Proposal Title: Active Tropospheric Ozone and Moisture Sounder (ATOMS)
ATOMS consists of low-cost microwave crosslinks at frequencies up to 200 GHz between pairs of low-orbiting spacecraft to perform active atmospheric limb-sounding. By observing signal absorption at selected frequencies we can measure the concentrations of ozone, water vapor, and possibly other species throughout the troposphere and into the stratosphere. Deployed on a constellation of low-cost "sensorcraft," ATOMS can deliver many thousands of atmospheric profiles each day with a vertical resolution well under 1 km, distributed evenly around the globe. By combining ATOMS with GPS occultation sensors, such a constellation will open an efficient new window on atmospheric chemistry and climate. Current technology for microwave crosslinks above 100 GHz is inadequate, lacking sufficient broadcast power and instrument efficiency, but this is expected to change as space-based telecommunications blossoms in the next few years. Here we propose a three-phased investigation to assess and demonstrate the ATOMS technique. A one-year Study Phase will survey the current state of and prospects for technology above 100 GHz and perform rigorous simulation and engineering studies to assess its technical feasibility, examine principal error sources and strategies for their calibration and removal, and assess its performance against alternative techniques. If justified, a one-year Development Phase will then design and build breadboard instruments and conduct laboratory tests. Finally, a one-year Demonstration Phase will conduct field demonstrations to further refine and validate the ATOMS technique and ready it for flight development.