Executive Summary ARENA

8/9/2019 Executive Summary ARENA

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A Visionfor European Astronomy and Astrophysics

at the Antarctic station Concordia, Dome CIn the next decade 2010-2020

ARENAPrepared by the

Executive Summary

consortium in fulfilment

of the work programme

of the EC-FP6 contract

RICA 026150

antarctic research,

a european network

for astrophysics


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A Vision for European Astronomy and Astrophysics at the Antarctic station Concordia, Dome C (2010-2020)

ExecutiveSummary

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Map of the Antarctic continent with the main research stationsMapproducedbytheAustra

lianAntarcticDataCentreStationsaslistedathttp:/

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ilities(September2009)-

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A Vision for European Astronomy and Astrophysics at the Antarctic station Concordia, Dome C (2010-2020) .

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Astronomers have always sought thebest possible observing conditions.The inner Antarctic continent is the

wildest, coldest, and driest desert on earth,offering an almost pristine nature withouthuman contamination, or even faunal or

oral presence. It is therefore, in essence,

an outstandingly appealing area to explorefor the construction of major astronomi-

cal facilities of the future. Astronomershave for decades been attracted by thisopportunity. Several pioneering attempts

have been made to set up increasinglysophisticated instruments over the last 40years, encompassing a wide range of tech-

niques and scientic goals. The only majorastronomical facility so far established isat the US Amundsen-Scott station, right at

the geographic South Pole, and named theMartin A. Pomerantz Observatory in tributeto one of the most active astronomers in

Antarctica over the last half century.

France and Italy have recently joined the ef-fort: they have built and, since 2005, operate yearround a multidisciplinary station at

Dome C called Concordia. Dome C is one

of the highest domes on the Antarctic Pla-teau, located about 1,200km from the coastat a latitude of about 75 and an elevation

of 3,202m. Dome C is an extremely promi-sing location for the establishment of therst European astronomical observatory in

Antarctica, which could eventually become

a major item of an international researchinfrastructure.

To explore this opportunity in all its aspects,a network, ARENA, was created under the

auspices of the European Commission.ARENA has had as a goal the investigationof the scientic prospects and the possibi-

lity of implementing an astronomical ob-servatory at Concordia, and to documenta suite of instrumental projects that could

benet greatly from the conditions on theAntarctic plateau.ARENA created the impe-tus necessary to form international consor-

tia in charge of preparing detailed studies(Phase A and B) of at least a couple of theproposed projects; consortia that could pos-

sibly undertake their construction beforethe end of the coming decade, 2010-2020.Preliminary site assessments and atmos-

Executive Summary

ARENA, a consortium

of European and Australian

laboratories gathered in

a network funded by an

EC-FP6 contract in 2006-2009

has released a roadmap

for the development of astro-

nomy and astrophysics on the

Antarctic Plateau. This docu-

ment based on the results of

the investigations made by a

hundred of experts in atmos-

pheric physics and several

relevant elds of astrophysics

from 8 countries identies the

science cases that would most

benet from the Antarcticplateau conditions and

describes a suite of

appropriately designed

instrumental projects.

A set of statements and

recommendations supporting

the creation of an internatio-

nal astronomical observatory

offering exceptional conditions

at the French-Italian station

Concordia at Dome C

are drawn out.

The Concordia station and the site testing equipmentPhoto:A.A

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ExecutiveSummary

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mology, and infrared imaging photometry

(IRAIT), v) cosmic microwave backgroundexperiments (the QUBIC project) and, vi)high angular resolution solar measure-

ments (the AFSIIC project).

A series of recommendations have been

drawn from the discussions held duringthe ten workshops and three conferencesthat took place during the last 4 years.

Site assessmentA large amount of data have been collec-

ted with the aim of quantifying the day-and night-time astronomical observingconditions at Dome C. The available data

show that the precipitable water vapour isusually below 0.7mm and drops to 0.3mmfor 50% of the time, thus offering excellent

conditions for submillimetre observa-tions. The extreme cold of the atmospheremeans that its thermal emission is greatly

reduced. This, in turn, leads to signicant sa-vings in the time required to carry out large

observing programmes at wavelengths lon-ger than 2m.

The absence of strong turbulence in the up-

per atmosphere results in low scintillationand creates favourable conditions for pho-tometric programmes. The median free-

atmosphere seeing in the visible is 0.36,but achieving this imaging accuracy in theoptical is limited by the presence of a very

strongly turbulent boundary layer whichextends up to median altitudes of some40m in winter and up to 400m in summer.

