Issued: 20 April 2010
Updated: 20 April 2012

Note for Cycle-7 and up warm IRAC proposers

Take well-dithered data whenever possible and use medium- or large-scale
dither patterns unless combining dithers with mapping steps of 1/3-1/2 
of an array width. 

Residual features from slews across bright sources are more common in 
warm data than in cryogenic data, and some residuals at 3.6 microns can 
take hours to decay below the noise level.

In general, it is best to avoid repeats. For most observations, the data 
from the repeats are less well calibrated as there is a significant 
pattern noise due to the as yet uncorrected first-frame effect.

Current absolute calibration accuracy is 5% and will improve to 3% as 
in the cryogenic mission in later reprocessings of the data.

Milli-magnitude relative photometry is available in the staring mode. 
Warm IRAC observers have reported approaching 80% of the photon-noise 
limit in these cases but your sensitivity will depend on the ability 
to remove the pixel-phase effect in your particular data. The ability 
to coadd different epochs for staring observations has not been studied in 
detail, but from a limited amount of analysis, it appears that the 
noise will coadd down as N**0.4, where N is the number of epochs.

For precision (1%) photometry of bright sources, the pixel phase effect
needs to be considered in determining the signal-to-noise. Please consider 
adding more redundancy to account for residuals in the correction.