时事探讨——卫星有助马航客机搜索 但能力有限

An international charter of 15 space agencies was activated last week to search for the missing Malaysia Airlines jet, and by Thursday it provided what appeared to be the best lead yet to the airliner's disappearance.

自上周启动国际宪章向15个空间局调用卫星寻觅马来西亚航空(Malaysia Airlines)失联飞机以来,周四卫星数据似乎提供了迄今为止关于这架飞机的最佳线索。
However, experts warned that satellite technology is limited in its capability when it comes to searching huge swaths of territory.
Satellite data has been critically important to the search, from narrowing down the aircraft's likely destination to spotting possible debris in a vast area of ocean. Flight 370 disappeared from radar early on March 8 en route to Beijing from Kuala Lumpur. It was carrying 239 passengers and crew.
'This is a very difficult case. Normally we know what the area of interest is. This is essentially a camera in space, and if you don't know where to point it then it's a big challenge,' said Adina Gillespie, product development manager at DMC International Imaging, a UK-based commercial satellite imaging provider.
总部位于英国的商业卫星影像提供商DMC International Imaging产品开发经理艾迪娜•吉莱斯皮(Adina Gillespie)称,这次的情况非常棘手,通常情况下需要知道关注的区域在哪里。她表示,从本质上讲卫星就是太空中的照相机,如果不知道要对准哪里,那么将面临非常大的挑战。
Ms. Gillespie is also a secretariat member of the International Disasters Charter, an alliance of 15 space agencies including NASA and the China National Space Administration, which pools satellite assets during times of crisis. China invoked the charter on March 11, three days after Flight 370 disappeared.
吉莱斯皮还是《空间和重大灾害国际宪章》(International Disasters Charter)秘书处成员。该宪章是由美国航空航天局(NASA)、中国国家航天局(China National Space Administration)等15个空间机构组成的合作机制,在发生危机时可集中调用卫星资源。在370航班失联三天后,中国于3月11日要求启动该宪章。
The charter is usually invoked for natural disasters, such as the February eruption of Mount Kelud in Indonesia, which forced tens of thousands of people in East Java to flee their homes.
自然灾害通常可启动这一宪章,比如2月份印尼克卢德火山(Mount Kelud)喷发,导致东爪哇数万居民撤离。
'For events like this we will task a satellite [to cover the area of interest] once a day, or more,' Ms. Gillespie said. 'We can automate some aspects of it. For example we can run a program to identify bright things [in the images].' She said such programs had been run in the search for Flight 370, but cloud cover in the target areas had limited their usefulness.
In the case of missing Flight 370, satellite images from commercial operator DigitalGlobe were used to locate two objects that authorities believe may be from the aircraft. DigitalGlobe is a Colorado-based provider of high-resolution satellite imagery used by both public and private clients.
According to Australian authorities, who are leading the search efforts where the objects have been sighted in the southern Indian Ocean, the images were captured on March 16 but took four days to be analyzed and passed to the appropriate authority. 'The biggest delay in the process is in the analysis part of it,' Ms. Gillespie said.
Australia's maritime agency has been careful to emphasize that the images are not conclusive evidence that Flight 370 crashed. 'The images have been assessed as being credible but it is possible they do not relate to the search,' it said in a statement.
DigitalGlobe declined to comment in detail on their images. 'We do not have any additional information at this time as relevant search parties follow up on this important lead,' the company said Thursday.
Commercial imaging satellites typically have a range of capabilities, according to the German Aerospace Center, which says satellites typically scan areas 15 square kilometers (nearly 6 square miles) but can zoom out to 60 square kilometers or 2,300 square kilometers.
据德国航空航天中心(German Aerospace Center)表示,商业影像卫星的能力通常有一定的范围。该中心表示,卫星通常能够扫描15平方公里(近6平方英里)的区域,但可以扩大到60平方公里乃至2,300平方公里。
'Satellites could definitely be helpful to detect a crashed airplane on land, which has been most probably burnt or exploded,' said Hendrik Zwenzner, deputy head of the Center for Satellite-Based Crisis Information at the German Aerospace Center. 'As for the ocean the main problem is to narrow down the area where the plane possibly crashed.' He said most satellites would need the search area to be limited to just a few hundred square kilometers, which would take a 'couple' of days to scan.
德国航空航天中心星基危机信息中心(Center for Satellite-Based Crisis Information)副主任茨文茨纳(Hendrik Zwenzner)称,毫无疑问,卫星有助于探测在陆地上坠毁的飞机,在陆地上坠毁的飞机很有可能烧毁或发生了爆炸。他还说,至于对海上进行探测,主要问题是要缩小飞机可能坠毁区域的范围。他说,大部分卫星需要搜索区域限制在只有几百平方公里,扫描需要花几天时间。
In answer to a question about the usefulness of satellites to track the movements of Flight 370, Mr. Zwenzner's colleague and the head of the Center, Tobias Schneiderhan, added that only low resolution satellites acquire data continuously. 'But those are not useful for the search. Even those pass each point on earth only once or twice a day,' he said.
在回答一个有关卫星追踪MH370航班活动情况的有效性的问题时,茨文茨纳的同事、星基危机信息中心主任施奈德汉(Tobias Schneiderhan)说,只有低分辨率卫星才能连续获取数据。他说,但这类卫星对搜索没有用处,即便是这类卫星每天也只经过地面各点一两次。


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