iasinat

This is a library for reading IASI level 1C and level 2 files in EUMETSAT's so-called "NAT" binary file format.

There is also a tool "iasinat" for converting L1C and L2 files to NetCDF.

This code was developed in collaboration with SPASCIA under the CNES CH4 SWIR-TIR contract.

Status and completeness

Currently this code only handles a subset of the available data, based on the needs of the SWIR-TIR and related projects.

The library can read MPHR, GIADR and MDR records.

This tool is in a beta state, except for footprint generation, which is alpha.

The outputs of this tool have been compared on a number of NAT files to NetCDF files provided by EUMETSAT or converted using CODA. SPASCIA did some preliminary sanity-checking of the posterior errors.

Level 1C

The L1C NetCDF output from this tool has been found to be in agreement with NetCDF files provided by EUMETSAT, but the files are partial, as some of the information present in the NAT files is not present in the NetCDF files.

The iasinat tool converts L1C raw measurements to spectral radiances using the conversion factors.

Level 2

As for level 1C, the level 2 output is partial (but fairly complete) and is in complete agreement with the EUMETSAT Level2 output, as well as CODA output, except for the error data.

The current EUMETSAT L2 product format specification and product guide documents incorrectly describe the error data records. Contrary to what is stated in these documents, the data records for temperature, water vapour and ozone do not have fixed sizes. The CODA description handles these variable-length records, but fails to reorder the vectors so that they can be attributed to individual pixels.

This tool handles both issues, but due to a lack of information we have not yet been able to fully validate its output.

Build instructions for the tool

• The code is written in Rust, you need to install the Rust package manager cargo
• For the tool, you need libnetcdf (apt install libnetcdf-dev on Debian-like systems)
• Checkout the repository and simply run cargo build --release

Dependencies

The dependencies of the library are minimal:

• anyhow for error handling
• log for logging (error messages etc.)
• ndarray for handling multi-dimensional arrays
• regex for parsing product header strings
• tofas for Julian date/time conversions
• circfp (optional) for computing elliptical footprints (see below)
• footprint (optional) for exporting footprints in an MPK format (see below)

The tool uses netcdf, simple_logger and pico-args.

The iasinat code contains no unsafe code, nor does it use unchecked operations.

Starting from version 0.1.2, the tool can be compiled with the "footprints" feature, which uses circfp to compute the elliptical footprints.

From version 0.1.3, the tool can be compiled with the "footprints-mpk" feature, which enables the footprints to be exported in the MPK format used by the footprint crate.

Library usage

For using the library in your Rust project, simply do cargo add iasinat

Version history

Author

Berke DURAK bd@exhrd.fr

References

• MTG Generic Format Specification, EUM/MTG/SPE/11/0252, v4A
• IASI Level 1 Product Guide, EUM/OPS-EPS/MAN/04/0032, v5
• IASI Level 1 Product Format Specification, EUM.EPS.SYS.SPE.990003, v9E
• IASI Level 2 Product Guide, EUM/OPS-EPS/MAN/04/0033, v3E
• IASI Level 2: Product Format Specification, EPS.MIS.SPE.980760, v9B