At 8.31 GMT, software on Mars Express was scheduled to send the command for the Beagle 2 lander to separate from the orbiter. This would fire a pyrotechnic device that would slowly release a loaded spring and gently push Beagle 2 away from the mother spacecraft at around 1 ft/s (0.3 m/s).
If all goes according to plan, the release mechanism will also cause Beagle 2 to rotate like a spinning top, stabilising its motion during the final stage of its flight towards Mars.
Since Beagle 2 does not have a propulsion system of its own, it must be carefully targeted at its destination. With Mars Express acting as a champion darts player aiming at a bullseye, Beagle 2 should be placed on a collision course with the planet, following a precise ballistic path that will enable it to hit a specific point at the top of the Martian atmosphere in six days' time.
Initial confirmation that the separation manoeuvre has been successful is expected at 10.40 GMT, when the European Space Operations Centre (ESOC) in Darmstadt, Germany, should receive X-band telemetry data from Mars Express. Further information from Mars Express and Beagle 2 telemetry confirming separation should be returned by 11.10 GMT.
In addition, it is hoped that the orbiter's onboard Visual Monitoring Camera (VMC) will provide pictures showing the lander moving slowly away. The images are expected to be available within hours of the separation event.
However, after six months in space, during which the spacecraft were buffeted by solar storms, the manoeuvre is not without risk. Although it has been tested many times on Earth, there is always the outside possibility that something may go wrong during the all-important separation.