They need to be certain of several hours of clear air as it will take two hours for an initial reconnaissance team to reach the area where the missing men are.

搜救人员需要确定干净的空气能保持数小时，因为打头阵的侦察队确定被困矿工的位置就需要两个小时。

youdao

This image was taken in February 2009 by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. It covers an area around.6 miles across.

该照片由美国宇航局火星探测轨道器上的高清晰科学实验成像仪(HRISE)拍摄，摄于2009年2月。

youdao

During the process of reconnaissance, exploitation, transportation and deposit, a large area around the oil field suffered from serious pollution.

在石油的勘察、开采、运输以及储存过程中，油田周围大面积土壤都受到严重的污染。

youdao

Aircraft was sent to the area on Monday and was expected to resume reconnaissance work on Tuesday, he said.

CNN: Tropical Storm Emily forms in the Caribbean

China's central Air Force Command sent two reconnaissance planes from Beijing to take aerial photographs of the area, state media said, adding that 2, 600 soldiers from the People's Armed Police had already arrived in six towns in the quake zone.

WSJ: Quake Kills More Than 100 in Sichuan

The peacekeepers were on a reconnaissance patrol because U.N. officials had heard rumors several days earlier of armed men in the area threatening to attack a village, she said.

CNN: Thousands flee in wake of clashes in western Ivory Coast