The TanSat mission: preliminary global observations

The Chinese global carbon dioxide monitoring satellite (TanSat) was launched successfully in December 2016 and has completed its on-orbit tests and calibration. TanSat aims to measure the atmospheric column-averaged dry air mole fractions of carbon dioxide (XCO2) with a precision of 4 ppm at the regional scale, and in addition, to derive global and regional CO2 fluxes. Progress towards these objectives is reviewed and the first scientific results from TanSat measurements are presented. TanSat on-orbit tests indicate that the Atmospheric Carbon dioxide Grating Spectrometer is in normal working status and is beginning to produce L1B products. The preliminary TanSat XCO2 products have been retrieved by an algorithm and compared to NASA Orbiting Carbon Observatory-2 (OCO-2) measurements during an overlapping observation period. Furthermore, the XCO2 retrievals have been validated against eight ground-site measurement datasets from the Total Carbon Column Observing Network, for which the preliminary conclusion is that TanSat has met the precision design requirement, with an average bias of 2.11 ppm. The first scientific observations are presented, namely, the seasonal distributions of XCO2 over land on a global scale.