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.

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:

  • Queen Mary and Westfield College, London will design and
    manufacture filters and some of the optics.

  • Rutherford Appleton Laboratory and the Royal Observatory Edinburgh
    will be involved with the cooling systems.

  • The University of Leicester will offer electronic ground support.
  • The UK data analysis will be centred at the University of Cambridge
    and Imperial College, London, and also involve scientists at Edinburgh.

    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.

  • Planck mission