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First Post
30-07-2025
- Science
- First Post
Nisar launch: Why Nasa-Isro joint satellite is a big deal
Nasa-Isro Synthetic Aperture Radar, or Nisar, will liftoff onboard the Indian space agency's GSLV Mk-II rocket from Sriharikota on Wednesday (July 30). Jointly developed by Isro and Nasa, it is the first major earth-observing satellite with two frequencies — L-band and S-band. Here's what makes it special read more Nisar is built at a cost of over $1.5 billion. X/@isro Nisar, one of the most expensive earth-observation satellites, is set to be launched on Wednesday (July 30). The satellite will liftoff at 5.40 pm from the Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh. Jointly developed by the Indian Space Research Organisation (Isro) and the National Aeronautics and Space Administration (Nasa), the Indian space agency's GSLV Mk-II rocket will inject the Nisar satellite into a 747 km sun-synchronous polar orbit. Here's a look at why the mission is significant. STORY CONTINUES BELOW THIS AD What is Nisar? Nisar, which stands for Nasa-Isro Synthetic Aperture Radar, weighs 2,392 kg. It is the first major earth-observing satellite with two frequencies — Nasa's L-band and Isro's S-band. The dual-band radar will equip the mission to observe changes more accurately than any other satellite. 'Each system's signal is sensitive to different sizes of features on Earth's surface, and each specialises in measuring different attributes, such as moisture content, surface roughness, and motion,' according to Nasa. The satellite, which costs over $1.5 billion, was built in a decade. It features a 12-meter unfurlable gold mesh antenna, the largest of its kind in low-Earth orbit, integrated into Isro's I‑3K spacecraft bus. This platform contains controls handling command and data, propulsion, and attitude, along with 4 kW of solar power. Built across continents in phases, NISAR is a result of global teamwork and tech. NISAR came together through years of integration and testing. 2 Nations, 1 Mission. NISAR's build journey is a story of teamwork. Milestone of Firsts ✅ First dual-band radar satellite ✅ First… — ISRO (@isro) July 25, 2025 How Nisar will work The unique Earth imaging satellite will enter the sun-synchronous polar orbit at 747 km altitude and inclination of 98.4 degrees after launch. However, Nisar will not start capturing images immediately. Instead, the first 90 days will be spent by the satellite on commissioning, or In-Orbit Checkout (IOC), which will prepare it for science operations, according to Isro. STORY CONTINUES BELOW THIS AD The synthetic aperture radar (SAR) of the satellite will bounce radar waves off the planet's surface, measuring the time it takes for the signal to return and how its phase changes, reported The Hindu. Nisar will observe the Earth in L-band SAR (1.257 GHz), which uses longer-wavelength radiowaves to monitor changes under thick forests and soil and deformations on the ground. The S-band SAR (3.2 GHz) will utilise shorter-wavelength radiowaves to capture surface details, including crops and water surfaces, as per the newspaper. The satellite will observe the Earth with a swath of 242 km and high spatial resolution, using SweepSAR technology for the first time, as per Isro. Nisar will scan the globe every 12 days, providing detailed images of the Earth's surface. The dual radar payload on the satellite employing SweepSAR technology will ensure very high-resolution data, in all weather conditions, and during the day and the night. Why Nisar is a big deal The Nisar mission signals the growing partnership between India and the US in the space sector. 'This mission is not just about a satellite launch — it is a moment that symbolises what two democracies committed to science and global welfare can achieve together. Nisar will not only serve India and the United States but will also provide critical data for countries around the world, especially in areas like disaster management, agriculture, and climate monitoring,' Union Minister for Science and Technology Dr Jitendra Singh said earlier. STORY CONTINUES BELOW THIS AD The satellite will help study the changes in Earth's ecosystems, ice mass, vegetation biomass, forest cover, groundwater, sea level rise, as well as natural hazards, including earthquakes, tsunamis, volcanoes, and landslides. We've teamed up with @ISRO on the NISAR mission, a satellite that will measure changes on Earth's surface in fine detail. Data from NISAR can help us better manage natural resources, and understand the pace and effects of climate change. — NASA (@NASA) January 11, 2024 The data produced by Nisar will be freely available to all users, usually, within a few hours. 'The data will be placed in the public archive almost instantly after processing. Nasa and Isro have agreed - this is a science mission, and all radar data will be open,' Dr Paul Rosen, a Nasa Project Scientist for Nisar at the Jet Propulsion Laboratory in California, told NDTV. STORY CONTINUES BELOW THIS AD He underlined the satellite's role in tracking landslides and glacial lake outburst floods (GLOFs), which are becoming more common due to climate change. 'We can see precursory motion before landslides. And we will monitor glacier dynamics to assess GLOF risks,' Dr Rosen said. The satellite will also help monitor seismic zones, such as the Himalayas. 'We can measure ground motion to millimetre precision. That helps us understand the earthquake cycle - before, during, and after seismic events,' he added. The satellite can trace the path of a storm and the Earth's movements during earthquakes and volcanic eruptions. Nisar is expected to provide new insights into climate change or natural disasters, which can help in mitigation measures and early response. With inputs from agencies
