For data taken in IOC/SV or the first 4 MIPS campaigns in nominal operations, the bias setting of the 70 micron array was set at a level that attempted to increase the sensitivity of both sides of the array, but a consequence was that the stimulator flashes left latents in the data. For bright sources, this is less of a concern than for extended regions or long integrations built up from short exposures (e.g., in photometry mode). The stim latents and variations of the slow response as a function of time can be mitigated by median filtering the data, if you are only interested in faint point sources.
The amplitude of the stim latents depends on background and appears to increase with the time since anneal. The stim latents linger longer for 70 microns than 160 microns, since the decay time constants associated with the stim latents are larger at 70 microns. Data taken after the bias change (MIPS-5 or later, after 14 March 2004) should still see these effects, but at a much lower level.
The stim latents and variations of the slow response as a function of time can be mitigated by median filtering the data if you are only interested in faint point sources (see section 8.2). Be careful, however, about using filtered data for extended sources (see sections 8.2.8 and 8.2.9 below).
Figure 7.21: Automatically-produced mosaics of NGC 300. Left is 70 microns, and right is 160 microns. Stim latents are indicated. On the left, the vertical streaking is from residual slow response drifts (columns 5-9 are most affected at 70 microns). On the right, the dotted blue oval indicates a changed response in the stim calibration that comes from the bright source.
