Communications satellite
From Halopedia, the Halo wiki
Communication satellites, sometimes abbreviated as comsats, are small, automated satellites placed in orbit around UNSC colonies and in space to relay communications signals.
They are found in orbit above several major UNSC worlds, including Earth, Reach, and Sigma Octanus IV. They can be accessed through the planetary network, and AIs such as Cortana and Serina have done so for various purposes.