The third 鈥� and final 鈥� radar boom has been deployed aboard Europe鈥檚 Mars Express spacecraft, clearing the way for scientists to begin searching for water beneath the Red Planet鈥檚 surface.
Mission managers in Darmstadt, Germany, deployed the 7-metre-long boom on 17 June at 1400 GMT. So far, engineers have not been able to detect the deployment鈥檚 tiny effect on the spacecraft鈥檚 gyroscopes, which measure its rotation, to see if the boom deployed straight. But the spacecraft is functioning normally and mission managers see the lack of a signal from the third boom as a good sign.
鈥淚f you can鈥檛 find it, then it can鈥檛 harm the mission,鈥� mission manager Fred Jansen told New 杏吧原创. But to be sure, engineers will fire the spacecraft鈥檚 thrusters periodically on Tuesday to search for a signal in the craft鈥檚 recoil, a process Jansen likens to 鈥渓ooking for a needle in a haystack鈥�.
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No special precautions were taken in deploying this boom which, at just 7 m long, was expected to pop out with less energy than the first two booms, which each measure 20 m long. With those booms, Mars Express was turned so the Sun heated and straightened the booms 鈥� a procedure put in place after a hinge on the first boom鈥檚 failed to lock into place during a 鈥渃old鈥� deployment.
The third boom completes the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument and mission managers will begin two weeks of tests on Thursday.
Avoiding confusion
During this commissioning phase, engineers will make sure the antenna does not produce 鈥渋nterference鈥� with the spacecraft鈥檚 other electronic instruments 鈥� similar to a ringing mobile phone disturbing the reception of a nearby TV.
In the coming weeks, MARSIS will look at Mars鈥檚 northern latitudes 鈥� where the planet鈥檚 flat northern plains will provide a good test ground for the radar. The signals collected by MARSIS are more complex when the surface topography is hilly, though its third boom will help correct for this by analysing waves reflected from the surface.
鈥淚 am thrilled to be so close to finally beginning the experiment that we have spent seven years developing,鈥� says MARSIS co-leader Jeff Plaut of NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California, US.
High hopes
MARSIS works by sending out pulses of radio waves and analysing the time delay and strength of the waves that return. Most will rebound from the surface, but some of the longer wavelength waves may penetrate the porous rocky soil, bouncing back when the waves encounter a transition between two materials with different electrical properties.
Waves from subsurface water should take longer to bounce back and have weaker signals than surface waves, raising hopes that MARSIS might deliver a groundbreaking discovery.
鈥淚 have high hopes MARSIS will allow us to 鈥榮ee鈥� Mars in the third dimension, and to provide a lot of surprises,鈥� Plaut told New 杏吧原创. But he says understanding the experiment鈥檚 data could prove very challenging. 鈥淭his is an experiment 鈥� no one has tried this before and we don鈥檛 really know what we might find.鈥�
