Stellar Sphere was one of several Imperial projects developed in secret by the Tarkin Initiative. The technical schematics for Stellar Sphere were kept at the Citadel Tower on Scarif, along with those of Project War-Mantle and the Death Star. Tenzigo Weems found a mention of it in an intercepted data packet that was pulled from the Balmorra relay. He reported it to Davits Draven.
- Star Wars: The Rebel Files