A system for remotely sensing a target material in situ include a broad-band laser source, at least one tunable filter coupled to the source laser for generating a swept-frequency signal an optical device for splitting the swept-frequency signal into a first illumination signal and second illumination signal, a first optical path for directing the first illumination signal unto the target material and receiving a reflected signal from the target material, a second optical path for receiving the second illumination signal and generating a spectral reference signal, and a controller coupled to the first optical path and the second optical path for adjusting the frequency and spatial resolution of the laser source based at least in part on a comparison of the spectral reference signal and the reflected signal.