experimental duration is initially non-linear but becomes linear for experiments of 30 min duration or longer. For any given sample, abrasion appears to be more effective for coarser samples and larger initial mass. The observed range of ash generated in our experiments is between 1 and 35 wt.%. We find that this amount generally increases with increasing initial clast size or increasing breadth of the initial grain-size distribution. Despite the limits in the complexity that is experimentally attainable in this simulation of ash generation, our results clearly testify the rapid and efficient generation of ash by abrasion, strongly influenced by the material properties (e.g., crystallinity, pore textures).

Kueppers, Ulrich; Putz, Constanze; Spieler, Oliver; Dingwell, Donald B.

2012-01-01

88

Electron paramagnetic resonance studies of slowly tumbling vanadyl spin probes in nematic liquid crystals  

NASA Technical Reports Server (NTRS)

An analysis of EPR line shapes by the method of Polnaszek, Bruno, and Freed is made for slowly tumbling vanadyl spin probes in viscous nematic liquid crystals. The use of typical vanadyl complexes as spin probes for nematic liquid crystals is shown to simplify the theoretical analysis and the subsequent interpretation. Rotational correlation times tau and orientational ordering parameters S sub Z where slow tumbling effects are expected to be observed in vanadyl EPR spectra are indicated in a plot. Analysis of the inertial effects on the probe reorientation, which are induced by slowly fluctuating torque components of the local solvent structure, yield quantitative values for tau and S sub Z. The weakly ordered probe VOAA is in the slow tumbling region and displays these inertial effects throughout the nematic range of BEPC and Phase V. VOAA exhibits different reorientation behavior near the isotropic-nematic transition temperature than that displayed far below this transition temperature.

Bruno, G. V.; Harrington, J. K.; Eastman, M. P.

1978-01-01

89

Finding rendezvous: An approach to locating Rocky Mountain Rendezvous sites through use of historic documents, geophysical survey, and LiDAR  

Microsoft Academic Search

The general locations of the Rocky Mountain Rendezvous have been known to historians through documentary evidence since the mid to late 1800s. While the approximate locations of the rendezvous sites provided through historic documents have sufficed for the placement of signs and markers commemorating these annual events, archaeologists seeking to learn more about the yearly gathering of mountain men and

Rory J. Becker

2010-01-01

90

Theory of Tumbling Bodies Entering Planetary Atmospheres with Application to Probe Vehicles and the Australian Tektites  

NASA Technical Reports Server (NTRS)

The tumbling motion of aerodynamically stable bodies entering planetary atmospheres is analyzed considering that the tumbling, its arrest, and the subsequent oscillatory motion are governed by the equation for the fifth Painleve' transcendent. Results based on the asymptotic behavior of the transcendent are applied to study (1) the oscillatory behavior of planetary probe vehicles in relation to aerodynamic heating and loads and (2) the dynamic behavior of the Australian tektites on entering the Earth's atmosphere, under the hypothesis that their origin was the Moon.

Tobak, Murray; Peterson, Victor L.

1964-01-01

91

Rendezvous and Proximity Operations of the Space Shuttle  

NASA Technical Reports Server (NTRS)

Space Shuttle rendezous missions presented unique challenges that were not fully recognized when the Shuttle was designed. Rendezvous targets could be passive (i.e., no lights or transponders), and not designed to facilitate Shuttle rendezvous, proximity operations and retrieval. Shuttle reaction control system jet plume impingement on target spacecraft presented induced dynamics, structural loading and contamination concerns. These issues, along with limited forward reaction control system propellant, drove a change from the Gemimi/Apollo coelliptic profile heritage to a stable orbit profile, and the development of new proximity operations techniques. Multiple scientific and on-orbit servicing missions and crew exchange, assembly and replinishment flights to Mir and to the International Space Station drove further profile and piloting technique changes, including new relative navigation sensors and new computer generated piloting cues.

Goodman, John L.

2005-01-01

92

Genetic algorithm based fuzzy control of spacecraft autonomous rendezvous  

NASA Technical Reports Server (NTRS)

The U.S. Bureau of Mines is currently investigating ways to combine the control capabilities of fuzzy logic with the learning capabilities of genetic algorithms. Fuzzy logic allows for the uncertainty inherent in most control problems to be incorporated into conventional expert systems. Although fuzzy logic based expert systems have been used successfully for controlling a number of physical systems, the selection of acceptable fuzzy membership functions has generally been a subjective decision. High performance fuzzy membership functions for a fuzzy logic controller that manipulates a mathematical model simulating the autonomous rendezvous of spacecraft are learned using a genetic algorithm, a search technique based on the mechanics of natural genetics. The membership functions learned by the genetic algorithm provide for a more efficient fuzzy logic controller than membership functions selected by the authors for the rendezvous problem. Thus, genetic algorithms are potentially an effective and structured approach for learning fuzzy membership functions.

Karr, C. L.; Freeman, L. M.; Meredith, D. L.

1990-01-01

93

Design and fabrication of an autonomous rendezvous and docking sensor using off-the-shelf hardware  

NASA Technical Reports Server (NTRS)

NASA Marshall Space Flight Center (MSFC) has developed and tested an engineering model of an automated rendezvous and docking sensor system composed of a video camera ringed with laser diodes at two wavelengths and a standard remote manipulator system target that has been modified with retro-reflective tape and 830 and 780 mm optical filters. TRW has provided additional engineering analysis, design, and manufacturing support, resulting in a robust, low cost, automated rendezvous and docking sensor design. We have addressed the issue of space qualification using off-the-shelf hardware components. We have also addressed the performance problems of increased signal to noise ratio, increased range, increased frame rate, graceful degradation through component redundancy, and improved range calibration. Next year, we will build a breadboard of this sensor. The phenomenology of the background scene of a target vehicle as viewed against earth and space backgrounds under various lighting conditions will be simulated using the TRW Dynamic Scene Generator Facility (DSGF). Solar illumination angles of the target vehicle and candidate docking target ranging from eclipse to full sun will be explored. The sensor will be transportable for testing at the MSFC Flight Robotics Laboratory (EB24) using the Dynamic Overhead Telerobotic Simulator (DOTS).

Grimm, Gary E.; Bryan, Thomas C.; Howard, Richard T.; Book, Michael L.

1991-01-01

94

Rendezvous and docking considerations for a cargo delivery vehicle  

NASA Astrophysics Data System (ADS)

This paper describes the results of a feasibility study of using expendable launch vehicles (ELV), for example Atlas/Centaur, to deliver payloads to the Space Station Freedom (SSF). It is found that ELVs and their upper stages with some modifications can perform the delivery operations including rendezvous and docking/berthing. An outer phasing orbit with supervised automatic control philosophy was found to be the best. Additional identification and quantification of SSF operational requirements and constraints will refine the results.

Emmet, B. R.; Thompson, W. E.

1992-08-01

95

Low-energy multiple rendezvous of main belt asteroids  

NASA Technical Reports Server (NTRS)

An approach to multiple asteroid rendezvous missions to the main belt region is proposed. In this approach key information which consists of a launch date and delta V can be generated for all possible pairs of asteroids satisfying specific constraints. This information is made available on a computer file for 1000 numbered asteroids with reasonable assumptions, limitations, and approximations to limit the computer requirements and the size of the data file.

Penzo, Paul A.; Bender, David F.

1992-01-01

96

Supervised autonomous rendezvous and docking system technology evaluation  

NASA Technical Reports Server (NTRS)

Technology for manned space flight is mature and has an extensive history of the use of man-in-the-loop rendezvous and docking, but there is no history of automated rendezvous and docking. Sensors exist that can operate in the space environment. The Shuttle radar can be used for ranges down to 30 meters, Japan and France are developing laser rangers, and considerable work is going on in the U.S. However, there is a need to validate a flight qualified sensor for the range of 30 meters to contact. The number of targets and illumination patterns should be minimized to reduce operation constraints with one or more sensors integrated into a robust system for autonomous operation. To achieve system redundancy, it is worthwhile to follow a parallel development of qualifying and extending the range of the 0-12 meter MSFC sensor and to simultaneously qualify the 0-30(+) meter JPL laser ranging system as an additional sensor with overlapping capabilities. Such an approach offers a redundant sensor suite for autonomous rendezvous and docking. The development should include the optimization of integrated sensory systems, packaging, mission envelopes, and computer image processing to mimic brain perception and real-time response. The benefits of the Global Positioning System in providing real-time positioning data of high accuracy must be incorporated into the design. The use of GPS-derived attitude data should be investigated further and validated.

Marzwell, Neville I.

1991-01-01

97

Autonomous rendezvous, docking, and landing system using cruise missile technologies  

NASA Astrophysics Data System (ADS)

General Dynamics has been developing an Autonomous Rendezvous Docking and Landing (ARD&L) system that utilizes cruise missile technologies. In November 1990 the Autonomous Rendezvous and Docking (AR&D) system was first demonstrated for members of NASA's Strategic Avionics Technology Working Group (SATWG). This simulation utilized prototype hardware from the Cruise Missile and Advanced Centaur Avionics systems. The objective was to show that all the accuracy, reliability, and operational requirements established for a spacecraft to dock with Space Station Freedom could be met by the proposed system. Rapid prototyping techniques were used to evaluate the proposed system in a real time, hardware in the loop simulation of the rendezvous and docking reference mission. The simulation is currently being upgraded to test an Autonomous Approach and Landing (AA&L) system. Both systems use inertial guidance and control systems supplemented by the Global Positioning System (GPS) and an Image Processing System (IPS), for target recognition and tracking. The IPS includes a general purpose multiprocessor computer and a selected suite of sensors that will provide the required relative position and orientation data. Graphic displays can provide the astronaut/operator with realtime guidance and navigation data with enhanced video or sensor imagery.

Jones, Ruel E.

1992-07-01

98

Trajectory Control of Rendezvous with Maneuver Target Spacecraft  

NASA Technical Reports Server (NTRS)

In this paper, a nonlinear trajectory control algorithm of rendezvous with maneuvering target spacecraft is presented. The disturbance forces on the chaser and target spacecraft and the thrust forces on the chaser spacecraft are considered in the analysis. The control algorithm developed in this paper uses the relative distance and relative velocity between the target and chaser spacecraft as the inputs. A general formula of reference relative trajectory of the chaser spacecraft to the target spacecraft is developed and applied to four different proximity maneuvers, which are in-track circling, cross-track circling, in-track spiral rendezvous and cross-track spiral rendezvous. The closed-loop differential equations of the proximity relative motion with the control algorithm are derived. It is proven in the paper that the tracking errors between the commanded relative trajectory and the actual relative trajectory are bounded within a constant region determined by the control gains. The prediction of the tracking errors is obtained. Design examples are provided to show the implementation of the control algorithm. The simulation results show that the actual relative trajectory tracks the commanded relative trajectory tightly. The predicted tracking errors match those calculated in the simulation results. The control algorithm developed in this paper can also be applied to interception of maneuver target spacecraft and relative trajectory control of spacecraft formation flying.

Zhou, Zhinqiang

2012-01-01

99

Mission options for rendezvous with the most accessible Near-Earth Asteroid - 1989 ML  

NASA Technical Reports Server (NTRS)

The recent discovery of the Amor-class 1989 ML, the most accessible known asteroid for minimum-energy rendezvous missions, has expedited the search for frequent, low-cost Near-Earth Asteroid rendezvous and round-trip missions. This paper identifies trajectory characteristics and assesses mass performance for low Delta V ballistic rendezvous opportunities to 1989 ML during the period 1996-2010. This asteroid also offers occasional unique extended mission opportunities, such as the lowest known Delta V requirement for any asteroid sample return mission as well as pre-rendezvous asteroid flyby and post-rendezvous comet flyby opportunities requiring less than 5.25 km/sec total Delta V. This paper also briefly comments concerning mission opportunities for asteroid 1991 JW, which recently replaced other known asteroids as the most accessible Near-Earth Asteroid for fast rendezvous and round-trip missions.

Mcadams, Jim V.

1992-01-01

100

Use of automated rendezvous trajectory planning to improve spacecraft operations efficiency  

NASA Technical Reports Server (NTRS)

The current planning process for space shuttle rendezvous with a second Earth-orbiting vehicle is time consuming and costly. It is a labor-intensive, manual process performed pre-mission with the aid of specialized maneuver processing tools. Real-time execution of a rendezvous plan must closely follow a predicted trajectory, and targeted solutions leading up to the terminal phase are computed on the ground. Despite over 25 years of Gemini, Apollo, Skylab, and shuttle vehicle-to-vehicle rendezvous missions flown to date, rendezvous in Earth orbit still requires careful monitoring and cannot be taken for granted. For example, a significant trajectory offset was experienced during terminal phase rendezvous of the STS-32 Long Duration Exposure Facility retrieval mission. Several improvements can be introduced to the present rendezvous planning process to reduce costs, produce more fuel-efficient profiles, and increase the probability of mission success.

Mulder, Tom A.

1991-01-01

101

Totally percutaneous rendezvous techniques for the treatment of bile strictures and leakages.  

PubMed

Some challenging pathologic conditions of the biliary tract cannot be treated with endoscopy alone, and a combined approach with rendezvous techniques is frequently needed. Three different totally percutaneous rendezvous techniques were successfully applied in three cases. The rendezvous techniques were performed either with bilateral catheterization of bile ducts to treat a challenging type IV biliary stenosis and iatrogenic biliary damage or with biliary catheterization and percutaneous puncture of the anastomotic loop to treat a biliodigestive anastomosis failure with bile leakage. PMID:24674222

De Robertis, Riccardo; Contro, Alberto; Zamboni, Giulia; Mansueto, Giancarlo

2014-04-01

102

Apollo experience report: Evolution of the rendezvous-maneuver plan for the lunar-landing missions  

NASA Technical Reports Server (NTRS)

The evolution of the nominal rendezvous-maneuver plan for the lunar landing missions is presented along with a summary of the significant development for the lunar module abort and rescue plan. A general discussion of the rendezvous dispersion analysis that was conducted in support of both the nominal and contingency rendezvous planning is included. Emphasis is placed on the technical developments from the early 1960's through the Apollo 15 mission (July to August 1971), but pertinent organizational factors also are discussed briefly. Recommendations for rendezvous planning for future programs relative to Apollo experience also are included.

Alexander, J. D.; Becker, R. W.

1973-01-01

103

Mechanics of media motion in tumbling mills with 3d discrete element method  

Microsoft Academic Search

The charge motion in a tumbling mill is analyzed in detail using a numerical simulation scheme known as the discrete element method (DEM). In particular, the profile of the ball charge, impact energy distribution and power draft are predicted as a function of mill operating conditions. The analyses are verified by direct experimentation in a 90-cm diameter ball mill of

S. Agrawala; R. K. Rajamani; P. Songfack; B. K. Mishra

1997-01-01

104

Electron Paramagnetic Resonance Studies of Slowly Tumbling Vanadyl Spin Probes in Nematic Liquid Crystals.  

National Technical Information Service (NTIS)

An analysis of EPR line shapes by the method of Polnaszek, Bruno, and Freed is made for slowly tumbling vanadyl spin probes in viscous nematic liquid crystals. The use of typical vanadyl complexes as spin probes for nematic liquid crystals is shown to sim...

G. V. Bruno J. K. Harrington M. P. Eastman

1978-01-01

105

A phenomenological model for perforation of moderately thick plates by tumbling projectiles  

Microsoft Academic Search

A phenomenological model has been developed to describe the mechanism of tumbling perforation of blunt-faced cylindrical projectiles in moderately thick aluminum plates. The perforation process, based on experimental observations, consists of four stages: erosion; plugging; hole enlargement and petaling. The modeling in the plugging stage consists sequentially of cratering, plug formation, plug separation, plug slipping and post perforation deformation. Bulging

Kezhun Li; Werner Goldsmith

1996-01-01

106

An analytical model for tumbling projectile perforation of thin aluminum plates  

Microsoft Academic Search

An analytical model for the perforation of thin aluminum targets by tumbling cylindrical projectiles was developed. The target material was considered to be rigid—perfectly plastic without strain hardening, while the projectile was treated as undeformable. The perforation process was experimentally found to consist of three stages: plugging, hole enlargement, and front petaling. Both conservation of energy and conservation of momentum

Kezhun Li; Werner Goldsmith

1996-01-01

107

76 FR 37663 - Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Tumbling Creek...  

Federal Register 2010, 2011, 2012, 2013

...software. (5) Tumbling Creek Cavesnail Critical Habitat Unit. (i) U.S. Geological Survey 7.5' Topographic Protem Quad. Land bounded by the following UTM Zone 15N, North American Datum of 1983 (NAD83) coordinates (W, N): from the...

2011-06-28

108

Tumbling motion of magnetic particles on a magnetic substrate induced by a rotational magnetic field  

Microsoft Academic Search

We analyze the dynamics of paramagnetic particles on a paramagnetic substrate under a rotational magnetic field. When the paramagnetic particles are subjected to a rotational magnetic field, the rotational plane of which is perpendicular to the substrate surface, the particles form chain clusters caused by the dipole-dipole interaction between the particles and these clusters display a tumbling motion under certain

Hisao Morimoto; Tomofumi Ukai; Yutaka Nagaoka; Nicole Grobert; Toru Maekawa

2008-01-01

109

Is Father-Child Rough-and-Tumble Play Associated with Attachment or Activation Relationships?  

ERIC Educational Resources Information Center

The activation relationship theory, primarily focused on parental stimulation of risk-taking along with parental control during exploration, predicts that boys will be activated more than girls by their fathers. This theory may explain why fathers engage in rough-and-tumble play (RTP) with children more frequently than mothers, especially with…

Paquette, Daniel; Dumont, Caroline

2013-01-01

110

Stereoscopic multi-planar PIV measurements of in-cylinder tumbling flow  

NASA Astrophysics Data System (ADS)

The non-reacting flow field within the combustion chamber of a motored direct-injection spark-ignition engine with tumble intake port is measured. The three-dimensionality of the flow necessitates the measurement of all three velocity components via stereoscopic particle-image velocimetry in multiple planes. Phase-locked stereoscopic PIV is applied at 15 crank angles during the intake and compression strokes, showing the temporal evolution of the flow field. The flow fields are obtained within a set of 14 axial planes, covering nearly the complete cylinder volume. The stereoscopic PIV setup applied to engine in-cylinder flow and the arising problems and solutions are discussed in detail. The three-dimensional flow field is reconstructed and analyzed using vortex criteria. The tumble vortex is the dominant flow structure, and this vortex varies significantly regarding shape, strength, and position throughout the two strokes. The tumble vortex center moves clockwise through the combustion chamber. At first, the tumble has a c-shape which turns into an almost straight tube at the end of the compression. Small-scale structures are analyzed by the distribution of the turbulent kinetic energy. It is evident that the symmetry plane only represents the 3D flow field after 100 CAD. For earlier crank angles, both kinetic energy (KE) and turbulent kinetic energy (TKE) in the combustion chamber are well below the KE and TKE in the symmetry plane. This should be taken into account when the injection and breakup of the three-dimensional fuel jet are studied. The mean kinetic energy is conserved until late compression by the tumble motion. This conservation ensures through the excited air motion an enhancement of the initial air-fuel mixture which is of interest for direct-injection gasoline engines.

Bücker, I.; Karhoff, D.-C.; Klaas, M.; Schröder, W.

2012-12-01

111

Guidance laws for spacecraft pursuit-evasion and rendezvous  

NASA Astrophysics Data System (ADS)

Nonlinear feedback guidance laws are developed for a pursuit-evasion differential game between two spacecraft, and for the more traditional spacecraft rendezvous problem using the complete nonlinear point-mass models. These guidance laws are suitable for on-board implementation. They are applicable for large amplitude maneuvers and can account for the presence of more than one gravitational field. An exact method for computing time-to-go required in guidance law implementation is developed. The guidance law performance is demonstrated using a three-degree-of-freedom simulation with a six harmonic gravitational model.

Menon, P. K. A.; Calise, A. J.; Leung, S. K. M.

112

A study of autonomous rendezvous and docking systems  

NASA Astrophysics Data System (ADS)

An overview of activities in the automatic rendezvous and docking area is presented. A representative mission scenario is covered. A statement of the problem is made and the requirements for the extraction of relative attitude and position data are delineated. A systems block diagram is included and the integral functions which go to make up an autonomous docking system is described. A system was simulated, and the digital simulation is described along with some representative results of a system based a laser ranging device as the sensor. A television camera as the ranging sensor was also considered, one video based automatic docking scheme is discussed along with some representative results.

Michael, J. D.

1982-03-01

113

Reference equations of motion for automatic rendezvous and capture  

NASA Technical Reports Server (NTRS)

The analysis presented in this paper defines the reference coordinate frames, equations of motion, and control parameters necessary to model the relative motion and attitude of spacecraft in close proximity with another space system during the Automatic Rendezvous and Capture phase of an on-orbit operation. The relative docking port target position vector and the attitude control matrix are defined based upon an arbitrary spacecraft design. These translation and rotation control parameters could be used to drive the error signal input to the vehicle flight control system. Measurements for these control parameters would become the bases for an autopilot or feedback control system (FCS) design for a specific spacecraft.

Henderson, David M.

1992-01-01

114

On-line robust pose estimation for Rendezvous and Docking in space using photonic mixer devices  

NASA Astrophysics Data System (ADS)

In this paper a new approach for estimating the pose of an unknown object using Photonic Mixer Devices (PMD) based cameras is presented. The algorithm works on-line by making use of the amplitude and depth information provided at high frame rates by the camera. The aim of the work is to provide a robust pose estimation as an input for control systems in Rendezvous and Docking (RvD) maneuvers in space. The performance of the developed algorithm is evaluated in six different simple scenarios corresponding to the six degrees-of-freedom (DoF) of the object. Final results with errors less than 1% are obtained for the distance estimation and errors ranging from less than 1% up to less than 9% for the velocity estimation.

Regoli, L.; Ravandoor, K.; Schmidt, M.; Schilling, K.

2014-03-01

115

Rendezvous and docking (RVD) long range RF sensor definition study, executive summary  

NASA Astrophysics Data System (ADS)

A 90 GHz radar, an S-band lobe switching sensor, and S-band phase switching sensors were compared for use as rendezvous and docking long range sensor aboard the chaser satellite. The lobe switching concept best meets requirements of target satellite acquisition (at a range of the order of 100 km) and operation at a range less than 100 m; measurement of relative distance (between chaser and target) with accuracy of 1 m (at short range); measurement of relative velocity (between chaser and target) with accuracy of 1 cm/sec (at short range); measurement of relative position (between chaser and target) expressed as bearing angles with respect to reference frame in the chaser, with accuracy of 0.5 deg in the field of view of +/- 30 deg; and measurement of bearing angle rates with respect to the reference frame in the chaser with accuracy of 0.05 deg/sec.

116

Vision-based relative pose estimation for autonomous rendezvous and docking  

Microsoft Academic Search

Autonomous rendezvous and docking is necessary for planned space programs such as DARPA ASTRO, NASA MSR, ISS assembly and servicing, and other rendezvous and proximity operations. Estimation of the relative pose between the host platform and a resident space object is a critical ability. We present a model-based pose refinement algorithm, part of a suite of algorithms for vision-based relative

Jed M. Kelsey; Jeffrey Byrne; Martin Cosgrove; Sanjeev Seereeram; Raman K. Mehra

2006-01-01

117

Advances in multi-mission autonomous rendezvous and docking and relative navigation capabilities  

Microsoft Academic Search

Relative Navigation (RelNav) applications, have been identified as an enabling function of many of NASA's future mission architectures, including Rendezvous, Proximity Operations and Docking (RPOD), as well as planetary surface rendezvous and landing, surface mobility and in space servicing. Functional capabilities have been maintained and exercised for decades, but recent design and test efforts have validated revolutionary improvements in functionality

Kevin Miller; Jim Masciarelli; Reuben Rohrschneider

2012-01-01

118

An automated rendezvous and capture system design concept for the cargo transfer vehicle and Space Station Freedom  

NASA Technical Reports Server (NTRS)

A rendezvous sensor system concept was developed for the cargo transfer vehicle (CTV) to autonomously rendezvous with and be captured by Space Station Freedom (SSF). The development of requirements, the design of a unique Lockheed developed sensor concept to meet these requirements, and the system design to place this sensor on the CTV and rendezvous with the SSF are described .

Fuchs, Ron; Marsh, Steven

1991-01-01

119

An autonomous rendezvous and docking system using cruise missile technologies  

NASA Astrophysics Data System (ADS)

In November 1990 the Autonomous Rendezvous & Docking (AR&D) system was first demonstrated for members of NASA's Strategic Avionics Technology Working Group. This simulation utilized prototype hardware from the Cruise Missile and Advanced Centaur Avionics systems. The object was to show that all the accuracy, reliability and operational requirements established for a space craft to dock with Space Station Freedom could be met by the proposed system. The rapid prototyping capabilities of the Advanced Avionics Systems Development Laboratory were used to evaluate the proposed system in a real time, hardware in the loop simulation of the rendezvous and docking reference mission. The simulation permits manual, supervised automatic and fully autonomous operations to be evaluated. It is also being upgraded to be able to test an Autonomous Approach and Landing (AA&L) system. The AA&L and AR&D systems are very similar. Both use inertial guidance and control systems supplemented by GPS. Both use an Image Processing System (IPS), for target recognition and tracking. The IPS includes a general purpose multiprocessor computer and a selected suite of sensors that will provide the required relative position and orientation data. Graphic displays can also be generated by the computer, providing the astronaut / operator with real-time guidance and navigation data with enhanced video or sensor imagery.

Jones, Ruel Edwin

120

The effects of tumbling and sodium tripolyphosphate on the proteins of döner.  

PubMed

This study was designed to investigate the influence of tumbling and sodium tripolyphosphate (STPP) with marination on the protein structure of raw and cooked döner, a traditional Middle East product consumed widely in many areas of the world. Proximate composition (%moisture, %protein, %fat, %ash, and pH value), salt soluble protein (SSP) and total ?-amino grup amount were determined. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used to investigate alterations in the sarcoplasmic and myofibrillar proteins. Utilization of STPP increased the moisture content and ash contents, and pH value of raw döner (p<0.05). Only tumbling and STPP had a significant two-way interaction for moisture content, SSP and total ?-amino group amounts of cooked döner (p<0.05). None of the treatments significantly affected the fraction of sarcoplasmic and myofibrillar proteins. In addition, cooking caused proteolysis of these proteins. PMID:21561722

Demirok, Eda; Kolsar?c?, Nuray; Ako?lu, ?lker Turan; Özden, Esma

2011-10-01

121

Electron paramagnetic resonance studies of slowly tumbling vanadyl spin probes in nematic liquid crystals  

NASA Technical Reports Server (NTRS)

The purposes of this vanadyl spin probe study are threefold: (1) to establish when the breakdown of motionally narrowed formulas occurs; (2) to analyze the experimental vanadyl EPR line shapes by the stochastic Lioville method as developed by Polnaszek et al. (1973) for slow tumbling in an anisotropic liquid; and (3) to compare the vanadyl probe study results with those of Polnaszek and Freed (1975). Spectral EPR line shapes are simulated for experimental spectra of vanadyl acetylacetonate (VOAA) in nematic liquid crystal butyl p-(p-ethoxyphenoxycarbonyl) phenyl carbonate (BEPC) and Phase V of EM laboratories. It is shown that the use of typical vanadyl complexes as spin probes for nematic liquid crystals simplifies the theoretical analysis and the subsequent interpretation. Guidelines for the breakdown of motionally narrowed formulas are established. Both the slow tumbling aspects and the effects of non-Brownian rotation should be resolved in order to extract quantitative information about molecular ordering and rotational mobility.

Bruno, G. V.; Harrington, J. K.; Eastman, M. P.

1978-01-01

122

Squaring, Parity Breaking, and S Tumbling of Vesicles under Shear Flow  

NASA Astrophysics Data System (ADS)

The numerical study of 3D vesicles with a reduced volume equal to that of human red blood cells leads to the discovery of three types of dynamics: (i) squaring motion, in which the angle between the direction of the longest distance and the flow velocity undergoes discontinuous jumps over time, (ii) spontaneous parity breaking of the shape leading to cross-streamline migration, and (iii) S tumbling where the vesicle tumbles, exhibiting a pronounced S-like shape with a waisted morphology in the center. We report on the phase diagram within a wide range of relevant parameters. Our estimates reveal that healthy and pathological red blood cells are also prone to these types of motion, which may affect blood microcirculation and impact oxygen transport.

Farutin, Alexander; Misbah, Chaouqi

2012-12-01

123

Membrane compression in tumbling and vacillating-breathing regimes for quasispherical vesicles  

NASA Astrophysics Data System (ADS)

We derive some analytical results of a well-known model for quasispherical vesicles in a linear shear flow at low deformability. Attention is focussed on the oscillatory regimes: the tumbling (TB) mode, vacillating-breathing (VB) mode, and the transition from vacillating-breathing to tumbling, depending on a control parameter ?. It is shown that, during the VB-to-TB transition (? =1), the vesicle momentarily attains its maximal extension in the vorticity direction and transits through a circular profile in the shear plane for which the radius is exactly determined. In addition, we provide an explicit analytical expression for the effective membrane tension for different types of motions. We find a critical bending number below which the membrane undergoes compression at each instant and show that, during the VB-to-TB transition, a fourth-order membrane deformation is possible.

Guedda, M.

2014-01-01

124

Predicting the overall specific energy requirement of crushing, high pressure grinding roll and tumbling mill circuits  

Microsoft Academic Search

In a previous paper [Morrell, S. 2008a. A method for predicting the specific energy requirement of comminution circuits and assessing their energy utilisation efficiency. Minerals Engineering 21(3), 5–9] an approach was described which enabled the specific energy of tumbling mills such as Autogenous (AG), Semi-autogenous (SAG) and ball mills to be estimated from laboratory-derived ore characterisation data. The following paper

S. Morrell

2009-01-01

125

STS-41 MS Akers tumbles out of JSC's CCT during egress exercises  

NASA Technical Reports Server (NTRS)

STS-41 Mission Specialist (MS) Thomas D. Akers, wearing a launch and entry suit (LES) and launch and entry helmet (LEH), tumbles out of JSC's crew compartment trainer (CCT) during side hatch emergency egress exercises. Using the crew escape system (CES) pole, Akers simulated the procedures necessary to bailout of the Shuttle during the ascent phase. A technician assists Akers, rolling across an inflated safety pad, as a second technician looks on. In the open side hatch, another crewmember prepares for egress.

1990-01-01

126

ESR studies of the slow tumbling of vanadyl spin probes in nematic liquid crystals  

NASA Technical Reports Server (NTRS)

ESR line shapes that are appropriate for slowly tumbling vanadyl spin probes in viscous nematic liquid crystals were calculated by the stochastic Liouville method. Because of the symmetry possessed by vanadyl, the analysis and interpretation of these line shapes was simplified considerably. Spectral line shapes agreed well with experimental spectra of VOAcAc in the nematic liquid crystal Phase V and BEPC. Deviations from Brownian rotational diffusion were noted. A slowly fluctuating torque analysis yielded good agreement with the experimental spectra.

Eastman, M. P.; Bruno, G. V.; Lawson, J. O.

1977-01-01

127

Cell balance equation for chemotactic bacteria with a biphasic tumbling frequency  

Microsoft Academic Search

Alt’s three-dimensional cell balance equation characterizing the chemotactic bacteria was analyzed under the presence of one-dimensional spatial chemoattractant gradients. Our work differs from that of others who have developed rather general models for chemotaxis in the use of a non-smooth anisotropic tumbling frequency function that responds biphasically to the combined temporal and spatial chemoattractant gradients. General three-dimensional expressions for the

Kevin C. Chen; Roseanne M. Ford; Peter T. Cummings

2003-01-01

128

Tumbling Cerium Atoms Inside the Fullerene Cage: iCe2C80  

NASA Astrophysics Data System (ADS)

We report the spectroscopic work of two Ce-containing incar-fullerenes, iCeC82 and iCe2C80. UV/Vis, IR, Raman, TOF-MALDI and 13C NMR were employed to investigate the structural and electronic information of these two major isomers of Ce incar-fullerenes. Tumbling motion of two Ce atoms inside the Ih-C80 cage was confirmed and analysed by temperature-dependant 13C NMR.

Kanai, M.; Porfyrakis, K.; Khlobystov, A. N.; Shinohara, H.; Dennis, T. J. S.

2003-10-01

129

Analytical and Preliminary Simulation Study of a Pilot's Ability to Control the Terminal Phase of a Rendezvous with Simple Optical Devices and a Timer  

NASA Technical Reports Server (NTRS)

One method of controlling the terminal phase of a space rendezvous between two vehicles is first to correct the flight path of the controlled vehicle so that a constant line of sight is established between the vehicles. This correction is accomplished by thrusting normal to the sight line in a direction to arrest the angular motion of this line. Once this collision course has been established, the second step is to control the closure rate for a safe approach along the line of sight. Adequate control of this maneuver requires range and closure-rate information. A combined analytical and preliminary simulation study was conducted to determine the ability of a human pilot to control the rendezvous by this method using visual sightings made during the initial collision-course control to obtain the range and closure rate. The analytical phase of the study reviewed the geometric relations between the vehicles and formed the basis for techniques to transform the angular sightings into range and closure rate. A preliminary simulation was then made to investigate the accuracy of these techniques. The simulation consisted of an analog computer, an oscilloscope to represent the view a pilot would have-with a stabilized sight, and a timer. Results indicate that pilots, using an optical sight and a timer, can successfully arrest the angular motion of the line of sight between two rendezvous vehicles and obtain relative range and closure rate with sufficient accuracy to perform the final braking maneuver successfully.

Lineberry, Edgar C., Jr.; Brissenden, Roy F.; Kurbjun, Max C.

1961-01-01

130

Tumbling dynamics in a nematic surfactant solution in transient shear flows  

SciTech Connect

We report rheological and structural studies of a nematic surfactant solution (CPCl/hex) in transient shear flows. Upon step changes in steady shear flow conditions, the shear stress exhibits damped oscillations that scale with shear strain, attributed to director tumbling under shear. {ital In situ} small-angle x-ray scattering spectroscopy is used to measure changes in average micellar orientation during similar transient shear protocols; the measured orientation parameter also exhibits damped oscillations reflecting the underlying tumbling dynamics. Stress and structure data are compared with predictions of the Larson{endash}Doi tumbling polydomain model. The model predictions are qualitatively similar to the experimental observations. In particular, orientation is observed to initially decrease upon shear flow reversal in CPCl/hex, in agreement with the Larson{endash}Doi predictions but in contrast to previous results for model lyotropic solutions of poly(benzyl glutamate). Shear stress and average orientation are closely related during the oscillatory response to transient flows. The data suggest that higher orientation in the flow direction leads to low instantaneous stresses, and vice versa. The Larson{endash}Doi model does not predict this relationship. {copyright} {ital 1999 Society of Rheology.}

Caputo, F.E.; Burghardt, W.R. [Department of Chemical Engineering, Northwestern University, Evanston, Illinois 60208 (United States)] [Department of Chemical Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Berret, J. [CC026/Groupe de Dynamique des Phases Condensees, Universite de Montpellier II, F-34095 Montpellier Cedex 05 (France)] [CC026/Groupe de Dynamique des Phases Condensees, Universite de Montpellier II, F-34095 Montpellier Cedex 05 (France)

1999-05-01

131

A Study of the Inclination of Satellites of a Planet After Spin Axis Forced Tumbling  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): In order to analyze the theory of satellite loss resulting from a giant impact on Uranus, we decided to do few a study about this problem using forced tumbling of the spin axis of planet. We used two different kinds of forced tumbling to simulate the obliquity variation: linear variation and damped variation. To do this, we made numerical simulations of N-body problem with J2 oblateness coefficient of the central body. First, we studied the relation of the time tumbling of Uranus' spin axis and the semi-major axis of the hypothetical satellite with a specific final inclination. In both cases the results are a power law. Later we study the final inclination of the satellite in relation to the number of collisions (pseudo collision). And finally we studied the final inclination of several different initial conditions (orbital elements) of the satellites. We concluded that the initial inclination and initial longitude of ascending node are important to the final satellite inclination. For future studies we want implement a more realistic model using the attitude equations of the central body and study the origin of the obliquity of the others planets of the solar system. Aknowledments: FAPESP, CAPES and CNPq.

Boldrin, Luiz Augusto; Winter, O.; Vieira Neto, E.

2013-05-01

132

The Evolution of the Rendezvous Profile During the Space Shuttle Program  

NASA Technical Reports Server (NTRS)

The rendezvous and proximity operations approach design techniques for space shuttle missions has changed significantly during the life of the program in response to new requirements that were not part of the original mission design. The flexibility of the shuttle onboard systems design and the mission planning process has allowed the program to meet these requirements. The design of the space shuttle and the shift from docking to grappling with a robotic ann prevented use of legacy Apollo rendezvous techniques. Over the life of the shuttle program the rendezvous profile has evolved due to several factors, including lowering propellant consumption and increasing flexibility in mission planning. Many of the spacecraft that the shuttle rendezvoused with had unique requirements that drove the creation of mission-unique proximity operations. The dockings to the Russian Mir space station and International Space Station (ISS) required further evolution of rendezvous and proximity operations techniques and additional sensors to enhance crew situational awareness. After the Columbia accident, a Rendezvous Pitch Maneuver (RPM) was added to allow tile photography from ISS. Lessons learned from these rendezvous design changes are applicable to future vehicle designs and operations concepts.

Summa, William R.

2010-01-01

133

The effects of low salt concentrations on the mechanism of adhesion between two pieces of pork semimembranosus muscle following tumbling and cooking.  

PubMed

The aim of this research was to gain deeper insight into the effect of salt content on the adhesion between pieces of semimembranosus pork muscle bound by a tumbling exudate gel. Hydrophobic site number, free thiol and carbonyl content were measured in tumbling exudate and meat protein to evaluate the protein-protein interactions involved in the adhesion process. Proteins were far more oxidized in exudate than in meat, and under our experimental conditions, salt content increased protein bonding in the exudate but not in the meat. Breaking stress increased between non-salted meat and 0.8%-salted meat but did not depend on the protein physicochemical properties of the tumbling exudate. Modifying the meat surface by tumbling alone, tumbling and salting, or scarification had no effect on breaking stress. It is suggested that the break between the meat pieces occurred between the tumbling exudate and the meat surface due to weaker chemical bonds at this location. PMID:23896131

Bombrun, Laure; Gatellier, Philippe; Carlier, Martine; Kondjoyan, Alain

2014-01-01

134

Rendezvous, proximity operations and capture quality function deployment report  

NASA Technical Reports Server (NTRS)

Rendezvous, Proximity Operations, and Capture (RPOC) is a missions operations area which is extremely important to present and future space initiatives and must be well planned and coordinated. To support this, a study team was formed to identify a specific plan of action using the Quality Function Deployment (QFD) process. This team was composed of members from a wide spectrum of engineering and operations organizations which are involved in the RPOC technology area. The key to this study's success is an understanding of the needs of potential programmatic customers and the technology base available for system implementation. To this end, the study team conducted interviews with a variety of near term and future programmatic customers and technology development sponsors. The QFD activity led to a thorough understanding of the needs of these customers in the RPOC area, as well as the relative importance of these needs.

