Studies for the first generation of instruments for the European ELT Sandro D Odorico a, Mark Casali a, Juan-Carlos Gonzalez a, Markus Kasper a, Hans Ulrich Käufl a, Markus Kissler Patig a, Luca Pasquini a, Suzanne Ramsay a, Ralf Siebenmorgen a, Joel Vernet a, Filippo M. Zerbi a,b a European Southern Observatory, K. Schwarzschild Str. 2, 85748 Garching bei München, Germany b INAF Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy ABSTRACT The European Southern Observatory (ESO) is conducting a phase B study of an European Extremely Large Telescope (E-ELT). The baseline concept foresees a 42m primary, 5 mirror adaptive telescope with two of the mirrors giving the possibility of very fast correction of the atmospheric turbulence. In parallel to the telescope study, ESO is coordinating 8 studies of instruments and 2 of post-focus Adaptive Optics systems, carried out in collaboration with Institutes in the member states. Scope of the studies, to be completed by 1Q 2010, is to demonstrate that the high priority scientific goals of the E-ELT project can be achieved with feasible and affordable instruments. The main observing modes being considered are: NIR wide field imaging and spectroscopy to the diffraction limit or with partial correction of the atmospheric seeing; high spectral resolution, high stability visible spectroscopy; high contrast, diffraction limited imaging and spectroscopy; DL mid-infrared imaging and spectroscopy. The status of the 8 current studies is presented. Keywords: ELT, Instrumentation 1.1 Phase B Study of the E-ELT 1. INTRODUCTION Following the review of the 100m telescope (OWL) project in 2005, ESO prepared a proposal for a 3 year long Phase B study of a 42m adaptive optics telescope. This was approved by the ESO Council in December 2006. The initial design of the European ELT is based on a 5 mirror optical design. The optical configuration for the Nasmyth focus is shown in Fig.1. The status of the E-ELT telescope and AO studies has been presented at this Symposium [1]. A discussion of the instrument-telescope interfaces is given in [2]. 1.2 Scope of the Instruments and Post-Focal AO Modules Studies The E-ELT Phase B Study proposal contained a roadmap to arrive by the beginning of 2010 to the selection of a first generation of instruments to be included in the construction proposal. The study proposal did foresee 2300k and 30 ESO FTE to support the instrumentation studies and the definition of the telescope-instrument interfaces. Following the approval by Council in December 2006, a detailed plan of E-ELT studies was finalized in April 2007. It identified 6 high-priority instrument concepts to be studied by the end of 2009. The studies will have a typical duration of 15-24 months. The final reports will have to include a detailed scientific case, the full instrument concept at Phase A level ( in specific cases to feasibility level only), calculated scientific capabilities, cost estimates, FTE effort and a construction schedule. In this phase of the E-ELT Project, the studies will also contribute to the definition of the interface with the telescope. The results will be used to prepare the Technical Specifications and Statement of Work of the first instrument construction contracts, should the current priority and the feasibility be confirmed by 2009. In addition to the 6 high priority instrument studies, ESO identified the need to carry out two additional Concept Studies during this phase. These are centered on observing modes which although not identified as of highest priority appear important to explore the potential capabilities of the telescope. The choice followed an open call for proposals in the ESO community. These two studies at feasibility level will have a duration of ~15months.
