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RevMexAA (Serie de Conferencias), 16, 1–8 (2003)

THE GTC: STATUS AND OPERATION PLANS

J. M. Rodrıguez Espinosa and P. AlvarezGTC Project, Instituto de Astrofısica de Canarias

RESUMEN

El Gran Telescopio Canarias (GTC), un telescopio segmentado de 10 m de diametro equivalente, esta enavanzado estado de construccion en la Isla de La Palma, y entrara proximamente en su fase de integracion.La primera luz esta prevista para la segunda mitad del ano 2003, esperando comenzar la operacion cientıficaa finales de 2004, lo que representa un ligero retraso sobre el calendario original. Cuando el GTC comiencesu fase de operacion cientıfica estara provisto de sus dos focos Nasmyth cada uno de ellos con un instrumentocientıfico de primera luz, ası como sus correspondientes rotadores de instrumento y cajas de adquisicion yguiado. Una vez en operacion, el GTC ofrecera excelentes capacidades de observacion gracias a la primerageneracion de instrumentos cientıficos, OSIRIS y CanariCam. En lo que sigue, hablare del estado del proyectode construccion del GTC ası como de los planes para su proxima operacion cientıfica.

ABSTRACT

The Gran Telescopio Canarias (GTC), a 10 meter segmented-mirror telescope, now at an advanced stage ofconstruction on La Palma (Spain), will shortly be entering its integration phase. First light is planned forthe second half of 2003, with science operations scheduled for the end of 2004. This represents a small delayagainst the originally planned calendar. When the GTC enters its operational phase it will be provided withtwo Nasmyth focal stations, each supplied with a science instrument, as well as their corresponding rotatoradaptors and acquisition and guiding boxes. On entering into operation, the GTC will offer exciting capabilitiesfor astronomy, thanks to its complement of first generation instruments, namely OSIRIS, and CanariCam. Inthe following, the status of the projects and the plans for its scientific operation will be addressed.

Key Words: H II REGIONS — ISM: JETS AND OUTFLOWS —STARS: MASS LOSS —

STARS: PRE-MAIN SEQUENCE

1. INTRODUCTION

The GTC Project is a Spanish initiative of theInstituto de Astrofısica de Canarias (IAC) to builda 10.4 m segmented telescope at the Roque de losMuchachos Observatory (ORM), on the Island of LaPalma (see Figure 1). The project was approvedearly in 1996 and is 90% funded by the Central Gov-ernment of Spain and the Regional Government ofthe Canary Islands. Mexico (through the Institutode Astronomıa of the Universidad Nacional Autono-ma de Mexico, IA-UNAM, and the Instituto Na-cional de Astrofısica, Optica y Electronica, INAOE)and the University of Florida at Gainsville have re-cently joined the GTC project, with a 5% share each.

The telescope is presently in an advanced stageof construction, with all major contracts well underway and various subsystems already delivered. Firstlight is expected to occur by the end of 2003, withscience operations starting at the end of 2004. Thisimplies a delay of about a year with respect to theoriginal schedule established in 1997. This delay isdue to unexpected problems with the civil works anddome construction. The GTC Project Office is do-

ing its best to meet the main GTC science objectives,namely excellent image quality, high operational ef-ficiency and reliability. Moreover, the GTC is alsoset to achieve full capabilities in the shortest possibletime after Day One.

2. GENERAL

As a reminder, and since this is the first timethat the three GTC communities have gathered to-gether, I will begin by reviewing the main featuresof the GTC. These are a 10-meter equivalent col-lecting surface and excellent image quality, which isspecified at 0.18 arcseconds (FWHM) for the com-bined optical figure. This requires 11 nm rms on theoptical surfaces, which is very demanding for the pri-mary mirror polishing. Finally, there are two furtherdesign requirements; namely, operational reliabilityand efficiency. These are important first to minimizethe time not dedicated to scientific observations ow-ing to technical failures, thereby reducing costs, andsecond, to maximize the scientific return through theuse of flexible observing modes. These allow us todedicate the best atmospheric conditions for those

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Fig. 1. Aerial view of the ORM with the GTC site on the left, the Telescopio Nazionale Galileo is in the center and the

Nordic Optical Telescope and Isaac Newton Group telesopes are on the far right of the picture. The steep slope at the

bottom right of the picture is the Caldera de Taburiente, a geological formation that is preserved as a National Park.

projects that really require them.

