Later this year, China will launch a robotic spacecraft to the Moon and back. We have known about this mission for some time, and we know roughly what the mission hopes to achieve. A bell-shaped re-entry capsule will be carried by a boxy spacecraft out to the Moon, and it will then return for a soft landing on Earth.

This is intended as a test of technology to be used on a future Chinese mission to return rock samples from the Moon. That's China's official explanation for the mission, and it seems right.

This analyst also suspects that China is also testing technology for a future Chinese astronaut launch to the Moon. The re-entry capsule is a scale replica of the capsule used on China's Shenzhou astronaut spacecraft.

China has not released a lot of information on the mission, and has not even revealed any diagrams or photographs of the entire spacecraft. We have seen the re-entry module in photographs, but little else.

China has stated that the main spacecraft will be based on the Chang'e lunar orbiter. With this in mind, this analyst previously created a simple diagram of the probable design of the entire spacecraft. The capsule fits neatly atop the boxy Chang'e bus.

We believed that China would fly this mission in a free-return trajectory to the Moon. This meant that the spacecraft would fly around the far side of the Moon and use the Moon's gravity to sling it back to Earth.

This mission profile was used by the Soviet Union's "Zond" lunar probes, which were themselves tests for a cosmonaut launch to the Moon that never happened. A free-return trajectory was also used to bring the ill-fated Apollo 13 mission back to Earth.

Recently, a story published by China's state news agency Xinhua gave a different perspective. It claims that the spacecraft will actually enter orbit around the Moon.

This seems plausible, and useful. The sample-return mission will require the capsule to enter and leave lunar orbit. Flying an identical mission profile will give it a thorough testing. It will also presumably give the spacecraft more time to operate instruments and experiments at the Moon.

China has already sent two orbiters to map the Moon. The latest mission seems to be more about engineering tests than lunar science. We shouldn't expect the same sorts of high-resolution images returned by the Chang'e-1 and 2 lunar orbiters. But the capsule will be stuffed with experiments, probably biological samples.

China has a long and proud tradition of flying seeds and other lifeforms in orbit, but it has never launched a biological experiment into deep space. This will be a big breakthrough for China's space biomedical program. The lunar environment will expose the samples to different levels of radiation than are found in near-Earth space.

How long will the spacecraft stay in lunar orbit? It could literally be weeks. The spacecraft must simulate the time it would take for another robotic spacecraft to land on the Moon, collect samples, place those samples in a small launch vehicle and fly them to a rendezvous in lunar orbit.

We don't know how long that will take, but it should at least be a matter of days. Then there's the question of windows for the return to Earth and a touchdown at China's landing site in Inner Mongolia. The on-board samples would also gain from a prolonged exposure to deep space. So China will probably be in no hurry to bring its spacecraft home.

We still have no official word on the launch date. Hopefully the latest Xinhua story is the first step in a new trickle of information.

Dr Morris Jones is an Australian space analyst who has written for spacedaily.com since 1999. Email morrisjonesNOSPAMhotmail.com. Replace NOSPAM with @ to send email. Dr Jones will answer media inquiries.