Every Kilowatt Shines: Orbital Data Centers After Dark
Abstract
Orbital data centers have been filed by the million, and every kilowatt they compute needs square meters of solar array and radiator. We model a compute node whose power sizes its surfaces and sets its attitude, and we turn a production renderer into a calibrated photometer to measure it. The renderer matches closed-form reflectance to 0.1%, and the model reproduces measured satellites to about 0.2 magnitudes. For SpaceX's filed fleet of one million nodes, Sun-facing arrays hide their lit side from mid-latitude observers for half the year. On winter evenings, up to 31,000 nodes outshine the naked-eye limit for two hours after sunset and before dawn, and the equator sees about ten thousand all year. Power per node, attitude, surface finish, and altitude move these numbers by orders of magnitude. Brightness is a data-center design parameter, and we can engineer it before the fleets fly.
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BibTeX
@misc{fraire2026every,
title = {{Every Kilowatt Shines: Orbital Data Centers After Dark}},
author = {Juan A Fraire},
howpublished = {HAL},
year = {2026},
month = sep,
url = {https://hal.science/hal-05849199v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Every Kilowatt Shines: Orbital Data Centers After Dark
AU - Juan A Fraire
PY - 2026
DA - 2026/09/30
PB - HAL
UR - https://hal.science/hal-05849199v1
AB - Orbital data centers have been filed by the million, and every kilowatt they compute needs square meters of solar array and radiator. We model a compute node whose power sizes its surfaces and sets its attitude, and we turn a production renderer into a calibrated photometer to measure it. The renderer matches closed-form reflectance to 0.1%, and the model reproduces measured satellites to about 0.2 magnitudes. For SpaceX's filed fleet of one million nodes, Sun-facing arrays hide their lit side from mid-latitude observers for half the year. On winter evenings, up to 31,000 nodes outshine the naked-eye limit for two hours after sunset and before dawn, and the equator sees about ten thousand all year. Power per node, attitude, surface finish, and altitude move these numbers by orders of magnitude. Brightness is a data-center design parameter, and we can engineer it before the fleets fly.
ER -