Orbiter integrated active thermal control subsystem test

NASA Technical Reports Server (NTRS)

Jaax, J. R.

1980-01-01

Integrated subsystem level testing of the systems within the orbiter active thermal chamber capable of simulating ground, orbital, and entry temperature and pressure profiles. The test article was in a closed loop configuration that included flight type and functionally simulated protions of all ATCS components for collecting, transporting, and rejecting orbiter waste heat. Specially designed independently operating equipment simulated the transient thermal input from the cabin, payload, fuel cells, freon cold plates, hydraulic system, and space environment. Test team members using data, controls, and procedures available to a flight crew controlled the operation of the ATCS. The ATCS performance met or exceeded all thermal and operational requirements for planned and contingency mission support.

Act-and-wait time-delayed feedback control of autonomous systems

NASA Astrophysics Data System (ADS)

Pyragas, Viktoras; Pyragas, Kestutis

2018-02-01

Recently an act-and-wait modification of time-delayed feedback control has been proposed for the stabilization of unstable periodic orbits in nonautonomous dynamical systems (Pyragas and Pyragas, 2016 [30]). The modification implies a periodic switching of the feedback gain and makes the closed-loop system finite-dimensional. Here we extend this modification to autonomous systems. In order to keep constant the phase difference between the controlled orbit and the act-and-wait switching function an additional small-amplitude periodic perturbation is introduced. The algorithm can stabilize periodic orbits with an odd number of real unstable Floquet exponents using a simple single-input single-output constraint control.

Lissajous Orbit Control for the Deep Space Climate Observatory Sun-Earth L1 Libration Point Mission

NASA Technical Reports Server (NTRS)

Roberts, Craig; Case, Sarah; Reagoso, John

2015-01-01

DSCOVR Lissajous Orbit sized such that orbit track never extends beyond 15 degrees from Earth-Sun line (as seen from Earth). Requiring delta-V maneuvers, control orbit to obey a Solar Exclusion Zone (SEZ) cone of half-angle 4 degrees about the Earth-Sun line. Spacecraft should never be less than 4 degrees from solar center as seen from Earth. Following Lissajous Orbit Insertion (LOI), DSCOVR should be in an opening phase that just skirts the 4-degree SEZ. Maximizes time to the point where a closing Lissajous will require avoidance maneuvers to keep it out of the SEZ. Station keeping maneuvers should take no more than 15 minutes.

Concept Design of the Payload Handling Manipulator System. [space shuttle orbiters

NASA Technical Reports Server (NTRS)

1975-01-01

The design, requirements, and interface definition of a remote manipulator system developed to handle orbiter payloads are presented. End effector design, control system concepts, and man-machine engineering are considered along with crew station requirements and closed circuit television system performance requirements.

GN/C translation and rotation control parameters for AR/C (category 2)

NASA Technical Reports Server (NTRS)

Henderson, David M.

1991-01-01

Detailed analysis of the Automatic Rendezvous and Capture problem indicate a need for three different regions of mathematical description for the GN&C algorithms: (1) multi-vehicle orbital mechanics to the rendezvous interface point, i.e., within 100 n.; (2) relative motion solutions (such as Clohessy-Wiltshire type) from the far-field to the near-field interface, i.e., within 1 nm; and (3) close proximity motion, the nearfield motion where the relative differences in the gravitational and orbit inertial accelerations can be neglected from the equations of motion. This paper defines the reference coordinate frames and control parameters necessary to model the relative motion and attitude of spacecraft in the close proximity of another space system (Region 2 and 3) during the Automatic Rendezvous and Capture phase of an orbit operation.

Closeup view of the reflective insulation protecting the Crew Compartment ...

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

Close-up view of the reflective insulation protecting the Crew Compartment bulkhead, orbiter structure and landing gear housing in the void created by the removal of the Forward Reaction Control System Module from the forward section of the Orbiter Discovery. This image was taken from the service platform in the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

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

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

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

Analyses of shuttle orbiter approach and landing conditions

NASA Technical Reports Server (NTRS)

Teper, G. L.; Dimarco, R. J.; Ashkenas, I. L.; Hoh, R. H.

1981-01-01

A study of one shuttle orbiter approach and landing conditions are summarized. Causes of observed PIO like flight deficiencies are identified and potential cures are examined. Closed loop pilot/vehicle analyses are described and path/attitude stability boundaries defined. The latter novel technique proved of great value in delineating and illustrating the basic causes of this multiloop pilot control problem. The analytical results are shown to be consistent with flight test and fixed base simulation. Conclusions are drawn relating to possible improvements of the shuttle orbiter/digital flight control system.

On the shape and orientation control of an orbiting shallow spherical shell structure

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Reddy, A. S. S. R.

1982-01-01

The dynamics of orbiting shallow flexible spherical shell structures under the influence of control actuators was studied. Control laws are developed to provide both attitude and shape control of the structure. The elastic modal frequencies for the fundamental and lower modes are closely grouped due to the effect of the shell curvature. The shell is gravity stabilized by a spring loaded dumbbell type damper attached at its apex. Control laws are developed based on the pole clustering techniques. Savings in fuel consumption can be realized by using the hybrid shell dumbbell system together with point actuators. It is indicated that instability may result by not including the orbital and first order gravity gradient effects in the plant prior to control law design.

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

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

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

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

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

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

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

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

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

Macroinformational analysis of conditions for controllability of space-vehicle orbit

NASA Astrophysics Data System (ADS)

Glazov, B. I.

2011-12-01

The general axiomatics of information measures for the macro analysis of relations of an information-cybernetic system in the control is introduced. The general structure of a semantically marked graph of open and closed relations of an information-cybernetic system between the participants in the environment, as well as thenecessary axiomatic and technological information-cybernetic system conditions of controllability and observability of objects, for the case of a space vehicle in orbit, are justified.

Shuttle/tethered satellite system conceptual design study

NASA Technical Reports Server (NTRS)

1976-01-01

A closed-loop control system was added to the tether reel which improves control over the tethered satellite. In addition to increasing the stability of the tethered satellite along local vertical, this control system is used for deployment and retrieval of tethered satellites. This conceptual design study describes a tether system for suspending a science payload at an altitude of 120 km from space shuttle orbiter flying at an altitude of 200 km. In addition to the hardware conceptual designs, various aspects concerning Orbiter accommodations are discussed.

Angles-only relative orbit determination in low earth orbit

NASA Astrophysics Data System (ADS)

Ardaens, Jean-Sébastien; Gaias, Gabriella

2018-06-01

The paper provides an overview of the angles-only relative orbit determination activities conducted to support the Autonomous Vision Approach Navigation and Target Identification (AVANTI) experiment. This in-orbit endeavor was carried out by the German Space Operations Center (DLR/GSOC) in autumn 2016 to demonstrate the capability to perform spaceborne autonomous close-proximity operations using solely line-of-sight measurements. The images collected onboard have been reprocessed by an independent on-ground facility for precise relative orbit determination, which served as ultimate instance to monitor the formation safety and to characterize the onboard navigation and control performances. During two months, several rendezvous have been executed, generating a valuable collection of images taken at distances ranging from 50 km to only 50 m. Despite challenging experimental conditions characterized by a poor visibility and strong orbit perturbations, angles-only relative positioning products could be continuously derived throughout the whole experiment timeline, promising accuracy at the meter level during the close approaches. The results presented in the paper are complemented with former angles-only experience gained with the PRISMA satellites to better highlight the specificities induced by different orbits and satellite designs.

Analyses of Shuttle Orbiter approach and landing

NASA Technical Reports Server (NTRS)

Ashkenas, I. L.; Hoh, R. H.; Teper, G. L.

1982-01-01

A study of the Shuttle Orbiter approach and landing conditions is summarized. The causes of observed PIO-like flight deficiencies are listed, and possible corrective measures are examined. Closed-loop pilot/vehicle analyses are described, and a description is given of path-attitude stability boundaries. The latter novel approach is found to be of great value in delineating and illustrating the basic causes of this multiloop pilot control problem. It is shown that the analytical results are consistent with flight test and fixed-base simulation. Conclusions are drawn concerning possible improvements in the Shuttle Orbiter/Digital Flight Control System.

APPARATUS FOR CONTROL OF HIGH-ENERGY ACCELERATORS

DOEpatents

Heard, H.G.

1961-10-24

A particle beam positioning control for a synchrotron or the like is described. The control includes means for selectively impressing a sinusoidal perturbation upon the rising voltage utilized to sweep the frequency of the f-m oscillator which is conventionally coupled to the accelerating electrode of a synchrotron. The perturbation produces a variation in the normal rate of change of frequency of the accelerating voltage applied to the accelerating electrode, resulting in an expansion or contraction of the particle beam orbit diameter during the perturbation. The beam may thus be controlled such that a portion strikes a target positioned close to the expanded or contracted orbit diameter and returns to the original orbit for further acceleration to the final energy. (AEC)

Simple control laws for low-thrust orbit transfers

NASA Technical Reports Server (NTRS)

Petropoulos, Anastassios E.

2003-01-01

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

Analytical solutions to optimal underactuated spacecraft formation reconfiguration

NASA Astrophysics Data System (ADS)

Huang, Xu; Yan, Ye; Zhou, Yang

2015-11-01

Underactuated systems can generally be defined as systems with fewer number of control inputs than that of the degrees of freedom to be controlled. In this paper, analytical solutions to optimal underactuated spacecraft formation reconfiguration without either the radial or the in-track control are derived. By using a linear dynamical model of underactuated spacecraft formation in circular orbits, controllability analysis is conducted for either underactuated case. Indirect optimization methods based on the minimum principle are then introduced to generate analytical solutions to optimal open-loop underactuated reconfiguration problems. Both fixed and free final conditions constraints are considered for either underactuated case and comparisons between these two final conditions indicate that the optimal control strategies with free final conditions require less control efforts than those with the fixed ones. Meanwhile, closed-loop adaptive sliding mode controllers for both underactuated cases are designed to guarantee optimal trajectory tracking in the presence of unmatched external perturbations, linearization errors, and system uncertainties. The adaptation laws are designed via a Lyapunov-based method to ensure the overall stability of the closed-loop system. The explicit expressions of the terminal convergent regions of each system states have also been obtained. Numerical simulations demonstrate the validity and feasibility of the proposed open-loop and closed-loop control schemes for optimal underactuated spacecraft formation reconfiguration in circular orbits.

Design and implementation of satellite formations and constellations

NASA Technical Reports Server (NTRS)

Folta, David; Newman, Lauri Kraft; Quinn, David

1998-01-01

The direction to develop small low cost spacecraft has led many scientists to recognize the advantage of flying spacecraft in constellations and formations to achieve the correlated instrument measurements formerly possible only by flying many instruments on a single large platform. Yet, constellations and formation flying impose additional complications on orbit selection and orbit maintenance, especially when each spacecraft has its own orbit or science requirements. The purpose of this paper is to develop an operational control method for maintenance of these missions. Examples will be taken from the Earth Observing-1 (EO-1) spacecraft that is part of the New Millennium Program (NMP) and from proposed Earth System Science Program Office (ESSPO) constellations. Results can be used to determine the appropriateness of constellations and formation flying for a particular case as well as the operational impacts. Applications to the ESSPO and NMP are highly considered in analysis and applications. After constellation and formation analysis is completed, implementation of a maneuver maintenance strategy becomes the driver. Advances in technology and automation by GSFC's Guidance, Navigation, and Control Center allow more of the burden of the orbit selection and maneuver maintenance to be automated and ultimately placed onboard the spacecraft, mitigating most of the associated operational concerns. This paper presents the GSFC closed-loop control method to fly in either constellations or formations through the use of an autonomous closed loop three-axis navigation control and innovative orbit maintenance support. Simulation results using AutoCon(TM) and FreeFlyer(TM) with various fidelity levels of modeling and algorithms are presented.

Design and Implementation of Satellite Formations and Constellations

NASA Technical Reports Server (NTRS)

Folta, David; Newman, Lauri Kraft; Quinn, David

1998-01-01

The direction to develop small low cost spacecraft has led many scientists to recognize the advantage of flying spacecraft in constellations and formations to achieve the correlated instrument measurements formerly possible only by flying many instruments on a single large platform. Yet, constellations and formation flying impose additional complications on orbit selection and orbit maintenance, especially when each spacecraft has its own orbit or science requirements. The purpose of this paper is to develop an operational control method for maintenance of these missions. Examples will be taken from the Earth Observing-1 (EO-1) spacecraft that is part of the New Millennium Program (NMP) and from proposed Earth System Science Program Office (ESSPO) constellations. Results can be used to determine the appropriateness of constellations and formation flying for a particular case as well as the operational impacts. Applications to the ESSPO and NMP are highly considered in analysis and applications. After constellation and formation analysis is completed, implementation of a maneuver maintenance strategy becomes the driver. Advances in technology and automation by GSFC's Guidance, Navigation, and Control Center allow more of the burden of the orbit selection and maneuver maintenance to be automated and ultimately placed onboard the spacecraft, mitigating most of the associated operational concerns. This paper presents the GSFC closed-loop control method to fly in either constellations or formations through the use of an autonomous closed loop three-axis navigation control and innovative orbit maintenance support. Simulation results using AutoCon(Trademark) and FreeFlyer(Trademark) with various fidelity levels of modeling and algorithms are presented.

Compensator-based 6-DOF control for probe asteroid-orbital-frame hovering with actuator limitations

NASA Astrophysics Data System (ADS)

Liu, Xiaosong; Zhang, Peng; Liu, Keping; Li, Yuanchun

2016-05-01

This paper is concerned with 6-DOF control of a probe hovering in the orbital frame of an asteroid. Considering the requirements of the scientific instruments pointing direction and orbital position in practical missions, the coordinate control of relative attitude and orbit between the probe and target asteroid is imperative. A 6-DOF dynamic equation describing the relative translational and rotational motion of a probe in the asteroid's orbital frame is derived, taking the irregular gravitation, model and parameter uncertainties and external disturbances into account. An adaptive sliding mode controller is employed to guarantee the convergence of the state error, where the adaptation law is used to estimate the unknown upper bound of system uncertainty. Then the controller is improved to deal with the practical problem of actuator limitations by introducing a RBF neural network compensator, which is used to approximate the difference between the actual control with magnitude constraint and the designed nominal control law. The closed-loop system is proved to be asymptotically stable through the Lyapunov stability analysis. Numerical simulations are performed to compare the performances of the preceding designed control laws. Simulation results demonstrate the validity of the control scheme using the compensator-based adaptive sliding mode control law in the presence of actuator limitations, system uncertainty and external disturbance.

Closeup view of the Pilot's Seat on the Flight Deck ...

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

Close-up view of the Pilot's Seat on the Flight Deck of the Orbiter Discovery. It appears the Orbiter is in the roll out / launch pad configuration. A protective cover is over the Rotational Hand Controller to protect it during the pilot's ingress. Control panels R1 and R2 are prominent in this view. Panel R1 has switches for control and maintenance of on-board cryogenics for the fuel cells among other functions and panel R2 has switches and controls for the Auxiliary Power Units, ET umbilical doors as well as other operational controls. Note the portable fire extinguisher in the lower right corner of the image. This photograph was taken at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Integration of Libration Point Orbit Dynamics into a Universal 3-D Autonomous Formation Flying Algorithm

NASA Technical Reports Server (NTRS)

Folta, David; Bauer, Frank H. (Technical Monitor)

2001-01-01

The autonomous formation flying control algorithm developed by the Goddard Space Flight Center (GSFC) for the New Millennium Program (NMP) Earth Observing-1 (EO-1) mission is investigated for applicability to libration point orbit formations. In the EO-1 formation-flying algorithm, control is accomplished via linearization about a reference transfer orbit with a state transition matrix (STM) computed from state inputs. The effect of libration point orbit dynamics on this algorithm architecture is explored via computation of STMs using the flight proven code, a monodromy matrix developed from a N-body model of a libration orbit, and a standard STM developed from the gravitational and coriolis effects as measured at the libration point. A comparison of formation flying Delta-Vs calculated from these methods is made to a standard linear quadratic regulator (LQR) method. The universal 3-D approach is optimal in the sense that it can be accommodated as an open-loop or closed-loop control using only state information.

Closeup oblique view of the forward and starboard sides of ...

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

Close-up oblique view of the forward and starboard sides of the Orbiter Discovery in the Vehicle Assembly Building at NASA's Kennedy Space Center. The view shows the void created by the removal of the Forward Reaction Control System Module. The void has a clear flexible covering to maintain positive pressure in the void to minimize foreign object contamination possibilities in the orbiter. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Closeup view of the forward and starboard sides of the ...

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

Close-up view of the forward and starboard sides of the Orbiter Discovery in the Vehicle Assembly Building at NASA's Kennedy Space Center. The view shows the void created by the removal of the Forward Reaction Control System Module. The void has a clear flexible covering to maintain positive pressure in the void to minimize foreign object contamination possibilities in the orbiter. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

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

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

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

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

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

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

Viking Orbiter 1975 articulation control subsystem design analysis

NASA Technical Reports Server (NTRS)

Horiuchi, H. H.; Vallas, L. J.

1973-01-01

The articulation control subsystem, developed for the Viking Orbiter 1975 spacecraft, is a digital, multiplexed, closed-loop servo system used to control the pointing and positioning of the science scan platform and the high-gain communication antenna, and to position the solar-energy controller louver blades for the thermal control of the propellant tanks. The development, design, and anlaysis of the subsystem is preliminary. The subsystem consists of a block-redundant control electronics multiplexed among eight control actuators. Each electronics block is capable of operating either individually or simultaneously with the second block. This provides the subsystem the capability of simultaneous two-actuator control or a single actuator control with the second block in a stand-by redundant mode. The result of the preliminary design and analysis indicates that the subsystem will perform satisfactorily in the Viking Orbiter 1975 mission. Some of the parameter values used, particularly those in the subsystem dynamics and the error estimates, are preliminary and the results will be updated as more accurate parameter values become available.

Overload control of artificial gravity facility using spinning tether system for high eccentricity transfer orbits

NASA Astrophysics Data System (ADS)

Gou, Xing-wang; Li, Ai-jun; Tian, Hao-chang; Wang, Chang-qing; Lu, Hong-shi

2018-06-01

As the major part of space life supporting systems, artificial gravity requires further study before it becomes mature. Spinning tether system is a good alternative solution to provide artificial gravity for the whole spacecraft other than additional devices, and its longer tether length could significantly reduce spinning velocity and thus enhance comfortability. An approximated overload-based feedback method is proposed to provide estimated spinning velocity signals for controller, so that gravity level could be accurately controlled without complicated GPS modules. System behavior in high eccentricity transfer orbits is also studied to give a complete knowledge of the spinning stabilities. The application range of the proposed method is studied in various orbit cases and spinning velocities, indicating that it is accurate and reliable for most of the mission phases especially for the final constant gravity level phase. In order to provide stable gravity level for transfer orbit missions, a sliding mode controller based on estimated angular signals is designed for closed-loop control. Numerical results indicate that the combination of overload-based feedback and sliding mode controller could satisfy most of the long-term artificial gravity missions. It is capable of forming flexible gravity environment in relatively good accuracy even in the lowest possible orbital radiuses and high eccentricity orbits of crewed space missions. The proposed scheme provides an effective tether solution for the artificial gravity construction in interstellar travel.

Early Mission Maneuver Operations for the Deep Space Climate Observatory

NASA Technical Reports Server (NTRS)

Roberts, Craig; Case, Sara; Reagoso, John

2015-01-01

DSCOVR Lissajous Orbit sized such that orbit track never extends beyond 15 degrees from Earth-Sun line (as seen from Earth). Requiring delta-V maneuvers, control orbit to obey a Solar Exclusion Zone (SEZ) cone of half-angle 4 degrees about the Earth-Sun line. Spacecraft should never be less than 4 degrees from solar center as seen from Earth. Following Lissajous Orbit Insertion (LOI), DSCOVR should be in an opening phase that just skirts the 4-degree SEZ. Maximizes time to the point where a closing Lissajous will require avoidance maneuvers to keep it out of the SEZ. Station keeping maneuvers should take no more than 15 minutes

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

NASA Technical Reports Server (NTRS)

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

1980-01-01

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

Physical Meaning of Virtual Kohn-Sham Orbitals and Orbital Energies: An Ideal Basis for the Description of Molecular Excitations.

PubMed

van Meer, R; Gritsenko, O V; Baerends, E J

2014-10-14

In recent years, several benchmark studies on the performance of large sets of functionals in time-dependent density functional theory (TDDFT) calculations of excitation energies have been performed. The tested functionals do not approximate exact Kohn-Sham orbitals and orbital energies closely. We highlight the advantages of (close to) exact Kohn-Sham orbitals and orbital energies for a simple description, very often as just a single orbital-to-orbital transition, of molecular excitations. Benchmark calculations are performed for the statistical average of orbital potentials (SAOP) functional for the potential [J. Chem. Phys. 2000, 112, 1344; 2001, 114, 652], which approximates the true Kohn-Sham potential much better than LDA, GGA, mGGA, and hybrid potentials do. An accurate Kohn-Sham potential does not only perform satisfactorily for calculated vertical excitation energies of both valence and Rydberg transitions but also exhibits appealing properties of the KS orbitals including occupied orbital energies close to ionization energies, virtual-occupied orbital energy gaps very close to excitation energies, realistic shapes of virtual orbitals, leading to straightforward interpretation of most excitations as single orbital transitions. We stress that such advantages are completely lost in time-dependent Hartree-Fock and partly in hybrid approaches. Many excitations and excitation energies calculated with local density, generalized gradient, and hybrid functionals are spurious. There is, with an accurate KS, or even the LDA or GGA potentials, nothing problematic about the "band gap" in molecules: the HOMO-LUMO gap is close to the first excitation energy (the optical gap).

The Precession Index, A Nonlinear Energy Balance Model, And Seversmith Psychroterms

NASA Technical Reports Server (NTRS)

Rubincam, David Parry

2004-01-01

An important component of Milankovitch's astronomical theory of climate change is the precession index. The precession index, along with the Earth's tilt and orbital eccentricity, are believed to be the major controlling factors of climate change in the last few million years. The precession index is e sin omega(sub s) where e is the Earth's orbital eccentricity and omega(sub s) measures how close the Sun is to the Earth at midsummer. When omega(sub s) = 90deg the Sun is close to the Earth during northern summer, and at 270deg it is far from the Earth during northern summer. The precession index varies with time, because both the eccentricity e and the parameter omega(sub s) are constantly changing due to disturbances in the Earth's orbit by other planets, and due to the precession of the Earth, The change is largely periodic, with a period of about 23,000 years.

Fuzzy logic techniques for rendezvous and docking of two geostationary satellites

NASA Technical Reports Server (NTRS)

Ortega, Guillermo

1995-01-01

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.

Mars NanoOrbiter: A CubeSat for Mars System Science

NASA Astrophysics Data System (ADS)

Ehlmann, Bethany; Klesh, Andrew; Alsedairy, Talal

2017-10-01

The Mars NanoOrbiter mission consists of two identical 12U spacecraft, launched simultaneously as secondary payloads on a larger planetary mission launch, and deployed to Earth-escape, as early as with Mars 2020. The nominal mission will last for 1 year, during which time the craft will independently navigate to Mars, enter into elliptical orbit, and achieve close flybys of Phobos and Deimos, obtaining unprecedented coverage of each moon. The craft will additionally provide high temporal resolution data of Mars clouds and atmospheric phenomena at multiple times of day. Two spacecraft provide redundancy to reduce the risk in meeting the science objectives at the Mars moons and enhanced coverage of the dynamic Mars atmosphere. This technology is enabled by recent advances in CubeSat propulsion technology, attitude control systems, guidance, navigation and control. NanoOrbiter builds directly on the systems heritage of the MarCO mission, scheduled to launch with the 2018 Discovery mission Insight.

Investigation of the McDonnell-Douglas orbiter and booster shuttle models in proximity at Mach numbers 2.0 to 6.0. Volume 7: Proximity data at Mach 4 and 6, interference free and launch vehicle data

NASA Technical Reports Server (NTRS)

Trimmer, L. L.; Love, D. A.; Decker, J. P.; Blackwell, K. L.; Strike, W. T.; Rampy, J. M.

1972-01-01

Aerodynamic data obtained from a space shuttle abort stage separation wind tunnel test are presented. The .00556 scale models of the orbiter and booster configuration were tested in close proximity using dual balances during the time period of April 21 to April 27 1971. Data were obtained for both booster and orbiter over an angle of attack range from -10 to 10 deg for zero degree sideslip angle. The models were tested at several relative incidence angles and separation distances and power conditions. Plug nozzles utilizing air were used to simulate booster and orbiter plumes at various altitudes along a nominal ascent trajectory. Powered conditions were 100, 50, 25 and 0 percent of full power for the orbiter and 100, 50 and 0 percent of full power for the booster. Pitch control effectiveness data were obtained for both booster and orbiter with power on and off. In addition, launch vehicle data with and without booster power were obtained utilizing a single balance in the booster model. Data were also obtained with the booster canard off in close proximity and for the launch configuration.

Cardiac arrhythmias and degradation into chaotic behavior prevention using feedback control

NASA Astrophysics Data System (ADS)

Uzelac, Ilija; Sidorov, Veniamin; Wikswo, John; Gray, Richard

2012-02-01

During normal heart rhythm, cardiac cells behave as a set of oscillators with a distribution of phases but with the same frequency. The heart as a dynamical system in a phase space representation can be modeled as a set of oscillators that have closed overlapping orbits with the same period. These orbits are not stable and in the case of disruption of the cardiac rhythm, such as due to premature beats, the system will have a tendency to leave its periodic unstable orbits. If these orbits become attracted to phase singularities, their disruption may lead to chaotic behavior, which appears as a life-threating ventricular fibrillation. By using closed-loop feedback in the form of an adjustable defibrillation shock, any drift from orbits corresponding to the normal rhythm can be corrected by forcing the system to maintain its orbits. The delay through the feedback network coincides with the period of normal heart beats. To implement this approach we developed a 1 kW arbitrary waveform voltage-to-current converter with a 1 kHz bandwidth driven by a photodiode system that records an optical electrocardiogram and provides a feedback signal in real time. Our goal is to determine whether our novel method to defibrillate the heart will require much lower energies than are currently utilized in single shock defibrillators.

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

PubMed

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

2012-08-03

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

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

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

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

NASA/MSFC ground experiment for large space structure control verification

NASA Technical Reports Server (NTRS)

Waites, H. B.; Seltzer, S. M.; Tollison, D. K.

1984-01-01

Marshall Space Flight Center has developed a facility in which closed loop control of Large Space Structures (LSS) can be demonstrated and verified. The main objective of the facility is to verify LSS control system techniques so that on orbit performance can be ensured. The facility consists of an LSS test article which is connected to a payload mounting system that provides control torque commands. It is attached to a base excitation system which will simulate disturbances most likely to occur for Orbiter and DOD payloads. A control computer will contain the calibration software, the reference system, the alignment procedures, the telemetry software, and the control algorithms. The total system will be suspended in such a fashion that LSS test article has the characteristics common to all LSS.

CNES Strategic Plan for Space Traffic Control

NASA Astrophysics Data System (ADS)

Alby, Fernand

2013-09-01

The increasing orbital debris population represents a growing risk to operational satellites on-orbit and also to populations and properties on-ground. Today available space surveillance data allow a better implementation of protection activities which are now part of operational services. The overall frame of these activities at CNES is given by a strategic plan defining the long term views and the corresponding activities to be carried out during the next years. This plan, established in close cooperation with French Defence organizations, includes, among others, two operational space traffic control activities: prevention of on-orbit collisions and atmospheric re-entries predictions.This paper presents first the national organization relative to these activities together with the internal CNES process starting from a high level roadmap, up to a detailed action plan. This plan contains operational activities and supporting studies and models development.The content of this plan is given with a focus on operational activities dealing with space traffic control.

LETTER TO THE EDITOR: Quantum manifestations of closed orbits in the photoexcitation scaled spectrum of the hydrogen atom in crossed fields

NASA Astrophysics Data System (ADS)

Rao, Jianguo; Delande, D.; Taylor, K. T.

2001-06-01

The scaled photoexcitation spectrum of the hydrogen atom in crossed electric and magnetic fields has been obtained by means of accurate quantum mechanical calculation using a new algorithm. Closed orbits in the corresponding classical system have also been obtained, using a new, efficient and practical searching procedure. Two new classes of closed orbit have been identified. Fourier transforming each photoexcitation quantum spectrum to yield a plot against scaled action has allowed direct comparison between peaks in such plots and the scaled action values of closed orbits. Excellent agreement has been found with all peaks assigned.

Proceedings from the 2nd International Symposium on Formation Flying Missions and Technologies

NASA Technical Reports Server (NTRS)

2004-01-01

Topics discussed include: The Stellar Imager (SI) "Vision Mission"; First Formation Flying Demonstration Mission Including on Flight Nulling; Formation Flying X-ray Telescope in L2 Orbit; SPECS: The Kilometer-baseline Far-IR Interferometer in NASA's Space Science Roadmap Presentation; A Tight Formation for Along-track SAR Interferometry; Realization of the Solar Power Satellite using the Formation Flying Solar Reflector; SIMBOL-X : Formation Flying for High-Energy Astrophysics; High Precision Optical Metrology for DARWIN; Close Formation Flight of Micro-Satellites for SAR Interferometry; Station-Keeping Requirements for Astronomical Imaging with Constellations of Free-Flying Collectors; Closed-Loop Control of Formation Flying Satellites; Formation Control for the MAXIM Mission; Precision Formation Keeping at L2 Using the Autonomous Formation Flying Sensor; Robust Control of Multiple Spacecraft Formation Flying; Virtual Rigid Body (VRB) Satellite Formation Control: Stable Mode-Switching and Cross-Coupling; Electromagnetic Formation Flight (EMFF) System Design, Mission Capabilities, and Testbed Development; Navigation Algorithms for Formation Flying Missions; Use of Formation Flying Small Satellites Incorporating OISL's in a Tandem Cluster Mission; Semimajor Axis Estimation Strategies; Relative Attitude Determination of Earth Orbiting Formations Using GPS Receivers; Analysis of Formation Flying in Eccentric Orbits Using Linearized Equations of Relative Motion; Conservative Analytical Collision Probabilities for Orbital Formation Flying; Equations of Motion and Stability of Two Spacecraft in Formation at the Earth/Moon Triangular Libration Points; Formations Near the Libration Points: Design Strategies Using Natural and Non-Natural Ares; An Overview of the Formation and Attitude Control System for the Terrestrial Planet Finder Formation Flying Interferometer; GVE-Based Dynamics and Control for Formation Flying Spacecraft; GNC System Design for a New Concept of X-Ray Distributed Telescope; GNC System for the Deployment and Fine Control of the DARWIN Free-Flying Interferometer; Formation Algorithm and Simulation Testbed; and PLATFORM: A Formation Flying, RvD and Robotic Validation Test-bench.

Optimal spacecraft formation establishment and reconfiguration propelled by the geomagnetic Lorentz force

NASA Astrophysics Data System (ADS)

Huang, Xu; Yan, Ye; Zhou, Yang

2014-12-01

The Lorentz force acting on an electrostatically charged spacecraft as it moves through the planetary magnetic field could be utilized as propellantless electromagnetic propulsion for orbital maneuvering, such as spacecraft formation establishment and formation reconfiguration. By assuming that the Earth's magnetic field could be modeled as a tilted dipole located at the center of Earth that corotates with Earth, a dynamical model that describes the relative orbital motion of Lorentz spacecraft is developed. Based on the proposed dynamical model, the energy-optimal open-loop trajectories of control inputs, namely, the required specific charges of Lorentz spacecraft, for Lorentz-propelled spacecraft formation establishment or reconfiguration problems with both fixed and free final conditions constraints are derived via Gauss pseudospectral method. The effect of the magnetic dipole tilt angle on the optimal control inputs and the relative transfer trajectories for formation establishment or reconfiguration is also investigated by comparisons with the results derived from a nontilted dipole model. Furthermore, a closed-loop integral sliding mode controller is designed to guarantee the trajectory tracking in the presence of external disturbances and modeling errors. The stability of the closed-loop system is proved by a Lyapunov-based approach. Numerical simulations are presented to verify the validity of the proposed open-loop control methods and demonstrate the performance of the closed-loop controller. Also, the results indicate the dipole tilt angle should be considered when designing control strategies for Lorentz-propelled spacecraft formation establishment or reconfiguration.

Closed Loop System Identification with Genetic Algorithms

NASA Technical Reports Server (NTRS)

Whorton, Mark S.

2004-01-01

High performance control design for a flexible space structure is challenging since high fidelity plant models are di.cult to obtain a priori. Uncertainty in the control design models typically require a very robust, low performance control design which must be tuned on-orbit to achieve the required performance. Closed loop system identi.cation is often required to obtain a multivariable open loop plant model based on closed-loop response data. In order to provide an accurate initial plant model to guarantee convergence for standard local optimization methods, this paper presents a global parameter optimization method using genetic algorithms. A minimal representation of the state space dynamics is employed to mitigate the non-uniqueness and over-parameterization of general state space realizations. This control-relevant system identi.cation procedure stresses the joint nature of the system identi.cation and control design problem by seeking to obtain a model that minimizes the di.erence between the predicted and actual closed-loop performance.

Current Status of the Beam Position Monitoring System at TLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuo, C. H.; Hu, K. H.; Chen, Jenny

2006-11-20

The beam position monitoring system is an important part of a synchrotron light source that supports its routine operation and studies of beam physics. The Taiwan light source is equipped with 59 BPMs. Highly precise closed orbits are measured by multiplexing BPMs. Data are acquired using multi-channel 16-bit ADC modules. Orbit data are sampled every millisecond. Fast orbit data are shared in a reflective memory network to support fast orbit feedback. Averaged data were updated to control database at a rate of 10 Hz. A few new generation digital BPMs were tested to evaluate their performance and functionality. This reportmore » summarizes the system structure, the software environment and the preliminary beam test of the BPM system.« less

Current Status of the Beam Position Monitoring System at TLS

NASA Astrophysics Data System (ADS)

Kuo, C. H.; Hu, K. H.; Chen, Jenny; Lee, Demi; Wang, C. J.; Hsu, S. Y.; Hsu, K. T.

2006-11-01

The beam position monitoring system is an important part of a synchrotron light source that supports its routine operation and studies of beam physics. The Taiwan light source is equipped with 59 BPMs. Highly precise closed orbits are measured by multiplexing BPMs. Data are acquired using multi-channel 16-bit ADC modules. Orbit data are sampled every millisecond. Fast orbit data are shared in a reflective memory network to support fast orbit feedback. Averaged data were updated to control database at a rate of 10 Hz. A few new generation digital BPMs were tested to evaluate their performance and functionality. This report summarizes the system structure, the software environment and the preliminary beam test of the BPM system.

Space shuttle flying qualities and criteria assessment

NASA Technical Reports Server (NTRS)

Myers, T. T.; Johnston, D. E.; Mcruer, Duane T.

1987-01-01

Work accomplished under a series of study tasks for the Flying Qualities and Flight Control Systems Design Criteria Experiment (OFQ) of the Shuttle Orbiter Experiments Program (OEX) is summarized. The tasks involved review of applicability of existing flying quality and flight control system specification and criteria for the Shuttle; identification of potentially crucial flying quality deficiencies; dynamic modeling of the Shuttle Orbiter pilot/vehicle system in the terminal flight phases; devising a nonintrusive experimental program for extraction and identification of vehicle dynamics, pilot control strategy, and approach and landing performance metrics, and preparation of an OEX approach to produce a data archive and optimize use of the data to develop flying qualities for future space shuttle craft in general. Analytic modeling of the Orbiter's unconventional closed-loop dynamics in landing, modeling pilot control strategies, verification of vehicle dynamics and pilot control strategy from flight data, review of various existent or proposed aircraft flying quality parameters and criteria in comparison with the unique dynamic characteristics and control aspects of the Shuttle in landing; and finally a summary of conclusions and recommendations for developing flying quality criteria and design guides for future Shuttle craft.

Stability of Multi-Planet Systems Orbiting in the Alpha Centauri AB System

NASA Astrophysics Data System (ADS)

Lissauer, Jack

2018-04-01

We evaluate how closely-spaced planetary orbits in multiple planet systems can be and still survive for billion-year timescales within the alpha Centauri AB system. Although individual planets on nearly circular, coplanar orbits can survive throughout the habitable zones of both stars, perturbations from the companion star imply that the spacing of such planets in multi-planet systems must be significantly larger than the spacing of similar systems orbiting single stars in order to be long-lived. Because the binary companion induces a forced eccentricity upon circumstellar planets, stable orbits with small initial eccentricities aligned with the binary orbit are possible to slightly larger initial semimajor axes than are initially circular orbits. Initial eccentricities close to the appropriate forced eccentricity can have a much larger affect on how closely planetary orbits can be spaced, on how many planets may remain in the habitable zones, although the required spacing remains significantly higher than for planets orbiting single stars.

First Results from a Hardware-in-the-Loop Demonstration of Closed-Loop Autonomous Formation Flying

NASA Technical Reports Server (NTRS)

Gill, E.; Naasz, Bo; Ebinuma, T.

2003-01-01

A closed-loop system for the demonstration of autonomous satellite formation flying technologies using hardware-in-the-loop has been developed. Making use of a GPS signal simulator with a dual radio frequency outlet, the system includes two GPS space receivers as well as a powerful onboard navigation processor dedicated to the GPS-based guidance, navigation, and control of a satellite formation in real-time. The closed-loop system allows realistic simulations of autonomous formation flying scenarios, enabling research in the fields of tracking and orbit control strategies for a wide range of applications. The autonomous closed-loop formation acquisition and keeping strategy is based on Lyapunov's direct control method as applied to the standard set of Keplerian elements. This approach not only assures global and asymptotic stability of the control but also maintains valuable physical insight into the applied control vectors. Furthermore, the approach can account for system uncertainties and effectively avoids a computationally expensive solution of the two point boundary problem, which renders the concept particularly attractive for implementation in onboard processors. A guidance law has been developed which strictly separates the relative from the absolute motion, thus avoiding the numerical integration of a target trajectory in the onboard processor. Moreover, upon using precise kinematic relative GPS solutions, a dynamical modeling or filtering is avoided which provides for an efficient implementation of the process on an onboard processor. A sample formation flying scenario has been created aiming at the autonomous transition of a Low Earth Orbit satellite formation from an initial along-track separation of 800 m to a target distance of 100 m. Assuming a low-thrust actuator which may be accommodated on a small satellite, a typical control accuracy of less than 5 m has been achieved which proves the applicability of autonomous formation flying techniques to formations of satellites as close as 50 m.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagasawa, M.; Ida, S., E-mail: nagasawa.m.ad@m.titech.ac.jp

2011-12-01

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

A closed-loop photon beam control study for the Advanced Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Portmann, G.; Bengtsson, J.

1993-05-01

The third generation Advanced Light Source (ALS) will produce extremely bright photon beams using undulators and wigglers. In order to position the photon beams accurate to the micron level, a closed-loop feedback system is being developed. Using photon position monitors and dipole corrector magnets, a closed-loop system can automatically compensate for modeling uncertainties and exogenous disturbances. The following paper will present a dynamics model for the perturbations of the closed orbit of the electron beam in the ALS storage ring including the vacuum chamber magnetic field penetration effects. Using this reference model, two closed-loop feedback algorithms will be compared --more » a classical PI controller and a two degree-of-freedom approach. The two degree-of-freedom method provides superior disturbance rejection while maintaining the desired performance goals. Both methods will address the need to gain schedule the controller due to the time varying dynamics introduced by changing field strengths when scanning the insertion devices.« less

A simple method to design non-collision relative orbits for close spacecraft formation flying

NASA Astrophysics Data System (ADS)

Jiang, Wei; Li, JunFeng; Jiang, FangHua; Bernelli-Zazzera, Franco

2018-05-01

A set of linearized relative motion equations of spacecraft flying on unperturbed elliptical orbits are specialized for particular cases, where the leader orbit is circular or equatorial. Based on these extended equations, we are able to analyze the relative motion regulation between a pair of spacecraft flying on arbitrary unperturbed orbits with the same semi-major axis in close formation. Given the initial orbital elements of the leader, this paper presents a simple way to design initial relative orbital elements of close spacecraft with the same semi-major axis, thus preventing collision under non-perturbed conditions. Considering the mean influence of J 2 perturbation, namely secular J 2 perturbation, we derive the mean derivatives of orbital element differences, and then expand them to first order. Thus the first order expansion of orbital element differences can be added to the relative motion equations for further analysis. For a pair of spacecraft that will never collide under non-perturbed situations, we present a simple method to determine whether a collision will occur when J 2 perturbation is considered. Examples are given to prove the validity of the extended relative motion equations and to illustrate how the methods presented can be used. The simple method for designing initial relative orbital elements proposed here could be helpful to the preliminary design of the relative orbital elements between spacecraft in a close formation, when collision avoidance is necessary.

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

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

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

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

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

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

The development of optimal control laws for orbiting tethered platform systems

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Woodard, S.; Juang, J.-N.

1986-01-01

A mathematical model of the open and closed loop in-orbit plane dynamics of a space platform-tethered-subsatellite system is developed. The system consists of a rigid platform from which an (assumed massless) tether is deploying (retrieving) a subsatellite from an attachment point which is, in general, offset from the platform's mass center. A Lagrangian formulation yields equations describing platform pitch, subsatellite tether-line swing, and varying tether length motions. These equations are linearized about the nominal station keeping motion. Control can be provided by both modulation of the tether tension level and by a momentum type platform-mounted device; system controllability depends on the presence of both control inputs. Stability criteria are developed in terms of the control law gains, the platform inertia ratio, and tether offset parameter. Control law gains are obtained based on linear quadratic regulator techniques. Typical transient responses of both the state and required control effort are presented.

The development of optimal control laws for orbiting tethered platform systems

NASA Technical Reports Server (NTRS)

Bainum, P. M.

1986-01-01

A mathematical model of the open and closed loop in orbit plane dynamics of a space platform-tethered-subsatellite system is developed. The system consists of a rigid platform from which an (assumed massless) tether is deploying (retrieving) a subsatellite from an attachment point which is, in general, offset from the platform's mass center. A Langrangian formulation yields equations describing platform pitch, subsatellite tetherline swing, and varying tether length motions. These equations are linearized about the nominal station keeping motion. Control can be provided by both modulation of the tether tension level and by a momentum type platform-mounted device; system controllability depends on the presence of both control inputs. Stability criteria are developed in terms of the control law gains, the platform inertia ratio, and tether offset parameter. Control law gains are obtained based on linear quadratic regulator techniques. Typical transient responses of both the state and required control effort are presented.

Optimal thrust level for orbit insertion

NASA Astrophysics Data System (ADS)

Cerf, Max

2017-07-01

The minimum-fuel orbital transfer is analyzed in the case of a launcher upper stage using a constantly thrusting engine. The thrust level is assumed to be constant and its value is optimized together with the thrust direction. A closed-loop solution for the thrust direction is derived from the extremal analysis for a planar orbital transfer. The optimal control problem reduces to two unknowns, namely the thrust level and the final time. Guessing and propagating the costates is no longer necessary and the optimal trajectory is easily found from a rough initialization. On the other hand the initial costates are assessed analytically from the initial conditions and they can be used as initial guess for transfers at different thrust levels. The method is exemplified on a launcher upper stage targeting a geostationary transfer orbit.

The self-calibration method for multiple systems at the CHARA Array

NASA Astrophysics Data System (ADS)

O'Brien, David

The self-calibration method, a new interferometric technique at the CHARA Array, has been used to derive orbits for several spectroscopic binaries. This method uses the wide component of a hierarchical triple system to calibrate visibility measurements of the triple's close binary system. At certain baselines and separations, the calibrator in one of these systems can be observed quasi-simultaneously with the target. Depending on the orientation of the CHARA observation baseline relative to the orientation of the wide orbit of the triple system, separated fringe packets may be observed. A sophisticated observing scheme must be put in place to ensure the existence of separated fringe packets on nights of observation. Prior to the onset of this project, the reduction of separated fringe packet data had never included the goal of deriving visibilities for both fringe packets, so new data reduction software has been written. Visibilities obtained with separated fringe packet data for the target close binary are run through both Monte Carlo simulations and grid search programs in order to determine the best-fit orbital elements of the close binary. Several targets have been observed in this fashion, and orbits have been derived for seven targets, including three new orbits. Derivation of the orbit of the close pair in a triple system allows for the calculation of the mutual inclination, which is the angle between the planes of the wide and close orbit. Knowledge of this quantity may give insight into the formation processes that create multiple star systems. INDEX WORDS: Long-baseline interferometry, Self calibration, Separated fringe packets, Triple systems, Close binaries, Multiple systems, Orbital parameters, Near-infrared interferometry

Closed almost-periodic orbits in semiclassical quantization of generic polygons

PubMed

Biswas

2000-05-01

Periodic orbits are the central ingredients of modern semiclassical theories and corrections to these are generally nonclassical in origin. We show here that, for the class of generic polygonal billiards, the corrections are predominantly classical in origin owing to the contributions from closed almost-periodic (CAP) orbit families. Furthermore, CAP orbit families outnumber periodic families but have comparable weights. They are hence indispensable for semiclassical quantization.

Late type close binary system CM Dra

NASA Astrophysics Data System (ADS)

Kalomeni, Belinda

2015-08-01

In this study, we present new observations of the close binary system CM Dra. We analyzed all the available data of the system and estimated the physical parameters of the system stars highly accurately. Using the newly obtained parameters the distance of the system is determined to be 11.6 pc. A possible giant planet orbiting the close binary system has been detected. This orbital period would likely make it one of the longest known orbital period planet.

Model-independent and fast determination of optical functions in storage rings via multiturn and closed-orbit data

NASA Astrophysics Data System (ADS)

Riemann, Bernard; Grete, Patrick; Weis, Thomas

2011-06-01

Multiturn (or turn-by-turn) data acquisition has proven to be a new source of direct measurements for Twiss parameters in storage rings. On the other hand, closed-orbit measurements are a long-known tool for analyzing closed-orbit perturbations with conventional beam position monitor (BPM) systems and are necessarily available at every storage ring. This paper aims at combining the advantages of multiturn measurements and closed-orbit data. We show that only two multiturn BPMs and four correctors in one localized drift space in the storage ring (diagnostic drift) are sufficient for model-independent and absolute measuring of β and φ functions at all BPMs, including the conventional ones, instead of requiring all BPMs being equipped with multiturn electronics.

Stability of Multi-Planet Systems in the Alpha Centauri System

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.

2017-01-01

We evaluate the extent of the regions within the alpha Centauri AB star system where small planets are able to orbit for billion-year timescales (Quarles & Lissauer 2016, Astron. J. 151, 111), as well as how closely-spaced planetary orbits can be within those regions in which individual planets can survive. Although individual planets on low inclination, low eccentricity, orbits can survive throughout the habitable zones of both stars, perturbations from the companion star imply that the spacing of planets in multi-planet systems within the habitable zones of each star must be significantly larger than the spacing of similar multi-planet systems orbiting single stars in order to be long-lived. Because the binary companion induces a forced eccentricity upon the orbits of planets in orbit around either star, appropriately-aligned circumstellar orbits with small initial eccentricities are stable to slightly larger initial semimajor axes than are initially circular orbits. Initial eccentricities close to forced eccentricities can have a much larger affect on how closely planetary orbits can be spaced, and therefore on how many planets may remain in the habitable zones, although the required spacing remains significantly higher than for planets orbiting single stars.

Orbital alignment of circumbinary planets that form in misaligned circumbinary discs: the case of Kepler-413b

NASA Astrophysics Data System (ADS)

Pierens, A.; Nelson, R. P.

2018-06-01

Although most of the circumbinary planets detected by the Kepler spacecraft are on orbits that are closely aligned with the binary orbital plane, the systems Kepler-413 and Kepler-453 exhibit small misalignments of ˜2.5°. One possibility is that these planets formed in a circumbinary disc whose midplane was inclined relative to the binary orbital plane. Such a configuration is expected to lead to a warped and twisted disc, and our aim is to examine the inclination evolution of planets embedded in these discs. We employed 3D hydrodynamical simulations that examine the disc response to the presence of a modestly inclined binary with parameters that match the Kepler-413 system, as a function of disc parameters and binary inclinations. The discs all develop slowly varying warps, and generally display very small amounts of twist. Very slow solid body precession occurs because a large outer disc radius is adopted. Simulations of planets embedded in these discs resulted in the planet aligning with the binary orbit plane for disc masses close to the minimum mass solar nebular, such that nodal precession of the planet was controlled by the binary. For higher disc masses, the planet maintains near coplanarity with the local disc midplane. Our results suggest that circumbinary planets born in tilted circumbinary discs should align with the binary orbit plane as the disc ages and loses mass, even if the circumbinary disc remains misaligned from the binary orbit. This result has important implications for understanding the origins of the known circumbinary planets.

Mechanical systems with closed orbits on manifolds of revolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kudryavtseva, E A; Fedoseev, D A

We study natural mechanical systems describing the motion of a particle on a two-dimensional Riemannian manifold of revolution in the field of a central smooth potential. We obtain a classification of Riemannian manifolds of revolution and central potentials on them that have the strong Bertrand property: any nonsingular (that is, not contained in a meridian) orbit is closed. We also obtain a classification of manifolds of revolution and central potentials on them that have the 'stable' Bertrand property: every parallel is an 'almost stable' circular orbit, and any nonsingular bounded orbit is closed. Bibliography: 14 titles.

The Spacelab Instrument Pointing System (IPS) and its first flight

NASA Astrophysics Data System (ADS)

Heusmann, H.; Wolf, P.

1985-11-01

The development of the Instrument Pointing System (IPS) as part of Spacelab's experimental apparatus for open Pallet direct space exposure, and its test flight aboard the Shuttle Orbiter are discussed. The IPS is a three-axis-controlled platform with stellar, sun and earth pointing modes, and a better than 1 arcsec pointing ability. The development of an 'inside-out gimbal' configuration with the platform acting like a joint between the unstable Shuttle and the inertially stabilized payload facilitated close to hemispherical pointing and the adaptability for payloads of almost any size. Gimbal axes torquers counteract Orbiter acceleration due to crew movement and thruster firings, and facilitate target acquisition and precision pointing, by command from a crew-engaged computer preprogrammed for all possible control steps. Carrying an experimental solar-physics payload, the IPS correctly performed all intended functions and withstood launch and orbital loads. Several anomalies were detected and successfully corrected in-flight.

Integrated guidance and control for microsatellite real-time automated proximity operations

NASA Astrophysics Data System (ADS)

Chen, Ying; He, Zhen; Zhou, Ding; Yu, Zhenhua; Li, Shunli

2018-07-01

This paper investigates the trajectory planning and control of autonomous spacecraft proximity operations with impulsive dynamics. A new integrated guidance and control scheme is developed to perform automated close-range rendezvous for underactuated microsatellites. To efficiently prevent collision, a modified RRT* trajectory planning algorithm is proposed under this context. Several engineering constraints such as collision avoidance, plume impingement, field of view and control feasibility are considered simultaneously. Then, the feedback controller that employs a turn-burn-turn strategy with a combined impulsive orbital control and finite-time attitude control is designed to ensure the implementation of planned trajectory. Finally, the performance of trajectory planner and controller are evaluated through numerical tests. Simulation results indicate the real-time implementability of the proposed integrated guidance and control scheme with position control error less than 0.5 m and velocity control error less than 0.05 m/s. Consequently, the proposed scheme offers the potential for wide applications, such as on-orbit maintenance, space surveillance and debris removal.

Tidal Dissipation In Rotating Low Mass Stars: Implications For The Orbital Evolution Of Close In Planets

NASA Astrophysics Data System (ADS)

Gallet, Florian; Bolmont, Emeline; Mathis, Stéphane; Charbonnel, Corinne; Amard, Louis; Alibert, Yann

2017-10-01

Close-in planets represent a large fraction of the population of confirmed exoplanets. To understand the dynamical evolution of these planets, star-planet interactions must be taken into account. In particular, the dependence of the tidal interactions on the structural parameters of the star, its rotation, and its metallicity should be treated in the models. We quantify how the tidal dissipation in the convective envelope of rotating low-mass stars evolves in time. We also investigate the possible consequences of this evolution on planetary orbital evolution. In Gallet et al. (2017) and Bolmont et al. (2017) we generalized the work of Bolmont & Mathis (2016) by following the orbital evolution of close-in planets using the new tidal dissipation predictions for advanced phases of stellar evolution and non-solar metallicity. We find that during the pre-main sequence the evolution of tidal dissipation is controlled by the evolution of the internal structure of the star through the stellar contraction. On the main-sequence tidal dissipation is strongly driven by the evolution of the surface rotation that is impacted by magnetized stellar winds braking. Finally, during the more evolved phases, the tidal dissipation sharply decreases as radiative core retreats in mass and radius towards the red-giant branch. Using an orbital evolution model, we also show that changing the metallicity leads to diUerent orbital evolutions (e.g., planets migrate farther out from an initially fast rotating metal rich star). By using this model, we qualitatively reproduced the observational trends of the population of hot Jupiters with the metallicity of their host stars. However, more work still remain to be do so as to be able to quantitatively fit our results to the observations.

Close-up of Shuttle Thermal Tiles in Space

NASA Technical Reports Server (NTRS)

2005-01-01

Launched on July 26 2005, from the Kennedy Space Center in Florida, STS-114 was classified as Logistics Flight 1. Among the Station-related activities of the mission were the delivery of new supplies and the replacement of one of the orbital outpost's Control Moment Gyroscopes (CMGs). STS-114 also carried the Raffaello Multi-Purpose Logistics Module and the External Stowage Platform-2. A major focus of the mission was the testing and evaluation of new Space Shuttle flight safety, which included new inspection and repair techniques. Upon its approach to the International Space Station (ISS), the Space Shuttle Discovery underwent a photography session in order to assess any damages that may have occurred during its launch and/or journey through Space. The mission's third and final Extra Vehicular Activity (EVA) included taking a close-up look and the repair of the damaged heat shield. Gap fillers were removed from between the orbiter's heat-shielding tiles located on the craft's underbelly. Never before had any repairs been done to an orbiter while still in space. This close up of the thermal tiles was taken by astronaut Stephen K. Robinson, STS-114 mission specialist (out of frame). Astronaut Soichi Noguchi, STS-114 mission specialist representing the Japan Aerospace Exploration (JAXA), can be seen in the background perched on a Space Station truss.

Particle simulations on transport control in divertors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashiwagi, Mieko; Ido, Shunji

1995-04-01

Particle orbit simulations are carried out to study the reflection of He ions recycled from a tokamak divertor by RF electric fields, which have the frequency close to ion cyclotron resonance frequency (ICRF). The performance of particle reflection and the requirement to the intensity of RF fields are studied. The control of He recycling by ICRF fields is found to be available. 4 refs., 4 figs.

Analysis of Parallel Burn Without Crossfeed TSTO RLV Architectures and Comparison to Parallel Burn With Crossfeed and Series Burn Architectures

NASA Technical Reports Server (NTRS)

Smith, Garrett; Phillips, Alan

2002-01-01

There are currently three dominant TSTO class architectures. These are Series Burn (SB), Parallel Burn with crossfeed (PBw/cf), and Parallel Burn without crossfeed (PBncf). The goal of this study was to determine what factors uniquely affect PBncf architectures, how each of these factors interact, and to determine from a performance perspective whether a PBncf vehicle could be competitive with a PBw/cf or SB vehicle using equivalent technology and assumptions. In all cases, performance was evaluated on a relative basis for a fixed payload and mission by comparing gross and dry vehicle masses of a closed vehicle. Propellant combinations studied were LOX: LH2 propelled orbiter and booster (HH) and LOX: Kerosene booster with LOX: LH2 orbiter (KH). The study conclusions were: 1) a PBncf orbiter should be throttled as deeply as possible after launch until the staging point. 2) a detailed structural model is essential to accurate architecture analysis and evaluation. 3) a PBncf TSTO architecture is feasible for systems that stage at mach 7. 3a) HH architectures can achieve a mass growth relative to PBw/cf of < 20%. 3b) KH architectures can achieve a mass growth relative to Series Burn of < 20%. 4) center of gravity (CG) control will be a major issue for a PBncf vehicle, due to the low orbiter specific thrust to weight ratio and to the position of the orbiter required to align the nozzle heights at liftoff. 5 ) thrust to weight ratios of 1.3 at liftoff and between 1.0 and 0.9 when staging at mach 7 appear to be close to ideal for PBncf vehicles. 6) performance for all vehicles studied is better when staged at mach 7 instead of mach 5. The study showed that a Series Burn architecture has the lowest gross mass for HH cases, and has the lowest dry mass for KH cases. The potential disadvantages of SB are the required use of an air-start for the orbiter engines and potential CG control issues. A Parallel Burn with crossfeed architecture solves both these problems, but the mechanics of a large bipropellant crossfeed system pose significant technical difficulties. Parallel Burn without crossfeed vehicles start both booster and orbiter engines on the ground and thus avoid both the risk of orbiter air-start and the complexity of a crossfeed system. The drawback is that the orbiter must use 20% to 35% of its propellant before reaching the staging point. This induces a weight penalty in the orbiter in order to carry additional propellant, which causes a further weight penalty in the booster to achieve the same staging point. One way to reduce the orbiter propellant consumption during the first stage is to throttle down the orbiter engines as much as possible. Another possibility is to use smaller or fewer engines. Throttling the orbiter engines soon after liftoff minimizes CG control problems due to a low orbiter liftoff thrust, but may result in an unnecessarily high orbiter thrust after staging. Reducing the number or size of engines size may cause CG control problems and drift at launch. The study suggested possible methods to maximize performance of PBncf vehicle architectures in order to meet mission design requirements.

Analysis of close encounters with Ganymede and Callisto using a genetic n-body algorithm

NASA Astrophysics Data System (ADS)

Winter, Philip M.; Galiazzo, Mattia A.; Maindl, Thomas I.

2018-05-01

In this work we describe a genetic algorithm which is used in order to study orbits of minor bodies in the frames of close encounters. We find that the algorithm in combination with standard orbital numerical integrators can be used as a good proxy for finding typical orbits of minor bodies in close encounters with planets and even their moons, saving a lot of computational time compared t0 long-term orbital numerical integrations. Here, we study close encounters of Centaurs with Callisto and Ganymede in particular. We also perform n-body numerical simulations for comparison. We find typical impact velocities to be between v rel = 20[v esc ] and v rel = 30[v esc ] for Ganymede and between v rel = 25[v esc ] and v rel = 35[v esc ] for Callisto.

First Results from a Hardware-in-the-Loop Demonstration of Closed-Loop Autonomous Formation Flying

NASA Technical Reports Server (NTRS)

Gill, E.; Naasz, Bo; Ebinuma, T.

2003-01-01

A closed-loop system for the demonstration of formation flying technologies has been developed at NASA s Goddard Space Flight Center. Making use of a GPS signal simulator with a dual radio frequency outlet, the system includes two GPS space receivers as well as a powerful onboard navigation processor dedicated to the GPS-based guidance, navigation, and control of a satellite formation in real-time. The closed-loop system allows realistic simulations of autonomous formation flying scenarios, enabling research in the fields of tracking and orbit control strategies for a wide range of applications. A sample scenario has been set up where the autonomous transition of a satellite formation from an initial along-track separation of 800 m to a final distance of 100 m has been demonstrated. As a result, a typical control accuracy of about 5 m has been achieved which proves the applicability of autonomous formation flying techniques to formations of satellites as close as 50 m.

The Role of the Immune Response in the Pathogenesis of Thyroid Eye Disease: A Reassessment

PubMed Central

Rosenbaum, James T.; Choi, Dongseok; Wong, Amanda; Wilson, David J.; Grossniklaus, Hans E.; Harrington, Christina A.; Dailey, Roger A.; Ng, John D.; Steele, Eric A.; Czyz, Craig N.; Foster, Jill A.; Tse, David; Alabiad, Chris; Dubovy, Sander; Parekh, Prashant K.; Harris, Gerald J.; Kazim, Michael; Patel, Payal J.; White, Valerie A.; Dolman, Peter J.; Edward, Deepak P.; Alkatan, Hind M.; al Hussain, Hailah; Selva, Dinesh; Yeatts, R. Patrick; Korn, Bobby S.; Kikkawa, Don O.; Stauffer, Patrick; Planck, Stephen R.

2015-01-01

Background Although thyroid eye disease is a common complication of Graves’ disease, the pathogenesis of the orbital disease is poorly understood. Most authorities implicate the immune response as an important causal factor. We sought to clarify pathogenesis by using gene expression microarray. Methods An international consortium of ocular pathologists and orbital surgeons contributed formalin fixed orbital biopsies. RNA was extracted from orbital tissue from 20 healthy controls, 25 patients with thyroid eye disease (TED), 25 patients with nonspecific orbital inflammation (NSOI), 7 patients with sarcoidosis and 6 patients with granulomatosis with polyangiitis (GPA). Tissue was divided into a discovery set and a validation set. Gene expression was quantified using Affymetrix U133 Plus 2.0 microarrays which include 54,000 probe sets. Results Principal component analysis showed that gene expression from tissue from patients with TED more closely resembled gene expression from healthy control tissue in comparison to gene expression characteristic of sarcoidosis, NSOI, or granulomatosis with polyangiitis. Unsupervised cluster dendrograms further indicated the similarity between TED and healthy controls. Heat maps based on gene expression for cytokines, chemokines, or their receptors showed that these inflammatory markers were associated with NSOI, sarcoidosis, or GPA much more frequently than with TED. Conclusion This is the first study to compare gene expression in TED to gene expression associated with other causes of exophthalmos. The juxtaposition shows that inflammatory markers are far less characteristic of TED relative to other orbital inflammatory diseases. PMID:26371757

Using Solar Radiation Pressure to Control L2 Orbits

NASA Technical Reports Server (NTRS)

Tene, Noam; Richon, Karen; Folta, David

1998-01-01

The main perturbations at the Sun-Earth Lagrange points L1 and L2 are from solar radiation pressure (SRP), the Moon and the planets. Traditional approaches to trajectory design for Lagrange-point orbits use maneuvers every few months to correct for these perturbations. The gravitational effects of the Moon and the planets are small and periodic. However, they cannot be neglected because small perturbations in the direction of the unstable eigenvector are enough to cause exponential growth within a few months. The main effect of a constant SRP is to shift the center of the orbit by a small distance. For spacecraft with large sun-shields like the Microwave Anisotropy Probe (MAP) and the Next Generation Space Telescope (NGST), the SRP effect is larger than all other perturbations and depends mostly on spacecraft attitude. Small variations in the spacecraft attitude are large enough to excite or control the exponential eigenvector. A closed-loop linear controller based on the SRP variations would eliminate one of the largest errors to the orbit and provide a continuous acceleration for use in controlling other disturbances. It is possible to design reference trajectories that account for the periodic lunar and planetary perturbations and still satisfy mission requirements. When such trajectories are used the acceleration required to control the unstable eigenvector is well within the capabilities of a continuous linear controller. Initial estimates show that by using attitude control it should be possible to minimize and even eliminate thruster maneuvers for station keeping.

