Developed by CNES and its Indian counterpart ISRO, the Trishna mission is designed to observe Earth’s surface in the thermal infrared domain. Temperature is an indicator of the energy budget of all kinds of land surfaces, for example croplands, pastures and forests, urban areas or snow and ice. This budget yields a wealth of information such as plant water stress and evapotranspiration. For water surfaces, time-series of satellite temperature images are dynamic indicators of the structures involved in mixing the waters of lakes, rivers, their estuaries and the oceans.

Today, temperature measurements from space can only be obtained monthly at a resolution of about 100 metres, and daily global measurements are only available at a resolution of one kilometre.

The goal of Trishna—for Thermal infraRed Imaging Satellite for High-resolution Natural resource Assessment—is to reach a resolution of 57 metres with a revisit interval of three days. That kind of detailed spatial and temporal resolution will enable scientists to understand the local evolution of biological (water stress, transpiration), physical (evaporation, sublimation, plumes) and climatic (global observation over time) phenomena in relation to the water cycle. Ultimately, Trishna will be a precious aid to inform policy decisions for farming, water resource management and land planning.

Trishna’s thermal infrared instrument, developed by CNES, will be supplemented by an optical sensor supplied by ISRO. Observing simultaneously in the visible and thermal portions of the spectrum will make it easier to juxtapose data for analysis in several fields of investigation:

• ecosystem water stress and water resource management
• hydrology of coastal strips and land surfaces
• urban heat islands
• cryosphere
• atmosphere