Landsat Program on Track for 2011

by Barbara J. Ryan and Bruce K. Quirk

After years of uncertainty, the United States took decisive steps in 2007 toward ensuring the continued availability of moderate-resolution satellite image data to support global land monitoring activities for years to come. As a result, the Department of the Interior/U.S. Geological Survey (USGS) and NASA Landsat Data Continuity Mission (LDCM) is on track for launch by mid-2011, and the long-term future of the program has never looked better.
Two important milestones in LDCM development came in 2007 when the first major contracts were awarded to build and launch the follow-on satellite to Landsat 7. In July, Ball Aerospace and Technologies Corp. of Boulder, Colo., received a $127.9 million contract to develop the Operational Land Imager sensor that will fly on the satellite. And in October, Lockheed Martin Commercial Launch Services of Littleton, Colo., was selected to launch the new satellite, which will be known as Landsat 8 upon reaching orbit.
The recent progress in LDCM development is great news to the multitude of scientific, commercial, and governmental users who have relied on Landsat for more than 35 years as their primary source of moderate-resolution multispectral Earth observation data. With the two operational satellites—Landsats 5 and 7—experiencing technical malfunctions in recent years, users worldwide view the timely development of LDCM as critical to avoiding a significant gap in this vital imagery source.
While high-resolution imaging satellites seem to grab the headlines, the Landsat satellites have quietly remained the workhorses of global land monitoring and mapping efforts. The 30-meter resolution of Landsat multispectral bands is ideal for detecting, measuring, and analyzing changes to the Earth’s land surfaces at a level of detail where the impacts of natural and human-induced activities can be accurately identified and assessed.
“Population growth, resource development, natural disasters, and climate change are having significant impacts on the Earth’s surface,” said Department of the Interior Secretary Dirk Kempthorne. “The use of remote sensing satellites to monitor these developments more effectively and sustainably will play a critical role in shaping our national as well as international response plans.”
The greatest asset provided to these vital endeavors by Landsat may be the longevity of the program itself. Through more than three decades of operation, Landsat satellites have amassed a U.S. archive of over 2 million images representing the longest uninterrupted record of the Earth’s surface conditions. This unique archive, augmented worldwide by International Cooperator receiving-station archives, gives researchers the unparalleled opportunity to map and track changes in land characteristics almost anywhere on Earth from 1972 to the present.
With this archive in mind, LDCM development has focused on keeping the imaging specifications and orbital characteristics of the new satellite consistent with previous Landsats. The continuity of the data stream will thus be preserved, so users can make apples-to-apples comparisons between archived and new imagery. But the need for data continuity hasn’t kept the program from evolving. In fact, users will be pleased with an innovative, new data distribution policy to be implemented by the USGS in the Landsat 8 era.
As the agency with the sole responsibility for collecting, archiving, processing, and disseminating all Landsat data, the USGS plans to make orthorectified Landsat 8 image products available at no cost to users worldwide via the Internet. USGS has already begun testing this no-fee distribution policy and web-based delivery with some Landsat 7 data. Users are invited to visit the pilot website at http://landsat.usgs.gov to try out the new delivery mechanism. [Click on “Landsat website” button.]

