Abstract Satellite‐based estimates of fossil fuel carbon dioxide (FFCO2) emissions are crucial for global stocktaking but are limited by sparse coverage. As nitrogen dioxide (NO2) observations can enhance CO2 emission estimates, we use NO2 observations from twin polar‐orbiting satellites (GaoFen‐5B and DaQi‐1) to constrain carbon emission estimates based on the OCO‐3 XCO2 measurements. Compared previous CO2 estimation constrained by polar‐orbiting satellites (e.g., Tropospheric Monitoring Instrument), this approach detects 40% more daily emission cases and reduces uncertainties by up to 12%, primarily due to reduced temporal differences and increased observation frequency. The improved estimates cover 69 global emission cases, mainly in East Asia, Europe, the Middle East, and North America. About 45% of the estimated emissions are lower than bottom‐up inventory values, potentially reflecting the impact of local emission control efforts. These findings highlight the importance of satellite monitoring for FFCO2 emissions and the value of future missions with high‐resolution collocated NO2/CO2 measurements.

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