Two first light instruments will be commissionedbefore the telescope is handed over to the operationsgroup; namely, OSIRIS and CanariCam. A furtherinstrument, ELMER, is being built to reduce therisks of reaching first light without having any firstlight instruments available.

The GTC uses a Ritchey–Chretien optical designwith an f/1.65 segmented primary mirror. Thereare 36 segments, 1.80 m each from vertex to ver-tex. The secondary is a lightweight beryllium mirror,which, together with the primary, produces an over-all focal ratio of f/17, or a plate scale of 1.2 arcsecmm−1. The GTC, although initially equipped withonly two Nasmyth foci, will in the future have a to-

tal of seven focal stations, namely the two Nasmyths,the Cassegrain focus, and four bent-Cassegrain foci.The available field of view at the two Nasmyth andCassegrain foci is 20 arcminutes.

The GTC will be fairly well optimized for infrared(IR) work since an undersized secondary mirror de-fines the entrance pupil, and care has been taken toreduce the emissivity of the telescope as far as pos-sible.

3. MAIN DIFFERENCES BETWEEN THE GTCAND KECK

Although the GTC design is very similar to thatof the Keck telescopes, there are a few important dif-ferences that will make the GTC a much more versa-

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GTC STATUS 3

tile telescope than the Kecks. The main differencesare:

• The GTC will have a single optical configura-tion. This will be used for both the opticaland the infrared, and has the advantage thatno changes in configuration are necessary de-pending on whether an infrared or an opticalinstrument is to be used. To achieve this, a1.20 m lightweight beryllium secondary mirror,weighing only 45 kg, is being produced.

• A controllable tertiary mirror that can be park-ed in a position such that the optical beam canprogress to the Cassegrain focus allows sendingthe beam to any of the seven focal stations inreal time. This means easy access to the cali-bration camera any time it is required, as wellas to any instrument that is on standby at anyof the focal stations.

• The GTC will have wavefront sensors at the ac-quisition and guiding (hereinafter A&G) boxes.This allows the monitoring of any degradationin the image quality in real time.

• The primary mirror segment figure can be con-trolled via software in real time, unlike on Keck,where the warping harnesses under the primarymirror segments can only be adjusted manuallyby trial and error.

The GTC will therefore be a more user-friendlytelescope than the Kecks. We expect that this willresult in more time for science and reduced opera-tional costs.

4. PROJECT STATUS

In what follows the status of the major areas ofthe project construction will be described. Noticethat all major contracts are now awarded to severaldifferent companies after a process of open interna-tional bidding for each of the major project subsys-tems.

4.1. Civil Works

The GTC enclosure and auxiliary buildings aresituated at an altitude of 2267 m in the ORM. Thecivil works will occupy a surface area of about 2400m2 over a ground platform of 5000 m2. Three differ-ent areas will be built: the telescope enclosure, anannex building, where the telescope control room, di-rect services for the telescope, and some office spacewill be housed, and an auxiliary building, well sepa-rated from the telescope area, where the major heat

load producing equipment will be situated togetherwith the warm air exhaust.

The enclosure and dome were the first contractsto be awarded and at present are close to being fin-ished. A few problem with the dome shutter, whichdid not operate properly when first mounted at thefactory, have led to a six-month delay. The domewas nevertheless closed by the end of 2001 and isnow undergoing tests of the various mechanisms. Acurrent picture of the site can be seen in Figure 2

Figure 2 shows the two rows of windows situatedaround the GTC Dome plus the additional row ofwindows situated around the concrete Dome base.These will provide a total of 228 square meters ofopen surface to facilitate the natural ventilation ofthe telescope enclosure. A forced ventilation systemwill be available for ventilating the telescope cham-ber when the natural ventilation is not sufficient.

