China Ready For Another Lunar Encounter

Discussion in 'China' started by Patriot, Sep 27, 2010.

  1. Patriot

    Patriot Senior Member Senior Member

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    China Ready For Another Lunar Encounter

    by Morris Jones
    Sydney, Australia (SPX) Sep 27, 2010
    China could launch its second lunar probe within days. The Chang'e 2 spacecraft was originally built as a back-up to China's first lunar orbiter, Chang'e 1, which was launched successfully in 2007. Rather than mothballing the spare spacecraft, China has sensibly planned a follow-up mission that will examine the Moon even more closely than the first.

    Chang'e 2 has been fairly camera-shy for the media, and we have received only a basic disclosure of its mission. We can expect that it will look pretty much the same as Chang'e 1, a boxy orbiter with large solar panel wings. Some of the instruments have been changed, and the overall mission plan is also being tweaked.

    Some changes will take place soon after launch. China is planning a more direct climb out of Earth orbit to the Moon, which will see the spacecraft reach its goal in roughly five days. This is less than half the transit time of the first mission.

    Chinese officials claim that they have greater confidence in their ability to track and navigate the spacecraft, which leads to a faster trip. This is fair enough, but it will also possibly reduce the exposure of Chang'e 2 to Earth's radiation belts. This could help the longevity of some instruments, but it's probably not a core reason for the change.

    Reaching the Moon, Chang'e 2 will be placed in an orbit "100 kilometres closer to the Moon", according to a Xinhua report. The math is simple. Chang'e 1 was placed in an orbit of roughly 200 kilometres, so we can expect Chang'e 2 to orbit at roughly 100 kilometres above the surface. The orbital altitude has halved!

    This means that Chang'e 2 is China's first "close encounter" probe with the Moon. This is a fairly low orbit that will allow very close studies of the surface. NASA's Lunar Reconnaissance Orbiter (LRO) is currently in a similar orbit.

    It was stated that Chang'e 2 will return higher resolution images than its predecessor. It's clear that the camera itself is a better instrument (Chang'e 1's resolution was around 120 metres), but some of the improvements in the images will also be a result of the lower orbit. Chinese statements speak of resolutions between one metre and seven metres, depending on the distance to the Moon.

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    It's a fairly large difference, and it suggests a lot of variation in the orbit. It is probable that Chang'e 2 will mostly operate in a near-circular polar orbit, like its predecessor. The spacecraft could be directed into a very low orbit during the final phases of its mission. Some reports have spoken of passes across the surface lower than 10 kilometres, a trajectory that will probably be performed during the final phases of the mission.

    What will the spacecraft see? The resolution won't be as good as LRO, which can see details on other spacecraft that have landed on the Moon. But China will be able to map the Moon with greater precision, and can use its existing global lunar map from Chang'e 1 as a reference framework for the new data.

    It hasn't been long since Chang'e 1 returned its data, but it's almost certain that some new craters will be discovered. One crater that China may want to search for will be the impact site of Chang'e 1, which was steered to a controlled hard landing. The impact site of Japan's Kaguya orbiter, which was also deorbited, could also be explored.

    Chang'e 2 will also release an impactor to strike the Moon, a feat earlier performed by India's Chandrayaan-1 orbiter. The Chang'e 2 impactor will serve several functions. It will give China experience in descending a spacecraft from lunar orbit and tracking it.

    This will be good practice for China's plans to softly land spacecraft on the Moon later this decade. It will also allow the surface environment to be explored more closely. The Chang'e 2 orbiter will observe the results of this impact, which is expected to generate a dust plume.

    NASA may also elect to explore the crater formed by the Chang'e 2 impactor with the Lunar Reconnaissance Orbiter, assuming it's large and bright enough to be seen by its camera. It would be ironic if NASA released such an image before China did! But it's not entirely clear if such a crater would be visible to the cameras of either spacecraft.

    Xinhua has also stated that Chang'e 2 will photograph the landing site planned for the Chang'e 3 robot lander, which is still apparently slated for 2013. This suggests that the landing site has already been tentatively chosen, or at the very least, China now has a short list of candidate sites.

