Closed Sky is a live electromagnetic observatory I built in Ukraine. It scans the radio-frequency spectrum from 80 MHz to 1 GHz, where signals from daily life, infrastructure, and military systems occupy neighboring bands.

Custom software learns the city’s normal pattern of radio activity, then tracks changes as signals appear, persist, disappear, and overlap. Each frequency is observed across three timescales, mapped directly to RGB: red for slow change, green for medium, and blue for fast. Through additive color mixing, red and green produce yellow, green and blue produce cyan, and blue and red produce magenta.

The resulting grid plots radio activity across time and frequency. Each pixel combines the RGB channels according to the amount of change at each timescale, allowing several durations to register in a single color. Together, these traces form an archive of contested airspace, where everyday devices such as a car key fob or a wireless doorbell operate alongside military communications.