Figure 3 shows a view inside of the enclosure. Al-though the outside view is more spectacular, manycomplicated systems are involved in having an appro-priate environment for the GTC or in providing therequired services (cooling system, oil pumps, venti-lation system, etc.) The work to install all thesesystems is proceeding as planned.

4.2. Telescope Structure

The telescope mechanical structure is also at anadvanced stage of its construction at a factory inCatalonia, in northeast Spain. The telescope hasbeen erected on the factory premises with the pur-pose of, first, checking that the pieces fit togetherproperly, and second, making tests of the elevationaxis movements. The telescope was therefore fullyfinished by the end of 2001 and tests have startedsince then. Figure 4 shows the telescope in the fac-tory. So far the telescope oil bearings have beentested, and the tube has been driven to zero degreesof elevation. Once the tests are finished the tele-scope structure will be dismounted for shipping toLa Palma where the telescope will subsequently bemounted. Indeed for this to happen the dome has tobe completed.

4.3. Optics

All 36 primary mirror segments have been deliv-ered by SCHOTT to SAGEM. The remaining sparesegments will be delivered shortly. The productionof the primary mirror blanks at SCHOTT has pro-ceeded very well. All blanks exceed the requiredspecifications in terms of homogeneity and otherspecifications.

Polishing at SAGEM is now starting mass pro-duction with several robots working simultaneously.

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4 RODRıGUEZ ESPINOSA & ALVAREZ

Fig. 2. Current view of the building site. Note that both the dome and building are nearly completed.

All testing equipment is now being tested and com-missioned. However, reaching this point has takenlonger than expected and SAGEM now is accumulat-ing a nine month delay. Fabrication of the primarymirror segment actuators (CESA) and edge sensors(IS) is proceeding as planned and no delays are an-ticipated.

The secondary mirror is a key element in theGTC optical design. Built in beryllium for light-ness, the secondary mirror will have five degrees offreedom in order to 1) maintain the alignment be-tween primary and secondary mirror, 2) focus thetelescope, 3) perform IR chopping, and 4) allow im-age motion correction through fast guiding.

The secondary mirror blank production, however,is in trouble (AXIS & SAGEM). One beryllium blankbroke while being machined, and two more blankshave been broken while in production. This is a ma-jor concern for the project, which is now looking for

alternatives to mitigate both the risk of new failuresin the production of a beryllium blank and possi-ble first light delays if the secondary is not ready ontime.

The tertiary mirror production is proceeding asplanned and there are no major concerns. This isalso the case with the commissioning camera beingproduced in Mexico. This camera will be used duringthe commissioning period to make fine adjustmentsto the optical figure of the primary mirror.

Another key system for the operation of the GTCis the A&G units. These modules, currently be-ing fabricated (AMOS), will perform not only themore standard functions of source acquisition andtelescope guiding but also the function of primarymirror calibration on tip, tilt, and phasing, closingthe loop for fast guiding, and seeing monitoring.

Finally, the coating chamber (VTD) has suc-cessfully undergone its acceptance tests. Its per-

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GTC STATUS 5

Fig. 3. Inside the GTC dome. Many complicated systems are required for the operation of the GTC. Some of the

cooling subsystems are seen here.

formance exceeds specifications with a remarkablyshort pumping time.

5. CONTROL SOFTWARE

The GTC Control System is progressing well.Extensively based on object-oriented programming,CORBA and ATM communications, it is at the fore-front of technology. The GTC control system willcater for every subsystem in the GTC, including thetelescope axes, optics, science instruments, observ-ing schedule, data processing and archiving, domeand building, etc. The advantages of this approachinclude the possibility that the entire system can bemonitored from any terminal, problems can be de-tected and solved remotely, and indeed remote ob-servations would be possible should the need arise.

An important aspect for its scientific implicationis the development of adequate data handling soft-ware, including facilities for generating the observing

proposals, pipelines for performing a basic data re-duction, and archiving software. Tools for data min-ing in the archive will probably be developed else-where, though this is still under discussion.

