The successful docking of the unmanned Shenzhou 8 spacecraft with China's Tiangong 1 space laboratory is the end of a long saga. The road to a successful rendezvous in space has been tricky for China, and this docking is long overdue.

China has been confronted by technical difficulties with its docking systems and also with the Tiangong laboratory itself, which pushed this mission back several years.

This is more than just another step forward. It's the end of a sequence of problems that have inhibited China's overall progress in human spaceflight.

Let's review what has happened so far on the mission. The Shenzhou 8 spacecraft itself is a new vehicle, the first in a new series of production-line models for Shenzhou.

It seems that the design of China's crew-carrying spacecraft is finally resolved, and the vehicle seems to be working well.

Shenzhou 8 has more tasks ahead of it, including another run at docking practice with Tiangong. The spacecraft is also carrying a payload of physiology experiments that will return useful data.

The final task for this newly upgraded Shenzhou will be a successful return to Earth. But it seems fair to expect that all these tasks will be accomplished without problems.

The relief inside China's space program must be enormous. Media statements have suggested that controllers are satisfied with the progress of the mission, but this is probably an understatement.

So many bugbears have been chased away, and so many doubts resolved. Although there are no astronauts aboard Shenzhou 8, there's probably a much joy for this flight as for a crewed one.

China has been modestly hedging its predictions for the Shenzhou 9 mission, which will launch to Tiangong 1 next year.

It's long been expected that this mission would carry the first crew to Tiangong 1, but recent Chinese media statements have been coy about this. Media statements wisely suggested that Shenzhou 9 would also be unmanned if problems appeared on the Shenzhou 8 mission.

China would not launch astronauts to Tiangong until docking had been successfully demonstrated. The success of Shenzhou 8 suggests that the next flight should carry astronauts.

So, when will it fly? China has stated that the mission will fly in the first half of 2012, but hasn't fixed a date yet. The temptation to fly must be strong, but this will be tempered by caution. China will want to dissect every piece of data it obtains from this complex test flight, and look for any latent problems.

That will take time, even if the mission seems to be a textbook flight. Training for the astronauts will probably be influenced by these results, as the crews are briefed on the actual flight data. There could even be some minor changes to procedures.

There's really no need to rush the next flight, even though we crave another astronaut launch. Tiangong itself is healthy, and in a stable orbit. It can wait for months. More time on the ground also means less pressure on engineers and technicians. More safety checks can be performed.

Chinese plans call for two flights to Tiangong this year. Shenzhou 9 will be followed by Shenzhou 10 in the second half of 2012. Sending two crews into space in a year is not unusual for Russian and American

spaceflight, but for China, this represents a rapid acceleration. Gaps between Chinese astronaut launches are normally measured in years instead of months.

China is now poised for its busiest year in human spaceflight, which auspiciously falls in the Year of the Dragon. The flight of Shenzhou 8 is historic in its own right, but its real legacy will be the missions that build on its success.

Dr Morris Jones is an Australian space analyst and writer. Email morrisjonesNOSPAMhotmail.com. Replace NOSPAM with @ to send email. Dr Jones will answer media inquiries.