Day 10 - Keeping an eye on the ESP
September 15, 2011

Roman Marin (foreground) and Gene Massion monitor the Environmental Sample Processor from the computer lab on board the Kilo Moana. Using a radio link to the instrument, they can download data on its movements and physical condition, as well as on the experiments that the robotic instrument is performing.

We’ve had amazingly calm, sunny weather for the last eight days, and we knew it couldn’t last. We had hints of a change yesterday, as a few squalls blew through periodically during the day. Nonetheless, it was a little disappointing to look out my stateroom window this morning and see gray skies, a rain-wet deck, and white-capped seas.

Not that the weather is actually bad, the temperature is still in the 70s (Fahrenheit), the wind is only blowing 15–18 knots, and the rain is intermittent. In fact, after breakfast this morning, I counted three rainbows simultaneously arcing over different parts of the horizon, as sun rays darted here and there between the clouds. In short, we’re getting back into normal trade-wind conditions.

I chatted with Gene Massion this morning about how the changed sea conditions are affecting the drifting Environmental Sample Processor (ESP). He showed me graphs plotting the movement of both the ESP and its surface float. These graphs show that the ESP is definitely moving more in response to the short, choppy waves that we’re seeing today. But so far, the motion has not been severe enough to endanger the instrument.

For the last eight days, Gene Massion and Roman Marin have been taking turns keeping an eye on the ESP. They don’t have to babysit the instrument continuously, but they do check in at least once an hour, 24 hours a day. Gene has the 9:00 a.m. to 9:00 p.m. shift, and Roman has been taking 9:00 p.m. to 9:00 a.m.

This picture (modified from an image created by Gene Massion) shows the paths that three of our drifting instruments have taken over the last week. These include the ESP (red line), the Lagrangian sediment traps (green line), and the Submersible Incubation Device (yellow line). The short, colored lines radiating from the path of the ESP indicate the relative abundances of various microbes that the instrument is monitoring.

The ESP continually sends a variety of diagnostic information back to the ship by radio. These data not only include information on the DNA and RNA analyses that the ESP is performing, but also on the location of the instrument, its movement in the water, the state of its electronics, and the humidity within the ESP’s water-tight pressure housing.

Ever since we put the ESP in the water, the humidity within the ESP’s housing has been slowly rising. About three days ago, the humidity had risen to about 80 percent, which could put the instrument’s electronics at risk. To make matters worse, a water sensor at the bottom of the housing sent out an alarm.

For a few hours, it appeared that water might be collecting in the ESP’s pressure housing. The ESP team—Gene, Roman, and Julie Robidart—held several meetings, trying to decide if the Kilo Moana should rush over to the instrument and pull it from the water before serious damage occurred. However, this would have caused major interruptions to deployments of the CTD array and other instruments. In the end, the ESP team decided to give it a day and see what happened.

Over the next 24 hours, Gene and Roman pored over the data from the ESP and discovered that the relative humidity inside the housing had not changed. But the seawater around the ESP has been really warm—over 26.5 degrees Celsius (80 degrees Fahrenheit)—and the temperature inside the housing was several degrees higher than this. These high temperatures allowed more water to evaporate into the air inside the housing, thus increasing the absolute humidity. This humidity became so high that it triggered the water sensor at the bottom of the housing, but there did not appear to be actual liquid water inside the housing after all. So we are watching the ESP closely, but letting it run for now.

As I write (around 10:00 p.m. Hawaiian time), there seems to be a problem with the software controlling the accelerometer that measures the motion of the ESP. Gene and Roman are trading emails with MBARI software engineer Brent Roman, who is diagnosing the problem from back on the mainland, using an Internet link to a computer network on the ship that lets him talk to the computers on board the ESP. It sounds like something that they can fix, but it also shows how these types of cutting-edge efforts require continual vigilance and teamwork.

One late afternoon we came close enough to the drifting ESP for me to take some video of the instrument’s surface float. This frame grab from the video shows several boobies resting on the float.

Almost every day, I walk along the upper deck of the Kilo Moana and look around to find a small yellow dot out there on the blue expanse of the ocean. I can’t see any details, but I know that this is the ESP float, rising and falling with the waves. We typically stay about a kilometer or two away from it so that we can sample similar water with the instruments on board the ship.

Just before sunset on September 9, we brought the ship closer to the float so that I could videotape the motion of the float in the waves. At least that was the official reason. Personally, I suspect that Gene also wanted to get a close-up view of his “baby.” Based on the videos, the ESP float seems to ride the waves well, and is also quite popular with the local seabirds.

The instrument is very popular with the researchers on board the Kilo Moana as well. Every few days Julie posts an updated plot of the populations of different microbes that the ESP is monitoring. Researchers on board gather around and discuss what the various trends might mean. We’re all curious to see if and how these microbial communities will change, now that we have real trade-wind conditions to work with.

—Kim Fulton-Bennett

Trevor Goodman prepares to lower the CTD array into the water at sunset. Even high-tech instruments such as the ESP cannot yet replace some of the tried-and-true tools of oceanographic research, such as the CTD array.
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