TROPOMI Validation will rely on data from satellite instruments, balloon-borne sondes, and data from ground-based measurement networks. Use of data from satellite instruments with similar global coverage, overpass time, and data product characteristics like those from OMI and OMPS will be important for both initial and long-term assessment of the TROPOMI Level 2 data products. The validation will take place in two phases. A rapid, but thorough first check of the Level 2 products will take place during the E1 Commissioning Phase occurring in the first six months after launch. In this phase, the data user community will be able to see how the earliest data stream from TROPOMI is used to create the suite of TROPOMI data products and how they  each compare with select validation datasets. In the following E2 Operational Phase, validation will be carried out to systematically evaluate the quality of TROPOMI data products.

Currently, the plan for the E2 operational phase of TROPOMI validation is being created including a selection of datasets to be used for validation and a description of the software and other tools needed to carry out validation efforts. Validation activities will be taking place on several scales:  at the broad ESA level aimed at all products and on a slightly smaller, more focused institutional level. That is, the institutes which are responsible for the production of various Level 2 data products including KNMI and SRON will also be coordinating their own validation activities.