Unity hatch closed in preparation for launch on STS-88

NASA Technical Reports Server (NTRS)

1998-01-01

Workers in the Space Station Processing Facility hold part of the equipment to close the hatch to the Unity connecting module, part of the International Space Station, before its launch aboard Space Shuttle Endeavour on STS-88 in December. Unity will now undergo a series of leak checks before a final purge of clean, dry air inside the module to ready it for initial operations in space. Other testing includes the common berthing mechanism to which other space station elements will dock and the Pad Demonstration Test to verify the compatibility of the module with the Space Shuttle as well as the ability of the astronauts to send and receive commands to Unity from the flight deck of the orbiter. The next time the hatch will be opened it will be by astronauts on orbit. Unity is expected to be ready for installation into the payload canister on Oct. 25, and transported to Launch Pad 39-A on Oct. 27. The Unity will be mated to the Russian-built Zarya control module which should already be in orbit at that time.

Unity hatch closed in preparation for launch on STS-88

NASA Technical Reports Server (NTRS)

1998-01-01

Workers in the Space Station Processing Facility close the access hatch to the Unity connecting module, part of the International Space Station, before its launch aboard Space Shuttle Endeavour on STS-88 in December. Unity will now undergo a series of leak checks before a final purge of clean, dry air inside the module to ready it for initial operations in space. Other testing includes the common berthing mechanism to which other space station elements will dock and the Pad Demonstration Test to verify the compatibility of the module with the Space Shuttle as well as the ability of the astronauts to send and receive commands to Unity from the flight deck of the orbiter. The next time the hatch will be opened it will be by astronauts on orbit. Unity is expected to be ready for installation into the payload canister on Oct. 25, and transported to Launch Pad 39-A on Oct. 27. The Unity will be mated to the Russian-built Zarya control module which should already be in orbit at that time.

Unity hatch closed in preparation for launch on STS-88

NASA Technical Reports Server (NTRS)

1998-01-01

Workers in the Space Station Processing Facility make final preparations for closing the access hatch to the Unity connecting module, part of the International Space Station, before its launch aboard Space Shuttle Endeavour on STS-88 in December. Unity will now undergo a series of leak checks before a final purge of clean, dry air inside the module to ready it for initial operations in space. Other testing includes the common berthing mechanism to which other space station elements will dock and the Pad Demonstration Test to verify the compatibility of the module with the Space Shuttle as well as the ability of the astronauts to send and receive commands to Unity from the flight deck of the orbiter. The next time the hatch will be opened it will be by astronauts on orbit. Unity is expected to be ready for installation into the payload canister on Oct. 25, and transported to Launch Pad 39-A on Oct. 27. The Unity will be mated to the Russian-built Zarya control module which should already be in orbit at that time.

Multi-Objective Online Initialization of Spacecraft Formations

NASA Technical Reports Server (NTRS)

Jeffrey, Matthew; Breger, Louis; How, Jonathan P.

2007-01-01

This paper extends a previously developed method for finding spacecraft initial conditions (ICs) that minimize the drift resulting from J2 disturbances while also minimizing the fuel required to attain those ICs. It generalizes the single spacecraft optimization to a formation-wide optimization valid for an arbitrary number of vehicles. Additionally, the desired locations of the spacecraft, separate from the starting location, can be specified, either with respect to a reference orbit, or relative to the other spacecraft in the formation. The three objectives (minimize drift, minimize fuel, and maintain a geometric template) are expressed as competing costs in a linear optimization, and are traded against one another through the use of scalar weights. By carefully selecting these weights and re-initializing the formation at regular intervals, a closed-loop, formation-wide control system is created. This control system can be used to reconfigure the formations on the fly, and creates fuel-efficient plans by placing the spacecraft in semi-invariant orbits. The overall approach is demonstrated through nonlinear simulations for two formations a GEO orbit, and an elliptical orbit.

Precision Closed-Loop Orbital Maneuvering System Design and Performance for the Magnetospheric Multi-Scale Mission (MMS) Formation

NASA Technical Reports Server (NTRS)

Chai, Dean; Queen, Steve; Placanica, Sam

2015-01-01

NASA's Magnetospheric Multi-Scale (MMS) mission successfully launched on March 13, 2015 (UTC) consists of four identically instrumented spin-stabilized observatories that function as a constellation to study magnetic reconnection in space. The need to maintain sufficiently accurate spatial and temporal formation resolution of the observatories must be balanced against the logistical constraints of executing overly-frequent maneuvers on a small fleet of spacecraft. These two considerations make for an extremely challenging maneuver design problem. This paper focuses on the design elements of a 6-DOF spacecraft attitude control and maneuvering system capable of delivering the high-precision adjustments required by the constellation designers---specifically, the design, implementation, and on-orbit performance of the closed-loop formation-class maneuvers that include initialization, maintenance, and re-sizing. The maneuvering control system flown on MMS utilizes a micro-gravity resolution accelerometer sampled at a high rate in order to achieve closed-loop velocity tracking of an inertial target with arc-minute directional and millimeter-per-second magnitude accuracy. This paper summarizes the techniques used for correcting bias drift, sensor-head offsets, and centripetal aliasing in the acceleration measurements. It also discusses the on-board pre-maneuver calibration and compensation algorithms as well as the implementation of the post-maneuver attitude adjustments.

Precision Closed-Loop Orbital Maneuvering System Design and Performance for the Magnetospheric Multiscale Formation

NASA Technical Reports Server (NTRS)

Chai, Dean J.; Queen, Steven Z.; Placanica, Samuel J.

2015-01-01

NASAs Magnetospheric Multiscale (MMS) mission successfully launched on March 13,2015 (UTC) consists of four identically instrumented spin-stabilized observatories that function as a constellation to study magnetic reconnection in space. The need to maintain sufficiently accurate spatial and temporal formation resolution of the observatories must be balanced against the logistical constraints of executing overly-frequent maneuvers on a small fleet of spacecraft. These two considerations make for an extremely challenging maneuver design problem. This paper focuses on the design elements of a 6-DOF spacecraft attitude control and maneuvering system capable of delivering the high-precision adjustments required by the constellation designers specifically, the design, implementation, and on-orbit performance of the closed-loop formation-class maneuvers that include initialization, maintenance, and re-sizing. The maneuvering control system flown on MMS utilizes a micro-gravity resolution accelerometer sampled at a high rate in order to achieve closed-loop velocity tracking of an inertial target with arc-minute directional and millimeter-per second magnitude accuracy. This paper summarizes the techniques used for correcting bias drift, sensor-head offsets, and centripetal aliasing in the acceleration measurements. It also discusses the on-board pre-maneuver calibration and compensation algorithms as well as the implementation of the post-maneuver attitude adjustments.

Parametric control of maneuver of a space tether system

NASA Astrophysics Data System (ADS)

Bezglasnyi, S. P.; Piyakina, E. E.

2015-07-01

Planar motion of a space tether system (STS) simulated by a massless rod with two masses fixed on its edges and a third mass moving along the rod is considered. An equation of the pendulum-controlled motion of the system in an elliptical orbit is obtained. Problems of parametric control that takes the STS from one stable radial equilibrium state to another and stabilizes it with respect to planar excitations of two diametrically opposite positions of the relative equilibrium of the STS in a circular orbit are investigated. The control is a continuous law of motion for a moving mass along the tether on the swing principle. The solution is obtained in a closed form based on the second method of the classical stability theory by the construction of the corresponding Lyapunov functions. Asymptotic convergence of solutions is confirmed by the results of numerical modeling of the system motion.

Coherent transfer of orbital angular momentum to excitons by optical four-wave mixing.

PubMed

Ueno, Y; Toda, Y; Adachi, S; Morita, R; Tawara, T

2009-10-26

We demonstrate the coherent transfer of optical orbital angular momentum (OAM) to the center of mass momentum of excitons in semiconductor GaN using a four-wave mixing (FWM) process. When we apply the optical vortex (OV) as an excitation pulse, the diffracted FWM signal exhibits phase singularities that satisfy the OAM conservation law, which remain clear within the exciton dephasing time (approximately 1ps). We also demonstrate the arbitrary control of the topological charge in the output signal by changing the OAM of the input pulse. The results provide a way of controlling the optical OAM through carriers in solids. Moreover, the time evolution of the FWM with OAM leads to the study of the closed-loop carrier coherence in materials.

Guidance, Navigation, and Control Techniques and Technologies for Active Satellite Removal

NASA Astrophysics Data System (ADS)

Ortega Hernando, Guillermo; Erb, Sven; Cropp, Alexander; Voirin, Thomas; Dubois-Matra, Olivier; Rinalducci, Antonio; Visentin, Gianfranco; Innocenti, Luisa; Raposo, Ana

2013-09-01

This paper shows an internal feasibility analysis to de- orbit a non-functional satellite of big dimensions by the Technical Directorate of the European Space Agency ESA. The paper focuses specifically on the design of the techniques and technologies for the Guidance, Navigation, and Control (GNC) system of the spacecraft mission that will capture the satellite and ultimately will de-orbit it on a controlled re-entry.The paper explains the guidance strategies to launch, rendezvous, close-approach, and capture the target satellite. The guidance strategy uses chaser manoeuvres, hold points, and collision avoidance trajectories to ensure a safe capture. It also details the guidance profile to de-orbit it in a controlled re-entry.The paper continues with an analysis of the required sensing suite and the navigation algorithms to allow the homing, fly-around, and capture of the target satellite. The emphasis is placed around the design of a system to allow the rendezvous with an un-cooperative target, including the autonomous acquisition of both the orbital elements and the attitude of the target satellite.Analysing the capture phase, the paper provides a trade- off between two selected capture systems: the net and the tentacles. Both are studied from the point of view of the GNC system.The paper analyses as well the advanced algorithms proposed to control the final compound after the capture that will allow the controlled de-orbiting of the assembly in a safe place in the Earth.The paper ends proposing the continuation of this work with the extension to the analysis of the destruction process of the compound in consecutive segments starting from the entry gate to the rupture and break up.

Classical eighth- and lower-order Runge-Kutta-Nystroem formulas with a new stepsize control procedure for special second-order differential equations

NASA Technical Reports Server (NTRS)

Fehlberg, E.

1973-01-01

New Runge-Kutta-Nystrom formulas of the eighth, seventh, sixth, and fifth order are derived for the special second-order (vector) differential equation x = f (t,x). In contrast to Runge-Kutta-Nystrom formulas of an earlier NASA report, these formulas provide a stepsize control procedure based on the leading term of the local truncation error in x. This new procedure is more accurate than the earlier Runge-Kutta-Nystrom procedure (with stepsize control based on the leading term of the local truncation error in x) when integrating close to singularities. Two central orbits are presented as examples. For these orbits, the accuracy and speed of the formulas of this report are compared with those of Runge-Kutta-Nystrom and Runge-Kutta formulas of earlier NASA reports.

Growth in the Number of SSN Tracked Orbital Objects

NASA Technical Reports Server (NTRS)

Stansbery, Eugene G.

2004-01-01

The number of objects in earth orbit tracked by the US Space Surveillance Network (SSN) has experienced unprecedented growth since March, 2003. Approximately 2000 orbiting objects have been added to the "Analyst list" of tracked objects. This growth is primarily due to the resumption of full power/full time operation of the AN/FPS-108 Cobra Dane radar located on Shemya Island, AK. Cobra Dane is an L-band (23-cm wavelength) phased array radar which first became operational in 1977. Cobra Dane was a "Collateral Sensor" in the SSN until 1994 when its communication link with the Space Control Center (SCC) was closed. NASA and the Air Force conducted tests in 1999 using Cobra Dane to detect and track small debris. These tests confirmed that the radar was capable of detecting and maintaining orbits on objects as small as 5-cm diameter. Subsequently, Cobra Dane was reconnected to the SSN and resumed full power/full time space surveillance operations on March 4, 2003. This paper will examine the new data and its implications to the understanding of the orbital debris environment and orbital safety.

A Physical Interpretation of the Titius-Bode Rule and Its Connection to the Closed Orbits of Bertrand's Theorem

NASA Technical Reports Server (NTRS)

Christodoulou, Dimitris M.; Kazanas, Demosthenes

2017-01-01

We consider the geometric Titius-Bode rule for the semimajor axes of planetary orbits. We derive an equivalent rule for the midpoints of the segments between consecutive orbits along the radial direction and we interpret it physically in terms of the work done in the gravitational field of the Sun by particles whose orbits are perturbed around each planetary orbit. On such energetic grounds, it is not surprising that some exoplanets in multiple-planet extrasolar systems obey the same relation. However, it is surprising that this simple interpretation of the Titius-Bode rule also reveals new properties of the bound closed orbits predicted by Bertrand's theorem, which has been known since 1873.

A physical interpretation of the Titius-Bode rule and its connection to the closed orbits of Bertrandʼs theorem

NASA Astrophysics Data System (ADS)

Christodoulou, Dimitris M.; Kazanas, Demosthenes

2017-12-01

We consider the geometric Titius-Bode rule for the semimajor axes of planetary orbits. We derive an equivalent rule for the midpoints of the segments between consecutive orbits along the radial direction and we interpret it physically in terms of the work done in the gravitational field of the Sun by particles whose orbits are perturbed around each planetary orbit. On such energetic grounds, it is not surprising that some exoplanets in multiple-planet extrasolar systems obey the same relation. However, it is surprising that this simple interpretation of the Titius-Bode rule also reveals new properties of the bound closed orbits predicted by Bertrand’s theorem, which has been known since 1873.

Air-breathing hypersonic vehicle guidance and control studies; An integrated trajectory/control analysis methodology: Phase 1

NASA Technical Reports Server (NTRS)

Hattis, Philip D.; Malchow, Harvey L.

1991-01-01

A tool which generates optimal trajectory/control histories in an integrated manner is generically adapted to the treatment of single-stage-to-orbit air-breathing hypersonic vehicles. The methodology is implemented as a two point boundary value problem solution technique. Its use permits an assessment of an entire near-minimum-fuel trajectory and desired control strategy from takeoff to orbit while satisfying physically derived inequality constraints and while achieving efficient propulsive mode phasing. A simpler analysis strategy that partitions the trajectory into several boundary condition matched segments is also included to construct preliminary trajectory and control history representations with less computational burden than is required for the overall flight profile assessment. A demonstration was accomplished using a tabulated example (winged-cone accelerator) vehicle model that is combined with a newly developed multidimensional cubic spline data smoothing routine. A constrained near-fuel-optimal trajectory, imposing a dynamic pressure limit of 1000 psf, was developed from horizontal takeoff to 20,000 ft/sec relative air speed while aiming for a polar orbit. Previously unspecified propulsive discontinuities were located. Flight regimes demanding rapid attitude changes were identified, dictating control effector and closed-loop controller authority was ascertained after evaluating effector use for vehicle trim. Also, inadequacies in vehicle model representations and specific subsystem models with insufficient fidelity were determined based on unusual control characteristics and/or excessive sensitivity to uncertainty.

Wobbly Planet Orbital Schematic Illustration

NASA Image and Video Library

2014-02-04

This illustration shows the unusual orbit of planet Kepler-413b around a close pair of orange and red dwarf stars. The planet 66-day orbit is tilted 2.5 degrees with respect to the plane of the binary stars orbit.

The Capture of Interstellar Dust: The Pure Poynting-Robertson Case

NASA Technical Reports Server (NTRS)

Jackson, A. A.

2001-01-01

Ulysses and Galileo spacecraft have discovered interstellar dust particles entering the solar system. In general, particles trajectories not altered by Lorentz forces or radiation pressure should encounter the sun on open orbits. Under Newtonian forces alone these particles return to the interstellar medium. Dissipative forces, such as Poynting Robertson (PR) and corpuscular drag and non-dissipative Lorentz forces can modify open orbits to become closed. In particular, it is possible for the orbits of particles that pass close to the Sun to become closed due to PR drag. Further, solar irradiation will cause modification of the size of the dust particle by evaporation. The combination of these processes gives rise a class of capture orbits and bound orbits with evaporation. Considering only the case of pure PR drag a minimum impact parameter is derived for initial capture by Poynting-Robertson drag. Orbits in the solar radiation field are computed numerically accounting for evaporation with optical and material properties for ideal interstellar particles modeled. The properties of this kind of particle capture are discussed for the Sun but is applicable to other stars.

KOI2138 -- a Spin-Orbit Aligned Intermediate Period Super-Earth

NASA Astrophysics Data System (ADS)

Barnes, Jason W.

2015-11-01

A planet's formation and evolution are encoded in spin-orbit alignment -- the planet's inclination relative to its star's equatorial plane. While the solar system's spin-orbit aligned planets indicate our own relatively quiescent history, many close-in giant planets show significant misalignment. Some planets even orbit retrograde! Hot Jupiters, then, have experienced fundamentally different histories than we experienced here in the solar system. In this presentation, I will show a new determination of the spin-orbit alignment of 2.1 REarth exoplanet candidate KOI2138. KOI2138 shows a gravity-darkened transit lightcurve that is consistent with spin-orbit alignment. This measurement is important because the only other super-Earth with an alignment determination (55 Cnc e, orbit period 0.74 days) is misaligned. With an orbital period of 23.55 days, KOI2138 is far enough from its star to avoid tidal orbit evolution. Therefore its orbit is likely primordial, and hence it may represent the tip of an iceberg of terrestrial, spin-orbit aligned planets that have histories that more closely resemble that of the solar system's terrestrial planets.

Migration of comets to near-Earth space

NASA Astrophysics Data System (ADS)

Ipatov, S. I.

The orbital evolution of more than 21000 Jupiter-crossing objects under the gravitational influence of planets was investigated. For orbits close to that of Comet 2P, the mean collision probabilities of Jupiter-crossing objects with the terrestrial planets were greater by two orders of magnitude than for some other comets. For initial orbital elements close to those of Comets 2P, 10P, 44P, and 113P, a few objects (<0.1%) got Earth-crossing orbits with semi-major axes a<2 AU and aphelion distances Q<4.2 AU and moved in such orbits for more than 1 Myr (up to tens or even hundreds of Myrs). Some of them even got inner-Earth orbits (Q<0.983 AU) and Aten orbits for millions of years. Most former trans-Neptunian objects that have typical near-Earth object orbits moved in such orbits for millions of years, so during most of this time they were extinct comets or disintegrated into mini-comets.

Long-term orbital evolution of short-period comets found in Project Cosmo-DICE

NASA Technical Reports Server (NTRS)

Nakamura, Tsuko; Yoshikawa, Makoto

1992-01-01

Orbital evolutions of about 160 short-period (SP) comets are numerically integrated for 4400 years in the framework of a realistic dynamical model. By the round-trip error in closure test, a reliable time space of the integrated orbits is estimated for each comet. Majority of the SP comets with their Tisserand's constant(J) between 2.8 and 3.1 are found to evolve within the past 1000-2000 years from the orbits whose perihelia are near the Jovian orbit to the orbits with perihelia of 1-2 AU. This evolution is much more rapid than that expected from Monte Carlo simulations based on symmetric distribution of planetary perturbations, thus suggesting that asymmetry of perturbation distribution play an important role in cometary evolution. Several comets are shown to evolve from the near-Saturn orbits and then to be handed over under the control of Jupiter. We also find that a few comets were captured from long-period orbits (a = 75-125 AU) via only a few close encounters with Jupiter. It is confirmed that the captured SP comets of low-inclination with 2.7 less than J less than 3.1 show more or less strong chaotic behavior. On the other hand, comets with longer orbital period and/or of high inclination reveal slow or quasi-periodic orbital evolution.

Space shuttle: High angle of attack transition and low angle of attack launch phase aerodynamic stability and control of GD/C B-18E-2, B-18E-3 delta wing booster, and launch configuration of MSC-040A orbiter and twin pressure fed boosters

NASA Technical Reports Server (NTRS)

Debevoise, J. M.; Mcginnis, R. F.

1972-01-01

The test was a conventional stability and control test except for two aspects. One was the very high angles of attack at which the delta wing configurations were tested (up to 60 degrees) at Mach numbers of 3 and 4.96. The other was the installation of the orbiter and twin boosters in a manner that caused the support system to induce normal forces and side forces on the aft portion of the boosters at all Mach numbers; i.e., the support and the booster bodies were close together, side by side.

Analysis of Parallel Burn, No-Crossfeed TSTO RLV Architectures and Comparison to Parallel Burn with Crossfeed and Series Burn Architectures

NASA Technical Reports Server (NTRS)

Smith, Garrett; Philips, Alan

2003-01-01

Three dominant Two Stage To Orbit (TSTO) class architectures were studied: Series Burn (SB), Parallel Bum with crossfeed (PBw/cf), and Parallel Burn, no-crossfeed (PBncf). The study goal was to determine what factors uniquely affect PBncf architectures, how each of these factors interact, and to determine from a performance perspective whether a PBncf vehicle could be competitive with a PBw/cf or a SB vehicle using equivalent technology and assumptions. In all cases, performance was evaluated on a relative basis for a fixed payload and mission by comparing gross and dry vehicle masses of a closed vehicle. Propellant combinations studied were LOX: LH2 propelled booster and orbiter (HH) and LOX: Kerosene booster with LOX: LH2 orbiter (KH). The study observations were: 1) A PBncf orbiter should be throttled as deeply as possible after launch until the staging point. 2) A PBncf TSTO architecture is feasible for systems that stage at mach 7. 2a) HH architectures can achieve a mass growth relative to PBw/cf of <20%. 2b) KH architectures can achieve a mass growth relative to Series Burn of <20%. 3) Center of gravity (CG) control will be a major issue for a PBncf vehicle, due to the low orbiter specific thrust to weight ratio and to the position of the orbiter required to align the nozzle heights at liftoff. 4) Thrust to weight ratios of 1.3 at liftoff and between 1.0 and 0.9 when staging at mach 7 appear to be close to ideal for PBncf vehicles. 5) Performance for HH vehicles was better when staged at mach 7 instead of mach 5. The study suggests possible methods to maximize performance of PBncf vehicle architectures in order to meet mission design requirements.

KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, STS-114 Mission Specialist Wendy Lawrence takes a close look at the some of the tiles underneath Atlantis. Lawrence is a new addition to the mission crew. The STS-114 crew is at KSC to take part in crew equipment and orbiter familiarization.

NASA Image and Video Library

2003-10-30

KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, STS-114 Mission Specialist Wendy Lawrence takes a close look at the some of the tiles underneath Atlantis. Lawrence is a new addition to the mission crew. The STS-114 crew is at KSC to take part in crew equipment and orbiter familiarization.

KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, STS-114 Mission Specialist Andy Thomas takes a close look at the some of the tiles underneath Atlantis. Thomas is a new addition to the mission crew. The STS-114 crew is at KSC to take part in crew equipment and orbiter familiarization.

NASA Image and Video Library

2003-10-30

KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, STS-114 Mission Specialist Andy Thomas takes a close look at the some of the tiles underneath Atlantis. Thomas is a new addition to the mission crew. The STS-114 crew is at KSC to take part in crew equipment and orbiter familiarization.

Close Approach Prediction Analysis of the Earth Science Constellation with the Fengyun-1C Debris

NASA Technical Reports Server (NTRS)

Duncan, Matthew; Rand, David K.

2008-01-01

Routine satellite operations for the Earth Science Constellation (ESC) include collision risk assessment between members of the constellation and other orbiting space objects. Each day, close approach predictions are generated by a U.S. Department of Defense Joint Space Operations Center Orbital Safety Analyst using the high accuracy Space Object Catalog maintained by the Air Force's 1" Space Control Squadron. Prediction results and other ancillary data such as state vector information are sent to NASAJGoddard Space Flight Center's (GSFC's) Collision Risk Assessment analysis team for review. Collision analysis is performed and the GSFC team works with the ESC member missions to develop risk reduction strategies as necessary. This paper presents various close approach statistics for the ESC. The ESC missions have been affected by debris from the recent anti-satellite test which destroyed the Chinese Fengyun- 1 C satellite. The paper also presents the percentage of close approach events induced by the Fengyun-1C debris, and presents analysis results which predict the future effects on the ESC caused by this event. Specifically, the Fengyun-1C debris is propagated for twenty years using high-performance computing technology and close approach predictions are generated for the ESC. The percent increase in the total number of conjunction events is considered to be an estimate of the collision risk due to the Fengyun-1C break- UP.

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

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

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

Tracking Data Certification for the Lunar Reconnaissance Orbiter

NASA Technical Reports Server (NTRS)

Morinelli, Patrick J.; Socoby, Joseph; Hendry, Steve; Campion, Richard

2010-01-01

This paper details the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF) tracking data certification effort of the Lunar Reconnaissance Orbiter (LRO) Space Communications Network (SCN) complement of tracking stations consisting of the NASA White Sands 1 antenna (WS1), and the commercial provider Universal Space Network (USN) antennas at South Point, Hawaii; Dongara Australia; Weilheim, Germany; and Kiruna, Sweden. Certification assessment required the cooperation and coordination of parties not under the control of either the LRO project or ground stations as uplinks on cooperating spacecraft were necessary. The LRO range-tracking requirement of 10m 1 sigma could be satisfactorily demonstrated using any typical spacecraft capable of range tracking. Though typical Low Earth Orbiting (LEO) or Geosynchronous Earth Orbiting (GEO) spacecraft may be adequate for range certification, their measurement dynamics and noise would be unacceptable for proper Doppler certification of 1-3mm/sec 1 sigma. As LRO will orbit the Moon, it was imperative that a suitable target spacecraft be utilized which can closely mimic the expected lunar orbital Doppler dynamics of +/-1.6km/sec and +/-1.5m/sq sec to +/-0.15m/sq sec, is in view of the ground stations, supports coherent S-Band Doppler tracking measurements, and can be modeled by the FDF. In order to meet the LRO metric tracking data specifications, the SCN ground stations employed previously uncertified numerically controlled tracking receivers. Initial certification testing revealed certain characteristics of the units that required resolution before being granted certification.

VizieR Online Data Catalog: Double stars with wide separations in the AGK3 (Halbwachs+, 2016)

NASA Astrophysics Data System (ADS)

Halbwachs, J. L.; Mayor, M.; Udry, S.

2016-10-01

A large list of common proper motion stars selected from the third Astronomischen Gesellschaft Katalog (AGK3) was monitored with the CORAVEL (for COrrelation RAdial VELocities) spectrovelocimeter, in order to prepare a sample of physical binaries with very wide separations. In paper I,66 stars received special attention, since their radial velocities (RV) seemed to be variable. These stars were monitored over several years in order to derive the elements of their spectroscopic orbits. In addition, 10 of them received accurate RV measurements from the SOPHIE spectrograph of the T193 telescope at the Observatory of Haute-Provence. For deriving the orbital elements of double-lined spectroscopic binaries (SB2s), a new method was applied, which assumed that the RV of blended measurements are linear combinations of the RV of the components. 13 SB2 orbits were thus calculated. The orbital elements were eventually obtained for 52 spectroscopic binaries (SBs), two of them making a triple system. 40 SBs received their first orbit and the orbital elements were improved for 10 others. In addition, 11 SBs were discovered with very long periods for which the orbital parameters were not found. It appeared that HD 153252 has a close companion, which is a candidate brown dwarf with a minimum mass of 50 Jupiter masses. In paper II, 80 wide binaries (WBs) were detected, and 39 optical pairs were identified. Adding CPM stars with separations close enough to be almost certain they are physical, a "bias-controlled" sample of 116 wide binaries was obtained, and used to derive the distribution of separations from 100 to 30,000 au. The distribution obtained doesn't match the log-constant distribution, but is in agreement with the log-normal distribution. The spectroscopic binaries detected among the WB components were used to derive statistical informations about the multiple systems. The close binaries in WBs seem to be similar to those detected in other field stars. As for the WBs, they seem to obey the log-normal distribution of periods. The number of quadruple systems is in agreement with the "no correlation" hypothesis; this indicates that an environment conducive to the formation of WBs doesn't favor the formation of subsystems with periods shorter than 10 years. (9 data files).

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

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

Close-up view of the aft fuselage of the Orbiter Discovery looking at the thrust structure that supports the Space Shuttle Main Engines (SSMEs). In this view, SSME number two position is on the left and SSME number three position is on the right. The thrust structure transfers the forces produce by the engines into and through the airframe of the orbiter. The thrust structure includes the SSMEs load reaction truss structure, engine interface fittings and the hydraulic-actuator support structure. The propellant feed lines are the plugged and capped orifices within the engine bays. Note that SSME position two is rotated ninety degrees from position three and one. This was needed to enable enough clearance for the engines to fit and gimbal. Note in engine bay three is a clear view of the actuators that control the gambling of that engine. This view was taken from a service platform in the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Statistical methods for launch vehicle guidance, navigation, and control (GN&C) system design and analysis

NASA Astrophysics Data System (ADS)

Rose, Michael Benjamin

A novel trajectory and attitude control and navigation analysis tool for powered ascent is developed. The tool is capable of rapid trade-space analysis and is designed to ultimately reduce turnaround time for launch vehicle design, mission planning, and redesign work. It is streamlined to quickly determine trajectory and attitude control dispersions, propellant dispersions, orbit insertion dispersions, and navigation errors and their sensitivities to sensor errors, actuator execution uncertainties, and random disturbances. The tool is developed by applying both Monte Carlo and linear covariance analysis techniques to a closed-loop, launch vehicle guidance, navigation, and control (GN&C) system. The nonlinear dynamics and flight GN&C software models of a closed-loop, six-degree-of-freedom (6-DOF), Monte Carlo simulation are formulated and developed. The nominal reference trajectory (NRT) for the proposed lunar ascent trajectory is defined and generated. The Monte Carlo truth models and GN&C algorithms are linearized about the NRT, the linear covariance equations are formulated, and the linear covariance simulation is developed. The performance of the launch vehicle GN&C system is evaluated using both Monte Carlo and linear covariance techniques and their trajectory and attitude control dispersion, propellant dispersion, orbit insertion dispersion, and navigation error results are validated and compared. Statistical results from linear covariance analysis are generally within 10% of Monte Carlo results, and in most cases the differences are less than 5%. This is an excellent result given the many complex nonlinearities that are embedded in the ascent GN&C problem. Moreover, the real value of this tool lies in its speed, where the linear covariance simulation is 1036.62 times faster than the Monte Carlo simulation. Although the application and results presented are for a lunar, single-stage-to-orbit (SSTO), ascent vehicle, the tools, techniques, and mathematical formulations that are discussed are applicable to ascent on Earth or other planets as well as other rocket-powered systems such as sounding rockets and ballistic missiles.

STS_135_SAIL

NASA Image and Video Library

2011-07-12

JSC2011-E-067676 (12 July 2011) --- A close-up view of controls and displays on the forward flight deck of OV-095 in the Shuttle Avionics Integration Laboratory (SAIL) at the Johnson Space Center in Houston, July 12, 2011. The laboratory is a skeletal avionics version of the shuttle that uses actual orbiter hardware and flight software. Photo credit: NASA Photo/Houston Chronicle, Smiley N. Pool

Machine vision and the OMV

NASA Technical Reports Server (NTRS)

Mcanulty, M. A.

1986-01-01

The orbital Maneuvering Vehicle (OMV) is intended to close with orbiting targets for relocation or servicing. It will be controlled via video signals and thruster activation based upon Earth or space station directives. A human operator is squarely in the middle of the control loop for close work. Without directly addressing future, more autonomous versions of a remote servicer, several techniques that will doubtless be important in a future increase of autonomy also have some direct application to the current situation, particularly in the area of image enhancement and predictive analysis. Several techniques are presentet, and some few have been implemented, which support a machine vision capability proposed to be adequate for detection, recognition, and tracking. Once feasibly implemented, they must then be further modified to operate together in real time. This may be achieved by two courses, the use of an array processor and some initial steps toward data reduction. The methodology or adapting to a vector architecture is discussed in preliminary form, and a highly tentative rationale for data reduction at the front end is also discussed. As a by-product, a working implementation of the most advanced graphic display technique, ray-casting, is described.

APPLIED OPTICS. Voltage-tunable circular photogalvanic effect in silicon nanowires.

PubMed

Dhara, Sajal; Mele, Eugene J; Agarwal, Ritesh

2015-08-14

Electronic bands in crystals can support nontrivial topological textures arising from spin-orbit interactions, but purely orbital mechanisms can realize closely related dynamics without breaking spin degeneracies, opening up applications in materials containing only light elements. One such application is the circular photogalvanic effect (CPGE), which is the generation of photocurrents whose magnitude and polarity depend on the chirality of optical excitation. We show that the CPGE can arise from interband transitions at the metal contacts to silicon nanowires, where inversion symmetry is locally broken by an electric field. Bias voltage that modulates this field further controls the sign and magnitude of the CPGE. The generation of chirality-dependent photocurrents in silicon with a purely orbital-based mechanism will enable new functionalities in silicon that can be integrated with conventional electronics. Copyright © 2015, American Association for the Advancement of Science.

Navigation for the new millennium: Autonomous navigation for Deep Space 1

NASA Technical Reports Server (NTRS)

Reidel, J. E.; Bhaskaran, S.; Synnott, S. P.; Desai, S. D.; Bollman, W. E.; Dumont, P. J.; Halsell, C. A.; Han, D.; Kennedy, B. M.; Null, G. W.;

Closedness of orbits in a space with SU(2) Poisson structure

NASA Astrophysics Data System (ADS)

Fatollahi, Amir H.; Shariati, Ahmad; Khorrami, Mohammad

2014-06-01

The closedness of orbits of central forces is addressed in a three-dimensional space in which the Poisson bracket among the coordinates is that of the SU(2) Lie algebra. In particular it is shown that among problems with spherically symmetric potential energies, it is only the Kepler problem for which all bounded orbits are closed. In analogy with the case of the ordinary space, a conserved vector (apart from the angular momentum) is explicitly constructed, which is responsible for the orbits being closed. This is the analog of the Laplace-Runge-Lenz vector. The algebra of the constants of the motion is also worked out.

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

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

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

An algorithm for enhanced formation flying of satellites in low earth orbit

NASA Astrophysics Data System (ADS)

Folta, David C.; Quinn, David A.

1998-01-01

With scientific objectives for Earth observation programs becoming more ambitious and spacecraft becoming more autonomous, the need for innovative technical approaches on the feasibility of achieving and maintaining formations of spacecraft has come to the forefront. The trend to develop small low-cost spacecraft has led many scientists to recognize the advantage of flying several spacecraft in formation to achieve the correlated instrument measurements formerly possible only by flying many instruments on a single large platform. Yet, formation flying imposes additional complications on orbit maintenance, especially when each spacecraft has its own orbit requirements. However, advances in automation and technology proposed by the Goddard Space Flight Center (GSFC) allow more of the burden in maneuver planning and execution to be placed onboard the spacecraft, mitigating some of the associated operational concerns. The purpose of this paper is to present GSFC's Guidance, Navigation, and Control Center's (GNCC) algorithm for Formation Flying of the low earth orbiting spacecraft that is part of the New Millennium Program (NMP). This system will be implemented as a close-loop flight code onboard the NMP Earth Orbiter-1 (EO-1) spacecraft. Results of this development can be used to determine the appropriateness of formation flying for a particular case as well as operational impacts. Simulation results using this algorithm integrated in an autonomous `fuzzy logic' control system called AutoCon™ are presented.

Low-Latency Telerobotics from Mars Orbit: The Case for Synergy Between Science and Human Exploration

NASA Technical Reports Server (NTRS)

Valinia, A.; Garvin, J. B.; Vondrak, R.; Thronson, H.; Lester, D.; Schmidt, G.; Fong, T.; Wilcox, B.; Sellers, P.; White, N.

2012-01-01

Initial, science-directed human exploration of Mars will benefit from capabilities in which human explorers remain in orbit to control telerobotic systems on the surface (Figure 1). Low-latency, high-bandwidth telerobotics (LLT) from Mars orbit offers opportunities for what the terrestrial robotics community considers to be high-quality telepresence. Such telepresence would provide high quality sensory perception and situation awareness, and even capabilities for dexterous manipulation as required for adaptive, informed selection of scientific samples [1]. Astronauts on orbit in close communication proximity to a surface exploration site (in order to minimize communication latency) represent a capability that would extend human cognition to Mars (and potentially for other bodies such as asteroids, Venus, the Moon, etc.) without the challenges, expense, and risk of putting those humans on hazardous surfaces or within deep gravity wells. Such a strategy may be consistent with goals for a human space flight program that, are currently being developed within NASA.

Reference equations of motion for automatic rendezvous and capture

NASA Technical Reports Server (NTRS)

Henderson, David M.

1992-01-01

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.

RS-34 (Peacekeeper Post Boost Propulsion System) Orbital Debris Application Concept Study

NASA Technical Reports Server (NTRS)

Esther, Elizabeth A.; Burnside, Christopher G.

2013-01-01

The Advanced Concepts Office (ACO) at the NASA Marshall Space Flight Center (MSFC) lead a study to evaluate the Rocketdyne produced RS-34 propulsion system as it applies to an orbital debris removal design reference mission. The existing RS-34 propulsion system is a remaining asset from the de-commissioned United States Air Force Peacekeeper ICBM program; specifically the pressure-fed storable bi-propellant Stage IV Post Boost Propulsion System. MSFC gained experience with the RS-34 propulsion system on the successful Ares I-X flight test program flown in the Ares I-X Roll control system (RoCS). The heritage hardware proved extremely robust and reliable and sparked interest for further utilization on other potential in-space applications. Subsequently, MSFC is working closely with the USAF to obtain all the remaining RS-34 stages for re-use opportunities. Prior to pursuit of securing the hardware, MSFC commissioned the Advanced Concepts Office to understand the capability and potential applications for the RS-34 Phoenix stage as it benefits NASA, DoD, and commercial industry. Originally designed, the RS-34 Phoenix provided in-space six-degrees-of freedom operational maneuvering to deploy multiple payloads at various orbital locations. The RS-34 Concept Study, preceded by a utilization study to understand how the unique capabilities of the RS-34 Phoenix and its application to six candidate missions, sought to further understand application for an orbital debris design reference mission as the orbital debris removal mission was found to closely mimic the heritage RS-34 mission. The RS-34 Orbital Debris Application Concept Study sought to identify multiple configurations varying the degree of modification to trade for dry mass optimization and propellant load for overall capability and evaluation of several candidate missions. The results of the RS-34 Phoenix Utilization Study show that the system is technically sufficient to successfully support all of the missions analyzed. The results and benefits of the RS-34 Orbital Debris Application Concept Study are presented in this paper.

Off the beaten path: a new approach to realistically model the orbital decay of supermassive black holes in galaxy formation simulations

NASA Astrophysics Data System (ADS)

Tremmel, M.; Governato, F.; Volonteri, M.; Quinn, T. R.

2015-08-01

We introduce a sub-grid force correction term to better model the dynamical friction experienced by a supermassive black hole (SMBH) as it orbits within its host galaxy. This new approach accurately follows an SMBH's orbital decay and drastically improves over commonly used `advection' methods. The force correction introduced here naturally scales with the force resolution of the simulation and converges as resolution is increased. In controlled experiments, we show how the orbital decay of the SMBH closely follows analytical predictions when particle masses are significantly smaller than that of the SMBH. In a cosmological simulation of the assembly of a small galaxy, we show how our method allows for realistic black hole orbits. This approach overcomes the limitations of the advection scheme, where black holes are rapidly and artificially pushed towards the halo centre and then forced to merge, regardless of their orbits. We find that SMBHs from merging dwarf galaxies can spend significant time away from the centre of the remnant galaxy. Improving the modelling of SMBH orbital decay will help in making robust predictions of the growth, detectability and merger rates of SMBHs, especially at low galaxy masses or at high redshift.

Characterizing omega-limit sets which are closed orbits

NASA Astrophysics Data System (ADS)

Bautista, S.; Morales, C.

Let X be a vector field in a compact n-manifold M, n⩾2. Given Σ⊂M we say that q∈M satisfies (P) Σ if the closure of the positive orbit of X through q does not intersect Σ, but, however, there is an open interval I with q as a boundary point such that every positive orbit through I intersects Σ. Among those q having saddle-type hyperbolic omega-limit set ω(q) the ones with ω(q) being a closed orbit satisfy (P) Σ for some closed subset Σ. The converse is true for n=2 but not for n⩾4. Here we prove the converse for n=3. Moreover, we prove for n=3 that if ω(q) is a singular-hyperbolic set [C. Morales, M. Pacifico, E. Pujals, On C robust singular transitive sets for three-dimensional flows, C. R. Acad. Sci. Paris Sér. I 26 (1998) 81-86], [C. Morales, M. Pacifico, E. Pujals, Robust transitive singular sets for 3-flows are partially hyperbolic attractors or repellers, Ann. of Math. (2) 160 (2) (2004) 375-432], then ω(q) is a closed orbit if and only if q satisfies (P) Σ for some Σ closed. This result improves [S. Bautista, Sobre conjuntos hiperbólicos-singulares (On singular-hyperbolic sets), thesis Uiversidade Federal do Rio de Janeiro, 2005 (in Portuguese)] and [C. Morales, M. Pacifico, Mixing attractors for 3-flows, Nonlinearity 14 (2001) 359-378].

Star System Bonanza Illustration

NASA Image and Video Library

2014-02-27

This illustration shows the unusual orbit of planet Kepler-413b around a close pair of orange and red dwarf stars. The planet 66-day orbit is tilted 2.5 degrees with respect to the plane of the binary stars orbit.

Do Close-in Giant Planets Orbiting Evolved Stars Prefer Eccentric Orbits?

NASA Astrophysics Data System (ADS)

Grunblatt, Samuel K.; Huber, Daniel; Gaidos, Eric; Lopez, Eric D.; Barclay, Thomas; Chontos, Ashley; Sinukoff, Evan; Van Eylen, Vincent; Howard, Andrew W.; Isaacson, Howard T.

2018-07-01

The NASA Kepler and K2 Missions have recently revealed a population of transiting giant planets orbiting moderately evolved, low-luminosity red giant branch stars. Here, we present radial velocity (RV) measurements of three of these systems, revealing significantly non-zero orbital eccentricities in each case. Comparing these systems with the known planet population suggests that close-in giant planets around evolved stars tend to have more eccentric orbits than those around main sequence stars. We interpret this as tentative evidence that the orbits of these planets pass through a transient, moderately eccentric phase where they shrink faster than they circularize due to tides raised on evolved host stars. Additional RV measurements of currently known systems, along with new systems discovered by the recently launched NASA Transiting Exoplanet Survey Satellite (TESS) mission, may constrain the timescale and mass dependence of this process.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrovich, Cristobal; Rafikov, Roman; Tremaine, Scott, E-mail: cpetrovi@princeton.edu

Many exoplanets in close-in orbits are observed to have relatively high eccentricities and large stellar obliquities. We explore the possibility that these result from planet-planet scattering by studying the dynamical outcomes from a large number of orbit integrations in systems with two and three gas-giant planets in close-in orbits (0.05 AU < a < 0.15 AU). We find that at these orbital separations, unstable systems starting with low eccentricities and mutual inclinations (e ≲ 0.1, i ≲ 0.1) generally lead to planet-planet collisions in which the collision product is a planet on a low-eccentricity, low-inclination orbit. This result is inconsistentmore » with the observations. We conclude that eccentricity and inclination excitation from planet-planet scattering must precede migration of planets into short-period orbits. This result constrains theories of planet migration: the semi-major axis must shrink by 1-2 orders of magnitude without damping the eccentricity and inclination.« less

Learning from ISS-modular adaptive NN control of nonlinear strict-feedback systems.

PubMed

Wang, Cong; Wang, Min; Liu, Tengfei; Hill, David J

2012-10-01

This paper studies learning from adaptive neural control (ANC) for a class of nonlinear strict-feedback systems with unknown affine terms. To achieve the purpose of learning, a simple input-to-state stability (ISS) modular ANC method is first presented to ensure the boundedness of all the signals in the closed-loop system and the convergence of tracking errors in finite time. Subsequently, it is proven that learning with the proposed stable ISS-modular ANC can be achieved. The cascade structure and unknown affine terms of the considered systems make it very difficult to achieve learning using existing methods. To overcome these difficulties, the stable closed-loop system in the control process is decomposed into a series of linear time-varying (LTV) perturbed subsystems with the appropriate state transformation. Using a recursive design, the partial persistent excitation condition for the radial basis function neural network (NN) is established, which guarantees exponential stability of LTV perturbed subsystems. Consequently, accurate approximation of the closed-loop system dynamics is achieved in a local region along recurrent orbits of closed-loop signals, and learning is implemented during a closed-loop feedback control process. The learned knowledge is reused to achieve stability and an improved performance, thereby avoiding the tremendous repeated training process of NNs. Simulation studies are given to demonstrate the effectiveness of the proposed method.

Long-term Stability of Tightly Packed Multi-planet Systems in Prograde, Coplanar, Circumstellar Orbits within the α Centauri AB System

NASA Astrophysics Data System (ADS)

Quarles, B.; Lissauer, Jack J.

2018-03-01

We perform long-term simulations, up to ten billion years, of closely spaced configurations of 2–6 planets, each as massive as the Earth, traveling on nested orbits about either stellar component in α Centauri AB. The innermost planet initially orbits at either the inner edge of its star’s empirical habitable zone (HZ) or the inner edge of its star’s conservative HZ. Although individual planets on low inclination, low eccentricity, orbits can survive throughout the HZs of both stars, perturbations from the companion star require that the minimum spacing of planets in multi-planet systems within the HZs of each star must be significantly larger than the spacing of similar multi-planet systems orbiting single stars in order to be long-lived. The binary companion induces a forced eccentricity upon the orbits of planets in orbit around either star. Planets on appropriately phased circumstellar orbits with initial eccentricities equal to their forced eccentricities can survive on more closely spaced orbits than those with initially circular orbits, although the required spacing remains higher than for planets orbiting single stars. A total of up to nine planets on nested prograde orbits can survive for the current age of the system within the empirical HZs of the two stars, with five of these orbiting α Centauri B and four orbiting α Centauri A.

The Fate of Exomoons when Planets Scatter

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-03-01

Four examples of close-encounter outcomes: a) the moon stays in orbit around its host, b) the moon is captured into orbit around its perturber, c) and d) the moon is ejected from the system from two different starting configurations. [Adapted from Hong et al. 2018]Planet interactions are thought to be common as solar systems are first forming and settling down. A new study suggests that these close encounters could have a significant impact on the moons of giant exoplanets and they may generate a large population of free-floating exomoons.Chaos in the SystemIn the planetplanet scattering model of solar-system formation, planets are thought to initially form in closely packed systems. Over time, planets in a system perturb each other, eventually entering an instability phase during which their orbits cross and the planets experience close encounters.During this scattering process, any exomoons that are orbiting giant planets can be knocked into unstable orbits directly by close encounters with perturbing planets. Exomoons can also be disturbed if their host planets properties or orbits change as a consequence of scattering.Led by Yu-Cian Hong (Cornell University), a team of scientists has now explored the fate of exomoons in planetplanet scattering situations using a suite of N-body numerical simulations.Chances for SurvivalHong and collaborators find that the vast majority roughly 80 to 90% of exomoons around giant planets are destabilized during scattering and dont survive in their original place in the solar system. Fates of these destabilized exomoons include:moon collision with the star or a planet,moon capture by the perturbing planet,moon ejection from the solar system,ejection of the entire planetmoon system from the solar system, andmoon perturbation onto a new heliocentric orbit as a planet.Unsurprisingly, exomoons that have close-in orbits and those that orbit larger planets are the most likely to survive close encounters; as an example, exomoons on orbits similar to Jupiters Galilean satellites (i.e., orbiting at a distance of less than 4% of their host planets Hill radius) have a 2040% chance of survival.Moon initial semimajor axis vs. moon survival rate. Three of Jupiters Galilean moons are shown for reference. [Hong et al. 2018]Free-Floating MoonsAn intriguing consequence of Hong and collaborators results is the prediction of a population of free-floating exomoons that were ejected from solar systems during planetplanet scattering and now wander through the universe alone. According to the authors models, there may be as many of these free-floating exomoons as there are stars in the universe!Future surveys that search for objects using gravitational microlensing like that planned with the Wide-Field Infrared Survey Telescope (WFIRST) may be able to detect such objects down to masses of a tenth of an Earth mass. In the meantime, were a little closer to understanding the complex dynamics of early solar systems.CitationYu-Cian Hong et al 2018 ApJ 852 85. doi:10.3847/1538-4357/aaa0db

KSC-98pc1219

NASA Image and Video Library

1998-10-03

KENNEDY SPACE CENTER, FLA. -- Lowered on a movable work platform or bucket inside the payload bay of orbiter Endeavour, STS-88 Mission Specialists Jerry L. Ross (far right) and James H. Newman (second from right) get a close look at the Orbiter Docking System. At left is the bucket operator and Wayne Wedlake, with United Space Alliance at Johnson Space Center. The STS-88 crew members are in Orbiter Processing Facility Bay 1 to participate in a Crew Equipment Interface Test (CEIT) to familiarize themselves with the orbiter's midbody and crew compartments. Targeted for liftoff on Dec. 3, 1998, STS-88 will be the first Space Shuttle launch for assembly of the International Space Station (ISS). The primary payload is the Unity connecting module which will be mated to the Russian-built Zarya control module, expected to be already on orbit after a November launch from Russia. While on orbit during STS-88, Unity will be latched atop the Orbiter Docking System in the forward section of Endeavour's payload bay for the mating of the two modules. After the mating, Ross and Newman are scheduled to perform three spacewalks to connect power, data and utility lines and install exterior equipment. The first major U.S.-built component of ISS, Unity will serve as a connecting passageway to living and working areas of the space station. Unity has two attached pressurized mating adapters (PMAs) and one stowage rack installed inside. PMA-1 provides the permanent connection point between Unity and Zarya; PMA-2 will serve as a Space Shuttle docking port. Zarya is a self-supporting active vehicle, providing propulsive control capability and power during the early assembly stages. It also has fuel storage capability

Close-up of Shuttle Thermal Tiles in Space

NASA Technical Reports Server (NTRS)

2005-01-01

Launched on July 26, 2005 from the Kennedy Space Center in Florida, STS-114 was classified as Logistics Flight 1. Among the Station-related activities of the mission were the delivery of new supplies and the replacement of one of the orbital outpost's Control Moment Gyroscopes (CMGs). STS-114 also carried the Raffaello Multi-Purpose Logistics Module and the External Stowage Platform-2. A major focus of the mission was the testing and evaluation of new Space Shuttle flight safety, which included new inspection and repair techniques. Upon its approach to the International Space Station (ISS), the Space Shuttle Discovery underwent a photography session in order to assess any damages that may have occurred during its launch and/or journey through Space. The mission's third and final Extra Vehicular Activity (EVA) included taking a close-up look and the repair of the damaged heat shield. Gap fillers were removed from between the orbiter's heat-shielding tiles located on the craft's underbelly. Never before had any repairs been done to an orbiter while still in space. This particular photo was taken by astronaut Stephen K. Robinson, STS-114 mission specialist, whose shadow is visible on the thermal protection tiles, and a portion of the Canadian built Remote Manipulator System (RMS) robotic arm and the Nile River is visible at the bottom.

Resonance and Capture of Jupiter Comets

NASA Astrophysics Data System (ADS)

Koon, W. S.; Lo, M. W.; Marsden, J. E.; Ross, S. D.

A number of Jupiter family comets such as Oterma and Gehrels 3 make a rapid transition from heliocentric orbits outside the orbit of Jupiter to heliocentric orbits inside the orbit of Jupiter and vice versa. During this transition, the comet can be captured temporarily by Jupiter for one to several orbits around Jupiter. The interior heliocentric orbit is typically close to the 3:2 resonance while the exterior heliocentric orbit is near the 2:3 resonance. An important feature of the dynamics of these comets is that during the transition, the orbit passes close to the libration points L_1 and L_2, two of the equilibrium points for the restricted three-body problem for the Sun-Jupiter system. Studying the libration point invariant manifold structures for L_1 and L_2 is a starting point for understanding the capture and resonance transition of these comets. For example, the recently discovered heteroclinic connection between pairs of unstable periodic orbits (one around the L_1 and the other around L_2) implies a complicated dynamics for comets in a certain energy range. Furthermore, the stable and unstable invariant manifold `tubes' associated to libration point periodic orbits, of which the heteroclinic connections are a part, are phase space conduits transporting material to and from Jupiter and between the interior and exterior of Jupiter's orbit.

A well-scaling natural orbital theory

DOE PAGES

Gebauer, Ralph; Cohen, Morrel H.; Car, Roberto

2016-11-01

Here, we introduce an energy functional for ground-state electronic structure calculations. Its variables are the natural spin-orbitals of singlet many-body wave functions and their joint occupation probabilities deriving from controlled approximations to the two-particle density matrix that yield algebraic scaling in general, and Hartree–Fock scaling in its seniority-zero version. Results from the latter version for small molecular systems are compared with those of highly accurate quantum-chemical computations. The energies lie above full configuration interaction calculations, close to doubly occupied configuration interaction calculations. Their accuracy is considerably greater than that obtained from current density-functional theory approximations and from current functionals ofmore » the oneparticle density matrix.« less

Command and data handling of science signals on Spacelab

NASA Technical Reports Server (NTRS)

Mccain, H. G.

1975-01-01

The Orbiter Avionics and the Spacelab Command and Data Management System (CDMS) combine to provide a relatively complete command, control, and data handling service to the instrument complement during a Shuttle Sortie Mission. The Spacelab CDMS services the instruments and the Orbiter in turn services the Spacelab. The CDMS computer system includes three computers, two I/O units, a mass memory, and a variable number of remote acquisition units. Attention is given to the CDMS high rate multiplexer, CDMS tape recorders, closed circuit television for the visual monitoring of payload bay and cabin area activities, methods of science data acquisition, questions of transmission and recording, CDMS experiment computer usage, and experiment electronics.

A well-scaling natural orbital theory

PubMed Central

Gebauer, Ralph; Cohen, Morrel H.; Car, Roberto

2016-01-01

We introduce an energy functional for ground-state electronic structure calculations. Its variables are the natural spin-orbitals of singlet many-body wave functions and their joint occupation probabilities deriving from controlled approximations to the two-particle density matrix that yield algebraic scaling in general, and Hartree–Fock scaling in its seniority-zero version. Results from the latter version for small molecular systems are compared with those of highly accurate quantum-chemical computations. The energies lie above full configuration interaction calculations, close to doubly occupied configuration interaction calculations. Their accuracy is considerably greater than that obtained from current density-functional theory approximations and from current functionals of the one-particle density matrix. PMID:27803328

The Earth Science Afternoon Constellation: Preparing for Autonomous but Coordinated Operations

NASA Technical Reports Server (NTRS)

Case, Warren; Kelly, Angelita C.; Work, Kevin; Guit, William

2005-01-01

This paper describes how the challenges of coordinating the autonomous operations of geographically dispersed mission control centers for several small and large satellites are being overcome. The Earth Science Afternoon Constellation, also referred to as the "A-Train", is an international grouping of five NASA satellites (two major NASA EOS missions and three NASA/Earth System Science Pathfinder missions) and one French satellite orbiting in close proximity. This grouping of satellites provides scientists with the opportunity to perform coincident observations using data from two or more instruments on various satellites with measurements taken at approximately the same time. Three of the six missions are currently on-orbit, with the two missions expected to join the constellation later this year and one mission in 2007. The operational challenges are daunting for several reasons. There are several Mission Control Centers (widely separated on two continents), operating autonomously under tight budget constraints. All of the Mission Control Centers have reasons to be concerned about safety while flying in close proximity to other satellites, but most Centers did not have the resources or the desire to address this concern alone - the interfaces are too numerous and anticipated operations too costly. Clearly, an efficient approach was needed. This paper describes the steps taken to make this Earth science constellation a reality. Agreements were forged to allow the Mission Control Centers to maintain their autonomy, while ensuring their satellite's safety. Each member mission in the constellation operates independently in accordance with its own mission requirements, but the member missions have agreed to coordinate their operations, i.e., orbital positions and control to ensure the safety of the entire constellation. A centralized system was developed at NASA Goddard Space Flight Center to collect, analyze, and distribute ephemeris data used by each of the mission teams to determine the positions of the satellites in the constellation. The system issues warnings regarding possible dangerous configurations, eliminating the need for redundant capabilities at each Mission Control Center. On-orbit contingency situations were identified and analyzed; agreements were reached in advance of contingency operations to ensure that coordination between the Mission Control Centers can be handled expeditiously and fairly. In this manner, recovery from anomalous situations can be more quickly realized, thereby increasing the science return and reducing costs. The process used to develop these contingency procedures and the systems used to facilitate the contingency resolution are described as well.

Tidal effects on stellar activity

NASA Astrophysics Data System (ADS)

Poppenhaeger, K.

2017-10-01

The architecture of many exoplanetary systems is different from the solar system, with exoplanets being in close orbits around their host stars and having orbital periods of only a few days. We can expect interactions between the star and the exoplanet for such systems that are similar to the tidal interactions observed in close stellar binary systems. For the exoplanet, tidal interaction can lead to circularization of its orbit and the synchronization of its rotational and orbital period. For the host star, it has long been speculated if significant angular momentum transfer can take place between the planetary orbit and the stellar rotation. In the case of the Earth-Moon system, such tidal interaction has led to an increasing distance between Earth and Moon. For stars with Hot Jupiters, where the orbital period of the exoplanet is typically shorter than the stellar rotation period, one expects a decreasing semimajor axis for the planet and enhanced stellar rotation, leading to increased stellar activity. Also excess turbulence in the stellar convective zone due to rising and subsiding tidal bulges may change the magnetic activity we observe for the host star. I will review recent observational results on stellar activity and tidal interaction in the presence of close-in exoplanets, and discuss the effects of enhanced stellar activity on the exoplanets in such systems.

Design development and test: Two-gas atmosphere control subsystem

NASA Technical Reports Server (NTRS)

Jackson, J. K.

1974-01-01

An atmosphere control subsystem (ACS) was developed for NASA-IBJSC which is designed to measure the major atmospheric constituents in the manned cabin of the space shuttle orbiter and control the addition of oxygen and nitrogen to maintain the partial pressures of these gases within very close limits. The ACS includes a mass spectrometer sensor (MSS) which analyzes the atmosphere of a shuttle vehicle pressurized cabin, and an electronic control assembly (ECA). The MSS was built and tested to meet the requirements for flight equipment for the M-171 Metabolic Analyzer experiment for the Skylab flight program. The instrument analyzes an atmospheric gas sample and produces continuous 0-5 vdc analog signals proportional to the partial pressures of H2, O2, N2, H2O, CO2 and total hydrocarbons having a m/e ratio between 50 and 120. It accepts signals from the MSS proportional to the partial pressures of N2 and O2 and controls the supply of these gases to the closed cabin.

Controls for space structures

NASA Astrophysics Data System (ADS)

Balas, Mark

1991-11-01

Assembly and operation of large space structures (LSS) in orbit will require robot-assisted docking and berthing of partially-assembled structures. These operations require new solutions to the problems of controls. This is true because of large transient and persistent disturbances, controller-structure interaction with unmodeled modes, poorly known structure parameters, slow actuator/sensor dynamical behavior, and excitation of nonlinear structure vibrations during control and assembly. For on-orbit assembly, controllers must start with finite element models of LSS and adapt on line to the best operating points, without compromising stability. This is not easy to do, since there are often unmodeled dynamic interactions between the controller and the structure. The indirect adaptive controllers are based on parameter estimation. Due to the large number of modes in LSS, this approach leads to very high-order control schemes with consequent poor stability and performance. In contrast, direct model reference adaptive controllers operate to force the LSS to track the desirable behavior of a chosen model. These schemes produce simple control algorithms which are easy to implement on line. One problem with their use for LSS has been that the model must be the same dimension as the LSS - i.e., quite large. A control theory based on the command generator tracker (CGT) ideas of Sobel, Mabins, Kaufman and Wen, Balas to obtain very low-order models based on adaptive algorithms was developed. Closed-loop stability for both finite element models and distributed parameter models of LSS was proved. In addition, successful numerical simulations on several LSS databases were obtained. An adaptive controller based on our theory was also implemented on a flexible robotic manipulator at Martin Marietta Astronautics. Computation schemes for controller-structure interaction with unmodeled modes, the residual mode filters or RMF, were developed. The RMF theory was modified to compensate slow actuator/sensor dynamics. These new ideas are being applied to LSS simulations to demonstrate the ease with which one can incorporate slow actuator/sensor effects into our design. It was also shown that residual mode filter compensation can be modified for small nonlinearities to produce exponentially stable closed-loop control.

Controls for space structures

NASA Technical Reports Server (NTRS)

Balas, Mark

1991-01-01

Assembly and operation of large space structures (LSS) in orbit will require robot-assisted docking and berthing of partially-assembled structures. These operations require new solutions to the problems of controls. This is true because of large transient and persistent disturbances, controller-structure interaction with unmodeled modes, poorly known structure parameters, slow actuator/sensor dynamical behavior, and excitation of nonlinear structure vibrations during control and assembly. For on-orbit assembly, controllers must start with finite element models of LSS and adapt on line to the best operating points, without compromising stability. This is not easy to do, since there are often unmodeled dynamic interactions between the controller and the structure. The indirect adaptive controllers are based on parameter estimation. Due to the large number of modes in LSS, this approach leads to very high-order control schemes with consequent poor stability and performance. In contrast, direct model reference adaptive controllers operate to force the LSS to track the desirable behavior of a chosen model. These schemes produce simple control algorithms which are easy to implement on line. One problem with their use for LSS has been that the model must be the same dimension as the LSS - i.e., quite large. A control theory based on the command generator tracker (CGT) ideas of Sobel, Mabins, Kaufman and Wen, Balas to obtain very low-order models based on adaptive algorithms was developed. Closed-loop stability for both finite element models and distributed parameter models of LSS was proved. In addition, successful numerical simulations on several LSS databases were obtained. An adaptive controller based on our theory was also implemented on a flexible robotic manipulator at Martin Marietta Astronautics. Computation schemes for controller-structure interaction with unmodeled modes, the residual mode filters or RMF, were developed. The RMF theory was modified to compensate slow actuator/sensor dynamics. These new ideas are being applied to LSS simulations to demonstrate the ease with which one can incorporate slow actuator/sensor effects into our design. It was also shown that residual mode filter compensation can be modified for small nonlinearities to produce exponentially stable closed-loop control. A theory for disturbance accommodating controllers based on reduced order models of structures was developed, and stability results for these controllers in closed-loop with large-scale finite element models of structures were obtained.

