The NASA-ISRO Synthetic Aperture Radar (SAR), or NISAR Mission is a multi-disciplinary radar mission to make integrated measurements to understand the causes and consequences of land surface changes. NISAR will make global measurements of the causes and consequences of land surface changes for integration into Earth system models. NISAR provides a means of disentangling and clarifying spatially and temporally complex phenomena, ranging from ecosystem disturbances, to ice sheet collapse and natural hazards including earthquakes, tsunamis, volcanoes and landslides. The purpose of this handbook is to prepare scientists and algorithm developers for NISAR by providing a basic description of the mission and its data characteristics that will allow them to take full advantage of this comprehensive data set when it becomes available.
NISAR is a joint partnership between the National Aeronautics and Space Administration (NASA) and the Indian Space Research Organization (ISRO). Since the 2007 National Academy of Science “Decadal Survey” report, “Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond,” NASA has been studying concepts for a Synthetic Aperture Radar mission to determine Earth change in three disciplines: ecosystems (vegetation and the carbon cycle), deformation (solid earth studies), and cryospheric sciences (primarily as related to climatic drivers and effects on sea level). In the course of these studies, a partnership with ISRO developed, which led to a joint space-borne mission with both L-band and S-band SAR systems onboard. The current 2018 Decadal Survey, “Thriving on Our Changing Planet: A Decadal Strategy for Earth Observation from Space”, confirms the importance of NISAR and encourages the international partnership between NASA and ISRO.
The Earth Science Division (ESD) within the Science Mission Directorate (SMD) at NASA Headquarters has directed the Jet Propulsion Laboratory (JPL) to manage the United States component of the NISAR project. ESD has assigned the Earth Science Mission Program Office (ESMPO), located at Goddard Space Flight Center (GSFC), the responsibility for overall program management. The NISAR mission is derived from the Deformation, Ecosystem Structure and Dynamics of Ice (DESDynI) Radar Mission concept, which was one of the four Tier 1 missions recommended in the 2007 Decadal Survey. To satisfy requirements of three distinct scientific communities with global perspectives, as well as address the potentials of the system for new applications, the NISAR system comprises a dual frequency, fully polarimetric radar, with an imaging swath greater than 240 km.
This design permits complete global coverage in a 12-day exact repeat to generate interferometric time-series and perform systematic global mapping of the changing surface of the Earth. The recommended Lidar component of DESDynI will be accomplished with the GEDI mission (Global Ecosystem Dynamics Investigation Lidar). NISAR’s launch is planned for December 2021. After a 90-day commissioning period, the mission will conduct a minimum of three full years of science operations with the L-band SAR in a near-polar, dawn-dusk, frozen, sun-synchronous orbit to satisfy NASA’s requirements; ISRO requires five years of operations with the S-band SAR. If the system does not use its fuel reserved excess capacity during the nominal mission, it is possible to extend mission operations further for either instrument.
NISAR’s science objectives are based on priorities identified in the 2007 Decadal Survey and rearticulated in the 2010 report on NASA’s Climate-Centric Architecture. NISAR will be the first NASA radar mission to systematically and globally study solid Earth, ice masses, and ecosystems. NISAR will measure ice mass and the land surface motions and changes, ecosystem disturbances, and biomass, elucidating underlying processes and improving fundamental scientific understanding. The measurements will improve forecasts and assessment of changing ecosystems, response of ice sheets, and natural hazards. NASA also supports use of the NISAR data for a broad range of applications that benefit society, including response to disasters around the world. In addition to the original NASA objectives, ISRO has identified a range of applications of particular relevance to India that the mission will address, including monitoring of agricultural biomass over India, monitoring and assessing disasters to which India responds, studying snow and glaciers in the Himalayas, and studying Indian coastal and near-shore oceans. All NISAR science data (L- and S-band) will be freely available and open to the public, consistent with the long-standing NASA Earth Science open data policy. With its global acquisition strategy, cloud-penetrating capability, high spatial resolution, and 12-day repeat pattern, NISAR will provide a reliable, spatially dense time-series of radar data that will be a unique resource for exploring Earth change.
