ELSA – How researchers prepared for the Gaia space mission's scientific harvest
August 2013 will see the launch of Gaia, a five-year space mission packed with scientific ambition that is quite literally astronomical. The European Space Agency (ESA) aims to chart about one billion stars, or roughly 1% of the Milky Way. It is expected to discover thousands of new celestial objects, from extra-solar planets to failed stars called brown dwarfs. It is an extraordinary endeavour, taking astrometry to a new level of complexity and precision, but it will mean little if Europe's science community cannot handle the volume of data that Gaia space mission is expected to send back to Earth. And this is where ELSA comes in.
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ELSA, or the European Leadership in Space Astrometry project, has trained young researchers for the challenge of processing the data and eventually creating a comprehensive sky catalogue. The four-year project was one of the European Union (EU)'s Marie Curie Actions (MCAs) of support for the mobility of researchers. Launched in October 2006 with a €2.79 million EU grant, ELSA involved partnerships with universities and institutes from across Europe to help 15 PhD and post-doctorate students collaborate on the astrophysical, instrument modelling, algorithmic, numerical and software engineering aspects of the mission.
"ELSA has helped prepare for the creation of the Gaia catalogue," says project coordinator Lennart Lindegren, from Sweden's Lund Observatory. "It has also provided invaluable training for the next generation of researchers in this unique European specialty."
Gaia's scientific mission is not just about mapping the galaxy but also about testing theories of star formation and evolution, and conducting stringent new tests of Albert Einstein's general relativity theory. Lindegren says the complex data analysis needed requires a mix of specialist skills in space astrometry, software engineering, numerical methods and instrument modelling. "ELSA offered training in a combination that is rarely found at a single institute and never in current PhD programmes," he says.
The projects undertaken by the ELSA fellows included development of improved models of stars, their spectra and spatial distributions, and methods to solve the complex mathematical equations required to determine their positions.
Gaia will map the stars from the L2 Lagrange Point, 1.5 million kilometres from Earth, where it will be fully exposed to charged particles from the Sun. One key contribution from ELSA was to model this particle radiation on Gaia's optical detectors, the Charged Coupled Devices (CCD) cameras, and minimize its impact on the measurements.
ELSA also helped strengthen the collaboration between the various participating teams in Gaia, which in turn improved the quality of their research. "The research was of outstanding quality and some of it could probably not have been done without the infrastructure provided by the ELSA network in the form of generous travel grants, workshops, secondments and informal personal contacts," Lindegren says.
As for the young researchers that took part, Lindegren says they relished the chance to be part of the wider Gaia community. "They have made invaluable contacts for their future careers and, on a more personal level, developed a great sense of solidarity and friendship." And he points out that when ELSA project ended in 2010, some of its researchers transferred to a related initiative, the Gaia Research for European Astronomy Training (GREAT) project.