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Level 1 Science Requirements

The Science Definition Team has worked with the NISAR project, 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.
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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:

  • 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 gap in temporal sampling of 60 days, over specified regions* of Earth’s land surface: accuracy shall be 3.5 (1+L1/2) mm or better, over length scales 0.1 km < L < 50 km, with resolution of 100 meters, over at least 70% of the specified regions.
(Specified regions include all land areas predicted to have relative velocities faster than 1 mm/yr over 50 km; Earth’s known volcanoes above sea-level; areas of rapid glacial mass changes; selected sites, including a representative set of aquifers, hydrocarbon and geothermal reservoirs, CO2 sequestration sites, and landslide-prone areas; and sites where earthquakes and other disaster-related events have occurred. L is defined as the distance between two points in the displacement field, as described in the footnote.)
  • The NISAR mission shall measure time-varying displacements over 90% or more of the Earth's ice-covered surfaces with an average sampling capability of 6 days or shorter at 100-m scale; displacement accuracy shall be 100 mm or better over at least 70% of 12-day or shorter intervals.
  • 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.
  • The NISAR mission shall measure aboveground woody vegetation biomass and its disturbance and recovery globally at the hectare scale; biomass accuracy shall be 20 Mg/ha or better for areas of woody biomass less than 100 Mg/ha over at least 80% of these areas.
  • The NISAR mission shall measure seasonally global cropland and inundated areas; classification accuracy shall be 80% or better at hectare scale.
  • 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:

  • 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 the India’s coast.
  • The NISAR mission will measure bathymetry every six months on a 100 m grid from India’s coast to an off-shore 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.
  • 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.
  • 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. (Selected regions include paleochannels in Rajasthan, lineaments and structural studies in Himalayas and in Deccan plateau.)
  • 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 2 years, with accuracy specified as 1-sigma:

  • 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) mm or better, over length scales 0.1 km < L < 50 km, with resolution of 100 meters, over at least 70% of these specified regions. (High-priority regions shall 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.)
  • 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 areas shall include all coastal ice sheets and tide water glaciers.)
  • The NISAR mission shall measure sea ice velocities on a 5 km grid in the Western Arctic (0 deg. west to 180 deg. 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.
  • The NISAR mission shall measure areal extent of aboveground biomass disturbance and recovery globally at the hectare scale annually; classification accuracy shall be 80% or better for woody canopy cover changes greater than 50%.
  • The NISAR mission shall measure seasonally global cropland and inundated areas; classification accuracy shall be 80% or better at hectare scale.
  • In support of response 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.