India Today
27-07-2025
- Science
- India Today
Nisar: The billion-dollar radar that can see through clouds and darkness
When Nisar, a.k.a the Nasa-Isro Synthetic Aperture Radar, takes flight aboard India's GSLV Mk-II rocket from the Satish Dhawan Space Centre, Sriharikota, on July 30, 2025, it won't just be another Earth observation satellite in orbit, it will be a technological marvel, the likes of which the world has never seen satellite will be placed in a sun-synchronous polar orbit, 747 km above Earth, completing 14 orbits every just 97 minutes, Nisar will circle the planet once, and in 12 days, it will have mapped nearly every inch of Earth's landmass and ice sheets. For scientists, climate researchers, and disaster managers, this is a dream come true. The mission's open-source data will be freely available to researchers. (Photo: Isro) WHAT MAKES NISAR A GAME-CHANGER? At its heart, Nisar carries a world-first technology – a dual-frequency Synthetic Aperture Radar (SAR). Most radar imaging satellites work with a single frequency, but Nisar carries two powerful radar systems: L-band radar (24 cm wavelength) built by Nasa and S-band radar (12 cm wavelength) developed by unique combination allows Nisar to 'see' through clouds, thick forest canopies, smoke, and even in complete importantly, it can detect tiny changes in the Earth's surface, as small as a few millimeters. That means scientists can track how much a glacier has shifted, how much a fault line has moved after an earthquake, or even how much a city is sinking due to groundwater depletion. Nisar is set to become something more – a guardian that can sense Earth's heartbeat. (Photo: Nasa) Nisar achieves this precision through a special technique called Interferometric Synthetic Aperture Radar (InSAR). Think of it like taking two radar 'photos' of the same place a few days apart and comparing them to spot tiny sends out invisible radar waves to Earth's surface and listens for the waves that bounce back. By carefully analysing the timing (or 'phase') of these returning waves, InSAR can detect changes as small as a centimeter, like the ground shifting slightly after an earthquake or a glacier moving over creates detailed maps showing how Earth's surface is changing, helping scientists predict disasters or monitor climate shifts with incredible accuracy, no matter the weather or time of this data is made possible thanks to its massive 12-meter gold-plated deployable mesh antenna – the largest radar imaging antenna ever launched into space. For comparison, it's almost as wide as a badminton court when fully unfolded. WHY THE WORLD NEEDS NISAREarth's rapid changes are outpacing the capabilities of traditional satellites, which often lack the precision needed to capture critical details. Nisar bridges this gap with its high-resolution, all-weather, day-and-night imaging, delivering a near real-time view of our planet's dynamic will revolutionise our understanding by:advertisementTracking climate change: Observing polar ice loss, glacier shifts, and permafrost thawing with unprecedented management: Identifying subtle signs of land subsidence, landslide risks, and fault-line movements to predict earthquakes & water security: Forecasting crop yields, monitoring soil moisture, and mapping groundwater depletion to ensure resource & ecosystems: Measuring deforestation, forest biomass, and the carbon storage potential of vegetation to support conservation simple terms, Nisar will give us a near-real-time 'health check-up' of the Earth every few days. It has the largest radar imaging antenna ever launched into space. (Photo: Nasa) A BILLION-DOLLAR PARTNERSHIPNisar is one of the most expensive Earth observation missions ever undertaken, with a total cost estimated at $1.5 billion (Rs 12,500 crore).Nasa's contribution, covering the L-band radar, radar electronics, GPS receivers, and engineering support, is approximately $1.2 billion (Rs 10,000 crore).Isro's contribution, which includes the S-band radar, satellite bus, launch vehicle, and ground systems, is around Rs 788 crore (approximately $93 million).Despite the significant investment, the mission's open-source data will be freely available to researchers and governments worldwide, offering immense value for global scientific and climate research efforts. THE ROAD AHEADFor decades, satellites have been our eyes in the sky, but Nisar is set to become something more – a guardian that can sense Earth's tracking movements invisible to the naked eye, it promises to help humanity understand natural hazards, prepare for disasters, and fight climate it finally unfurls its giant golden antenna in orbit, Nisar will mark not just a triumph of space technology but also a symbol of international cooperation for the planet's future.(This is an authored article by Manish Purohit. Manish is a solar energy and spacecraft solar panel expert with extensive experience in managing critical space missions, including Chandrayaan-2 and Mangalyaan)- EndsMust Watch
The Hindu
27-07-2025
- Science
- The Hindu
What makes the NASA-ISRO NISAR satellite so special?
