Nisar only in 2nd half of 2024; Trishna gets nod

BENGALURU: The $1.5 billion Nasa-Isro Synthetic Aperture Radar (Nisar) satellite launch, which was expected to happen in March is unlikely before the end of May. “GSLV for Nisar will be built by March-April but the satellite is still undergoing tests and we are looking at some delay. It (launch) could happen in the second half of this year,” Somanath told TOI in an exclusive interview.Nisar, a dual radar satellite, with both Isro and Nasa building one radar each, is to launch on India's GSLV. According to Nasa’s Jet Propulsion Lab (JPL), the lead agency from the US, “Nisar is the first satellite mission to collect radar data in two microwave bandwidth regions, called the L-band and the S-band, to measure changes of our planet’s surface, including movements as small as centimetre.The satellite, after initial integration in the US, has been at the UR Rao Satellite Centre (URSC) in Bengaluru. Once launched Nisaar will measure Earth’s changing ecosystems, dynamic surfaces, and ice masses providing information about biomass, natural hazards, sea level rise, and groundwater, and will support a host of other applications.It will observe Earth’s land and ice-covered surfaces globally with 12-day regularity on ascending and descending passes, sampling Earth on average every six days for a baseline 3-year mission.Meanwhile, another joint mission Isro is taking up — with the French space agency — has got the space commission’s nod. The project is called Trishna — Thermal infraRed Imaging Satellite for High-resolution Natural resource Assessment.“Trishna has been on cards for a long time but it wasn’t approved by the government. We’ve now got the approval, the last space commission cleared it. The project teams have been formed. The French side’s approach is to build the payload through another agency, work on that is progressing, and so is work on our side,” Somanath said.According to French space agency CNES (National Centre for Space Studies), Trishna will acquire imagery of Earth’s surface in the thermal infrared with a resolution and revisit frequency never seen before. “Trishna is designed to observe Earth’s surface in the thermal infrared domain. Temperature is an indicator of the energy budget of land surfaces — croplands, pastures, forests, urban areas, snow and ice — and yields a wealth of information such as plant water stress and evapotranspiration,” CNES’ description of Trishna, reads.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, CNES says, adding that Trishna’s aims to reach a resolution of 57 metres with a revisit interval of three days. “This will enable scientists to understand local evolution of biological (water stress, transpiration), physical (evaporation, sublimation, plumes) and climatic (global observation over time) phenomena in relation to water cycle. Trishna will be a precious aid to inform policy decisions for farming, water resource management and land planning,” it added.Trishna’s thermal infrared instrument, developed by CNES, will be supplemented by an optical sensor supplied by Isro.