John Schott laughs about it now. For years, graduate students he mentored as a professor at the Rochester Institute of Technology focused their work on one Landsat image because that’s all they could afford. At Virginia Tech, Professor Jim Campbell said his university had four or five Landsat images it owned. “And if we had an image, we had to keep using that same image in our classes, for this purpose or that purpose, over and over again,” Campbell said.

All that changed in January 2008 when Barb Ryan, the Associate Director for Geography at the U.S. Geological Survey, and Michael Freilich, NASA’s Director of the Earth Science Division, signed off on a Landsat Data Distribution Policy that made Landsat images free to the public. The USGS announced the free-and-open data policy on April 21, 2008.

It was a decision that Boston University Professor Curtis Woodcock says brought about “the biggest change, really, other than the launch of individual sensors, in the whole history of the Landsat program.”

With the development of the Internet, Ryan could see the global possibilities for Landsat data that would no longer have to be sent out on physical tapes, but could be distributed easier and faster on the World Wide Web. Paying for Landsat scenes historically meant much of this rich trove of information sat locked away unused in the archive. But unleashed by the change in policy, that no-cost data became “a paradigm shift for the world,” said Ryan, who went on to become the Secretariat Director of the Group on Earth Observations (GEO) in Geneva, Switzerland.

Indeed, though it took a few years to prepare the Landsat archive—and to develop tools and processes needed to handle massive amounts of data—the impact of the policy was transformational. Where 53 Landsat scenes had been leaving the archive every day when there was a cost for them, the number jumped to 5,775 daily when the price tag was removed.

Up to that point, scientists never really had the opportunity to take all Landsat data for a single location and study it over time. Even when they could, there were issues like clouds and shadows to be overcome, all of which evolved into a desire for such things as more meaningful surface reflectance.

So while it is simple to say free and open Landsat data has been around for 10 years, “the opportunities to explore what’s possible given all of the observations, we’re still really building the tools to do that,” Woodcock said.

Still, what a glorious time in Earth observation it has become. The world is moving to analysis ready data (ARD), taking most of the processing out of Landsat data and making it available almost immediately for scientists to run their algorithms against. That ARD in turn enables the evolution of time-series analysis and data cubes, much as USGS EROS is pursuing with its Land Change Monitoring, Assessment, and Projection (LCMAP) initiative.

With the development of Cloud-based processing, massive amounts of data now can be processed in hours instead of weeks.

“We’ve had this interesting convergence of analytical capabilities, computing capabilities, better imagination and, of course, all of that is surrounded by serious problems that need to be solved,” said Tom Loveland, Chief Scientist at USGS EROS. “I think we’re poised to really start a more real-time focus on understanding the condition of the Earth.”

And really, that’s only because of a decision made 10 years ago to give scientists across the world free and open access to perhaps the greatest and richest civilian treasure chest of remotely sensed images Earth has ever known.

“The archive is just going to continue to yield good information, good science, better management, reduced costs,” Schott at RIT said. “The biggest contribution of Landsat will be that archive.”