System for Meteorology, Ionosphere, and Climate and Formosa Satellite mission #3; hereafter COSMIC)
mission, a constellation of six micro-satellites, was launched into a 512-km orbit from Vandenberg Air
Force Base in California. Using on-board propulsion these satellites are being deployed to their final orbits
at 800 km with 30 degrees of separation. This process will take about 17 months following the launch.
There are three instruments aboard each COSMIC satellite: the GPS Occultation Experiment (GOX), the
Tri-Band Beacon (TBB), and the Tiny Ionospheric Photometer (TIP). These three instruments constitute a
unique suite of instruments for studying the Earth's ionosphere. The GOX instrument operates by inferring
the slant total electron content (the integral of the electron density along the line-of-sight) between the
COSMIC satellites and the GPS satellites as a function of tangent height above the Earth's limb. These
data can be inverted to produce electron density profiles in the E and F regions of the ionosphere. The TBB
is a three frequency radio beacon that radiates coherently at 150, 400, and 1067 MHz. When the relative
phases of the signals are measured between the COSMIC satellites and ground-based or space-based
receivers, the total electron content along the line-of-sight can be determined. By making the
measurements from a set of receivers, the two-dimensional distribution of electrons beneath the satellite
can be determined using tomographic techniques. The TIP instrument measures the optical signature of the
natural decay of the ionosphere produced via recombination of the O+ ions and electrons. The TIP
measurements can be used to characterize the morphology and dynamics of the global ionosphere.
Additionally, the TIP measurements can be inverted in conjunction with the GPS occultation
measurements, using tomographic techniques, to produce the two-dimensional distribution of electrons
beneath the satellite. We present an overview of the COSMIC mission, the instruments, and their
application to ionospheric sensing.
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