Beginning with the 1972 NASA launch of the Earth Resources Technology Satellite (ERTS), later renamed Landsat 1, and continuing with the February 2013 launch of Landsat 8, the United States has amassed a sustained 40-year record of land remote sensing data acquired by satellites. Despite the transformational value of the data for diverse applications—including agriculture, forestry, hydrology, urbanization, homeland security, disaster mitigation, and climate change—the availability of these critical data for planning our nation’s future is at risk.1
The Department of the Interior’s (DOI’s) U.S. Geological Survey (USGS) tasked the National Research Council’s (NRC’s) Committee on Implementation of a Sustained Land Imaging Program to assess the needs and opportunities to develop a national space-based operational land imaging capability. The committee was asked to identify stakeholders and their data needs, recommend characteristics and critical program support areas expected of a sustained land imaging program, suggest critical baseline products and services derived from land imaging, and provide recommendations to facilitate the transition from NASA’s research-based series of satellites to a sustained USGS land imaging program.2
The committee met with stakeholders, including the DOI, NASA, the Office of Science and Technology Policy, the National Oceanic and Atmospheric Administration, the U.S Department of Agriculture, the U.S. Forest Service, commercial data providers, and multiple land imaging data users, and analyzed earlier reports on the uses and value of moderate-resolution multispectral data.
In this report, the committee recommends that a systematic and deliberate program, aimed at continuing to collect vital data within lower, well-defined, manageable budgets, replace the historical pattern of chaotic programmatic support and ad hoc design and implementation of spacecraft and sensors in the Landsat series. The committee concurred with former NASA Administrator James Fletcher’s perspective and provided recommendations for the robust land imaging program he envisioned, albeit nearly 40 years later:
If I had to pick one spacecraft, one Space Age development to save the world I would pick ERTS and the satellites which I believe will be evolved from it later in this decade.
James C. Fletcher, NASA Administrator, 1975
1 Benefits of land imaging to the United States are discussed in Chapter 1 in the section “Benefits of Land Imaging for the Nation.”
2 See Appendix A for the complete statement of task.
IMPERATIVE FOR A SUSTAINED AND ENHANCED LAND IMAGING PROGRAM
Landsat 8, launched on February 11, 2013, has a 5-year design life, 10 years of fuel, and no assured successor. A successor mission has been under discussion in the U.S. executive and congressional branches, but their deliberations have not yet been made public. Moreover, the potential sharing of responsibilities with commercial and foreign contributors has not been articulated. The cost for Landsat 8 runs to approximately $1 billion. Although a budget to start planning the next Landsat mission has been provided to NASA in the fiscal year 2014 budget request, replacing Landsat 8 with a mission of similar scope will not be possible within the currently planned budget, unless it is a mission with a reduced set of requirements. Several of the Landsat satellites have been justified, planned, and executed separately, and the 40-year record owes more to the remarkable survival of Landsat 5 for two decades beyond its design life than to careful planning.3 Given this history and uncertainties about the future of the Landsat series of satellites, the committee, as a result of its activities over the course of the study, arrived at the following findings:
• The United States pioneered global, synoptic, frequent-repeat global imaging. Other nations are now developing systems whose capability rivals or exceeds that of U.S. systems. National needs require the United States to reassert leadership and maintain and expand capabilities.
• Space-based land imaging is essential to U.S. national security as it is a critical resource for ensuring our food, energy, health, environmental, and economic interests.
• The economic and scientific benefits to the United States of Landsat imagery far exceed the investment in the system.
• To best serve the needs of the United States, the land imaging program of the future requires an overarching national strategy and long-term commitment, including clearly defined program requirements, management responsibilities, and funding.
• The continuity of Landsat imagery has never been ensured through the development of a sustained government program. Instead, responsibility has been shifted from one organization to another over Landsat’s 40-year history, resulting in persistent uncertainty for the future of this important asset.
• NASA has demonstrated that it is the civil agency with the technical capacity and the congressional support to design and build civilian space missions.
• The USGS-operated data management and distribution systems function effectively and efficiently.
• Building a satellite sequence with new requirements and technologies for each individual instrument is an expensive way to acquire land imaging data and inhibits the addition of new capabilities.
• A sustained land imaging program will not be viable under the current mission development and management practices.
