IRAC Instrument Handbook - IRSA - California Institute of Technology
IRAC Instrument Handbook - IRSA - California Institute of Technology
IRAC Instrument Handbook - IRSA - California Institute of Technology
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Pipeline History Log 143<br />
<strong>IRAC</strong> <strong>Instrument</strong> <strong>Handbook</strong><br />
applied to channel 3 data. The derived correction values for each channel are located in the header in the<br />
keywords DRICORR1, DRICORR2, DRICORR3, and DRICORR4. The overall background term<br />
determined is DRIBKGND.<br />
5. Distortion Files<br />
The subarray distortion files were found to be derived from the incorrect place on the full array and have<br />
now been updated with correct ones. This should only make a small, but noticeable difference in pixel<br />
sizes when measuring relative separations in the subarray.<br />
6. Super-Skyflat<br />
A new "super-skyflat" has been derived from the first two years <strong>of</strong> flatfield data on <strong>IRAC</strong> and will be<br />
used as the flatfield for all reprocessing and further campaigns. Uncertainties in the pixel-to-pixe l<br />
responsivity calibration are only 0.5%, 0.2%, 0.2%, and 0.05% for channels 1−4, respectively.<br />
7. Flux Conversion<br />
The flux conversion has been updated to reflect the derivation described in the <strong>IRAC</strong> calibration paper.<br />
The currently used numbers were from a nearly complete phase <strong>of</strong> this derivation, but different by 3% in<br />
ch 4.<br />
8. Other Added Keywords<br />
1. Median brightness <strong>of</strong> Calibration Skydark (SKYDKMED)<br />
2. More Precise Start time <strong>of</strong> observation (SCLK_OBS).<br />
S12.0<br />
Since S11.0 there have been no significant changes to the <strong>IRAC</strong> pipeline affecting calibration. The<br />
majority <strong>of</strong> changes have to do with header keyword additions.<br />
1. New observing mode: “Stellar Mode” has multiple full-array short time exposures within channel<br />
1 and 2 and at the same time has a longer integration in channels 3 and 4. This allows for brighter<br />
objects to be observed in the longer wavelength channels to higher signal-to-noise without<br />
saturating in the shorter wavelength observations. Available frame times are 0.4/2 sec, 2x2/12 sec<br />
and 2x12 sec/30 sec. The first number(s) refer to channels 1 and 2, the last number to channels 3<br />
and 4.<br />
2. The median value <strong>of</strong> the frames used to create the skydark subtracted from the data will be placed<br />
in the header <strong>of</strong> the BCD: keyword SKYDKMED.<br />
3. The name <strong>of</strong> the labdark subtracted from the data will be placed in the header: keyword<br />
LBDRKFLE.<br />
4. The time <strong>of</strong> the observation (SCLK_OBS) will be computed using telemetry only to allow for a<br />
more exact timing. This keyword will be placed in the database and header. Further S13 changes<br />
will include calculating the first frame correction from this more exact timing.<br />
5. Keywords PTGDIFFX, PTGDIFFY were inserted to refer to the pointing differences in actual<br />
pixels along the X & Y axis.<br />
S11.0<br />
1. The EQUINOX header keyword for BCDs has been fixed.
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