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 Geomagnetism
provides one of three space-based techniques to probe the Earth's
interior. (The other two are gravity and Earth rotation.) Geomagnetic
studies are currently limited by a paucity of observations and attendant
difficulty in their interpretation. Recent advances in nanosatellite
technology hold the promise for cost-effective geomagnetic constellation
operations.
Constellation
measurements provide a number of advantages over single-satellite
measurements, including improved tracking of external field variability
with local time and latitude, by observing the field simultaneously
at a range of local times; improved observation of the main field
and short-period temporal variations; and magnetic gradient measurements
for the determination of magnetospheric and ionospheric current
systems and the determination of an accurate external field model.
Suggested
mission phasing and requirements
Immediate
(1–5 years): Support of analysis of geomagnetic
observations from current satellite missions. Development of a modularized
instrument package to facilitate taking advantage of missions of
opportunity.
Near Term (5–10 years):
Constellation of 4-6 satellites at a range of local times in polar
orbit at approximately 800-km altitude.
Long term (10–25 years):
Complete, 12-satellite constellation by adding satellites at lower
altitude (300 km) in polar orbit (to enhance study of the crustal
field) and at 800 km in a low-inclination orbit (to enhance recovery
of mantle electrical conductivity). Technological advancements on
incorporating star trackers on magnetometers and improved lifetimes
at low altitudes.
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