At 1.49pm, the piano-sized New Horizon probe will reach its closest point to Pluto. After nine years of travel the probe will take close-up photographs of the open blob that used to occupy the end of high school solar system charts.
Getting there has been quite a feat:
1) In order to escape the gravity field of both the Earth and the Sun, New Horizon had to be launched at over 50 000km/h. The Atlas V rocket that hurled it out of orbit ensured the fastest launch in history. This meant it passed the moon nine hours later – when it took the Apollo astronauts three days. It has been flying for nine years to cover the seven-billion kilometres.
2) When New Horizon launched on January 6 2006, Pluto was still our ninth planet. But a similarly-sized object – Eris – forced a reclassification of Pluto. It is so small that Earth’s moon is five times bigger. As a result – just eight months after the launch – Pluto’s status as a planet was removed.
3) New Horizon is carrying the ashes of Clyde Tombaugh, the man who discovered Pluto in 1930. At the time it was thought that Pluto was the same size as the Earth. The spacecraft also carries a CD containing the names of 434 000 people who added their name to the “Send Your Name to Pluto” list Nasa circulated prior to launch.
4) New Horizon also has a 1991 US postage stamp. The postal agency had a commemorative collection, listing the names of the planets and which ship had explored them. Pluto’s stamp has a vague picture with the caption, “Pluto: Not Yet Explored.”
5) New Horizon is travelling so far from the Sun that it cannot rely on solar panels. Instead, it has a nuclear power plant. To save energy, it shuts down its navigation systems and spins to ensure direction when it points its dish back to Earth to transmit information.
6) There are seven main instruments for observation on New Horizon. Five have serious acronyms as names – such as PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation). Two are named from characters in the 1950s television series “The Honeymooners”. Alice will study the atmosphere, while Ralph will be taking the surface photographs of Pluto that will get beamed back after New Horizon has zipped past the dwarf planet.
7) The spacecraft is so far away that its messages can only be picked up by the giant dishes of the Deep Space Network – each 70m wide. These can pick up the 2.5-megabit photographs New Horizon sends back. But there is so much competition for the use of the network’s three dishes that Nasa normally only gets on eight-hour communication session a day to get information from New Horizon.
8) New Horizon can also only turn its dish in one direction, so will be focusing on Pluto. Nasa will therefore only know after midnight local time if the mission was successful. That message will be picked up by dishes based in Australia.