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Instruments

Instruments

Introduction

The Planck science payload consists of two instruments that are designed to study the Cosmic Microwave Background (CMB) radiation field by making high sensitivity measurements in the frequency range 27 GHz to 1 THz, and a telescope that collects the microwave radiation and focuses it onto the instrument detector arrays.

Planck's primary science objectives are to:

  • Map Cosmic Microwave Background anisotropies
  • Test inflationary models of the early universe
  • Measure the amplitude of structures in the Cosmic Microwave Background
  • Perform measurements of the Sunyaev-Zeldovich effect

Planck has the ability to:

  • Detect much smaller temperature variations in the CMB than previous missions
  • Perform CMB measurements with a higher angular resolution than ever before
  • Measure over a wider band of frequencies to enhance the separation of the CMB from interfering foreground signals

The CMB anisotropy map produced using Plank's observations will be markedly superior to those currently available and will be used to set constraints on the values of the main parameters that govern the large scale structure of the Universe.

The instruments and telescope are provided by collaborative efforts between scientific institutes in ESA member states and the USA. Principal investigators in different countries lead the nationally funded collaborations.

Planck Instruments

Instrument Name

Instrument Description

Principal Investigator (PI)

Deputy PI

Low Frequency Instrument (LFI)

High Electron Mobility Transistor (HEMT) radio receiver array

Nazzareno  Mandolesi, Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, (Bologna, Italy)

Marco Bersanelli,
Universita' degli Studi di Milano (Milan, Italy)

High Frequency Instrument (HFI)

Bolometric detector array

Jean-Loup Puget, Institut d'Astrophysique Spatiale,  (Orsay, France)

François Bouchet,
Institut d'Astrophysique de Paris (Paris, France)

Telescope

Off-axis tilted Gregorian telescope with baffling system

Hans-Ulrik Norgaard Nielsen, Danish Space Research Institute, (Copenhagen, Denmark)

 

 

Instruments In Brief

The Planck scientific instrument complement comprises two instruments, LFI, a radio receiver array covering the lower frequency range, and HFI, a bolometric detector array covering the higher frequencies. The instruments share a common telescope. Principal Investigator (PI) consortia provide the instruments and telescope. 

Planck Principal Investigators

LFI

Nazzareno  Mandolesi, Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, (Bologna, Italy). Deputy PI: Marco Bersanelli, Universita' degli Studi di Milano (Milan, Italy)

HFI

Jean-Loup Puget, Institut d'Astrophysique Spatiale,  (Orsay, France). Deputy PI: François Bouchet, Institut d'Astrophysique de Paris (Paris, France)

Telescope

Hans-Ulrik Norgaard Nielsen, Danish Space Research Institute, (Copenhagen, Denmark)


Low Frequency Instrument

The Low Frequency Instrument (LFI) is designed to produce high-sensitivity, multi-frequency measurements of the microwave sky in the frequency range 27 to 77 GHz (wavelength range 11.1 to 3.9 mm).

LFI Performance Goals

Centre frequency (GHz)

30

44

70

Bandwidth (GHz)

6

8.8

14

Beamwidth (arcminutes, FWHM)

33

24

14

Detector technology

High electron mobility transistor (HEMT) radio receiver arrays

Detector temperature (K)

~ 20

Cooling technology

H2 sorption cooler

Average ΔT/T1 per pixel*

2

2.7

4.7

Average ΔT/T2 per pixel*

2.8

3.9

6.7

Flux sensitivity per pixel* (mJy)

13

19

25

 

* A pixel is a square whose side is the full width, half maximum (FWHM) extent of the beam. These sensitivity figures are calculated for the average integration time per pixel. The integration time will be very inhomogeneously distributed over the sky and will be much higher in certain regions.

1Sensitivity (1 σ) to intensity (Stokes I) fluctuations, measured in thermodynamic temperature units × 10-6, relative to the average temperature of the CMB (2.73 K), achievable after two sky surveys (14 months).

2Sensitivity (1 σ) to polarised intensity (Stokes U and Q) fluctuations, measured in thermodynamic temperature units × 10-6, relative to the average temperature of the CMB (2.73 K), achievable after two sky surveys (14 months).


High Frequency Instrument

The High Frequency Instrument (HFI) is designed to produce high-sensitivity, multi-frequency measurements of the diffuse sky radiation in the frequency range 84 GHz to 1 THz (wavelength range 3.6 to 0.3 mm).

HFI Performance Goals

Centre frequency (GHz)

100

143

217

353

545

857

Bandwidth (GHz)

33

47

72

116

180

283

Beamwidth (arcminutes, FWHM)

9.2

7.1

5

5

5

5

Detector technology

Spider bolometer arrays,
neutron transmutation doped (NTD) germanium thermistors

Detector
temperature (K)

~ 0.1

Cooling technology

H2 sorption cooler + Joule-Thomson cooler + 3He/4He dilution cooler

Average ΔT/T3
per pixel*

2

2.2

4.8

14.7

147

6700

Average ΔT/T4
per pixel*

 

4.2

9.8

29.8

 

 

Flux sensitivity
per pixel* (mJy)

9

12.6

9.4

20

46

52

 

* A pixel is a square whose side is the full width, half maximum (FWHM) extent of the beam. These sensitivity figures are calculated for the average integration time per pixel. The integration time will be very inhomogeneously distributed over the sky and will be much higher in certain regions.

3Sensitivity (1 σ) to intensity (Stokes I) fluctuations, measured in thermodynamic temperature units × 10-6, relative to the average temperature of the CMB (2.73 K), achievable after two sky surveys (14 months).

4Sensitivity (1 σ) to polarised intensity (Stokes U and Q) fluctuations, measured in thermodynamic temperature units × 10-6, relative to the average temperature of the CMB (2.73 K), achievable after two sky surveys (14 months).


Measurement Results

The measurements made by the two instruments will be combined and used to produce a full-sky map of the anisotropies in the Cosmic Microwave Background (CMB) with unprecedented precision. This map will in turn be used to derive a wealth of cosmological information, including an accurate determination of the values of the main parameters that characterise the large-scale structure and evolution of the Universe.

Telescope

The telescope design is an off-axis tilted Gregorian system, offering the advantages of no blocking of the optical path combined with compactness. The eccentricity and tilt angle of the secondary mirror and the off-axis angle obey the Dragone-Mizuguchi condition, which allows the system to operate without significant degradation over a large focal plane array, while simultaneously minimizing the polarization effects introduced by the telescope.

The baffling system is composed of two elements. The shield element is a large, self-supporting and roughly conical structure covered with multi-layer insulation (MLI), which surrounds the telescope and focal plane instruments. Together with the optical bench, it defines the optical enclosure. It has two important functions, reducing the level of straylight (which at the chosen orbit is in large part due to the spacecraft itself) and promoting the radiative cooling of the optical enclosure towards deep space. The baffle element consists of one half of a conically shaped surface that links the focal plane instruments to the bottom edge of the sub-reflector. The function of the baffle is to shield the detectors from thermal radiation originating within the optical enclosure. 

Telescope characteristics
Type

Off-axis tilted Gregorian

Primary mirror

1.9 × 1.5 m, off-axis paraboloid

Secondary mirror

1.1 × 1.0 m, off-axis paraboloid

 

Last Update: 1 September 2019
17-Sep-2019 19:52 UT

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Shortcut URL

https://sci.esa.int/s/84yL3mA

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