I was curious how Rosetta is able to communicate over that long distance, here is a link to how it does it.

Radio communications between Rosetta and the ground will use a newly developed deep-space antenna which was built by ESA at New Norcia, near Perth in Western Australia. This 35-metre diameter parabolic antenna concentrates the energy of the radio signal in a narrow beam, allowing it to reach distances of more than 1000 million kilometres from Earth.

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The spacecraft will be visible from the New Norcia antenna for an average of 12 hours per day. In addition, there will be several periods of communications black-out when the spacecraft passes behind the Sun.

To overcome these breaks in communication, Rosetta’s solid-state memory of 25 Gbits capacity is able to store all scientific data and then transmit them to Earth at the next opportunity.