Satellite duo performs space pas de deux

As if engaged in a slow-motion dance, two mated satellites used a robot arm to draw apart, then come together again several hours later on Monday. It is the first step towards the mission's ultimate goal of separating completely and docking with each other autonomously from a distance of 7 kilometres away. The $300-million Orbital Express mission – run by the US Defense Advanced Research Projects Agency (DARPA) – uses two satellites. One, called ASTRO (Autonomous Space Transport Robotic Operations), is designed to dock with and test repairs on another, called NextSat. The 90-day mission is meant to test autonomous operations in a spacecraft so that one day, a fix-it satellite might be deployed to fuel, inspect or even repair a wounded satellite without help from human controllers.