The Impact on Astronomy of Data Centres Orbiting Earth

Artificial intelligence computing is projected to require electrical power of ∼100 gigawatt (GW) by 2035. In response, companies and governments have proposed placing computing infrastructure in Sun-synchronous, low-Earth orbit, where continuous sunlight could supply electrical power. Generating 5 GW would require solar arrays 4 × 4 km in size. Such structures at roughly 500 km altitude would be visible above the western horizon after sunset for about 1 1/2 hours and above the eastern horizon before sunrise during 1 1/2 hours while the sky is in twilight. They would not be above the horizon during the dark hours of the night. At 1000 km altitude, they would be visible for 2 hours after sunset and before sunrise. A 4 × 4 km array in low-Earth orbit would span about 0.4°, comparable to the angular size of the Moon. Reflected sunlight would make it shine at magnitude g ≈ - 5 to $- 7$ mag, 100 times brighter than the brightest stars. The structures would occupy a north–south swath across the sky. During twilight, they would block the view of stars and planets for a few seconds. These structures increase the likelihood of collisions that could trigger runaway debris production and thus merit study.