The more difficult second level requires a flight of 180 seconds followed by a landing on simulated lunar terrain, complete with rocks and craters.

更困难的第二个级别，要求飞行180秒，接着在遍布岩石和陨石坑的模拟月球地形上降落。

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This method can be applied to terrain correction point by point for the airborne gamma energy spectrum in cases of any flight ways and arbitrary topographic conditions.

该方法特点是适合于任意飞行方式(缓地形和水平飞行均可)和任意地形条件航空伽玛能谱的逐点地形改正。

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The serious incident is officially classified in international aviation terms as "controlled flight into terrain only marginally avoided".

国际航空术语把这种严重事件正式归类为“控制中的飞机进入只能险险避开的地带”。

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The devices help pilots avoid "terrain" by coupling global-positioning technology with flight data on speed, altitude and other readings, and a database containing the topography of the planet.

FORBES: Cockpit Fight

And, because the GPS shows terrain regardless of the weather, it will also reduce flight delays.

BBC: The futurist: The US�� new air traffic control system

Flight instruments now warn pilots about potentially hazardous terrain and weather conditions.

NPR: For Air Travelers, More Safety and More Problems