The TANGO mission: A satellite tandem to measure major sources of anthropogenic greenhouse gas emissions

In this contribution, we present the Twin ANthropogenic Greenhouse Gas Observers (TANGO) mission, which is one of four candidate missions of ESA’s SCOUT program for the rapid prototyping and demonstration of observation techniques and science application using small-satellites. Over the period 2024-2027, TANGO will provide the unique opportunity for the global and independent monitoring of the major emission sources of the anthropogenic greenhouse gases CH₄ and CO₂. It will demonstrate a distributed monitoring system that can pave the way for future larger constellations of small-satellites allowing for enhanced coverage and temporal resolution. The TANGO mission consists of two agile small-satellites, each carrying one spectrometer flying in conjunction with the Copernicus Sentinel 5 mission. Regular joint TANGO and Sentinel 5 observations will be used to enhance the radiometric accuracy of the TANGO spectrometers. The first satellite measures spectral radiances in the shortwave infrared part of the solar spectrum (1.6 µm) to determine moderate to strong emissions of CH₄ (≥ 10 Kt/yr) and CO₂ (≥ 5 Mt/yr). The instrument has a field of view of 30 x 30 km² at spatial resolutions small enough to monitor individual large industrial facilities (300 x 300 m²), with an accuracy to determine emissions on the basis of a single observation. Using the same strategy, the second satellite yields collocated NO₂ observations from radiance measurements in the visible spectral range, supporting plume detection and exploiting the use of CO₂/NO₂ ratio observations to estimate CO₂ emissions from offshore NO₂ sources. TANGO will provide surface fluxes of specific emission types based on the combination of CH₄, CO₂ and NO₂ observations at a high spatial resolution. In doing so, TANGO aims to uniquely complement the large current and planned Copernicus monitoring missions like Sentinel-5(P) and the CO2M High Priority Candidate Mission (HPCM) by providing unrivalled high-resolution monitoring of the major anthropogenic greenhouse gas emissions at a regular basis.