Lamkin, Stephen L. (editor)

1991-01-01

135

Rendezvous, proximity operations and capture quality function deployment report  

NASA Astrophysics Data System (ADS)

Rendezvous, Proximity Operations, and Capture (RPOC) is a missions operations area which is extremely important to present and future space initiatives and must be well planned and coordinated. To support this, a study team was formed to identify a specific plan of action using the Quality Function Deployment (QFD) process. This team was composed of members from a wide spectrum of engineering and operations organizations which are involved in the RPOC technology area. The key to this study's success is an understanding of the needs of potential programmatic customers and the technology base available for system implementation. To this end, the study team conducted interviews with a variety of near term and future programmatic customers and technology development sponsors. The QFD activity led to a thorough understanding of the needs of these customers in the RPOC area, as well as the relative importance of these needs.

Lamkin, Stephen L.

1991-12-01

136

Halo: Managing Node Rendezvous in Opportunistic Sensor Networks  

NASA Astrophysics Data System (ADS)

One vision of an opportunistic sensor network (OSN) uses sensor access points (SAPs) to assign mobile sensors with sensing tasks submitted by applications that could be running anywhere. Tasked mobile sensors might upload sensed data back to these applications via subsequent encounters with this SAP tier. In a people-centric OSN, node mobility is uncontrolled and the architecture relies on opportunistic rendezvous between human-carried sensors and SAPs to provide tasking/uploading opportunities. However, in many reasonable scenarios application queries have a degree of time sensitivity such that the sensing target must be sampled and/or the resulting sensed data must be uploaded within a certain time window to be of greatest value. Halo efficiently, in terms of packet overhead and mobile sensor energy, provides improved delay performance in OSNs by: (i) managing tasking/uploading opportunity, and (ii) using mobility-informed scheduling at the SAP.

Eisenman, Shane B.; Lu, Hong; Campbell, Andrew T.

137

Near Earth Asteroid Rendezvous (NEAR) Spacecraft/Delta II launch  

NASA Technical Reports Server (NTRS)

The Near Earth Asteroid Rendezvous (NEAR) spacecraft undergoing preflight preparation in the Spacecraft Assembly Encapsulation Facility-2 (SAEF-2) at Kennedy Space Center (KSC). NEAR will perform two critical mission events - Mathilde flyby and the Deep-Space maneuver. NEAR will fly-by Mathilde, a 38-mile (61-km) diameter C-type asteroid, making use of its imaging system to obtain useful optical navigation images. The primary science instrument will be the camera, but measurements of magnetic fields and mass also will be made. The Deep-Space Maneuver (DSM) will be executed about a week after the Mathilde fly-by. The DSM represents the first of two major burns during the NEAR mission of the 100-pound bi-propellant (Hydrazine/nitrogen tetroxide) thruster. This maneuver is necessary to lower the perihelion distance of NEAR's trajectory. The DSM will be conducted in two segments to minimize the possibility of an overburn situation.

1996-01-01

138

Orion Rendezvous, Proximity Operations, and Docking Design and Analysis  

NASA Technical Reports Server (NTRS)

The Orion vehicle will be required to perform rendezvous, proximity operations, and docking with the International Space Station (ISS) and the Earth Departure Stage (EDS)/Lunar Landing Vehicle (LLV) stack in Low Earth Orbit (LEO) as well as with the Lunar Landing Vehicle in Low Lunar Orbit (LLO). The RPOD system, which consists of sensors, actuators, and software is being designed to be flexible and robust enough to perform RPOD with different vehicles in different environments. This paper will describe the design and the analysis which has been performed to date to allow the vehicle to perform its mission. Since the RPOD design touches on many areas such as sensors selection and placement, trajectory design, navigation performance, and effector performance, it is inherently a systems design problem. This paper will address each of these issues in order to demonstrate how the Orion RPOD has been designed to accommodate and meet all the requirements levied on the system.

D'Souza, Christopher; Hanak, F. Chad; Spehar, Pete; Clark, Fred D.; Jackson, Mark

2007-01-01

139

New developments in astrodynamics algorithms for autonomous rendezvous  

NASA Technical Reports Server (NTRS)

A the core of any autonomous rendezvous guidance system must be two algorithms for solving Lambert's and Kepler's problems, the two fundamental problems in classical astrodynamics. Lambert's problem is to determine the trajectory connecting specified initial and terminal position vectors in a specified transfer time. The solution is the initial and terminal velocity vectors. Kepler's problem is to determine the trajectory that stems from a given initial state (position and velocity). The solution is the state of an earlier or later specified time. To be suitable for flight software, astrodynamics algorithms must be totally reliable, compact, and fast. Although solving Lambert's and Kepler's problems has challenged some of the world's finest minds for over two centuries, only in the last year have algorithms appeared that satisfy all three requirements just stated. This paper presents an evaluation of the most highly regarded Lambert and Kepler algorithms.

Klumpp, Allan R.

1991-01-01

140

Differential drag spacecraft rendezvous using an adaptive Lyapunov control strategy  

NASA Astrophysics Data System (ADS)

This paper introduces a novel Lyapunov-based adaptive control strategy for spacecraft maneuvers using atmospheric differential drag. The control forces required for rendezvous maneuvers at low Earth orbits can be generated by varying the aerodynamic drag affecting each spacecraft. This can be accomplished, for example, by rotating dedicated sets of drag panels. Thus, the relative spacecraft motion can be controlled without using any propellant since the motion of the panels can be powered by solar energy. A novel adaptive Lyapunov controller is designed, and a critical value for the relative drag acceleration that ensures Lyapunov stability is found. The critical value is used to adapt the Lyapunov controller, enhancing its performance. The method is validated using simulations. The results show that the Adaptive Lyapunov technique outperforms previous control strategies for differential drag based spacecraft maneuvering.

Pérez, David; Bevilacqua, Riccardo

2013-02-01

141

Control software for the Near Earth Asteroid Rendezvous laser rangefinder  

NASA Astrophysics Data System (ADS)

The near earth asteroid rendezvous (NEAR) laser rangefinder (NLR), an instrument on the NEAR spacecraft, was designed to measure range from the NEAR spacecraft to the surface of the asteroid 433 EROS. The instrument consists of a laser transmitter, a calibration fiber, an optical receiver, analog electronics, power converting and conditioning electronics, and a digital processing unit. The digital processing unit controls configuration and operation of the transmitter and analog electronics. Software running in the processor handles communication between the spacecraft data bus and the NLR. The software includes functions for command handling, telemetry data formatting and data transfer to the command and data handling computer, transmitter control, measurement of the receiver noise floor, and correction of some timing delays. A brief overview of the software is given along with descriptions of auto-calibration sequences and test results.

El-Dinary, Ashruf S.; Cole, Timothy D.; Reiter, R. Alan; Rodriguez, Daniel E.

1996-10-01

142

Mission opportunity maps for rendezvous with earth-crossing asteroids  

NASA Technical Reports Server (NTRS)

Rendezvous missions to earth-crossing asteroids are of interest to NASA, for scientific purposes as well as for technological applications and ecological implications. To provide a comprehensive data base for planners of such missions, a mission opportunity map (MOM) has been created for eight relatively easy-to-access asteroids. A MOM presents such mission data as launch dates, flight times, and launch and postlaunch delta V requirements for all useful mission opportunities. The merits of a MOM are: (1) searches for all useful mission oportunities are completed in the process of generating a MOM, and (2) a MOM provides a clear view of good and bad opportunities, the extent of performance variations, and the repeatability of the missions.

Yen, Chen-Wan L.

1989-01-01

143

STS 63 Flight Day 4 Highlights/MIR-Shuttle Rendezvous  

NASA Technical Reports Server (NTRS)

STS 63 Flight, day 4, the MIR-Shuttle rendezvous is highlighted in this video. The six-member team in the Shuttle are introduced and discuss their functions and tests for this day of the flight. There is actual footage of earth from space, of the MIR Space Station, a tour of the Shuttle cockpit, some footage from the MIR of the Space Shuttle, and footage from inside the MIR with the cosmonauts. Mission control communications with the Shuttle, communication between the Shuttle and MIR, and an historic communication between the Shuttle's astronauts and President Bill Clinton are included. President Clinton interviews each of the six-member team and discusses the upcoming space walk by Dr. Bernard Harris, the first black astronaut to walk in space. This video was recorded on February 6, 1995.

1995-01-01

144

The comet rendezvous asteroid flyby mission: A status report  

NASA Technical Reports Server (NTRS)

The Comet Rendezvous Asteroid Flyby (CRAF) mission received a new start in fiscal year 1990. CRAF will match orbits with an active short-period comet and follow it around the Sun, making scientific measurements of the nucleus, coma, and tail. The Imaging system will map the nucleus surface at a resolution of 1 meter/line-pair or better, while Visible and Infrared Mapping Spectrometer (VIMS) and Thermal Infrared Radiometer Experiment (TIREX) will produce spectral and thermal maps of the surface. Onboard instruments will collect cometary dust, ice, and gases and perform elemental and molecular analysis. A suite of fields and particles instruments will observe the solar wind interaction with the cometary atmosphere and tail. Radio tracking of the spacecraft will provide an accurate measure of the nucleus mass and higher harmonics in the comet's gravity field. En route to the comet, the spacecraft will make a close flyby of a large asteroid, preferably a primitive type from the outer main belt. Observations at the asteroid include remote sensing mapping of the surface, detection of any solar wind interaction observable at the flyby distance, and measurement of the asteroid mass to better than 10 percent accuracy. Detailed design of the CRAF spacecraft is currently underway at the Jet Propulsion Laboratory (JPL). Recent mass growth has necessitated a switch to Venus-Earth gravity assist type trajectories, similar to that used by the Galileo spacecraft. These trajectories require longer flight times from launch to rendezvous with the target comet. The details of the current baseline mission, spacecraft design, and instrument payload will be reviewed.

Weissman, Paul R.; Neugebauer, Marcia

1991-01-01

145

Evaluation of GPS Position and Attitude Determination for Automated Rendezvous and Docking Missions.  

National Technical Information Service (NTIS)

The use of the Global Positioning System for position and attitude determination is evaluated for an automated rendezvous and docking mission. The typical mission scenario involves the chaser docking with the target for resupply or repair purposes, and is...

M. D. Diprinzio R. H. Tolson

1994-01-01

146

Space Operations Simulation Center (SOSC) and Closed-loop Hardware Testing for Orion Rendezvous System Design.  

National Technical Information Service (NTIS)

The Space Operations Simulation Center (SOSC) at the Lockheed Martin (LM) Waterton Campus in Littleton, Colorado is a dynamic test environment focused on Autonomous Rendezvous and Docking (AR&D) development testing and risk reduction activities. The S...

A. Kibler C. D'Souza D. Huich J. Bendle Z. Milenkovich Z. Wilson

2011-01-01

147

Fuzzy Logic Techniques for Rendezvous and Docking of Two Geostationary Satellites.  

National Technical Information Service (NTIS)

Large assemblings in space require the ability to manage rendezvous and docking operations. In future these techniques will be required for the gradual build up of big telecommunication platforms in the geostationary orbit. The paper discusses the use of ...

G. Ortega

1995-01-01

148

Rough-and-Tumble Play and the Regulation of Aggression: An Observational Study of Father-Child Play Dyads  

PubMed Central

Rough-and-tumble play (RTP) is a common form of play between fathers and children. It has been suggested that RTP can contribute to the development of selfregulation. This study addressed the hypothesis that the frequency of father–child RTP is related to the frequency of physically aggressive behavior in early childhood. This relationship was expected to be moderated by the dominance relationship between father and son during play. Eighty-five children between the ages of 2 and 6 years were videotaped during a free-play session with their fathers in their homes and questionnaire data was collected about father–child RTP frequency during the past year. The play dyads were rated for the degree to which the father dominated play interactions. A significant statistical interaction revealed that RTP frequency was associated with higher levels of physical aggression in children whose fathers were less dominant. These results indicate that RTP is indeed related to physical aggression, though this relationship is moderated by the degree to which the father is a dominant playmate.

Flanders, Joseph L.; Leo, Vanessa; Paquette, Daniel; Pihl, Robert O.; Seguin, Jean R.

2012-01-01

149

Numerical study of viscosity and inertial effects on tank-treading and tumbling motions of vesicles under shear flow  

NASA Astrophysics Data System (ADS)

An inextensible vesicle under shear flow experiences a tank-treading motion on its membrane if the viscosity contrast between the interior and exterior fluids is small. Above a critical threshold of viscosity contrast, the vesicle undergoes a tumbling bifurcation. In this paper, we extend our previous work [Kim and Lai, J. Comput. Phys.JCTPAH0021-999110.1016/j.jcp.2010.03.020 229, 4840 (2010)] to the case of different viscosity and investigate the transition between the tank-treading and tumbling motions in detail. The present numerical results are in a good agreement with other numerical and theoretical studies qualitatively. In addition, we study the inertial effect on this transition and find that the inertial effect might inhibit the tumbling motion in favor of the tank-treading motion, which is observed recently in the literature. The critical viscosity contrast for the transition to the tumbling motion usually increases as the reduced area increases in the Stokes regime. However, we surprisingly observe that the critical viscosity contrast decreases as the reduced area increases to some point in the flow of slightly higher Reynolds number. Our numerical result also shows that the inertial effect has stronger inhibition to tumbling motion when the reduced area is small.

Kim, Yongsam; Lai, Ming-Chih

2012-12-01

150

A guidance and navigation system for two spacecraft rendezvous in translunar halo orbit  

Microsoft Academic Search

This research considers the design of a representative end-to-end guidance and navigation system for the terminal phase rendezvous of two spacecraft in the circular restricted three-body problem. It assumes the target vehicle is in a small radius translunar halo orbit; the target vehicle remains passive with respect to the rendezvous profile. The chaser vehicle is in an independent small radius

Brian L. Jones

1993-01-01

151

Exploring the Behavioural Effects of Location-Aware Computing While Rendezvousing  

Microsoft Academic Search

This paper presents an exploratory field study investigating the behavioral effects of mobile location-aware computing on rendezvousing. We introduce a study where participants took part in one of three mobile device conditions (a mobile phone, a location-aware handheld or both a mobile phone and a location-aware handheld) and completed three different rendezvousing scenarios. We discuss the difference in communication patterns

David Dearman; Kirstie Hawkey; Kori Inkpen

152

Exploring the Behavioural Effect of Location-Awareness within the Social Context of Rendezvousing  

Microsoft Academic Search

This paper presents an exploratory field study investigating the behavioral effects of mobile location-aware computing within the social context of rendezvousing. We introduce a study where participants took part in one of three mobile device conditions (a mobile phone, a location-aware handheld or both a mobile phone and a location-aware handheld) and completed three different rendezvousing scenarios. We discuss the

David Dearman; Kirstie Hawkey

153

Design of an algorithm for autonomous docking with a freely tumbling target  

NASA Astrophysics Data System (ADS)

For complex unmanned docking missions, limited communication bandwidth and delays do not allow ground operators to have immediate access to all real-time state information and hence prevent them from playing an active role in the control loop. Advanced control algorithms are needed to make mission critical decisions to ensure safety of both spacecraft during close proximity maneuvers. This is especially true when unexpected contingencies occur. These algorithms will enable multiple space missions, including servicing of damaged spacecraft and missions to Mars. A key characteristic of spacecraft servicing missions is that the target spacecraft is likely to be freely tumbling due to various mechanical failures or fuel depletion. Very few technical references in the literature can be found on autonomous docking with a freely tumbling target and very few such maneuvers have been attempted. The MIT Space Systems Laboratory (SSL) is currently performing research on the subject. The objective of this research is to develop a control architecture that will enable safe and fuel-efficient docking of a thruster based spacecraft with a freely tumbling target in presence of obstacles and contingencies. The approach is to identify, select and implement state estimation, fault detection, isolation and recovery, optimal path planning and thruster management algorithms that, once properly integrated, can accomplish such a maneuver autonomously. Simulations and demonstrations on the SPHERES testbed developed by the MIT SSL will be executed to assess the performance of different combinations of algorithms. To date, experiments have been carried out at the MIT SSL 2-D Laboratory and at the NASA Marshall Space Flight Center (MSFC) flat floor.

Nolet, Simon; Kong, Edmund; Miller, David W.

2005-05-01

154

Multiple NEO Rendezvous, Reconnaissance and In Situ Exploration  

NASA Astrophysics Data System (ADS)

We propose a two spacecraft mission (Mother Ship and Small Body Lander) rendezvous with multiple Near Earth Objects (NEO). This two spacecraft mission mimics the likely architecture approach that human explorers will use: a “mother ship”(MS) designed to get from Earth to the NEO and a “Small Body Lander”(SBL) that performs in situ investigation on or close to the NEO’s surface. The MS carries the SBL to the target NEO. Once at the target NEO, the MS conducts an initial reconnaissance in order to produce a high resolution map of the surface. This map is used to identify coordinates of interest which are sent to the SBL. The SBL un-docks from the MS to rendezvous with the NEO and collect data. Landings are possible, though the challenges of anchoring to the NEO surface are significant. The SBL design is flexible and adaptable, enabling science data collection on or near the surface. After surface investigations are completed on the first NEO, the SBL will return and autonomously rendezvous and dock with the MS. The MS then goes to the next NEO target. During transit to the next NEO, the SBL could be refueled by the MS, a TRL8 capability demonstrated on the DARPA/NASA Orbital Express mission in 2007, or alternately sized to operate without requiring refueling depending on the mission profile. The mission goals are to identify surface hazards; quantify engineering boundary conditions for future human visits, and identify resources for future exploitation. The mission goals will be accomplished through the execution of key mission objectives: (1) high-resolution surface topography; (2) surface composition and mineralogy; (3) radiation environment near NEO; and (4) mechanical properties of the surface. Essential SBL instruments include: a) LIDAR (Obj. 1); b) 3D, high- resolution hyperspectral imaging cameras (Obj. 2); c) radiation sensor package (Obj. 3); and d) strain gauges (Obj. 4). Additional or alternative instruments could include: e) x-ray fluorescence or laser-induced breakdown spectroscopy (LIBS) sensor package (Obj. 2); f) gamma ray/neutron spectrometry package (Obj. 2); and g) radiometer package (to address variations in thermal environment). The ability to reach, survey, sample, and analyze multiple NEOs at close proximity is an enormous capability that can enable NASA to rapidly achieve the primary Exploration Precursor Robotic Mission (xPRM) Program goal of characterizing NEOs for future human exploration. Instead of launching multiple dedicated missions to each NEO of interest, a multi-NEO sortie mission can be planned and executed to achieve the same mission objectives with one launch, dramatically reducing the cost of NEO exploration. Collectively, our NEO Exploration System Architecture provides solutions for a wide variety of exploration activities using a common spacecraft bus and common core instrumentation for the spacecraft. This engineering consistency will substantially improve the probability of mission success, increase the likelihood of maintaining an aggressive launch schedule, and decrease the total cost of multiple missions. NASA successfully used this approach with the robotic precursors leading up to the Apollo missions, and we see significant benefits from this same programmatic approach for the xPRM program.

Klaus, K.; Elsperman, M. S.; Cook, T.; Smith, D.

2010-12-01

155

Autonomous Mission Manager for Rendezvous, Inspection and Mating  

NASA Technical Reports Server (NTRS)

To meet cost and safety objectives, space missions that involve proximity operations between two vehicles require a high level of autonomy to successfully complete their missions. The need for autonomy is primarily driven by the need to conduct complex operations outside of communication windows, and the communication time delays inherent in space missions. Autonomy also supports the goals of both NASA and the DOD to make space operations more routine, and lower operational costs by reducing the requirement for ground personnel. NASA and the DoD have several programs underway that require a much higher level of autonomy for space vehicles. NASA's Space Launch Initiative (SLI) program has ambitious goals of reducing costs by a factor or 10 and improving safety by a factor of 100. DARPA has recently begun its Orbital Express to demonstrate key technologies to make satellite servicing routine. The Air Force's XSS-ll program is developing a protoflight demonstration of an autonomous satellite inspector. A common element in space operations for many NASA and DOD missions is the ability to rendezvous, inspect anclJor dock with another spacecraft. For DARPA, this is required to service or refuel military satellites. For the Air Force, this is required to inspect un-cooperative resident space objects. For NASA, this is needed to meet the primary SLI design reference mission of International Space Station re-supply. A common aspect for each of these programs is an Autonomous Mission Manager that provides highly autonomous planning, execution and monitoring of the rendezvous, inspection and docking operations. This paper provides an overview of the Autonomous Mission Manager (AMM) design being incorporated into many of these technology programs. This AMM provides a highly scalable level of autonomous operations, ranging from automatic execution of ground-derived plans to highly autonomous onboard planning to meet ground developed mission goals. The AMM provides the capability to automatically execute the plans and monitor the system performance. In the event of system dispersions or failures the AMM can modify plans or abort to assure overall system safety. This paper describes the design and functionality of Draper's AMM framework, presents concept of operations associated with the use of the AMM, and outlines the relevant features of the flight demonstrations.

Zimpfer, Douglas J.

2003-01-01

156

Selection of rendezvous sites and reuse of pup raising areas among wolves Canis lupus of north-eastern Apennines, Italy  

Microsoft Academic Search

A coarse scale analysis was carried out of factors affecting rendezvous site selection and fidelity to pup raising areas in\\u000a wolfCanis lupus Linnaeus, 1758 packs inhabiting the north eastern Apennines, Italy. From 1993 to 2004, 44 rendezvous sites were identified,\\u000a and compared with random sites for variables related to topography, habitat, and human presence. Rendezvous sites were significantly\\u000a more frequent

Claudia Capitani; Luca Mattioli; Elisa Avanzinelli; Andrea Gazzola; Paolo Lamberti; Lorenza Mauri; Massimo Scandura; Alessia Viviani; Marco Apollonio

2006-01-01

157

The Successful Development of an Automated Rendezvous and Capture (AR&C) System for the National Aeronautics and Space Administration  

Microsoft Academic Search

During the 1990's, the Marshall Space Flight Center (MSFC) conducted pioneering research in the development of an automated rendezvous and capture\\/docking (AR&C) system for U.S. space vehicles. Development and demonstration of a rendezvous sensor was identified early in the AR&C Program as the critical enabling technology that allows automated proximity operations and docking. A first generation rendezvous sensor, the Video

Fred D. Roe; Richard T. Howard

2003-01-01

158

The Successful Development of an Automated Rendezvous and Capture (AR&C) System for the National Aeronautics and Space Administration  

Microsoft Academic Search

During the 1990’s, the Marshall Space Flight Center (MSFC) conducted pioneering research in the development of an automated rendezvous and capture\\/docking (AR&C) system for U.S. space vehicles. Development and demonstration of a rendezvous sensor was identified early in the AR&C Program as the critical enabling technology that allows automated proximity operations and docking. A first generation rendezvous sensor, the Video

Fred D. Roe; Richard T. Howard

2003-01-01

159

Multi-Sensor Testing for Automated Rendezvous and Docking  

NASA Astrophysics Data System (ADS)

During the past two years, many sensors have been tested in an open-loop fashion in the Marshall Space Flight Center (MSFC) Flight Robotics Laboratory (FRL) to both determine their suitability for use in Automated Rendezvous and Docking (AR&D) systems and to ensure the test facility is prepared for future multi-sensor testing. The primary focus of this work was in support of the CEV AR&D system, because the AR&D sensor technology area was identified as one of the top risks in the program. In 2006, four different sensors were tested individually or in a pair in the MSFC FRL. In 2007, four sensors, two each of two different types, were tested simultaneously. In each set of tests, the target was moved through a series of pre-planned trajectories while the sensor tracked it. In addition, a laser tracker ``truth'' sensor also measured the target motion. The tests demonstrated the functionality of testing four sensors simultaneously as well as the capabilities (both good and bad) of all of the different sensors tested. This paper outlines the test setup and conditions, briefly describes the facility, summarizes the earlier results of the individual sensor tests, and describes in some detail the results of the four-sensor testing. Post-test analysis includes data fusion by minimum variance estimation and sequential Kalman filtering. This Sensor Technology Project work was funded by NASA's Exploration Technology Development Program.

Howard, Richard T.; Carrington, Connie K.

2008-01-01

160

Ku-Band rendezvous radar performance computer simulation model  

NASA Technical Reports Server (NTRS)

All work performed on the Ku-band rendezvous radar performance computer simulation model program since the release of the preliminary final report is summarized. Developments on the program fall into three distinct categories: (1) modifications to the existing Ku-band radar tracking performance computer model; (2) the addition of a highly accurate, nonrealtime search and acquisition performance computer model to the total software package developed on this program; and (3) development of radar cross section (RCS) computation models for three additional satellites. All changes in the tracking model involved improvements in the automatic gain control (AGC) and the radar signal strength (RSS) computer models. Although the search and acquisition computer models were developed under the auspices of the Hughes Aircraft Company Ku-Band Integrated Radar and Communications Subsystem program office, they have been supplied to NASA as part of the Ku-band radar performance comuter model package. Their purpose is to predict Ku-band acquisition performance for specific satellite targets on specific missions. The RCS models were developed for three satellites: the Long Duration Exposure Facility (LDEF) spacecraft, the Solar Maximum Mission (SMM) spacecraft, and the Space Telescopes.

Magnusson, H. G.; Goff, M. F.

1984-01-01

161

Video-Guidance Design for the DART Rendezvous Mission  

NASA Technical Reports Server (NTRS)

NASA's Demonstration of Autonomous Rendezvous Technology (DART) mission will validate a number of different guidance technologies, including state-differenced GPS transfers and close-approach video guidance. The video guidance for DART will employ NASA/Marshall s Advanced Video Guidance Sensor (AVGS). This paper focuses on the terminal phase of the DART mission that includes close-approach maneuvers under AVGS guidance. The closed-loop video guidance design for DART is driven by a number of competing requirements, including a need for maximizing tracking bandwidths while coping with measurement noise and the need to minimize RCS firings. A range of different strategies for attitude control and docking guidance have been considered for the DART mission, and design decisions are driven by a goal of minimizing both the design complexity and the effects of video guidance lags. The DART design employs an indirect docking approach, in which the guidance position targets are defined using relative attitude information. Flight simulation results have proven the effectiveness of the video guidance design.

Ruth, Michael; Tracy, Chisholm

2004-01-01

162

Multi-sensor Testing for Automated Rendezvous and Docking  

NASA Technical Reports Server (NTRS)

During the past two years, many sensors have been tested in an open-loop fashion in the Marshall Space Flight Center (MSFC) Flight Robotics Laboratory (FRL) to both determine their suitability for use in Automated Rendezvous and Docking (AR&D) systems and to ensure the test facility is prepared for future multi-sensor testing. The primary focus of this work was in support of the CEV AR&D system, because the AR&D sensor technology area was identified as one of the top risks in the program. In 2006, four different sensors were tested individually or in a pair in the MSFC FRL. In 2007, four sensors, two each of two different types, were tested simultaneously. In each set of tests, the target was moved through a series of pre-planned trajectories while the sensor tracked it. In addition, a laser tracker "truth" sensor also measured the target motion. The tests demonstrated the functionality of testing four sensors simultaneously as well as the capabilities (both good and bad) of all of the different sensors tested. This paper outlines the test setup and conditions, briefly describes the facility, summarizes the earlier results of the individual sensor tests, and describes in some detail the results of the four-sensor testing. Post-test analysis includes data fusion by minimum variance estimation and sequential Kalman filtering. This Sensor Technology Project work was funded by NASA's Exploration Technology Development Program.

Howard, Richard T.; Carrington, Connie K.

2008-01-01

163

Active sensor system for automatic rendezvous and docking  

NASA Astrophysics Data System (ADS)

NASA's Marshall Space Flight Center has developed an active sensor system, the ideo guidance sensor (VGS), to provide near-range relative position and attitude data. The VGS will be part of an automatic rendezvous and docking system. The VGS determines the relative positions and attitudes between the active sensor and the passive target. It works by using laser diodes to illuminate the retro-reflectors in the target, a solid-state camera to detect the return from the target retro-reflectors, and a frame grabber and digital signal processor to convert the video information into relative positions and attitudes. The current sensor design is the result of several years of development and testing, and it is being built to fly as an experiment payload on the space shuttle. The VGS system is designed to operate with the target completely visible within a relative azimuth of +/- 10.5 degrees and a relative elevation of +/- 8 degrees. The system will acquire and track and target within that field-of-view anywhere from 1.0 meters to 110 meters range at any relative roll angle and relative pitch and yaw attitudes of up to +/- 10 degrees. The data is output from the sensor at 5 Hz, and the target and sensor software have been designed to permit two independent sensors to operate simultaneously for redundancy.

Howard, Richard T.; Bryan, Thomas C.; Book, Michael L.; Jackson, John L.

1997-08-01

164

Motility-Induced Phase Separation in Active Matter: a generic formalism for active brownian particles and run-and-tumble particles  

NASA Astrophysics Data System (ADS)

In this talk I will show that several classes of active particles admit an identical coarse-grained description in terms of fluctuating hydrodynamic fields. This equivalence holds as long as the microscopic parameters (e.g. swim speed v, diffusivity or tumbling rate), that may be spatially varying, depend on the local density ? of particles but not on their orientation. This equivalence can thus extend to interacting particles and shows that motility-induced phase separation is generic in these systems: a steeply enough decreasing v(?) generates phase separation in dimensions d=1,2,3. I will discuss the consequences of this phenomenon for pattern formation in bacterial colony and effective temperatures in Active Matter.

Tailleur, Julien

2013-03-01

165

Prediction of flow-aligning and tumbling in a bent-core nematic liquid crystal using measurements of orienation order parameters  

NASA Astrophysics Data System (ADS)

The flow behavior of bent-core nematic liquid crystal (A131), which has been known to exhibit a biaxial nematic phase, is predicted by measurements of 2^nd and 4^th rank orientation order parameters. Using experimentally determined uniaxial, and , and biaxial orientation order parameters, , and from polarized micro-Raman spectroscopy, we compute the tumbling parameter, ?. The relationships between the order parameters and tumbling parameter derived by 2 different groups are used and the results are computed: a molecular theory by Archer and Larson (1995), that by Kroger and Seller (1995) for uniaxial system, and Leslie's theory for 2-director continuum. Temperature evolution of tumbling parameter shows the transition from a flow alignment regime to a tumbling instability. The results of the temperature evolution of tumbling parameter of bent-core nematic LC are compared to those of pure nematic LC (5CB) and LC mixture (E7).

Park, Min Sang; Park, Beom-Jin; Park, Jung Ok; Srinivasarao, Mohan

2010-03-01

166

Characterization of the morphology of fast-tumbling bicelles with varying composition.  

PubMed

Small, fast-tumbling bicelles are frequently used in solution NMR studies of protein-lipid interactions. For this purpose it is critical to have information about the organization of the lipids within the bicelle structure. We have studied the morphology of small, fast-tumbling bicelles containing DMPC and DHPC as a function of temperature, lipid concentration, and the relative ratio (q value) of lipid (DMPC) to detergent (DHPC) amounts. Dynamic light scattering and cryo-transmission electron microscopy techniques were used to measure the size of the bicelles and to monitor the shape and dispersity of the particles in the samples. The stability and size of DMPC-containing bicelle mixtures were found to be highly dependent on temperature and the total lipid concentration for mixtures with q = 1 and q = 1.5. Stable DMPC/DHPC bicelles are only formed at low q values (0.5). Bicelle mixtures with q > 0.5 appear to be multidisperse containing more than one component, one with rH around 2.5 nm and one with rH of 6-8 nm. This is interpreted as a coexistence of small (possibly mixed micelles) bicelles and much larger bicelles. Incubating the sample at 37 °C increases the phase separation. Moreover, low total amphiphile concentrations and low q values lead to the formation of a temperature-independent morphology, interpreted as the formation of small particles in which the DHPC and DMPC are more mixed. On the basis of these results, we propose the existence of a critical bicelle concentration, a parameter that determines the existence of bilayered bicelles, which varies with q value. This polymorphism was not observed at any concentrations for q = 0.5 bicelles, for which a small but detectable temperature dependence was observed at high concentrations. The results demonstrate that q = 0.5 mixtures predominantly form "classical" bicelles, but that caution is needed when using fast-tumbling mixtures with q values higher than 0.5. PMID:24785902

Ye, Weihua; Lind, Jesper; Eriksson, Jonny; Mäler, Lena

2014-05-20

167

Flight data results of estimate fusion for spacecraft rendezvous navigation from shuttle mission STS-69  

NASA Technical Reports Server (NTRS)

A recently developed rendezvous navigation fusion filter that optimally exploits existing distributed filters for rendezvous and GPS navigation to achieve the relative and inertial state accuracies of both in a global solution is utilized here to process actual flight data. Space Shuttle Mission STS-69 was the first mission to date which gathered data from both the rendezvous and Global Positioning System filters allowing, for the first time, a test of the fusion algorithm with real flight data. Furthermore, a precise best estimate of trajectory is available for portions of STS-69, making possible a check on the performance of the fusion filter. In order to successfully carry out this experiment with flight data, two extensions to the existing scheme were necessary: a fusion edit test based on differences between the filter state vectors, and an underweighting scheme to accommodate the suboptimal perfect target assumption made by the Shuttle rendezvous filter. With these innovations, the flight data was successfully fused from playbacks of downlinked and/or recorded measurement data through ground analysis versions of the Shuttle rendezvous filter and a GPS filter developed for another experiment. The fusion results agree with the best estimate of trajectory at approximately the levels of uncertainty expected from the fusion filter's covariance matrix.

Carpenter, J. Russell; Bishop, Robert H.

1996-01-01

168

Manned maneuvering unit applications for automated rendezvous and capture  

NASA Technical Reports Server (NTRS)

Automated Rendezvous and Capture (AR&C) is an important technology to multiple National Aeronautics and Space Administration (NASA) programs and centers. The recent Johnson Spacecraft Center (JSC) AR&C Quality Function Deployment (QFD) has listed on-orbit demonstration of related technologies as a near term priority. Martin Marietta has been evaluating use of the Manned Maneuvering Unit (MMU) for a low cost near term on-orbit demonstration of AR&C technologies such as control algorithms, sensors, and processors as well as system level performance. The MMU Program began in 1979 as the method of repairing the Space Shuttle (STS) Thermal Protection System (the tiles). The units were not needed for this task, but were successfully employed during three Shuttle flights in 1984: a test flight was flown in in February as proof of concept, in April the MMU participated in the Solar Max Repair Mission, and in November the MMU's returned to space to successfully rescue the two errant satellites, Westar and Palapa. In the intervening years, the MMU simulator and MMU Qualification Test Unit (QTU) have been used for Astronaut training and experimental evaluations. The Extra-Vehicular Activities (EVA) Retriever has used the QTU, in an unmanned form, as a free-flyer on the Johnson Space Center (JSC) Precision Air Bearing Floor (PABF). Currently, the MMU is undergoing recertification for flight. The two flight units were removed from storage in September, 1991 and evaluation tests were performed. The tests demonstrated that the units are in good shape with no discrepancies that would preclude further use. The Return to Flight effort is currently clearing up recertification issues and evaluating the design against the present Shuttle environments.

Brehm, Donald L.; Cuseo, John A.; Lenda, Joseph A.; Ray, Lex; Whitsett, C. Edward

1991-01-01

169

Manned maneuvering unit applications for automated rendezvous and capture  

NASA Astrophysics Data System (ADS)

Automated Rendezvous and Capture (AR&C) is an important technology to multiple National Aeronautics and Space Administration (NASA) programs and centers. The recent Johnson Spacecraft Center (JSC) AR&C Quality Function Deployment (QFD) has listed on-orbit demonstration of related technologies as a near term priority. Martin Marietta has been evaluating use of the Manned Maneuvering Unit (MMU) for a low cost near term on-orbit demonstration of AR&C technologies such as control algorithms, sensors, and processors as well as system level performance. The MMU Program began in 1979 as the method of repairing the Space Shuttle (STS) Thermal Protection System (the tiles). The units were not needed for this task, but were successfully employed during three Shuttle flights in 1984: a test flight was flown in in February as proof of concept, in April the MMU participated in the Solar Max Repair Mission, and in November the MMU's returned to space to successfully rescue the two errant satellites, Westar and Palapa. In the intervening years, the MMU simulator and MMU Qualification Test Unit (QTU) have been used for Astronaut training and experimental evaluations. The Extra-Vehicular Activities (EVA) Retriever has used the QTU, in an unmanned form, as a free-flyer on the Johnson Space Center (JSC) Precision Air Bearing Floor (PABF). Currently, the MMU is undergoing recertification for flight. The two flight units were removed from storage in September, 1991 and evaluation tests were performed. The tests demonstrated that the units are in good shape with no discrepancies that would preclude further use. The Return to Flight effort is currently clearing up recertification issues and evaluating the design against the present Shuttle environments.

Brehm, Donald L.; Cuseo, John A.; Lenda, Joseph A.; Ray, Lex; Whitsett, C. Edward

170

An Automatic Terminal Guidance System for Rendezvous with a Satellite  

NASA Technical Reports Server (NTRS)

This study includes a consideration of the design philosophy for an automatic terminal guidance system, a derivation of guidance equations required, and an outline of the general type of instrumentation necessary to provide the essential information. A control system for a sample vehicle is analyzed. A representative case, rendezvous with a satellite in circular orbit at 400 nautical miles, was examined. Terminal-stage nominal burning times of 200 and 400 seconds were used. For the 200-second case, initial errors in circumferential displacement of +/- 25,000 feet, in radial displacement of 7,000 to -9,000 feet, and in lateral displacement of +/- 20,000 feet were within the capabilities of the system. Velocity errors of 300 to -400 ft/sec in the circumferential direction, 180 to -200 ft/sec in the radial direction, and velocity offsets of at least 20 (+/- 800 ft/sec) in the lateral direction could also be handled. The 400-second case was capable of correcting larger errors, but limits were not determined. The dependence of required characteristic velocity on initial errors was determined and it was found that increases over the nominal terminal-stage characteristic velocity of the order of 15 percent covered most of the previously mentioned in-plane errors. The requirements were more severe for cases with lateral velocity offsets. A simplified set of guidance equations was tested and produced only slight variations in performance. Overall velocity requirements and mass ratios were determined for terminal-stage burning times of 100, 200, 300, and 400 seconds and for a range of transfer angles by using exact calculations for the terminal stage and an impulsive launching velocity. These results indicated that the shortest burning time consistent with the launch guidance errors expected gave the best mass ratio.

Carney, Terrance M.

1961-01-01

171

Recent developments in electropolishing and tumbling R&D at Fermilab  

SciTech Connect

Fermi National Accelerator Lab (Fermilab) is continuing to improve its infrastructure for research and development on the processing of superconducting radio frequency cavities. A single cell 3.9 GHz electropolishing tool built at Fermilab and operated at an industrial partner was recently commissioned. The EP tool was used to produce a single cell 3.9 GHz cavity that reached an accelerating gradient of 30 MV/m with a quality factor of 5 x 10{sup 9}. A single cell 1.3 GHz cavity was also electropolished at the same industrial vendor using the vendor's vertical full-immersion technique. On their first and only attempt the vendor produced a single cell 1.3 GHz cavity that reached 30 MV/m with a quality factor of 1 x 10{sup 10}. These results will be detailed along with preliminary tumbling results.

