Wednesday, July 21, 2010

Satellite Imaging of Oil Slicks - A Primer

We get a lot of questions from folks interested in our work using satellite images to detect and monitor oil spills around the world. The Montara spill off Australia last year, and the ongoing BP / Deepwater Horizon spill in the Gulf of Mexico, are striking examples of how this technology can help us investigate and illustrate what's happening far out to sea and in remote locations.

Like all data sources, satellite imagery has its strengths but also some important limitations. Few imaging satellites (the ones taking pictures of Planet Earth) are "turned on" all the time, so images are not necessarily available. Usually somebody has to contact the satellite operators - some operators are government agencies, some are commercial for-profit businesses - and request that images be collected over an area of interest. Often, you've got to pay to have this done. NASA makes images from their taxpayer-supported systems, including MODIS, available for free, but satellite images from private vendors can cost thousands of dollars each.

Imaging systems that operate at visible to infrared wavelengths of light, like the MODIS system we've used so often, can't see through clouds, smoke, dust or haze. And oil slick imaging is sometimes dependent on the sunglint pattern, which varies considerably from one image to the next, and is also affected by wind and wave conditions on the water. Radar imagery gets around some of these problems, but NASA doesn't operate any radar satellites so the cost can be prohibitive.

For all of these reasons, we haven't been able to produce good images of the BP oil slick every day (NASA just published an excellent illustrated article on this topic). But at SkyTruth we have acquired good images often enough to illustrate the enormity of the spill and inadequacy of our initial spill response efforts; provide the first estimate of the spill size and rate that made any sense; to identify oil making landfall along the Alabama coast before it was being acknowledged by officials; to show clear entrainment of the spill in the Loop Current while officials were actively denying it; and to detect small but chronic leaks from other damaged wells, raising the related issue of inadequate plugging and abandonment.

This spill has also provided a unique opportunity to collect imagery from multiple different remote-sensing systems, both satellite and airborne, working at visible to infrared to microwave wavelengths, over a long period of time under a wide range of weather and illumination conditions. A systematic analysis of this dataset will yield a much better understanding of how imagery can be used to accurately measure and monitor oil pollution events in the future. We're looking for funding opportunities to conduct such an analysis.

Because as long as we continue to produce and transport oil offshore, there will be a next time.

Hopefully not too soon.

2 comments:

  1. Great article, John. Hopefully, what may have been viewed by you as "just doing your job" will help to lead to significant changes in the way the Feds and the oil industry do theirs.

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  2. Eric_7 - we are hopeful there will be some substantial positive changes to the ways we produce and consume energy as a result of this awful spill. But there is a long hard battle to fight to make sure those changes actually happen, and stick over the long haul. If our politicians don't hear from us, then we could end up back where we were on April 19.

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