Mission controllers at the European Space Agency are now planning to deploy the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument (MARSIS) on Mars Express in the first half of May. They delayed deploying the two 20-metre (65 foot) booms (and another, smaller boom) because simulations predicted that they could swing back and actually hit the spacecraft. They will put the spacecraft in a mode that will allow it to tumble freely while the deployment is performed to minimize risk to Mars Express.