Fig. 1. Optical design for the E-ELT. M4 is an adaptive mirror, M5 provides a fast tip-tilt option. There are two F/17.7 Nasmyth foci. In addition the telescope has two gravity-invariant foci (F/18.8) below the Nasmyth platform floors and one F/60 coudè focus. In conjunction with an array of up to 6 Laser Guide stars and the associated WF sensors, the telescope AO system (M4+M5) will contribute both to keep an excellent image quality and to provide atmospheric correction for the ground layer turbulence. Many of the current high priority E-ELT instruments require high Strehl or enhanced Encircled Energy values to reach the scientific goals. This calls for higher order AO systems in one of the currently explored flavors, Laser Tomography AO (LTAO), Multi Conjugate AO (MCAO), Multi Object AO (MOAO) or Extreme AO (XAO). The MCAO and LTAO modules could in principle feed different instruments and they will be the subject of two specific studies. Other AO observing modes are strictly related to a specific instrument and they will be part of the instrument studies (see section 2). As it was the case for the VLT, development of ELT Instrumentation is very much planned as an activity that ESO will conduct in strict cooperation with Institutes in its community, with ESO paying the largest share of the hardware cost and the Institutes providing FTE in exchange of GTO time. For selected instruments ESO will keep the coordinating role and might be responsible for part of the design and the system engineering. For the majority of the instruments, ESO s role will be that of a controller of the project progress according to the agreed Technical Specifications and Statement of Work and of developer and supplier of standard components and critical subsystems such as detectors. The selection of a Consortium to carry out the study and later possibly the construction of the instrument is obviously a crucial step in the process. For VLT instrumentation different schemes have been applied for different projects. There have been competitive proposals and even competitive Feasibility Studies in response to a Call for Proposals. This phase has been followed by the selection of one of the proposals or by a merging of separate groups in a single project. There have been cases of single source procurement of an instrument by an external Consortium that was considered highly if not uniquely qualified for the job. Experience has proved that there are merits and shortcomings in any of these options. In the case of the E-ELT and for the current study phase in particular, ESO has followed different approaches. For instrument types where ESO has well proven experience and/or there is a strong need of coordinating the activity with the telescope studies, ESO has taken the role of leading the consortium. For other complex instruments a direct negotiation has been carried out with an external consortium that had already a well demonstrated capability in the field.
Finally, and for the majority of instruments, the consortia have been chosen as the result of an open call for a study proposal at a fixed cost. 2. INSTRUMENT STUDIES Table 1 lists the current instrument and AO module studies and their status. The first 6 address the instrument types considered of higher priority and they are all under way. ESO has provided for these studies a SoW (outlining in detail the expected content of the final report and its schedule) and an initial set of specifications. After an initial phase of the study, the instrument concept specifications will be frozen in agreement between the consortium and ESO. OPTIMOS and SIMPLE are the two new concepts which have been selected on the basis of an open call to the community. At the date of closure of this contribution, negotiations are going with the two proposing consortia for a study contract. MAORY is the MCAO module which could feed the MICADO camera and/or the HARMONI spectrograph. Table. 1. Instruments and AO Modules NAME INSTRUMENT TYPE PROCUREMENT MODE/ START EAGLE Wide Field, Multi IFU NIR Spectrograph with MOAO Direct negotiation with EAGLE Consortium/ 09.2007 CODEX High Resolution, High Stability Visual Spectrograph ESO coordination of Consortium with external Institutes/ 03.2008 MICADO Diffraction-limited NIR Camera Open Call based on initial ESO specs/ 02.2008 EPICS Planet Imager and Spectrograph with XAO ESO coordination of Consortium with external Institutes/ HARMONI Single Field, Wide Band Open Call based on initial ESO specs/ 04.2008 Spectrograph METIS Mid Infrared Imager & Spectrograph Open Call based on initial ESO specs/ 05.2008 with AO OPTIMOS Wide Field, Visual, MOS Open Call for new concept/ 09.2008 (tbc) SIMPLE High Spectral Resolution NIR Spectrograph Open Call for new concept /09.2008(tbc) MAORY Multi Conjugate AO module Direct Negotiation/ 12.2007 