The mid-infrared spectral region (2-20µm) contains the characteristic vibrational transitions of important atmospheric gases (H2O, N2O, CO2, NF3, CH4, O3…). Moreover, in this range there are two atmospheric transparency windows at 3-5µm and 8-13µm and therefore a light beam can propagate over very long distances and investigate the atmosphere remotely. Furthermore, mid-infrared radiation has a lower sensitivity to atmospheric turbulence than at telecoms wavelengths. This is crucial to have accurate, precise and very sensitive measurements for environmental sensing, spectrometry and greenhouse gases (GHG) monitoring. The objective of our proposal is to provide an accurate and compact mid-infrared solar occultation heterodyne radiometry and LIDAR systems. They will employ quantum cascade laser as a source, while the room temperature ultrafast quantum well detectors recently developed at LPENS will be a key advantage in our systems.