The Potential of Spaceborne High Performance Computers for Onboard Space Physics Data Analysis Abstract submitted to 1999 Fall Meeting of the American Geophysical Union. M. Rilee (Raytheon ITSS) S. Curtis A. Figueroa-Vinas B. Farrell, J. Houser M. Kaiser M. Reiner (Raytheon ITSS) NASA/Goddard Space Flight Center Future Space Science missions will involve multiple spacecraft seeking to sense phenomena that occur across a wide range of spatial and temporal scales. Some missions will be required to provide real-time feedback for space weather studies or monitoring. The operational and communication needs of constellations of spacecraft with highly capable sensors are immense and for some missions are currently beyond our technical ability. To examine the problem of science data flow at its source, the Solar-Terrestrial (ST) Probe Science Application Team of NASA's Remote Exploration and Experimentation (REE) project has developed two data analysis applications for a spaceworthy scalable parallel computer being developed by NASA's High Performance Computing and Communication Program. To investigate the possible benefits of spaceborne high performance computing for Solar-Terrestrial missions, the team chose to model data analyses that arise in radio frequency interferometry and plasma particle spectrometry. Radio frequency interferometry was chosen as a fundamental technique for imaging and plasma wave spectrometry. Plasma particle spectrometry was chosen because of its central importance in ST physics. Both kinds of science instruments produce large amounts of high-dimensional data that places severe demands on mission communications infrastructure. The science communication burden may be eased if a way could be found to extract scientifically meaningful information from the raw data in place onboard the spacecraft. Our work shows that the REE computer architecture is well suited to the data analysis problems we have studied. We present results of our modelling efforts and discuss how well our data analyses perform on the {\it REE Flight Processor} testbed. In particular, new results from our plasma spectrometry model will be presented: a highly parallel, efficient, robust, and flexible approach to reducing plasma spectrometer data will be presented.