6. SCIENCE INSTRUMENTS

The GTC will be equipped on Day One withtwo science instruments, OSIRIS and CanariCam. Athird instrument, EMIR, is now at the preliminarydesign stage. EMIR is the first of the second gener-ation instruments and should be on line at the tele-scope in 2006. An additional instrument, ELMER,is being designed and built at the GTC Project Of-fice and will also be ready by Day One. ELMER isconsidered as a contingency instrument in the eventthat the above instruments are not ready by DayOne.

In this paper I will only describe the GTCinstruments very briefly. A more detailed de-

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6 RODRıGUEZ ESPINOSA & ALVAREZ

scription of these can be found elsewhere in theseproceedings. It is worth mentioning, though, thatall these instruments include features not present insimilar instruments on other large telescopes. TheGTC thus will offer unique capabilities to its usercommunity.

6.1. OSIRIS

OSIRIS will be the first instrument to be in-stalled on the GTC. It is an optical imager featuringadditional multiobject low resolution capabilitiesand combines a very wide field of view (8′ × 8′) withthe use of tunable filters and innovative CCD read-out schemes. These translate into a very versatileinstrument ideal for the study of field and clustergalaxies at high z. Additionally, OSIRIS offers thepossibility of performing multiobject spectroscopyof up to 500 objects. Finally, OSIRIS is capableof performing time-resolved observations both inimaging and spectroscopy with up to 1 ms timesteps. OSIRIS is led by Dr. Jordi Cepa of the IACin collaboration with the Universidad de Cantabriain Spain, and the Institute of Astronomy (UNAM)in Mexico.

6.2. CanariCam

CanariCam is a mid-infrared instrument capableof performing imaging, spectroscopy, polarimetry,and coronography in the 10 and 20 µm atmosphericwindows. CanariCam will provide essentiallydiffraction-limited imaging with narrow and broadfilters beyond about 8µm. It is an ideal instrumentfor the observation of low mass objects (extrasolargiant planets and brown dwarfs), of dust-enshroudedstar formation regions, and of IR galaxies, etc. Ca-nariCam is being produced at the University ofFlorida and is based on its successful predecessorsOSCIR and TRecs (Gemini).

6.3. ELMER

ELMER is an optical imager with a moderatelylarge field of view (4′ × 4′) with additional capabili-ties for low resolution spectroscopy. Key to ELMERis its minimum risk approach. This can be used toadvantage as the optics can be optimized for highthroughput. Elmer will also benefit from the ad-vantage of the new CCDs with frame-transfer ca-pabilities. These will result in improved sky sub-traction for deep exposures. Like OSIRIS, ELMERwill also be able to perform time-resolved photome-try, as well as spectrophotometry. ELMER is being

constructed within the Project Office as a back-upinstrument. When finished, it can be installed in oneof the folded-Cassegrain foci, thereby being alwayson standby for deep imaging.

6.4. EMIR

EMIR is the first second-generation instrument,now starting its preliminary design phase. EMIRshould be at the telescope in the second half of2006. It is a near infrared multiobject spectrograph,additionally offering imaging capabilities. It will bethe first multiobject spectrograph reaching the K

window. This imposes serious challenges to EMIR,which will need to be cooled to about 70 K; at thesame time a mechanism for exchanging the maskswithout having to warm up the full instrument willalso need to be devised. Further features of EMIRare its very wide field of view (6′ × 6′), which isalso quite challenging for a cryogenically cooledinstrument. Additionally, EMIR requires a spectralresolution greater than about 4500 to be able toresolve the sky lines to keep down the sky noise.A fair number of challenges for EMIR, which hasalready started feasibility studies.

EMIR is lead by Dr. F. Garzon of the IAC, incollaboration with the Universidad Complutense(Madrid) and the Laboratoire d’Astrophysique(Toulouse). EMIR is driven by the COSMOSproject, whose primary aim is the determination ofthe history of star formation in the Universe out toz = 3.

6.5. Integration, Commissioning, and Operation

As the civil works near completion, the telescopestructure will be moved to the site to begin integra-tion in the second half of the current year. A carefulintegration plan has been worked out with clearly de-fined milestones to be met. Meeting the milestoneswill indicate that the GTC is on a steady progressiontowards achieving its nominal specifications.

