  Satellite-based greenhouse gases (GHG) sensing technologies play a critical
role in the study of global carbon emissions and climate change. However, none
of the existing satellite-based GHG sensing technologies can achieve the
measurement of broad bandwidth, high temporal-spatial resolution, and high
sensitivity at the same time. Recently, dual-comb spectroscopy (DCS) has been
proposed as a superior candidate technology for GHG sensing because it can
measure broadband spectra with high temporal-spatial resolution and high
sensitivity. The main barrier to DCS's display on satellites is its short
measurement distance in open air achieved thus far. Prior research has not been
able to implement DCS over 20 km of open-air path. Here, by developing a
bistatic setup using time-frequency dissemination and high-power optical
frequency combs, we have implemented DCS over a 113 km turbulent horizontal
open-air path. Our experiment successfully measured GHG with 7 nm spectral
bandwidth and a 10 kHz frequency and achieved a CO2 sensing precision of <2 ppm
in 5 minutes and <0.6 ppm in 36 minutes. Our results represent a significant
step towards advancing the implementation of DCS as a satellite-based
technology and improving technologies for GHG monitoring
