THEMIS Extended Mission:

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THEMIS Extended Mission THEMIS
ARTEMIS Mission Design Concept (to be proposed
in Senior Review, Feb 21)
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P3,4,5, orbits for T3/D3/R3Separations gt0.5RE in
dR-dZ
Y
R3 (Year-round)
X
Z
P5
P3
P4
R3, GSE coords View from topdZ(P3-P5), as in
T3.Variable along-trackseparations
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P3,4,5 orbits for T4, D4, R4, T5Separations lt
0.5RE in dR-dZ
T4 (2011-05-10)T5 (2012-06-21)
D4 (2011-12-01)
Z
Z
1000km
Y
Y
X
T4 (and T5), GSE coords View from dawn along
NS dZ(P3-P5) 100-500km dR(P3-P4)1000km gt
dZ every day Apogee 12RE
X
D4, GSE coords dZ(P3-P5) 1000-3000kmdR(P3-P4)
1000km lt dZevery day Apogee12Re
R4 (at Dawn/dusk)
P5
P4
P3
R4, GSE coords View from topString-of-Pearls.V
ariable along-trackseparations 100km-2RE
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P3,4,5 prime maneuvers and deltaV
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Maneuvers/Operations THEMIS

• P3,4,5 have been maneuvered to close proximity
  before (coast-phase experience)
• Un-optimized string-of-pearls, but sufficient to
  build experience in clustering probes
• Orbits are stable and shadows benign
• Operations are anticipated to be standard, but
  could get numerous (trimming)
• Maneuver planning is rather complex (as complex
  as THEMIS prime)
• Contacted MMS and Cluster teams (Hughes/GSFC,
  Detlef Sieg/ESA)
• Careful orbit design to ensure science benefits
  is required and will start early
• Triangle (THEMIS) is easier than tetrahedron
  (Cluster) but orientation and scales are critical
• Like for the THEMIS prime mission, we need to
  make careful science, deltaV and operational
  complexity trades to obtain a balance between
  science and available resources
• The THEMIS P3,4,5 extended mission design builds
  on tremendous heritage in maneuver and orbit
  reconstruction operations and is expected to not
  necessitate additional operational tools except
  for additional science orbit optimization to
  ensure a balance between science and resources .

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Maneuvers/Operations ARTEMIS

• P1, P2 have sufficient fuel to raise apogee to
  the moon
• Easier to go up than down
• Lunar gravity perturbs orbits sufficiently to
  remove long shadows
• Probes need not stay any longer in Earth orbit
• Mission design and operations can become complex
  and expensive unless new target is found
• Use the moon as anchor to perform new tail and
  new Solar Wind science
• Permits exploration of a unique Lunar-Solar and
  Lunar-Tail environment like never done before
• Optimal use of de-orbit fuel (lunar re-entry)
• Design considerations for Lunar insertion, result
  in a robust mission
• Spin axis at ecliptic normal throughout mission
  optimal communications
• Equatorial Lunar orbit stable for many years
• After Lunar Orbit Insertion operations are
  routine
• A 24hr orbit guarantees
• Less than 3.5hr shadows, acceptable for probe
  design
• Familiar, low risk power, thermal and operations
  environment
• Mission design that satisfies above criteria is
  robust
• Under study by JPL since April 2005
• By same team which validated the THEMIS mission
  design in 2004-2005
• JPL review on 2007-Nov-02 found no technical
  issues

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ARTEMIS Acceleration, Reconnection, Turbulence
and Electrodynamics of the Moons Interaction
with the Sun
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ARTEMIS Selective Orbits
Phase I (Oct 09 Oct 10) - placement
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ARTEMIS Selective Orbits
Phase II (Oct 10 Jan 11) opposite
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ARTEMIS Selective Orbits
Phase II (Oct 10 Jan 11) opposite
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ARTEMIS Selective Orbits
Phase III (Jan 11 Apr 11) same side
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Phase III (Jan 11 Apr 11) same side
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Phase III (Jan 11 Apr 11) same side
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ARTEMIS Wake Crossings Phase II,III
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ARTEMIS Distant Wake CrossingsA Perspective
dB
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Phase IV (Apr 11 Sep 12) ARTEMIS After
Insertion
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ARTEMIS Wake Crossings
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ARTEMIS Mission Profile
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Trajectory Characteristics

• There are 2 spacecraft (P1 and P2) that need to
  go from Earth orbit to Lunar Lissajous orbits to
  Lunar orbit.
• Limited total ?V available (P1 300.0 m/s, P2
  448.5 m/s)
• A low-energy trajectory is used for the
  Trans-lunar trajectory leg.
• Spacecraft will be in orbit around opposing
  Lagrange points for 3 months.
• Spacecraft will be in orbit around the same
  Lagrange point for 2 months.
• Models and Assumptions
• Planetary bodies
• Point Bodies Sun and Moon
• Earth Including J2
• Deterministic, impulsive maneuvers

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Fuel summary P1,P2
P1
Total DV 205.22 m/s
P2
Total DV 297.19 m/s
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Fuel from inefficiencies P1,P2
Grand TotalP1 257m/s (have 300m/s)P2 363m/s
(have 450m/s)