Laboratory for Adaptative Opti s for the GMT Proje t

(Laboratório de Ópti a Adaptativa para o Projeto GMT)

Regular Resear h Award

(Projeto de Pesquisa Regular)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) &

The Netherlands Organisation for S ienti� Resear h (NWO)

Prof. Dr. Mar elo Augusto Leigui de Oliveira

(Prin ipal Investigator)

Universidade Federal do ABC (UFABC)

Blo o B, 10◦andar, Sala 1015

Av. dos Estados, 5001

CEP 09210-580 Santo André - SP

e-mail: leigui�ufab .edu.br

September, 2015

Abstra t

All of the proposed Extremely Large Teles opes (ELTs, in luding the E-ELT, GMT, and TMT)

are limited by opti al distortions introdu ed by the Earth's atmosphere. These distortions will be par-

tially ompensated by the use of Adaptive Opti s (AO), optome hani al systems that an measure the

in oming wavefronts of light from elestial obje ts and rapidly apply an approptiate opti al orre tion

using an a tive opti al element, typi ally a deformable mirror.

The development of AO is driven by the need for more photons from the s ien e target being

delivered into fewer pixels within dete ting instruments, minimising the noise from sky ba kground

photons. Seeing limited instruments s ale approximately linearly with teles ope size, but AO fed

instruments remain the same size or an be ome smaller with di�ra tion limited imaging. An AO

for ELT laboratory in Brazil will enable rapid testing of new hardware and software algorithms, and

provide a teles ope simulator with whi h to test new instrument on epts.

Keywords: Astronomi al instrumentation, adaptive opti s.

Resumo

Todos os Teles ópios Extremamente Grandes (ELTs, na sigla em inglês) in luindo o E-ELT,

o GMT e o TMT, são limitados por distorções ópti as introduzidas pela atmosfera da Terra. Tais

distorções serão par ialmente ompensadas pelo uso de Ópti a Adaptativa (AO, na sigla em inglês),

sistemas optome âni os que podem medir a frente de onda da luz in idente de objetos elestes e rap-

idamente apli ar uma orreção ópti a apropriada usando um elemento ópti o ativo, tipi amente um

espelho deformável.

O desenvolvimento de AO é impulsionado pela ne essidade de mais fótons do objeto ientí� o

sendo entregue em um número menor de pixels dentro dos instrumentos dete tores, minimizando os

fótons do ruído de fundo do éu. Instrumentos de visão limitada es alonam aproximadamente linear-

mente om o tamanho do teles ópio, mas instrumentos alimentados om AO permane em do mesmo

tamanho ou tornam-se menores om o imageamento no limite de difração.

Neste projeto, propomos a instalação de um laboratório de AO para ELTs no Brasil que permitirá

testes rápidos de novos dispositivos (hardware) e de algoritmos (software) e proverá uma simulação dos

teles ópios om a qual novos on eitos de instrumentos poderão ser testados.

Palavras- have: Instrumentação astron�mi a, ópti a adaptativa.

1 Introdu tion

Ground-based instruments that allow studies in modern-day astronomy demand the employment

of very large apertures to a hieve the proper sensibility and angular aperture in order to observe very

distant obje ts in the universe. The Giant Magellan Teles ope (GMT) is an Extremely Large Teles opes

(ELT) that will have a system of seven mirrors of 8.4 m of diameter, totalizing 25.4 m of diameter.

However, atmospheri distortions must be orre ted by the use of optome hani al systems, known as

Adapatative Opti s (AO). In the ase of GMT, the AO will be performed by deformable mirrors, after

measurements of the in oming light wavefronts from elestial obje ts. The 25 m diameter of GMT

mirrors will open up new horizons in almost all astronomi al subje ts of interest today. It will a ess

a volume of the universe 30 times larger than the present day generation of very large (8 - 10 m lass)

teles opes, giving it 3 - 4 times higher �delity in the quality of its images. And the GMT proje t will

bring unique opportunities of s ienti� dis overies for Brazilian s ientists.

The following proje t is fo used on our parti ipation in the international ollaboration that

aims to build the GMT observatory. Among the large s ope of the GMT proje t we have hosen to

ollaborate with the ones our work is going to have a large impa t. First, we des ribe the international

GMT e�ort and, in the sequen e, the plans and needs of s ientists involved in this proje t. We are

going to use the riveting features, namely, wide range of subje ts, fundamental and te hnologi al tasks

and international insertion to attra t young resear hers and students. Our most important goals are

the installation of a laboratory of AO � with modern te hnologies, in many ases unkown in Brazilian

institutions �, the edu ation of graduate and undergraduate students and the sinergy with national

industries.

