This paper introduces the science software of HARMONI. The Instrument Numerical Model simulates the instrument from the optical point of view and provides synthetic exposures simulating detector readouts from data-cubes containing astrophysical scenes. The Data Reduction Software converts raw-data frames into a fully calibrated, scientifically usable data cube. We present the functionalities and the preliminary design of this software, describe some of the methods and algorithms used and highlight the challenges that we will have to face.
HARMONI is the E-ELT’s first light visible and near-infrared integral field spectrograph. It will provide four different spatial scales, ranging from coarse spaxels of 60 × 30 mas best suited for seeing limited observations, to 4 mas spaxels that Nyquist sample the diffraction limited point spread function of the E-ELT at near-infrared wavelengths. Each spaxel scale may be combined with eleven spectral settings, that provide a range of spectral resolving powers (R ~3500, 7500 and 20000) and instantaneous wavelength coverage spanning the 0.5 – 2.4 μm wavelength range of the instrument. In autumn 2015, the HARMONI project started the Preliminary Design Phase, following signature of the contract to design, build, test and commission the instrument, signed between the European Southern Observatory and the UK Science and Technology Facilities Council. Crucially, the contract also includes the preliminary design of the HARMONI Laser Tomographic Adaptive Optics system. The instrument’s technical specifications were finalized in the period leading up to contract signature. In this paper, we report on the first activity carried out during preliminary design, defining the baseline architecture for the system, and the trade-off studies leading up to the choice of baseline.
HARMONI is a visible and near-infrared integral field spectrograph designed to be a first-light instrument on the European extremely large telescope. It will use both single-conjugate and laser tomographic adaptive optics to fully exploit high-performance and sky coverage. Using a fast AO modelling toolbox, we simulate anisoplanatism effects on the point spread function of the single-conjugate adaptive optics of HARMONI. We investigate the degradation of the correction performance with respect to the off-axis distance in terms of Strehl ratio and ensquared energy. In addition, we analyse what impact the natural guide source magnitude, AO sampling frequency and number of sub-apertures have on performance. <p> </p>We show, in addition to the expected PSF degradation with the field direction, that the PSF retains a coherent core even at large off-axis distances. We demonstrated the large performance improvement of fine tuning the sampling frequency for dimer natural guide stars and an improvement of approx. 50% in SR can be reached above the nominal case. We show that using a smaller AO system with only 20x20 sub-apertures it is possible to further increase performance and maintain equivalent performance even for large off-axis angles.
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 Very Large Telescope (VLT) integral field spectrograph developed for the European Southern Observatory (ESO). It combines a 1’ x 1’ field of view sampled at 0.2 arcsec for its Wide Field Mode (WFM) and a 7.5"x7.5" field of view for its Narrow Field Mode (NFM). Both modes will operate with the improved spatial resolution provided by GALACSI (Ground Atmospheric Layer Adaptive Optics for Spectroscopic Imaging), that will use the VLT deformable secondary mirror and 4 Laser Guide Stars (LGS) foreseen in 2015. MUSE operates in the visible wavelength range (0.465-0.93 μm). A consortium of seven institutes is currently commissioning MUSE in the Very Large Telescope for the Preliminary Acceptance in Chile, scheduled for September, 2014. <p> </p>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 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 2012 and 2013, all MUSE subsystems were integrated, aligned and tested to the P.I. institute at Lyon. After successful PAE in September 2013, MUSE instrument was shipped to the Very Large Telescope in Chile where that was aligned and tested in ESO integration hall at Paranal. After, MUSE was directly transported, fully aligned and without any optomechanical dismounting, onto VLT telescope where the first light was overcame the 7<sup>th</sup> of February, 2014. <p> </p>This paper describes the alignment procedure of the whole MUSE instrument with respect to the Very Large Telescope (VLT). It describes how 6 tons could be move with accuracy better than 0.025mm and less than 0.25 arcmin in order to reach alignment requirements. The success of the MUSE alignment is demonstrated by the excellent results obtained onto MUSE image quality and throughput directly onto the sky.
MUSE (Multi Unit Spectroscopic Explorer) is a second generation Very Large Telescope (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 commissioning MUSE in the
Very Large Telescope for the Preliminary Acceptance in Chile, scheduled for September, 2014.
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 2012 and 2013, all MUSE subsystems were integrated, aligned and tested to the P.I. institute at
Lyon. After successful PAE in September 2013, MUSE instrument was shipped to the Very Large Telescope in Chile
where that was aligned and tested in ESO integration hall at Paranal. After, MUSE was directly transferred in monolithic
way without dismounting onto VLT telescope where the first light was overcame.
This talk describes the IFU Simulator which is the main alignment and performance tool for MUSE instrument. The IFU
Simulator mimics the optomechanical interface between the MUSE pre-optic and the 24 IFUs. The optomechanical
design is presented. After, the alignment method of this innovative tool for identifying the pupil and image planes is
depicted. At the end, the internal test report is described. The success of the MUSE alignment using the IFU Simulator is
demonstrated by the excellent results obtained onto MUSE positioning, image quality and throughput.
