The Ecliptic contract sets the rules for what is and is not possible on Azimuth. It's the point of entry for interacting with the Azimuth ledger data; the Azimuth contract itself is just data, and the Ecliptic contract is the logic for controlling that data. Examples of such logic include verifying permissions of the person asking to access their data, and ensuring a requested change is actually valid.
The Senate (the voting body of galaxies) has the power to replace Ecliptic via an upgrade proposal.