2 The Giant Magellan Teles ope proje t

The Giant Magellan Teles ope (GMT) is a 25.4 m diameter ground-based opti al and infrared

teles ope being developed by a onsortium of universities, resear h institutions, and national govern-

ments [1℄. The teles ope has a Gregorian opti al design, with an f/0.7 primary mirror omposed of

seven 8.4 m diameter ir ular segments, an identi ally segmented on ave se ondary mirror (see Fig. 1

and Table 1 for the main properties of the GMT). The GMT will be built on Cerro Las Campanas, at

Las Campanas Observatory in northern Chile. Preparation of the site has already begun.

The GMT proje t had its origin in a series of dis ussions between 2000 and 2003 among the

original Magellan partners and interested parties outside the Magellan ommunity. A number of groups

were onsidering the s ienti� apabilities of a next generation large teles ope and a variety of te hni al

approa hes to apertures beyond ten meters were being onsidered.

Some of the GMT's highest s ien e priorities require Adaptive Opti s (AO) observing modes,

whi h an provide vastly improved spatial resolution, sensitivity, and ontrast over that allowed by

natural seeing. However, as the potential gain provided by AO in reases with aperture, so does the

hallenge. Alignment and vibration toleran es be ome tighter with the smaller di�ra tion limit, and

the required number of a tuators, wavefront sensor subapertures, and guidestars in reases. The GMT

AO system is based on an Adaptive Se ondary Mirror (ASM), whi h provides AO orre tion to every

instrument on the teles ope. Wavefront sensor assemblies at ea h teles ope fo us implement the AO

observing modes required by the instruments at that lo ation, similar to the Multiple Mirror Teles ope

(MMT) and Large Bino ular Teles ope (LBT) AO systems [2℄ [3℄. This design eliminates any ommon

�AO relay� and provides high throughput and low emissivity, with a maximum of only 3 re�e tions

between the sky and any instrument.

The approa h to reating the large olle ting area and aperture employed in the GMT draws on

the outstanding image quality derived from the stru tured honey omb mirrors in use on the Multiple

Mirror Teles ope (MMT) and Magellan teles opes. These mirrors, with their high sti�ness and short

thermal times ales deliver images that mat h the natural seeing and an be made with very fast fo al

ratios, enabling large �elds of view while keeping the teles ope and en losure relatively small.

1

Figure 1: Rendering of the Giant Magellan Teles ope (right) with a detail of the segmented Adaptive

Se ondary Mirror (left) [4℄.

Property Value Notes

Colle ting Area 368 square meters 7 x 8.4m diameter segments

Angular Resolution 10 mas at 1µm Rayleigh riterion � 1.2λ/DOpti al Pres ription Aplanati Gregorian �

Final Fo al Ratio f/8 �

Fo al Plane S ale 0.997 ar se onds per mm �

Wavelength Range 0.32 25µm Al oatings baseline

Field of View 20 ar minute diameter With wide-�eld orre tor

Table 1: Basi properties of the GMT.

2.1 The GMT s ien e ase

We re ognize that many of the important ontributions from s ienti� fa ilities, and astronomi al

observatories in parti ular, ome from unanti ipated dis overies of new phenomena and pro esses.

Examples in modern astronomy abound. The dis overies of quasars, pulsars, dark matter, Gamma

Ray Bursts (GRBs), and other phenomena arose when new windows on the Universe were opened

by te hnologi al advan es. Many of these dis overies (e.g. quasars, GRBs) were made possible by

multi-wavelength observations using a range of fa ilities.

The gain from an in reased aperture in seeing-limited appli ations is easily hara terized. The

number of photons olle ted per unit time in reases as the olle ting area, orD2. Thus the signal to noise

per unit time in reases as the �rst power of the diameter in ba kground- and sour e-limited appli ations,

and as the square for dete tor-limited environments. The time needed to rea h a given signal-to-noise

ratio for a �xed �ux, often alled the "sensitivity", in reases as the �rst or se ond power of the diameter

in the ba kground or dete tor-noise limited regimes, respe tively. Many s ien e appli ations with large

teles opes are sky or ba kground-limited. High-dispersion spe tros opy is o asionally dete tor-noise

limited, while high signal-to-noise high-resolution spe tros opy of bright targets is often sour e-noise

limited.

