New measurement technologies are required to support science campaigns to better quantify rapid changes in the Earth atmosphere system. A key factor in this heightened focus on risk and uncertainty is the growing recognition that the climate is changing far more rapidly than was thought just five years ago. Aurora Flight Sciences and Harvard University propose to miniaturize the Harvard Integrated Cavity Output Spectroscopy (ICOS) instrument for use in the unique reel-down payload pod of the "StratoCruiser", a proposed propulsive high-altitude balloon gondola. Combining the persistence of balloon platforms, the vertical measurements of soundings, and the mobility of aircraft the StratoCruiser will enable new understanding of stratospheric phenomenon. The focus of the proposed effort will be to enhance the StratoCruiser reel-down payload capability through size, weight, and/or power (SWaP) reduction in the dual laser, 50 cm cell, ICOS instrument. The soundings from the StratoCruiser ICOS-based observing system provide laboratory quality, in situ detection of radicals, isotopes, ozone, reactive intermediates, long-lived tracers and condensed and vapor phase H2O and HDO over the US for a period of 4-6 weeks.