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  • 1
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    A Non-Linear Approach to Spacecraft Trajectory Control in the Vicinity of a Libration Point (2001)
    In:  CASI
    Details
    Publication Date: 2017-09-27
    Description: An expanding interest in mission design strategies that exploit libration point regions demands the continued development of enhanced, efficient, control algorithms for station-keeping and formation maintenance. This paper discusses the development of a non-linear, station-keeping, control algorithm for trajectories in the vicinity of a libration point. The control law guarantees exponential convergence, based on a Lyaponov analysis. Controller performance is evaluated using FreeFlyer(R) and MATLAB(R) for a spacecraft stationed near the L2 libration point in the Earth-Moon system, tracking a pre-defined reference trajectory. Evaluation metrics are fuel usage and tracking accuracy. Simulation results are compared with a linear-based controller for a spacecraft tracking the same reference trajectory. Although the analysis is framed in the context of station-keeping, the control algorithm is equally applicable to a formation flying problem with an appropriate definition of the reference trajectory.
    Keywords: Spacecraft Design, Testing and Performance
    Type: 2001 Flight Mechanics Symposium; 15-24; NASA/CP-2001-209986
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Formation Control for the MAXIM Mission (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Over the next twenty years, a wave of change is occurring in the space-based scientific remote sensing community. While the fundamental limits in the spatial and angular resolution achievable in spacecraft have been reached, based on today s technology, an expansive new technology base has appeared over the past decade in the area of Distributed Space Systems (DSS). A key subset of the DSS technology area is that which covers precision formation flying of space vehicles. Through precision formation flying, the baselines, previously defined by the largest monolithic structure which could fit in the largest launch vehicle fairing, are now virtually unlimited. Several missions including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), and the Stellar Imager will drive the formation flying challenges to achieve unprecedented baselines for high resolution, extended-scene, interferometry in the ultraviolet and X-ray regimes. This paper focuses on establishing the feasibility for the formation control of the MAXIM mission. MAXIM formation flying requirements are on the order of microns, while Stellar Imager mission requirements are on the order of nanometers. This paper specifically addresses: (1) high-level science requirements for these missions and how they evolve into engineering requirements; and (2) the development of linearized equations of relative motion for a formation operating in an n-body gravitational field. Linearized equations of motion provide the ground work for linear formation control designs.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings from the 2nd International Symposium on Formation Flying Missions and Technologies; NASA/CP-2005-212781
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    NASA TECHNICAL REPORTS
  • 3
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    Expanding Hardware-in-the-Loop Formation Navigation and Control with Radio Frequency Crosslink Ranging (2007)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The Formation Flying Testbed (FFTB) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) provides a hardware-in-the-loop test environment for formation navigation and control. The facility continues to evolve as a modular, hybrid, dynamic simulation facility for end-to-end guidance, navigation, and control (GN&C) design and analysis of formation flying spacecraft. The core capabilities of the FFTB, as a platform for testing critical hardware and software algorithms in-the-loop, are reviewed with a focus on recent improvements. With the most recent improvement, in support of Technology Readiness Level (TRL) 6 testing of the Inter-spacecraft Ranging and Alarm System (IRAS) for the Magnetospheric Multiscale (MMS) mission, the FFTB has significantly expanded its ability to perform realistic simulations that require Radio Frequency (RF) ranging sensors for relative navigation with the Path Emulator for RF Signals (PERFS). The PERFS, currently under development at NASA GSFC, modulates RF signals exchanged between spacecraft. The RF signals are modified to accurately reflect the dynamic environment through which they travel, including the effects of medium, moving platforms, and radiated power.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings of the 20th International Symposium on Space Flight Dynamics; NASA/CP-2007-214158
    Format: application/pdf
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  • 4
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    Linear State-Space Representation of the Dynamics of Relative Motion, Based on Restricted Three Body Dynamics (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Precision Formation Flying is an enabling technology for a variety of proposed space-based observatories, including the Micro-Arcsecond X-ray Imaging Mission (MAXIM) , the associated MAXIM pathfinder mission, Stellar Imager (SI) and the Terrestrial Planet Finder (TPF). An essential element of the technology is the control algorithm, requiring a clear understanding of the dynamics of relative motion. This paper examines the dynamics of relative motion in the context of the Restricted Three Body Problem (RTBP). The natural dynamics of relative motion are presented in their full nonlinear form. Motivated by the desire to apply linear control methods, the dynamics equations are linearized and presented in state-space form. The stability properties are explored for regions in proximity to each of the libration points in the Earth/Moon - Sun rotating frame. The dynamics of relative motion are presented in both the inertial and rotating coordinate frames.
    Keywords: Spacecraft Design, Testing and Performance
    Type: AIAA Guidance and Control Conference; Aug 16, 2004 - Aug 19, 2004; Providence, RI; United States
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  • 5
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    A Non-Linear Approach to Spacecraft Formation Control in the Vicinity of a Collinear Libration Point (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: An expanding interest in mission design strategies that exploit libration point regions, demands the continued development of enhanced, efficient, control algorithms for station-keeping and formation maintenance. Linear control strategies have been developed for station-keeping. However, their region of stability is bounded by the assumptions required for linearizing the governing equations of motion. For example, reference [I] discusses the development of a linear control design for maintaining a halo orbit about the Earth-Moon L2 libration point. Trial runs indicated the trajectory was unstable for starting points exceeding 45,000 km from the L2 point. Also, there was significant growth in the control effort required to maintain the orbit as the nominal radius increased. This result is a consequence of the increased influence of the system non-linearities, as the trajectory deviated from the linearization point, L2. As an alternative, this paper presents the development of a non-linear control strategy, based on a Hamiltonian formulation of the equations of motion. The control strategy is applied to the problem of formation maintenance, rather than simple station
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: 2001 Astrodynamics Specialist Conference; Jul 30, 2001 - Aug 02, 2001; Quebec; Canada
    Format: text
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  • 6
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    Systems and methods for determining a spacecraft orientation (2004)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Disclosed are systems and methods of determining or estimating an orientation of a spacecraft. An exemplary system generates telemetry data, including star observations, in a satellite. A ground station processes the telemetry data with data from a star catalog, to generate display data which, in this example, includes observed stars overlaid with catalog stars. An operator views the display and generates an operator input signal using a mouse device, to pair up observed and catalog stars. Circuitry in the ground station then processes two pairs of observed and catalog stars, to determine an orientation of the spacecraft.
