Overview of in-flight sensitivity limits

Table 1 gives the detection limit of ISOPHOT. It is determined by the detector noise, by the photon noise from the source plus the expected background, flat-field uncertainties, as well as by the galaxy and cirrus confusion noise. We have added in this table values for the cirrus confusion and galaxy confusion limits for representative background values.

Table 1: Sensitivity limit ( ) for typical filters compared to cirrus confusion (CC) and galaxy confusion (GC) limits per aperture/pixel for representative background levels. The noise values are given for S/N=10, 5 sigma in the case of CC and GC noise, 128 sec on-source integration time, and a source to background distance of 180'' (one background position) without any detector transients. Note that 5 sigma CC or CG noise peaks are rare, but nevertheless likely to occur in samples.  

Table 1 indicates that for C100 and C200 the cirrus confusion is an important factor in the determination of the limiting terms.