NASA-ISRO: SAR (NISAR) Satellite

NASA-ISRO: NASA and ISRO are developing the Low Earth Orbit (LEO) observatory NASA-ISRO SAR (NISAR). NISAR will provide spatially and temporally consistent data for comprehending changes in Earth’s ecosystems, ice mass, vegetation biomass, sea level rise, ground water, and natural hazards such as earthquakes, tsunamis, and volcanoes. The NISAR. It contains L and S dual band Synthetic Aperture Radar (SAR), which employs the Sweep SAR technique to acquire data with a wide swath and high resolution. Together, the SAR payloads installed on Integrated Radar Instrument Structure (IRIS) and the spacecraft bus constitute an observatory. Jet Propulsion Laboratories and ISRO are constructing an observatory that will not only meet their respective national requirements, but will also provide the scientific community with data that will facilitate surface deformation measurement studies using the repeat-pass InSAR method.

Both agencies would contribute significantly to this flagship partnership. NASA is responsible for providing the L-Band SAR payload system, while ISRO is responsible for providing the S-Band SAR payload. Both SAR systems will utilize a large (approximately 12m in diameter) unfurlable reflector antenna. NASA would also provide engineering payloads, such as a Payload Data Subsystem, High-rate Science Downlink System, GPS receivers, and a Solid State Recorder.

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NASA-ISRO: This would be the first dual frequency radar imaging mission in L-Band & S-Band utilizing an advanced Sweep SAR technique to provide L & S band space-borne SAR data with a high repeat cycle, high resolution, and larger swath, as well as the capability of full-polar metric and interferometric modes of operation. It will provide a way to disentangle and elucidate spatially and temporally complex phenomena, such as ecosystem disturbances, ice sheet collapse, and natural hazards such as earthquakes, tsunamis, and landslides. This is anticipated to stimulate the rapid development of microwave remote sensing applications in geosciences. The mission’s precise interferometric orbits will enable the measurement of land surface deformations of a few millimeters or less. The selection of lower frequency bands will accommodate the requirement for improved vegetation characterization, which is essential for global carbon stock estimation and the monitoring of carbon fluxes from vegetation. Similarly, the selection of L- and S-band frequencies will permit the characterization of sub-canopy and sub-surface targets due to differential signal penetration in the two frequency bands. NISAR investigating concepts for a Synthetic Aperture Radar mission is to determine Earth change in three disciplines: ecosystems (vegetation and the carbon cycle), deformation (study of solid Earth), and cryosphere sciences (primarily as related to climate drivers and sea level effects). NISAR will collect data over the Indian Coasts and track annual bathymetric changes along deltaic regions. Additionally, the shoreline and erosion accumulation will be monitored. The NISAR mission will observe sea ice characteristics encircling India’s Antarctic polar stations, which can be used to detect marine oil spills and disseminate spill locations during accidental oil seepage for preventative purposes.

The NISAR observatory is equipped with a 12 m wide deployable mesh reflector suspended on a 9 m deployable boom that was developed by JPL for use by both-ISRO developed the S-Band SAR payload system, while JPL-NASA developed the L-Band SAR payload system. The S-SAR and L-SAR modules, as well as their electronic and data processing systems, are housed within the IRIS. The spacecraft incorporates all elements of attitude and orbit control, as well as power and thermal management systems. JPL will also supply the LSAR Data Handling system, the High-rate Science data Downlink System, GPS receivers, and a Solid State Recorder. ISRO is in charge of providing the SSAR data management system, High rate downlink system, spacecraft bus systems, GSLV launch system, and Mission Operations Related Services. NISAR is a combination of two cultures and the work of two groups of artisans.

NASA-ISRO: As shown below, NISAR is being developed in three distinct phases. During the SIT-2 phase, the SAR payloads and Engineering Systems will be developed independently in their respective soils. During the SIT-3 phase, the SAR payload and other associated systems will be integrated with the Radar Instrument Structure and tested at JPL. ISRO is responsible for both the development and testing of spacecraft systems concurrently. ISRO is responsible for the ensuing activities of integrating IRIS with the spacecraft and evaluating it as an observatory. This phase is referred to as SIT-4 and is currently ongoing. The IRIS is available for shipment from the Jet Propulsion Laboratory, and a spacecraft is preparing to receive its counterpart. As a performance evaluation of the entire observatory is scheduled to occur during the SIT-4 testing phase, this phase will be extremely complex and crucial. The NISAR observatory will be launched from Indian soil in the first quarter of 2024, and the scientific community will undoubtedly profit from the resulting data.

Stage Of The Mission

Initiation Phase

NASA-ISRO: The NISAR Observatory will be launched by the ISRO-provided GSLV expendable launch vehicle from the Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota, on the southeast coast of the Indian peninsula. The anticipated date of launch readiness is January 2024. The launch sequence begins when the observatory is on the ground, encased in the launch vehicle fairing, and continues until solar array deployment is complete, the observatory is in an Earth-facing orientation, and it is in two-way communication with the ground. The sequence of launch is a crucial occasion.

The Commissioning Stage

The first ninety days after launch will be devoted to commissioning, also known as in-orbit inspection (IOC), which will prepare the observatory for science operations. Initial checkout (ISRO engineering systems and JPL engineering payload checkout), spacecraft checkout, and instrument checkout are sub-phases of commissioning. Philosophically, the sub-phases are designed as a gradual increase in observatory capability, beginning with the physical deployment of all deployable parts (including the boom and radar antenna, but not the solar arrays, which are deployed during the launch phase), checking out the engineering systems, turning on the radars and testing them independently, and then conducting joint tests with both radars operating.

Phase of Science Operations

NASA-ISRO: The science operations phase commences at the conclusion of commissioning, lasts for three years, and entails the collection of all data necessary to achieve the L1 science objectives. During this phase, the science orbit will be maintained through routine maneuvers that are timed to prevent or minimize interference with science observations. Throughout the first five months, extensive calibration and validation (CalVal) activities will be conducted, with annual updates lasting one month. The observation plan for both L- and S-band instruments, as well as engineering activities (maneuvers, parameter adjustments, etc.), will be generated prior to launch through frequent coordination between JPL and ISRO. This plan is referred to as the reference mission, while the science observations within the reference mission are referred to as the reference observation plan (ROP). Multiple inputs, including L- and S-band target maps, radar mode tables, and spacecraft and ground-station constraints and capabilities, will determine the schedule of scientific observations. This schedule will be determined by the mission planning team at JPL, and the project will make every effort to fly the reference mission, which includes these scientific observations, precisely as planned prior to launch (with small timing adjustments based on the actual orbit).