At 1:21:25 in the film, the director of the Chinese space agency decides to help save Watney and says, "We need to keep this among the scientists, a co-operation between the space agencies."
How close could the two space agencies help without government interference from one side or the other?
"The secret of life is honesty and fair dealing. If you can fake that, you've got it made."
How close could the two space agencies help without government interference from one side or the other?
The book explained it much better.
The Chinese rationalized the offer to help with; We will be publicly rescuing the Americans, Chinese tech will be seen to be the equal of American tech, the Americans will put a Chinese astronaut on Mars for us. If Chinese and NASA administrators were able to arrange the deal before hand, then it is likely that the two governments would play along. The Chinese space official mentioned that his government ministers would trade their mothers for the chance to help the Americans in this fashion.
Understand that this movie takes place about 30 years in the future.
The movie merely shows an asian astronaut appearing in the final scene on the launch of an Ares mission.