IRAC Conceptual Layout Diagram

IRAC Layout

Light enters from the telescope and reflects off the pickoff mirrors which define two separate fields in the focal plane. The light is then refracted by the doublet camera lenses, and the short wavelength light is reflected by the beamsplitter and the long wavelength light is transmitted. The light for each channel then passes through a filter and enters the array. All channels have a Lyot stop near the bandpass filter for stray light rejection.

A cold shutter can also be flipped into the beam for calibration. Dark frames can be obtained in this configuration, and calibration lamps in the transmission calibrator can be turned on to send light through the optical system for flat-field measurement. In addition, "flood calibrators" exists which can illuminate the individual arrays.

Last updated 1999 August 4