|  | | | | | | | Rendezvous with a comet
The most difficult phase of the Rosetta mission is the final rendezvous with the fast-moving comet. After the braking manoeuvre in November 2011, the priority will be to edge closer to the nucleus. Since this takes place before Rosetta's cameras have imaged the comet, accurate calculations of Wirtanen's orbit, based on ground-based observations, are essential.
9 Comet Approach (November 2011– May 2012):
As Rosetta drifts towards the heart of the comet, the mission
team will try to achieve good comet illumination conditions, in
order to study the dynamic properties of the comet in great
detail: the first camera images will dramatically improve
calculations of the comet's position and orbit, as well as its size, shape and rotation. The relative velocities of the spacecraft and comet will gradually be reduced, slowing to 2 m/s after about 90 days. This phase could be reduced to four months.
10 Comet Mapping / Characterisation (May – June 2012):
Less than 200 km from the nucleus, images
from Rosetta show the comet's attitude, angular velocity, major landmarks and other basic characteristics. Eventually, the spacecraft is inserted into orbit around the nucleus at a
distance of about 35 km. Their relative velocity
is now down to a few cm/s. The Orbiter starts to map the nucleus in great detail. Eventually, five potential landing sites are selected for close observation.
11 Landing on the Comet (July 2012):
Once a suitable landing site is chosen, the Lander is released
from a height of about 1 km. Touch-down takes place at
walking speed – less than 1 m/s. Once it is anchored to the
nucleus, the Lander sends back high-resolution pictures and
other information on the nature of the comet's ices and
organics in the crust. The data are relayed to the Orbiter,which
stores them for downlinking to Earth during the next groundstation contact.
12 Escorting the Comet (July 2012 – July 2013):
The Orbiter continues to orbit Comet Wirtanen, observing what
happens as the icy nucleus approaches the Sun. The mission
ends in July 2013, at the time of the comet's closest approach
to the Sun (perihelion). Rosetta will once again be close to
Earth's orbit, more than 3800 days after its adventure began.
| | Last update: 13 December 2002 |  |
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