NASA-ISRO SAR (NISAR): Low Earth Orbit (LEO) Observatory


A Low Earth Orbit (LEO) observatory being collaboratively constructed by NASA and ISRO is called NASA-ISRO SAR (NISAR). To comprehend changes in Earth's ecosystems, ice mass, vegetation biomass, sea level rise, ground water, and natural hazards including earthquakes, tsunamis, volcanoes, and landslides, NISAR will map the entire planet in 12 days. It will also give geographically and temporally consistent data. NISAR. It is equipped with L and S dual band Synthetic Aperture Radar (SAR), which uses the sweep SAR technique to produce high resolution data over a wide swath. An observatory is the collective name for the SAR payloads mounted on the Integrated Radar Instrument Structure (IRIS) and the spacecraft bus. In addition to fulfilling their respective national requirements, Jet Propulsion Laboratories and ISRO are building an observatory that will provide the scientific community with data that will support studies relating to surface deformation measurements made using the repeat-pass InSAR technique.

Flagship Partnership

Both organisations would make significant contributions to this flagship relationship. The L-Band SAR payload system will be supplied by NASA, while the S-Band SAR payload will be provided by ISRO. Both of these SAR systems will use a large size (about 12m in diameter) common unfurl able reflector antenna. NASA would also supply engineering payloads for the project, including as a Solid State Recorder, GPS receivers, Payload Data Subsystem, and High-rate Science Downlink System.

In order to deliver L & S band space-borne SAR data with high repeat cycle, high resolution, and broader swath, as well as the capacity of full-polar metric and interferometric modes of operation, this mission would be the first dual frequency radar imaging mission in L & S band. It will give a way to unravel and make sense of spatially and temporally complex occurrences, from ecosystem disruptions to the melting of ice sheets and natural disasters like earthquakes, tsunamis, volcanoes, and landslides. This is anticipated to give the rapidly developing geosciences applications of microwave remote sensing a boost. The mission's precise interferometric orbits will make it possible to map minor land surface deformations of a few millimetres. The choice of lower frequency bands will meet the demand for improved vegetation classification, which is essential for estimating the global carbon stock and tracking carbon fluxes from vegetation. In a similar vein, the choice of L- and S-band frequencies will allow characterising objects under tree canopy and sub-surface characteristics due to differential penetration of the signals in two frequency bands. The three disciplines of ecosystems (vegetation and the carbon cycle), deformation (studying solid Earth), and cryosphere sciences (mainly in relation to climatic factors and effects on sea level) are being studied by NISAR as concepts for a Synthetic Aperture Radar mission to ascertain Earth change. Data will be collected over the Indian Coasts by NISAR, which will also track yearly variations in bathymetry in the deltaic zones. Additionally, the shoreline and erosion accumulation will be watched. The NISAR project will monitor sea ice features across the waters around India's polar installations in Antarctica. It can be used to locate marine oil spills and discover them early enough to take preventative action.

The JPL-developed deployable 9-meter boom set on a 12-meter wide deployable mesh reflector is carried by the NISAR observatory and will be used by both-Both the L-band and S-band SAR payload systems were designed by JPL-NASA and ISRO, respectively. The S-SAR and L-SAR tiles, as well as their electronic and data handling systems, are housed in the IRIS. The spaceship includes all of the power systems, thermal management systems, and attitude and orbit control components. JPL will also supply GPS receivers, a Solid State Recorder, a High-rate Science data Downlink System, and LSAR Data Handling System. The SSAR data handling system, High rate downlink system, satellite bus systems, GSLV launch system, and Mission Operations Related Services are all provided by ISRO. NISAR is a flawless fusion of two cultures and a product of two teams of artisans.

The three phases of NISAR's development are listed below. During SIT-2, the engineering systems and SAR payloads must be independently developed in their respective soils. The SAR payload and other connected equipment will be integrated with the radar instrument structure during the SIT-3 phase and evaluated at JPL. ISRO is carrying out parallel initiatives for the realisation and testing of spacecraft systems. ISRO is responsible for the ensuing tasks of integrating IRIS with the spacecraft and evaluating it as an observatory. This is the SIT-4 phase, which is currently in progress. JPL is preparing to ship the IRIS, while the spacecraft is preparing to receive its counterpart. The SIT-4 testing phase will be particularly detailed and crucial, as the entire observatory's performance will be evaluated during this phase. The NISAR observatory will be launched from Indian soil in the first quarter of 2024, and the data gathered will undoubtedly assist the scientific community.

Officials from NASA


On the GSLV expendable launch vehicle provided by ISRO, the NISAR Observatory will be launched from Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota on the southeast coast of the Indian peninsula. The launch is anticipated to be ready in January 2024. The launch sequence starts with the observatory on the ground, enclosed in the launch vehicle fairing, and ends with the solar arrays fully deployed, the observatory in an Earth-pointing attitude, and the observatory in two-way communication with the ground. A crucial event is the launch sequence.


Commissioning, also known as in-orbit checkout (IOC), will take place within the first 90 days following launch with the aim of getting the observatory ready for scientific operations. Initial checkout (ISRO engineering systems and JPL engineering payload checkout), spacecraft checkout, and instrument checkout are the three sub-phases of commissioning. The sub-phases are conceptualised as a gradual increase in capability leading up to full observatory operations, starting with the physical deployment of all deployable parts (particularly the boom and radar antenna, but excluding the solar arrays, which are deployed during launch phase), checking the engineering systems, turning on the radars and testing them separately, and finally conducting joint tests with both radars operational.


The three-year science operations phase, which starts after commissioning, includes all data gathering necessary to meet the L1 science objectives. Regular manoeuvres will be performed during this phase to maintain the science orbit while avoiding or reducing interference with scientific observations. The first five months will be filled with a lot of calibration and validation (CalVal) work, with yearly upgrades lasting one month. Pre-launch engineering operations (such as manoeuvres, parameter changes, etc.) and the observation plan for both L- and S-band sensors will be generated through frequent cooperation between JPL and ISRO. The science observations made solely as part of this plan are referred to as the reference observation plan (ROP), which is also known as the reference mission. A number of factors, such as L- and S-band target maps, radar mode tables, spacecraft and ground-station limits and capabilities, will influence the timetable of science observations. The project will try to fly the reference mission, which includes these science observations exactly as planned prior to launch (accommodating for modest temporal adjustments based on the actual orbit), according to this schedule, which will be decided by JPL's mission planning team.

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