The small outer scale of turbulence measu-red at Dome C, combined with the long co-herence time and large isoplanatic angle, is

benecial for high angular resolution tech-niques at this site. Detailed measurementsof the vertical and temporal variation of

the atmospheric parameters are now nee-

ded, in order to draw robust conclusionsabout short- and long-term stabilities and

trends, and to constrain the specicationsof instruments to be deployed at Dome C.

Near-infrared high angularresolution wide-eld imagingVarious countries have for some time pro-posed the construction of a large optical/infrared telescope in Antarctica. The condi-

tions on the Antarctic plateau particularlyfavour exploitation of the spectral windowsnot easily accessible from the ground, i.e.,

in the thermal IR beyond 2.3 m whereobservations are normally hampered bythe strong thermal background emission

of the sky and from the ground. Thanks tothe exceptional seeing conditions abovethe turbulent layer, Dome C is an ideal site

to make large-scale, high angular resolu-tion, extremely deep imaging surveys inthis wavelength regime.

ThePLT(Polar Large Telescope) project is

the result of extensive discussions betweenEuropeans and Australians to propose arealistic, albeit ambitious, project for such

a telescope with a 2.5m aperture. A limitednumber of programs will be performedaimed at surveying very distant galaxies,

dusty SNIa, and extreme stellar populationsin the local group, and at characterizingexoplanets by transit and microlensingmilli-magnitude photometry. The project

will be based on a European-Australiancollaboration. A preliminary evaluation ofthe cost points toward a 11 Meuros teles-

cope and 5 Meuros focal instrument witha Phase B study in 2010-2013 potentiallyfunded by the FP7 and a rst light before

the end of the decade.

Submillimetre-wave astronomyPerforming ground-based astronomical

pheric modelling by several expert

teams, primarily from Australia, France,and Italy, have demonstrated that thisregion offers exceptional conditions for

astronomy mainly thanks to the cold, dry,and calm atmosphere. The atmosphereabove the highest spots of the Antarctic

continent offers the best conditions onearth to investigate astronomical objectsat high angular resolution in the near

thermal IR and submillimetre-waveranges. The high latitude location allowsvery long continuous night-time photo-

metric observations, which are essentialfor the study of periodic variability ofcelestial objects. In several well-identi-

ed domains (niches) the Antarcticplateau may even compete with spacemissions, but at a much lower cost, and

with the invaluable bonus of using themost advanced technologies.

The ARENA network has identied 6 par-ticularly promising astrophysical areas

with well-dened research programmes.Taking into account the constraints oflogistics and environment, the networkhas been able to outline the top-level

requirements for the instrumentationable to address these programmes.They are, i) wide-eld, extremely sensi-tive imaging and spectro-imaging in the

near and thermal infrared (2.3-4m)with a 2.5m-class telescope (the PLTproject), ii) extremely sensitive submilli-

metre wave imager with a collectingarea equivalent to a 25m dish (projectAST), iii) near IR interferometry for the

detection of exoplanets and exozodia-cal light (the ALADDIN project), iv) aset of smaller dedicated instruments

(some of them already in the construc-tion phase on-site) for planetary transits(ASTEP), stellar variability, asteroseis-

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The 40cm planetary transit telescope ASTEPPhoto:A.A

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ments, the architecture of the system is

specically focussed and optimised for thepurpose: ALADDIN implements the nullinginterferometry technique at the focal plane

of a two-telescope interferometer mountedon a rotating beam structure. Thanks to theAntarctic environment, such a nulling in-

terferometer coupled to a pair of 1m-classtelescopes operated at thermal infraredwavelengths would perform signicantly

better than a similar instrument workingon 8m-class telescopes in a temperate site(e.g., at ESO Paranal).

Long time-seriesphotometric observationsTime-series data are the result of astrono-mical observations of temporal phenome-na; to be valuable such observations typi-

cally require one or more of the followingconditions:.Long observing duration in stable condi-tions, particularly in combination with high

duty cycles.Very good seeing and/or low scintillation.Observations in spectral ranges that havebeen little explored to date.

Contributing to all of these requirements,Dome C provides unique opportunities

for ground-based observations. Becauseof the need for long and continuous timecoverage, most such observations require

a dedicated telescope, typically of sub-1msize. However, there are also scientic casesfor which the use of signicant time allo-

cations on larger multi-purpose facilities ismore appropriate. The major science casesfor time-series at Dome C are: detection

and characterization of extrasolar planets(transits), asteroseismology, and stellar ac-tivity studies. The panel reviewed several

projects that were presented:

large telescope facility consisting of a 25mdiameter class, single-dish telescope at

Dome C, or an equivalent collecting areaachieved with a network of medium-sizeradio antennas, operating at submillimetre

wavelengths and offering unique sciencepossibilities. Its performance at 200,350 and 450m would be superior to an

equivalent telescope on any of the Andeansites. Furthermore, a single-dish telescopecould be used as a Very Long Baseline

Interferometry station with the ALMA andother antennas in South America.

