Dynamical Systems and Control in Celestial Mechanics and ...marsden/old/academics/...Jul 11, 2001...
Transcript of Dynamical Systems and Control in Celestial Mechanics and ...marsden/old/academics/...Jul 11, 2001...
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Control & Dynamical Systems
CA L T EC H
Dynamical Systems and Controlin Celestial Mechanics
and Space Mission Design
Jerrold E. MarsdenControl and Dynamical Systems, Caltechhttp://www.cds.caltech.edu/ marsden/
Wang Sang Koon (CDS), Martin Lo (JPL), Shane Ross (CDS)
SIAM meeting, San Diego, CA, Wednesday, July 11, 2001
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Introductory Remarks� Topics for discussion:� solar system dynamics (eg, dynamics of comets)
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Introductory Remarks� Topics for discussion:� solar system dynamics (eg, dynamics of comets)� the role of the three and four body problems
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Introductory Remarks� Topics for discussion:� solar system dynamics (eg, dynamics of comets)� the role of the three and four body problems� space mission trajectory design
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Introductory Remarks� Topics for discussion:� solar system dynamics (eg, dynamics of comets)� the role of the three and four body problems� space mission trajectory design• and the relationships between these topics
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Introductory Remarks� Some history:� 1700-1850 : Euler, Lagrange, Gauss, began to lay
the mathematical foundations� 1880-1890 : Poincare: fundamental work on the
3-body problem; creates the research area chaos� 1900-1965 : Moser, Conley, and others make fun-
damental contributions to the 3-body problem� 1965-present . Research in the 3 and 4 body prob-
lems and other topics in geometric mechanics andassociated applications continues by many people:by no means finished!
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Introductory Remarks�Current research importance� design of some NASA mission trajectories
—such as the Genesis Discovery Mission to belaunched July 30, 2001—EXCITING DAY!!
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Introductory Remarks�Current research importance� design of some NASA mission trajectories
—such as the Genesis Discovery Mission to belaunched July 30, 2001—EXCITING DAY!!
� of current astrophysical interest for understandingthe transport of solar system material (eg, how dopieces of Mars get to the Earth, etc)
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Introductory Remarks�Current research importance� design of some NASA mission trajectories
—such as the Genesis Discovery Mission to belaunched July 30, 2001—EXCITING DAY!!
� of current astrophysical interest for understandingthe transport of solar system material (eg, how dopieces of Mars get to the Earth, etc)
�Acknowledgements◦ the Genesis team, the groups of Kathy Howell (Purdue), Michael
Dellnitz (Paderborn), Linda Petzold (UC Santa Barbara), GerardGomez, Josep Masdemont, Carles Simo (the Barcelona group),etc.
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Dynamical Orbits� Some dynamical systems concepts� Simple pendulum� three kinds of orbits:• oscillating orbits• running orbits• special separating orbits
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Dynamical Orbits� Some dynamical systems concepts� Simple pendulum� three kinds of orbits:• oscillating orbits• running orbits• special separating orbits
� Via F = ma, can visualize solutions as trajectoriesin the (θ, θ) plane (θ is the angle of the pendulumfrom the vertical downward position)
� the resulting phase portrait allows one to put to-gether the basic orbits in one figure:
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Dynamical Orbits
connecting (homoclinic) orbit
saddlepoint
upright pendulum (unstable point)
downward pendulum (stable point)
θ = pendulum angle
θ = velocity•
Phase portrait of the simple pendulum6
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Invariant Manifolds�Higher dimensional analog of the invariant curves
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Invariant manifolds7
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Periodic Orbits� Can replace equilibria by periodic orbits:
