Expeditionary Drone
An expeditionary drone (EDR) is an unmanned robot sent into a a foreign dimension in order to ascertain its habitability and the presence of any threats from local flora or fauna. Because bridges are kept open just long enough to pass an object through and no longer for both security and cost reasons, drones are designed to enter, spend time collecting data, wait for the exit bridge to open, and then return. They are thus designed with advanced algorithms to independently collect as much data as possible and navigate on their own.
Most EDRs are unmanned airborne vehicles (UAVs) with large sensor arrays and tools to take samples of soil and atmospheric gases. When deployed in dimensions that are known to contain sapient life, EDRs with advanced cloaking systems are used, though EDRs are never armed.