我想一要份關於宇宙的英文文章10分

June 12th, 2007 by Fraser Cain


圖片參考：http://www.universetoday.com/wp-content/uploads/2007/06/Earth.thumbnail.jpg




Most detailed true-color image of the entire Earth to date Image credit: NASA/GSFC



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NASA researchers have developed a new technique that gives them a precise measurement for the position of the centre of the Earth, to the closest millimetre. This is harder than it sounds, since the centre doesn't stay in one position.



As the Earth rotates in space, its centre of mass ranges over a distance of 2 to 5 millimetres (.08 to .20 inches) a year. Until now, the best calculations differed by 1.8 millimetres a year. That doesn't sound like much, but its actually important for very precise measurements. For example, the rise in global sea level due to increasing temperatures is measured in a handful millimetres. In other places, the Earth is rebounding after the weight of glaciers during the last ice age, 20,000 years ago.



The researchers combined 4 different space-based techniques to get this accurate measurement: the global positioning system, laser stations that track orbiting satellites, radio telescopes that measure the position of the Earth against quasars, and a French



June 12th, 2007 by Fraser Cain




圖片參考：http://www.universetoday.com/wp-content/uploads/2007/06/arctic_arc_rough_ice_H.thumbnail.jpg




Struggling over rough sea ice during the Arctic Arc expedition Credits: Arctic Arc 2007



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A duo of Belgian adventurers are receiving some guidance from the heavens during their 2,000 km (1,200 mile) trek across the Arctic Ocean. Okay, it's nothing magical, they're just received detailed observations from ESA's Envisat Mission, which is providing readings on sea ice.



The explorers, Alan Hubert and Dixie Dansercoer, are collecting snow depth data which will help calibrate the upcoming CryoSat-2 mission. They're used to dealing with the harsh and rapidly changing Arctic environment, but they were caught off guard when a portion of the ice in the Lincoln Sea broke up. Thanks to observations from Envisat, they were able to avoid the rapidly disintegrating ice pack, and steer to safer conditions further to the east.



Their Arctic Arc expedition is part of the International Polar Year 2007-2008. They started in March 1, 2007, and have already traveled 1,600 km (1,000 miles) taking snow depth measurements along the way. When CryoSat-2 finally launches in 2009, scientists will compare the satellite's observations against these measurements, to better calibrate its data on snow levels.



June 12th, 2007 by Fraser Cain




圖片參考：http://www.universetoday.com/wp-content/uploads/2007/06/Ist%20spacwalk.thumbnail.jpg




New solar array wings wait to be fully unfurled. Image credit: NASA



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Astronauts Jim Reilly and Danny Olivas spent a good portion of their Monday evening out in space, beginning the installation of the International Space Station's new solar arrays.



The spacewalk started at 2008 UTC (4:08 pm EDT), and ended 6.5 hours later. During their time outside the station, the duo performed a series of tasks to activate the new Starboard 3 and 4 (S3/S4) segment delivered by the space shuttle Atlantis. This included making power, data, and cooling connections between the station and the new segment. They also released locks and restraints on the solar arrays, enabling their deployment today.



NASA has also decided to extend the current mission of Atlantis, giving the astronauts an additional 2 days to do a new spacewalk to repair some minor damage to its heat shield. During this fourth and final spacewalk, the astronauts will tuck a protective thermal blanket back into position. Although NASA doesn't consider this to be a huge risk, they're not taking any chances after the catastrophic loss of Columbia.