zt采到小行星岩石样本 隼鸟探测器却愁回家路(图)

　　日研究人员正绞尽脑汁，但“隼鸟”号能否平安归来还需拭目以待
　　
　　新华网东京11月27日电（记者何德功）日本小行星探测器“隼鸟”号不辱使命，26日成功采集小行星丝川地表岩石样本，日本研究人员在欢呼雀跃的同时，正在为“隼鸟”号如何顺利回家绞尽脑汁。
　　
　　“隼鸟”号预定12月上旬踏上归途，现在离地球距离是2.9亿公里，但不能直线回归，必须绕行10亿公里，于2007年6月到达地球。由于“隼鸟”号此前故障不断，空耗很多燃料，返航途中一旦燃料不足，就有可能功亏一篑，现在研究人员正在探讨节约燃料对策。
　　
　　“隼鸟”号着陆丝川行动可谓是一波三折，先是12日向丝川投放微型探测器“智慧女神”失败。原计划让“智慧女神”率先着陆后，利用机载相机和温度感应器对小行星进行拍照和研究，可是“智慧女神”却失去踪影，据称现在仍在太空中飘浮。
　　
　　20日“隼鸟”号首次尝试着陆，却和地面失去联系长达3个小时。据后来数据显示，它的确着陆了，可折腾了30分钟，也没能投下岩石采集装置。26日早上7点多，“隼鸟”号最后一搏终于成功，并完成了采集岩石样本的任务。
　　
　　从小行星丝川地面采集岩石样本之所以备受关注，一是因为有望探明落在地球上的陨石和小行星的关系。陨石被认为是小行星的碎片，受地球引力的影响落在地表，通过陨石和小行星岩石样本的比较分析，可验明陨石的“母体”。二是有望揭示太阳系形成之谜。小行星约在45亿年前与太阳同时诞生，而后小行星之间在相互撞击的同时，表面会受飞来的太阳高能粒子袭击。通过研究小行星岩石样本光的反射，和通过望远镜看到的小行星光线进行比较，会增加人类对小行星表面的进一步了解。分析小行星表面岩石结构，可以了解太阳系曾遭受怎样的风化，捕捉太阳系早期的信息。三是有望探明在宇宙中漂浮的微小尘埃，专家认为尘埃可能含有与地球生命起源有关的有机物。小行星岩石可能残留有远古尘埃，岩石中含有什么样的有机物令人关注。
　　
　　日本最近几年在发射天文卫星和彗星探测器方面屡遭挫折，如火星探测器“希望”号因没有进入火星运行轨道成为太空垃圾，火箭发射几度失败等，此次“隼鸟”号成功采集小行星岩石样本，无疑给日本宇航业注射了一针强心剂。但“隼鸟”号能否平安归来，人们还需拭目以待。
　　
　　
　　（来源：新华每日电讯）

没有金刚钻，硬揽瓷器活。

日本果然是小强.

Spacecraft makes a grab for asteroid sample
Is it second time lucky for Hayabusa probe?
Ichiko Fuyuno

Japan's Hayabusa spacecraft may have succeeded in its second attempt to collect pieces of a small asteroid. If so, this will be the first time a sample has been collected for return to the Earth from any object in the Solar System apart from the Moon.

On 26 November, the Japan Aerospace Exploration Agency (JAXA) said data sent from Hayabusa shows that every stage of the sampling process went well. Agency engineers said it was almost certain that Hayabusa's sampler had touched down on the Itokawa asteroid as planned, and shot two metal pellets into the rock to throw up fragments of the surface. "I think we were able to collect a sample," said project manager Jun'ichiro Kawaguchi.

Hayabusa was launched in May 2003 and in September 2005, arrived at Itokawa - a potato-shaped, 540-metre-long asteroid located about 300 million kilometres from Earth. Hayabusa is expected to leave Itokawa by early December for its return journey. Whether a sample was definitely collected won't be known until the spacecraft reaches Earth in the summer of 2007.

To get this far, members of the Hayabusa team have endured a rough passage. Two of the craft's three reaction wheels, which stabilize the probe and help it to navigate, stopped working; the first failed in July and the second in October. Chemical engines on board were used instead, but their lower accuracy made landing more difficult and practice descents didn't go perfectly. In the first landing attempt on 20 November, Hayabusa seemed to park on the asteroid's hot surface for more than 30 minutes, and failed to collect a sample.  

Time and fuel were running short, so the 26 November try was almost the last chance to collect a sample. "It was learning in real-time," says Donald Yeomans, US project scientist for Hayabusa and senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. With each attempt, he says, "they learned more and more about how the spacecraft behaves".

Balancing act

Still, concerns remain. Hayabusa lost its balance soon after departing from the asteroid. Engineers are investigating the cause, but one possibility is that the craft's long stay on Itokawa's hot surface during the first landing attempt damaged one or more of 12 chemical engines. That, combined with the two lost reaction wheels, means the probe could run out of fuel halfway home.

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But astronomers have praised Hayabusa's achievements so far as showing the way for future asteroid missions - especially those involving the operation of ion-propulsion engines, the delivery of high-resolution images, sampling and autonomous navigation. Analysing the sample, assuming it makes it back to Earth, would also help answer questions about how the Solar System was created.

The mission is renewing Japan's confidence in space activities. JAXA has recently tried a string of high-risk missions, but has seen many failures over the past few years. "The success of Hayabusa has become a tailwind for Japan's space development," Hajime Inoue, JAXA's executive director, said at a press conference. "It proves that the way we have been doing things wasn't wrong."