The European Space Agencys Rosetta mission has made the first in a series of essential manoeuvres on its mission to reach a comet later this year. A number of thruster burns through May and until August will steadily bring Rosetta in line with the comet 67P/Churyumov–Gerasimenko. Currently Rosetta is on a trajectory that would, if unchanged, take it past the comet at a distance of approximately 50,000 km and at a relative velocity of 800 metres per second (m/s). The aim of the manoeuvres is to reduce Rosettas relative velocity to 1 m/s and bring it to within 100 km distance of the comet by 6 August. The series of burns—termed “delta-v” manoeuvres—is vital to prevent Rosetta from missing the comet. And a worry for ESAs mission controllers is that the Reaction Control System that operates the thrusters ran into problems in September 2006. It forced engineers to find a workaround to get the thrusters to perform at lower pressure. Rosetta’s Mission Manager Fred Jansen told Sen: “The delta-v manoeuvres this month and next are crucial events to line-up the Rosetta orbit with that of the comet, both in terms of direction and velocity, and thus pivotal to the success of the whole mission. “As the relevant system on Rosetta has had some problems in the past, this calls for a careful approach with a fast response to anything out of the ordinary, and most definitely the next few weeks will be a very intense time.” The Rosetta team have planned a series of eight thruster burns through to the end of July, one every two weeks for the first four burns, then weekly thereafter. Today’s manoeuvre was essentially a test, to make sure that all systems work as expected, and was expected to decrease Rosettas relative velocity to the comet by 20 m/s.Rosetta launched in March 2004 embarking on a circuitous ten-year trek across the Solar System, crossing the asteroid belt and traveling into deep space, more than five times Earths distance from the Sun. Rosetta was woken from deep-space hibernation on 20 January. All 11 science instruments and the lander Philae have now been successfully reactivated and the necessary measurements have been taken. This instrument commissioning period is expected to be completed on 13 May. The majority of instruments have since been switched back off until the science readiness reviews are complete and Rosetta is closer to comet 67P/CG. Rosettas Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS) and the spacecrafts NavCams continue to take images for navigation purposes. OSIRIS is also taking lightcurve measurements to determine the comets rotation period. Two first light images of comet 67P/CG were taken on 20 and 21 March by the OSIRIS wide-angle camera and narrow-angle camera.The orbiter will rendezvous with Comet 67P/CG in August and become the first spacecraft to orbit a comets nucleus and to fly alongside a comet as it heads towards the inner Solar System. After catching up with the comet Rosetta will slightly overtake and enter orbit from the front of the comet as both the spacecraft and 67P/CG move along their orbits around the Sun. Rosetta will carry out a complex series of manoeuvres to reduce the separation between the spacecraft and comet from around 100 km to 25-30 km. Then in November, the small Philae lander will be released onto the surface of the comet. The landers instruments will obtain the first images from a comets surface and make the first in situ analysis to find out what it is made of.
Posted on: Thu, 08 May 2014 16:05:41 +0000
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