Sydney - Jul 21, 2003
Since China announced its plans for human spaceflight, plans for Chinese exploration of the solar system have also featured in media reports. The human and robotic elements of China's space program together form an overall increase in China's ambitions in space.
While information on the Shenzhou crew-carrying spacecraft is relatively abundant, Chinese officials have been extremely vague about their plans for exploring the moon and beyond. Some media reports have even painted wild speculations of Chinese astronauts on the moon within ten years, a clearly ludicrous proposition.
More light on China's lunar program was recently provided at the 25th Annual Congress of the International Astronomical Union in Sydney this year, when a delegate from the Chinese Academy of Sciences gave a brief presentation.
In a fashion that's typical of Chinese space disclosures, very precise facts were given on some aspects of what's ahead, while more obvious points were not discussed at all. The result was a presentation that was informative, but short on detail.
Ye Shuhua from the Shanghai Astronomical Observatory discussed the overall plans China has drawn for a series of robotic lunar exploration missions. Starting in 2005, an orbiter will be launched on a mission that is nominally tipped to last for more than a year.
In 2010, China hopes to make a soft lunar landing with a robot probe, and carry out investigations of the lunar surface. The climax of this plan appears in 2020, when a robotic sample return mission will be launched to the moon.
Ye provided absolutely no details at all on the landing missions proposed in this timeline. It is presumed that plans for these missions have not bee precisely drawn. The rest of her short talk focused on discussing the payload for the upcoming lunar orbiter.
Using nothing more than a set of text-based overhead projector transparencies, Ye provided many details on the experiments China is expecting to conduct from lunar orbit.
Surprisingly, she was unable to supply any illustrations or commentary on the spacecraft bus that will be used for the orbiter, apart from saying that it would be a three axis stabilised spacecraft. When SpaceDaily asked her about potential plans for using an existing Chinese satellite bus, Ye replied that she did not know.
The Chief Scientist for the mission is Professor Ouyang Ziyuan of the National Astronomical Observatory, Beijing, who is also a member of the Chinese Academy of Sciences. Ye claimed that the lunar orbiter project enjoyed the support of the Chinese Academy of Sciences, but did not say which state organ would actually be responsible for the conduct of the mission.
The Lunar Orbiter (no mention was made of previously reported names such as Lunar E) will be launched by a Long March 3A launch vehicle. No discussion was made about the use of additional upper stages or the total mass of the spacecraft.
A simple diagram suggested that the orbiter would first be placed into a parking orbit around the Earth, before making another burn to send it to the moon. It would then be braked into an elliptical orbit which would be lowered through engine burns. The orbiter would finally be placed into a polar orbit of 200 kilometres around the moon, where it would carry out its tasks.
The year-long mission would communicate with a 50 metre antenna at a ground station in Beijing. No mention was made of China's fleet of tracking ships or its ground stations in other parts of the world.
Ye was surprisingly modest in characterising China's first lunar mission, but the suite of experiments planned for the orbiter is quite impressive. There will be cameras, a battery of spectrometers, a laser rangefinder, a microwave sensor and particle detectors.
A lunar orbiter was seen as a feasible task that would minimise risks. "For the first mission, you must be successful," explained Ye, who hinted that a failure of the orbiter could make subsequent Chinese lunar exploration difficult.
The News In Detail
The experiment payload and energy loads were summarised as follows:
A "managing-storage system for payloads" (even NASA can't find a more complex designation for a computer!) weighs 15 kg and draws 19 watts of power. The total payload weight for the lunar orbiter was stated to be 130.4 kilograms, drawing 161 watts of power. (Note that no figures for the total mass or power budget for the entire spacecraft were provided.)
The CCD cameras and laser altimeter are designed for lunar topography experiments. The two CCD cameras are arranged to provide stereo imaging of the same area (a 51 kilometre by 51 kilometre square). The camera angles are each offset by plus or minus 25 degrees.
Ye could not provide data on the resolution of the cameras. The laser altimeter will use red light (1064 nanometre wavelength) and have a diameter of approximately 100 metres when it intersected the lunar surface. No data on its accuracy was provided.
"(Orbiter mission chief scientist) Professor Ouyang is a specialist in chemistry", according to Ye. Hence, chemical analysis of the lunar surface is another objective of the payload. This involves the use of the gamma and X-ray spectrometer for detecting specific elements, and an interferometric imaging spectrometer for two dimensional infrared images of rock types.
The instrument dubbed a "Microwave Meter" by the Chinese would probably be called a microwave sounder in other places. It will be used to study the lunar regolith, including temperature differences with a resolution of 0.5 Kelvins. Three different bands would be used, at 9.4 GHz (C band), 19.4 GHz (Ku Band) and 37 Ghz (K Band). The antenna aperture is 50 cm.
It was claimed by Ye that this instrument would be used to map helium 3 deposits. Chinese statements issued in the past have indicated interest in mining helium 3 from the moon as a potential fuel for fusion power reactors, assuming that fusion reactors become feasible in the future. Penetration depths of around 10 metres were proposed for this instrument.
Some non-Chinese delegates at the talk expressed doubts about the ability of this instrument to penetrate deeply enough into the regolith for meaningful measurements, and the ability of the instrument to make accurate measurements of helium-3 deposits. Ye did not comment specifically on any of these issues.
The particle environment around the moon will be investigated by a high-energy particle detector and low-energy ion detectors. The influence of the solar wind on near-lunar space was mentioned as a topic of interest. The high-energy particle detector will analyse heavy ions in energy ranges from 12 MeV to 2 MeV, with six channels. Protons with energies from 3 to 300 MeV will also be analysed.
Two low-energy ion detectors would be used to study the solar wind when the lunar orbiter is facing the Sun. "When the orbiter is in shadow, the detector can observe the tail of the interaction between the solar wind and the moon", according to Ye's projector slides.
No other information on the experiments, the mission architecture or the spacecraft itself was provided.
Dr Morris Jones is a Sydney-based journalist and lecturer. Email morrisjonesNOSPAMhotmail.com. Replace NOSPAM with @ to send email.
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