Artemis and SPOT 4 communicating via the SILEX system (Source: ESA)

The so-called SILEX system which makes the link-up possible consists of two terminals: one on board ESA's advanced communication satellite - Artemis - and the other on the French space agency's earth observation satellite - SPOT 4. Both terminals were designed and built by Astrium, while the definition and procurement of the system were carried out jointly by ESA and the French national space agency, CNES.
When the two satellites are in direct line of sight, the laser data link can transmit real-time images taken by SPOT 4 to the image processing centre at Spot Image in Toulouse, France. In this preliminary experiment a link was established four times. During four successive SPOT 4 orbits, the Artemis SILEX terminal scanned the area where SPOT 4 was expected to be with its optical beacon. SPOT 4 then responded by sending back its own laser beam to Artemis, allowing an optical link to be maintained for a pre-programmed period lasting from four to 20 minutes.

Timed to perfection
During this 'communication', SPOT 4 transmitted a highly accurate data stream to the ground via Artemis at a rate of 50 000 000 bits per second (50 Mbps). Establishing such an optical link between satellites is a delicate operation and this experiment was performed under difficult conditions since Artemis is not yet in its final geostationary orbit at 36 000 km, but is in a lower parking orbit, circling the earth every 19 hours. The first experimental transmission of a SPOT 4 image is planned for early December this year. By mid-2002, the operational phase will get under way allowing the link between the two satellites to be established at least five times a day.

Every year the prestigious Latsis prize is awarded to an individual or group for significant contributions to a certain field of European research. This year's prize, with a value of €68 000, was awarded on November 22 to Professor Berger of the Catholic University of Louvain (BE) for his outstanding contributions to the understanding of the Ice Age climate cycle. Almost 30 years ago Professor Berger, who works in the university's Institute of Astronomy and Geophysics, was the first to accurately describe the variations of astronomical factors influencing our global climate. Since then his research work has focused on using complex computer models to better understand what triggers climatic changes during ice ages.

Building on the past
According to the early orbital theories of climatic change, polar insulation in summer is the critical determining factor behind ice ages. Persistent ice sheets are formed when frozen snow from the previous winter accumulates and then causes further cooling by reflecting sunlight. However, Berger's research went beyond these theories to accurately recalculate the long-term variations, over more than 1 million years, in the seasonal and latitudinal distributions of the insulation experienced daily by the earth. His work also showed the influence that these variations had on the energy received from the Sun and the subsequent effects on global sea level and ice volume. According to Professor Berger's astronomical data, the current levels of carbon dioxide in the atmosphere are already much greater than has been the case over the last 400 000 years - a phenomenon which may eventually lead to the disappearance of the Greenland and western Antarctic ice sheets and cause sea levels to rise by as much as 12 metres during the coming thousands of years.

The project to measure and monitor selenium supplements and arsenic presence in food will involve researchers from 20 laboratories across Europe. Selenium is an essential but highly toxic element, and today it is thought that the lack of the beneficial forms of this nutrient in our diet may be one of the reasons behind growing numbers of prostate cancer cases. The researchers plan to incorporate selenium into yeast, hence converting it into a favourable chemical form which can then be used as a reference standard for monitoring 'beneficial' dietary supplements currently on the market. 'Without this reference material, harmful supplements could be on chemists' shelves alongside beneficial ones. If, as expected, the clinical trails of these supplements show a way to reduce the incidence of prostate cancer, they will be of enormous interest,' explained Professor Les Ebdon of the University of Plymouth in the UK, who is leading the project.

Safe limits
The laboratories participating in the project will also investigate arsenic levels in chicken, rice, fish and oil in an attempt to improve the standardisation of food safety checks. Previous studies have highlighted the presence of a harmless chemical form of arsenic in fish which remains safe through cooking and digestion processes. Since fish-meal is now commonly included in the diet of many animals, especially chickens, it is important to check that it remains only in the harmless form. The project, which will continue until February 2003, is being carried out under the Growth programme's 'measurements and testing' activity.