Why the Victorian Challenger was an expedition ship

Was the 1870s HMS Challenger a survey ship ahead of her time?

She did survey work, but her primary role was scientific exploration, making her an expedition ship.

The Victorian HMS Challenger was exceptionally well equipped and produced historic oceanographic results. Her primary role was expedition and exploration rather than dedicated surveying. She performed measurements as part of discovering and describing the ocean, including the work associated with Challenger Deep. A hydrographic survey vessel instead exists primarily to gather recurring navigational and operational data.