Cooper, C.; Brandt, J.; Cooley, L.; Ge, M.; Harms, E.; Khabiboulline, T.; Ozelis, J.; /Fermilab; Boffo, C.; /Babcock Noell, Wuerzburg

2009-10-01

172

Electron spin-lattice relaxation mechanisms of rapidly-tumbling nitroxide radicals  

NASA Astrophysics Data System (ADS)

Electron spin relaxation times at 295 K were measured at frequencies between 250 MHz and 34 GHz for perdeuterated 2,2,6,6-tetramethyl-4-piperidone-1-oxyl (PDT) in five solvents with viscosities that result in tumbling correlation times, ?R, between 4 and 50 ps and for three 14N/15N pairs of nitroxides in water with ?R between 9 and 19 ps. To test the impact of structure on relaxation three additional nitroxides with ?R between 10 and 26 ps were studied. In this fast tumbling regime T2-1˜T1-1 at frequencies up to about 9 GHz. At 34 GHz T2-1>T1-1 due to increased contributions to T2-1 from incomplete motional averaging of g-anisotropy, and T2-1-T1-1 is proportional to ?R. The contribution to T1-1 from spin rotation is independent of frequency and decreases as ?R increases. Spin rotation dominates T1-1 at 34 GHz for all ?R studied, and at all frequencies studied for ?R = 4 ps. The contribution to T1-1 from modulation of nitrogen hyperfine anisotropy increases as frequency decreases and as ?R increases; it dominates at low frequencies for ?R > ˜15 ps. The contribution from modulation of g anisotropy is significant only at 34 GHz. Inclusion of a thermally-activated process was required to account for the observation that for most of the radicals, T1-1 was smaller at 250 MHz than at 1-2 GHz. The significant 15N/14N isotope effect, the small H/D isotope effect, and the viscosity dependence of the magnitude of the contribution from the thermally-activated process suggest that it arises from intramolecular motions of the nitroxide ring that modulate the isotropic A values.

Biller, Joshua R.; Elajaili, Hanan; Meyer, Virginia; Rosen, Gerald M.; Eaton, Sandra S.; Eaton, Gareth R.

2013-11-01

173

Robust rendezvous maneuver point conditions. M.S. Thesis - Massachusetts Inst. of Tech.  

NASA Technical Reports Server (NTRS)

This study develops rendezvous maneuver point conditions that are robust to one dimensional errors in state estimation and burn execution. Allowing small deviations in the time of intercept provides a degree of freedom that can be used to compensate for these errors. The direction of allowable burn deviation is developed for errors in state estimation and burn execution. The maneuver points for which the error is aligned with the insensitive direction provide excellent rendezvous initiation points. The method is applied to sample rendezvous for vehicles in circular and elliptic orbits. Robust maneuver points are selected and the vehicles' relative motion plotted, demonstrating the validity of the maneuver points. Finally, a graphical illustration of the error focusing effect is demonstrated by means of a Monte Carlo simulation.

Fogle, Debra Ann

1992-01-01

174

An Assessment of the Technology of Automated Rendezvous and Capture in Space  

NASA Technical Reports Server (NTRS)

This paper presents the results of a study to assess the technology of automated rendezvous and capture (AR&C) in space. The outline of the paper is as follows. First, the history of manual and automated rendezvous and capture and rendezvous and dock is presented. Next, the need for AR&C in space is established. Then, today's technology and ongoing technology efforts related to AR&C in space are reviewed. In light of these, AR&C systems are proposed that meet NASA's future needs, but can be developed in a reasonable amount of time with a reasonable amount of money. Technology plans for developing these systems are presented; cost and schedule are included.

Polites, M. E.

1998-01-01

175

Methodology for Developing a Probabilistic Risk Assessment Model of Spacecraft Rendezvous and Dockings  

NASA Technical Reports Server (NTRS)

In 2007 NASA was preparing to send two new visiting vehicles carrying logistics and propellant to the International Space Station (ISS). These new vehicles were the European Space Agency s (ESA) Automated Transfer Vehicle (ATV), the Jules Verne, and the Japanese Aerospace and Explorations Agency s (JAXA) H-II Transfer Vehicle (HTV). The ISS Program wanted to quantify the increased risk to the ISS from these visiting vehicles. At the time, only the Shuttle, the Soyuz, and the Progress vehicles rendezvoused and docked to the ISS. The increased risk to the ISS was from an increase in vehicle traffic, thereby, increasing the potential catastrophic collision during the rendezvous and the docking or berthing of the spacecraft to the ISS. A universal method of evaluating the risk of rendezvous and docking or berthing was created by the ISS s Risk Team to accommodate the increasing number of rendezvous and docking or berthing operations due to the increasing number of different spacecraft, as well as the future arrival of commercial spacecraft. Before the first docking attempt of ESA's ATV and JAXA's HTV to the ISS, a probabilistic risk model was developed to quantitatively calculate the risk of collision of each spacecraft with the ISS. The 5 rendezvous and docking risk models (Soyuz, Progress, Shuttle, ATV, and HTV) have been used to build and refine the modeling methodology for rendezvous and docking of spacecrafts. This risk modeling methodology will be NASA s basis for evaluating the addition of future ISS visiting spacecrafts hazards, including SpaceX s Dragon, Orbital Science s Cygnus, and NASA s own Orion spacecraft. This paper will describe the methodology used for developing a visiting vehicle risk model.

Farnham, Steven J., II; Garza, Joel, Jr.; Castillo, Theresa M.; Lutomski, Michael

2011-01-01

176

Six-impulse maneuvers for rendezvous of spacecraft in near-circular noncoplanar orbits  

NASA Astrophysics Data System (ADS)

The problem of a rendezvous of two spacecraft in close near-circular noncoplanar orbits is considered. The angles of applying velocity impulses and their orientation are determined from necessary conditions of optimality derived using the basis vector theory. For non-degenerate six-impulse solutions the analytical formulas are found that approximate the dependence of moments of applying velocity impulses and angles determining their orientation on the rendezvous duration. The total characteristic velocity of six-impulse solutions (or five-impulse solutions derived from them) is compared to the total characteristic velocity obtained when solving the Lambert problem.

Baranov, A. A.; Roldugin, D. S.

2012-11-01

177

Halley comet rendezvous with a SEPS vehicle. [Solar Electric Propulsion System  

NASA Technical Reports Server (NTRS)

An analysis of the performance of a Solar Electric Propulsion System (SEPS) vehicle rendezvousing with Halley's comet just prior to its Frebruary 1986 perihelion is described. A calculus of variations mathematical formulation is used to maximize Halley arrival mass while giving effect to the influence of solar array size, launch date, arrival date, and insertion hyperbolic excess velocity. Numerical sensitivity relief, thrust system modeling, trajectory characteristics and ion engine operating conditions are discussed and illustrated. Results indicate a rendezvous is feasible with a minimal advance in solar cell and ion engine technology.

Burrows, R. R.

1978-01-01

178

Star tracker axis-to-sunlit earth horizon angle constraint evaluations for rendezvous operations  

NASA Technical Reports Server (NTRS)

The results are presented of a study initiated to evaluate the star tracker axis-to-sunlit earth horizon angle constraint with respect to limitations imposed on the passive target rendezvous capability. The data presented include considerations for dispersions and sensor pointing capabilities and generalizations with respect to the uncertainties associated with the angle constraint available in practice.

Hutchison, W. L.

1975-01-01

179

Robust rendezvous for mobile autonomous agents via proximity graphs in arbitrary dimensions  

Microsoft Academic Search

This paper presents coordination algorithms for networks of mobile autonomous agents. The objective of the proposed algorithms is to achieve rendezvous, that is, agreement over the location of the agents in the network. We provide analysis and design results for multiagent networks in arbitrary dimensions under weak requirements on the switching and failing communication topology. The novel correctness proof relies

Jorge Cortes; Sonia Martínez; Francesco Bullo

2006-01-01

180

A relative navigation application of ULTOR technology for automated rendezvous and docking  

Microsoft Academic Search

NASA's initiative for space exploration will require the development of robotic servicing and unmanned resupply of permanent space borne facilities. An enabling technology to accomplish these goals is by sensor systems capable of Rendezvous, Proximity Operations and Docking (RPOD) missions. Marshall Space Flight Center (MSFC) conducted an experiment whose objective intent was to characterize sensor systems for potential use in

S. Joel Hannah

2006-01-01

181

An analytic approach to optimal rendezvous using Clohessy-Wiltshire equations  

NASA Technical Reports Server (NTRS)

An analytic approach is used to obtain the optimal solution time that minimizes the sum of the two applied impulses necessary to rendezvous for the Clohessy-Wiltshire equations. A plume impingement inequality constraint on the solution is examined, and an optimal policy is developed. Numerical tests are conducted to verify the analysis and to illustrate the optimal solution algorithm.

Jezewski, D. J.; Donaldson, J. D.

1979-01-01

182

Peer-to-peer refuelling within a satellite constellation part I: zero-cost rendezvous case  

Microsoft Academic Search

In this paper, we study the scheduling problem arising from refuelling multiple satellites in a constellation. The satellites in the constellation are assumed to be capable of refuelling each other. The cost of the rendezvous maneuver between two satellites exchanging fuel is assumed to be negligible. The goal of this refuelling problem is to equalize the fuel stored among all

Haijun Shen; Panagiotis Tsiotras

2003-01-01

183

Sensory Fusion for Planetary Surface Robotic Navigation, Rendezvous, and Manipulation Operations  

Microsoft Academic Search

The upcoming missions to Mars planned by NASMJPL in 2009 and 2013 are more ambitious than any previouslyjlown. Included in these missions are extended multi-kilometer traverses, and autonomous rover rendezvous with science targets and man-made structures such as landers. This paper reports some of the ongoing work at JPL in the areas of autonomous sensory fusion of both raw and

Terry Huntsberger; Yang Cheng; Eric T. Baumgartner; Matthew Robinson; Paul S. Schenker

184

Sensory fusion for planetary surface robotic navigation, rendezvous, and manipulation operations  

NASA Technical Reports Server (NTRS)

This paper reports some of the ongoing work at JPL in the areas of autonomous sensory fusion of both raw and derived inputs for better localization during long traverses, precision rendezvous operations with both labeled and unlabeled targets, and precision manipulation of targets.

Huntsberger, T.; Cheng, Y.; Baumgartner, E. T.; Robinson, M.; Schenker, P. S.

2003-01-01

185

Rendezvous terminal phase automatic braking sequencing and targeting. [for space shuttle orbiter  

NASA Technical Reports Server (NTRS)

The purpose of the rendezvous terminal phase braking program is to provide the means of automatically bringing the primary orbiter within desired station keeping boundaries relative to the target satellite. A detailed discussion is presented on the braking program and its navigation, targeting, and guidance functions.

Kachmar, P. M.

1973-01-01

186

The Direction of Synthetic Actors in the Film RendezVous a Montreal  

Microsoft Academic Search

This article describes how the synthetic actors Marilyn Monroe and Humphrey Bogart were directed in the film Rendez-vous a Montreal, using the Human Factory software. Innovative points are emphasized. The recreation of famous persons and reconstitution of their personalities, as well as the corresponding animation, are considered from an artistic point of view. Technical points discussed are personalized expressions, abstract

N. Magnenat-Thalmann; Daniel Thalmann

1987-01-01

187

Rendezvous and Docking Strategy for Crewed Segment of the Asteroid Redirect Mission  

NASA Technical Reports Server (NTRS)

This paper will describe the overall rendezvous, proximity operations and docking (RPOD) strategy in support of the Asteroid Redirect Crewed Mission (ARCM), as part of the Asteroid Redirect Mission (ARM). The focus of the paper is on the crewed mission phase of ARM, starting with the establishment of Orion in the Distant Retrograde Orbit (DRO) and ending with docking to the Asteroid Redirect Vechicle (ARV). The paper will detail the sequence of maneuvers required to execute the rendezvous and proximity operations mission phases along with the on-board navigation strategies, including the final approach phase. The trajectories to be considered will include target vehicles in a DRO. The paper will also discuss the sensor requirements for rendezvous and docking and the various trade studies associated with the final sensor selection. Building on the sensor requirements and trade studies, the paper will include a candidate sensor concept of operations, which will drive the selection of the sensor suite; concurrently, it will be driven by higher level requirements on the system, such as crew timeline constraints and vehicle consummables. This paper will address how many of the seemingly competing requirements will have to be addressed to create a complete system and system design. The objective is to determine a sensor suite and trajectories that enable Orion to successfully rendezvous and dock with a target vehicle in trans lunar space. Finally, the paper will report on the status of a NASA action to look for synergy within RPOD, across the crewed and robotic asteroid missions.

Hinkel, Heather D.; Cryan, Scott P.; D'Souza, Christopher; Dannemiller, David P.; Brazzel, Jack P.; Condon, Gerald L.; Othon, William L.; Williams, Jacob

2014-01-01

188

Partial Order Reduction in Presence of Rendezvous Communications with Unless Constructs and Weak Fairness  

Microsoft Academic Search

If synchronizing (rendez-vous) communications are used in the Promela models, the unless construct and the weak fairness algorithm are not compatible with the partial order reduction algorithm used in Spin's verifier. After identifying the wrong partial order reduction pattern that causes the incompatibility, we give solutions for these two problems. To this end we propose corrections in the identification of

Dragan Bosnacki

1999-01-01

189

SPARTAN: A High-Fidelity Simulation for Automated Rendezvous and Docking Applications.  

National Technical Information Service (NTIS)

Bd Systems (a subsidiary of SAIC) has developed the Simulation Package for Autonomous Rendezvous Test and ANalysis (SPARTAN), a high-fidelity on-orbit simulation featuring multiple six-degree-of-freedom (6DOF) vehicles. SPARTAN has been developed in a mod...

B. K. DeKock C. K. Carrington J. H. McDuffie K. M. Betts M. A. Turbe

2007-01-01

190

Comparison of transhepatic and extrahepatic routes for EUS-guided rendezvous procedure for distal CBD obstruction  

PubMed Central

Background EUS-guided rendezvous procedure (EUS-RV) can be done by the transhepatic (TH) or the extrahepatic (EH) route. There is no data on the preferred access route when both routes are available. Study aim To compare the success, complications, and duration of hospitalization for patients undergoing EUS-RV by the TH or the EH route. Patients and methods Patients with distal common bile duct (CBD) obstruction, who failed selective cannulation, underwent EUS-RV by the TH route through the stomach or the EH route through the duodenum. Results A total of 35 patients were analysed (17 TH, 18 EH). The mean procedure time was significantly longer for the TH group (34.4 vs. 25.7?min; p?=?0.0004). There was no difference in the technical success (94.1 vs. 100%). However, the TH group had a higher incidence of post-procedure pain (44.1 vs. 5.5%; p?=?0.017), bile leak (11.7 vs. 0; p?=?0.228), and air under diaphragm (11.7 vs. 0; p?=?0.228). All bile leaks were small and managed conservatively. Duration of hospitalization was significantly higher for the TH group (2.52 vs. 0.17 days; p?=?0.015). Conclusions EUS-RV has similar success rate by the TH or the EH route. However, the TH route has higher post-procedure pain, longer procedure time, and longer duration of hospitalization. The EH route should be preferred for EUS-RV in patients with distal CBD obstruction when both access routes are technically feasible.

Bhandari, Suryaprakash; Bapat, Mukta; Joshi, Nitin; Vivekanandarajah, Suhirdan; Maydeo, Amit

2013-01-01

191

Usage of pre-flight data in short rendezvous mission of Soyuz-TMA spacecrafts  

NASA Astrophysics Data System (ADS)

The paper describes the reduction of the vehicle autonomous flight duration before docking to the ISS. The Russian Soyuz-TMA spacecraft dock to the ISS two days after launch. Due to the limited volume inside Soyuz-TMA the reduction of time until docking to the ISS is very important, since the long stay of the cosmonauts in the limited volume adds to the strain of the space flight. In the previous papers of the authors it was shown that the existing capabilities of Soyuz-TMA, the ISS and the ground control loop make it possible to transfer to the five-orbit rendezvous profile. However, the analysis of the cosmonauts' schedule on the launch day shows that its duration is at the allowable limit and that is why it is necessary to find a way to further reduce the flight duration of Soyuz-TMA before docking to less than five orbits. In a traditional rendezvous profile, the calculation of rendezvous burns begins only after determination of the actual vehicle insertion orbit. The paper describes an approach in which the first two rendezvous burns are performed as soon as the spacecraft reaches the reference orbit and the values of the burns are calculated prior to the launch based on the pre-flight data for the nominal insertion. This approach decreases the duration of the rendezvous by one orbit. The demonstration flight of a Progress vehicle using the proposed profile was implemented on August 1, 2012 and completely confirmed the correctness of the imbedded principles. The paper considers the possible improvements of the proposed approach and recovery from the contingencies.

Murtazin, Rafail; Petrov, Nikolay

2014-01-01

192

Impedance Control for a Free-Floating Robot in the Grasping of a Tumbling Target with Parameter Uncertainty  

Microsoft Academic Search

This paper addresses an impedance control for a free-floating space robot in the grasping of a tumbling target with model uncertainty. Firstly, the operational space dynamics for a free-floating robot is derived with a novel, computationally efficient formulation. Then, considering the grasped target as a disturbance force on the end-effector, the proposed control method is completely independent of the target

Satoko Abiko; Roberto Lampariello; Gerd Hirzinger

2006-01-01

193

Assessing the Size, Stability, and Utility of Isotropically Tumbling Bicelle Systems for Structural Biology  

PubMed Central

Aqueous phospholipid mixtures that form bilayered micelles (bicelles) have gained wide use by molecular biophysicists during the past 20 years for spectroscopic studies of membrane-bound peptides and structural refinement of soluble protein structures. Nonetheless, the utility of bicelle systems may be compromised by considerations of cost, chemical stability, and preservation of the bicelle aggregate organization under a broad range of temperature, concentration, pH, and ionic strength conditions. In the current work, 31P nuclear magnetic resonance (NMR) and atomic force microscopy (AFM) have been used to monitor the size and morphology of isotropically tumbling small bicelles formed by mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (DIOMPC) with either 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) or 1,2-di-O-hexyl-sn-glycero-3-phospho-choline (DIOHPC), testing their tolerance of variations in commonly used experimental conditions. 1H-15N 2D NMR has been used to demonstrate the usefulness of the robust DMPC-DIOHPC system for conformational studies of a fatty acid-binding protein that shuttles small ligands to and from biological membranes.

Wu, Hongwei; Su, Kai; Guan, Xudong; Sublette, M. Elizabeth; Stark, Ruth E.

2009-01-01

194

Lipid dynamics in fast-tumbling bicelles with varying bilayer thickness: effect of model transmembrane peptides.  

PubMed

The morphology of q=0.5 fast-tumbling bicelles prepared with three different acyl chain lengths has been investigated by NMR. It is shown that bicelles prepared with DLPC (12 C) and DHPC are on average larger than those containing DMPC or DPPC (14 and 16 C) and DHPC, which may be due to a higher degree of mixing between DLPC and DHPC. The fast internal mobility of the lipids was determined from natural abundance carbon-13 relaxation. A similar dynamical behaviour of the phospholipids in the three different bicelles was observed, although the DPPC lipid acyl chain displayed a somewhat lower degree of mobility, as evidenced by higher generalized order parameters throughout the acyl chain. Carbon-13 relaxation was also used to determine the effect of different model transmembrane peptides, with flanking Lys residues, on the lipid dynamics in the three different bicelles. All peptides had the effect of increasing the order parameters for the DLPC lipid, while no effect was observed on the longer lipid chains. This effect may be explained by a mismatch between the hydrophobic length of the peptides and the DLPC lipid acyl chain. PMID:18692021

Lind, Jesper; Nordin, Jon; Mäler, Lena

2008-11-01

195

von Braun and the lunar-orbit rendezvous decision: finding a way to go to the moon  

Microsoft Academic Search

Wernher von Braun's historic talk at Huntsville on June 7, 1962, when he endorsed “lunar-orbit rendezvous” (LOR) as the mode for landing on the Moon, has long been seen as one of the most critical dates in the Apollo program. It effectively ended a months-long, divisive debate inside NASA over LOR versus “earth-orbit rendezvous” (EOR) versus “direct ascent” (a single

Michael J. Neufeld

2008-01-01

196

Diffusion, sedimentation equilibrium, and harmonic trapping of run-and-tumble nanoswimmers.  

PubMed

The diffusion of self-propelling nanoswimmers is explored by dissipative particle dynamics in which a nanoswimmer swims by forming an instantaneous force dipole with one of its nearest neighboring solvent beads. Our simulations mimic run-and-tumble behavior by letting the swimmer run for a time ?, then it randomly changes its direction for the next run period. Our simulations show that the swimming speed (?(a)) of a nanoswimmer is proportional to the propulsion force and the mobility of a pusher is the same as that of a puller. The effective diffusivity is determined by three methods: mean squared displacement, velocity autocorrelation function, and sedimentation equilibrium. The active colloid undergoes directed propulsion at short time scales but changes to random motion at long time scales. The velocity autocorrelation function decreases with time and becomes zero beyond the run time. Under gravity, the concentration profile of active colloids follows Boltzmann distribution with a sedimentation length consistent with that acquired from the drift-diffusion equation. In our simulation, all three methods yield the same result, the effective diffusivity of an active colloid is the sum of the diffusivity of a passive colloid and ?(a)²?/6. When the active colloids are confined by a harmonic well, they are trapped within a confinement length defined by the balance between the swimmer active force and restoring force of the well. When the confinement length is large compared to the run length, the stationary density profile follows the Boltzmann distribution. However, when the run length exceeds the confinement length, the density distribution is no longer described by Boltzmann distribution, instead we found a bimodal distribution. PMID:24718999

Wang, Zhengjia; Chen, Hsuan-Yi; Sheng, Yu-Jane; Tsao, Heng-Kwong

2014-05-14

197

Guidance and Navigation for Rendezvous and Proximity Operations with a Non-Cooperative Spacecraft at Geosynchronous Orbit  

NASA Technical Reports Server (NTRS)

The feasibility and benefits of various spacecraft servicing concepts are currently being assessed, and all require that the servicer spacecraft perform rendezvous, proximity, and capture operations with the target spacecraft to be serviced. Many high-value spacecraft, which would be logical targets for servicing from an economic point of view, are located in geosynchronous orbit, a regime in which autonomous rendezvous and capture operations are not commonplace. Furthermore, existing GEO spacecraft were not designed to be serviced. Most do not have cooperative relative navigation sensors or docking features, and some servicing applications, such as de-orbiting of a non-functional spacecraft, entail rendezvous and capture with a spacecraft that may be non-functional or un-controlled. Several of these challenges have been explored via the design of a notional mission in which a nonfunctional satellite in geosynchronous orbit is captured by a servicer spacecraft and boosted into super-synchronous orbit for safe disposal. A strategy for autonomous rendezvous, proximity operations, and capture is developed, and the Orbit Determination Toolbox (ODTBX) is used to perform a relative navigation simulation to assess the feasibility of performing the rendezvous using a combination of angles-only and range measurements. Additionally, a method for designing efficient orbital rendezvous sequences for multiple target spacecraft is utilized to examine the capabilities of a servicer spacecraft to service multiple targets during the course of a single mission.

Barbee, Brent William; Carpenter, J. Russell; Heatwole, Scott; Markley, F. Landis; Moreau, Michael; Naasz, Bo J.; VanEepoel, John

2010-01-01

198

Six degree of freedom simulation system for evaluating automated rendezvous and docking spacecraft  

NASA Technical Reports Server (NTRS)

Future logistics supply and servicing vehicles such as cargo transfer vehicles (CTV) must have full 6 degree of freedom (6DOF) capability in order to perform requisite rendezvous, proximity operations, and capture operations. The design and performance issues encountered when developing a 6DOF maneuvering spacecraft are very complex with subtle interactions which are not immediately obvious or easily anticipated. In order to deal with these complexities and develop robust maneuvering spacecraft designs, a simulation system and associated family of tools are used at TRW for generating and validating spacecraft performance requirements and guidance algorithms. An overview of the simulator and tools is provided. These are used by TRW for autonomous rendezvous and docking research projects including CTV studies.

Rourke, Kenneth H.; Tsugawa, Roy K.

1991-01-01

199

Application of particle swarm optimization technique in optimal parameters determination of the spacecraft remote rendezvous  

NASA Astrophysics Data System (ADS)

Beginning with the mathematics model of the spacecrafts remote rendezvous, we research the problem of space maneuver vehicle (SMV) remote rendezvous on-orbit target basing on Lambert orbit maneuver method. To find a minimum velocity impulse transfer orbit, we set up object functions when the SMV's initial orbit parameters are known or unknown. We use an advanced intelligent optimal technology, particle swarm optimal technology, to get the object function's extremum. So we can obtain the SMV's proper initial orbit parameters and transfer occasion. On this condition the SMV needs little velocity impulse to approach the target spacecraft. Last, the simulation results show that we can get a transfer orbit to rapidly approaching on-orbit target which needs very little velocity impulse by using this method.

Wang, Qiyu; Yuan, Jianping; Zhu, Zhanxia

2007-11-01

200

The asteroid rendezvous spacecraft. An adaptation study of TIROS/DMSP technology  

NASA Technical Reports Server (NTRS)

The feasibility of using the TIROS/DMSP Earth orbiting meteorological satellite in application to a near Earth asteroid rendezvous mission. System and subsystems analysis was carried out to develop a configuration of the spacecraft suitable for this mission. Mission analysis studies were also done and maneuver/rendezvous scenarios developed for baseline missions to both Anteros and Eros. The fact that the Asteroid mission is the most complex of the Pioneer class missions currently under consideration notwithstanding, the basic conclusion very strongly supports the suitability of the basic TIROS bus for this mission in all systems and subsystems areas, including science accommodation. Further, the modifications which are required due to the unique mission are very low risk and can be accomplished readily. The key issue is that in virtually every key subsystem, the demands of the Asteroid mission are a subset of the basic meteorological satellite mission. This allows a relatively simple reconfiguration to be accomplished without a major system redesign.

1982-01-01

201

The X-ray\\/Gamma-ray Spectrometer on the Near Earth Asteroid Rendezvous Mission  

Microsoft Academic Search

An X-ray\\/gamma-ray spectrometer has been developed as part of a rendezvous mission with the near-Earth asteroid, 433 Eros, in an effort to answer fundamental questions about the nature and origin of asteroids and comets. During about 10 months of orbital operations commencing in early 1999, the X-ray\\/Gamma-ray Spectrometer will develop global maps of the elemental composition of the surface of

J. O. Goldsten; R. L. McNutt; R. E. Gold; S. A. Gary; E. Fiore; S. E. Schneider; J. R. Hayes; J. I. Trombka; S. R. Floyd; W. V. Boynton; S. Bailey; J. Brueckner; S. W. Squyres; L. G. Evans; P. E. Clark; R. Starr

1997-01-01

202

The X-Ray\\/Gamma-ray spectrometer on the near Earth Asteroid Rendezvous mission  

Microsoft Academic Search

The X-ray\\/Gamma-ray Spectrometer on the Near Earth Asteroid Rendezvous spacecraft is a remote sensing instrument designed to develop elemental composition maps of the surface of the asteroid 433 Eros. This mapping operation will occur during about 10 months of orbital operations commencing in early 1999. Solar excited x-ray fluorescence in the 1 to 10 keV range will be used to

J. I. Trombka; R. L. McNutt Jr.; R. E. Gold; S. A. Gary; E. Fiore; S. E. Schneider; J. R. Hayes

1996-01-01

203

Modeling, simulation, testing, and verification of the Orbital Express Autonomous Rendezvous and Capture Sensor System (ARCSS)  

NASA Astrophysics Data System (ADS)

The Orbital Express Autonomous Rendezvous and Capture Sensor System (ARCSS) ALONG WITH ITS Vision-based Software for Track, Attitude and Ranging (Vis-STAR) provided relative target position and attitude measurements for guidance and relative navigation during autonomous vehicle proximity operations. The use of computer and physical models during simulation, ground testing and verification of ARCSS imaging camera and software performance prior to and during on-orbit operations is discussed.

Leinz, Manny R.; Chen, Chih-Tsai; Scott, Peter; Gaumer, William; Sabasteanski, Peter; Beaven, Michael

2008-05-01

204

SIMONE: near-Earth asteroid rendezvous microsatellites with solar-electric propulsion  

Microsoft Academic Search

The SIMONE mission proposal is led by QinetiQ, with scientific aspects led by the Open University's Planetary and Space Science Research Institute. Currently the focus of an ESA-funded study, the concept is to help understand the diversity of the NEO population using a fleet of microsatellite-class (~120 kg) interplanetary spacecraft. These will individually rendezvous with specific Near-Earth Objects of interest

Andrew J. Ball; Simon F. Green; Nigel S. Wells

2002-01-01

205

Laser range finder of the RendezVous sensor for ATV and HTV  

NASA Astrophysics Data System (ADS)

This paper describes the design and expected performance of the Laser Range Finder (LRF) as part of the Rendez-Vous Sensor (RVS) on the Automatic Transfer Vehicle and the H II Transfer Vehicle for the International Space Station. The LRF determines the distance between the RVS and a target (retro-reflector) by measuring the time-of-flight of a short laser pulse.

Luther, Juergen; Meissner, Dieter H.

2000-10-01

206

Analytical Evaluation of a Method of Midcourse Guidance for Rendezvous with Earth Satellites  

NASA Technical Reports Server (NTRS)

A digital-computer simulation was made of the midcourse or ascent phase of a rendezvous between a ferry vehicle and a space station. The simulation involved a closed-loop guidance system in which both the relative position and relative velocity between ferry and station are measured (by simulated radar) and the relative-velocity corrections required to null the miss distance are computed and applied. The results are used to study the effectiveness of a particular set of guidance equations and to study the effects of errors in the launch conditions and errors in the navigation data. A number of trajectories were investigated over a variety of initial conditions for cases in which the space station was in a circular orbit and also in an elliptic orbit. Trajectories are described in terms of a rotating coordinate system fixed in the station. As a result of this study the following conclusions are drawn. Successful rendezvous can be achieved even with launch conditions which are substantially less accurate than those obtained with present-day techniques. The average total-velocity correction required during the midcourse phase is directly proportional to the radar accuracy but the miss distance is not. Errors in the time of booster burnout or in the position of the ferry at booster burnout are less important than errors in the ferry velocity at booster burnout. The use of dead bands to account for errors in the navigational (radar) equipment appears to depend upon a compromise between the magnitude of the velocity corrections to be made and the allowable miss distance at the termination of the midcourse phase of the rendezvous. When approximate guidance equations are used, there are limits on their accuracy which are dependent on the angular distance about the earth to the expected point of rendezvous.

Eggleston, John M.; Dunning, Robert S.

1961-01-01

207

Multiple spacecraft rendezvous maneuvers by differential drag and low thrust engines  

Microsoft Academic Search

A novel two-phase hybrid controller is proposed to optimize propellant consumption during multiple spacecraft rendezvous maneuvers\\u000a in Low Earth Orbit. This controller exploits generated differentials in aerodynamic drag on each involved chaser spacecraft\\u000a to effect a propellant-free trajectory near to the target spacecraft during the first phase of the maneuver, and then uses\\u000a a fuel optimal control strategy via continuous

Riccardo Bevilacqua; Jason S. Hall; Marcello Romano

2010-01-01

208

A Ground Testbed to Advance US Capability in Autonomous Rendezvous and Docking Project  

NASA Technical Reports Server (NTRS)

This project will advance the Autonomous Rendezvous and Docking (AR&D) GNC system by testing it on hardware, particularly in a flight processor, with a goal of testing it in IPAS with the Waypoint L2 AR&D scenario. The entire Agency supports development of a Commodity for Autonomous Rendezvous and Docking (CARD) as outlined in the Agency-wide Community of Practice whitepaper entitled: "A Strategy for the U.S. to Develop and Maintain a Mainstream Capability for Automated/Autonomous Rendezvous and Docking in Low Earth Orbit and Beyond". The whitepaper establishes that 1) the US is in a continual state of AR&D point-designs and therefore there is no US "off-the-shelf" AR&D capability in existence today, 2) the US has fallen behind our foreign counterparts particularly in the autonomy of AR&D systems, 3) development of an AR&D commodity is a national need that would benefit NASA, our commercial partners, and DoD, and 4) an initial estimate indicates that the development of a standardized AR&D capability could save the US approximately $60M for each AR&D project and cut each project's AR&D flight system implementation time in half.

D'Souza, Chris

2014-01-01

209

Automated Rendezvous and Docking Sensor Testing at the Flight Robotics Laboratory  

NASA Technical Reports Server (NTRS)

The Exploration Systems Architecture defines missions that require rendezvous, proximity operations, and docking (RPOD) of two spacecraft both in Low Earth Orbit (LEO) and in Low Lunar Orbit (LLO). Uncrewed spacecraft must perform automated and/or autonomous rendezvous, proximity operations and docking operations (commonly known as Automated Rendezvous and Docking, (AR&D).) The crewed versions of the spacecraft may also perform AR&D, possibly with a different level of automation and/or autonomy, and must also provide the crew with relative navigation information for manual piloting. The capabilities of the RPOD sensors are critical to the success of the Exploration Program. NASA has the responsibility to determine whether the Crew Exploration Vehicle (CEV) contractor-proposed relative navigation sensor suite will meet the CEV requirements. The relatively low technology readiness of relative navigation sensors for AR&D has been carried as one of the CEV Projects top risks. The AR&D Sensor Technology Project seeks to reduce this risk by increasing technology maturation of selected relative navigation sensor technologies through testing and simulation, and to allow the CEV Project to assess the relative navigation sensors.

Howard, Richard T.; Williamson, Marlin L.; Johnston, Albert S.; Brewster, Linda L.; Mitchell, Jennifer D.; Cryan, Scott P.; Strack, David; Key, Kevin

2007-01-01

210

Automated Rendezvous and Docking Sensor Testing at the Flight Robotics Laboratory  

NASA Technical Reports Server (NTRS)

The Exploration Systems Architecture defines missions that require rendezvous, proximity operations, and docking (RPOD) of two spacecraft both in Low Earth Orbit (LEO) and in Low Lunar Orbit (LLO). Uncrewed spacecraft must perform automated and/or autonomous rendezvous, proximity operations and docking operations (commonly known as Automated Rendezvous and Docking, AR&D). The crewed versions may also perform AR&D, possibly with a different level of automation and/or autonomy, and must also provide the crew with relative navigation information for manual piloting. The capabilities of the RPOD sensors are critical to the success of the Exploration Program. NASA has the responsibility to determine whether the Crew Exploration Vehicle (CEV) contractor-proposed relative navigation sensor suite will meet the CEV requirements. The relatively low technology readiness of relative navigation sensors for AR&D has been carried as one of the CEV Projects top risks. The AR&D Sensor Technology Project seeks to reduce this risk by increasing technology maturation of selected relative navigation sensor technologies through testing and simulation, and to allow the CEV Project to assess the relative navigation sensors.

Mitchell, J.; Johnston, A.; Howard, R.; Williamson, M.; Brewster, L.; Strack, D.; Cryan, S.

2007-01-01

211

NMR spectra of oligosaccharides at ultra-high field (900 MHz) have better resolution than expected due to favourable molecular tumbling  

PubMed Central

Nuclear magnetic resonance (NMR) remains the most promising technique for acquiring atomic-resolution information in complex carbohydrates. Significant obstacles to the acquisition of such data are the poor chemical-shift dispersion and artifacts resultant from their degenerate chemical structures. The recent development of ultra-high-field NMR (at 900 MHz and beyond) gives new potential to overcome these problems, as we demonstrate on a hexasaccharide of the highly repetitive glycosaminoglycan hyaluronan. At 900 MHz, the expected increase in spectral dispersion due to higher resonance frequencies and reduction in strong coupling-associated distortions are observed. In addition, the fortuitous molecular tumbling rate of oligosaccharides results in longer T2-values that further significantly enhances resolution, an effect not available to proteins. Combined, the resolution enhancement can be as much as twofold relative to 600 MHz, allowing all 1H-resonances in the hexasaccharide to be unambiguously assigned using standard natural-abundance experiments. The use of ultra-high-field spectrometers is clearly advantageous and promises a new and exciting era in carbohydrate structural biology.

Blundell, Charles D.; Reed, Michelle A.C.; Overduin, Michael; Almond, Andrew

2006-01-01

212

Poisson equations of rotational motion for a rigid triaxial body with application to a tumbling artificial satellite  

NASA Technical Reports Server (NTRS)

A mathematical model is developed for studying the effects of gravity gradient torque on the attitude stability of a tumbling triaxial rigid satellite. Poisson equations are used to investigate the rotation of the satellite (which is in elliptical orbit about an attracting point mass) about its center of mass. An averaging method is employed to obtain an intermediate set of differential equations for the nonresonant, secular behavior of the osculating elements which describe the rotational motions of the satellite, and the averaged equations are then integrated to obtain long-term secular solutions for the osculating elements.

Liu, J. J. F.; Fitzpatrick, P. M.

1975-01-01

213

The Space Operations Simulation Center (SOSC) and Closed-loop Hardware Testing for Orion Rendezvous System Design  

NASA Technical Reports Server (NTRS)

The Space Operations Simulation Center (SOSC) at the Lockheed Martin (LM) Waterton Campus in Littleton, Colorado is a dynamic test environment focused on Autonomous Rendezvous and Docking (AR&D) development testing and risk reduction activities. The SOSC supports multiple program pursuits and accommodates testing Guidance, Navigation, and Control (GN&C) algorithms for relative navigation, hardware testing and characterization, as well as software and test process development. The SOSC consists of a high bay (60 meters long by 15.2 meters wide by 15.2 meters tall) with dual six degree-of-freedom (6DOF) motion simulators and a single fixed base 6DOF robot. The large testing area (maximum sensor-to-target effective range of 60 meters) allows for large-scale, flight-like simulations of proximity maneuvers and docking events. The facility also has two apertures for access to external extended-range outdoor target test operations. In addition, the facility contains four Mission Operations Centers (MOCs) with connectivity to dual high bay control rooms and a data/video interface room. The high bay is rated at Class 300,000 (. 0.5 m maximum particles/m3) cleanliness and includes orbital lighting simulation capabilities.