Anticipated scientific results over the course of the mission include:
• Comprehensive assessment of motion along plate boundaries that are on land, identifying areas of increasing strain, and capturing signatures of several hundred earthquakes that will contribute to our understanding of fault systems; NISAR will image Earth’s dynamic surface over time. NISAR will provide information on changes in ice sheets and glaciers, the evolution of natural and managed ecosystems, earthquake and volcano deformation, subsidence from groundwater and oil pumping, and the human impact of these and other phenomena:
• Comprehensive inventories of global volcanoes, their state of activity and associated risks;
• Comprehensive biomass assessment in low biomass areas where dynamics are greatest, and global disturbance assessments, agricultural change, and wetlands dynamics, informing carbon flux models at the most critical spatial and temporal scales;
• In combination with GEDI and other missions, comprehensive global biomass to set the decadal boundary conditions for carbon flux models;
• Complete assessments of the velocity state of Greenland’s and Antarctica’s ice sheets, each month over the mission life, as a key boundary condition for ice sheet models;
• Regular monitoring of the world’s most dynamic mountain glaciers;
• Comprehensive mapping of sea ice motion and deformation, improving our understanding of ocean-atmosphere interaction at the poles;
• A rich data set for exploring a broad range of applications that benefit from fast, reliable, and regular sampling of virtually any areas of interest on land or ice. These include infrastructure monitoring, agriculture and forestry, disaster response, aquifer utilization, and ship navigability.
Earth’s land and ice surface is constantly changing and interacting with its interior, oceans and atmosphere. In response to interior forces, plate tectonics deform the surface, causing earthquakes, volcanoes, mountain building and erosion. These events shaping the Earth’s surface can be violent and damaging. Human and natural forces are rapidly modifying the global distribution and structure of terrestrial ecosystems on which life depends, causing steep reductions in species diversity, endangering sustainability, altering the global carbon cycle and affecting climate. Changes in ice sheets, sea ice, and glaciers are key indicators of these climate effects and are undergoing dramatic changes. Increasing melt rates of land-fast ice contribute to sea-level rise.
NISAR addresses the needs of Solid Earth, Ecosystems, and Cryospheric science disciplines, and provides data for many applications. NISAR is an all-weather, global geodetic and polarimetric radar-imaging mission with the following key scientific objectives:
1. Determine the likelihood of earthquakes, volcanic eruptions, landslides and land subsidence.
2. Understand the dynamics of carbon storage and uptake in wooded, agricultural, wetland, and permafrost systems.
3. Understand the response of ice sheets to climate change, the interaction of sea ice and climate, and impacts on sea level rise worldwide.
Applications key objectives are to:
1. Understand dynamics of water, hydrocarbon, and sequestered CO2 reservoirs, which impact societies;
2. Provide agricultural monitoring capability to support sufficient food security objectives;
3. Apply NISAR’s unique data set to hazard identification and mitigation;
4. Providing information to support disaster response and recovery.
5. Provide observations of relative sea level rise from melting land ice and land subsidence.
NISAR will provide systematic global measurements to characterize processes, frequent measurements to understand temporal changes, and a minimum three-year duration to estimate long-term trends and determine subtle rates and rate changes. NISAR will serve the objectives of a number of major science disciplines and will meet the needs of a broad science community with numerous applications, including earthquakes, volcanoes, landslides, ice sheets, sea ice, snow and glaciers, coastal processes, ocean and land parameter retrieval, and ecosystems.
In addition, NISAR will play a role in monitoring and assessment of natural disasters such as floods, forest fires and earthquakes. NISAR will provide systematic global measurements to characterize processes, frequent measurements to understand temporal changes, and a minimum three-year duration to estimate long-term trends and determine subtle rates and rate changes. NISAR will serve the objectives of a number of major science disciplines and will meet the needs of a broad end-user community with numerous applications, including assessing geologic and anthropogenic hazards, monitoring critical infrastructure for risk management, supporting agriculture and forestry agencies, identifying pollution in coastal waters, and evaluating ground surface changes associated with fluid extraction, e.g., groundwater withdrawal during droughts or elevation changes associated with oil or gas production. In addition, NISAR will play a role in response to and recovery from natural disasters such as floods, forest fires and earthquakes.
NISAR observations will address several science and applications area that the 2018 Decadal survey recommends progress in:
• Determining the extent to which the shrinking of glaciers and ice sheets, and their contributions to sea-level rise is accelerating, decelerating or remaining unchanged;
• Quantifying trends in water stored on land (e.g., in aquifers) and the implications for issues such as water availability for human consumption and irrigation;
• Understanding alterations to surface characteristics and landscapes (e.g., snow cover, snow melt, landslides, earthquakes, eruptions, urbanization, land-cover and land use) and the implications for applications, such as risk management and resource management;
• Assessing the evolving characteristics and health of terrestrial vegetation and aquatic ecosystems, which is important for understanding key consequences such as crop yields, carbon uptake and biodiversity; and
• Examining movement of land and ice surfaces to determine, in the case of ice, the likelihood of rapid ice loss and significantly accelerated rates of sea-level rise, and in the case of land, changes in strain rates that impact and provide critical insights into earthquakes, volcanic eruptions, landslides and tectonic plate deformation.
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