The VIIRS instrument used for Black Marble has only one band, a single panchromatic channel spanning roughly 500 to 900 nanometers that measures total visible and infrared brightness rather than distinguishing colors. It was designed to track clouds at night for weather monitoring, not to study city lights, so it cannot detect blue light. Because white LED streetlights emit strongly in the blue part of the spectrum, outside this band's range, a city's actual light output can stay the same while the satellite data shows it getting dimmer, simply because the lighting technology changed, not because of any economic decline.
- 01
The example given is a recent Nature paper showing Europe's night lights appearing to dim, which the speaker attributes to a region-wide switch to LED lighting within a few years rather than any drop in prosperity or power use.
286 words · auto-generated from the episode video
14:36>> Oh, it's the Wait, so hold on. So let's start from just the satellite. Okay. What are the what are the wavelengths that it's sensitive to? >> So it there's only one band. There's >> there's only one band. There's only one pancreatic one from 0.5 to 900 nanometers and it captures all the infrared visible and infrared in that >> and >> so it's just brightness. >> It's just brightness. >> Okay, that's crazy actually. So >> and and because had it been designed by someone with expertise in night time would have been done completely different including the L LED pump or 20 which a lot of the lights that we see now are transitioning to LEDs. We can't
15:17see that. Why? Because it was not built to do that. It was built to measure clouds at night for weather. This is a letter sound. >> Wait, so wait, no, now I'm jumping the gun because like So the last paper that I wanted to Yeah, we're just going for it. So the last the last figure I have is this one. This the very recent um nature paper and there you see Europe dimming, but that's because of the it's just >> because Europe is poor. It's not dimming because there's some power out. It's different because all of Europe decided to switch to LED lights in three years. >> Right. So the brightness could remain the same. >> Yes. >> Right. It's not that the brightness >> the brightness is getting worse. >> Yeah. Yeah. >> But in our data it looks like it's going down because we don't see the blue. >> Yeah. That was unclear to me. So before
Remote SensingEarth ObservationEnergy AccessOpen Data