Simplified adaptive control of an orbiting flexible spacecraft

NASA Astrophysics Data System (ADS)

Maganti, Ganesh B.; Singh, Sahjendra N.

2007-10-01

The paper presents the design of a new simple adaptive system for the rotational maneuver and vibration suppression of an orbiting spacecraft with flexible appendages. A moment generating device located on the central rigid body of the spacecraft is used for the attitude control. It is assumed that the system parameters are unknown and the truncated model of the spacecraft has finite but arbitrary dimension. In addition, only the pitch angle and its derivative are measured and elastic modes are not available for feedback. The control output variable is chosen as the linear combination of the pitch angle and the pitch rate. Exploiting the hyper minimum phase nature of the spacecraft, a simple adaptive control law is derived for the pitch angle control and elastic mode stabilization. The adaptation rule requires only four adjustable parameters and the structure of the control system does not depend on the order of the truncated spacecraft model. For the synthesis of control system, the measured output error and the states of a third-order command generator are used. Simulation results are presented which show that in the closed-loop system adaptive output regulation is accomplished in spite of large parameter uncertainties and disturbance input.

Approximate approach for optimization space flights with a low thrust on the basis of sufficient optimality conditions

NASA Astrophysics Data System (ADS)

Salmin, Vadim V.

2017-01-01

Flight mechanics with a low-thrust is a new chapter of mechanics of space flight, considered plurality of all problems trajectory optimization and movement control laws and the design parameters of spacecraft. Thus tasks associated with taking into account the additional factors in mathematical models of the motion of spacecraft becomes increasingly important, as well as additional restrictions on the possibilities of the thrust vector control. The complication of the mathematical models of controlled motion leads to difficulties in solving optimization problems. Author proposed methods of finding approximate optimal control and evaluating their optimality based on analytical solutions. These methods are based on the principle of extending the class of admissible states and controls and sufficient conditions for the absolute minimum. Developed procedures of the estimation enabling to determine how close to the optimal founded solution, and indicate ways to improve them. Authors describes procedures of estimate for approximately optimal control laws for space flight mechanics problems, in particular for optimization flight low-thrust between the circular non-coplanar orbits, optimization the control angle and trajectory movement of the spacecraft during interorbital flights, optimization flights with low-thrust between arbitrary elliptical orbits Earth satellites.

Consensus-based distributed cooperative learning from closed-loop neural control systems.

PubMed

Chen, Weisheng; Hua, Shaoyong; Zhang, Huaguang

2015-02-01

In this paper, the neural tracking problem is addressed for a group of uncertain nonlinear systems where the system structures are identical but the reference signals are different. This paper focuses on studying the learning capability of neural networks (NNs) during the control process. First, we propose a novel control scheme called distributed cooperative learning (DCL) control scheme, by establishing the communication topology among adaptive laws of NN weights to share their learned knowledge online. It is further proved that if the communication topology is undirected and connected, all estimated weights of NNs can converge to small neighborhoods around their optimal values over a domain consisting of the union of all state orbits. Second, as a corollary it is shown that the conclusion on the deterministic learning still holds in the decentralized adaptive neural control scheme where, however, the estimated weights of NNs just converge to small neighborhoods of the optimal values along their own state orbits. Thus, the learned controllers obtained by DCL scheme have the better generalization capability than ones obtained by decentralized learning method. A simulation example is provided to verify the effectiveness and advantages of the control schemes proposed in this paper.

Geosynchronous Patrol Orbit for Space Situational Awareness

NASA Astrophysics Data System (ADS)

Thompson, B.; Kelecy, T.; Kubancik, T.; Flora, T.; Chylla, M.; Rose, D.

Applying eccentricity to a geosynchronous orbit produces both longitudinal and radial motion when viewed in Earth-fixed coordinates. An interesting family of orbits emerges, useful for “neighborhood patrol” space situational awareness and other missions. The basic result is a periodic (daily), quasielliptical, closed path around a fixed region of the geosynchronous (geo) orbit belt, keeping a sensor spacecraft in relatively close vicinity to designated geo objects. The motion is similar, in some regards, to the relative motion that may be encountered during spacecraft proximity operations, but on a much larger scale. The patrol orbit does not occupy a fixed slot in the geo belt, and the east-west motion can be combined with north-south motion caused by orbital inclination, leading to even greater versatility. Some practical uses of the geo patrol orbit include space surveillance (including catalog maintenance), and general space situational awareness. The patrol orbit offers improved, diverse observation geometry for angles-only sensors, resulting in faster, more accurate orbit determination compared to simple inclined geo orbits. In this paper, we analyze the requirements for putting a spacecraft in a patrol orbit, the unique station keeping requirements to compensate for perturbations, repositioning the patrol orbit to a different location along the geo belt, maneuvering into, around, and out of the volume for proximity operations with objects within the volume, and safe end-of-life disposal requirements.

Electrical Control of Structural and Physical Properties via Strong Spin-Orbit Interactions in Sr2IrO4

NASA Astrophysics Data System (ADS)

Cao, G.; Terzic, J.; Zhao, H. D.; Zheng, H.; De Long, L. E.; Riseborough, Peter S.

2018-01-01

Electrical control of structural and physical properties is a long-sought, but elusive goal of contemporary science and technology. We demonstrate that a combination of strong spin-orbit interactions (SOI) and a canted antiferromagnetic Mott state is sufficient to attain that goal. The antiferromagnetic insulator Sr2IrO4 provides a model system in which strong SOI lock canted Ir magnetic moments to IrO6 octahedra, causing them to rigidly rotate together. A novel coupling between an applied electrical current and the canting angle reduces the Néel temperature and drives a large, nonlinear lattice expansion that closely tracks the magnetization, increases the electron mobility, and precipitates a unique resistive switching effect. Our observations open new avenues for understanding fundamental physics driven by strong SOI in condensed matter, and provide a new paradigm for functional materials and devices.

A CDMA synchronisation scheme

NASA Technical Reports Server (NTRS)

Soprano, C.

1993-01-01

CDMA (Code Division Multiple Access) is known to decrease inter-service interference in Satellite Communication Systems. Its performance is increased by chip quasi-synchronous operation which virtually eliminates the self-noise; however, the theory shows that the time error on the synchronization has to be kept at less than one tenth of a chip which, for 1 Mchip/sec. spreading rate, corresponds to 10(exp -7) sec. This, on the return-link, may only be achieved by means of a closed loop control system which, for mobile communication systems, has to be capable of autonomous operation. Until now some results have been reported on the feasibility of chip quasi-synchronous operation for mobile communication systems only including satellites on GEO (Geostationary Earth Orbit). In what follows, the basic principles are exposed, and results are presented showing how low chip synchronism error may be achieved by means of an autonomous control loop operating through satellites on any Earth orbit.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, H.; Meot, F.; Ptitsyn, V.

RHIC has provided polarized proton collisions from 31 GeV to 255 GeV in the past decade. To preserve polarization through numerous depolarizing resonances through the whole accelerator chain, harmonic orbit correction, partial snakes, horizontal tune jump system and full snakes have been used. In addition, close attentions have been paid to betatron tune control, orbit control and beam line alignment. The polarization of 60% at 255 GeV has been delivered to experiments with 1.8×10 11 bunch intensity. For the eRHIC era, the beam brightness has to be maintained to reach the desired luminosity. Since we only have one hadron ringmore » in the eRHIC era, existing spin rotator and snakes can be converted to six snake configuration for one hadron ring. With properly arranged six snakes, the polarization can be maintained at 70% at 250 GeV. This paper summarizes the effort and plan to reach high polarization with small emittance for eRHIC.« less

Hardware-in-the-Loop Rendezvous Tests of a Novel Actuators Command Concept

NASA Astrophysics Data System (ADS)

Gomes dos Santos, Willer; Marconi Rocco, Evandro; Boge, Toralf; Benninghoff, Heike; Rems, Florian

2016-12-01

Integration, test and validation results, in a real-time environment, of a novel concept for spacecraft control are presented in this paper. The proposed method commands simultaneously a group of actuators optimizing a given set of objective functions based on a multiobjective optimization technique. Since close proximity maneuvers play an important role in orbital servicing missions, the entire GNC system has been integrated and tested at a hardware-in-the-loop (HIL) rendezvous and docking simulator known as European Proximity Operations Simulator (EPOS). During the test campaign at EPOS facility, a visual camera has been used to provide the necessary measurements for calculating the relative position with respect to the target satellite during closed-loop simulations. In addition, two different configurations of spacecraft control have been considered in this paper: a thruster reaction control system and a mixed actuators mode which includes thrusters, reaction wheels, and magnetic torqrods. At EPOS, results of HIL closed-loop tests have demonstrated that a safe and stable rendezvous approach can be achieved with the proposed GNC loop.

Accelerating wavefunction in density-functional-theory embedding by truncating the active basis set

NASA Astrophysics Data System (ADS)

Bennie, Simon J.; Stella, Martina; Miller, Thomas F.; Manby, Frederick R.

2015-07-01

Methods where an accurate wavefunction is embedded in a density-functional description of the surrounding environment have recently been simplified through the use of a projection operator to ensure orthogonality of orbital subspaces. Projector embedding already offers significant performance gains over conventional post-Hartree-Fock methods by reducing the number of correlated occupied orbitals. However, in our first applications of the method, we used the atomic-orbital basis for the full system, even for the correlated wavefunction calculation in a small, active subsystem. Here, we further develop our method for truncating the atomic-orbital basis to include only functions within or close to the active subsystem. The number of atomic orbitals in a calculation on a fixed active subsystem becomes asymptotically independent of the size of the environment, producing the required O ( N 0 ) scaling of cost of the calculation in the active subsystem, and accuracy is controlled by a single parameter. The applicability of this approach is demonstrated for the embedded many-body expansion of binding energies of water hexamers and calculation of reaction barriers of SN2 substitution of fluorine by chlorine in α-fluoroalkanes.

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

NASA Astrophysics Data System (ADS)

Braviner, Harry J.; Ogilvie, Gordon I.

2015-02-01

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

NASA Advanced Exploration Systems: Advancements in Life Support Systems

NASA Technical Reports Server (NTRS)

Shull, Sarah A.; Schneider, Walter F.

2016-01-01

The NASA Advanced Exploration Systems (AES) Life Support Systems (LSS) project strives to develop reliable, energy-efficient, and low-mass spacecraft systems to provide environmental control and life support systems (ECLSS) critical to enabling long duration human missions beyond low Earth orbit (LEO). Highly reliable, closed-loop life support systems are among the capabilities required for the longer duration human space exploration missions assessed by NASA’s Habitability Architecture Team.

A semi-analytic theory for the motion of a close-earth artificial satellite with drag

NASA Technical Reports Server (NTRS)

Liu, J. J. F.; Alford, R. L.

1979-01-01

A semi-analytic method is used to estimate the decay history/lifetime and to generate orbital ephemeris for close-earth satellites perturbed by the atmospheric drag and earth oblateness due to the spherical harmonics J2, J3, and J4. The theory maintains efficiency through the application of the theory of a method of averaging and employs sufficient numerical emphasis to include a rather sophisticated atmospheric density model. The averaged drag effects with respect to mean anomaly are evaluated by a Gauss-Legendre quadrature while the averaged variational equations of motion are integrated numerically with automatic step size and error control.

Programmable Thermostat Module Upgrade for the Multipurpose Logistics Module

NASA Technical Reports Server (NTRS)

Clark, D. W.; Glasgow, S. d.; Reagan, S. E.; Presson, K. H.; Howard, D. E.; Smith, D. A.

2007-01-01

The STS-121/ULF 1.1 mission was the maiden flight of the programmable thermostat module (PTM) system used to control the 28 V shell heaters on the multi-purpose logistics module (MPLM). These PTMs, in conjunction with a data recorder module (DRM), provide continuous closed loop temperature control and data recording of MPLM on-orbit heater operations. This Technical Memorandum discusses the hardware design, development, test, and verification (DDT&V) activities performed at the Marshall Space Flight Center as well as the operational implementation and mission performance.

Programmable Thermostat Module Upgrade for the Multi-Purpose Logistics Module

NASA Technical Reports Server (NTRS)

Clark, Dallas; Glasgow, Shaun; Reagan, Shawn; Presson, Keith; Howard, David; Smith, Dennis

2007-01-01

The STS-121/ULF1.1 mission was the maiden flight of the Programmable Thermostat Module (PTM) system used to control the 28 V shell heaters on the Multi-Purpose Logistics Module (MPLM). These PTMs, in conjunction with a Data Recorder Module (DRM), provide continuous closed loop temperature control and data recording of MPLM on-orbit heater operations. This paper will discuss the hardware design, development, test and verification (DDT&V) activities performed at the Marshall Space Flight Center (MSFC) as well as the operational implementation and mission performance.

Transiting circumbinary planets Kepler-34 b and Kepler-35 b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welsh, William F.; Orosz, Jerome A.; Carter, Joshua A.

Most Sun-like stars in the Galaxy reside in gravitationally-bound pairs of stars called 'binary stars'. While long anticipated, the existence of a 'circumbinary planet' orbiting such a pair of normal stars was not definitively established until the discovery of Kepler-16. Incontrovertible evidence was provided by the miniature eclipses ('transits') of the stars by the planet. However, questions remain about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we present two additional transiting circumbinary planets, Kepler-34 and Kepler-35. Each is a low-density gas giant planet on an orbit closely aligned with that of its parentmore » stars. Kepler-34 orbits two Sun-like stars every 289 days, while Kepler-35 orbits a pair of smaller stars (89% and 81% of the Sun's mass) every 131 days. Due to the orbital motion of the stars, the planets experience large multi-periodic variations in incident stellar radiation. The observed rate of circumbinary planets implies > ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.« less

Tidal evolution of close binary asteroid systems

NASA Astrophysics Data System (ADS)

Taylor, Patrick A.; Margot, Jean-Luc

2010-12-01

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

Genealogy and stability of periodic orbit families around uniformly rotating asteroids

NASA Astrophysics Data System (ADS)

Hou, Xiyun; Xin, Xiaosheng; Feng, Jinglang

2018-03-01

Resonance orbits around a uniformly rotating asteroid are studied from the approach of periodic orbits in this work. Three periodic families (denoted as I, II, and III in the paper) are fundamental in organizing the resonance families. For the planar case: (1) Genealogy and stability of Families I, II and the prograde resonance families are studied. For extremely irregular asteroids, family genealogy close to the asteroid is greatly distorted from that of the two body-problem (2BP), indicating that it is inappropriate to treat the orbital motions as perturbed Keplerian orbits. (2) Genealogy and stability of Family III are also studied. Stability of this family may be destroyed by the secular resonance between the orbital ascending node's precession and the asteroid's rotation. For the spatial case: (1) Genealogy of the near circular three-dimensional periodic families are studied. The genealogy may be broken apart by families of eccentric frozen orbits whose argument of perigee is ;frozen; in space. (2) The joint effects between the secular resonance and the orbital resonances may cause instability to three-dimensional orbital motion with orbit inclinations close to the critical values. Applying the general methodology to a case study - the asteroid Eros and also considering higher order non-spherical terms, some extraordinary orbits are found, such as the ones with orbital plane co-rotating with the asteroid, and the stable frozen orbits with argument of perigee librating around values different from 0°, 90°, 180°, 270°.

Symmetry breaking and optical negative index of closed nanorings

NASA Astrophysics Data System (ADS)

Kanté, Boubacar; Park, Yong-Shik; O'Brien, Kevin; Shuldman, Daniel; Lanzillotti-Kimura, Norberto D.; Jing Wong, Zi; Yin, Xiaobo; Zhang, Xiang

2012-11-01

Metamaterials have extraordinary abilities, such as imaging beyond the diffraction limit and invisibility. Many metamaterials are based on split-ring structures, however, like atomic orbital currents, it has long been believed that closed rings cannot produce negative refractive index. Here we report a low-loss and polarization-independent negative-index metamaterial made solely of closed metallic nanorings. Using symmetry breaking that negatively couples the discrete nanorings, we measured negative phase delay in our composite ‘chess metamaterial’. The formation of an ultra-broad Fano-resonance-induced optical negative-index band, spanning wavelengths from 1.3 to 2.3 μm, is experimentally observed in this structure. This discrete and mono-particle negative-index approach opens exciting avenues towards symmetry-controlled topological nanophotonics with on-demand linear and nonlinear responses.

Operating Small Sat Swarms as a Single Entity: Introducing SODA

NASA Technical Reports Server (NTRS)

Conn, Tracie; Plice, Laura; Dono Perez, Andres; Ho, Michael

2017-01-01

NASA's decadal survey determined that simultaneous measurements from a 3D volume of space are advantageous for a variety of studies in space physics and Earth science. Therefore, swarm concepts with multiple spacecraft in close proximity are a growing topic of interest in the small satellite community. Among the capabilities needed for swarm missions is a means to maintain operator-specified geometry, alignment, or separation. Swarm stationkeeping poses a planning challenge due to the limited scalability of ground resources. To address scalable control of orbital dynamics, we introduce SODA - Swarm Orbital Dynamics Advisor - a tool that accepts high-level configuration commands and provides the orbital maneuvers needed to achieve the desired type of swarm relative motion. Rather than conventional path planning, SODA's innovation is the use of artificial potential functions to define boundaries and keepout regions. The software architecture includes high fidelity propagation, accommodates manual or automated inputs, displays motion animations, and returns maneuver commands and analytical results. Currently, two swarm types are enabled: in-train distribution and an ellipsoid volume container. Additional swarm types, simulation applications, and orbital destinations are in planning stages.

The distribution of ion orbit loss fluxes of ions and energy from the plasma edge across the last closed flux surface into the scrape-off layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stacey, Weston M.; Schumann, Matthew T.

A more detailed calculation strategy for the evaluation of ion orbit loss of thermalized plasma ions in the edge of tokamaks is presented. In both this and previous papers, the direct loss of particles from internal flux surfaces is calculated from the conservation of canonical angular momentum, energy, and magnetic moment. The previous result that almost all of the ion energy and particle fluxes crossing the last closed flux surface are in the form of ion orbit fluxes is confirmed, and the new result that the distributions of these fluxes crossing the last closed flux surface into the scrape-off layermore » are very strongly peaked about the outboard midplane is demonstrated. Previous results of a preferential loss of counter current particles leading to a co-current intrinsic rotation peaking just inside of the last closed flux surface are confirmed. Various physical details are discussed.« less

RESONANCES REQUIRED: DYNAMICAL ANALYSIS OF THE 24 Sex AND HD 200964 PLANETARY SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wittenmyer, Robert A.; Horner, Jonathan; Tinney, C. G., E-mail: rob@phys.unsw.edu.au

We perform several suites of highly detailed dynamical simulations to investigate the architectures of the 24 Sextantis and HD 200964 planetary systems. The best-fit orbital solution for the two planets in the 24 Sex system places them on orbits with periods that lie very close to 2:1 commensurability, while that for the HD 200964 system places the two planets therein in orbits whose periods lie close to a 4:3 commensurability. In both cases, the proposed best-fit orbits are mutually crossing-a scenario that is only dynamically feasible if the planets are protected from close encounters by the effects of mutual mean-motionmore » resonance (MMR). Our simulations reveal that the best-fit orbits for both systems lie within narrow islands of dynamical stability, and are surrounded by much larger regions of extreme instability. As such, we show that the planets are only feasible if they are currently trapped in mutual MMR-the 2:1 resonance in the case of 24 Sex b and c, and the 4:3 resonance in the case of HD 200964 b and c. In both cases, the region of stability is strongest and most pronounced when the planetary orbits are mutually coplanar. As the inclination of planet c with respect to planet b is increased, the stability of both systems rapidly collapses.« less

Spaceborne Autonomous and Ground Based Relative Orbit Control for the TerraSAR-X/TanDEM-X Formation

NASA Technical Reports Server (NTRS)

Ardaens, J. S.; D'Amico, S.; Kazeminejad, B.; Montenbruck, O.; Gill, E.

2007-01-01

TerraSAR-X (TSX) and TanDEM-X (TDX) are two advanced synthetic aperture radar (SAR) satellites flying in formation. SAR interferometry allows a high resolution imaging of the Earth by processing SAR images obtained from two slightly different orbits. TSX operates as a repeat-pass interferometer in the first phase of its lifetime and will be supplemented after two years by TDX in order to produce digital elevation models (DEM) with unprecedented accuracy. Such a flying formation makes indeed possible a simultaneous interferometric data acquisition characterized by highly flexible baselines with range of variations between a few hundreds meters and several kilometers [1]. TSX has been successfully launched on the 15th of June, 2007. TDX is expected to be launched on the 31st of May, 2009. A safe and robust maintenance of the formation is based on the concept of relative eccentricity/inclination (e/i) vector separation whose efficiency has already been demonstrated during the Gravity Recovery and Climate Experiment (GRACE) [2]. Here, the satellite relative motion is parameterized by mean of relative orbit elements and the key idea is to align the relative eccentricity and inclination vectors to minimize the hazard of a collision. Previous studies have already shown the pertinence of this concept and have described the way of controlling the formation using an impulsive deterministic control law [3]. Despite the completely different relative orbit control requirements, the same approach can be applied to the TSX/TDX formation. The task of TDX is to maintain the close formation configuration by actively controlling its relative motion with respect to TSX, the leader of the formation. TDX must replicate the absolute orbit keeping maneuvers executed by TSX and also compensate the natural deviation of the relative e/i vectors. In fact the relative orbital elements of the formation tend to drift because of the secular non-keplerian perturbations acting on both satellites. The goal of the ground segment is thus to regularly correct this configuration by performing small orbit correction maneuvers on TDX. The ground station contacts are limited due to the geographic position of the station and the costs for contact time. Only with a polar ground station a contact visibility is possible every orbit for LEO satellites. TSX and TDX use only the Weilheim ground station (in the southern part of Germany) during routine operations. This station allows two scheduled contact per day for the nominal orbit configuration, meaning that the satellite conditions can be checked with an interval of 12 hours. While this limitation is usually not critical for single satellite operations, the visibility constraints drive the achievable orbit control accuracy for a LEO formation if a ground based approach is chosen. Along-track position uncertainties and maneuver execution errors affect the relative motion and can be compensated only after a ground station contact.

Electrostatic Model Applied to ISS Charged Water Droplet Experiment

NASA Technical Reports Server (NTRS)

Stevenson, Daan; Schaub, Hanspeter; Pettit, Donald R.

2015-01-01

The electrostatic force can be used to create novel relative motion between charged bodies if it can be isolated from the stronger gravitational and dissipative forces. Recently, Coulomb orbital motion was demonstrated on the International Space Station by releasing charged water droplets in the vicinity of a charged knitting needle. In this investigation, the Multi-Sphere Method, an electrostatic model developed to study active spacecraft position control by Coulomb charging, is used to simulate the complex orbital motion of the droplets. When atmospheric drag is introduced, the simulated motion closely mimics that seen in the video footage of the experiment. The electrostatic force's inverse dependency on separation distance near the center of the needle lends itself to analytic predictions of the radial motion.

Homoclinic orbits and critical points of barrier functions

NASA Astrophysics Data System (ADS)

Cannarsa, Piermarco; Cheng, Wei

2015-06-01

We interpret the close link between the critical points of Mather's barrier functions and minimal homoclinic orbits with respect to the Aubry sets on {{T}}n . We also prove a critical point theorem for barrier functions and the existence of such homoclinic orbits on {{T}}2 as an application.

Closeup view of the Reinforced CarbonCarbon nose cap on the ...

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

Close-up view of the Reinforced Carbon-Carbon nose cap on the front fuselage of the Orbiter Discovery. Note the 76-wheeled orbiter transfer system attached to the orbiter at the forward attach point, the same attach point used to mount the orbiter onto the External Tank. This view was taken at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Uncertainty Modeling for Structural Control Analysis and Synthesis

NASA Technical Reports Server (NTRS)

Campbell, Mark E.; Crawley, Edward F.

1996-01-01

The development of an accurate model of uncertainties for the control of structures that undergo a change in operational environment, based solely on modeling and experimentation in the original environment is studied. The application used throughout this work is the development of an on-orbit uncertainty model based on ground modeling and experimentation. A ground based uncertainty model consisting of mean errors and bounds on critical structural parameters is developed. The uncertainty model is created using multiple data sets to observe all relevant uncertainties in the system. The Discrete Extended Kalman Filter is used as an identification/parameter estimation method for each data set, in addition to providing a covariance matrix which aids in the development of the uncertainty model. Once ground based modal uncertainties have been developed, they are localized to specific degrees of freedom in the form of mass and stiffness uncertainties. Two techniques are presented: a matrix method which develops the mass and stiffness uncertainties in a mathematical manner; and a sensitivity method which assumes a form for the mass and stiffness uncertainties in macroelements and scaling factors. This form allows the derivation of mass and stiffness uncertainties in a more physical manner. The mass and stiffness uncertainties of the ground based system are then mapped onto the on-orbit system, and projected to create an analogous on-orbit uncertainty model in the form of mean errors and bounds on critical parameters. The Middeck Active Control Experiment is introduced as experimental verification for the localization and projection methods developed. In addition, closed loop results from on-orbit operations of the experiment verify the use of the uncertainty model for control analysis and synthesis in space.

Mapping sequence performed during the STS-121 R-Bar Pitch Maneuver

NASA Image and Video Library

2006-07-06

ISS013-E-47629 (6 July 2006) --- A close-up view of Space Shuttle Discovery's tail section is featured in this image photographed by an Expedition 13 crewmember on the International Space Station during STS-121 R-Pitch Maneuver survey on Flight Day 3. Visible are the shuttle's main engines, vertical stabilizer, orbital maneuvering system (OMS) pods, reaction control system (RCS) jets and a portion of payload bay door radiator and wings.

Analysis of closed orbit deviations for a first direct deuteron electric dipole moment measurement at the cooler synchrotron COSY

NASA Astrophysics Data System (ADS)

Schmidt, V.; Lehrach, A.

2017-07-01

The Jülich Electric Dipole moment Investigations (JEDI) collaboration in Julich is preparing a direct EDM measurement of protons and deuterons first at the storage ring COSY (COoler SYnchrotron) and later at a dedicated storage ring. Ensuring a precise measurement, various beam and spin manipulating effects have to be considered and investigated. A distortion of the closed orbit is one of the major sources for systematic uncertainties. Therefore misalignments of magnets and residual power supply oscillations are simulated using the MAD-X code in order to analyse their effect on the orbit. The underlying model for all simulations includes the dipoles, quadrupoles and sextupoles at COSY as well as the corrector magnets and BPMs (Beam Position Monitors). Since most sextupoles are only used during beam extraction, the sextupole strengths are set to zero resulting in a linear machine. The optics is adjusted in a way that the dispersion is zero in the straight sections. The closed orbit studies are performed for deuterons with a momentum of 970 MeV/c.

Binary Star Orbits. V. The Nearby White Dwarf/Red Dwarf Pair 40 Eri BC

NASA Astrophysics Data System (ADS)

Mason, Brian D.; Hartkopf, William I.; Miles, Korie N.

2017-11-01

A new relative orbit solution with new dynamical masses is determined for the nearby white dwarf-red dwarf pair 40 Eri BC. The period is 230.09 ± 0.68 years. It is predicted to close slowly over the next half-century, getting as close as 1.″32 in early 2066. We determine masses of 0.575 ± 0.018 {{ M }}⊙ for the white dwarf and 0.2041 ± 0.0064 {{ M }}⊙ for the red dwarf companion. The inconsistency of the masses determined by gravitational redshift and dynamical techniques, due to a premature orbit calculation, no longer exists.

ISS Payload Racks Automated Flow Control Calibration Method

NASA Technical Reports Server (NTRS)

Simmonds, Boris G.

2003-01-01

Payload Racks utilize MTL and/or LTL station water for cooling of payloads and avionics. Flow control range from valves of fully closed, to up to 300 Ibmhr. Instrument accuracies are as high as f 7.5 Ibm/hr for flow sensors and f 3 Ibm/hr for valve controller, for a total system accuracy of f 10.5 Ibm/hr. Improved methodology was developed, tested and proven that reduces accuracy of the commanded flows to less than f 1 Ibmhr. Uethodology could be packed in a "calibration kit" for on- orbit flow sensor checkout and recalibration, extending the rack operations before return to earth. -

DOE Office of Scientific and Technical Information (OSTI.GOV)

Araujo, R. A. N.; Sfair, R.; Winter, O. C., E-mail: ran.araujo@gmail.com, E-mail: rsfair@feg.unesp.br, E-mail: ocwinter@gmail.com

The Centaur population is composed of minor bodies wandering between the giant planets that frequently perform close gravitational encounters with these planets, leading to a chaotic orbital evolution. Recently, the discovery of two well-defined narrow rings was announced around the Centaur 10199 Chariklo. The rings are assumed to be in the equatorial plane of Chariklo and to have circular orbits. The existence of a well-defined system of rings around a body in such a perturbed orbital region poses an interesting new problem. Are the rings of Chariklo stable when perturbed by close gravitational encounters with the giant planets? Our approachmore » to address this question consisted of forward and backward numerical simulations of 729 clones of Chariklo, with similar initial orbits, for a period of 100 Myr. We found, on average, that each clone experiences during its lifetime more than 150 close encounters with the giant planets within one Hill radius of the planet in question. We identified some extreme close encounters that were able to significantly disrupt or disturb the rings of Chariklo. About 3% of the clones lose their rings and about 4% of the clones have their rings significantly disturbed. Therefore, our results show that in most cases (more than 90%), the close encounters with the giant planets do not affect the stability of the rings in Chariklo-like systems. Thus, if there is an efficient mechanism that creates the rings, then these structures may be common among these kinds of Centaurs.« less

Excitations and relaxation dynamics in multiferroic GeV4S8 studied by terahertz and dielectric spectroscopy

NASA Astrophysics Data System (ADS)

Reschke, S.; Wang, Zhe; Mayr, F.; Ruff, E.; Lunkenheimer, P.; Tsurkan, V.; Loidl, A.

2017-10-01

We report on THz time-domain spectroscopy on multiferroic GeV4S8 , which undergoes orbital ordering at a Jahn-Teller transition at 30.5 K and exhibits antiferromagnetic order below 14.6 K. The THz experiments are complemented by dielectric experiments at audio and radio frequencies. We identify a low-lying excitation close to 0.5 THz, which is only weakly temperature dependent and probably corresponds to a molecular excitation within the electronic level scheme of the V4 clusters. In addition, we detect complex temperature-dependent behavior of a low-lying phononic excitation, closely linked to the onset of orbitally driven ferroelectricity. In the high-temperature cubic phase, which is paramagnetic and orbitally disordered, this excitation is of relaxational character becomes an overdamped Lorentzian mode in the orbitally ordered phase below the Jahn-Teller transition, and finally appears as well-defined phonon excitation in the antiferromagnetic state. Abrupt changes in the real and imaginary parts of the complex dielectric permittivity show that orbital ordering appears via a structural phase transition with strong first-order character and that the onset of antiferromagnetic order is accompanied by significant structural changes, which are of first-order character, too. Dielectric spectroscopy documents that at low frequencies, significant dipolar relaxations are present in the orbitally ordered, paramagnetic phase only. In contrast to the closely related GaV4S8 , this relaxation dynamics that most likely mirrors coupled orbital and polar fluctuations does not seem to be related to the dynamic processes detected in the THz regime.

Orbital stability close to asteroid 624 Hektor using the polyhedral model

NASA Astrophysics Data System (ADS)

Jiang, Yu; Baoyin, Hexi; Li, Hengnian

2018-03-01

We investigate the orbital stability close to the unique L4-point Jupiter binary Trojan asteroid 624 Hektor. The gravitational potential of 624 Hektor is calculated using the polyhedron model with observational data of 2038 faces and 1021 vertexes. Previous studies have presented three different density values for 624 Hektor. The equilibrium points in the gravitational potential of 624 Hektor with different density values have been studied in detail. There are five equilibrium points in the gravitational potential of 624 Hektor no matter the density value. The positions, Jacobian, eigenvalues, topological cases, stability, as well as the Hessian matrix of the equilibrium points are investigated. For the three different density values the number, topological cases, and the stability of the equilibrium points with different density values are the same. However, the positions of the equilibrium points vary with the density value of the asteroid 624 Hektor. The outer equilibrium points move away from the asteroid's mass center when the density increases, and the inner equilibrium point moves close to the asteroid's mass center when the density increases. There exist unstable periodic orbits near the surface of 624 Hektor. We calculated an orbit near the primary's equatorial plane of this binary Trojan asteroid; the results indicate that the orbit remains stable after 28.8375 d.

Galileo Jupiter approach orbit determination

NASA Technical Reports Server (NTRS)

Miller, J. K.; Nicholson, F. T.

1984-01-01

Orbit determination characteristics of the Jupiter approach phase of the Galileo mission are described. Predicted orbit determination performance is given for the various mission events that occur during Jupiter approach. These mission events include delivery of an atmospheric entry probe, acquisition of probe science data by the Galileo orbiter for relay to earth, delivery of an orbiter to a close encounter of the Galilean satellite Io, and insertion of the orbiter into orbit about Jupiter. The orbit determination strategy and resulting accuracies are discussed for the data types which include Doppler, range, optical imaging of Io, and a new Very Long Baseline Interferometry (VLBI) data type called Differential One-Way Range (DOR).

Space Shuttle Projects

NASA Image and Video Library

1984-04-01

The Long Duration Exposure Facility (LDEF) was designed by the Marshall Space Flight Center (MSFC) to test the performance of spacecraft materials, components, and systems that have been exposed to the environment of micrometeoroids and space debris for an extended period of time. The LDEF proved invaluable to the development of future spacecraft and the International Space Station (ISS). The LDEF carried 57 science and technology experiments, the work of more than 200 investigators. MSFC`s experiments included: Trapped Proton Energy Determination to determine protons trapped in the Earth's magnetic field and the impact of radiation particles; Linear Energy Transfer Spectrum Measurement Experiment which measures the linear energy transfer spectrum behind different shielding configurations; Atomic oxygen-Simulated Out-gassing, an experiment that exposes thermal control surfaces to atomic oxygen to measure the damaging out-gassed products; Thermal Control Surfaces Experiment to determine the effects of the near-Earth orbital environment and the shuttle induced environment on spacecraft thermal control surfaces; Transverse Flat-Plate Heat Pipe Experiment, to evaluate the zero-gravity performance of a number of transverse flat plate heat pipe modules and their ability to transport large quantities of heat; Solar Array Materials Passive LDEF Experiment to examine the effects of space on mechanical, electrical, and optical properties of lightweight solar array materials; and the Effects of Solar Radiation on Glasses. Launched aboard the Space Shuttle Orbiter Challenger's STS-41C mission April 6, 1984, the LDEF remained in orbit for five years until January 1990 when it was retrieved by the Space Shuttle Orbiter Columbia STS-32 mission and brought back to Earth for close examination and analysis.

Long Duration Exposure Facility (LDEF)

NASA Technical Reports Server (NTRS)

1984-01-01

The Long Duration Exposure Facility (LDEF) was designed by the Marshall Space Flight Center (MSFC) to test the performance of spacecraft materials, components, and systems that have been exposed to the environment of micrometeoroids and space debris for an extended period of time. The LDEF proved invaluable to the development of future spacecraft and the International Space Station (ISS). The LDEF carried 57 science and technology experiments, the work of more than 200 investigators. MSFC`s experiments included: Trapped Proton Energy Determination to determine protons trapped in the Earth's magnetic field and the impact of radiation particles; Linear Energy Transfer Spectrum Measurement Experiment which measures the linear energy transfer spectrum behind different shielding configurations; Atomic oxygen-Simulated Out-gassing, an experiment that exposes thermal control surfaces to atomic oxygen to measure the damaging out-gassed products; Thermal Control Surfaces Experiment to determine the effects of the near-Earth orbital environment and the shuttle induced environment on spacecraft thermal control surfaces; Transverse Flat-Plate Heat Pipe Experiment, to evaluate the zero-gravity performance of a number of transverse flat plate heat pipe modules and their ability to transport large quantities of heat; Solar Array Materials Passive LDEF Experiment to examine the effects of space on mechanical, electrical, and optical properties of lightweight solar array materials; and the Effects of Solar Radiation on Glasses. Launched aboard the Space Shuttle Orbiter Challenger's STS-41C mission April 6, 1984, the LDEF remained in orbit for five years until January 1990 when it was retrieved by the Space Shuttle Orbiter Columbia STS-32 mission and brought back to Earth for close examination and analysis.

Search for and Study of Nearly Periodic Orbits in the Plane Problem of Three Equal-Mass Bodies

NASA Astrophysics Data System (ADS)

Martynova, A. I.; Orlov, V. V.

2005-09-01

We analyze nearly periodic solutions in the plane problem of three equal-mass bodies by numerically simulating the dynamics of triple systems. We identify families of orbits in which all three points are on one straight line (syzygy) at the initial time. In this case, at fixed total energy of a triple system, the set of initial conditions is a bounded region in four-dimensional parameter space. We scan this region and identify sets of trajectories in which the coordinates and velocities of all bodies are close to their initial values at certain times (which are approximately multiples of the period). We classify the nearly periodic orbits by the structure of trajectory loops over one period. We have found the families of orbits generated by von Schubart’s stable periodic orbit revealed in the rectilinear three-body problem. We have also found families of hierarchical, nearly periodic trajectories with prograde and retrograde motions. In the orbits with prograde motions, the trajectory loops of two close bodies form looplike structures. The trajectories with retrograde motions are characterized by leafed structures. Orbits with central and axial symmetries are identified among the families found.

Transiting circumbinary planets Kepler-34 b and Kepler-35 b.

PubMed

Welsh, William F; Orosz, Jerome A; Carter, Joshua A; Fabrycky, Daniel C; Ford, Eric B; Lissauer, Jack J; Prša, Andrej; Quinn, Samuel N; Ragozzine, Darin; Short, Donald R; Torres, Guillermo; Winn, Joshua N; Doyle, Laurance R; Barclay, Thomas; Batalha, Natalie; Bloemen, Steven; Brugamyer, Erik; Buchhave, Lars A; Caldwell, Caroline; Caldwell, Douglas A; Christiansen, Jessie L; Ciardi, David R; Cochran, William D; Endl, Michael; Fortney, Jonathan J; Gautier, Thomas N; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer R; Holman, Matthew J; Howard, Andrew W; Howell, Steve B; Isaacson, Howard; Jenkins, Jon M; Klaus, Todd C; Latham, David W; Li, Jie; Marcy, Geoffrey W; Mazeh, Tsevi; Quintana, Elisa V; Robertson, Paul; Shporer, Avi; Steffen, Jason H; Windmiller, Gur; Koch, David G; Borucki, William J

2012-01-11

Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries). Although long anticipated, the existence of a 'circumbinary planet' orbiting such a pair of normal stars was not definitively established until the discovery of the planet transiting (that is, passing in front of) Kepler-16. Questions remained, however, about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we report two additional transiting circumbinary planets: Kepler-34 (AB)b and Kepler-35 (AB)b, referred to here as Kepler-34 b and Kepler-35 b, respectively. Each is a low-density gas-giant planet on an orbit closely aligned with that of its parent stars. Kepler-34 b orbits two Sun-like stars every 289 days, whereas Kepler-35 b orbits a pair of smaller stars (89% and 81% of the Sun's mass) every 131 days. The planets experience large multi-periodic variations in incident stellar radiation arising from the orbital motion of the stars. The observed rate of circumbinary planets in our sample implies that more than ∼1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.

The magnetic field in the very close neighborhood of Mars according to data from the Mars 2 and Mars 3 spacecraft

NASA Technical Reports Server (NTRS)

Dolginov, S. S.; Yeroshenko, Y. G.; Zhuzgov, L. N.

1972-01-01

The magnetic field in the close proximity of planet Mars according to data from Mars 2 and Mars 3 spacecraft is discussed. The magnetometers on the spacecraft detected a field whose intensity near the orbital periapses was 7 to 10 times higher than the interplanetary field at the distance of the Martian orbit. The nature of the observed field is described.

Hypervelocity stars from young stellar clusters in the Galactic Centre

NASA Astrophysics Data System (ADS)

Fragione, G.; Capuzzo-Dolcetta, R.; Kroupa, P.

2017-05-01

The enormous velocities of the so-called hypervelocity stars (HVSs) derive, likely, from close interactions with massive black holes, binary stars encounters or supernova explosions. In this paper, we investigate the origin of HVSs as consequence of the close interaction between the Milky Way central massive black hole and a passing-by young stellar cluster. We found that both single and binary HVSs may be generated in a burst-like event, as the cluster passes near the orbital pericentre. High-velocity stars will move close to the initial cluster orbital plane and in the direction of the cluster orbital motion at the pericentre. The binary fraction of these HVS jets depends on the primordial binary fraction in the young cluster. The level of initial mass segregation determines the value of the average mass of the ejected stars. Some binary stars will merge, continuing their travel across and out of the Galaxy as blue stragglers.

KSC-04pd1599

NASA Image and Video Library

2004-07-14

KENNEDY SPACE CENTER, FLA. - At Vandenberg Air Force Base in California, Orbital Sciences technicians watch closely as the DART (Demonstration for Autonomous Rendezvous Technology) flight demonstrator is lowered onto a stand. The spacecraft was developed to prove technologies for locating and maneuvering near an orbiting satellite. Future applications of technologies developed by the DART project will benefit the nation in future space-vehicle systems development requiring in-space assembly, services or other autonomous rendezvous operations. Designed and developed for NASA by Orbital Sciences Corporation in Dulles, Va., the DART spacecraft will be launched on a Pegasus launch vehicle. At about 40,000 feet over the Pacific Ocean, the Pegasus will be released from Orbital’s Stargazer L-1011 aircraft, fire its rocket motors and boost DART into a polar orbit approximately 472 miles by 479 miles. Once in orbit, DART will rendezvous with a target satellite, the Multiple Paths, Beyond-Line-of-Site Communications satellite, also built by Orbital Sciences. DART will then perform several close proximity operations, such as moving toward and away from the satellite using navigation data provided by onboard sensors. DART is scheduled for launch no earlier than Oct. 18.

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

Polarized proton beams are accelerated in RHIC to 250 GeV energy with the help of Siberian Snakes. The pair of Siberian Snakes in each RHIC ring holds the design spin tune at 1/2 to avoid polarization loss during acceleration. However, in the presence of closed orbit errors, the actual spin tune can be shifted away from the exact 1/2 value. It leads to a corresponding shift of locations of higher-order ('snake') resonances and limits the available betatron tune space. The largest closed orbit effect on the spin tune comes from the horizontal orbit angle between the two snakes. During RHICmore » Run in 2009 dedicated measurements with polarized proton beams were taken to verify the dependence of the spin tune on the local orbits at the Snakes. The experimental results are presented along with the comparison with analytical predictions.« less

Unity hatch closed in preparation for launch on STS-88

NASA Technical Reports Server (NTRS)

1998-01-01

Workers in the Space Station Processing Facility prepare the Unity connecting module for closure before its launch aboard Space Shuttle Endeavour on STS-88 in December. Unity will now undergo a series of leak checks before a final purge of clean, dry air inside the module to ready it for initial operations in space. Other testing includes the common berthing mechanism to which other space station elements will dock and the Pad Demonstration Test to verify the compatibility of the module with the Space Shuttle as well as the ability of the astronauts to send and receive commands to Unity from the flight deck of the orbiter. The next time the hatch will be opened it will be by astronauts on orbit. Unity is expected to be ready for installation into the payload canister on Oct. 25, and transported to Launch Pad 39-A on Oct. 27. The Unity will be mated to the Russian-built Zarya control module which should already be in orbit at that time.

Unity hatch closed in preparation for launch on STS-88

NASA Technical Reports Server (NTRS)

1998-01-01

Workers in the Space Station Processing Facility prepare the hatch of the Unity connecting module for closure before its launch aboard Space Shuttle Endeavour on STS-88 in December. Unity will now undergo a series of leak checks before a final purge of clean, dry air inside the module to ready it for initial operations in space. Other testing includes the common berthing mechanism to which other space station elements will dock and the Pad Demonstration Test to verify the compatibility of the module with the Space Shuttle as well as the ability of the astronauts to send and receive commands to Unity from the flight deck of the orbiter. The next time the hatch will be opened it will be by astronauts on orbit. Unity is expected to be ready for installation into the payload canister on Oct. 25, and transported to Launch Pad 39-A on Oct. 27. The Unity will be mated to the Russian-built Zarya control module which should already be in orbit at that time.

The Torino Impact Hazard Scale

NASA Astrophysics Data System (ADS)

Binzel, Richard P.

2000-04-01

Newly discovered asteroids and comets have inherent uncertainties in their orbit determinations owing to the natural limits of positional measurement precision and the finite lengths of orbital arcs over which determinations are made. For some objects making predictable future close approaches to the Earth, orbital uncertainties may be such that a collision with the Earth cannot be ruled out. Careful and responsible communication between astronomers and the public is required for reporting these predictions and a 0-10 point hazard scale, reported inseparably with the date of close encounter, is recommended as a simple and efficient tool for this purpose. The goal of this scale, endorsed as the Torino Impact Hazard Scale, is to place into context the level of public concern that is warranted for any close encounter event within the next century. Concomitant reporting of the close encounter date further conveys the sense of urgency that is warranted. The Torino Scale value for a close approach event is based upon both collision probability and the estimated kinetic energy (collision consequence), where the scale value can change as probability and energy estimates are refined by further data. On the scale, Category 1 corresponds to collision probabilities that are comparable to the current annual chance for any given size impactor. Categories 8-10 correspond to certain (probability >99%) collisions having increasingly dire consequences. While close approaches falling Category 0 may be no cause for noteworthy public concern, there remains a professional responsibility to further refine orbital parameters for such objects and a figure of merit is suggested for evaluating such objects. Because impact predictions represent a multi-dimensional problem, there is no unique or perfect translation into a one-dimensional system such as the Torino Scale. These limitations are discussed.

Solar Orbiter Status Report

NASA Astrophysics Data System (ADS)

Gilbert, Holly; St. Cyr, Orville Chris; Mueller, Daniel; Zouganelis, Yannis; Velli, Marco

2017-08-01

With the delivery of the instruments to the spacecraft builder, the Solar Orbiter mission is in the midst of Integration & Testing phase at Airbus in Stevenage, U.K. This mission to “Explore the Sun-Heliosphere Connection” is the first medium-class mission of ESA’s Cosmic Vision 2015-2025 program and is being jointly implemented with NASA. The dedicated payload of 10 remote-sensing and in-situ instruments will orbit the Sun as close as 0.3 A.U. and will provide measurments from the photosphere into the solar wind. The three-axis stabilized spacecraft will use Venus gravity assists to increase the orbital inclination out of the ecliptic to solar latitudes as high as 34 degrees in the extended mission. The science team of Solar Orbiter has been working closely with the Solar Probe Plus scientists to coordinate observations between these two highly-complementary missions. This will be a status report on the mission development; the interested reader is referred to the recent summary by Müller et al., Solar Physics 285 (2013).

Saturn's Magnetic Field from the Cassini Grand Finale orbits

NASA Astrophysics Data System (ADS)

Dougherty, M. K.; Cao, H.; Khurana, K. K.; Hunt, G. J.; Provan, G.; Kellock, S.; Burton, M. E.; Burk, T. A.

2017-12-01

The fundamental aims of the Cassini magnetometer investigation during the Cassini Grand Finale orbits were determination of Saturn's internal planetary magnetic field and the rotation rate of the deep interior. The unique geometry of the orbits provided an unprecedented opportunity to measure the intrinsic magnetic field at close distances never before encountered. The surprising close alignment of Saturn's magnetic axis with its spin axis, known about since the days of Pioneer 11, has been a focus of the team's analysis since Cassini Saturn Orbit Insertion. However, the varying northern and southern magnetospheric planetary period oscillations, which fill the magnetosphere, has been a factor in masking the field signals from the interior. Here we describe an overview of the magnetometer results from the Grand Finale orbits, including confirmation of the extreme axisymmetric nature of the planetary magnetic field, implications for knowledge of the rotation rate and the behaviour of external magnetic fields (arising from the ring current, field aligned currents both at high and low latitudes and the modulating effect of the planetary period oscillations).

IGARSS 89: Canadian Symposium on Remote Sensing (12th) (Symposium Canadien sur la Teledetection): Quantitative Remote Sensing: An Economic Tool for the Nineties Held in Vancouver, Canada on 10-14 July 1989. Volume 2. Tuesday, July 11

DTIC Science & Technology

1989-07-14

blunder-free DEMs, the manual verification group of Ground Control Points (GCPs); (ii) and editing stage is still needed. the orbit and attitude of... control the influence (weight) of the sources and model the that each information class only had one subclass! To set non -Gaussian data. When the...clear line of infinitesimally close laminae sliding parallel to a shear line of shear; a quasi -brittle inner regime and a non -linear viscous outer

Tidal dissipation in rotating low-mass stars and implications for the orbital evolution of close-in planets. I. From the PMS to the RGB at solar metallicity

NASA Astrophysics Data System (ADS)

Gallet, F.; Bolmont, E.; Mathis, S.; Charbonnel, C.; Amard, L.

2017-08-01

Context. Star-planet interactions must be taken into account in stellar models to understand the dynamical evolution of close-in planets. The dependence of the tidal interactions on the structural and rotational evolution of the star is of particular importance and should be correctly treated. Aims: We quantify how tidal dissipation in the convective envelope of rotating low-mass stars evolves from the pre-main sequence up to the red-giant branch depending on the initial stellar mass. We investigate the consequences of this evolution on planetary orbital evolution. Methods: We couple the tidal dissipation formalism previously described to the stellar evolution code STAREVOL and apply this coupling to rotating stars with masses between 0.3 and 1.4 M⊙. As a first step, this formalism assumes a simplified bi-layer stellar structure with corresponding averaged densities for the radiative core and the convective envelope. We use a frequency-averaged treatment of the dissipation of tidal inertial waves in the convection zone (but neglect the dissipation of tidal gravity waves in the radiation zone). In addition, we generalize a recent work by following the orbital evolution of close-in planets using the new tidal dissipation predictions for advanced phases of stellar evolution. Results: On the pre-main sequence the evolution of tidal dissipation is controlled by the evolution of the internal structure of the contracting star. On the main sequence it is strongly driven by the variation of surface rotation that is impacted by magnetized stellar winds braking. The main effect of taking into account the rotational evolution of the stars is to lower the tidal dissipation strength by about four orders of magnitude on the main sequence, compared to a normalized dissipation rate that only takes into account structural changes. Conclusions: The evolution of the dissipation strongly depends on the evolution of the internal structure and rotation of the star. From the pre-main sequence up to the tip of the red-giant branch, it varies by several orders of magnitude, with strong consequences for the orbital evolution of close-in massive planets. These effects are the strongest during the pre-main sequence, implying that the planets are mainly sensitive to the star's early history.

The Eccentric Behavior of Nearly Frozen Orbits

NASA Technical Reports Server (NTRS)

Sweetser, Theodore H.; Vincent, Mark A.

2013-01-01

Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argument of periapse, so that they basically keep a fixed orientation within their plane of motion. Nearly frozen orbits are those whose eccentricity and argument of periapse have values close to those of a frozen orbit. We call them "nearly" frozen because their eccentricity vector (a vector whose polar coordinates are eccentricity and argument of periapse) will stay within a bounded distance from the frozen orbit eccentricity vector, circulating around it over time. For highly inclined orbits around the Earth, this distance is effectively constant over time. Furthermore, frozen orbit eccentricity values are low enough that these orbits are essentially eccentric (i.e., off center) circles, so that nearly frozen orbits around Earth are bounded above and below by frozen orbits.

Closeup view if the starboard side of the crew compartment ...

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

Close-up view if the starboard side of the crew compartment mid-deck of the Orbiter Discovery. This is a close up view of the galley for meal preparations. In the center right of the image is stowage lockers that are designated to store meals for the mission. This photograph was taken at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Search for kinematic siblings of the sun based on data from the XHIP catalog

NASA Astrophysics Data System (ADS)

Bobylev, V. V.; Bajkova, A. T.

2014-06-01

From the XHIP catalogue, we have selected 1872 F-G-K stars with relative parallax measurement errors <20% and absolute values of their space velocities relative to the Sun <15 km s-1. For all these stars, we have constructed their Galactic orbits for 4.5 Gyr into the past using an axisymmetric Galactic potential model with allowance made for the perturbations from the spiral density wave. Parameters of the encounter with the solar orbit have been calculated for each orbit. We have detected three new stars whose Galactic orbits were close to the solar one during a long time interval in the past. These stars are HIP 43852, HIP 104047, and HIP 112158. The spectroscopic binary HIP 112158 is poorly suited for the role of a kinematic sibling of the Sun by its age and spectroscopic characteristics. For the single star HIP 43852 and the multiple system HIP 104047, this role is quite possible. We have also confirmed the status of our previously found candidates for close encounters, HIP 47399 and HIP 87382. The star HIP 87382 with a chemical composition very close to the solar one is currently the most likely candidate, because it persistently shows close encounters with the Sun on time scales of more than 3 Gyr when using various Galactic potential models both without and with allowance made for the influence of the spiral density wave.

Orbit correction in a linear nonscaling fixed field alternating gradient accelerator

DOE PAGES

Kelliher, D. J.; Machida, S.; Edmonds, C. S.; ...

2014-11-20

In a linear non-scaling FFAG the large natural chromaticity of the machine results in a betatron tune that varies by several integers over the momentum range. In addition, orbit correction is complicated by the consequent variation of the phase advance between lattice elements. Here we investigate how the correction of multiple closed orbit harmonics allows correction of both the COD and the accelerated orbit distortion over the momentum range.

SKYLAB (SL)-3 - TELEVISION

NASA Image and Video Library

1973-09-29

S73-34619 (28 July 1973) --- A composite of four frames taken from 16mm movie camera footage showing an overhead view of the Skylab space station cluster in Earth orbit. The Maurer motion picture camera scenes were being filmed during the Skylab 3 Command/Service Module's (CSM) first "fly around" inspection of the space station. Close comparison of the four frames reveals movement of the improvised parasol solar shield over the Orbital Workshop (OWS). The "flapping" of the sun shade was caused from the exhaust of the reaction control subsystem (RCS) thrusters of the Skylab 3 CSM. The one remaining solar array system wing on the OWS is in the lower left background. The solar panel in the lower left foreground is on the Apollo Telescope Mount (ATM). Photo credit: NASA

CAM controlled retractable door latch

NASA Technical Reports Server (NTRS)

Carsley, R. B. (Inventor)

1982-01-01

A latching mechanism in which there is linear movement and rotational movement is described. The umbilical doors of the space shuttle orbiter are required to be open during vehicle launch. After the external tank is released, the doors are closed. Presently, the device for maintaining the doors in an open position is mounted on the external tank and therefore has a single mission life. The latching mechanism of the invention is mounted in the orbiter and therefore is returned and has multimission capability. The latching mechanism is comprised of a pair of concentric nested, cylindrical cams and motors to actuate the cams, and latch pin all contained within a cover mounted on a support bracket carried by the substructure. A shaft having a latch pin is mounted inside the inner cylindrical cam.

Astronaut James McDivitt photographed inside Command Module during Apollo 9

NASA Image and Video Library

1969-03-06

AS09-20-3154 (3-13 March 1969) --- This close-up view of astronaut James A. McDivitt shows several days' beard growth. The Apollo 9 mission commander was onboard the Lunar Module (LM) "Spider" in Earth orbit, near the end of the flight. He was joined on the mission by astronauts David R. Scott, command module pilot, and Russell L. Schweickart, lunar module pilot. Schweickart took this picture while Scott remained in the Command Module (CM) "Gumdrop." In Earth orbit, the three tested the transposition and docking systems of the lunar module and command module. On a scheduled lunar landing mission later this year, a team of three astronauts and ground controllers will use what this crew and its support staff have learned in handling the systems of the two spacecraft.

The Space Station Freedom - International cooperation and innovation in space safety

NASA Technical Reports Server (NTRS)

Rodney, George A.

1989-01-01

The Space Station Freedom (SSF) being developed by the United States, European Space Agency (ESA), Japan, and Canada poses novel safety challenges in design, operations, logistics, and program management. A brief overview discloses many features that make SSF a radical departure from earlier low earth orbit (LEO) space stations relative to safety management: size and power levels; multiphase manned assembly; 30-year planned lifetime, with embedded 'hooks and scars' forevolution; crew size and skill-mix variability; sustained logistical dependence; use of man, robotics and telepresence for on-orbit maintenance of station and free-flyer systems; closed-environment recycling; use of automation and expert systems; long-term operation of collocated life-sciences and materials-science experiments, requiring control and segregation of hazardous and chemically incompatible materials; and materials aging in space.

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

NASA Technical Reports Server (NTRS)

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

1961-01-01

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

Closeup view of the nose and landing gear on the ...

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

Close-up view of the nose and landing gear on the forward section of the Orbiter Discovery in the Orbiter Processing Facility at Kennedy Space Center. The Orbiter is being supported by jack stands in the left and right portion of the view. The jack stands attach to the Orbiter at the four hoist attach points, two located on the forward fuselage and two on the aft fuselage. Note the access platforms that surround and nearly touch the orbiter. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Efficient and accurate local single reference correlation methods for high-spin open-shell molecules using pair natural orbitals

NASA Astrophysics Data System (ADS)

Hansen, Andreas; Liakos, Dimitrios G.; Neese, Frank

2011-12-01

A production level implementation of the high-spin open-shell (spin unrestricted) single reference coupled pair, quadratic configuration interaction and coupled cluster methods with up to doubly excited determinants in the framework of the local pair natural orbital (LPNO) concept is reported. This work is an extension of the closed-shell LPNO methods developed earlier [F. Neese, F. Wennmohs, and A. Hansen, J. Chem. Phys. 130, 114108 (2009), 10.1063/1.3086717; F. Neese, A. Hansen, and D. G. Liakos, J. Chem. Phys. 131, 064103 (2009), 10.1063/1.3173827]. The internal space is spanned by localized orbitals, while the external space for each electron pair is represented by a truncated PNO expansion. The laborious integral transformation associated with the large number of PNOs becomes feasible through the extensive use of density fitting (resolution of the identity (RI)) techniques. Technical complications arising for the open-shell case and the use of quasi-restricted orbitals for the construction of the reference determinant are discussed in detail. As in the closed-shell case, only three cutoff parameters control the average number of PNOs per electron pair, the size of the significant pair list, and the number of contributing auxiliary basis functions per PNO. The chosen threshold default values ensure robustness and the results of the parent canonical methods are reproduced to high accuracy. Comprehensive numerical tests on absolute and relative energies as well as timings consistently show that the outstanding performance of the LPNO methods carries over to the open-shell case with minor modifications. Finally, hyperfine couplings calculated with the variational LPNO-CEPA/1 method, for which a well-defined expectation value type density exists, indicate the great potential of the LPNO approach for the efficient calculation of molecular properties.

Stirring of a planetesimal swarm - The role of distant encounters

NASA Technical Reports Server (NTRS)

Weidenschilling, Stuart J.

1989-01-01

The viscous stirring algorithm developed by Stewart and Wetherill (1988) to treat the random velocities induced in planetesimals by their mutual gravitational perturbations encompasses only the scattering of bodies in crossing orbits by close encounters. Expressions are presently derived for the stirring rate due to distant encounters on the basis of three-body formalism, using a stirring rate that has the same mass-dependence as that for close encounters. The relative importance of both the close encounter and distant encounter mechanisms depends on the Safronov number. Perturbations by a planetary embryo in scenarios that involve explosive growth are found capable of affecting planetesimal evolution in noncrossing orbits.

Autonomous docking system for space structures and satellites

NASA Astrophysics Data System (ADS)

Prasad, Guru; Tajudeen, Eddie; Spenser, James

2005-05-01

Aximetric proposes Distributed Command and Control (C2) architecture for autonomous on-orbit assembly in space with our unique vision and sensor driven docking mechanism. Aximetric is currently working on ip based distributed control strategies, docking/mating plate, alignment and latching mechanism, umbilical structure/cord designs, and hardware/software in a closed loop architecture for smart autonomous demonstration utilizing proven developments in sensor and docking technology. These technologies can be effectively applied to many transferring/conveying and on-orbit servicing applications to include the capturing and coupling of space bound vehicles and components. The autonomous system will be a "smart" system that will incorporate a vision system used for identifying, tracking, locating and mating the transferring device to the receiving device. A robustly designed coupler for the transfer of the fuel will be integrated. Advanced sealing technology will be utilized for isolation and purging of resulting cavities from the mating process and/or from the incorporation of other electrical and data acquisition devices used as part of the overall smart system.

Scanning Mechanism of the FY-3 Microwave Humidity Sounder

NASA Technical Reports Server (NTRS)

Schmid, Manfred; Jing, Li; Hehr, Christian

2010-01-01

Astrium GmbH Germany, developed the scanning equipment for the instrument package of the MicroWave Humidity Sounder (MWHS) flying on the FY-3 meteorological satellite (FY means Feng Yun, Wind and Cloud) in a sun-synchronized orbit of 850-km altitude and at an inclination of 98.8 . The scanning mechanism rotates at variable velocity comprising several acceleration / deceleration phases during each revolution. The Scanning Mechanism contains two output shafts, each rotating a parabolic offset Antenna Reflector. The mechanism is operated in closed loop by means of redundant control electronics. MWHS is a sounding radiometer for measurement of global atmospheric water vapour profiles. An Engineering Qualification Model was developed and qualified and a first Flight Model was launched early 2008. The system is now working for more than two years successful in orbit. A second Flight Model of the Antenna Scanning Mechanism and of its associated control electronics was built and delivered to the customer for application on the follow-on spacecraft that will be launched by the end of 2010.

