Dr. Miguel Román explains that the VIIRS day-night band satellite instrument uses a single, narrow wavelength band that favors infrared over blue light, a tradeoff made to monitor fires and flaring rather than to capture blue LED streetlights. The band's design was driven by weather-forecasting requirements shared across NASA, NOAA, and other agencies, such as detecting low fog and cloud cover in Alaska, not by any interest in tracking city lights or holidays. The chapter closes by noting that the light reaching the sensor is also shaped by moonlight, airglow, and clouds before it ever hits the instrument.
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Román frames instrument design as a series of tradeoffs: gaining infrared sensitivity for fires and flaring meant sacrificing blue wavelength detection.
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He describes the VIIRS instrument as a shared multi-mission tool built to also measure clouds, ocean color, fires, and forests, which drives up cost and limits what can be added.
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He gives a rough cost figure, noting the instrument already runs a quarter million dollars and adding blue LED sensitivity would cost roughly two million dollars more.
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He attributes the band's design priorities to a broad set of federal stakeholders, including NOAA and EOD, whose primary need was weather forecasting rather than nighttime human activity.
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15:59this before we did this interview um we did like a deep dive on five papers that you were co-author on and that was the last one. And it it was kind of unclear to me why the brightness would go I mean the the explanation was in the paper that you know there's policy changes and there's different types of lights but now it's very clear that it's just a single band and the thing is outside the band >> and it's not only a single band it's a single end with a narrow aperture in wavelength that we made traits at the time we needed to be more in the infrared because I I sacrifice the blue, but I gain infrared life to monitor fires and flaring.
16:40>> Okay, fair enough. Yeah. >> So, that's always the trade when you build an instrument. What do you give off and what do you gain? And at NASA, we've had to do that many, many times to help address the needs and priorities of broader science communities. You know, when we build it, this same instrument was built to measure clouds, to measure ocean color, to measure fires, to measure forests. So, by the time you build those requirements, you're talking about a $700 million instrument. And so, at the end, you add, oh, and I want to add blue LEDs. Okay, that's going to be another 2 million. Like, at some point, you got to stop, you know? So you can't just you can't what's the
17:22what's the technical reason why the band has to be like a certain width. Why can't it be a little like why why is it more expensive so much? >> It's driven by requirements. It's not it's not just this one decision. It's decisions going back to the requirements of a large swath of stakeholders across the federal community. Yeah. >> Do the Noah and NASA. They all have different customers. >> They all have different stakeholders. You've got folks who need to support weather, you know, you got and so at the time the requirement was we need to be able to see low fog and cloud in Alaska and these are the bands that allows us to optimize
18:03again that Christmas lights is not a factor. >> Yeah. Yeah. And it's about it's about weather at the end of the day. >> It's all about this is our nation's weather workhorse. >> Yeah. And so the priority is let's try the 5day forecast. If there's size that comes out of that, we'll revisit it later,
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