IRAC Instrument Handbook - IRSA - California Institute of Technology

IRAC Instrument Handbook
the BCD that contains the star that produces the stray light. Figure 7.11 and Figure 7.12 show scattered
light in the two short-wavelength channels, from zones 1A, 1B, 2A, and 2B. Figure 7.13 and Figure 7.14
show examples of scattered light in channels 3 and 4.
Because stars are much fainter in these channels, and the scattering geometry is much less favorable,
these scattered light spots are much less obvious than in the short-wavelength channels. Dithering by
more than a few pixels will take the bright star off the channel 3 and 4 “scattering strip," so the scattered
light spots should be removed from mosaics made with adequately dithered data.
Figure 7.13: Channel 3 image showing scattered light from a scattering strip around the edge of the array
where a bright star is located. The scattered light patches are marked with white “S" letters. The images were
taken from program PID 30 data.
Data Features and Artifacts 123 Optical Artifacts