June 18, 2018

Strateole-2: Pico-SDLA, a new story for a balloon instrument

Pico-SDLA is one of the instruments that has the highest number of flights under open stratospheric balloons. In January 2019, "to celebrate" the 20 years of this family of instruments, a new mission will begin: the adventure of long-term flights!

As a successor to the SDLA-LAMA instrument developed in the late 1990s, Pico-SDLA has participated in all the recent balloon campaigns organised by CNES as part of the "climate" flights.

Pico-SDLA is a tunable laser diode spectrometer developed jointly by the CNRS Molecular and Atmospheric Spectroscopy Group and the Technical Division of INSU, under the responsibility of Georges Durry and Nadir Amarouche.

Working in the near infrared (2.6 μm), the instrument is able to determine the concentration of greenhouse gases in the atmosphere by measuring the extinction of the light signal emitted by laser diodes along an optical path about 1 m. A bi-gas version of the instrument (water vapour and carbon dioxide) has been specially developed for Strateole 2.

The main technological challenge in this long-term version of the pico-SDLA instrument was to comply with the drastic constraints of onboard mass and available energy imposed by long-term flights.

Therefore, the open optical cell which constitutes the critical part of the instrument was designed in carbon fibre. The cell is suspended at approximately 3 m under the Zephyr payload gondola. A special effort also focused on the thermal insulation of the laser diodes located at the end of the cell, and exposed to the air temperature (which can reach -80 °C) but requiring to be thermostated around 0 °C to work properly!


  • Philippe Cocquerez, Strateole-2 Project Manager
  • Georges Durry, Pico-SDLA Head Scientist (georges.durry at univ-reims.fr)
  • Nadir Amarouche, Pico-SDLA Project Manager (nadir.amarouche at cnrs.fr)
  • Albert Hertzog, Strateole 2 Head Scientist

Fabien Frérot (on the right) and Nadir Amarouche (on the left) - DT-INSU finalise the integration of the Pico-SDLA electronics. Credits: LMD Ecole Polytechnique