ISRO successfully demonstrates satellite tech to study ocean, and soil parameters

The Indian space agency, ISRO, has successfully demonstrated a technique to capture data on soil moisture, surface inundation, and ocean surface wind and wave measurements, using a satellite-based sensor that is 475 km above the earth. This novel method is known as GNSS-Reflectometry (GNSS-R). An instrument capable of performing this role was mounted on ISRO's EOS-08 satellite that was launched on August 16, and it began operations two days later.

GNSS-R is a new method of remote sensing. Simply put, remote sensing is the process of acquiring information about objects or places from a distance, typically using aircraft, satellites, or drones equipped with sensors. These sensors collect data by detecting the energy that is reflected from Earth.

There are dozens of satellites circling the Earth tospecifically provideus with position, navigation and timing services. India has the NavIC constellation of satellites, the United Stateshas the GPS, Europe has the Galileo, China has BeiDou, and Russia has GLONASS. All these satellites which are part of such constellations are constantly emitting signals towards the Earth. As these signals hit different geographical features on Earth, such as oceans, agricultural land, freshwater bodies, these signals are reflected back to space.

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Aboard its 175kg EOS-08 satellite, ISRO has placed a small-sized, lightweight, low-power precision receiver that can collect these reflected signals. This GNSS-R instrument is developed by ISRO's Space Applications Centre, and it is India’s first space-borne precision receiver.

This receiver measures the power and other characteristics of the reflected signal that it receives. Based on the characteristics of the signal, the sensor can offer raw data, which can be processed to derive specific scientific information about the regions covered by the receiver, including soil moisture, surface inundation, and ocean surface wind and wave measurements.

The observations made so far

As the EOS-08 satellite circles 475 km above the Earth, it gets to fly over different regions. Therefore, the GNSS-R instrument can capture a wide range of data from various sources and generate the corresponding raw data.

For instance, during the bygone week, the GNSS-R instrument collected its first land data, as it flew over the Sahara Desert (North Africa). This data was processed to retrieve soil moisture. Likewise, when the satellite flew over a part of the Pacific Ocean, the data it captured was processed to derive the wind speed and wave height.

All the science data products are generated at SAC-ISRO using algorithms developed in-house. Given that the GNSS-R sensors are small and lightweight, and consume less power, such sensors can be mounted on multiple satellites to gather global data at a greater frequency and therefore they could help in monitoring several natural phenomena, evolving weather patterns, climatic conditions etc.