D'Souza, Christopher; Milenkovich, Zoran; Wilson, Zachary; Huich, David; Bendle, John; Kibler, Angela

2011-01-01

214

SPARTAN: A High-Fidelity Simulation for Automated Rendezvous and Docking Applications  

NASA Technical Reports Server (NTRS)

bd Systems (a subsidiary of SAIC) has developed the Simulation Package for Autonomous Rendezvous Test and ANalysis (SPARTAN), a high-fidelity on-orbit simulation featuring multiple six-degree-of-freedom (6DOF) vehicles. SPARTAN has been developed in a modular fashion in Matlab/Simulink to test next-generation automated rendezvous and docking guidance, navigation,and control algorithms for NASA's new Vision for Space Exploration. SPARTAN includes autonomous state-based mission manager algorithms responsible for sequencing the vehicle through various flight phases based on on-board sensor inputs and closed-loop guidance algorithms, including Lambert transfers, Clohessy-Wiltshire maneuvers, and glideslope approaches The guidance commands are implemented using an integrated translation and attitude control system to provide 6DOF control of each vehicle in the simulation. SPARTAN also includes high-fidelity representations of a variety of absolute and relative navigation sensors that maybe used for NASA missions, including radio frequency, lidar, and video-based rendezvous sensors. Proprietary navigation sensor fusion algorithms have been developed that allow the integration of these sensor measurements through an extended Kalman filter framework to create a single optimal estimate of the relative state of the vehicles. SPARTAN provides capability for Monte Carlo dispersion analysis, allowing for rigorous evaluation of the performance of the complete proposed AR&D system, including software, sensors, and mechanisms. SPARTAN also supports hardware-in-the-loop testing through conversion of the algorithms to C code using Real-Time Workshop in order to be hosted in a mission computer engineering development unit running an embedded real-time operating system. SPARTAN also contains both runtime TCP/IP socket interface and post-processing compatibility with bdStudio, a visualization tool developed by bd Systems, allowing for intuitive evaluation of simulation results. A description of the SPARTAN architecture and capabilities is provided, along with details on the models and algorithms utilized and results from representative missions.

Turbe, Michael A.; McDuffie, James H.; DeKock, Brandon K.; Betts, Kevin M.; Carrington, Connie K.

2007-01-01

215

Constant-thrust glideslope guidance algorithm for time-fixed rendezvous in real halo orbit  

NASA Astrophysics Data System (ADS)

This paper presents a fixed-time glideslope guidance algorithm that is capable of guiding the spacecraft approaching a target vehicle on a quasi-periodic halo orbit in real Earth-Moon system. To guarantee the flight time is fixed, a novel strategy for designing the parameters of the algorithm is given. Based on the numerical solution of the linearized relative dynamics of the Restricted Three-Body Problem (expressed in inertial coordinates with a time-variant nature), the proposed algorithm breaks down the whole rendezvous trajectory into several arcs. For each arc, a two-impulse transfer is employed to obtain the velocity increment (delta-v) at the joint between arcs. Here we respect the fact that instantaneous delta-v cannot be implemented by any real engine, since the thrust magnitude is always finite. To diminish its effect on the control, a thrust duration as well as a thrust direction are translated from the delta-v in the context of a constant thrust engine (the most robust type in real applications). Furthermore, the ignition and cutoff delays of the thruster are considered as well. With this high-fidelity thrust model, the relative state is then propagated to the next arc by numerical integration using a complete Solar System model. In the end, final corrective control is applied to insure the rendezvous velocity accuracy. To fully validate the proposed guidance algorithm, Monte Carlo simulation is done by incorporating the navigational error and the thrust direction error. Results show that our algorithm can effectively maintain control over the time-fixed rendezvous transfer, with satisfactory final position and velocity accuracies for the near-range guided phase.

Lian, Yijun; Meng, Yunhe; Tang, Guojian; Liu, Luhua

2012-10-01

216

Interplanetary trajectory design for the Mariner Mark II Comet Rendezvous/Asteroid Flyby mission  

NASA Technical Reports Server (NTRS)

The primary purpose of the first mission utilizing a Mariner Mark II spacecraft will be to rendezvous with the short-period comet Wild 2 and conduct a proximal examination during the comet's quiescent and active phases. The purpose of the present study is to elucidate, using an accurate dynamic model, some of the characteristics of the interplanetary trajectory that are relevant to the mission design. Optimal transfer trajectories are generated, constrained by the Shuttle/Centaur launch vehicle capability and the total spacecraft mass and performance. Asteroid flyby opportunities are examined, and the effects of selected asteroid encounters on mission performance are discussed.

Myers, M. R.; Stetson, D. S.

1986-01-01

217

Theoretical basis for state vector comparison, relative position display, and relative position/rendezvous prediction  

NASA Astrophysics Data System (ADS)

This thesis outlines the theoretical underpinnings used for the software designed to meet Detailed Technical Objectives 700-6 and 700-7 for the Space Shuttle Discovery mission STS-51. The primary goal was to compare state vector information produced by an onboard GPS receiver and Discovery's computers and provide real time display of the results. Because state vector information for the ORFEUS/SPAS payload was also available, relative position and rendezvous information between Discovery and ORFEUS/SPAS was made possible. Analysis of the various state vectors was used to produce a graphical display, in an operationally meaningful format, to the flight crew of Discovery.

Makepeace, Lester B., III

1993-12-01

218

Embedded Relative Navigation Sensor Fusion Algorithms for Autonomous Rendezvous and Docking Missions  

NASA Technical Reports Server (NTRS)

bd Systems (a subsidiary of SAIC) has developed a suite of embedded relative navigation sensor fusion algorithms to enable NASA autonomous rendezvous and docking (AR&D) missions. Translational and rotational Extended Kalman Filters (EKFs) were developed for integrating measurements based on the vehicles' orbital mechanics and high-fidelity sensor error models and provide a solution with increased accuracy and robustness relative to any single relative navigation sensor. The filters were tested tinough stand-alone covariance analysis, closed-loop testing with a high-fidelity multi-body orbital simulation, and hardware-in-the-loop (HWIL) testing in the Marshall Space Flight Center (MSFC) Flight Robotics Laboratory (FRL).

DeKock, Brandon K.; Betts, Kevin M.; McDuffie, James H.; Dreas, Christine B.

2008-01-01

219

NASA Automated Rendezvous and Capture Review. A compilation of the abstracts  

NASA Technical Reports Server (NTRS)

This document presents a compilation of abstracts of papers solicited for presentation at the NASA Automated Rendezvous and Capture Review held in Williamsburg, VA on November 19-21, 1991. Due to limitations on time and other considerations, not all abstracts could be presented during the review. The organizing committee determined however, that all abstracts merited availability to all participants and represented data and information reflecting state-of-the-art of this technology which should be captured in one document for future use and reference. The organizing committee appreciates the interest shown in the review and the response by the authors in submitting these abstracts.

1991-01-01

220

Advanced opto-electronical sensors for autonomous Rendezvous-/Docking and proximity operations in space  

NASA Astrophysics Data System (ADS)

Experimental work on three types of candidate optical sensors for rendezvous and docking tasks, active laser diode radars, CCD cameras and position detector sensors, plus a combination of these is presented. The results obtained up to now with a test lab (including motion simulation) make each of them a promising candidate for this kind of application for different range regimes. These sensors are conceived as multisensor head systems together with a central processing unit to provide applicability beyond docking of space platforms. A description of the sensors, their technical development requirements, achieved performance results, and combination packages, plus a proposal for in-orbit test missions is given.

Kunkel, B.; Lutz, R.; Manhart, S.

1986-01-01

221

An EPR line shape study of anisotropic rotational reorientation and slow tumbling in liquid and frozen jojoba oil  

NASA Astrophysics Data System (ADS)

Spin probe investigation of jojoba oil was carried out by electron paramagnetic rresonance (EPR) spectroscopy. The spin probe used was 2,2,6,6-tetramethyl-4-piperidone- N-oxide. The EPR line shape studies were carried out in the lower temperature range of 192 to 275 K to test the applicability of the stochastic Liouville theory in the simulation of EPR line shapes where earlier relaxation theories do not apply. In an earlier study, this system was analysed by employing rotational diffusion at the fast-motional region. The results show that PD-Tempone exhibits asymmetric rotational diffusion with N = 3.3 at an axis z'= Y in the plane of the molecule and perpendicular to the N?O bond direction. In this investigation we have extended the temperature range to lower temperatures and observed slow tumbling EPR spectra. It is shown that the stochastic Liouville method can be used to simulate all but two of the experimentally observed EPR spectra in the slow-motional region and details of the slow-motional line shape are sensitive to the anisotropy of rotation and showed good agreement for a moderate jump model. From the computer simulation of EPR line shapes it is found that the information obtained on ? R, and N in the motional-narrowing region can be extrapolated into the slow-tumbling region. It is also found that ln (? R) is linear in 1/ T in the temperature range studied and the resulting activation energy for rotation is 51 kJ/mol. The two EPR spectra at 240 and 231 K were found to exhibit the effects of anisotropic viscosity observed by B IRELL for nitroxides oriented in tubular cavities in inclusion crystals in which the molecule is free to rotate about the long axis but with its rotation hindered about the other two axes because of the cavity geometry. These results proved that the slow-tumbling spectra were very sensitive to the effects of anisotropy in the viscosity.

Hwang, J. S.; Al-Rashid, W. A.

222

Androgen and the Development of Human Sex-Typical Behavior: Rough-and-Tumble Play and Sex of Preferred Playmates in Children with Congenital Adrenal Hyperplasia (CAH).  

ERIC Educational Resources Information Center

Examined the rough-and-tumble play and gender of preferred playmates in three- to eight-year olds with congenital adrenal hyperplasia (CAH)--hypothesized to masculinize behaviors that show sex differences--and in unaffected three- to eight-year-old relatives. Found that CAH girls did not exhibit increased levels of masculine behavior when compared…

Hines, Melissa; Kaufman, Francine R.

1994-01-01

223

A relative navigation application of ULTOR technology for automated rendezvous and docking  

NASA Astrophysics Data System (ADS)

NASA's initiative for space exploration will require the development of robotic servicing and unmanned resupply of permanent space borne facilities. An enabling technology to accomplish these goals is by sensor systems capable of Rendezvous, Proximity Operations and Docking (RPOD) missions. Marshall Space Flight Center (MSFC) conducted an experiment whose objective intent was to characterize sensor systems for potential use in RPOD scenarios. The MSFC experiment integrated candidate sensors with the Small Air Sled (SAS) on the air bearing floor of the MSFC Flight Robotics Lab. Advanced Optical Systems Inc. (AOS) has developed several different sensor technologies for Automated Rendezvous and Docking (AR&D). For the MSFC experiment, we applied AOS ULTOR advanced correlation technology as an AR&D sensor. The ULTOR system applied Automatic Target Recognition (ATR) algorithms to provide six-degrees-of-freedom (6DOF) information for target position and attitude. In addition, ULTOR provided a data-link interface to the SAS for closed loop guidance and navigation commands. Navigational data from the ULTOR system was collected during the experiment and compared to a MSFC truth sensor for position and attitude estimation accuracy. This data will be presented as well as videos recording the progression of the SAS under ULTOR control to the target.

Hannah, S. Joel

2006-05-01

224

Orbital Express Autonomous Rendezvous and Capture Sensor System (ARCSS) flight test results  

NASA Astrophysics Data System (ADS)

The Orbital Express flight demonstration was established by the Defense Advanced Research Projects Agency (DARPA) to develop and validate key technologies required for cost-effective servicing of next-generation satellites. A contractor team led by Boeing Advanced Network and Space Systems built two mated spacecraft launched atop an Atlas V rocket from Cape Canaveral, Florida, on March 8, 2007. The low earth orbit test flight demonstrated on orbit transfer of hydrazine propellant, transfer of a spare battery between spacecraft and the ability to replace a spacecraft computer on orbit. It also demonstrated autonomous rendezvous and capture (AR&C) using advanced sensor, guidance, and relative navigation hardware and software. This paper summarizes the results of the on-orbit performance testing of the ARCSS (Autonomous Rendezvous and Capture Sensor System). ARCSS uses onboard visible, infrared and laser rangefinder sensors to provide real time data and imagery to the onboard sensor computer. The Boeing-developed Vis-STAR software executing on the sensor computer uses the ARCSS data to provide precision real-time client bearing, range and attitude as needed, from long range to soft capture. The paper summarizes the ARCSS and Vis-STAR on orbit performance.

Leinz, Manny R.; Chen, Chih-Tsai; Beaven, Michael W.; Weismuller, Thomas P.; Caballero, David L.; Gaumer, William B.; Sabasteanski, Peter W.; Scott, Peter A.; Lundgren, Mark A.

2008-05-01

225

Space Shuttle Guidance, Navigation, and Rendezvous Knowledge Capture Reports. Revision 1  

NASA Technical Reports Server (NTRS)

This document is a catalog and readers guide to lessons learned, experience, and technical history reports, as well as compilation volumes prepared by United Space Alliance personnel for the NASA/Johnson Space Center (JSC) Flight Dynamics Division.1 It is intended to make it easier for future generations of engineers to locate knowledge capture documentation from the Shuttle Program. The first chapter covers observations on documentation quality and research challenges encountered during the Space Shuttle and Orion programs. The second chapter covers the knowledge capture approach used to create many of the reports covered in this document. These chapters are intended to provide future flight programs with insight that could be used to formulate knowledge capture and management strategies. The following chapters contain descriptions of each knowledge capture report. The majority of the reports concern the Space Shuttle. Three are included that were written in support of the Orion Program. Most of the reports were written from the years 2001 to 2011. Lessons learned reports concern primarily the shuttle Global Positioning System (GPS) upgrade and the knowledge capture process. Experience reports on navigation and rendezvous provide examples of how challenges were overcome and how best practices were identified and applied. Some reports are of a more technical history nature covering navigation and rendezvous. They provide an overview of mission activities and the evolution of operations concepts and trajectory design. The lessons learned, experience, and history reports would be considered secondary sources by historians and archivists.

Goodman, John L.

2011-01-01

226

Use of industrial robots for hardware-in-the-loop simulation of satellite rendezvous and docking  

NASA Astrophysics Data System (ADS)

One of the most challenging and risky operations for spacecraft is to perform rendezvous and docking autonomously in space. To ensure a safe and reliable operation, such a mission must be carefully designed and thoroughly verified before a real space mission can be launched. This paper describes the control strategy for achieving high fidelity contact dynamics simulation of a new, robotics-based, hardware-in-the-loop (HIL) rendezvous and docking simulation facility that uses two industrial robots to physically simulate the 6-DOF dynamic maneuvering of two docking satellites. The facility is capable of physically simulating the final approaching within a 25-meter range and the entire docking/capturing process for a satellite on-orbit servicing mission. The key difficulties of using industrial robots for high-fidelity HIL contact dynamics simulation were found and different solution techniques were investigated in the presented project. An admittance control method was proposed to achieve the goal of making the robots in the HIL simulation process match the impedance of the two docking satellites. Simulation study showed the effectiveness and performance of the proposed solution method.

Ma, Ou; Flores-Abad, Angel; Boge, Toralf

2012-12-01

227

A Comparison of Trajectory Optimization Methods for the Impulsive Minimum Fuel Rendezvous Problem  

NASA Technical Reports Server (NTRS)

In this paper we present, a comparison of trajectory optimization approaches for the minimum fuel rendezvous problem. Both indirect and direct methods are compared for a variety of test cases. The indirect approach is based on primer vector theory. The direct approaches are implemented numerically and include Sequential Quadratic Programming (SQP). Quasi- Newton and Nelder-Meade Simplex. Several cost function parameterizations are considered for the direct approach. We choose one direct approach that appears to be the most flexible. Both the direct and indirect methods are applied to a variety of test cases which are chosen to demonstrate the performance of each method in different flight regimes. The first test case is a simple circular-to-circular coplanar rendezvous. The second test case is an elliptic-to-elliptic line of apsides rotation. The final test case is an orbit phasing maneuver sequence in a highly elliptic orbit. For each test case we present a comparison of the performance of all methods we consider in this paper.

Hughes, Steven P.; Mailhe, Laurie M.; Guzman, Jose J.

2003-01-01

228

Progress in navigation filter estimate fusion and its application to spacecraft rendezvous  

NASA Technical Reports Server (NTRS)

A new derivation of an algorithm which fuses the outputs of two Kalman filters is presented within the context of previous research in this field. Unlike other works, this derivation clearly shows the combination of estimates to be optimal, minimizing the trace of the fused covariance matrix. The algorithm assumes that the filters use identical models, and are stable and operating optimally with respect to their own local measurements. Evidence is presented which indicates that the error ellipsoid derived from the covariance of the optimally fused estimate is contained within the intersections of the error ellipsoids of the two filters being fused. Modifications which reduce the algorithm's data transmission requirements are also presented, including a scalar gain approximation, a cross-covariance update formula which employs only the two contributing filters' autocovariances, and a form of the algorithm which can be used to reinitialize the two Kalman filters. A sufficient condition for using the optimally fused estimates to periodically reinitialize the Kalman filters in this fashion is presented and proved as a theorem. When these results are applied to an optimal spacecraft rendezvous problem, simulated performance results indicate that the use of optimally fused data leads to significantly improved robustness to initial target vehicle state errors. The following applications of estimate fusion methods to spacecraft rendezvous are also described: state vector differencing, and redundancy management.

Carpenter, J. Russell

1994-01-01

229

COMPASS Final Report: Near Earth Asteroids Rendezvous and Sample Earth Returns (NEARER)  

NASA Technical Reports Server (NTRS)

In this study, the Collaborative Modeling for Parametric Assessment of Space Systems (COMPASS) team completed a design for a multi-asteroid (Nereus and 1996 FG3) sample return capable spacecraft for the NASA In-Space Propulsion Office. The objective of the study was to support technology development and assess the relative benefits of different electric propulsion systems on asteroid sample return design. The design uses a single, heritage Orion solar array (SA) (approx.6.5 kW at 1 AU) to power a single NASA Evolutionary Xenon Thruster ((NEXT) a spare NEXT is carried) to propel a lander to two near Earth asteroids. After landing and gathering science samples, the Solar Electric Propulsion (SEP) vehicle spirals back to Earth where it drops off the first sample s return capsule and performs an Earth flyby to assist the craft in rendezvousing with a second asteroid, which is then sampled. The second sample is returned in a similar fashion. The vehicle, dubbed Near Earth Asteroids Rendezvous and Sample Earth Returns (NEARER), easily fits in an Atlas 401 launcher and its cost estimates put the mission in the New Frontier s (NF's) class mission.

Oleson, Steven R.; McGuire, Melissa L.

2009-01-01

230

Active rendezvous between a low-earth orbit user spacecraft and the Space Transportation System (STS) shuttle  

NASA Technical Reports Server (NTRS)

Active rendezvous of an unmanned spacecraft with the Space Transportation System (STS) Shuttle is considered. The various operational constraints facing both the maneuvering spacecraft and the Shuttle during such a rendezvous sequence are discussed. Specifically, the actively rendezvousing user spacecraft must arrive in the generic Shuttle control box at a specified time after Shuttle launch. In so doing it must at no point violate Shuttle separation requirements. In addition, the spacecraft must be able to initiate the transfer sequence from any point in its orbit. The four-burn rendezvous sequence incorporating two Hohmann transfers and an intermediate phasing orbit as a low-energy solution satisfying the above requirements are discussed. The general characteristics of the four-burn sequence are discussed, with emphasis placed on phase orbit altitude and delta-velocity requirements. The planning and execution of such a sequence in the operational environment are then considered. Factor crucial in maintaining the safety of both spacecraft, such as spacecraft separation and contingency analysis, are considered in detail.

Hooper, H. L.; Herrnstein, J. R.

1989-01-01

231

Active rendezvous between a low-earth orbit user spacecraft and the Space Transportation System (STS) shuttle  

NASA Astrophysics Data System (ADS)

Active rendezvous of an unmanned spacecraft with the Space Transportation System (STS) Shuttle is considered. The various operational constraints facing both the maneuvering spacecraft and the Shuttle during such a rendezvous sequence are discussed. Specifically, the actively rendezvousing user spacecraft must arrive in the generic Shuttle control box at a specified time after Shuttle launch. In so doing it must at no point violate Shuttle separation requirements. In addition, the spacecraft must be able to initiate the transfer sequence from any point in its orbit. The four-burn rendezvous sequence incorporating two Hohmann transfers and an intermediate phasing orbit as a low-energy solution satisfying the above requirements are discussed. The general characteristics of the four-burn sequence are discussed, with emphasis placed on phase orbit altitude and delta-velocity requirements. The planning and execution of such a sequence in the operational environment are then considered. Factor crucial in maintaining the safety of both spacecraft, such as spacecraft separation and contingency analysis, are considered in detail.

Hooper, H. L.; Herrnstein, J. R.

1989-10-01

232

The Successful Development of an Automated Rendezvous and Capture (AR&C) System for the National Aeronautics and Space Administration  

NASA Technical Reports Server (NTRS)

During the 1990's, the Marshall Space Flight Center (MSFC) conducted pioneering research in the development of an automated rendezvous and capture/docking (AR&C) system for U.S. space vehicles. Development and demonstration of a rendezvous sensor was identified early in the AR&C Program as the critical enabling technology that allows automated proximity operations and docking. A first generation rendezvous sensor, the Video Guidance Sensor (VGS), was developed and successfully flown on STS-87 and STS-95, proving the concept of a video- based sensor. A ground demonstration of the entire system and software was successfully tested. Advances in both video and signal processing technologies and the lessons learned from the two successful flight experiments provided a baseline for the development, by the MSFC, of a new generation of video based rendezvous sensor. The Advanced Video Guidance Sensor (AGS) has greatly increased performance and additional capability for longer-range operation with a new target designed as a direct replacement for existing ISS hemispherical reflectors.

Roe, Fred D.; Howard, Richard T.

2003-01-01

233

Evaluation of Formation Flight Control Accuracy by Flight Data of Rendezvous Docking Experiment of ETS-VII  

Microsoft Academic Search

Formation flight is a new technology which enables various missions such as high resolution interferometer, virtual antenna instead of huge antenna for a large amount of communication, etc. To realize formation flight, navigation and control of relative position and velocity among related spacecraft are necessary. ETS-VII is a test satellite to perform in-orbit demonstration of autonomous rendezvous docking (RVD) technology.

Isao Kawano; Masaaki Mokuno; Takashi Suzuki

2003-01-01

234

A Summary of the Rendezvous, Proximity Operations, Docking, and Undocking (RPODU) Lessons Learned from the Defense Advanced Research Project Agency (DARPA) Orbital Express (OE) Demonstration System Mission  

NASA Technical Reports Server (NTRS)

The Guidance, Navigation, and Control (GN&C) Technical Discipline Team (TDT) sponsored Dr. J. Russell Carpenter, a Navigation and Rendezvous Subject Matter Expert (SME) from NASA's Goddard Space Flight Center (GSFC), to provide support to the Defense Advanced Research Project Agency (DARPA) Orbital Express (OE) rendezvous and docking flight test that was conducted in 2007. When that DARPA OE mission was completed, Mr. Neil Dennehy, NASA Technical Fellow for GN&C, requested Dr. Carpenter document his findings (lessons learned) and recommendations for future rendezvous missions resulting from his OE support experience. This report captures lessons specifically from anomalies that occurred during one of OE's unmated operations.

Dennehy, Cornelius J.; Carpenter, James R.

2011-01-01

235

Development of an autonomous video rendezvous and docking system, phase 2  

NASA Technical Reports Server (NTRS)

The critical elements of an autonomous video rendezvous and docking system were built and used successfully in a physical laboratory simulation. The laboratory system demonstrated that a small, inexpensive electronic package and a flight computer of modest size can analyze television images to derive guidance information for spacecraft. In the ultimate application, the system would use a docking aid consisting of three flashing lights mounted on a passive target spacecraft. Television imagery of the docking aid would be processed aboard an active chase vehicle to derive relative positions and attitudes of the two spacecraft. The demonstration system used scale models of the target spacecraft with working docking aids. A television camera mounted on a 6 degree of freedom (DOF) simulator provided imagery of the target to simulate observations from the chase vehicle. A hardware video processor extracted statistics from the imagery, from which a computer quickly computed position and attitude. Computer software known as a Kalman filter derived velocity information from position measurements.

Tietz, J. C.; Richardson, T. E.

1983-01-01

236

Orbit determination for the Mariner Mark II Comet Rendezvous/Asteroid Flyby mission - The orbiting phase  

NASA Technical Reports Server (NTRS)

The Comet Rendezvous/Asteroid Flyby (CRAF) mission is the first of the Mariner Mark II mission set, designed to explore the outer solar system. Major objectives of orbit determination will be determine the positions and masses of the comet and asteroid and the relative position of the spacecraft, which is important to accurate pointing of the scan platform on which the narrow angle camera and scientific instruments are positioned. Position prediction is also important, since continuous commuication with the spacecraft will not be possible. The small gravitational attractions and poorly known ephemerides of the comet and asteroid, and the small, slow spacecraft orbit about the comet, pose significant new problems for orbit determination. Results of simulations studying the effectiveness of key data types, the accuracies of estimates, and prediction capabilities, are presented.

Weeks, C. J.

1986-01-01

237

Autonomous rendezvous and docking: A commercial approach to on-orbit technology validation  

NASA Astrophysics Data System (ADS)

SpARC, in conjunction with its corporate affiliates, is planning an on-orbit validation of autonomous rendezvous and docking (ARD) technology. The emphasis in this program is to utilize existing technology and commercially available components wherever possible. The primary subsystems to be validated by this demonstration include GPS receivers for navigation, a video-based sensor for proximity operations, a fluid connector mechanism to demonstrate fluid resupply capability, and a compliant, single-point docking mechanism. The focus for this initial experiment will be ELV based and will make use of two residual Commercial Experiment Transporter (COMET) service modules. The first COMET spacecraft will be launched in late 1992 and will serve as the target vehicle. After the second COMET spacecraft has been launched in late 1994, the ARD demonstration will take place. The service module from the second COMET will serve as the chase vehicle.

Tchoryk, Peter, Jr.; Whitten, Raymond P.

1991-11-01

238

Autonomous rendezvous and docking: A commercial approach to on-orbit technology validation  

NASA Technical Reports Server (NTRS)

SpARC, in conjunction with its corporate affiliates, is planning an on-orbit validation of autonomous rendezvous and docking (ARD) technology. The emphasis in this program is to utilize existing technology and commercially available components wherever possible. The primary subsystems to be validated by this demonstration include GPS receivers for navigation, a video-based sensor for proximity operations, a fluid connector mechanism to demonstrate fluid resupply capability, and a compliant, single-point docking mechanism. The focus for this initial experiment will be ELV based and will make use of two residual Commercial Experiment Transporter (COMET) service modules. The first COMET spacecraft will be launched in late 1992 and will serve as the target vehicle. After the second COMET spacecraft has been launched in late 1994, the ARD demonstration will take place. The service module from the second COMET will serve as the chase vehicle.

Tchoryk, Peter, Jr.; Whitten, Raymond P.

1991-01-01

239

Solar array study for solar electric propulsion spacecraft for the Encke rendezvous mission  

NASA Technical Reports Server (NTRS)

The work is described which was performed on the design, analysis and performance of a 20 kW rollup solar array capable of meeting the design requirements of a solar electric spacecraft for the 1980 Encke rendezvous mission. To meet the high power requirements of the proposed electric propulsion mission, solar arrays on the order of 186.6 sq m were defined. Because of the large weights involved with arrays of this size, consideration of array configurations is limited to lightweight, large area concepts with maximum power-to-weight ratios. Items covered include solar array requirements and constraints, array concept selection and rationale, structural and electrical design considerations, and reliability considerations.

Sequeira, E. A.; Patterson, R. E.

1974-01-01

240

A proposed Comet Nucleus Penetrator for the Comet Rendezvous Asteroid Flyby mission.  

PubMed

Among the major objectives of NASA's program of space exploration is a better understanding of the origin and evolution of the solar system. Crucial to this objective is the study of comets, which are thought to be the most primitive, pristine bodies remaining in the solar system. The importance of the study of comets has led NASA to plan a mission to rendezvous with comet Tempel 2 in 1997. Critical to the understanding of comets will be measurements of the nucleus material to determine its elemental and isotopic composition, its mechanical properties, and its thermal state and properties. This paper describes a proposal for a Comet Nucleus Penetrator to accomplish these measurement goals. The Comet Nucleus Penetrator will implant instruments into the comet's nucleus beneath a probable volatile-depleted surface mantle into material more representative of the bulk composition of the nucleus. PMID:11538848

Swenson, B L; Squyres, S W; Knight, T C

1987-01-01

241

Near Earth Asteroid Rendezvous (NEAR) Revised Eros Orbit Phase Trajectory Design  

NASA Technical Reports Server (NTRS)

Trajectory design of the orbit phase of the NEAR mission involves a new process that departs significantly from those procedures used in previous missions. In most cases, a precise spacecraft ephemeris is designed well in advance of arrival at the target body. For NEAR, the uncertainty in the dynamic environment around Eros does not allow the luxury of a precise spacecraft trajectory to be defined in advance. The principal cause of this uncertainty is the limited knowledge oi' the gravity field a,-id rotational state of Eros. As a result, the concept for the NEAR trajectory design is to define a number of rules for satisfying spacecraft, mission, and science constraints, and then apply these rules to various assumptions for the model of Eros. Nominal, high, and low Eros mass models are used for testing the trajectory design strategy and to bracket the ranges of parameter variations that are expected upon arrival at the asteroid. The final design is completed after arrival at Eros and determination of the actual gravity field and rotational state. As a result of the unplanned termination of the deep space rendezvous maneuver on December 20, 1998, the NEAR spacecraft passed within 3830 km of Eros on December 23, 1998. This flyby provided a brief glimpse of Eros, and allowed for a more accurate model of the rotational parameters and gravity field uncertainty. Furthermore, after the termination of the deep space rendezvous burn, contact with the spacecraft was lost and the NEAR spacecraft lost attitude control. During the subsequent gyrations of the spacecraft, hydrazine thruster firings were used to regain attitude control. This unplanned thruster activity used Much of the fuel margin allocated for the orbit phase. Consequently, minimizing fuel consumption is now even more important.

Helfrich, J; Miller, J. K.; Antreasian, P. G.; Carranza, E.; Williams, B. G.; Dunham, D. W.; Farquhar, R. W.; McAdams, J. V.

1999-01-01

242

The application of depot transfer/rendezvous in space based cyclic orbit missions  

NASA Technical Reports Server (NTRS)

Mission planning for future national space programs will seek means to abate the high dollar cost of mass delivery. To meet the fiscal objectives of these programs requires the development of improved transportation logistics, both in the primary Earth-to-Low Earth Orbit (LEO) and secondary orbit-to-orbit space transportation segments for delivery of construction materials, scientific payloads, and personnel. The deployment of space-based orbit transfer vehicles (OTV's) and development of innovative orbit transfer methodologies that reduce secondary cyclic mission support mass requirements (e.g. propellants) is a crucial step in meeting program budgetary goals. The research performed in this thesis has developed an improved efficiency cyclic orbit transfer method, based on non-traditional optimization criteria, through the use of intermediate propellant depot orbits and rendezvous transfer. The technique was optimized for a reference cyclic transfer between LEO and Geostationary Earth Orbit (GEO) in the presence of realistic mission affects including the following: (1) non-planar transfers; (2) perturbed (non-Keplerian) orbit motions; and (3) mission transfer risk mitigation techniques. A semianalytic model was developed to optimize the depot orbit selection and sizing for LEO/GEO cyclic missions for three NASA reference OTV mission payload profiles. The results demonstrated significant reductions in cyclic mission propellant requirements, when compared to current NASA aerobrake OTV missions, for durations of up to one week in GEO. The magnitude of the propellant mass savings was found to depend on GEO on-orbit durations, mission risk strategies, and payload profiles, with maximum propellant savings amounting to approximately 11 metric tons/mission. A first-order cost benefit analysis showed a recurring dollar savings from the use of the depot transfer/rendezvous method ranging from 5 to 83 million dollars per mission.

Coffey, Randall E.

1990-01-01

243

Evaluation of GPS position and attitude determination for automated rendezvous and docking missions. M.S. Thesis  

NASA Technical Reports Server (NTRS)

The use of the Global Positioning System for position and attitude determination is evaluated for an automated rendezvous and docking mission. The typical mission scenario involves the chaser docking with the target for resupply or repair purposes, and is divided into three sections. During the homing phase, the chaser utilizes coarse acquisition pseudorange data to approach the target; guidance laws for this stage are investigated. In the second phase, differential carrier phase positioning is utilized. The chaser must maintain a quasiconstant distance from the target, in order to resolve the initial integer ambiguities. Once the ambiguities are determined, the terminal phase is entered, and the rendezvous is completed with continuous carrier phase tracking. Attitude knowledge is maintained in all phases through the use of the carrier phase observable. A Kalman filter is utilized to estimate all states from the noisy measurement data. The effects of selective availability and cycle slips are also investigated.

Diprinzio, Marc D.; Tolson, Robert H.

1994-01-01

244

String method for calculation of minimum free-energy paths in Cartesian space in freely-tumbling systems  

PubMed Central

The string method is a molecular-simulation technique that aims to calculate the minimum free-energy path of a chemical reaction or conformational transition, in the space of a pre-defined set of reaction coordinates that is typically highly dimensional. Any descriptor may be used as a reaction coordinate, but arguably the Cartesian coordinates of the atoms involved are the most unprejudiced and intuitive choice. Cartesian coordinates, however, present a non-trivial problem, in that they are not invariant to rigid-body molecular rotations and translations, which ideally ought to be unrestricted in the simulations. To overcome this difficulty, we reformulate the framework of the string method to integrate an on-the-fly structural-alignment algorithm. This approach, referred to as SOMA (String method with Optimal Molecular Alignment), enables the use of Cartesian reaction coordinates in freely tumbling molecular systems. In addition, this scheme permits the dissection of the free-energy change along the most probable path into individual atomic contributions, thus revealing the dominant mechanism of the simulated process. This detailed analysis also provides a physically-meaningful criterion to coarse-grain the representation of the path. To demonstrate the accuracy of the method we analyze the isomerization of the alanine dipeptide in vacuum and the chair-to-inverted-chair transition of ?-D mannose in explicit water. Notwithstanding the simplicity of these systems, the SOMA approach reveals novel insights into the atomic mechanism of these isomerizations. In both cases, we find that the dynamics and the energetics of these processes are controlled by interactions involving only a handful of atoms in each molecule. Consistent with this result, we show that a coarse-grained SOMA calculation defined in terms of these subsets of atoms yields nearidentical minimum free-energy paths and committor distributions to those obtained via a highly-dimensional string.

Branduardi, Davide; Faraldo-Gomez, Jose D.

2014-01-01

245

Fuzzy logic techniques for rendezvous and docking of two geostationary satellites  

NASA Technical Reports Server (NTRS)

Large assemblings in space require the ability to manage rendezvous and docking operations. In future these techniques will be required for the gradual build up of big telecommunication platforms in the geostationary orbit. The paper discusses the use of fuzzy logic to model and implement a control system for the docking/berthing of two satellites in geostationary orbit. The system mounted in a chaser vehicle determines the actual state of both satellites and generates torques to execute maneuvers to establish the structural latching. The paper describes the proximity operations to collocate the two satellites in the same orbital window, the fuzzy guidance and navigation of the chaser approaching the target and the final Fuzzy berthing. The fuzzy logic system represents a knowledge based controller that realizes the close loop operations autonomously replacing the conventional control algorithms. The goal is to produce smooth control actions in the proximity of the target and during the docking to avoid disturbance torques in the final assembly orbit. The knowledge of the fuzzy controller consists of a data base of rules and the definitions of the fuzzy sets. The knowledge of an experienced spacecraft controller is captured into a set of rules forming the Rules Data Base.

Ortega, Guillermo

1995-01-01

246

Autonomous rendezvous and docking: A commercial approach to on-orbit technology validation  

NASA Astrophysics Data System (ADS)

The Space Automation and Robotics Center (SpARC), a NASA-sponsored Center for the Commercial Development of Space (CCDS), in conjunction with its corporate affiliates, is planning an on-orbit validation of autonomous rendezvous and docking (ARD) technology. The emphasis in this program is to utilize existing technology and commercially available components whenever possible. The primary subsystems that will be validated by this demonstration include GPS receivers for navigation, a video-based sensor for proximity operations, a fluid connector mechanism to demonstrate fluid resupply capability, and a compliant, single-point docking mechanism. The focus for this initial experiment will be expendable launch vehicle (ELV) based and will make use of two residual Commercial Experiment Transporter (COMET) service modules. The first COMET spacecraft will be launched in late 1992 and will serve as the target vehicle. The ARD demonstration will take place in late 1994, after the second COMET spacecraft has been launched. The service module from the second COMET will serve as the chase vehicle.

Tchoryk, Peter, Jr.; Dobbs, Michael E.; Conrad, David J.; Apley, Dale J.; Whitten, Raymond P.

247

The applications of laser tracking and ranging technology in space rendezvous and docking  

NASA Astrophysics Data System (ADS)

With the development of space technology, more and more Rendezvous and Docking (RVD) mission require more precise measurement of relative position and attitude between tracking spacecraft and target spacecraft. In the procedure of docking between near spacecraft , the optical retroreflector on the target Spacecraft were tracked by the laser tracking and ranging device on the tracking spacecraft , the distance data were provided by laser ranging system, and the azimuth data were provided by tracking gimbal, Synthesized the distance data and azimuth data, the relative position information between two spacecraft were provided to the target spacecraft. Furthermore, through tracking more than three point on the target spacecraft ,the complete information of relative position and attitude between two spacecraft were calculated rapidly by the measurement system?which were presented to the control system during the whole RVD operating stage. The laser tracking technology guaranteed continuous measurement and supplied accurate azimuth information, and the laser ranging technology ensured high accuracy of distance information. In addition, the untouched measure mode give no disturbance to the docking operation, moreover, the monochromaticity of laser make the tracking and ranging procedure avoiding to be disturbed by parasitic light of space, thus there will be a effective measurement accompanying the whole docking operating procedure and affording valid data to the control system of docking.

She, Wenji; Gao, Limin; Zhou, Liang; Li, Dawei; Wang, Rong

2013-09-01

248

Optimal two-impulse rendezvous using constrained multiple-revolution Lambert solutions  

NASA Astrophysics Data System (ADS)

A solution to the fixed-time minimum-fuel two-impulse rendezvous problem for the general non-coplanar elliptical orbits is provided. The optimal transfer orbit is obtained using the constrained multiple-revolution Lambert solution. Constraints consist of lower bound for perigee altitude and upper bound for apogee altitude. The optimal time-free two-impulse transfer problem between two fixed endpoints implies finding the roots of an eighth order polynomial, which is done using a numerical iterative technique. The set of feasible solutions is determined by using the constraints conditions to solve for the short-path and long-path orbits semimajor axis ranges. Then, by comparing the optimal time-free solution with the feasible solutions, the optimal semimajor axis for the two fixed-endpoints transfer is identified. Based on the proposed solution procedure for the optimal two fixed-endpoints transfer, a contour of the minimum cost for different initial and final coasting parameters is obtained. Finally, a numerical optimization algorithm (e.g., evolutionary algorithm) can be used to solve this global minimization problem. A numerical example is provided to show how to apply the proposed technique.