The story so far: The Indian Space Research Organisation (ISRO) is planning to launch the NISAR satellite from Sriharikota on July 30 onboard a GSLV Mk-II rocket. 'NISAR' stands for NASA-ISRO Synthetic Aperture Radar and is a joint mission of the two space agencies. It is a sophisticated earth-observation satellite designed to study changes on the earth's surface in fine detail, covering earthquakes, volcanoes, ecosystems, ice sheets, farmland, floods, and landslides. What's the need for NISAR? NISAR is the first major earth-observing mission with a dual-band radar, which will allow it to observe changes more precisely than any other satellite. It will be able to see through clouds, smoke, and even thick vegetation, both at day and night, in all weather conditions. The three-tonne machine has been a decade in the making and costs more than $1.5 billion, also making it one of the most expensive earth-observing satellites to date. The earth's surface is constantly changing. Natural disasters, human-driven changes, and climate shifts all affect environments and human societies. Satellites provide critical information by taking snapshots of these changes from space, helping scientists, governments, and relief agencies prepare for, respond to or study them. To this end, NASA and ISRO have created a powerful global mission that also allows ISRO guaranteed access to a stream of high‑resolution data tailored to India's needs. NISAR's science and application goals span six areas: solid earth processes, ecosystems, ice dynamics, coastal and ocean processes, disaster response, and additional applications (including tracking groundwater, oil reservoirs, and infrastructure like levees, dams, and roads for subsidence or deformation and supporting food security research). The planned mission lifetime is three years although its design lifetime is at least five years. Notably, the mission's data policy entails that the data NISAR produces will be freely available to all users (typically) within a few hours. How does NISAR work? Once it is launched, NISAR will enter into a sun-synchronous polar orbit at 747 km altitude and an inclination of 98.4°. From here, instead of snapping pictures, NISAR's synthetic aperture radar (SAR) will bounce radar waves off the planet's surface and measure how long the signal takes to come back and how its phase changes. The ability of a radar antenna to resolve smaller details increases with its length, called its aperture. In orbit, deploying an antenna hundreds of metres long is impractical. SAR gets around this by mimicking a giant antenna. As the spacecraft moves forward, it transmits a train of radar pulses and records the echoes. Later, a computer coherently combines all those echoes as if they had been captured simultaneously by one very long antenna, hence the 'synthetic aperture'. NISAR will combine an L-band SAR (1.257 GHz), which uses longer-wavelength radiowaves to track changes under thick forests and soil and deformations on the ground, and an S-band SAR (3.2 GHz), which uses shorter-wavelength radiowaves to capture surface details, such as crops and water surfaces. Although NISAR will operate globally at L‑band, ISRO has reserved routine, planned acquisitions with the S‑band SAR over India. The latter acquisitions have extended sensitivity to biomass, better soil‑moisture retrieval, and mitigate ionospheric noise — all capabilities tuned to India's needs in agriculture, forestry, and disaster management. Because the L‑band radar is the principal tool for NASA's mission goals, the instrument is expected to operate in up to 70% of every orbit. This said, operating both radars together is an official implementation goal so that mode conflicts over the Indian subcontinent are minimised. Polarisation is the direction in which the electric field of some electromagnetic radiation, like radiowaves, oscillates. SAR can transmit and receive radar signals with horizontal or vertical polarisation. Using different combinations will allow the instruments to identify the structure and types of different surface materials, like soil, snow, crop or wood. The swath width, i.e. the breadth of the bands on the ground the SARs will scan, is an ultra-wide 240 km. The radars' SweepSAR design will transmit this beam and, upon its return, digitally steer multiple small sub‑apertures in sequence, synthesising beams that sweep across the ground track. This scan‑on‑receive method allows the 240‑km swath without compromising resolution. The resulting scans will have a spatial resolution of 3-10 m and centrimetre-scale vertical mapping — enough to spot impending land subsidence in cities, for example — depending on the mode. Each spot on the ground will be scanned once every 12 satellite also features a large 12-m-wide mesh antenna. NISAR will produce annual maps of aboveground woody biomass of 1 ha resolution and quarterly maps of active and inactive cropland. High-resolution maps of flooded versus dry areas will be available as well. During a disaster, NISAR