Notes from the Field

Seaglider #189 Away!

September 14th, 2012 by Maria-Jose Viñas

By Eric Lindstrom

We just launched the first of our autonomous vehicles – a pink Seaglider with the sexy name of #189.

The story of Seaglider 189 begins.

Underwater gliders are the longest-range autonomous undersea vehicles in the oceans by virtue of their very simple propulsion mechanism: the translation of a vertical force into an horizontal one through use of wings. Gliders adjust their buoyancy by alternately inflating and deflating a small swim bladder appended to the vehicle’s body, a mostly rigid pressure hull. A volume variation of only a couple of thousandths of the overall vehicle’s volume is enough to provide an upward or downward buoyancy force that balances a combination of lift and drag forces, resulting in forward and vertical motion, the essence of gliding. Gliders, in effect, use wings as their propellers.

About an hour away from deployment.

Once made heavy, Seagliders sink to a prescribed depth where an electric motor drives a pump to change the vehicle’s density from heavier to lighter than the surroundings, causing them to ascend. They slice through the ocean along sawtooth paths.

The fixed supply of electrical energy aboard the glider in the batteries is used for propulsion and instrument operation. At SPURS we are using gliders in somewhat opposite extremes: some of them (the Slocum gliders — more about them later) are packed with power-needy instruments that limit their mission length to a couple of weeks, while others (Seagliders) direct a greater portion of energy to propulsion and operate a less hungry suite of sensors to achieve the 7-month mission duration required by the SPURS ship schedule.

Gliders were developed to probe the oceans independently of ships. Persistence is their virtue. The Seagliders launched from R/V Knorr are meant to repeatedly survey a limited region of the ocean, every fortnight repeating a 150-nautical mile (480-kilometer) circuit to provide a four-dimensional description of the upper ocean across wide area of ocean centered on the SPURS moored array. Profiles of temperature, salinity, oxygen, chlorophyll fluorescence, and optical backscatter will be transmitted ashore at the end of dive cycles to 0.6 miles (1 km) depth, repeated about thrice daily.

A close-up of Seglider 189’s sensors.

These gliders are completely autonomous once submerged, until they make a call over the Iridium satellite network to report data collected and accept new instructions from ashore controllers that manage everything, from flight to sampling strategy. They steer toward instructed target positions by moving the battery pack to one side or the other, inducing a vehicle roll that results in a turn. They follow a calculated compass heading to approach each target and, once there, dive toward the next. Seagliders even predict the effects of currents on their progress to choose an efficient heading with which to approach the next target. Vehicle pitch is similarly controlled during flight and the nose is depressed at the sea surface to raise the trailing antenna above the waves to gather position information and communicate.

In addition to the standard suite of measurements, the SPURS Seagliders are carrying brand new temperature microstructure probes. These are intended to measure turbulence in the upper ocean over nearly 2000 km (more than 1000 nautical miles) of track through the ocean by each vehicle on each mission. The hope is that upper ocean turbulence, long exclusively measured by ship surveys, will in SPURS be extended over the course of a year in autonomous surveys. The salinity and temperature profiles collected by more conventional aboard instrumentation, together with turbulence profiles, will reveal where the ocean mixes with respect to the myriad fronts and eddies to be encountered in the SPURS region.

Members of the SPURS team, ready to deploy the Seaglider.

Getting lowered…

Free at last!

Finally, to answer the inevitable question: to what does Seaglider #189 owe its garish color? The original project engineer in Seaglider development, Jim Osse, had some paint left over from a human powered submarine contest his University of Washington team entered in Florida. He chose the hue selected by the customer ahead of him at the counter of a Seattle auto parts store, destined for a 1942 Ford Coupe (and, it turns out, a bevy of Seagliders, too): Hot Rod Pink. We are hoping that #189 stays in the pink and safely hot rods around the ocean until recovered next March!

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13 Responses to “Seaglider #189 Away!”

  1. MIKE ROSE SR says:

    I am glad to see that nasa has adopted this research and is using the accumilated knowledge and extensive technoligy to explore the oceans and search within as well as its space exploration .well done . yours truly Mike Rose Sr

    • Eric Lindstrom says:

      Thanks for your comment. I have found it very rewarding to connect NASA’s “big picture,” technology and systems engineering approach to “real world” oceanography problems. Once again, here at sea, I am reminded how small we are and how big the ocean is. Aquarius, Jason, and many other Earth observing satellites help us with context and perspective, and to make the most of the ship and instruments we have in the waters. These days, with this technology, we really can attempt to assemble the picture of something like ocean salinity from the global scale right down to its microstructure in turbulence. Pretty awesome. Proud to work for NASA.