Optical and infrared interferometryStudying the warm inner parts of debrisdisks, the extrasolar counterparts of thezodiacal dust cloud, is of prime impor-tance to characterize the global architec-

ture of planetary systems. Furthermore, thepresence of large quantities of warm dustaround nearby main sequence stars repre-

sents a possible obstacle for future spacemissions dedicated to the direct detection

and characterization of Earth-like planets.The frequency of the occurrence of brightexozodiacal disks around solar-type starsis currently mostly unknown. As of today,

exozodiacal disks have been directlyresolved around a small number of mainsequence stars, at a sensitivity level of about

1000 times our Solar System zodiacal dustcloud. In this context, the Antarctic plateaucould provide the optimal ground-based

conditions for an infrared nulling interfe-rometer dedicated to the direct detectionof warm dust clouds around nearby main

sequence stars.

Joint efforts between several European ins-

titutes within the ARENA consortium led tothe denition of the ALADDIN concept. In

order to achieve a signicantly improvedsensitivity with respect to existing instru-

observations in the submillimetre part of

the electromagnetic spectrum requires,at a minimum, very dry conditions. TheAntarctic plateau, a unique desert on

Earth, is an obvious candidate site.

The atmospheric transmission in the

submillimetre windows centred at e.g.,200, 350, 450, and 850 m has been esti-mated by the team of CEA-IRFU/Saclay

using measurements with a tipper instru-ment and the MOLIERE radiative trans-fer modelling code. The 200m window

opens up to better than 20% transmis-sion for 25% of the time. Observationsat 350 and 450m would be possible all

year. Theses values of transmission indi-cate that observing conditions at DomeC are superior to the known sites in

Chile or Argentina. The estimated trans-mission values were used as lters toselect science cases. Cosmic history of

star formation, black holes and galaxies,Origins of stellar masses, Galactic en-

gines, and Galaxy clusters in the farUniverse and dark energy were selec-ted as the four main science cases for asubmillimetre-wave telescope facility in

Antarctica.One of the functions of the thermal in-frared telescope (the Italian IRAIT 80cm

telescope) can be as a pathndingexperiment for submillimetre astronomy.It will perform atmospheric and sky-

noise measurements with a bolometerarray, prepare a catalogue of sourcecalibrators in the far southern sky, and

attempt several science observations ofthe Sun and of star formation.

Finally, this roadmap provides a visionfor an Antarctic Submillimetre Teles-cope (AST) project. This could be a

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The 80cm infrared telescope IRAIT The 2.5m millemetre-wave telescope COCHISE Photo:Y.F

ante-Caujolle

Photo:Y.F

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ExecutiveSummary

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. ASTEP 400, a 40cm telescope for pla-net detection, received its rst light at

Dome C in November 2009. It shouldprovide scientic data rapidly (2010-2011) and thus should be stronglysupported by the relevant agencies.. Of projects in the development phase,ICE-T (International Concordia Explorer

Telescope), a 2 x 60cm binocular teles-cope, is graded the top priority instrumentfor time-series photometry; it is expected

to become the reference instrument forstellar activity studies. Its construction isfunded, but site-access and operational

issues need to be resolved as soon aspossible for an anticipated deploymentaround 2013-2014..SIAMOIS(Seismic Interferometer Aimingto Measure Oscillations in the Interior ofStars) is the top priority instrument for

advanced time-series spectroscopy, andis expected to become the referenceinstrument for stellar Doppler velocity

studies. Its deployment with two small-

aperture telescopes is anticipated for2013-2014. In a second phase, the scientic

return can be enhanced to include speci-c faint targets by feeding the instrumentfrom a 2m-class telescope... Finally, PLT (Polar Large Telescope) isconsidered critical for shorter time-seriesprojects requiring a larger and exible ins-

trument, where open access for the scien-tic community will be important.

