Mission Requirements
The science team has worked with the NISAR project team, ISRO and NASA to develop a set of achievable science requirements. The Level 1 Science Requirements define the specific science measurements that NISAR must perform to satisfy NASA's and most of ISRO's science goals. In addition to these joint requirements, ISRO has identified a number of additional Level 1 science requirements that are to be satisfied by the L-band radar instrument. These requirements then flow down to lower-level science and mission requirements that define the scope of the mission development and operations.
Baseline Requirements
The Baseline Level 1 Science requirements define the capabilities that NISAR is designed to achieve on orbit.
Joint NASA-ISRO Requirements
For a minimum of 3 years, with accuracy specified as 1-sigma:
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The NISAR mission shall measure at least two components of the point-to-point vector displacements with a sampling interval of 12 days or shorter over at least 80% of 12-day or shorter intervals , and a maximum time gap in sampling of 60 days, over specified regions of Earth’s land surface. Accuracy shall be 3.5 (1+L1/2) millimeters or better, over length scales greater than 0.1 kilometer and less than 50 kilometers, with resolution of 100 meters, over at least 70% of the specified regions. (These include all land areas predicted to have relative velocities faster than 1 millimeter per year over 50 kilometers; Earth's known volcanoes above sea level; areas of rapid glacial mass changes; representative aquifers, hydrocarbon and geothermal reservoirs, CO2 sequestration sites, and landslide-prone areas; and the sites of earthquakes and other disasters.)
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The NISAR mission shall measure time-varying displacements over 90% or more of Earth's ice-covered surfaces with an average sampling capability of 6 days or shorter at a scale of 100 meters; displacement accuracy shall be 100 mm or better over at least 70% of 12-day or shorter intervals.
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The NISAR mission shall measure both Arctic and Antarctic sea ice velocities on a 5 km grid with an average sampling capability of three days; velocity accuracy shall be 100 m/day or better over at least 70% of the sea ice area.
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The NISAR mission shall measure above-ground woody vegetation and its disturbance and recovery globally at the hectare scale; accuracy shall be 20 metric tons (Mg) per hectare (ha) or better for areas of woody biomass less than 100 Mg/ha over at least 80% of these areas.
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The NISAR mission shall measure seasonally global cropland and inundated areas; classification accuracy shall be 80% or better at the scale of 1 ha.
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In support of response to major natural or anthropogenic disasters, the mission system shall be capable of providing revised scheduling for new acquisitions within 24 hours of an event or an event forecast notification and delivering data within 5 hours of being collected, and shall exercise this capability on a best efforts basis.
Additional ISRO Requirements
The NISAR mission shall collect the L-band SAR data to support the following ISRO baseline science goals.
During science operations, with accuracy specified as 1-sigma:
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The NISAR mission will measure coastal wind velocity on a 1 km grid with an average sampling capability of 6 days, with an accuracy goal of 2 m/s over at least 80% of oceans within 200 km of India's coast.
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The NISAR mission will measure bathymetry every six months on a 100 m grid from India’s coast to an offshore distance where the depth of the ocean is 20 m or less, with an accuracy goal of 20 cm over at least 80% of the coverage area.
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The NISAR mission will measure the position of India’s coastal shorelines at 10 m resolution at an average sampling interval of 12 days, with an accuracy goal of 5 m over 80% of India’s shorelines.
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The NISAR mission will image geological features over selected regions of India at 10 m resolution at an average sampling interval of 90 days with at least two viewing geometries. The regions include paleochannels in Rajasthan, linear features, and structural studies in the Himalayas and on the Deccan plateau.
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The NISAR mission will observe sea ice characteristics over the seas surrounding India’s Arctic and Antarctic polar stations at 10 m resolution at an average sampling interval of 12 days.
Threshold Requirements
The Threshold Level 1 Science Requirements define the minimum capability NISAR must be able to achieve on orbit.
Joint NASA-ISRO Requirements
For a minimum of two years, with accuracy specified as 1-sigma:
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The NISAR mission shall measure at least two components of the point-to-point vector displacements with a sampling interval of 18 days or shorter over at least 80% of 18-day or shorter intervals, and a maximum gap in temporal sampling of 60 days, over specified high-priority regions of Earth’s land surface. Accuracy shall be 3.5 (1.5 + L1/2) millimeters or better, over length scales greater than 0.1 kilometer and less than 50 kilometers, with resolution of 100 meters, over at least 70% of the specified regions. High-priority regions include seismically active zones with relative velocities greater than 2 mm/yr. over 50 km and a limited selection of high-priority aquifers, reservoirs and landslides.
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The NISAR mission shall measure time-varying displacements over high-priority ice-covered surfaces with an average sampling capability of 9 days or shorter at 100-m scale; displacement accuracy shall be 100 mm or better over at least 70% of 18-day or shorter intervals. High-priority surfaces include all coastal ice sheets and tidewater glaciers.
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The NISAR mission shall measure sea ice velocities on a 5 km grid in the western Arctic (0 to 180 degrees west extending from land to the North Pole); velocity accuracy shall be 100 m/day or better over 50% or greater of these sea ice areas.
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The NISAR mission shall measure the areal extent of disturbance and recovery in above-ground biomass around the globe at the hectare scale annually; classification accuracy shall be 80% or better for changes greater than 50% in woody canopy cover.
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The NISAR mission shall measure seasonally global cropland and inundated areas; classification accuracy shall be 80% or better at the hectare scale.
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In support of responses to major natural or anthropogenic disasters, the mission system shall be capable of providing revised scheduling for new acquisitions within 36 hours of an event or an event forecast notification and delivering data within 9 hours of being collected, and shall exercise this capability on a best efforts basis.