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The Low Frequency Instrument

The High Frequency Instrument


Planck's payload will include two instruments offering much greater sensitivity than any previous spacecraft observing the Cosmic Microwave Background (CMB).

The instruments include two arrays of about 50 detectors each, sensitive to a broad range of microwave frequencies: from 25 to 1000 GigaHertz (GHz). They will measure the temperature of the background radiation over the whole sky, and will be able to detect differences as slight as a few micro-Kelvin (corresponding to a few parts in one million).

Apart from the huge improvement in sensitivity and angular resolution, Planck's major advance comes from the fact that its two instruments will cover a very broad range of frequencies. This makes it possible to remove the radiation from sources other than the CMB, including our own galaxy, the Milky Way. Otherwise these sources would bury the signal from the CMB within a lot of noise.

More information about CMB experiments

CMB related links

The Low Frequency Instrument

The Low Frequency Instrument (or LFI) is an array of 56 tuned radio receivers - the detectors - that will be operated at -253°C (20 degrees above absolute zero). These receivers will work grouped in four frequency channels, centred between 30 and 100 GHz. They are based on devices called 'HEMTs' (High Electron Mobility Transistors), and work just like transistor radios: the transistors amplify the signal collected by the antenna (the telescope), and the amplified signal is then converted to a voltage. In a normal radio, the detected signal would then be passed on to a speaker, but in Planck it will instead be stored in a computer for later analysis.

The Low Frequency Instrument (LFI)

This instrument will be designed and built by a Consortium of more than 22 scientific institutes, led by Reno Mandolesi of the Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (CNR) in Bologna (Italy).

More information on the LFI

[Links to technical articles and institutes]

The High Frequency Instrument

The High Frequency Instrument (or HFI) is an array of 48 so-called 'bolometric' detectors, which work by converting radiation to heat. The amount of heat is then measured by a tiny thermometer, which is read out and converted to a real temperature in a computer. The HFI detectors will work in six frequency channels centred between 100 and 857 GHz. They are operated at -272.9°C (only one tenth of one degree above absolute zero). To achieve that temperature a complex system of refrigerators is put on board the satellite, each of which uses a different technology to provide a successively colder temperature.

The High Frequency Instrument (HFI)

The HFI will be designed and built by a Consortium of more than 20 scientific institutes [link to institute list page], led by Jean-Loup Puget of the Institut d'Astrophysique Spatiale (CNRS) in Orsay (France).

More information on the HFI: [Links to technical articles and institutes]

More information on HFI

Last update: 17 January 2001

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