Marsis radar deployment success

The booms have been folded up on the spacecraft since it launched in 2003 Enlarge Image

Europe's search for water reservoirs beneath Mars can proceed apace after the smooth deployment of a second radar boom on the Mars Express spacecraft.

Deployment was delayed for more than a year amid concerns that the booms might swing back and damage the spacecraft.

Officials said the second boom, which had been folded up like an accordion on Mars Express since launch, had extended and locked into place successfully.

The Marsis instrument could begin collecting data as early as 21 June.

Two 20m-long (65ft) hollow fibreglass "dipole" booms make up Marsis' primary antenna, while a 7m-long (23ft) "monopole" boom acts as a receive-only antenna.

Reflected waves

Marsis sends out pulses of radio waves from the primary antenna to the planet's surface and analyses the time delay and strength of the waves that return.

Marsis needed to deploy its two longest booms in order to function (Image: European Space Agency)

Analysis of those waves that penetrate the soil and bounce back will give information on transitions between materials with different electrical properties, such as rock and liquid water, beneath the Martian surface.

The 7m-long "monopole" boom remains to be deployed, but Marsis (Mars Advanced Radar for Subsurface and Ionosphere Sounding) needs only the two 20m-long booms to operate.

Nonetheless, the monopole is important to help scientists confirm that reflected radio waves are indeed coming from beneath the Martian surface, below the craft, and not bouncing off the surface further away from Mars Express.

Slow rotation

For deployment on Tuesday 14 June, controllers at the European Space Agency's operations centre in Darmstadt, Germany, sent Mars Express into a 30-minute-long slow rotation to ensure the boom's hinges were heated by the Sun.

When the first radar boom was deployed in May it did not lock fully into place. However, swinging the spacecraft round to warm the pole's cold parts in the Sun fixed the problem.

Shortly after, an autonomous manoeuvre oriented Mars Express towards the Sun, in order to recharge the spacecraft's batteries and for a further heating of the hinges.

Data received from the spacecraft later on in the day confirmed that the spacecraft's behaviour was consistent with two correctly deployed antenna booms.

The radar altimeter can search for water, liquid and frozen, up to 5km (3 miles) beneath Mars.