Sound Bytes: Synchronous Swimming (With Robots) – Behind the Glider Challenge

I’ve been working with passive acoustic underwater gliders for greater than 10 years—from early engineering assessments to multi-week ocean surveys. But NOAA Fisheries’ Hawaiʻi glider problem was not like something I’ve performed earlier than. Now that it’s wrapped up, I wish to present you what the problem seemed like behind the scenes—how we “flew” underwater gliders, how we coordinated a number of groups, and a little bit of what we realized alongside the way in which.

How do you steer this factor anyway?

Glider operators are referred to as pilots as a result of we “fly” these autos underwater. Buoyancy-driven gliders function a bit like airplanes. When an airplane speeds down a runway, its ahead movement permits the wings to create elevate, making it rise. Similarly, once we make the glider barely heavier or lighter than the encompassing water, we will make it sink or rise. Because it has wings, the up-and-down motion propels the glider in a zig-zag sample, fairly than a straight movement like an elevator.

Each glider has its personal management system. That’s one motive we would have liked so many pilots for this problem. Each of us makes a speciality of a unique automobile. I understand how to fly a Seaglider, and my colleague Tony Cossio from our Southwest Fisheries Science Center is a professional at flying Slocum gliders.

Meet the Hawaiʻi Glider Challenge pilots

Every time a Seaglider reaches the floor, it calls dwelling to a base station utilizing a satellite tv for pc connection. First it sends again fundamental well being and knowledge information with info equivalent to how deep it dove, how briskly it traveled, and a few security checks for leaks in addition to uncooked temperature and salinity knowledge. Then the glider downloads a small textual content file with new directions. Those directions inform the glider the place to go, how deep to dive, and what sensors to run such because the temperature probe or the passive acoustic recorder. The info it sends again is processed into plots that I evaluate on my laptop, on the lookout for patterns or warning indicators. Each glider sort has a barely completely different base station and option to ship and obtain instructions, however the concept is usually the identical. 

Piloting isn’t like driving in actual time. I don’t steer with a joystick. Instead, it really works dive by dive. I ship instructions to the glider. Then it dives. When the glider completes the instructions and resurfaces, I evaluate the information, regulate instructions, and the method repeats. We make piloting choices after which wait about 6 hours to see the outcomes.

Even although we aren’t glued to our computer systems 24/7, now we have to be able to “talk” to the gliders at any time. During the problem, my co-pilot Maria Visilkin from Cornell University and I took a brief break over the weekend to observe a browsing competitors and search for whales. We introduced our laptops and sat within the automobile so Maria may verify on her gliders earlier than we walked right down to the seashore. Thanks to cell hotspots and satellite tv for pc communication, we will pilot from virtually anyplace, although this additionally means you by no means totally loosen up—particularly when your robotic is alone in the course of the Pacific Ocean.

Choreographing Underwater Moves

Coordinating a number of gliders to function in the identical place at roughly the identical time made this problem way more concerned than a typical survey. Pilots used cloud-based platforms and group texts to consistently replace one another on glider positions and progress. We shortly realized that some gliders had been quicker than others, or higher at shifting in opposition to currents. For instance, the SeaExplorer usually reached locations first. It’ll be fascinating to see if the information exhibits it had the very best trackline protection per day.

What We Learned from the Gliders

Now that a lot of the gliders are again on land (just a few are on a brand new mission to hear for whales), we’re starting months of information processing and evaluation. But we’ve already realized just a few issues.

Not all gliders deal with the ocean the identical approach. Some had been quicker, some slower, and a few dealt with currents higher. I used to be particularly inquisitive about how in another way every sort might be managed. With a Seaglider, I set dive depth, period, and most thrust, and the glider calculates its pitch angle for environment friendly flight. Other gliders permit pilots to set pitch angle immediately, or produce other settings to alter vertical velocity. I’m desperate to see how these variations present up within the knowledge.

I’m comfortable to report that we undoubtedly recorded marine mammals! Some gliders despatched again small pictures of sound recordings that confirmed dolphins, humpback whales, and sperm whales. It’s peak breeding season for humpbacks in Hawaiʻi, so we count on many hours of singing whales within the recordings.

Performing Under Pressure

This problem was additionally a lesson in humility. Field work not often goes precisely as deliberate. We handled transport delays for a tiny substitute microSD card, a flood and energy outage at our glider lab, and a winter storm that shut down the whole state of Hawaiʻi. We revised our schedule a number of occasions to regulate for climate and variations in glider efficiency.

Ocean work requires cautious planning and the willingness to adapt when issues change—nevertheless it additionally means this type of work is rarely boring!