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������ ���� �� � ����� � �� � ���� ��� ���� ��� �����
Invariant manifolds attached to a periodic orbit
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Three body problem�General Three Body Problem
� Three bodies move under mutual gravitational inter-action
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Three body problem�General Three Body Problem
� Three bodies move under mutual gravitational inter-action
� Some interesting new orbits discovered in the lastfew years by Richard Montgomery, Alain Chenciner,Carles Simo. Movies by Randy Paffenroth (Caltech)generated using AUTO
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Three body problem
Figure 8 Orbits: 3-body-figure-8.qt
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Three body problem
Fancy Orbit A: 3-body-exoticA.qt
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Three body problem
Fancy Orbit B: 3-body-exoticB.qt
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Three body problem�Restricted Circular Problem
� the two primaries move in circles; the smaller thirdbody moves in the field of the primaries (without af-fecting them); view the motion in a rotating frame
�we consider the planar and the spatial problems
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Three body problem�Restricted Circular Problem
� the two primaries move in circles; the smaller thirdbody moves in the field of the primaries (without af-fecting them); view the motion in a rotating frame
�we consider the planar and the spatial problems
� there are places of balance; eg, a point between thetwo bodies where the attraction balances
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Three body problem�Restricted Circular Problem
� the two primaries move in circles; the smaller thirdbody moves in the field of the primaries (without af-fecting them); view the motion in a rotating frame
�we consider the planar and the spatial problems
� there are places of balance; eg, a point between thetwo bodies where the attraction balances
� There are five such equilibrium points:• Three collinear (Euler,1750) on the x-axis—L1, L2, L3
• Two equilateral points (Lagrange,1760)—L4, L5.
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Three body problem
-1 -0.5 0 0.5 1
-1
-0.5
0
0.5
1
x (nondimensional units, rotating frame)
y (n
ondi
men
sion
al u
nits
, rot
atin
g fr
ame)
mS = 1 - µ mJ = µ
S J
Jupiter's orbit
L2
L4
L5
L3 L1
comet
Equilibrium points for the three body problem
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Three body problem� if a spacecraft is at L1 or at L2, it will stay there
� one can go into orbit about the L1 and L2 points,even though there is no material object there!
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Three body problem� if a spacecraft is at L1 or at L2, it will stay there
� one can go into orbit about the L1 and L2 points,even though there is no material object there!
� some of these orbits are called Liapunov orbits , oth-ers are called halo and Lissajous orbits .
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Three body problem� if a spacecraft is at L1 or at L2, it will stay there
� one can go into orbit about the L1 and L2 points,even though there is no material object there!
� some of these orbits are called Liapunov orbits , oth-ers are called halo and Lissajous orbits .
� just as in the pendulum, one can draw the invariantmanifolds associated to L1 (and L2) and the periodicorbits surrounding them.
� these invariant manifolds play a key role in whatfollows
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Three body problem
-10 -8 -6 -4 -2 0 2 4 6 8 10-10
-8
-6
-4
-2
0
2
4
6
8
10
x (AU, Sun-Jupiter rotating frame)
y (A
U, S
un-J
upite
r ro
tatin
g fr
ame)
L4
L5
L2L1L3 S J
Jupiter's orbit Jupiter
Invariant manifolds for the 3-body problem16
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Three body problem◦ consider the planar case; the spatial case is similar
◦ Kinetic energy (wrt inertial frame) in rotating coordinates:
K(x,y, x, y) = 12
[(x −ωy)2 + (y +ωx)2
]
◦ Lagrangian is K.E. − P.E., given by
L(x,y, x, y) = K(x,y, x, y)− V(x,y); V(x,y) = −1− µr1
− µr2.
◦ Euler-Lagrange equations:
x − 2ωy = −∂Vω∂x
, y + 2ωx = −∂Vω∂y
where the effective potential is
Vω = V −ω2(x2 +y2)
2.
