The three science questions to be addressed by the proposed TRAQ mission are:

• How fast is air quality changing on a global and regional scale ?
• What is the strength and distribution of the sources and sinks of trace gases and aerosols influencing air quality ?
• What is the role of tropospheric composition in global change ?

TRAQ will carry a balanced suite of four instruments: a UV-Vis and ShortWave-InfraRed (SWIR) nadir grating spectrometer TROPOMI, a novel static infrared Fourier transform spectrometer SIFTI, a multi-viewing polarisation-resolving imaging radiometer OCAPI and a cloud imager CLIM. The TRAQ instruments will have unprecedented pixel sizes of 10 x 10 km2 or smaller (at nadir), in combination with near-global daily coverage and temporal sampling up to 5 times a day with 1.5 hour intervals over Europe. The latter can be achieved using a so-called non-synchronous, drifting orbit at 744 km altitude and inclination of 55°.
The following target constituents will be retrieved: O3 total column and surface UV from the UV-Vis; O3, NO2, SO2, HCHO tropospheric columns from the UV-Vis; height resolved tropospheric profiles of O3 and CO from the thermal infrared channels in combination with UV-Vis; CO and CH4 tropospheric columns from the SWIR; aerosols from a polarizing multidirectional multichannel imager and from UV-Vis-SWIR. Additional products include cloud information derived from the imager and from O2 and O2-O2 absorption features, and surface albedo.

Tasks of BIRA-IASB in the project
(To be confirmed)
• Contribution to TIR retrievals
• Contribution to UV-VIs retrievals for SO2 and H2CO
• Inverse modeling
• Validation
• Contribution to Ground segment ? TBD

Responsibility of BIRA-IASB in the project
partner