THEMIS Science Requirements

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• THEMIS Science Requirements
• Dr. Vassilis Angelopoulos
• Principal Investigator
• Space Sciences Laboratory
• University of California, Berkeley

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THEMIS primary objectives
Understand substorm onset and evolution (baseline
mission, primary objective) As a minimum Where
does substorm eruption start? (ionosphere, CD, Rx
?).
Themis overcomes Meridional onset confinement
(GBOs) Mapping distortions (in situ
probes) Global timing (GBOs-probes)
SOLARWIND
Aurora
MAGNETOSPHERE
EQUATORIAL PLANE
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Events that comprise the substorm
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Distinguishes among competing models impartially
answers a well-posed question

• Primary Objectives, Goals and Means
• Onset and evolution of substorms
• Time History of Events (Onset)
• Delineate cause and effect
• Measure When?Where
• and Macroscale Interactionsduring Substorms
  (Evolution)
• Coupling in the magnetosphere
• Measure plasma flows and waves
• Coupling to the ionosphere
• Measure currents and structures

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Mission elements
Probe conjunctions along Sun-Earth line recur
once per 4 days over North America.
Ground based observatories completely cover North
American sector determine auroral breakup within
1-3s
while THEMISs space-based probes determine
onset of Current Disruption and Reconnection each
within lt10s.
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First bonus What producesstorm-time killer
MeV electrons?
Affect satellites and humans in space
ANIK telecommunicationsatellites lost for days
to weeksduring space storm

• Source
• Radially inward diffusion?
• Wave acceleration at radiation belt?
• THEMIS
• Tracks radial motion of electrons
• Measures source and diffusion
• Frequent crossings
• Measures E, B waves locally

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Second bonus What controls efficiencyof solar
wind magnetosphere coupling?

• Important for solar wind energy transfer in
  Geospace
• Need to determine how
• Localized pristine solar wind features
• interact with magnetosphere
• THEMIS
• Alignments track evolution of solar wind
• Inner probes determine entry type/size

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Mission Science Objectives in a Nutshell
CSR, Table E-1
Minimum mission
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Ground Rules
Mission Level Science Adherence to
requirement Minimum mission Primary Performanc
e floor Primary Design driver Ancillary
(HF modes) Design goal Baseline mission Secondary
(Rad Belt) Design goal Tertiary (Dayside) Des
ign goal Extended mission 3rd year baseline
orbits At negligible impact if on target Phase F
mission 4th, 5th year shock/pause At negligible
impact if on target
Explicitlyincluded In Level1 Reqs