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TRISHNA: the ISRO-CNES thermal infrared satellite for water stress

By CAShorts DeskPublished Updated Source: ISRO; CNES; The Hindu

Why in news: On 11 October 2026, a U.R. Rao Satellite Centre director said TRISHNA had reached the realisation stage and could launch within 12-16 months.

TRISHNA: the ISRO-CNES thermal infrared satellite for water stress
Illustration (AI-generated)

TRISHNA is a joint ISRO-CNES satellite that will map the temperature of land and coastal waters at 57 metres, to estimate evapotranspiration and crop water stress. France's CNES supplies its thermal infrared payload and ISRO its visible-shortwave infrared payload. On 11 October 2026, a URSC director said it was due for launch within 12-16 months.

Syllabus: GS3 · Agriculture & Irrigation; Prelims · Science & Technology; GS3 · IT, Space, Biotech & IPR

In short

TRISHNA (Thermal Infra-Red Imaging Satellite for High-resolution Natural Resource Assessment), a joint ISRO-CNES mission, reads surface heat to show where crops and soils lose water.

From surface heat toirrigation advisoriesSurfacetemperatureand emissivitySurfaceenergybalanceHeat fluxesandevapotranspirationWater stressmapsIrrigationadvisories

TRISHNA will be judged by water saved, not images taken: its maps must reach irrigation advisories, canal schedules and city heat plans.

Why it matters

A farmer who irrigates by the calendar often waters a field that does not need it, and reaches a parched one too late. A crop that is short of water transpires less and its leaves warm up, so a temperature map shows where water is needed. TRISHNA's field-scale maps can feed irrigation advisories and canal schedules. Today, CNES notes, such detail from space comes only about once a month, while frequent images are 1 km coarse. The same data will map urban heat islands for heat alerts and track drought, snowmelt and pollution in lakes and coastal waters. With an open data policy promised, the benefit reaches well beyond India and France.

Prelims pointers

  • Thermal infrared remote sensing records heat emitted by a surface, giving its temperature; it works at night but cannot see through cloud.
  • Evapotranspiration: water lost by evaporation from soil and water bodies plus transpiration from plants; a warm canopy signals water stress.
  • Sun-synchronous orbit: a near-polar orbit that passes over each place at about the same local solar time on every visit.
  • Geostationary satellites view an area often, but give surface temperature only at about 1 km resolution, per CNES.
  • Megha-Tropiques (ISRO-CNES): studied the water cycle and energy exchanges in the tropical atmosphere.
  • SARAL (ISRO-CNES): Satellite with ARGOS and ALTIKA; AltiKa measured sea-surface height by radar altimetry, ARGOS relayed data from field platforms.
  • Do not confuse: NISAR is the NASA-ISRO radar mission; TRISHNA is the ISRO-CNES thermal infrared mission.
  • TRISHNA's secondary uses (ISRO): urban heat islands, volcanic and geothermal heat anomalies, snowmelt runoff and glacier dynamics.

Practise a UPSC-style question

With reference to the TRISHNA satellite mission, consider the following statements:

1. The thermal infrared payload of TRISHNA is being developed by ISRO.

2. The satellite is designed to operate in a sun-synchronous orbit.

3. The satellite bus is being built by ISRO's U.R. Rao Satellite Centre.

Which of the statements given above is/are correct?

  1. (a) 1 and 2 only
  2. (b) 2 and 3 only
  3. (c) 1 and 3 only
  4. (d) 1, 2 and 3
Show the answer

Answer: (b) 2 and 3 only

1 is incorrect: the Thermal Infra-Red payload is provided by France's CNES; ISRO develops the VNIR-SWIR payload. 2 is correct: ISRO places it in a sun-synchronous orbit at 761 km, crossing the equator at 12:30 local time. 3 is correct: URSC is responsible for building the satellite bus.

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