Design and performance of a diode laser spectrometer for a stratospheric aircraft

We report the instrument description and the results of the laboratory calibration and tests of a mid-infrared tunable diode spectrometer for in situ trace gas concentration measurements in the stratosphere operating on a stratospheric aircraft. The spectrometer is dedicated to the measurement of the HNO3 amount in the stratospheric aerosols by means of gas-phase absorption spectroscopy on molecular roto-vibrational lines in the mid-infrared, using a tunable diode laser and a multipass absorption cell. The instrument was specifically designed for operation aboard of the stratospheric aircraft M55 Geophysica, in the frame of the Airborne Platform for Earth observation (APE) project. The instrument is part of a measurement package for the measurement of the chemical content of Polar Stratospheric Clouds (PSCs) and other atmospheric aerosols. This system can be also used as a stand-alone detector of molecular trace gases. Design criteria include an efficient optical layout, with a very low sensitivity to the vibration and thermal stresses and a very small footprint, and a detection scheme based on the sweep integration technique for fast data acquisition and high signal-to-noise (S/N) ratio. We report a new set of testing measurements on ammonia as the calibration gas with one order of magnitude improvement with respect to what we previously reported

Design and performance of a diode laser spectrometer for a stratospheric aircraft

We report the instrument description and the results of the laboratory calibration and tests of a mid-infrared tunable diode spectrometer for in situ trace gas concentration measurements in the stratosphere operating on a stratospheric aircraft. The spectrometer is dedicated to the measurement of the HNO3 amount in the stratospheric aerosols by means of gas-phase absorption spectroscopy on molecular roto-vibrational lines in the mid-infrared, using a tunable diode laser and a multipass absorption cell. The instrument was specifically designed for operation aboard of the stratospheric aircraft M55 Geophysica, in the frame of the Airborne Platform for Earth observation (APE) project. The instrument is part of a measurement package for the measurement of the chemical content of Polar Stratospheric Clouds (PSCs) and other atmospheric aerosols. This system can be also used as a stand-alone detector of molecular trace gases. Design criteria include an efficient optical layout, with a very low sensitivity to the vibration and thermal stresses and a very small footprint, and a detection scheme based on the sweep integration technique for fast data acquisition and high signal-to-noise (S/N) ratio. We report a new set of testing measurements on ammonia as the calibration gas with one order of magnitude improvement with respect to what we previously reported

Fluorescence explorer (FLEX): An optimised payload to map vegetation photosynthesis from space

The FLuorescence EXplorer (FLEX) mission proposes to launch a satellite for the global monitoring of steady-state chlorophyll fluorescence in terrestrial vegetation. Fluorescence is a sensitive probe of photosynthetic function in both healthy and physiologically perturbed vegetation, and a powerful non-invasive tool to track the status, resilience, and recovery of photochemical processes and moreover provides important information on overall photosynthetic performance with implications for related carbon sequestration. The early responsiveness of fluorescence to atmospheric, soil and plant water balance, as well as to atmospheric chemistry and human intervention in land usage makes it an obvious biological indicator in improving our understanding of Earth system dynamics. The amenability of fluorescence to remote, even space-basedobservation qualifies it to join the emerging suite of space-based technologies for Earth observation. FLEX would encompass a three-instrument array for measurement of the interrelated features of fluorescence, hyperspectral reflectance, and canopy temperature. FLEX would involve a space and ground-truthing program of 3-years duration and would provide data formats for research and applied science