China is set to launch three astronauts into orbit to begin occupation of the country’s new space station.
The three men – Nie Haisheng, Liu Boming and Tang Hongbo – are expected to spend three months living and working aboard the Tianhe module some 380km (236 miles) above the Earth.
It will be China’s longest crewed space mission to date and the first in nearly five years.
Their Shenzhou-12 capsule is primed atop its Long March 2F rocket.
Lift-off from the Jiuquan satellite launch centre in the Gobi desert is expected at 09:22 Beijing time on Thursday (01:22 GMT).
The event is another demonstration of China’s growing confidence and capability in the space domain.
In the past six months, the Asian nation has returned rock and soil samples to Earth from the surface of the Moon, and landed a six-wheeled robot on Mars – both highly complex and challenging endeavours.
The primary objective for Commander Nie Haishen and his team on the Shenzhou-12 mission is to bring the 22.5-tonne Tianhe module into service.
This 16.6m-long, 4.2m-wide cylinder was launched in April.
It is the first and core component in what will eventually be a near 70-tonne orbiting outpost, comprising living quarters, science labs and even a Hubble-class telescope to view the cosmos.
The various elements will be launched in turn over the course of the next couple of years. The construction will be accompanied by regular cargo deliveries, as well as crew expeditions.
The Chinese authorities kept the identities of the Shenzhou-12 astronauts under wraps until a press conference on Wednesday.
Nie Haisheng (56) is a veteran of two previous flights, which included a 15-day visit in 2013 to the prototype space station, Tinagong-1. This has since been de-orbited.
Nie trained as a fighter pilot in the People’s Liberation Army Air Force.
His crewmates, Liu Boming (54) and Tang Hongbo (45), are also from an air force background. Liu’s earlier spaceflight experience was on the Shenzhou-7 mission in 2008 that saw him participate in China’s first ever spacewalk.
Tang is the rookie on this occasion, having never before gone into orbit.
The food, fuel and equipment the trio will need during their stay aboard Tianhe was delivered by a robotic freighter last month.
This freighter is still attached, and the men will make unpacking its supplies their first task as soon as they’ve settled in. Included in the delivery are two spacesuits they’ll need to conduct spacewalks on the exterior of Tianhe.
China has gone it alone in developing a space station, in part because it has been excluded from the International Space Station project. The US, which leads that partnership (with Russia, Europe, Canada and Japan) will not co-operate with the Asian nation in orbit.
For its part, China says it is prepared to open its station to foreign involvement. This is likely in the first instance to mean hosted scientific experiments, but very probably also will involve visits by non-Chinese nationals.
Russia, which has shared technology in the past with China, has mentioned in the past the possibility of sending its cosmonauts.
At Wednesday’s press conference to introduce the Shenzhou-12 crew, Ji Qiming, an assistant director with China’s human spaceflight agency, said: “We welcome co-operation in this regard in general.”
“It is believed that, in the near future, after the completion of the Chinese space station, we will see Chinese and foreign astronauts fly and work together,” he added.