19 Feb 2007

Open University space science nears close encounter with Mars



The European Space Agency’s (ESA) spacecraft Rosetta, one in a stable of space projects involving The Open University, is about to have a close encounter with Mars. Rosetta is en route to landing on a comet, and will swing-by Mars on 25th February 2007, helping to set it on the correct path to its final destination.

That destination is comet 67P Churyumov Gerasimenko, where Rosetta is scheduled to arrive in 2014. It will then home in towards the comet’s nucleus before deploying a lander onto its surface to make in situ measurements.

Philae lander

Philae lander

The Rosetta lander, Philae, can be powered independently from the orbiter, and some instruments will be taking scientific measurements during the entire close approach. Professor Ian Wright from The Open University is lead investigator on Ptolemy, an instrument on the lander. He said, “Rosetta’s close vicinity to Mars will provide an excellent opportunity to take a close look at the planet. It also means that some of Rosetta’s instruments, including the mass spectrometer built at the OU, will be able to be calibrated allowing us to check that they are operating correctly.”

Launched in March 2004 the three tonne spacecraft could not be sent on its correct trajectory by the launcher and so on its journey it will make a series of planned gravity assist manoeuvres past the Earth and Mars.

Rosetta’s closest approach to Mars will be made at 0153 GMT on 25th February 2007, 1090 days since launch.The distance from Rosetta to the surface of Mars will be around 250 km, and at its closest approach the spacecraft will be traveling at around 10.1 km/s (~36,400 kph ~22,700 mph) relative to the centre of Mars.

During the swing by there will be a 25 minute period when Rosetta is passing through the shadow of Mars, and during this time it will be impossible to generate power using the spacecraft’s vast solar arrays (which span 32 metres from tip to tip). To cope with this the orbiter will be placed in “eclipse mode”, and no science operations will take place onboard for approximately 3 hours around close approach. Rosetta will be able to view the planet Mars to either side of this 'blackout' .

This Mars swing-by is the second such manoeuvre that Rosetta has made following on from an Earth swing-by in March 2005. A further Earth swing-by will take place later this year on 13th November followed by a final Earth swing-by in November 2009.

UK scientists from 10 institutions are involved in the instruments on both the Rosetta orbiter and lander – some of which will be operating during the flyby. UK industry is also heavily involved in the mission, having provided key components, including the mission control system (SciSys UK Ltd) and the orbit control and propulsion system (EADS Astrium, UK). SciSys staff will be closely monitoring events at ESA’s European Space Operations Centre (ESOC) in Germany where the manoeuvre is being co-ordinated.

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