There are two separate monitors -- one for ions and one for electrons. Both are spherical-section electrostatic analyzers with extensive flight heritage, most recently from Ulysses.
The data from the ion and electron monitors measure not only the solar wind regime for controlling which collector is exposed, but also the solar wind speed for controlling the voltages on the concentrator. The velocity distribution functions measured by the ion monitor can be used to model any instrumental discrimination within the concentrator.
The monitor data will be used to determine the integrated implantation history for all the samples. In addition, the data are of potential importance to the space plasma physics community.