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