    Sites have possibly been earmarked for China's other landers, which include at least one sample-return mission. The need to scout landing sites is probably a major motivation in selecting the low orbit in the first place. Seeing boulders large enough to pose a hazard to these landers will require very high-resolution imagery, and it seems likely that these landing sites will be high-priority targets when Chang'e 2 makes its lowest orbits above the Moon.

    It is unclear how long the mission of Chang'e 2 will last. Keeping a spacecraft in a lower orbit requires more navigational skill, and also leads to a faster orbital decay. It's possible that this mission will end much sooner than Chang'e 1, but this will be an acceptable compromise for the closer look.

    As with Chang'e 1, the Chang'e 2 spacecraft will be launched aboard a Long March 3A rocket. This is a fairly reliable workhorse in China's steadily growing stable of launch vehicles. It should perform well on the flight, as it did for Chang'e 1.

    Soon, this long-anticipated mission will become a reality. We would like to know more about the spacecraft, but it seems that China's public relations policies are no more relaxed than they were in the past. For the moment, we can simply think about what we know for sure, and try to make educated guesses about what we don't.








    China Ready For Another Lunar Encounter
     
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  3. Patriot

    Patriot Senior Member Senior Member

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    China's Chang'e-2 lunar probe successfully reaches trajectory

    BEIJING (PTI): China's second unmanned lunar probe, Chang'e-2, was maneuvered to correct its trajectory on the earth-moon transfer orbit on Saturday, a day after it was launched as part of an ambitious space programme to put a man on the moon later this decade.

    Scientists successfully activated the altitude control engines on Chang'e-2 and trimmed the satellite for the first time on its journey, state-run Xinhua news agency said.

    "During Chang'e-2's 380,000-km journey to the moon, we will conduct more orbit corrections if necessary to ensure that it enters a lunar orbit," said Ma Yongping, vice director of the flight control centre in the capital.

    China, which seeks to put a man on the moon, launched its second unmanned lunar probe Friday to test soft-landing technologies for a mission slated for 2013, the same year when India plans to launch Chandrayaan-II.

    Chang'e-2 blasted off on a Long-March-3C carrier rocket from the Xichang Satellite Launch Centre in southwest China's Sichuan province.

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    It is China's first unmanned spacecraft to be boosted from the launch site directly to the earth-moon transfer orbit, greatly reducing the journey time from that of its predecessor Chang'e-1.

    Chang'e-1 took about 13 days to travel to a lunar orbit after orbiting the earth in a geosynchronous orbit and then transferring to the earth-moon transfer orbit.

    Chang'e-2 is expected to travel for about 112 hours, or almost five days, to arrive in a lunar orbit.

    To acquire more detailed moon data, the spacecraft will enter a lower lunar orbit about 100-km above the surface, compared with the 200-km altitude of Chang'e-1, according to the control centre.

    The satellite will eventually be maneuvered into an orbit just 15 kilometer above the moon.

    At that point, Chang'e-2 will take pictures of moon's Bay of Rainbows area, the proposed landing ground for Chang'e-3, with a resolution of 1.5 metres.

    The resolution on Chang'e-1's camera was 120 metres, Wu Weiren, chief designer of China's lunar orbiter project said.

    Under a three-phase moon exploration roadmap, China will land Chang'e-3 on the moon in 2013 while its first manned moon mission is expected in 2025.

    In comparision to India, China had a headstart by flying a man into space in 2003, thus becoming the third nation only after the US and the then Soviet Union.

    India, whose Chandrayaan-1 had discovered water on the moon, plans to launch its Chandrayaan-II mission in 2012-13.





    China's Chang'e-2 lunar probe successfully reaches trajectory :: Brahmand.com
     
  4. Patriot

    Patriot Senior Member Senior Member

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    China to explore deep space

    BEIJING (PTI): China is developing a deep space network with antennae and communication facilities to support its future interplanetary missions to be launched for the exploration of solar system, a top Chinese scientist has said.