In parallel, the plans for the operation of theGTC after Day One are also being laid down, in-cluding dimensioning the operation group and thestrategy for locating its numbers between the moun-tain and the current headquarters. In fact, the Op-eration and Maintenance group is already beginningto be staffed. Also, the Astronomy Support groupwill begin to be staffed shortly. The plan is that both

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GTC STATUS 7

Fig. 4. Picture of the telescope structure being mounted at the factory in Tarragona. The picture date is 2002

September 1.

astronomers and technicians participate actively inthe integration and commissioning of the GTC.

7. SHORT AND MEDIUM TERM ACTIVITIES

The Project office is undertaking some activitieswhose finalization is foreseen a few years after DayOne. These activities have been started so that theGTC will have a smooth rhythm of upgrades as wellas new instrumentation right from the first years ofoperation. In particular, the programs that have

been started or will be started shortly are EMIR,which has been described above, the adaptive opticsprogram, and an additional second generation in-strument that the Scientific Advisory Committee hasindicated should be an intermediate dispersion spec-trograph. In addition, the GTC focal stations, otherthan the two Nasmyth focal stations that will becommissioned by Day 1, will also need to be broughton line.

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7.1. Adaptive Optics Program

A conceptual design for the GTC adaptive opticssystem is now being finalized. The AO system is be-ing designed in three steps. Initially there will be arelatively simple system working with natural starsonly. This will allow understanding of the wavefrontsensing devices and the algorithms for recovering thecorrected signal. This first system should be avail-able at the telescope by the end of 2006. A sec-ond stage of development will introduce the use oflaser guide stars for increased sky coverage. Finally,a further upgrade will consist in exchanging one ofthe flats for an additional deformable mirror, therebyconverting the system into a multiconjugated adap-tive optics system. This will provide an increase inthe size of the corrected field of view while maintain-ing a very good uniformity throughout that field ofview.

In addition to the AO system described above,there will also be a science instrument capable ofexploiting the corrected AO beam. The AO systemwill be designed and built by the GTC project Office,while an instrument team, as for the other scientificinstruments, should build the high spatial resolutionscience instrument.

7.2. Intermediate–High Resolution Spectrograph

Following the recommendations of the SAC,the next second generation instrument will be anintermediate–high resolution optical spectrograph.This will fill the need for relatively high dispersionspectroscopy on the GTC, since the first light instru-ment only provide low resolution spectroscopy. Acommunity-wide questionnaire will be distributed inorder to gain an understanding of the requirementsof the community. Following this, an announcement

Pedro Alvarez and Jose M. Rodrıguez Espinosa: GTC Project, Instituto de Astrofısica de Canarias, Vıa Lacteas/n, E-38205 La Laguna, Tenerife, Spain (pam@ll.iac.es; jre@ll.iac.es)

of opportunity will be issued for the selection of asuitable instrument.

8. THE GTC PARTNERSHIP

The GTC is currently an international partner-ship whose members are Spain, Mexico, and the Uni-versity of Florida in the USA. All partners share thesame benefits and duties according to their percent-age participation. The partnership goes however be-yond a mere telescope time buy-in. In fact, it in-volves a program of graduate students fellowships atthe University of Florida, a postdoctoral

program both at the University of Florida andthe Instituto de Astronomıa (UNAM) and INAOE,and an exchange program of research and techni-cal staff between the IAC and the partner institu-tions. Additionally, the agreement with Mexico in-volves observing time for Spain on the GTM 50-mmillimeter antenna. Finally, it is worth mentioningthat a fraction of the observing time on the GTCwill be devoted :to collaboration programs as seedtime for fostering scientific collaborations betweenthe partner institutions.

9. ACKNOWLEDGEMENTS

I would like to acknowledge the generous sup-port provided by several of the companies that areparticipating in the construction of the GTC, espe-cially ACS (Spain), Empresarios Agrupados (Spain),SCHOOT (Germany), NTE (Spain), CESA (Spain),and VTD (Germany), as well as the additional sup-port that came from the Ministry of Science andTechnology under grant AYA2001-4446E. The suc-cess of this conference would not have been possiblewithout the decisive support granted by these.