The BICE focal plane instrument is a tandem Fabry-Perot spectrometer, which consists of two Fabry-Perot interferometers: one is a high-order interferometer to scan the wavelength (Scanning Fabry-Perot; SFP), and the other is a low-order interferometer (Fixed Fabry-Perot; FFP) as an order sorter of the SFP. Both of the interferometers, together with other optics of the spectrometer and a far-infrared detector, are cooled to 2 K with liquid helium, so that the instrumental radiation from the spectrometer is completely negligible. The detector is a stressed Ge:Ga photoconductor.
The telescope was designed to optimize detection of the diffuse emission with a beam size of 12.'4 (FWHM). Special attention was paid to minimizing instrumental emission, by using an off-axis paraboloidal primary mirror with an over size (35 cm dia) aperture, but only the central 20 cm of the diameter is used, to avoid the spill-over light due to diffraction.