Automatic Enhancement and Detection of IMAGE Radio Plasma Imager Echoes:
  1. Derivation and Models

William W. L. Taylor
  Raytheon ITSS

Michael L. Rilee
  Raytheon ITSS

Scott A. Boardsen
  Raytheon ITSS

James L. Green
  NASA/Goddard

B. W. Reinisch
  University of Massachusetts-Lowell


The Radio Plasma Imager (RPI) is a low power radar on board the IMAGE
spacecraft to be launched early in year 2000. The principal science
objective of RPI is to characterize the plasma in the Earth's
magnetosphere by radio frequency imaging. A key product of RPI is the
Plasmagram, a map of radio signal strength vs. echo delay-time vs.
frequency, on which magnetospheric structures appear as curves of varying
intensity. Noise and other emissions will also appear on RPI Plasmagrams
and when strong enough will obscure the radar echoes. To aid in the
analysis of RPI plasmagrams, a computer program is being implemented to
automatically detect and enhance the radar echoes. The techniques used are
derived within a Bayesian framework and include Maximum Likelihood and
Maximum Posterior analyses. A heuristic stochastic global optimization
method blending elements of simulated annealing and genetic algorithms is
used to determine what model echoes are supported by plasmagram evidence.
The application of this work to RPI data will be discussed.