2013 is set to be an important year for China's space program. We expect to see the first landing of a Chinese spacecraft on the Moon, in addition to a sequence of Earth satellite launches. We also expect another crew of Chinese astronauts to fly to Tiangong 1, China's first space laboratory. The launch of the Shenzhou 10 spacecraft, which will carry this crew to Tiangong, was originally expected before the end of 2012.

Shenzhou 10's launch has gradually slipped over time, and now seems placed at some time in the middle of this year. It's true that space launches are regularly delayed for various technical reasons, but the mission of Shenzhou 10 is probably being influenced by a sequence of reshuffles behind the scenes.

China's last human space mission, Shenzhou 9, carried two men and a woman to occupy Tiangong 1 for the first time in 2012. That mission was an outstanding success, with the astronauts living aboard the space laboratory for around 10 days.

Although there were no major problems to overcome, it made sense to wait a few months before launching the next mission. The Shenzhou 9 mission generated a lot of data to examine, and it would be worth combing through all of it before making the next flight.

It seemed reasonable to expect that Shenzhou 10 would undergo a revision of its mission plan. It is generally believed that Shenzhou 10 was originally designed as a back-up mission to Shenzhou 9, which would finish up any basic tasks that were not properly completed on this earlier mission. With Shenzhou 9 performing so well, the "take two" mission agenda became less relevant.

This author expected that engineers were probably creating a more ambitious mission plan for Shenzhou 10, which would include more scientific experiments. Reports in the Chinese media of a plan to fly around the Tiangong laboratory suggested that this was so. It was also reported that the Shenzhou 10 spacecraft would carry additional supplies for the crew, and that a longer occupation of the laboratory is planned this time.

In any case, there was no pressing reason to rush the launch of Shenzhou 10. By Chinese standards, one crewed mission per year is very brisk. The Tiangong 1 laboratory seems to be very robust and spaceworthy. Although China originally suggested that the module has an operational lifespan of two years, its on-orbit performance could lead mission controllers to grant it greater longevity.

By themselves, the aforementioned factors supplied plenty of reasons for a reshuffle of the Shenzhou 10 mission, both in terms of launch time and mission planning. But other factors seem to be influencing the development of the Shenzhou and Tiangong programs. Some broader changes in the long term could be influencing the mission of Shenzhou 10 in the short term.

A presentation in late 2012 by China's first astronaut Yang Liwei has caused much speculation among spaceflight analysts. Close reading and dissection of Yang's presentation suggests that there has been a major "snip and tuck" in the whole Tiangong space laboratory program. The original script called for Tiangong 1 to be followed by Tiangong 2, which would have been a module of the same basic design as Tiangong 1. Tiangong 2 was expected to have tested more advanced life-support systems than Tiangong 1, but there would be no major changes to the spacecraft. It was expected that two or three crews would be launched to this module.

Towards the end of the decade, China would then launch Tiangong 3, which was slated to be an entirely different class of spacecraft. It would be larger and more capable. Tiangong 3 was expected by some analysts to be a precursor to the types of modules to be used in China's future space station, slated for launch around 2020.

According to Yang's presentation, we can forget about Tiangong 2. Or at least, we can forget about Tiangong 2 as it was originally planned. China still plans to launch a mission with this name, but it would seem that the large laboratory module originally known as "Tiangong 3" has now been designated as the new Tiangong 2.

The original Tiangong 2, similar to Tiangong 1, will not fly at all. China will cut out an intermediate step in the evolution of its space laboratories and go straight to an advanced module!

The spacecraft originally built to fly as the Tiangong 2 laboratory will probably be used as a cargo module to carry supplies to the newly designated "big" Tiangong 2. This will be easy to do, as the small Tiangong module has been designed to serve as a cargo carrier for future space stations since its inception.

Clues to this change partially lie with references to experimental refueling operations to be performed on Tiangong 2. Another spacecraft will dock and transfer fuel to Tiangong's tanks. Such an operation is impossible with Tiangong 1, and it seems unlikely that even a modified small Tiangong module would be suitable for this.

Something much larger and sophisticated seems to be necessary for such a big step forward. Yang also mentions astronauts conducting a "mid-term stay", suggesting a longer period of occupation of the module. This would also seem more appropriate for a larger spacecraft with more room and logistics. Also, Yang's presentation makes no references to a Tiangong 3 laboratory, but begins discussions of the large modular space station when it finishes discussing Tiangong 2.

This is clearly a big step forward. It seems likely that China would not be prepared to make this major reshuffle without the successful performance of Tiangong 1 and the Shenzhou 9 mission. We can also add the achievements of the uncrewed Shenzhou 8 spacecraft, which performed docking tests with Tiangong 1, to this string of successes.

The move to launch a big module for Tiangong 2 is also a vote of confidence in the development of the Long March 5 class of launch vehicles. Tiangong 1 was launched by a modified Long March 2F rocket, similar to the vehicles that launch crewed Shenzhou spacecraft to this module. This is practical, as the small Tiangong is not much larger or heavier than a Shenzhou.

Launching a larger Tiangong will require more power. The Long March 5 "family" of rockets is a new, interchangeable collection of rocket stages and boosters that can be stacked in various configurations.

It promises more lifting capacity than anything China currently flies, but it has also experienced delays in its development. Construction of a launch site for the Long March 5 rockets is underway on Hainan Island in southern China, and this is another hint that it will not be too long before it is active.

Just as Shenzhou 10 has been redesigned as more than a back-up flight for Shenzhou 9, the next Tiangong launch will be more than a modified first-generation laboratory.

This leads to another question. Could this reshuffle in the Tiangong program also affect the mission of Shenzhou 10? It's possible. China will probably never fly a small, stand-alone laboratory module like Tiangong 1 again, or at least not for another decade. It makes sense to get as much use out of it as possible. Also, the crew could be testing new equipment and procedures that will be used on the larger Tiangong module.

The success of Shenzhou 9 and the reshuffle of the Tiangong program make the upcoming Shenzhou 10 mission seem a lot more interesting. Some analysts felt that the flight would be an anti-climax after the breakthroughs of the Shenzhou 9 mission. Now, it seems to be poised for breakthroughs that were not previously anticipated.

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.