The Beagle 2 spacecraft, aiming to land on Mars on Christmas Day, is set to separate from its mothership at 0831 GMT on Friday.
Jettisoning Beagle 2 successfully is not just critical for the lander itself, but also Mars Express, which might otherwise struggle to enter Mars orbit as planned.
Two-thirds of previous missions to Mars have failed, and the separation is only the first of several critical hurdles the European Space Agency mission must overcome as it nears its target.
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But, Barrie Kirk, former project manager for Beagle 2 at Astrium UK, is 鈥減erfectly relaxed鈥�. The Spin Up and Ejection Mechanism (SUEM), which will push Beagle 2 out of Mars Express, 鈥渋s a very reliable device,鈥� he told 快猫短视频. 鈥淲e tested it well over 30 times and it鈥檚 never failed.鈥�
Gentle nudge
On Friday, when Mars Express receives the go-ahead signal from the European Space Operations Centre (ESOC) in Darmstadt, Germany, it will fire up the SUEM.
The spring-like SUEM will gently nudge Beagle 2 away from Mars Express at a speed of 20 centimetres per second.
Importantly, the SUEM will also set the lander spinning at 12 rotations per minute. The spin will stabilise the probe and determine the orientation at which it will enter the Martian atmosphere.
Mars Express will feel a small recoil as Beagle 2 leaves. It will then take two hours for Mars Express to arrive in a position to communicate this recoil to ESOC, which will announce the separation鈥檚 success or failure at 1031 GMT.
Extra mass
The worst case scenario, says Kirk, is that Beagle 2 fails to eject at all. 鈥淭hat has a big impact on Mars Express because they鈥檝e then got to carry all that extra mass into orbit.鈥�
鈥淣eedless to say, we don鈥檛 really like thinking about it,鈥� says David Southwood, director of science at the European Space Agency. 鈥淏ut we do have a back-up plan.鈥�
There is a two-day window in which mission planners can keep trying to detach Beagle 2. 鈥淏ut if Beagle 2 is really so fond of its mothership and doesn鈥檛 want to let go, at some point we have to save the mothership,鈥� Southwood told 快猫短视频.
This is because Mars Express has to fly directly towards Mars to jettison the unpowered Beagle 2 in the right trajectory. But at some point Mars Express must fire its engines and change direction to enter orbit and avoid burning up in the Martian atmosphere.
If Beagle 2 does have to be carried into orbit, its 70 kilogram weight will require extra fuel to be burned. 鈥淭he nail biting will be, 鈥楢re we too heavy to get where we need to go?'鈥� says Southwood. 鈥淲e believe we will be able to do it.鈥�
Beagle 2鈥檚 presence should not impede any of Mars Express鈥檚 seven scientific instruments, which will look for subsurface water and study Mars鈥檚 atmosphere and geology.