Guidance and Control strategies for aerospace vehicles

NASA Technical Reports Server (NTRS)

Hibey, J. L.; Naidu, D. S.; Charalambous, C. D.

1989-01-01

A neighboring optimal guidance scheme was devised for a nonlinear dynamic system with stochastic inputs and perfect measurements as applicable to fuel optimal control of an aeroassisted orbital transfer vehicle. For the deterministic nonlinear dynamic system describing the atmospheric maneuver, a nominal trajectory was determined. Then, a neighboring, optimal guidance scheme was obtained for open loop and closed loop control configurations. Taking modelling uncertainties into account, a linear, stochastic, neighboring optimal guidance scheme was devised. Finally, the optimal trajectory was approximated as the sum of the deterministic nominal trajectory and the stochastic neighboring optimal solution. Numerical results are presented for a typical vehicle. A fuel-optimal control problem in aeroassisted noncoplanar orbital transfer is also addressed. The equations of motion for the atmospheric maneuver are nonlinear and the optimal (nominal) trajectory and control are obtained. In order to follow the nominal trajectory under actual conditions, a neighboring optimum guidance scheme is designed using linear quadratic regulator theory for onboard real-time implementation. One of the state variables is used as the independent variable in reference to the time. The weighting matrices in the performance index are chosen by a combination of a heuristic method and an optimal modal approach. The necessary feedback control law is obtained in order to minimize the deviations from the nominal conditions.

Deformation-Induced Precession of a Robot Moving on Curved Space

NASA Astrophysics Data System (ADS)

Li, Shengkai; Aydin, Yasemin; Lofaro, Olivia; Rieser, Jennifer; Goldman, Daniel

Previous studies have demonstrated that passive particles rolling on a deformed surface can mimic aspects of general relativity [Ford et al, AJP, 2015]. However, these systems are dissipative. To explore steady-state dynamics, we study the movement of a self-propelled robot car on a large deformable elastic membrane: a spandex sheet stretched over a metal frame with a diameter of 2.5 m. Two wheels in the rear of the car are differentially-driven by a DC motor, and a caster in the front helps maintain directional stability; in the absence of curvature the car drives straight. A linear actuator attached below the membrane allows for controlled deformation at the center of the membrane. We find that closed elliptic orbits occur when the membrane is highly depressed ( 10 cm). However, when the center is only slightly indented, the elliptical orbits precess at a rate depending on the orbit shape and the depression. Remarkably, this dynamic is well described by the Schwarzschild metric solution, typically used to describe the effects of gravity on bodies orbiting a massive object. Experiments with multiple cars reveal complex interactions that are mediated through car-induced deformations of the membrane.

Development of the Kiel sensors for the EPD instrument on-board Solar Orbiter

NASA Astrophysics Data System (ADS)

Martin, Cesar; Wimmer-Schweingruber, Robert F.; Kulkarni, Shrinivasrao R.; Tammen, Jan; Terasa, Christoph; Yu, Jia; Boden, Sebastian; Steinhagen, Jan; Panitzsch, Lauri; Ravanbakhsh, Ali; Boettcher, Stephan; Hamann, Christian; Seimetz, Lars; Rodriguez-Pacheco, Javier

2015-04-01

Solar Orbiter is ESA's next solar and heliospheric mission, planned for launch in January 2017 and approaching the Sun as close as 0.28 AU. One of the Solar Orbiter's scientific questions is "How do the solar eruptions produce energetic particle radiation that fills the heliosphere?". The Energetic Particle Detector (EPD) will provide key measurements for this and the other Solar Orbiter science objectives. The EPD suite consists of four sensors measuring electrons, protons, and ions from helium to iron, and operating at partly overlapping energy ranges from 2 keV/n up to 200 MeV/n. The EPD sensors are: SupraThermal Electrons and Protons(STEP), Suprathermal Ion Spectrograph (SIS), Electron Proton Telescope (EPT) and High Energy Telescope (HET). Besides, the EPD sensors share the Instrument Control Unit (ICU). The University of Kiel in Germany is responsible for developing the EPT-HET, STEP and SIS sensors. Here we present the development status of the EPT-HET and STEP sensors focusing on the activities planned for the current phase C. Those activities include results of the integration and EMC tests on the EPT-HET and STEP Engineering Model (EM) and the assembly of the Proto Qualification Model (PQM).

Development of the Kiel sensors for the EPD instrument on-board Solar Orbiter

NASA Astrophysics Data System (ADS)

Martin, Cesar; Wimmer-Schweingruber, Robert F.; Kulkarni, Shrinivasrao R.; Tammen, Jan; Terasa, Christoph; Yu, Jia; Boden, Sebastian; Steinhagen, Jan; Panitzsch, Lauri; Ravanbakhsh, Ali; Boettcher, Stephan; Hamann, Christian; Seimetz, Lars; Rodriguez-Pacheco, Javier

2014-05-01

Solar Orbiter is ESA's next solar and heliospheric mission, planned for launch in January 2017 and approaching the Sun as close as 0.28 AU. One of the Solar Orbiter's scientific questions is "How do the solar eruptions produce energetic particle radiation that fills the heliosphere?". The Energetic Particle Detector (EPD) will provide key measurements for this and the other Solar Orbiter science objectives. The EPD suite consists of four sensors measuring electrons, protons, and ions from helium to iron, and operating at partly overlapping energy ranges from 2 keV/n up to 200 MeV/n. The EPD sensors are: SupraThermal Electrons and Protons(STEP), Suprathermal Ion Spectrograph (SIS), Electron Proton Telescope (EPT) and High Energy Telescope (HET). Besides, the EPD sensors share the Instrument Control Unit (ICU). The University of Kiel in Germany is responsible for developing the EPT-HET, STEP and SIS sensors. Here we present the development status of the EPT-HET and STEP sensors focusing on the activities planned for the current phase C. Those activities include results of the environmental tests on the EPT-HET Structural Thermal Model (STM) and the assembly of the Engineering Model (EM).

APAS with petals extended after undocking

NASA Image and Video Library

2002-10-16

STS112-E-05777 (16 Oct. 2002) --- Close-up view of the Orbiter Docking System (ODS) Androgynous Peripheral Attachment System (APAS) petals extended in the STS-112 orbiter Atlantis payload bay after undocking with the International Space Station.

Optimisation of the Future Routine Orbit for Mars Express

NASA Technical Reports Server (NTRS)

Carranza, Manuel; Companys, Vincente

2007-01-01

Mars Express (MEX), the first planetary mission of the European Space Agency (ESA), reached Mars on December 25th 2003. Since then it is performing routine operations. Its operational phase had to cover one Martian year, with the possibility of an extension for a second Martian year (i.e. until November 2007). The end of the mission extension is approaching but, given the good health of the payload instruments and the high science return of the mission, there is a strong will to achieve further extensions. Mars Express is also seen as an important asset, capable to provide relay functions for future Martian missions. The ESA Science Program Committee has recently approved a second extension of the MEX mission until May 2009 and even further extensions are possible. Mars Express has an eccentric quasi-polar orbit with a period of approximately 6.72 hours and a pericentre height of about 300 km. Science observations are mainly performed at pericentre (but not only). In addition the orbit has a resonance of 11 revolutions per 3 Martian days. This means that ground tracks corresponding to orbits separated by 11 revolutions are adjacent, such that a given area can be covered by the on-board camera without leaving gaps. The J2 effect of Mars causes a drift of both ascending node and argument of pericentre. The drift of argument of pericentre makes it possible to observe periodically all Mars latitudes from close distance. Illumination conditions at pericentre are influenced by both the drift of the argument of pericentre and the drift of ascending node, as well as by the rotation of Mars around the Sun. The original MEX routine orbit was optimized for the duration of the nominal mission and extension, such that it produced a balanced share of day-side observations (for the optical instruments) and night-side observations (for the radar). The orbit was thus not optimized for the time beyond the assumed extension. Indeed, the evolution of the ascending node and argument of pericentre would cause in the following years a drift of the pericentre towards night-side observation conditions, hence uninteresting for the optical instruments. In order to prevent this an optimisation process for the future routine orbit has taken place. The share between day-side and night-side observations can be controlled by adjusting the drift of argument of pericentre and ascending node. This can in particular be achieved by changing the semimajor axis, eccentricity and/or inclination. A change of inclination is inefficient compared to a change in semimajor axis and eccentricity, and has therefore been discarded. An in-plane maneuvre can be performed to change both semi-major axis and eccentricity, and thus the period of the orbit. Although an apocentre manoeuvre is cheaper in terms of deltaV, it would result in raising the pericentre height, which is unfavourable for close observations. Hence a pericentre manoeuvre is proposed, which will increase the apocentre height. A repeat cycle is still required to allow mapping areas with adjacent ground tracks, so the change of semimajor axis must result in a new resonance. Resonances 18:5, 25:7 and 7:2 have been considered as potential candidates. The resulting long term evolution of the observation conditions has been analysed. Finally it has been decided to perform a change of orbit to reach the 18:5. Another aspect of the optimisation process is the control of the ground track. The previous MEX reference trajectory included regular maneuvres at every apocentre in order to adjust the orbital period, such that the separation of the ground tracks would be optimal, regardless of the latitude of pericentre. The implementation of the actual delatVs on-board was done partly by optimizing the attitude of reaction-wheel desaturation activities. Despite of it, this strategy has a significant propellant cost, because it prevents to optimize reaction wheel de-saturation activities to minimize propellant consumption. Therore, with the aim at preserving propellant resources for a long time extension it has been agreed to stop the ground-track control. This requires now a more accurate science operation planning, with improved attitude pointing control. Finally, the approach to phase Mars Express to provide back-up relay functions for NASA Phoenix landing is explained. In the context of the routine trajectory optimisation a new requirement for close fly-bys at Phobos, with different observation geometries, has been specified. The approach to fulfill this requirement is explained.

M2 ocean tide parameters and the deceleration of the moon's mean longitude from satellite orbit data

NASA Technical Reports Server (NTRS)

Felsentreger, T. L.; Marsh, J. G.; Williamson, R. G.

1979-01-01

An estimation is made of the principal long-period spherical harmonic parameters in the representation of the M2 ocean tide from the orbital histories of the three satellites 1967-92A, Starlette, and GEOS 3. The data used are primarily the evolution of the orbital inclinations of the satellites in conjunction with the longitude of the ascending node from GEOS 3. Analysis procedure and analytic formulation, as well as ocean tidal parameter estimation and deceleration of the lunar mean longitude are outlined. The credibility of the M2 ocean tide solution is further enhanced by the close accord between the computed value for the deceleration of the lunar mean longitude and other recently reported estimates. It is evident from the results presented that studies of close earth satellite orbits are able to provide important information about the tidal forces acting on the earth.

KSC-04pd1823

NASA Image and Video Library

2004-09-01

KENNEDY SPACE CENTER, FLA. - At Vandenberg Air Force Base in California, workers begin closing the gap between the second and third stages of the Orbital Sciences Pegasus XL launch vehicle that will launch the Demonstration of Autonomous Rendezvous Technology (DART) spacecraft. DART was designed and built for NASA by Orbital Sciences Corporation as an advanced flight demonstrator to locate and maneuver near an orbiting satellite. DART weighs about 800 pounds and is nearly 6 feet long and 3 feet in diameter. The Pegasus XL will launch DART into a circular polar orbit of approximately 475 miles. DART is designed to demonstrate technologies required for a spacecraft to locate and rendezvous, or maneuver close to, other craft in space. Results from the DART mission will aid in the development of NASA's Crew Exploration Vehicle and will also assist in vehicle development for crew transfer and crew rescue capability to and from the International Space Station.

WASP-47 and the Origin of Hot Jupiters

NASA Astrophysics Data System (ADS)

Vanderburg, Andrew; Becker, Juliette; Latham, David W.; Adams, Fred; Bryan, Marta; Buchhave, Lars; Haywood, Raphaelle; Khain, Tali; Lopez, Eric; Malavolta, Luca; Mortier, Annelies; HARPS-N Consortium

2018-01-01

WASP-47 b is a transiting hot Jupiter in a system with two additional short-period transiting planets and a long-period outer Jovian companion. WASP-47 b is the only known hot Jupiter with such close-in companions and therefore may hold clues to the origins of hot Jupiter systems. We report on precise radial velocity observations of WASP-47 to measure planet masses and determine their orbits to high precision. Using these improved masses and orbital elements, we perform a dynamical analysis to constrain the inclination of the outer planet, which we find likely orbits near the same plane as the inner transiting system. A similar dynamical analysis for five other hot Jupiter systems with long-period companions around cool host stars (Teff < 6200 K) shows that these outer companions likely also orbit close to the plane of the hot Jupiters. These constraints disfavor hot Jupiter models involving strong dynamical interactions like Kozai-Lidov migration.

Closeup view of the aft fuselage looking forward along the ...

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

Close-up view of the aft fuselage looking forward along the approximate centerline of the Orbiter Discovery looking at the expansion nozzles of the Space Shuttle Main Engines (SSME) and the Orbiter Maneuvering System. Also in the view is the orbiter's body flap with a protective covering over the High-temperature Reusable Surface Insulation tiles on the surface facing the SSMEs. This image was taken inside the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

KSC-98pc1217

NASA Image and Video Library

1998-10-03

KENNEDY SPACE CENTER, FLA. -- Inside the payload bay of Space Shuttle orbiter Endeavour in Orbiter Processing Facility Bay 1, STS-88 Mission Specialists Jerry L. Ross (crouching at left) and James H. Newman (far right) get a close look at equipment. Looking on is Wayne Wedlake (far left), with United Space Alliance at Johnson Space Center, and a KSC worker (behind Newman) who is operating the movable work platform or bucket. The STS-88 crew members are participating in a Crew Equipment Interface Test (CEIT), familiarizing themselves with the orbiter's midbody and crew compartments. Targeted for liftoff on Dec. 3, 1998, STS-88 will be the first Space Shuttle launch for assembly of the International Space Station (ISS). The primary payload is the Unity connecting module which will be mated to the Russian-built Zarya control module, expected to be already on orbit after a November launch from Russia. After the mating, Ross and Newman are scheduled to perform three spacewalks to connect power, data and utility lines and install exterior equipment. The first major U.S.-built component of ISS, Unity will serve as a connecting passageway to living and working areas of the space station. Unity has two attached pressurized mating adapters (PMAs) and one stowage rack installed inside. PMA-1 provides the permanent connection point between Unity and Zarya; PMA-2 will serve as a Space Shuttle docking port. Zarya is a self-supporting active vehicle, providing propulsive control capability and power during the early assembly stages. It also has fuel storage capability

Orbital Evolution of Jupiter-family Comets

NASA Astrophysics Data System (ADS)

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

2004-05-01

The orbital evolution of more than 25,000 Jupiter-family comets (JFCs) under the gravitational influence of planets was studied. After 40 Myr one considered object (with initial orbit close to that of Comet 88P) got aphelion distance Q<3.5 AU, and it moved in orbits with semi-major axis a=2.60-2.61 AU, perihelion distance 1.71.4 AU, Q<2.6 AU, e=0.2-0.3, and i=9-33 deg for 8 Myr (and it had Q<3 AU for 100 Myr). So JFCs can rarely get typical asteroid orbits and move in them for Myrs. In our opinion, it can be possible that Comet 133P (Elst--Pizarro) moving in a typical asteroidal orbit was earlier a JFC and it circulated its orbit also due to non-gravitational forces. JFCs got near-Earth object (NEO) orbits more often than typical asteroidal orbits. A few JFCs got Earth-crossing orbits with a<2 AU and Q<4.2 AU and moved in such orbits for more than 1 Myr (up to tens or even hundreds of Myrs). Three considered former JFCs even got inner-Earth orbits (with Q<0.983 AU) or Aten orbits for Myrs. The probability of a collision of one of such objects, which move for millions of years inside Jupiter's orbit, with a terrestrial planet can be greater than analogous total probability for thousands other objects. Results obtained by the Bulirsch-Stoer method and by a symplectic method were mainly similar (except for probabilities of close encounters with the Sun when they were high). Our results show that the trans-Neptunian belt can provide a significant portion of NEOs, or the number of trans-Neptunian objects migrating inside solar system could be smaller than it was earlier considered, or most of 1-km former trans-Neptunian objects that had got NEO orbits disintegrated into mini-comets and dust during a smaller part of their dynamical lifetimes if these lifetimes are not small. The obtained results show that during the accumulation of the giant planets the total mass of icy bodies delivered to the Earth could be about the mass of water in Earth's oceans. Several our papers on this problem were put in http://arXiv.org/format/astro-ph/ (e.g., 0305519, 0308448). This work was supported by NASA (NAG5-10776) and INTAS (00-240).

Survival of extrasolar giant planet moons in planet-planet scattering

NASA Astrophysics Data System (ADS)

CIAN HONG, YU; Lunine, Jonathan; Nicholson, Phillip; Raymond, Sean

2015-12-01

Planet-planet scattering is the best candidate mechanism for explaining the eccentricity distribution of exoplanets. Here we study the survival and dynamics of exomoons under strong perturbations during giant planet scattering. During close encounters, planets and moons exchange orbital angular momentum and energy. The most common outcomes are the destruction of moons by ejection from the system, collision with the planets and the star, and scattering of moons onto perturbed but still planet-bound orbits. A small percentage of interesting moons can remain bound to ejected (free-floating) planets or be captured by a different planet. Moons' survival rate is correlated with planet observables such as mass, semi-major axis, eccentricity and inclination, as well as the close encounter distance and the number of close encounters. In addition, moons' survival rate and dynamical outcomes are predetermined by the moons' initial semi-major axes. The survival rate drops quickly as moons' distances increase, but simulations predict a good chance of survival for the Galilean moons. Moons with different dynamical outcomes occupy different regions of orbital parameter space, which may enable the study of moons' past evolution. Potential effects of planet obliquity evolution caused by close encounters on the satellites’ stability and dynamics will be reported, as well as detailed and systematic studies of individual close encounter events.

ORBITAL SOLUTIONS FOR TWO YOUNG, LOW-MASS SPECTROSCOPIC BINARIES IN OPHIUCHUS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosero, V.; Prato, L.; Wasserman, L. H.

2011-01-15

We report the orbital parameters for ROXR1 14 and RX J1622.7-2325Nw, two young, low-mass, and double-lined spectroscopic binaries recently discovered in the Ophiuchus star-forming region. Accurate orbital solutions were determined from over a dozen high-resolution spectra taken with the Keck II and Gemini South telescopes. These objects are T Tauri stars with mass ratios close to unity and periods of {approx}5 and {approx}3 days, respectively. In particular, RX J1622.7-2325Nw shows a non-circularized orbit with an eccentricity of 0.30, higher than any other short-period pre-main-sequence (PMS) spectroscopic binary known to date. We speculate that the orbit of RX J1622.7-2325Nw has notmore » yet circularized because of the perturbing action of a {approx}1'' companion, itself a close visual pair. A comparison of known young spectroscopic binaries (SBs) and main-sequence (MS) SBs in the eccentricity-period plane shows an indistinguishable distribution of the two populations, implying that orbital circularization occurs in the first 1 Myr of a star's lifetime. With the results presented in this paper we increase by {approx}4% the small sample of PMS spectroscopic binary stars with known orbital elements.« less

Designing efficient photochromic dithienylethene dyads.

PubMed

Fihey, Arnaud; Jacquemin, Denis

2015-06-01

Aiming at designing more efficient multiphotochromes, we investigate with the help of ab initio tools the impact of the substitution on a series of dimers constituted of two dithienylethene (DTE) moieties, strongly coupled to each other through an ethynyl linker. The electronic structure and the optical properties of a large panel of compounds, substituted on different positions by various types of electroactive groups, have been compared with the aim of designing a dyad in which the three possible isomers (open-open, closed-open, closed-closed) can be reached. We show that appending the reactive carbons atoms of the DTE core with electroactive groups on one of the two photochromes allows cyclisation to be induced on a specific moiety, which leads to the formation of the desired closed-open isomer. Substituting the lateral positions of the thiophene rings provides further control of the topology of the frontier molecular orbitals, so that the electronic transition inducing the second ring closure stands out in the spectrum of the intermediate isomer.

Detail view of the port side of the payload bay ...

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

Detail view of the port side of the payload bay of the Orbiter Discovery. This view shows Remote Manipulator System, Canadarm, sensors in the center of the image and a close-up view of a small segment of the orbiter's radiator panel. This photograph was taken in the Orbiter Processing Facility at the Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

The variations in eccentricity and apse precession rate of a narrow ring perturbed by a close satellite

NASA Technical Reports Server (NTRS)

Borderies, N.; Goldreich, P.; Tremaine, S.

1983-01-01

The first-order perturbations of orbital eccentricity and apse precession rate for the case of a narrow ring, due to a close satellite whose orbit is also eccentric, are described by means of a Hamiltonian. The present treatment covers cases in which the satellite crosses the ring, and the level curves of the Hamiltonian are displayed for several parameter values. The results obtained are applied to the interaction of Saturn's F ring with its inner shepherd satellite.

Spectral types of four binaries based on photometric observations

NASA Astrophysics Data System (ADS)

Shimanskii, V. V.; Bikmaev, I. F.; Borisov, N. V.; Vlasyuk, V. V.; Galeev, A. I.; Sakhibullin, N. A.; Spiridonova, O. I.

2008-09-01

We present results of photometric and spectroscopic observations of four close binaries with subdwarf B components: PG 0918+029, PG 1000+408, PG 1116+301, PG 0001+275. We discovered that PG 1000+408 is a close binary, with the most probable orbital period being P orb = 1.041145 day. Based on a comparison of the observed light curves at selected orbital phases and theoretical predictions for their variations, all the systems are classified as doubly degenerate binaries with low-luminosity white-dwarf secondaries.

Modeling and control of a flexible space robot to capture a tumbling debris

NASA Astrophysics Data System (ADS)

Dubanchet, Vincent

After 60 years of intensive satellite launches, the number of drifting objects in Earth orbits is reaching a shifting point, where human intervention is becoming necessary to reduce the threat of collision. Indeed, a 200 year forecast, known as the "Kessler syndrome", states that space access will be greatly compromised if nothing is done to address the proliferation of these debris. Scientist J.-C. Liou from the National Aeronautics and Space Administration (NASA) has shown that the current trend could be reversed if at least five massive objects, such as dead satellites or rocket upper stages, were de-orbited each year. Among the various technical concepts considered for debris removal, robotics has emerged, over the last 30 years, as one of the most promising solutions. The International Space Station (ISS) already possesses fully operational robotic arms, and other missions have explored the potential of a manipulator embedded onto a satellite. During two of the latter, key capabilities have been demonstrated for on-orbit servicing, and prove to be equally useful for the purpose of debris removal. This thesis focuses on the close range capture of a tumbling debris by a robotic arm with light-weight flexible segments. This phase includes the motion planning and the control of a space robot, in order to smoothly catch a target point on the debris. The validation of such technologies is almost impossible on Earth and leads to prohibitive costs when performed on orbit. Therefore, the modeling and simulation of flexible multi-body systems has been investigated thoroughly, and is likewise a strong contribution of the thesis. Based on these models, an experimental validation is proposed by reproducing the on-orbit kinematics on a test bench made up of two industrial manipulators and driven by a real-time dynamic simulation. In a nutshell, the thesis is built around three main parts: the modeling of a space robot, the design of control laws, and their validation on a test case. (Abstract shortened by ProQuest.).

General view looking aft along the starboard side of the ...

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

General view looking aft along the starboard side of the Orbiter Discovery in the Vehicle Assembly Building at NASA's Kennedy Space Center. This view shows a close up view of the reinforced carbon-carbon leading edge of the Orbiter wing. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

KSC-04pd1598

NASA Image and Video Library

2004-07-14

KENNEDY SPACE CENTER, FLA. - At Vandenberg Air Force Base in California, Orbital Sciences technicians observe closely the movement of the DART (Demonstration for Autonomous Rendezvous Technology) flight demonstrator as it is lowered onto a stand. The spacecraft was developed to prove technologies for locating and maneuvering near an orbiting satellite. Future applications of technologies developed by the DART project will benefit the nation in future space-vehicle systems development requiring in-space assembly, services or other autonomous rendezvous operations. Designed and developed for NASA by Orbital Sciences Corporation in Dulles, Va., the DART spacecraft will be launched on a Pegasus launch vehicle. At about 40,000 feet over the Pacific Ocean, the Pegasus will be released from Orbital’s Stargazer L-1011 aircraft, fire its rocket motors and boost DART into a polar orbit approximately 472 miles by 479 miles. Once in orbit, DART will rendezvous with a target satellite, the Multiple Paths, Beyond-Line-of-Site Communications satellite, also built by Orbital Sciences. DART will then perform several close proximity operations, such as moving toward and away from the satellite using navigation data provided by onboard sensors. DART is scheduled for launch no earlier than Oct. 18.

Analysis of impulsive maneuvers to keep orbits around the asteroid 2001SN263

NASA Astrophysics Data System (ADS)

Santos, Willer G.; Prado, Antonio F. B. A.; Oliveira, Geraldo M. C.; Santos, Leonardo B. T.

2018-01-01

The strongly perturbed environment of a small body, such as an asteroid, can complicate the prediction of orbits used for close proximity operations. Inaccurate predictions may make the spacecraft collide with the asteroid or escape to the deep space. The main forces acting in the dynamics come from the solar radiation pressure and from the body's weak gravity field. This paper investigates the feasibility of using bi-impulsive maneuvers to avoid the aforementioned non-desired phenomena (collisions and escapes) by connecting orbits around the triple system asteroid 2001SN263, which is the target of a proposed Brazilian space mission. In terms of a mathematical formulation, a recently presented rotating dipole model is considered with oblateness in both primaries. In addition, a "two-point boundary value problem" is solved to find a proper transfer trajectory. The results presented here give support to identifying the best strategy to find orbits for close proximity operations, in terms of long orbital lifetimes and low delta-V consumptions. Numerical results have also demonstrated the significant influence of the spacecraft orbital elements (semi-major axis and eccentricity), angular position of the Sun and spacecraft area-to-mass ratio, in the performance of the bi-impulsive maneuver.

Propulsion Trade Studies for Spacecraft Swarm Mission Design

NASA Technical Reports Server (NTRS)

Dono, Andres; Plice, Laura; Mueting, Joel; Conn, Tracie; Ho, Michael

2018-01-01

Spacecraft swarms constitute a challenge from an orbital mechanics standpoint. Traditional mission design involves the application of methodical processes where predefined maneuvers for an individual spacecraft are planned in advance. This approach does not scale to spacecraft swarms consisting of many satellites orbiting in close proximity; non-deterministic maneuvers cannot be preplanned due to the large number of units and the uncertainties associated with their differential deployment and orbital motion. For autonomous small sat swarms in LEO, we investigate two approaches for controlling the relative motion of a swarm. The first method involves modified miniature phasing maneuvers, where maneuvers are prescribed that cancel the differential delta V of each CubeSat's deployment vector. The second method relies on artificial potential functions (APFs) to contain the spacecraft within a volumetric boundary and avoid collisions. Performance results and required delta V budgets are summarized, indicating that each method has advantages and drawbacks for particular applications. The mini phasing maneuvers are more predictable and sustainable. The APF approach provides a more responsive and distributed performance, but at considerable propellant cost. After considering current state of the art CubeSat propulsion systems, we conclude that the first approach is feasible, but the modified APF method of requires too much control authority to be enabled by current propulsion systems.

Pioneer probe mission with orbiter option

NASA Technical Reports Server (NTRS)

1975-01-01

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

Periodic Trojan-type orbits in the earth-sun system

NASA Technical Reports Server (NTRS)

Weissman, P. R.; Wetherill, G. W.

1974-01-01

Periodic orbits about the triangular equilibrium points are found for the planar restricted three-body problem using the earth-sun system. The maximum semimajor axis for tadpole orbits ranges from the infinitesimal orbit at 1.000 AU to the near-limiting orbit at 1.00285 AU. Horseshoe orbits are found for 1.0029 to 1.0080 AU, larger horseshoes being unstable because of close approaches to the earth. Using stability tests devised by Rabe (1961, 1962), the limit of stability for nonperiodic orbits is found to occur for maximum semimajor axes near 1.0020 AU. In addition, near-periodic tadpole orbits appear to be stable against perturbations by Jupiter and Venus for periods of at least 10,000 yr. The possibility that minor planets actually exist in such orbits is considered.

Tribology experiment in zero gravity

NASA Technical Reports Server (NTRS)

Pan, C. H. T.; Gause, R. L.; Whitaker, A. F.

1984-01-01

A tribology experiment in zero gravity was performed during the orbital flight of Spacelab 1 to study the motion of liquid lubricants over solid surfaces. The absence of a significant gravitational force facilitates studies of the motion of liquid lubricants over solid surfaces as controlled by interfacial and capillary forces. Observations were made of phenomena associated with the liquid on one solid surface and also with the liquid between a pair of closely spaced surfaces. Typical photographic records obtained on Spacelab 1 are described.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshizumi, K.; Sasaki, A.; Kohda, M.

We demonstrate gate-controlled switching between persistent spin helix (PSH) state and inverse PSH state, which are detected by quantum interference effect on magneto-conductance. These special symmetric spin states showing weak localization effect give rise to a long spin coherence when the strength of Rashba spin-orbit interaction (SOI) is close to that of Dresselhaus SOI. Furthermore, in the middle of two persistent spin helix states, where the Rashba SOI can be negligible, the bulk Dresselhaus SOI parameter in a modulation doped InGaAs/InAlAs quantum well is determined.

Dynamical Effects of Stellar Companions

NASA Astrophysics Data System (ADS)

Naoz, Smadar

2016-10-01

The fraction of stellar binaries in the field is extremely high (about 40% - 70% forM > 1M⊙ stars), and thus, given this frequency, a high fraction of all exoplanetary systems may reside in binaries. While close-in giant planets tend to be found preferentially in binary stellar systems it seems that the frequency of giant planets in close binaries (>100-1000 AU) is significantly lower than in the overall population. Stellar companions gravitational perturbations may significantly alter the planetary orbits around their partner on secular timescales. They can drive planets to large eccentric orbits which can either result in plunging these planets into the star or shrinking their orbits and forming short period planets. These planets typically are misaligned with the parent star.

KSC-04pd1691

NASA Image and Video Library

2004-08-31

KENNEDY SPACE CENTER, FLA. - Workers in the Orbiter Processing Facility prepare to close the nose wheel doors on Atlantis in preparation for the expected impact of Hurricane Frances on Saturday. Preparations at KSC include powering down the Space Shuttle orbiters, closing their payload bay doors and stowing their landing gear. They are also taking precautions against flooding by moving spacecraft hardware off the ground and sandbagging facilities. The Orbiter Processing Facility is constructed of concrete and steel and was designed to withstand winds of 105 mph. The Vehicle Assembly Building is constructed of concrete and steel and was designed to withstand winds of 125 mph. Other payload and flight hardware support facilities can endure winds of 110 mph. Launch pads and the Payload Hazardous Servicing Facility can withstand 125-mph winds.

KSC-04pd1690

NASA Image and Video Library

2004-08-31

KENNEDY SPACE CENTER, FLA. - Workers in the Orbiter Processing Facility prepare to close the nose wheel doors on Atlantis in preparation for the expected impact of Hurricane Frances on Saturday. Preparations at KSC include powering down the Space Shuttle orbiters, closing their payload bay doors and stowing their landing gear. They are also taking precautions against flooding by moving spacecraft hardware off the ground and sandbagging facilities. The Orbiter Processing Facility is constructed of concrete and steel and was designed to withstand winds of 105 mph. The Vehicle Assembly Building is constructed of concrete and steel and was designed to withstand winds of 125 mph. Other payload and flight hardware support facilities can endure winds of 110 mph. Launch pads and the Payload Hazardous Servicing Facility can withstand 125-mph winds.

KSC-04pd1689

NASA Image and Video Library

2004-08-31

KENNEDY SPACE CENTER, FLA. - Workers in the Orbiter Processing Facility prepare to close the nose wheel doors on Atlantis in preparation for the expected impact of Hurricane Frances on Saturday. Preparations at KSC include powering down the Space Shuttle orbiters, closing their payload bay doors and stowing their landing gear. They are also taking precautions against flooding by moving spacecraft hardware off the ground and sandbagging facilities. The Orbiter Processing Facility is constructed of concrete and steel and was designed to withstand winds of 105 mph. The Vehicle Assembly Building is constructed of concrete and steel and was designed to withstand winds of 125 mph. Other payload and flight hardware support facilities can endure winds of 110 mph. Launch pads and the Payload Hazardous Servicing Facility can withstand 125-mph winds.

Tidal Interaction among Red Giants Close Binary Systems in APOGEE Database

NASA Astrophysics Data System (ADS)

Sun, Meng; Arras, Phil; Majewski, Steven R.; Troup, Nicholas William; Weinberg, Nevin N.

2017-01-01

Motivated by the newly discovered close binary systems in the Apache Point Observatory Galactic Evolution Experiment (APOGEE-1), the tidal evolution of binaries containing a red giant branch (RGB) star with a stellar or substellar companion was investigated. The tide raised by the companion in the RGB star leads to exchange of angular momentum between the orbit and the stellar spin, causing the orbit to contract. The tidal dissipation rate is computed using turbulent viscosity acting on the equilibrium tidal flow, where careful attention is paid to the effects of reduced viscosity for close-in companions. Evolutionary models for the RGB stars, from the zero-age main sequence to the present, were acquired from the MESA code. "Standard" turbulent viscosity gives rise to such a large orbital decay that many observed systems have decay times much shorter than the RGB evolution time. Several theories for "reduced" turbulent viscosity are investigated, and reduce the number of systems with uncomfortably short decay times.

Migration-driven diversity of super-Earth compositions

NASA Astrophysics Data System (ADS)

Raymond, Sean N.; Boulet, Thibault; Izidoro, Andre; Esteves, Leandro; Bitsch, Bertram

2018-06-01

A leading model for the origin of super-Earths proposes that planetary embryos migrate inward and pile up on close-in orbits. As large embryos are thought to preferentially form beyond the snow line, this naively predicts that most super-Earths should be very water-rich. Here we show that the shortest-period planets formed in the migration model are often purely rocky. The inward migration of icy embryos through the terrestrial zone accelerates the growth of rocky planets via resonant shepherding. We illustrate this process with a simulation that provided a match to the Kepler-36 system of two planets on close orbits with very different densities. In the simulation, two super-Earths formed in a Kepler-36-like configuration; the inner planet was pure rock while the outer one was ice-rich. We conclude from a suite of simulations that the feeding zones of close-in super-Earths are likely to be broad and disconnected from their final orbital radii.

Spectroscopic orbits of symbiotic stars - Preliminary results

NASA Technical Reports Server (NTRS)

Garcia, M. R.

1986-01-01

The present search for radial velocity variations due to orbital motions in symbiotic stars involved observations of 17 such stars at approximately 1-month intervals, as well as of radial velocity variations in the M-giant primary in nine stars. The observed radial velocity curves are commensurate with those expected from a group of binaries having random sin i and about 20 km/sec orbital velocities. Four of the orbital periods thus suggested for seven stars confirm previously known photometric periods, while one confirms a previously known orbital period and two are completely new. Knowledge of the orbits allows identification of those symbiotics that are close to filling their Roche lobes.

Autonomous Closed-Loop Tasking, Acquisition, Processing, and Evaluation for Situational Awareness Feedback

NASA Technical Reports Server (NTRS)

Frye, Stuart; Mandl, Dan; Cappelaere, Pat

2016-01-01

This presentation describes the closed loop satellite autonomy methods used to connect users and the assets on Earth Orbiter- 1 (EO-1) and similar satellites. The base layer is a distributed architecture based on Goddard Mission Services Evolution Concept (GMSEC) thus each asset still under independent control. Situational awareness is provided by a middleware layer through common Application Programmer Interface (API) to GMSEC components developed at GSFC. Users setup their own tasking requests, receive views into immediate past acquisitions in their area of interest, and into future feasibilities for acquisition across all assets. Automated notifications via pubsub feeds are returned to users containing published links to image footprints, algorithm results, and full data sets. Theme-based algorithms are available on-demand for processing.

Spacecraft stability and control using new techniques for periodic and time-delayed systems

NASA Astrophysics Data System (ADS)

NAzari, Morad

This dissertation addresses various problems in spacecraft stability and control using specialized theoretical and numerical techniques for time-periodic and time-delayed systems. First, the effects of energy dissipation are considered in the dual-spin spacecraft, where the damper masses in the platform (?) and the rotor (?) cause energy loss in the system. Floquet theory is employed to obtain stability charts for different relative spin rates of the subsystem [special characters omitted] with respect to the subsystem [special characters omitted]. Further, the stability and bifurcation of delayed feedback spin stabilization of a rigid spacecraft is investigated. The spin is stabilized about the principal axis of the intermediate moment of inertia using a simple delayed feedback control law. In particular, linear stability is analyzed via the exponential-polynomial characteristic equations and then the method of multiple scales is used to obtain the normal form of the Hopf bifurcation. Next, the dynamics of a rigid spacecraft with nonlinear delayed multi-actuator feedback control are studied, where a nonlinear feedback controller using an inverse dynamics approach is sought for the controlled system to have the desired linear delayed closed-loop dynamics (CLD). Later, three linear state feedback control strategies based on Chebyshev spectral collocation and the Lyapunov Floquet transformation (LFT) are explored for regulation control of linear periodic time delayed systems. First , a delayed feedback control law with discrete delay is implemented and the stability of the closed-loop response is investigated in the parameter space of available control gains using infinite-dimensional Floquet theory. Second, the delay differential equation (DDE) is discretized into a large set of ordinary differential equations (ODEs) using the Chebyshev spectral continuous time approximation (CSCTA) and delayed feedback with distributed delay is applied. The third strategy involves use of both CSCTA and the reduced Lyapunov Floquet transformation (RLFT) in order to design a non-delayed feedback control law. The delayed Mathieu equation is used as an illustrative example in which the closed-loop response and control effort are compared for all three control strategies. Finally, three example applications of control of time-periodic astrodynamic systems, i.e. formation flying control for an elliptic Keplerian chief orbit, body-fixed hovering control over a tumbling asteroid, and stationkeeping in Earth-Moon L1 halo orbits, are shown using versions of the control strategies introduced above. These applications employ a mixture of feedforward and non-delayed periodic-gain state feedback for tracking control of natural and non-natural motions in these systems. A major conclusion is that control effort is minimized by employing periodic-gain (rather than constant-gain) feedback control in such systems.

OrbitMaster: An Online Tool for Investigating Solar System Dynamics and Visualizing Orbital Uncertainties in the Undergraduate Classroom

NASA Astrophysics Data System (ADS)

Puckett, Andrew W.; Rector, Travis A.; Baalke, Ron; Ajiki, Osamu

2016-01-01

OrbitMaster is a 3-D orbit visualization tool designed for the undergraduate astronomy classroom. It has been adapted from AstroArts' interactive OrbitViewer applet under the GNU General Public License, as part of the Research-Based Science Education for Undergraduates (RBSEU) curriculum. New features allow the user to alter an asteroid's orbital parameters using slider controls, and to monitor its changing position and speed relative to both Sun and Earth. It detects close approaches and collisions with Earth, and calculates revised distances and impact speeds due to Earth's gravitational attraction. It can also display many asteroid orbits at once, with direct application to visualizing the uncertainty in a single asteroid's orbital parameters. When paired with Project Pluto's Find_Orb orbit determination software and a source of asteroid astrometry, this enables monitoring of changes in orbital uncertainties with time and/or additional observational data. See http://facstaff.columbusstate.edu/puckett_andrew/orbitmaster.html.A series of undergraduate labs using the OrbitMaster applet are available as part of the RBSEU curriculum. In the first lab, students gain hands-on experience with the mechanics of asteroid orbits and confirm Kepler's laws of planetary motion. In the second, they study the orbits of Potentially Hazardous Asteroids as they build their own "Killer Asteroids" and investigate the minimum and maximum speed limits that apply to Earth-impacting objects. In the third and fourth labs, they discover the kinetic energy-crater size relationship, engage in their own Crater Scene Investigation (C.S.I.) to estimate impactor size, and understand the regional consequences of impacts. These labs may be used separately, or in support of a further seven-week sequence culminating in an authentic research project in which students submit measurements to the Minor Planet Center to refine a real asteroid's orbit. As with all RBSE projects, the overarching goal is for students to learn science by actually doing science, and to retain knowledge learned in-context. For more information, see http://rbseu.uaa.alaska.edu.

Colloidal Bandpass and Bandgap Filters

NASA Astrophysics Data System (ADS)

Yellen, Benjamin; Tahir, Mukarram; Ouyang, Yuyu; Nori, Franco

2013-03-01

Thermally or deterministically-driven transport of objects through asymmetric potential energy landscapes (ratchet-based motion) is of considerable interest as models for biological transport and as methods for controlling the flow of information, material, and energy. Here, we provide a general framework for implementing a colloidal bandpass filter, in which particles of a specific size range can be selectively transported through a periodic lattice, whereas larger or smaller particles are dynamically trapped in closed-orbits. Our approach is based on quasi-static (adiabatic) transition in a tunable potential energy landscape composed of a multi-frequency magnetic field input signal with the static field of a spatially-periodic magnetization. By tuning the phase shifts between the input signal and the relative forcing coefficients, large-sized particles may experience no local energy barriers, medium-sized particles experience only one local energy barrier, and small-sized particles experience two local energy barriers. The odd symmetry present in this system can be used to nudge the medium-sized particles along an open pathway, whereas the large or small beads remain trapped in a closed-orbit, leading to a bandpass filter, and vice versa for a bandgap filter. NSF CMMI - 0800173, Youth 100 Scholars Fund

Pulse-modulated dual-gas control subsystem for space cabin atmosphere

NASA Technical Reports Server (NTRS)

Jackson, J. K.

1974-01-01

An atmosphere control subsystem (ACS) was developed for use in a closed manned cabin, such as the Space Shuttle Orbiter. This subsystem uses the Perkin Elmer mass spectrometer for continuous measurement of major atmospheric constituents (H2, H2O, N2, O2, and CO2). The O2 and N2 analog signals are used as inputs to the controller, which produces a pulse-frequency-modulated output to operate the N2 gas admission solenoid valve and an on-off signal to operate the O2 valve. The proportional controller characteristic results in improved control accuracy as compared with previously used on-off controllers having significant dead-band. A 60-day evaluation test was performed on the ACS during which operation was measured at various values of control setpoint and simulated cabin leakage.

Predicting Instability Timescales in Closely-Packed Planetary Systems

NASA Astrophysics Data System (ADS)

Tamayo, Daniel; Hadden, Samuel; Hussain, Naireen; Silburt, Ari; Gilbertson, Christian; Rein, Hanno; Menou, Kristen

2018-04-01

Many of the multi-planet systems discovered around other stars are maximally packed. This implies that simulations with masses or orbital parameters too far from the actual values will destabilize on short timescales; thus, long-term dynamics allows one to constrain the orbital architectures of many closely packed multi-planet systems. A central challenge in such efforts is the large computational cost of N-body simulations, which preclude a full survey of the high-dimensional parameter space of orbital architectures allowed by observations. I will present our recent successes in training machine learning models capable of reliably predicting orbital stability a million times faster than N-body simulations. By engineering dynamically relevant features that we feed to a gradient-boosted decision tree algorithm (XGBoost), we are able to achieve a precision and recall of 90% on a holdout test set of N-body simulations. This opens a wide discovery space for characterizing new exoplanet discoveries and for elucidating how orbital architectures evolve through time as the next generation of spaceborne exoplanet surveys prepare for launch this year.

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

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

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

The Dynamics of Objects in the Inner Edgeworth Kuiper Belt

NASA Astrophysics Data System (ADS)

Jones, Daniel C.; Williams, Iwan P.; Melita, Mario D.

2005-12-01

Objects in 3:2 mean motion resonance with Neptune are protected from close encounters with Neptune by the resonance. Bodies in orbits with semi-major axis between 39.5 and about 42 AU are not protected by the resonance; indeed due to overlapping secular resonances, the eccentricities of orbits in this region are driven up so that a close encounter with Neptune becomes inevitable. It is thus expected that such orbits are unstable. The list of known Trans-Neptunian objects shows a deficiency in the number of objects in this gap compared to the 43 50 AU region, but the gap is not empty. We numerically integrate models for the initial population in the gap, and also all known objects over the age of the Solar System to determine what fraction can survive. We find that this fraction is significantly less than the ratio of the population in the gap to that in the main belt, suggesting that some mechanism must exist to introduce new members into the gap. By looking at the evolution of the test body orbits, we also determine the manner in which they are lost. Though all have close encounters with Neptune, in most cases this does not lead to ejection from the Solar System, but rather to a reduced perihelion distance causing close encounters with some or all of the other giant planets before being eventually lost from the system, with Saturn appearing to be the cause of the ejection of most of the objects.

Learning from adaptive neural dynamic surface control of strict-feedback systems.

PubMed

Wang, Min; Wang, Cong

2015-06-01

Learning plays an essential role in autonomous control systems. However, how to achieve learning in the nonstationary environment for nonlinear systems is a challenging problem. In this paper, we present learning method for a class of n th-order strict-feedback systems by adaptive dynamic surface control (DSC) technology, which achieves the human-like ability of learning by doing and doing with learned knowledge. To achieve the learning, this paper first proposes stable adaptive DSC with auxiliary first-order filters, which ensures the boundedness of all the signals in the closed-loop system and the convergence of tracking errors in a finite time. With the help of DSC, the derivative of the filter output variable is used as the neural network (NN) input instead of traditional intermediate variables. As a result, the proposed adaptive DSC method reduces greatly the dimension of NN inputs, especially for high-order systems. After the stable DSC design, we decompose the stable closed-loop system into a series of linear time-varying perturbed subsystems. Using a recursive design, the recurrent property of NN input variables is easily verified since the complexity is overcome using DSC. Subsequently, the partial persistent excitation condition of the radial basis function NN is satisfied. By combining a state transformation, accurate approximations of the closed-loop system dynamics are recursively achieved in a local region along recurrent orbits. Then, the learning control method using the learned knowledge is proposed to achieve the closed-loop stability and the improved control performance. Simulation studies are performed to demonstrate the proposed scheme can not only reuse the learned knowledge to achieve the better control performance with the faster tracking convergence rate and the smaller tracking error but also greatly alleviate the computational burden because of reducing the number and complexity of NN input variables.

Space station assembly/servicing capabilities

NASA Technical Reports Server (NTRS)

Joyce, Joseph

1986-01-01

The aim is to place a permanently manned space station on-orbit around the Earth, which is international in scope. The program is nearing the close of the system definition and preliminary design phase. The first shuttle launch for space station assembly on-orbit is estimated for January 1993. Topics perceived to be important to on-orbit assembly and servicing are discussed. This presentation is represented by charts.

Closeup view of the upper exterior of the forward fuselage ...

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

Close-up view of the upper exterior of the forward fuselage of the Orbiter Discovery in the Orbiter Processing Facility at NASA's Kennedy Space Center. The view show a detail of the flight deck windows with protective covers installed to protect the window surfaces during processing. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Why Are Hot Jupiters So Lonely?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-10-01

Jupiter-like planets with blisteringly close-in orbits are generally friendless, with no nearbyplanets transiting along with them. Giant planets with orbits a little further out, on the other hand, often have at least one companion. A new study examines the cause of hot Jupiters loneliness.Forming Close-In GiantsArtists impression of a planet forming within a protoplanetary disk. [NAOJ]Though weve studied close-in giant planets for decades now, we still dont fully understand how these objects form and evolve. Jupiter-like giant planets could form in situ next to their host stars, or they could form further out in the system beyond the ice line and then migrate inwards. And if they do migrate, this migration could occur early, while the protoplanetary disk still exists, or long after, via excitation of large eccentricities.We can try to resolve this mystery by examining the statistics of the close-in giant planets weve observed, but this often raises more questions than it answers. A prime example: the properties of close-in giants that have close-in companion planets orbiting in the same plane (i.e., co-transiting).About half of warm Jupiters Jupiter-like planets with periods of 1030 days appear to have close-in, co-transiting companions. In contrast, almost no hot Jupiters Jupiter-like planets with periods of less than 10 days have such companions. What causes this dichotomy?Schematic of the authors model, in which the close-in giant (m1) encounters a resonance with its host star, causing the orbit of the exterior companion (m2) to become tilted. [Spalding Batygin 2017]Friendless Hot JupitersWhile traditional models have argued that the two types of planets form via different pathways warm Jupiters form in situ, or else migrate inward early and smoothly, whereas hot Jupiters migrate inward late and violently, losing their companions in the process a new study casts doubt on this picture.Two scientists from the California Institute of Technology, Christopher Spalding and Konstantin Batygin, propose an alternative picture in which both types of planets form through identical pathways. Instead, they argue, a hot Jupiters apparent loneliness arises over time through interactions with its host star.Stellar Interactions Impact CompanionsSemimajor axis for the outer companion (a2) vs that of the close-in giant planet (a1) at three different system ages. Outer companions within the shaded region will not encounter the resonance investigated by the authors, instead remaining coplanar with the inner giant. For this reason, warm Jupiters will have evident companions whereas hot Jupiters will not. [Spalding Batygin 2017]Whether giant planets form in situ near their hosts or migrate inward, they can still have close-in, co-transiting companions outside of their orbit shortly after their birth, Spalding and Batygin argue. But after the disk in which they were born dissipates, the orbits of their companions may be altered.The authors demonstrate that because hot Jupiters are so close to their hosts, these giants eventually encounter a resonance with their stellar hosts quadrupole moment, which arises because rotating stars arent perfectly spherical. This resonance tilts the orbits of the hot Jupiters outer, lower-mass companions, rendering the companions undetectable in transit surveys.Warm Jupiters, on the other hand, are located just far enough away from their hosts to avoid feeling the effects of this resonance which allows them to keep their outer companions in the same plane.Based on their model, Spalding and Batygin make direct predictions for the systems they expect to be observed in large upcoming surveys like the Transiting Exoplanet Survey Satellite (TESS) which means we should soon have a sense of whether their picture is correct. If it is, it will confirm that the non-sphericity of stars can have significant impact on the dynamics and architecture of exoplanetary systems.CitationChristopher Spalding and Konstantin Batygin 2017 AJ 154 93. doi:10.3847/1538-3881/aa8174

Ulysses, one year after the launch

NASA Astrophysics Data System (ADS)

Petersen, H.

1991-12-01

Ulysses is currently one year underway in a huge heliocentric orbit. A late change in some of the blankets' external material was required to prevent electrical charging due to contamination by nozzle outgassing products. Test results are shown, governing various ranges of plasma parameters and sample temperatures. Even clean materials show a few volts charging due to imperfections in the conductive film. Thermal environment in the Shuttle cargo bay proved to be slightly different from prelaunch predictions: less warm with doors closed, and less cold with doors opened. Temperatures experienced in orbit are nominal. A problem was caused by a complex interaction of a Sun induced thermal gradient in a sensitive boom on the dynamic stability of the spacecraft. A user interface program was an invaluable tool to ease computations with the mathematical models, eliminate error risk and provide configuration control.

The Fate of Close-in Planets: Tidal or Magnetic Migration?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strugarek, A.; Bolmont, E.; Mathis, S.

Planets in close-in orbits interact magnetically and tidally with their host stars. These interactions lead to a net torque that makes close-in planets migrate inward or outward depending on their orbital distance. We systematically compare the strength of magnetic and tidal torques for typical observed star–planet systems (T-Tauri and hot Jupiter, M-dwarf and Earth-like planet, K star and hot Jupiter) based on state-of-the-art scaling laws. We find that depending on the characteristics of the system, tidal or magnetic effects can dominate. For very close-in planets, we find that both torques can make a planet migrate on a timescale as smallmore » as 10–100 thousands of years. Both effects thus have to be taken into account when predicting the evolution of compact systems.« less

Dancing to CHANGA: a self-consistent prediction for close SMBH pair formation time-scales following galaxy mergers

NASA Astrophysics Data System (ADS)

Tremmel, M.; Governato, F.; Volonteri, M.; Quinn, T. R.; Pontzen, A.

2018-04-01

We present the first self-consistent prediction for the distribution of formation time-scales for close supermassive black hole (SMBH) pairs following galaxy mergers. Using ROMULUS25, the first large-scale cosmological simulation to accurately track the orbital evolution of SMBHs within their host galaxies down to sub-kpc scales, we predict an average formation rate density of close SMBH pairs of 0.013 cMpc-3 Gyr-1. We find that it is relatively rare for galaxy mergers to result in the formation of close SMBH pairs with sub-kpc separation and those that do form are often the result of Gyr of orbital evolution following the galaxy merger. The likelihood and time-scale to form a close SMBH pair depends strongly on the mass ratio of the merging galaxies, as well as the presence of dense stellar cores. Low stellar mass ratio mergers with galaxies that lack a dense stellar core are more likely to become tidally disrupted and deposit their SMBH at large radii without any stellar core to aid in their orbital decay, resulting in a population of long-lived `wandering' SMBHs. Conversely, SMBHs in galaxies that remain embedded within a stellar core form close pairs in much shorter time-scales on average. This time-scale is a crucial, though often ignored or very simplified, ingredient to models predicting SMBH mergers rates and the connection between SMBH and star formation activity.

Cassini's Ring Grazing and Grand Finale Orbits: Topping Off an Awesome Mission

NASA Astrophysics Data System (ADS)

Edgington, Scott; Spilker, Linda; Coustenis, Athena

2017-04-01

The Cassini-Huygens mission, a joint collaboration between NASA, ESA, and the Italian Space Agency, is in its last year of operations after nearly 13 years in orbit around Saturn. Cassini will send back its final bits of unique data on September 15th, 2017 as it plunges into Saturn's atmosphere, vaporizing and satisfying planetary protection requirements. Before that time Cassini will continue its legacy of exploration and discovery in 2017 and return unique science data provided by orbits taking the spacecraft into unexplored regions near Saturn and its rings. From the new vantage points, Cassini will continue to study seasonal and temporal changes in the system as northern summer solstice approaches. With the exception of one remaining targeted Titan flyby, all of Cassini's close icy satellite flybys, including those of Enceladus, are now completed. In November 2016, Cassini transitioned to a series of orbits with peripases just outside Saturn's F ring. These 20 orbits include close flybys of some tiny ring moons and excellent views of the F ring and Saturn's outer A ring. The 126th and final close flyby of Titan will propel Cassini across Saturn's main rings and into its Grand Finale series of orbits. Cassini's Grand Finale, starting in April 2017, is comprised of 22 orbits at an inclination of 63 degrees. Cassini will repeatedly dive between Saturn's innermost rings and upper atmosphere providing insights into fundamental questions unattainable during the rest of the mission. Cassini will be the first spacecraft to explore this region. These close orbits provide the highest resolution observations of both the rings and Saturn, and direct in-situ sampling of the ring particles, composition, plasma, Saturn's exosphere and the innermost radiation belts. Saturn's gravitational field will be measured to unprecedented accuracy, providing information on the interior structure of the planet, winds in the outer layers of Saturn's atmosphere, and the mass distribution in the rings. Probing the magnetic field will give insight into the nature of the magnetic dynamo, telling us: why the magnetic field is weak; why it exhibits little, if any, axial tilt; and the true rotation rate of the planet. The ion and neutral mass spectrometer will sniff the exosphere and upper atmosphere for molecules that escape the atmosphere itself and water-based molecules originating from the rings. The cosmic dust analyzer will sample the composition of particles from different parts of the main rings. Until the execution of these final orbits, the answers to such new questions will remain mysteries. The science highlights of Cassini's Grand Finale orbits will be discussed. This work was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2017 California Institute of Technology. Government sponsorship is acknowledged.

STS-1 landing at Edwards - first orbital mission

NASA Technical Reports Server (NTRS)

1981-01-01

The first flight of a space shuttle into space and back occurred from April 12 to April 14, 1981. After years of testing of the space shuttle Columbia and training the astronauts in simulators, the orbiter lifted off into space on the 12th, boosted by the seven million pounds of thrust supplied by its solid-propellant rockets and liquid-hydrogen engines. The flight, one of four Orbital Flight Tests of Columbia, served as a two-day demonstration of the first reusable, piloted spacecraft's ability to go into orbit and return safely to Earth. Columbia carried as its main payload a Developmental Flight Instrumentation pallet with instruments to record pressures, temperatures, and levels of acceleration at various points on the vehicle during launch, flight, and landing. One of many cameras aboard--a remote television camera--revealed some of the thermal protection tiles had disengaged during launch. As Columbia reentered the atmosphere from space at Mach 24 (24 times the speed of sound) after 36 orbits, aerodynamic heating built up to over 3,000 degrees Fahrenheit, causing some concern during the moments when ionized gases disrupted radio communication. But at 188,000 feet and Mach 10, mission commander John W. Young and pilot Robert L. Crippen reported that the orbiter was performing as expected. After a series of maneuvers to reduce speed, the mission commander and pilot prepared to land. In flight, Young and Crippen tested the spacecraft's on-board systems, fired the orbital maneuvering system for changing orbits, employed the reaction control system for controlling attitude, and opened and closed the payload doors. Columbia was the first reusable, piloted spacecraft, the first piloted lifting-reentry vehicle, and the first piloted spacecraft without a crew escape system. Energy management for the space shuttles was based on previous experience with the X-15 at NASA's Flight Research Center (which had become the Dryden Flight Research Center in 1976). Landing the shuttles without power--and therefore without the weight penalty of an additional engine and fuel--was based on previous experience at the Flight Research Center with piloted lifting bodies that also landed without power, as had the X-15s. Dryden and Edwards Air Force Base (AFB) had also hosted the approach and landing tests of the shuttle prototype Enterprise in 1977 and had tested the computers used for the shuttles' flight control systems in the F-8 Digital Fly-By-Wire aircraft, which also contributed to the solution of a dangerous pilot induced oscillation that occurred on the final approach and landing test. In this clip Young and Crippen fly the orbiter Columbia to a picture-perfect, unpowered landing on the dry lakebed runway 23 at Edwards AFB, CA, after it's first orbital flight, which ended on April 14.

RHIC BPM system average orbit calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michnoff,R.; Cerniglia, P.; Degen, C.

2009-05-04

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

The Dynamical History of Chariklo and Its Rings

NASA Astrophysics Data System (ADS)

Wood, Jeremy; Horner, Jonti; Hinse, Tobias C.; Marsden, Stephen C.

2017-06-01

Chariklo is the only small solar system body confirmed to have rings. Given the instability of its orbit, the presence of rings is surprising, and their origin remains poorly understood. In this work, we study the dynamical history of the Chariklo system by integrating almost 36,000 Chariklo clones backward in time for 1 Gyr under the influence of the Sun and the four giant planets. By recording all close encounters between the clones and planets, we investigate the likelihood that Chariklo’s rings could have survived since its capture to the Centaur population. Our results reveal that Chariklo’s orbit occupies a region of stable chaos, resulting in its orbit being marginally more stable than those of the other Centaurs. Despite this, we find that it was most likely captured to the Centaur population within the last 20 Myr, and that its orbital evolution has been continually punctuated by regular close encounters with the giant planets. The great majority (>99%) of those encounters within 1 Hill radius of the planet have only a small effect on the rings. We conclude that close encounters with giant planets have not had a significant effect on the ring structure. Encounters within the Roche limit of the giant planets are rare, making ring creation through tidal disruption unlikely.

The Dynamical History of Chariklo and Its Rings

NASA Astrophysics Data System (ADS)

Wood, Jeremy R.; Horner, Jonti; Hinse, Tobias; Marsden, Stephen

2017-10-01

Chariklo is the only small Solar system body confirmed to have rings. Given the instability of its orbit, the presence of rings is surprising, and their origin remains poorly understood. In this work, we study the dynamical history of the Chariklo system by integrating almost 36,000 Chariklo clones backwards in time for one Gyr under the influence of the Sun and the four giant planets. By recording all close encounters between the clones and planets, we investigate the likelihood that Chariklo's rings could have survived since its capture to the Centaur population. Our results reveal that Chariklo's orbit occupies a region of stable chaos, resulting in its orbit being marginally more stable than those of the other Centaurs. Despite this, we find that it was most likely captured to the Centaur population within the last 20 Myr, and that its orbital evolution has been continually punctuated by regular close encounters with the giant planets. The great majority (> 99%) of those encounters within one Hill radius of the planet have only a small effect on the rings. We conclude that close encounters with giant planets have not had a significant effect on the ring structure. Encounters within the Roche limit of the giant planets are rare, making ring creation through tidal disruption unlikely.

The Dynamical History of Chariklo and Its Rings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, Jeremy; Horner, Jonti; Marsden, Stephen C.

Chariklo is the only small solar system body confirmed to have rings. Given the instability of its orbit, the presence of rings is surprising, and their origin remains poorly understood. In this work, we study the dynamical history of the Chariklo system by integrating almost 36,000 Chariklo clones backward in time for 1 Gyr under the influence of the Sun and the four giant planets. By recording all close encounters between the clones and planets, we investigate the likelihood that Chariklo’s rings could have survived since its capture to the Centaur population. Our results reveal that Chariklo’s orbit occupies amore » region of stable chaos, resulting in its orbit being marginally more stable than those of the other Centaurs. Despite this, we find that it was most likely captured to the Centaur population within the last 20 Myr, and that its orbital evolution has been continually punctuated by regular close encounters with the giant planets. The great majority (>99%) of those encounters within 1 Hill radius of the planet have only a small effect on the rings. We conclude that close encounters with giant planets have not had a significant effect on the ring structure. Encounters within the Roche limit of the giant planets are rare, making ring creation through tidal disruption unlikely.« less

Cislunar Near Rectilinear Halo Orbit for Human Space Exploration

NASA Technical Reports Server (NTRS)

Whitley, Ryan; Martinez, Roland; Condon, Gerald; Williams, Jacob; Lee, David; Davis, Diane; Barton, Gregg; Bhatt, Sagar; Jang, Jiann-Woei; Clark, Fred;

Secular resonances between bodies on close orbits II: prograde and retrograde orbits for irregular satellites

NASA Astrophysics Data System (ADS)

Li, Daohai; Christou, Apostolos A.

