NASA's New Horizons spacecraft will be flying by Ultima Thule, an object in the Kuiper Belt. In the space of one 72-hour period, Ultima Thule will be transformed from a pinpoint of light - a dot in the distance - to a fully explored world.
The US space agency will ring in the New Year with a live online broadcast to mark the historic flyby of the mysterious object located about four billion miles (6.4 billion kilometers) away in a dark and frigid region of space known as the Kuiper Belt. The craft is now so far from Earth that it takes six hours and eight minutes to receive a command sent from Earth.
It takes about six hours for the New Horizons data to get all the way back to Earth, and researchers expect that detailed images from the spacecraft's close flyby will be unveiled to the public on January 2.
Because of the power limits for New Horizons' transmitter, plus the extreme distances involved, the spacecraft will be sending back data at a rate of only 1,000 bits per second.
But New Horizons will finally fly by its target just after midnight on January 1, taking close-up photographs and sophisticated scientific measurements of what it sees.
Brian's "New Horizons" track (Ultima Thule mix) celebrates the whole 12-year journey of New Horizons probe, and includes a message from Stephen Hawking congratulating the team on their successful rendezvous with Pluto three years ago.
The exact shape and composition won't be known until Ultima Thule starts sending back data in a process expected to last nearly two years.
The Johns Hopkins University Applied Physics Laboratory, which built and operates the spacecraft, said Tuesday it had "zipped past" the object known as 2014 MU69, or Ultima Thule. And through the vehicle's 'eyes, ' we will begin to learn, for the very first time, what a Kuiper Belt Object is made of.More news: Trumps greet USA troops in Iraq
Alice Bowman, New Horizons' mission operations manager at APL, said the spacecraft entered "encounter mode" on Wednesday.
"In the coming days New Horizons will go down in history!"
Ultimate Thule was unknown until 2014, eight years after New Horizons departed Earth.
"We are straining the capabilities of this spacecraft, and by tomorrow we'll know how we did", New Horizons principal investigator Alan Stern said during the news conference at the Johns Hopkins Applied Physics Laboratory.
New Horizons was set to take a total of 900 highest-resolution images throughout the flyby and the mission team will know in time how many of those images clearly show Ultima Thule. Subsequent observations suggest it is small - no more 20 miles across - and peanut shaped.
"It was Alan Stern, the project instigator of this wonderful Nasa mission, who threw down the glove last May".
The New Horizons team used the Hubble Space Telescope to search for the next Kuiper Belt object to fly by after Pluto. Though nerve-wracking for engineers, encounter mode ensures that New Horizons makes the most of its brief time near Ultima Thule.
'Because of where it was formed and the fact that Ultima is not large enough to have a geologic engine like Pluto and larger planets, we expect that Ultima is the most well-preserved sample of a planetary building block ever explored.