Bathysnap IV - Development of a new time-lapse photography free-fall benthic lander

Bathysnap IV is the latest development of the Bathysnap family of free-fall benthic landers designed by the National Oceanography Centre (NOC) in Southampton, UK. In this paper, the driving factors for the design are covered such as the recent expedition to the Clarion Clipperton Zone in the Pacific Ocean, and a brief background on camera landers is presented with a focus on the history of the Bathysnap family.The main body of this paper is a reporting of the design process of the camera lander and the decisions made for each section. These include the decision to reuse a known frame design from the previous generation of Bathysnap, also known as Roughsnap; the upgrading of NOC’s Autonomous Ecological Survey of the Abyss (AESA) camera system to fit on Bathysnap and provide a base for reuse on other NOC systems, and the use of custom software to control the hibernation loop.The latter part of this paper discusses testing processes carried out including lab-based testing and trial deployments. The issues uncovered by these actions, such as under-exposure of images and intermittent boot issues are presented alongside the remedial actions taken to mitigate them. The science deployment that two Bathysnap IV landers were deployed on in 2023 is then summarised.