2017-09-01

In extending the analysis of the four secular resonances between close orbits in Li and Christou (Celest Mech Dyn Astron 125:133-160, 2016) (Paper I), we generalise the semianalytical model so that it applies to both prograde and retrograde orbits with a one-to-one map between the resonances in the two regimes. We propose the general form of the critical angle to be a linear combination of apsidal and nodal differences between the two orbits b_1 Δ π + b_2 Δ Ω, forming a collection of secular resonances in which the ones studied in Paper I are among the strongest. Test of the model in the orbital vicinity of massive satellites with physical and orbital parameters similar to those of the irregular satellites Himalia at Jupiter and Phoebe at Saturn shows that {>}20 and {>}40% of phase space is affected by these resonances, respectively. The survivability of the resonances is confirmed using numerical integration of the full Newtonian equations of motion. We observe that the lowest order resonances with b_1+|b_2|≤ 3 persist, while even higher-order resonances, up to b_1+|b_2|≥ 7, survive. Depending on the mass, between 10 and 60% of the integrated test particles are captured in these secular resonances, in agreement with the phase space analysis in the semianalytical model.

Tatooines Future: The Eccentric Response of Keplers Circumbinary Planets to Common-Envelope Evolution of their Host Stars

NASA Technical Reports Server (NTRS)

Kostov, Veselin B.; Moore, Keavin; Tamayo, Daniel; Jayawardhana, Ray; Rinehart, Stephen A.

2016-01-01

Inspired by the recent Kepler discoveries of circumbinary planets orbiting nine close binary stars, we explore the fate of the former as the latter evolve off the main sequence. We combine binary star evolution models with dynamical simulations to study the orbital evolution of these planets as their hosts undergo common-envelope stages, losing in the process a tremendous amount of mass on dynamical timescales. Five of the systems experience at least one Roche-lobe overflow and common-envelope stages (Kepler-1647 experiences three), and the binary stars either shrink to very short orbits or coalesce; two systems trigger a double-degenerate supernova explosion. Kepler's circumbinary planets predominantly remain gravitationally bound at the end of the common-envelope phase, migrate to larger orbits, and may gain significant eccentricity; their orbital expansion can be more than an order of magnitude and can occur over the course of a single planetary orbit. The orbits these planets can reach are qualitatively consistent with those of the currently known post-common-envelope, eclipse-time variations circumbinary candidates. Our results also show that circumbinary planets can experience both modes of orbital expansion (adiabatic and non-adiabatic) if their host binaries undergo more than one common-envelope stage; multiplanet circumbinary systems like Kepler-47 can experience both modes during the same common-envelope stage. Additionally, unlike Mercury orbiting the Sun, a circumbinary planet with the same semi-major axis can survive the common envelope evolution of a close binary star with a total mass of 1 Solar Mass.

PUMPING THE ECCENTRICITY OF EXOPLANETS BY TIDAL EFFECT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Correia, Alexandre C. M.; Boue, Gwenaeel; Laskar, Jacques, E-mail: correia@ua.pt

2012-01-10

Planets close to their host stars are believed to undergo significant tidal interactions, leading to a progressive damping of the orbital eccentricity. Here we show that when the orbit of the planet is excited by an outer companion, tidal effects combined with gravitational interactions may give rise to a secular increasing drift on the eccentricity. As long as this secular drift counterbalances the damping effect, the eccentricity can increase to high values. This mechanism may explain why some of the moderate close-in exoplanets are observed with substantial eccentricity values.

MAGNETIC GAMES BETWEEN A PLANET AND ITS HOST STAR: THE KEY ROLE OF TOPOLOGY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strugarek, A.; Brun, A. S.; Réville, V.

Magnetic interactions between a star and a close-in planet are postulated to be a source of enhanced emissions and to play a role in the secular evolution of the orbital system. Close-in planets generally orbit in the sub-alfvénic region of the stellar wind, which leads to efficient transfers of energy and angular momentum between the star and the planet. We model the magnetic interactions occurring in close-in star–planet systems with three-dimensional, global, compressible magnetohydrodynamic numerical simulations of a planet orbiting in a self-consistent stellar wind. We focus on the cases of magnetized planets and explore three representative magnetic configurations. Themore » Poynting flux originating from the magnetic interactions is an energy source for enhanced emissions in star–planet systems. Our results suggest a simple geometrical explanation for ubiquitous on/off enhanced emissions associated with close-in planets, and confirm that the Poynting fluxes can reach powers of the order of 10{sup 19} W. Close-in planets are also shown to migrate due to magnetic torques for sufficiently strong stellar wind magnetic fields. The topology of the interaction significantly modifies the shape of the magnetic obstacle that leads to magnetic torques. As a consequence, the torques can vary by at least an order of magnitude as the magnetic topology of the interaction varies.« less

Magnetic Games between a Planet and Its Host Star: The Key Role of Topology

NASA Astrophysics Data System (ADS)

Strugarek, A.; Brun, A. S.; Matt, S. P.; Réville, V.

2015-12-01

Magnetic interactions between a star and a close-in planet are postulated to be a source of enhanced emissions and to play a role in the secular evolution of the orbital system. Close-in planets generally orbit in the sub-alfvénic region of the stellar wind, which leads to efficient transfers of energy and angular momentum between the star and the planet. We model the magnetic interactions occurring in close-in star-planet systems with three-dimensional, global, compressible magnetohydrodynamic numerical simulations of a planet orbiting in a self-consistent stellar wind. We focus on the cases of magnetized planets and explore three representative magnetic configurations. The Poynting flux originating from the magnetic interactions is an energy source for enhanced emissions in star-planet systems. Our results suggest a simple geometrical explanation for ubiquitous on/off enhanced emissions associated with close-in planets, and confirm that the Poynting fluxes can reach powers of the order of 1019 W. Close-in planets are also shown to migrate due to magnetic torques for sufficiently strong stellar wind magnetic fields. The topology of the interaction significantly modifies the shape of the magnetic obstacle that leads to magnetic torques. As a consequence, the torques can vary by at least an order of magnitude as the magnetic topology of the interaction varies.

Unity hatch closed in preparation for launch on STS-88

NASA Technical Reports Server (NTRS)

1998-01-01

Workers in the Space Station Processing Facility work in the doorway of the Unity connecting module preparing it for closure before its launch aboard Space Shuttle Endeavour on STS-88 in December. Unity will now undergo a series of leak checks before a final purge of clean, dry air inside the module to ready it for initial operations in space. Other testing includes the common berthing mechanism to which other space station elements will dock and the Pad Demonstration Test to verify the compatibility of the module with the Space Shuttle as well as the ability of the astronauts to send and receive commands to Unity from the flight deck of the orbiter. The next time the hatch will be opened it will be by astronauts on orbit. Unity is expected to be ready for installation into the payload canister on Oct. 25, and transported to Launch Pad 39-A on Oct. 27. The Unity will be mated to the Russian-built Zarya control module which should already be in orbit at that time.

Controlling the motion of a spacecraft when approaching a large object of space debris

NASA Astrophysics Data System (ADS)

Baranov, A. A.; Budyanskiy, A. A.; Razumnyi, Yu. N.

2017-07-01

The problem of calculating the parameters of maneuvering a spacecraft as it approaches a large object of space debris (LOSD) in close near-circular noncoplanar orbits has been considered. In [1-4], the results of analyzing the problem of the flyby of the separated LOSD groups have been presented. It has been assumed that a collector spacecraft approaches the LOSD and captures it or it is inserted into the nozzle of a small spacecraft that has a proper propulsion system (PS). However, in these papers, the flight from one object to another was only analyzed and the problem of approaching to LOSD with a given accuracy was not considered. This paper is a supplement to the cycle of papers [1-4]. It is assumed that, the final stage of approaching the LOSD is implemented by maneuvering in many orbits (up to several dozens) with low-thrust engines, but the PS operating time is fairly small compared with the orbit period in order to make it possible to use impulse approximation in the calculations.

Contamination Examples and Lessons from Low Earth Orbit Experiments and Operational Hardware

NASA Technical Reports Server (NTRS)

Pippin, Gary; Finckenor, Miria M.

2009-01-01

Flight experiments flown on the Space Shuttle, the International Space Station, Mir, Skylab, and free flyers such as the Long Duration Exposure Facility, the European Retrievable Carrier, and the EFFU, provide multiple opportunities for the investigation of molecular contamination effects. Retrieved hardware from the Solar Maximum Mission satellite, Mir, and the Hubble Space Telescope has also provided the means gaining insight into contamination processes. Images from the above mentioned hardware show contamination effects due to materials processing, hardware storage, pre-flight cleaning, as well as on-orbit events such as outgassing, mechanical failure of hardware in close proximity, impacts from man-made debris, and changes due to natural environment factors.. Contamination effects include significant changes to thermal and electrical properties of thermal control surfaces, optics, and power systems. Data from several flights has been used to develop a rudimentary estimate of asymptotic values for absorptance changes due to long-term solar exposure (4000-6000 Equivalent Sun Hours) of silicone-based molecular contamination deposits of varying thickness. Recommendations and suggestions for processing changes and constraints based on the on-orbit observed results will be presented.

Ground-based adaptive optics coronagraphic performance under closed-loop predictive control

NASA Astrophysics Data System (ADS)

Males, Jared R.; Guyon, Olivier

2018-01-01

The discovery of the exoplanet Proxima b highlights the potential for the coming generation of giant segmented mirror telescopes (GSMTs) to characterize terrestrial-potentially habitable-planets orbiting nearby stars with direct imaging. This will require continued development and implementation of optimized adaptive optics systems feeding coronagraphs on the GSMTs. Such development should proceed with an understanding of the fundamental limits imposed by atmospheric turbulence. Here, we seek to address this question with a semianalytic framework for calculating the postcoronagraph contrast in a closed-loop adaptive optics system. We do this starting with the temporal power spectra of the Fourier basis calculated assuming frozen flow turbulence, and then apply closed-loop transfer functions. We include the benefits of a simple predictive controller, which we show could provide over a factor of 1400 gain in raw point spread function contrast at 1 λ/D on bright stars, and more than a factor of 30 gain on an I=7.5 mag star such as Proxima. More sophisticated predictive control can be expected to improve this even further. Assuming a photon-noise limited observing technique such as high-dispersion coronagraphy, these gains in raw contrast will decrease integration times by the same large factors. Predictive control of atmospheric turbulence should therefore be seen as one of the key technologies that will enable ground-based telescopes to characterize terrestrial planets.

Close encounters of a rotating star with planets in parabolic orbits of varying inclination and the formation of hot Jupiters

NASA Astrophysics Data System (ADS)

Ivanov, P. B.; Papaloizou, J. C. B.

2011-10-01

In this paper we extend the theory of close encounters of a giant planet on a parabolic orbit with a central star developed in our previous work (Ivanov and Papaloizou in MNRAS 347:437, 2004; MNRAS 376:682, 2007) to include the effects of tides induced on the central star. Stellar rotation and orbits with arbitrary inclination to the stellar rotation axis are considered. We obtain results both from an analytic treatment that incorporates first order corrections to normal mode frequencies arising from stellar rotation and numerical treatments that are in satisfactory agreement over the parameter space of interest. These results are applied to the initial phase of the tidal circularisation problem. We find that both tides induced in the star and planet can lead to a significant decrease of the orbital semi-major axis for orbits having periastron distances smaller than 5-6 stellar radii with tides in the star being much stronger for retrograde orbits compared to prograde orbits. Assuming that combined action of dynamic and quasi-static tides could lead to the total circularisation of orbits this corresponds to observed periods up to 4-5 days. We use the simple Skumanich law to characterise the rotational history of the star supposing that the star has its rotational period equal to one month at the age of 5 Gyr. The strength of tidal interactions is characterised by circularisation time scale, t ev , which is defined as a typical time scale of evolution of the planet's semi-major axis due to tides. This is considered as a function of orbital period P obs , which the planet obtains after the process of tidal circularisation has been completed. We find that the ratio of the initial circularisation time scales corresponding to prograde and retrograde orbits, respectively, is of order 1.5-2 for a planet of one Jupiter mass having P obs ~ 4 days. The ratio grows with the mass of the planet, being of order five for a five Jupiter mass planet with the same P orb . Note, however, this result might change for more realistic stellar rotation histories. Thus, the effect of stellar rotation may provide a bias in the formation of planetary systems having planets on close orbits around their host stars, as a consequence of planet-planet scattering, which favours systems with retrograde orbits. The results reported in the paper may also be applied to the problem of tidal capture of stars in young stellar clusters.

Guidance of a Solar Sail Spacecraft to the Sun - L(2) Point.

NASA Astrophysics Data System (ADS)

Hur, Sun Hae

The guidance of a solar sail spacecraft along a minimum-time path from an Earth orbit to a region near the Sun-Earth L_2 libration point is investigated. Possible missions to this point include a spacecraft "listening" for possible extra-terrestrial electromagnetic signals and a science payload to study the geomagnetic tail. A key advantage of the solar sail is that it requires no fuel. The control variables are the sail angles relative to the Sun-Earth line. The thrust is very small, on the order of 1 mm/s^2, and its magnitude and direction are highly coupled. Despite this limited controllability, the "free" thrust can be used for a wide variety of terminal conditions including halo orbits. If the Moon's mass is lumped with the Earth, there are quasi-equilibrium points near L_2. However, they are unstable so that some form of station keeping is required, and the sail can provide this without any fuel usage. In the two-dimensional case, regulating about a nominal orbit is shown to require less control and result in smaller amplitude error response than regulating about a quasi-equilibrium point. In the three-dimensional halo orbit case, station keeping using periodically varying gains is demonstrated. To compute the minimum-time path, the trajectory is divided into two segments: the spiral segment and the transition segment. The spiral segment is computed using a control law that maximizes the rate of energy increase at each time. The transition segment is computed as the solution of the time-optimal control problem from the endpoint of the spiral to the terminal point. It is shown that the path resulting from this approximate strategy is very close to the exact optimal path. For the guidance problem, the approximate strategy in the spiral segment already gives a nonlinear full-state feedback law. However, for large perturbations, follower guidance using an auxiliary propulsion is used for part of the spiral. In the transition segment, neighboring extremal feedback guidance using the solar sail, with feedforward control only near the terminal point, is used to correct perturbations in the initial conditions.

Creativity and borderline personality disorder: evidence from a voxel-based morphometry study.

PubMed

Leutgeb, Verena; Ille, Rottraut; Wabnegger, Albert; Schienle, Anne; Schöggl, Helmut; Weber, Bernhard; Papousek, Ilona; Weiss, Elisabeth M; Fink, Andreas

2016-05-01

Throughout the history, various examples of eminent creative people suffering from mental disorders along with some empirical research reports strengthened the idea of a potential link between creativity and psychopathology. This study investigated different facets of psychometrically determined creativity in 20 females diagnosed with borderline personality disorder (BPD) relative to 19 healthy female controls. In addition, group differences in grey matter (GM) were examined. Behavioural findings revealed no significant differences between the BPD group and healthy controls with respect to verbal and figural-graphic creative task performance and creativity-related personality characteristics. Whole-brain voxel-based morphometry analyses revealed a distinct pattern of GM reductions in the BPD group (relative to controls) in a network of brain regions closely associated with various cognitive and emotional functions (including the bilateral orbital inferior frontal gyri and the left superior temporal gyrus), partly overlapping with creativity-related brain regions. Correlation analyses moreover revealed that in the BPD group GM reductions in the orbital parts of the inferior and middle frontal gyri were associated with lower levels of creativity. This study provides no indications in favour of the putative link between creativity and psychopathology, as sometimes reported in the literature.

Building up the spin - orbit alignment of interacting galaxy pairs

NASA Astrophysics Data System (ADS)

Moon, Jun-Sung; Yoon, Suk-Jin

2018-01-01

Galaxies are not just randomly distributed throughout space. Instead, they are in alignment over a wide range of scales from the cosmic web down to a pair of galaxies. Motivated by recent findings that the spin and the orbital angular momentum vectors of galaxy pairs tend to be parallel, we here investigate the spin - orbit orientation in close pairs using the Illustris cosmological simulation. We find that since z ~ 1, the parallel alignment has become progressively stronger with time through repetitive encounters. The pair Interactions are preferentially in prograde at z = 0 (over 5 sigma significance). The prograde fraction at z = 0 is larger for the pairs influenced more heavily by each other during their evolution. We find no correlation between the spin - orbit orientation and the surrounding large-scale structure. Our results favor the scenario in which the alignment in close pairs is caused by tidal interactions later on, rather than the primordial torquing by the large-scale structures.

On the Milankovitch orbital elements for perturbed Keplerian motion

NASA Astrophysics Data System (ADS)

Rosengren, Aaron J.; Scheeres, Daniel J.

2014-03-01

We consider sets of natural vectorial orbital elements of the Milankovitch type for perturbed Keplerian motion. These elements are closely related to the two vectorial first integrals of the unperturbed two-body problem; namely, the angular momentum vector and the Laplace-Runge-Lenz vector. After a detailed historical discussion of the origin and development of such elements, nonsingular equations for the time variations of these sets of elements under perturbations are established, both in Lagrangian and Gaussian form. After averaging, a compact, elegant, and symmetrical form of secular Milankovitch-like equations is obtained, which reminds of the structure of canonical systems of equations in Hamiltonian mechanics. As an application of this vectorial formulation, we analyze the motion of an object orbiting about a planet (idealized as a point mass moving in a heliocentric elliptical orbit) and subject to solar radiation pressure acceleration (obeying an inverse-square law). We show that the corresponding secular problem is integrable and we give an explicit closed-form solution.

Angles-only navigation for autonomous orbital rendezvous

NASA Astrophysics Data System (ADS)

Woffinden, David C.

The proposed thesis of this dissertation has both a practical element and theoretical component which aim to answer key questions related to the use of angles-only navigation for autonomous orbital rendezvous. The first and fundamental principle to this work argues that an angles-only navigation filter can determine the relative position and orientation (pose) between two spacecraft to perform the necessary maneuvers and close proximity operations for autonomous orbital rendezvous. Second, the implementation of angles-only navigation for on-orbit applications is looked upon with skeptical eyes because of its perceived limitation of determining the relative range between two vehicles. This assumed, yet little understood subtlety can be formally characterized with a closed-form analytical observability criteria which specifies the necessary and sufficient conditions for determining the relative position and velocity with only angular measurements. With a mathematical expression of the observability criteria, it can be used to (1) identify the orbital rendezvous trajectories and maneuvers that ensure the relative position and velocity are observable for angles-only navigation, (2) quantify the degree or level of observability and (3) compute optimal maneuvers that maximize observability. In summary, the objective of this dissertation is to provide both a practical and theoretical foundation for the advancement of autonomous orbital rendezvous through the use of angles-only navigation.

Using Mean Orbit Period in Mars Reconnaissance Orbiter Maneuver Design

NASA Technical Reports Server (NTRS)

Chung, Min-Kun J.; Menon, Premkumar R.; Wagner, Sean V.; Williams, Jessica L.

2014-01-01

Mars Reconnaissance Orbiter (MRO) has provided communication relays for a number of Mars spacecraft. In 2016 MRO is expected to support a relay for NASA's Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) spacecraft. In addition, support may be needed by another mission, ESA's ExoMars EDL Demonstrator Module's (EDM), only 21 days after the InSight coverage. The close proximity of these two events presents a unique challenge to a conventional orbit synchronization maneuver where one deterministic maneuver is executed prior to each relay. Since the two events are close together and the difference in required phasing between InSight and EDM may be up to half an orbit (yielding a large execution error), the downtrack timing error can increase rapidly at the EDM encounter. Thus, a new maneuver strategy that does not require a deterministic maneuver in-between the two events (with only a small statistical cleanup) is proposed in the paper. This proposed strategy rests heavily on the stability of the mean orbital period. The ability to search and set the specified mean period is fundamental in the proposed maneuver design as well as in understanding the scope of the problem. The proposed strategy is explained and its result is used to understand and solve the problem in the flight operations environment.

Synthesis of a controller for stabilizing the motion of a rigid body about a fixed point

NASA Astrophysics Data System (ADS)

Zabolotnov, Yu. M.; Lobanov, A. A.

2017-05-01

A method for the approximate design of an optimal controller for stabilizing the motion of a rigid body about a fixed point is considered. It is assumed that rigid body motion is nearly the motion in the classical Lagrange case. The method is based on the common use of the Bellman dynamic programming principle and the averagingmethod. The latter is used to solve theHamilton-Jacobi-Bellman equation approximately, which permits synthesizing the controller. The proposed method for controller design can be used in many problems close to the problem of motion of the Lagrange top (the motion of a rigid body in the atmosphere, the motion of a rigid body fastened to a cable in deployment of the orbital cable system, etc.).

Longitudinal control effectiveness and entry dynamics of a single-stage-to-orbit vehicle

NASA Technical Reports Server (NTRS)

Vinh, N. X.; Lin, C. F.

1982-01-01

The classical theory of flight dynamics for airplane longitudinal stability and control analysis was extended to the case of a hypervelocity reentry vehicle. This includes the elements inherent in supersonic and hypersonic flight such as the influence of the Mach number on aerodynamic characteristics, and the effect of the reaction control system and aerodynamic controls on the trim condition through a wide range of speed. Phugoid motion and angle of attack oscillation for typical cases of cruising flight, ballistic entry, and glide entry are investigated. In each case, closed form solutions for the variations in altitude, flight path angle, speed and angle of attack are obtained. The solutions explicitly display the influence of different regions design parameters and trajectory variables on the stability of the motion.

View of the new CMG during Expedition 15/STS-118 EVA 2

NASA Image and Video Library

2007-08-13

ISS015-E-22366 (13 Aug. 2007) --- A close-up view of the new control moment gyroscope (CMG) photographed by a crewmember during the mission's second planned session of extravehicular activity (EVA). During the spacewalk, Canadian Space Agency's astronaut Dave Williams (out of frame) and astronaut Rick Mastracchio (out of frame), both STS-118 mission specialists, removed a faulty control moment gyroscope (CMG-3) and installed a new CMG into the station's Z1 truss. The failed CMG will remain at its temporary stowage location on the station's exterior before it is returned to Earth on a later shuttle mission. The new gyroscope is one of four CMGs that are used to control the station's attitude in orbit.

Application of X-Ray Pulsar Navigation: A Characterization of the Earth Orbit Trade Space

NASA Technical Reports Server (NTRS)

Yu, Wayne

2016-01-01

The potential for pulsars as a navigation source has been studied since their discovery in 1967. X-ray pulsar navigation (XNAV) is a celestial navigation system that uses the consistent timing nature of x-ray photons from milli-second pulsars (MSP) to perform space navigation. By comparing the detected arrival of x-ray photons to a reference database of expected pulsar lightcurve timing models, one can infer a range and range rate measurement based on light time delay. Much of the challenge of XNAV comes from the faint signal, availability, and distant nature of pulsars. This is a study of potential pulsar XNAV measurements to measure extended Kalman filter (EKF) tracking performance with a wide trade space of bounded Earth orbits, using a simulation of existing x-ray detector space hardware. An example of an x-ray detector for XNAV is the NASA Station Explorer for X-ray Timing and Navigation (SEXTANT) mission, a technology demonstration of XNAV set to perform on the International Space Station (ISS) in late 2016early 2017. XNAV hardware implementation is driven by trajectory and environmental influences which add noise to the x-ray pulse signal. In a closed Earth orbit, the radiation environment can exponentially increase the signal noise from x-ray pulsar sources, decreasing the quality and frequency of measurements. The SEXTANT mission in particular improves on the signal to noise ratio by focusing an array of 56 x-ray silicon drift detectors at one pulsar target at a time. This reduces timing glitches and other timing noise contributions from ambient x-ray sources to within a 100 nanosecond resolution. This study also considers the SEXTANT scheduling challenges inherent in a single target observation. Finally, as the navigation sources are now relatively inertial targets, XNAV measurements are also subject to periods of occultation from various celestial bodies. This study focuses on the characterization of these drivers in closed Earth orbits and is not a tuning analysis of the EKF. The study shows that the closed Earth orbit for XNAV performance is reliant on the orbit semi-major axis and eccentricity as well as orbit inclination. These parameters are the primary drivers of pulsar measurement availability and significantly influence the natural spacecraft orbit dynamics. Sensitivity to initial orbit determination error growth due to the scarcity of XNAV measurements within an orbital period require appropriate timing of initial XNAV measurements. The orbit angles of argument of perigee and right ascension of the ascending node, alongside the other orbit parameters, complete the initial cadence of XNAV measurements. The performance of initial XNAV measurements then propagates throughout the experimental period. The study provides a basis to missions who wish to consider XNAV as a potential navigation source in a closed Earth orbit design. It provides a family of orbit trajectories as well as other modeling considerations needed to effectively evaluate if XNAV is an effective navigation source for a potential mission. As an EKF is sensitive to a linearized estimated state, this study has a direct benefit of providing effective XNAV measurements to maintain spacecraft tracking, independent of other navigation sources. In the particular use case of the SEXTANT mission, it also provides a novel scheduling algorithm which addresses the need to prioritize and manage pulsar observations for effective navigation.

Application of X-Ray Pulsar Navigation: A Characterization of the Earth Orbit Trade Space

NASA Technical Reports Server (NTRS)

Yu, Wayne Hong

2016-01-01

The potential for pulsars as a navigation source has been studied since their discovery in 1967. X-ray pulsar navigation (XNAV) is a celestial navigation system that uses the consistent timing nature of x-ray photons from millisecond pulsars (MSP) to perform space navigation. By comparing the detected arrival of x-ray photons to a reference database of expected pulsar light-curve timing models, one can infer a range and range rate measurement based on light time delay. Much of the challenge of XNAV comes from the faint signal, availability, and distant nature of pulsars. This is a study of potential pulsar XNAV measurements to measure extended Kalman filter (EKF) tracking performance with a wide trade space of bounded Earth orbits, using a simulation of existing x-ray detector space hardware. An example of an x-ray detector for XNAV is the NASA Station Explorer for X-ray Timing and Navigation (SEXTANT) mission, a technology demonstration of XNAV set to perform on the International Space Station (ISS) in late 2016early 2017. XNAV hardware implementation is driven by trajectory and environmental influences which add noise to the x-ray pulse signal. In a closed Earth orbit, the radiation environment can exponentially increase the signal noise from x-ray pulsar sources, decreasing the quality and frequency of measurements. The SEXTANT mission in particular improves on the signal to noise ratio by focusing an array of 56 x-ray silicon drift detectors at one pulsar target at a time. This reduces timing glitches and other timing noise contributions from ambient x-ray sources to within a 100 nanosecond resolution. This study also considers the SEXTANT scheduling challenges inherent in a single target observation. Finally, as the navigation sources are now relatively inertial targets, XNAV measurements are also subject to periods of occultation from various celestial bodies. This study focuses on the characterization of these drivers in closed Earth orbits and is not a tuning analysis of the EKF. The study shows that the closed Earth orbit for XNAV performance is reliant on the orbit semi-major axis and eccentricity as well as orbit inclination. These parameters are the primary drivers of pulsar measurement availability and significantly influence the natural spacecraft orbit dynamics. Sensitivity to initial orbit determination error growth due to the scarcity of XNAV measurements within an orbital period require appropriate timing of initial XNAV measurements. The orbit angles of argument of perigee and right ascension of the ascending node, alongside the other orbit parameters, complete the initial cadence of XNAV measurements. The performance of initial XNAV measurements then propagates throughout the experimental period. The study provides a basis to missions who wish to consider XNAV as a potential navigation source in a closed Earth orbit design. It provides a family of orbit trajectories as well as other modeling considerations needed to effectively evaluate if XNAV is an effective navigation source for a potential mission. As an EKF is sensitive to a linearized estimated state, this study has a direct benefit of providing effective XNAV measurements to maintain spacecraft tracking, independent of other navigation sources. In the particular use case of the SEXTANT mission, it also provides a novel scheduling algorithm which addresses the need to prioritize and manage pulsar observations for effective navigation.

Optical Design of the Developmental Cryogenic Active Telescope Testbed (DCATT)

NASA Technical Reports Server (NTRS)

Davila, Pam; Wilson, Mark; Young, Eric W.; Lowman, Andrew E.; Redding, David C.

1997-01-01

In the summer of 1996, three Study teams developed conceptual designs and mission architectures for the Next Generation Space Telescope (NGST). Each group highlighted areas of technology development that need to be further advanced to meet the goals of the NGST mission. The most important areas for future study included: deployable structures, lightweight optics, cryogenic optics and mechanisms, passive cooling, and on-orbit closed loop wavefront sensing and control. NASA and industry are currently planning to develop a series of ground testbeds and validation flights to demonstrate many of these technologies. The Deployed Cryogenic Active Telescope Testbed (DCATT) is a system level testbed to be developed at Goddard Space Flight Center in three phases over an extended period of time. This testbed will combine an actively controlled telescope with the hardware and software elements of a closed loop wavefront sensing and control system to achieve diffraction limited imaging at 2 microns. We will present an overview of the system level requirements, a discussion of the optical design, and results of performance analyses for the Phase 1 ambient concept for DCATT,

Close-up view of Sunflower Seeds

NASA Image and Video Library

2013-11-04

ISS037-E-026274 (4 Nov. 2013) --- A two-day old sunflower sprout is being closely monitored in its temporary home inside a plastic bag by the Expedition 37 crew members onboard the Earth-orbiting International Space Station.

Trajectory Design for the Phobos and Deimos & Mars Environment Spacecraft

NASA Technical Reports Server (NTRS)

Genova, Anthony L.; Korsmeyer, David J.; Loucks, Michel E.; Yang, Fan Yang; Lee, Pascal

2016-01-01

The presented trajectory design and analysis was performed for the Phobos and Deimos & Mars Environment (PADME) mission concept as part of a NASA proposal submission managed by NASA Ames Research Center in the 2014-2015 timeframe. The PADME spacecraft would be a derivative of the successfully flown Lunar Atmosphere & Dust Environment Explorer (LADEE) spacecraft. While LADEE was designed to enter low-lunar orbit, the PADME spacecraft would instead enter an elliptical Mars orbit of 2-week period. This Mars orbit would pass by Phobos near periapsis on successive orbits and then raise periapsis to yield close approaches of Deimos every orbit thereafter.

Orbital evolution of some Centaurs

NASA Astrophysics Data System (ADS)

Kovalenko, Nataliya; Babenko, Yuri; Churyumov, Klim

2002-11-01

In this work we investigated the dynamical evolution of Centaurs objects 2060 (Chiron), 5145 (Pholus), 7066 (Nessus), 8405 (Asbolus), 10199 (Chariklo), 10370 (Hylonome), and Scattered-Disk object 15874. We have carried out orbital integration of test particles with initial orbits similar to those of these objects. Calculations were produced for +/-600kyr-10Myr starting at epoch and using the implicit single sequence Everhart methods. 12 variational orbits for each of selected Centaurs also have been numerically integrated for +/-200 kyr toward the past and the future. The most probable paths were traced up to +/-1 Myr. The character of orbital elements changes and peculiarities of close approaches to giant planets are discussed.

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

NASA Technical Reports Server (NTRS)

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

2010-01-01

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

Long-term evolution of 1991 DA: A dynamically evolved extinct Halley-type comet

NASA Technical Reports Server (NTRS)

Hahn, Gerhard; Bailey, M. E.

1992-01-01

The long-term dynamical evolution of 21 variational orbits for the intermediate-period asteroid 1991 DA was followed for up to +/-10(exp 5) years from the present. 1991 DA is close to the 2:7 resonance with Jupiter; it has avoided close encounters, within 1 AU, with this planet for at least the past 30,000 years, even at the node crossing. The future evolution typically shows no close encounters with Jupiter within at least 50,000 years. This corresponds to the mean time between node crossings with either Jupiter or Saturn. Close encounters with Saturn and Jupiter lead to a chaotic evolution for the whole ensemble, while secular perturbations cause large-amplitude swings in eccentricity and inclination (the latter covering the range 15 deg approximately less than i approximately less than 85 deg) which correlate with deep excursions of the perihelion distance to values much less than 1 AU. These variations are similar to those found in P/Machholz and a variety of other high-inclination orbits, e.g., P/Hartley-IRAS. We emphasize the connection between the orbital evolution of 1991 DA and that of Halley-type comets. If 1991 DA was once a comet, it is not surprising that it is now extinct.

WD1145+017 (Abstract)

NASA Astrophysics Data System (ADS)

Motta, M.

2017-12-01

(Abstract only) WD1145 is a 17th magnitude white dwarf star 570 light years away in Virgo that was discovered to have a disintegrating planetoid in close orbit by Andrew Vanderburg, a graduate student at Harvard CfA, while data mining the elucidate the nature of its rather bizarre transit light curves. I obtained multiple observations of WD1145 over the course of a year, and found a series of complex transit light curves that could only be interpreted as a ring complex or torus in close orbit around WD1145. Combined with data from other amateur astronomers, professional observations, and satellite data, it became clear that WD1145 has a small planetoid in close orbit at the Roche limit and is breaking apart, forming a ring of debris material that is then raining down on the white dwarf. The surface of the star is "polluted" by heavy metals, determined by spectroscopic data. Given that in the intense gravitational field of a white dwarf any heavy metals could not for long last on the surface, this confirms that we are tracking in real time the destruction of a small planet by its host star.

How to Take 30 Years Off the Life of an Earth-Orbiter Network

NASA Technical Reports Server (NTRS)

Berner, C. D.; Perkins, R. C.; Baker, N.

1995-01-01

In the mid 1960's the NASA/JPL Deep Space Network installed a global 26-meter antenna network to support a large group of Low Earth Orbiters and Highly Elliptical Orbiters. Although this network was equipped with then state-of-the-art equipment, operations were labor- intensive. A study is discussed which takes a close look at re- engineering the 26-meter antenna network from all aspects.

Closeup view of the payload bay side of the aft ...

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

Close-up view of the payload bay side of the aft crew compartment bulkhead of the Orbiter Discovery. Showing the airlock, the beam-truss attach structure supporting it and its attach points to the payload bay sill longerons. This photograph was taken in the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

General view looking aft from the starboard side of the ...

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

General view looking aft from the starboard side of the mid fuselage of the Orbiter Discovery. This view has a close-up view of the remote sensor boom and its retention mechanisms at its attach points to the starboard longeron. This photograph was taken in the Orbiter Processing Facility at the Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Closeup view of a Space Shuttle Main Engine (SSME) installed ...

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

Close-up view of a Space Shuttle Main Engine (SSME) installed in position number one on the Orbiter Discovery. A ground-support mobile platform is in place below the engine to assist in technicians with the installation of the engine. This Photograph was taken in the Orbiter Processing Facility at the Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Use of a caudal auricular axial pattern flap in three cats and one dog following orbital exenteration.

PubMed

Stiles, Jean; Townsend, Wendy; Willis, Michelle; Moore, Phillip A; Smith, Eric

2003-06-01

Orbital exenteration accompanied by wide eyelid excision in the cat and dog may leave a defect that cannot be closed in a primary fashion. This report describes the use of a caudal auricular axial pattern flap to effect closure following orbital exenteration in three cats and one dog. The most common complication was distal flap necrosis, which necessitated a second surgery in two patients.

Disruption of postural readaptation by inertial stimuli following space flight

NASA Technical Reports Server (NTRS)

Black, F. O.; Paloski, W. H.; Reschke, M. F.; Igarashi, M.; Guedry, F.; Anderson, D. J.

1999-01-01

Postural instability (relative to pre-flight) has been observed in all shuttle astronauts studied upon return from orbital missions. Postural stability was more closely examined in four shuttle astronaut subjects before and after an 8 day orbital mission. Results of the pre- and post-flight postural stability studies were compared with a larger (n = 34) study of astronauts returning from shuttle missions of similar duration. Results from both studies indicated that inadequate vestibular feedback was the most significant sensory deficit contributing to the postural instability observed post flight. For two of the four IML-1 astronauts, post-flight postural instability and rate of recovery toward their earth-normal performance matched the performance of the larger sample. However, post-flight postural control in one returning astronaut was substantially below mean performance. This individual, who was within normal limits with respect to postural control before the mission, indicated that recovery to pre-flight postural stability was also interrupted by a post-flight pitch plane rotation test. A similar, though less extreme departure from the mean recovery trajectory was present in another astronaut following the same post-flight rotation test. The pitch plane rotation stimuli included otolith stimuli in the form of both transient tangential and constant centripetal linear acceleration components. We inferred from these findings that adaptation on orbit and re-adaptation on earth involved a change in sensorimotor integration of vestibular signals most likely from the otolith organs.

A Free-Return Earth-Moon Cycler Orbit for an Interplanetary Cruise Ship

NASA Technical Reports Server (NTRS)

Genova, Anthony L.; Aldrin, Buzz

2015-01-01

A periodic circumlunar orbit is presented that can be used by an interplanetary cruise ship for regular travel between Earth and the Moon. This Earth-Moon cycler orbit was revealed by introducing solar gravity and modest phasing maneuvers (average of 39 m/s per month) which yields close-Earth encounters every 7 or 10 days. Lunar encounters occur every 26 days and offer the chance for a smaller craft to depart the cycler and enter lunar orbit, or head for a Lagrange point (e.g., EM-L2 halo orbit), distant retrograde orbit (DRO), or interplanetary destination such as a near-Earth object (NEO) or Mars. Additionally, return-to-Earth abort options are available from many points along the cycling trajectory.

EXPERIMENTS - APOLLO 17

NASA Image and Video Library

1972-11-17

S72-53470 (November 1972) --- The Far-Ultraviolet Spectrometer, Experiment S-169, one of the lunar orbital science experiments which will be mounted in the SIM bay of the Apollo 17 Service Module. Controls for activating and deactivating the experiment and for opening and closing a protective cover are located in the Command Module. Atomic composition, density and scale height for several constituents of the lunar atmosphere will be measured by the far-ultraviolet spectrometer. Solar far-UV radiation reflected from the lunar surface as well as UV radiation emitted by galactic sources also will be detected by the instrument.

Earth to Moon Transfers - Direct vs Via Libration Points (L1, L2)

NASA Technical Reports Server (NTRS)

Condon, Gerald L.; Wilson, Sam

2002-01-01

Recommend Direct Remote Ocean Area impact disposal for caseswithout hazardous (e.g., radioactive) material on LTV kickstage Controlled Earth contact. Relatively small disposal AV. Avoids close encounter with Moon. Trajectories can be very sensitive to initial conditions (at disposalmaneuver).V to correct for errors is small. Recommend Heliocentric Orbit disposal for cases with hazardousmaterial on LTV kickstage. No Earth or Lunar disposal issues (e.g.. impact location, debris footprint,litter). Relatively low disposal AV cost. Further study required to determine possibility of re-contact with Earth.

Closeup view of the reinforced carboncarbon nose on the forward ...

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

Close-up view of the reinforced carbon-carbon nose on the forward section of the Orbiter Discovery's in the Vehicle Assembly Building at NASA's Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Mars Orbiters Duck and Cover for Comet Siding Spring Flyby Artist Concept

NASA Image and Video Library

2014-10-09

This artist concept shows NASA Mars orbiters lining up behind the Red Planet for their duck and cover maneuver to shield them from comet dust that may result from the close flyby of comet Siding Spring C/2013 A1 on Oct. 19, 2014.

Path-integral invariants in abelian Chern-Simons theory

NASA Astrophysics Data System (ADS)

Guadagnini, E.; Thuillier, F.

2014-05-01

We consider the U(1) Chern-Simons gauge theory defined in a general closed oriented 3-manifold M; the functional integration is used to compute the normalized partition function and the expectation values of the link holonomies. The non-perturbative path-integral is defined in the space of the gauge orbits of the connections which belong to the various inequivalent U(1) principal bundles over M; the different sectors of configuration space are labelled by the elements of the first homology group of M and are characterized by appropriate background connections. The gauge orbits of flat connections, whose classification is also based on the homology group, control the non-perturbative contributions to the mean values. The functional integration is carried out in any 3-manifold M, and the corresponding path-integral invariants turn out to be strictly related with the abelian Reshetikhin-Turaev surgery invariants.

High-resolution rock-magnetic variability in shallow marine sediment: a sensitive paleoclimatic metronome

NASA Astrophysics Data System (ADS)

Arai, Kohsaku; Sakai, Hideo; Konishi, Kenji

1997-05-01

An outer shelf deposit in central Japan centered on the Olduvai normal polarity event in the reversed Matuyama chron reveals a close correlation of both the magnetic susceptibility and remanent intensity with the sedimentary cyclicities apparent in lithologies and molluscan assemblages. Two sedimentary cycles are characterized by distinctly similar, but double-peaked magnetic cyclicities. The rock-magnetic variability is primarily attributed to the relative abundance of terrigenous magnetic minerals, and the double peak of the variability is characterized by the concentration of finer-grained magnetic minerals. The concentration is suspected to be controlled by both climatic change and shifting proximity of the shoreline as a function of rise and fall of the sea level due to glacio-eustasy. Rock-magnetic study reveals the record of a 21 ka period of orbital precession cycles within the sedimentary cyclicity attributable to a 41 ka period of orbital obliquity forcing.

Stretch or contraction induced inversion of rectification in diblock molecular junctions

NASA Astrophysics Data System (ADS)

Zhang, Guang-Ping; Hu, Gui-Chao; Song, Yang; Xie, Zhen; Wang, Chuan-Kui

2013-09-01

Based on ab initio theory and nonequilibrium Green's function method, the effect of stretch or contraction on the rectification in diblock co-oligomer molecular diodes is investigated theoretically. Interestingly, an inversion of rectifying direction induced by stretching or contracting the molecular junctions, which is closely related to the number of the pyrimidinyl-phenyl units, is proposed. The analysis of the molecular projected self-consistent Hamiltonian and the evolution of the frontier molecular orbitals as well as transmission coefficients under external biases gives an inside view of the observed results. It reveals that the asymmetric molecular level shift and asymmetric evolution of orbital wave functions under biases are competitive mechanisms for rectification. The stretching or contracting induced inversion of the rectification is due to the conversion of the dominant mechanism. This work suggests a feasible technique to manipulate the rectification performance in molecular diodes by use of the mechanically controllable method.

Reducing Formation-Keeping Maneuver Costs for Formation Flying Satellites in Low-Earth Orbit

NASA Technical Reports Server (NTRS)

Hamilton, Nicholas

2001-01-01

Several techniques are used to synthesize the formation-keeping control law for a three-satellite formation in low-earth orbit. The objective is to minimize maneuver cost and position tracking error. Initial reductions are found for a one-satellite case by tuning the state-weighting matrix within the linear-quadratic-Gaussian framework. Further savings come from adjusting the maneuver interval. Scenarios examined include cases with and without process noise. These results are then applied to a three-satellite formation. For both the one-satellite and three-satellite cases, increasing the maneuver interval yields a decrease in maneuver cost and an increase in position tracking error. A maneuver interval of 8-10 minutes provides a good trade-off between maneuver cost and position tracking error. An analysis of the closed-loop poles with respect to varying maneuver intervals explains the effectiveness of the chosen maneuver interval.

Power Spectrum of a Noisy System Close to a Heteroclinic Orbit

NASA Astrophysics Data System (ADS)

Giner-Baldó, Jordi; Thomas, Peter J.; Lindner, Benjamin

2017-07-01

We consider a two-dimensional dynamical system that possesses a heteroclinic orbit connecting four saddle points. This system is not able to show self-sustained oscillations on its own. If endowed with white Gaussian noise it displays stochastic oscillations, the frequency and quality factor of which are controlled by the noise intensity. This stochastic oscillation of a nonlinear system with noise is conveniently characterized by the power spectrum of suitable observables. In this paper we explore different analytical and semianalytical ways to compute such power spectra. Besides a number of explicit expressions for the power spectrum, we find scaling relations for the frequency, spectral width, and quality factor of the stochastic heteroclinic oscillator in the limit of weak noise. In particular, the quality factor shows a slow logarithmic increase with decreasing noise of the form Q˜ [ln (1/D)]^2. Our results are compared to numerical simulations of the respective Langevin equations.

Doublet Pulse Coherent Laser Radar for Tracking of Resident Space Objects

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Rudd, Van; Shald, Scott; Sandford, Stephen; Dimarcantonio, Albert

2014-01-01

In this paper, the development of a long range ladar system known as ExoSPEAR at NASA Langley Research Center for tracking rapidly moving resident space objects is discussed. Based on 100 W, nanosecond class, near-IR laser, this ladar system with coherent detection technique is currently being investigated for short dwell time measurements of resident space objects (RSOs) in LEO and beyond for space surveillance applications. This unique ladar architecture is configured using a continuously agile doublet-pulse waveform scheme coupled to a closed-loop tracking and control loop approach to simultaneously achieve mm class range precision and mm/s velocity precision and hence obtain unprecedented track accuracies. Salient features of the design architecture followed by performance modeling and engagement simulations illustrating the dependence of range and velocity precision in LEO orbits on ladar parameters are presented. Estimated limits on detectable optical cross sections of RSOs in LEO orbits are discussed.

RS-34 Phoenix (Peacekeeper Post Boost Propulsion System) Utilization Study

NASA Technical Reports Server (NTRS)

Esther, Elizabeth A.; Kos, Larry; Bruno, Cy

2012-01-01

The Advanced Concepts Office (ACO) at the NASA Marshall Space Flight Center (MSFC) in conjunction with Pratt & Whitney Rocketdyne conducted a study to evaluate potential in-space applications for the Rocketdyne produced RS-34 propulsion system. The existing RS-34 propulsion system is a remaining asset from the decommissioned United States Air Force Peacekeeper ICBM program; specifically the pressure-fed storable bipropellant Stage IV Post Boost Propulsion System, renamed Phoenix. MSFC gained experience with the RS-34 propulsion system on the successful Ares I-X flight test program flown in October 2009. RS-34 propulsion system components were harvested from stages supplied by the USAF and used on the Ares I-X Roll control system (RoCS). The heritage hardware proved extremely robust and reliable and sparked interest for further utilization on other potential in-space applications. Subsequently, MSFC is working closely with the USAF to obtain all the remaining RS-34 stages for re-use opportunities. Prior to pursuit of securing the hardware, MSFC commissioned the Advanced Concepts Office to understand the capability and potential applications for the RS-34 Phoenix stage as it benefits NASA, DoD, and commercial industry. Originally designed, the RS-34 Phoenix provided in-space six-degrees-of freedom operational maneuvering to deploy multiple payloads at various orbital locations. The RS-34 Phoenix Utilization Study sought to understand how the unique capabilities of the RS-34 Phoenix and its application to six candidate missions: 1) small satellite delivery (SSD), 2) orbital debris removal (ODR), 3) ISS re-supply, 4) SLS kick stage, 5) manned GEO servicing precursor mission, and an Earth-Moon L-2 Waypoint mission. The small satellite delivery and orbital debris removal missions were found to closely mimic the heritage RS-34 mission. It is believed that this technology will enable a small, low-cost multiple satellite delivery to multiple orbital locations with a single boost. For both the small satellite delivery and the orbital debris mission candidates, the RS-34 Phoenix requires the least amount of modification to the existing hardware. The results of the RS-34 Phoenix Utilization Study show that the system is technically sufficient to successfully support all of the missions analyzed

RS-34 Phoenix (Peacekeeper Post Boost Propulsion System) Utilization Study

NASA Technical Reports Server (NTRS)

Esther, Elizabeth A.; Kos, Larry; Burnside, Christopher G.; Bruno, Cy

2013-01-01

The Advanced Concepts Office (ACO) at the NASA Marshall Space Flight Center (MSFC) in conjunction with Pratt & Whitney Rocketdyne conducted a study to evaluate potential in-space applications for the Rocketdyne produced RS-34 propulsion system. The existing RS-34 propulsion system is a remaining asset from the de-commissioned United States Air Force Peacekeeper ICBM program, specifically the pressure-fed storable bipropellant Stage IV Post Boost Propulsion System, renamed Phoenix. MSFC gained experience with the RS-34 propulsion system on the successful Ares I-X flight test program flown in October 2009. RS-34 propulsion system components were harvested from stages supplied by the USAF and used on the Ares I-X Roll control system (RoCS). The heritage hardware proved extremely robust and reliable and sparked interest for further utilization on other potential in-space applications. MSFC is working closely with the USAF to obtain RS-34 stages for re-use opportunities. Prior to pursuit of securing the hardware, MSFC commissioned the Advanced Concepts Office to understand the capability and potential applications for the RS-34 Phoenix stage as it benefits NASA, DoD, and commercial industry. As originally designed, the RS-34 Phoenix provided in-space six-degrees-of freedom operational maneuvering to deploy multiple payloads at various orbital locations. The RS-34 Phoenix Utilization Study sought to understand how the unique capabilities of the RS-34 Phoenix and its application to six candidate missions: 1) small satellite delivery (SSD), 2) orbital debris removal (ODR), 3) ISS re-supply, 4) SLS kick stage, 5) manned GEO servicing precursor mission, and an Earth-Moon L-2 Waypoint mission. The small satellite delivery and orbital debris removal missions were found to closely mimic the heritage RS-34 mission. It is believed that this technology will enable a small, low-cost multiple satellite delivery to multiple orbital locations with a single boost. For both the small satellite delivery and the orbital debris mission candidates, the RS-34 Phoenix requires the least amount of modification to the existing hardware. The results of the RS-34 Phoenix Utilization Study show that the system is technically sufficient to successfully support all of the missions analyzed.

A simultaneous estimation of the mass of Mars and its natural satellites, Phobos and Deimos, from the orbital perturbations on the Mariner 9, Viking 1, and Viking 2 orbiters

NASA Technical Reports Server (NTRS)

Lemoine, F. G.; Smith, D. E.; Fricke, S. K.; Mccarthy, J. J.

1993-01-01

The natural satellites of Mars, Phobos and Deimos, caused perturbations on the orbits of the Mariner 9, and the Viking spacecraft that were used to estimate the satellite masses. The Viking spacecraft were specifically targeted to make close flybys (within a few hundred kilometers) of Phobos in February 1977 and of Deimos in October 1977. These close encounters were used to estimate the moon's gravitational constant, GM (the universal constant of gravitation multiplied by the satellite mass). However, the Viking and Mariner 9 spacecraft made numerous flybys of Phobos and Deimos at distances of a few thousand kilometers. The tracking data from these more 'distant' encounters were processed to estimate the masses of Mars, Phobos, and Deimos.

Dynamical effects of stellar companions

NASA Astrophysics Data System (ADS)

Naoz, Smadar

2015-08-01

The fraction of stellar binaries in the field is extremely high (about 40% - 70% for > 1 Msun stars), and thus, given this frequency, a large fraction of all exoplanetary systems may reside in binaries. While close-in giant planets tend to be found preferentially in binary stellar systems it seems that the frequency of giant planets in close binaries (<100 AU) is significantly lower than in the overall population. Stellar companions’ gravitational perturbations may significantly alter the planetary orbits around their partner on secular timescales. They can drive planets to large eccentric orbits which can either result in plunging these planets into the star or shrinking their orbits and forming short period planets. I will review the dynamical effects stellar binaries have on a planetary systems. I will also present new results on the influence that stellar evolution has on the dynamical processes in these systems.

Preliminary input to the space shuttle reaction control subsystem failure detection and identification software requirements (uncontrolled)

NASA Technical Reports Server (NTRS)

Bergmann, E.

1976-01-01

The current baseline method and software implementation of the space shuttle reaction control subsystem failure detection and identification (RCS FDI) system is presented. This algorithm is recommended for conclusion in the redundancy management (RM) module of the space shuttle guidance, navigation, and control system. Supporting software is presented, and recommended for inclusion in the system management (SM) and display and control (D&C) systems. RCS FDI uses data from sensors in the jets, in the manifold isolation valves, and in the RCS fuel and oxidizer storage tanks. A list of jet failures and fuel imbalance warnings is generated for use by the jet selection algorithm of the on-orbit and entry flight control systems, and to inform the crew and ground controllers of RCS failure status. Manifold isolation valve close commands are generated in the event of failed on or leaking jets to prevent loss of large quantities of RCS fuel.

Architectures of planetary systems and implications for their formation.

PubMed

Ford, Eric B

2014-09-02

Doppler planet searches revealed that many giant planets orbit close to their host star or in highly eccentric orbits. These and subsequent observations inspired new theories of planet formation that invoke gravitation interactions in multiple planet systems to explain the excitation of orbital eccentricities and even short-period giant planets. Recently, NASA's Kepler mission has identified over 300 systems with multiple transiting planet candidates, including many potentially rocky planets. Most of these systems include multiple planets with closely spaced orbits and sizes between that of Earth and Neptune. These systems represent yet another new and unexpected class of planetary systems and provide an opportunity to test the theories developed to explain the properties of giant exoplanets. Presently, we have limited knowledge about such planetary systems, mostly about their sizes and orbital periods. With the advent of long-term, nearly continuous monitoring by Kepler, the method of transit timing variations (TTVs) has blossomed as a new technique for characterizing the gravitational effects of mutual planetary perturbations for hundreds of planets. TTVs can provide precise, but complex, constraints on planetary masses, densities, and orbits, even for planetary systems with faint host stars. In the coming years, astronomers will translate TTV observations into increasingly powerful constraints on the formation and orbital evolution of planetary systems with low-mass planets. Between TTVs, improved Doppler surveys, high-contrast imaging campaigns, and microlensing surveys, astronomers can look forward to a much better understanding of planet formation in the coming decade.

Architectures of planetary systems and implications for their formation

PubMed Central

Ford, Eric B.

2014-01-01

Doppler planet searches revealed that many giant planets orbit close to their host star or in highly eccentric orbits. These and subsequent observations inspired new theories of planet formation that invoke gravitation interactions in multiple planet systems to explain the excitation of orbital eccentricities and even short-period giant planets. Recently, NASA’s Kepler mission has identified over 300 systems with multiple transiting planet candidates, including many potentially rocky planets. Most of these systems include multiple planets with closely spaced orbits and sizes between that of Earth and Neptune. These systems represent yet another new and unexpected class of planetary systems and provide an opportunity to test the theories developed to explain the properties of giant exoplanets. Presently, we have limited knowledge about such planetary systems, mostly about their sizes and orbital periods. With the advent of long-term, nearly continuous monitoring by Kepler, the method of transit timing variations (TTVs) has blossomed as a new technique for characterizing the gravitational effects of mutual planetary perturbations for hundreds of planets. TTVs can provide precise, but complex, constraints on planetary masses, densities, and orbits, even for planetary systems with faint host stars. In the coming years, astronomers will translate TTV observations into increasingly powerful constraints on the formation and orbital evolution of planetary systems with low-mass planets. Between TTVs, improved Doppler surveys, high-contrast imaging campaigns, and microlensing surveys, astronomers can look forward to a much better understanding of planet formation in the coming decade. PMID:24778212

18-Degree-of-Freedom Controller Design for the ST7 Disturbance Reduction System

NASA Technical Reports Server (NTRS)

Markley, F. L.; Maghami, P. G.; Houghton, M. B.; Hsu, O. C.

2003-01-01

The Space Technology 7 experiment will perform an on-orbit system-level validation of a Disturbance Reduction System employing gravitational reference sensors and micronewton colloidal thrusters to maintain a spacecraft s position with respect to free-floating test masses in the gravitational reference sensors to less than 10 nm/dHz over the frequency range 1 to 30 mHz. This paper presents the design and analysis of the control system that closes the loop between the gravitational reference sensors and the micronewton thrusters while incorporating star tracker data at low frequencies. The effects of disturbances and actuation and measurement noise are evaluated in a eighteen-degree-of-freedom model.

Quantum computing with acceptor spins in silicon.

PubMed

Salfi, Joe; Tong, Mengyang; Rogge, Sven; Culcer, Dimitrie

2016-06-17

The states of a boron acceptor near a Si/SiO2 interface, which bind two low-energy Kramers pairs, have exceptional properties for encoding quantum information and, with the aid of strain, both heavy hole and light hole-based spin qubits can be designed. Whereas a light-hole spin qubit was introduced recently (arXiv:1508.04259), here we present analytical and numerical results proving that a heavy-hole spin qubit can be reliably initialised, rotated and entangled by electrical means alone. This is due to strong Rashba-like spin-orbit interaction terms enabled by the interface inversion asymmetry. Single qubit rotations rely on electric-dipole spin resonance (EDSR), which is strongly enhanced by interface-induced spin-orbit terms. Entanglement can be accomplished by Coulomb exchange, coupling to a resonator, or spin-orbit induced dipole-dipole interactions. By analysing the qubit sensitivity to charge noise, we demonstrate that interface-induced spin-orbit terms are responsible for sweet spots in the dephasing time [Formula: see text] as a function of the top gate electric field, which are close to maxima in the EDSR strength, where the EDSR gate has high fidelity. We show that both qubits can be described using the same starting Hamiltonian, and by comparing their properties we show that the complex interplay of bulk and interface-induced spin-orbit terms allows a high degree of electrical control and makes acceptors potential candidates for scalable quantum computation in Si.

Teetering Stars: Resonant Excitation of Stellar Obliquities by Hot and Warm Jupiters with External Companions

NASA Astrophysics Data System (ADS)

Anderson, Kassandra; Lai, Dong

2018-04-01

Stellar spin-orbit misalignments (obliquities) in hot Jupiter systems have been extensively probed in recent years thanks to Rossiter-McLaughlin observations. Such obliquities may reveal clues about hot Jupiter dynamical and migration histories. Common explanations for generating stellar obliquities include high-eccentricity migration, or primordial disk misalignment. This talk investigates another mechanism for producing stellar spin-orbit misalignments in systems hosting a close-in giant planet with an external, inclined planetary companion. Spin-orbit misalignment may be excited due to a secular resonance, occurring when the precession rate of the stellar spin axis (due to the inner orbit) becomes comparable to the precession rate of the inner orbital axis (due to the outer companion). Due to the spin-down of the host star via magnetic braking, this resonance may be achieved at some point during the star's main sequence lifetime for a wide range of giant planet masses and orbital architectures. We focus on both hot Jupiters (with orbital periods less than ten days) and warm Jupiters (with orbital periods around tens of days), and identify the outer perburber properties needed to generate substantial obliquities via resonant excitation, in terms of mass, separation, and inclination. For hot Jupiters, the stellar spin axis is strongly coupled to the orbital axis, and resonant excitation of obliquity requires a close perturber, located within 1-2 AU. For warm Jupiters, the spin and orbital axes are more weakly coupled, and the resonance may be achieved for more distant perturbers (at several to tens of AU). Resonant excitation of the stellar obliquity is accompanied by a decrease in the planets' mutual orbital inclination, and can thus erase high mutual inclinations in two-planet systems. Since many warm Jupiters are known to have outer planetary companions at several AU or beyond, stellar obliquities in warm Jupiter systems may be common, regardless of the formation/migration mechanism. Future observations probing warm Jupiter obliquities may indicate the presence of a hitherto undetected outer companion.

Jupiter Analogs Orbit Stars with an Average Metallicity Close to That of the Sun

NASA Astrophysics Data System (ADS)

Buchhave, Lars A.; Bitsch, Bertram; Johansen, Anders; Latham, David W.; Bizzarro, Martin; Bieryla, Allyson; Kipping, David M.

2018-03-01

Jupiter played an important role in determining the structure and configuration of the Solar System. Whereas hot-Jupiter type exoplanets preferentially form around metal-rich stars, the conditions required for the formation of planets with masses, orbits, and eccentricities comparable to Jupiter (Jupiter analogs) are unknown. Using spectroscopic metallicities, we show that stars hosting Jupiter analogs have an average metallicity close to solar, in contrast to their hot-Jupiter and eccentric cool-Jupiter counterparts, which orbit stars with super-solar metallicities. Furthermore, the eccentricities of Jupiter analogs increase with host-star metallicity, suggesting that planet–planet scatterings producing highly eccentric cool Jupiters could be more common in metal-rich environments. To investigate a possible explanation for these metallicity trends, we compare the observations to numerical simulations, which indicate that metal-rich stars typically form multiple Jupiters, leading to planet–planet interactions and, hence, a prevalence of either eccentric cool Jupiters or hot Jupiters with circularized orbits. Although the samples are small and exhibit variations in their metallicities, suggesting that numerous processes other than metallicity affect the formation of planetary systems, the data in hand suggests that Jupiter analogs and terrestrial-sized planets form around stars with average metallicities close to solar, whereas high-metallicity systems preferentially host eccentric cool Jupiter or hot Jupiters, indicating that higher metallicity systems may not be favorable for the formation of planetary systems akin to the Solar System.

Close encounters with PHOBOS

NASA Astrophysics Data System (ADS)

Zakharov, A. V.

1988-07-01

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

Space Shuttle Projects

NASA Image and Video Library

2005-08-03

Launched on July 26 2005, from the Kennedy Space Center in Florida, STS-114 was classified as Logistics Flight 1. Among the Station-related activities of the mission were the delivery of new supplies and the replacement of one of the orbital outpost's Control Moment Gyroscopes (CMGs). STS-114 also carried the Raffaello Multi-Purpose Logistics Module and the External Stowage Platform-2. A major focus of the mission was the testing and evaluation of new Space Shuttle flight safety, which included new inspection and repair techniques. Upon its approach to the International Space Station (ISS), the Space Shuttle Discovery underwent a photography session in order to assess any damages that may have occurred during its launch and/or journey through Space. The mission’s third and final Extra Vehicular Activity (EVA) included taking a close-up look and the repair of the damaged heat shield. Gap fillers were removed from between the orbiter’s heat-shielding tiles located on the craft’s underbelly. Never before had any repairs been done to an orbiter while still in space. This close up of the thermal tiles was taken by astronaut Stephen K. Robinson, STS-114 mission specialist (out of frame). Astronaut Soichi Noguchi, STS-114 mission specialist representing the Japan Aerospace Exploration (JAXA), can be seen in the background perched on a Space Station truss.

Orbit classification in an equal-mass non-spinning binary black hole pseudo-Newtonian system

NASA Astrophysics Data System (ADS)

Zotos, Euaggelos E.; Dubeibe, Fredy L.; González, Guillermo A.

2018-07-01

The dynamics of a test particle in a non-spinning binary black hole system of equal masses is numerically investigated. The binary system is modelled in the context of the pseudo-Newtonian circular restricted three-body problem, such that the primaries are separated by a fixed distance and move in a circular orbit around each other. In particular, the Paczyński-Wiita potential is used for describing the gravitational field of the two non-Newtonian primaries. The orbital properties of the test particle are determined through the classification of the initial conditions of the orbits, using several values of the Jacobi constant, in the Hill's regions of possible motion. The initial conditions are classified into three main categories: (i) bounded, (ii) escaping, and (iii) displaying close encounters. Using the smaller alignment index chaos indicator, we further classify bounded orbits into regular, sticky, or chaotic. To gain a complete view of the dynamics of the system, we define grids of initial conditions on different types of two-dimensional planes. The orbital structure of the configuration plane, along with the corresponding distributions of the escape and collision/close encounter times, allow us to observe the transition from the classical Newtonian to the pseudo-Newtonian regime. Our numerical results reveal a strong dependence of the properties of the considered basins with the Jacobi constant as well as with the Schwarzschild radius of the black holes.

