NASA-ISRO SAR Mission (NISAR)
NISAR Mission is a partnership mission between NASA & ISRO. The objective is to studying hazards and global environmental change.
The National Aeronautics and Space Administration (NASA) has been studying concepts for a Synthetic Aperture Radar (SAR) mission to determine Earth change in three disciplines
- Solid earth, and
- Cryospheric sciences.
In the course of these studies, a partnership with the Indian Space Research Organisation (ISRO) developed that has led to a joint mission with L-band and S-band SAR systems on board.
NISAR Mission Objective
- The NASA-ISRO Synthetic Aperture Radar, or NISAR, satellite is designed to observe and take measurements of some of the planet’s most complex processes, including ecosystem disturbances, ice-sheet collapse, and natural hazards such as earthquakes, tsunamis, volcanoes and landslides.
- Data collected from NISAR will reveal information about the evolution and state of Earth’s crust, help scientists better understand our planet’s processes and changing climate, and aid future resource and hazard management.
- Design, Develop and launch a Dual frequency (L and S Band) Radar Imaging Satellite.
- Explore newer application areas using L and S band microwave data, especially in natural resources mapping & monitoring
- Estimating agricultural biomass over full duration of crop cycle
- Assessing soil moisture
- Monitoring of floods and oil slicks
- Coastal erosion, coastline changes and variation of winds in coastal waters
- Assessment of mangroves
- Surface deformation studies due to seismic activities etc
Technology in NISAR Mission
Synthetic Aperture Radar (SAR)
It refers to a technique for producing fine resolution images from an intrinsically resolution-limited radar system. If we are in space observing the Earth 1000 km below, the beam size on the ground is then 1000 λ/D = 10 km. This intrinsic resolution of the radar system is insufficient for many applications and practical solutions for improving the resolution needed to be found.
A radar antenna can be designed to transmit and receive electromagnetic waves with a well-defined polarization, which is defined as the orientation of the electric field vector in the plane orthogonal to the wave propagation direction. By varying the polarization of the transmitted signal, SAR systems can provide information on the polarimetric properties of the observed surface.
Each resolution element encodes the phase related to the propagation distance from the radar to the ground as well as the intrinsic phase of the backscattering process. The resolution element comprises an arrangement of scatterers – trees, buildings, people, etc. – that is spatially random from element to element, and leads to a spatially random pattern of backscatter phase in an image.