Adaptive opti s allows one to on entrate the light from point or ompa t sour es against the

foreground sky. This in reased image on entration provides additional gains in sensitivity as a fun tion

of aperture size (see Fig. 2). In the sky- or ba kground-limited regime, the signal to noise ratio for

a point sour e per unit time in reases as D2, while the time needed to rea h a given signal to noise

ratio de reases as D4. The slightly dilute pupil provided by GMT makes this s aling somewhat more

2

Figure 2: Gains in sensitivity [5℄.

omplex. This D4fa tor is often ited as one of the primary drivers for extremely large teles opes

(ELTs). Some of the most interesting appli ations of adaptive opti s today, however, will likely not

s ale asD4, as they deal with obje ts that are partially or fully resolved at 100 mas resolution. Integral

�eld spe tros opy of distant galaxies, for example, is one of the key s ien e drivers for ELTs. In Figure

2 we illustrate the dis overy spa e opened by the GMT in terms of gains in sensitivity. In this ontext

we onsider sensitivity to mean the depth a hieved at a �xed signal-to-noise ratio in a �xed time as a

fun tion of wavelength.

Adaptive opti s also opens up a dis overy spa e in spatial resolution. In Fig. 3, we illustrate the

dis overy spa e opened by the in reased angular resolution o�ered by the GMT ompared to urrent

generations of teles opes. The gains in angular resolution simply s ale as the diameter of the aperture.

The fa tor of three in rease in resolution ompared to an 8 m aperture opens up a number of interesting

areas of parameter spa e. The GMT will dramati ally in rease the volume of spa e over whi h one an

image the sphere of in�uen e for massive bla k holes. Similarly, the mass range that one an probe for

entral bla k holes in nearby galaxies is improved. In the ase of exoplanet imaging, a fa tor of three

redu tion in the inner working angle opens up a large number of radial velo ity dete ted planetary

systems for imaging in re�e ted light, where only a handful are within rea h today. Similarly, in the

ase of thermal emission the improved angular resolution will allow GMT to rea h to stellar nurseries

in the southern Milky Way and to probe terrestrial zones in nearby stars and protoplanetary and debris

disks.

These gains in sensitivity and angular resolution by using AO enable the GMT to provide good

data for the study of several s ienti� topi s, among them, we an list (from lo al phenomena to distant

obje ts and the early Universe):

• Star, planet, and disk formation;

• Extrasolar planetary systems;

• Stellar populations and hemi al evolution;

• Galaxy assembly and evolution;

• Fundamental physi s;

• First light and reioinzation.

3

Figure 3: Angular resolution dis overy spa e opened up by the GMT using adaptive opti s [5℄.

3 Adaptive Opti s system

The GMT design in orporates adaptive opti s into the teles ope through the use of adaptive

se ondary mirrors. Adaptive Se ondary Mirrors (ASM) have been developed for the MMT and LBT

AO systems and produ e outstanding di�ra tion-limited images with high throughput and low thermal

ba kground. The Adaptive Opti s (AO) system will be an integral part of the GMT, providing laser

guidestar generation, wavefront sensing, and wavefront orre tion to every instrument urrently planned

on the 25.4 m diameter GMT. There will be three �rst generation AO observing modes: Natural

Guidestar (NGAO), Laser Tomography (LTAO), and Ground Layer AO (GLAO). All three will use a

segmented adaptive se ondary mirror to deliver a orre ted beam dire tly to the instruments.

The GMT will support three AO observing modes for the �rst generation of instruments, using

di�erent wavefront sensing approa hes to balan e turbulen e ompensation with sky overage and �eld

of view. The ASM is the primary wavefront orre tor for all of these modes.

• The Ground Layer AO (GLAO) observing mode uses natural guidestars (NGS) in the periphery

of the dire t Gregorian �eld of view to tomographi ally re onstru t the turbulen e below 1 km

altitude, providing modest image quality improvement at 0.35-25 µm over a �eld of view up to

20 ar min diameter;

• The Natural Guide Star AO (NGAO) observing mode uses a single NGS wavefront sensor lo ated

ahead of the instrument to provide all of the wavefront orre tion information for the AO System,

delivering di�ra tion-limited imaging at 0.9-25 µm wavelength over a �eld of view limited by

atmospheri anisoplanatism;

• The Laser Tomography AO (LTAO) observing mode uses a 1� diameter asterism of 6 Laser

Guidestars (LGS) to tomographi ally re onstru t the high-order omponents of the atmospheri

wavefront aberrations in the dire tion of a entral s ien e target. One NGS is used to measure

tip-tilt, fo us, segment piston, and dynami alibration terms. Wavefront aberration will be

ompensated by the ASM, providing di�ra tion-limited imaging at 0.9-25 µm wavelength over a

�eld of view limited by atmospheri anisoplanatism.