On the Pre-impact Orbital Evolution of 2018 LA, Parent Body of the Bright Fireball Observed Over Botswana on 2018 June 2

NASA Astrophysics Data System (ADS)

de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl

2018-06-01

On 2018 June 2, meteoroid 2018 LA became the third natural body ever to be observed before entering our atmosphere ---small asteroids 2014 AA and 2008 TC3 had stricken the Earth on 2014 January 2 and 2008 October 7, respectively. Here, we explore the pre-impact orbital evolution of 2018 LA and investigate the possible presence of known NEOs moving in similar orbits using N-body simulations and the D-criteria. We identify several objects moving in orbits similar to that of 2018 LA and focus on three of them: (454100) 2013 BO73, which is the largest of the group and a PHA, 2016 LR, and 2018 BA5, which follows a path very close to that of 2018 LA in terms of semimajor axis, eccentricity, and inclination. All these objects could be part of a dynamical grouping and their orbital evolution is rather chaotic, experiencing close encounters with Venus, the Earth-Moon system, and Mars. NEO encounters take place at the node and, on the short-term, the relative positions of our planet in its orbit around the Sun repeat every year. Besides the bright fireball observed over Botswana on 2018 June 2, three other bolides were observed early in June in recent years: Crete on 2002 June 6, Washington State on 2004 June 3, and Reisadalen on 2007 June 7.

Searching for co-orbital planets by combining transit and radial-velocity measurements

NASA Astrophysics Data System (ADS)

Robutel, p.; Leleu, A.; Correia, A.; Lillo-Box, J.

2017-09-01

Co-orbital planetary systems consist of two planets orbiting with the same period a central star. If co-orbital bodies are common in the solar system and are also a natural output of planetary formation models, so far none have been found in extrasolar systems. This lack may be due to observational biases, since the main detection methods are unable to spot co-orbital companions when they are small or near the Lagrangian equilibrium points. We propose a simple method, based on an idea from Ford & Gaudi (2006), that allows the detection of co-orbital companions, and relies on a single parameter proportional to the mass ratio of the two planets. This method is applied to archival radial velocity data of 46 close-in transiting planets among which a few are strong candidates to harbor a co-orbital companion.

Particle-Gas Temperature Differentials Resulting from Time-Dependent Radiative-Conductive Heat Flux Divergences in the Tenuous Dust-Laden Atmosphere of Mars.

DTIC Science & Technology

1987-01-01

The obliquity (inclination of the Martian equator to the Martian orbital plane) is 23059, very close to Earth’s value of 230271. The orbit of Mars...is inclined 1051’ to the ecliptic . The eccer.;ricity of the orbit (the ratio of the -iistanc, Detween the foci of the elliptical orbit 04.. I A m 1~0...and the major axis of the ellipse) is 0.0934, more .’ than five times the value for Earth (0.0167) (Pasachoff, 1979). The obliquity varies by 13

A Survey of Exoplanetary Spin-Orbit Angles

NASA Astrophysics Data System (ADS)

Winn, Josh

2010-02-01

Are the orbits of exoplanets aligned with the spin axes of their parent stars? One might expect a close alignment, but some of the proposed migration mechanisms predict otherwise. Indeed at least 4 planets with strongly tilted orbits are now known, including the first case of a retrograde or polar orbit. This raises the questions of how commonly misalignments occur, and which types of planets have them. We request 10 half-nights with Keck/HIRES spread over 2010A and 2010B, to measure spin-orbit angles for 9 exoplanets spanning a range of masses, periods, and eccentricities. Our measurement is based on the Rossiter-McLaughlin effect: the anomalous Doppler shift observed during planetary transits.

A Survey of Exoplanetary Spin-Orbit Angles

NASA Astrophysics Data System (ADS)

Winn, Josh

2010-08-01

Are the orbits of exoplanets aligned with the spin axes of their parent stars? One might expect a close alignment, but some of the proposed migration mechanisms predict otherwise. Indeed at least 4 planets with strongly tilted orbits are now known, including the first case of a retrograde or polar orbit. This raises the questions of how commonly misalignments occur, and which types of planets have them. We request 4 half-nights with Keck/HIRES spread over the 2010B semester, to measure spin-orbit angles for 4 exoplanets spanning a range of masses, periods, and eccentricities. Our measurement is based on the Rossiter-McLaughlin effect: the anomalous Doppler shift observed during planetary transits.

Orbital tuberculosis in childhood with intracranial extension: a case report.

PubMed

Tuli, Navneet

2010-01-28

The common causes of orbital masses in pediatric age group include pseudotumour, lymphomas, hemangioma and dermoid cyst. Orbital tuberculosis is rare especially in children. We report a case of 5 year old child who presented with proptosis and gross diminution of vision due to orbital tuberculoma. Ocular examination of the left eye revealed proptosis with the eyeball displaced downwards and forwards. Vision was counting finger close to face. CT Scan showed an extraconal soft tissue mass along posteromedial side of left orbit with lateral displacement of medial rectus muscle. On antitubercular treatment, proptosis regressed and visual recovery was observed over a period of six month vision, in the left eye at the last followup was 20/30.

Orbital cortex neuronal responses during an odor-based conditioned associative task in rats.

PubMed

Yonemori, M; Nishijo, H; Uwano, T; Tamura, R; Furuta, I; Kawasaki, M; Takashima, Y; Ono, T

2000-01-01

Neuronal activity in the rat orbital cortex during discrimination of various odors [five volatile organic compounds (acetophenone, isoamyl acetate, cyclohexanone, p-cymene and 1,8-cineole), and food- and cosmetic-related odorants (black pepper, cheese, rose and perfume)] and other conditioned sensory stimuli (tones, light and air puff) was recorded and compared with behavioral responses to the same odors (black pepper, cheese, rose and perfume). In a neurophysiological study, the rats were trained to lick a spout that protruded close to its mouth to obtain sucrose or intracranial self-stimulation reward after presentation of conditioned stimuli. Of 150 orbital cortex neurons recorded during the task, 65 responded to one or more types of sensory stimuli. Of these, 73.8% (48/65) responded during presentation of an odor. Although the mean breadth of responsiveness (entropy) of the olfactory neurons based on the responses to five volatile organic compounds and air (control) was rather high (0.795), these stimuli were well discriminated in an odor space resulting from multidimensional scaling using Pearson's correlation coefficients between the stimuli. In a behavioral study, a rat was housed in an equilateral octagonal cage, with free access to food and choice among eight levers, four of which elicited only water (no odor, controls), and four of which elicited both water and one of four odors (black pepper, cheese, rose or perfume). Lever presses for each odor and control were counted. Distributions of these five stimuli (four odors and air) in an odor space derived from the multidimensional scaling using Pearson's correlation coefficients based on behavioral responses were very similar to those based on neuronal responses to the same five stimuli. Furthermore, Pearson's correlation coefficients between the same five stimuli based on the neuronal responses and those based on behavioral responses were significantly correlated. The results demonstrated a pivotal role of the rat orbital cortex in olfactory sensory processing and suggest that the orbital cortex is important in the manifestation of various motivated behaviors of the animals, including odor-guided motivational behaviors (odor preference).

Trade Study for 9 kW Water Membrane Evaporator

NASA Technical Reports Server (NTRS)

Bue, Grant C.; Ungar, Gene; Stephan, Ryan

2010-01-01

Sublimators have been proposed and used in spacecraft for heat rejection. Sublimators are desirable heat rejection devices for short duration use because they can transfer large amounts of heat using little mass and are self-regulating devices. Sublimators reject heat into space by freezing water inside a porous substrate, allowing it to sublimate into vapor, and finally venting it into space. The state of the art thermal control system in orbiting spacecraft is a two loop, two fluid system. The external coolant loop typically uses a toxic single phase fluid that acquires heat from the spacecraft and rejects most of it via a radiator. The sublimator functions as a transient topper for orbiting spacecraft during day pass periods when radiator efficiency decreases. The sublimator interfaces with the internal loop through a built in heat exchanger. The internal loop fluid is non-toxic and is typically a propylene glycol and water solution with inhibitors to prevent corrosion with aluminum fins of the heat exchangers. Feedwater is supplied from a separate line to the sublimator to maintain temperature control of the cabin and vehicle hardware. Water membrane evaporators have been developed for spacecraft and spacesuits. They function similar to a sublimator but require a backpressure valve which could be actuated for this application with a simple fully open or fully closed modes. This technology would be applied to orbital thermal control (lunar or planetary). This paper details a trade study showing that evaporators would greatly reduce the consumable that is used, effectively wasted, by sublimators during start up and shut down during the topping phases of each orbit. State of the art for 9 kW sublimators reject about 870 W per kilogram of mass and 1150 W per liter of volume. If water with corrosion inhibitors is used the evaporators would be about 80% of the mass and volume of the equivalent system. The size and mass increases to about 110% if the internal fluid is 50% propylene glycol/50% water. The true benefit comes from the backpressure valve, that prevents the cyclical shutdown/startup loss of the sublimator and amounts to as much as 0.85 kg per orbit.

Effect of the stellar spin history on the tidal evolution of close-in planets

NASA Astrophysics Data System (ADS)

Bolmont, E.; Raymond, S. N.; Leconte, J.; Matt, S. P.

2012-08-01

Context. The spin rate of stars evolves substantially during their lifetime, owing to the evolution of their internal structure and to external torques arising from the interaction of stars with their environments and stellar winds. Aims: We investigate how the evolution of the stellar spin rate affects, and is affected by, planets in close orbits via star-planet tidal interactions. Methods: We used a standard equilibrium tidal model to compute the orbital evolution of single planets orbiting both Sun-like stars and very low-mass stars (0.1 M⊙). We tested two stellar spin evolution profiles, one with fast initial rotation (1.2 day rotation period) and one with slow initial rotation (8 day period). We tested the effect of varying the stellar and planetary dissipations, and the planet's mass and initial orbital radius. Results: For Sun-like stars, the different tidal evolution between initially rapidly and slowly rotating stars is only evident for extremely close-in gas giants orbiting highly dissipative stars. However, for very low-mass stars the effect of the initial rotation of the star on the planet's evolution is apparent for less massive (1 M⊕) planets and typical dissipation values. We also find that planetary evolution can have significant effects on the stellar spin history. In particular, when a planet falls onto the star, it can cause the star to spin up. Conclusions: Tidal evolution allows us to differentiate between the early behaviors of extremely close-in planets orbiting either a rapidly rotating star or a slowly rotating star. The early spin-up of the star allows the close-in planets around fast rotators to survive the early evolution. For planets around M-dwarfs, surviving the early evolution means surviving on Gyr timescales, whereas for Sun-like stars the spin-down brings about late mergers of Jupiter planets. In the light of this study, we can say that differentiating one type of spin evolution from another given the present position of planets can be very tricky. Unless we can observe some markers of former evolution, it is nearly impossible to distinguish the two very different spin profiles, let alone intermediate spin-profiles. Nevertheless, some conclusions can still be drawn about statistical distributions of planets around fully convective M-dwarfs. If tidal evolution brings about a merger late in the stellar history, it can also entail a noticeable acceleration of the star at late ages, so that it is possible to have old stars that spin rapidly. This raises the question of how the age of stars can be more tightly constrained.

PROPERTIES OF THE CLOSE-IN TERTIARY IN THE QUADRUPLE SYSTEM V401 CYG

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, L.-Y.; Qian, S.-B.; Zhou, X.

2013-08-01

V401 Cyg is a quadruple system in which the spectroscopic signature of a close-in tertiary and a distant visual companion star were reported. Orbital properties of the close-in companion should provide valuable information on the formation of close binaries and stellar dynamical interaction. By analyzing new times of minimum light together with those collected from the literature, we discovered that the observed-calculated (O - C) curve of V401 Cyg shows a cyclic change with a short period of 3.5 yr and a semi-amplitude of 0.00436 days while it undergoes an upward parabolic variation. Those photoelectric and CCD data covered moremore » than two cycles and were analyzed for the light-travel time effect via the presence of the tertiary companion. The mass of the third body was determined to be M{sub 3}sin i' = 0.65({+-} 0.08) M{sub Sun }, which is close to the value estimated from the spectroscopic data (M{sub 3} {approx} 0.64 M{sub Sun }). This reveals that the orbital inclination of the tertiary was about i' {approx} 90 Degree-Sign , indicating that the contact components of V401 Cyg have the possibility of being eclipsed by the tertiary at an orbital distance of about 3.0 AU, and it may be a triply eclipsing hierarchical triple system. The upward parabolic change indicates a period increase at a rate of (P-dot{sub 2} = 1.5 x 10{sup -7} revealing a mass transfer from the secondary to the primary (M-dot{sub 2} = 5.9 x 10{sup -8} M{sub Sun} yr{sup -1}). This is consistent with the predictions of the theory of thermal relaxation oscillation (TRO) suggesting that V401 Cyg is undergoing an expanding-orbit stage in the TRO cycles.« less

Integrated Orbit and Attitude Control for a Nanosatellite with Power Constraints

NASA Technical Reports Server (NTRS)

Naasz, Bo; Hall, Christopher; Berry, Matthew; Hy-Young, Kim

2003-01-01

Small satellites tend to be power-limited, so that actuators used to control the orbit and attitude must compete with each other as well as with other subsystems for limited electrical power. The Virginia Tech nanosatellite project, HokieSat, must use its limited power resources to operate pulsed-plasma thrusters for orbit control and magnetic torque coils for attitude control, while also providing power to a GPS receiver, a crosslink transceiver, and other subsystems. The orbit and attitude control strategies were developed independently. The attitude control system is based on an application of Linear Quadratic Regulator (LQR) to an averaged system of equations, whereas the orbit control is based on orbit element feedback. In this paper we describe the strategy for integrating these two control systems and present simulation results to verify the strategy.

Lazy orbits: An optimization problem on the sphere

NASA Astrophysics Data System (ADS)

Vincze, Csaba

2018-01-01

Non-transitive subgroups of the orthogonal group play an important role in the non-Euclidean geometry. If G is a closed subgroup in the orthogonal group such that the orbit of a single Euclidean unit vector does not cover the (Euclidean) unit sphere centered at the origin then there always exists a non-Euclidean Minkowski functional such that the elements of G preserve the Minkowskian length of vectors. In other words the Minkowski geometry is an alternative of the Euclidean geometry for the subgroup G. It is rich of isometries if G is "close enough" to the orthogonal group or at least to one of its transitive subgroups. The measure of non-transitivity is related to the Hausdorff distances of the orbits under the elements of G to the Euclidean sphere. Its maximum/minimum belongs to the so-called lazy/busy orbits, i.e. they are the solutions of an optimization problem on the Euclidean sphere. The extremal distances allow us to characterize the reducible/irreducible subgroups. We also formulate an upper and a lower bound for the ratio of the extremal distances. As another application of the analytic tools we introduce the rank of a closed non-transitive group G. We shall see that if G is of maximal rank then it is finite or reducible. Since the reducible and the finite subgroups form two natural prototypes of non-transitive subgroups, the rank seems to be a fundamental notion in their characterization. Closed, non-transitive groups of rank n - 1 will be also characterized. Using the general results we classify all their possible types in lower dimensional cases n = 2 , 3 and 4. Finally we present some applications of the results to the holonomy group of a metric linear connection on a connected Riemannian manifold.

Families of periodic orbits in Hill's problem with solar radiation pressure: application to Hayabusa 2

NASA Astrophysics Data System (ADS)

Giancotti, Marco; Campagnola, Stefano; Tsuda, Yuichi; Kawaguchi, Jun'ichiro

2014-11-01

This work studies periodic solutions applicable, as an extended phase, to the JAXA asteroid rendezvous mission Hayabusa 2 when it is close to target asteroid 1999 JU3. The motion of a spacecraft close to a small asteroid can be approximated with the equations of Hill's problem modified to account for the strong solar radiation pressure. The identification of families of periodic solutions in such systems is just starting and the field is largely unexplored. We find several periodic orbits using a grid search, then apply numerical continuation and bifurcation theory to a subset of these to explore the changes in the orbit families when the orbital energy is varied. This analysis gives information on their stability and bifurcations. We then compare the various families on the basis of the restrictions and requirements of the specific mission considered, such as the pointing of the solar panels and instruments. We also use information about their resilience against parameter errors and their ground tracks to identify one particularly promising type of solution.

On-orbit flight control algorithm description

NASA Technical Reports Server (NTRS)

1975-01-01

Algorithms are presented for rotational and translational control of the space shuttle orbiter in the orbital mission phases, which are external tank separation, orbit insertion, on-orbit and de-orbit. The program provides a versatile control system structure while maintaining uniform communications with other programs, sensors, and control effectors by using an executive routine/functional subroutine format. Software functional requirements are described using block diagrams where feasible, and input--output tables, and the software implementation of each function is presented in equations and structured flow charts. Included are a glossary of all symbols used to define the requirements, and an appendix of supportive material.

Landing on Enceladus: Mission Design Parameters and Techniques

NASA Astrophysics Data System (ADS)

Spilker, T. R.

2006-12-01

Since Cassini/Huygens mission results revealed the intriguing nature of Enceladus, scientists have discussed various ways to obtain more detailed information about the south-polar geysers and subsurface conditions that produce them. This includes potential science instruments and investigations, and also the kinds of spacecraft platforms that could deliver and support the instruments. The three most commonly discussed platforms are Saturn orbiters that perform multiple close Enceladus flybys, Enceladus orbiters, and landers (soft or hard). Some high-value science investigations, such as producing an accurate description of the gravity field to infer internal structure, are best done from an orbiter. Some, such as seismic investigations, can be done only with a landed package. Unlike larger satellites such as Europa and Ganymede, Enceladus's low mass yields low surface gravity (~0.11 m/s2), low orbital speeds (<200 m/s), and other mission design characteristics that make it a manageable destination for a practical, high-value lander mission. The main mission design challenge is deceleration from Enceladus approach to a direct landing approach or orbit insertion. A Hohmann transfer from Titan approaches Enceladus with a V- infinity of >4 km/s, most of which would have to be decelerated away propulsively - a sizeable, multi-stage task for current propulsion systems - if no gravity-assist pump-down is used. Preliminary conclusions from JPL mission designers suggest that a pump-down tour could reduce that V-infinity to 2 km/s or less, possibly as little as 1 km/s if a lengthy pump-down is tolerable (Strange, Russell, and Lam, 2006). Once in orbit, landing from a moderately stable, 100-km circular orbit can be accomplished with as little as 210 m/s delta-V, a relatively simple task for a simple propulsion system. Temporary use of marginally stable orbits could reduce that figure. Low surface gravity allows use of small, light thrusters and provides ample reaction time for landing control systems.

Rosetta mission operations for landing

NASA Astrophysics Data System (ADS)

Accomazzo, Andrea; Lodiot, Sylvain; Companys, Vicente

2016-08-01

The International Rosetta Mission of the European Space Agency (ESA) was launched on 2nd March 2004 on its 10 year journey to comet Churyumov-Gerasimenko and has reached it early August 2014. The main mission objectives were to perform close observations of the comet nucleus throughout its orbit around the Sun and deliver the lander Philae to its surface. This paper describers the activities at mission operations level that allowed the landing of Philae. The landing preparation phase was mainly characterised by the definition of the landing selection process, to which several parties contributed, and by the definition of the strategy for comet characterisation, the orbital strategy for lander delivery, and the definition and validation of the operations timeline. The definition of the landing site selection process involved almost all components of the mission team; Rosetta has been the first, and so far only mission, that could not rely on data collected by previous missions for the landing site selection. This forced the teams to include an intensive observation campaign as a mandatory part of the process; several science teams actively contributed to this campaign thus making results from science observations part of the mandatory operational products. The time allocated to the comet characterisation phase was in the order of a few weeks and all the processes, tools, and interfaces required an extensive planning an validation. Being the descent of Philae purely ballistic, the main driver for the orbital strategy was the capability to accurately control the position and velocity of Rosetta at Philae's separation. The resulting operations timeline had to merge this need of frequent orbit determination and control with the complexity of the ground segment and the inherent risk of problems when doing critical activities in short times. This paper describes the contribution of the Mission Control Centre (MOC) at the European Space Operations Centre (ESOC) to this mission phase and the lessons learned that can be derived from this experience.

Spacecraft exploration of Phobos and Deimos

NASA Astrophysics Data System (ADS)

Duxbury, Thomas C.; Zakharov, Alexander V.; Hoffmann, Harald; Guinness, Edward A.

2014-11-01

We review the previous exploration of Phobos and Deimos by spacecraft. The first close-up images of Phobos and Deimos were obtained by the Mariner 9 spacecraft in 1971, followed by much image data from the two Viking orbiters at the end of the 70s, which formed the basis for early Phobos and Deimos shape and dynamic models. The Soviet Phobos 2 spacecraft came within 100 km of landing on Phobos in 1988. Mars Global Surveyor (1996-2006) and Mars Reconnaissance Orbiter (since 2005) made close-up observations of Phobos on several occasions. Mars Express (since 2003) in its highly elliptical orbit is currently the only spacecraft to make regular Phobos encounters and has returned large volumes of science data for this satellite. Landers and rovers on the ground (Viking Landers, Mars Pathfinder, MER rovers, MSL rover) frequently made observations of Phobos, Deimos and their transits across the solar disk.

Baggie: A unique solution to an orbiter icing problem

NASA Technical Reports Server (NTRS)

Walkover, L. J.

1982-01-01

The orbiter icing problem, located in two lower surface mold line cavities, was solved. These two cavities are open during Shuttle ground operations and ascent, and are then closed after orbit insertion. If not protected, these cavities may be coated with ice, which may be detrimental to the adjacent thermal protection system (TPS) tiles if the ice breaks up during ascent, and may hinder the closing of the cavity doors if the ice does not break up. The problem of ice in these cavities was solved by the use of a passive mechanism called baggie, which is purge curtain used to enclose the cavity and is used in conjunction with gaseous nitrogen as the local purge gas. The baggie, the final solution, is unique in its simplicity, but its design and development were not. The final baggie design and its development testing are discussed. Also discussed are the baggie concepts and other solutions not used.

Closed-channel contribution in the BCS-BEC crossover regime of an ultracold Fermi gas with an orbital Feshbach resonance

NASA Astrophysics Data System (ADS)

Mondal, S.; Inotani, D.; Ohashi, Y.

2018-03-01

We theoretically investigate strong-coupling properties of an ultracold Fermi gas with an orbital Feshbach resonance (OFR). Including tunable pairing interaction associated with an OFR within the framework of the strong-coupling theory developed by Nozières and Schmitt-Rink (NSR), we examine the occupation of the closed channel. We show that, although the importance of the closed channel is characteristic of the system with an OFR, the occupation number of the closed channel is found to actually be very small at the superfluid phase transition temperature T c, in the whole BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover region, when we use the scattering parameters for an ultracold 173Yb Fermi gas. The occupation of the closed channel increases with increasing the temperature above T c, which is more remarkable for a stronger pairing interaction. We also present a prescription to remove effects of an experimentally inaccessible deep bound state from the NSR formalism, which we meet when we theoretically deal with a 173Yb Fermi gas with an OFR.

One-Dimensional Spacecraft Formation Flight Testbed for Terrestrial Charged Relative Motion Experiments

NASA Astrophysics Data System (ADS)

Seubert, Carl R.

Spacecraft operating in a desired formation offers an abundance of attractive mission capabilities. One proposed method of controlling a close formation of spacecraft is with Coulomb (electrostatic) forces. The Coulomb formation flight idea utilizes charge emission to drive the spacecraft to kilovolt-level potentials and generate adjustable, micronewton- to millinewton-level Coulomb forces for relative position control. In order to advance the prospects of the Coulomb formation flight concept, this dissertation presents the design and implementation of a unique one-dimensional testbed. The disturbances of the testbed are identified and reduced below 1 mN. This noise level offers a near-frictionless platform that is used to perform relative motion actuation with electrostatics in a terrestrial atmospheric environment. Potentials up to 30 kV are used to actuate a cart over a translational range of motion of 40 cm. A challenge to both theoretical and hardware implemented electrostatic actuation developments is correctly modeling the forces between finite charged bodies, outside a vacuum. To remedy this, studies of Earth orbit plasmas and Coulomb force theory is used to derive and propose a model of the Coulomb force between finite spheres in close proximity, in a plasma. This plasma force model is then used as a basis for a candidate terrestrial force model. The plasma-like parameters of this terrestrial model are estimated using charged motion data from fixed-potential, single-direction experiments on the testbed. The testbed is advanced to the level of autonomous feedback position control using solely Coulomb force actuation. This allows relative motion repositioning on a flat and level track as well as an inclined track that mimics the dynamics of two charged spacecraft that are aligned with the principal orbit axis. This controlled motion is accurately predicted with simulations using the terrestrial force model. This demonstrates similarities between the partial charge shielding of space-based plasmas to the electrostatic screening in the laboratory atmosphere.

Preliminary Planning for NEAR's Low-Altitude Operations at 433 Eros

NASA Technical Reports Server (NTRS)

Antreasian, P. G.; Helfrich, C. L.; Miller, J. K.; Owen, W. M.; Williams, B. G.; Yeomans, D. K.; Scheeres, D. J.; Dunham, D. W.; Farquhar, R. W.; McAdams, J. V.

1999-01-01

On February 14, 2000, an orbit insertion burn will place NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft (S/C) into orbit around asteroid 433 Eros. NEAR will initially orbit Eros with distances ranging from 500 to 100 km in order to characterize the shape, gravity and spin of Eros. Once the physical parameters of Eros are determined reasonably well, the plan is to establish an orbit of the NEAR S/C with increasingly lower altitudes as the one year orbital mission progresses while further characterizing the gravity and shape of Eros. Towards the end of the NEAR mission, after the shape, gravity and spin of Eros have been well characterized, the scientific interest of obtaining very close observations (< 5 km) can be realized. The navigation during this phase relies on a combination of NASA's Deep Space Network (DSN) radio metric tracking, laser ranging (LIDAR) data from the S/C to the surface of Eros, and onboard optical imaging of landmarks on Eros. This paper will provide preliminary plans for mission design and navigation during the last two months of the orbit phase, where several close passes to the surface will be incorporated to enhance the science return. The culmination of these close passes will result in the eventual landing of the S/C on the surface of Eros. Several considerations for these plans are given by Antreasian, et at. [1998]. The objective for the end of the mission will be to land the S/C autonomously using the surface relative information obtained from the onboard LIDAR instrument. The goal will be to soft land the S/C in such a way as to keep it operational. With the use of an onboard LIDAR landing algorithm as discussed by Antreasian et at. [1998], it is believed that the S/C impact velocity can be kept well under 7 m/s which is a requirement for allowing the S/C to remain operational.

NEA impactors: what direction to they come from?

NASA Astrophysics Data System (ADS)

Harris, Alan

2018-04-01

One might expect, if Earth-crossing NEAs are "thermalized" by prior close scattering encounters with the Earth, that final impact trajectories would be isotropic in direction. But orbital perturbations and other sources of entry and exit to the Earth-crossing zone are faster acting that thermalization, so the actual distribution of impacting orbits is quite anisotropic. I have studied impactor directions by adjusting the orbits of known Earth-crossing PHAs slightly to put them on intersecting orbits and then computed the direction of approach to the Earth. This arguably suffers from "looking under the lamp post", since NEAs are mostly discovered close to the opposition direction, so I also took the distribution of NEA orbits recently derived by Granvik and others and extracted, from a set of 100,000 synthetic orbits they provided, a subset of Earth-crossing PHAs and similarly adjusted them to be intersecting orbits. This should represent an unbiased set of orbits. I then weighted the impact directions by the individual Opik impact probability to obtain a distribution of impact directions weighted by actual impact probabilities. The result was that more than 40% of incoming trajectories clustered within 60 degrees of the opposition direction, and a similar fraction come from within 60 degrees of the solar direction. Thus ~80% of impactors come from only about 1/3 of the sky area, with almost none coming from 60-120 degrees solar elongation. The message is that existing ground-based surveys can hardly be improved upon by greater sky coverage with respect to detecting "death plunge" objects, and even space-based instruments offer very little improvement due to the very low solar elongation of most objects approaching from the solar direction.

Closed-loop suppression of chaos in nonlinear driven oscillators

NASA Astrophysics Data System (ADS)

Aguirre, L. A.; Billings, S. A.

1995-05-01

This paper discusses the suppression of chaos in nonlinear driven oscillators via the addition of a periodic perturbation. Given a system originally undergoing chaotic motions, it is desired that such a system be driven to some periodic orbit. This can be achieved by the addition of a weak periodic signal to the oscillator input. This is usually accomplished in open loop, but this procedure presents some difficulties which are discussed in the paper. To ensure that this is attained despite uncertainties and possible disturbances on the system, a procedure is suggested to perform control in closed loop. In addition, it is illustrated how a model, estimated from input/output data, can be used in the design. Numerical examples which use the Duffing-Ueda and modified van der Pol oscillators are included to illustrate some of the properties of the new approach.

Proceedings of the Space Surveillance Workshop (11th) Held in Lexington, Massachusetts on 30 March-1 April 1993. Volume 1

DTIC Science & Technology

1993-04-01

are so close together, there is a great deal of mistagged metric data from the SPACETRACK sensors on these objects. The resulting orbital element sets ...including an attempt to combine U.S. Space Command element sets for each Lageos-2 related object in orbit with DSN angle data to determine the actual...Predict error at next observation -Maintain track to minimize reacquistion load -Estimate orbital element sets -Update time for next observation

Possibility of exchange of a rectilinear three-body system with zero energy

NASA Astrophysics Data System (ADS)

Koda, Eiji

The possibility of exchange for a rectilinear three-body system with zero energy is examined by introducing regularized coordinates which are closely related to McGehee's (1974) coordinates. It is shown that all of the HE(-)-HE(+) orbits are of exchange type in a critical system whose orbits of parabolic-parabolic escape type experience odd times of binary collision. No exchange occurs in critical systems whose orbits of parabolic-parabolic escape type experience even times of binary collision.

Sentry: An Automated Close Approach Monitoring System for Near-Earth Objects

NASA Astrophysics Data System (ADS)

Chamberlin, A. B.; Chesley, S. R.; Chodas, P. W.; Giorgini, J. D.; Keesey, M. S.; Wimberly, R. N.; Yeomans, D. K.

2001-11-01

In response to international concern about potential asteroid impacts on Earth, NASA's Near-Earth Object (NEO) Program Office has implemented a new system called ``Sentry'' to automatically update the orbits of all NEOs on a daily basis and compute Earth close approaches up to 100 years into the future. Results are published on our web site (http://neo.jpl.nasa.gov/) and updated orbits and ephemerides made available via the JPL Horizons ephemeris service (http://ssd.jpl.nasa.gov/horizons.html). Sentry collects new and revised astrometric observations from the Minor Planet Center (MPC) via their electronic circulars (MPECs) in near real time as well as radar and optical astrometry sent directly from observers. NEO discoveries and identifications are detected in MPECs and processed appropriately. In addition to these daily updates, Sentry synchronizes with each monthly batch of MPC astrometry and automatically updates all NEO observation files. Daily and monthly processing of NEO astrometry is managed using a queuing system which allows for manual intervention of selected NEOs without interfering with the automatic system. At the heart of Sentry is a fully automatic orbit determination program which handles outlier rejection and ensures convergence in the new solution. Updated orbital elements and their covariances are published via Horizons and our NEO web site, typically within 24 hours. A new version of Horizons, in development, will allow computation of ephemeris uncertainties using covariance data. The positions of NEOs with updated orbits are numerically integrated up to 100 years into the future and each close approach to any perturbing body in our dynamic model (all planets, Moon, Ceres, Pallas, Vesta) is recorded. Significant approaches are flagged for extended analysis including Monte Carlo studies. Results, such as minimum encounter distances and future Earth impact probabilities, are published on our NEO web site.

First Results of the Juno Magnetometer Investigation in Jupiter's Magnetosphere

NASA Astrophysics Data System (ADS)

Connerney, Jack; Oliversen, Ronald; Espley, Jared; Kotsiaros, Stavros; Joergensen, John; Joergensen, Peter; Merano, Jose; Denver, Troelz; Benn, Mathias; Bloxham, Jeremy; Bolton, Scott; Levin, Steve

2017-04-01

The Juno spacecraft entered polar orbit about Jupiter on July 4, 2016, after a Jupiter Orbit Insertion (JOI) main engine burn lasting 35 minutes. Juno's science instruments were not powered during the critical maneuver sequence ( 5 days) but were fully operational shortly afterward. The 53.5-day capture orbit provides Juno's science instruments with the opportunity to sample the Jovian environment close up (to 1.06 Jovian radii, Rj) and in polar orbit extending to the outer reaches of the Jovian magnetosphere. Jupiter's gravity and magnetic fields will be globally mapped with unprecedented accuracy as Juno conducts a study of Jupiter's interior structure and composition, as well as the first comprehensive exploration of the polar magnetosphere. The magnetic field investigation onboard Juno is equipped with two magnetometer sensor suites, located at 10 and 12 m from the spacecraft body at the end of one of the three solar panel wings. Each contains a vector fluxgate magnetometer (FGM) sensor and a pair of co-located non-magnetic star tracker camera heads which provide accurate attitude determination for the FGM sensors. The first few periapsis passes available to date revealed an extraordinary spatial variation of the magnetic field close to the planet's surface, suggesting that Juno may be sampling the field closer to the dynamo region than widely anticipated, i.e., portending a dynamo surface extending to relatively large radial distance ( 0.9Rj?). We present the first observations of Jupiter's magnetic field obtained in close proximity to the planet, and speculate on what wonders await as more longitudes are drawn across the global map (32 polar orbits separated by <12° longitude) that the Juno mission was designed to acquire.

Fugitives from the Hungaria region: Close encounters and impacts with terrestrial planets

NASA Astrophysics Data System (ADS)

Galiazzo, M. A.; Bazsó, Á.; Dvorak, R.

2013-08-01

Hungaria asteroids, whose orbits occupy the region in element space between 1.78

Photographing Shuttle Thermal Tiles in Space

NASA Technical Reports Server (NTRS)

2005-01-01

Launched on July 26, 2005 from the Kennedy Space Center in Florida, STS-114 was classified as Logistics Flight 1. Among the Station-related activities of the mission were the delivery of new supplies and the replacement of one of the orbital outpost's Control Moment Gyroscopes (CMGs). STS-114 also carried the Raffaello Multi-Purpose Logistics Module and the External Stowage Platform-2. A major focus of the mission was the testing and evaluation of new Space Shuttle flight safety, which included new inspection and repair techniques. Upon its approach to the International Space Station (ISS), the Space Shuttle Discovery underwent a photography session in order to assess any damages that may have occurred during its launch and/or journey through Space. The mission's third and final Extra Vehicular Activity (EVA) included taking a close-up look and the repair of the damaged heat shield. Gap fillers were removed from between the orbiter's heat-shielding tiles located on the craft's underbelly. Never before had any repairs been done to an orbiter while still in space. This particular photo was taken by astronaut Stephen K. Robinson, STS-114 mission specialist, whose shadow is visible on the thermal protection tiles.

State-selective charge exchange in slow collisions of Si3+ ions with H atoms: A molecular state close coupling treatment*)

NASA Astrophysics Data System (ADS)

Joseph, Dwayne C.; Saha, Bidhan C.

2012-11-01

Charge transfer cross sections are calculated by employing both the quantal and semiclassical ɛ(R) molecular orbital close coupling (MOCC) approximations in the adiabatic representation and compared with other theoretical and experimental results

An identification method of orbit responses rooting in vibration analysis of rotor during touchdowns of active magnetic bearings

NASA Astrophysics Data System (ADS)

Liu, Tao; Lyu, Mindong; Wang, Zixi; Yan, Shaoze

2018-02-01

Identification of orbit responses can make the active protection operation more easily realize for active magnetic bearings (AMB) in case of touchdowns. This paper presents an identification method of the orbit responses rooting on signal processing of rotor displacements during touchdowns. The recognition method consists of two major steps. Firstly, the combined rub and bouncing is distinguished from the other orbit responses by the mathematical expectation of axis displacements of the rotor. Because when the combined rub and bouncing occurs, the rotor of AMB will not be always close to the touchdown bearings (TDB). Secondly, we recognize the pendulum vibration and the full rub by the Fourier spectrum of displacement in horizontal direction, as the frequency characteristics of the two responses are different. The principle of the whole identification algorithm is illustrated by two sets of signal generated by a dynamic model of the specific rotor-TDB system. The universality of the method is validated by other four sets of signal. Besides, the adaptability of noise is also tested by adding white noises with different strengths, and the result is promising. As the mathematical expectation and Discrete Fourier transform are major calculations of the algorithm, the calculation quantity of the algorithm is low, so it is fast, easily realized and embedded in the AMB controller, which has an important engineering value for the protection of AMBs during touchdowns.

Four-Formation In-Track Configuration Maintenance Strategy

NASA Technical Reports Server (NTRS)

Lamy, Alain; Costes, Thierry

2007-01-01

The aim of this paper is to present the analysis conducted by CNES for the maintenance of a formation made of several LEO satellites (typically 4) in several planes (typically 2), 100 km or so apart from each other. The along-track separations between the satellites have to be controlled to within 15 km thanks to orbit correction maneuvers supposed to be performed every 2 weeks. The main difficulty is related to solar activity which is expected to be close to its maximum for the entire mission s lifespan. As a matter of fact, a high solar activity makes orbit prediction harder, and makes it impossible to keep the altitude of the formation constant. Thus, a specific relative maintenance strategy had to be devised in order to meet the mission's requirements. The first part provides a few elements on the mission analysis process that has taken place. The method used for the evaluation of the maneuver frequency is detailed, based on the evaluation of the effects of atmospheric drag on the orbit. The second part is dedicated to the maintenance strategy that has been designed, and particularly to the computation of the reference orbits and of the velocity increments that enable the in-track inter-satellite distances to be maintained within the desired bounds. Finally a few simulation results are presented; they enable the performance of the maintenance strategy to be checked in a more realistic context.

Formation of Close-in Super-Earths in an Evolving Disk Due to Disk Winds

NASA Astrophysics Data System (ADS)

Ogihara, Masahiro; Kokubo, Eiichiro; Suzuki, Takeru; Morbidelli, Alessandro

2018-04-01

Planets with masses larger than Mars mass undergo rapid inward migration (type I migration) in a standard protoplanetary disk. Recent magnetohydrodynamical simulations revealed the presence of magnetically-driven disk winds, which would alter the disk profile and the type I migration in the close-in region (r<1 au). We investigate orbital evolution of planetary embryos in a disk that viscously evolves under effects of magnetically-driven disk winds. The aim is to examine whether observed distributions of close-in super-Earths can be reproduced by simulations. We find that the type I migration is significantly suppressed in a disk with flat surface density profile. After planetary embryos undergo slow inward migration, they are captured in a resonant chain. The resonant chain undergoes late orbital instability during the gas depletion, leading to a non-resonant configuration. We also find that observed distributions of close-in super-Earths (e.g., period ratio, mass ratio) can be reproduced by results of simulations.

Coupled attitude-orbit dynamics and control for an electric sail in a heliocentric transfer mission.

PubMed

Huo, Mingying; Zhao, Jun; Xie, Shaobiao; Qi, Naiming

2015-01-01

The paper discusses the coupled attitude-orbit dynamics and control of an electric-sail-based spacecraft in a heliocentric transfer mission. The mathematical model characterizing the propulsive thrust is first described as a function of the orbital radius and the sail angle. Since the solar wind dynamic pressure acceleration is induced by the sail attitude, the orbital and attitude dynamics of electric sails are coupled, and are discussed together. Based on the coupled equations, the flight control is investigated, wherein the orbital control is studied in an optimal framework via a hybrid optimization method and the attitude controller is designed based on feedback linearization control. To verify the effectiveness of the proposed control strategy, a transfer problem from Earth to Mars is considered. The numerical results show that the proposed strategy can control the coupled system very well, and a small control torque can control both the attitude and orbit. The study in this paper will contribute to the theory study and application of electric sail.

Coupled Attitude-Orbit Dynamics and Control for an Electric Sail in a Heliocentric Transfer Mission

PubMed Central

Huo, Mingying; Zhao, Jun; Xie, Shaobiao; Qi, Naiming

2015-01-01

The paper discusses the coupled attitude-orbit dynamics and control of an electric-sail-based spacecraft in a heliocentric transfer mission. The mathematical model characterizing the propulsive thrust is first described as a function of the orbital radius and the sail angle. Since the solar wind dynamic pressure acceleration is induced by the sail attitude, the orbital and attitude dynamics of electric sails are coupled, and are discussed together. Based on the coupled equations, the flight control is investigated, wherein the orbital control is studied in an optimal framework via a hybrid optimization method and the attitude controller is designed based on feedback linearization control. To verify the effectiveness of the proposed control strategy, a transfer problem from Earth to Mars is considered. The numerical results show that the proposed strategy can control the coupled system very well, and a small control torque can control both the attitude and orbit. The study in this paper will contribute to the theory study and application of electric sail. PMID:25950179

An Exoplanet Spinning Up Its Star

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-11-01

We know that the large masses of stars govern the orbits of the planets that circle them but a large, close-in planet can also influence the rotation of its host star. A recently discovered, unusual hot Jupiter may be causing its star to spin faster than it should.Exotic PlanetsHot Jupiters are gas giants of roughly Jupiters size that orbit close in to their host stars. Though these planets are easy to detect their large sizes and frequent transits mean surveys have a good chance of catching them we havent found many of them, suggesting that planetary systems containing hot Jupiters are fairly unusual.The period-folded light curve of HATS-18, revealing the transit of the hot Jupiter HATS-18b. The period is P=0.8378 days. [Penev et al. 2016]Studying this exotic population of planets, however, can help us to better understand how gas giants form and evolve in planetary systems. New observations of hot Jupiters may also reveal how stars and close-in planets interact through radiation, gravity, and magnetic fields.The recent discovery of a transiting hot Jupiter a little over 2000 light-years away therefore presents an exciting opportunity!A Speeding GiantThe discovery of HATS-18b, a planet of roughly 2 times Jupiters mass and 1.3 times its radius, was announced in a study led by Kaloyan Penev (Princeton University). The planet was discovered using the HATSouth transit survey network, which includes instruments in Chile, Namibia, and Australia, and follow-up photometry and spectroscopy was conducted at a variety of ground-based observatories.HATS-18bs properties are particularly unusual: this hot Jupiter is zipping around its host star which is very similar to the Sun at the incredible pace of one orbit every 0.84 days. HATS-18bs orbit is more than 20 times closer to its host star than Mercurys is to the Sun, bringing it so close it nearly grazes the stars surface!Size of the planetary orbit relative to the stellar radius as a function of the stellar rotation period, for transiting planets with orbital periods shorter than 2 days and masses greater than 0.1 Jupiter masses. HATS-18b is denoted by the red star. [Penev et al. 2016]Tidal InteractionsWhat happens when a massive planet orbits this close to its star? Tidal interactions between the star and the planet cause tidal dissipation in the star, resulting in decay of the planets orbit. But there may be an additional effect of this interaction in the case of HATS-18b, the authors claim: the planet may be transferring some of its angular momentum to the star.As stars age, they should gradually spin slower as they lose angular momentum viastellar winds. But Penev and collaborators note that this exoplanets host star, HATS-18, spins roughly three times as fast asits inferred age suggests it should. The authors conclude that the angular momentum lost by the planet as its orbit shrinks is deposited in the star, causing the star to spin up.HATS-18 is an excellent laboratory for studying how very short-period planets interact with their stars in fact, Penev and collaborators have already used their observations of the system to constrain models of tidal dissipation from Sun-like stars. Additional observations of HATS-18 and other short-period systems should allow us to further test models of how planetary systems form and evolve.CitationK. Penev et al 2016 AJ 152 127. doi:10.3847/0004-6256/152/5/127

Design and Technical Study of Neutrino Detector Spacecraft

NASA Technical Reports Server (NTRS)

Solomey, Niclolas

2017-01-01

A neutrino detector is proposed to be developed for use on a space probe in close orbit of the Sun. The detector will also be protected from radiation by a tungsten shield Sun shade, active veto array and passive cosmic shielding. With the intensity of solar neutrinos substantially greater in a close solar orbit than on the Earth only a small 250 kg detector is needed. It is expected that this detector and space probe studying the core of the Sun, its nuclear furnace and particle physics basic properties will bring new knowledge beyond what is currently possible for Earth bound solar neutrino detectors.

KSC-2012-5549

NASA Image and Video Library

2012-09-20

CAPE CANAVERAL, Fla. – Inside Orbiter Processing Facility-2 at NASA’s Kennedy Space Center in Florida, workers watch as the left payload bay door begins to close on space shuttle Atlantis. Both payload bay doors will be closed for the final time. The orbiter is undergoing final preparations for its transfer to the Kennedy Space Center Visitor complex targeted for November. The work is part of Transition and Retirement of the remaining shuttle. Atlantis is being prepared for public display at the visitor complex. Over the course of its 26-year career, Atlantis spent 293 days in space during 33 missions. For more information, visit http://www.nasa.gov/transition. Photo credit: NASA/Jim Grossmann

KSC-2012-5550

NASA Image and Video Library

2012-09-20

CAPE CANAVERAL, Fla. – Inside Orbiter Processing Facility-2 at NASA’s Kennedy Space Center in Florida, space shuttle Atlantis’ left payload bay door has been closed. Both payload bay doors will be closed for the final time. The orbiter is undergoing final preparations for its transfer to the Kennedy Space Center Visitor complex targeted for November. The work is part of Transition and Retirement of the remaining shuttle. Atlantis is being prepared for public display at the visitor complex. Over the course of its 26-year career, Atlantis spent 293 days in space during 33 missions. For more information, visit http://www.nasa.gov/transition. Photo credit: NASA/Jim Grossmann

Recurrence spectra of a helium atom in parallel electric and magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Dehua; Department of Mathematics and Physics, Shandong Architecture and Engineering Institute, Jinan 250014, People's Republic of China; Ding, Shiliang

2003-08-01

A model potential for the general Rydberg atom is put forward, which includes not only the Coulomb interaction potential and the core-attractive potential, but also the exchange potential between the excited electron and other electrons. Using the region-splitting consistent and iterative method, we calculated the scaled recurrence spectra of the helium atom in parallel electric and magnetic fields and the closed orbits in the corresponding classical system have also been obtained. In order to remove the Coulomb singularity of the classical motion of Hamiltonian, we implement the Kustaanheimo-Stiefel transformation, which transforms the system from a three-dimensional to a four-dimensional one.more » The Fourier-transformed spectra of the helium atom has allowed direct comparison between peaks in such a plot and the scaled action values of closed orbits. Considering the exchange potential, the number of the closed orbits increased, which led to more peaks in the recurrence spectra. The results are compared with those of the hydrogen case, which shows that the core-scattered effects and the electron exchange potential play an important role in the multielectron Rydberg atom.« less

WD1145+017

NASA Astrophysics Data System (ADS)

Motta, Mario

2017-06-01

WD1145 is a 17th magnitude white dwarf star 570 light years away in Virgo, that was discovered to have a disintegrating planetoid in close orbit by Andrew Vanderburg a graduate student at Harvard CFA, while data mining the Kepler 2 mission. He contacted me to obtain transit data to elucidate the nature of its rather bizarre transit light curves. I obtained multiple observations of WD1145 over the course of a year, and found a series of complex transit light curves that could only be interpreted as a ring complex or torus in close orbit around WD1145. Combined with data from other amateur astronomers, professional observations, and satellite data it became clear that WD1145 has a small planetoid in close orbit at the Roche limit and is breaking apart forming a ring of debris material that is then raining down on the white dwarf. The surface of the star is "polluted" by heavy metals by spectroscopic data. Given that in the intense gravitational field of a white dwarf any heavy metals could not for long last on the surface, this confirms that we are tracking in real time the destruction of a small planet by its host star.

Design and Stability of an On-Orbit Attitude Control System Using Reaction Control Thrusters

NASA Technical Reports Server (NTRS)

Hall, Robert A.; Hough, Steven; Orphee, Carolina; Clements, Keith

2016-01-01

NASA is providing preliminary design and requirements for the Space Launch System Exploration Upper Stage (EUS). The EUS will provide upper stage capability for vehicle ascent as well as on-orbit control capability. Requirements include performance of on-orbit burn to provide Orion vehicle with escape velocity. On-orbit attitude control is accommodated by a on-off Reaction Control System (RCS). Paper provides overview of approaches for design and stability of an attitude control system using a RCS.

Effect of the rotation and tidal dissipation history of stars on the evolution of close-in planets

NASA Astrophysics Data System (ADS)

Bolmont, Emeline; Mathis, Stéphane

2016-11-01

Since 20 years, a large population of close-in planets orbiting various classes of low-mass stars (from M-type to A-type stars) has been discovered. In such systems, the dissipation of the kinetic energy of tidal flows in the host star may modify its rotational evolution and shape the orbital architecture of the surrounding planetary system. In this context, recent observational and theoretical works demonstrated that the amplitude of this dissipation can vary over several orders of magnitude as a function of stellar mass, age and rotation. In addition, stellar spin-up occurring during the Pre-Main-Sequence (PMS) phase because of the contraction of stars and their spin-down because of the torque applied by magnetized stellar winds strongly impact angular momentum exchanges within star-planet systems. Therefore, it is now necessary to take into account the structural and rotational evolution of stars when studying the orbital evolution of close-in planets. At the same time, the presence of planets may modify the rotational dynamics of the host stars and as a consequence their evolution, magnetic activity and mixing. In this work, we present the first study of the dynamics of close-in planets of various masses orbiting low-mass stars (from 0.6~M_⊙ to 1.2~M_⊙) where we compute the simultaneous evolution of the star's structure, rotation and tidal dissipation in its external convective envelope. We demonstrate that tidal friction due to the stellar dynamical tide, i.e. tidal inertial waves excited in the convection zone, can be larger by several orders of magnitude than the one of the equilibrium tide currently used in Celestial Mechanics, especially during the PMS phase. Moreover, because of this stronger tidal friction in the star, the orbital migration of the planet is now more pronounced and depends more on the stellar mass, rotation and age. This would very weakly affect the planets in the habitable zone because they are located at orbital distances such that stellar tide-induced migration happens on very long timescales. We also demonstrate that the rotational evolution of host stars is only weakly affected by the presence of planets except for massive companions.

Closed Loop Software Control of the MIDEX Power System

NASA Technical Reports Server (NTRS)

Castell, Karen; Hernandez-Pellerano, Amri; Wismer, Margaret

1998-01-01

The Microwave Anisotropy Probe (MAP) is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. The design and analysis of the MAP attitude control system (ACS) have been refined since work previously reported. The full spacecraft and instrument flexible model was developed in NASTRAN, and the resulting flexible modes were plotted and reduced with the Modal Significance Analysis Package (MSAP). The reduced-order model was used to perform the linear stability analysis for each control mode, the results of which are presented in this paper. Although MAP is going to a relatively disturbance-free Lissajous orbit around the Earth-Sun L2 Lagrange point, a detailed disturbance-torque analysis is required because there are only a small number of opportunities for momentum unloading each year. Environmental torques, including solar pressure at L2, and aerodynamic and gravity gradient during phasing-loop orbits, were calculated and simulated. A simple model of fuel slosh was derived to model its effect on the motion of the spacecraft. In addition, a thruster mode linear impulse controller was developed to meet the accuracy requirements of the phasing loop burns. A dynamic attitude error limiter was added to improve the performance of the ACS during large attitude slews. The result of this analysis is a stable ACS subsystem that meets all of the mission's requirements.

Robust distributed control of spacecraft formation flying with adaptive network topology

NASA Astrophysics Data System (ADS)

Shasti, Behrouz; Alasty, Aria; Assadian, Nima

2017-07-01

In this study, the distributed six degree-of-freedom (6-DOF) coordinated control of spacecraft formation flying in low earth orbit (LEO) has been investigated. For this purpose, an accurate coupled translational and attitude relative dynamics model of the spacecraft with respect to the reference orbit (virtual leader) is presented by considering the most effective perturbation acceleration forces on LEO satellites, i.e. the second zonal harmonic and the atmospheric drag. Subsequently, the 6-DOF coordinated control of spacecraft in formation is studied. During the mission, the spacecraft communicate with each other through a switching network topology in which the weights of its graph Laplacian matrix change adaptively based on a distance-based connectivity function between neighboring agents. Because some of the dynamical system parameters such as spacecraft masses and moments of inertia may vary with time, an adaptive law is developed to estimate the parameter values during the mission. Furthermore, for the case that there is no knowledge of the unknown and time-varying parameters of the system, a robust controller has been developed. It is proved that the stability of the closed-loop system coupled with adaptation in network topology structure and optimality and robustness in control is guaranteed by the robust contraction analysis as an incremental stability method for multiple synchronized systems. The simulation results show the effectiveness of each control method in the presence of uncertainties and parameter variations. The adaptive and robust controllers show their superiority in reducing the state error integral as well as decreasing the control effort and settling time.

Satellite tour design for the Cassini mission. [Saturn

NASA Technical Reports Server (NTRS)

Diehl, R. E.

1985-01-01

The mission design for the Cassini satellite tour of Saturn is described. The use of Titan encounters for gravity-assisted trajectory shaping to satisfy atmosphere, magnetosphere, and satellite science requirements is discussed. Three candidate satellite tours that illustrate the tradeoffs between different strategies to satisfy the science objectives are presented. Tour characteristics for a 4yr mission include at least 30 Titan encounters to provide a minimum of 90 deg orbit rotation for either a magnetotail petal orbit or noon petal orbit; evenly distributed Titan ground tracks for radar mapping coverage; at least 2 Iapetus and 1 Enceladus close flybys; inclined orbits during the first 3 yr to provide Earth and Sun occultations by Saturn and its rings; and Polar orbits during the fourth year.

Formation of S-type planets in close binaries: scattering induced tidal capture of circumbinary planets

NASA Astrophysics Data System (ADS)

Gong, Yan-Xiang; Ji, Jianghui

2018-05-01

Although several S-type and P-type planets in binary systems were discovered in past years, S-type planets have not yet been found in close binaries with an orbital separation not more than 5 au. Recent studies suggest that S-type planets in close binaries may be detected through high-accuracy observations. However, nowadays planet formation theories imply that it is difficult for S-type planets in close binaries systems to form in situ. In this work, we extensively perform numerical simulations to explore scenarios of planet-planet scattering among circumbinary planets and subsequent tidal capture in various binary configurations, to examine whether the mechanism can play a part in producing such kind of planets. Our results show that this mechanism is robust. The maximum capture probability is ˜10%, which can be comparable to the tidal capture probability of hot Jupiters in single star systems. The capture probability is related to binary configurations, where a smaller eccentricity or a low mass ratio of the binary will lead to a larger probability of capture, and vice versa. Furthermore, we find that S-type planets with retrograde orbits can be naturally produced via capture process. These planets on retrograde orbits can help us distinguish in situ formation and post-capture origin for S-type planet in close binaries systems. The forthcoming missions (PLATO) will provide the opportunity and feasibility to detect such planets. Our work provides several suggestions for selecting target binaries in search for S-type planets in the near future.

Satellite services system analysis study. Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

1981-01-01

Service requirements are considered. Topics include development of on-orbit operations scenarios, service equipment summary, crew interaction, and satellite features facilitating servicing. Service equipment concepts are considered. Topics include payload deployment, close proximity retrieval, on-orbit servicing, backup/contingency, delivery/retrieval of high energy payloads, Earth return, optional service, and advanced capabilities. Program requirements are assessed.

Closeup view of the mid deck aft wall of the ...

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

Close-up view of the mid deck aft wall of the Orbiter Discovery showing a mission specific configuration of stowage lockers within the modular system designed for maximum flexibility. This photograph was taken at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Review of investigations performed in the USSR on close approaches of comets to Jupiter and the evolution of cometary orbits

NASA Technical Reports Server (NTRS)

Kazimirchak-Polonskaya, E. I.

1976-01-01

Methods are reviewed for calculating the evolution of cometary orbits with emphasis on the orbital changes that take place when comets pass within the spheres of action of giant planets. Topics discussed include: differences and difficulties in methods used for the calculation of large perturbations by Jupiter; the construction of numerical theories of motion covering the whole period of observations of each comet, allowing for planetary perturbations and the effects of nongravitational forces; and investigations of the evolution of cometary orbits over the 400 year interval 1660-2060. The classical theory of cometary capture is briefly discussed.

Integrated orbit and attitude hardware-in-the-loop simulations for autonomous satellite formation flying

NASA Astrophysics Data System (ADS)

Park, Han-Earl; Park, Sang-Young; Kim, Sung-Woo; Park, Chandeok

2013-12-01

Development and experiment of an integrated orbit and attitude hardware-in-the-loop (HIL) simulator for autonomous satellite formation flying are presented. The integrated simulator system consists of an orbit HIL simulator for orbit determination and control, and an attitude HIL simulator for attitude determination and control. The integrated simulator involves four processes (orbit determination, orbit control, attitude determination, and attitude control), which interact with each other in the same way as actual flight processes do. Orbit determination is conducted by a relative navigation algorithm using double-difference GPS measurements based on the extended Kalman filter (EKF). Orbit control is performed by a state-dependent Riccati equation (SDRE) technique that is utilized as a nonlinear controller for the formation control problem. Attitude is determined from an attitude heading reference system (AHRS) sensor, and a proportional-derivative (PD) feedback controller is used to control the attitude HIL simulator using three momentum wheel assemblies. Integrated orbit and attitude simulations are performed for a formation reconfiguration scenario. By performing the four processes adequately, the desired formation reconfiguration from a baseline of 500-1000 m was achieved with meter-level position error and millimeter-level relative position navigation. This HIL simulation demonstrates the performance of the integrated HIL simulator and the feasibility of the applied algorithms in a real-time environment. Furthermore, the integrated HIL simulator system developed in the current study can be used as a ground-based testing environment to reproduce possible actual satellite formation operations.

The Orbital Design of Alpha Centauri Exoplanet Satellite (ACESat)

NASA Technical Reports Server (NTRS)

Weston, Sasha; Belikov, Rus; Bendek, Eduardo

2015-01-01

Exoplanet candidates discovered by Kepler are too distant for biomarkers to be detected with foreseeable technology. Alpha Centauri has high separation from other stars and is of close proximity to Earth, which makes the binary star system 'low hanging fruit' for scientists. Alpha Centauri Exoplanet Satellite (ACESat) is a mission proposed to Small Explorer Program (SMEX) that will use a coronagraph to search for an orbiting planet around one of the stars of Alpha Centauri. The trajectory design for this mission is presented here where three different trajectories are considered: Low Earth Orbit (LEO), Geosynchronous Orbit (GEO) and a Heliocentric Orbit. Uninterrupted stare time to Alpha Centauri is desirable for meeting science requirements, or an orbit that provides 90% stare time to the science target. The instrument thermal stability also has stringent requirements for proper function, influencing trajectory design.

Modal control of an unstable periodic orbit

NASA Astrophysics Data System (ADS)

Wiesel, W.; Shelton, W.

1983-03-01

Floquet theory is applied to the problem of designing a control system for a satellite in an unstable periodic orbit. Expansion about a periodic orbit produces a time-periodic linear system, which is augmented by a time-periodic control term. It is shown that this can be done such that (1) the application of control produces only inertial accelerations, (2) positive real Poincareexponents are shifted into the left half-plane, and (3) the shift of the exponent is linear with control gain. These developments are applied to an unstable orbit near the earth-moon L(3) point pertubed by the sun. Finally, it is shown that the control theory can be extended to include first order perturbations about the periodic orbit without increase in control cost.

Modal control of an unstable periodic orbit

NASA Technical Reports Server (NTRS)

Wiesel, W.; Shelton, W.

1983-01-01

Floquet theory is applied to the problem of designing a control system for a satellite in an unstable periodic orbit. Expansion about a periodic orbit produces a time-periodic linear system, which is augmented by a time-periodic control term. It is shown that this can be done such that (1) the application of control produces only inertial accelerations, (2) positive real Poincareexponents are shifted into the left half-plane, and (3) the shift of the exponent is linear with control gain. These developments are applied to an unstable orbit near the earth-moon L(3) point pertubed by the sun. Finally, it is shown that the control theory can be extended to include first order perturbations about the periodic orbit without increase in control cost.

The Daytime Craterids, a radar-detected meteor shower outburst from hyperbolic comet C/2007 W1 (Boattini)

NASA Astrophysics Data System (ADS)

Wiegert, P. A.; Brown, P. G.; Weryk, R. J.; Wong, D. K.

2011-06-01

We report a new daytime meteor shower detected with the Canadian Meteor Orbit Radar (CMOR). This shower has a radiant in the southern constellation Crater. The Daytime Craterid shower was observed in 2003 and 2008 but not in any of the other years in the 2002-09 interval. The strength of this shower in the years observed is equivalent to a daily averaged zenithal hourly rate (ZHR) over 30, with a peak ZHR likely much higher at the time of the outburst. The orbital elements of the shower closely match those of Comet C/2007 W1 (Boattini), which passed perihelion in 2007. The orbit of C/2007 W1 is nominally hyperbolic orbit making this the first meteor shower detected from a clearly unbound comet. The 2003 outburst of the Daytime Craterid shower indicates that this comet must have recently been transferred to an unbound orbit from a bound one, likely through a close encounter with a giant planet. As a result we conclude that this shower provides us with one of the few examples of showers originating from the population of nearly isotropic comets. The stream is difficult to model owing to its proximity to the orbits of Jupiter, Saturn and the Earth. However, the intermittent nature of the shower can be largely understood from numerical simulations. No outbursts of similar strength are expected in the next decade, with the possible exception of 2015.

Orbit classification in an equal-mass non-spinning binary black hole pseudo-Newtonian system

NASA Astrophysics Data System (ADS)

Zotos, Euaggelos E.; Dubeibe, F. L.; González, Guillermo A.

