• Once launched, NISAR will be positioned in a sun-synchronous polar orbit, circling the Earth at an altitude of 747 kilometers with an orbital inclination of 98.4º. Unlike conventional satellites that capture images, NISAR will utilize synthetic aperture radar (SAR) technology, which sends radar pulses toward the Earth's surface and then measures the return time and phase shift of the reflected signals.
• The resolution of radar imaging improves with larger antenna sizes—known as aperture—but deploying physically large antennas in space is unfeasible. SAR overcomes this limitation by simulating a large antenna.
• As the satellite advances in its orbit, it emits repeated radar pulses and collects their echoes, which are later processed to reconstruct an image as if a giant antenna had captured them all at once—thus earning the term "synthetic aperture."
• NISAR will feature two radar systems: an L-band SAR operating at 1.257 GHz that penetrates vegetation and soil layers to detect subsurface changes and land deformations, and an S-band SAR at 3.2 GHz designed for observing finer surface details such as vegetation types and water bodies.
• Globally, the satellite will mainly operate using the L-band radar, which aligns with NASA’s scientific objectives. However, over India, ISRO will routinely utilize the S-band radar for targeted observations.
• These S-band acquisitions are tailored to India's specific needs, such as biomass estimation, soil moisture monitoring, and filtering out ionospheric interference, which are crucial for sectors like agriculture, forestry, and disaster response.
• Both space agencies aim to coordinate radar operations efficiently so that simultaneous use of both radars is possible over the Indian subcontinent, reducing data conflicts.
• In radar systems, polarisation refers to the orientation of the electric field in the radar wave. SAR can both send and receive horizontally or vertically polarised signals. Using various combinations of these allows NISAR to distinguish between different surface compositions such as snow, soil, crops, or forests.
• NISAR’s radar system will cover a wide area with a swath width of 240 km, thanks to a SweepSAR design. This approach uses a beam transmission system that, upon signal return, employs multiple smaller apertures that steer electronically to create scanning beams sweeping across the satellite’s ground path.
• This scan-on-receive method enables large-area coverage without sacrificing image clarity.
• The mission will deliver spatial resolutions ranging from 3 to 10 meters and vertical accuracy down to a few centimeters. This high level of detail is suitable for tracking urban land subsidence or other subtle ground movements. Each point on the Earth’s surface will be revisited every 12 days.
• NISAR is equipped with a massive 12-meter-wide mesh reflector antenna, enabling it to generate annual biomass maps at a resolution of 1 hectare and quarterly maps distinguishing between cultivated and fallow farmland.
• It will also provide detailed floodplain maps and, in emergencies, can generate ‘damage proxy maps’ within five hours of data capture.
• However, there are some limitations. Due to the satellite’s orbital geometry, certain data acquisition modes may not achieve full global coverage. At latitudes above 60º, NISAR will skip every other observation due to overlapping orbits.
• Furthermore, around 10% of Earth’s surface may not be covered from both ascending and descending passes within a given 12-day cycle