The ASM must also support the Natural Seeing (NS) observing mode, in whi h only fast tip-

tilt is orre ted. The AO observing modes will be deployed sequentially during the ommissioning

period of the teles ope, with the system �rst supporting GLAO orre tion for the GCLEF and GMACS

4

Figure 4: Left: proposed GMT wide-�eld instruments in the Gregorian Instrument Rotator (GIR);

right: proposed GMT narrow-�eld instruments mounted on the upper surfa e of the GIRm [4℄.

instruments, then NGAO mode and �nally LTAO mode for the di�ra tion-limited instruments. Se ond-

generation observing modes whi h use the ASM as the �rst-stage orre tor for an extreme, multi-

onjugate, or multi-obje t AO system are being onsidered.

4 The GMT instrument andidates

In the dis ussion that follows, we make spe i� referen es to GMT instruments. These referen es

allow to illustrate spe i� examples of where the GMT an address ontemporary s ien e questions. In

Table 2 we tabulate the six instruments and one fa ility system that are urrently under development

by the GMT partners. We do not expe t that all six of these instruments will be ready by �rst-light.

A pro ess is in motion that will sequen e the development of instruments and identify whi h of these

six will onstitute the �rst generation, and whi h may be in luded in the se ond generation. The latter

will be developed during the last few years of onstru tion and �rst few years of GMT operations.

Some of the instruments already have very advan ed developments, while others do not. Thus, in the

folowing se tion, we will fo us our dis ussion in one of these instruments, GMACS, whi h still has open

rooms for works within the GMT onsortium. Below we brie�y summarize the salient properties of

ea h instrument. In Fig. 4 one an �nd a view of the GMT instruments positioning in the teles ope

stru ture.

Name Capability Wavelength range (µ) AO Mode

G-CLEF Visible E helle 0.35 - 1.0 Seeing-limited

GMTNIRS Near-IR E helle 1.2 - 5.0 Di�ra tion-limited

GMACS Visible MOS 0.35 - 1.0 Seeing-limited

NIRMOS Near-IR MOS 0.85 - 2.5 Ground-layer AO

GMTIFS Integral Field Spe 0.9 - 2.5 Di�ra tion-limited

TIGER mid-IR planet imager 1.5 - 10.0 NGS di�ra tion-limited

MANIFEST Fiber-Feed system Instrument dependant

Table 2: Candidate �rst generation instruments.

G-CLEF: The GMT CfA-Carnegie-Chi ago Large Earth Finder is a pre ision radial velo ity

spe trograph that also provides a general high-resolution visible spe tros opi apability. G-CLEF

will reside in a gravity invariant and temperature ontrolled environment on the azimuth disk of the

teles ope. An opti al and �ber relay system will transfer light from the teles ope to G-CLEF and will

s ramble the light within the seven sub-apertures in the pro ess. The instrument will support several

observing modes with a range of spe tral resolutions and input aperture sizes.

5

GMTNIRS: The GMT Near-IR spe trometer is a 1.2 - 5 mi ron e helle optimized for studies of

young stellar obje ts, debris disks, and protoplanetary systems. It will use Sili on immersion gratings

to a hieve high spe tral resolution in a ompa t format. Using slits well mat hed to the di�ra tion-

limited image size from a single segment, GMTNIRS will deliver R = 100 - 120k spe tra over all of the

atmospheri windows in a single observation. This represents an enormous gain in observing e� ien y

ompared to urrent spe trographs that sample only a fra tion of a band in a single setting.

GMACS: The GMT visible multi-obje t spe trograph uses �eld and wavelength multiplexing

to deliver an enormous A- ombination. A tent mirror dire ts an 8 x 18 ar minute �eld of view to

four ollimators that are followed by di hroi s that feed red- and blue-optimized ameras. The full

instrument will deliver moderate resolution (R = 1500 - 5000) spe tros opy over a very large �eld of

view over the full visible (0.35 - 1.0 mi ron) region of the spe trum. The A produ t for GMACS is

ten times that of DEIMOS on Ke k and 1.5 - 2 times that of any multi-obje t spe trograph under

dis ussion for other ELT proje ts.

NIRMOS: The GMT Near-IR Multi-Obje t Spe trograph uses old slit masks and volume

phased holographi gratings to provide a highly e� ient moderate resolution (R = 3000) spe trograph

with a �eld of view of 6.5 x 6.5. Cold slit plates an be swapped out during the day using a gate value

to isolate the slit mask hamber. NIRMOS an be used in onjun tion with the fa ility ground-layer

AO (GLAO) system to in rease its sensitivity and image quality. The primary s ien e appli ation for

NIRMOS is spe tros opy of galaxies at intermediate and high redshifts.

GMTIFS: The GMT integral �eld spe trograph builds on the lega y of the NIFS instrument

on Gemini. It uses an image sli ing mi ro-mirror system to reformat the fo al plane onto the dete tor.

