Figure cont.1 : Changes in SSD/SMD Ratio. Changes in the SSD count rate to SMD count rate are shown for five different energies: 4.51, 2.29, 1.49, 1.25, and 0.93 keV from top to bottom. A clear trend toward lower SSD/SMD ratio with time is seen. The trend is also more pronounced at low energies. This suggests an accumulation of an absorbing layer over the SSD.

ddIDL> pspc_ref_hist, 'HX220', 99, /SSD
ddIDL> pspc_ref_plot, /LINES