    Keywords: Spacecraft Instrumentation and Astrionics
    Format: application/pdf
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  • 7
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    Formation Control for the Maxim Mission. (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Over the next twenty years, a wave of change is occurring in the spacebased scientific remote sensing community. While the fundamental limits in the spatial and angular resolution achievable in spacecraft have been reached, based on today's technology, an expansive new technology base has appeared over the past decade in the area of Distributed Space Systems (DSS). A key subset of the DSS technology area is that which covers precision formation flying of space vehicles. Through precision formation flying, the baselines, previously defined by the largest monolithic structure which could fit in the largest launch vehicle fairing, are now virtually unlimited. Several missions including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), and the Stellar Imager will drive the formation flying challenges to achieve unprecedented baselines for high resolution, extended-scene, interferometry in the ultraviolet and X-ray regimes. This paper focuses on establishing the feasibility for the formation control of the MAXIM mission. The Stellar Imager mission requirements are on the same order of those for MAXIM. This paper specifically addresses: (1) high-level science requirements for these missions and how they evolve into engineering requirements; (2) the formation control architecture devised for such missions; (3) the design of the formation control laws to maintain very high precision relative positions; and (4) the levels of fuel usage required in the duration of these missions. Specific preliminary results are presented for two spacecraft within the MAXIM mission.
    Keywords: Earth Resources and Remote Sensing
    Type: 2nd International Symposium on Formation Flying Missions and Technologies; Sep 14, 2004 - Sep 16, 2004; Washington, DC; United States
    Format: text
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  • 8
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    A Nonlinear, Six-Degree of Freedom Precision Formation Control Algorithm, Based on Restricted Three Body Dynamics (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Precision Formation Flying is an enabling technology for a variety of proposed space-based observatories, including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), the associated MAXIM pathfinder mission, and the Stellar Imager. An essential element of the technology is the control algorithm. This paper discusses the development of a nonlinear, six-degree of freedom (6DOF) control algorithm for maintaining the relative position and attitude of a spacecraft within a formation. The translation dynamics are based on the equations of motion for the restricted three body problem. The control law guarantees the tracking error convergences to zero, based on a Lyapunov analysis. The simulation, modelled after the MAXIM Pathfinder mission, maintains the relative position and attitude of a Follower spacecraft with respect to a Leader spacecraft, stationed near the L2 libration point in the Sun-Earth system.
    Keywords: Aircraft Stability and Control
    Type: AAS 03-007 , AAS Guidance and Control Conference; Feb 05, 2003 - Feb 09, 2003; Breckenridge, CO; United States
    Format: application/pdf
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  • 9
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    Linear State-Space Representation of the Dynamics of Relative Motion, Based on Restricted Three Body Dynamics (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Precision Formation Flying is an enabling technology for a variety of proposed space- based observatories, including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), Stellar Imager (SI) and the Terrestrial Planet Finder (TPF). An essential element of the technology is the control algorithm, requiring a clear understanding of the dynamics of relative motion. This paper examines the dynamics of relative motion in the context of the Restricted Three Body Problem (RTBP). The natural dynamics of relative motion are presented in their full nonlinear form. Motivated by the desire to apply linear control methods, the dynamics equations are linearized and presented in state-space form. The stability properties are explored for regions in proximity to each of the libration points in the Earth/Moon - Sun rotating frame. The dynamics of relative motion are presented in both the inertial and rotating coordinate frames.
    Keywords: Numerical Analysis
    Type: AIAA/AAS GNC Conference and Exhibit; Aug 16, 2004 - Aug 19, 2004; Providence, RI; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    New Worlds Observer Formation Control Design Based on the Dynamics of Relative Motion (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The New Worlds Observer (NWO) mission is designed for the direct detection and characterization of extrasolar planets. The NWO mission concept employs a two spacecraft leader-follower formation on a trajectory around the Earth/Moon-Sun L(sub 2) Libration Point. The leader spacecraft is baselined as a 4 meter optical telescope. The follower, Starshade spacecraft, is designed to suppress light from a central body star permitting direct detection of a surrounding exoplanetary system. The current design requires a nominal leader-follower separation range of 72 Megameters. NWO poses many challenges including formation control. NWO cycles between three principal control modes during the nominal mission timeline: science (fine pointing), realignment and transition. This paper examines formation control strategies in the context of dynamics of relative motion for two spacecraft operating in the vicinity of the Earth/Moon-Sun L(sub 2)libration point. The paper presents an overview of the equations of relative motion followed by a discussion of each of the control modes. Discussion and analysis characterize control strategies for each of the mission control modes, including requirements, implementation challenges and project fuel budgets.
    Keywords: Lunar and Planetary Science and Exploration
    Type: AIAA Guidance, Navigation and Control Conference and Exhibit; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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