The committee’s primary recommendation is that the U.S. government should establish a Sustained and Enhanced Land Imaging Program with persistent funding to respond to current and future national needs. Such a program would
• Develop a plan for a comprehensive, integrated program that capitalizes on the strengths of USGS and NASA, maintains current capability and the existing archive, and enhances the program as technology enables new imaging capabilities and data products;
• Ensure acquisition of land imaging data continuously from orbital platforms and, periodically, from airborne platforms, to respond to the needs of producers and consumers of derived data products along with users who analyze imagery;
• Establish partnerships with commercial firms and international land imaging programs to leverage enhanced capabilities;
• Coordinate land imaging data buys across the U.S. government; and
3 Discussion of the history of the Landsat series of satellites is included in Chapter 1 in the section “A Chaotic History.”
• Include a research and development component to improve data products based on core measurements and to develop new measurement methods and consider evolving requirements.
For the Sustained and Enhanced Land Imaging Program to be successful, program responsibilities should be divided between USGS and NASA such that the agency responsible for balancing science requirements with mission complexity and cost is also provided with the necessary budget. Both agencies should participate in an iterative process to design missions that meet the needs of research and operational communities, but final decisions should be made by the agency that has been given the budget.
The committee recommends key elements of a successful Sustained and Enhanced Land Imaging Program (SELIP) no matter where the federal government decides it should reside.
TECHNICAL CHARACTERISTICS OF THE CORE PROGRAM
SELIP would provide a core set of capabilities and measurements that continue to support operations and scientific investigations and maintain and enhance continuity with the information available since 1972. Landsat has provided an unequaled record of moderate-resolution (30-100 m) multispectral measurements of Earth’s surface, the long-term continuity of which is critical for quantifying ecological, environmental, and land-use change. Preserving program continuity requires a satellite system and launch schedule that provides a continuous stream of land images and data and at the same time implicitly requires strategies to contend with future instrument or launch failures. Risk mitigation strategies could range from instruments ready to launch to securing agreements with international partners for data access. A “hot spare” on orbit or available for quick launch—as weather satellites have been managed historically—is not required.
The core scientific and operational requirement for the SELIP is the capture and distribution of global, moderate-resolution, multispectral data calibrated sufficiently to allow the rigorous comparison of future image products with previous collections, easily accessible by all users, and free. Ensuring continuity of the ongoing data stream does not require continuing to fly the same sensor, nor does it require that all measurements be made from a single space platform. The section “Findings,” in Chapter 2, presents a detailed list of user requirements. These include spatial resolution no coarser than 30 m, except in the thermal band; spectral coverage from the visible through the thermal infrared; and temporal coverage at 7-to 10-day frequency.
The top priorities for the Sustained and Enhanced Land Imaging Program (SELIP) should be to ensure that the core program provides for continuity of Landsat products and coverage on a secure and sustainable path.
The SELIP should take advantage of technological innovation in sensors, spacecraft, and data management and analysis to improve system performance, allow for new analyses that better exploit the data and meet future needs. Because future measurements will derive from both current and new technologies, new implementations of existing data products derived from a multispectral sensor should be cross-calibrateable with Landsat legacy products and be essentially interchangeable for scientific and operational purposes.
To better meet these primary goals, the committee recommends that the program should
• Systematically monitor users and uses of Landsat data so that the program can evolve with changing user requirements and
• Consider alternative implementations that continue to enable the collection of global, moderate-resolution data with the full range of spectral capabilities.
ENHANCING A SUSTAINED LAND IMAGING PROGRAM
Landsat has been the cornerstone of U.S. land imaging, but it has never comprised the totality of that effort. Although the core program of SELIP is a set of measurements and data products that preserve the continuity of
the current record, the program can benefit from, and future users may require, the inclusion of data from other technologies. SELIP could benefit from defining land imaging more broadly, recognizing the increasing contributions from a diverse set of U.S. government, private-sector, and international airborne and spaceborne assets. The value added by increasing the synergistic use of these data is sufficient to consider broadening the scope of SELIP’s data holding, while retaining the focus on Landsat-type measurements to continue the historical legacy. Some incorporation of other types of data requires only better coordination across the government by increased sharing of existing or planned data.