    China's own deep space network will take shape in the next three to five years to support its exploration projects of the solar system, said Qian Weiping, chief designer of the tracking and control system Chang'e-II lunar probe which was successfully launched on Saturday.

    The deep space network consists of a network of large antennae and communication facilities that support interplanetary missions along with astronomical observations by radio and radar for the exploration of the solar system, he told state-run China Daily.

    Qian said that once the network was in place, "there will be no problem for China to carry out an exploration of the solar system".

    The Chang'e-II mission will test the X-spectrum telemetry, tracking and control system, a key technology in the deep space network.

    "If the test succeeds, it means we have mastered the technology of using the X-spectrum to fulfil functions like orbit determination and the remote control of spacecraft in deep space," he said.

    "With this technology, we only need to build larger antennae to explore planets in deep space," he said.

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    As part of the network, he said, two ground tracking stations with large antennae are currently under construction in the country - one in Kashgar in the Xinjiang autonomous region and the other in Jiamusi in Heilongjiang province.

    Deep space usually means 1.5 million kilometers away from the Earth. As the moon is 400,000 km away from the Earth and there are no large celestial bodies between 400,000 km and 1.5 million km.

    China regards the lunar mission as the starting point for its exploration of deep space, said Wu Weiren, chief designer of China's lunar exploration program.

    Experts had previously said that the lack of a deep space network and a powerful launch vehicle were two factors hindering the country's exploration of deep space.

    The lunar program is the technical basis for further exploration of the solar system, Wu said, adding the technology involved, such as the launch vehicle and the tracking and control systems which could be applied to exploring the planets Mars and Venus.

    "So it would be possible for us to explore Mars and Venus in the foreseeable future, as the two planets are the closest to the Earth," he said.

    China's space authorities have yet to announce any plan to explore the two planets.

    Ye Peijian, a consultant to the chief designer of the Chang'e-II probe system, said at a forum recently that China is capable of independently exploring Mars and Venus.

    Backing up his statement, he outlined a feasible route for China to explore Mars in 2013 and Venus in 2015, followed by a manned flight to the moon in 2025.





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  5. Patriot

    Patriot Senior Member Senior Member

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    China Touts Lunar Probe Braking Maneuver

    BEIJING — Chinese controllers have achieved a velocity within 1 cm./sec. of prediction in the braking maneuver that brought the Chang’e 2 spacecraft into its 100-km. (60-mi.) working orbit around the Moon this week.

    The lunar probe, China’s second, is now in a position to begin surveying the lunar surface, says China Aerospace Science and Technology Corp.

    Chang’e 2 has so far braked three times: once to bring it into an initial lunar orbit, once to achieve a 3.5-hr. elliptical transitional orbit and thirdly — but not finally — to move into the 118-min. circular working orbit.
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    “When the engine was shut down after this [third] braking maneuver, the actual velocity of the spacecraft differed from the predicted value by 0.01 meters per second,” says the program’s chief designer, Huang Jiangchuan, quoted via the company’s China Space News outlet.

    Such precise velocity is possible, but might be achieved randomly, says one U.S. space engineer.

    Chang’e 2 will autonomously execute its next maneuver, braking on the far side of the Moon to achieve a 100 x 15-km. orbit from which it will examine Sinis Iridium (the Bay of Rainbows) on the near side.

    The spacecraft’s engine can develop a thrust of 490 newtons (110 lb.) X-band communications and measurement technology are among the six technological breakthroughs that Chang’e 2 represents for China, according to the deputy chief designer of the probe, Dong Guangliang.

    The technology not only helps to raise the precision of the measurement of the spacecraft’s trajectory, he says, but also aids in the miniaturization of the onboard equipment, reducing power consumption, and can transmit information at a higher rate.






    http://www.aviationweek.com/aw/generic/story.jsp?id=news/asd/2010/10/15/08.xml&headline=China%20Touts%20Lunar%20Probe%20Braking%20Maneuver&channel=space
     

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