At the Beijing Aerospace Control Center, there is a team specializing in the long-term operation control of spacecraft in orbit, like China's space station, lunar and the Mars probes.

Hu Guolin, the deputy commander of the team, said they work 24 hours a day and seven days a week to monitor and control the target spacecraft, so as to ensure their smooth operations.

He cited the example of China's space station, which was completed at the end of last year. Many scientific experiments are conducted in the space station.

"Our daily work starts with communication with the astronauts. And we begin to calculate the position of the station, update some in-orbit flight programs and keep monitoring the status of the station and astronauts," he said. 

Through the big screens at the control center, Hu's team can monitor the real-time working status of the astronauts in the space station.

"Now, we can see our astronauts are busy working. And the Spring Festival scrolls here are written by them in orbit. They are well written and add a very good festival atmosphere," Hu said. 

Their job may look easy, but behind it are intricate factors that the team is closely monitoring.

"The number of parameters to monitor the space station now exceeds 150,000, while in the past it's only about hundreds or more than a thousand. It reflects the complexity of the equipment and technology," he noted.

"Our space station has three modules now. We have more than 5,000 emergency plans for it. If there are malfunctions, we will need to evaluate the situation and handle them step by step," the commander stressed.

He said that everything should be thought through clearly, which is the pre-condition for the long-term stable operation control of the spacecraft.

And they are also closely monitoring China's lunar and Mars probes and their relay satellites.

"During our long-term management, we want to increase the efficiency of control, and we are making technical innovation and optimizing the working procedures," he said.

"We've changed the traditional control methods and under the new mode, we could save propellants by up to 90 percent. That could support our Yutu-2 lunar rover and help our lunar lander work for a longer time," he added.

In the future, the difficulty and complexity of these missions will gradually increase. Hu said that they will try their best to overcome any difficulties they will face.