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Three body problem� Effective potential• In the circular planar restricted three body problem, and
in a rotating frame, the equations for the third body arethose of a particle moving in an effective potential plus amagnetic field (goes back to work of Jacobi, Hill, etc)
S J
Effective Potential Level set shows the Hill region
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Three body problem� Invariant Manifolds of Periodic Orbits
� red = unstable, green = stable
0.820.84
0.860.88
0.90.92
0.940.96
0.981
1.02−0.02
0
0.02
0.04
0.06
0.08
0.1−0.010
0.01
x
z
y
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Three body problem� These manifold tubes play a crucual role in what
passes through the resonance (transit orbits)
� and what bounces back (non-transit orbits)
� transit possible if you are “inside” the tube, otherwisenontransit—important for transport issues
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Comet Oterma�we consider the historical record of the orbit of comet
Oterma from 1910 to 1980• first in an inertial frame (fixed relative to the stars)• and then a rotating frame• very special case of pattern evocation
� similar pictures for many other comets
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Comet Oterma
oterma-inertial.qt
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Comet Oterma
oterma-rotating.qt
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Genesis Discovery Mission�Mission Purpose: To gather solar wind samples and
to return them to Earth for analysis
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Genesis Discovery Mission�Mission Purpose: To gather solar wind samples and
to return them to Earth for analysis
�Mission Constraints/Features:• Return in Utah during the daytime• Descend with a parachute for a helicopter snatch• lunar swingby contingency in case of bad weather• Energy efficient (small thrust required): makes use of
the dynamical sensitivity to design a low-cost trajectory
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Genesis Discovery Mission
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Genesis Discovery Mission
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Genesis Discovery Mission�Mission Trajectory
� Four phases:
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Genesis Discovery Mission�Mission Trajectory
� Four phases:1. from low Earth orbit, insertion onto an L1 halo orbit
stable manifold
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Genesis Discovery Mission�Mission Trajectory
� Four phases:1. from low Earth orbit, insertion onto an L1 halo orbit
stable manifold2. using saddle point controllers, remain on the halo orbit
for about 2 years (4 revolutions)
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Genesis Discovery Mission�Mission Trajectory
� Four phases:1. from low Earth orbit, insertion onto an L1 halo orbit
stable manifold2. using saddle point controllers, remain on the halo orbit
for about 2 years (4 revolutions)3. return to a near halo orbit around L2 via a near hetero-
clinic connection
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Genesis Discovery Mission�Mission Trajectory
� Four phases:1. from low Earth orbit, insertion onto an L1 halo orbit
stable manifold2. using saddle point controllers, remain on the halo orbit
for about 2 years (4 revolutions)3. return to a near halo orbit around L2 via a near hetero-
clinic connection4. return to Earth on an impact orbit (guided by the un-
stable manifold of a halo orbit around L2).
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Genesis Discovery Mission�Mission Trajectory
� Four phases:1. from low Earth orbit, insertion onto an L1 halo orbit
stable manifold2. using saddle point controllers, remain on the halo orbit
for about 2 years (4 revolutions)3. return to a near halo orbit around L2 via a near hetero-
clinic connection4. return to Earth on an impact orbit (guided by the un-
stable manifold of a halo orbit around L2).
� Final trajectory computation takes into account allthe major bodies in the solar system.
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Genesis Discovery Mission
0
500000
z (k
m)
-1E+06
0
1E+06
x (km)
-500000
0
500000
y (km)
Moon's orbit
Earth
Halo orbit
Genesis trajectory
The Genesis trajectory28
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Genesis Discovery Mission
0 0.5 1 1.5 2 2.5 3
x 106
6
4
2
< SUN
L1EARTH
LUNAR ORBIT
RETURN PARKING ORBIT
HETEROCLINICRETURN ORBIT
L2*0
2
4
6
8
GENESIS TRAJECTORY IN ROTATING COORDINATESx 10
5
View of the Genesis trajectory in the plane
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Genesis Discovery Mission
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0.985 0.99 0.995 1 1.005 1.01 1.015
-0.01
-0.005
0
0.005
0.01
y (A
U, S
un-E
arth
Rot
atin
g Fr
ame)
x (AU, Sun-Earth Rotating Frame)
L1
(b)
y (A
U, S
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arth
Rot
atin
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ame)
x (AU, Sun-Earth Rotating Frame)(a)
L2EarthSun
Earth
Forbidden Region
Forbidden Region
HeteroclinicConnection
L2 Homoclinic Orbit
L1 Homoclinic Orbit
Genesis orbit and the Sun-Earth dynamical structure
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Genesis Discovery Mission� Some planet-impacting asteroids use invariant man-
ifolds as a pathway from nearby heliocentric orbits.This phenomena has been observed in the impact ofcomet Shoemaker-Levy 9 with Jupiter.
