我们不知道月亮有多亮，但我们需要知道

我们不知道月亮有多亮，但我们需要知道

Even though millions of us gaze at the moon every night, we don't know exactly how bright it is — which seems strange. I mean, we've already walked on it, tested moon rocks and NASA is planning a return to the lunar surface in 2024.

尽管我们数百万人每天晚上都注视着月亮，但我们并不知道它到底有多亮——这似乎很奇怪。我的意思是，我们已经在月球上行走，测试了月球岩石，美国宇航局计划在2024年重返月球表面。

A crescent moon is an ideal time to think about the brightness of the lunar surface. Its appearance is created by the shadow of Earth and the light of the sun. (Photo: GreenSprocket/Shutterstock)

But there's a more practical reason: It's also incredibly important to know this detail with precision to keep our satellites running properly. That's because the way satellites work includes an important process of calibration.

但还有一个更实际的原因:精确地了解这些细节对保持我们的卫星正常运行也非常重要。这是因为卫星的工作方式包括一个重要的校准过程。

To ensure they're getting the most accurate images, they regularly take photos at the same place and compare the brightness of the images to one other. The moon is a useful source as it's bright but not as harsh as the sun. If one of the images is off, the satellite will reset itself to make sure its sensitivity is correct. All of this is done automatically.

为了确保获得最精确的图像，他们经常在同一地点拍照，并比较图像的亮度。月亮是一个有用的来源，因为它明亮但不像太阳那样刺眼。如果其中一幅图像是关闭的，卫星将自动复位，以确保其灵敏度是正确的。所有这些都是自动完成的。

This ensures that information from those satellites — which track weather, wildfires, floods, agricultural crops, and sometimes even wildlife (like mass migrations) — is accurate. To work properly, they need to have measurements of the moon that are 99 percent accurate, but we can't get that accuracy here on Earth.

这确保了来自那些卫星的信息——跟踪天气、野火、洪水、农作物，有时甚至野生动物(如大规模迁徙)——是准确的。为了正常工作，他们需要对月球进行99%的精确测量，但我们在地球上无法做到这一点。

The best we can do from the planet's surface is about 95-97 percent accuracy due to atmospheric influences, from everything from clouds and weather to smoke, natural haze, and air pollution. Scientists at Hawaii's Moana Loa Observatory are taking the best Earth-based measurements they can and trying to calculate out the interference.

由于大气的影响，从云层、天气到烟雾、自然阴霾和空气污染，我们对地球表面的最准确估计大约是95%到97%。夏威夷莫阿纳罗亚观测站的科学家们正在进行他们所能做的最好的基于地球的测量，并试图计算出干扰。

But another team from the University of Guelph in Ontario, NASA, the United States Geological Survey (USGS) and the National Institute of Standards and Technology (NIST) have another plan to get hyper accurate moon-brightness measurements.

但是来自安大略省圭尔夫大学的另一个团队，美国国家航空航天局，美国地质调查局(USGS)和国家标准与技术研究所(NIST)有另一个计划来获得超级精确的月球亮度测量。

The air-LUSI telescope during a calibration. The light on the other side of the room is an 'artificial moon,' a stable source of light that has already been well-characterized. (Photo: Ken Ulbrich/NASA)

Flying up into the stratosphere, above all visual interference, the air-LUSI (Airborne Lunar Spectral Irradiance Mission) is a NASA-sponsored mission that will take a set of measurements to determine lunar brightness from closer to the moon's surface. The 500-pound airborne telescope "uses optical and robotic equipment to autonomously capture radiometric measurements of the Moon from within the science pod of an ER-2 aircraft while flying at an altitude of 70,000 feet," according to a journal article that describes it in detail. Air-LUSI can provide 99 percent accurate measurements.

美国国家航空航天局发起的“空中月球光谱辐照度任务”(air-LUSI，即“空中月球光谱辐照度任务”)将飞行到平流层，首先是视觉干扰。这架500磅重的机载望远镜“使用光学和机器人设备，从一架ER-2型飞机的科学舱内自动捕获月球的辐射测量数据，而飞行高度为7万英尺，”一篇详细描述它的期刊文章称。Air-LUSI可以提供99%的精确测量。

A number of flights are needed, since the moon's brightness has to be measured during the various phases of the moon. And these are detailed measurements — the camera captured light from 380 to 1,000 nanometers, which is across the visible spectrum and includes the near-infrared.

由于月球的亮度必须在月球的不同阶段进行测量，因此需要多次飞行。这些都是详细的测量数据——相机捕捉了380到1000纳米的光，这些光横跨可见光谱，包括近红外光谱。

The first flights began in November, and so far, so good. "The data we collected looks really nice," John Woodward, NIST physicist said in a NIST statement. "The whole team has done a great job getting this instrument to fly, and the ER-2 team at Armstrong has been a great partner in making this a success."

第一次飞行开始于11月，到目前为止，一切顺利。NIST的物理学家约翰·伍德沃德在NIST的一份声明中说:“我们收集的数据看起来真的很不错。”“整个团队在让这个仪器飞起来方面做得很好，阿姆斯特朗的ER-2团队是让它成功的一个很好的合作伙伴。”

The full survey will probably take three to vive years to get all the needed data.

完整的调查可能需要3到5年才能获得所有需要的数据。

Then and only then will we really know how bright the moon truly is.

只有到那时，我们才能真正知道月亮到底有多亮。