The Value of Landsat
The United States launched seven Landsat satellites between 1972 and 1999. All except Landsat 6, which failed at launch, met or exceeded their design lives.
Launched in 1984, Landsat 5 has continued to collect high-quality imagery for more than 23 years, but recent equipment anomalies have resulted in occasional interruptions in imaging operations. Landsat 7 launched in April 1999 and functioned extremely well until May 2003 when a failure of its Scan Line Corrector resulted in a 24 percent data loss along the outer edges of each of its images, adding a sense of urgency to LDCM development.
Multispectral imaging capabilities have long been the centerpiece of the Landsat program. These satellites carry sensors capable of detecting reflected and emitted electromagnetic radiation in multiple discrete wavelengths of the visible and infrared spectrum. By combining these bands into color images, users are able to identify and differentiate even the most subtle difference in the characteristics and conditions of land cover features, whether natural or anthropogenic.
The modern applications of Landsat imagery have expanded into thousands of research fields and commercial industries. In the United States and around the world, Landsat data are now a tool routinely applied in agricultural forecasting, energy exploration, ecosystem monitoring, natural resource management, land use/land cover mapping, military intelligence gathering, and disaster mitigation.
The universal value of the Landsat program may have been best articulated by Gilberto Camara, Director of Brazil’s National Institute for Space Research, during a 2006 speech in Washington, D.C. He said, “Landsat is seen by the rest of the world as the most important contribution of the United States to the world.”
Possibly the most significant application of multispectral Landsat imagery is the detection and tracking of changes on the Earth’s surface. By digitally combining two or more images collected over the same ground area at different times and applying computerized change detection algorithms, users can pinpoint change to measure its extent and rate over time. [See pairs of images illustrating this article.]
“Landsat imagery is well-suited to detecting land changes associated with human activities,” said Dr. Thomas R. Loveland, Landsat Science Team Leader, USGS Earth Resources Observation and Science (EROS) Center. “Both new and archived Landsat imagery lend critical support to researchers and governments in their attempts to accurately assess the impacts and consequences that human activities and climate change are inflicting on land, snow, and ice surfaces worldwide.”

What’s New, What’s the Same
Landsats 4 and 5 carried imaging sensors called the Thematic Mapper (TM), which collected seven bands of multispectral data: three visible (red, green, blue), three infrared, and one thermal infrared. All were acquired with 30-meter spatial resolution, except for the thermal infrareds, which was 120 meters. For Landsat 7, an upgraded sensor called the Enhanced Thematic Mapper Plus (ETM+) was developed with spatial and spectral capabilities nearly identical to the TM. The additions were a new panchromatic band at 15-meter resolution and a sharper 60-meter resolution in the thermal band.
To ensure data continuity for monitoring global land change, the Landsat 8 Operational Land Imager (OLI) will be very similar to the ETM+. The OLI’s six reflective visible and near infrared bands will cover the same wavelengths at 30-meter resolution. At this writing, inclusion of a thermal band is still being negotiated. The OLI will, however, have two additional bands, referred to as the Coastal Aerosol and Cirrus Cloud bands. The aerosol band is expected to improve imaging of sediment content in shallow coastal waters, while the cirrus band will detect clouds, facilitating automated cloud-cover assessment of the imagery.
The OLI will include several other noteworthy enhancements that will directly benefit data users. For example, the dynamic range of the data will be 12-bit instead of 8-bit, providing an improved ability to map mountains, deserts, and polar regions where features can be lost in shadows or obliterated by bright reflections. In addition, the Landsat 8 satellite will carry a larger onboard recorder that will enable it to regularly collect up to 400 scenes worldwide per day.
In terms of orbital characteristics, Landsat 8 will be identical to Landsat 4, 5 and 7. It will orbit at an altitude of 705 kilometers with a mid-morning equatorial crossing, 185-kilometer-wide imaging swath, and 16-day revisit cycle. These parameters will ensure that image scenes collected by Landsat 8 will align precisely with those of its three immediate predecessors. As has been the case with Landsats 5 and 7, USGS will operate the satellite and process and distribute all Landsat 8 products from EROS in Sioux Falls, South Dakota.

Looking Beyond Landsat 8
In addition to LDCM finally going into development, the long-term outlook for the Landsat program has never been better. Despite its unequaled record of success and utility, Landsat program management and operations have historically bounced among agencies, often casting its future in doubt. But those uncertainties may have come to an end in August 2007 when the White House released its plan for a National Land Imaging Program (NLIP).
“The importance of [Landsat] imagery to the Nation requires a more sustainable effort to ensure that land imaging data are available far into the future,” said Dr. John H. Marburger, Science Advisor to the President and Director of the Office of Science and Technology Policy (OSTP).
Developed by the Future of Land Imaging Interagency Working Group under the OSTP’s direction, NLIP plans call, for the first time, for one organization—the Department of the Interior—to take responsibility for the funding, development, launch, and operation of future land remote-sensing satellites beyond Landsat 8. NLIP, which will incorporate the requirements of U.S. federal, state, and local data users, will develop the framework for the United States to establish a stable space-based imaging capability that will provide a steady stream of civilian Earth observation data for many years to come.