Planck Focal Plane
Artist's impression of the Planck focal plane which is located directly below the telescope primary mirror (visible at the top). It comprises the HFI bolometric detector array (small feedhorns on golden circular base) and the LFI radio receiver array (larger feedhorns around the HFI). The box holding the feedhorns is made transparent in this view, to also show the elements inside and behind it.
The Low Frequency Instrument (LFI) will observe in the frequency range between 27 to 77 GHz (λ = 11.1 to 3.9 mm).
The High Frequency Instrument (HFI) will observe in the frequency range between 84 GHz to 1 THz (λ = 3.6 to 0.3 mm).