A New Eye in the Storm
For decades, weather forecasting for India's 7,500-kilometre coastline has been a high-stakes challenge. Meteorologists at the India Meteorological Department (IMD) have relied on a combination of ground-based stations, weather balloons, and conventional
optical satellites. While these tools are effective, they have a critical weakness: they struggle to see through the dense cloud walls of a developing cyclone. Optical satellites, much like a regular camera, cannot penetrate thick cloud cover, leaving forecasters to infer what is happening inside the storm's core. This has historically limited the precision of predictions about a cyclone's intensity and exact landfall location, variables that are crucial for effective disaster management and evacuations.
The Power of Radar from Space
Enter Synthetic Aperture Radar (SAR), the game-changing technology at the heart of ISRO's advanced earth observation satellites, including the RISAT (Radar Imaging Satellite) series and the joint NASA-ISRO mission, NISAR. Unlike optical satellites that are passive and rely on sunlight, SAR is an active system. It transmits its own microwave pulses towards the Earth and analyses the signals that bounce back. Because these microwave signals can penetrate clouds, rain, and darkness, SAR provides an uninterrupted, all-weather view of the Earth's surface. This means that even in the middle of a raging cyclone at night, ISRO's radar satellites can gather detailed information about the sea surface, a feat previously impossible.
Seeing the Unseen
The high-precision data from SAR is transforming how forecasters understand cyclones in real-time. By analysing how the radar signals scatter off the ocean, scientists can derive crucial parameters from right inside the storm. This includes measuring surface wind speeds and direction with greater accuracy, determining wave heights, and precisely locating the cyclone's eye. Where earlier predictions were based on the storm's cloud patterns, SAR provides direct physical measurements of the storm's interaction with the ocean. This allows the IMD and other agencies like the Indian National Centre for Ocean Information Services (INCOIS) to create more accurate models for predicting a cyclone's track, its intensification rate, and the potential height of the storm surge—often the most destructive element of a coastal storm.
From Data to Life-Saving Decisions
This enhanced accuracy has profound real-world consequences. More precise landfall predictions mean that evacuation warnings can be targeted to smaller, specific areas, reducing unnecessary disruption and panic. Authorities can pre-position disaster response teams, medical aid, and essential supplies with greater confidence. The data from ISRO satellites like Oceansat and SCATSAT, which are tailored for oceanographic studies, are fed into the national disaster management framework. This information is disseminated through portals like MOSDAC and Bhuvan, providing state and district-level authorities with actionable intelligence. This seamless flow of information from space to the ground is a cornerstone of India's strategy to minimise the loss of life and property from natural disasters.
Beyond Cyclone Alley
While cyclone forecasting is the most dramatic application, the utility of ISRO's high-precision radar data extends much further. This technology is invaluable for a host of other coastal and maritime challenges. It is used for detecting and monitoring oil spills, which appear as smooth patches on the radar's view of the ocean surface. It helps in mapping and monitoring coastal erosion by providing precise shoreline delineation over time. Furthermore, SAR is a powerful tool for maritime surveillance, capable of identifying ships that may have turned off their tracking systems, thereby aiding in efforts to curb illegal fishing and enhance national security. Even applications in agriculture and monitoring glaciers are being unlocked with this versatile technology.
