The invention is directed to improved systems, methods, and computer readable media for detecting gas leaks. More particularly, the invention detects gas leaks or discharges, such as methane or any other suitable gases, by analyzing reflected or direct light that passes through a region of enhanced target gas concentration. The invention collects light and processes spectral data of the light. All molecules are subject to rotational motions, vibrational motions, and/or combinations thereof (rovibrational motions), in which the atoms in the molecule are vibrating with respect to each other and/or rotating around each other. When the light passes through the region of the target gas, a portion of the light with certain wavelengths will be absorbed by the target gas due to the rovibrational motions of the target gas molecules. By analyzing the magnitude of absorption at certain wavelengths, one can determine the concentration of certain target gas or gases.