2018-04-01

The dynamics of a test particle in a non-spinning binary black hole system of equal masses is numerically investigated. The binary system is modeled in the context of the pseudo-Newtonian circular restricted three-body problem, such that the primaries are separated by a fixed distance and move in a circular orbit around each other. In particular, the Paczyński-Wiita potential is used for describing the gravitational field of the two non-Newtonian primaries. The orbital properties of the test particle are determined through the classification of the initial conditions of the orbits, using several values of the Jacobi constant, in the Hill's regions of possible motion. The initial conditions are classified into three main categories: (i) bounded, (ii) escaping and (iii) displaying close encounters. Using the smaller alignment index (SALI) chaos indicator, we further classify bounded orbits into regular, sticky or chaotic. To gain a complete view of the dynamics of the system, we define grids of initial conditions on different types of two-dimensional planes. The orbital structure of the configuration plane, along with the corresponding distributions of the escape and collision/close encounter times, allow us to observe the transition from the classical Newtonian to the pseudo-Newtonian regime. Our numerical results reveal a strong dependence of the properties of the considered basins with the Jacobi constant as well as with the Schwarzschild radius of the black holes.

The Influence of the Orbital Evolution of Main Belt Asteroids on Their Spin Vectors

NASA Astrophysics Data System (ADS)

Skoglöv, E.; Erikson, A.

2002-11-01

It was found that certain features in the observed spin vector distribution of main belt asteroids can be explained by the differences in the dynamical spin vector evolution between objects with high and low orbital inclinations. In particular, the deficiency of high-inclination objects whose spin vectors are close to the ecliptic plane can be accounted for. The present spin vector distribution of main belt asteroids is due to several factors connected with their collisional and dynamical evolution. In this paper, the influence of the orbital evolution on the spin axis of asteroids is examined in the case of 25 objects with typical main belt orbital evolution and 125 synthetic objects, during an integration over a time period of 1 Myr. This investigation produced the following general results: • The difference between maximum and minimum obliquity increases in an approximately linear fashion with increasing orbital inclination of the studied objects. • The inclination is the major factor influencing the magnitude of the obliquity variation. This variation is generally larger for asteroids with their initial spin vectors located close to the orbital plane. • In general, the regular obliquity differences are relatively insensitive to differences in the shape, composition, and spin rate of the asteroids. The result is compared with the properties of the observed spin vectors for 73 main belt asteroids and good agreement is found between the above results and the existing spin vector distribution.

Comprehensive analysis of airborne contaminants from recent Spacelab missions

NASA Technical Reports Server (NTRS)

Matney, M. L.; Boyd, J. F.; Covington, P. A.; Leano, H. J.; Pierson, D. L.; Limero, T. F.; James, J. T.

1993-01-01

The Shuttle experiences unique air contamination problems because of microgravity and the closed environment. Contaminant build-up in the closed atmosphere and the lack of a gravitational settling mechanism have produced some concern in previous missions about the amount of solid and volatile airborne contaminants in the Orbiter and Spacelab. Degradation of air quality in the Orbiter/Spacelab environment, through processes such as chemical contamination, high solid-particulate levels, and high microbial levels, may affect crew performance and health. A comprehensive assessment of the Shuttle air quality was undertaken during STS-40 and STS-42 missions, in which a variety of air sampling and monitoring techniques were employed to determine the contaminant load by characterizing and quantitating airborne contaminants. Data were collected on the airborne concentrations of volatile organic compounds, microorganisms, and particulate matter collected on Orbiter/Spacelab air filters. The results showed that STS-40/42 Orbiter/Spacelab air was toxicologically safe to breathe, except during STS-40 when the Orbiter Refrigerator/Freezer unit was releasing noxious gases in the middeck. On STS-40, the levels of airborne bacteria appeared to increase as the mission progressed; however, this trend was not observed for the STS-42 mission. Particulate matter in the Orbiter/Spacelab air filters was chemically analyzed in order to determine the source of particles. Only small amounts of rat hair and food bar (STS-40) and traces of soiless medium (STS-42) were detected in the Spacelab air filters, indicating that containment for Spacelab experiments was effective.

Feasibility study of the solar scientific instruments for Spacelab/Orbiter

NASA Technical Reports Server (NTRS)

Leritz, J.; Rasser, T.; Stone, E.; Lockhart, B.; Nobles, W.; Parham, J.; Eimers, D.; Peterson, D.; Barnhart, W.; Schrock, S.

1981-01-01

The feasibility and economics of mounting and operating a set of solar scientific instruments in the backup Skylab Apollo Telescope Mount (ATM) hardware was evaluated. The instruments used as the study test payload and integrated into the ATM were: the Solar EUV Telescope/Spectrometer; the Solar Active Region Observing Telescope; and the Lyman Alpha White Light Coronagraph. The backup ATM hardware consists of a central cruciform structure, called the "SPAR', a "Sun End Canister' and a "Multiple Docking Adapter End Canister'. Basically, the ATM hardware and software provides a structural interface for the instruments; a closely controlled thermal environment; and a very accurate attitude and pointing control capability. The hardware is an identical set to the hardware that flow on Skylab.

Identification of New Orbits to Enable Future Missions for the Exploration of the Martian Moon Phobos

NASA Astrophysics Data System (ADS)

Zamaro, Mattia; Biggs, James D.

One of the paramount stepping stones towards NASA's long-term goal of undertaking human missions to Mars is the exploration of the Martian moons. In this paper, a showcase of various classes of non-Keplerian orbits are identified and a number of potential mission applications in the Mars-Phobos system are proposed. These applications include: low-thrust hovering around Phobos for close-range observations; Libration Point Orbits in enhanced three-body dynamics to enable unique low-cost operations for space missions in the proximity of Phobos; their manifold structure for high-performance landing/take-off maneuvers to and from Phobos' surface; Quasi-Satellite Orbits for long-period station-keeping and maintenance. In particular, these orbits could exploit Phobos' occulting bulk as a passive radiation shield during future manned flights to Mars to reduce human exposure to radiation. Moreover, the latter orbits can be used as an orbital garage, requiring no orbital maintenance, where a spacecraft could make planned pit-stops during a round-trip mission to Mars.

Analytical method for the effects of the asteroid belt on planetary orbits

NASA Technical Reports Server (NTRS)

Mayo, A. P.

1979-01-01

Analytic expressions are derived for the perturbation of planetary orbits due to a thick constant-density asteroid belt. The derivations include extensions and adaptations of Plakhov's (1968) analytic expressions for the perturbations in five of the orbital elements for closed orbits around Saturn's rings. The equations of Plakhov are modified to include the effect of ring thickness, and additional equations are derived for the perturbations in the sixth orbital element, the mean anomaly. The gravitational potential and orbital perturbations are derived for the asteroid belt with and without thickness, and for a hoop approximation to the belt. The procedures are also applicable to Saturn's rings and the newly discovered rings of Uranus. The effects of the asteroid belt thickness on the gravitational potential coefficients and the orbital motions are demonstrated. Comparisons between the Mars orbital perturbations obtained by using the analytic expressions and those obtained by numerical integration are discussed. The effects of the asteroid belt on earth-based ranging to Mars are also demonstrated.

Operating Small Sat Swarms as a Single Entity: Introducing SODA

NASA Technical Reports Server (NTRS)

Conn, Tracie; Dono Perez, Andres

2017-01-01

Swarm concepts are a growing topic of interest in the small satellite community. Compared to a small satellite constellation, a swarm has the distinction of being multiple spacecraft in close proximity, in approximately the same orbit. Furthermore, we envision swarms to have capabilities for cross-link communication and station-keeping. Of particular interest is a means to maintain operator-specified geometry, alignment, and/or separation.From NASA's decadal survey, it is clear that simultaneous measurements from a 3D volume of space are desired for a variety of Earth scientific studies. As this mission concept is ultimately extended to deep space, some degree of local control for the swarm to self-correct its configuration is required. We claim that the practicality of ground commanding each individual satellite in the swarm is simply not a feasible concept of operations. In other words, the current state-of-practice does not scale to very large swarms (e.g. 100 spacecraft or more) without becoming cost prohibitive. To contain the operations costs and complexity, a new approach is required: the swarm must be operated as a unit, responding to high-level specifications for relative position and velocity.The Mission Design Division at NASA Ames Research Center is looking to the near future for opportunities to develop satellite swarm technology. As part of this effort, we are developing SODA (Swarm Orbital Dynamics Advisor), a tool that provides the orbital maneuvers required to achieve a desired type of relative swarm motion. The purpose of SODA is two-fold. First, it encompasses the algorithms and orbital dynamics model to enable the desired relative motion of the swarm satellites. The process starts with the user specifying the properties of a swarm configuration. This could be as simple as varying in-track spacing of the swarm in one orbit, or as complex as maintaining a specified 3D geometrical orientation. We presume that science objectives will drive this choice. Given these inputs, the tool provides the most efficient maneuver(s) to achieve the objective.Second, SODA provides a variety of visualization tools. We acknowledge that the relationship between a desired relative motion amongst the swarm, and the corresponding orbital parameters for each individual satellite may not be immediately apparent for ground controllers and mission planners. The purpose of SODA's visualization tools is to illustrate this concept clearly with a variety of graphics and animations. After computing the optimal orbital maneuvers to modify the swarm, these results are simulated to demonstrate successful swarm control.Our emphasis in this paper is on the importance of relating the desired motion of the swarm satellites relative to one another with the required orbital element changes. One cannot joystick a drifting swarm satellite back into position; the underlying orbital mechanics dictate the most efficient recovery maneuvers. To illustrate this point, results from several case study simulations are presented. We conclude with our forward work for ongoing SODA development and potential science applications.

Docking Mechanism on Progress 52

NASA Image and Video Library

2014-02-03

ISS038-E-041175 (3 Feb. 2014) --- This close-up view shows the docking mechanism of the unpiloted Russian ISS Progress 52 resupply ship as it undocks from the International Space Station's Pirs Docking Compartment at 11:21 a.m. (EST) on Feb. 3, 2014. The Progress backed away to a safe distance from the orbital complex to begin several days of tests to study thermal effects of space on its attitude control system. Filled with trash and other unneeded items, the Russian resupply ship will be commanded to re-enter Earth's atmosphere Feb. 11 and disintegrate harmlessly over the Pacific Ocean.

A Brayton cycle solar dynamic heat receiver for space

NASA Technical Reports Server (NTRS)

Sedgwick, L. M.; Nordwall, H. L.; Kaufmann, K. J.; Johnson, S. D.

1989-01-01

The detailed design of a heat receiver developed to meet the requirements of the Space Station Freedom, which will be assembled and operated in low earth orbit beginning in the mid-1990's, is described. The heat receiver supplies thermal energy to a nominal 25-kW closed-Brayton-cycle power conversion unit. The receiver employs an integral thermal energy storage system utilizing the latent heat of a eutectic-salt phase-change mixture to store energy for eclipse operation. The salt is contained within a felt metal matrix which enhances heat transfer and controls the salt void distribution during solidification.

The GOES In-Situ Geomagnetism Experiment Reimagined

NASA Technical Reports Server (NTRS)

Abraham, Bereket; Chu, Donald; Comeyne, Gustave J.; Concha, Marco; Fellows, David W.; Heacock, Matthew G.; Tadikonda, Sivakumara K.

2017-01-01

The Geostationary Operational Environmental Satellites (GOES) carry several instruments each with its own requirements. Because accommodating all of them is difficult, there is interest in putting some on their own smaller platforms. The simplest instruments are the magnetometers. These are small and have low communication, attitude control and cleanliness requirements. Getting on-station and operating in close proximity with another satellite, however, requires significant propulsion capabilities. This paper describes a CubeSat mission that goes from geo-transfer to geostationary orbit and operates next to a GOES spacecraft. Requirements, a notional design and performance predictions are provided.

KSC-00pp0917

NASA Image and Video Library

2000-07-12

In the Orbiter Processing Facility bay 1, STS-92 crew members, along with Boeing workers, look closely at the tools they will be using on their mission. The crew comprises Commander Brian Duffy, Pilot Pam Melroy and Mission Specialists Koichi Wakata, Leroy Chiao, Jeff Wisoff, Michael Lopez-Alegria and Bill McArthur. STS-92 is scheduled to launch Oct. 5 on Shuttle Discovery from Launch Pad 39A on the fifth flight to the International Space Station. Discovery will carry the Integrated Truss Structure (ITS) Z1, Pressurized Mating Adapter 3, Ku-band Communications System, and Control Moment Gyros (CMGs)

N-Body Simulations of Planetary Accretion Around M Dwarf Stars

NASA Astrophysics Data System (ADS)

Ogihara, Masahiro; Ida, Shigeru

2009-07-01

We have investigated planetary accretion from planetesimals in terrestrial planet regions inside the ice line around M dwarf stars through N-body simulations including tidal interactions with disk gas. Because of low luminosity of M dwarfs, habitable zones (HZs) are located in inner regions (~0.1 AU). In the close-in HZ, type-I migration and the orbital decay induced by eccentricity damping are efficient according to the high disk gas density in the small orbital radii. Since the orbital decay is terminated around the disk inner edge and the disk edge is close to the HZ, the protoplanets accumulated near the disk edge affect formation of planets in the HZ. Ice lines are also in relatively inner regions at ~0.3 AU. Due to the small orbital radii, icy protoplanets accrete rapidly and undergo type-I migration before disk depletion. The rapid orbital decay, the proximity of the disk inner edge, and large amount of inflow of icy protoplanets are characteristic in planetary accretion in terrestrial planet regions around M dwarfs. In the case of full efficiency of type-I migration predicted by the linear theory, we found that protoplanets that migrate to the vicinity of the host star undergo close scatterings and collisions, and four to six planets eventually remain in mutual mean-motion resonances and their orbits have small eccentricities (lsim0.01) and they are stable both before and after disk gas decays. In the case of slow migration, the resonant capture is so efficient that densely packed ~40 small protoplanets remain in mutual mean-motion resonances. In this case, they start orbit crossing, after the disk gas decays and eccentricity damping due to tidal interaction with gas is no more effective. Through merging of the protoplanets, several planets in widely separated non-resonant orbits with relatively large eccentricities (~0.05) are formed. Thus, the final orbital configurations (separations, resonant or non-resonant, eccentricity, and distribution) of the terrestrial planets around M dwarfs sensitively depend on strength of type-I migration. We also found that large amount of water-ice is delivered by type-I migration from outer regions and final planets near the inner disk edge around M dwarfs are generally abundant in water-ice except for the innermost one that is shielded by the outer planets, unless type-I migration speed is reduced by a factor of more than 100 from that predicted by the linear theory.

Development and experimentation of LQR/APF guidance and control for autonomous proximity maneuvers of multiple spacecraft

NASA Astrophysics Data System (ADS)

Bevilacqua, R.; Lehmann, T.; Romano, M.

2011-04-01

This work introduces a novel control algorithm for close proximity multiple spacecraft autonomous maneuvers, based on hybrid linear quadratic regulator/artificial potential function (LQR/APF), for applications including autonomous docking, on-orbit assembly and spacecraft servicing. Both theoretical developments and experimental validation of the proposed approach are presented. Fuel consumption is sub-optimized in real-time through re-computation of the LQR at each sample time, while performing collision avoidance through the APF and a high level decisional logic. The underlying LQR/APF controller is integrated with a customized wall-following technique and a decisional logic, overcoming problems such as local minima. The algorithm is experimentally tested on a four spacecraft simulators test bed at the Spacecraft Robotics Laboratory of the Naval Postgraduate School. The metrics to evaluate the control algorithm are: autonomy of the system in making decisions, successful completion of the maneuver, required time, and propellant consumption.

A Comprehensive Orbit Reconstruction for the Galileo Prime Mission in the J2000 System

NASA Technical Reports Server (NTRS)

Jacobson, Robert A.; Haw, Robert J.; McElrath, Tim P.; Antreasian, Peter G.

1999-01-01

The Galileo spacecraft arrived at Jupiter in December of 1995 to begin an orbital tour of the Jovian system. The objective of the tour was up close study of the planet, its satellites, and its magnetosphere. The spacecraft completed its 11 orbit prime mission in November of 1997 having had 16 successful close encounters with the Galilean satellites (including two prior to Jupiter orbit insertion). Galileo continues to operate and will have made an additional 10 orbits of Jupiter by the date of this Conference. Earlier papers discuss the determination of the spacecraft orbit in support of mission operations from arrival at Jupiter through the first 9 orbits. In this paper we re-examine those earlier orbits and extend the analysis through orbit 12, the first orbit of the Galileo Europa Mission (GEM). The objective of our work is the reconstruction of the spacecraft trajectory together with the development of a consistent set of ephemerides for the Galilean satellites. As a necessary byproduct of the reconstruction we determine improved values for the Jovian system gravitational parameters and for the Jupiter pole orientation angles. Our preliminary analyses have already led to many of the results reported in the scientific literature. Unlike the Galileo Navigation Team which operates in the EME-1950 coordinate system, we elected to work in the (J2000) International Celestial Reference Frame (ICRF), the reference frame of the current JPL planetary and satellite ephemerides as well as the standard frame of the international astronomical and planetary science community. Use of this frame permits more precise modelling of the spacecraft and satellite observations. Moreover, it is the frame of choice for all other operational JPL missions and will probably be the frame for future missions for some time. Consequently, our adoption of the ICRF will facilitate the combination of our results with any obtained from future missions (e.g. the proposed Europa Orbiter mission). In addition, our results may be used by the science community, without need of a reference frame conversion.

A close examination of under-actuated attitude control subsystem design for future satellite missions' life extension

NASA Astrophysics Data System (ADS)

Lam, Quang M.; Barkana, Itzhak

2014-12-01

Satellite mission life, maintained and prolonged beyond its typical norm of their expectancy, are primarily dictated by the state of health of its Reaction Wheel Assembly (RWA), especially for commercial GEO satellites since torquer bars are no longer applicable while thruster assistant is unacceptable due to pointing accuracy impact during jet firing. The RWA is the primary set of actuators (as compared to thrusters for orbit maintenance and maneuvering) mainly responsible for the satellite mission for accurately and precisely pointing its payloads to the right targets to conduct its mission operations. The RWA consisting of either a set of four in pyramid or three in orthogonal is the primary set of actuators to allow the satellite to achieve accurate and precise pointing of the satellite payloads towards the desired targets. Future space missions will be required to achieve much longer lives and are currently perceived by the GEO satellite community as an "expected norm" of 20 years or longer. Driven by customers' demands/goals and competitive market have challenged Attitude Control Subsystems (ACS) engineers to develop better ACS algorithms to address such an emerging need. There are two main directions to design satellite's under-actuated control subsystem: (1) Attitude Feedback with Zero Momentum Principle and (2) Attitude Control by Angular Velocity Tracking via Small Time Local Controllability concept. Successful applications of these control laws have been largely demonstrated via simulation for the rest to rest case. Limited accuracy and oscillatory behaviors are observed in three axes for non-zero wheel momentum while realistic loss of a wheel scenario (i.e., fully actuated to under-actuated) has not been closely examined! This study revisits the under-actuated control design with detailed set ups of multiple scenarios reflecting real life operating conditions which have put current under-actuated control laws mentioned earlier into a re-evaluation mode since rest to rest case is not adequate to truly represent an on orbit failure of a single wheel. The study is intended to facilitate the ACS community to further develop a more practical under-actuated control law and present a path to extend these current thinking to address a more realistic reconfigurable ACS subject to a dynamic transition from a 3 RWs mode to 2 RWs mode.

Biotechnology

NASA Image and Video Library

2003-02-09

Dwarf wheat were photographed aboard the International Space Station in April 2002. Lessons from on-orbit research on plants will have applications to terrestrial agriculture as well as for long-term space missions. Alternative agricultural systems that can efficiently produce greater quantities of high-quality crops in a small area are important for future space expeditions. Also regenerative life-support systems that include plants will be an important component of long-term space missions. Data from the Biomass Production System (BPS) and the Photosynthesis Experiment and System Testing and Operations (PESTO) will advance controlled-environment agricultural systems and will help farmers produce better, healthier crops in a small area. This same knowledge is critical to closed-loop life support systems for spacecraft. The BPS comprises a miniature environmental control system for four plant growth chambers, all in the volume of two space shuttle lockers. The experience with the BPS on orbit is providing valuable design and operational lessons that will be incorporated into the Plant Growth Units. The objective of PESTO was to flight verify the BPS hardware and to determine how the microgravity environment affects the photosynthesis and metabolic function of Super Dwarf wheat and Brassica rapa (a member of the mustard family).

Dwarf Wheat grown aboard the International Space Station

NASA Technical Reports Server (NTRS)

2003-01-01

Dwarf wheat were photographed aboard the International Space Station in April 2002. Lessons from on-orbit research on plants will have applications to terrestrial agriculture as well as for long-term space missions. Alternative agricultural systems that can efficiently produce greater quantities of high-quality crops in a small area are important for future space expeditions. Also regenerative life-support systems that include plants will be an important component of long-term space missions. Data from the Biomass Production System (BPS) and the Photosynthesis Experiment and System Testing and Operations (PESTO) will advance controlled-environment agricultural systems and will help farmers produce better, healthier crops in a small area. This same knowledge is critical to closed-loop life support systems for spacecraft. The BPS comprises a miniature environmental control system for four plant growth chambers, all in the volume of two space shuttle lockers. The experience with the BPS on orbit is providing valuable design and operational lessons that will be incorporated into the Plant Growth Units. The objective of PESTO was to flight verify the BPS hardware and to determine how the microgravity environment affects the photosynthesis and metabolic function of Super Dwarf wheat and Brassica rapa (a member of the mustard family).

Design, Development and Testing of the Miniature Autonomous Extravehicular Robotic Camera (Mini AERCam) Guidance, Navigation and Control System

NASA Technical Reports Server (NTRS)

Wagenknecht, J.; Fredrickson, S.; Manning, T.; Jones, B.

2003-01-01

Engineers at NASA Johnson Space Center have designed, developed, and tested a nanosatellite-class free-flyer intended for future external inspection and remote viewing of human spaceflight activities. The technology demonstration system, known as the Miniature Autonomous Extravehicular Robotic Camera (Mini AERCam), has been integrated into the approximate form and function of a flight system. The primary focus has been to develop a system capable of providing external views of the International Space Station. The Mini AERCam system is spherical-shaped and less than eight inches in diameter. It has a full suite of guidance, navigation, and control hardware and software, and is equipped with two digital video cameras and a high resolution still image camera. The vehicle is designed for either remotely piloted operations or supervised autonomous operations. Tests have been performed in both a six degree-of-freedom closed-loop orbital simulation and on an air-bearing table. The Mini AERCam system can also be used as a test platform for evaluating algorithms and relative navigation for autonomous proximity operations and docking around the Space Shuttle Orbiter or the ISS.

An Updated Process for Automated Deepspace Conjunction Assessment

NASA Technical Reports Server (NTRS)

Tarzi, Zahi B.; Berry, David S.; Roncoli, Ralph B.

2015-01-01

There is currently a high level of interest in the areas of conjunction assessment and collision avoidance from organizations conducting space operations. Current conjunction assessment activity is mainly focused on spacecraft and debris in the Earth orbital environment [1]. However, collisions are possible in other orbital environments as well [2]. This paper will focus on the current operations of and recent updates to the Multimission Automated Deep Space Conjunction Assessment Process (MADCAP) used at the Jet Propulsion Laboratory for NASA to perform conjunction assessment at Mars and the Moon. Various space agencies have satellites in orbit at Mars and the Moon with additional future missions planned. The consequences of collisions are catastrophically high. Intuitive notions predict low probability of collisions in these sparsely populated environments, but may be inaccurate due to several factors. Orbits of scientific interest often tend to have similar characteristics as do the orbits of spacecraft that provide a communications relay for surface missions. The MADCAP process is controlled by an automated scheduler which initializes analysis based on a set timetable or the appearance of new ephemeris files either locally or on the Deep Space Network (DSN) Portal. The process then generates and communicates reports which are used to facilitate collision avoidance decisions. The paper also describes the operational experience and utilization of the automated tool during periods of high activity and interest such as: the close approaches of NASA's Lunar Atmosphere & Dust Environment Explorer (LADEE) and Lunar Reconnaissance Orbiter (LRO) during the LADEE mission. In addition, special consideration was required for the treatment of missions with rapidly varying orbits and less reliable long term downtrack estimates; in particular this was necessitated by perturbations to MAVEN's orbit induced by the Martian atmosphere. The application of special techniques to non-operational spacecraft with large uncertainties is also studied. Areas for future work are also described. Although the applications discussed in this paper are in the Martian and Lunar environments, the techniques are not unique to these bodies and could be applied to other orbital environments.

James Webb Space Telescope Mid Infra-Red Instrument Pulse-Tube Cryocooler Electronics

NASA Technical Reports Server (NTRS)

Harvey, D.; Flowers, T.; Liu, N.; Moore, K.; Tran, D.; Valenzuela, P.; Franklin, B.; Michaels, D.

2013-01-01

The latest generation of long life, space pulse-tube cryocoolers require electronics capable of controlling self-induced vibration down to a fraction of a newton and coldhead temperature with high accuracy down to a few kelvin. Other functions include engineering diagnostics, heater and valve control, telemetry and safety protection of the cryocooler subsystem against extreme environments and operational anomalies. The electronics are designed to survive the thermal, vibration, shock and radiation environment of launch and orbit, while providing a design life in excess of 10 years on-orbit. A number of our current generation high reliability radiation-hardened electronics units are in various stages of integration on several space flight payloads. This paper describes the features and performance of our latest flight electronics designed for the pulse-tube cryocooler that is the pre-cooler for a closed cycle Joule-Thomson cooler providing 6K cooling for the James Webb Space Telescope (JWST) Mid Infra-Red Instrument (MIRI). The electronics is capable of highly accurate temperature control over the temperature range from 4K to 15K. Self-induced vibration is controlled to low levels on all harmonics up to the 16th. A unique active power filter controls peak-to-peak reflected ripple current on the primary power bus to a very low level. The 9 kg unit is capable of delivering 360W continuous power to NGAS's 3-stage pulse-tube High-Capacity Cryocooler (HCC).

Orbit control of a stratospheric satellite with parameter uncertainties

NASA Astrophysics Data System (ADS)

Xu, Ming; Huo, Wei

2016-12-01

When a stratospheric satellite travels by prevailing winds in the stratosphere, its cross-track displacement needs to be controlled to keep a constant latitude orbital flight. To design the orbit control system, a 6 degree-of-freedom (DOF) model of the satellite is established based on the second Lagrangian formulation, it is proven that the input/output feedback linearization theory cannot be directly implemented for the orbit control with this model, thus three subsystem models are deduced from the 6-DOF model to develop a sequential nonlinear control strategy. The control strategy includes an adaptive controller for the balloon-tether subsystem with uncertain balloon parameters, a PD controller based on feedback linearization for the tether-sail subsystem, and a sliding mode controller for the sail-rudder subsystem with uncertain sail parameters. Simulation studies demonstrate that the proposed control strategy is robust to uncertainties and satisfies high precision requirements for the orbit flight of the satellite.

Typical teleoperator time delay profiles, phase 2. [remotely controlled manipulator arms

NASA Technical Reports Server (NTRS)

Wetherington, R. D.; Walsh, J. R.

1974-01-01

The results of the second phase of a study on time delays in communications systems applicable to the teleoperator program are presented. Estimates of the maximum time delays that will be encountered and presents time delay profiles are given for (1) ground control to teleoperator in low earth orbit, (2) ground control to teleoperator in geosynchronous orbit, and (3) low earth orbit control to teleoperator in low earth orbit.

International Ultraviolet Explorer observations of the peculiar variable spectrum of the eclipsing binary R Arae

NASA Technical Reports Server (NTRS)

Mccluskey, G. E.; Kondo, Y.

1983-01-01

The eclipsing binary system R Arae = HD 149730 is a relatively bright southern system with an orbital period of about 4.4 days. It is a single-lined spectroscopic binary. The spectral class of the primary component is B9 Vp. The system was included in a study of mass flow and evolution in close binary systems using the International Ultraviolet Explorer satellite (IUE). Four spectra in the wavelength range from 1150 to 1900 A were obtained with the far-ultraviolet SWP camera, and six spectra in the range from 1900 to 3200 range were obtained with the mid-ultraviolet LWR camera. The close binary R Arae exhibits very unusual ultraviolet spectra. It appears that no other close binary system, observed with any of the orbiting satellites, shows outside-eclipse ultraviolet continuum flux variations of this nature.

An Orbit And Dispersion Correction Scheme for the PEP II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Y.; Donald, M.; Shoaee, H.

2011-09-01

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

Orbital fractures due to domestic violence: an epidemiologic study.

PubMed

Goldberg, Stuart H.; McRill, Connie M.; Bruno, Christopher R.; Ten Have, Tom; Lehman, Erik

2000-09-01

Domestic violence is an important cause of orbital fractures in women. Physicians who treat patients with orbital fractures may not suspect this mechanism of injury. The purpose of this study was to assess the association between domestic violence and orbital fractures. A medical center-based case-control study with matching on age and site of admission was done. Medical center databases were searched using ICD-9 codes to identify all cases of orbital fractures encountered during a three-year period. Medical records of female patients age 13 and older were reviewed along with those of age, gender and site of admission matched controls. A stratified exact test was employed to test the association between domestic violence and orbital fracture. Among 41 adult female cases with orbital fractures treated at our medical center, three (7.3%) reported domestic violence compared to zero among the matched controls (p = 0.037). We believe that domestic violence may be under-reported in both orbital fracture cases and controls. This may result in an underestimate of the orbital fracture versus domestic violence association. Domestic violence is a serious women's health and societal problem. Domestic violence may have a variety of presentations, including illnesses and injuries. Orbital fracture is an identifiable manifestation of domestic violence. Domestic violence is more likely to be detected in adult female hospital patients with orbital fracture than in matched controls with any other diagnosis. Physicians who treat patients with orbital fractures should be familiar with this mechanism of injury.

Preliminary control/structure interaction study of coupled Space Station Freedom/Assembly Work Platform/orbiter

NASA Technical Reports Server (NTRS)

Singh, Sudeep K.; Lindenmoyer, Alan J.

1989-01-01

Results are presented from a preliminary control/structure interaction study of the Space Station, the Assembly Work Platform, and the STS orbiter dynamics coupled with the orbiter and station control systems. The first three Space Station assembly flight configurations and their finite element representations are illustrated. These configurations are compared in terms of control authority in each axis and propellant usage. The control systems design parameters during assembly are computed. Although the rigid body response was acceptable with the orbiter Primary Reaction Control System, the flexible body response showed large structural deflections and loads. It was found that severe control/structure interaction occurred if the stiffness of the Assembly Work Platform was equal to that of the station truss. Also, the response of the orbiter Vernier Reaction Control System to small changes in inertia properties is examined.

Analytical modeling of soliton interactions in a nonlocal nonlinear medium analogous to gravitational force

NASA Astrophysics Data System (ADS)

Zeng, Shihao; Chen, Manna; Zhang, Ting; Hu, Wei; Guo, Qi; Lu, Daquan

2018-01-01

We illuminate an analytical model of soliton interactions in lead glass by analogizing to a gravitational force system. The orbits of spiraling solitons under a long-range interaction are given explicitly and demonstrated to follow Newton's second law of motion and the Binet equation by numerical simulations. The condition for circular orbits is obtained and the oscillating orbits are proved not to be closed. We prove the analogy between the nonlocal nonlinear optical system and gravitational system and specify the quantitative relation of the quantity between the two models.

Closeup detail of the jackstand head and the attach mechanism ...

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

Close-up detail of the jack-stand head and the attach mechanism connection to the hoist attach point on the starboard forward fuselage of the Orbiter Discovery. Note the profile of the wing intersection with the fuselage and the payload bay door in an open position with the strongback support structure attached. This view was taken from a service platform in the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Closeup view of the underside of the forward fuselage of ...

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

Close-up view of the underside of the forward fuselage of the Orbiter Discovery looking at the nose landing-gear and into the landing-gear well. The vehicle is elevated and supported by jack stands attached to the hoist attach points and the rear External Tank attach points on the propellant disconnect plate assemblies. This photo was taken inside the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Expansion of the gravitational potential with computerized Poisson series

NASA Technical Reports Server (NTRS)

Broucke, R.

1976-01-01

The paper describes a recursive formulation for the expansion of the gravitational potential valid for both the tesseral and zonal harmonics. The expansion is primarily in rectangular coordinates, but the classical orbit elements or equinoctial orbit elements can be easily substituted. The equations of motion for the zonal harmonics in both classical and equinoctial orbital elements are described in a form which will result in closed-form expressions for the first-order perturbations. In order to achieve this result, the true longitude or true anomaly have to be used as independent variables.

Orbital Analysis of Two Triple Systems in the Open Cluster NGC 2516

NASA Astrophysics Data System (ADS)

Veramendi, M. E.; González, J. F.

2010-12-01

We report the discovery of two hierarchical triple systems in the open cluster NGC 2516. Both systems are double-lined spectroscopic binaries whose center-of-mass velocity varies in a time scale of a few years. The system BDA 19 consists of an eccentric spectroscopic binary with a period of 8.7 days and a third body orbiting with a period of about 3300 days. The close pair in the triple BDA 2 has an orbital period of 11.2 days and contains a HgMn star.

Moments of inclination error distribution computer program

NASA Technical Reports Server (NTRS)

Myler, T. R.

1981-01-01

A FORTRAN coded computer program is described which calculates orbital inclination error statistics using a closed-form solution. This solution uses a data base of trajectory errors from actual flights to predict the orbital inclination error statistics. The Scott flight history data base consists of orbit insertion errors in the trajectory parameters - altitude, velocity, flight path angle, flight azimuth, latitude and longitude. The methods used to generate the error statistics are of general interest since they have other applications. Program theory, user instructions, output definitions, subroutine descriptions and detailed FORTRAN coding information are included.

TRAPPIST-1 Statistics Table

NASA Image and Video Library

2017-02-22

This chart shows, on the top row, artist concepts of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii and masses as compared to those of Earth. On the bottom row, the same numbers are displayed for the bodies of our inner solar system: Mercury, Venus, Earth and Mars. The TRAPPIST-1 planets orbit their star extremely closely, with periods ranging from 1.5 to only about 20 days. This is much shorter than the period of Mercury, which orbits our sun in about 88 days. The artist concepts show what the TRAPPIST-1 planetary system may look like, based on available data about their diameters, masses and distances from the host star. The system has been revealed through observations from NASA's Spitzer Space Telescope and the ground-based TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) telescope, as well as other ground-based observatories. The system was named for the TRAPPIST telescope. The seven planets of TRAPPIST-1 are all Earth-sized and terrestrial, according to research published in 2017 in the journal Nature. TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius, and its planets orbit very close to it. http://photojournal.jpl.nasa.gov/catalog/PIA21425

The Uncertain Nature of Cometary Motions

NASA Technical Reports Server (NTRS)

Yeomans, Donald K.

1997-01-01

The number of active short- and long-periodic comets crossing the Earth's orbit each year is less than 10 percent of the corresponding number of asteroids crossing the Earth's orbit. However, the higher relative velocities of comets with respect to the Earth and the uncertainties associated with accurately computing their future trajectories can cause considerable problems when assessing the risks of Earth-crossing objects. Unlike asteroids, the motions of active comets are often affected by so-called nongravitational (outgassing) forces that are imperfectly modeled. In addition, the astrometric optical observations that are used to refine a comet's orbit are often imprecise because a comet's center of mass can be hidden by atmospheric gas and dust. For long-period comets, there is the additional problem of having to base orbital solutions on relatively short observational data intervals. Long-term numerical integrations extending two centuries into the future have been carried out to investigate upcoming Earth-close approaches by known periodic comets. Error analyses and impact probabilities have been computed for those comets that will pass closest to the Earth. Although there are no known comets that will make dangerously close Earth approaches in the next two centuries, there are a few objects that warrant future monitoring.

Dynamic Portrait of the Retrograde 1:1 Mean Motion Resonance

NASA Astrophysics Data System (ADS)

Huang, Yukun; Li, Miao; Li, Junfeng; Gong, Shengping

2018-06-01

Asteroids in mean motion resonances with giant planets are common in the solar system, but it was not until recently that several asteroids in retrograde mean motion resonances with Jupiter and Saturn were discovered. A retrograde co-orbital asteroid of Jupiter, 2015 BZ509 is confirmed to be in a long-term stable retrograde 1:1 mean motion resonance with Jupiter, which gives rise to our interests in its unique resonant dynamics. In this paper, we investigate the phase-space structure of the retrograde 1:1 resonance in detail within the framework of the circular restricted three-body problem. We construct a simple integrable approximation for the planar retrograde resonance using canonical contact transformation and numerically employ the averaging procedure in closed form. The phase portrait of the retrograde 1:1 resonance is depicted with the level curves of the averaged Hamiltonian. We thoroughly analyze all possible librations in the co-orbital region and uncover a new apocentric libration for the retrograde 1:1 resonance inside the planet’s orbit. We also observe the significant jumps in orbital elements for outer and inner apocentric librations, which are caused by close encounters with the perturber.

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

NASA Technical Reports Server (NTRS)

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

1978-01-01

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

Semiclassical relation between open trajectories and periodic orbits for the Wigner time delay.

PubMed

Kuipers, Jack; Sieber, Martin

2008-04-01

The Wigner time delay of a classically chaotic quantum system can be expressed semiclassically either in terms of pairs of scattering trajectories that enter and leave the system or in terms of the periodic orbits trapped inside the system. We show how these two pictures are related on the semiclassical level. We start from the semiclassical formula with the scattering trajectories and derive from it all terms in the periodic orbit formula for the time delay. The main ingredient in this calculation are correlations between scattering trajectories which are due to trajectories that approach the trapped periodic orbits closely. The equivalence between the two pictures is also demonstrated by considering correlation functions of the time delay. A corresponding calculation for the conductance gives no periodic orbit contributions in leading order.

TIDALLY DRIVEN ROCHE-LOBE OVERFLOW OF HOT JUPITERS WITH MESA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valsecchi, Francesca; Rasio, Frederic A.; Rappaport, Saul

2015-11-10

Many exoplanets have now been detected in orbits with ultra-short periods very close to the Roche limit. Building upon our previous work, we study the possibility that mass loss through Roche lobe overflow (RLO) may affect the evolution of these planets, and could possibly transform a hot Jupiter into a lower-mass planet (hot Neptune or super-Earth). We focus here on systems in which the mass loss occurs slowly (“stable mass transfer” in the language of binary star evolution) and we compute their evolution in detail with the binary evolution code Modules for Experiments in Stellar Astrophysics. We include the effectsmore » of tides, RLO, irradiation, and photo-evaporation (PE) of the planet, as well as the stellar wind and magnetic braking. Our calculations all start with a hot Jupiter close to its Roche limit, in orbit around a Sun-like star. The initial orbital decay and onset of RLO are driven by tidal dissipation in the star. We confirm that such a system can indeed evolve to produce lower-mass planets in orbits of a few days. The RLO phase eventually ends and, depending on the details of the mass transfer and on the planetary core mass, the orbital period can remain around a few days for several Gyr. The remnant planets have rocky cores and some amount of envelope material, which is slowly removed via PE at a nearly constant orbital period; these have properties resembling many of the observed super-Earths and sub-Neptunes. For these remnant planets, we also predict an anti-correlation between mass and orbital period; very low-mass planets (M{sub pl} ≲ 5 M{sub ⊕}) in ultra-short periods (P{sub orb} < 1 day) cannot be produced through this type of evolution.« less

Natural motion around the Martian moon Phobos: the dynamical substitutes of the Libration Point Orbits in an elliptic three-body problem with gravity harmonics

NASA Astrophysics Data System (ADS)

Zamaro, M.; Biggs, J. D.

2015-07-01

The Martian moon Phobos is becoming an appealing destination for future scientific missions. The orbital dynamics around this planetary satellite is particularly complex due to the unique combination of both small mass-ratio and length-scale of the Mars-Phobos couple: the resulting sphere of influence of the moon is very close to its surface, therefore both the classical two-body problem and circular restricted three-body problem (CR3BP) do not provide an accurate approximation to describe the spacecraft's dynamics in the vicinity of Phobos. The aim of this paper is to extend the model of the CR3BP to consider the orbital eccentricity and the highly-inhomogeneous gravity field of Phobos, by incorporating the gravity harmonics series expansion into an elliptic R3BP, named ER3BP-GH. Following this, the dynamical substitutes of the Libration Point Orbits (LPOs) are computed in this more realistic model of the relative dynamics around Phobos, combining methodologies from dynamical systems theory and numerical continuation techniques. Results obtained show that the structure of the periodic and quasi-periodic LPOs differs substantially from the classical case without harmonics. Several potential applications of these natural orbits are presented to enable unique low-cost operations in the proximity of Phobos, such as close-range observation, communication, and passive radiation shielding for human spaceflight. Furthermore, their invariant manifolds are demonstrated to provide high-performance natural landing and take-off pathways to and from Phobos' surface, and transfers from and to Martian orbits. These orbits could be exploited in upcoming and future space missions targeting the exploration of this Martian moon.

Shape of the orbital opening: individual characterization and analysis of variability in modern humans, Gorilla gorilla, and Pan troglodytes.

PubMed

Schmittbuhl, M; Le Minor, J M; Allenbach, B; Schaaf, A

1999-05-01

The description of the human orbital shape is principally qualitative in the classical literature, and characterised by adjectives such as circular, rectangular or quadrangular. In order to provide a precise quantification and interpretation of this shape, a study based on automatic image analysis and Fourier analysis was carried out on 45 human skulls (30 males, 15 females), and for comparison on 61 skulls of Gorilla gorilla (40 males, 21 females), and 34 skulls of Pan troglodytes (20 males, 14 females). Sexual dimorphism in the shape of the orbital opening was not demonstrated. Its dominant morphological features could be characterized by Fourier analysis; elliptical elongation and quadrangularity were dominant morphological features of the shape of the orbital opening in the three species. Elliptical elongation was more marked in humans and Pan, whereas quadrangularity was particularly emphasized in Gorilla. An intraspecific variability of the shape of the orbital opening existed in humans, Gorilla and Pan, and seemed close in the three species. Interspecific partition between humans, Gorilla and Pan was demonstrated despite the variability observed in the three species studied. Interspecific differences between Gorilla and the Pan-humans group were principally explained by the differences in quadrangularity, and by differences in orientation of triangularity and pentagonality. Differences in the shape of the orbital opening between humans and Pan were principally explained by differences in hexagonality, and by differences in orientation of quadrangularity. A closeness of shape between some humans and some individuals in Pan and, to a lesser degree, with some individuals in Gorilla was observed, demonstrating the existence of a morphological continuum of the shape of the orbital opening in hominoids.

Study of electronic and magnetic properties of h-BN on Ni surfaces: A DFT approach

NASA Astrophysics Data System (ADS)

Sahoo, M. R.; Sahu, S.; Kushwaha, A. K.; Nayak, S.

2018-04-01

Hexagonal boron nitride (h-BN) is a promising material for implementation in spintronics due to large band gap, low spin-orbit coupling, and a small lattice mismatch to graphene and close-packedsurfaces of fcc-Ni(111). Electronic and magnetic properties of single layer hexagonal Boron Nitride (h-BN) on Ni (111) surface have been studied with density functional calculation. Since lattice constants of nickel surfaces are very close to that of h-BN, nickel acts as a good substrate. We found that the interaction between 2Pz - 3dz2 orbitals leads to change in electronic band structure as well as density of states which results spin polarization in h-BN.

Two Years of International Cooperation on Conjunction Mitigation

NASA Astrophysics Data System (ADS)

Kelso, T. S.

2010-09-01

In an effort to mitigate the risks associated with satellite close approaches in the geostationary belt, several satellite operators came together in early 2008 to establish what is now known as the GEO Data Center. The GEO Data Center initially provided a framework for satellite operators to share orbital data for their fleets of satellites to be used to perform conjunction analysis and provide automated notification of close approaches via the SOCRATES-GEO system. After two years of operations, the GEO Data Center now has 14 members providing data for 186 satellites. Since the Iridium 33-Cosmos 2251 collision, a parallel system was set up with a LEO Data Center, which already has seven members providing data for 101 satellites. These data centers have already shown the significant benefit of sharing orbital data, particularly in terms of reducing positional uncertainty and, thereby, the number of false alarms. This paper will address the current framework for these efforts, highlighting how a service-oriented architecture is used to support orbital operations and increase efficiency of analysis and resolution of risk-mitigation tasks. It will show how the interactive work flow is used to quickly assess new maneuvers to determine whether they have successfully reduced the chances of a particular close approach without causing other close approaches elsewhere. It will also show how independent space situational awareness organizations can be employed to provide a more complete picture of the threat from nonparticipating satellites and the debris population.

Analysis of Tank PMD Rewetting Following Thrust Resettling

NASA Astrophysics Data System (ADS)

Weislogel, M. M.; Sala, M. A.; Collicott, S. H.

2002-10-01

Recent investigations have successfully demonstrated closed-form analytical solutions of spontaneous capillary flows in idealized cylindrical containers with interior corners. In this report, the theory is extended and applied to complex containers modeling spacecraft fuel tanks employing propellant management devices (PMDs). The specific problem investigated is one of spontaneous rewetting of a typical partially filled liquid fuel/cryogen tank with PMD after thrust resettling. The transients of this flow impact the logistics of orbital maneuvers and potentially tank thermal control. The general procedure to compute the initial condition (mean radius of curvature for the interface) for the closed-form transient flows is first outlined then solved for several 'complex' cylindrical tanks exhibiting symmetry. The utility and limitations of the technique as a design tool are discussed in a summary, which also highlights comparisons with NASA flight data of a model propellant tank with PMD.

Analysis of Tank PMD Rewetting Following Thrust Resettling

NASA Technical Reports Server (NTRS)

Weislogel, M. M.; Sala, M. A.; Collicott, S. H.; Rame, Enrique (Technical Monitor)

2002-01-01

Recent investigations have successfully demonstrated closed-form analytical solutions of spontaneous capillary flows in idealized cylindrical containers with interior corners. In this report, the theory is extended and applied to complex containers modeling spacecraft fuel tanks employing propellant management devices (PMDs). The specific problem investigated is one of spontaneous rewetting of a typical partially filled liquid fuel/cryogen tank with PMD after thrust resettling. The transients of this flow impact the logistics of orbital maneuvers and potentially tank thermal control. The general procedure to compute the initial condition (mean radius of curvature for the interface) for the closed-form transient flows is first outlined then solved for several 'complex' cylindrical tanks exhibiting symmetry. The utility and limitations of the technique as a design tool are discussed in a summary, which also highlights comparisons with NASA flight data of a model propellant tank with PMD.

A Closed Ecological System in a Space Experiment

NASA Astrophysics Data System (ADS)

Strauch, S. M.; Schuster, M.; Lebert, M.; Richter, P.; Schmittnagel, M.; Hader, D.-P.

2008-06-01

The Russian FOTON-M3 mission, a satellite for mid-length experiments in space and recovery afterwards, included a closed artificial ecosystem (OMEGAHAB for Oreochromis Mossambicus-Euglena Gracilis-Aquatic HABitat) with the photosynthetic flagellate Euglena gracilis as oxygen producer and larvae of Oreochromis mossambicus, a Tilapia species, as consumer. During the 12-day orbital flight the algae were observed 10 minutes per day by means of a miniaturized microscope to analyse their swimming behavior. The fishes were also filmed to monitor their development and movement. An identical experiment was carried out as ground control. A data downlink provided the measured temperature values of the space experiment every day to readjust the temperature of the ground reference in order to eliminate the influence of the different temperature on the velocity of the development of the fishes. The system worked very well and confirmed the design in principle. OMEGAHAB was the most successful German experiment of that kind as yet.

A retrograde object near Jupiter's orbit

NASA Astrophysics Data System (ADS)

Connors, M.; Wiegert, P.

2018-02-01

Asteroid 2007 VW266 is among the rare objects with a heliocentric retrograde orbit, and its semimajor axis is within a Hill sphere radius of that of Jupiter. This raised the interesting possibility that it could be in co-orbital retrograde resonance with Jupiter, a second "counter-orbital" object in addition to recently discovered 2015 BZ509. We find instead that the object is in 13/14 retrograde mean motion resonance (also referred to as 13/-14). The object is shown to have entered its present orbit about 1700 years ago, and it will leave it in about 8000 years, both through close approach to Jupiter. Entry and exit states both avoid 1:1 retrograde resonance, but the retrograde nature is preserved. The temporary stable state is due to an elliptic orbit with high inclination keeping nodal passages far from the associated planet. We discuss the motion of this unusual object based on modeling and theory, and its observational prospects.

RS-34 Phoenix In-Space Propulsion System Applied to Active Debris Removal Mission

NASA Technical Reports Server (NTRS)

Esther, Elizabeth A.; Burnside, Christopher G.

2014-01-01

In-space propulsion is a high percentage of the cost when considering Active Debris Removal mission. For this reason it is desired to research if existing designs with slight modification would meet mission requirements to aid in reducing cost of the overall mission. Such a system capable of rendezvous, close proximity operations, and de-orbit of Envisat class resident space objects has been identified in the existing RS-34 Phoenix. RS-34 propulsion system is a remaining asset from the de-commissioned United States Air Force Peacekeeper program; specifically the pressure-fed storable bi-propellant Stage IV Post Boost Propulsion System. The National Aeronautics and Space Administration (NASA) Marshall Space Flight Center (MSFC) gained experience with the RS-34 propulsion system on the successful Ares I-X flight test program flown in the Ares I-X Roll control system (RoCS). The heritage hardware proved extremely robust and reliable and sparked interest for further utilization on other potential in-space applications. Subsequently, MSFC has obtained permission from the USAF to obtain all the remaining RS-34 stages for re-use opportunities. The MSFC Advanced Concepts Office (ACO) was commissioned to lead a study for evaluation of the Rocketdyne produced RS-34 propulsion system as it applies to an active debris removal design reference mission for resident space object targets including Envisat. Originally designed, the RS-34 Phoenix provided in-space six-degrees-of freedom operational maneuvering to deploy payloads at multiple orbital locations. The RS-34 Concept Study lead by sought to further understand application for a similar orbital debris design reference mission to provide propulsive capability for rendezvous, close proximity operations to support the capture phase of the mission, and deorbit of single or multiple large class resident space objects. Multiple configurations varying the degree of modification were identified to trade for dry mass optimization and propellant load. The results of the RS-34 Phoenix Concept Study show that the system is technically sufficient to successfully support all of the missions to rendezvous, capture, and de-orbit targets including Envisat and Hubble Space Telescope. The results and benefits of the RS-34 Orbital Debris Application Concept Study are presented in this paper.

Detail view of the "underside" of the Orbiter Maneuvering/Reaction Control ...

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

Detail view of the "underside" of the Orbiter Maneuvering/Reaction Control Systems pod looking at the two spherical propellant tanks for the Reaction Control System, and the elongated propellant tanks for the Orbiter Maneuvering System. This view was taken at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Full-size solar dynamic heat receiver thermal-vacuum tests

NASA Technical Reports Server (NTRS)

Sedgwick, L. M.; Kaufmann, K. J.; Mclallin, K. L.; Kerslake, Thomas W.

1991-01-01

The testing of a full-size, 120 kW, solar dynamic heat receiver utilizing high-temperature thermal energy storage is described. The purpose of the test program was to quantify receiver thermodynamic performance, operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber with liquid nitrogen cold shrouds and an aperture cold plate to partly simulate a low-Earth-orbit environment. The cavity of the receiver was heated by an infrared quartz lamp heater with 30 independently controllable zones to allow axially and circumferentially varied flux distributions. A closed-Brayton cycle engine simulator conditioned a helium-xenon gas mixture to specific interface conditions to simulate the various operational modes of the solar dynamic power module on the Space Station Freedom. Inlet gas temperature, pressure, and flow rate were independently varied. A total of 58 simulated orbital cycles, each 94 minutes in duration, was completed during the test conduct period.

Full-size solar dynamic heat receiver thermal-vacuum tests

NASA Technical Reports Server (NTRS)

Sedgwick, L. M.; Kaufmann, K. J.; Mclallin, K. L.; Kerslake, T. W.

1991-01-01

The testing of a full-size, 102 kW, solar dynamic heat receiver utilizing high-temperature thermal energy storage is described. The purpose of the test program was to quantify receiver thermodynamic performance, operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber with liquid nitrogen cold shrouds and an aperture cold plate to partly simulate a low-Earth-orbit environment. The cavity of the receiver was heated by an infrared quartz lamp heater with 30 independently controllable zones to allow axially and circumferentially varied flux distributions. A closed-Brayton cycle engine simulator conditioned a helium-xenon gas mixture to specific interface conditions to simulate the various operational modes of the solar dynamic power module on the Space Station Freedom. Inlet gas temperature, pressure, and flow rate were independently varied. A total of 58 simulated orbital cycles, each 94 minutes in duration, was completed during the test period.

Solar thermal vacuum tests of Magellan spacecraft

NASA Technical Reports Server (NTRS)

Neuman, James C.

1990-01-01

The Magellen solar/thermal/vacuum test involved a number of unique requirements and approaches. Because of the need to operate in orbit around Venus, the solar intensity requirement ranged up to 2.3 suns or Earth equivalent solar constants. Extensive modification to the solar simulator portion of the test facility were required to achieve this solar intensity. Venus albedo and infrared emission were simulated using temperature controlled movable louver panels to allow the spacecraft to view either a selectable temperature black heat source with closed louvers, or the chamber coldwall behind open louvers. The test conditions included widely varying solar intensities, multiple sun angles, alternate hardware configurations, steady state and transient cases, and cruise and orbital power profiles. Margin testing was also performed, wherein supplemental heaters were mounted to internal thermal blankets to verify spacecraft performance at higher than expected temperatures. The test was successful, uncovering some spacecraft anomalies and verifying the thermal design. The test support equipment experienced some anomalous behavior and a significant failure during the test.

Full-size solar dynamic heat receiver thermal-vacuum tests

NASA Astrophysics Data System (ADS)

Sedgwick, L. M.; Kaufmann, K. J.; McLallin, K. L.; Kerslake, T. W.

The testing of a full-size, 102 kW, solar dynamic heat receiver utilizing high-temperature thermal energy storage is described. The purpose of the test program was to quantify receiver thermodynamic performance, operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber with liquid nitrogen cold shrouds and an aperture cold plate to partly simulate a low-Earth-orbit environment. The cavity of the receiver was heated by an infrared quartz lamp heater with 30 independently controllable zones to allow axially and circumferentially varied flux distributions. A closed-Brayton cycle engine simulator conditioned a helium-xenon gas mixture to specific interface conditions to simulate the various operational modes of the solar dynamic power module on the Space Station Freedom. Inlet gas temperature, pressure, and flow rate were independently varied. A total of 58 simulated orbital cycles, each 94 minutes in duration, was completed during the test period.

STS-88 Mission Commander Cabana looks at the mission payload Unity at pad

NASA Technical Reports Server (NTRS)

1998-01-01

At Launch Pad 39A, STS-88 Mission Commander Robert D. Cabana gets a close look at the Unity connecting module that is in the payload bay of the orbiter Endeavour. Cabana and the STS-88 crew arrived at KSC in the early morning hours of Nov. 30 for pre- launch preparations. The other crew members are Pilot Frederick W. 'Rick' Sturckow, Mission Specialist Nancy J. Currie, Mission Specialist James H. Newman and Mission Specialist Sergei Konstantinovich Krikalev, a Russian cosmonaut. The scheduled lift-off is at 3:56 a.m. on Dec. 3. Unity is the primary payload of the mission, which is the first U.S. launch for the International Space Station. The crew will be mating Unity with the Russian-built Zarya control module already in orbit. In addition to Unity, two small replacement electronics boxes are on board for possible repairs to Zarya batteries. Endeavour is expected to land at KSC at 10:17 p.m. on Monday, Dec. 14.

Closeup view from the starboard side looking towards the port ...

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

Close-up view from the starboard side looking towards the port side of the Orbiter Discovery looking at the airlock and payload bay. The docking ring has been removed from the airlock prior to this photo being taken. Note that the Orbiter Boom Sensor System is still attached while the Remote Manipulator System has been removed. Also note the suspended protective panels and walkways in place to protect the interior surfaces of the payload bay doors while in their open position. This view was taken from a service platform in the Orbiter Processing Facility at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

The study of the physics of cometary nuclei

NASA Technical Reports Server (NTRS)

Whipple, Fred L.

1987-01-01

The numerical calculations of stability for many possible orbits of the double nucleus for P/Holmes showed that the likelihood of such a precollision history was quite high. A number of investigations were made of hypothetical orbits for particles about the asteroid Amphitrite to test for stability. The purpose was to establish more favorable fly-by orbits close to the asteroid for the Galileo missions en-route to Jupiter, reducing the collisional hazards. A statistical study was made of the orbits of long-period comets with small original semi-major axes recently perturbed from the great Opik-Oort Cloud. The results from the space missions to Halley's comet are partially reported in the two papers in the appendices.

A Close Hidden Stellar Companion to the SX Phe-Type Variable Star DW Psc

NASA Astrophysics Data System (ADS)

Qian, S.-B.; Li, L.-J.; Wang, S.-M.; He, J.-J.; Zhou, X.; Jiang, L.-Q.

2015-01-01

DW Psc is a high-amplitude SX Phe-type variable with a period of pulsation of 0.05875 days. Using a few newly determined times of maximum light together with those collected from the literature, the changes in the observed-calculated (O-C) diagram are analyzed. It is discovered that the O-C curve of DW Psc shows a cyclic variation with a period of 6.08 years and a semi-amplitude of 0.0066 days. The periodic variation is analyzed for the light travel time effect, which is due to the presence of a stellar companion ({{M}2}sin i˜ 0.45(+/- 0.03) {{M}⊙ }). The two-component stars in the binary system are orbiting each other in an eccentric orbit (e ˜ 0.4) at an orbital separation of about 2.7(±0.3) AU. The detection of a close stellar companion to an SX Phe-type star supports the idea that SX Phe-type pulsating stars are blue stragglers that were formed from the merging of close binaries. The stellar companion has played an important role in the merging of the original binary by removing angular momentum from the central binary during early dynamical interaction or/and late dynamical evolution. After the more massive component in DW Psc evolves into a red giant, the cool close companion should help to remove the giant envelope via possible critical Roche-lobe overflow, and the system may be a progenitor of a cataclysmic variable. The detection of a close stellar companion to DW Psc makes it a very interesting system to study in the future.

Periodic orbits of solar sail equipped with reflectance control device in Earth-Moon system

NASA Astrophysics Data System (ADS)

Yuan, Jianping; Gao, Chen; Zhang, Junhua

2018-02-01

In this paper, families of Lyapunov and halo orbits are presented with a solar sail equipped with a reflectance control device in the Earth-Moon system. System dynamical model is established considering solar sail acceleration, and four solar sail steering laws and two initial Sun-sail configurations are introduced. The initial natural periodic orbits with suitable periods are firstly identified. Subsequently, families of solar sail Lyapunov and halo orbits around the L1 and L2 points are designed with fixed solar sail characteristic acceleration and varying reflectivity rate and pitching angle by the combination of the modified differential correction method and continuation approach. The linear stabilities of solar sail periodic orbits are investigated, and a nonlinear sliding model controller is designed for station keeping. In addition, orbit transfer between the same family of solar sail orbits is investigated preliminarily to showcase reflectance control device solar sail maneuver capability.

Chandra observations of Jupiter's X-ray Aurora during Juno upstream and apojove intervals

NASA Astrophysics Data System (ADS)

Dunn, W.; Jackman, C. M.; Kraft, R.; Gladstone, R.; Branduardi-Raymont, G.; Knigge, C.; Altamirano, D.; Elsner, R.; Kammer, J.

2017-12-01

The Chandra space telescope has recently conducted a number of campaigns to observe Jupiter's X-ray aurora. The first set of campaigns took place in summer 2016 while the Juno spacecraft was upstream of the planet sampling the solar wind. The second set of campaigns took place in February, June and August 2017 at times when the Juno spacecraft was at apojove. These campaigns were planned following the Juno orbit correction to capitalise on the opportunity to image the X-ray emission while Juno was orbiting close to the expected position of the magnetopause. Previous work has suggested that the auroral X-ray emissions map close to the magnetopause boundary [e.g. Vogt et al., 2015; Kimura et al., 2016; Dunn et al., 2016] and thus in situ spacecraft coverage in this region combined with remote observation of the X-rays afford the chance to constrain the drivers of these energetic emissions and determine if they originate on open or closed field lines. We aim to examine possible drivers of X-ray emission including reconnection and the Kelvin-Helmholtz instability and to explore the role of the solar wind in controlling the emissions. We report on these upstream and apojove campaigns including intensities and periodicities of auroral X-ray emissions. This new era of jovian X-ray astronomy means we have more data than ever before, long observing windows (up to 72 ks for this Chandra set), and successive observations relatively closely spaced in time. These features combine to allow us to pursue novel methods for examining periodicities in the X-ray emission. Our work will explore significance testing of emerging periodicities, and the search for coherence in X-ray pulsing over weeks and months, seeking to understand the robustness and regularity of previously reported hot spot X-ray emissions. The periods that emerge from our analysis will be compared against those which emerge from radio and UV wavelengths.

Predictions of asteroid hazard to the Earth for the 21st century

NASA Astrophysics Data System (ADS)

Petrov, Nikita; Sokolov, Leonid; Polyakhova, Elena; Oskina, Kristina

2018-05-01

Early detection and investigation of possible collisions and close approaches of asteroids with the Earth are necessary to exept the asteroid-comet hazard. The difficulty of prediction of close approaches and collisions associated with resonant returns after encounters with the Earth due to loss of precision in these encounters. The main research object is asteroid Apophis (99942), for which we found many possible orbits of impacts associated with resonant returns. It is shown that the early orbit change of Apophis allows to avoid main impacts, associated with resonant returns. Such a change of the orbit, in principle, is feasible. We also study the possible impacts with the Ground asteroid 2015 RN35. We present 21 possible collisions in this century, including 7 collisions with large gaps presented in NASA website. The results of observations by the telescope ZA-320M at Pulkovo Obser-vatory of the three near-Earth asteroids, namely, 7822, 20826, 68216, two of which 7822 and 68216 are potentially hazardous, are presented.

Ecology of dark matter haloes - II. Effects of interactions on the alignment of halo pairs

NASA Astrophysics Data System (ADS)

L'Huillier, Benjamin; Park, Changbom; Kim, Juhan

2017-04-01

We use the Horizon Run 4 cosmological N-body simulation to study the effects of distant and close interactions on the alignments of the shapes, spins and orbits of targets haloes with their neighbours, and their dependence on the local density environment and neighbour separation. Interacting targets have a significantly lower spin and higher sphericity and oblateness than all targets. Interacting pairs initially have antiparallel spins, but the spins develop parallel alignment as time goes on. Neighbours tend to evolve in the plane of rotation of the target, and in the direction of the major axis of prolate haloes. Moreover, interactions are preferentially radial, while pairs with non-radial orbits are preferentially prograde. The alignment signals are stronger at high mass and for close separations, and independent of the large-scale density. Positive alignment signals are found at redshifts up to 4, and increase with decreasing redshifts. Moreover, the orbits tend to become prograde at low redshift, while no alignment is found at high redshift (z = 4).

