Day 2: First Sentry Dive

Sentry 1 better

Today was our first launch of Sentry, one of the two deep submergence vehicles that are supporting our research mission (stay tuned for a later post about Jason II).

Sentry is an AUV, or autonomous underwater vehicle. “Autonomous” means that before being deployed from the ship, Sentry is pre-programmed to trace a particular course along the seafloor, then resurface at a specified location. Its job is to map and survey the seafloor in high resolution. The information it brings back will help the science team decide where to collect samples and interpret their results in a broader spatial context. We expect to have about 5–10 Sentry dives on this cruise.

Sentry looks sort of like an orange Tic-Tac, blown up to the scale of a Zipcar.

Sentry 2

It takes a team of 5 engineers to handle Sentry, plus support from the ship’s crew. Carl (bottom right corner), our Sentry team leader, has a PhD in robotics and likes working with Sentry because it’s on the cutting edge of robot technology, with a practical application that keeps it frequently in use.

Sentry can dive to depths of up to 6,000 meters and operates in such extreme deep-sea environments as mid-ocean ridges, submerged calderas, and cold seeps—as well as hydrothermal vents like the ones we’ll be exploring at Loihi. Although it mainly functions autonomously, the Sentry team can communicate with the USBL acoustic navigation system if they want Sentry to change course during a dive. This is sort of like trying to drive a car by text message, at a rate of only 1 or 2 text messages per minute. Still, it’s a valuable tool that maximizes Sentry’s versatility.

Sentry 3

Sentry tells us about the deep sea through a variety of instrumentation. Some of its equipment includes:

  • camera system for photo-mosaic mapping of the seafloor
  • multibeam sonar for recording bathymetry
  • sidescan sonar to help determine the texture of the seafloor
  • sensors for chemical parameters, such as a redox probe and an in-situ mass spectrometer

Sentry 4

Here’s Sentry slipping free of its cables and beginning its dive.

Check back in tomorrow to hear about our other deep submergence vehicle, the very different ROV Jason II.

–Cat Wolner, NSF


Photo credits: Cat Wolner


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