Final commands given to distant probe

What are likely the final commands before Tuesday's historic flyby of a distant icy world have been sent to Nasa's New Horizons spacecraft.

The probe's pass of the 30km-wide object known as Ultima Thule will set a new record for the farthest ever exploration of a Solar System body - at 6.5 billion km from Earth.

The upload included a two-second timing correction that ensures New Horizons knows precisely when and where to point its cameras as it sweeps alongside its target at a breathtaking 14km/s.

"The spacecraft is healthy and we're excited!" said Mission Operations Manager Alice Bowman when she briefed reporters at the control centre embedded in the Johns Hopkins University Applied Physics Lab (JHU-APL) in Maryland.