NASA将向火星发射直升机，拍摄火星鸟瞰图

　　NASA announced this afternoon that it plans to launch a tiny, four-pound, autonomous helicopter along with its 2020 rover mission. And if you think this sounds relatively cool, well: you're right.

　　今天下午美国国家航空暨太空总署(NASA)拟送微型、约四磅(3.6斤)的无人直升机完成2020年的火星探测任务，如果你觉得听起来很酷，那就对了。

　　The experimental, softball-sized drone would be the first airborne vehicle to fly around within Mars's atmosphere other than the landers that have delivered other, ground-based rovers.

　　这架垒球大小的实验无人机，不同于之前送到火星地表上探测仪，它被直接送到火星的大气层。

　　In order to design a flying vehicle that would actually work on another planet, NASA scientists faced a number of chanllenges.

　　为了使这家飞行器真正能够在火星上运行，NASA的科学家面对了一系列的挑战。

　　For example: the Red Planet's particularly-weak atmosphere and the communication delay between ground control here on Earth and the rover.

　　比如，火星的大气层非常的薄，而且探测器和地球上的控制沟通会有所延时。

　　Traveling at the speed of light, it'll still take several minutes for any commands sent from Earth to reach the helicopter, so the flying rover will have to be at least partially autonomous as it provides scientists and other autonomous vehicles with the first long-term bird's-eye view of the planet.

　　尽管传递速度是光速，从地球上发射出的信号到达探测器的时候还是需要好几分钟，所以该探测器半自动化地向科学家和其他自动仪器长期提供火星鸟瞰图。

　　Also, the Martian atmosphere is practically non-existent. The air pressure at the planet's surface is lower than it is at a helicopter's maximum altitude when flying above Earth.

　　加之，火星的大气层几乎没有存在感，大气层的高度比探测机的垂直高度比在地球飞行时的最大值还要低。

　　In order to take off, the tiny flying robot needs to spin it's two blades ten times faster - 3,000 times per minute - than it would on Earth while carrying batteries and other hardware crafted to be as light as possible.

　　所以哪怕是飞行器装载最轻的电池和硬件设备起飞，两个螺旋桨的也要比地球起飞时转速快10倍，达到每分钟3000转。

　　When the rover arrives at Mars in February 2021, it'll perform scouting missions to look for ideal landing zones on the surface, as well as scan the planet for signs of life, hazards that might matter to the future astronauts who finally venture to Mars.

　　预计2020年2月到达火星，通过在火星上完美着陆来完成初步勘察工作，探查在火星上是否有生命存在迹象，以及未来宇航员登陆火星有什么危险因素等问题。

　　It'll also assist with the ongoing geology research currently underway by ground-based rovers.

　　它还会协助现有陆地探测器来完成地理研究。