Multiple spaxel s ales are possible; all feed an R = 5000 spe trograph that an over any one of the J,

H, or K-bands in a single setting. The instrument also has an imaging hannel that will over the laser

tomography AO (LTAO) �eld with riti al sampling in the J-band.

TIGER: The GMT thermal IR imager targets exoplanets, debris disks and low mass stars, but

will also provide a powerful apability for studying AGN and starburst nu lei. The amera operates

from the H-band through the 10 mi ron band and will employ a variety of te hniques to provide high

ontrast for exoplanet imaging.

MANIFEST: The GMT has an unusually large �eld of view for an ELT. While some of the

proposed instruments use a signi� ant portion of the �eld, none make full use of the 20 diameter. The

GMT fa ility �ber system provides a means to observe multiple targets over the entire �eld of view with

one or more of the spe trographs. MANIFEST an, in prin iple, feed GMACS, NIRMOS, and G-CLEF.

The pre ise multiplexing gains vary for ea h spe trograph depending on the available slit length. The

MANIFEST on ept uses �Starbugs� - self-motile �ber heads deployed on a glass plate. MANIFEST

o�ers a means by whi h GMT an be optimized for high A survey s ien e without reimaging the full

fo al plane.

5 GMACS - The GMT Wide-Field Opti al Spe trograph

The wide-�eld opti al spe trograph for GMT is alled GMACS by analogy with IMACS, the

wide-�eld opti al spe trograph for Magellan. The urrent on ept for GMACS provides omplete,

simultaneous spe tral overage over the wavelength range from 0.36 to 1.02 µ, for hundreds of obje tsin an 8 x 18 ar min �eld of view. The resolution with a 0.7 ar se slit is 1400 in the blue and 2700 in

the red. The opti al design of the GMACS ollimator and the GMT se ondary mirror have all been

developed together as a system. The instrument is modular and lends itself to a staged deployment

with an initial set of apabilities whi h an be expanded to the full set as time and resour es permit.

A 3-D view of all 4 arms is shown in Figure 5 and an opti al layout of a single arm of GMACS is

shown in Figure 6. The 4 diagonal mirrors have been arranged into an assembly alled the "tent mirror"

whi h dire ts light from the four quadrants of the �eld into two main "opti s modules" on opposite sides

of the instrument platform. In the enter of the platform is the fo al plane assembly whi h in ludes

the �eld lens, aperture plate and tent mirror together with guiders for maintaining the alignment of

6

Figure 5: 3-D view of GMACS [6℄.

Figure 6: Layout of a single arm of GMACS [6℄.

obje ts on the aperture plate, and image analyzers for maintaining the a tive-opti s alignment of the

teles ope.

Sin e the emphasis in GMT is on the olle ting area for seeing-limited observations (and on

the di�ra tion limit for AO observations), the multislit approa h has been sele ted as the baseline in

order to avoid ompromising the ultimate magnitude limit of the spe trograph. However the ollimator

design for the multislit spe trograph may also be suitable for use with �bers, and an optional �ber

input appears to be an interesting upgrade path for future study.

Two approa hes are ommonly used to take many spe tra simultaneously over a large area of

the sky. The �rst is to use a multislit spe trograph and an aperture plate. The se ond is to use a

�ber spe trograph and a �ber positioner. The �ber spe trograph is subje t to �ber losses and generally

will have somewhat lower e� ien y per obje t than the multislit spe trograph. On the other hand the

multislit spe trograph must ope with a semi-random distribution of dispersed images over the �eld

of view, whi h typi ally results in a somewhat lower multiplex advantage. High-a ura y te hniques

for ba kground subtra tion, for example nod-and-shu�e [7℄, appear to be equally appli able to either

approa h.

The desirable �eld of view for a seeing-limited spe trograph falls into the ategory of "more is

7

better." The multiplex advantage will go up in proportion to the total slit length and there will always

be some programs whi h an utilize this advantage, whether be ause they aim to over the maximum

possible area on the sky or be ause they on entrate on obje ts of a parti ular size. The real question

is what is the maximum pra ti al �eld of view.

For a wide-�eld ollimator, opti al solutions based on re�e ting opti s tend to su�er from the

problem that the exit pupil is in onveniently lo ated. Creating an external pupil in a S hmidt- like

opti usually requires large obs urations or an o�-axis arrangement, neither of whi h is desirable.

Transmitting opti s, on the other hand, an in ertain ir umstan es be orre ted for extremely wide

�elds of view while maintaining good olor orre tion, high throughput, and an a essible exit pupil. In

the IMACS design [8℄, the se ondary fo al ratio is optimized in order to mat h the fo al plane urvature

of the teles ope to the fo al plane urvature of the transmitting ollimator. The hoi e of a Gregorian

rather than a Cassegrain se ondary is required to obtain the desired sign of the �eld urvature. The

opti al performan e of the IMACS ollimator is very high ompared to other ollimators whi h do not

take advantage of this arrangement.