Cosmic Microwave BackgroundCosmic Microwave Background (CMB)observations have been extensively

developed since the discovery of thisradiation in 1965 by Penzias and Wilson.It has been demonstrated that Antarctica

is the best place on Earth to study its ani-sotropies in temperature and polarization.The US M.A. Pomerantz Observatory at the

South Pole is essentially dedicated to this

research with, today, the largest astrophysi-cal instrument ever built on this continent,the South Pole Telescope (SPT), a 10m

aperture millimetre-wave dish and theBICEP polarization experiment. The basicadvantage of the polar environment forCMB research is the unique atmospheric

stability, particularly of the terrestrial mole-cular oxygen lines, and the fact that onecan observe the same area of the sky over

very long periods at almost constant ele-vation. Dome C appears to be even betterbecause of a lower atmospheric optical

depth and lower wind speeds, and thuseven better stability (with respect to theSouth Pole). Moreover, its location 14 in

latitude away from the pole allows cross-linked scans and drift removal techniques.

Members of the CMB working group arecurrently implementing the QUBIC expe-riment through a collaboration betweenItaly, France, Ireland, UK and the USA. This

instrument (formerly called BRAIN) willtake advantage of the conditions at DomeC to mainly measure the B-mode of the

CMB polarization with a bolometric inter-ferometer, combining the extreme sensiti-vity of bolometric detectors with the opti-cal purity of interferometers. The project is

supported by IN2P3 in France and PNRAin Italy and by the ARENA CMC.

The working group also supports a projectfor a single millimetre and submillimetre-wave large dish mainly for high angular

resolution observations of intra-clusterstructures and the study of the differentpopulations of thermal and non-thermal

electrons that produce distinct Sunyaev-Zeldovich effects (SZE) and that couldprovide new clues on Dark Matter candi-

dates.

Solar astrophysicsThe Dome C site where Concordia stationis located also offers unique qualities forsolar observations, combining excellent

seeing, low coronal sky brightness, low wa-ter vapour, continuity and an impressiveduty cycle (4 months, i.e., 3 times more

than at mid-latitudes sites, under excellentobserving conditions). This allows bothvery high angular resolution (


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copes will suffer from winter conditions.

ARENA roadmapConsidering the various propositions

made by the working groups and on thebasis of the present knowledge of thesite assessment, the following statements

and recommendations are made by theARENA CMC. We recommend that a pro-cess be fostered to lead to the creation of

an internationally managed astrophysicalstation at Dome C aimed at collectingunique data over a wide range of wave-

lengths from the visible to the millimetre.We strongly recommend continuationof the site quality characterization to

conrm the promising results alreadyobtained, and to study their variations withtime. Atmospheric parameters that have

thus far not been fully studied should bemeasured and monitored with someurgency. These include: the atmospheric

opacity at all wavelengths, the photome-tric stability, the sky background emission

(particularly in the near thermal infrared),the turbulence prole and the outer scaleof turbulence. We strongly recommendmaking these data rapidly available to the

community and implementing a regularlyupdated data-base to archive the data andprovide long-term, easy access to them.We strongly recommend using, as far as

possible, the same instruments, calibra-tion and data processing in the differentpolar sites currently under investigation, to

enable objective comparison. We expressour interest in the exploration of as yet un-documented sites (such as the Antarctic

Ridges A and B).

We have identied a wide range of science

cases, as detailed above, that wouldstrongly benet from the unique Antarcticconditions. A suite of appropriately desig-

ned instruments is identied; these can beclassied into 3 main categories:. small instruments, some of which are

currently in the construction phase (IRAIT,COCHISE, BRAIN/QUBIC, ASTEP) or readyto be built (SIAMOIS, ICE-T). They all t wi-

thin the present logistics capabilities. Theircost is in the range of a few million euros.For obvious reasons of manpower capa-

city on site, and to leave room for moreambitious projects, their number shouldnot increase without limit in the future. An

international peer-reviewing process to se-lect future projects based on their scienti-c excellence should be established,. mid-size facilities (mesoscale projects,cost range of a few tens of million euros,(such as PLT or a solar telescope/interfero-

meter) that will need affordable upgradesof the logistics (power supply, transport, e-communication). They will require, howe-

ver, a very large deployment of personnelto the site over several summer seasonsfor the construction,

. large to extremely large projects that, ac-cording to the conclusions of the dedica-ted ARENA activity NA4 would require a

sufciently large increase in the resourcesavailable for logistics that one could notexpect them to be deployed in the comingdecade (such as ALADDIN, AST, AFSIIC

and, a fortiori, KEOPS - the km-scale opti-cal/infrared interferometer array).

