Three astronauts stationed in China's Tiangong space station are preparing for their return trip in the middle of April, packing up personal items, experimental products and other materials, putting equipment into place and exercising to prepare their bodies for Earth's gravity.

The astronauts, Zhai Zhigang, Wang Yaping and Ye Guangfu, have to tidy up a large number of materials, including goods on the Tianzhou 3 cargo spacecraft, said Zhong Weiwei, an associate researcher at the China Astronaut Research and Training Center.

Living in space about six months, a record in China's history, they have completed more than 20 scientific tasks and will bring back samples with them, according to Zhong.

He said the astronauts have to put all equipment in place since there will be a gap of more than one month before the astronauts of Shenzhou XIV enter the space station.

The physical conditions and psychological states of the three astronauts are better than expected, meeting the requirements for a return trip, said the associate researcher from the center's aerospace medical engineering office.

Based on their in-orbit physical examinations and data, experts have adjusted exercise plans for them to keep fitness in order to ensure a safe landing, Zhong said.

The Shenzhou XIII mission was launched on Oct 16 by a Long March 2F carrier rocket that blasted off from the Jiuquan Satellite Launch Center in northwestern China's Gobi Desert, with the crew soon entering the Tiangong station.

Besides their tasks, they have also delivered two live lectures from the space station, showing the students their living and working areas at the Tianhe core module and several scientific experiments under zero-gravity conditions and answering real-time questions from students.