Planck telescope focal plane unit

Planck carries two scientific instruments: the High Frequency Instrument, or HFI, and the Low Frequency Instrument, or LFI. Their detectors convert the microwave and radio light gathered by the telescope into very accurate maps of the microwave sky. This data will then be used to extract the most accurate estimates of the spatial variations of the temperature of the Cosmic Microwave Background (CMB) radiation, a key to understanding the origin of the Universe and the evolution of galaxies.

The Planck instrument detectors feature the highest sensitivity and angular resolution ever for a space observatory at these wavelengths. The angular resolution indicates the smallest separation between regions in the sky that the detectors are able to distinguish; the smaller the separation, the sharper (better) will be the information gathered on the temperature of the cosmic background. The angular resolution can be compared to the ability to distinguish fine details, the 'sharpness' of vision.

The detectors are so sensitive that they can measure temperature variations in the sky of millionths of a degree - a task similar to measuring from Earth the heat produced by a rabbit sitting on the Moon. In order to achieve this, some of Planck's detectors must be cooled to about one-tenth of a degree above absolute zero (-273.15 °C), so that their own heat does not swamp the signal from the sky.

The Low Frequency Instrument (LFI)

Combined focal plane of Planck's two instruments

LFI is designed to produce high-sensitivity, multi-frequency measurements of the microwave sky in the frequency range of 27 to 77 GHz (wavelength range 11.1 to 3.9 mm). The instrument consists of an array of 22 tuned radio receivers located in the focal plane of the telescope. These radio receivers gather microwaves from the sky and convert them to a measure of the intensity of radiation at each frequency.

Principal Investigator: Nazzareno Mandolesi, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna Italy.