Doug Daniels, who co-chairs the 2019 NASA-USGS Sustainable Land Imaging (SLI) Architecture Study Team (AST) for USGS along with his NASA counterpart, Dr. Jeff Masek, says his group is getting closer to answering those questions. Or at least offering several recommendations.

With a late November deadline to deliver its findings to USGS and NASA Headquarters, the AST is now winnowing down what it’s investigated and assessed over the past year to three or four potential options for the next mission after Landsat 9’s scheduled launch in mid-December 2020, said Daniels, a Principal Systems Engineer with The Aerospace Corporation at EROS.

Each option will have a roadmap, Daniels said, including information on how it fits in with the potential evolution of remote-sensing technology over the next 15 to 20 years. There will be a mixing and matching of different capabilities in those options, he said. And they will provide technical and schedule risk assessments for each possibility, too, as well as cost profiles and recommendations for partnering options.

That said, “In the end, we don’t really decide anything,” Daniels noted. “Our recommendations inform USGS and NASA Headquarters leadership and acquisition processes.  We expect AST recommendations will also get discussed within the Department of Interior, as well as other federal agencies.”

Part of the joint agency Sustainable Land Imaging initiative, NASA and USGS officials were chartered as a study team and officially began their work in August 2018. Since then, they have:

• Assessed and modeled hundreds of agnostic users’ needs and applications;
• Talked with over 20 different corporations about evolving space technologies, potential data buys, subscription activities, and such things as full commercial cloud applications as they relate to ground system technologies;
• Communicated with potential partners, such as the European Commission—which flies the Sentinel satellites through the European Space Agency (ESA)—about harmonization of requirements, phasing of capabilities, and other potential partnership options;
• Discussed evolution of requirements for Landsat next generation architectures with the Landsat Science Team.

Among those evolutionary requirements, the AST is considering a superspectral capability that would increase the number of spectral bands from 11 bands on Landsats 8 and 9 to 20-plus bands on Landsat Next, thus providing users more specific spectral information.

For Landsat Next, the AST is also recommending enhanced ground sample distance resolution of 10 meters for the visible near infrared, 20 meters for shortwave infrared, and 60 meters for thermal—compared to 30-meter resolution for visible and shortwave infrared bands, and 100-meter resolution for thermal capabilities, that are on Landsats 8 and 9. That will result “in much more data with a tremendous improvement in ground sample distance, and smaller pixels,” Daniels said.

Finally, the AST is trying to achieve a higher temporal, or revisit rate. The goal there is every three to six days “so we can get as much cloud free imagery as possible,” Daniels said. Again, a partnership with ESA’s Sentinel satellites, or the use of commercial data buys, could help to accomplish or exceed that, he said.

“We’ve learned a lot,” Daniels said. “We have some follow-up to do with the commercial sector and will continue to do that through the course of our study. We’re also working with some other government agencies to make sure we understand what their needs might be and how each may correlate to future capabilities. We’re trying to keep as much of an open mind as we can as we start to nail things down.”

Of course, one of the factors in any recommendation is cost. The sustainability of any program like Landsat includes components of cost and schedule, Daniels said. Are the options for the next generation of Landsat observing systems affordable? Can you arrive at a desired launch readiness date based on your funding profile?

Architecture options believed to have substantial cost and schedule risk will receive a great deal of additional assessment and scrutiny, he said.

“So, for example, within architecture alternatives there are variations in cost and schedule based on what the capabilities are,” Daniels said. “Some capabilities cost more than others. We may be able to launch a certain capability in calendar year 2026, while another capability, based on the costs, may not be able to launch until calendar year 2028. Understanding these types of differences are all part of the equation.”

In studying whether fees should be charged for data acquired by Landsats 8 and 9, the Landsat Advisory Group (LAG)—a subcommittee of the National Geospatial Advisory Committee—reported in June 2019 that rather than charging for data, a better approach might be an analysis of how the cost of building and launching Landsat sensors in the future can be reduced.

Daniels said the AST is in fact looking at potential cost reductions as part of its study.

“We’re working to make recommendations that balance capability and cost in the most beneficial way possible,” he said. The LAG “talked about the fact that ground architecture could support revenue-based generation of data analytics, and that is actually a possibility given the direction that things are going with the commercial cloud,” he said. “Finally, the AST and the LAG both made recommendations with respect to commercial engagement strategies, and those recommendations are consistent in nature.”

Less costly could mean a lot of things, Daniels said. Sensors at a level of quality of the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS) on Landsats 8 and 9 today are much smaller. That means they could fly on a satellite that’s much smaller, he said, and thus potentially bring down overall costs.

Beyond that, the AST has looked at the possibility of flying more than one satellite—perhaps a constellation of small satellites, Daniels said. The AST has also looked at a single satellite with a complex instrument. “We actually have much more to consider this time around than we did just five to six years ago,” he said.

In a few short months, those considerations will result in architecture recommendations. While he doesn’t know when NASA and the USGS will settle on the best option or combination of options for Sustainable Land Imaging, Daniels is hopeful that it will be sooner than later—though again, he doesn’t know how the decision process for the new architecture timeline will play out.

“We’ll all be curious and excited to see what is ultimately selected for the next Landsat observing system,” Daniels said.