The detector bias and dark current of the Infrared Array Camera (IRAC) on the Spitzer Space Telescope is calibrated by periodically observing a patch of sky within it’s continuous viewing zone, located near the north ecliptic pole at 17h40m +69d00m. This calibration field, known as “The IRAC Dark Field”, is roughly 15 arc minutes in diameter. Over the five years of the cryogenic mission and the 10 years of the warm mission, this has drilled an incredibly deep image of the infrared sky that reaches deep into the confusion limit. Additionally, the field has a large array of ancillary data spanning the x-ray to far-infrared.
Subregions of the field are observed to a typical depth of 0.7 µJy 5-sigma at 3.6µm with a roughly weekly cadence. With over 1000 individual epochs at the short (3.6-4.5µm) wavelengths, these form the longest baseline synoptic survey at these depths at mid-IR wavelengths.