� Some NEO’s are subject to similar dynamics and arethe most dangerous ones; perhaps the KT impactevent was one of these too!
� These ideas apply to any planet or moon system!
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Lunar Missions� in 1991, the Japanese mission, Muses-A, was given
new life with a radical new mission concept & re-named the Hiten Mission
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Lunar Missions� in 1991, the Japanese mission, Muses-A, was given
new life with a radical new mission concept & re-named the Hiten Mission
� the mission was “saved” by finding a more fuel effi-cient pathway to the moon (Miller and Belbruno)
� now a deeper understanding of this is emerging
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Lunar Missions� in 1991, the Japanese mission, Muses-A, was given
new life with a radical new mission concept & re-named the Hiten Mission
� the mission was “saved” by finding a more fuel effi-cient pathway to the moon (Miller and Belbruno)
� now a deeper understanding of this is emerging
�we approach this problem by• systematically implementing the view that the Sun-
Earth-Moon-Spacecraft 4-body system can be modelledas two coupled 3-body systems
• and using invariant manifold ideas
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Lunar Missions� Idea: put two Genesis-type trajectories together;
we transfer from• the Sun-Earth-spacecraft system to• the Earth-Moon-spacecraft system
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Lunar Missions� Idea: put two Genesis-type trajectories together;
we transfer from• the Sun-Earth-spacecraft system to• the Earth-Moon-spacecraft system
� 20% more fuel efficient than the Hohmann transfer(accelerate to an ellipse that reaches to the Moon,accelerating to catch the moon, then circularize).
� But : takes longer (6 months as opposed to 5 days).[OK for cargo ships, but not human missions]
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Lunar Missions� Idea: put two Genesis-type trajectories together;
we transfer from• the Sun-Earth-spacecraft system to• the Earth-Moon-spacecraft system
� 20% more fuel efficient than the Hohmann transfer(accelerate to an ellipse that reaches to the Moon,accelerating to catch the moon, then circularize).
� But : takes longer (6 months as opposed to 5 days).[OK for cargo ships, but not human missions]
� Fuel savings and the time of flight in other missions(eg, to Jupiter’s moon’s) is more dramatic
� Schematic of the idea33
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Lunar Missions
0.996 0.998 1 1.002 1.004 1.006 1.008 1.01 1.012
-0.008
-0.006
-0.004
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0.002
0.004
0.006
0.008
x
y
Earth
energeticallyinaccessible
region
Sun
Moon
periodic orbitaround the Sun-Earth L2
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Lunar Missions
shootthemoon-inertial.qt
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Lunar Missions
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Jovian Lunar Tour�Construction of new trajectories that visit the
Jovian system.
