Another very limiting factor of any ISOCAM observations is the
importance to avoid saturation. Only observations without any
potential saturation effect on the detector can be released for
scheduling. For all the C05 observations the brightest pixel of the
detector must be below 2800 ADU/s/g (detector saturation), and below
4096 ADU for any gain (ADC saturation). Note that the first criterion
may be met while the second is violated, for gains 2 and 4.
Equally important is the possible saturation caused by the so called
parallel mode configuration. ISOCAM is used in its so-called parallel
mode while observations are performed using other ISO
instruments. When an ISOCAM observation is scheduled, it arrives on
the source in parallel mode and it is put back in parallel mode at the
end of the AOT, before leaving the source. There are two standard
parallel mode configurations, but ISOCAM can be assumed to arrive on
most pointings in the most sensitive of the two, which uses the LW2
filter and the 6" pixel field-of-view (pfov) lens. This mode will
saturate for point sources brighter than about 0.5 Jy in the IRAS 12
micron band, assuming a stellar spectrum. The saturation limit in the
LW2 filter in this configuration is 0.6 Jy.
Therefore, if the target source is bright enough, ISOCAM may saturate
when the source is acquired, even though the observation itself is
safe with regard to saturation risks. ISOCAM saturation is highly
undesirable as it introduces transients which can affect the
instrument for a long period, up to 1 hour or even more. For more
details on saturation effects please consult the Addendum of the
Observer's Manual.