COSMOS Missions are non-repeatable missions from agents in space in specific regions (each faction has it's own COSMOS region). They require a minimum standing to be available to you like other missions.

The rewards for these missions are often very high including blueprints for named or faction ships and modules, and large standings improvements for both the agent's faction and corporation. It is recommended to look into the requirements of these missions before undertaking them if possible as they are not repeatable and some can be difficult to complete within the time constraints but the item required can be obtained without accepting the mission (there are others where the item is acquired in a deadspace pocket spawned for the mission as normal).

The missions can include many different activities similar to chain missions and require you to transport large loads (an industrial is appropriate), engage in combat, and perhaps other requirements.

Specific information for some factions can be difficult to find with Caldari being the most widely available, for example here: http://cosmos.awardspace.com/caldari.htm