Zhang, Gang; Zhou, Di; Mortari, Daniele

2011-08-01

249

Rosetta—one comet rendezvous and two asteroid fly-bys  

NASA Astrophysics Data System (ADS)

One of the two planetary cornerstone missions of the European Space Agency is the Rosetta mission to comet 67P/Churyumov-Gerasimenko. Rosetta is a rendezvous mission with a comet nucleus, which combines an Orbiter with a Lander. It will monitor the evolution of the comet nucleus and the coma as a function of increasing and decreasing solar flux input along the comet’s pre- and post-perihelion orbit. Different instrumentations will be used in parallel, from multi-wavelength spectrometry to in-situ measurements of coma and nucleus composition and physical properties. Rosetta will go in orbit around the nucleus of its target comet 67P/Churyumov-Gerasimenko, when it is still far from the Sun and accompany the comet along its way to perihelion and beyond. In addition the Rosetta Lander Philae will land on the nucleus surface, before the comet is too active to permit such a landing (i.e. at around r = 3 AU) and examine the surface and subsurface composition of the comet nucleus as well as its physical properties.

Schulz, R.

2009-08-01

250

The Ion Propulsion System on NASA's Space Technology 4/Champollion Comet Rendezvous Mission  

NASA Technical Reports Server (NTRS)

The ST4/Champollion mission is designed to rendezvous with and land on the comet Tempel 1 and return data from the first-ever sampling of a comet surface. Ion propulsion is an enabling technology for this mission. The ion propulsion system on ST4 consists of three ion engines each essentially identical to the single engine that flew on the DS1 spacecraft. The ST4 propulsion system will operate at a maximum input power of 7.5 kW (3.4 times greater than that demonstrated on DS1), will produce a maximum thrust of 276 mN, and will provide a total (Delta)V of 11.4 km/s. To accomplish this the propulsion system will carry 385 kg of xenon. All three engines will be operated simultaneously for the first 168 days of the mission. The nominal mission requires that each engine be capable of processing 118 kg. If one engine fails after 168 days, the remaining two engines can perform the mission, but must be capable of processing 160 kg of xenon, or twice the original thruster design requirement. Detailed analyses of the thruster wear-out failure modes coupled with experience from long-duration engine tests indicate that the thrusters have a high probability of meeting the 160-kg throughput requirement.

Brophy, John R.; Garner, Charles E.; Weiss, Jeffery M.

1999-01-01

251

Fourth Report of the Task Force on the Shuttle-Mir Rendezvous and Docking Missions  

NASA Technical Reports Server (NTRS)

On December 6, 1994, the NASA Administrator, Mr. Daniel Goldin, requested that Lt. Gen. Thomas P. Stafford, in his role as the Chairman of the NASA Advisory Council Task Force on the Shuttle-Mir Rendezvous and Docking Missions, lead a team composed of several Task Force members and technical advisors' to Russia with the goal of reviewing preparations and readiness for the upcoming international Space Station Phase 1 missions. In his directions to Gen. Stafford, Mr. Goldin requested that the review team focus its initial efforts on safety of flight issues for the following Phase 1A missions: the Soyuz TM-21 mission which will carry U.S. astronaut Dr. Norman Thagard and cosmonauts Lt. Col. Vladimir Dezhurov and Mr. Gennady Strekalov aboard a Soyuz spacecraft to the Mir Station; the Mir 18 Main Expedition during which Thagard and his fellow cosmonauts, Dezhurov and Strokalov, will spend approximately three months aboard the Mir Station; the STS-71 Space Shuttle mission which will perform the first Shuttle-Mir docking, carry cosmonauts Col. Anatoly SoloViev and Mr. Nikolai Budarin to the Mir Station, and return Thagard, Dezhurov, and Strekalov to Earth.

1995-01-01

252

Concluding Report of Free-Spinning, Tumbling, and Recovery Characteristics of a 1/18-Scale Model of the Ryan X-13 Airplane, Coord. No. AF-199  

NASA Technical Reports Server (NTRS)

An investigation has been completed in the Langley 20-foot free-spinning tunnel on a l/18-scale model of the Ryan X-13 airplane to determine its spin, recovery, and tumbling characteristics, and to determine the minimum altitude from which a belly landing could be made in case of power failure in hovering flight. Model spin tests were conducted with and without simulated engine rotation. Tests without simulated engine rotation indicated two types of spins: one, a slightly oscillatory flat spin; and the other, a violently oscillatory spin. Tests with simulated engine rotation indicated that spins to the left were fast rotating and steep and those to the right were slow rotating and flat. The optimum technique for recovery is reversal of the rudder to against the spin and simultaneous movement of the ailerons to full with the spin followed by movement of the elevators to neutral after the spin rotation ceases. Tumbling tests made on the model indicated that although the Ryan X-13 airplane will not tumble in the ordinary sense (end-over-end pitching motion), it may instead tend to enter a wild gyrating'motion. Tests made to simulate power failure in hovering flight by dropping the model indicated that the model entered what appeared to be a right spin. An attempt should be made to stop this motion immediately by moving the rudder to oppose the rotation (left pedal), moving the ailerons to with the spin (stick right), and moving the stick forward after the spin rotation ceases to obtain flying speed for pullout. The minimum altitude required for a belly landing in case of power failure in hovering flight was indicated to be about 4,200 feet.

Bowman, James S., Jr.

1957-01-01

253

Proximity Operations for Space Situational Awareness Spacecraft Rendezvous and Maneuvering using Numerical Simulations and Fuzzy Logic  

NASA Astrophysics Data System (ADS)

The authors present several spacecraft rendezvous and close proximity maneuvering techniques modeled with a high-precision numerical integrator using full force models and closed loop control with a Fuzzy Logic intelligent controller to command the engines. The authors document and compare the maneuvers, fuel use, and other parameters. This paper presents an innovative application of an existing capability to design, simulate and analyze proximity maneuvers; already in use for operational satellites performing other maneuvers. The system has been extended to demonstrate the capability to develop closed loop control laws to maneuver spacecraft in close proximity to another, including stand-off, docking, lunar landing and other operations applicable to space situational awareness, space based surveillance, and operational satellite modeling. The fully integrated end-to-end trajectory ephemerides are available from the authors in electronic ASCII text by request. The benefits of this system include: A realistic physics-based simulation for the development and validation of control laws A collaborative engineering environment for the design, development and tuning of spacecraft law parameters, sizing actuators (i.e., rocket engines), and sensor suite selection. An accurate simulation and visualization to communicate the complexity, criticality, and risk of spacecraft operations. A precise mathematical environment for research and development of future spacecraft maneuvering engineering tasks, operational planning and forensic analysis. A closed loop, knowledge-based control example for proximity operations. This proximity operations modeling and simulation environment will provide a valuable adjunct to programs in military space control, space situational awareness and civil space exploration engineering and decision making processes.

Carrico, T.; Langster, T.; Carrico, J.; Alfano, S.; Loucks, M.; Vallado, D.

254

A multiple-rendezvous, sample-return mission to two near-Earth asteroids  

NASA Astrophysics Data System (ADS)

We propose a dual-rendezvous mission, targeting near-Earth asteroids, including sample-return. The mission, Asteroid Sampling Mission (ASM), consists of two parts: (i) flyby and remote sensing of a Q-type asteroid, and (ii) sampling of a V-type asteroid. The targeted undifferentiated Q-type are found mainly in the near-Earth space, and to this date have not been the target of a space mission. We have chosen, for our sampling target, an asteroid from the basaltic class (V-type), as asteroids in this class exhibit spectral signatures that resemble those of the well-studied Howardite-Eucrite-Diogenite (HED) meteorite suite. With this mission, we expect to answer specific questions about the links between differentiated meteorites and asteroids, as well as gain further insight into the broader issues of early Solar System (SS) evolution and the formation of terrestrial planets. To achieve the mission, we designed a spacecraft with a dry mass of less than 3 tonnes that uses electric propulsion with a solar-electric power supply of 15 kW at 1 Astronomical Unit (AU). The mission includes a series of remote sensing instruments, envisages landing of the whole spacecraft on the sampling target, and employs an innovative sampling mechanism. Launch is foreseen to occur in 2018, as the designed timetable, and the mission would last about 10 years, bringing back a 150 g subsurface sample within a small re-entry capsule. This paper is a work presented at the 2008 Summer School Alpbach,"Sample return from the Moon, asteroids and comets" organized by the Aeronautics and Space Agency of the Austrian Research Promotion Agency. It is co-sponsored by ESA and the national space authorities of its Member and Co-operating States, with the support of the International Space Science Institute and Austrospace.

Duffard, R.; Kumar, K.; Pirrotta, S.; Salatti, M.; Kubínyi, M.; Derz, U.; Armytage, R. M. G.; Arloth, S.; Donati, L.; Duricic, A.; Flahaut, J.; Hempel, S.; Pollinger, A.; Poulsen, S.

2011-07-01

255

A new way in intelligent recognition improves control accuracy and efficiency for spacecrafts' rendezvous and docking  

NASA Astrophysics Data System (ADS)

Spacecrafts rendezvous and docking (RVD) by human or autonomous control is a complicated and difficult problem especially in the final approach stage. Present control methods have their key technology weakness. It is a necessary, important and difficult step for RVD through human's aiming chaser spacecraft at target spacecraft in a coaxial line by a three-dimension bulge cross target. At present, there is no technology to quantify the alignment in image recognition direction. We present a new practical autonomous method to improve the accuracy and efficiency of RVD control by adding image recognition algorithm instead of human aiming and control. Target spacecraft has a bulge cross target which is designed for chaser spacecraft's aiming accurately and have two center points, one is a plate surface center point(PSCP), another is a bulge cross center point(BCCP), while chaser spacecraft has a monitoring ruler cross center point(RCCP) of the video telescope optical system for aiming . If the three center points are coincident at the monitoring image, the two spacecrafts keep aligning which is suitable for closing to docking. Using the trace spacecraft's video telescope optical system to acquire the real-time monitoring image of the target spacecraft's bulge cross target. Appling image processing and intelligent recognition algorithm to get rid of interference source to compute the three center points' coordinate and exact digital offset of two spacecrafts' relative position and attitude real-timely, which is used to control the chaser spacecraft pneumatic driving system to change the spacecraft attitude in six direction: up, down, front, back, left, right, pitch, drift and roll precisely. This way is also practical and economical because it needs not adding any hardware, only adding the real-time image recognition software into spacecrafts' present video system. It is suitable for autonomous control and human control.

Wang, JiaQing; Lu, Yaodong; Wang, JiaFa

2013-08-01

256

Tumbling in Space  

NSDL National Science Digital Library

The first activity in this newsletter was written to engage students in an investigation related to the Fast Plants that traveled into space in May of 1995. Students explore how plants use guidance systems which sense and respond to gravity (gravitropism) ensuring that roots anchor plants and access water and that shoots emerge into the light.This activity includes substantial background discussion about gravitropism in plants.

Program, The W.

257

Fifth Report of the NASA Advisory Council Task Force on the Shuttle-Mir Rendezvous and Docking Missions  

NASA Technical Reports Server (NTRS)

The NASA Advisory Council Task Force on the Shuttle-Mir rendezvous and docking missions examine a number of specific issues related to the Shuttle-Mir program. Three teams composed of Task Force members and technical advisors were formed to address the follow issues: preliminary results from STS-71 and the status of preparations for STS-74; NASA's presence in Russia; and NASA's automated data processing and telecommunications (ADP/T) infrastructure in Russia. The three review team reports have been included in the fifth report of the Task Force.

1995-01-01

258

Infrared focal plane design for the Comet Rendezvous/Asteroid Flyby and Cassini Visible and Infrared Mapping Spectrometers  

NASA Astrophysics Data System (ADS)

A focal plane assembly combining hybrid electronic components with passive optical components within a single hermetically sealed package has been designed by Cincinnati Electronics to meet the performance requirements imposed by the Comet Rendezvous/Asteroid Flyby (CRAF) and Cassini Visible and Infrared Mapping Spectrometers (VIMSs). A single line array of 256 InSb photodiodes, accessed by two 1 x 128 multiplexers, provides continuous spectral coverage from 0.85 to 5.1 microns. Intrinsic field-of-view apertures and a unique order sorting filter require critical optical alignment within the hybrid. FPA performance requirements, design approach, and critical issues are discussed.

Staller, Craig; Niblack, Curtiss; Evans, Thomas; Blessinger, Michael; Westrick, Anthony

1991-12-01

259

TASTER: Trojan ASteroid Tour, Exploration and Rendezvous, a NASA Planetary Science Summer School Mission Design Exercise  

NASA Astrophysics Data System (ADS)

A detailed investigation of the Trojan asteroids occupying Jupiter's L4 and L5 Lagrangian points has been identified as a priority for future missions by the 2011 Planetary Science Decadal Survey. Observing these asteroids and getting clear measurements of their physical characteristics and composition may yield answers to fundamental questions relating to the early Solar System. In particular, Trojan asteroids are believed to harbor primordial material dating from the time of its formation. The source region for Trojans is still unknown; the Nice model predicts that some bodies may have originated in the primordial Kuiper belt and were subsequently scattered inward during the migration of Neptune and Uranus and settled in their current location. In alternative models, less radial scattering of small bodies would imply Trojans formed from material at a similar orbital distance to Jupiter. Determination of Trojan composition and structure will help identify their birth location, provide information about the impact history and subsequent evolution. Earth-based observations of size and surface characteristics are sparse; spectral measurements are unable to resolve composition (and show a puzzling lack of volatile signatures), indicating that close-range observation is needed. We present a mission design for a Trojan Tour and Rendezvous mission that is consistent with NASA's New Frontiers candidate recommended by the Decadal Survey, and which is the final result of the 2011 NASA-JPL Planetary Science Summer School Mission Design Exercise. Our proposed mission includes a tour phase that features a 500 km altitude fly-by of 1999 XS143. The spacecraft will then orbit and make detailed observations of 1919FD Agamemnon, a 167 km diameter asteroid located in the leading Lagrangian point (L4), from orbital altitudes of 1000 - 100 km over a 12 month nominal science data capture period. The mission's planned primary observations aim to (1) detect and identify volatile species and rock-forming elements on or just below the surface, (2) map the surface geology, and (3) determine size, shape, and rotational state. Our payload will provide unprecedented high-resolution, global dataset for the target bodies, yielding crucial information about the early history and evolution of the Solar System.

Diaz-silva, R.; Sayanagi, K. M.; Gil, S.; Diniega, S.; Balcerski, J.; Benneke, B.; Carande, B.; Fraeman, A. A.; Hudson, J. S.; Guzewich, S. D.; Livi, R.; Nahm, A.; Potter, S.; Route, M.; Urban, K. D.; Vasisht, S.; Williams, B.; Budney, C. J.; Lowes, L. L.

2011-12-01

260

An Investigation of Multipath Effects on the GPS System During Auto-Rendezvous and Capture  

NASA Technical Reports Server (NTRS)

The proposed use of a Cargo Transport Vehicle (CTV) to carry hardware to the Space Station Freedom (SSF) during the construction phase of the SSF project requires remote maneuvering of the CTV. The CTV is not a manned vehicle. Obtaining the relative positions of the CTV and SSF for remote auto-rendezvous and capture (AR&C) scenarios will rely heavily on the Global Positioning System (GPS). The GPS system is expected to guide the CTV up to a distance of 100 to 300 meters from the SSF. At some point within this range, an optical docking system will take over the remote guidance for capture. During any remote guidance by GPS it is possible that significant multipath signals may be caused by large objects in the vicinity of the module being remotely guided. This could alter the position obtained by the GPS system from the actual position. Due to the nature of the GPS signals, it has been estimated that if the difference in distance between the Line of Sight (LOS) path and the multipath is greater than 300 meters, the GPS system is capable of discriminating between the direct signal and the reflected (or multipath) signal. However, if the path difference is less than 300 meters, one must be concerned. This report details the work accomplished by the Electromagnetic Simulations Laboratory at Marquette University over the period December 1993 to May 1995. This work is an investigation of the strength and phase of a multipath signal arriving at the CTV relative to the direct or line of sight (LOS) signal. The signal originates at a GPS satellite in half geo-stationary orbit and takes two paths to the CTV: (1) the direct or LOS path from the GPS satellite to the CTV; and (2) a scattered path from the GPS satellite to the SSF module and then to the CTV. The scattering from a cylinder has been computed using the physical optics approximation for the current. No other approximations or assumptions have been made including no assumptions regarding the far field or Fresnel field approximations. The integrations required to obtain the scattered field have been computed numerically using an N dimensional Romberg integration. The total scattered electric field is then projected onto the RCP component in the direction of propagation only. The direct or line of sight signal is then used to compute the relative strength and phase of the scattered field. The trajectory of the CTV has been parameterized into 4,214 points that are calculated for each of the geometries investigated. The motion of the CTV between points is small enough for the magnitude data (dB down from direct signal) to appear very smooth; however, because of the distances and wavelengths involved, the phase of the scattered field relative to the direct signal varies very rapidly.

Richie, James E.; Forest, Francis W.

1995-01-01

261

Multi-objective and reliable control for trajectory-tracking of rendezvous via parameter-dependent Lyapunov functions  

NASA Astrophysics Data System (ADS)

A reliable, multi-objective and state-feedback controller design algorithm is presented for trajectory-tracking of circular-orbit rendezvous, in which H? performance, H2 performance and regional pole placement are taken into account. Given actuator failures and exogenous disturbances, the dynamical model is described as a polytopic system. By applying parameter-dependent Lyapunov functions and introducing slack matrices, the condition for the existence of multi-objective controller is described as a non-convex optimization subject to nonlinear matrix inequality constraints. Then, a hybrid genetic algorithm is proposed to obtain the desired controller. Numerical simulations are given to show that the proposed method can (a) handle actuator failures and exogenous disturbances effectively, and (b) provide better disturbance-attenuation performances than conventional methods.

Ma, Lichao; Meng, Xiuyun; Liu, Zaozhen; Du, Lifu

2012-12-01

262

Rosetta rendezvous and CONSERT operations in 2014: A chimeric surface model of 67P/Churyumov Gerasimenko  

NASA Astrophysics Data System (ADS)

In 2014 the European Space Agency's Rosetta probe will rendezvous with the comet 67P/Churyumov Gerasimenko (67P) and the Philae Lander will land on the surface of the nucleus. Following the landing, the COmet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) radar will perform the tomography of the nucleus by measuring radiowave propagation through the comet between the Lander and the orbiter. Preparation for these operations, in particular the development and validation of simulation software, requires a shape model of the surface of 67P. The complexity of this model should reflect the environmental conditions that will be found in 2014. In this paper, we show that existing models of 67P are not of a sufficiently high resolution to constitute interesting test cases. Following a review of current shape models for other comets, we propose a composite which is a hybrid of the 67P and 81P/Wild 2 models.

Herique, Alain; Lasue, Jéremie; Rogez, Yves; Zine, Sonia; Kofman, Wlodek

2012-07-01

263

Maneuver strategy for NEAR’s rendezvous with 433 Eros 1 1 Paper IAF 97-A4.01. presented at the 48th International Astronautical Congress, 6–10 October, 1997, Turin, Italy  

Microsoft Academic Search

On 17 February, 1996, a Delta-2 rocket placed NASA’s Near-Earth Asteroid Rendezvous (NEAR) spacecraft into a 2-year ?VEGA trajectory that will rendezvous with the large near-Earth asteroid, 433 Eros in early January 1999. This paper discusses the strategy for performing NEAR’s two large deterministic ?Vs, the Deep Space Maneuver (DSM; 269 m\\/s) 4 months after aphelion of the initial 2-year orbit

David W Dunham; James V McAdams; Larry E Mosher; Clifford E Helfrich

2000-01-01

264

Electron Spin Relaxation Rates for Semiquinones between 25 and 295 K in Glass-Forming Solvents  

PubMed Central

Electron spin lattice relaxation rates for five semiquinones (2,5-di-t-butyl-1,4-benzosemiquinone, 2,5-di-t-amyl-1,4-benzosemiquinone, 2,5-di-phenyl-1,4-benzosemiquinone, 2,6-di-t-butyl-1,4-benzosemiquinone, tetrahydroxy-1,4-benzosemiquione) were studied by long-pulse saturation recovery EPR in 1:4 glycerol:ethanol, 1:1 glycerol:ethanol, and triethanolamine between 25 and 295 K. Although the dominant process changes with temperature, relaxation rates vary smoothly with temperature, even near the glass transition temperatures, and could be modeled as the sum of contributions that have the temperature dependence that is predicted for the direct, Raman, local mode and tumbling dependent processes. At 85 K, which is in a temperature range where the Raman process dominates, relaxation rates along the gxx (g~2.006) and gyy (g~2.005) axes are about 2.7 to 1.5 times faster than along the gzz axis (g = 2.0023). In highly viscous triethanolamine, contributions from tumbling-dependent processes are negligible. At temperatures above 100 K relaxation rates in triethanolamine are unchanged between X-band (9.5 GHz) and Q-band (34 GHz), so the process that dominates in this temperature interval was assigned as a local mode rather than a thermally-activated process. Because the largest proton hyperfine couplings are only 2.2 G, spin rotation makes a larger contribution than tumbling-dependent modulation of hyperfine anisotropy. Since g anisotropy is small, tumbling dependent modulation of g anisotropy make a smaller contribution than spin rotation at X-band. Although there was negligible impact of methyl rotation on T1, rotation of t-butyl or t-amyl methyl groups enhances spin echo dephasing between 85 and 150 K.

Kathirvelu, Velavan; Sato, Hideo; Eaton, Sandra S.; Eaton, Gareth R.

2009-01-01

265

Magnetometer-Only Attitude and Rate Estimates for Spinning Spacecraft  

NASA Technical Reports Server (NTRS)

A deterministic algorithm and a Kalman filter for gyroless spacecraft are used independently to estimate the three-axis attitude and rates of rapidly spinning spacecraft using only magnetometer data. In-flight data from the Wide-Field Infrared Explorer (WIRE) during its tumble, and the Fast Auroral Snapshot Explorer (FAST) during its nominal mission mode are used to show that the algorithms can successfully estimate the above in spite of the high rates. Results using simulated data are used to illustrate the importance of accurate and frequent data.

Challa, M.; Natanson, G.; Ottenstein, N.

2000-01-01

266

RendezVous sensor for automatic guidance of transfer vehicles to ISS concept of the operational modes depending on actual optical and geometrical-dynamical conditions  

NASA Astrophysics Data System (ADS)

Based on an ATV RendezVous Predevelopment Program initiated by ESTEC, an automatically operating Rendez Vous Sensor has been developed. The sensor--a Scanning Tele-Goniometer--shall guide docking and retreat of the European Automatic Transfer Vehicle as well as berthing and retreat of the Japanese H-II Transfer Vehicle. The sensor performance will be strongly connected with the properties of cooperative targets, consisting of an arrangement of retro reflectors mounted on ISS each.

Moebius, Bettina G.; Kolk, Karl-Hermann

2000-10-01

267

Cosmic Ray Induced Degradation in X-Ray Detectors On Board the Near Earth Asteroid Rendezvous Spacecraft  

NASA Technical Reports Server (NTRS)

The Near-Earth Asteroid Rendezvous (NEAR) mission is the first in NASA's new Discovery Program to explore the solar system. Launched in February 1996, the NEAR spacecraft will take a long cruise flight arriving at the asteroid 433 Eros in January 1999 for a one year orbiting survey operation. This long exposure to the space environment has already proven to be an additional complication for the x-ray spectrometer. The asteroid pointing detectors for the x-ray spectrometer are three gas-filled proportional counters with resolving power in the range of 1 keV. Therefore, to resolve the important but closely spaced magnesium, aluminum and silicon k alpha lines( 1.255, 1.487, 1.739 keV respectively), magnesium and aluminum balanced filters are used on two of the detectors. The x-ray florescence from the surface of Eros is stimulated by solar x-rays. A proportional counter and a silicon PIN detector are used to monitor the solar incident x-ray flux. The proportional counters are single wire gas filled beryllium lined steel tubes operating at about 1100 volt. The 25 cm(exp 2) optical window is one mil. thick beryllium. To define the detector's active region, two boron nitride disks were incorporated in the tube just outside window area. It appears from the space flight data that the space environment is creating a charge on these boron nitride disks which ultimately distorts the tube gain and resolution. This broadening of the photo peak makes it more difficult to identify weak peaks and so degrades the statistical accuracy for some very important elements such as sulfur, calcium and iron (2.307, 3.690, 6.403 keV respectively). If the broadening is severe enough in the low energy region, counts will be lost as the photo peak spreads below the lower level discriminator (0.7 keV).

Floyd, S. R.; Trombka, J. I.; Goldsten, J. O.; Fiore, E. M.

1997-01-01

268

Target acquisition dynamics with application to the rendezvous radar of the Space Shuttle orbiter  

NASA Astrophysics Data System (ADS)

A statistical approach is used in formulating the transition from search to automatic angle tracking for search and tracking radars. The angular separation between the target position and the antenna line of sight following detection is derived as a function of both target and system parameters. Using a simple computer program, the probability density function of the angular separation at the end of the acquisition phase is found as a function of both target and system parameters. The results can then be used to develop specifications for the antenna control servo for established limits on target angular rates so as to obtain a high probability of successful transition from search to automatic angle tracking.

Kassem, A. M.; McQuillan, W. F.

1982-08-01

269

Light scattering observations and simulations, as hints about the media encountered by future rendezvous missions to comets and asteroids  

NASA Astrophysics Data System (ADS)

The success of future rendezvous mission to comets (i.e. Rosetta, which will explore the innermost coma of 67P/Churyumov-Gerasimenko, before deploying a lander on its nucleus in 2014) and asteroids (e.g. Marco-Polo candidate mission for ESA Cosmic Vision) require some understanding of the physical properties of the dust particles encountered in the coma (if any) and on the solid surface. Analysis of observations of the linear polarization of solar light scattered by such media may provide clues to their properties [1]. The polarization is actually a dimension-less ratio, which only varies with the geometry of the observations (i.e. phase angle), with the wavelength, and with the properties of the scattering medium. Comparisons between the shapes of the polarimetric phase curves of asteroids [2] and comets [3] provide a classification with respect to the dust properties. As far as asteroids are concerned, this classification is reminiscent of the taxonomic classes, and more information is expected from detailed studies of the wavelength dependence. As far as comets are concerned, an extensive programme of numerical and laboratory simulations with various irregular compact grains and aggregates has been developed in the past years [4,5]. Comparisons of the results with observations (tentatively on a large range of phase angles and wavelengths) have allowed us to suggest that cometary dust particles are built of both very fluffy aggregates and of more compact grains, with significant proportions of both rather transparent silicates and absorbing materials [6]. These estimations are confirmed by the analysis of Stardust samples, with, e.g. evidence for dense grains and aggregates with low bulk density within the coma of comet Wild 2 [7]. It may thus be concluded that the analysis of remote light scattering observations allows us to infer some properties of the scattering media, to point out some similarities and discrepancies between small solar system bodies, and to contribute to the success of future space missions. [1] Levasseur-Regourd and Hadamcik, J. Quant. Spectros. Radiat. Transfer 79, 903-910, 2003. [2] Pentill¨ et al., Astron. Astrophys. 432, 1081-1090, 2005. [3] Levasseur-Regourd a et al., Astron. Astrophys. 313, 327-333, 1996. [4] Lasue and Levasseur-Regourd, J. Quant. Spectros. Radiat. Transfer 100, 220-236, 2006. [5] Hadamcik et al., Icarus 190, 660-671, 2007. [6] Levasseur-Regourd et al., Planet. Space Sci. 55, 1010-1020, 2007. [7] H¨rz et al., Science o 314, 1716-1719 (2006).

Levasseur-Regourd, Anny-Chantal

270

Precise Attitude Determination for Rendez-Vous and Docking by Information Fusion of Laser Range Finder Measurements  

NASA Astrophysics Data System (ADS)

For the docking of spacecrafts a highly precise attitude and position control is necessary. This requires an adequate measurement of the relative position and attitude of the docking spacecrafts. Here is presented, how a rendezvous and docking sensor (RVS) consisting of a laser range finder (LRF) with a scanning mirror system and a set of retro reflectors can be used to measure the necessary data. The active part of the measurement system is mounted on the chaser. The passive part forms the target pattern and is a set of three or more retro reflectors mounted on the space station. A laser beam scans the field of view and detects the range and the line of sight of each retro reflector of the target successively (Fig. 1). The sequence of the LRF measurements of the moving chaser is processed in a special multi-model state observer (Fig. 2). In this way the results of the retro measurements are composed to the relative position and attitude between chaser and target. Because of the sequential measurement y of the single retro reflectors from the moving chaser, a precise determination of the attitude can only be performed, if all the state variables x* of position and attitude with the belonging velocities of the rigid chaser are estimated. The availability of the complete state vector also supports the application of state feedback control of the chaser motion. Fig. 1. Scanning laser radar with target pattern Fig. 2. Multi-model state observer for sequential retro measurements (right) The observer computes with increasing accuracy in time the 12 state variables of relative position and attitude (Euler angles or quaternions) with respect to the target as well as the translatory and rotatory velocities. It models a reduced discrete-time state equation system (k, ) of the chaser and the LRF measurements to the different retro reflectors. So for each retro reflector a partial model depending on its position in the target pattern exists (As, C). Information fusion to reduce the uncertainty of the state vector means, that each retro reflector measurement gives a specific contribution to determine the state variables and to increase their accuracy in the sequence. The dynamic behaviour of the observer, its stability, its approaching behaviour and its accuracy depend mainly on the set of observer feedback matrices H and the initial conditions of the state vector x*(0) to be estimated. The obtained algorithms are simulated under the conditions of a usual flight scenario and the results are discussed. A short observer transient time of 4 or 5 measurement cycles k can be reached.

Strietzel, Roland

271

A Modified Technique Reduced Operative Time of Laparoendoscopic Rendezvous Endoscopic Retrograde Cholangiopancreatography Combined with Laparoscopic Cholecystectomy for Concomitant Gallstone and Common Bile Ductal Stone  

PubMed Central

Laparoendoscopic rendezvous (LERV) endoscopic retrograde cholangiopancreatography (ERCP) and laparoscopic cholecystectomy (LC+ERCP/LERV) are considered an optimal approach for concomitant gallstones and common bile duct stones. The rendezvous technique is essential for the success of procedure. We applied two different LERV techniques, traditional technique and modified technique, in 60 consecutive cases from January 2011 to November 2012. 32 cases who underwent modified technique (group 1) from February 2012 to November 2012 were retrospectively compared to 28 cases (group 2) who underwent traditional technique from January 2011 to January 2012. There was no significant difference between two groups with respect to preoperative demographic features. Although the difference was not statistically significant, the procedure was successfully performed in 31 cases (96.9%) in group 1 and 24 cases (86.2%) in group 2. The mean operative time and time of endoscopic part were 82.6?±?19.6?min and 26.5?±?5.99?min in group 1 which were significantly shorter than those in group 2 (118.0?±?23.1?min and 58.7?±?13.3?min, resp.). There was no postoperative pancreatitis and mortality in both groups. The mean hospital stay, blood loss, incidence of complications, and residual stone were of no difference in both groups. This study proved that this modified technique can effectively reduce the operative time and time of endoscopic part of LC+ERCP/LERV compared with traditional technique.

Liu, Wei; Wang, Qunwei; Xiao, Jing; Zhao, Liying; Huang, Jiangsheng; Tan, Zhaohui; Li, Pengfei

2014-01-01

272

A modified technique reduced operative time of laparoendoscopic rendezvous endoscopic retrograde cholangiopancreatography combined with laparoscopic cholecystectomy for concomitant gallstone and common bile ductal stone.  

PubMed

Laparoendoscopic rendezvous (LERV) endoscopic retrograde cholangiopancreatography (ERCP) and laparoscopic cholecystectomy (LC+ERCP/LERV) are considered an optimal approach for concomitant gallstones and common bile duct stones. The rendezvous technique is essential for the success of procedure. We applied two different LERV techniques, traditional technique and modified technique, in 60 consecutive cases from January 2011 to November 2012. 32 cases who underwent modified technique (group 1) from February 2012 to November 2012 were retrospectively compared to 28 cases (group 2) who underwent traditional technique from January 2011 to January 2012. There was no significant difference between two groups with respect to preoperative demographic features. Although the difference was not statistically significant, the procedure was successfully performed in 31 cases (96.9%) in group 1 and 24 cases (86.2%) in group 2. The mean operative time and time of endoscopic part were 82.6?±?19.6?min and 26.5?±?5.99?min in group 1 which were significantly shorter than those in group 2 (118.0?±?23.1?min and 58.7?±?13.3?min, resp.). There was no postoperative pancreatitis and mortality in both groups. The mean hospital stay, blood loss, incidence of complications, and residual stone were of no difference in both groups. This study proved that this modified technique can effectively reduce the operative time and time of endoscopic part of LC+ERCP/LERV compared with traditional technique. PMID:25024701

Liu, Wei; Wang, Qunwei; Xiao, Jing; Zhao, Liying; Huang, Jiangsheng; Tan, Zhaohui; Li, Pengfei

2014-01-01

273

Millennials: Rendezvous with Destiny.  

National Technical Information Service (NTIS)

The Millennial Generation (born between 1982 and about 2002) is showing characteristics and tendencies that lead generational theorists to believe that this generation will become America's next 'Hero' generation. However, the post-Cold War/post-9/11 'glo...

F. L. Fahlbusch

2008-01-01

274

Noncooperative rendezvous radar system  

NASA Technical Reports Server (NTRS)

A fire control radar system was developed, assembled, and modified. The baseline system and modified angle tracking system are described along with the performance characteristics of the baseline and modified systems. Proposed changes to provide additional techniques for radar evaluation are presented along with flight test data.

1974-01-01

275

Proposed Strategy for the U.S. to Develop and Maintain a Mainstream Capability Suite ('Warehouse') for Automated/Autonomous Rendezvous and Docking in Low Earth Orbit and Beyond.  

National Technical Information Service (NTIS)

The ability of space assets to rendezvous and dock/capture/berth is a fundamental enabler for numerous classes of NASA fs missions, and is therefore an essential capability for the future of NASA. Mission classes include: ISS crew rotation, crewed explora...

A. Bradley J. E. Riedel K. S. Krishnakumar M. Babula M. C. Moreau R. A. Stillwater R. B. Mrozinski T. C. Bryan

2012-01-01

276

Data processing system for the Near-Earth Asteroid Rendezvous (NEAR) x-ray and gamma-ray spectrometer (XGRS) ground system  

NASA Astrophysics Data System (ADS)

An x-ray and gamma-ray spectrometer (XGRS) is onboard the Near Earth Asteroid Rendezvous (NEAR) spacecraft to determine the elemental composition of the surface of the asteroid 433 Eros. The Eros asteroid is highly non-spherical in physical shape and the development of data management and analysis methodologies are in several areas a divergence from traditional remotely sensed geographical information systems techniques. Field of view and asteroid divergence from traditional remotely sensed geographical information system techniques. Field of view and asteroid surface geometry must be derived virtually and then combined with real measurements of solar, spectral and instrument calibration information to derive meaningful scientific results. Spatial resolution of planned geochemical maps will be improved from the initial conditions of low statistical significance per integration by repeated surface flyovers and regional spectral accumulation. This paper describes the results of a collaborative effort of design and development of the NEAR XGRS instrument ground system undertaken by participants at the Goddard Space Flight Center, University of Arizona, Cornell University, Applied Physics Laboratory, and Max Planck Institute.

McClanahan, Timothy P.; Mikheeva, Irina; Trombka, Jacob I.; Floyd, Samuel R.; Boynton, William V.; Bailey, H.; Bhangoo, Jasbir; Starr, Richard D.; Clark, Pamela E.; Evans, Larry G.; Squyres, Steven W.; McCartney, Elaina; Noe, E.; McNutt, Ralph L.; Brueckner, Johannes

1999-10-01

277

Randomised study on single stage laparo-endoscopic rendezvous (intra-operative ERCP) procedure versus two stage approach (Pre-operative ERCP followed by laparoscopic cholecystectomy) for the management of cholelithiasis with choledocholithiasis  

PubMed Central

INTRODUCTION: The ‘Rendezvous’ technique consists of laparoscopic cholecystectomy (LC) standards with intra-operative cholangiography followed by endoscopic sphincterotomy. The sphincterotome is driven across the papilla through a guidewire inserted by the transcystic route. In this study, we intended to compare the two methods in a prospective randomised trial. MATERIALS AND METHODS: From 2005 to 2012, we enrolled 83 patients with a diagnosis of cholecysto-choledocolithiasis. They were randomised into two groups. In ‘group-A’,41 patients were treated with two stages management, first by pre-operative endoscopic retrograde cholangiopancreatography (ERCP) and common bile duct (CBD) clearance and second by LC. In ‘group-B’, 42 patients were treated with LC and intra-operative cholangiography; and when diagnosis of choledocholithiasis was confirmed, patients had undergone one stage management of by Laparo-endoscopic Rendezvous technique. RESULTS: In arm-A and arm-B groups, complete CBD clearance was achieved in 29 and 38 patients, respectively. Failure of the treatment in arm-A was 29% and in arm-B was 9.5%. In arm-A, selective CBD cannulation was achieved in 33 cases (80.5%) and in arm-B in 39 cases (93%). In arm-Agroup, post-ERCP hyperamylasia was presented in nine patients (22%) and severe pancreatitis in five patients (12%) versus none of the patients (0%) in arm-B group, respectively. Mean post-operative hospital stay in arm-A and arm-B groups are 10.9 and 6.8 days, respectively. CONCLUSION: One stage laparo-endoscopic rendezvous approach increases selective cannulation of CBD, reduces post-ERCP pancreatitis, reduces days of hospital stay, increases patient's compliance and prevents unnecessary intervention to CBD.

Sahoo, Manash Ranjan; Kumar, Anil T; Patnaik, Aashish

2014-01-01

278

Modification of Platelet Margination Rate via Reduction of Viscosity Ratio  

NASA Astrophysics Data System (ADS)

Experimental investigations of platelet margination have primarily been limited to effects of hematocrit (Ht.) and shear rate. The suspending fluids used commonly have viscosities greater than plasma which can modify the transition in dynamical regimes from tumbling to tank-treading for isolated RBCs. This work focuses on the effects of ?, the ratio of internal to suspending fluid viscosity of RBCs, on the rate of platelet margination in a rigid 41.3 ?m diameter vessel. Simulations are performed with a lattice-Boltzmann fluid solver using the standard bounce-back boundary condition coupled with a coarse-grained spectrin-link RBC membrane model and a Newtonian dynamics solver for rigid platelets. Our results are consistent with observations that an increase in Ht. increases the rate of platelet margination for Ht.=20-40%, but we focus on the modification of ? at Ht.=20%. Our results show that rigid RBCs inhibit margination, but modifying ? with deformable RBCs show significant increases in margination rate. Our observations demonstrate an increase in platelet wall-normal velocity fluctuations, enhanced margination rate, and an increase in the wall-normal diffusivity as ? is reduced from the physiological value of five.

