Tuesday, September 2, 2014

Rosetta set for 'capture' manoeuvres

The Rosetta probe is about to begin the manoeuvres that will place it properly into orbit around Comet 67P/Churyumov-Gerasimenko.


The European spacecraft is currently flying arcs over the 'ice mountain' that take it no closer than 52km.


But from Wednesday, Rosetta will gradually drop this distance so that come next week it will be at an altitude of just 29km.


At that point, 67P's gravity should capture the spacecraft.


European Space Agency flight director Andrea Accomazzo said: 'The first orbit - we will actually fly only half of it for seven days, and then we'll change the orbital plane and fly for another seven days.


'And then, if the comet environment allows us to continue, we'll go further down, first to 19km and then 10km from the centre of the comet.'


Scientists and engineers on the mission are busy trying to determine the best place to land on 67P.


They have selected a longlist of five sites on the 4km-wide object and need to reduce this to two - a primary and a back-up - by 15 September, when Esa expects to announce the preferences in a media conference in Paris.


The landing itself - which will be performed by Rosetta's contact robot Philae - is scheduled to take place on 11 November.


67P/Churyumov-Gerasimenko



  • Named after its 1969 discoverers Klim Churyumov and Svetlana Gerasimenko

  • Referred to as a 'Jupiter class' comet that takes 6.45 years to orbit the Sun

  • Orbit takes it as close as 180 million km from the Sun, and as far as 840 million km

  • The icy core, or nucleus, is about 4km (2.5 mi) across and takes 12.4 hours to rotate


Accomazzo said mission controllers had 'some headaches' currently in trying to work out precisely where the centre of mass is on the 10-billion-tonne, rubber-duck-shaped comet.


It is an important detail for designing a safe orbit, but the flight director said this information ought to become clear in the coming days.


At the moment, the comet remains quiet, with very little gas and dust streaming from its surface.


This could change at any moment, however, and Accomazzo's team is ready to modify Rosetta's manoeuvres if 67P suddenly comes to life.


Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos