Carine Morel

First characterization of the gene RGD1 in the yeast Saccharomyces cerevisiae

We identified the ORF YBR260c during systematic sequencing of one region of chromosome II of Saccharomyces cerevisiae. This ORF encodes a putative protein of 666 aa, of which the C-terminal part of the deduced amino acid sequence resembles human and yeast Rho/Rac GTPase activating proteins (GAP). An initial study is reported in the paper. This gene was expressed in haploid and diploid cells and was called RGD1 for related GAP domain 1. Inactivation of RGD1 was carried out and phenotypic analysis of the mutant strain revealed only a slight viability defect when cells grown in minimal medium were close to stationary phase. Northern and western analyses showed that the RGD1 transcript and the corresponding protein were still abundant in cells cultivated in YNB during the stationary phase. No functional link seems to exist with the highly conserved GTPase Cdc42 involved in cytoskeletal polarization and cell polarity.

Experience with wavefront sensor and deformable mirror interfaces for wide-field adaptive optics systems

Recent advances in adaptive optics (AO) have led to the implementation of wide field-of-view AO systems. A number of wide-field AO systems are also planned for the forthcoming Extremely Large Telescopes. Such systems have multiple wavefront sensors of different types, and usually multiple deformable mirrors (DMs). Here, we report on our experience integrating cameras and DMs with the real-time control systems of two wide-field AO systems. These are CANARY, which has been operating on-sky since 2010, and DRAGON, which is a laboratory AO real-time demonstrator instrument. We detail the issues and difficulties that arose, along with the solutions we developed. We also provide recommendations for consideration when developing future wide-field AO systems.

RGD1 genetically interacts with MID2 and SLG1, encoding two putative sensors for cell integrity signalling in Saccharomyces cerevisiae.

The RGD1 gene was identified during systematic genome sequencing of Saccharomyces cerevisiae. To further understand Rgd1p function, we set up a synthetic lethal screen for genes interacting with RGD1. Study of one lethal mutant made it possible to identify the SLG1 and MID2 genes. The gene SLG1/HCS77/WSC1 was mutated in the original synthetic lethal strain, whereas MID2/SMS1 acted as a monocopy suppressor. The SLG1 gene has been described to be an upstream component in the yeast PKC pathway and encodes a putative cell surface sensor for the activation of cell integrity signalling. First identified by viability loss of shmoos after pheromone exposure, and since found in different genetic screens, MID2 was recently reported as also encoding an upstream activator of the PKC pathway. The RGD1 gene showed genetic interactions with both sensors of cell integrity pathway. The rgd1 slg1 synthetic lethality was rescued by osmotic stabilization, as expected for mutants altered in cell wall integrity. The slight viability defect of rgd1 in minimal medium, which was exacerbated by mid2, was not osmoremediated. As for mutants altered in PKC pathway, the accumulation of small‐budded dead cells in slg1, rgd1 and mid2 after heat shock was prevented by 1 M sorbitol. In addition, the rgd1 strain also displayed dead shmoos after pheromone treatment, like mid2. Taken together, the present results indicate close functional links between RGD1, MID2 and SLG1 and suggest that RGD1 and MID2 interact in a cell integrity signalling functionally linked to the PKC pathway. Copyright

Pipelining computational stages of the tomographic reconstructor for multi-object adaptive optics on a multi-GPU system

The European Extremely Large Telescope project (E-ELT) is one of Europes highest priorities in ground-based astronomy. ELTs are built on top of a variety of highly sensitive and critical astronomical instruments. In particular, a new instrument called MOSAIC has been proposed to perform multi-object spectroscopy using the Multi-Object Adaptive Optics (MOAO) technique. The core implementation of the simulation lies in the intensive computation of a tomographic reconstruct or (TR), which is used to drive the deformable mirror in real time from the measurements. A new numerical algorithm is proposed (1) to capture the actual experimental noise and (2) to substantially speed up previous implementations by exposing more concurrency, while reducing the number of floating-point operations. Based on the Matrices Over Runtime System at Exascale numerical library (MORSE), a dynamic scheduler drives all computational stages of the tomographic reconstruct or simulation and allows to pipeline and to run tasks out-of order across different stages on heterogeneous systems, while ensuring data coherency and dependencies. The proposed TR simulation outperforms asymptotically previous state-of-the-art implementations up to 13-fold speedup. At more than 50000 unknowns, this appears to be the largest-scale AO problem submitted to computation, to date, and opens new research directions for extreme scale AO simulations.

A novel fast and accurate pseudo-analytical simulation approach for MOAO

Multi-object adaptive optics (MOAO) is a novel adaptive optics (AO) technique for wide-field multi-object spectrographs (MOS). MOAO aims at applying dedicated wavefront corrections to numerous separated tiny patches spread over a large field of view (FOV), limited only by that of the telescope. The control of each deformable mirror (DM) is done individually using a tomographic reconstruction of the phase based on measurements from a number of wavefront sensors (WFS) pointing at natural and artificial guide stars in the field. We have developed a novel hybrid, pseudo-analytical simulation scheme, somewhere in between the end-to- end and purely analytical approaches, that allows us to simulate in detail the tomographic problem as well as noise and aliasing with a high fidelity, and including fitting and bandwidth errors thanks to a Fourier-based code. Our tomographic approach is based on the computation of the minimum mean square error (MMSE) reconstructor, from which we derive numerically the covariance matrix of the tomographic error, including aliasing and propagated noise. We are then able to simulate the point-spread function (PSF) associated to this covariance matrix of the residuals, like in PSF reconstruction algorithms. The advantage of our approach is that we compute the same tomographic reconstructor that would be computed when operating the real instrument, so that our developments open the way for a future on-sky implementation of the tomographic control, plus the joint PSF and performance estimation. The main challenge resides in the computation of the tomographic reconstructor which involves the inversion of a large matrix (typically 40 000 × 40 000 elements). To perform this computation efficiently, we chose an optimized approach based on the use of GPUs as accelerators and using an optimized linear algebra library: MORSE providing a significant speedup against standard CPU oriented libraries such as Intel MKL. Because the covariance matrix is symmetric, several optimization schemes can be envisioned to speedup even further the computation. Optimizing the speed of the reconstructor computation is of major interest not only for the design study of MOAO instruments, but also for future routine operations of the system as the reconstructor has to be updated regularly to cope for atmospheric variability.