• When NASA and ISRO agreed to collaborate on the NISAR project, both agencies committed to contributing equally in terms of funding, technology, and expertise.
• ISRO was responsible for providing the I-3K satellite bus — the core spacecraft framework that handles system commands, propulsion, orientation, and includes solar panels capable of generating 4 kW of power.
• In addition, ISRO delivered the complete S-band radar electronics system, a high-speed Ka-band communication unit, and a steerable high-gain antenna. The development of the S-band radar components was carried out at the Space Applications Centre in Ahmedabad.
• On the other hand, NASA’s primary input was the L-band synthetic aperture radar system. This was developed at the Jet Propulsion Laboratory (JPL), which supplied all related radio-frequency components, a 12-meter radar antenna, a 9-meter carbon fiber boom, and the structural assembly that supports both radar units.
• NASA also provided the L-band feed array and avionics systems, including a solid-state recorder with large data capacity, a GPS system, autonomous data management tools, and a Ka-band communication unit.
• After integration of the radar payloads at JPL, the spacecraft was sent to ISRO’s Satellite Centre in Bengaluru for final assembly. Once fully tested, NISAR will be launched aboard ISRO’s GSLV Mk-II rocket from the spaceport in Sriharikota, with ISRO overseeing the entire launch sequence.
• While the overall mission will be coordinated through NASA's Mission Operations Center at JPL, routine flight control and monitoring will be managed by ISRO’s Telemetry, Tracking and Command Network (ISTRAC) in Bengaluru.
• After deployment into orbit, the bulk of the mission’s data—approximately 3 terabytes daily—will be transmitted through NASA’s Near Earth Network ground stations located in Alaska, Norway’s Svalbard, and Punta Arenas in Chile.
• These facilities will work in conjunction with ISRO’s data reception stations in Shadnagar and Antarctica. Once the raw data are received, India’s National Remote Sensing Centre (NRSC) will process and distribute mission outputs tailored for Indian applications, in a workflow that parallels NASA’s global data distribution system

ECO SENSITIVE ZONE(ESZ)

1.Context

The Environment Ministry’s Forest Advisory Committee (FAC) has, for now, declined Stage-II or final approval for Hindalco Industries Ltd’s bauxite mine in Maharashtra’s Kolhapur, as it falls under the eco-sensitive areas (ESA) of the Western Ghats, according to the minutes of the FAC meeting.

2. Eco-Sensitive Zone

• As per the National Wildlife Action Plan (2002-2016), issued by the Union Ministry of Environment, Forest and Climate Change, land within 10 km of the boundaries of national parks and wildlife sanctuaries is to be notified as eco-fragile zones or Eco-Sensitive Zones (ESZ).
• While the 10-km rule is implemented as a general principle, the extent of its application can vary. 
• Areas beyond 10 km can also be notified by the Union government as ESZs, if they hold larger ecologically important “sensitive corridors.”

1.1 Eco-Sensitive Zone (ESZ)

• The Eco-Sensitive Zone (ESZ) are areas in India notified by the Ministry of Environment, Forest and Climate Change (MoEFCC), GoI around Protected Areas, National Park and Wildlife sanctuaries. 

• Purpose: 

• To create some kind of "shock absorbers" to the protected areas by regulating and managing the activities around such areas. 
• Therefore, these areas act as a buffer for protected areas and reduce developmental pressures around a wildlife sanctuary or national park.
• They also act as a transition zone from areas of high protection to areas involving lesser protection.

• Range:

• All identified areas around Protected Areas and wildlife corridors to be declared as ecologically fragile under the Environment (Protection) Act, 1986 (National Wildlife Action Plan, 2002-2016).
• Eco-sensitive Zone could go up to 10 Kms around Protected Areas. 
• In cases where sensitive corridors, connectivity and ecologically important patches, crucial for landscape linkage, are even beyond 10 Kms width. 
• Further, Eco-sensitive zones may not be uniform all around and they could be variable in width and extent.

• Prohibited activities: 

• Activities like industries which cause pollution Commercial mining, sawmills, the establishment of major hydroelectric projects (HEP), commercial use of wood, Tourism, discharge of effluents or any solid waste or production of hazardous substances are all prohibited.

• Regulated activities:

• Activities like the felling of trees, establishment of hotels and resorts, commercial use of natural water, erection of electrical cables, drastic change of agriculture system, e.g. adoption of heavy technology, pesticides etc., widening of roads.

• Permitted activities:

• Activities like ongoing agricultural or horticultural practices, rainwater harvesting, organic farming, use of renewable energy sources, and adoption of green technology for all activities are permitted.

