Abstract: A method for characterizing gas emissions includes sampling each of a plurality of sectors having a common geographic center. For each sector, a first laser beam is transmitted from the geographic center to a first retroreflection location, where it is retroreflected into a first retroreflected beam. Near the geographic center, the first retroreflected beam is measured to obtain a first absorption. A second laser beam is then transmitted from the geographic center to a second retroreflection location, where it is retroreflected into a second retroreflected beam. Near the geographic center, the second retroreflected beam is measured to obtain a second absorption. The first and second retroreflection locations are both located within the same sector. First and second concentrations are determined from the first and second absorptions and processed to determine emission information about a known or potential gas source whose source lies within the sector.

Abstract: A method for adaptive dual frequency-comb spectroscopy includes repeatedly (i) recording a single interferogram with a dual frequency-comb spectrometer, (ii) averaging the single interferogram into an averaged interferogram, and (iii) determining a signal-to-noise ratio (SNR) of the averaged interferogram, until the SNR of the averaged interferogram exceeds a SNR threshold. In certain embodiments, determining the SNR includes determining a signal amplitude of a center burst of the averaged interferogram and determining a noise level of the averaged interferogram from data points of the averaged interferogram located away from the center burst. In certain embodiments, determining the SNR includes Fourier transforming the averaged interferogram into a frequency spectrum and numerically integrating the frequency spectrum.

Abstract: A frequency-measurement method uses a dual frequency-comb spectrometer as an optical wavemeter to measure the frequency of a reference laser that is used to frequency-stabilize the spectrometer. The method includes measuring a walking rate of center bursts in a sequence of interferograms recorded by the spectrometer, determining a number of teeth in each of a plurality of Nyquist windows formed by the dual frequency-comb spectrometer, and determining a Nyquist number of the one Nyquist window covering the laser frequency. The reference laser frequency can then be determined from the number of teeth in each Nyquist window, the Nyquist number, and the comb spacing of either one of the two frequency combs of the dual frequency-comb spectrometer. The reference laser frequency does not need to be measured with a separate wavemeter, or calibrated with respect to a known atomic or molecular transition.

Abstract: A frequency-measurement method uses a dual frequency-comb spectrometer as an optical wavemeter to measure the frequency of a reference laser that is used to frequency-stabilize the spectrometer. The method includes measuring a walking rate of center bursts in a sequence of interferograms recorded by the spectrometer, determining a number of teeth in each of a plurality of Nyquist windows formed by the dual frequency-comb spectrometer, and determining a Nyquist number of the one Nyquist window covering the laser frequency. The reference laser frequency can then be determined from the number of teeth in each Nyquist window, the Nyquist number, and the comb spacing of either one of the two frequency combs of the dual frequency-comb spectrometer. The reference laser frequency does not need to be measured with a separate wavemeter, or calibrated with respect to a known atomic or molecular transition.

Abstract: A system for detecting gas leaks and determining their location and size. A data gathering portion of the system utilizes a chosen geometrical configuration to collect path-integrated spectroscopic data over multiple paths around an area. A processing portion of the system applies a transport model together with meteorological data of the area to generate an influence function of possible leak locations on gas detector measurement paths, and applies an inversion model to the influence function, prior data, and the spectroscopic data to generate gas source size and location.

Abstract: A system for detecting gas leaks and determining their location and size. A data gathering portion of the system utilizes a chosen geometrical configuration to collect path-integrated spectroscopic data over multiple paths around an area. A processing portion of the system applies a transport model together with meteorological data of the area to generate an influence function of possible leak locations on gas detector measurement paths, and applies an inversion model to the influence function, prior data, and the spectroscopic data to generate gas source size and location.