The Merlin mission will provide the following data products:
- Level 0: for each individual laser shot, the range-gated backscatter signal data (vertical profile) together with auxiliary data such as laser pulse energy, wavelength, time of pulse, satellite position, velocity and pointing at time of pulse plus coarse geolocation of shot in a chronological data sequence for the instrument operating in observation mode,
- Level 1a: Level 0 data (vertical profiles) with all calibrations computed and applied. The most accurate geolocation of each shot is appended to Level 1a products,
- Level 1b: Integrated column signal data, processed to get the slant DAOD (Differential Atmospheric Optical Depth) and the scattering surface elevation (SSE) corresponding to the required horizontal resolution (for each shot, or averaged over a cell). This data is annotated with information on observation-level calibration, preliminary pulse classification, geolocation, geometric angles and time,
- Level 2: column-weighted dry-air mixing ratios of methane (XCH4) and associated weighting function, pulse classification, geolocation (latitude, longitude, SSE), geometric angles and time,
- Level 3: Daily XCH4 worldwide maps visualising level 2 data.
The level 0, 1 and 2 products are chronologically and spatially organised; product coverage is defined in accordance with the orbit (one product <=> one orbit).
The Merlin scientific data and products architecture is shown in the diagram below.
Merlin scientific data and products
Level 3 product - Example of XCH4 map
Besides the L0 to L3 data products delivered directly by the Merlin mission, level 4 data products will be available. Level 4 products concern methane surface fluxes at various temporal and spatial scales. Inverse modelling with an atmospheric transport model will be used to generate these products. Since there are many different models and philosophies, these Level 4 data products will not be generated by the specific Merlin data processing center, but provided by scientists at various scientific research centres using lower level Merlin data.