The camera’s first good image came back a month ago, which was cutting things a little close for the July 16 moon crossing (NASA released the images on Wednesday), according to Szabo. “We were very much aware that the moon would be passing in view, and we worked very hard for it,” he says. The next opportunity to catch the passing won’t come until sometime next year.

“The beauty of the moon is it doesn’t have cloud layers, so color is pretty constant,” says Szabo. That tells scientists exactly how many watts per square inch are being reflected (and also accounts for the moon looking so strange and flat in the GIF). Using the moon’s brightness, Szabo and the others could calibrate their readings of the reflectance values coming from the Earth.

Source: The Satellite That Took This Incredible Photo Almost Didn’t Leave Earth