PPARC town meeting on ESA cornerstone missions

Press Release From: Particle Physics and Astronomy Research Council
Posted: Thursday, May 18, 2000

Mr Mark Wells
Particle Physics & Astronomy Research Council
01793 442100

On 23 May at the DTI Conference Centre,1 Victoria St, London, members of the UK Space Science community will meet to discuss candidates for the 'Cornerstone' missions of the European Space Agency's science programme during the next ten years

.Cornerstones are the largest, most ambitious, missions of the ESA Horizons 2000 programme. Each is devoted to a key area of science in which the mission is expected to make unique measurements, unsurpassed by any other technique. Cornerstones also play a key role in stimulating the industrial development of key space technologies.

This September, ESA will decide which mission to adopt as its next Cornerstone. The choice is between three outstanding candidates:

Mercury, the second smallest planet and the closest one to the Sun, is the least well-known of the rocky, terrestrial planets. Only one previous spacecraft, NASA's Mariner 10, has visited Mercury and only hemisphere has been imaged. BepiColombo will investigate many of the mysteries of Mercury, including the origin and nature of its strong magnetic field, the influence of the solar wind, and the presence of water ice at its poles. Reaching Mercury and entering orbit around the planet is very difficult. To achieve this, BepiColombo will use a new solar-electric propulsion system and special gallium arsenide solar cells that will have to cope with high light intensities as well as high temperatures. Three separate exploratory modules are planned. The Planetary Orbiter will be dedicated to planet-wide remote sensing and radio science. The Magnetospheric Orbiter will conduct studies of the field, wave and particle instruments. A small lander will perform in situ measurements of the surface and tenuous atmosphere.

GAIA is the successor to ESA's Hipparcos satellite. It will pinpoint the stars far more accurately than ever before and is intended to give precise and detailed information about the billion brightest objects in the sky, whatever they may be. This unprecedented census should have a major impact on astronomy. If approved, GAIA will be launched by Europe's Ariane-5 rocket in 2009. GAIA is currently envisaged as a 3-ton spacecraft. It will operate 1.5 million km out on the dark side of the Earth, at Lagrange Point No. 2 (L2) where the gravity of Sun and Earth combine to create a place of rest relative to the Earth. With its back turned to the Earth, and shielded from the light of Sun, Earth and Moon by a wide collar carrying the solar cells that power the spacecraft, GAIA will revolve slowly, scanning circles around the sky. Two identical main telescopes, each 1.7 metres wide, will look simultaneously at stars in two different parts of the sky. The detectors of each main telescope will record the position of every star, and its brightness in four broad wavelength bands. A third telescope, 75 cm wide, will look out between the main telescopes. It will see the same stars and measure their brightness in 14 narrow wavelength bands. It will also measure the redshift or blueshift of light, which shows the speed at which an object is receding or approaching. These measurements should enable astronomers to determine the composition, formation and evolution of our Galaxy. GAIA will achieve (i) a census of the contents of a large, representative, part of the Galaxy; (ii) quantification of the present spatial structure; (iii) knowledge of three-dimensional space motions to determine the gravitational field and stellar orbits.

LISA's primary objective will be to detect and observe gravitational waves from massive black holes and binary stars. Useful measurements in this frequency range cannot be made on the ground because of the unshieldable background of local gravitational noise. Up to now, our understanding of the Universe has been limited as it is based solely on observations of electromagnetic waves, ranging from radio to gamma-ray wavelengths. Electromagnetic waves come almost entirely from weak gravity, low-velocity regions. By contrast, gravitational waves are emitted most strongly in regions of space-time where gravity is relativistic and where velocities are close to the speed of light.LISA will search for these elusive waves by using three widely separated satellites that are linked by infrared laser beams. These will form a giant 5 million km triangular interferometer which is sensitive to tiny fluctuations in the separation between the satellites that are caused by gravitational waves.

There will also be a short presentation on the DARWIN, a Cornerstone mission that is planned for beyond the next ten years. Darwin will be an imaging interferometer for astrophysics and will study topics such as the formation of planets and stars. It will also seek to answer the question of whether other planets similar to our own, with plentiful oxygen and liquid water, exist in our Galaxy.

Notes for Editors

10:00 Introduction - P. Murdin (PPARC/BNSC)

10:15 GAIA - G. Gilmore (Cambridge), T. de Zeeuw (Leiden), L. Lindegren (Lund)

11:35 LISA - J. Hough (Glasgow), R. Reinhardt (ESA)

12:55 Lunch

13:45 BepiColombo - A. Balogh (ICSTM), S. Dunkin (UCL), R. Grard (ESA)

15:05 Discussion

16:00 End of Meeting

The meeting is open to the scientific community and members of the media. However, spaces are limited so pre-booking is recommended.

For (free) tickets contact: Clare ChambersTel : 01793 442119Fax: 01793 442036Email: of the programme are listed at the end of this press notice.


Charlotte AllenParticle Physics and Astronomy Research CouncilPress Officer.Tel: 01793-442012Mobile: 07881-654121 E-mail:

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