F. Laurent

The MUSE second-generation VLT instrument

Summary: The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph currently in manufacturing, assembly and integration phase. MUSE has a field of 1x1 arcmin2 sampled at 0.2x0.2 arcsec2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The instrument is a large assembly of 24 identical high performance integral field units, each one composed of an advanced image slicer, a spectrograph and a 4kx4k detector. In this paper we review the progress of the manufacturing and report the performance achieved with the first integral field unit.

Evaluation of the relaxant effects of SCA40, a novel charybdotoxin‐sensitive potassium channel opener, in guinea‐pig isolated trachealis

1 Experiments have been performed in order to analyse the mechanism whereby SCA40, a new imidazo[1,2‐α]pyrazine derivative relaxes airway smooth muscle. 2 SCA40 (0.01–10 μm) caused a complete and concentration‐dependent relaxation of guinea‐pig isolated trachea contracted with 20 mm KCl but failed to inhibit completely the spasmogenic effects of 80 mm KCl. 3 Quinine (30 μm) antagonized the relaxant activity of SCA40 in 20 mm KCl‐contracted guinea‐pig isolated trachea. The ATP‐sensitive K+‐channel blocker, glibenclamide (3 μm), did not antagonize the relaxant activity of SCA40 in either 20 mm KCl or 1 μm carbachol‐contracted isolated trachea. 4 SCA40 (0.01–10 μm) and isoprenaline (0.1 nm‐10 μm) caused a complete and concentration‐dependent relaxation of guinea‐pig isolated trachea contracted with carbachol 1 μm. 5 The large‐conductance Ca2+‐activated K+‐channel blocker, charybdotoxin (60–180 nm), non‐competitively antagonized the relaxant activity of isoprenaline on 1 μm carbachol‐contracted trachea. The inhibition was characterized by rightward shifts of the isoprenaline concentration‐relaxation curves with depression of their maxima. 6 The relaxant activity of SCA40 in 1 μm carbachol‐contracted trachea was antagonized by charybdotoxin (60–600 nm) in an apparently competitive manner. The concentration‐relaxation curves to SCA40 were shifted to the right with no significant alteration in the maximum response. 7 It is concluded that SCA40 is a novel potassium channel opener which is a potent relaxant of guinea‐pig airway smooth muscle in vitro. The relaxant activity of SCA40 does not involve ATP‐sensitive K+‐channels but rather large‐conductance Ca2+‐activated K+‐channels or other charybdotoxin‐sensitive K+‐channels.

Cardiovascular effects of SCA40, a novel potassium channel opener, in rats

1 Experiments have been performed to investigate the cardiovascular actions in the rat of SCA40, a novel potassium channel opener which is a potent relaxant of guinea‐pig airway smooth muscle in vivo and in vitro. 2 SCA40 (0.01–30 μm) caused a complete and concentration‐dependent relaxation of rat isolated thoracic aorta contracted with 20 mm KCl but failed to inhibit completely the spasmogenic effects of 80 mm KCl. 3 The ATP‐sensitive K+‐channel blocker, glibenclamide (3 μm), failed to antagonize the relaxant action of SCA40 on 20 mm KCl‐contracted rat isolated thoracic aorta. 4 SCA40 (0.001–100 μm) had dual effects on rat isolated atria. At low concentrations, SCA40 produced a concentration‐dependent decrease in the rate and force of contractions. At higher concentrations (greater than 1 μm) SCA40 induced concentration‐dependent increases of atrial rate and force. 5 In vivo, in normotensive Wistar rats, SCA40 elicited a dose‐dependent (1–100 μg kg−1) decrease in mean arterial pressure which was accompanied by a moderate dose‐dependent increase in heart rate. SCA40 (100 μg kg−1) had a slightly greater hypotensive effect than cromakalim (100 μg kg−1) but the duration of the hypotension was longer with cromakalim than with SCA40. 6 The hypotensive effect of SCA40 was not reduced by propranolol, atropine, NG‐nitro‐l‐arginine methyl ester (l‐NAME) or glibenclamide. 7 It is concluded that the mechanism by which SCA40 relaxes vascular smooth muscle in vitro and in vivo involves activation of K+‐channels distinct from glibenclamide‐sensitive ATP‐sensitive K+‐channels.

