Starfleet first encountered the spheres in 2153, when Enterprise NX-01 entered the Expanse in search of the Xindi. The first sphere they came across was being used as a base for Osaarian pirates. Enterprise engaged in battle with an Osaarian vessel within the cloaking barrier of the sphere, and was able to take a series of detailed scans. Quantum scans of the sphere indicated it was nearly one thousand years old. (ENT: "Anomaly")