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GEC
TECHNOLOGY
GEC consists of multiple dipping spacecraft with planned
changes in their spatial separations and with excursions
down into the dense edge of the Earth’s atmosphere where
atmospheric drag introduces a variable effect on the spacecraft.
Precise formation flying and accurate control of the locations
of the science measurements is necessary. This will entail
the utilization of improvements in navigation (particularly
inter-spacecraft ranging and direction), inter-spacecraft
communications and autonomous operations. Efficient aerodynamic
structures, lightweight structures and instruments, and maximally
efficient power systems will be needed to minimize system
resources and to maximize instrument duty cycles. This is
especially important because of the dipping requirements
and orbital configuration changes, which require the use
of large amounts of propulsion fuel and stringent attitude
control.
PRELIMINARY
SPACECRAFT DESIGN
While new technologies are not required to perform the basic
mission, there are new technologies that can be adapted
to the GEC mission that could significantly increase the
mass and power margins, improve measurement performance and
reduce risk. This will translate to additional instrument
capability and reduced spacecraft cost. Technologies currently
being explored include aerodynamic trim tabs, integrated
power and attitude control system (IPACS), lightweight electric
field instrument booms, electrically conductive solar arrays
and atomic oxygen resistant material.
MEASURMENTS
Measurements are needed of the concentrations of all relevant
IT constituents, their temperatures and velocities, the local
electric and magnetic fields and the energetic particle distributions.
The core measurements will be made by in situ measuring sensors.
To provide a global context to the in situ observations
(e.g., the flow fields and plasma effects away from the spacecraft)
would require remote-sensing detectors. The preliminary spacecraft
design includes both in-situ measuring detectors and remote
viewing sensors. The spacecraft are 3-axis spin stabilized
to avoid compromising the in situ sampling instrument observations.
This attitude configuration will allow for the positioning
of nadir looking or limb scanning optical devices. The flat,
front ram face of the spacecraft will hold the instruments
for thermal plasma and neutral gas measurements, which use
the ram speed of the spacecraft to efficiently sample the
environment. The solar arrays are to be body mounted and
electrically conducting, in order to minimize perturbations
on the plasma measurements due to spacecraft shadowing and
spacecraft electric fields.
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