Upon arrival, the spacecraft hovers above the asteroid and matches its rotation. If the asteroid has a stable, penetrable surface, the astronauts could fire tethers into it to anchor the craft. They could then leave the craft and pull themselves to the surface or use a robotic arm to drill and collect samples.
An Ares I rocket [left] launches the astronauts and their Orion crew capsule into orbit. By this point, the Earth Departure Stage (EDS), which will propel the astronauts toward their deep-space destination, is already in orbit, having been launched into space 90 minutes earlier by an unmanned Ares V rocket.