The 'ins and outs' of a celestial dance by Cluster 2
EUROPEAN SPACE AGENCY SCIENCE RELEASE
Posted: June 12, 2001
At the start of the two-day gathering, Cluster deputy project manager Alberto Gianolio told the SWT that the recent orbital manoeuvres had been extremely successful. With the quartet now flying some 2000 km apart in a tetrahedron formation, the spacecraft are ready to begin their first observations of the Earth's huge magnetic tail or magnetotail.
Further details were provided by Cluster spacecraft operations manager Sandro Matussi, who explained that the complex sequence of engine firings had been completed with great precision. The manoeuvres had been carried out so meticulously that only two of the four spacecraft orbits had to be altered on 3 June, the final day of the four-week phase to set up the new orbital configuration.
"Rumba and Salsa had been moved so precisely during previous manoeuvres that there was no need to fire their thrusters," said Matussi. "Even Samba and Tango required only very small drift manoeuvres."
"Our original plan was designed to cover possible errors in the manoeuvres," he explained. "However, the excellent performance of the spacecraft and the very thorough mathematical calculations of our flight dynamics colleagues at the European Space Operations Centre in Darmstadt, Germany, meant that we only had to make 23 of the 28 scheduled engine firings."
Even as the Cluster quartet were beginning their latest celestial dance, the 11 Cluster principal investigators met to discuss their preferences for the next mission phase that will start in February 2002. They eventually agreed to close the gap between each spacecraft to just 100 km - an intimacy unrivalled by any flotilla of scientific spacecraft during more than four decades of space exploration.
"By bringing the spacecraft so close together, we will be able to study the key regions of the magnetic bubble that surrounds the Earth - the magnetosphere - in unprecedented detail," said Cluster project scientist Philippe Escoubet. "This will probably be our only opportunity to obtain small-scale, three-dimensional measurements of the polar cusps, the bow shock and the magnetopause."
"The observations will revolutionise our understanding of the physical processes taking place where the electrically charged particles in the supersonic solar wind collide with the Earth's magnetic field," he said.
"Since four identical spacecraft have never before examined near-Earth space, the data from Cluster are continually breaking new ground," said Dr. Escoubet. "The analysis is very complex but also extremely exciting."
"We have completed the first chapter of the Cluster adventure, but the rest of the story promises to be even more compelling," he added.
The Hubble Space Telescope's majestic view of the Eskimo Nebula. This spectacular poster is available now from the Astronomy Now Store.