2008A&A...478..575K

To analyze diffuse emission that fills the field of view, one must accurately characterize the instrumental backgrounds. For the XMM-Newton EPIC-MOS instrument these backgrounds include a temporally variable ``quiescent'' component, as well as the strongly variable soft proton contamination. We have characterized the spectral and spatial response of the EPIC-MOS detectors to these background components and have developed tools to remove these backgrounds from observations. The ``quiescent'' component was characterized using a combination of the filter-wheel-closed data and a database of unexposed-region data. The soft proton contamination was characterized by differencing images and spectra taken during flared and flare-free intervals. After application of our modeled backgrounds, the differences between independent observations of the same region of blank sky are consistent with the statistical uncertainties except when there is clear spectral evidence of solar wind charge exchange emission. Using a large sample of blank sky data, we show that strong magnetospheric SWCX emission requires elevated solar wind fluxes; observations through the densest part of the magnetosheath are not necessarily strongly contaminated with SWCX emission.