IRAC Instrument Handbook - IRSA - California Institute of Technology

Table 5.1: Bandwidth correction coefficients.
Channel 1
Readout 1 2 3 4
κ 1.58e-3 2.17e-3 2.33e-3 1.64e-3
κ(end of row) 1.2e-5 2.1e-5 2.4e-5 1.3e-5
Channel 2
Readout 1 2 3 4
κ 1.71e-3 3.63e-3 1.06e-3 1.11e-3
κ (end of row) 1.4e-5 5.2e-5 6.0e-5 6.6e-5
Channel 3
Readout 1 2 3 4
κ 3.19e-3 1.04e-2 3.3e-3 2.09e-3
κ (end of row) 4.2e-5 3.3e-4 4.4e-5 2.0e-5
Channel 4
Readout 1 2 3 4
κ 3.74e-3 3.74e-3 3.74e-3 3.74e-3
κ (end of row) 5.5e-5 5.5e-5 5.5e-5 5.5e-5
IRAC Instrument Handbook
5.1.10 Dark Subtraction I: FFCORR (first frame effect correction) or LABDARKSUB (lab dark
subtraction)
The true dark current in the IRAC detectors is actually very low − the most notable dark current features
are the electronic glows seen in the Si:As arrays (channels 3 & 4). However, the IRAC arrays experience
considerable pedestal offsets which are commonly of the order of tens of DN. These offsets are dependent
on the Fowler sampling, exposure time, and operation history of the arrays, and are believed to be due to
very small thermal changes in the internal IRAC cold electronics. The most significant of these offsets is
the “first-frame" effect: the laboratory measurements show that the dark patterns and DC levels change as
a function of the time elapsed between the end of the previous frame and the start of the current frame
(called “delay time"). The first frame of a series of exposures is most affected, and therefore this effect is
Pipeline Processing 77 Level 1 (BCD) Pipeline