Development and use of compact instruments for tropospheric investigations based on optical spectroscopy from mobile platforms

This thesis presents the development of four different remote-sensing instruments dedicated to atmospheric research and their use in field campaigns between 2008 and 2012. The instruments are based on uv-visible spectrometers and installed respectively on a scientific aircraft (Safire ATR-42), ultralight aircraft, and cars. One of the instruments is targeted to operate from an Unmanned Aerial Vehicle (UAV). The Differential Optical Absorption Spectroscopy (DOAS) technique is used to quantify the molecular absorption in the spectra of scattered sky light. These absorptions are then interpreted by modeling the radiative transfer in the atmosphere. Depending on the instrument, different information on trace gases and aerosols are retrieved: vertical distributions, tropospheric columns, or maps of surface abundances. Airborne platforms enable new measurement geometries, leading for instance to a high sensitivity in the free troposphere. On the other hand, a miniaturization effort is required, especially for the instruments on board ultralight aircraft and UAV. Reaching the limited size, weight, and power consumption is possible through the use of compact spectrometers and computers, together with custom built electronics circuits and housings. The inversion strategies are optimized for each instrument with proper error budgets and the results are compared with other datasets when available. In April 2008, the Airborne Limb Scanning DOAS (ALS-DOAS) was first used on the ATR-42 to derive NO2 and aerosol extinction profiles during the POLar study using Aircraft, Remote sensing, surface measurements and models, of Climate chemistry, Aerosols and Transport (POLARCAT). It revealed in particular that NO2, despite its typical lifetime of a few hours, may be transported from mid-latitude Europe to the Arctic. This is not visible in satellite data since the involved concentrations are under the detection limit. The Ultralight Motorized-DOAS (ULM-DOAS) was operated during the Eart
(PHYS 3) -- UCL, 2013