Optical design, fabrication, and testing a prototype of the NIRSpec IFU

A group of European Research Institutes (Centre de Recherche Astronomique de Lyon (CRAL), Laboratoire dAstrophysique de Marseille (LAM), University of Durham) and company (CYBERNETIX) have proposed to implement an Integral Field Unit (IFU) in NIRSpec instrument for the James Webb Space Telescope (JWST). After a brief presentation of the optical design of NIRSpec IFU, we will focus on the prototype of this module built by CRAL. This prototype is composed of two optical elements: a stack of eleven spherical tilted slices associated with a row of ten spherical tilted pupil mirrors. All the optical elements were manufactured by CYBERNETIX. We will introduce the fabrication procedures and an original method of assembling by molecular adhesion in order to comply with environment specifications. Afterwards, the image slicer is tested on the optical bench at CRAL. In fact, the first measure consists in placing a CCD camera in the pupil mirrors plane and determining the characteristics of the eleven images of the telescope pupil such as sizes, positions, photometric quality, diffraction effects and angular errors on slices and comparing these results with specifications. Then, the row of pupil mirrors is installed on the optical bench. In the slit mirrors plane, we observe a pseudo slit (ten images of the slices). We establish the same characteristics as in the first measure. Moreover, in the same plane, some Point Spread Function (PSF) measurements are made and we analyse the PSF in comparison with the simulation. The main results of the tests of the first image slicer prototype are presented. With the exploitation of the results, we validate and improve the image slicer systems for others instruments such as Multi Unit Spectroscopic Explorer (MUSE, study of a second generation instrument for the European Very Large Telescope (VLT)) and the European Space Agency (ESA) Integral Field Spectrograph (IFS) prototype.

Optical design, manufacturing, and tests of the MUSE image slicer

MUSE (Multi Unit Spectroscopic Explorer) is a second generation integral field spectrograph proposed to the European Southern Observatory (ESO) for the VLT. MUSE combines a 1 x 1 Field of View (FoV) with a spectral resolution going to 3000 and a spatial resolution of 0.2 provided by the GALACSI adaptive optics system. MUSE is operating in the visible and near IR wavelength range (0.465-0.93 μm). It is composed of 24 identical integral field units; each one incorporates an advanced image slicer made of a combination of mirrors and mini-lenses arrays. During the feasibility study, a slicer prototype has been designed, manufactured and tested. This paper firstly describes an original approach for the slicer optical design and manufacturing. Then, we will focus on the optical tests of the prototype. These tests included the control of the angular tilts and assembling method of the slicer, the measurements of the position, size and shape of the pseudo-slits, the measurements of the Point Spread Function (PSF) for the slice-slit imagery on the whole FoV and an estimation of the size of the global exit pupil. We finally conclude on the feasibility of MUSE image slicer and its possible improvement for the next design phase.

The calibration unit and detector system tests for MUSE

The Multi-Unit Spectroscopic Explorer (MUSE) is an integral-field spectrograph for the ESO Very Large Telescope. After completion of the Final Design Review in 2009, MUSE is now in its manufacture and assembly phase. To achieve a relative large field-of-view with fine spatial sampling, MUSE features 24 identical spectrograph-detector units. The acceptance tests of the detector sub-systems, the design and manufacture of the calibration unit and the development of the Data Reduction Software for MUSE are under the responsibility of the AIP. The optical design of the spectrograph implies strict tolerances on the alignment of the detector systems to minimize aberrations. As part of the acceptance testing, all 24 detector systems, developed by ESO, are mounted to a MUSE reference spectrograph, which is illuminated by a set of precision pinholes. Thus the best focus is determined and the image quality of the spectrograph-detector subsystem across wavelength and field angle is measured.