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Jovian Lunar Tour�Construction of new trajectories that visit the
Jovian system.� Example 1: Europa → Io → Jupiter collision
1. Begin tour2. Europa encounter3. Jump between tubes4. Io encounter5. Collide with Jupiter
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Jovian Lunar Tour� Strategy:
� use burns (controls) that enable a transfer from onethree body system to another• from the Jupiter-Europa-spacecraft system to• the Jupiter-Io-spacecraft system
� this strategy is similar to that used in the lunar mis-sions together with some symbolic dynamics
� trajectories do well on fuel savings
� here is a close-up of the Io encounter
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Jovian Lunar Tour
1
1.02
1.04 – 0.010
0.01x
z
y
Close-up of the Io encounter
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Jovian Lunar Tour� Example 2: Ganymede → Europa → orbit in-
jection around Europa
pgt-3d-movie-inertial.qt
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Jovian Lunar Tour
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Jovian Lunar Tour
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Uses of Optimal Control�Halo Orbit Insertion
� After launch, the Genesis Discovery Mission will getonto the stable manifold of its eventual periodic orbitaround L1
� Errors in, eg, launch velocity, means that there mustbe corrective manouvers
� The software COOPT is very useful in determining thenecessary corrections (burn sizes and timing) system-atically for a variety of launch conditions
� It gets one onto the orbit at the right time, whileminimizing fuel (what is being optimized)
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Uses of Optimal Control� A number of unusual features, such as the nature of
the boundary conditions
� A very nice mixture of dynamical systems (providingguidance and first guesses) and optimal control
� See the talk of Linda Petzold in the satellite dynamicsminisymposium (work with Radu Serban, Martin Lo,Wang Sang Koon, JEM and Shane Ross)
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Uses of Optimal Control
hoi
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Uses of Optimal Control� Satellite reconfiguration, stationkeeping and de-
configuration
� This application makes use of the software NTG (Non-linear Trajectory Generation) developed at Caltech
�Details were in the minisymposium talk: Richard Mur-ray (together with Mark Milam and Nicolas Petit)
� This involves near Earth spacecraft clusters
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Uses of Optimal Control�Why clusters?� Clusters can achieve the same resolution as a large
telescope using vision systems coordinated in soft-ware and modern optics
� coordinated clusters can obtain unprecedented res-olution for both Earth-pointing systems and thosepointing into deep space
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Uses of Optimal Control� Two basic problems
� Formation maintenance: keep the satellites in rela-tive position–use small controls
� Formation changes: get the formation as a whole toreposition itself for the next task—use larger controls
� Especially for reconfiguration, one wants to dothis optimally (again, minimize fuel)
�Handles constraints , such as imaging and communi-cation constraints very nicely
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Uses of Optimal Control
Formation maintenance with guaranteed Earth coverage.
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Formation Flying Methodology�Active Formation Methodology
� Passive Formation Methodology
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Stationkeeping
Stationkeeping
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Reconfiguration
Reconfiguration
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Deconfiguration
Deconfiguration
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Terrestrial Planet Finder�Goal : probe for Earth-like planets using a large base-
line group of satellites–this time a deep space cluster�Orbiting around L2 is a candidate position: away from
the Earth.
� Each halo orbit is surrounded by a torus that providesa natural dynamical formation
� Very nice visualizations of this by Ken Museth, Mar-tin Lo and Al Barr; see Martin’s talk in the satelliteminisymposium
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Terrestrial Planet Finder
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Getting to TPF and Beyond� The L1 Gateway Station
� A gateway at the Earth-Moon L1 point is of interestas a semi-permanent manned site .
� Can be used for going to the moon, servicing TPFand possibly for missions to other planets.
� Efficient transfers can be created using the 3-bodyand invariant manifold techniques that our group hasdeveloped
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Getting to TPF and Beyond
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Getting to TPF and Beyond
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Getting to TPF and Beyond
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More Information� http://www.cds.caltech.edu/˜marsden/
http://www.cds.caltech.edu/˜koon/� email: [email protected]� two of the main publications:
• Koon, W. S., M. Lo, J. E. Marsden and S. Ross [2000], Het-eroclinic Connections between periodic orbits and reso-nance transitions in celestial mechanics, Chaos, 10, 427–469.
• Serban, R, W.S. Koon, M.W. Lo, J.E. Marsden, L.R. Petzold,S.D. Ross and R.S. Wilson [2001], Halo Orbit Mission Cor-rection Maneuvers Using Optimal Control , Automatica, toappear.
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The End
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