  2. Vishnu P Nair says:

    Wow, its just encouraging and thrilling to see and read about all the NASA research program all over the world and being an engineering student (Aeronautical), I just wish some day I could join NASA or be a volunteer in some research and prove myself be of some use to NASA and the whole world.

    • Eric Lindstrom says:

      Well, if you have the dream and the drive, likely one day you will be running the show! I wish you the best of luck in your aeronautics education.

      NASA has one “A” for Aeronautics…but as an oceanographer, I often wished that “A” could stand for “Aqua-nautics!” This month, here at sea, it does feel like the “National Aqua-nautics and Space Administration.” All kidding aside, NASA is deeply involved in just about every aspect of Earth System Science. Certainly in the field of physical oceanography, the space age and NASA investments have revolutionized the science. I’ve been lucky to start my career in old-fashioned sea-going oceanography and heading to the finish line with this fantastic array of ocean sampling wizardry.

      Keep after the education, be the best you can be, and maybe we will be following your aeronautics-blog-from-the-leading-edge someday soon.

  3. James says:

    Fortnight & thrice? What century do you think this is?

    • John Richardson says:

      How nice it is to read modern (and scientific!) commentary from such a well-read person as Mr. Lindstrom. It just shows what someone with a well-rounded education could do to enliven any subject they chose to write about.

      Scientific commentary can be (and usually is) very dry and heavily laden with subject-focused, technical terms and words aimed at other experts in that field. It certainly does not lend itself to be of interest to any in the non-scientific, rest-of-world population.

      There are plenty of non-scientific people in this world (alas, yours truly, for one) who love reading about the various scientific endeavors going on in this world. It is appreciated when the article is written to convey what is happening without bogging down with unnecessary technical terms. The author can show a link to those papers as interest warrants.

      I, for one, thank you, Mr. Lindstrom, for your eloquence. It is sorely missed in this world of ours.

      • Eric Lindstrom says:

        Mr John Richardson.
        You made my day. (That and a few more successful glider deployments!) Thank you for your kind words. It has been a pleasure to work on these postings from the field and try to share some of my decades of enthusiasm for oceanography. Its much easier to do this while in the middle of such an exciting expedition. I would certainly like the science to be interesting and approachable by all. The ocean does play a key role in our lives and welfare.
        Kindest Regards

  4. V. Muralidhar says:

    It is very interesting to see the technology which will monitor ocean parameters from close ranges, instead of the usual method of observations through low altitude remote sensing satellites which will not give a close situation reading this type of sensors can give. The development of sensors for such a mission must have been challenging. It will be nice to know what type of macro result or scenario is expected to be derived out of these observations.

    • Eric Lindstrom says:

      I think you have captured some of the goals of SPURS in your comment. Satellites are excellent in providing large-scale context of properties at the ocean surface. Likewise, in situ monitoring via Argo floats and surface drifters provide some more detail but relatively sparse in space and time. SPURS uses some of the same technologies from the ship, but we are looking in detail at one small piece of the ocean (representative of some larger expanses). Putting all these pieces together into a seamless whole is what we are trying to achieve – for salinity in particular.

  5. Nemo Hua says:

    Autonomous mechanism is great!!!! More and more systems like this is coming to life. I am so excited!!! I am a Chinese student in Senior 3 when life is busy and boring. It’s pretty great to read articles like this-intruducing a brand new Seaglider! And the sexy pink makes me really freshed. 🙂

    • Eric Lindstrom says:

      Thanks for you comment. We are indeed excited to be using the Seagliders. We launched 2 more today (#190 and #191). This technology is now quite mature and we at NASA owe much to those who developed the ocean glider technology over the last few decades. I plan to talk more about that in a future post.

  6. Prof. Vikas Nayak says:

    If this glider succeeds to gather more information from beneath the sea and ocean then a lot of natural calamities can be learnt quite in advance along with the nature and extent of the peril.

  7. Eric Lindstrom says:

    One glider makes a small contribution to our understanding of the overall ocean structure and prediction. As we learn the value of their data and how they are best used we may see them deployed in larger numbers. Argo floats are a good example of a successful technology development of the 1990s that is now deployed globally (3561 reporting last time I checked a few days ago). That has revolutionized our knowledge of temperature and salinity in the upper ocean. The Argo floats are a workhorse of SPURS. The Seagliders and Wavegliders will get a good workout in in SPURS during the next year.