Background radiation affects XMM-Newton observations. Experience shows that observations aiming to detect faintest point-like sources or extended structure like clusters of galaxies, require a ``low'' background radiation level and that only about 60% of the observing time can be considered as low background radiation level. There are different observing strategies to handle the high background radiation level. Most common are:
The feasibility study of extended sources requires special attention. Proposers should consider that besides the X-ray background also the instrumental background has to be taken into account. Experience shows that in the absolute minimum proposers should provide the background count rate per unit area (count/s/cm) and the signal to background ratio required for the most critical region, i.e. the region for which the spectral analysis or deeper source detection is proposed. Proposers should also specify the energy bands to which these numbers are referring.