Reasor, Daniel; Mehrabadi, Marmar; Ku, David; Aidun, Cyrus

2011-11-01

279

Rendezvous scheduling in Bluetooth scatternets  

Microsoft Academic Search

Bluetooth scatternets are formed by interconnecting Bluetooth piconets in an ad-hoc fashion and consists typically of the handheld electronic devices from one or more user(s). Thus, scatternets may be used to form and interconnect ad-hoc Bluetooth personal area networks (PANs). The inter-piconet Bluetooth units, i.e. the gateways interconnecting the piconets in a scatternet, need to time division multiplex their presence

P. Johansson; R. Kapoor; A. Kazantzidis; M. Gerla

2002-01-01

280

Unsteady aerodynamics of fluttering and tumbling plates  

Microsoft Academic Search

We investigate the aerodynamics of freely falling plates in a quasi-two-dimensional flow at Reynolds number of 10(3) , which is typical for a leaf or business card falling in air. We quantify the trajectories experimentally using high-speed digital video at sufficient resolution to determine the instantaneous plate accelerations and thus to deduce the instantaneous fluid forces. We compare the measurements

A. Andersen; U. Pesavento; Z. Jane Wang

2005-01-01

281

Unsteady aerodynamics of fluttering and tumbling plates  

Microsoft Academic Search

We investigate the aerodynamics of freely falling plates in a quasi-two-dimensional flow at Reynolds number of 103, which is typical for a leaf or business card falling in air. We quantify the trajectories experimentally using high-speed digital video at sufficient resolution to determine the instantaneous plate accelerations and thus to deduce the instantaneous fluid forces. We compare the measurements with

U. P ESAVENTO; Z. J ANE W ANG

2005-01-01

282

Wet Autogenous Grinding in Tumbling Mills.  

National Technical Information Service (NTIS)

After a general introduction the article discusses at length the various grinding mechanisms operative in autogenous grinding. The viewpoints developed are then used for a review of the operational aspects, especially concerning process limitations, regul...

M. Digre

1969-01-01

283

Tumbling: From Rally Cars to Toast  

ERIC Educational Resources Information Center

The article by Rod Cross describing the translational and rotational motion of the "Launch of a Vehicle from a Ramp" motivated us to create two computer models showing this type of dynamical behavior.

Belloni, Mario; Christian, Wolfgang

2012-01-01

284

A Proposed Strategy for the U.S. to Develop and Maintain a Mainstream Capability Suite ("Warehouse") for Automated/Autonomous Rendezvous and Docking in Low Earth Orbit and Beyond  

NASA Technical Reports Server (NTRS)

The ability of space assets to rendezvous and dock/capture/berth is a fundamental enabler for numerous classes of NASA fs missions, and is therefore an essential capability for the future of NASA. Mission classes include: ISS crew rotation, crewed exploration beyond low-Earth-orbit (LEO), on-orbit assembly, ISS cargo supply, crewed satellite servicing, robotic satellite servicing / debris mitigation, robotic sample return, and robotic small body (e.g. near-Earth object, NEO) proximity operations. For a variety of reasons to be described, NASA programs requiring Automated/Autonomous Rendezvous and Docking/Capture/Berthing (AR&D) capabilities are currently spending an order-of-magnitude more than necessary and taking twice as long as necessary to achieve their AR&D capability, "reinventing the wheel" for each program, and have fallen behind all of our foreign counterparts in AR&D technology (especially autonomy) in the process. To ensure future missions' reliability and crew safety (when applicable), to achieve the noted cost and schedule savings by eliminate costs of continually "reinventing the wheel ", the NASA AR&D Community of Practice (CoP) recommends NASA develop an AR&D Warehouse, detailed herein, which does not exist today. The term "warehouse" is used herein to refer to a toolbox or capability suite that has pre-integrated selectable supply-chain hardware and reusable software components that are considered ready-to-fly, low-risk, reliable, versatile, scalable, cost-effective, architecture and destination independent, that can be confidently utilized operationally on human spaceflight and robotic vehicles over a variety of mission classes and design reference missions, especially beyond LEO. The CoP also believes that it is imperative that NASA coordinate and integrate all current and proposed technology development activities into a cohesive cross-Agency strategy to produce and utilize this AR&D warehouse. An initial estimate indicates that if NASA strategically coordinates the development of a robust AR&D capability across the Agency, the cost of implementing AR&D on a spacecraft could be reduced from roughly $70M per mission to as low as $7M per mission, and the associated development time could be reduced from 4 years to 2 years, after the warehouse is completely developed. Table 1 shows the clear long-term benefits to the Agency in term of costs and schedules for various missions. (The methods used to arrive at the Table 1 numbers is presented in Appendices A and B.)

Krishnakumar, Kalmanje S.; Stillwater, Ryan A.; Babula, Maria; Moreau, Michael C.; Riedel, J. Ed; Mrozinski, Richard B.; Bradley, Arthur; Bryan, Thomas C.

2012-01-01

285

The First Joint Report of the General Thomas P. Stafford Task Force and the Academician Vladimir F. Utkin Advisory Expert Council on the Shuttle-Mir Rendezvous and Docking Missions  

NASA Technical Reports Server (NTRS)

In October 1992, the National Aeronautics and Space Administration (NASA) and the Russian Space Agency (RSA) formally agreed to conduct a fundamentally new program of human cooperation in space. The 'Shuttle-Mir Program' encompassed combined astronaut-cosmonaut activities on the Shuttle, Soyuz Test Module(TM), and Mir station spacecraft. At that time, NASA and RSA limited the project to: the STS-60 mission carrying the first Russian cosmonaut to fly on the U.S. Space Shuttle; the launch of the first U.S. astronaut on the Soyuz vehicle for a multi-month mission as a member of a Mir crew; and the change-out of the U.S.-Russian Mir crews with a Russian crew during a Shuttle rendezvous and docking mission with the Mir Station. The objectives of the Phase 1 Program are to provide the basis for the resolution of engineering and technical problems related to the implementation of the ISS and future U.S.-Russian cooperation in space. This, combined with test data generated during the course of the Shuttle flights to the Mir station and extended joint activities between U.S. astronauts and Russian cosmonauts aboard Mir, is expected to reduce the technical risks associated with the construction and operation of the ISS. Phase 1 will further enhance the ISS by combining space operations and joint space technology demonstrations. Phase 1 also provides early opportunities for extended U.S. scientific and research activities, prior to utilization of the ISS.

1996-01-01

286

Bedrock Incision Rates Through A Knickpoint Reach  

NASA Astrophysics Data System (ADS)

Bedrock river incision is a fundamental process in landscape evolution, controlling, for example, the rate at which base-level fall is propagated through the drainage net and hence the rate of sediment flux from source areas to sedimentary basin ­rsinks'. Particular attention has been focused on the processes and erosion rates upstream and downstream of knickpoints. These key bedrock river landforms propagate headwards to transmit the ­rmessage­_ to the drainage net that base-level has fallen. Knickpoints may be sharply defined as waterfalls or cascades, which separate reaches controlled by different environmental settings. They may originate as a result of base-level changes, tectonic uplift, lithologic and structural controls, tributary sediment inputs or environmental changes. Information on changes in bed incision rates through a knickpoint reach provides insight into the role of knickpoints in landscape evolution. The River Etive, Scotland, has alternating alluvial and bedrock reaches and a stepped long profile caused by series of knickpoints. To investigate the controls over bedrock incision in this river, numerical simulations were performed using a process-based incision model. Physical modelling of the impact of bedload on abrasion has been used to verify the numerical simulations and cosmogenic nuclides have been used to estimate incision rates as a final test. To characterise and assess changes in incision rates through the knickpoint reach, five bedrock samples were collected for cosmogenic isotope analysis from above and below a knickpoint in the bed of the River Etive. The samples were taken from as close to the low flow water surface as practically possible and are overtopped even at moderate flows; it is therefore highly unlikely that they have ever been shielded by either peat or alluvial sediment. The sample sites have clearly been fluvially sculpted and are smooth and rounded; they are therefore highly appropriate for the analysis. Quartz was extracted from the samples and fully prepared, following standard procedures. In addition, the overall incision rates in the reach have been estimated using a bedrock incision model. The numerical model, in which incision is dominated by abrasion by saltating sediment particles, shows how interactions between sediment dynamics and hydraulic conditions determine the incision rates. Sensitivity analyses incorporating a wide range of model parameterisations confirmed that erosion rates in bedrock rivers are controlled by stream power, but changes in sediment discharge and size also play important roles in incision. The numerical simulation results are further tested through tumbling mill experiments. Topographic and sedimentological data from the River Etive are used to estimate the erosion rates in the knickpoint reach using the numerical model. The numerical simulations show that the spatial patterns of incision are changed as model parameters are changed. A conventional, diffusion style, model produced declining slopes at knickpoints, while the new model, which incorporates sediment dynamics, produced more complicated pattern of incision. The physical processes operating in knickpoint reaches determined the mode and rate of incision, and these physical processes change with location within the reach. For abrasion, changes in effective sediment flux as transport stage changes plays the critical role in determining incision rates. These conclusions will be evaluated using the cosmogenically derived incision rates.

Kim, J.; Hoey, T.; Bishop, P.; Fifield, K.; Levchenko, V.

2003-12-01

287

Growth Rate  

NSDL National Science Digital Library

This lesson from Illuminations uses growth charts for girls and boys to examine rates of change. The material uses slope to approximate the rate of change in height. Students will learn how to translate this data into a graph. The lesson is appropriate for grades 9-12 and should require 1 class period to complete.

2011-01-14

288

Full relaxation matrix analysis of apparent cross-correlated relaxation rates in four-spin systems  

NASA Astrophysics Data System (ADS)

Cross-correlated relaxation (CCR) rates are an established tool for the extraction of relative bond orientations in biomolecules in solution. CCR between dipolar interactions in four-spin systems is a particularly well-suited mechanism. In this paper, a simple approach to analyze systematic experimental errors is formulated in a subspace of the complete four-spin Hilbert space. It is shown that, contrary to the common assumption, the secular approximation of the relaxation matrix is marginal for the most prominent spin systems. With the main focus on the model protein GB3 at room temperature, it is shown that the apparent experimental CCR rates have errors between -12% and +4% for molecules with a molecular tumbling time of 3.5 ns. Although depending on the specific pulse sequence used, the following rule-of-thumb can be established: Judged by absolute values, the errors for H?-C?/H?-C?, HN-N/C?-C', HN-N/C?-C? and HN-N/H?-C? CCR rates can safely be neglected. However, errors for HN-N/HN-N and HN-N/H?-C? CCR rates are on the order of 0.1-0.3 s-1 and must be considered. Tabulated correction factors may be used for their extraction. If larger systems are studied, in most cases the errors cannot be neglected anymore. On the other hand, well-calibrated pulses can safely be assumed to be perfect.

Vögeli, Beat

2013-01-01

289

Method and associated apparatus for capturing, servicing, and de-orbiting earth satellites using robotics  

NASA Technical Reports Server (NTRS)

This invention is a method and supporting apparatus for autonomously capturing, servicing and de-orbiting a free-flying spacecraft, such as a satellite, using robotics. The capture of the spacecraft includes the steps of optically seeking and ranging the satellite using LIDAR, and matching tumble rates, rendezvousing and berthing with the satellite. Servicing of the spacecraft may be done using supervised autonomy, which is allowing a robot to execute a sequence of instructions without intervention from a remote human-occupied location. These instructions may be packaged at the remote station in a script and uplinked to the robot for execution upon remote command giving authority to proceed. Alternately, the instructions may be generated by Artificial Intelligence (AI) logic onboard the robot. In either case, the remote operator maintains the ability to abort an instruction or script at any time as well as the ability to intervene using manual override to teleoperate the robot.

Cepollina, Frank J. (Inventor); Burns, Richard D. (Inventor); Holz, Jill M. (Inventor); Corbo, James E. (Inventor); Jedhrich, Nicholas M. (Inventor)

2009-01-01

290

The Near-Earth Asteroid Rendezvous (NEAR) Mission, the Mars Surveyor 2001 (MS01) Mission, and the Planetary Instrument Definition and Development Program (PIDDP)  

NASA Technical Reports Server (NTRS)

The NEAR Mission was launched on February 17, 1996 for a three year cruise to the asteroid 433 Eros. During October, November, and December 1998 cruise measurements with the gamma-ray spectrometer were made at three different escape-window-width settings. These were done in order to understand how the count rate and peak width change as the window width settings change. Analysis of these spectra was completed using the latest version of the spectral analysis program, RobWin. Results as a function of energy were combined with the results from the Schlumberger-Doll Research experiments (described below). Laboratory measurements were needed to confirm efficiency calculations above 6 MeV and to understand the relationship between the full energy peak areas and the areas of the first and second escape peaks as a function of the escape peak widths. A week of measurements was made at Schlumberger-Doll Research using their 14-MeV pulsed neutron generator and large soil samples. Data were collected after adding iron and nickel to the sample to increase the emission of high-energy lines. Approximately 24 hours of data were accumulated at each of three escape peak window widths. These data were analyzed with RobWin. Combining results from the cruise measurements and the laboratory measurements indicated that both data sets had similar energy dependence and that this energy dependence was different from that obtained using standard Monte Carlo calculations. Alternate methods of simulating the response of the detector to changes in the escape window widths are being investigated.

1999-01-01

291

STORRM To Test Future Rendezvous and Docking  

NASA Video Gallery

A state-of-the-art relative navigation system will be demonstrated on the STS-134 mission to the International Space Station called the Sensor Test for Orion Relative Navigation Risk Mitigation or ...

292

Telerobotic rendezvous and docking vision system architecture  

NASA Technical Reports Server (NTRS)

This research program has successfully demonstrated a new target label architecture that allows a microcomputer to determine the position, orientation, and identity of an object. It contains a CAD-like database with specific geometric information about the object for approach, grasping, and docking maneuvers. Successful demonstrations were performed selecting and docking an ORU box with either of two ORU receptacles. Small, but significant differences were seen in the two camera types used in the program, and camera sensitive program elements have been identified. The software has been formatted into a new co-autonomy system which provides various levels of operator interaction and promises to allow effective application of telerobotic systems while code improvements are continuing.

Gravely, Ben; Myers, Donald; Moody, David

1992-01-01

293

Long range targeting for space based rendezvous  

NASA Technical Reports Server (NTRS)

The work performed under this grant supported the Dexterous Flight Experiment one STS-62 The project required developing hardware and software for automating a TRAC sensor on orbit. The hardware developed by for the flight has been documented through standard NASA channels since it has to pass safety, environmental, and other issues. The software has not been documented previously, therefore, this report provides a software manual for the TRAC code developed for the grant.

Everett, Louis J.; Redfield, R. C.

1995-01-01

294

75 FR 44794 - Rendezvous International v.  

Federal Register 2010, 2011, 2012, 2013

...released only upon presentation by Respondents of Original endorsed Negotiable Bills of Lading. The payment terms were on a CAD (Cash Against Documents) basis.'' Complainant alleges that the terms of the Bill of Lading were ``violated by...

2010-07-29

295

Operator learning effects in teleoperated rendezvous & docking  

NASA Astrophysics Data System (ADS)

Teleoperation of spacecraft proximity operations and docking requires delicate timing and coordination of spacecraft maneuvers. Experience has shown that human operators show large performance fluctuations in these areas, which are a major factor to be addressed in operator training. In order to allow the quantification of the impact of these human fluctuations on control system performance and the human perception of this performance, a learning curve study was conducted with teleoperated final approach and docking scenarios. Over a period of ten experiment days, three test participants were tasked with repeatedly completing a set of three training scenarios. The scenarios were designed to contain different combinations of the major elements of any final approach and docking situation, and to feature an increasing difficulty level. The individual difficulty levels for the three operators furthermore differed in the level of operator support functions available in their human-machine interfaces. Operator performance in the test scenarios were evaluated in the fields approach success and precision, docking safety, and approach efficiency by a combination of recorded maneuver data and questionnaires. The results show that operator experience and the associated learning curves increase operator performance substantially, regardless of the support system used. The paper also shows that the fluctuations in operator performance and self-perception are substantial between as well as within experiment days, and must be reckoned with in teleoperation system design and mission planning.

Wilde, M.; Harder, J.; Purschke, R.

296

Discovery: Near-Earth Asteroid Rendezvous (NEAR)  

NASA Technical Reports Server (NTRS)

The work carried out under this grant consisted of two parallel studies aimed at defining candidate missions for the initiation of the Discovery Program being considered by NASA's Solar System Exploration Division. The main study considered a Discover-class mission to a Near Earth Asteroid (NEA); the companion study considered a small telescope in Earth-orbit dedicated to ultra violet studies of solar system bodies. The results of these studies are summarized in two reports which are attached (Appendix 1 and Appendix 2).

Veverka, Joseph

1992-01-01

297

NOTES: cadaveric rendezvous hybrid small bowel resection  

Microsoft Academic Search

Background  Natural orifice translumenal endoscopic surgery (NOTES) is an emerging field in minimally invasive surgery that is driving\\u000a the development of new technology and techniques [1–4]. Before NOTES gains widespread popularity, it must be proven to be\\u000a a safe and efficacious technique [5]. There are several proposed benefits to the NOTES approach, including potentially decreased\\u000a abdominal pain, wound infections, and hernia

Edward D. Auyang; Khashayar Vaziri; Eric Volckmann; John A. Martin; Nathaniel J. Soper; Eric S. Hungness

2008-01-01

298

Mars Researchers Rendezvous on Remote Arctic Island  

NASA Technical Reports Server (NTRS)

Devon Island is situated in an isolated part of Canada's Nunavut Territory, and is usually considered to be the largest uninhabited island in the world. However, each summer since 1999, researchers from NASA's Haughton-Mars Project and the Mars Society reside at this 'polar desert' location to study the geologic and environmental characteristics of a site which is considered to be an excellent 'Mars analog': a terrestrial location wherein specific conditions approximate environmental features reported on Mars. Base camps established amidst the rocks and rubble surrounding the Haughton impact crater enable researchers to conduct surveys designed to test the habitat, equipment and technology that may be deployed during a human mission to Mars. One of the many objectives of the project scientists is to understand the ice formations around the Haughton area, in the hopes that this might ultimately assist with the recognition of areas where ice can be found at shallow depth on Mars.

These images of Devon Island from NASA's Multi-angle Imaging SpectroRadiometer (MISR) instrument provide contrasting views of the spectral and angular reflectance 'signatures' of different surfaces within the region. The top panel is a natural color view created with data from the red, green and blue-bands of MISR's nadir (vertical-viewing) camera. The bottom panel is a false-color multiangular composite of the same area, utilizing red band data from MISR's 60-degree backward, nadir, and 60-degree forward-viewing cameras, displayed as red, green and blue, respectively. In this representation, colors highlight textural properties of elements within the scene, with blue tones indicating smooth surfaces (which preferentially forward scatter sunlight) and red hues indicating rougher surfaces (which preferentially backscatter). The angular reflectance 'signature' of low clouds causes them to appear purple, and this visualization provides a unique way of distinguishing clouds from snow and ice.

The data were captured on June 28, 2001, during the early part of the arctic summer, when sea ice becomes thinner and begins to move depending upon localized currents and winds. In winter the entire region is locked with several meters of nearly motionless sea ice, which acts as a thermodynamic barrier to the loss of heat from the comparatively warm ocean to the colder atmosphere. Summer melting of sea ice can be observed at the two large, dark regions of open water; one is present in the Jones Sound (near the top to the left of center), and another appears in the Wellington Channel (left-hand edge). A large crack caused by tidal heaving has broken the ice cover over the Parry Channel (lower right-hand corner). A substantial ice cap permanently occupies the easternmost third of the island (upper right). Surface features such as dendritic meltwater channels incised into the island's surface are apparent. The Haughton-Mars project site is located slightly to the left and above image center, in an area which appears with relatively little surface ice, near the island's inner 'elbow.'

The images were acquired during Terra orbit 8132 and cover an area of about 334 kilometers x 229 kilometers. They utilize data from blocks 27 to 31 within World Reference System-2 path 42.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

2002-01-01

299

Automated Rendezvous and Docking: 1994-2004  

NASA Technical Reports Server (NTRS)

This custom bibliography from the NASA Scientific and Technical Information Program lists a sampling of records found in the NASA Aeronautics and Space Database. The scope of this topic includes technologies for human exploration and robotic sample return missions. This area of focus is one of the enabling technologies as defined by NASA s Report of the President s Commission on Implementation of United States Space Exploration Policy, published in June 2004.

2004-01-01

300

14 CFR 1214.111 - Rendezvous services.  

Code of Federal Regulations, 2010 CFR

...the Space Shuttle orbiter with an orbiting spacecraft for one or more of the following purposes...Retrieval and return to Earth of the orbiting spacecraft (or part thereof), including a spacecraft deployed earlier on the same Space...

2009-01-01

301

14 CFR 1214.111 - Rendezvous services.  

Code of Federal Regulations, 2010 CFR

...the Space Shuttle orbiter with an orbiting spacecraft for one or more of the following purposes...Retrieval and return to Earth of the orbiting spacecraft (or part thereof), including a spacecraft deployed earlier on the same Space...

2010-01-01

302

Near Earth Asteroid Rendezvous - A Pictorial Voyage  

NSDL National Science Digital Library

This site offers students an opportunity to participate in a pictorial voyage that follows the NEAR spacecraft from its inception through the cruise phase to asteroid 433 Eros. They will learn about the rationale for visiting an asteroid, the instruments and construction of the spacecraft, and follow its flyby of the asteroid Mathilde, swingby of Earth, and encounter with Eros.

303

The gas production rate of periodic comet d'Arrest  

NASA Technical Reports Server (NTRS)

Comet P/d'Arrest is a potential target for a rendezvous mission to a short period comet. Its light curve is rather peculiar, the comet being active only after perihelion passage. One apparition out of two is easy to observe from the ground. The 1995 apparition of the comet will offer a unique opportunity to characterize the outgassing properties of its nucleus.

Festou, Michel C.; Feldman, Paul D.; Ahearn, Michael F.

1992-01-01

304

Correlating field and laboratory rates of particle abrasion, Rio Medio, Sangre de Cristo Mountains, New Mexico  

NASA Astrophysics Data System (ADS)

River bed sediments commonly fine downstream due to a combination of particle abrasion, selective transport of finer grains, and fining of the local sediment supply from hillslopes and tributaries. Particle abrasion rates can be directly measured in the laboratory using tumbling barrels and annular flumes, however, scaling experimental particle abrasion rates to the field has proven difficult due to the confounding effects of selective transport and local supply variations. Here we attempt to correlate laboratory and field rates of particle abrasion in a field setting where these confounding effects can be controlled. The Rio Medio, which flows westward from the crest of the Sangre de Cristo Mountains in north central New Mexico, is one of several streams studied by John P. Miller in the early 1960's. Several kilometers downstream of its headwaters, the river crosses the Picuris-Pecos fault. Upstream of the fault the river receives quartzite, sandstone and shale clasts from the Ortega Formation, while downstream sediments are supplied by the Embudo Granite. Because the upstream lithologies are not resupplied downstream of the fault, any observed fining of these clasts should be due only to abrasion and selective transport. We hypothesize that we can account for the effects of selective transport by comparing relative fining rates for the different upstream lithologies from both the field and a laboratory tumbler. By correlating laboratory abrasion rates with rock strength, we can predict the relative fining rates due solely to abrasion expected in the field; differences between the predicted and observed fining rates could then be attributed to selective transport. We used point counts to measure bed surface sediment grain size distributions at 15 locations along a 25 kilometer reach of the Rio Medio, beginning just downstream of the fault and ending upstream of a developed area with disturbed channel conditions. We recorded intermediate particle diameter as well as lithologic composition for 100 clasts at each location. To better characterize the size distribution of poorly represented lithologies we also measured every grain we could find of these minority lithologies within a one square meter area on adjacent bar top surfaces. At each sampling site we also measured channel gradient, and bank-full width and depth. We collected gravel samples for laboratory tumbling experiments and larger bedrock blocks from which we extracted cores for the Brazilian tensile splitting strength test. Preliminary results show very rapid fining of the weak sedimentary rocks downstream of the fault, much less rapid fining of the quartzite and a net downstream coarsening of the granitic sediments, which dominate the bed in the downstream end of the study reach. This enigmatic downstream coarsening may be a legacy of Pliestocene glaciation, which is evident in the landscape upstream of the fault. Outburst floods or debris flows from upstream moraines may have delivered large quantities of coarse sediments to downstream reaches, which are now relatively immobile. Despite these complications, the Rio Medio site may yet provide sufficient information to test our proposed method for scaling laboratory particle abrasion rates to the field.

Polito, P. J.; Sklar, L. S.

2006-12-01

305

Take a Tumble: Weathering and Erosion Using a Rock Tumbler  

ERIC Educational Resources Information Center

Weathering--the physical and chemical breakdown of geologic materials--and erosion--the transport of materials by wind, water, or ice--can be subtle, yet powerful forces. For example, shale, a rock made of mud-sized particles, is by far the most common sedimentary rock, a testament to the ability of weathering and erosion to take a rock and reduce…

Coffey, Patrick; Mattox, Steve

2006-01-01

306

The NOAA -14 September 28, 2006(DOY271) Tumble Anomaly  

Microsoft Academic Search

This paper describes a NOAA-14 spacecraft loss of control event and the lessons learned from it. The lessons learned are in two categories; contingency recovery operations and on-orbit propulsion system isolation methods. The work is motivated in recognition of the effort of the NOAA off-line engineering support team and their NOAA civil servant mission leads and operations support staff.

M. C. Phenneger; J. Woodward; R. Cox; C. Gliniak

2008-01-01

307

NOAA -14 September 28, 2006 (DOY 271) tumble anomaly  

Microsoft Academic Search

This describes a NOAA-14 spacecraft loss of control event and the lessons learned. The lessons learned are in two categories: contingency recovery operations; and on-orbit propulsion system isolation methods. The work is motivated in recognition of the effort of the NOAA off-line engineering support team and their NOAA civil servant mission leads and operations support staff.

M. Phenneger; J. Woodward; R. Cox; C. Gliniak

2008-01-01

308

A Miniature, High-Resolution Laser Radar Operating at Video Rates  

SciTech Connect

The authors are developing a laser radar to meet the needs of NASA for a 5-lb, 150 in{sup 3} image sensor with a pixel range accuracy of 0.1-inch. NASA applications include structural dynamics measurements, navigation guidance in rendezvous and proximity operations, and space vehicle inspection. The sensor is based on the scannerless range imager architecture developed at Sandia. This architecture modulates laser floodlight illumination and a focal plane receiver to phase encode the laser time of flight (TOF) for each pixel. They believe this approach has significant advantages over architectures directly measuring TOF including high data rate, reduced detector bandwidth, and conventional FPA detection. A limitation of the phase detection technique is its periodic nature, which provides relative range information over a finite ambiguity interval. To extend the operating interval while maintaining a given range resolution, a LADAR sensor using dual modulation frequencies has been developed. This sensor also extends the relative range information to absolute range by calibrating a gating function on the receiver to the TOF. The modulation frequency values can be scaled to meet the resolution and range interval requirements of different applications. Results from the miniature NASA sensor illustrate the advantages of the dual-frequency operation and the ability to provide the range images of 640 by 480 pixels at 30 frames per second.

SMITHPETER,COLIN L.; NELLUMS,ROBERT O.; LEBIEN,STEVEN M.; STUDOR,GEORGE

2000-06-26

309

On the relationship between visual magnitudes and gas and dust production rates in target comets to space missions  

NASA Astrophysics Data System (ADS)

In this paper, we report the results of a cometary research, developed during the last 10 years by us, involving a criterious analysis of gas and dust production rates in comets directly associated to recent space missions. For the determination of the water release rates we use the framework of the semi-empirical model of observed visual magnitudes [Newburn Jr., R.L. A semi-empirical photometric theory of cometary gas and dust production. Application to P/Halley's production rates, ESA-SP 174, 3, 1981; de Almeida, A.A., Singh, P.D., Huebner, W.F. Water release rates, active areas, and minimum nuclear radius derived from visual magnitudes of comets - an application to Comet 46P/Wirtanen, Planet. Space Sci. 45, 681-692, 1997; Sanzovo, G.C., de Almeida, A.A., Misra, A. et al. Mass-loss rates, dust particle sizes, nuclear active areas and minimum nuclear radii of target comets for missions STARDUST and CONTOUR, MNRAS 326, 852-868, 2001.], which once obtained, were directly converted into gas production rates. In turn, the dust release rates were obtained using the photometric model for dust particles [Newburn Jr., R.L., Spinrad, H. Spectrophotometry of seventeen comets. II - the continuum, AJ 90, 2591-2608, 1985; de Freitas Pacheco, J.A., Landaberry, S.J.C., Singh, P.D. Spectrophotometric observations of the Comet Halley during the 1985-86 apparition, MNRAS 235, 457-464, 1988; Sanzovo, G.C., Singh, P.D., Huebner, W.F. Dust colors, dust release rates, and dust-to-gas ratios in the comae of six comets, A&AS 120, 301-311, 1996.]. We applied these models to seven target comets, chosen for space missions of "fly-by"/impact and rendezvous/landing.

de Almeida, A. A.; Sanzovo, G. C.; Singh, P. D.; Misra, A.; Miguel Torres, R.; Boice, D. C.; Huebner, W. F.

310

Exchange rates and fundamentals  

Microsoft Academic Search

Standard economic models hold that exchange rates are influenced by fundamental variables such as relative money supplies, outputs, inflation rates and interest rates. Nonetheless, it has been well documented that such variables little help predict changes in floating exchange rates Š that is, exchange rates follow a random walk. We show that the data do exhibit a related link suggested

Charles Engel; Kenneth D. West

2003-01-01

311

Exchange rates and fundamentals  

Microsoft Academic Search

Standard economic models hold that exchange rates are influenced by fundamental variables such as relative money supplies, outputs, inflation rates and interest rates. Nonetheless, it has been well documented that such variables little help predict changes in floating exchange rates - that is, exchange rates follow a random walk. We show that the data do exhibit a related link suggested

Charles Engel; Kenneth D. West

2003-01-01

312

Raters & Rating Scales.  

ERIC Educational Resources Information Center

The first article in this section, "Rating Scales and Shared Meaning," by Winifred A. Lopez, discusses the analysis of rating scale data. The second article, "Rating Scale Categories: Dichotomy, Double Dichotomy, and the Number Two," by Mark H. Stone, argues that dichotomies in rating scales are more useful than multiple ratings. (SLD)

Lopez, Winifred A.; Stone, Mark H.

1998-01-01

313

Target Heart Rates  

MedlinePLUS

... learn how to calculate and monitor your target training heart rate, you have to know your resting heart rate. ... Now you’re ready to determine your target training heart rate. As you exercise, periodically: Take your pulse on ...

314

Regulating the Rating Agencies  

Microsoft Academic Search

The major rating agencies—Moody’s Investor Services, Standard and Poor’s, and Fitch—rate debt instruments and companies. A debt instrument’s rating principally reflects whether the instrument is likely to be repaid on a timely basis, and, increasingly, the amount that might be recovered should the instrument default. The rating agencies’ terminology, and in particular, the designation for the highest rating category, AAA,

Claire A. Hill

2004-01-01

315

Calculating Divorce Rates  

NSDL National Science Digital Library

This exercise from a course in family sociology asseses students' ability to interpret divorce rates from provided spreadsheet data and to critically analyze three articles that use divorce rates in their content.

Carroll, Joseph

316

Airline Quality Rating 2001.  

National Technical Information Service (NTIS)

The Airline Quality Rating (AQR) was developed and first announced in early 1991 as an objective method of comparing airline quality on combined multiple performance criteria. This current report, Airline Quality Rating 2001, reflects monthly Airline Qual...

B. D. Bowen D. E. Headley

2001-01-01

317

Diagnostic Ratings of Hypnotizability.  

National Technical Information Service (NTIS)

A clinically derived system for the diagnostic rating of hypnotizability is described. Five major categories of hypnotizability are differentiated. Diagnostic ratings are contrasted with standardized verbatim tests of hypnotic susceptibility. Potential us...

D. N. O'Connell M. T. Orne

1966-01-01

318

Handbook of noise ratings  

NASA Technical Reports Server (NTRS)

The handbook was compiled to provide information in a concise form, describing the multitude of noise rating schemes. It is hoped that by describing the noise rating methods in a single volume the user will have better access to the definitions, application and calculation procedures of the current noise rating methods.

Pearsons, K. S.; Bennett, R. L.

1974-01-01

319

River Flow Rate  

NSDL National Science Digital Library

Students build on their understanding and feel for flow rates, as gained from the associated Faucet Flow Rate activity, to estimate the flow rate of a local river. The objective is to be able to relate laboratory experiment results to the environment. They use the U.S. Geological Survey website (http://waterdata.usgs.gov/nwis/rt) to determine the actual flow rate data for their river, and compare their estimates to the actual flow rate. For this activity to be successful, choose a nearby river and take a field trip or show a video so students gain a visual feel for the flow of the nearby river.

Civil And Environmental Engineering Department

320

RateNet  

NSDL National Science Digital Library

RateNet was jointly developed by DataTrac, PR Newswire (discussed in the February 7, 1997 Scout Report) and IDC Financial Publishing. RateNet connects consumers to financial institutions on the Internet by providing a ranking service for the banking industry. Users may examine the current and historic interest rates of over 11,000 financial institutions from 175 markets across America. There are also 116 RateNet indices which monitor the deposit and lending rates for 776 of the largest institutions.

1998-01-01

321

Rate theories for biologists  

PubMed Central

Some of the rate theories that are most useful for modeling biological processes are reviewed. By delving into some of the details and subtleties in the development of the theories, the review will hopefully help the reader gain a more than superficial perspective. Examples are presented to illustrate how rate theories can be used to generate insight at the microscopic level into biomolecular behaviors. Attempt is made to clear up a number of misconceptions in the literature regarding popular rate theories, including the appearance of Planck’s constant in the transition-state theory and the Smoluchowski result as an upper limit for protein-protein and protein-DNA association rate constants. Future work in combining the implementation of rate theories through computer simulations with experimental probes of rate processes, and in modeling effects of intracellular environments so theories can be used for generating rate constants for systems biology studies is particularly exciting.

Zhou, Huan-Xiang

2012-01-01

322

Beyond rate of living.  

PubMed

The validity of the rate of living theory of aging in mammals has been seriously questioned over the last two decades because it does not account for the life span of many mammalian species. However, though this concept is an oversimplification and inapplicable in general, this does not mean that aging is unrelated to cellular metabolic processes. In general agreement with previous discussions, it can be stated that the rate of aging is proportional to the difference between the rate of cellular entropy production (which is by necessity roughly proportional to the rate of cellular biochemical processes and thus specific metabolic rate) and the cellular "counterentropic' mechanisms (such as cellular repair, antioxidant protection, etc.). These counterentropic mechanisms may have evolved to a different degree in some mammals. This could be effected indirectly by natural selection of certain traits, particularly those expressed in differences in the rates of embryonic and postnatal development. These rates, relatively to basal metabolic rate, determine a species' rate of becoming, which is proposed to be a predictor of mammalian life span. Data from 22 species, from shrew to elephant, with representatives from the main mammalian orders (including many exceptions to the rate of living concept), agree with this hypothesis. A mechanism underlying such natural selection, proposed elsewhere, is based on differential selection pressures among orders for which the different life-styles (particularly with respect to the birth of young) are responsible. PMID:7274681

Economos, A C

1981-01-01

323

Observed Barium Emission Rates  

NASA Technical Reports Server (NTRS)

The barium releases from the CRRES satellite have provided an opportunity for verifying theoretically calculated barium ion and neutral emission rates. Spectra of the five Caribbean releases in the summer of 1991 were taken with a spectrograph on board a U.S. Air Force jet aircraft. Because the line of sight release densities are not known, only relative rates could be obtained. The observed relative rates agree well with the theoretically calculated rates and, together with other observations, confirm the earlier detailed theoretical emission rates. The calculated emission rates can thus with good accuracy be used with photometric observations. It has been postulated that charge exchange between neutral barium and oxygen ions represents a significant source for ionization. If so. it should be associated with emissions at 4957.15 A and 5013.00 A, but these emissions were not detected.

Stenbaek-Nielsen, H. C.; Wescott, E. M.; Hallinan, T. J.

1993-01-01

324

Rate of Solution Demonstration  

NSDL National Science Digital Library

In this chemistry demonstration, learners investigate the factors that increase the rate of dissolution for a solid. Learners will compare how crushing sugar cubes, stirring and water temperature affect the rate at which the sugar dissolved. This resource guide includes extensions and notes about factors that accelerate dissolution and Henry's Law.

House, The S.

2014-01-28

325

Mortality Rate, Under-5  

NSDL National Science Digital Library

Under five mortality data for nearly all countries in the world from 2005-2008. A broader measure of child health than infant mortality, this is the probability of dying before ones fifth birthday given the current rates. Rates in countries vary widely from the world average of 67-per-1000 which is decreasing.

Bank, World

326

Vital Signs Rate Meter.  

National Technical Information Service (NTIS)

The design of the vital signs rate meter described in this report is an outgrowth from previous studies on noninvasive measurement methods and systems for vital signs detection. The purpose of the vital signs rate meter is to assist medical technicians in...

C. S. Lessard W. C. Wong E. T. Schorsch J. J. Im S. Mesibov

1987-01-01

327

Applications of Reaction Rate  

ERIC Educational Resources Information Center

This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…

Cunningham, Kevin

2007-01-01

328

Distance Rate Time  

NSDL National Science Digital Library

Measurement is one of the core NCTM Principals and Standards for School Mathematics content standards, and rate is central to its practical application. While most middle school students know the distance-rate-time formula, they may still benefit from a closer study of the relationship through these online resources.

National Science Digital Library (NSDL) Middle School Portal Staff

2008-03-10

329

Stability of rating transitions  

Microsoft Academic Search

The distribution of ratings changes plays a crucial role in many credit risk models. As is well-known, these distributions vary across time and different issuer types. Ignoring such dependencies may lead to inaccurate assessments of credit risk. In this paper, we quantify the dependence of rating transition probabilities on the industry and domicile of the obligor, and on the stage

Pamela Nickell; William Perraudin; Simone Varotto

2000-01-01

330

Rates and Time  

NSDL National Science Digital Library

This website showcases teaching activities, strategies and methods for teaching about dates, rates, and time that are used in the many disciplines encompassed by geoscience education. This site was created to support a session on Geologic Rates and Time at the Geological Society of America meeting in 2005.

331

Electric rate book  

SciTech Connect

Electric tariff information for 110 investor-owned utilities allows comparison between companies in different parts of the US. It includes rate schedule designation/description; effective date; availability; applicability; character of service; customer charge, demand and energy charges; charges by peaking hours; time-of-use rates; discounts and late payment charges; billing demand; demand modifications; communities served; and energy cost adjustments.

Not Available

1992-01-01

332

Target Heart Rate Calculator  

MedlinePLUS

... workout Enter your age to find a target heart rate during exercise. You'll get the most out of your activities by staying within this range of heartbeats/minute. What is your age? years. How to Check Your Heart Rate Right after you stop exercising, take your pulse: ...

333

Metabolic rate measurement system  

NASA Technical Reports Server (NTRS)

The Metabolic Rate Measurement System (MRMS) is an uncomplicated and accurate apparatus for measuring oxygen consumption and carbon dioxide production of a test subject. From this one can determine the subject's metabolic rate for a variety of conditions, such as resting or light exercise. MRMS utilizes an LSI/11-03 microcomputer to monitor and control the experimental apparatus.

Koester, K.; Crosier, W.