There are six main omponents of the GMACS instrument pa kage:

1. The �eld lens assembly, whi h ontains the last element of the �eld orre tor/ADC. The �eld lens

is mounted just below the bottom of the instrument platform, and just above the orre ted fo al

plane/aperture mask;

2. The aperture mask shuttle, whi h arries the mask ontaining multiple entran e apertures for the

imaging spe trographs. The aperture mask must be made of a thin opaque material and shaped

to onform to the urvature of the teles ope plane;

3. The aperture mask hanger, whi h an load one of several aperture masks onto the aperture mask

shuttle. Ea h aperture mask is ustom-made for a parti ular observation by utting holes or slits

into a blank mask;

4. The tent mirror assembly, whi h ontains the diagonal tent mirrors as well as movable guide

ameras for aligning the aperture mask on the sky and omparison sour es for a tive �exure

ompensation;

5. One opti s module whi h ontains the ollimator opti s, di hroi mirrors, red and blue gratings,

amera opti s and CCD mosai s for two of the four �y's-eye spe trographs;

6. And another opti s module, identi al to the previous one.

There are two distin t regimes for the dete tion of very faint obje ts. In the �blue� (0.35 to 0.70µ)there are relatively few night sky lines and the ba kground is more or less ontinuous. As long as the

sky ba kground safely ex eeds the dete tor noise, the quality of the result will not depend strongly

on resolution. In the �red� (0.70 to 1.00µ) there are many bright night sky lines. At su� iently high

resolution, the spe tral overage between the lines dominates, and for at least some observations the

su essful strategy will be to ut out the lines and either leave gaps in the spe tra where the S/N ratio

is very low, or interpolate over them.

The GMACS ameras should be fast enough that the entire 9 ar min slit an be imaged onto

the length of 2 CCD's in a 2 x n mosai of 3-side buttable CCD's. Depending on the exa t length of

the CCD's, the interesting range of fo al ratios is between 2 and 3. Note that imaging the slit along

the mosai in this dire tion is required for nod-and-shu�e operation.

In Figure 7 the opti s modules are shown. There are two of these in the full GMACS implemen-

tation, separated by 180 degrees. The ameras (blue and red) are illustrated in Figure 8.

6 Proje t

GMT will be 25 meter teles ope to be built in Chile by a onsortium formed by the Carnegie

Institution for S ien e, The University of Texas at Austin, Harvard University, The Australian National

8

Figure 7: Opti s modules [9℄.

Figure 8: Blue amera (left) and red amera (right) showing lens arrangement, stru ture, and ryostat

for dete tors [9℄.

9

Figure 9: The measurement setup for phase modulation hara teristi s [10℄.

University, Smithsonian Astrophysi al Observatory, University of Arizona, Texas A&M University,

Astronomy Australia Ltd., Korea Astronomy and Spa e S ien e Institute and the University of Chi ago.

The onstru tion ost is 706 million dollars (in 2008 US$) and operating ost is 20 million US$ annually.

It is anti ipated that 13 million US$ will be required annually for an instrumentation program. Brazil

has re eived an o�er to parti ipate with a minimum of 5% in this proje t. The GMT seems to be

an appropriate hoi e to our ommunity sin e it is the heapest of the ELT proje ts. We ould be

responsible for signi� ant pa kages, for example, pa kages in the �ber-fed instruments and the e helle

opti al spe trographs. And, as the teles ope will be installed in Chile and no partner will have in-

kind ontributions, our industry would be very ompetitive for signi� ant ontra ts (for example: the

en losure).

GMT has many times the olle ting area of an 8-m lass teles ope, and obje ts observed at the

spe tros opi limit will be extremely faint ompared to sky. Subtra tion of sky ba kground will depend

on a hieving high systemati a ura y, for example by using AO in order to in rease the throughput

in the di�ra tion limit regime. The AO system will be an integral part of the teles ope, providing

laser guidestar generation, wavefront sensing, and wavefront orre tion to every instrument urrently

planned on the 25.4 m diameter GMT. There will be three �rst generation AO observing modes:

Natural Guidestar, Laser Tomography, and Ground Layer AO. All three will use a segmented adaptive

se ondary mirror to deliver a orre ted beam dire tly to the instruments.

