The Earth Resources Technology Satellite (ERTS) mock-up is shown here in a space chamber test at General Electric’s Space Division. Later dubbed Landsat-1, the satellite was built on a weather satellite platform, which is why the satellite so closely resembles the Nimbus weather satellites. Courtesy of NASA.
The Landsat Data Continuity Mission (LDCM) satellite will continue the Landsat observatories’ heritage, obtaining unique multi-spectral land images and data to be used in agriculture, geology, forestry, regional planning, education, mapping, global change research, emergency response and disaster relief. Courtesy of Orbital Sciences.
Garden City, Kansas image shows center pivot irrigation systems creating these circular patterns in crop land. The red circles indicate irrigated crops of healthy vegetation. The light-colored circles represent harvested crops. Landsat-7 image taken Sept. 1, 2000, courtesy of USGS.
This image of the Rocky Mountain Trench was taken Feb. 1, 2004 by Landsat 5. What appears to be a stroke of thick red paint is actually a remarkable interplay of low sun elevation and low clouds in the Canadian Rockies. The trench is a valley that extends from Montana in the U.S. to just south of the Yukon Territory. The red stripe is near the border between the Canadian provinces of Alberta and British Columbia.
For man must rise above this Earth – to the top of the atmosphere and beyond – for only thus will he fully understand the world in which he lives.
– Socrates, roughly 400 B.C.
That comment by the classical Greek Athenian philosopher is fitting as part of celebrations marking the 40th anniversary of the U.S. Landsat program.
Since 1972, Landsat spacecraft have cast their respective sensor sets on Earth, collecting spectral information from the planet’s surface and producing a historical archive unmatched in quality, detail, coverage, and duration. See Figure 1.
The Landsat Program is jointly managed by NASA and the U.S. Geological Survey (USGS). “Because Landsat enables us to see Earth’s surface so clearly, so broadly, so objectively, we gain invaluable insights about the complexity of Earth systems and the condition of our natural resources,” said USGS Director, Marcia McNutt.
Many others have also heralded the value of Landsat over the decades. “Landsat is akin to the Earth’s free press. With its global perspective, we have objective and indisputable evidence of the condition of the planet,” contends Curtis Woodcock, team leader for the USGS Landsat Science Team and a Boston University professor.
But while being heralded, Landsat is a program in limbo. There’s the lack of a permanent agency home for Landsat and the threat of a data gap. Also, as reviewed in a recent Congressional Research Service report on Landsat and its future, “Despite its wide use, efforts in the past to commercialize Landsat operations have not been successful. Most of the users of the data are other government agencies. For that reason, funding a replacement for the failing Landsat orbiters has been a federal responsibility. A number of factors have made it difficult for Congress to assure that the project successfully meets the goal of bridging the impending Landsat data gap.”
Speaking before the Association of American Geographers during their annual meeting in February, Anne Castle, Assistant Secretary for Water and Science, U.S. Department of the Interior, titled her talk, “Landsat at 40: Prime Productive Years or Mid-Life Crisis?”
Castle noted in her talk that in October 2008, the USGS made the entire Landsat archive — over 3 million images — available via the Internet at no cost. The opening of the Landsat archive reshaped the future of moderate-resolution Earth observations, she reported. Indeed, that act, she said, spurred Adam Gerrand of the Food and Agriculture Organization of the United Nations to observe, “The opening of the Landsat archive to free, web-based access is like giving a library card for the world’s best library of Earth conditions to everyone in the world.” Castle underscored in her talk, in regard to Landsat, that studies indicate societal value exceeds data acquisition and distribution costs. Furthermore, the program encourages development of research applications leading to innovative commercial endeavors. “Commercial data use has increased under the free distribution policy,” she noted.
Time Is of the Essence
“The 40th anniversary of the Landsat program is definitely a cause for celebration,” said William Townsend, an aerospace consultant and former NASA and industry executive. “Landsat has produced an incredible, unbroken 40-year record of global land surface multispectral imagery that is unparalleled in the history of satellite remote sensing,” he told Imaging Notes.
These data are routinely utilized today, Townsend emphasized, to support such diverse activities as mapping environmental changes and supporting decision making in fields such as agriculture, forestry and land use.
“When the Earth Resources Technology Satellite (ERTS, aka Landsat-1) was successfully launched on July 23, 1972, the designers and builders of that system could hardly have imagined that the program would demonstrate so much utility that it would continue for another 40 years,” Townsend said. See Figure 2.
“But this has not been easy…nor without some old fashioned good luck,” Townsend noted. The failed attempt to privatize the system in the 1980’s, coupled with the failure of Landsat-6 to achieve orbit in 1993, seriously threatened the continuation of the program. Offsetting this were the incredible 25-plus years of successful Landsat-5 operations that managed to carry the program through these difficult times and beyond until just this past fall.
“But now the program is threatened again. Landsat-7 is expected to run out of fuel in the not-too-distant future. The Landsat Data Continuity Mission — or LDCM, aka Landsat-8 — has yet to be launched, although that event is coming up in January of next year. And, most importantly, there are no concrete plans for the continuation of the Landsat program beyond LDCM.”
