SAN FRANCISCO — As one of the nation’s two primary land-imaging satellites nears the end of its operational life, NASA and the U.S. Geological Survey (USGS) are evaluating ways to acquire future observations, such as continued reliance on large spacecraft, flying multiple small satellites and working with international partners.
Each of those approaches was suggested in multiple submissions NASA received in response to its Sept. 18 request for information on the space agency’s Sustainable Land Imaging Architecture Study. In April, the Obama administration directed NASA and USGS to conduct that study and to develop plans for a space-based Earth imaging system capable of providing observations for the next 20 years of similar quality to those the Landsat Earth imaging constellation has acquired since 1972.
“What we are happy about is the administration’s commitment to this program,” said Tim Newman, coordinator for the USGS Land Remote Sensing Program. “It is a long-term, multidecadal commitment to space-based land observation systems. We’ve never had that over the course of this program.”
Nevertheless, the challenge facing the NASA-USGS team is daunting because of the long timeline being addressed, budget constraints and the fact that one of the two operational land imaging spacecraft, Landsat 7, is running low on fuel.
Launched in 1999, Landsat 7 has enough fuel remaining to last approximately three years. The satellite also is exhibiting some gyroscope problems, Newman said Dec. 4 during the Sustainable Land Imaging Users Forum at NASA’s Goddard Space Flight Center in Greenbelt, Md., and accessible by webcast.
In contrast, Landsat 8, which was launched in February on aAtlas 5 rocket from Vandenberg Air Force Base, “could not be operating any better at this point,” Newman said. “It is collecting more than 500 scenes every day.”
Still, researchers at the forum emphasized the need for additional space-based instruments to provide more frequent observations than Landsat 8 alone could provide. Landsat 8, like Landsat 7, gathers imagery of specific areas once every 16 days. The orbits are complimentary to enable the two satellites to cut Landsat revisit times in half, providing researchers with new images of a given area every eight days. For most of the duration of the Landsat program, data customers have been able to obtain observations for specific regions of interest on an eight-day cycle. Many of the researchers at the forum were concerned that if Landsat 7 fails before another satellite is launched they will not have access to observations as frequently as they do now.
“It’s great to have a Cadillac-type instrument like Landsat up there,” said Rick Mueller of the U.S. Agriculture Department’s National Agriculture Statistics Service. “But 16 days, if this is what we are going to get with Landsat 9, is just not enough for the government’s agriculture monitoring. If there was the ability to have a lesser calibrated system of small satellites, that would be a lovely idea. If we had the ability to have one Cadillac and a couple of Pintos surrounding it, that would be OK.”
NASA and USGS are weighing the advantages and disadvantages of turning to small satellites as well as other platforms capable of obtaining land imaging data. “The point of the Land Imaging Study is to gather all land imaging requirements,” Newman said. “Some may be met by a Landsat-like system in space, some may be met by unmanned aircraft systems, some may be met by other aircraft and ground sensors. It is our intent to understand all land imaging activity.”
In addition, the team is talking to researchers about new capabilities they would like land imaging systems to provide during the next two decades, such as hyperspectral imagery. “It’s very difficult to look at technology that may come into play over the next two decades,” Newman said. “So we seek a solution that is flexible enough to assure continuity with past data, continues to assure access in the present and is extensible enough to meet the needs of tomorrow.”
NASA and USGS are scheduled to make recommendations for acquiring land imaging data and deliver a proposed implementation plan to the White House by Aug. 15, 2014. That plan must be designed to fit within the anticipated budget for the future land imaging program, which is expected to receive approximately $120 million a year beginning in the 2018-2019 time frame.
“One of the challenges we have been given is to provide architectures that fit within that budget profile, said David Jarrett, program executive for Earth science missions at NASA headquarters. “We’ve got to figure out how to incorporate future technology so we don’t have a stagnant program going forward.”