Building a reliable, scalable and affordable RTC for AO instruments on ELTs

International audienc

Building a reliable, scalable and affordable RTC for AO instruments on ELTs

International audienc

GPUs for adaptive optics: simulations and real-time control

International audienceWith the emergence of General Purpose computations on Graphic Processing Units (GP-GPUs) this architecture has become amazingly attractive for large scale applications such as numerical simulations of complex systems. While the number of degrees of freedom of an adaptive optics (AO) system scales with the square of the telescope diameter, the system model exhibits a rather high level of parallelism especially when simulating Shack-Hartmann (SH) wavefront sensors (WFS). The use of massively parallel devices such as GPUs to simulate next generation AO systems for the European Extremely Large Telescope (E-ELT) thus makes a lot of sense. Our team has developed such simulation tools and first results show that speeds of about a thousand of iterations per second were achievable on a single high-end GPU for an eXtreme (X)AO system such as SPHERE including a single layer turbulence model generated on-the-fly. These numerical models include all the operations executed by the real-time controller (RTC) of a real system. The achieved simulation speeds show that a single high-end GPU could drive a XAO system on the VLT and, depending on the centroiding algorithm and the control scheme chosen, could even drive a classical AO system on the E-ELT. While the main challenge resides in the data transfer speed to and from the GPU, developing and testing AO control algorithms for the simulation code on the same hardware as the system RTC would bring a lot of benefits. In this paper we present the simulation results as well as strategies to build GPU-powered AO systems

Building a reliable, scalable and affordable RTC for AO instruments on ELTs

International audienc

Pushing Raman spectroscopy over the edge: purported signatures of organic molecules in fossil animals are instrumental artefacts

International audienceWidespread preservation of fossilized biomolecules in many fossil animals has recently been reported in six studies, based on Raman microspectroscopy. Here, we show that the putative Raman signatures of organic compounds in these fossils are actually instrumental artefacts resulting from intense background luminescence. Raman spectroscopy is based on the detection of photons scattered inelastically by matter upon its interaction with a laser beam. For many natural materials, this interaction also generates a luminescence signal that is often orders of magnitude more intense than the light produced by Raman scattering. Such luminescence, coupled with the transmission properties of the spectrometer, induced quasi-periodic ripples in the measured spectra that have been incorrectly interpreted as Raman signatures of organic molecules. Although several analytical strategies have been developed to overcome this common issue, Raman microspectroscopy as used in the studies questioned here cannot be used to identify fossil biomolecules

Pushing Raman spectroscopy over the edge: purported signatures of organic molecules in fossil animals are instrumental artefacts

International audienceWidespread preservation of fossilized biomolecules in many fossil animals has recently been reported in six studies, based on Raman microspectroscopy. Here, we show that the putative Raman signatures of organic compounds in these fossils are actually instrumental artefacts resulting from intense background luminescence. Raman spectroscopy is based on the detection of photons scattered inelastically by matter upon its interaction with a laser beam. For many natural materials, this interaction also generates a luminescence signal that is often orders of magnitude more intense than the light produced by Raman scattering. Such luminescence, coupled with the transmission properties of the spectrometer, induced quasi-periodic ripples in the measured spectra that have been incorrectly interpreted as Raman signatures of organic molecules. Although several analytical strategies have been developed to overcome this common issue, Raman microspectroscopy as used in the studies questioned here cannot be used to identify fossil biomolecules

TERS characterization of Functionnalied Gold nanostructure for improved Biosensors

International audienc