ESA

Paris, 11 March 1999

Go-ahead for ESA's new millennium space observatories Planck and FIRST

European scientific institutes has been given the go-ahead for the development of instruments for two major ESA missions for the new millennium: Planck, a satellite to study the radiation considered to be the "echo" of the Big Bang and FIRST, an infrared space telescope. ESA's Science Programme Committee (SPC) approved on 17 February the scientific instruments for both missions, which will be built by more than 80 institutes from all around Europe. The go-ahead will also allow ESA and European industry to begin in earnest the development of the Planck and FIRST spacecrafts.

Planck and FIRST will be launched together in the year 2007.

Planck is a cosmology mission, designed to test the models describing the origin and evolution of the early Universe. It will do so by studying the Cosmic Background Radiation, a light emitted shortly after the Big Bang that fills the whole Universe and can be detected today, like an "echo" of that primeval explosion. Astronomers consider it a "fossil" radiation, since it holds a lot of information about both the past and the future of the Universe.

"Planck will determine fundamental characteristics of the Universe, such as its geometry, its density, and the rate at which it expands. It will also provide important clues as to the kind of matter that fills the Universe", explains Planck Project Scientist Jan Tauber, at ESA's European Space Research and Technology Centre (ESTEC) in The Netherlands.

More precisely, the task of Planck will be to measure the temperature of the "echo" of the Big Bang over the whole sky. Though at the time of its emission the Cosmic Background Radiation was very hot, some 3000 degrees, it has since expanded and cooled together with the entire cosmos to a much lower temperature, namely about minus 270 degrees centigrade (3 degrees Kelvin).

Planck will look for differences in this temperature as slight as a few microkelvin, thin variations like clots that are, in fact, the "seeds" of the huge condensations of matter in today's Universe. "It will be like watching the birth of the galaxies, the galaxy clusters, all the large-scale structures that we observe today", Tauber says.

The two instruments on board Planck, now approved by ESA, are the Low Frequency Instrument (LFI) and the High Frequency Instrument (HFI).They will cover a very broad range of frequencies (between 30 and 857 Gigahertz).

The HFI will be designed and built by a Consortium of about 20 institutes led by Jean-Loup Puget of the Institut d'Astrophysique Spatiale in Orsay (France). The LFI will be designed and built by a Consortium of about 20 institutes led by Reno Mandolesi of the Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri in Bologna (Italy).

FIRST, the "Far InfraRed and Submillimetre Telescope", is the successor of ESA's Infrared Space Observatory ISO. It will be more powerful than any of its predecessors, with a primary mirror of 3.5 metres in diameter - the largest ever for an infrared space telescope. It will observe at wavelength's range never covered before (from 80 to 670 microns). Like Planck, it will be located about 1.5 million kilometres away from Earth.

FIRST will look for planetary systems and study processes like the evolution of galaxies in the early universe. It will provide very detailed information about the coldest objects in the Universe, and those enshrouded by dust. The pre-stellar cores from which the stars hatch at nearly minus 260 degrees C, or the dusty distant galaxies undergoing violent collisions are some examples. Also, FIRST will show the composition, temperature, density and motion of the gas and dust of the clouds in the interstellar space.

Its payload will consist of three instruments: two cameras called PACS and SPIRE, and HIFI, a high-resolution spectrometer. "They are real technological challenges. Instruments like these have never been used in a space telescope", says FIRST Project Scientist Goeran Pilbratt, at ESA/ESTEC.

To avoid the "noise" caused by the emission of the instruments themselves, a cryostat full of superfluid liquid helium will cool them down to a temperature below minus 271 degrees C, very close to the absolute zero (at -273 degrees C).

The Heterodyne Instrument for FIRST (HIFI) takes very high resolution spectra of the astronomical objects in thousands of frequencies simultaneously. It will be designed and built by a consortium led by Thijs de Graauw, SRON, Groningen, in The Netherlands.

The Photoconductor Array Camera and Spectrometer (PACS) instrument is an infrared camera and a spectrometer that will be developed and built by a consortium led by Albrecht Poglitsch, MPE, Garching, in Germany.

The Spectral and Photometric Imaging REceiver (SPIRE) is also a camera and spectrometer, but will observe at longer wavelengths than PACS. It will be developed and built by a consortium led by Matt J. Griffin, Queen Mary and Westfield College, London, UK.

ROYAL ASTRONOMICAL SOCIETY PRESS NOTICE

27th March 1998

NEW SPACE MISSION WILL LOOK BACK TO THE BIG BANG

About seven years from now, an ambitious new space science mission will get under way with the launch of the European Space Agency's Planck satellite. Planck will be looking back to a time shortly after the Big Bang created the Universe. Dr Alan Heavens of the University of Edinburgh will be describing this exciting project and the UK's participation during the UK National Astronomy Meeting at the University of St Andrews. Dr Heavens is a Scientific Associate for the Planck mission.

The Cosmic Microwave Background

A few minutes after its creation, the Universe had a temperature of billions of degrees. Since then, it has gradually cooled to the point where its temperature is now just a few degrees above absolute zero (-273 degrees C). Since this faint glow was first discovered in 1965 as the so-called Microwave Background Radiation, it has played a crucial role in our understanding of the Universe. The very existence of this radiation is firm evidence for the Big Bang theory of the expanding Universe.

Since then, the Cosmic Background Explorer (COBE) satellite has discovered 'ripples' in the temperature of the Universe. These represent small variations in the density of the material in the early Universe, and help to explain how matter clumped together to form stars and galaxies.

Planck

This European Space Agency (ESA) mission, currently scheduled to fly in about 2005, is a major follow-up to the COBE mission. By using detectors cooled to within a tenth of a degree of absolute zero, Planck will map the entire microwave background sky with unprecedented detail. Its two instruments will operate simultaneously at nine frequencies, with a sensitivity of two parts in a million, and an angular resolution of a few arcminutes (compared with COBE's 7 degree-wide view).

Planck's design gives it the capability of measuring many of the characteristics of the Universe - its geometry, its contents and its ultimate fate - to a high degree of accuracy for the first time. By using Planck to look at the fine detail in the temperature pattern of the sky, cosmologists should be able to test models for the origin and structure of the Universe. For example, how fast the Universe is expanding; whether it will eventually halt its expansion; the nature and quantity of dark matter, which appears to be the dominant constituent in the Universe; and the nature of the initial irregularities - did structure develop from small quantum fluctuations, or from a more exotic origin?

"It is tremendously exciting that this experiment should answer not just one, but practically all of the major questions of cosmology in one go," said Alan Heavens. In addition to this primary aim, the decoding of Planck's microwave sky maps will also produce a catalogue of more than 10,000 clusters of galaxies, and tens of thousands of quasars, starburst galaxies and other unusual objects. The clusters will be detected by the effect their hot gas has on the microwave radiation as it passes through them.

The UK and Planck

The UK's involvement is both in hardware and in the formidable data analysis task. The following centres are involved in the High Frequency Instrument:

Nuffield Radio Astronomy Laboratories at Jodrell Bank (University of Manchester) are designing and building the most sensitive radio amplifiers ever constructed for the Low Frequency Instrument.

Planck was formerly known as COBRAS/SAMBA. It is a medium size mission in ESA's Horizon 2000 space science programme. ESA is currently examining the possibility of reducing costs by launching Planck and FIRST (Far Infrared Space Telescope) on the same satellite.

Further information on the Planck mission is available following the links on the ESA Web page at: http://astro.estec.esa.nl

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