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Mars Express and MSL
On 6 August, NASA will land its Curiosity rover on Mars to study whether conditions on the red planet have ever been, or could be in the future, favourable to life.
The landing is part of its Mars Science Laboratory (MSL) mission.
During the rover's descent, the MSL spacecraft will slow its velocity using a parachute, and lower the rover in the final moments of descent using a tether.
MSL will enter the Martian atmosphere at almost at almost 21,000km per hour, and in seven minutes should decelerate to less than 3.6km per hour.
The European Space Agency (ESA) will track the mission's progress using the ESA Mars Express orbiter.
"We began optimising our orbit several months ago, so that Mars Express will have an orbit that... provides good visibility of MSL's planned trajectory," Michel Denis, Mars Express spacecraft operations manager, said in a statement.
This image shows an artist's impression of the Mars Express orbiter (left) and the MSL mission.
Image credit: Alex Lutkus