Calibration of the Infrared Array Camera (IRAC) for SIRTF

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Space Infrared Telescope Facility (SIRTF). IRAC is a four-channel camera that obtains simultaneous images at 3.6, 4.5, 5.8, and 8 μm. Two adjacent 5.12 arcmin × 5.12 arcmin fields of view in the SIRTF focal plane are viewed by the four channels in pairs (3.6 and 5.8 μm; 4.5 and 8 μm). All four detector arrays in the camera are 256×256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors.

We describe the results of the instrument calibration measurements completed at Goddard Space Flight Center, including the characterisation of the arrays, optical quality, and the radiometric performance of the assembled instrument. The in-flight calibration strategy is outlined, and an estimate of the point source sensitivity of IRAC in SIRTF is presented.