Megha-Tropiques

Megha-Tropiques was a joint CNES-ISRO tropical climate mission launched 12 October 2011 on PSLV-C18. The satellite operated in a near-circular orbit at 867 km altitude and 20 degree inclination, a low-inclination design chosen specifically to maximise revisit frequency over the tropics rather than achieve polar or sun-synchronous coverage.^[1][2]

The instrument suite comprised four payloads: SAPHIR (Sounder for Atmospheric Profiling of Humidity in the Intertropical Regions), a six-channel microwave humidity sounder at 183.31 GHz; MADRAS (Microwave Analysis and Detection of Rain and Atmospheric Structures), a conical-scanning microwave imager; ScaRaB (Scanner for Radiation Budget), measuring outgoing shortwave and longwave radiation; and ROSA, a GPS radio occultation receiver. MADRAS developed a defect from December 2012 and was deactivated the following year, according to mission documentation.^[2] ROSA ceased functioning after the GPS week-number rollover in April 2019.^[1]

An attitude control failure brought operations to an end on 15 December 2021. ISRO formally declared the mission concluded in April 2022; WMO OSCAR records January 2022 as the inactive date.^[3][1][4] A controlled destructive re-entry over the South Pacific Ocean was executed on 7 March 2023.^[3] SAPHIR and ScaRaB operated from launch in October 2011 until the mission's decommissioning in December 2021, exceeding the design lifetime and providing a 10-year tropical humidity and radiation-budget record.