MUSE commissioning at the VLT is planned for September, 2014.
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<sup>2</sup> 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) 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 Centre de Recherche Astrophysique de Lyon (CRAL) has recently developed two instrument simulators
for spectrographic instruments. They are based on Fourier optics, and model the whole chain of acquisition,
taking into account both optical aberrations and diffraction effects, by propagating a wavefront through the
instrument, according to the Fourier optics concept. One simulates the NIRSpec instrument, a near-infrared
multi-object spectrograph for the future James Webb Space Telescope (JWST). The other one models the
Multi Unit Spectroscopic Explorer (MUSE) instrument, a second-generation integral-field spectrograph for the
Very Large Telescope (VLT). The two simulators have been developed in different contexts (subcontracted
versus developed internally), and for very different instruments (space-based versus ground-based), which
strengthen the CRAL experience. This paper describes the lessons learned while developing these simulators:
development methods, phasing with the project, points to focus on, getting data, interacting with scientists
and users, etc.
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 (Multi Unit Spectroscopic Explorer) is an integral-field spectrograph which will be mounted on the Very Large
Telescope (VLT). MUSE is being built for ESO by a European consortium under the supervision of the Centre de
Recherche Astrophysique de Lyon (CRAL).
In this context, CRAL is responsible for the development of dedicated software to help MUSE users prepare and submit
their observations. This software, called MUSE-PS, is based on the ESO SkyCat tool that combines visualization of
images and access to catalogs and archive data for astronomy. MUSE-PS has been developed as a plugin to SkyCat to
add new features specific to MUSE observations.
In this paper, we present the MUSE observation preparation tool itself and especially its specific functionalities:
definition of the center of the MUSE field of view and orientation, selection of the VLT guide star for the different
modes of operations (Narrow Field Mode or Wide Field Mode, with or without AO). We will also show customized
displays for MUSE (zoom on specific area, help with MUSE mosaïcing and generic offsets, finding charts …).
The James Webb Space Telescope (JWST) is the successor mission to the Hubble Space Telescope and will
operate in the near- and mid-infrared wavelength ranges. One of the four science instruments on board the
spacecraft is the multi-object spectrograph NIRSpec, currently developed by the European Space Agency (ESA)
with EADS Astrium Germany GmbH as the prime contractor. NIRSpec will be able to measure the spectra of
more than 100 objects simultaneously and will cover the near infrared wavelength range from 0.6 to 5.0 μm at
various spectral resolutions. To verify the performance of NIRSpec and simulate future on-ground and in-orbit
observations with this instrument, the Instrument Performance Simulator (IPS) software is developed at Centre
de Recherche Astrophysique de Lyon (CRAL) as subcontractor to Astrium.
In early and mid-2009, the NIRSpec Demonstration Model (DM), fully representative up to the slit plane,
underwent cryogenic tests and calibration runs. The detector was placed at the slit plane in case of the DM to
measure specific optical performance aspects. A simplified version of the IPS was prepared, matching the DM
configuration and also serving as a testbed for the final software for the flight model. In this paper, we first
present the simulation approach used in the IPS, followed by results of the DM calibration campaign. Then, for
the first time, simulation outputs are confronted with measured data to verify their validity.
NIRSpec is the near-infrared multi-object spectrograph for the future James Webb Space Telescope (JWST). It is
developed by EADS Astrium for the European Space Agency. The Centre de Recherche Astrophysique de Lyon (CRAL)
has developed the Instrument Performance Simulator (IPS) software that is being used for the modeling of NIRSpec's
performances and to simulate raw NIRSpec exposures. In this paper, we present the IPS software itself (main simulation
modules and user's interface) and discuss its intrinsic accuracy. We also show the results of simulations of calibration
exposures as they will be obtained during the NIRSpec on-ground calibration campaign.
The future James Webb space telescope (JWST), developed jointly by the American, European and Canadian space
agencies (NASA, ESA and CSA), is scheduled for launch in 2013. Among its instrument suite, the spectrograph
NIRSpec will provide astronomers with multi-object, integral-field and classical slit spectrographic capabilities in the
near-infrared (0.6-5.0 μm). NIRSpec is being built by EADS Astrium for ESA and it was quickly realized that given the
complexity of the instrument, it was necessary to develop dedicated software for the modeling of its performances. In
this context, the Centre de Recherche Astrophysique de Lyon (CRAL) is responsible of the development of the so-called
NIRSpec instrument performance simulator (IPS) that will serve as a basis for early performance verification purposes;
provide inputs and support for the verification and calibration campaigns, as well as for the development of the
instrument calibration, target acquisition and data reduction procedures.
In this paper, we present the IPS software itself, emphasizing its capability to generate simulated NIRSpec detector
exposures for the various modes of the instrument (multi-object, integral field unit, fixed slits) and for a large variety of
situations (test, calibration, scientific observations...). We will also show simulations results.