This is a proposal for a joint resear h ooperation between Federal University of ABC (UFABC)

and the University of Leiden (in the Netherlands), attending a joint all by FAPESP (São Paulo

Reasear h Foundation) and (NWO) the Netherlands Organisation For S ienti� Resear h. Our aim is

to develop systems and expertise in advan ed instrumentation for GMT. Thus, in the present proje t

we propose the following a tivities:

1. Assembling and alignment of a system that will simulate (in a smaller s ale, ∼ 1 : 20) the

main opti al systems of the GMT, i.e., the primary and the se ondary mirrors. The GMT

AO system ar hite ture is based around an ASM as the primary wavefront orre tor. When

ombined with a �dire t feed� of the high-order wavefront sensors, this hoi e naturally provides

high throughput, low emissivity, a wide orre ted �eld of view, and low di�erential aberrations

between the wavefront sensors and instruments. The dire t-feed wavefront sensing ar hite ture

is so named be ause light from the teles ope is passed dire tly from the tertiary mirror to the

s ien e instruments. High-order wavefront sensing is performed using visible light re�e ted from

a di hroi instrument window, tilted 20◦to the in oming beam.

2. Installation of a Spatial Light Modulator (SLM) that will simulate the addi tion of a phase in

the wavefront, due to atmospheri turbulen es. A SLM is an obje t that imposes some form of

spatially varying modulation on a beam of light. Usually, it modulates the intensity of the light

beam. However, it is also possible to introdu e modulations of phase in the beam. Or even to

introdu e both: modulations of intensity and phase. In our appli ation, the SLM will be used to

10

introdu e the e�e ts aused by atmospheri turbulen es in the beam. In Figure 9, the reader an

see the proposed setup for this implemantation;

3. Studies of the performan e of dire t feed sensing, through the use of a multislit spe trograph and

an aperture plate, in omparision with a �ber spe trograph and a �ber positioner. We will test

both possibilities measuring the light intensity and spot size obtained in ea h on�guration;

4. Development of an instrument similar to GMACS, but in the s ale of the intended laboratory

prototype (∼ 1 : 20). After the a omplishment of this prototype, studies will start for building

a real size instrument.

5. Development of omputer simulations in order to pre isely des ribe the light propagation and

output in ea h studied on�guration of the opti al systems. The omputer simulations will follow

obje t-oriented programming paradigm, in whi h di�erent parts of the problem are treated within

di�erent lasses, su h as: �Geometry�, �Opti s� or �Dete tor�. This is an approa h that the authors

of this proposal have great experien e [11℄;

6. Ex hange of resear hes within the s ope of the ollaboration. The resear hes from the Brazilian

side will work a ouple of months per year in the laboratory of adaptive opti s of the University

of Leiden, as well as, the resear hes from the Dut h side will ome to visit and help us on the

installation of the systems and on the analysis of the data. Video onferen es and the realization

of annual meetings are also foreseen;

7. The submission of a postdo fellowship proje t, on ea h side of the ollaboration. The resear hers

from ea h side will be in lose onta t to ea h other and his/her main a tivities will be the

implementation of the AO systems, as des ribed above.

UFABC has fa ulty of ex ellen e, with 100% of PhD professors in several �elds of s ien es and

engineering. Many of them are involved in postgraduate programs, su h as: Physi s, Computer S ien es

and the Information, Ele tri al and Me hani al Engineerings. There is a great support of this proposal

by the university organizational leaders in order to start a program in Advan ed Instrumentation for

Astronomy. Indeed, a laboratory room of about 50m2is reserved for the installation of the equipments,

if this proposal is su essful.

The s ientists parti ipating in this proposal are:

• Prof. Dr. Mar elo Augusto Leigui de Oliveira - CCNH/UFABC

• Prof. Dr. Annibal Hetem - CECS/UFABC

• Prof. Dr. Pieter Willem Westera - CCNH/UFABC

• Prof. Dr. Guiou Kobayashi - CMCC/UFABC

• Prof. Dr. Matthew Kenworthy - Leiden University/The Netherlands

• Prof. Dr. Christoph Keller - Leiden University/The Netherlands

7 Materials

The installation of the Laboratory of Adaptative Opti s for the GMT Proje t will a omplish

the obje tive of giving the ne essary infrastru ture for a ademi and applied resear hes in the �eld of

Astronomy and Astrophysi s. The dire t appli ation of the produ ed instruments and the resulting

data will be the GMT proje t. However, other teles opes of smaller sizes may also take advantage of

their produ ts. They have a strong hara ter of innovation and an start patent requests.

