Article Posted on : - Nov 18, 2016

An internet imagery.

BEIJING (PTI): China's spacecraft Shenzhou-11, carrying two taikonauts separated from orbiting experimental space lab Tiangong-2 on Thursday as they prepared for their journey to return to earth after a month's stay in space, the longest by Chinese astronauts.

The separation marks the beginning of the journey home for the two men, Jing Haipeng and Chen Dong, having lived and worked in Tiangong-2 for 30 days, the longest stay in space by Chinese astronauts.

Before the separation, the astronauts thanked their ground team and to everyone who had supported China's space programme, state-run Xinhua news agency reported.

After the separation, Shenzhou-11 will remain at a point near the space lab before they are given signal by the ground team to embark on their return journey.

Around one day later, the re-entry module will descend from an orbit about 393 kilometers above Earth, a true test to its re-entry system as it has to withstand heavy friction on its outer surface.

However Tiangong-2, which is the second experimental space lab will remain in its orbit and remote experiments will continue until it docks with Tianzhou-1, China's first cargo spacecraft, which is set to be launched in April 2017.

The Chinese astronauts entered the space lab on October 19 after their spacecraft which was launched a day before successfully docked with the orbiting experimental space station.

The rendezvous between the spacecraft and lab took place over 393 kilometres above Earth. The space lab was launched as part of efforts to set up its own manned space station by 2022, which will make it the only the country to have such a facility in service as the current in-service International Space Station (ISS) retires by 2024.

During their stay they carried out medical experiments, space science experiments and in-orbit maintenance with human participation.

They were also tasked to undertake ultrasound tests during space travel for the first time, cultivate plants in space, and test the three winners of an experiment design competition run in Hong Kong for secondary school students.

Before they winded up their mission, the astronauts spoke about their life in the space station.

Jing who is the senior of the two said: "During these 30 days, after work we look out through the porthole to see the landscape and view the world. When the spaceship is over China, we two feel especially excited."

Chen Dong said: "I feel a bit reluctant to depart but I also feel happy and thrilled. I feel reluctant because soon we will be leaving Tiangong-2, where we have lived and worked for 30 days. It is like our home in space so I still have a sense of reluctance and attachment. I feel happy and thrilled because we are getting back to our "big family" soon."

Jing said before leaving the space lab some preparatory work like recovering experimental data, cleaning up the compartment and setting up the conditions needed to be done.

He said most of the experiments have been completed and some data transmitted back to Earth.

"The rest is saved on memory cards to be taken back to earth due to the large size of the data set. Vegetables grown in space and the silkworm cocoons will also be brought back.

Urine and saliva samples, as well as microorganisms sampled before leaving orbit will also be brought back onto the ground for analysis," he said.

Chen said one of the tasks for moving out of the lab is compartment clean-up and packing.

"When we entered Tiangong-2, we moved many things in including our necessities and experimental items, in all sizes. The bicycle which we use to exercise was unfolded in orbit," he said.

"That was equal to decorating a home in space. Now we are moving back to Earth and need to put some items back where they should be. Some items need binding while aboard Tiangong and the work is time-consuming," he said.

Chen said packing in space is strenuous.

"Both people and ropes are floating. When one end is tied, the other end of the rope flies. But carelessness is not allowed in packing. There are clear requirements on how an item should be packed, including what a packed item should look like, where it should be placed, and even whether an item should be wrapped horizontally or slantwise," he said.

Meanwhile, Jing said, "We need to sweep Tiangong clean before leaving and take away items that should be taken away; this is very important. Some trash, if left aboard Tiangong, will be dangerous. To make Tiangong's follow-up tasks possible, they must be taken away."

"Residual food waste, sanitary product waste, and some trash created during in-orbit experiments, including batteries and electrodes, will be packed and placed in the orbital compartment. The trash will then crash into the atmosphere and be destroyed together with the compartment," he said.

Different from throwing trashes into waste containers on Earth, we need to put them into compressed bags, similar to vacuum bags that are used to pack quilts at home. There is a valve in the centre and after the zipping we use a pump to remove the air," he added.

Chen said setting up the conditions before departure is similar to turning off the water and electricity before leaving a house for a long time.