MERLIN IPDA Lidar Instrument

The MERLIN IPDA Lidar Instrument is the science payload for the MERLIN (MEthane Remote Sensing LIdar missioN) satellite, a joint mission of CNES and DLR. The instrument uses Integrated Path Differential Absorption (IPDA) lidar to measure the column-averaged dry-air mole fraction of methane (XCH4) from orbit. MERLIN operates at a near-infrared wavelength of approximately 1645 nm; eoPortal documentation gives the online and offline channel wavelengths as 1645.552 nm and 1645.846 nm respectively,^[1] and SPIE 2023 conference proceedings confirm the 1645.55 nm methane absorption feature.^[2] The instrument transmits paired laser pulses at the two wavelengths alternately, and the ratio of the differential absorption gives the integrated methane column. DLR leads instrument development; CNES is the system prime for the mission.^[3] Airbus Defence and Space is reported as the satellite platform contractor, according to eoPortal documentation as of 2026-06-04.^[1] Launch is planned for 2028 according to CNES and DLR official sources;^[4][1] some secondary publications cite 2029. MERLIN is intended to provide global methane flux constraints relevant to greenhouse gas monitoring and climate modelling.