The committee recommends that the Sustained and Enhanced Land Imaging Program integrate measurements from commercial partners, spaceborne sensors recommended by the 2007 NRC report Earth Science and Applications from Space,4and a variety of airborne sensors and acquisitions to enable analyses not possible using only moderate-resolution multispectral data. These measurements should include, but not be restricted to, the following:
• Airborne and spaceborne fine-resolution remote sensing data from public and commercial sources that can be used for detailed land use and land cover, urban infrastructure, transportation, hydrology, and disaster response;
• LiDAR data that can be used to extract precise digital surface and terrain models, building and vegetation height information, and vegetation canopy and its internal structure information;
• Synthetic aperture radar (SAR) and interferometric SAR (InSAR) images at resolutions suitable for studies of deformation, elevations, and surface cover; and
• Hyperspectral data collection and information extraction capabilities for hydrology, ecosystem health and biodiversity, and soil science and mineralogy.
The decision in 2008 to allow Landsat images to be downloaded free of charge greatly expanded the use of Landsat data and set a standard for international cooperation. There are now more downloads in 1 day than there were sales in an entire year when Landsat data were sold. USGS websites effectively provide access to imagery and derived products, with varying degrees of ease of use. Moreover, several commercial companies—for example, the Earth Sciences Resources Institute (ESRI), Google, Microsoft, and Yahoo—also provide high-resolution aerial and spaceborne images, Landsat imagery, and products based on imagery. Although these sites and services offer innovative ways to search for, display, and provide images and derivative products, they lack the comprehensive access to land imaging archives that are best offered to the public from an authoritative federal government source.
USGS, as part of the Sustained and Enhanced Land Imaging Program, should continue to deliver derived products from imagery without explicit cost to the end users.
• Improve search capabilities and transparency to users and
• Continue to interface with the private sector to improve access to public-and private-domain land imaging data products and services.
The Sustained and Enhanced Land Imaging Program should develop a systematic process for identifying and prioritizing a wider suite of products, including essential climate variables, that can be derived from moderate-resolution land imagery, and for documenting and validating algorithms, including their modifications or replacements. In doing so, the program should
4 National Research Council, Earth Science and Applications from Space, National Imperatives for the Next Decade and Beyond, The National Academies Press, Washington, D.C., 2007.
• Define criteria that government-provided authoritative data sets should meet, among them such attributes as calibration, accuracy assessment, and validation, and including ground truth;
• Define criteria for which products should be provided by the government and which by the private sector;
• Implement procedures for development, cost estimation, peer review, and publication of algorithms that produce derived products; and
• Implement plans, procedures, and budgets for ongoing validation.
OPPORTUNITIES ON THE PATH FORWARD
A sustained land imaging program will not be viable with current mission development and management practices. However, following the launch of Landsat 8 on February 11, 2013, there are several options for a sustainable land imaging program of core requirements that also allow for enhanced capabilities and data products. Important opportunities include ensuring stable funding, programmatic improvements, and less cumbersome contracting processes.
The Sustained and Enhanced Land Imaging Program should create an ambitious plan to incorporate opportunities to improve land imaging capabilities while at the same time increasing operational efficiency and reducing overall program cost.
The program should consider a combination of the following to increase capabilities while reducing the costs for land imaging beyond Landsat 8:
• Shift the acquisition paradigm by means of block buys and fixed-price contracting and by collaborating with commercial and international partners;
• Streamline the process by which satellites and sensors are designed, built, and launched, using a single organizational unit approach (a collaborative team approach) consisting of both government employees and contractors working together as a fully integrated team;
• Identify foreign sources of land imaging data that complement the U.S. core land imaging requirements and seek formal data-sharing agreements with them;
• Consider technological innovations, such as increasing the swath width and employing constellations of small satellites;
• Incrementally incorporate new technologies that leverage industry, international, and other technology development activities but do not compromise core operational capabilities;
• Accommodate candidates for improved or new instruments on a small satellite for the purpose of demonstrating new technologies; and
• Take advantage of opportunities to fly as a secondary payload or as a shared ride.
Looking forward, a new, comprehensive, integrated operational approach is needed, one based on a federal commitment to an operational land imaging capability in parallel with the existing operational space-based observation programs for weather forecasting and for study of the atmosphere and oceans. This integrated approach, as recommended, will take into consideration the land-imaging needs of federal and state agencies, academia, and value-added providers and will determine which data are critical to national interests, including national security, food security, natural resource management, and natural hazard risk reduction. An optimized program will look to the future, ensuring readily interoperable data among spaceborne and airborne sensors, some with finer spatial resolution and some with more frequent coverage.
The capabilities of the program can also be enhanced by incorporating other types of data, some already available. Other aspects of an evolving program may be achieved through partnerships or arrangements with other countries and entities that pursue advanced remote sensing technologies.