The TRISHNA program marks a step further in the fruitful cooperation built between CNES and ISRO since many years, through a new Earth observation mission dedicated to the improvement of water cycle understanding and water resource management. Thanks to its unprecedented high spatial resolution in the thermal infrared domain, together with a high revisit frequency, TRISHNA mission will significantly contribute to the detection of ecosystem stress and to the optimization of water use in agriculture in a context of global climate change. This paper presents the TRISHNA mission context and main requirements, gives an overview of TRISHNA system architecture and describes TIR (Thermal InfraRed) instrument design with a highlight on its specific innovative features and the current development status.