What makes the NASA-ISRO NISAR satellite so special? | Explained

The story so far: The Indian Space Research Organization (ISRO) plans to launch the Nisar satellite from Sriharikota in a GSLV MK-II rocket on July 30th. ‘Nisar’ represents NASA-isro synthetic diaphragm radar and is a common task of two space agencies. An earthquakes, volcanoes, ecosystems, ice sheets, agricultural lands, floods and earth shifts, are a sophisticated world observation designed to examine the changes on the surface of the earth in detail.

What is the need for Nisar?

Nisar is the task that observes the first big world with a double -band radar, which will allow him to observe changes more precisely than other satellites. Both day and night will be able to see clouds, smoke and even thick vegetation in all weather conditions. It has been ten years in making three -ton machine and costs more than $ 1.5 billion, which makes it one of the most expensive world of satellites that have ignored the world.

The surface of the world is constantly changing. Natural disasters, human -oriented changes and climate changes affect their environment and human societies. Satellites provide critical information by taking the instant images of these changes from space and helping scientists, governments and charitable organizations to prepare, respond or examine them. For this purpose, NASA and ISRO have created a powerful global task that provides guaranteed access to a high -resolution data flow adapted to the needs of Isro’s needs.

Nisar’s science and application objectives are spread over six areas: Solid soil processes, ecosystems, ice dynamics, coastal and ocean processes, disaster response and additional applications (infrastructure such as groundwater, oil reservoirs and roads for leve or deformation, dams and roads and food safety research).

Although the design life is at least five years, the planned task life is three years. In particular, the data policy of the mission requires that the data produced by NISAR can be freely available for all users (usually) within a few hours.

How does Nisar work?

Once it has been released, Nisar will enter the sun synchronized polar orbit at a height of 747 km and a slope of 98.4º. From here, instead of capturing pictures, Nisar’s synthetic diaphragm radar (SAR) will jump the radar waves from the surface of the planet and measure how much the signal returns and how the phase has changed.

The ability of a radar antenna to solve smaller details increases with its length called openness. In orbit, it is not practical to distribute an antenna of hundreds of meters long. Sar transcends it by imitating a giant antenna. As the spacecraft progresses, the radar impacts transmits the train and records echoes. Later, a computer combines all these echoes consistently as if it were caught simultaneously by a very long antenna, so the “synthetic diaphragm”.

Nisar will combine a S-Bant SAR (3.2 GHz) to capture surface details such as a L-Bantic SAR (1.257 GHz) using RadiWawes to monitor the changes under thick forests and the deformations on the ground and the surface details such as crops and water surfaces.

Although Nisar will operate globally in L -Band, Isro Rutine has separated purchases planned with S -Band Sar via India. Second Purchases Sensitivity to Biomuting, Better Soil – Multiply reduced the transportation and ionospheric noise – all capabilities set according to India’s needs in agriculture, forestry and disaster management.

L Band Radar is the main instrument of NASA’s task targets, the instrument is expected to work in 70% of each orbit. However, it is an official application goal to operate both radar together, thus minimizing mode conflicts on the Indian sub -continent.

Polarization is the direction that the electric field of some electromagnetic radiation, such as RadiWawaves, is released. Sar can transmit and take radar signals with horizontal or vertical polarization. The use of different combinations will allow tools to define the structure and types of different surface materials such as soil, snow, crops or wood.

The width of the shares, that is, the width of the bands in the place where the SAR will scan, is a wide range of 240 km. The Sweepsar design of the radars will transmit this beam, and after the return, it will directly direct more than one small sub -opening in order, and synthesize the beams that sweep the ground path. This scanning method allows 240 km areas without sacrificing resolution.

The resulting scans will have a syllable-scale vertical mapping that is sufficient to detect the approaching land collapse in cities, depending on a 3-10 m spatial resolution and fashion. Each point on the ground will be scanned every 12 days.The satellite also has a large knitted antenna with 12 m wide.

Nisar will produce the annual maps of underground woody biomasses of 1 Ha resolution and three -month active and inactive cultivated lands. High resolution maps of flooded and dry areas will also be available. During a disaster, Nisar can also be directed to collect data for ‘damage proxy maps’ to be delivered under five hours.

This said that Nisar for some acquisition modes cannot achieve full global scope at the highest resolution. Roughly above 60º latitude, every alternative observation will be confused due to the closer floor tracks. Similarly, approximately 10% of the surface may not match in any 12 -day cycle (from the passage of the satellite over the ground).

How was Nisar built?

At that time, the two space agencies agreed to build Nisar, NASA and Isro decided that each organ would contribute to equivalent equipment, expertise and finance. Especially the contributions of Isro is critical to the mission.

The organization provided the Platform I – 3K spacecraft bus and 4 kW solar energy, which contains controls to process commands and data, provocation and attitude. The same package also contained the entire S band radar electronics, a high -ranking Ka Band Telecom subset and Gimballed High Pirate Antenna. S Band electronics were designed and built at the Space Applications Center in Ahmedabad.

NASA’s biggest contribution was the L -Band Sar system. NASA’s jet propulsion laboratory provided all radio frequency electronics, 12 m antenna, a 9 m carbon composite boom and a device carrying both radar. The agency also produced the L Band feed diaphragm and provided supportive avionics, including a high -capacity solid status recorder, a GPS receiver, autonomous load data system and a Ka Band Load Communication Subsidium.

The spacecraft would be integrated into the Isro Satellite Center in Bengaluru after mating in two radar JPLs. For this reason, the latest observatory level tests will be performed on Indian territory. After that, the task will be removed from a GSLV MK-II launch tool Sriharikota and will provide recent launch services and documentation from the ISRO end.

WhileTask operations will be centered at the JPL Task Operations Center, daily flight operations will be managed from the Isro Telemetry, Monitoring and Command Network in Bengaluru. When Nisar is in orbit, most of its data will be sent to NASA’s Alaska, Svalbard (Norway) and Earth Network facilities in Punta Arenas (Chile). They will be completed with Isro’s ground stations in Shadnagar and Antarctica.

After raw data arrival, India’s National Remote Perception Center will process and distribute all the products required for Indian users reflecting NASA’s pipeline.