Townsend pointed out that the leadership of the program was recently transferred from NASA to USGS via the 2010 National Space Policy — and has yet to get any significant traction in its new home. The Congress has questioned the wisdom of this transfer, and has refused to fund it at the requested levels. Accordingly, the White House Office of Science Technology Policy (OSTP), Office of Management and Budget (OMB), USGS, NASA and NOAA have formed a team to study possible options for future Landsat missions, with an emphasis on dramatically reducing the cost of future Landsat systems, given that the cost of LDCM is approaching a billion dollars.
“With Landsat-9 planned for launch in 2018, 5 years after LDCM, time is of the essence given the vagaries of government studies and the funding approval cycle. Even assuming a successful launch and activation of LDCM, the program is once again threatened with a break in coverage, given the current lack of concrete plans for a Landsat-9,” Townsend said.
In reviewing the history of Landsat, Ray Williamson, editor of Imaging Notes and Senior Advisor to the Secure World Foundation, underscored the program’s shaky and skeptical start.
“For one thing, there was a lot of argument over whether we needed the Landsat at all,” Williamson said, recalling the claims of some that it could all be done with aerial photography. “Those making that case didn’t appreciate the synoptic view that satellite imagery can provide…and they weren’t looking at its international value.”
There was early debate about Landsat utility strictly in economic terms. There were those who said, if it has value, then it ought to have value in the marketplace. “Also, the whole system was over-sold early on in terms of what it was going to produce…and that hurt it in the sense that advocates couldn’t show immediate return,” Williamson said.
Given the 80-meter resolution of the initial Landsats — while scientists by and large embraced that view of Earth from space — it was clear they wanted higher resolution, which became available with Landsat 4 and 5, Williamson added.
Fast forward to today: Williamson said that he feels the worth of Landsat and systems like it should be seen more in the “public good” realm. One of the lessons to be learned, in developing a new technology that’s not well known in user circles, is that it takes time.
Likewise, “One of the great values of Landsat was demonstrating to the world community that ‘satellite imagery works’ and could be used for a variety of applications,” Williamson said. “In my view, one of the greatest accomplishments of the Landsat program is that it engendered many of the optical systems in orbit right now.”
Lastly, the value of merging moderate-resolution data with other types of remote sensing, be they radar, higher-resolution satellite or aerial imagery, is yet another plus for Landsat, Williamson suggested. “So there’s room for the Landsat data to continue, and as a public good. The continuity of the data enables users to look back on changes in an area and understand what those changes mean. You really need that longevity of information.”
Kudos aside, Williamson said he continues to be perplexed that the continuity of the Landsat program “has always been a cliffhanger.” In his view, there’s been lack of innovative approaches and ingenuity to chip away at expensive systems like Landsat. A philosophy of ‘build the system that you can afford and then upgrade over time’ is worth considering, he advised.
“I use the term ‘evolutionary’ in looking at our advancement,” said James Irons, Landsat Data Continuity Mission (LDCM) project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “I think Landsat itself has been a notably successful program throughout its history, despite a rather chaotic history of the program’s management and operation,” Irons said. “The program has yet to find a secure, permanent home in either the government or the private sector.”
Irons said that he considers the Landsat data archive a public good and the program itself a public service. “At the scale we collect data, and the purposes to which the data are intended and applied,” he told Imaging Notes, “it’s not an area where private industry could expect to have a return on investment commensurate with the large investment to begin a spaceflight project.”
In terms of the Landsat user community, “We still have a ways to go…to make the data and the information inferred from the data user-friendly,” Irons said. “We have historically left challenges to the people who download the data that they had to overcome, before they could get the data into a form that was immediately useful.”
The 2008 judgment by the USGS to provide Landsat data at no cost was an action that Irons considers “institutionally courageous,” in addition to terrain-correcting the data. “That was a big step forward in making the data more user-friendly,” he said.
At present two spacecraft — Landsat-5, launched in 1984, and Landsat-7, launched in 1999 — are in orbit and continuing to supply images and data. Both, however, are experiencing technical issues. Irons flags a good dose of luck that’s ensured Landsat data continuity. Many of the spacecraft are lasting well beyond their design life.
The LDCM spacecraft is being built by Orbital Sciences Corporation. See Figure 3 on page 17. The main instrument onboard Landsat 8 (LCDM-1) payload is the Operational Land Imager (OLI) instrument. A passive (i.e., fixed) imaging radiometer, OLI will capture imagery of the Earth’s surface via panchromatic/multi-spectral bands at 30 meters to 15 meters (moderate) resolution. This capability is similar to instruments deployed on Landsat missions 4 through 7. In addition, a Thermal Infrared Sensing Instrument (TIRS) is being flown.
“The good news is that we’re going to collect data from both that will extend the historical archive. The advancements of Landsat-8 will improve our capacity to characterize and detect changes in all sorts of land cover, which is the primary objective of the mission,” Irons said.
After four decades, the Landsat program commemorates the longest continuous global record of the Earth’s surface and continues to deliver visually stunning and scientifically priceless images of our home planet. See Figures 4-5.
Still, putting festivities aside, William Townsend concluded, “So, while the 40th anniversary of Landsat is indeed a cause for celebration, it is also a time for a call for renewal of the Nation’s commitment to a sustained Landsat program…because good luck can last only so long.”