http://xmm.esac.esa.int/docs/documents/CAL-SRN-0269-1-0.ps.gz
http://xmm.esac.esa.int/docs/documents/CAL-SRN-0262-1-0.ps.gz
http://xmm.esac.esa.int/docs/documents/CAL-SRN-0238-1-0.ps.gz
http://xmm.esac.esa.int/docs/documents/CAL-SRN-0216-1-0.ps.gz