3. Reasons for the creation of an ecologically sensitive zone

• According to the guidelines issued by the Environment Ministry on February 9, 2011, ESZs are created as “shock absorbers” for the protected areas, to minimize the negative impact on the “fragile ecosystems” by certain human activities taking place nearby. Furthermore, these areas are meant to act as a transition zone from areas requiring higher protection to those requiring lesser protection.
• The guidelines also state that the ESZs are not meant to hamper the daily activities of people living in the vicinity, but are meant to guard the protected areas and “refine the environment around them”.
• To do so, the guidelines list the activities prohibited in an ESZ, such as commercial mining, saw mills, commercial use of wood, etc., apart from regulated activities like the felling of trees. Lastly, there are permitted activities like ongoing agricultural or horticultural practices, rainwater harvesting, and organic farming, among others.

Judgement of Supreme Court

• On June 3, a three-judge bench of the Supreme Court heard a PIL which sought to protect forest lands in the Nilgiris in Tamil Nadu, but was later expanded to cover the entire country.
• In its judgment, the court while referring to the 2011 guidelines as “reasonable”, as reported by Live Law, directed all states to have a mandatory 1-km ESZ from the demarcated boundaries of every protected forest land, national park and wildlife sanctuary.
• It also stated that no new permanent structure or mining will be permitted within the ESZ.
• If the existing ESZ goes beyond a 1-km buffer zone or if any statutory instrument prescribes a higher limit, then such extended boundary shall prevail, the court, as per the Live Law report, said.

4. Protests by the people

• Protests erupted across the high ranges of Kerala in response to the apex court’s directions. Due to the high density of human population near the notified protected areas, farmer’s groups and political parties have been demanding that all human settlements be exempt from the ESZ ruling.
• Alex Ozhukayil, the chairman of Kerala Independent Farmers’ Association (KIFA) claimed that the court’s decision would severely impact the livelihoods of farmers.
• He said, “The total extent of the wildlife sanctuaries in Kerala is eight lakh acres. If one km of ESZ is demarcated from their boundaries, around 4 lakh acres of human settlements, including farmlands, would come within that purview. This is a matter of sheer survival of lakhs of people.”
• The ruling Left Democratic Front and the Congress-led United Democratic Fund have both called for strikes in Idukki and Wayanad districts over the past weeks to oppose the 1-km order.
• Before the SC judgment, the Kerala state government had stated during an expert committee meeting of the Union Environment Ministry in March that all human settlements should be excluded from the buffer zones.
• The Kerala state government had proposed that for some national parks, such as the Thattekad Bird Sanctuary, the extent of the ESZ area should be reduced from the proposed uniform 1 km to an ESZ ranging from zero to 1 km in the eastern and south-eastern side of the national park.
• This was because the villagers occupying the densely populated settlements in these areas believed that the ESZ would restrict their agricultural and related activities.

4. Other similar challenges

• Developmental activities:

• Activities such as the construction of dams, roads, and urban and rural infrastructures in the ESZ, create interference, negatively impact the environment and imbalance the ecological system. 

• Blatant violations:

• To cater to the increasing demand for eco-tourism, the land around parks and sanctuaries are being cleared through deforestation, displacement of local people etc. 
• Failing to recognize the rights of forest communities and curbing poaching of animals, environmental legislations undermine the ESZs in favour of developmental activities. 

• Climate change:

• Biodiversity and climate change are interconnected, for example, the rise in global temperature has generated land, water and ecological stress on the ESZs. 

• Tourism-related Pollution:

• As the pressure of tourism is rising, the government is developing new sites and gateways to the ESZ. The tourists leave behind garbage such as plastic bags and bottles etc. which leads to environmental degradation.

• Local communities:

• Slash and burn techniques used in agriculture, the pressure of increasing population and the rising demand for firewood and forest produce, etc. exerts pressure on the protected areas.

5. Earlier protests 

• This is not the first time that Kerala has faced such protests. 
• In 2013, hartals first erupted in Idukki and Wayanad after the Kasturirangan committee report recommended that 60,000 km of the Western Ghats, covering 12 of Kerala’s 14 districts, be notified as ecologically sensitive areas.