The software divides into two programs. The first is
a simulation program that generates a model ionosphere
and calculates TEC values based on user-defined receiver
arrays and satellite constellations. The second program
uses TEC output from the first to reconstruct the ionosphere
in four dimensions. Each allows native visualization of
electron density in contour, three-dimensional and false
color plots, as well as contours of peak density and peak
height. The software can display TEC values versus time
for all receivers and satellites, and includes a 3-D interactive
plot of the geometry.
Ongoing work includes the adaptation of the current 4-D
ionospheric tomography software for the purpose of simulating
and investigating the effect of satellite-based receivers
on the tomography problem. The software includes the ability
to place any number of both ground- and satellite-based
receivers using any possible orbit to simulate various
arrangements. Satellite-based receivers may have their
own beacons, increasing the total amount of TEC data.
In addition, users may load the actual GPS constellation,
or any other satellite or satellites, into the software.
A number of methods can simulate the ionosphere, including
the Air Force PIM model, IRI and a simple slab, and Chapman.
Users can adjust the base ionosphere, including height
and density gradients, as well as localized bulges. The
models can represent any location of the world with variable
resolution in height, latitude, and longitude. The reconstruction
software will use these simulated TEC values in its reconstruction.
The software includes many standard tomography algorithms
as well as some proprietary algorithms developed by CRS.
In addition, support for input other than TEC is available
to improve overall reconstruction. Other models could
easily work with the software as well.
After the software modifications are complete, tests
will investigate the improvements to reconstruction that
satellite-based GPS receivers offer.