In the laboratory, an experimental and omputational apparatus will be setup. Initially, it will

ontain the following equipments:

11

• Spheri al mirrors (primary and se ondary) with 10-20 mm of diameter and 40-80 mm of fo al

length;

• Spatial Light Modulator (SLM) from visible up to 2 µ, lear aperture of 7.6 mm and 512× 512

a tuator version;

• Turbulen e plates of 20 mm diameter disks with atmospheri turbulen e written into them;

• Laser (He-Ne) with power of 5-10 mW;

• Kit of opti al elements: lenses, �lters, opti al �bers, and positioning systems;

8 S hedule

The present resear h proje t will be exe uted in within 2 years and the a tivities will be performed

by the team of the listed resear hes as well as by the future postdo resear her. The s hedule is the

following:

Month A tivities of the 1styear

1

2 A quisition Simulations Call for

3 of equipments postdo

4

5 Assembling and

6 alignments Visit to

7 Leiden laboratory

8

9 Data

10 analyses Workshop

11

12 Report/A ounting

Month A tivities of the 2nd

year

1

2 A quisition Simulations

3 of equipments

4

5 Assembling and

6 alignments Visit to

7 Leiden laboratory

8

9 Data Workshop

10 analyses

11

12 Report/A ounting

9 Con lusion

We presented in this Resear h Proje t a proposal to insert UFABC in the GMT onsortium.

GMT will be a next-generation ELT whi h will provide quality data to study very faint obje ts in the

universe, expanding the observing distan es and our knowledge in important subje ts in Astronomy

12

and Astrophysi s. The use of AO will be mandatory sin e, at GMT's level of sensitivity and angular

resolution, Earth's atmosphere generates non-negligible distortions in the images.

Our aim is to install at UFABC a laboratory of AO in whi h, by the use of a spatial light

attenuator and turbulen e plates, we will be able to simulate GMT's light throughput. Therefore, we

will study and propose implementations of devi es that ould provide an enhan ement in the formation

of images.

This proje t will be led by resear hes from UFABC in lose ollaboration with our olleagues

at the University of Leiden and at Instituto de Astronomia, Geofísi a e Ciên ias Atmosféri as (IAG)

from University of São Paulo. Taking advantage of our experien e in big ollaborations and in the

assembling of big teles opes for Astrophysi s, we are very on�dent that the proje t will run and the

laboratory will be implemented su essfully.

Referen es

[1℄ Johns M., M Carthy, P. J., Raybould, K., Bou hez, A., Farahani, A., Filgueira, J. M., Ja oby, G.,

She tman, S., Sheehan, M., Giant Magellan Teles ope: Overview, Pro . SPIE 8444, (2012).

[2℄ Hart, M., Milton, N. M., Barane , C., Powell, K., Stal up, T., M Carthy, D., Kulesa, C., Bendek,

E., A groundlayer adaptive opti s system with multiple laser guide star, Nature 466, 727-729 (2010).

[3℄ Esposito, S., et al., First light AO (FLAO) system for LBT: �nal integration, a eptan e test in

Europe, and preliminary on-sky ommissioning results, Pro . SPIE 7736, (2010).

[4℄ Bou hez, A., et al., The Giant Magellan Teles ope adaptive opti s system, Pro . SPIE 8447-054;

http://www.gmto.org/SPIE_2012/1340895643986_GMTO_SPIE_8447_54_v1.pdf

[5℄ http://www.gmto.org/Resour es/GMT-ID-01404-GMT_S ien e_Case.pdf

[6℄ http://www.gmto.org/Resour es/GMT-ID-01478-Se tion_13.6_GMACS.pdf

[7℄ Glazebrook, K. and Bland-Hawthorn, J. 2001, Pub. A. S. P. 113, 197

[8℄ Bigelow, B. C. and Dressler, A. M. 2003, in Instrument Design and Performan e for Opti-

al/Infrared Ground-based Teles opes, eds. M. Iye and A. Moorwood, Pro . SPIE, 4841, 1727

[9℄ D. L. DePoy, et al., 2012 SPIE.8446E. GMACS: a Wide Field, Multi-Obje t, Moderate-Resolution,

Opti al Spe trograph for the Giant Magellan Teles ope.

[10℄ Phase spatial light modulator, Hamamatsu Photoni s, http://www.hamamatsu. om

[11℄ M. A. L. de Oliveira, H. C. Reis, R. Sato and V. de Souza, Manufa turing the S hmidt orre tor

lens for the Pierre Auger Observatory, Nu lear Instruments and Methods in Physi s Resear h: A

522 (2004) 360-370.

10 Summary of Frequent Used Abbreviations

AO Adaptative Opti s

GMT Giant Magellan Teles ope

ELT Extreme Large Teles ope

FAPESP Fundação de Amparo a Pesquisa do Estado de São Paulo - São Paulo Resear h Foundation

NWO The Netherlands Organisation for S ienti� Resear h

UFABC Universidade Federal do ABC - Federal University of ABC

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