Satellite to begin gravity quest 欧盟卫星开始勘测地球重力图
文章来源:未知 文章作者:meng 发布时间:2009-09-23 03:25 字体: [ ]  进入论坛
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A European spacecraft will begin its quest this week to make the most detailed1 global map of the Earth's gravity field.

一艘欧洲宇宙飞船本周将要绘制详细的全球重力场图片。

Goce can fly much lower than was expected
Goce can fly much lower than was expected

The arrow-shaped Goce satellite can sense tiny variations in the planet's tug2 as it sweeps around the world at the very low altitude(高度,海拔) of just 255km.

The map will help scientists understand better how the oceans move.

It should also give them a universal reference to compare heights anywhere across the globe.

Goce was launched from the Plesetsk Cosmodrome in north-west Russia in March.

Engineers have since commissioned the spacecraft, satisfying themselves that all its systems are working properly.

But the satellite has had to wait until now for the right conditions to start its science campaign.

"We've been in the so-called eclipse(日蚀,月蚀) mode where the Sun doesn't shine fully3 on the solar panels, but now we are entering the measurement mode," said Dr Volker Liebig, the director of Earth observation at the European Space Agency (Esa).

"Being able to fly low is very good for the measurements, and the Sun is so low in its activity at the moment that we can fly lower than we expected; and that will give us a better signal," he told BBC News.

The data return will be the first to come from Esa's Earth Explorer programme, which is sending up a fleet of small satellites tasked with acquiring key information on issues of environmental concern.

The precision with which Goce expects to make its gravity measurements means every disturbance4 the satellite could experience has to be minimised.

This includes avoiding the rapid and deep swings in temperature that come from different parts of the spacecraft going into and out of sunlight.

Goce now flies with the Sun's rays constantly streaming on to one side of the satellite. Its permanently5 shadowed side radiates heat out into space.

To make its map, the satellite carries a set of six state-of-the-art accelerometers housed in a device called a gradiometer(倾斜计).

As the spacecraft "bumps" through Earth's gravity field, the accelerometers sense fantastically small deviations6(脱离,偏离) - as small as one part in 10,000,000,000,000 of the gravity experienced at the Earth's surface.

But to make the most of this sensitivity, Goce flies extremely low - much lower than is normal for Earth observation satellites.

Mission controllers have been fortunate in that solar activity which acts to excite the Earth's atmosphere and raise its upper reaches has been exceptionally calm. The density7 of residual8 air(残余空气) molecules9 that might otherwise buffet10(打击) the spacecraft and introduce further noise into the data has been greatly reduced as a consequence.



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1 detailed xuNzms     
adj.详细的,详尽的,极注意细节的,完全的
参考例句:
  • He had made a detailed study of the terrain.他对地形作了缜密的研究。
  • A detailed list of our publications is available on request.我们的出版物有一份详细的目录备索。
2 tug 5KBzo     
v.用力拖(或拉);苦干;n.拖;苦干;拖船
参考例句:
  • We need to tug the car round to the front.我们需要把那辆车拉到前面。
  • The tug is towing three barges.那只拖船正拖着三只驳船。
3 fully Gfuzd     
adv.完全地,全部地,彻底地;充分地
参考例句:
  • The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气,然后全部呼出。
  • They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。
4 disturbance BsNxk     
n.动乱,骚动;打扰,干扰;(身心)失调
参考例句:
  • He is suffering an emotional disturbance.他的情绪受到了困扰。
  • You can work in here without any disturbance.在这儿你可不受任何干扰地工作。
5 permanently KluzuU     
adv.永恒地,永久地,固定不变地
参考例句:
  • The accident left him permanently scarred.那次事故给他留下了永久的伤疤。
  • The ship is now permanently moored on the Thames in London.该船现在永久地停泊在伦敦泰晤士河边。
6 deviations 02ee50408d4c28684c509a0539908669     
背离,偏离( deviation的名词复数 ); 离经叛道的行为
参考例句:
  • Local deviations depend strongly on the local geometry of the solid matrix. 局部偏离严格地依赖于固体矩阵的局部几何形状。
  • They were a series of tactical day-to-day deviations from White House policy. 它们是一系列策略上一天天摆脱白宫政策的偏向。
7 density rOdzZ     
n.密集,密度,浓度
参考例句:
  • The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
  • The region has a very high population density.该地区的人口密度很高。
8 residual SWcxl     
adj.复播复映追加时间;存留下来的,剩余的
参考例句:
  • There are still a few residual problems with the computer program.电脑程序还有一些残留问题。
  • The resulting residual chromatism is known as secondary spectrum.所得到的剩余色差叫做二次光谱。
9 molecules 187c25e49d45ad10b2f266c1fa7a8d49     
分子( molecule的名词复数 )
参考例句:
  • The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
  • Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里,大分子裂变为小分子。
10 buffet 8sXzg     
n.自助餐;饮食柜台;餐台
参考例句:
  • Are you having a sit-down meal or a buffet at the wedding?你想在婚礼中摆桌宴还是搞自助餐?
  • Could you tell me what specialties you have for the buffet?你能告诉我你们的自助餐有什么特色菜吗?
TAG标签: satellite global map gravity
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