can also be directed to collect data for 'damage proxy maps' to be delivered in under five hours. This said, for certain acquisition modes, NISAR won't be able to achieve full global coverage at the highest resolution. Above roughly 60° latitude, every alternative observation will be skipped due to converging ground tracks. Similarly, some 10% of the surface may not be mapped from either direction (of the satellite's passage over the ground) in any given 12-day cycle. How was NISAR built? At the time the two space organisations agreed to build NISAR, NASA and ISRO decided each body would contribute equivalent‑scale hardware, expertise, and funding. ISRO's contributions in particular are mission‑critical. The organisation supplied the I‑3K spacecraft bus, the platform that houses the controls to handle command and data, propulsion, and attitude, plus 4 kW of solar power. The same package also included the entire S‑band radar electronics, a high‑rate Ka‑band telecom subsystem, and a gimballed high‑gain antenna. The S‑band electronics were designed and built at the Space Applications Centre in Ahmedabad. NASA's biggest contribution was the complete L‑band SAR system. NASA's Jet Propulsion Laboratory supplied all radio‑frequency electronics, the 12‑m antenna, a 9-m carbon-composite boom, and the instrument structure that carries both radars. The agency also fabricated the L‑band feed aperture and provided the supporting avionics, including a high‑capacity solid‑state recorder, a GPS receiver, an autonomous payload data system, and a Ka‑band payload communications subsystem. The spacecraft was to be integrated at the ISRO Satellite Centre in Bengaluru after the two radars were mated at JPL. The final observatory‑level tests will therefore have taken place on Indian soil. After that the mission will lift off from Sriharikota onboard a GSLV Mk-II launch vehicle, with ISRO providing end‑to‑end launch services and documentation. While themission operations are to be centred at the JPL Mission Operations Center, day‑to‑day flight operations will be led from the ISRO Telemetry, Tracking and Command Network in Bengaluru. Once NISAR is in orbit, most of its data will be sent through NASA's Near Earth Network facilities in Alaska, Svalbard (Norway), and Punta Arenas (Chile), which can together receive around 3 TB of radar data per day. They will be complemented by ISRO's ground stations in Shadnagar and Antarctica. After the raw data arrive, India's National Remote Sensing Centre will process and distribute all products required for Indian users, mirroring NASA's pipeline.
The Hindu
27-07-2025
- Science
- The Hindu
What makes the NASA-ISRO NISAR satellite special?
The story so far: The Indian Space Research Organisation (ISRO) is planning to launch the NISAR satellite from Sriharikota on July 30 onboard a GSLV Mk-II rocket. 'NISAR' stands for NASA-ISRO Synthetic Aperture Radar and is a joint mission of the two space agencies. It is a sophisticated earth-observation satellite designed to study changes on the earth's surface in fine detail, covering earthquakes, volcanoes, ecosystems, ice sheets, farmland, floods, and landslides. What's the need for NISAR? NISAR is the first major earth-observing mission with a dual-band radar, which will allow it to observe changes more precisely than any other satellite. It will be able to see through clouds, smoke, and even thick vegetation, both at day and night, in all weather conditions. The three-tonne machine costs more than $1.5 billion, making it one of the most expensive earth-observing satellites to date. The earth's surface is constantly changing. Natural disasters, human-driven changes, and climate shifts all affect environments and human societies. Satellites provide critical information by taking snapshots of these changes from space, helping scientists, governments, and relief agencies prepare for, respond to or study them. To this end, NASA and ISRO have created a powerful global mission that also allows ISRO guaranteed access to a stream of high-resolution data tailored to India's needs. NISAR's science and application goals span six areas: solid earth processes, ecosystems, ice dynamics, coastal and ocean processes, disaster response, and additional applications (including tracking groundwater, oil reservoirs, and infrastructure like levees, dams etc.). The planned mission lifetime is three years although its design lifetime is at least five years. Notably, the mission's data policy entails that the data NISAR produces will be freely available to all users (typically) within a few hours. How does NISAR work? Once it is launched, NISAR will enter into a sun-synchronous polar orbit at 747 km altitude and an inclination of 98.4°. From here, instead of snapping pictures, NISAR's synthetic aperture radar (SAR) will bounce radar waves off the planet's surface and measure how long the signal takes to come back and how its phase changes. The ability of a radar antenna to resolve smaller details increases with its length, called its