The effects of pile-up can be mitigated by reducing the accumulation
time. The main methods to achieve this are reading fewer CCDs, reading
the most brightly illuminated CCDs more often or using the RGS Small
Window mode, or even a combination of these. The XMM-SOC document
XMM-SOC-CAL-TN-0075, available from
gives more details about pile-up in RGS.