22 - 09 - 2026

ISRO-CNES TRISHNA Mission to Map Earth’s Heat, Water Stress and Climate in High Resolution

India and France are developing a new Earth-observation mission that could provide scientists with an unprecedented view of how heat and water move across the planet’s land and coastal environments. The TRISHNA (Thermal Infra-Red Imaging Satellite for High-resolution Natural Resource Assessment) mission, jointly developed by ISRO and France’s CNES, is designed to deliver high-resolution measurements of Earth’s surface temperature, emissivity and related biophysical variables.

The mission is currently under development, with CNES listing 2027 as the planned launch year. It will operate in a 761-km sun-synchronous orbit and is designed for a five-year mission. TRISHNA is being developed to address a major gap in Earth observation: obtaining thermal measurements at both high spatial resolution and frequent revisit intervals. Its observations will help scientists study the relationship between surface temperature, energy balance and the water cycle across agricultural land, forests, urban areas, inland waters, coastal regions, snow and ice.

ISRO says the mission is intended to provide high spatial and temporal resolution monitoring of surface temperature, emissivity, biophysical parameters and radiation-budget variables, with particular relevance to water and food security and water-resource management.

A thermal ‘thermometer’ for the planet

At the heart of TRISHNA is the ability to measure the temperature of Earth’s surface in much greater detail than conventional satellite observations.

Surface temperature provides an important indicator of the energy balance of land and water systems. When combined with other observations, it can help reveal plant water stress, evapotranspiration, evaporation, heat fluxes and changes in ecosystems.

The mission is therefore expected to support applications ranging from precision irrigation and agricultural monitoring to water-resource management, urban climate studies and assessment of changes in snow and ice.

CNES says TRISHNA is designed to deliver observations at roughly 60-metre product resolution, with a revisit of about three days at the equator. Its camera resolution ranges from 57 metres at nadir to 90 metres at the edge of the swath.

Two instruments, two complementary views

TRISHNA will carry two primary imaging instruments developed through the Indo-French partnership.

The Thermal Infra-Red (TIR) instrument is being provided by CNES and features four long-wave infrared channels. It will enable high-resolution mapping of surface temperature and emissivity.

The second instrument, the Visible–Near Infra-Red–Short Wave Infra-Red (VNIR-SWIR) payload, is being developed by ISRO. It contains seven spectral bands designed to measure surface reflectance and generate biophysical and radiation-budget variables.

Combining observations from the two instruments will allow researchers to derive surface-energy-balance parameters and estimate heat fluxes and evapotranspiration.

From water stress to urban heat

One of TRISHNA’s major scientific objectives is monitoring terrestrial water stress and water use. The satellite’s observations could help determine how vegetation responds to water availability and provide information relevant to irrigation and agricultural water management.

The mission will also observe inland and coastal waters, supporting studies of water quality and the dynamics of lakes, rivers, estuaries and coastal environments.

Urban areas will provide another important application. High-resolution thermal observations can help identify and quantify urban heat islands, allowing researchers to study how built-up environments absorb and release heat.

TRISHNA will also support monitoring of snow-melt runoff and glacier dynamics, as well as the detection of thermal anomalies associated with volcanic and geothermal activity. Atmospheric observations will include parameters such as aerosol optical depth, water vapour and cloud characteristics.

The agricultural applications could be among the most significant. By repeatedly measuring surface temperature at relatively fine spatial resolution, TRISHNA can help identify variations in crop water stress and evapotranspiration.

CNES says such information could help improve irrigation by enabling water application to be better matched to the actual requirements of crops.

This capability becomes particularly relevant as agriculture faces increasing pressure from water scarcity, changing rainfall patterns and rising temperatures.

The mission’s data is also expected to contribute to international initiatives including GEOGLAM, the UN Sustainable Development Goals and Global Water Watch. Some of its products are expected to contribute to Essential Agricultural Variables and Essential Climate Variables.

TRISHNA represents another major collaboration between ISRO and CNES, combining India’s capabilities in spacecraft development, Earth observation and launch systems with France’s expertise in thermal infrared sensing.

The mission’s scientific value comes from the combination of its spatial resolution, revisit frequency and multi-spectral observations. CNES describes the mission as an effort to resolve the trade-off that has historically existed between high spatial resolution and frequent thermal observations.

ISRO’s latest annual report indicates that the mission is progressing, with the preliminary design review completed for the satellite bus and VNIR/SWIR payloads, alongside continued international scientific cooperation.

Once operational, TRISHNA is expected to generate a detailed time series of Earth-surface temperature and related environmental variables, giving researchers a new way to study interactions between water, energy, ecosystems and climate.

For India and France, the mission is therefore more than another Earth-observation satellite. It represents a joint attempt to build a finer-resolution picture of how the planet is heating, where water is being consumed and how terrestrial and coastal ecosystems are responding to a changing climate.

By Subramanya Joshi

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