A miniature in-situ CH4 concentration measurement instrument based upon tunable laser spectroscopy (TLS) was developed and applied in numerous field campaigns. The instrument, a 3.4 μm laser spectrometer developed at NASA Jet Propulsion Lab (JPL), is lightweight (250g), low power (< 8 W), and high sensitivity (10 ppb s−1). The payload was further developed and integrated onto a small UAV at UC Merced, rendering an overall payload weight of 400 g and real-time data acquisition. The remarkable characteristics of the instrument and prior investigative work regarding sensor placement yielded excellent trial and field results, which are presented in this work.