aperture. In orbit, deploying an antenna hundreds of metres long is impractical. SAR gets around this by mimicking a giant antenna. As the spacecraft moves forward, it transmits a train of radar pulses and records the echoes. Later, a computer coherently combines all those echoes as if they had been captured simultaneously by one very long antenna, hence the 'synthetic aperture'. NISAR will combine an L-band SAR (1.257 GHz), which uses longer-wavelength radiowaves to track changes under thick forests and soil and deformations on the ground, and an S-band SAR (3.2 GHz), which uses shorter-wavelength radiowaves to capture surface details, such as crops and water surfaces. Although NISAR will operate globally at L-band, ISRO has reserved routine, planned acquisitions with the S-band SAR over India. The latter acquisitions have extended sensitivity to biomass, better soil-moisture retrieval, and mitigate ionospheric noise — all capabilities tuned to India's needs in agriculture, forestry, and disaster management. Because the L-band radar is the principal tool for NASA's mission goals, the instrument is expected to operate in up to 70% of every orbit. This said, operating both radars together is an official implementation goal so that mode conflicts over the Indian subcontinent are minimised. Polarisation is the direction in which the electric field of some electromagnetic radiation, like radiowaves, oscillates. SAR can transmit and receive radar signals with horizontal or vertical polarisation. Using different combinations will allow the instruments to identify the structure and types of different surface materials, like soil, snow, crop or wood. The swath width, that is, the breadth of the bands on the ground the SARs will scan, is an ultra-wide 240 km. The radars' SweepSAR design will transmit this beam and, upon its return, digitally steer multiple small sub-apertures in sequence, synthesising beams that sweep across the ground track. This scan-on-receive method allows the 240-km swath without compromising resolution. The resulting scans will have a spatial resolution of 3-10 m and centimetre-scale vertical mapping — enough to spot impending land subsidence in cities, for example — depending on the mode. Each spot on the ground will be scanned once every 12 days. The satellite also features a large 12-m-wide mesh antenna. NISAR will produce annual maps of aboveground woody biomass of 1 ha resolution and quarterly maps of active and inactive cropland. High-resolution maps of flooded versus dry areas will be available as well. During a disaster, NISAR can also be directed to collect data for 'damage proxy maps' to be delivered in under five hours. This said, for certain acquisition modes, NISAR won't be able to achieve full global coverage at the highest resolution. Above roughly 60° latitude, every alternative observation will be skipped due to converging ground tracks. Similarly, some 10% of the surface may not be mapped from either direction (of the satellite's passage over the ground) in any given 12-day cycle. How was NISAR built? At the time the two space organisations agreed to build NISAR, NASA and ISRO decided each body would contribute equivalent-scale hardware, expertise, and funding. ISRO supplied the I-3K spacecraft bus, the platform that houses the controls to handle command and data, propulsion, and attitude, plus 4kW of solar power. The same package also included the entire S-band radar electronics, a high-rate Ka-band telecom subsystem, and a gimballed high-gain antenna. The S-band electronics were designed and built at the Space Applications Centre in Ahmedabad. NASA's biggest contribution was the complete L-band SAR system. NASA's Jet Propulsion Laboratory (JPL) supplied all radio-frequency electronics, the 12-m antenna, a 9-m carbon-composite boom, and the instrument structure that carries both radars. The agency also fabricated the L-band feed aperture and provided the supporting avionics, including a high-capacity solid-state recorder, a GPS receiver, an autonomous payload data system, and a Ka-band payload communications subsystem. The spacecraft was to be integrated at the ISRO Satellite Centre in Bengaluru after the two radars were mated at JPL. Following observatory-level tests, the mission will lift off from Sriharikota onboard a GSLV Mk-II rocket, with ISRO providing end-to-end launch services. While the mission operations are to be centred at the JPL Mission Operations Center, day-to-day flight operations will be led from the ISRO Telemetry, Tracking and Command Network in Bengaluru. Once NISAR is in orbit, most of its data will be sent through NASA's Near Earth Network facilities in Alaska, Svalbard (Norway), and Punta Arenas (Chile), which can together receive around 3 TB of radar data per day. They will be complemented by ISRO's ground stations in Shadnagar and Antarctica. After the raw data arrive, India's National Remote Sensing Centre will process and distribute all products required for Indian users, mirroring NASA's pipeline.
