Minimize Data Formats & Sizes

A TROPOMI Level-1B or Level-2 product is a logical file composed of two physical files: one header and one data block.

The physical header file is defined as an XML file containing a fixed part and a variable part of header/metadata information. The header contains descriptive or configuration control information. A physical header file has a file name extension .HDR.

This physical header XML file is not generated by the SENTINEL-5P processors. Indeed, the metadata is first stored by the processor directly in the NetCDF data block file in a specific METADATA group. The METADATA group is then extracted by external tools (still at PDGS) to create the header XML file.

The format of the data block physical file is the NetCDF4 enhanced model. Compared to the classic model, the enhanced (starting from version 4) offers some important features such as the support for groups, user-defined vlen (variable length) and compound types (structures), and parallel I/O access.