For the coming decade and in conside-ration of the reections of the differentworking groups the following recommen-

dations of ARENA are made:.to continue the site assessment.to establish a major funding plan in order

to run the currently on-going telescopesor instruments (COCHISE, IRAIT, ASTEP,

QUBIC) and obtain, as soon as possible,high-quality science from them

.to make plans for the rapid implementa-tion of SIAMOIS and ICE-T. to start immediately, in 2010, a phase Bstudy forPLT on the basis of the phase Astudies made by the Australians for PILOT,

for rst light before the end of the decade..to commence phase A studies for: - a large submillimetre-wave telescope

facility (AST) to exploit the extraordinarypotential of the site in the THz regime,- a pathnder for interferometry in the

optical/NIR range (such as ALADDIN),-an instrument dedicated to high angularresolution astrophysical studies of the Sun

(such asAFSIIC).

It is unlikely that all these actions will be

funded in the next decade. ARENA refrai-ned from ranking these projects, however,

leaving the strategic decisions to the natio-nal, european, and international agenciesthat are expressed, for instance, in the bodyof the ASTRONET recommendations.

However, we believe that the only projectin the mid-size (cost) range that can effec-tively be carried out in the next decade is

PLT. This project has the potential for widesupport from the community and will bemade possible only if a strong and sustai-

nable international collaboration is set uparound it. We point out that several studiesthat will be carried out for this project, such

as the implementation of a Ground LayerAdaptative Optics (GLAO) device specicto polar conditions, the construction of astiff tower and the mitigation of frosting,

will also be useful for other projects, inparticular future optical/IR interferometricand solar projects. Fostering european and

international collaborations and aggre-gating a critical mass of resources havebeen constantly emphasized by ARENA.

The internationalisation of Concordia forastrophysics to the status of a EuropeanResearch Infrastructure is essential, but

it is strongly dependent on the decision

to build rapidly at least one signicantlyambitious project, now, and to propose an

ambitious vision beyond. The Concordiastation at Dome C represents a real op-portunity for Europe (and collaborators)

to develop one of the best astronomicalsites on the Earth, operated all year round.Concordia is ready to implement, host, and

operate a new generation of mesoscaleastronomical instruments capable ofmajor advances in several cutting-edge

astrophysical areas during the next de-cades. The momentum created by ARENAshould denitely be sustained though new

vigorous actions, such as a better coordi-nation of the site testing operations anddata access, the establishment of consortia

to submit excellent proposals to the rele-vant funding calls, and above all the PhaseB design study of mesoscale projects.

Artist view of ALADDIN at ConcordiaPhoto:O.A

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Concordia station (Dome C, Antarctica)

ARENA - Antarctic Research,

a European Network for Astrophysics

AddressLaboratoire Hippolyte Fizeau

UMR 6525 (UNSA/CNRS/OCA)

Universit de Nice Sophia Antipolis (Facult des Sciences)

Centre National de la Recherche Scientique

Observatoire de la Cte dAzur

28 avenue Valrose (Parc Valrose)

06108 Nice cedex 2 - France

WebsitesARENA Portal: http://arena.unice.fr/

ARENA Public outreach: http://www.arena.ulg.ac.be/

Tel. +33 (0)4 92 07 63 22Fax +33 (0)4 92 07 63 21

ARENA partners:

Centre National de la Recherche Scientique, Nice, Lyon, Paris, Marseille, France

Istituto Nazionale di Astrosica, Rome, Italy

Max Planck Institut fr Astronomie, Heidelberg, Germany

Astrophysikalisches Institut Potsdam, Germany

Universidad de Granada, Spain

Consejo Superior de Investigaciones Cientcas, Barcelona, Spain

Instituto de Astrofsica de Canarias, Tenerife, Spain

University of Exeter, United Kingdom

Universit degli Studi di Perugia, Italy

Institut Paul-Emile Victor, Brest, France

Deutsches Zentrum fr Luft-und Raumfahrt, Berlin, Germany

Observatoire de Paris , France

Commissariat lEnergie Atomique, Saclay, France

Universit de Lige, Belgium

Programma Nazionale di Ricerche in Antartide, Rome and Bologna, Italy

University of New South Wales, Sydney, Australia

SHAKTIWARE , Marseille, France

Advanced Mechanical and Optical Systems, Lige, Belgium

Socit Europenne des Systmes Optiques, Aix-en-Provence, France

Centro de Astrosica da Universidade do Porto, Portugal

European Southern Observatory, Garching-bei-Mnchen, GermanyThals Alenia Space, Toulouse and Cannes, France

Editor

ARENA Coordinator :Nicolas Epchtein

[email protected]

Editorial conception

ARENA Project manager :Marie-Laure Pronne

[email protected]

Graphic conception

NovaTerra/ Delphine Bonnet

http://www.novaterra.fr

Photogravure : Noir EbenePrinter : Yatooprint

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