tbd Laser Tomography AO Module Open Call based on initial ESO specs/ deadline 07/2008 In the text below, the basic information for each instrument is provided. With the exception of EAGLE, all studies have been running for less than 9 months and hence they have not gone through the review at the end of the first phase, when the specification are frozen and an instrument concept to be studied in detail is identified. The instruments parameters are hence not necessarily the final ones. The initial parameters and the preliminary concept of the Multi Conjugate AO module, MAORY, can be found in [3]. As of today, 29 Institutes in the ESO member countries are involved with scientists and engineers in the instrument and AO modules studies for a planned effort of more than 100 FTEs. 2.1 EAGLE Primary scientific goals: highest redshift galaxies, physics of galaxies at z=2-3 Main Observing Mode/Initial Specifications: Wide Field, Multi IFU NIR Spectroscopy with dedicated AO (MOAO, tbc)/ Wavelength range: 0.8-2.5 μm ; >20 positionable IFUs; patrol field >=5 ; Spectral resolution: R=4000 (R>10000 optional ) ; ensquared energy >30% EE in 100mas in the H band. P.I.: J.G. Cuby (LAM) Institutes in the Consortium: : LAM, OPM GEPI and LESIA, ONERA- UK: ATC, University of Durham Instrument Responsibles at ESO: M.Casali, N. Hubin(MOAO)
Status: This type of multi-object, NIR spectrograph had been studied with the OWL project and later on within the EC FP6 E-ELT Design program. The present study is running from July 2007. In this first phase the consortium has concentrated on the definition of the primary science cases, on the simulation of a distributed AO system, on the study of the interfaces with the telescope and on the development of a first instrument concept to be located at the gravity invariant focus. A review of this first phase has taken place in July 2008. Several contributions by the EAGLE consortium are included in the Proceedings of SPIE Conference 7012 and 7014. 2.2 EPICS Primary scientific goals: heavy, rocky planets at 1-10AU in start within 30pc, warm Jupiters at < 1 AU Main Observing Mode/ Initial Specifications: Planet imaging and spectroscopy /Wav. range: 0.6-1.8 μm ; Field Diameter 2 (4 goal); Contrast: for a star of V<9, 10-9 (at 100-800mas); Spectroscopy R>50, Imaging in Y to H bands; Differential Polarimetry (R Band) P.I. M. Kasper (ESO), co PI: J.L. Beuzit(LAOG) Institutes: ESO, LAOG, LESIA, FIZEAU UNSA-OCA., LAM, ONERA, Univ. Oxford, INAF Padova, ETH Zurich, ASTRON-NOVA, Univ. Amsterdam and Utrecht. Status: The instrument concept and its science case have been explored and documented first as an OWL instrument and more recently as an FP 6 instrument study. The instrument will be a natural follow-up of the SPHERE instrument which is under development for the VLT. The starting concept includes three observing modes (integral field spectroscopy, differential polarimetry and speckle imaging ).The current study has started in January 2008. It will explore the effects by the telescope optics and the atmosphere as seen by the instrument subsystems and on the scientific goals. The first study phase will be reviewed by the end of 2008. A contribution on EPICS is published in the proceedings of the SPIE Conference 7012. 2.3 CODEX Primary scientific goals: terrestrial planets in extra-solar systems, direct measurements of the dynamics of the Universe, cosmological behavior of the fine structure constant Main Observing Mode/ Initial Specifications: High-resolution, high stability visual spectrograph at the coude focus/ Wavelength range: 0.37-0.69μm (goal 0.35-0.72 μm) ; Spectral resolution: R> 120000 ; Stability: 2 cm/sec over 30 years P.I.: L. Pasquini (ESO) Institutes: ESO, INAF Trieste & Brera, IAC, IoA Cambridge, Obs. Geneve Status: The instrument concept and its science case have been extensively explored and documented first as an OWL instrument and more recently as an FP 6 instrument study. The current study has started in March 2008. It will refine the science case, investigate the most critical subsystems and the interface to the E-ELT (coudè focus). A contribution on CODEX is published in the Proceedings of the SPIE Conference 7014. 2.4 MICADO Primary scientific goals: Galactic center astrometry, resolved stellar populations to Virgo Main Observing Mode/ Initial Specifications: MCAO-assisted, High angular resolution imaging/ Wavelength range: 0.8-2.4 μm ; Field of view: =>30 ; sampling of diffraction-limited PSF P.I.: R. Genzel (MPE) Institutes: MPE, MPIA, US München, INAF Padova, NOVA -Univ. Leiden and Groningen Instrument Responsible at ESO: M. Kissler-Patig Status: The KO meeting took place in February, the first science and technical team meetings in February and March. The review meeting ( choice of the baseline concept) is planned for December 2008.
