Point and shoot (Forwarded)

ESA News
http://www.esa.int

17 December 2003

Point and shoot

Any football or rugby fan knows that when a player kicks the ball, there is no
longer anything they can do to influence its path. The player must trust to
their own skill for the ball to reach its intended destination.

What has all this to do with Mars Express? Three days from now, on 19 December
2003, Mars Express must, like an expert rugby player, 'pass' Beagle 2 on to the
next player, Mars. The problem is that Beagle 2 has no thrusters on board, so
cannot influence its own trajectory.

Right place at the right time

To equip the lander with rockets would have made it far too heavy to transport
on Mars Express. Instead, engineers at the European Space Operations Centre
(ESOC) in Darmstadt, Germany, will precisely orientate the Mars Express
spacecraft to point Beagle 2 at Mars. Everything relies on dropping Beagle 2 in
the right place at the right time.

Collision course ...

In order to do this, Mars Express has been following a trajectory that will lead
to Beagle 2's touchdown point. That puts the whole mission in danger, because it
means that Mars Express is effectively on a collision course with the planet.

If nothing is done to alter its trajectory, instead of falling into orbit, Mars
Express will slam into Mars on 25 December. Yet nothing can be done to avert
this impending catastrophe until Beagle 2 has been released, since to move the
spacecraft beforehand would ruin the landing.

At ejection, the spacecraft simply lets go of the lander. Beagle 2 will be spun
to keep it stable and pushed away with the gentlest of forces; nothing dramatic
like a 'blast off' at launch. Then, and only then, can engineers send the
necessary commands for Mars Express to fire its engine and alter its course to
avoid destruction on the surface of Mars.

More about ...

* Europe goes to Mars
http://www.esa.int/SPECIALS/Mars_Express/index.html
* Mars Express overview
http://www.esa.int/esaSC/120379_index_0_m.html
* Christmas on Mars: be there with ESA
http://www.esa.int/esaCP/SEM06Q274OD_index_0.html
* Getting it right: An interview with Rudi Schmidt
http://www.esa.int/esaSC/SEMDILXLDMD_people_0_iv.html
* Testing times: An interview with Con McCarthy
http://www.esa.int/esaSC/SEMZTOXLDMD_people_0_iv.html

Related links

* Beagle 2 lander homepage
http://www.beagle2.com

IMAGE CAPTIONS:

[Image 1:
http://www.esrin.esa.int/export/esaC..._index_1.html]
Beagle 2 and Mars Express after separation. Credits: All rights reserved Beagle 2.

[Image 2:
http://www.esrin.esa.int/export/esaC...html#subhead2]
Beagle 2 separation. Credits: All rights reserved Beagle 2.