Phase A AO system design and performance for MOSAIC at the ELT

MOSAIC is a mixed-mode multiple object spectrograph planned for the ELT that uses a tiled focal plane to support a variety of observing modes. The MOSAIC AO system uses 4 LGS WFS and up to 4 NGS WFS positioned anywhere within the full 10 arcminute ELT field of view to control either the ELT M4/5 alone for GLAO operation feeding up to 200 targets in the focal plane, or M4/5 in conjunction with 10 open-loop DMs for MOAO correction. In this paper we present the overall design and performance of the MOSAIC GLAO and MOAO systems.

Turbulence profiling for adaptive optics tomographic reconstructors

To approach optimal performance advanced Adaptive Optics (AO) systems deployed on ground-based telescopes must have accurate knowledge of atmospheric turbulence as a function of altitude. Stereo-SCIDAR is a high-resolution stereoscopic instrument dedicated to this measure. Here, its profiles are directly compared to internal AO telemetry atmospheric profiling techniques for CANARY (Vidal et al. 20141), a Multi-Object AO (MOAO) pathfinder on the William Herschel Telescope (WHT), La Palma. In total twenty datasets are analysed across July and October of 2014. Levenberg-Marquardt fitting algorithms dubbed Direct Fitting and Learn 2 Step (L2S; Martin 20142) are used in the recovery of profile information via covariance matrices - respectively attaining average Pearson product-moment correlation coefficients with stereo-SCIDAR of 0.2 and 0.74. By excluding the measure of covariance between orthogonal Wavefront Sensor (WFS) slopes these results have revised values of 0.65 and 0.2. A data analysis technique that combines L2S and SLODAR is subsequently introduced that achieves a correlation coefficient of 0.76.

Adaptive optics for MOSAIC: design and performance of the wide(st)-field AO system for the E-ELT

MOSAIC is the proposed multiple-object spectrograph for the E-ELT that will utilise the widest possible field of view provided by the telescope. In terms of adaptive optics, there are two distinct operating modes required to meet the top-level science requirements. The MOSAIC High Multiplex Mode (HMM) requires either seeing-limited or GLAO correction within a 0.6 (NIR) and 0.9 (VIS) arcsecond sub-fields over the widest possible field for a few hundred objects. To achieve seeing limited operation whilst maintaining the maximum unvignetted field of view for scientific observation will require recreating some of the functionality present in the Pre-Focal Station relating to control of the E-ELT active optics. MOSAIC High Definition Mode Control (HDM) requires a 25% Ensquared Energy (EE) within 150mas in the H-band element for approximately 10 targets distributed across the full E-ELT field, implying the use of Multiple Object AO (MOAO). Initial studies have shown that to meet the EE requirements whilst maintaining high-sky coverage will require the combination of wavefront signals from both high-order NGS and LGS to provide a tomographic estimate for the correction to be applied to the open-loop MOAO DMs. In this paper we present the current MOSAIC AO design and provide the first performance estimates for the baseline instrument design. We then report on the various trade-offs that will be investigated throughout the course of the Phase A study, such as the requirement to mix NGS and LGS signals tomographically. Finally, we discuss how these will impact the AO architecture, the MOSAIC design and ultimately the scientific performance of this wide-field workhorse instrument at the E-ELT.

Pseudo-analytic simulation of woofer-tweeter MOAO system: application to MOSAIC

MOSAIC is the MOAO-assisted multi-object spectrograph of the European ELT (E-ELT) under Phase A study. In order to maximise the ensquared energy, each of its near-infrared MOAO channels has is own deformable mirror to supplement the build-in E-ELT deformable mirror M4. This secondary DM uses a tomographic reconstructor optimized for the direction of the target, that comes as a complement to the M4 global ground layer correction. We had described in previous work a simulation scheme that allows us to assess the performance of a E-ELT scaled MOAO instrument. In this article, we will show how we have modified this previous single DM simulation to the 2-DM case through two different ways of computing the tomographic error. We compare the performances and the computation time of each method. Finally we present the application of our simulation tool to the MOSAIC case.

Validation of tomographic laser guide star uplink tip-tilt determination with CANARY

Laser Guide Stars (LGS) have greatly increased the sky-coverage of Adaptive Optics (AO) systems. Due to the up-link turbulence experienced by LGSs, a Natural Guide Star (NGS) is still required, limiting sky-coverage. A method has recently been presented that promises to determine the LGS uplink tip-tilt in tomographic LGS AO systems by using the fact that each LGS Wave Front Sensor (WFS) in a tomographic AO system observes the uplink path of other LGSs. Such a technique has the potential to greatly increase the sky-coverage of Multi- Object, Laser Tomographic and Multi-Conjugate AO systems by allowed further off-axis NGS tip-tilt stars to be used for correction. Here we use an approach based on phase gradient covariance matrices to create on-sky capable tomographic reconstructors that account for some tip-tilt from LGS WFSs. We present analysis of open loop wave front sensor data from the CANARY Multi-Object AO demonstrator, providing early validation for the technique.