2.5 HARMONI Primary scientific goals: faint, high z galaxies, QSO and GRBs, extragalactic stars Main Observing Mode/Initial Specifications : Single-field, medium resolution, 2D spectroscopy/ Primary wavelength range 0.8-2.4μm (goal 0.5-2.4μm), field of view(tbd) P.I.: N. Thatte (Oxford University) Institutes: Oxford University, CRA Lyon, DAMI Madrid, IAC, UK ATC Instrument Responsible at ESO: J. Vernet Status: This instrument concept had not been explored within the OWL study or the FP6 program, however to explore the concept of a simple field spectrograph was recommended as a first light capability to operate e.g. in parallel to the JWST for the study of the faintest sources within reach of a 42m telescope. The kick-off meeting took place May 7, the review of the first phase ( choice of the baseline concept) is planned for January 2009. 2.6 METIS Primary scientific goals: Main Observing Mode/Initial Specifications: Mid-IR imaging and spectroscopy, AO assisted / Wav. range: 3-13 μm (L,M,N) ( Q,16-20 μm, option) ; Imaging at DL and high Strehl,(>0.9 at N); Field of view: 30 diameter; Spectroscopic modes to be considered: low (R=100 at N band), high (R=100000), optional observing modes polarimetry, differential imaging P.I. B.Brandl (Leiden) Institutes: NOVA-Leiden and ASTRON, MPIfA, CE Saclay DSM/IRFU/Sap, KU Leuven, ATC UK ESO Instrument Responsible: R. Siebenmorgen Status: The instrument concept and its science case have been extensively explored and documented first as an OWL instrument and more recently as an FP 6 instrument study (MIDIR Study). The kick-off meeting took place May 7, the review of the first phase ( choice of the baseline concept) is planned for January 2009. 2.7 SIMPLE Primary scientific goals: stellar chemical abundances, intergalactic medium, search for planets Main Observing Mode/Initial Specifications: High resolution spectroscopic in the J and H band (K band tbc)/ Initial specifications under discussion with the Consortium P.I. : L. Origlia (INAF-OAB) Institutes: INAF OABO, UAO, TLS, PUC (Chile) Instrument Responsible at ESO: H.U. Käufl Status: This is one of the two instruments selected after the open call for new E-ELT instrument concepts. Negotiations are going on to define Technical Specifications and a Statement of Work of a study contract, with a kick-off meeting foreseen in September 2008 2.8 OPTIMOS Primary scientific goals: high redshift galaxy surveys, stellar populations in external galaxies Main Observing Mode/Initial Specifications: MOS spectroscopy from the B to the J band/ Field of view : 5 ; other specifications under discussion with the Consortium P.I. : G. Dalton (STCF RAL-Oxford), F. Hammer (OP-GEPI), O. Le Fèvre (LAM), Institutes: STCF RAL, Oxford, LAM, IASF-MI, OP-GEPI, NOVA-Univ. of Amsterdam and ASTRON, INAF Oss. Brera and Trieste, Nils Bohr Institute-Copenhagen University Instrument Responsible at ESO: S. Ramsay Status: This is one of the two instruments selected after the open call for new E-ELT instrument concepts. Negotiations are going on with two consortia which have submitted proposals related to this observing mode of the E-
ELT to define a common set of initial Technical Specifications and a Statement of Work for a merged study. The kickoff meeting is foreseen in September 2008 3. INSTRUMENT PIXEL SAMPLING AND ENERGY CONCENTRATION In section 2, the initial specifications of the 8 instruments under study have been briefly summarized. These will be reviewed with ESO after the first phase of the studies and finalized for the detailed opto-mechanical instrument design phase. The European ELT is conceived from the start as an adaptive telescope, with M4 and M5 partly correcting for atmospheric turbulence. Post-focal AO modules will provide images close to the diffraction limit at various Strehl values. Figure 2 and 3 are a first attempt to visualize the resolution capability that each AO-supported instrument under study is expected to provide. The Strehl values and the Ensquared Energy values of fig. 2 are taken from the requirements of the different instruments and they are estimated from the first