LOCUS: low cost upper atmosphere sounder

We present the results of an instrument concept study for a low cost terahertz sounder of the mesosphere and lower thermosphere (MLT). Recent advances in the development of Quantum Cascade Laser (QCL) technology to be used for Local Oscillators (LOs) mean that it has now become viable for the first time to build compact, low weight heterodyne receivers in the terahertz (THz) frequency range [28]. Some of the most important atmospheric constituents of the MLT region, e.g. atomic oxygen (O) and the hydroxyl radical (OH), can only realistically be measured at THz frequencies. The technical challenges of THz remote sensing result in a large uncertainly of the global distribution of these species. Recent research indicates that the MLT region exhibits links to processes associated with climate change. From this follows a strong need to measure the composition and dynamic of the MLT region more accurately and more comprehensively.