How Iridium data are processed
A down-sampled data stream from the Iridium system is sent to the Johns Hopkins University Applied Physics Laboratory (USA). Algorithms developed by Dr Brian Anderson subtract off the ambient magnetic field, correct for cross-talk, and filter the data. The process is described further here (http://dysprosium.jhuapl.edu/introduction.html)
Since 2010, a higher data sampling of the Iridium magnetometer data has been made available through a National Science Foundation research grant and the Johns Hopkins University Applied Physics Laboratory. The project is called AMPERE. Newcastle (C. L. Waters) provides the software to take the processed magnetic field data and estimate the Birkeland currents.