ESA Science & Technology - 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.

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. 

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).

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).

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.