MUSE instrument global performance test

MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument developed for ESO (European Southern Observatory) and will be assembled to the VLT (Very Large Telescope) in 2013. The MUSE instrument can simultaneously record 90.000 spectra in the visible wavelength range (465-930nm), across a 1*1arcmin² field of view, thanks to 24 identical Integral Field Units (IFU). A collaboration of 7 institutes has partly validated and sent their subsystems to CRAL (Centre de Recherche Astrophysique de Lyon) in 2011, where they have been assembled together. The global test and validation process is currently going on to reach the Preliminary Acceptance in Europe in 2012. The sharing of performances has been based on 5 main functional sub-systems. The Fore Optics sub-system derotates and anamorphoses the VLT Nasmyth focal plane image, the Splitting and Relay Optics associated with the Main Structure are feeding each IFU with 1/24th of the field of view. Each IFU is composed of a 3D function insured by an image slicer system and a spectrograph, and a detection function by a 4k*4k CCD cooled down to 163°K. The 5th function is the calibration and data reduction of the instrument. This article depicts the sequence of tests that has been completely reshafled mainly due to planning constraints. It highlights the priority given to the most critical performances tests of the sub-systems and their results. It enhances then the importance given to global tests. Finally, it makes a status on the verification matrix and the validation of the instrument and gives a critical view on the risks taken.

MUSE Optical Alignment Procedure

MUSE (Multi Unit Spectroscopic Explorer) is a second generation VLT integral field spectrograph (1x1arcmin² Field of View) developed for the European Southern Observatory (ESO), operating in the visible wavelength range (0.465-0.93 μm). A consortium of seven institutes is currently assembling and testing MUSE in the Integration Hall of the Observatoire de Lyon for the Preliminary Acceptance in Europe, scheduled for 2013. MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units (IFU), that are mounted within a large monolithic instrument mechanical structure. Each IFU incorporates an image slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and cryogenic system. During 2011, all MUSE subsystems were integrated, aligned and tested independently in each institute. After validations, the systems were shipped to the P.I. institute at Lyon and were assembled in the Integration Hall This paper describes the end-to-end optical alignment procedure of the MUSE instrument. The design strategy, mixing an optical alignment by manufacturing (plug and play approach) and few adjustments on key components, is presented. We depict the alignment method for identifying the optical axis using several references located in pupil and image planes. All tools required to perform the global alignment between each subsystem are described. The success of this alignment approach is demonstrated by the good results for the MUSE image quality. MUSE commissioning at the VLT (Very Large Telescope) is planned for 2013.

Characterization of Low Affinity Complexes Between Calmodulin and Pyrazine Derivatives by Electrospray Ionization Mass Spectrometry

Electrospray ionization mass spectrometry (ESIMS) was used to study the weak non-covalent interactions occurring between 6-bromo-3-(hydroxymethyl)-8-(methylamino)imidazo [1,2-a]pyrazine (1) and calmodulin. The formation of a 2:1 (ligand: protein) complex was observed. Using 2, a (diazomethyl)carbonyl derivative of 1 which under UV irradiation generates a highly reactive carbene entity, calmodulin was photo-labeled and the mass spectrum of the covalent adduct was recorded. Under these circumstances, two species were detected, one corresponding to the binding of calmodulin to four carbenes derived from 2 and another corresponding to calmodulin five carbenes after their loss of a bromine atom. These results strongly confirm that ESIMS is a powerful technique for the characterization of low-affinity complexes, even if part of the noncovalent interactions could be lost during the ESI process.

The MUSE project face to face with reality

MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument built for ESO (European Southern Observatory) to be installed in Chile on the VLT (Very Large Telescope). The MUSE project is supported by a European consortium of 7 institutes. After the critical turning point of shifting from the design to the manufacturing phase, the MUSE project has now completed the realization of its different sub-systems and should finalize its global integration and test in Europe. To arrive to this point many challenges had to be overcome, many technical difficulties, non compliances or procurements delays which seemed at the time overwhelming. Now is the time to face the results of our organization, of our strategy, of our choices. Now is the time to face the reality of the MUSE instrument. During the design phase a plan was provided by the project management in order to achieve the realization of the MUSE instrument in specification, time and cost. This critical moment in the project life when the instrument takes shape and reality is the opportunity to look not only at the outcome but also to see how well we followed the original plan, what had to be changed or adapted and what should have been.