Light detection and ranging (LIDAR) systems have become an important technology in a variety of industrial and scientific applications. In spectroscopy, LIDAR systems can improve the sensitivity by orders of magnitude but require the laser source to have a sufficient small linewidth and stability. For terrestrial applications, such systems have been developed over the last decade and are commercially available. In space, this technology does not have a comparable maturity level and is still far from being a standard technology.In this paper, we present the design and first measurement results of a spaceborne absolute frequency reference based on the absorption feature at 1645.55 nm of methane gas. The frequency reference unit is used in the instrument of the French-German Methane Remote Sensing LIDAR Mission, MERLIN. It provides the stabilized seed lasers for the high power laser sources at the required wavelengths and measures the absolute frequency of the outgoing laser pulses by means of a wavemeter.