Linda Tatreau, FEBRUARY 28, 2010

NOAA Teacher at Sea: Linda Tatreau
Onboard NOAA Ship Oscar Elton Sette

Mission: Fisheries Surveys
Geographical Area of Cruise: Equatorial Pacific
Date: February 28, 2010

 

Old Dog, New Trick

What is the most exciting, most awesome, most unusual event of the expedition? These are the most common questions I have received from students following the blog. The whole trip has been exciting and awesome. It’s also been unusual as I don’t normally spend a lot of time at sea.
Unexpectedly for me, on February 23rd came the most exciting,most awesome and most unusual event of this trip. By then, I was familiar with the Autonomous Underwater Vehicle. I had read about it, talked about it, written about it and taken dozens of pictures. What I didn’t know was that Chris (see Meet the Science Team) was working to teach the AUV a new trick. AUVs run a preprogrammed route for about 4 hours and then return to the surface. It’s not until the AUV is back in its cradle on deck that the cameras can be retrieved. Only then can the photos be seen. Chris spent the trip devising a method whereby the AUV can send pictures to the ship while still underwater.
Seven miles of cabel used by the Remotely Operated Vehicle Jason II.
Keep in mind that the AUV is not attached to the ship. Remotely Operated Vehicles (ROVs) are attached to the ship via cables and can send pictures and receive instructions from the control room on the ship. On the AUV’s last dive, Chris’s program worked―underwater pictures on his computer. He got 13 photos at about 20 minutes each. The information is sent to the computer in small bits that must be assembled. HE DID IT! I wanted to break out the champagne in celebration, but there is none onboard so we had to settle for enthusiastic applause. I still get chicken skin (goose bumps) just thinking about the magnitude of his success.
AUV, no cables.

In the following paragraph, Chris talks about AUVs and communication.”Wirelessly communicating with Autonomous Underwater Vehicles (AUVs) is very difficult―the type of wireless communications that we rely on in our day-to-day lives does not work underwater. Most wireless systems, like WiFi or mobile phones, rely upon high frequency electromagnetic waves―millions or billions of cycles per second. Underwater, high frequency signals are attenuated, or blocked, over short distances. That is part of why when you are snorkeling or SCUBA diving everything looks blue―the higher frequency red light has been blocked out. To communicate with SeaBED AUVs, we rely upon sound waves, which use only around 12 thousand cycles per second. Echoes, other noise, and a number of other challenges presented by the ocean result in us having a very slow connection to the robot. Also, like using a walkie talkie, only one person can be talking at a time. If we are sending commands to the robot, it can’t be sending us information. Finally, sound travels slowly through the water, so it takes time for the message to even get to the boat (this is called latency). That all means we have to heavily compress images so that they are very small on disk before we transmit them, and we don’t get all the pieces in the right order. Putting together the image ends up being like putting together a puzzle―you have to make sure you have all the pieces, and then put them together in the right order. The compression means that the images look pretty rough, but they still give us an idea of what the robot is doing, and an early glimpse at the seafloor. For the rest, you have to wait until it comes back up! SeaBED AUVs can take over a thousand images every hour! ”

OK, me again. Chris will continue working on this project. He wants to make it easier and faster. With this new trick, the scientists will know, while the AUV is still below, that all systems are working and the AUV is taking quality photos.

Author

Leave a Reply