Curiosity changes course

During the night of 11 to 12 January, the spaceship that is transporting NASA’s rover Curiosity successfully completed a tricky course correction manoeuvre. The spacecraft is now directly heading for a landing, scheduled on 6 August 2012.

 

The spaceship transporting Curiosity (artist’s impression). The rover is in a capsule that will protect it during its entry into the Martian atmosphere. The video at the end of this article explains the entire landing sequence. Credit: NASA/JPL

We would reiterate that Curiosity blasted off from Florida’s Cape Canaveral Air Force Station atop an Atlas V rocket on 26 November 2011, (see this article with videos). Once in orbit, the upper stage of this rocket (dubbed Centaur) provided the momentum required such that the capsule-shaped spaceship transporting the rover gained sufficient speed for reaching Mars. And yet, the path it was following was not leading towards the Red Planet... An error? No, not all!

Centaur not allowed on Mars
This task having been successfully completed, Curiosity separated from its Centaur stage. We would point out that the reality of current interplanetary journeys is not at all like those of the sci-fi spaceships that travel with their thrusters permanently firing! A strong boost is given at the beginning (role of the Centaur stage) and then the spacecraft continues on its momentum (there is no air in space and therefore no slowing friction) and makes direction corrections.

uriosity blasted off atop an Atlas V rocket on 26 November 2011. Credit: NASA/Scott Andrews/Canon

And in fact, once the Centaur stage and Curiosity had separated, they continued on exactly the same trajectory. But Centaur was not sterilised like the rover. Consequently, if this rocket stage had been aimed directly at Mars, it would have crashed on its surface with the risk of contaminating the planet with microbes from Earth. It would be a terrible waste to send probes to this world in order to discover life that we had negligently transported there! Centaur is therefore banned from Mars. And so, the solution was to use the stage to give the rover transportation spaceship the right speed, but to aim it slightly to one side of the target. Then, Curiosity used its small thrusters to carry out the necessary adjustment whilst the separated Centaur continued on a course that missed Mars.

A successful manoeuvre
And this is exactly what happened during the night of 11 to 12 January 2012. The manoeuvre began on 11 January at 23:00 Universal Time and was completed 2 hours and 55 minutes later in the early hours of the following day. During this time, Curiosity’s transportation spaceship fired its 8 thrusters (grouped into two blocks of 4) according to a very specific sequence. A long firing that lasted 19 minutes, and that only used one of the 4 thrusters from each of the 2 blocks, was the beginning of operations. The spacecraft therefore accelerated. Then, said spacecraft turning on itself, when a group of thrusters was well placed, it was activated for 5 seconds in order to obtain a boost on just one side and gradually change the direction followed. However, this was very gradually as 200 such firings had to be carried out over a period of 2 hours and forty minutes. NASA’s rover was then heading to Mars, bringing its arrival forward by 14 hours with a view to being in a position to land in Gale crater (see this Enjoy Space article). On 12 January, its speed in relation to the Earth reached 16,600 km/h (110,500 km/h in relation to the Sun) and it had travelled 130.6 million km out of the 567 million km separating it from its objective (the path being curved and not straight).

The Curiosity rover “at work” on Mars (artist’s impression). Credit: NASA/JPL

Other course corrections are scheduled, but they will not be as important as they are just a matter of fine-tuning the route to be followed. For example, the next manoeuvre scheduled on 26 March will be 6 times less important in terms of the changes made.
We would reiterate that Curiosity is carrying two French instruments as the Enjoy Space video below explains.



And speaking of robots, let’s not forget the season of films entitled “L’Odyssée de l’espace” (Space Odyssey) at Toulouse’s Cinémathèque (in partnership with the CNES and the Cité de l’Espace). The next film scheduled on 25 January is Short Circuit which relates the adventures of a robot that becomes aware of its condition. And with its two cameras in the form of a pair of eyes (photograph below), it immediately brings the Spirit and Opportunity rovers, not to mention Curiosity, to mind (see this full article on Short Circuit at Toulouse’s Cinémathèque).



Publié le 13 janvier 2012