The terminology,
in plain language.

Aircraft Communications Addressing and Reporting System. A messaging system used for operational information; its absence is not a continuous record of the aircraft’s position.

An aircraft radio responder used by surveillance systems. Loss of a transponder-derived return and loss of primary radar tracking are different events.

Burst Timing Offset. A satellite-communication timing measurement used to constrain the aircraft’s distance from the satellite.

Burst Frequency Offset. A frequency measurement affected by relative motion and equipment behaviour; interpretation depends on the model and assumptions.

A distance constraint derived from the final satellite exchange. It is a set of possible positions, not a single confirmed crash point.

An underwater sound sensor. A recorded acoustic event requires analysis before it can be associated with a particular source.

A description of seafloor depth and terrain. Mapping an area is not the same as searching it at a resolution suitable for identifying wreckage.

Autonomous Underwater Vehicle. An underwater vehicle that can carry survey instruments along a programmed mission.