<tt id="6hsgl"><pre id="6hsgl"><pre id="6hsgl"></pre></pre></tt>
          <nav id="6hsgl"><th id="6hsgl"></th></nav>
          国产免费网站看v片元遮挡,一亚洲一区二区中文字幕,波多野结衣一区二区免费视频,天天色综网,久久综合给合久久狠狠狠,男人的天堂av一二三区,午夜福利看片在线观看,亚洲中文字幕在线无码一区二区

          Science and Health

          Comet-hunting spacecraft shuts down after 12 years


          Updated: 2011-03-25 22:24
          Large Medium Small

          DENVER?- NASA ordered its comet-hunting Stardust probe to burn its remaining fuel on Thursday, setting off a sequence that shut down the spacecraft after a 12-year career.

          Stardust had finished its main mission in 2006, sending particles from a comet to Earth. It took on another job last month, photographing a crater on an asteroid.

          It accomplished one last experiment on Thursday, firing its thrusters until its last hydrazine fuel was gone. The length of that burn, a little under 2 1/2 minutes, will tell engineers exactly how much fuel was left so they can see how accurate their calculations were.

          That in turn will help with the design and operation of future probes.

          Spacecraft don't carry fuel gauges because they don't work in zero gravity.

          It will take a few days to analyze the fuel data, said Jim Neuman, a mission operations manager for Lockheed Martin, which built and operated the probe at its complex south of Denver.

          Engineers gave Stardust the order to begin its final burn at 4:41 pm local time. Once the fuel was gone, the probe lost its ability to keep its antennas pointed toward Earth, and the control room lost radio contact at 5:33 p.m. local time.

          "Like saying goodbye to a friend," said Allan Cheuvront, the Stardust program manager for Lockheed Martin, who has worked on the probe since 1996, when it was in the detailed design stage.

          He paused, fighting back tears.

          "It's been an amazing spacecraft. It's done everything we asked, it's done it perfectly."

          Since launching in 1999, Stardust has traveled 3.5 billion miles (5.63 billion kilometers). In 2004, it flew through a cloud of dust and gas enveloping the Wild 2 comet, capturing tiny samples. Those were sent back to Earth for study in 2006, via a parachute-equipped canister.

          NASA then recycled Stardust, sending it past the Tempel 1 comet last month to photograph a crater left by a projectile launched by another space probe, Deep Impact.

          If Stardust executed all of its final orders as expected, it put itself in "safe mode," turning most of its systems off, about 1 1/2 hours after the last command was sent.

          With no fuel, Stardust can't keep its solar panels aimed at the sun, and once its batteries are drained it will shut down for good.

          Stardust will be left in an orbit around the sun. Engineers project that in the next 100 years, Stardust won't get any closer than 1.7 million miles (2.74 million kilometers) of Earth's orbit or 13 million miles (20.9 million kilometers) of Mars' orbit.

           

          分享按鈕
          主站蜘蛛池模板: 亚洲码国产精品高潮在线| av在线播放国产一区| 亚洲成人资源在线观看| √天堂中文在线最新版| 久久er99热精品一区二区| 色综合久久久久久久久久| 国产在线拍揄自揄视精品不卡| 亚洲精品天堂在线观看| 92自拍偷拍精品视频| 日韩精品av一区二区三区| 亚成区成线在人线免费99| 国产午夜福利免费入口| 亚洲免费人成网站在线观看| 另类国产ts人妖合集| 欧美肥老太交视频免费| 欧日韩无套内射变态| 青青草原亚洲| 日本一区二区三本视频在线观看| 日韩精品18禁一区二区| 国产一二三五区不在卡| 国产精品久久久久久免费软件| 女性裸体啪啪拍无遮挡的网站| 亚洲精品成人7777在线观看| 国产精品高清国产三级囯产AV| 99精品国产一区二区青青| 亚洲中文字幕无线无码毛片| 欧美精品国产综合久久| 国产原创自拍三级在线观看| 久热综合在线亚洲精品| 香蕉在线精品一区二区| 日韩一卡2卡3卡4卡2021免费观看国色天香| 国产精品户外野外| 亚洲国产精品乱码一区二区| 国产一区二区日韩在线| 极品少妇无套内射视频| P尤物久久99国产综合精品| 青草成人在线视频观看| 国产成人av一区二区三区在线观看 | 色综合久久综合中文综合网| 内地自拍三级在线观看| 视频一区视频二区在线视频|