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Last week, scientists from the National Institute of Standards and Technology (NIST), the National Aeronautics and Space Administration (NASA), the United States Geological Survey (USGS) and the University of Guelph sent a telescope to the top of the sky, almost to space itself. The trip was a moonlight-gathering mission that has yielded some of the best measurements ever taken of the brightness, or more specifically the surface reflectance, of Earth's nearest neighbor, the Moon.
The ultimate goal of the work is to improve measurements made by satellites that look down at Earth and help researchers track weather patterns, trends in crop health, the locations of harmful algal blooms in water and much more.
NIST - Equipment - NASA - ER-2 - Plane
NIST's equipment flew aboard NASA's ER-2, a "near-space plane" that travels as high as 21 kilometers (about 13 miles) above sea level. That kind of distance, twice the cruising altitude of a typical commercial aircraft, got the equipment above 95% of Earth's atmosphere, which interferes with moonlight measurements. The mission, called the Airborne Lunar Spectral Irradiance Mission (air-LUSI), launched from the NASA Armstrong Flight Research Center in California.
Hundreds of Earth-facing satellites provide information about weather and vegetation that allows researchers to predict famines and floods and can help communities plan emergency response and disaster relief. To collect this crucial data, space-based imagers rely on the brightness of different wavelengths—which it sometimes helps to think of as colors—of sunlight reflecting off our planet.
Satellite - Camera - Camera - Source - Space
To make sure that one satellite camera's "green" isn't another's "yellow," each camera has to be calibrated against a common source while in space. The Moon makes a convenient target because, unlike Earth, it has no atmosphere and its surface changes very little.
In theory, if scientists know the relative alignment of the Sun, Moon and satellite, they should be able to predict the amount of light coming off...
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