Lofty lunar ambitions
Mainland space officials poured cold water on attempts to report on China's lunar expedition programme in the lead-up to this week's 80th anniversary of the People's Liberation Army.
Responses to questions were particularly frosty from Costind, the Commission of Science, Technology and Industry for National Defence, where communications officers trumpeted anniversary propaganda but turned down all interview requests about the lunar programme.
'We accept no interviews about the programme,' one said. 'It's just not appropriate timing.'
According to a previously released schedule, the nation's first lunar orbiting satellite will take off soon, and staff at Costind's Lunar Exploration Programme Centre said this could be one explanation for the chilliness.
'The countdown has begun,' a staff member said.
Despite the lack of new detail, the lunar programme, hailed as the third milestone in Chinese space technology, is still the mainland's most transparent space project.
There have been timely announcements in unprecedented detail about the objectives, technical aspects and implemented plans, and mainland scientists have attended international forums and invited overseas colleagues for site visits. The programme's leaders frequently appear on television and in newspapers, and there is even an official website accessible to the public.
It is a long way from the time when almost everything about the space programme used to be regarded as a state secret.
When a group of leading space scientists proposed a lunar expedition to the nation's pragmatic leadership in 1991, they knew it could be a long shot. That's because deeper space exploration has fewer direct military applications than satellite positioning systems and the manned space programme, the mainland's two other major space priorities.
But they probably did not expect it to take 13 years for the proposal to be accepted. In 2004, the State Council approved the first phase of the programme - to send a satellite into lunar orbit. Phases two and three, still to be approved, will land a lunar vehicle and bring back samples in the next one or two decades.
In a paper published last year in the academic journal Engineering Science, phase one commander-in-chief Luan Enjie said the objectives included mastering the basic technology of lunar orbits and gaining experience for future projects.
The scientific objective, he said, was to obtain three-dimensional images of the lunar surface, to detect and analyse the content and distribution of useful elements and types of materials on the lunar surface and examine the characteristics and depth of the soil.
The project would also explore the space environment between the Earth and the moon, record solar wind data and study the effect of solar activities on the Earth-moon space environment.
These objectives present daunting scientific and technological problems, and experts have been debating how to solve them for more than a decade. A scientist working at exploration programme said neither the astronomers nor the mathematicians had so far worked out the exact theoretical formula to describe the three-way movement of the Earth, moon and the satellite. This means that to send a satellite from the Earth to the moon, scientists can only rely on orbit approximations, a situation no other space programme had confronted, he said.
One scientist at the centre said that once in lunar orbit, all the onboard detectors would need to face the lunar surface to complete the exploration missions. But the antennas would need to face the Earth to transmit and receive data, and the solar panels would also need to be pointed towards the Sun.
'The control process is 100 times more complex than before,' he said.
Meanwhile, the strong radiation of space will have a big effect on the satellite's electronics and temperatures will range from 130 degrees Celsius on the side facing the Sun to minus-170 degrees on the dark side of the moon. A whole new series of designs and materials must be developed to meet the requirements of the extreme environment.
The biggest headache, however, is the telecommunications system. The exploration programme's previous satellites operated up to 80,000km above the Earth, but the engineers will have to develop technology that can work at five times that distance.
According to Professor Luan, the programme will benefit China in various fields of scientific research, ranging from lunar geology and physics to remote sensing.
When the lunar satellite does head off into space, it will be aboard a CZ-3A rocket, the flagship of the mainland's space carrier fleet.
The rocket weighs about 220 tonnes and can lift a 2.6-tonne payload. It is about six times heavier than DF-2, the first rocket made on the mainland, and 75 times more powerful.
But the engineers will not know until launch day whether it has the capacity to carry the weight needed for the lunar programme.