simulations. They represent a first approximation only. They will have to be updated once the instrument concepts will be better defined and the simulation will be refined. Concerning the instruments intended to operate close to the DL, fig.2, left panel, (METIS, MICADO, HARMONI and EPICS), the pixel size is taken for convenient sampling of the diffraction peak of a 42m telescope depending on the instrument primary science goals. On the right panel, the same parameter space is shown for the two large (5 x5 ) field instruments intended to operate seeing-limited or with GLAO (OPTIMOS) and with MOAO (EAGLE). In this case, the light concentration is expressed in terms of ensquared energy (EE), that is the fraction of light of a point source included within a 2x2 pixel box. A pixel size of 40 mas and 100 mas are taken for EAGLE and OPTIMOS respectively. Fig. 2. These 3D views visualize the initial specifications of different E-ELT instruments in terms of pizel size(x-axis), field of view (size of cylinders or squares) and light concentration. On the left panel, for the instruments intended to operate close to the diffraction limit, the latter is expressed in terms of Strehl ratio at a given band. As a reference, the pixel size of the JWST instruments MIRI and NIRCam are plotted on the same scale. On the right panel, the same parameter space is shown for the two large field instrument EAGLE and OPTIMOS (or equivalent wide-field imager and spectrograph, operating with GLAO). Here the light concentration is expressed in terms of ensquared energy (EE), that is the fraction of light of a point source included within a 2x2 pixel box. 4. INSTRUMENT DISTRIBUTION AT THE TELESCOPE One of the top level requirement of the E-ELT is the need to mount a large set of instrument addressing different observing modes and ready to operate at short notice to take maximum advantage of the atmospheric conditions with flexible scheduling. With the full complement of instruments installed at the telescope, the E-ELT could have up 10 instruments permanently on line: six on the two Nasmyth platforms, two at the two gravity invariant foci and two in the telescope basement fed by the coudè optical train. The full configuration will be possibly reached many years after the first light, but it is necessary to explore it now to verify that the observatory will be able to deal with it when it will be
needed. We are using the current instrument studies to verify the requirements on volume, handling and services to be provided at the different foci. As a Gedankenexperiment, we have assigned the instruments under study to the different focal stations. This exercise will have to be revisited when the instruments concepts will be further defined. Figure 3,4 and 5 show the current seat booking for the instruments under study at Nasmyth, GI and coudè foci. SIMPLE (not shown) could go either in the second GI or to the coudè laboratory focus. Fig.3. A possible distribution of instruments and AO post focal modules (MCAO and LTAO) on the two Nasmyth platforms. Choice of instruments, volume allocations and coupling with the AO modules represent a Gedankenexperiment only. Fig. 4. The configuration of the gravity-invariant focus below the Nasmyth platform floor is shown in the two figures. To the right the optical configuration, to the left the 3-D view of the volume assigned to the instrument at that focus. In the current set of studies, EAGLE is the instrument designed to occupy one of the GI foci.
Fig. 5. The configuration of the coudè focus in the current E-ELT optical design (left panel). The size of the coudè train optics has been magnified for illustration purposes. The right panel shows the possible location of the spectrograph CODEX in the telescope basement. REFERENCES [1] [2] [3] Gilmozzi, R.. The European ELT, Proceeding of the SPIE Conference 7012 (2008) Casali M, Gonzalez J.C, D Odorico S., Making Instruments work on the European ELT, Proceedings of the SPIE 7014 Conference (2008) Diolaiti, E. et al A Preliminary Overview of the MCAO Module for the E-ELT, Proceedings of the SPIE Conference 7015 (2008)