Geospace Electrodynamic Connections (GEC) Mission

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Geospace Electrodynamic Connections (GEC) Mission

• The GEC mission has been in the formulation phase
  as part of NASAs Solar Terrestrial Probe program
  for nearly 5 years. It is to be launched after
  the Magnetosphere Multiscale Mission. It is a
  challenging multi-satellite mission of 3
  spacecraft with each spacecraft carrying
  sufficient propulsion fuel to make extensive deep
  dipping campaigns to the lower boundary of outer
  space. This is where the neutral atmosphere
  begins to play the dominant role in the
  dissipation of magnetosphere energy and in the
  creation of electric currents that close the
  magnetosphere current network. The three
  spacecraft will be launched from a single launch
  vehicle into high inclination, 2000X 200 km
  orbits (i.e., a pearls-on-a-string
  configuration). They will have the capability to
  change orbit separations to study multiple scaled
  structures. They also will have the exciting
  capability to dip to 130 km or lower, in
  coordinated campaigns with ground based
  measurements, to explore for the first time in
  situ the electrodynamic connections of the
  atmosphere to the magnetosphere.
• The spacecraft, identically instrumented, will
  measure the ionosphere/atmosphere composition,
  temperatures and concentrations, magnetic and
  electric field and energetic particle
  distributions, providing a complete picture of
  the underlying physics. Focused, deep dipping
  campaigns (e.g., over a radar station, or in the
  auroral region) will measure the atmospheres
  impact on the electrodynamics as a function of
  altitude. This will lead to complete
  understanding of how the collisionally-coupled
  charged and neutral particle constituents in the
  ionosphere- thermosphere boundary layer respond
  to electromagnetic inputs from space. With its
  multiple spacecraft, the mission will determine
  how the spatial variations and persistence of the
  electrodynamic drivers relate to the neutral
  responses. And importantly, by making
  measurements of both the field and particle
  distributions it can be determined how the
  responses evolve and feed back on the
  magnetosphere drivers.

• Current understanding of the effect of the solar
  wind on planetary atmosphere environments is at
  the point where complex, multi-scaled phenomena
  are recognized to be key elements of the
  interactions. To understand these effects in
  situ measurements from multi-satellite missions
  are the only viable approaches. This holds also
  for the exploration of the lower boundary of
  geospace and, coining an analogous term, the
  lower boundary of planetospace for other
  planetary bodies. These upper atmosphere/lower
  ionosphere regions, are where ultimately the
  energy and momentum of the solar wind are
  converted into atmospheric energy and momentum
  and where horizontal electric currents complete
  the circuits generated by the solar wind
  interaction.
• GECs goal to penetrate deep into the Earths
  upper atmosphere and to explore for the first
  time with in situ measurements the complexity of
  the transition of Earths upper atmosphere to
  outer space, is of paramount value to both NASAs
  science and exploration initiatives. Besides the
  technical experience and knowledge it will gather
  by penetrating and gathering ambient measurements
  in a region with large aerodynamic torques and
  consequent heating of the spacecraft, it will
  also provide first-hand information on the
  atmosphere-plasma interactions that are the final
  low-altitude links in the dynamical coupling of
  the Suns solar wind to planetary atmospheres.
  From a Space Weather perspective this region
  includes the electrical currents and atmospheric
  perturbations that affect terrestrial
  ground-based power systems, radio communication
  and satellite drag. The same basic processes
  occur in other planetary atmospheres. A mission
  dedicated to providing comprehensive in situ
  measurements in the region where the neutral
  atmosphere begins to take preeminent control of
  the plasma dynamics and with multiple spacecraft
  to separate the spatial/temporal scales, has yet
  to be flown. GEC will fulfill this role.
• For GEC Science Definition Team Report and recent
  update see
• http//stp.gsfc.nasa.gov/missions/gec/gec.htm

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Geospace Electrodynamic Connections (GEC)
Science Objectives Determine how the
collisionally coupled charged and neutral
atmospheric constituents in the
ionosphere/thermosphere boundary layer respond
to electromagnetic inputs imposed from
space. Determine how the spatial variations
and persistence of the electrodynamic drivers
relate to the neutral atmosphere
responses Delineate how, and under what
conditions the responses evolve and feed back
on the drivers Mission Description (Launch next
decade) Example Mission Design - 3
identical spacecraft pearls-on- a-string
configuration - Delta II Launch (3000 kg total
to 2000 km X 200 k, 83 degree inclination
orbits) - Each spacecraft carries fuel
(100kg) for extensive deep dipping
campaigns to lt130 km and for changing orbit
separations - Two year baseline
mission Flight System Concept - Electr
omagnetically clean spacecraft - Aerodynamic
design - Three axis stabilized, ram facing
instrument platform Measurement
Strategy Measure, in situ, the
motion,temperature and composition of
the ionosphere and neutral atmosphere, the
energetic particle distributions and the
electric/magnetic fields. Have coordinated
dipping campaigns of all spacecraft to 130 km or
lower to determine altitude effects of neutral
atmosphere on the dynamics. Change relative
spacings of spacecraft to study key
spatial- temporal scales.

• Enhancing Technology Development
• No engineering show-stoppers
• Formation Flying
• Enhanced propulsion efficiency
• Aerodynamic Spacecraft design
• Light weight,low cross-seciton E-field booms
• Momentum unloading system that minimally affects
  the measurements.