The probe is set to hurtle past the dwarf world on Tuesday, grabbing a mass of pictures and other science data.

Controllers got a last health status report, before the robotic craft turned its antenna away from the Earth to concentrate on its target.

Only when New Horizons has its trove of images safely in its onboard memory will it call home again.

This is not expected to happen until just after midnight (GMT) into Wednesday.

It means there will be a long, anxious wait for everyone connected with the mission, as they hold out for a signal that will be coming from almost five billion km away.

New Horizons' flyby of 2,370km-wide Pluto is a key moment in the history of space exploration.

Its successful execution will complete the initial reconnaissance of the "classical" nine planets in our Solar System.

It will mark the fact that every body in that system - from Mercury through to Pluto - will have been visited at least once by a space probe.

(BBC News)