A compact, lightweight, and efficient fiber laser lidar system has been developed to measure water vapor profiles in the lower atmosphere of Earth or Mars. The line narrowed laser consist of a Tm:germanate fiber pumped by two 792nm diode arrays. The fiber laser transmits ~0:5mJ Q- switched pulses at 5 Hz and can be tuned to water vapor lines near 1:94 µmwith linewidth of ~20pm. A lightweight lidar receiver telescope was constructed of carbon epoxy fiber with a 30cm Fresnel lens and an advanced HgCdTe APD detector. This system has made preliminary atmospheric measurements.