1980-01-01

334

Interest rates mapping  

NASA Astrophysics Data System (ADS)

The present study deals with the analysis and mapping of Swiss franc interest rates. Interest rates depend on time and maturity, defining term structure of the interest rate curves (IRC). In the present study IRC are considered in a two-dimensional feature space-time and maturity. Exploratory data analysis includes a variety of tools widely used in econophysics and geostatistics. Geostatistical models and machine learning algorithms (multilayer perceptron and Support Vector Machines) were applied to produce interest rate maps. IR maps can be used for the visualisation and pattern perception purposes, to develop and to explore economical hypotheses, to produce dynamic asset-liability simulations and for financial risk assessments. The feasibility of an application of interest rates mapping approach for the IRC forecasting is considered as well.

Kanevski, M.; Maignan, M.; Pozdnoukhov, A.; Timonin, V.

2008-06-01

335

Optimal firing rate estimation  

NASA Technical Reports Server (NTRS)

We define a measure for evaluating the quality of a predictive model of the behavior of a spiking neuron. This measure, information gain per spike (Is), indicates how much more information is provided by the model than if the prediction were made by specifying the neuron's average firing rate over the same time period. We apply a maximum Is criterion to optimize the performance of Gaussian smoothing filters for estimating neural firing rates. With data from bullfrog vestibular semicircular canal neurons and data from simulated integrate-and-fire neurons, the optimal bandwidth for firing rate estimation is typically similar to the average firing rate. Precise timing and average rate models are limiting cases that perform poorly. We estimate that bullfrog semicircular canal sensory neurons transmit in the order of 1 bit of stimulus-related information per spike.

Paulin, M. G.; Hoffman, L. F.

2001-01-01

336

Growth rates made easy.  

PubMed

In the 1960s-1980s, determination of bacterial growth rates was an important tool in microbial genetics, biochemistry, molecular biology, and microbial physiology. The exciting technical developments of the 1990s and the 2000s eclipsed that tool; as a result, many investigators today lack experience with growth rate measurements. Recently, investigators in a number of areas have started to use measurements of bacterial growth rates for a variety of purposes. Those measurements have been greatly facilitated by the availability of microwell plate readers that permit the simultaneous measurements on up to 384 different cultures. Only the exponential (logarithmic) portions of the resulting growth curves are useful for determining growth rates, and manual determination of that portion and calculation of growth rates can be tedious for high-throughput purposes. Here, we introduce the program GrowthRates that uses plate reader output files to automatically determine the exponential portion of the curve and to automatically calculate the growth rate, the maximum culture density, and the duration of the growth lag phase. GrowthRates is freely available for Macintosh, Windows, and Linux. We discuss the effects of culture volume, the classical bacterial growth curve, and the differences between determinations in rich media and minimal (mineral salts) media. This protocol covers calibration of the plate reader, growth of culture inocula for both rich and minimal media, and experimental setup. As a guide to reliability, we report typical day-to-day variation in growth rates and variation within experiments with respect to position of wells within the plates. PMID:24170494

Hall, Barry G; Acar, Hande; Nandipati, Anna; Barlow, Miriam

2014-01-01

337

Twinning rates in Tamilnadu.  

PubMed Central

A prospective study of human reproduction was conducted in Tamilnadu State, South India, from 1969 to 1975. This paper reports twinning rates and relates these to maternal age, parity, and consanguinity. Birth weights and other dimensions at birth and infant mortality are also studied. The overall twinning rate was 1 in 115 births. Dizygotic twinning rates increased significantly with maternal age and parity. The measurements at birth for like-sexed twin pairs were lower than that of unlike-sexed, but the mortalities did not differ significantly. Twins, in general, had a several fold increase in mortality as compared with singletons.

Rao, P S; Inbaraj, S G; Muthurathnam, S

1983-01-01

338

Rice Drying Rates.  

National Technical Information Service (NTIS)

Rice is ordinarily harvested at moisture contents above safe storage levels, so additional drying is usually necessary. The purpose of the research discussed in this report was to determine the factors which affect rice drying rates. The basic approach us...

J. F. Robayo H. B. Pfost

1973-01-01

339

Burning Rate Emulator  

NASA Video Gallery

The Burning Rate Emulator is a gas fuel investigation attempting to emulate the burning of solids to improve our understanding of materials''flammability over a wide range of conditions. The approa...

340

Combustion Stability Rating Techniques.  

National Technical Information Service (NTIS)

The objectives of a comprehensive investigation of three techniques for rating the combustion stability of liquid-propellant rocket engines were the establishment of the characteristics of the techniques and of their intercorrelations. The techniques stud...

L. P. Combs F. W. Hoehn S. R. Webb E. E. Lockwood D. T. Campbell

1966-01-01

341

Heart Rate Monitor  

NASA Technical Reports Server (NTRS)

In the mid 70's, NASA saw a need for a long term electrocardiographic electrode suitable for use on astronauts. Heart Rate Inc.'s insulated capacitive electrode is constructed of thin dielectric film applied to stainless steel surface, originally developed under a grant by Texas Technical University. HRI, Inc. was awarded NASA license and continued development of heart rate monitor for use on exercise machines for physical fitness and medical markets.

1984-01-01

342

Firing Rate Models  

Microsoft Academic Search

\\u000a One of the most common ways to model large networks of neurons is to use a simplification called a firing rate model. Rather\\u000a than track the spiking of every neuron, instead one tracks the averaged behavior of the spike rates of groups of neurons within\\u000a the circuit. These models are also called population models since they can represent whole populations

G. Bard Ermentrout; David H. Terman

343

Rating Scales for Depression  

Microsoft Academic Search

\\u000a Over the past few decades, a number of clinician-rated and patient-rated instruments have been developed as primary efficacy\\u000a measures in depression clinical trials. All those scales have relative strengths and weaknesses and some of them have been\\u000a more successful than others, and have become the gold standards for depression clinical research. With all these measures\\u000a available and with the evidence

Cristina Cusin; Huaiyu Yang; Albert Yeung; Maurizio Fava

344

Heart Rate Monitors  

NASA Technical Reports Server (NTRS)

Under a NASA grant, Dr. Robert M. Davis and Dr. William M. Portnoy came up with a new type of electrocardiographic electrode that would enable long term use on astronauts. Their invention was an insulated capacitive electrode constructed of a thin dielectric film. NASA subsequently licensed the electrode technology to Richard Charnitski, inventor of the VersaClimber, who founded Heart Rate, Inc., to further develop and manufacture personal heart monitors and to produce exercise machines using the technology for the physical fitness, medical and home markets. Same technology is on both the Home and Institutional Model VersaClimbers. On the Home Model an infrared heart beat transmitter is worn under exercise clothing. Transmitted heart rate is used to control the work intensity on the VersaClimber using the heart rate as the speedometer of the exercise. This offers advantages to a full range of users from the cardiac rehab patient to the high level physical conditioning of elite athletes. The company manufactures and markets five models of the 1*2*3 HEART RATE monitors that are used wherever people exercise to accurately monitor their heart rate. Company is developing a talking heart rate monitor that works with portable headset radios. A version of the heart beat transmitter will be available to the manufacturers of other aerobic exercise machines.

1990-01-01

345

Rate of return inequity  

SciTech Connect

Utility stock and bond prices will be increasingly sensitive to differences between allowed rates of return and market rates for comparable investments. Allowed rates of return on equity (ROE) are traditionally set at a level commensurate with the returns on alternative investments of comparable risk. This focus on financial market conditions is becoming increasingly important as deregulation and market innovations increase competition among alternate financial instruments. Accurate estimates of the market rate are essential if the utility is to compete for investment capital. The discounted cash flow (DCF) model provides one widely used approach for estimating the market-determined rate of return. Jurisdictions using the model prefer the annual version, which assumes that the utility pays only one annual dividend. This assumption, however, reduces the accuracy of the estimate for utilities that pay quarterly dividends. Indeed, using an annual model to approximate the DCF model for a firm that pays quarterly dividends consistently and significantly underestimates the market rate of return. Despite the importance of such understatement, only two states permit a quarterly version of the DCF model: Illinois and Nevada. This article highlights the effect of financial reform and deregulation on the process for determining the allowed ROE, explains the relevance of annual and quarterly dividends for the DCF model, and discusses in nontechnical terms two methods for adjusting the DCF model to account for quarterly dividend payments.

Cargill, T.F.; Wendel, J.

1994-04-15

346

Method and associated apparatus for capturing, servicing, and de-orbiting earth satellites using robotics  

NASA Technical Reports Server (NTRS)

This invention is a method and supporting apparatus for autonomously capturing, servicing and de-orbiting a free-flying spacecraft, such as a satellite, using robotics. The capture of the spacecraft includes the steps of optically seeking and ranging the satellite using LIDAR; and matching tumble rates, rendezvousing and berthing with the satellite. Servicing of the spacecraft may be done using supervised autonomy, which is allowing a robot to execute a sequence of instructions without intervention from a remote human-occupied location. These instructions may be packaged at the remote station in a script and uplinked to the robot for execution upon remote command giving authority to proceed. Alternately, the instructions may be generated by Artificial Intelligence (AI) logic onboard the robot. In either case, the remote operator maintains the ability to abort an instruction or script at any time, as well as the ability to intervene using manual override to teleoperate the robot.In one embodiment, a vehicle used for carrying out the method of this invention comprises an ejection module, which includes the robot, and a de-orbit module. Once servicing is completed by the robot, the ejection module separates from the de-orbit module, leaving the de-orbit module attached to the satellite for de-orbiting the same at a future time. Upon separation, the ejection module can either de-orbit itself or rendezvous with another satellite for servicing. The ability to de-orbit a spacecraft further allows the opportunity to direct the landing of the spent satellite in a safe location away from population centers, such as the ocean.

Cepollina, Frank J. (Inventor); Burns, Richard D. (Inventor); Holz, Jill M. (Inventor); Corbo, James E. (Inventor); Jedhrich, Nicholas M. (Inventor)

2009-01-01

347

Method and associated apparatus for capturing, servicing and de-orbiting earth satellites using robotics  

NASA Technical Reports Server (NTRS)

This invention is a method and supporting apparatus for autonomously capturing, servicing and de-orbiting a free-flying spacecraft, such as a satellite, using robotics. The capture of the spacecraft includes the steps of optically seeking and ranging the satellite using LIDAR; and matching tumble rates, rendezvousing and berthing with the satellite. Servicing of the spacecraft may be done using supervised autonomy, which is allowing a robot to execute a sequence of instructions without intervention from a remote human-occupied location. These instructions may be packaged at the remote station in a script and uplinked to the robot for execution upon remote command giving authority to proceed. Alternately, the instructions may be generated by Artificial Intelligence (AI) logic onboard the robot. In either case, the remote operator maintains the ability to abort an instruction or script at any time, as well as the ability to intervene using manual override to teleoperate the robot.In one embodiment, a vehicle used for carrying out the method of this invention comprises an ejection module, which includes the robot, and a de-orbit module. Once servicing is completed by the robot, the ejection module separates from the de-orbit module, leaving the de-orbit module attached to the satellite for de-orbiting the same at a future time. Upon separation, the ejection module can either de-orbit itself or rendezvous with another satellite for servicing. The ability to de-orbit a spacecraft further allows the opportunity to direct the landing of the spent satellite in a safe location away from population centers, such as the ocean.

Cepollina, Frank J. (Inventor); Burns, Richard D. (Inventor); Holz, Jill M. (Inventor); Corbo, James E. (Inventor); Jedhrich, Nicholas M. (Inventor)

2007-01-01

348

Method and associated apparatus for capturing, servicing, and de-orbiting earth satellites using robotics  

NASA Technical Reports Server (NTRS)

This invention is a method and supporting apparatus for autonomously capturing, servicing and de-orbiting a free-flying spacecraft, such as a satellite, using robotics. The capture of the spacecraft includes the steps of optically seeking and ranging the satellite using LIDAR; and matching tumble rates, rendezvousing and berthing with the satellite. Servicing of the spacecraft may be done using supervised autonomy, which is allowing a robot to execute a sequence of instructions without intervention from a remote human-occupied location. These instructions may be packaged at the remote station in a script and uplinked to the robot for execution upon remote command giving authority to proceed. Alternately, the instructions may be generated by Artificial Intelligence (AI) logic onboard the robot. In either case, the remote operator maintains the ability to abort an instruction or script at any time, as well as the ability to intervene using manual override to teleoperate the robot.In one embodiment, a vehicle used for carrying out the method of this invention comprises an ejection module, which includes the robot, and a de-orbit module. Once servicing is completed by the robot, the ejection module separates from the de-orbit module, leaving the de-orbit module attached to the satellite for de-orbiting the same at a future time. Upon separation, the ejection module can either de-orbit itself or rendezvous with another satellite for servicing. The ability to de-orbit a spacecraft further allows the opportunity to direct the landing of the spent satellite in a safe location away from population centers, such as the ocean.

Cepollina, Frank J. (Inventor); Burns, Richard D. (Inventor); Holz, Jill M. (Inventor); Corbo, James E. (Inventor); Jedhrich, Nicholas M. (Inventor)

2007-01-01

349

Method and associated apparatus for capturing, servicing and de-orbiting earth satellites using robotics  

NASA Technical Reports Server (NTRS)

This invention is a method and supporting apparatus for autonomously capturing, servicing and de-orbiting a free-flying spacecraft, such as a satellite, using robotics. The capture of the spacecraft includes the steps of optically seeking and ranging the satellite using LIDAR; and matching tumble rates, rendezvousing and berthing with the satellite. Servicing of the spacecraft may be done using supervised autonomy, which is allowing a robot to execute a sequence of instructions without intervention from a remote human-occupied location. These instructions may be packaged at the remote station in a script and uplinked to the robot for execution upon remote command giving authority to proceed. Alternately, the instructions may be generated by Artificial Intelligence (AI) logic onboard the robot. In either case, the remote operator maintains the ability to abort an instruction or script at any time, as well as the ability to intervene using manual override to teleoperate the robot.In one embodiment, a vehicle used for carrying out the method of this invention comprises an ejection module, which includes the robot, and a de-orbit module. Once servicing is completed by the robot, the ejection module separates from the de-orbit module, leaving the de-orbit module attached to the satellite for de-orbiting the same at a future time. Upon separation, the ejection module can either de-orbit itself or rendezvous with another satellite for servicing. The ability to de-orbit a spacecraft further allows the opportunity to direct the landing of the spent satellite in a safe location away from population centers, such as the ocean.

Cepollina, Frank J. (Inventor); Burns, Richard D. (Inventor); Holz, Jill M. (Inventor); Corbo, James E. (Inventor); Jedhrich, Nicholas M. (Inventor)

2008-01-01

350

Landsliding rates revisited  

NASA Astrophysics Data System (ADS)

Landslides are purportedly the dominant agents of erosion in humid and tectonically active mountain ranges. The rate of landsliding is also thought to compensate for effects of rock uplift on mountainous landscapes by maintaining threshold hillslopes and limiting growth of topographic relief. Still few data exist to corroborate this widely held notion. Here I review rates of landslide erosion from around the world, and show that they vary by at least six orders of magnitude, i.e. from 10-3 to 102 mm/yr. Part of this variability is systematically linked to the timescales of interpolation, such that mean rates are hardly meaningful let alone representative. The highest rates are invariably tied to tectonically active mountain belts that experience frequent earthquake shaking, high precipitation, and sustain dense forest vegetation. Landslide erosion rates derived for short-term periods (100-102 yr) rely on higher data density, but are prone to bias by regional triggering events such as earthquakes and rainstorms, anthropogenic changes to land cover, and the occurrence of large, infrequent landslides. In contrast, the considerably lower long-term landslide erosion rates (103-104 yr) suffer from incomplete records because of erosional censoring, and thus remain underestimates. Despite this shortcoming, there is strong evidence that the larger landslides are dominating volumetric sediment production in tectonically active mountain belts. At a global scale, soil erosion appears to be the only other process capable of matching the rates of landslide erosion. Yet, data on specific yields of mountain rivers and glacier-dominated drainage basins indicate that landslide-produced sediment may be routed more or less at capacity in many settings.

Korup, O.

2009-04-01

351

A finite-rate chemistry model for using in-situ gas composition measurements within a cometary diamagnetic cavity as a remote sensing tool for studying volatile materials on the nucleus surface  

NASA Astrophysics Data System (ADS)

If everything goes according to plan, Rosetta will rendez-vous with comet 67P/Churyumov-Gerasimenko in May 2014 and will, among other objectives, study the physicochemical evolution of the cometary coma from onset of activity at large solar distances through perihelion at 1.2 AU. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) allows the determination of both neutrals and positive ions in the coma. In situ gas density and composition measurements within the diamagnetic cavity at a certain distance from the nucleus can be used to obtain estimates of particle densities throughout the cavity, as well as give an estimate of the outgassing rates and volatile material composition at the nucleus surface. This is an inverse problem that has been implemented using a finite-rate chemistry model. It requires knowledge of the solar UV flux, the outgassing flow field, and the chemical reactions that transform the neutral gas as it expands outward (e.g. photo-ionization). In this way, in situ measurements in the coma can be used as a remote sensing tool for studying nucleus surface composition. This will be compared to the "ground truth" provided by the instruments on the Philae lander. This contribution will explain the finite-rate chemistry model used and illustrate the data inversion technique. Attention is paid to the opportunities and limitations of the proposed technique.

Dhooghe, Frederik; De Keyser, Johan; Gunnel, Herbert; Maggiolo, Romain

2014-05-01

352

Sulfur rate control system  

SciTech Connect

A sulfur rate control system is described for substantially optimizing particulate removal performance of an electrostatic precipitator in fluid communication with a flue carrying combustion products of a fossil fuel, comprising: an electrostatic precipitator having an inlet for receiving a flue gas: means for injecting sulfur trioxide into a flue for mixing with said flue gas at a location preceding entry of said flue gas into said electrostatic precipitator, said injection of sulfur trioxide being varied responsive to a proportional control signal; and, control means coupled to both said flue and said sulfur trioxide injection means for generating said proportional control signal, said control means including (1) means for measuring a sulfur dioxide concentration quantity in said flue gas at a location preceding said sulfur trioxide injection means, (2) means for measuring a flow rate of particulates in said flue gas at a location preceding said sulfur trioxide injection means, and (3) a controller for calculating a ratio between said sulfur dioxide concentration quantity and said flow rate of particulates, said ratio calculating controller having a first input coupled to said sulfur dioxide measuring means and a second input coupled to said particulate flow rate measuring means for generating said proportional control signal in proportion to a difference between a predetermined value and said ratio between said sulfur dioxide concentration quantity and said flow rate of particulates, said ratio controller having an output coupled to said sulfur trioxide injection means for maximizing particulate removal efficiency of said electrostatic precipitator.

Bell, T.A.; Mullendore, M.G.; Kleinfeldt, T.E.; Walker, H.G. Jr.

1993-07-20

353

Federal Reserve Rate Cuts  

NSDL National Science Digital Library

This week's In the News chronicles recent Federal Reserve Board decisions to lower interest rates. The eleven resources discussed provide news, opinion, and consumer information on the FRB BOG action. Following the first US interest rate cut in three years on September 29, 1998, FED Chairman Alan Greenspan caught fire from Wall Street. "Traders were disappointed" in the mere quarter point drop, according to Time business reporter Bernard Baumohl, but "Greenspan will have to make do with the gratitude of the rest of the world." Although the DOW initially fell 54 points Tuesday, a second 0.25% cut to short-term interest rates on October 15, 1998 sent stocks soaring 330 points--the third largest one-day point gain in history. Analysts now hope that US investor optimism--coupled with IMF and World Bank action in Brazil, Russia, and Asia--will ease the world-wide economic crises.

Waters, Megan.

1998-01-01

354

Time rate collision matrix  

SciTech Connect

The collision integral terms in Boltzmann equation are reformulated numerically leading to the substitution of the multiple integrals with a multiplicative matrix of the two colliding species velocity distribution functions which varies with the differential collision cross section. A matrix of lower rank may be constructed when one of the distribution functions is specified, in which case the matrix elements represent kinetic transition probabilities in the velocity space and the multiplication of the time rate collision matrix with the unknown velocity distribution function expresses the time rate of change of the distribution. The collision matrix may be used to describe the time evolution of systems in nonequilibrium conditions, to evaluate the rate of momentum and energy transfer between given species, or to generate validity criteria for linearized kinetic equations.

Stoenescu, M.L.; Smith, T.M.

1980-02-01

355

Calculating graduation rates.  

PubMed

In recent years, the focus has been on increasing the number of registered nurse (RN) graduates. Numerous states have initiated programs to increase the number and quality of students entering nursing programs, and to expand the capacity of their programs to enroll additional qualified students. However, little attention has been focused on an equally, if not more, effective method for increasing the number of RNs produced-increasing the graduation rate of students enrolling. This article describes a project that undertook the task of compiling graduation data for 15 entry-level programs, standardizing terms and calculations for compiling the data, and producing a regional report on graduation rates of RN students overall and by type of program. Methodology is outlined in this article. This effort produced results that were surprising to program deans and directors and is expected to produce greater collaborative efforts to improve these rates both locally and statewide. PMID:18662655

Starck, Patricia L; Love, Karen; McPherson, Robert

2008-01-01

356

Strain-rate effects for high-strain-rate computations  

Microsoft Academic Search

This paper examines the effect of strain rates for computations involving high strain-rates, beyond 103 s - 1. Although it is generally agreed that there is an enhanced rate effect at these higher rates, there is uncertainty regarding the interpretation of dynamic test data, the form of the high-rate effect, and the effect of the high rates on practical problems

G. R. Johnson; T. J. Holmquist; C. E. Anderson Jr.; A. E. Nicholls

2006-01-01

357

Improving HPV vaccination rates.  

PubMed

Despite national guidelines and proven health benefits, vaccination rates for the human papillomavirus (HPV) remain far below those of other vaccines recommended for adolescents. HPV is the most common sexually transmitted infection in the U.S; it is responsible for about 25,000 new cancers each year. A series of three shots is recommended for all girls and boys at age 11-12, but significant barriers exist to starting and finishing this series. This Issue Brief examines some of the barriers and summarizes a successful, multipronged clinical intervention to improve vaccination rates. PMID:24660247

Fiks, Alexander G

2014-03-01

358

Understanding Rates of Change.  

ERIC Educational Resources Information Center

This paper presents three activities on how to analyze rates of change in real-life situations using TI-83 calculators and computer-based laboratories. Activities include 24 hour temperature data, the temperature of a light bulb, and an M&M toss. Each section contains descriptions of equipment/materials, data collection, and data analysis. The…

Weil, Aurelia; Russell, Larry

359

DATA ATTRIBUTE RATING SYSTEM  

EPA Science Inventory

The paper discusses a data attribute rating system (DARS), developed by EPA to assist in evaluating data associated with emission inventories. he paper presents DARS for evaluation by the potential user community. ARS was originally conceived as a method for evaluating country-sp...

360

Faucet Flow Rate  

NSDL National Science Digital Library

Students conduct experiments to determine the flow rate of faucets by timing how long it takes to fill gallon jugs. They do this for three different faucet flow levels (quarter blast, half blast, full blast), averaging three trials for each level. They convert their results from gallons per second (gps) to cubic feet per second (cfs).

Civil And Environmental Engineering Department

361

Poetry Methods Rating Scale.  

ERIC Educational Resources Information Center

Designed to assess high school teachers' attitudes about teaching poetry, this questionnaire asked teachers to respond to a 38-item poetry methods rating scale (PMRS) on a seven-point scale (from "strongly agree" to "strongly disagree"). The items for the questionnaire were derived from a study of popular methods texts for teaching literature.…

Gallo, Donald R.

362

What's in a Rating?  

ERIC Educational Resources Information Center

We examine the relationship between the formal ratings that principals give teachers and a variety of observable teacher characteristics, including proxies for productivity. Prior work has shown that principals can differentiate between more and less effective teachers, especially at the tails of the quality distribution, and that subjective…

Jacob, Brian A.; Walsh, Elias

2011-01-01

363

Average Rate of Change  

NSDL National Science Digital Library

This demo provides students with a concrete understanding of the average rate of change for physical situations and for functions described in tabular or graphic form. Animations in gif and Quicktime format are available, as well as Excel programs for classroom or student use.

Roberts, Lila F.; Hill, David R.

2005-04-21

364

Cohort Default Rate Guide.  

National Technical Information Service (NTIS)

The Cohort Default Rate Guide (Guide) is a publication that the U.S.Department of Education (the Department) designed to assist schools with their Federal Family Education Loan (FFEL) Program and William D. Ford Federal Direct Loan (Direct Loan) Program c...

2001-01-01

365

Calculating California Seismicity Rates  

USGS Publications Warehouse

Empirically the rate of earthquakes = magnitude M is well fit by the Gutenberg-Richter relationship, logN=a-bM (1) where N is the number of earthquakes = M over a given time period, a is the number of M = 0 earthquakes over the same period, and b is a parameter that determines the ratio of larger to smaller earthquakes (Ishimoto and Iida 1939; Gutenberg and Richter 1944). Thus to characterize the seismicity rate, N, and risk in a given region we need to solve for the values of a and b. Here we are concerned with solving for the long term average values of these parameters for the state of California. My primary data source is a catalog of 1850-2006 M = 4.0 seismicity compiled with Tianqing Cao (Appendix H). Because earthquakes outside of the state can influence California I consider both earthquakes within the state and within 100 km of the state border (Figure 1).

Felzer, Karen R.

2008-01-01

366

Rating Scales in Schizophrenia  

Microsoft Academic Search

\\u000a In the field of schizophrenia treatment and research, psychiatric symptom rating scales have served to evaluate and elucidate\\u000a the value of antipsychotic medications and psychosocial interventions in treating this disorder. Useful scales have also been\\u000a developed to assist in measuring side effects of medications, to assess areas of cognitive functioning, to evaluate quality\\u000a of life, and to monitor medication treatment

Jennifer D. Gottlieb; Xiaoduo Fan; Donald C. Goff

367

Rate Tornado Damage  

NSDL National Science Digital Library

Tornadoes can produce damage that ranges from broken tree limbs to a block of houses swept from their foundations. They can inflict utter devastation across a wide swath of land or, destroy one house and leave others on either side largely untouched. In this interactive feature from NOVA Online, sudents examine a series of photos of tornado damage and assign intensity ratings (on the Fulita scale) based on what they see.

2011-02-24

368

Rotational rate sensor  

DOEpatents

A rate sensor for angular/rotational acceleration includes a housing defining a fluid cavity essentially completely filled with an electrolyte fluid. Within the housing, such as a toroid, ions in the fluid are swept during movement from an excitation electrode toward one of two output electrodes to provide a signal for directional rotation. One or more ground electrodes within the housing serve to neutralize ions, thus preventing any effect at the other output electrode.

Hunter, Steven L. (Livermore, CA)

2002-01-01

369

Rate Tornado Damage  

NSDL National Science Digital Library

Tornadoes can produce damage that ranges from broken tree limbs to a block of houses swept from their foundations. They can inflict utter devastation across a wide swath of land or, destroy one house and leave others on either side largely untouched. In this interactive feature from NOVA Online, sudents examine a series of photos of tornado damage and assign intensity ratings (on the Fulita scale) based on what they see.

370

29 CFR 778.112 - Day rates and job rates.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Day rates and job rates. 778.112 Section 778.112...âregular Rateâ § 778.112 Day rates and job rates. If the employee is paid a flat...a day's work or for doing a particular job, without regard to the number of...

2013-07-01

371

Consideration of radar target glint from ST during OMV rendezvous  

NASA Technical Reports Server (NTRS)

The nature of radar target glint and the factors upon which it depends when using the Hubble Space Telescope as a radar target is discussed. An analysis of the glint problem using a 35 MHz or 94 MHz radar on the orbital maneuvering vehicle is explored. A strategy for overcoming glint is suggested.

Mcdonald, M. W.; Malone, L. B.; Gleason, E. H.

1985-01-01

372

Secured Bilateral Rendezvous using self interference cancellation in wireless networks  

Microsoft Academic Search

Secure transmission among mobile nodes in hostile environments has often been achieved by trading off security with communication latency. However, in time critical applica- tions (e.g., tactical wireless networks, civilian law enforcement operations, homeland security missions, etc.), latency is more critical than any other parameters. Long latency is generally attributed to the time required by authentication in the presence of

Eun-Kyu Lee; Mario Gerla

2011-01-01

373

Challenges to situated morality: Maintaining respectability in a sexual rendezvous  

Microsoft Academic Search

A clandestine motel operation is described, concentrating upon the staff and patrons as they attempt to maintain respectability within a context of situated morality that is shifting, challenging previously negotiated realities. The staff members tend toward a refulgent respectability, using vocabularies of denial to maintain respectability. Patrons, categorized as regular customers, special customers, careful people and problem people, may seek

J. Robert Lilly; Richard A. Ball

1980-01-01

374

Tutorial 1-2: Rendezvous on Faulty Autonomous Mobile Robots  

Microsoft Academic Search

The autonomous mobile robots system is one of the distributed systems such that communications between robots are done by observations of all the other robots' locations and state transitions are done by changing their locations on two-dimensional space or graphs etc. Recent years, this system has attracted a lot of researchers in distributed systems and some kind of fundamental problems

Y. Katayama

2009-01-01

375

Trajectory Planning For Coordinated Rendezvous Of Unmanned Air Vehicles  

Microsoft Academic Search

A trajectory generation strategy that facilitatesthe coordination of multiple unmanned air vehiclesis developed. Of particular interest is the planning ofthreat-avoiding trajectories that result in the simultaneousarrival of multiple UAVs at their targets. Inthis approach, paths to the target are modeled usingthe physical analogy of a chain. A unique strengthof the planning approach is the ability to specify oralter the pathlength

Timothy W. Mclain; Randal W. Beard

2000-01-01

376

Saturn/Titan Rendezvous: A Solar-Sail Aerocapture Mission  

NASA Technical Reports Server (NTRS)

A low-mass Titan orbiter is proposed that uses conservative or optimistic solar sails for all post-Earth-escape propulsion. After accelerating the probe onto a trans-Saturn trajectory, the sail is used parachute style for Saturn capture during a pass through Saturn's outer atmosphere. If the apoapsis of the Saturn-capture orbit is appropriate, the aerocapture maneuver can later be repeated at Titan so that the spacecraft becomes a satellite of Titan. An isodensity-atmosphere model is applied to screen aerocapture trajectories. Huygens/Cassini should greatly reduce uncertainties regarding the upper atmospheres of Saturn and Titan.

Matloff, Gregory L.; Taylor, Travis; Powell, Conley

2004-01-01

377

Rendezvous Layer Protocols for Bluetooth-Enabled Smart Devices  

Microsoft Academic Search

Communication platforms for ubiquitous computing need to be flexible, self-organizing, highly scalable and energy efficient, because in the envisioned scenarios a large number of autonomous entities com- municate in potentially unpredictable ways. Short-range wireless technologies form the basis of such communi- cation platforms. In this paper we investigate device discovery in Bluetooth, a candidate wireless technology for ubiquitous computing. Detecting

Frank Siegemund; Michael Rohs

2002-01-01

378

Technology of H-II Transfer Vehicle Rendezvous System  

NASA Astrophysics Data System (ADS)

The H-II Transfer Vehicle (HTV), which is a Japanese unmanned cargo transfer spacecraft, will deliver supplies to the International Space Station (ISS). The first HTV will be launched in 2009 from the Tanegashima Space Center aboard an H-IIB launch vehicle with up to 6,000kg of supplies. HTV approaches to the ISS and the Space Station Remote Manipulator System (SSRMS), known as Canadarm2, will grapple the HTV and berth it to the ISS. After the supplies, the HTV will then be loaded with waste materials and then separated from the ISS by SSRMS. HTV conducts departure sequence from ISS after release from SSRMS and reentry to the atmosphere. In this paper, technology of HTV automated Guidance, Navigation and Control (GN&C) system is presented.

Kasai, Toru; Ueda, Satoshi; Uematsu, Hirohiko

379

LADAR vision technology for automated rendezvous and capture  

NASA Technical Reports Server (NTRS)

LADAR Vision Technology at Autonomous Technologies Corporation consists of two sensor/processing technology elements: high performance long range multifunction coherent Doppler laser radar (LADAR) technology; and short range integrated CCD camera with direct detection laser ranging sensors. Algorithms and specific signal processing implementations have been simulated for both sensor/processing approaches to position and attitude tracking applicable to AR&C. Experimental data supporting certain sensor measurement accuracies have been generated.

Frey, Randy W.

1991-01-01

380

Efficient Rendezvous Algorithms for Mobility-Enabled Wireless Sensor Networks  

Microsoft Academic Search

Recent research shows that significant energy saving can be achieved in mobility-enabled wireless sensor networks (WSNs) that visit sensor nodes and collect data from them via short-range communications. However, a major performance bottleneck of such WSNs is the significantly increased latency in data collection due to the low movement speed of mobile base stations. To address this issue, we propose

Guoliang Xing; Minming Li; Tian Wang; Weijia Jia; Jun Huang

2012-01-01

381

Laser space rendezvous and docking system trade-off study  

NASA Technical Reports Server (NTRS)

The use, design, and fabrication feasibility of scanning the laser beam by swiveling the outside mirror with a ball joint swivel system is examined along with the applicability of graphite reinforced epoxy material for the construction of reflective optics. It is indicated that (1) the cost of graphite-epoxy will be more than that of many other materials due to the amount of special tooling required; (2) the weight advantage of graphite-epoxy over beryllium is minimal; the ball joint swivel system is accurate enough to perform the scanning function; and that the ball joint will result in a simpler and more cost effective scanning mechanism.

Adelman, S.; Levinson, S.

1975-01-01

382

Orbital Express AVGS Validation and Calibration for Automated Rendezvous  

NASA Technical Reports Server (NTRS)

From March to July of 2007, the DARPA Orbital Express mission achieved a number of firsts in autonomous spacecraft operations. The NASA Advanced Video Guidance Sensor (AVGS) was the primary docking sensor during the first two dockings and was used in a blended mode three other automated captures. The AVGS performance exceeded its specification by approximately an order of magnitude. One reason that the AVGS functioned so well during the mission was that the validation and calibration of the sensor prior to the mission advanced the state-of-the-art for proximity sensors. Some factors in this success were improvements in ground test equipment and truth data, the capability for ILOAD corrections for optical and other effects, and the development of a bias correction procedure. Several valuable lessons learned have applications to future proximity sensors.

Heaton, Andrew F.; Howard, Richard T.; Pinson, Robin M.

2008-01-01

383

A Low Cost Rendezvous Mission to 99942 Apophis  

Microsoft Academic Search

In recent years the public has become more aware of the potentially catastrophic consequences of an asteroid collision with Earth. Congress has taken note of this and instructed NASA to develop a program to determine the resources required to detect, track, characterize, and, if necessary, mitigate potentially hazardous objects. Characterization of an asteroid deemed sufficiently dangerous requires a space mission

Regan Howard; Ross Gillett

2007-01-01

384

Gemini - John W. Young in Rendezvous Docking Simulator  

NASA Technical Reports Server (NTRS)

Astronaut John Young (above) was one of 14 astronauts, 8 NASA test pilots, and 2 McDonnell test pilots who took part in simulator studies. Young piloted the simulator on November 12, 1963 Arthur Vogeley wrote: 'Many of the astronauts have flown this simulator in support of the Gemini studies and they, without exception, appreciated the realism of the visual scene. The simulator has also been used in the development of pilot techniques to handle certain jet malfunctions in order that aborts could be avoided. In these situations large attitude changes are sometimes necessary and the false motion cues that were generated due to earth gravity were somewhat objectionable; however, the pilots were readily able to overlook these false motion cues in favor of the visual realism.' Roy F. Brissenden wrote:'The basic Gemini control studies developed the necessary techniques and demonstrated the ability of human pilots to perform final space docking with the specified Gemini-Agena systems using only visual references. ... Results... showed that trained astronauts can effect the docking with direct acceleration control and even with jet malfunctions as long as good visual conditions exist.... Probably more important than data results was the early confidence that the astronauts themselves gained in their ability to perform the maneuver in the ultimate flight mission.'

1963-01-01

385

Plasma adiabatic lapse rate.  

PubMed

The plasma analog of an adiabatic lapse rate (or temperature variation with height) in atmospheric physics is obtained. A new source of plasma temperature gradient in a binary ion species mixture is found that is proportional to the concentration gradient ?? and difference in average ionization states Z(2)-Z(1). Application to inertial-confinement-fusion implosions indicates a potentially strong effect in plastic (CH) ablators that is not modeled with mainline (single-fluid) simulations. An associated plasma thermodiffusion coefficient is derived, and charge-state diffusion in a single-species plasma is also predicted. PMID:23006377

Amendt, Peter; Bellei, Claudio; Wilks, Scott

2012-08-17

386

Heart Rate and Function  

NSDL National Science Digital Library

The purpose of this activity is to discover and learn about heart rate and the function of the heart. The students will investigate whether their hearts beat slower/faster at different times; develop an understanding of why their hearts beat slower/faster at different times; use data to develop an explanation of why their hearts beat slower/faster at different times; be aware of the effect of exercise on respiration; and be able to describe the major function of the heart.

Mr. Mike Peterson (Frazer Public School)

1999-07-01

387

Flow Rates Model  

NSDL National Science Digital Library

The Flow Rates activity is highly recommended both for math teachers and for science teachers in all fields. It can be used effectively for a variety of content applications and at various points in a course sequence. By allowing students to practice making and testing hypotheses about liquid flowing through a simple burette, it provides an excellent introduction to the scientific method. The collection and analysis of real-time data provides students with the opportunity to use their graphing and algebra skills in a real problem-solving situation. Finally, it facilitates a direct mental mapping between students' demonstration observations and mathematical modeling using STELLA software.

School, Maryland V.

388

76 FR 8946 - Security Ratings  

Federal Register 2010, 2011, 2012, 2013

...RIN 3235-AK18 Security Ratings AGENCY: Securities and Exchange...ever, rate the securities of small entities...further note most security ratings are obtained...fixed income securities with comparable maturity and security...

2011-02-16

389

The Effects of Rating Purpose and Anonymity on Self Ratings.  

ERIC Educational Resources Information Center

The present study was designed to answer four questions: (1) do anonymity and purpose affect the leniency of self ratings in general, (2) do these factors interact, (3) do self ratings approximate supervisor ratings under certain conditions, and (4) is self-assessment a useful method of determining training needs? Self-ratings and supervisory…

Arnaut, Lynn Y.; Bownas, David A.

