Every school day, someone decides whether to open the windows.
Most days it's a guess. SkyWindow answers with data, and the data starts 824 km up.
This is the Earth right now, lit by the real sun.
Satellites watch for fire.
NASA's Suomi NPP passes over twice a day. Its VIIRS camera spots fires by their heat, and SkyWindow downloads those detections every hour to see whether smoke could reach PHS.
Air is a column.
Smoke, dust and haze fill it from the ground to the edge of space. Scientists measure how much sunlight that column blocks and call it aerosol optical depth.
June 2023: smoke from Quebec.
Wildfires in Quebec sent smoke about 1,000 km south. Keep scrolling to play June 6 to 8, hour by hour, from the CAMS atmosphere model.
From 824 km up, down to one school.
Princeton High School.
Every few minutes SkyWindow pulls the air above this exact spot: AQI, fine particles, ozone, haze and wind, from the CAMS atmosphere model.
Reading the air over PHS…
The wind decides where smoke goes.
These lines follow the live wind over PHS. If NASA sees a large fire upwind, SkyWindow raises a Fire Watch before the smoke arrives.
Streets and buildings: OpenStreetMap contributors.
The sunbeam test.
The thicker the haze and the lower the sun, the less of the direct beam reaches the ground. It's the Beer–Lambert law, the same physics that turns sunsets red.
T = e−AOD / sin θ
Sun 37° up, as at 5 pm on June 7, 2023. The haze starts at today's reading over PHS (…) and rises to that afternoon's 1.44.
On a classroom windowsill sits SkyWindow.
A Raspberry Pi, two sensors and a small screen. Once a second it compares the sky outside with the air in the room.
Five parts, off the shelf.
Grove sensors plug into a Raspberry Pi with Grove cables. No soldering.
The air sensor
A Grove gas sensor that reacts to cleaning sprays, markers and stale air. SkyWindow turns it into a stale index from 0 to 100, measured against the room's own clean baseline. It never pretends to be an AQI.
The light sensor
It faces the sky. Calibrated against clear-sky sunlight for this time and place, it shows how much light really gets through.
The Raspberry Pi
It reads both sensors, pulls the outdoor data, checks NASA fire detections upwind and decides once a second. A model we trained on our own labelled readings recognises what's happening in the room.
The screen and the speaker
One answer in one color, readable from across the room, and read out loud when it changes.
October 6, noon. AQI 23 outside, cleaner than the room, so the sash goes up.
Tonight. AQI 60 outside and a fresh room, so it barely matters.
June 7, 2023. Wildfire smoke, AQI 147. Keep it shut and run a fan instead.
Someone sprays cleaner and the room spikes. Open up until it clears.
Then it says it out loud. Gemini writes one sentence from the facts, and an ElevenLabs voice reads it to the class:
“SkyWindow update: the air in this room just spiked, so ventilate right away.”
Should PHS open its windows right now?
…
Checking the sky over PHS.
Built at hackPHS 2026 by Mahit's Team.
Data: Open-Meteo and the CAMS atmosphere model (CC BY 4.0). Fire detections: NASA FIRMS. Satellite model: NASA 3D Resources. Map: OpenStreetMap contributors (ODbL).
Music: “Penumbra”, “Cirrus” and “Hymn to the Dawn” by Scott Buckley (CC BY 4.0). Radiation-belt chorus: NASA/University of Iowa. Field recordings: Freesound contributors (CC0). Sound credits