Lecturer: How synthetic aperture radar (SAR) works in Nisar’s heart

Unlike optical sensors, Synthesis aperture radar (SAR) Nisar mission Today (30 July) is expected to be launched at 5.40 pm, it is not dependent on visual light. The SAR uses microwaves, allowing satellites to “see” and operate day or night through clouds. This capacity makes the SAR a powerful tool to monitor everything from Antarctic snow to earthquake and deforestation.From traditional radar to SARTraditional radar systems send microwave pulses that bounce from the Earth’s surface. The radar then catchs the returning echo, measuring how long it took for the signal to return, its strength and frequency shift. These data reveal information about the distance, movement and texture of the object – but not with high visual clarity.SAR takes this concept forward by adding movement and calculation to the equation. As a satellite like Nisar, it revolves around the Earth, its radar antenna continues to emit and receive microwave pulses. Since the satellite is running, each return signal comes from slightly different angle. These slight differences create changes in the frequency of the returned signal – an event known as the Doppler shift, is familiar how a siren feels different when it comes near and then trauma.Synthesis of an antennaTypically, to get a radar image with high resolution, one will need a physically huge antenna – very large to launch or operate in space. For example, Nisar’s L-Band radar will require a 19-mm wide antenna to produce 10-meter resolution images using traditional radar techniques. Instead, SAR “synthesis” using a small antenna’s time with a small speed. Nisar’s actual radar antenna stretches up to 12 meters when deployed – about the length of a city bus – but through SAR processing, it receives comparable resolution of a very large antenna.In fact, SAR uses the front speed of the satellite to simulate a large antenna. It stitches several radar returns together, aligning them through complex onboard data processing. The flight tract of the spacecraft becomes like a camera lens, which sweeps in a scenario, which focuses echoes in a sharp, high-resolution image.SAR to imagineOnce raw SAR data is collected, they can be processed in various types of images for scientific analysis. IntervalMetry (insar): By comparing two SAR images of the same place taken at different times, scientists can produce an interferogram. They look like colored contour maps and highlight subtle changes in the height of the land – important for earthquakes, landslides and monitoring of glacier movement. The closer the band in the image, the higher the surface displacement. Polarity: This involves analyzing how radar waves are oriented when they return. For example, vertical structures such as buildings often reflect waves in the same orientation that were sent to them, while complex, irregular surfaces such as trees canopies change that orientation. This helps researchers distinguish between different types of land cover and assess damage after floods or storms.Why Sir MattersSAR’s ability to inspect surface changes in any season, at any time, makes it necessary to study the dynamic systems of the Earth. It supports disaster response, environmental monitoring, and supports Climatic scienceFor example, SAR can measure how much a glacier has retreated, tracks changes in soil moisture during drought, or find out whether the mistake has moved to the land subtle near the line.As a former director of NASA’s Jet Propulsion Laboratory Charles Elchi, it is called: SAR “allows us to refine the things very accurately.” By capturing persistent and wide images of the same places, missions such as Nisar can monitor changes over time, converting the raw radar echo into important knowledge about the developed surface of the Earth.