We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs ($R = \lambda/\Delta\lambda \sim 6500$), and 812 fibres transferring light to the high-resolution spectrograph ($R \sim 20\,000$). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations.

MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument, built for ESO (European Southern Observatory) and dedicated to the VLT (Very Large Telescope). This instrument is an innovative integral field spectrograph (1x1 arcmin(2) Field of View), operating in the visible wavelength range, from 465 nm to 930 nm. The MUSE project is supported by a European consortium of 7 institutes.After the finalisation of its integration and test in Europe validated by its Preliminary Acceptance in Europe, the MUSE instrument has been partially dismounted and shipped to the VLT (Very Large Telescope) in Chile. From October 2013 till February 2014, it has then been reassembled, tested and finally installed on the telescope its final home. From there it will collect its first photons coming from the outer limit of the visible universe.To come to this achievement, many tasks had to be completed and challenges overcome. These last steps in the project life have certainly been ones of the most critical. Critical in terms of risk, of working conditions, of operational constrains, of schedule and finally critical in terms of outcome: The first light and the final performances of the instrument on the sky.

MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument built for ESO (European Southern Observatory). The MUSE project is supported by a European consortium of 7 institutes. After the finalisation of its integration in Europe, the MUSE instrument has been partially dismounted and shipped to the VLT (Very Large Telescope) in Chile. From October 2013 till February 2014, it has then been reassembled, tested and finally installed on the telescope its final home. From there it collects its first photons coming from the outer limit of the visible universe. This critical moment when the instrument finally meets its destiny is the opportunity to look at the overall outcome of the project and the final performance of the instrument on the sky. The instrument which we dreamt of has become reality. Are the dreamt performances there as well? These final instrumental performances are the result of a step by step process of design, manufacturing, assembly, test and integration. Now is also time to review the path opened by the MUSE project. What challenges were faced during those last steps, what strategy, what choices did pay off? What did not?

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*1arcmin(2) 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 degrees 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 (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.

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.

MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument developed for ESO (European Southern Observatory) to be installed on the VLT (Very Large Telescope) in year 2012. The MUSE project is supported by a European consortium of 7 institutes. After a successful Final Design Review the project is now facing a turning point which consist in shifting from design to manufacturing, from calculation to test, ... from dream to reality. At the start, many technical and management challenges were there as well as unknowns. They could all be derived of the same simple question: How to deal with complexity? The complexity of the instrument, of the work to de done, of the organization, of the interfaces, of financial and procurement rules, etc. This particular moment in the project life cycle is the opportunity to look back and evaluate the management methods implemented during the design phase regarding this original question. What are the lessons learn? What has been successful? What could have been done differently? Finally, we will look forward and review the main challenges of the MAIT (Manufacturing Assembly Integration and Test) phase which has just started as well as the associated new processes and evolutions needed.

The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation instrument in development for the Very Large Telescope (VLT) of the European Southern Observatory (ESO), due to begin operation in 2011/12. MUSE will be an extremely powerful integral-field spectrograph fed by a new multiple-laser adaptive optics system on the VLT. In its usual operating mode, MUSE will, in a single observation, produce a 3-dimensional data cube consisting of 90,000 R 3000 spectra, each covering a full spectral octave (480–930 nm), and fully sampling a contiguous 1×1 arcmin2 field with 0.2×0.2 arcsec2 apertures. A high-resolution mode will increase the spatial sampling to 0.025 arcsec per pixel. MUSE is built around a novel arrangement of 24 identical spectrographs (each comparable to a 1st generation VLT instrument), which are fed by a set of 24 precision image slicers. MUSE is designed for stability, with only 2 modes, and virtually no moving parts, allowing very long exposures to be accumulated. Together with high throughput, this ensures that MUSE will have extreme sensitivity for observing faint objects. We overview the technical and scientific aspects of MUSE, highlighting the key challenges for dealing with the unprecedented quantity and complexity of the data, and the integration with the VLT adaptive optics facility (AOF) – a key development on the path to extremely large telescopes (ELTs).

The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph under preliminary design study. MUSE has a field of 1x1 arcmin**2 sampled at 0.2x0.2 arcsec**2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The simultaneous spectral range is 465-930 nm, at a resolution of R 3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5x7.5 arcsec**2 field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to obtain diffraction limited data-cubes in the 600-930 nm wavelength range. Although the MUSE design has been optimized for the study of galaxy formation and evolution, it has a wide range of possible applications; e.g. monitoring of outer planets atmosphere, environment of young stellar objects, super massive black holes and active nuclei in nearby galaxies or massive spectroscopic surveys of stellar fields in the Milky Way and nearby galaxies.

We describe MUSE (Multi Unit Spectroscopic Explorer), a second-generation integral-field spectrograph for the VLT, operating in the visible and near IR wavelength range. It combines a 1' x 1' Field of View with the improved spatial resolution (0.2") provided by adaptive optics and covers a large simultaneous spectral range (0.48 - 1 μm). With this unique combination of capabilities, MUSE has a wide domain of application, and a large discovery potential. It will provide ultra deep fields with a limiting magnitude for spectroscopy of R = 28. After a brief presentation of the scientific case and the derived instrument requirements, we will focus on the MUSE optical design, including the overall architecture, the major trade-off that were conducted in order to optimize the cost and performance, and a provisional implementation scheme of the instrument on the VLT Nasmyth platform. Then the most important optical subsystems (as the 3 x 8 Field-splitter, the Image Slicers and the Spectrometers) are described. One of MUSE special feature is the impressive number of Image Slicer and Spectrometer modules which must be manufactured, that is 24. The realization of such series has been studied in collaboration with an industrial company. Finally a preliminary estimation of the expected performance and a technological development program in order to secure the realization of the critical optical subsystems will be presented.