Silvère Gousset, Juana M. Rodrigo, Etienne Le Coarer, Hélène Ehrhardt, Eric Stadler, Zoltán Hubert, Yves Magnard, Laurence Croizé, Yann Ferrec, Florence de la Barrière, Roland Domel, Christophe Coudrain, Remi Gouyon, Mathieu Chambon, Philippe Perrault, Jumana Boussey, Cécile Gourgon, Marie Panabière, Nadine Gerges
The Space CARBon Observatory (SCARBO) European program aims at assessing the monitoring of anthropogenic emissions of Green House Gas (GHG) with the uncovered goal of a sub-daily revisit of the Earth at an affordable cost. One of the main project scopes is the feasibility study of a hybrid constellation including both high accuracy reference missions (Copernicus CO2M or CNES MicroCarb mission) and 24 small-satellites onboarding innovative miniaturized payloads. The key GHG-sensor of the smallsat constellation is the NanoCarb concept, an unprecedently kilogram-class Fourier Transform imaging spectrometer. We are reporting here some preliminary experimental results from a demonstration airborne campaign. A low cost, 2-bands prototype designed for CO2 and CH4 measurement has been developed then integrated over a Falcon-20 from SAFIRE, jointly to SPEX aerosol sensor from SRON. During October 2020, we flew over Spain, Italy, and towards Poland from Francazal airport in Toulouse, France. Even if we did not have the opportunity to flight over a powerplant, a lot of data has been acquired and are being processed. After presented the instrument, mission and data products, we assess the data quality and the reliability of the model. We derive finally an expected sensitivity over CO2 and CH4 columns according to the background respectively about 1.5-2.5% and 5%. We finally demonstrate the operability of this first TRL5 prototype of NanoCarb.
KEYWORDS: Fiber lasers, Target detection, Turbulence, Laser development, Signal detection, Signal analyzers, Near field optics, Near field, Laser beam propagation, Fiber amplifiers
Coherent beam combining (CBC) by active phase control is an efficient way to power scale fiber amplifiers. Most often, CBC operates from measuring the phase differences between the lasers at their outputs, hence resulting in efficient combination of the laser beams in the very near-field. We developed a laser testbed coherently combining seven 1.5-µm fiber lasers through active phase control, using frequency-tagging to assess the phase fluctuations to be compensated for. The testbed can operate in a target-in-the-loop (TIL) configuration, with a detection sub-system designed to analyse the optical signal back-scattered by a remote target, in order to achieve coherent combining on the target rather than at the output of the lasers. In this paper, we present the testbed and its components, as well as the results obtained in direct coherent combining, operated at the output of the lasers, during the preliminary tests of the setup. Then, we present the results of the outdoor experimental campaign where the testbed is operated in a TIL-CBC configuration. Measurement of TIL-CBC efficiency when distance to the target is progressively increased from 15 meters to 1 km is detailed. As the experimental campaign took place in hot weather, with a close to the ground horizontal path of propagation for the laser beams, very strong turbulence conditions were encountered. However, efficient atmospheric turbulence compensation was demonstrated, confirming that TIL-CBC can be achieved, even under such detrimental turbulence conditions.
Recent developments in unmanned aerial vehicles have increased the demand for more and more compact
optical systems. In order to bring solutions to this demand, several infrared systems are being developed at
ONERA such as spectrometers, imaging devices, multispectral and hyperspectral imaging systems. In the field
of compact infrared hyperspectral imaging devices, ONERA and Sagem Défense et Sécurité have collaborated
to develop a prototype called SIBI, which stands for "Spectro-Imageur Birefringent Infrarouge". It is a static
Fourier transform imaging spectrometer which operates in the mid-wavelength infrared spectral range and
uses a birefringent lateral shearing interferometer. Up to now, birefringent interferometers have not been
often used for hyperspectral imaging in the mid-infrared because of the lack of crystal manufacturers, contrary
to the visible spectral domain where the production of uniaxial crystals like calcite are mastered for various
optical applications. In the following, we will present the design and the realization of SIBI as well as the first
experimental results.
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