l12_ff2_resizing

l12_ff2_resizing - Minimum Energy Trajectories for Techsat...

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Minimum Energy Trajectories for Minimum Energy Trajectories for Techsat Techsat 21 21 Earth Orbiting Clusters Earth Orbiting Clusters Edmund M. C. Kong SSL Graduate Research Assistant Prof David W. Miller Director, MIT Space Systems Lab Space 2001 Conference & Exposition Albuquerque August 28-30, 2001
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Space Systems Laboratory Massachusetts Institute of Technology Objective and Outline Objective and Outline Objective : To determine the optimal trajectories to re- orient a cluster of spacecraft Motivation : To maximize the full potential of a cluster of spacecraft with minimal resources Presentation Outline Techsat 21 Overview Optimal Control Formulation Equations of Motions (Dynamics) Propulsion System (Cost) LQ Formulation Terminal Constraints Results Tolerance setting Cluster Initialization Cluster Re-sizing (Geolocation) Future Work Conclusions
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Space Systems Laboratory Massachusetts Institute of Technology Techsat Techsat 21 21 To explore the technologies required to enable a Distributed Satellite System Sparse Aperture Space Based Radar Full operational system of 35 clusters of 8 satellites to provide global coverage 2003 Flight experiment with 3 spacecraft Spacecraft will be equipped with Hall Thrusters Techsat 21 Flight Experiment Number of Spacecraft : 3 Spacecraft Mass : 129.4 kg Cluster Size : 500 m Orbital Altitude : 600 km Orbital Period : 84 mins 2 large thrusters for orbit raising and de-orbit 10 micro-thrusters for full three- axis control Geo-location size : 5000 m * Figure courtesy of AFOSR Techsat21 Research Review (29 Feb - 1 Mar 2000)
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Space Systems Laboratory Massachusetts Institute of Technology Equations of Motions Equations of Motions First order perturbation about natural circular Keplerian orbit Modified Hill’s Equations: ( ) ( ) ( ) 2 2 2 5 2 2 2 x y z a x c n x nc y a y nc x a z k z = = + = + && & && & && cos( 1 ) 2 1 sin( 1 ) 1 2 1 cos( ) 1 o o o x A nt s s y A nt s s s z A kt s = + = − + = − Possible trajectory for Techsat 21: -400 -200 0 200 400 -400 -200 0 200 400 -400 -200 0 200 400 Velocity Vector Elliptical Trajectory Projected Circle 2x1 Ellipse Cross Axis Zenith-Nadir ( ) 2 2 2 3 1 3cos 2 8 e ref ref J R s i r = + where 1 c s
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