ACCELERATORS: Beam based alignment of the SSRF storage ring

NASA Astrophysics Data System (ADS)

Zhang, Man-Zhou; Li, Hao-Hu; Jiang, Bo-Cheng; Liu, Gui-Min; Li, De-Ming

2009-04-01

There are 140 beam position monitors (BPMs) in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring used for measuring the closed orbit. As the BPM pickup electrodes are assembled directly on the vacuum chamber, it is important to calibrate the electrical center offset of the BPM to an adjacent quadrupole magnetic center. A beam based alignment (BBA) method which varies individual quadrupole magnet strength and observes its effects on the orbit is used to measure the BPM offsets in both the horizontal and vertical planes. It is a completely automated technique with various data processing methods. There are several parameters such as the strength change of the correctors and the quadrupoles which should be chosen carefully in real measurement. After several rounds of BBA measurement and closed orbit correction, these offsets are set to an accuracy better than 10 μm. In this paper we present the method of beam based calibration of BPMs, the experimental results of the SSRF storage ring, and the error analysis.

Neural network-based sliding mode control for atmospheric-actuated spacecraft formation using switching strategy

NASA Astrophysics Data System (ADS)

Sun, Ran; Wang, Jihe; Zhang, Dexin; Shao, Xiaowei

2018-02-01

This paper presents an adaptive neural networks-based control method for spacecraft formation with coupled translational and rotational dynamics using only aerodynamic forces. It is assumed that each spacecraft is equipped with several large flat plates. A coupled orbit-attitude dynamic model is considered based on the specific configuration of atmospheric-based actuators. For this model, a neural network-based adaptive sliding mode controller is implemented, accounting for system uncertainties and external perturbations. To avoid invalidation of the neural networks destroying stability of the system, a switching control strategy is proposed which combines an adaptive neural networks controller dominating in its active region and an adaptive sliding mode controller outside the neural active region. An optimal process is developed to determine the control commands for the plates system. The stability of the closed-loop system is proved by a Lyapunov-based method. Comparative results through numerical simulations illustrate the effectiveness of executing attitude control while maintaining the relative motion, and higher control accuracy can be achieved by using the proposed neural-based switching control scheme than using only adaptive sliding mode controller.

Detail view of a starboard Orbiter Maneuvering and Reaction Control ...

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

Detail view of a starboard Orbiter Maneuvering and Reaction Control Systems pod, removed from the orbiter and in it's carrier/transport vehicle at Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

The stabilities and electron structures of Al-Mg clusters with 18 and 20 valence electrons

NASA Astrophysics Data System (ADS)

Yang, Huihui; Chen, Hongshan

2017-07-01

The spherical jellium model predicts that metal clusters having 18 and 20 valence electrons correspond to the magic numbers and will show specific stabilities. We explore in detail the geometric structures, stabilities and electronic structures of Al-Mg clusters containing 18 and 20 valence electrons by using genetic algorithm combined with density functional theories. The stabilities of the clusters are governed by the electronic configurations and Mg/Al ratios. The clusters with lower Mg/Al ratios are more stable. The molecular orbitals accord with the shell structures predicted by the jellium model but the 2S level interweaves with the 1D levels and the 2S and 1D orbitals form a subgroup. The clusters having 20 valence electrons form closed 1S21P61D102S2 shells and show enhanced stability. The Al-Mg clusters with a valence electron count of 18 do not form closed shells because one 1D orbital is unoccupied. The ionization potential and electron affinity are closely related to the electronic configurations; their values are determined by the subgroups the HOMO or LUMO belong to. Supplementary material in the form of one pdf file available from the Journal web page at http://https://doi.org/10.1140/epjd/e2017-80042-9

Possible Outcomes of Coplanar High-eccentricity Migration: Hot Jupiters, Close-in Super-Earths, and Counter-orbiting Planets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, Yuxin; Masuda, Kento; Suto, Yasushi, E-mail: yuxin@utap.phys.s.u-tokyo.ac.jp

We investigate the formation of close-in planets in near-coplanar eccentric hierarchical triple systems via the secular interaction between an inner planet and an outer perturber (Coplanar High-eccentricity Migration; CHEM). We generalize the previous work on the analytical condition for successful CHEM for point masses interacting only through gravity by taking into account the finite mass effect of the inner planet. We find that efficient CHEM requires that the systems should have m {sub 1}≪m {sub 0} and m {sub 1} ≪ m {sub 2}. In addition to the gravity for point masses, we examine the importance of the short-range forces,more » and provide an analytical estimate of the migration timescale. We perform a series of numerical simulations in CHEM for systems consisting of a Sun-like central star, giant gas inner planet, and planetary outer perturber, including the short-range forces and stellar and planetary dissipative tides. We find that most of such systems end up with a tidal disruption; a small fraction of the systems produce prograde hot Jupiters (HJs), but no retrograde HJ. In addition, we extend CHEM to super-Earth mass range, and show that the formation of close-in super-Earths in prograde orbits is also possible. Finally, we carry out CHEM simulation for the observed hierarchical triple and counter-orbiting HJ systems. We find that CHEM can explain a part of the former systems, but it is generally very difficult to reproduce counter-orbiting HJ systems.« less

Atlantis TPS Processing

NASA Image and Video Library

2003-10-01

In the Orbiter Processing Facility, Harrell Watts (left), with United Space Alliance, removes a tile from the thermal barrier around the umbilical areas, the external tank attach points, on the underside of Atlantis. The umbilical areas are closed off after ET separation by a door, seen here. The exposed area of each closed door is covered with reusable surface insulation.

Identification of new orbits to enable future mission opportunities for the human exploration of the Martian moon Phobos

NASA Astrophysics Data System (ADS)

Zamaro, Mattia; Biggs, James D.

2016-02-01

One of the paramount stepping stones towards NASA's long-term goal of undertaking human missions to Mars is the exploration of the Martian moons. Since a precursor mission to Phobos would be easier than landing on Mars itself, NASA is targeting this moon for future exploration, and ESA has also announced Phootprint as a candidate Phobos sample-and-return mission. Orbital dynamics around small planetary satellites are particularly complex because many strong perturbations are involved, and the classical circular restricted three-body problem (R3BP) does not provide an accurate approximation to describe the system's dynamics. Phobos is a special case, since the combination of a small mass-ratio and length-scale means that the sphere-of-influence of the moon moves very close to its surface. Thus, an accurate nonlinear model of a spacecraft's motion in the vicinity of this moon must consider the additional perturbations due to the orbital eccentricity and the complete gravity field of Phobos, which is far from a spherical-shaped body, and it is incorporated into an elliptic R3BP using the gravity harmonics series-expansion (ER3BP-GH). In this paper, a showcase of various classes of non-keplerian orbits is identified and a number of potential mission applications in the Mars-Phobos system are proposed: these results could be exploited in upcoming unmanned missions targeting the exploration of this Martian moon. These applications include: low-thrust hovering and orbits around Phobos for close-range observations; the dynamical substitutes of periodic and quasi-periodic Libration Point Orbits in the ER3BP-GH to enable unique low-cost operations for space missions in the proximity of Phobos; their manifold structure for high-performance landing/take-off maneuvers to and from Phobos' surface and for transfers from and to Martian orbits; Quasi-Satellite Orbits for long-period station-keeping and maintenance. In particular, these orbits could exploit Phobos' occulting bulk and shadowing wake as a passive radiation shield during future manned flights to Mars to reduce human exposure to radiation, and the latter orbits can be used as an orbital garage, requiring no orbital maintenance, where a spacecraft could make planned pit-stops during a round-trip mission to Mars.

Detectable close-in planets around white dwarfs through late unpacking

NASA Astrophysics Data System (ADS)

Veras, Dimitri; Gänsicke, Boris T.

2015-02-01

Although 25-50 per cent of white dwarfs (WDs) display evidence for remnant planetary systems, their orbital architectures and overall sizes remain unknown. Vibrant close-in (≃1 R⊙) circumstellar activity is detected at WDs spanning many Gyr in age, suggestive of planets further away. Here we demonstrate how systems with 4 and 10 closely packed planets that remain stable and ordered on the main sequence can become unpacked when the star evolves into a WD and experience pervasive inward planetary incursions throughout WD cooling. Our full-lifetime simulations run for the age of the Universe and adopt main-sequence stellar masses of 1.5, 2.0 and 2.5 M⊙, which correspond to the mass range occupied by the progenitors of typical present-day WDs. These results provide (i) a natural way to generate an ever-changing dynamical architecture in post-main-sequence planetary systems, (ii) an avenue for planets to achieve temporary close-in orbits that are potentially detectable by transit photometry and (iii) a dynamical explanation for how residual asteroids might pollute particularly old WDs.

The journey of Typhon-Echidna as a binary system through the planetary region

NASA Astrophysics Data System (ADS)

Araujo, R. A. N.; Galiazzo, M. A.; Winter, O. C.; Sfair, R.

2018-06-01

Among the current population of the 81 known trans-Neptunian binaries (TNBs), only two are in orbits that cross the orbit of Neptune. These are (42355) Typhon-Echidna and (65489) Ceto-Phorcys. In this work, we focused our analyses on the temporal evolution of the Typhon-Echidna binary system through the outer and inner planetary systems. Using numerical integrations of the N-body gravitational problem, we explored the orbital evolutions of 500 clones of Typhon, recording the close encounters of those clones with planets. We then analysed the effects of those encounters on the binary system. It was found that only {≈ }22 per cent of the encounters with the giant planets were strong enough to disrupt the binary. This binary system has an ≈ 3.6 per cent probability of reaching the terrestrial planetary region over a time-scale of approximately 5.4 Myr. Close encounters of Typhon-Echidna with Earth and Venus were also registered, but the probabilities of such events occurring are low ({≈}0.4 per cent). The orbital evolution of the system in the past was also investigated. It was found that in the last 100 Myr, Typhon might have spent most of its time as a TNB crossing the orbit of Neptune. Therefore, our study of the Typhon-Echidna orbital evolution illustrates the possibility of large cometary bodies (radii of 76 km for Typhon and 42 km for Echidna) coming from a remote region of the outer Solar system and that might enter the terrestrial planetary region preserving its binarity throughout the journey.

TOWARD CHEMICAL CONSTRAINTS ON HOT JUPITER MIGRATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madhusudhan, Nikku; Amin, Mustafa A.; Kennedy, Grant M., E-mail: nmadhu@ast.cam.ac.uk

The origin of hot Jupiters—gas giant exoplanets orbiting very close to their host stars—is a long-standing puzzle. Planet formation theories suggest that such planets are unlikely to have formed in situ but instead may have formed at large orbital separations beyond the snow line and migrated inward to their present orbits. Two competing hypotheses suggest that the planets migrated either through interaction with the protoplanetary disk during their formation, or by disk-free mechanisms such as gravitational interactions with a third body. Observations of eccentricities and spin-orbit misalignments of hot Jupiter systems have been unable to differentiate between the two hypotheses.more » In the present work, we suggest that chemical depletions in hot Jupiter atmospheres might be able to constrain their migration mechanisms. We find that sub-solar carbon and oxygen abundances in Jovian-mass hot Jupiters around Sun-like stars are hard to explain by disk migration. Instead, such abundances are more readily explained by giant planets forming at large orbital separations, either by core accretion or gravitational instability, and migrating to close-in orbits via disk-free mechanisms involving dynamical encounters. Such planets also contain solar or super-solar C/O ratios. On the contrary, hot Jupiters with super-solar O and C abundances can be explained by a variety of formation-migration pathways which, however, lead to solar or sub-solar C/O ratios. Current estimates of low oxygen abundances in hot Jupiter atmospheres may be indicative of disk-free migration mechanisms. We discuss open questions in this area which future studies will need to investigate.« less

Long-term eclipse timing of white dwarf binaries: an observational hint of a magnetic mechanism at work

NASA Astrophysics Data System (ADS)

Bours, M. C. P.; Marsh, T. R.; Parsons, S. G.; Dhillon, V. S.; Ashley, R. P.; Bento, J. P.; Breedt, E.; Butterley, T.; Caceres, C.; Chote, P.; Copperwheat, C. M.; Hardy, L. K.; Hermes, J. J.; Irawati, P.; Kerry, P.; Kilkenny, D.; Littlefair, S. P.; McAllister, M. J.; Rattanasoon, S.; Sahman, D. I.; Vučković, M.; Wilson, R. W.

2016-08-01

We present a long-term programme for timing the eclipses of white dwarfs in close binaries to measure apparent and/or real variations in their orbital periods. Our programme includes 67 close binaries, both detached and semi-detached and with M-dwarfs, K-dwarfs, brown dwarfs or white dwarfs secondaries. In total, we have observed more than 650 white dwarf eclipses. We use this sample to search for orbital period variations and aim to identify the underlying cause of these variations. We find that the probability of observing orbital period variations increases significantly with the observational baseline. In particular, all binaries with baselines exceeding 10 yr, with secondaries of spectral type K2 - M5.5, show variations in the eclipse arrival times that in most cases amount to several minutes. In addition, among those with baselines shorter than 10 yr, binaries with late spectral type (>M6), brown dwarf or white dwarf secondaries appear to show no orbital period variations. This is in agreement with the so-called Applegate mechanism, which proposes that magnetic cycles in the secondary stars can drive variability in the binary orbits. We also present new eclipse times of NN Ser, which are still compatible with the previously published circumbinary planetary system model, although only with the addition of a quadratic term to the ephemeris. Finally, we conclude that we are limited by the relatively short observational baseline for many of the binaries in the eclipse timing programme, and therefore cannot yet draw robust conclusions about the cause of orbital period variations in evolved, white dwarf binaries.

DYNAMICS OF TIDALLY CAPTURED PLANETS IN THE GALACTIC CENTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trani, Alessandro A.; Bressan, Alessandro; Mapelli, Michela

2016-11-01

Recent observations suggest ongoing planet formation in the innermost parsec of the Galactic center. The supermassive black hole (SMBH) might strip planets or planetary embryos from their parent star, bringing them close enough to be tidally disrupted. Photoevaporation by the ultraviolet field of young stars, combined with ongoing tidal disruption, could enhance the near-infrared luminosity of such starless planets, making their detection possible even with current facilities. In this paper, we investigate the chance of planet tidal captures by means of high-accuracy N -body simulations exploiting Mikkola's algorithmic regularization. We consider both planets lying in the clockwise (CW) disk andmore » planets initially bound to the S-stars. We show that tidally captured planets remain on orbits close to those of their parent star. Moreover, the semimajor axis of the planetary orbit can be predicted by simple analytic assumptions in the case of prograde orbits. We find that starless planets that were initially bound to CW disk stars have mild eccentricities and tend to remain in the CW disk. However, we speculate that angular momentum diffusion and scattering by other young stars in the CW disk might bring starless planets into orbits with low angular momentum. In contrast, planets initially bound to S-stars are captured by the SMBH on highly eccentric orbits, matching the orbital properties of the clouds G1 and G2. Our predictions apply not only to planets but also to low-mass stars initially bound to the S-stars and tidally captured by the SMBH.« less

In-Flight Operation of the Dawn Ion Propulsion System - The First Nine Months

NASA Technical Reports Server (NTRS)

Garner, Charles E.; Brophy, John R.; Mikes, Steven C.; Raymond, Marc D.

2008-01-01

The Dawn mission, part of NASA's Discovery Program, has as its goal the scientific exploration of the two most massive main-belt asteroids, Vesta and Ceres. The Dawn spacecraft was launched from Cape Canaveral Air Force Station on September 27, 2007 on a Delta-II 7925H-9.5 (Delta-II Heavy) rocket that placed the 1218 kg spacecraft into an Earth-escape trajectory. On-board the spacecraft is an ion propulsion system (IPS) which will provide most of the delta-V needed for heliocentric transfer to Vesta, orbit capture at Vesta, transfer to Vesta science orbits, departure and escape from Vesta, heliocentric transfer to Ceres, orbit capture at Ceres, and transfer to Ceres science orbits. The Dawn ion engine design is based on the design validated on NASA's Deep Space 1 mission. However, because of the very substantial (11 km/s) delta-V requirements for this mission Dawn requires two engines to complete its mission objectives. The power processor units (PPU), digital control and interface units (DCIU) slice boards and the xenon control assembly (XCA) are also based on the DS1 design. The DCIUs and thrust gimbal assemblies (TGA) were developed at the Jet Propulsion Laboratory. The spacecraft was provided by Orbital Sciences Corporation, Sterling, Virginia, and the mission is managed by and operated from the Jet Propulsion Laboratory. Dawn partnered with Germany, Italy and Los Alamos National Laboratory for the science instruments. The mission is led by the principal investigator, Dr. Christopher Russell, from the University of California, Los Angeles. The first 80 days after launch were dedicated to the initial checkout of the spacecraft prior to the initiation of long-term thrusting for the heliocentric transfer to Vesta. The IPS hardware, consisting of three ion thrusters and TGAs, two PPUs and DCIUs, xenon feed system, and spacecraft control software, was investigated extensively. Thrust measurements, roll torque measurements, pointing capabilities, control characteristics, and thermal behavior of the spacecraft and IPS were carefully evaluated. The Dawn IPS fully met all its initial checkout performance objectives. Deterministic thrusting for cruise began on December 17, 2007. Over the subsequent approximately 330 days the IPS will be operated virtually continuously at full power thrusting (approximately 91 mN) leading to a Mars flyby in February 2009. The encounter with Mars provides a gravity assist for a plane change and is the only source of post-launch delta-V apart from the IPS. Following the Mars gravity assist IPS will be operated for approximately one year at full power and for 1.3 years at throttled power levels leading to rendezvous with Vesta in August of 2011. Following nine months of orbital operations with IPS providing the propulsion needed for orbit capture, science orbit transfer and orbit maintenance and Vesta escape, Dawn will transit to Ceres with an expected arrival date of February 2015. As of June 16, 2008 the ion thrusters on Dawn have operated for close to 3,846 hours and have delivered nearly 1 km/s of delta-V to the spacecraft. Dawn IPS operation has been almost flawless during the initial checkout and six months of cruise. This paper provides an overview of Dawn's mission objectives, mission and system design, and the results of the post-launch Dawn IPS mission operations through June 2008

The final year of the Rosetta mission

NASA Astrophysics Data System (ADS)

Accomazzo, Andrea; Ferri, Paolo; Lodiot, Sylvain; Pellon-Bailon, Jose-Luis; Hubault, Armelle; Urbanek, Jakub; Kay, Ritchie; Eiblmaier, Matthias; Francisco, Tiago

2017-07-01

The International Rosetta Mission was launched on 2nd March 2004 on its 10 year journey to rendezvous with comet 67P Churyumov-Gerasimenko. Rosetta performed comet orbit insertion on the 6th of August 2014, after which it characterised the nucleus and orbited it at altitudes as low as a few kilometres. In November 2014 Rosetta delivered the lander Philae to perform the first soft landing ever on the surface of a comet. After this critical operation, Rosetta began the escort phase of the comet in its journey in the Solar System heading to the perihelion, reached in August 2015. Originally foreseen till the end of 2015, the mission was extended for another nine months to follow the comet on its outbound arc of the orbit. In view of the acquired experience and of the approaching end of mission the spacecraft was flown at much closer distances from the nucleus so that the scientific instruments had the chance to perform unique measurements. Following this phase of very close orbits, on the 30th of September 2016 Rosetta was set on a collision course trajectory with the comet to terminate the mission with a controlled impact. This paper describes the details of the extended mission phase and the issues encountered during these months. It also includes the changes implemented on the spacecraft and in the operations concept to optimise the remaining mission time. The paper also includes the lessons learned from this unique and complex mission phase.

Irregular wave functions of a hydrogen atom in a uniform magnetic field

NASA Technical Reports Server (NTRS)

Wintgen, D.; Hoenig, A.

1989-01-01

The highly excited irregular wave functions of a hydrogen atom in a uniform magnetic field are investigated analytically, with wave function scarring by periodic orbits considered quantitatively. The results obtained confirm that the contributions of closed classical orbits to the spatial wave functions vanish in the semiclassical limit. Their disappearance, however, is slow. This discussion is illustrated by numerical examples.

Spacecraft Formation Flying near Sun-Earth L2 Lagrange Point: Trajectory Generation and Adaptive Full-State Feedback Control

NASA Technical Reports Server (NTRS)

Wong, Hong; Kapila, Vikram

2004-01-01

In this paper, we present a method for trajectory generation and adaptive full-state feedback control to facilitate spacecraft formation flying near the Sun-Earth L2 Lagrange point. Specifically, the dynamics of a spacecraft in the neighborhood of a Halo orbit reveals that there exist quasi-periodic orbits surrounding the Halo orbit. Thus, a spacecraft formation is created by placing a leader spacecraft on a desired Halo orbit and placing follower spacecraft on desired quasi-periodic orbits. To produce a formation maintenance controller, we first develop the nonlinear dynamics of a follower spacecraft relative to the leader spacecraft. We assume that the leader spacecraft is on a desired Halo orbit trajectory and the follower spacecraft is to track a desired quasi-periodic orbit surrounding the Halo orbit. Then, we design an adaptive, full-state feedback position tracking controller for the follower spacecraft providing an adaptive compensation for the unknown mass of the follower spacecraft. The proposed control law is simulated for the case of the leader and follower spacecraft pair and is shown to yield global, asymptotic convergence of the relative position tracking errors.

On the long-period evolution of the sun-synchronous orbits

NASA Astrophysics Data System (ADS)

Kuznetsov, E. D.; Jasim, A. T.

2016-05-01

The dynamic evolution of sun-synchronous orbits at a time interval of 20 years is considered. The numerical motion simulation has been carried out using the Celestial Mechanics software package developed at the Institute of Astronomy of the University of Bern. The dependence of the dynamic evolution on the initial value of the ascending node longitude is examined for two families of sun-synchronous orbits with altitudes of 751 and 1191 km. Variations of the semimajor axis and orbit inclination are obtained depending on the initial value of the ascending node longitude. Recommendations on the selection of orbits, in which spent sun-synchronous satellites can be moved, are formulated. Minimal changes of elements over a time interval of 20 years have been observed for orbits in which at the initial time the angle between the orbit ascending node and the direction of the Sun measured along the equator have been close to 90° or 270°. In this case, the semimajor axis of the orbit is not experiencing secular perturbations arising from the satellite's passage through the Earth's shadow.

STS-96 Mission Highlights. Part 2

NASA Technical Reports Server (NTRS)

1999-01-01

In this second part of a three-part video mission-highlights set, on-orbit spacecrew activities performed on the STS-96 Space Shuttle Orbiter Discovery and the International Space Station are reviewed. The flight crew consists of Kent V. Rominger, Commander; Rick D. Husband, Pilot; and Mission Specialists Ellen Ochoa, Tamara E. Jernigan, Daniel T. Barry, Julie Payette (Canadian), and Valery Ivanovich Tokarev (Russian). The primary goals of this mission were to work on logistics and resupply the International Space Station. This second part in the mission series features video from Flight Day 4-7 (FD 4-7). FD 4 of STS-96 presents astronauts Tammy Jernigan and Dan Barry completing the second longest space walk in shuttle history. Footage includes Jernigan and Barry transferring and installing two cranes from the shuttle's payload bay to locations on the outside of the station. The astronauts enter the International Space Station delivering supplies and prepare the outpost to receive its first resident crew, scheduled to arrive in early 2000 on FD 5. The video also captures the crew involved in logistics transfer activities within the Discovery/ISS orbiting complex. FD 6 includes footage of Valery Tokarev and Canadian astronaut Julie Payette charging out the final six battery recharge controller units for two of Zarya's power-producing batteries and all crew members' involvement in logistics transfer activities from the SPACEHAB module to designated locations in the International Space Station. With the transfer work of FD 6 all but complete, the astronauts conduct some additional work, installing parts of a wireless strain gauge system that will help engineers track the effects of adding modules to the station throughout its assembly. Moving the few remaining items from Discovery to the ISS, then closing a series of hatches within the station's modules leading back to the shuttle are the primary activities contained in FD 7. Final coverage features Discovery's astronauts finishing their work inside the International Space Station, closing all of the hatches and readying the shuttle's small thrusters to be fired to raise the entire complex's orbit in preparation for the undocking and departure set for FD 8.

Lessons Learned from the Hubble Space Telescope (HST) Contamination Control Program

NASA Technical Reports Server (NTRS)

Hansen, Patricia A.; Townsend, Jacqueline A.; Hedgeland, Randy J.

2004-01-01

Over the past two decades, the Hubble Space Telescope (HST) Contamination Control Program has evolved from a ground-based integration program to a space-based science-sustaining program. The contamination controls from the new-generation Scientific Instruments and Orbital Replacement Units were incorporated into the HST Contamination Control Program to maintain scientific capability over the life of the telescope. Long-term on-orbit scientific data has shown that these contamination controls implemented for the instruments, Servicing Mission activities (Orbiter, Astronauts, and mission), and on-orbit operations successfully protected the HST &om contamination and the instruments from self-contamination.

Lessons Learned from the Hubble Space Telescope (HST) Contamination Control Program

NASA Technical Reports Server (NTRS)

Hansen, Patricia A.; Townsend, Jacqueline A.; Hedgeland, Randy J.

2004-01-01

Over the past two decades, the Hubble Space Telescope (HST) Contamination Control Program has evolved from a ground-based integration program to a space-based science-sustaining program. The contamination controls from the new-generation Scientific Instruments and Orbital Replacement Units were incorporated into the HST Contamination Control Program to maintain scientific capability over the life of the telescope. Long-term on-orbit scientific data has shown that these contamination controls implemented for the instruments, Servicing Mission activities (Orbiter, Astronauts, and mission), and on-orbit operations successfully protected the HST from contamination and the instruments from self-contamination.

Correlation of the Hubble Space Telescope (HST) Space Telescope Imaging Spectrometer (STIS) On-Orbit Data with Pre-launch Predictions and Ground Contamination Controls

NASA Technical Reports Server (NTRS)

Hansen, Patricia A.

2003-01-01

The Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) was deployed on-orbit in February 1997. The contamination program for STIS was stringently controlled as the five-year end-of-life deposition was set at 158, per optical element. Contamination was controlled through materials selection, extensive vacuum outgassing certifications, cleaning techniques, and environmental controls. In addition to ground contamination controls, on-orbit contamination controls were implemented for both the HST servicing mission activities and early post-servicing mission checkout. The extensive contamination control program will be discussed and the STIS on-orbit data will be correlated with the prelaunch analytical predictions.

Magnetic attitude control torque generation of a gravity gradient stabilized satellite

NASA Astrophysics Data System (ADS)

Suhadis, N. M.; Salleh, M. B.; Rajendran, P.

2018-05-01

Magnetic torquer is used to generate a magnetic dipole moment onboard satellites whereby a control torque for attitude control purposes is generated when it couples with the geomagnetic field. This technique has been considered very attractive for satellites operated in Low Earth Orbit (LEO) as the strength of the geomagnetic field is relatively high below the altitude of 1000 km. This paper presents the algorithm used to generate required magnetic dipole moment by 3 magnetic torquers mounted onboard a gravity gradient stabilized satellite operated at an altitude of 540 km with nadir pointing mission. As the geomagnetic field cannot be altered and its magnitude and direction vary with respect to the orbit altitude and inclination, a comparison study of attitude control torque generation performance with various orbit inclination is performed where the structured control algorithm is simulated for 13°, 33° and 53° orbit inclinations to see how the variation of the satellite orbit affects the satellite's attitude control torque generation. Results from simulation show that the higher orbit inclination generates optimum magnetic attitude control torque for accurate nadir pointing mission.

Analysis of the Image Quality of no Ground Controlled Positioning Precision about Surveying and Mapping Satellite

NASA Astrophysics Data System (ADS)

Wang, Y.; Hu, X.; Yang, X.; Xie, G.

2018-04-01

The image quality of the surveying camera will affect the stereoscopic positioning accuracy of the remote sensing satellite. The key factors closely related to the image quality are Modulation Transfer Function(MTF),Signal to Noise Ratio(SNR) and Quantization Bits(QB). In "Mapping Satellite-1" image as the background, research the effect of positioning precision about the image quality in no ground controlled conditions, and evaluate the quantitative relationship with the positioning precision. At last verify the validity of the experimental results by simulating three factors of the degraded data on orbit, and counting the number of matching points, the mismatch rate, and the matching residuals of the degraded data. The reason for the variety of the positioning precision was analyzed.

Evidence for a planetary mass third body orbiting the binary star KIC 5095269

NASA Astrophysics Data System (ADS)

Getley, A. K.; Carter, B.; King, R.; O'Toole, S.

2017-07-01

In this paper, we report the evidence for a planetary mass body orbiting the close binary star KIC 5095269. This detection arose from a search for eclipse timing variations amongst the more than 2000 eclipsing binaries observed by Kepler. Light curve and periodic eclipse time variations have been analysed using systemic and a custom Binary Eclipse Timings code based on the Transit Analysis Package which indicates a 7.70 ± 0.08MJup object orbiting every 237.7 ± 0.1 d around a 1.2 M⊙ primary and a 0.51 M⊙ secondary in an 18.6 d orbit. A dynamical integration over 107 yr suggests a stable orbital configuration. Radial velocity observations are recommended to confirm the properties of the binary star components and the planetary mass of the companion.

Further studies on criteria for the onset of dynamical instability in general three-body systems

NASA Technical Reports Server (NTRS)

Pendleton, Y. J.; Black, D. C.

1983-01-01

Numerical experiments designed for the elucidation of the conditions under which self-gravitating, three-body systems become dynamically unstable are examined of the cases of four orbital configuration types: circular, prograde, and coplanar; circular, retrograde, and coplanar; circular, direct, and inclined; and eccentric, direct, and coplanar. Results indicate that orbital inclination does not significantly affect stability in 'outer planet' configurations, while the stability of 'inner planet' configurations, where the tertiary is in close orbit about one member of the binary, is markedly less affected, once the relative orbital inclination is greater than 50 deg. It is found that the onset of dynamical instability is only weakly dependent on the eccentricity of either the binary or tertiary orbit, as long as the mass of the tertiary is comparable to the reduced mass of the binary.

Long term evolution of planetary systems with a terrestrial planet and a giant planet.

NASA Astrophysics Data System (ADS)

Georgakarakos, Nikolaos; Dobbs-Dixon, Ian; Way, Michael J.

2017-06-01

We study the long term orbital evolution of a terrestrial planet under the gravitational perturbations of a giant planet. In particular, we are interested in situations where the two planets are in the same plane and are relatively close. We examine both possible configurations: the giant planet orbit being either outside or inside the orbit of the smaller planet. The perturbing potential is expanded to high orders and an analytical solution of the terrestrial planetary orbit is derived. The analytical estimates are then compared against results from the numerical integration of the full equations of motion and we find that the analytical solution works reasonably well. An interesting finding is that the new analytical estimates improve greatly the predictions for the timescales of the orbital evolution of the terrestrial planet compared to an octupole order expansion.

Geometric phase due to orbit-orbit interaction: rotating LP11 modes in a two-mode fiber

NASA Astrophysics Data System (ADS)

Pradeep Chakravarthy, T.; Naik, Dinesh N.; Viswanathan, Nirmal K.

2017-10-01

Accumulation of geometric phase due to non-coplanar propagation of higher-order modes in an optical fiber is experimentally demonstrated. Vertically-polarized LP11 fiber mode, excited in a horizontally-held, torsion-free, step-index, two-mode optical fiber, rotates due to asymmetry in the propagating k-vectors, arising due to off-centered beam location at the fiber input. Perceiving the process as due to rotation of the fiber about the off-axis launch position, the orbital Berry phase accumulation upon scanning the launch position in a closed-loop around the fiber axis manifests as rotational Doppler effect, a consequence of orbit-orbit interaction. The anticipated phase accumulation as a function of the input launch position, observed through interferometry is connected to the mode rotation angle, quantified using the autocorrelation method.

HERRO Mission to Mars Using Telerobotic Surface Exploration from Orbit

NASA Technical Reports Server (NTRS)

Oleson, Steven R.; Landis, Geoffrey A.; McGuire, Melissa L.; Schmidt, George R.

2013-01-01

This paper presents a concept for a human mission to Mars orbit that features direct robotic exploration of the planet s surface via teleoperation from orbit. This mission is a good example of Human Exploration using Real-time Robotic Operations (HERRO), an exploration strategy that refrains from sending humans to the surfaces of planets with large gravity wells. HERRO avoids the need for complex and expensive man-rated lander/ascent vehicles and surface systems. Additionally, the humans are close enough to the surface to effectively eliminate the two-way communication latency that constrains typical robotic space missions, thus allowing real-time command and control of surface operations and experiments by the crew. Through use of state-of-the-art telecommunications and robotics, HERRO provides the cognitive and decision-making advantages of having humans at the site of study for only a fraction of the cost of conventional human surface missions. It is very similar to how oceanographers and oil companies use telerobotic submersibles to work in inaccessible areas of the ocean, and represents a more expedient, near-term step prior to landing humans on Mars and other large planetary bodies. Results suggest that a single HERRO mission with six crew members could achieve the same exploratory and scientific return as three conventional crewed missions to the Mars surface.

Analysis and correction of linear optics errors, and operational improvements in the Indus-2 storage ring

NASA Astrophysics Data System (ADS)

Husain, Riyasat; Ghodke, A. D.

2017-08-01

Estimation and correction of the optics errors in an operational storage ring is always vital to achieve the design performance. To achieve this task, the most suitable and widely used technique, called linear optics from closed orbit (LOCO) is used in almost all storage ring based synchrotron radiation sources. In this technique, based on the response matrix fit, errors in the quadrupole strengths, beam position monitor (BPM) gains, orbit corrector calibration factors etc. can be obtained. For correction of the optics, suitable changes in the quadrupole strengths can be applied through the driving currents of the quadrupole power supplies to achieve the desired optics. The LOCO code has been used at the Indus-2 storage ring for the first time. The estimation of linear beam optics errors and their correction to minimize the distortion of linear beam dynamical parameters by using the installed number of quadrupole power supplies is discussed. After the optics correction, the performance of the storage ring is improved in terms of better beam injection/accumulation, reduced beam loss during energy ramping, and improvement in beam lifetime. It is also useful in controlling the leakage in the orbit bump required for machine studies or for commissioning of new beamlines.

Field-controlled magnetic order with insulator-metal transitions in a periodic Anderson-like organic polymer.

PubMed

Ding, L J; Yao, K L; Fu, H H

2011-01-07

The zero- and low-temperature behaviors of a quasi-one-dimensional organic polymer proposed as a symmetrical periodic Anderson-like chain model, in which the localized f orbitals hybridize with the conduction orbitals at even sites, are investigated by means of many-body Green's function theory. In the absence of magnetic field, the ground state of the system turns out to be ferrimagnetic. The temperature-induced phase diagrams have been explored, where the competition between the Hubbard repulsion U on the localized f orbital and the hybridization strength V makes an important impact on the transition temperature. In a magnetic field, it is found that a 1/3 magnetization plateau appears and two critical fields indicating the insulator-metal transitions at zero temperature emerge, which are closely related to the energy bands. Furthermore, the single-site entanglement entropy is a good indicator of quantum phase transitions. The temperature-field-induced phase diagram has also been attained, wherein the magnetization plateau state, the gapless phase and the spin polarized state are revealed. The temperature dependence of thermodynamic quantities such as the magnetization, susceptibility and specific heat are calculated to characterize the corresponding phases. It is also found that the up-spin and down-spin hole excitations are responsible for the thermodynamic properties.

A strong-focusing 800 MeV cyclotron for high-current applications

NASA Astrophysics Data System (ADS)

Pogue, N.; Assadi, S.; Badgley, K.; Comeaux, J.; Kellams, J.; McInturff, A.; McIntyre, P.; Sattarov, A.

2013-04-01

A superconducting strong-focusing cyclotron (SFC) is being developed for high-current applications. It incorporates four innovations. Superconducting quarter-wave cavities are used to provide >20 MV/turn acceleration. The orbit separation is thereby opened so that bunch-bunch interactions between successive orbits are eliminated. Quadrapole focusing channels are incorporated within the sectors so that alternating-gradient strong-focusing transport is maintained throughout. Dipole windings on the inner and outer orbits provide enhanced control for injection and extraction of bunches. Finally each sector magnet is configured as a flux-coupled stack of independent apertures, so that any desired number of independent cyclotrons can be integrated within a common footprint. Preliminary simulations indicate that each SFC should be capable of accelerating 10 mA CW to 800 MeV with very low loss and >50% energy efficiency. A primary motivation for SFC is as a proton driver for accelerator-driven subcritical fission in a molten salt core. The cores are fueled solely with the transuranics from spent nuclear fuel from a conventional nuclear power plant. The beams from one SFC stack would destroy all of the transuranics and long-lived fission products that are produced by a GWe reactor [1]. This capability offers the opportunity to close the nuclear fuel cycle and provide a path to green nuclear energy.

Optimum Guidance Law and Information Management for a Large Number of Formation Flying Spacecrafts

NASA Astrophysics Data System (ADS)

Tsuda, Yuichi; Nakasuka, Shinichi

In recent years, formation flying technique is recognized as one of the most important technologies for deep space and orbital missions that involve multiple spacecraft operations. Formation flying mission improves simultaneous observability over a wide area, redundancy and reconfigurability of the system with relatively small and low cost spacecrafts compared with the conventional single spacecraft mission. From the viewpoint of guidance and control, realizing formation flying mission usually requires tight maintenance and control of the relative distances, speeds and orientations between the member satellites. This paper studies a practical architecture for formation flight missions focusing mainly on guidance and control, and describes a new guidance algorithm for changing and keeping the relative positions and speeds of the satellites in formation. The resulting algorithm is suitable for onboard processing and gives the optimum impulsive trajectory for satellites flying closely around a certain reference orbit, that can be elliptic, parabolic or hyperbolic. Based on this guidance algorithm, this study introduces an information management methodology between the member spacecrafts which is suitable for a large formation flight architecture. Routing and multicast communication based on the wireless local area network technology are introduced. Some mathematical analyses and computer simulations will be shown in the presentation to reveal the feasibility of the proposed formation flight architecture, especially when a very large number of satellites join the formation.

Packed Planetary Systems

NASA Astrophysics Data System (ADS)

Barnes, R.; Greenberg, R.

2005-08-01

Planetary systems display a wide range of appearances, with apparently arbitrary values of semi-major axis, eccentricity, etc. We reduce the complexity of orbital configurations to a single value, δ , which is a measure of how close, over secular timescales ( ˜10,000 orbits), two consecutive planets come to each other. We measure this distance relative to the sum of the radii of their Hill spheres, sometimes referred to as mutual Hill radii (MHR). We determine the closest approach distance by numerically integrating the entire system on coplanar orbits, using minimum masses. For non-resonant systems, close approach occurs during apsidal alignment, either parallel or anti-parallel. For resonant pairs the distance at conjunction determines the closest approach distance. Previous analytic work found that planets on circular orbits were assuredly unstable if they came within 3.5 MHR (i.e. Gladman 1993; Chambers, Wetherill & Boss 1996). We find that most known pairs of jovian planets (including those in our solar system) come within 3.5 -- 7 MHR of each other. We also find that several systems are unstable (their closest approach distance is less than 3.5 MHR). These systems, if they are real, probably exist in an observationally permitted location somewhat different from the current best fit. In these cases, the planets' closest approach distance will most likely also be slightly larger than 3.5 MHR. Most pairs beyond 7 MHR probably experienced post-formation migration (i.e. tidal circularization, inward scattering of small bodies) which moved them further apart. This result is even more remarkable since we have used the minimum masses; most likely the systems are inclined to the line of sight, making the Hill spheres larger, and shrinking δ . This dense packing may reflect a tendency for planets to form as close together as they can without being dynamically unstable. This result further implies there may be a large number of smaller, currently undetectable companions packed in orbits around stars with known planets.

Design of relative trajectories for in orbit proximity operations

NASA Astrophysics Data System (ADS)

Opromolla, Roberto; Fasano, Giancarmine; Rufino, Giancarlo; Grassi, Michele

2018-04-01

This paper presents an innovative approach to design relative trajectories suitable for close-proximity operations in orbit, by assigning high-level constraints regarding their stability, shape and orientation. Specifically, this work is relevant to space mission scenarios, e.g. formation flying, on-orbit servicing, and active debris removal, which involve either the presence of two spacecraft carrying out coordinated maneuvers, or a servicing/recovery spacecraft (chaser) performing monitoring, rendezvous and docking with respect to another space object (target). In the above-mentioned scenarios, an important aspect is the capability of reducing collision risks and of providing robust and accurate relative navigation solutions. To this aim, the proposed approach exploits a relative motion model relevant to two-satellite formations, and developed in mean orbit parameters, which takes the perturbation effect due to secular Earth oblateness, as well as the motion of the target along a small-eccentricity orbit, into account. This model is used to design trajectories which ensure safe relative motion, to minimize collision risks and relax control requirements, providing at the same time favorable conditions, in terms of target-chaser relative observation geometry for pose determination and relative navigation with passive or active electro-optical sensors on board the chaser. Specifically, three design strategies are proposed in the context of a space target monitoring scenario, considering as design cases both operational spacecraft and debris, characterized by highly variable shape, size and absolute rotational dynamics. The effectiveness of the proposed design approach in providing favorable observation conditions for target-chaser relative pose estimation is demonstrated within a simulation environment which reproduces the designed target-chaser relative trajectory, the operation of an active LIDAR installed on board the chaser, and pose estimation algorithms.

The globe and orbit in Laron syndrome.

PubMed

Kornreich, L; Konen, O; Lilos, P; Laron, Z

2011-09-01

Patients with LS have an inborn growth hormone resistance, resulting in failure to generate IGF-1. The purpose of this study was to evaluate the size of the eye and orbit in LS. We retrospectively reviewed the MR imaging of the brain in 9 patients with LS for the following parameters: axial diameter of the globe, interzygomatic distance, perpendicular distance from the interzygomatic line to margins of the globe, medial-to-lateral diameter of the orbit at the anterior orbital rim, distance from the anterior orbital rim to the anterior globe, maximal distance between the medial walls of the orbits, lateral orbital wall angle, lateral orbital wall length, and mediolateral thickness of the intraorbital fat in the most cranial image of the orbit. All measurements were made bilaterally. Twenty patients referred for MR imaging for unrelated reasons served as control subjects. Compared with the control group, the patients with LS had a significantly smaller maximal globe diameter and shallower but wider orbits due to a shorter lateral wall, a smaller medial distance between the orbits, and a larger angle of the orbit. The ratio between the most anterior orbital diameter and the globe was greater than that in controls. The position of the globe was more anterior in relation to the interzygomatic line. Shallow and wide orbits and small globes relative to orbital size are seen in LS and may be secondary to IGF-1 deficiency.

View of Mission Control during Apollo 9 earth orbital mission

NASA Image and Video Library

1969-03-03

S69-26301 (March 1969) --- Overall view of the Mission Operations Control Room in the Mission Control Center, Building 30, during the Apollo 9 Earth-orbital mission. When this photograph was taken a live television transmission was being received from Apollo 9 as it orbited Earth.

Orbit determination error analysis and comparison of station-keeping costs for Lissajous and halo-type libration point orbits and sensitivity analysis using experimental design techniques

NASA Technical Reports Server (NTRS)

Gordon, Steven C.

1993-01-01

Spacecraft in orbit near libration point L1 in the Sun-Earth system are excellent platforms for research concerning solar effects on the terrestrial environment. One spacecraft mission launched in 1978 used an L1 orbit for nearly 4 years, and future L1 orbital missions are also being planned. Orbit determination and station-keeping are, however, required for these orbits. In particular, orbit determination error analysis may be used to compute the state uncertainty after a predetermined tracking period; the predicted state uncertainty levels then will impact the control costs computed in station-keeping simulations. Error sources, such as solar radiation pressure and planetary mass uncertainties, are also incorporated. For future missions, there may be some flexibility in the type and size of the spacecraft's nominal trajectory, but different orbits may produce varying error analysis and station-keeping results. The nominal path, for instance, can be (nearly) periodic or distinctly quasi-periodic. A periodic 'halo' orbit may be constructed to be significantly larger than a quasi-periodic 'Lissajous' path; both may meet mission requirements, but perhaps the required control costs for these orbits are probably different. Also for this spacecraft tracking and control simulation problem, experimental design methods can be used to determine the most significant uncertainties. That is, these methods can determine the error sources in the tracking and control problem that most impact the control cost (output); it also produces an equation that gives the approximate functional relationship between the error inputs and the output.

Gravitational waves from neutron star excitations in a binary inspiral

NASA Astrophysics Data System (ADS)

Parisi, Alessandro; Sturani, Riccardo

2018-02-01

In the context of a binary inspiral of mixed neutron star-black hole systems, we investigate the excitation of the neutron star oscillation modes by the orbital motion. We study generic eccentric orbits and show that tidal interaction can excite the f -mode oscillations of the star by computing the amount of energy and angular momentum deposited into the star by the orbital motion tidal forces via closed form analytic expressions. We study the f -mode oscillations of cold neutron stars using recent microscopic nuclear equations of state, and we compute their imprint into the emitted gravitational waves.

A Jupiter Orbiter mother/daughter spacecraft concept

NASA Technical Reports Server (NTRS)

Duxbury, J. H.

1975-01-01

The feasibility of a tandem launch of a mother/daughter spacecraft pair with a single launch vehicle for a 1981 Mariner Jupiter Orbiter mission is described. The mother is a close derivative of the three-axis stabilized Mariner Jupiter Saturn 1977 spacecraft with the addition of a Viking-type propulsion module for orbit capture; it concentrates on the planetology and satellite science objectives. The daughter is a small, simple spin-stabilized spacecraft taking advantage of the mother's transit and delivery capabilities; it obtains in-situ measurements of the surrounding planetary environment. A conceptual design of the daughter spacecraft is presented.

Migration of comets to the terrestrial planets

NASA Astrophysics Data System (ADS)

Ipatov, Sergei I.; Mather, John C.

2007-05-01

The orbital evolution of 30,000 objects with initial orbits close to those of Jupiter-family comets (JFCs) and also of 15,000 dust particles was integrated [1-3]. For initial orbital elements close to those of Comets 2P, 10P, 44P, and 113P, a few objects got Earth-crossing orbits with semi-major axes a<2 AU and aphelion distances Q<4.2 AU, or even got inner-Earth (Q<0.983 AU), Aten, or typical asteroidal orbits, and moved in such orbits for more than 1 Myr (up to tens or even hundreds of Myrs). Most of former trans-Neptunian objects that have typical near-Earth object (NEO) orbits moved in such orbits for Myrs, so during most of this time they were extinct comets. From a dynamical point of view, the fraction of extinct comets among NEOs can exceed several tens of percent, but, probably, many extinct comets disintegrated into mini-comets and dust during a smaller part of their dynamical lifetimes if these lifetimes were large. The probability of the collision of Comet 10P with the Earth during a dynamical lifetime of the comet was P[E]≈1.4•10-4, but 80% of this mean probability was due only to one object among 2600 considered objects with orbits close to that of Comet 10P. For runs for Comet 2P, P[E]≈(1-5)•10-4. For most other considered JFCs, 10-6 < P[E] < 10-5. For Comets 22P and 39P, P[E]≈ (1-2)•10-6; and for Comets 9P, 28P and 44P, P[E]≈(2-5)•10-6. For all considered JFCs, P[E]>4•10-6. The Bulirsh-Stoer method of integration and a symplectic method gave similar results. In our runs the probability of a collision of one object with the Earth could be greater than the sum of probabilities for thousands of other objects. The ratios of probabilities of collisions of JFCs with Venus and Mars to the mass of a planet usually were not smaller than that for Earth. For dust particles started from comets and asteroids, P[E ]was maximum for diameters d~100 μm. These maximum values of P [E] were usually (exclusive for 2P) greater at least by an order of magnitude than the values for parent comets. [1] Ipatov S.I. and Mather J.C. (2004) Annals of the New York Acad. of Sci., v. 1017, 46-65. [2] Ipatov S.I. et al. (2004) Annals of the New York Acad. of Sci., v. 1017, 66-80. [3] Ipatov S.I. and Mather J.C. (2006) Adv. in Space Res., v. 37, N 1, 126-137.

Investigation of conductive thermal control coatings by a contactless method in vacuo

NASA Technical Reports Server (NTRS)

Viehmann, W.; Shai, C. M.; Sanford, E. L.

1977-01-01

A technique for determining the conductance per unit area of thermal control coatings for electrostatically clean spacecraft is described. In order to simulate orbital conditions more closely, current-density-voltage (j-V) curves are obtained by a contactless method in which the paint on an aluminum substrate is the anode of a vacuum diode configuration with a tungsten filament cathode. Conductances per unit area which satisfy the International Sun Earth Explorer (ISEE) requirement were observed on black paints containing carbon and in white and green paints filled with zinc oxide which were fired in order to induce defect conductivity. Because of surface effects and the nonhomogeneous nature of paints, large discrepancies were found between measurements with the contactless method and measurements employing metallic contacts, particularly at low current densities. Therefore, measurements with metallic contacts are considered to be of questionable value in deciding the suitability of coatings for electrostatic charge control.

Determination and characterization of the Hubble Space Telescope pointing stability

NASA Technical Reports Server (NTRS)

Bradley, A. J.; Connor, C. T.; Del Toro, Y.; Andersen, G. C.; Bely, Pierre Y.; Decker, J.; Franz, O. G.; Wasserman, L. H.; Van Altena, William F.

1993-01-01

The Hubble Space Telescope (HST) was designed to maintian a pointing stability (jitter) of 0.007 arc seconds rms throughout every observing period, which can last from a few seconds to several orbits. On-orbit measurements indicate that the hardware excitation induced by the reaction wheels. gyros, high gain antennae, science instrument mechanisms and tape recorders are well within specifications. Unexpectedly, the solar arrays because the dominant source of jitter. Every passage through an orbital terminator produces vibrations which emanate from the solar arrays due to thermal effects, which affect the relative positional stability. Broadband frequencies centered about 0.11 and 0.65 Hz were detected in the frequency content of the vehicle jitter. On-board modifications to the control law have attenuated the disturbance torques and reduced the vehicle jitter close to specification. Replacement of the solar arrays in December, 1993, should eliminate the torque distubances. Astrometric science observations are extremely susceptible to corruption from vehicle jitter. The removal of vehicle jitter from astrometric Transfer function scans of binary stars is explained in detail. A binary star separation of 16 milli-seconds of arc has been achieved, a separation resolution of 10 to 12 milli-seconds of arc appears feasible, with a binary star magnitude of 9 m(sub V). The achievement of this resolution is in part due to vehicle jitter removal. Comparison of vehicle jitter measurements from the position path of the vehicle control law, or from the guiding Fine Guidance Sensors (FGS), are shown to be equivalent to approximately 0.001 arc second.

Determination and characterization of the Hubble Space Telescope pointing stability

NASA Astrophysics Data System (ADS)

Bradley, A. J.; Connor, C. T.; del Toro, Y.; Andersen, G. C.; Bely, Pierre Y.; Decker, J.; Franz, O. G.; Wasserman, L. H.; van Altena, William F.

The Hubble Space Telescope (HST) was designed to maintian a pointing stability (jitter) of 0.007 arc seconds rms throughout every observing period, which can last from a few seconds to several orbits. On-orbit measurements indicate that the hardware excitation induced by the reaction wheels. gyros, high gain antennae, science instrument mechanisms and tape recorders are well within specifications. Unexpectedly, the solar arrays because the dominant source of jitter. Every passage through an orbital terminator produces vibrations which emanate from the solar arrays due to thermal effects, which affect the relative positional stability. Broadband frequencies centered about 0.11 and 0.65 Hz were detected in the frequency content of the vehicle jitter. On-board modifications to the control law have attenuated the disturbance torques and reduced the vehicle jitter close to specification. Replacement of the solar arrays in December, 1993, should eliminate the torque distubances. Astrometric science observations are extremely susceptible to corruption from vehicle jitter. The removal of vehicle jitter from astrometric Transfer function scans of binary stars is explained in detail. A binary star separation of 16 milli-seconds of arc has been achieved, a separation resolution of 10 to 12 milli-seconds of arc appears feasible, with a binary star magnitude of 9 m(sub V). The achievement of this resolution is in part due to vehicle jitter removal. Comparison of vehicle jitter measurements from the position path of the vehicle control law, or from the guiding Fine Guidance Sensors (FGS), are shown to be equivalent to approximately 0.001 arc second.

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

NASA Technical Reports Server (NTRS)

Senent, Juan

2011-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2005-08-01

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

The structure of non-hierarchical triple system stability regions

NASA Astrophysics Data System (ADS)

Martynova, A. I.; Orlov, V. V.; Rubinov, A. V.

2009-08-01

A detailed study of the two-dimensional initial conditions region section in the planar three-body problem is performed. The initial conditions for the three well-known stable periodic orbits (the Schubart’s orbit, the Broucke’s orbit and the eight-like orbit) belong to this section. Continuous stability regions (for the fixed integration interval) generated by these periodic orbits are found. Zones of the quick stability violation are outlined. The analysis of some concrete trajectories coming from various stability regions is performed. In particular, trajectories possessing varying number of “eights” formed by moving triple system components are discovered. Orbits with librations are also found. The new periodic orbit originated from the zone siding with the Schubart’s orbit region is discovered. This orbit has reversibility points (each of the outer bodies possess a reversibility point) and two points of close double approach of the central body to each of the outer bodies. The influence of the numerical integration accuracy on the results is studied. The stability regions structure is preserved during calculations with different values of the precision parameter, numerical integration methods and regularization algorithms of the equations of motion.

Wind-accelerated orbital evolution in binary systems with giant stars

NASA Astrophysics Data System (ADS)

Chen, Zhuo; Blackman, Eric G.; Nordhaus, Jason; Frank, Adam; Carroll-Nellenback, Jonathan

2018-01-01

Using 3D radiation-hydrodynamic simulations and analytic theory, we study the orbital evolution of asymptotic giant branch (AGB) binary systems for various initial orbital separations and mass ratios, and thus different initial accretion modes. The time evolution of binary separations and orbital periods are calculated directly from the averaged mass-loss rate, accretion rate and angular momentum loss rate. We separately consider spin-orbit synchronized and zero-spin AGB cases. We find that the angular momentum carried away by the mass loss together with the mass transfer can effectively shrink the orbit when accretion occurs via wind-Roche lobe overflow. In contrast, the larger fraction of mass lost in Bondi-Hoyle-Lyttleton accreting systems acts to enlarge the orbit. Synchronized binaries tend to experience stronger orbital period decay in close binaries. We also find that orbital period decay is faster when we account for the non-linear evolution of the accretion mode as the binary starts to tighten. This can increase the fraction of binaries that result in common envelope, luminous red novae, Type Ia supernovae and planetary nebulae with tight central binaries. The results also imply that planets in the habitable zone around white dwarfs are unlikely to be found.

Integrated Simulation Design Challenges to Support TPS Repair Operations

NASA Technical Reports Server (NTRS)

Quiocho, Leslie J.; Crues, Edwin Z.; Huynh, An; Nguyen, Hung T.; MacLean, John

2006-01-01

During the Orbiter Repair Maneuver (OM) operations planned for Return to Flight (RTF), the Shuttle Remote Manipulator System (SRMS) must grapple the International Space Station (ISS), undock the Orbiter, maneuver it through a long duration trajectory, and orient it to an EVA crewman poised at the end of the Space Station Remote Manipulator System (SSRMS) to facilitate the repair of the Thermal Protection System (TPS). Once repair has been completed and confirmed, then the SRMS proceeds back through the trajectory to dock the Orbiter to the Orbiter Docking System. In order to support analysis of the complex dynamic interactions of the integrated system formed by the Orbiter, ISS, SRMS, and SSMS during the ORM, simulation tools used for previous nominal mission support required substantial enhancements. These upgrades were necessary to provide analysts with the capabilities needed to study integrated system performance. Prevalent throughout this ORM operation is a dynamically varying topology. In other words, the ORM starts with the SRMS grappled to the mated Shuttle/ISS stack (closed loop topology), moves to an open loop chain topology consisting of the Shuttle, SRMS, and ISS, and then, at the repair configuration, extends the chain topology to one consisting of the Shuttle, SMS, ISS, and SSRMS/EVA crewman. The resulting long dynamic chain of vehicles and manipulators may exhibit significant motion between the Shuttle worksite and the EVA crewman due to the system flexibility throughout the topology (particularly within the SRMS/SSRMS joints and links). Since the attachment points of both manipulators span the flexible structure of the ISS, simulation analysis may also need to take that into consideration. Moreover, due to the lengthy time duration associated with the maneuver and repair, orbital effects become a factor and require the ISS vehicle control system to maintain active attitude control. Several facets of the ORM operation make the associated analytical efforts different from previous mission support, including: (1) the magnitude of the SRMS handled payload (Le., Orbiter class), (2) the orbital effects induced on the integrated system consisting of the large Shuttle and ISS masses connected by a light flexible SRMS, (3) long duration environmental consequences due to the lengthy operational times associated with the maneuver and repair of the TPS, (4) active attitude control (as opposed to free drift) interacting with the SRMS and SSRMS manipulators (also due to the length of the maneuver and repair), (5) relative dynamics between the EVA crewman and thc worksite influenced by the extended flexible topology. In order to meet these analysis challenges, an O Msi mulation architecture was developed leveraging upon numerous pre-existing simulation elements to analyze the various subsystems individually. For example, core manipulator subsystem simulations for both the SRMS and SSRMS were originally combined to provide the dual-arm dynamics topology simulation (in the absence of orbital dynamics and vehicle control). This capability was later merged with the simulation used to analyze SRMS loading with a heavy payload in the orbital environment with an active payload control system (in this case, the ISS Attitude Control System (ACS)), configured for the ORM. The resulting worksite dynamics simulation, based off of the modified ORM simulation, provided the extended topological chain of vehicles and manipulators, while taking into account the orbital effects of both the Shuttle and ISS (as well as its ACS). Verification and validation (V&V) of these integrated simulations became a challenge in itself. A systematic approach needed to be developed such that integration simulation results could be tested against previous constituent simulations upon which these simulations were built. General V&V categories included: (1) core orbital state propagation, (2), stand-alone SRMS, (3) stand-alone SSRMS, (4) stand-alone ISS ACS, (5)ntegrated Shuttle, SRMS, ISS (with active ACS) in the orbital environment, and (5) dual-arm SRMS/SSRMS dynamics topology. Integrated simulation V&V run suites were created and correlated to verification runs from subsystem simulations, in order to establish the validity of the results. This paper discusses the simulation design challenges encountered while developing simulation capabilities to mirror the ORM operations. The paper also describes the incremental build approach that was utilized, starting with the subsystem simulation elements and integration into increasing more complex simulations until the resulting ORM worksite dynamics simulation had been assembled. Furthermore, the paper presents an overall integrated simulation V&V methodology based upon a subsystem level testing, integrated comparisons, and phased checkout.

Energy level diagrams for black hole orbits

NASA Astrophysics Data System (ADS)

Levin, Janna

2009-12-01

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

KSC-04pd1692

NASA Image and Video Library

2004-08-31

KENNEDY SPACE CENTER, FLA. - Workers in the Orbiter Processing Facility prepare to stow the landing gear on the orbiter Atlantis in preparation for the expected impact of Hurricane Frances on Saturday. Other preparations at KSC include powering down the Space Shuttle orbiters, and closing their payload bay doors. Workers are also taking precautions against flooding by moving spacecraft hardware off the ground and sandbagging facilities. The Orbiter Processing Facility is constructed of concrete and steel and was designed to withstand winds of 105 mph. The Vehicle Assembly Building is constructed of concrete and steel and was designed to withstand winds of 125 mph. Other payload and flight hardware support facilities can endure winds of 110 mph. Launch pads and the Payload Hazardous Servicing Facility can withstand 125-mph winds.

KSC-04pd1688

NASA Image and Video Library

2004-08-31

KENNEDY SPACE CENTER, FLA. - Workers in the Orbiter Processing Facility prepare the orbiter Atlantis and related equipment for the expected impact of Hurricane Frances on Saturday. Preparations at KSC include powering down the Space Shuttle orbiters, closing their payload bay doors and stowing their landing gear. They are also taking precautions against flooding by moving spacecraft hardware off the ground and sandbagging facilities. The Orbiter Processing Facility is constructed of concrete and steel and was designed to withstand winds of 105 mph. The Vehicle Assembly Building is constructed of concrete and steel and was designed to withstand winds of 125 mph. Other payload and flight hardware support facilities can endure winds of 110 mph. Launch pads and the Payload Hazardous Servicing Facility can withstand 125-mph winds.

KSC-04pd1693

NASA Image and Video Library

2004-08-31

KENNEDY SPACE CENTER, FLA. - Workers in the Orbiter Processing Facility prepare to stow the landing gear on the orbiter Atlantis in preparation for the expected impact of Hurricane Frances on Saturday. Other preparations at KSC include powering down the Space Shuttle orbiters, and closing their payload bay doors. Workers are also taking precautions against flooding by moving spacecraft hardware off the ground and sandbagging facilities. The Orbiter Processing Facility is constructed of concrete and steel and was designed to withstand winds of 105 mph. The Vehicle Assembly Building is constructed of concrete and steel and was designed to withstand winds of 125 mph. Other payload and flight hardware support facilities can endure winds of 110 mph. Launch pads and the Payload Hazardous Servicing Facility can withstand 125-mph winds.

On-orbit checkout of satellites, volume 2. Part 3 of on-orbit checkout study. [space maintenance

NASA Technical Reports Server (NTRS)

Pritchard, E. I.

1978-01-01

Early satellite failures significantly degrading satellite operations are reviewed with emphasis on LANDSAT D, the Technology Demonstration Satellite, the ATREX/AEM spacecraft, STORMSAT 2, and the synchronous meteorological satellite. Candidates for correction with on-orbit checkout and appropriate actions are analyzed. On-orbit checkout subsystem level studies are summarized for electrical power, attitude control, thermal control, reaction control and propulsion, instruments, and angular rate matching for alignment of satellite IRU.