Turns out, the number of farm fires in Punjab and Haryana is being seriously underestimated.
While India's INSAT-3DS satellite spotted 447 fires on Diwali (November 8), NASA scientist Hiren Jethva says the real number for this season could be as high as 34,000.
That's a huge gap, and it matters for air quality.
Satellite timing misses fires, Delhi smoke
The big difference comes down to when satellites check for fires: INSAT-3DS catches more because it scans all day, especially during peak burning hours, while NASA's satellites pass by earlier and miss a lot.
This undercounting isn't just about stats: smoke from these missed fires gets blown into Delhi by a north-westerly wind.