We estimate the amount of avoided deforestation due to the use of near-real-time satellite imagery (DETER) to support the Action Plan for the Prevention and Control of Deforestation in the Legal Amazon (PPCDAm), the conservation of indigenous and other protected areas, and compliance with the Brazilian Forest Code (FC). We develop a Directed Acyclical Graph (DAG) that outlines some of the econometric challenges that arise from the role of policy in the estimation of satellite data on deforestation and consider that policy could be a mediator and/or a moderator along this causal chain. We control for other policies that were introduced simultaneously with DETER, and allow for changes in the influences of prices, agricultural settlement, and forest conservation policies on deforestation after near-real-time monitoring was introduced. We find both direct impacts of DETER on deforestation, and indirect impacts via changes in the influences of commodity prices on deforestation. Our counterfactual estimates suggest that 652,216 km2 of forest was saved from 2000 to 2015 in the Legal Amazon region due to the presence of satellites (43,481 km2 per year). We estimate that avoided emissions amount to approximately 24 Pg CO2 during our study period. At the municipality level, standardized carbon emission reductions ranged from -1447 to 288,611 Mg CO2 per km