The CCD dark current increases about a factor of 2 for each 8 degree C
increase in CCD temperature. The dark current at our normal operating
temperature of 
C is about 1 DN/sec for each full resolution pixel. Dark
spikes or ``hot pixels'' have a corresponding rate of increase but, with
a much higher dark current to begin with, can become quite dominant at CCD
bakeout temperatures of +20 C. Although the analysis software tries to
match dark frames of the appropriate temperature to the data being analyzed
users should be alert for incorrect background subtraction during periods
surrounding CCD bakeout. Dates of CCD bakeout can be obtained with the
program PR_DATES_WARM and are listed in the appendix of the
Reference Guide.