NASA's Black Marble team turns nighttime satellite images into measurements of human activity on the ground, correcting for clouds, moonlight, snow, and viewing angle so that only artificial light from people remains. The work grew out of a 2012 observation that Cairo's nighttime brightness spiked during Ramadan as meals and shopping shifted after dark, a pattern also seen around Christmas and New Year's in US cities. The same measurement approach lets researchers track when power goes out during disasters, such as Hurricane Maria's blackout across Puerto Rico in 2017 and Hurricane Ian's effect on Fort Myers in 2022, and follow how and where electricity returns afterward.
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The satellite sensor behind this work is the VIIRS day-night band, flown on the joint NASA-NOAA Suomi NPP satellite launched in 2011.
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Researchers named in connection with Black Marble include Miguel Roman, Eleanor Stokes, Zushen Wang, and Virginia Kalb, among other collaborators.
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A widely cited 2012 nighttime Earth image showed North Korea almost dark except for Pyongyang, next to a brightly lit South Korea, with a bright ribbon along the demilitarized zone.
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Tracking power restoration street by street and month by month, rather than just a single before-and-after snapshot, is described as key to identifying communities left waiting longer for power.
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49:22holiday lights from space recognizing NASA's black marble team. In 2012, researchers studying satellite observations of Cairo noticed an unexpected jump in nighttime brightness. They traced it to Ramadan when meals, shopping, and social gatherings shifted into the night. And they also found holiday brightening around Christmas in US cities. patterns of human activity were showing up in satellite data. With NASA's funding support, which is one of the most popular federal agencies currently in the US government, the team's broader work produced Black Marble, a system that turns nighttime
50:03satellite observations into consistent measurements of lighting on the ground. And the same ability to measure those changes also helps to know, for example, when the lights go out. And this next image here is comparing Fort Meyers before and after Hurricane Ian in 2022. Areas that had been brightly lit became much darker as the storm knocked out power. And this kind of makes intuitive sense conceptually. By following these changes over time, researchers can map outages and track recovery, helping identify communities that may need support. Obviously, if the lights come
50:43back on, you don't have to send first responders into that area necessarily because we've now restored power. But how do you tell whether a place has actually lost power or whether clouds or moonlight or other atmospheric effects are changing what the satellite sees? This is the setup for our next Golden Goose Award winner. >> That's right. So, in September 2017, if we take another specific example, Hurricane Maria crossed Puerto Rico and the electrical grid failed across much of the island. And you can see a before and after. It's almost like the whole island goes dark. And from orbit, the change is immediate, right? Places that
51:24admitted light after night suddenly go dark. Now, scientifically, there's an interesting question, and it's not simply whether the island went dark. It's how the power returned, >> right? Street after street, month by month, and whether some communities were left waiting longer than others. Now, that question can't be answered simply by taking a before and after and after and after photo because there's a lot that happens between a satellite getting light from an area and that light being attributed to human activity. Okay. So Miguel Ramon, Eleanor Stokes, Zushen
52:07Wang, Virginia Calb, and Ranj Fista and their collaborators, they've been working on a way to measure artificial light from space with enough care to answer questions like that. How much of this is because of humans? And this is NASA's black marble. It begins with a remarkably sensitive satellite camera. And the real work is actually taking the measurements from the satellite camera and turning it into how much of this is human activity, how much of this is a different moon phase, how much of this is a cloud, a different viewing angle, snow on the ground, all of these other effects, taking all of that out and focusing directly on human
52:49activity. So, in the same tradition that we talked about the previous one, we're going to do five papers that are connected to this group. Um it's an incredible incredible set of papers and we'll keep the distinction in mind throughout that the satellite measures light but what we are interested in is human activity. Right? There's a longer history here because military weather satellites have revealed city lights decades before black marble. There's a joint NASA and NOAA Suomi NPP satellite that had the VIRS instrument. This was launched in 2011. And this has a day and night band. Okay.
53:30Its sensitivity made a new class of nighttime observations possible. And in 2012, we got this striking image incredible >> of Earth at night. I remember actually this was one of the first big images of Earth at night. And you could see some very >> stark differences based on geography. One of the big ones that was very famous was that if you looked at North Korea versus South Korea, it was massive. like South Korea has lit up so much city lights and then there's a band which is the demilitarized zone which is an extremely bright ribbon in between South Korea and
54:10North Korea and then in North Korea there's just really one kind of tiny pocket compared to South Korea and that tiny pocket is Pyongyang which is so much smaller than Seoul which is just across the border and you could just see the stark difference between the lighting that tells tell you so much about the economic activity and about the people and the regimes there, right? Um, so that was an early wonderfully specific observation and Ramon and Stokes studied how this nighttime lighting changed during Christmas and New Year's in the United States and during Ramadan as you were saying and they showed that lights during Ramadan and Eid the green in this plot is an upscaling
54:54of nighttime lights and you can see that in Aman Georgia and in Cairo >> there's a giant upscaling of lights that happen during the nighttime, during Ramadan and during Eid, >> Mh, >> which shows so much about the people who live there and like their ways of life and things like that. So, this already tells you that like there's variations between places that these satellite observations might capture and these satellite observations can tell us about human activity, the locations of cities and it's an open scientific question how far that idea can be taken. >> Yeah. >> Right. And so that's where we're going to start
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