390

The Rate Decision: Adjustable vs Fixed Rate Mortgages  

Microsoft Academic Search

Homebuyers and commercial real estate buyers who borrow funds using mortgages all must face the choice of whether to assume a fixed or an adjustable rate mortgage. Other mortgage forms with alternative characteristics are available, but the deciding question remains the same. Fixed rate mortgages never change over time, but have a high initial rate: adjustable rate, interest-only or hybrid

Hossein Arsham; Deborah Ford

2007-01-01

391

Evolution of NEO rotation rates due to close encounters with Earth and Venus  

NASA Astrophysics Data System (ADS)

In this paper we study the statistical effect of planetary flybys on the rotation rates and states of Near Earth Objects (NEOs). Our approach combines numerical and analytical methods within a Monte Carlo model that simulates the evolution of the NEO spin rates. We take as input for the simulation a source distribution of spin states and evolve it to find their steady state distribution. In performing this evolution we track the changes in the spin rate and state distribution for the different components of the NEO population. We show that the cumulative effect of planetary encounters is to spin up the overall population of NEOs. This spin up effect holds on average only, and particular members of the population may experience an overall decrease in rotation rate. This effect is clearly seen across all components of the NEO population and is significant both statistically and physically. For initially slow rotators the spin up effect is strong, lowering the mean rotation period by 32%. For faster rotating populations the effect is less, lowering the spin period by 15% for the intermediate case, 6% for fast rotating rubble piles, and 8% for fast rotating monoliths. Physically, the spin up effect pushes 1% of the fast rotating rubble-pile NEOs over the disruption limit, while 6% of these bodies experience a sub-disruption event that could modify their physical structure. For monolithic NEOs, the spin up effect is self-limiting, reaching a minimum spin period of 1.1 hr, with a strong cut-off between 2-3 hr. This has two implications. First, it may not be necessary to invoke the rubble-pile hypothesis to recover a cut-off in spin period. Second, it shows that planetary flybys cannot account for the extremely rapid rotation rates of some small NEOs. We also tested a different balance between the effects of Earth and Venus by treating the Aten sub-class of asteroids separately. Due to increased interactions with the planets, the spin up effect is more pronounced (10%) and disruptions increase by a factor of three. The slow rotation tails of the spin distributions are increased to longer periods, in general, with rotation periods of over 100 hr occurring for a few tenths of a percent for some component populations. Thus, this mechanism may account for some of the noted excess in slow rotators among the NEOs. Planetary flybys also cause NEOs to enter a tumbling state, with approximately 0.5% of the population being placed into a long-axis rotation mode. Finally, based on the evolution of spin states of different components of the NEO population, we compared the evolved states with the measured distribution of NEOs to estimate the relative populations of these components that comprise the NEOs.

Scheeres, D. J.; Marzari, F.; Rossi, A.

2004-08-01

392

Sequential Effects in Essay Ratings  

ERIC Educational Resources Information Center

Contrary to previous research on sequential ratings of student performance, this study found that professional essay raters of a large-scale standardized testing program produced ratings that were drawn toward previous ratings, creating an assimilation effect. Longer intervals between the two adjacent ratings and higher degree of agreement with…

Attali, Yigal

2011-01-01

393

Intramolecular electron transfer rates  

NASA Astrophysics Data System (ADS)

The initial goals of this project were: (1) to construct pulsed-accelerated-flow and pulsed-laser (transient absorbance) instruments for intramolecular electron-transfer rate measurements, (2) to design and synthesize appropriate molecules and perform such measurements, (3) to develop further an electrochemical method for gauging site-to-site electronic coupling, and (4) to apply time-dependent Raman scattering theory to the problem of inner-shell reorganization in charge-transfer reactions. Although all four goals were met, we also found it necessary to pursue studies in some unforeseen directions. For example, early on we discovered that medium effects (aggregation and ion pairing) could play a very large, and previously unrecognized, role in some optical intervalence reactions. Given the importance of the effects to the areas above, we chose to map them in a fairly complete fashion. Also, in anticipation of possible renewal we initiated studies in a new area: bimolecular photoredox kinetics in supercritical media. Finally, in a small project carried out largely by undergraduates we examined solvent tuning effects upon lifetimes of photo-excited ruthenium am(m)ine bipyridine complexes. The key new findings and other highlights of these studies are outlined.

Hupp, Joseph T.

394

Behaviorally Anchored Rating Scales vs. Summated Rating Scales: Psychometric Properties and Susceptibility to Rating Bias.  

ERIC Educational Resources Information Center

Using both the Behaviorally Anchored Rating Scales (BARS) and the Purdue University Scales, 727 undergraduates rated 32 instructors. The BARS had less halo effect, more leniency error, and lower interrater reliability. Both formats were valid. The two tests did not differ in rate discrimination or susceptibility to rating bias. (Author/GDC)

Kinicki, Angelo J.; And Others

1985-01-01

395

Association between heart rate variability and manual pulse rate  

PubMed Central

Introduction: One model for neurological assessment in chiropractic pertains to autonomic variability, tested commonly with heart rate variability (HRV). Since HRV may not be convenient to use on all patient visits, more user-friendly methods may help fill-in the gaps. Accordingly, this study tests the association between manual pulse rate and heart rate variability. The manual rates were also compared to the heart rate derived from HRV. Methods: Forty-eight chiropractic students were examined with heart rate variability (SDNN and mean heart rate) and two manual radial pulse rate measurements. Inclusion criteria consisted of participants being chiropractic students. Exclusion criteria for 46 of the participants consisted of a body mass index being greater than 30, age greater than 35, and history of: a) dizziness upon standing, b) treatment of psychiatric disorders, and c) diabetes. No exclusion criteria were applied to the remaining two participants who were also convenience sample volunteers. Linear associations between the manual pulse rate methods and the two heart rate variability measures (SDNN and mean heart) were tested with Pearson’s correlation and simple linear regression. Results: Moderate strength inverse (expected) correlations were observed between both manual pulse rate methods and SDNN (r = ?0.640, 95% CI ?0.781, ?0.435; r = ?0.632, 95% CI ?0.776, ?0.425). Strong direct (expected) relationships were observed between the manual pulse rate methods and heart rate derived from HRV technology (r = 0.934, 95% CI 0.885, 0.962; r = 0.941, 95% CI 0.897, 0.966). Conclusion: Manual pulse rates may be a useful option for assessing autonomic variability. Furthermore, this study showed a strong relationship between manual pulse rates and heart rate derived from HRV technology.

Hart, John

2013-01-01

396

Instructed heart rate control in a high heart rate population  

Microsoft Academic Search

Forty college students were selected from a large number of introductory psychology students on the basis of high heart rate during an initial screening session. Subjects were then contacted and participated in two additional sessions during which heart rate, respiration rate, and skin conductance measures were obtained. Each session consisted of a baseline period followed by five trial periods during

Craig T. Twentyman; Paul F. Malloy; Alex S. Green

1979-01-01

397

Rating Scale Format as it Affects Ratings in Student Teaching.  

ERIC Educational Resources Information Center

To assess the impact of various rating scale formats in rating student teachers, a Likert-type scale (Highly agree/slightly agree/neither/slightly disagree/highly disagree) was derived from the graphic scale currently used by the cooperating teachers and university supervisors. They rated the music student teachers on an eight-point scale from…

Allison, Howard K., II

398

Development of Angular Rate Sensor.  

National Technical Information Service (NTIS)

The primary object of this program is the development of a solid state rate sensor of improved reliability for use with the Automatic Flight Control System of high performance Naval aircraft and helicopter. Existing rate sensors utilizing conventional gyr...

1966-01-01

399

Tests for Monotone Failure Rate.  

National Technical Information Service (NTIS)

Physical considerations often lead one to expect that a distribution has increasing failure rate, and knowledge of increasing failure rate is mathematically useful in solving a variety of practical problems. In this paper, a nonparametric test to determin...

F. Proschan R. Pyke

1965-01-01

400

Determinants of heart rate variability  

Microsoft Academic Search

Objectives. This study sought to examine clinical determinants of heart rate variability and to report normative reference values for eight heart rate variability measures.Background. Although the clinical implications of heart rate variability have been described, clinical determinants and normative values of heart rate variability measures have not been studied systematically in a large community-based population.Methods. The first 2 h of

Hisako Tsuji; Ferdinand J. Venditti; Emily S. Manders; Jane C. Evans; Martin G. Larson; Charles L. Feldman; Daniel Levy

1996-01-01

401

PROBLEMS OF MEASURING SPEECH RATE.  

ERIC Educational Resources Information Center

A DISCUSSION WAS PRESENTED ON THE PROBLEMS OF MEASURING SPEECH RATE, A CRITICAL VARIABLE IN SPEECH COMPRESSION, BOTH IN DESCRIBING THE INPUT TO ANY SPEECH COMPRESSION SYSTEM AND IN CHARACTERIZING THE OUTPUT. THE DISCUSSION WAS LIMITED TO SPEECH RATE MEASUREMENT OF "ORAL READING RATE," ONLY, AND DID NOT DEAL WITH THE MEASUREMENT OF "SPONTANEOUS…

CARROLL, JOHN B.

402

AGRICULTURAL EXCHANGE RATE DATA SHEET  

EPA Science Inventory

The ERS data set contains annual and monthly data for exchange rates important to U.S. agriculture. It includes both nominal and real exchange rates for 80 countries (plus the European Union) as well as real trade-weighted exchange rate indexes for many commodities and aggregatio...

403

Incidence rates in dynamic populations  

PubMed Central

The purpose of the present article is to explain the calculation of incidence rates in dynamic populations with the use of simple mathematical and statistical concepts. The first part will consider incidence rates in dynamic populations, and how they can best be taught in basic, intermediate and advanced courses. The second part will briefly explain how and why incidence rates are calculated in cohorts.

Vandenbroucke, Jan P; Pearce, Neil

2012-01-01

404

Rate and Occupancy Survey Results.  

ERIC Educational Resources Information Center

In its annual effort to determine rate and occupancy trends in the Mid-Atlantic region, MACUHO surveyed by questionnaire the chief housing officers on its mailing list and received 99 usable responses, compared with 65 the previous year. The average double room rate was reported to be $691, compared with $646 in 1975; the average board rate rose…

Mid-Atlantic Association of Coll. and Univ. Housing Officers.

405

Validity of Cerebrovascular Mortality Rates  

Microsoft Academic Search

Cerebrovascular disease (CVD) mortality rates are being increasingly used to establish a relationship with coronary heart disease risk factors. Cerebrovascular mortality rates suffer from the same general defects as coronary heart disease mortality rates but with greater diagnostic error in regard to subdivisions of CVD or stroke. These vital statistics, whether national or regional, are too inaccurate for scientific use

William E. Stehbens

1991-01-01

406

Generalized Linear Failure Rate Distribution  

Microsoft Academic Search

The exponential and Rayleigh are the two most commonly used distributions for analyzing lifetime data. These distributions have several desirable properties and nice physical interpretations. Unfortunately the exponential distribution only has constant failure rate and the Rayleigh distribution has increasing failure rate. The linear failure rate distribution generalizes both these distributions which may have non-increasing hazard function also. This paper

Ammar M. Sarhan; Debasis Kundu

2009-01-01

407

Mirage of Floating Exchange Rates  

Microsoft Academic Search

This note summarizes some of the highlights of my longer paper with Guillermo Calvo”Fear of Floating.” Many emerging market countries have suffered financial crises. One view blames soft pegs for these crises. Adherents to that view suggest that countries move to corner solutions--hard pegs or floating exchange rates. We analyze the behavior of exchange rates, reserves, and interest rates to

Carmen M. Reinhart

2000-01-01

408

Factors Related to Reading Rates.  

ERIC Educational Resources Information Center

A summary of research on reading rate is presented. Cited studies dating from 1884 to 1965 suggest a relationship among reading rate and visual perception, practice in reading, power of concentration, mental alertness, complex reaction times, intelligence, amount of vocalization, content, rate of thinking, intensity of illumination, typographical…

Hanson, Earl

1968-01-01

409

[Rate Justification for Child Care.  

ERIC Educational Resources Information Center

This brief report argues against the cost analysis process currently used as a form of rate justification by states and central agencies who are purchasing child care. Instead, a logic is proposed for negotiated rates based on expected levels of necessary costs and reasonable rates in comparison with open market levels as shown on day care…

Community Coordinated Child Care (4-C) for Central Florida, Inc., Orlando.

410

Saturn component failure rate and failure rate modifiers  

NASA Technical Reports Server (NTRS)

Failure mode frequency ratios, environmental adjustment factors, and failure rates for mechanical and electromechanical component families are presented. The failure rates and failure rate modifiers resulted from a series of studies whose purpose was to provide design, tests, reliability, and systems engineers with accurate, up-to-date failure rate information. The results of the studies were achieved through an extensive engineering analysis of the Saturn Program test data and Unsatisfactory Condition Reports (UCR's) and the application of mathematical techniques developed for the studies.

1971-01-01

411

The mutation rate and cancer.  

PubMed Central

The stability of the human genome requires that mutations in the germ line be exceptionally rare events. While most mutations are neutral or have deleterious effects, a limited number of mutations are required for adaptation to environmental changes. Drake has provided evidence that DNA-based microbes have evolved a mechanism to yield a common spontaneous mutation rate of approximately 0.003 mutations per genome per replication (Drake 1991). In contrast, mutation rates of RNA viruses are much larger (Holland et al. 1982) and can approach the maximum tolerable deleterious mutation rate of one per genome (Eigen and Schuster 1977; Eigen 1993). Drake calculates that lytic RNA viruses display spontaneous mutation rates of approximately one per genome while most have mutation rates that are approximately 0.1 per genome (Drake 1993). This constancy of germline mutation rates among microbial species need not necessarily mean constancy of the somatic mutation rates. Furthermore, there need not be a constant rate for somatic mutations during development. In this review, we consider mutations in cancer, a pathology in which there appears to be an increase in the rate of somatic mutations throughout the genome. Moreover, within the eukaryotic genome, as in microbes, there are "hot-spots" that exhibit unusually high mutation frequencies. It seems conceivable to us that many tumors contain thousands of changes in DNA sequence. The major question is: how do these mutations arise, and how many are rate-limiting for tumor progression?

Jackson, A L; Loeb, L A

1998-01-01

412

Optimizing rating scale category effectiveness.  

PubMed

Rating scales are employed as a means of extracting more information out of an item than would be obtained from a mere "yes/no", "right/wrong" or other dichotomy. But does this additional information increase measurement accuracy and precision? Eight guidelines are suggested to aid the analyst in optimizing the manner in which rating scales categories cooperate in order to improve the utility of the resultant measures. Though these guidelines are presented within the context of Rasch analysis, they reflect aspects of rating scale functioning which impact all methods of analysis. The guidelines feature rating-scale-based data such as category frequency, ordering, rating-to-measure inferential coherence, and the quality of the scale from measurement and statistical perspectives. The manner in which the guidelines prompt recategorization or reconceptualization of the rating scale is indicated. Utilization of the guidelines is illustrated through their application to two published data sets. PMID:11997586

Linacre, John M

2002-01-01

413

Fed to Raise Interest Rates  

NSDL National Science Digital Library

As expected, the Federal Reserve voted to raise interest rates 0.25 percent, the fifth rate raise since June. The interest rate boost is expected to help keep inflation in check during this record period (108 months) of economic expansion. Technology companies have continued to signal healthy economic growth, and unemployment rates remain low. Despite drastic price hikes in gasoline and heating oil prices, consumers are still spending. This worries economists who watched consumers pay little heed to the last four interest rate increases. The quarter point interest rate increase will average out to an extra $1 a month on consumers's credit cards, which in this period of prosperity, will not curb consumers's spending.

Missner, Emily D.

414

Generalizability of Interpersonal Communications Rating Scale Ratings across Presentation Modes.  

ERIC Educational Resources Information Center

Examined variance in observational ratings of Interpersonal Communications Rating Scale (ICRS) attributable to individual raters and mode of presentation (videotape, audiotape, transcript, videotape plus transcript, audiotape plus transcript). Nine raters used ICRS to code six films for which presentation mode was varied. Found transcript-only…

Tracey, Terence J.; Guinee, James P.

1990-01-01

415

RADIOTELEMETRY OF HEART RATES FROM  

Microsoft Academic Search

A lightweight radiotelemetry system with a range of 80 km was used to monitor heart rate from free-ranging Herring Gulls on flights of up to 20 km. Heart rate varied from 130 beats\\/min in a resting bird to 625 beats\\/min for sustained flight. Soaring birds showed rates similar to those of birds sitting quietly on the ground. Simultaneous records of

JOHN W. mANWISHER; TIMOTHY C. WILLIAMS; JOHN M. TEAL; KENNETH O. LAWSON

1978-01-01

416

Calculating Follow-up Rates  

Microsoft Academic Search

Follow-up rates are presented as a percentage but the method of calculation is seldom discussed. Determining a follow-up rate\\u000a begins with identifying the numerator and denominator used in the calculation. Four methods of calculating follow-up rate\\u000a after surgical treatment for weight reduction were studied. Method 1 follow-up rate, 91.2%, was calculated using patients\\u000a with at least one follow-up contact as

Kathleen Renquist; Gary Jeng; Edward E. Mason; NBSR Data Contributors

1992-01-01

417

Laser range and range rate finder. Study and development of critical technologies. Volume 1: Laser diode range finder  

NASA Astrophysics Data System (ADS)

Performance analysis and concept description of laser diode optical radar systems for precision tracking and ranging between spaceborne targets are presented. Intersatellite ranging for determining gravity disturbances on satellite orbits and range measurement for spacecraft rendezvous and docking maneuvers support are considered. Both tasks can be performed, according to theoretical studies, using diode laser systems. A ground based continuous wave (CW) laser diode ranging system was successfully tested as a first step towards creating a functional model of a spaceborne unit. For the intersatellite mission, a combination of pulsed and CW systems is proposed, that is a pulsed laser for rapid scanning and coarse ranging and a CW laser for precision ranging. Both systems are suitable for rendezvous or docking maneuvers.

Diehl, C.; Halldorsson, T.; Kunkel, B.; Lill, E.; Manhart, S.; Sepp, G.; Siemsen, D.; Thalmair, K.

1981-06-01

418

ratings  

Cancer.gov

Informative 36 36 37 37 Interesting 23 30 23 35 Meaningful 23 28 --- --- Relevant 28 29 25 29 Something you could relate to 36 37 37 34 Told you something important 23 25 28 28 Told you something new 30 28 26 27 Worth remembering 22 33 19 --- 1 This table, based on the Ipsos-ASI, Inc., Market Research Database of Diagnostic Norms, includes national averages for standard copy test questions used in testing commercial ads.

419

Risk, Uncertainty and Exchange Rates  

Microsoft Academic Search

This paper explores a new direction for empirical models of exchange rate determination. The motivation arises from two well documented facts, the failure of log-linear empirical exchange rate models of the 1970's and the variability of risk premiums in the forward market. Rational maximizing models of economic behavior imply that changes in the conditional variances of exogenous processes, such as

Robert J. Hodrick

1989-01-01

420

What Is a Reaction Rate?  

ERIC Educational Resources Information Center

The definition of reaction rate is derived and demonstrations are made for the care to be taken while using the term. Reaction rate can be in terms of a reaction property, the extent of reaction and thus it is possible to give a definition applicable in open and closed systems.

Schmitz, Guy

2005-01-01

421

The Psychological Maltreatment Rating Scales.  

ERIC Educational Resources Information Center

The Psychological Maltreatment Rating Scales (PMRS) were developed for assessing psychological maltreatment in the mother-child interaction, and were used to rate the videotaped interaction of 49 high-risk mother-child dyads and predict child protective service involvements. The PMRS was found to be a moderately reliable and valid measure.…

Brassard, Marla R.; And Others

1993-01-01

422

Exchange Rate Regimes: Middling Through  

Microsoft Academic Search

The appropriate exchange rate regime, in the context of integration of currency markets with financial markets and of large international capital flows, continues to be a policy dilemma. It is found that the majority of countries are moving towards somewhat higher exchange and lower interest rate volatility. Features of foreign exchange (forex) markets could be partly motivating these choices. A

Ashima Goyal

2006-01-01

423

Towards Smart Grid Dynamic Ratings  

NASA Astrophysics Data System (ADS)

The energy distribution industry is giving greater attention to smart grid solutions as a means for increasing the capabilities, efficiency and reliability of the electrical power network. The smart grid makes use of intelligent monitoring and control devices throughout the distribution network to report on electrical properties such as voltage, current and power, as well as raising network alarms and events. A further aspect of the smart grid embodies the dynamic rating of electrical assets of the network. This fundamentally involves a rating of the load current capacity of electrical assets including feeders, transformers and switches. The mainstream approach to rate assets is to apply the vendor plate rating, which often under utilizes assets, or in some cases over utilizes when environmental conditions reduce the effective rated capacity, potentially reducing lifetime. Using active intelligence we have developed a rating system that rates assets in real time based upon several events. This allows for a far more efficient and reliable electrical grid that is able to extend further the life and reliability of the electrical network. In this paper we describe our architecture, the observations made during development and live deployment of the solution into operation. We also illustrate how this solution blends with the smart grid by proposing a dynamic rating system for the smart grid.

Cheema, Jamal; Clark, Adrian; Kilimnik, Justin; Pavlovski, Chris; Redman, David; Vu, Maria

2011-08-01

424

Rating Scale Instruments and Measurement  

ERIC Educational Resources Information Center

The article examines theoretical issues associated with measurement in the human sciences and ensuring data from rating scale instruments are measures. An argument is made that using raw scores from rating scale instruments for subsequent arithmetic operations and applying linear statistics is less preferable than using measures. These theoretical…

Cavanagh, Robert F.; Romanoski, Joseph T.

2006-01-01

425

Increasing undergraduate student retention rates  

Microsoft Academic Search

Based on data from a questionnaire survey of the new undergraduate intake to the University of Birmingham, the factors which influence withdrawal\\/retention rates in the first term were examined. The effectiveness of counselling intervention with first-year undergraduate students at risk of leaving university in their first term is also explored. The implications for universities wishing to increase retention rates and

Barbara Rickinson; Desmond Rutherford

1995-01-01

426

Predicting the Divorce Rate: Down?  

ERIC Educational Resources Information Center

Predicted a decline in the divorce rate based on 10 factors including: decline in marriage rate, older age at marriage, mental health improvement, upper limit on employed women, less migration, end of the cultural revolution, exhaustion of latency effect of no-fault divorce, and fear of the consequences of divorce. (JAC)

Kemper, Theodore D.

1983-01-01

427

Supergranule Rotation Rates and Lifetimes  

NASA Technical Reports Server (NTRS)

Previous measurements of the rotation rate of the supergranule Doppler pattern have revealed three interesting characteristics. 1) The supergranule pattern rotates faster than the plasma at the surface and, at each latitude, it rotates faster than the plasma at any level below the surface. 2) Larger cells rotate more rapidly than smaller cells. 3) Faster rotation rates are found when using larger time lags between Doppler images. These last two characteristics are consistent with the idea that large cells live longer and extend deeper into the Sun where the rotation rate is faster. A re-examination of the rotation rates and lifetimes of the Doppler patterns seen with the Michelson Doppler Imager (MDI) instrument on Solar and Heliospheric Observatory (SOHO) confirms these characteristics. However, a simulation of the data using a spectrum for the cellular flows that matches the observed spectrum shows that these characteristics can be largely reproduced by cellular patterns that rotate at the same rate without any dependence upon cell size, The rotation rate , and its dependence on latitude, is nonetheless still faster than the surface or internal rotation rate. The difference in rotation rates as functions of cell size and time lag between observations is attributed to projection effects on the line-of-sight Doppler signal. This data simulation is also used to determine characteristic lifetimes for the cellular patterns as a function of cell size. These lifetime determinations are also affected by projection effects on the line-of-sight Doppler signal.

Hathaway, David H.; Six, N. Frank (Technical Monitor)

2002-01-01

428

Evolution & the Cesarean Section Rate  

ERIC Educational Resources Information Center

"Nothing in biology makes sense except in the light of evolution." This was the title of an essay by geneticist Theodosius Dobzhansky writing in 1973. Many causes have been given for the increased Cesarean section rate in developed countries, but biologic evolution has not been one of them. The C-section rate will continue to rise, because the…

Walsh, Joseph A.

2008-01-01

429

Swap Rates and Credit Quality  

Microsoft Academic Search

This article presents a model for valuing claims subject to default by both contracting parties, such as swaps and forwards. With counterparties of different default risk, the promised cash flows of a swap are discounted by a switching discount rate that, at any given state and time, is equal to the discount rate of the counterparty for whom the swap

Darrell Duffie; Ming Huang

1996-01-01

430

Age-Specific Divorce Rates  

Microsoft Academic Search

This paper examines the various types of divorce rates and concludes that the age-specific rate is most precise. Using data from 1970 and 1980 the teen and early twenties marriages are most at risk to divorce. Contrary to general belief, divorce does not increase during the \\

Phillip R. Kunz; J. Lynn England

1989-01-01

431

Regulation of Human Heart Rate  

NSDL National Science Digital Library

Students learn how to measure heart rate accurately. Then students design and carry out an experiment to test the effects of an activity or stimulus on heart rate, analyze and interpret the data, and present their experiments in a poster session. In this activity students learn about both cardiac physiology and experimental method.

Waldron, Ingrid

432

Rating Cattle for Physical Condition.  

National Technical Information Service (NTIS)

The amply illustrated instructional booklet explains a 7-point scale for rating the physical condition of cattle. Ratings are based on an animal's finish (degree of fatness) and fleshing (degree of natural flesh and muscle) and use the common names of the...

G. Wellington

1981-01-01

433

High Rate Digital Demodulator ASIC  

NASA Technical Reports Server (NTRS)

The architecture of High Rate (600 Mega-bits per second) Digital Demodulator (HRDD) ASIC capable of demodulating BPSK and QPSK modulated data is presented in this paper. The advantages of all-digital processing include increased flexibility and reliability with reduced reproduction costs. Conventional serial digital processing would require high processing rates necessitating a hardware implementation in other than CMOS technology such as Gallium Arsenide (GaAs) which has high cost and power requirements. It is more desirable to use CMOS technology with its lower power requirements and higher gate density. However, digital demodulation of high data rates in CMOS requires parallel algorithms to process the sampled data at a rate lower than the data rate. The parallel processing algorithms described here were developed jointly by NASA's Goddard Space Flight Center (GSFC) and the Jet Propulsion Laboratory (JPL). The resulting all-digital receiver has the capability to demodulate BPSK, QPSK, OQPSK, and DQPSK at data rates in excess of 300 Mega-bits per second (Mbps) per channel. This paper will provide an overview of the parallel architecture and features of the HRDR ASIC. In addition, this paper will provide an over-view of the implementation of the hardware architectures used to create flexibility over conventional high rate analog or hybrid receivers. This flexibility includes a wide range of data rates, modulation schemes, and operating environments. In conclusion it will be shown how this high rate digital demodulator can be used with an off-the-shelf A/D and a flexible analog front end, both of which are numerically computer controlled, to produce a very flexible, low cost high rate digital receiver.

Ghuman, Parminder; Sheikh, Salman; Koubek, Steve; Hoy, Scott; Gray, Andrew

1998-01-01

434

The Airline Quality Rating 2004  

NASA Technical Reports Server (NTRS)

The Airline Quality Rating (AQR) was developed and first announced in early 1991 as an objective method of comparing airline quality on combined multiple performance criteria. This current report, the Airline Quality Rating 2004, reflects monthly Airline Quality Rating scores for 2003. AQR scores for the calendar year 2003 are based on 15 elements in four major areas that focus on airline performance aspects important to air travel consumers. The Airline Quality Rating 2004 is a summary of month-by-month quality ratings for U.S. airlines that have at least 1 % of domestic passenger volume during 2003. Using the Airline Quality Rating system of weighted averages and monthly performance data in the areas of on-time arrivals, involuntary denied boardings, mishandled baggage, and a combination of 12 customer complaint categories, airlines comparative performance for the calendar year of 2003 is reported. This research monograph contains a brief summary of the AQR methodology, detailed data and charts that track comparative quality for domestic airline operations for the 12-month period of 2003, and industry results. Also, comparative Airline Quality Rating data for 2002 are included, where available, to provide historical perspective regarding performance quality in the industry.

Fink, Mary M. (Editor); Bowen, Brent D.; Headley, Dean E.

2004-01-01

435

The Airline Quality Rating 2003  

NASA Technical Reports Server (NTRS)

The Airline Quality Rating (AQR) was developed and first announced in early 1991 as an objective method of comparing airline quality on combined multiple performance criteria. This current report, the Airline Quality Rating 2003, reflects monthly Airline Quality Rating scores for 2002. AQR scores for the calendar year 2002 are based on 15 elements that focus on airline performance areas important to air travel consumers. The Airline Quality Rating 2003 is a summary of month-by-month quality ratings for the 10 largest U.S. airlines operating during 2002. Using the Airline Quality Rating system of weighted averages and monthly performance data in the areas of ontime arrivals, involuntary denied boardings, mishandled baggage, and a combination of 12 customer complaint categories, airlines comparative performance for the calendar year of 2002 is reported. This research monograph contains a brief summary of the AQR methodology, detailed data and charts that track comparative quality for domestic airline operations for the 12-month period of 2002, and industry average results. Also, comparative Airline Quality Rating data for 2001 are included for each airline to provide historical perspective regarding performance quality in the industry.

Bowen, Brent D.; Headley, Dean E.

2003-01-01

436

The Airline Quality Rating 2004  

NASA Technical Reports Server (NTRS)

The Airline Quality Rating (AQR) was developed and first announced in early 1991 as an objective method of comparing airline quality on combined multiple performance criteria. This current report, the Airline Quality Rating 2004, reflects monthly Airline Quality Rating scores for 2003. AQR scores far the calendar year 2003 are based on 15 elemnts in four major areas that focus on airline performance aspects important to air travel consumers. The Airline Quality Rating 2004 is a summary of month-by-month quality ratings for U.S. airlines that have at least 1% of domestic passenger volume during 2003. Using the Airline Quality Rating system of weighted averages and monthly performance data in the areas of on-time arrivals, involuntary denied boardings, mishandled baggage, and a combination of 12 customer complaint categories, airlines comparative performance for the calendar year of 2003 is reported. This research monograph contains a brief summary of the AQR methodology, detailed data and charts that track comparative quality for domestic airline operations for the 12-month period of 2003, and industry results. Also, comparative Airline Quality Rating data for 2002 are included, where available, to provide historical perspective

Bowen, Brent D.; Headley, Dean E.

2004-01-01

437

Comment on "Tank-treading and tumbling frequencies of capsules and red blood cells".  

PubMed

In a recent computational investigation, Yazdani et al. [Phys. Rev. E 83, 046305 (2011)] reported an exponential (logarithmic) dependence of the tank-treading frequency F(tt) with the viscosity ratio ? at low (moderate) viscosity ratios for erythrocytes in shear flows. We argue that the authors misinterpreted the inverse linear dependence on ? of the tank-treading frequency F(tt), as found by Wodson and Dimitrakopoulos [Biophys. J. 99, 2906 (2010)], owing to the fact that Yazdani et al. plotted their frequency-versus-? results in a log-log plot. PMID:22181550

Dimitrakopoulos, P

2011-11-01

438

Design of an algorithm for autonomous docking with a freely tumbling target  

Microsoft Academic Search

For complex unmanned docking missions, limited communication bandwidth and delays do not allow ground operators to have immediate access to all real-time state information and hence prevent them from playing an active role in the control loop. Advanced control algorithms are needed to make mission critical decisions to ensure safety of both spacecraft during close proximity maneuvers. This is especially

Simon Nolet; Edmund Kong; David W. Miller

2005-01-01

439

New membrane mimetics with galactolipids: lipid properties in fast-tumbling bicelles.  

PubMed

Galactolipids are the main structural component of plant chloroplastic (thylakoid) membranes and of blue-green algae cell membranes. The predominant lipids in this class are monogalactosyl-diacylglycerol (MGDG) and digalactosyl-diacylglycerol (DGDG). We here present a method for the preparation of bicelles that contain these galactolipids together with a characterization of the bicelles, and the lipids within the bicelles. NMR diffusion data show that up to 30% of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in a q = 0.5 DMPC/DHPC lipid matrix can be replaced with either monogalactosyl-diacylglycerol or digalactosyl-diacylglycerol and that these lipids incorporate into the bicelles. No evidence for phase separation is observed. Bicelles made with monogalactosyl-diacylglycerol are significantly larger than bicelles containing only DMPC, already with only 10% of the DMPC replaced with the galactolipid. The effect of digalactosyl-diacylglycerol on bicelle size is much smaller. These observations are likely to be correlated with the different bilayer-forming properties of the lipids. Monogalactosyl-diacylglycerol is a non-bilayer-forming lipid, while digalactosyl-diacylglycerol is a bilayer-forming lipid. Both galactolipids display extensive local motion within the bilayer, as evidenced by natural abundance carbon-13 relaxation of the lipid molecules. The sugar headgroup regions are motionally restricted and cannot be described by a model that does not take into account anisotropic reorientation of the sugar units. No significant effect of the galactolipids on DMPC dynamics was observed. Our results indicate that these bicelles may become useful as model membrane mimetic media for studies of galactolipid-protein interactions. PMID:23301930

Ye, Weihua; Liebau, Jobst; Mäler, Lena

2013-01-31

440

75 FR 35751 - Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Tumbling Creek...  

Federal Register 2010, 2011, 2012, 2013

...Creek can reach 150 cubic feet per second (cfs) during flash flood events (Aley 2010...of 0.07-150 cubic feet per second (cfs) was necessary to maintain good water quality...between 0.07 and 150 cubic feet per second (cfs), inclusive of both surface runoff...

2010-06-23

441

Quantifying the sorting efficiency of self-propelled run-and-tumble swimmers by geometrical ratchets  

NASA Astrophysics Data System (ADS)

Suitable asymmetric microstructures can be used to control the direction of motion in microorganism populations. This rectification process makes it possible to accumulate swimmers in a region of space or to sort different swimmers. Here we study numerically how the separation process depends on the specific motility strategies of the microorganisms involved. Crucial properties such as the separation efficiency and the separation time for two bacterial strains are precisely defined and evaluated. In particular, the sorting of two bacterial populations inoculated in a box consisting of a series of chambers separated by columns of asymmetric obstacles is investigated. We show how the sorting efficiency is enhanced by these obstacles and conclude that this kind of sorting can be efficiently used even when the involved populations differ only in one aspect of their swimming strategy.

Berdakin, Iván; Silhanek, Alejandro V.; Moyano Cortéz, Hernán N.; Marconi, Verónica I.; Condat, Carlos A.

2013-12-01

442

Prevalence of Father-Child Rough-and-Tumble Play and Physical Aggression in Preschool Children  

ERIC Educational Resources Information Center

Three samples of francophone subjects from Quebec (Canada) are used to establish the prevalence of parent-child RTP according to different personal, social and family variables, and to verify if children who engage in more RTP with their father exhibit less physical aggression towards other children and are more competitive without resorting to…

Paquette, Daniel; Carbonneau, Rene; Dubeau, Diane; Bigras, Marc; Tremblay, Richard E.

2003-01-01

443

Flapping, ratcheting, bursting, and tumbling: A selection of problems in fluid-body interaction dynamics  

NASA Astrophysics Data System (ADS)

The dynamics of bodies immersed in fluids is a subject of great practical and biological interest. Fluid-body interaction systems are ubiquitous, ranging from large scale applications like swimming and flying, to more recent work on micro-scale biofluiddynamics. We consider a selection of fluid-body interactions, employing numerical methods in order to deduce their salient features. This work is separated into two parts, each focusing on problems in one of two fluid regimes: the intermediate Reynolds number regime, where inertia and viscous dissipation are both important, and the low Reynolds number regime, where viscous dissipation dominates inertial effects. First, in order to understand the role of flexibility in flapping flight, we analyze a heaving wing system with passive pitching. We reproduce qualitatively the results of recent experiments: we find flapping frequencies corresponding to very efficient locomotion, a regime of under-performance compared to a rigid wing, and a bi-stable regime where the flapping wing can move horizontally in either direction. We find that a particular phase relationship corresponds to this direction reversal, and we consider the importance of various dimensionless parameters. Subsequently, we examine a fluid-ratchet mechanism that is exhibited by a shape-changing body in an oscillating fluid. We find that such a body can maintain its altitude, or even ascend, against a gravitational force. Other related phenomena are also considered. In the second section, we begin by studying a special sedimentation phenomenon in a highly viscous fluid. We find that a periodic sedimentation orbit may be experienced by two identical settling bodies. We consider numerically the stability of these orbits, and we show that free-surface effects are likely responsible for body collisions observed in a related experiment. In addition, we find that a similar orbit for three bodies is unstable, and uncover other, new types of periodic sedimentation dynamics. We conclude with a brief introduction to a novel form of locomotion at the micro-scale, a special form of locomotion involving a re-hinging body with only two links at low Reynolds number, in a variation on Purcell's three-link swimmer.

Spagnolie, Saverio E.

444

Growth rates of protein crystals.  

PubMed

Protein crystallization is important for structural biology. The rate at which a protein crystallizes is often the bottleneck in determining the protein's structure. Here, we give a physical model for the growth rates of protein crystals. Most materials crystallize faster under stronger growth conditions; however, protein crystallization slows down under the strongest conditions. Proteins require a crystallization slot of 'just right' conditions. Our model provides an explanation. Unlike simpler materials, proteins are orientationally asymmetrical. Under strong conditions, protein molecules attempt to crystallize too quickly, in wrong orientations, blocking surface sites for more productive crystal growth. The model explains the observation that increasing the net charge on a protein increases the crystal growth rate. The model predictions are in good agreement with experiments on the growth rates of tetragonal lysozyme crystals as a function of pH, salt concentration, temperature, and protein concentration. PMID:22339624

Schmit, Jeremy D; Dill, Ken

2012-03-01

445

Cooling Rates in Splat Cooling.  

National Technical Information Service (NTIS)

Calculations and experimental observations made on cooling rates during splat quenching are presented. Three possible types of cooling behavior are discussed: ideal cooling, intermediate cooling, and Newtonian cooling. The effects of splatting-process var...

R. C. Ruhl

1966-01-01

446

Raising Response Rates: What Works?  

ERIC Educational Resources Information Center

This chapter discusses the theoretical literature on why people choose to respond to a survey and reviews the latest empirical research on how survey administration and the characteristics of a survey affect response rates. (Contains 1 figure.)

Porter, Stephen R.

2004-01-01

447

TRMM Sees Chantal's Rainfall Rates  

NASA Video Gallery

On July 8, NASA's TRMM satellite saw Tropical Storm Chantal's heaviest rainfall happening at a rate of over 115.5 mm/hr. (~4.5 inches) near Chantal's center where thunderstorms reached heights of o...

448

Sun-Protective Behavior Rates  

MedlinePLUS

... Your Cover Campaign Buttons and Badges Cancer Home Sun-Protective Behavior Rates National surveys supported by CDC ... usually practice at least one of the three sun-protective behaviors (use sunscreen, wear sun-protective clothing, ...

449

Solid Propellant Burning Rate Detector.  

National Technical Information Service (NTIS)

The instrument measures accurately the burning rate of solid propellant rocket motors. This is accomplished by use of light-transmitting rods of different lengths embedded in a propellant grain and transmitting light energy during burning of the grain to ...

J. E. Fitzgerald N. C. Allen

1965-01-01

450

Vocalization of Heart Rate Variability.  

National Technical Information Service (NTIS)

In this paper we have proposed vocalization of heart rate variability (HRV) as a perceptual analysis tool. We adapted a phonation-production model to encode external signals and generate audible representations of them. HRV changes caused by induced pertu...

S. Saliu A. Birand G. Kudaiberdieva

2001-01-01