CHARA Collaboration Year-Two Science Review D. Mourard VEGA and CHARA VEGA and CHARA Denis Mourard Observatoire de la Côte d’Azur, Dépt GEMINI Proposal

CHARA Collaboration Year-Two Science Review D. Mourard VEGA and CHARA

VEGA and CHARA

Denis MourardObservatoire de la Côte d’Azur, Dépt GEMINI

Proposal for a Visible spEctroGraph and polArimeter on CHARA


Outline

• General presentation of VEGA

• Characteristics and expected performances

• Summary of the science cases

• Technical proposition

• Organisation, schedule, budget


General presentation of VEGA (1)

• GI2T is closed now and we propose to move and adapt the spectrograph REGAIN on CHARA.

• VEGA intends to offer access to the visible band (0.45 to 0.9µm), with spectroscopic (spectral resolution from 1500 to 30000) and polarimetric capabilities.

• VEGA will combine 2 to 4 telescopes in a dispersed fringes mode.


General presentation of VEGA (2)We already have:- a spectrograph with its calibration sources,- 2 new generation photon counting detectors,- a global control system and a data reduction pipeline.

We will have to modify:- the magnification of the cameras of the spectrograph- the injection of the calibration sources.

We will have to:- develop the interface optic system,- adapt the control system in the CHARA framework- upgrade the software control for the 3/4 telescopes mode and

the dedicated data reduction pipeline.

Our current plan is to install VEGA at Mt Wilson by the end of 2007 and to begin operation at the beginning of 2008:Immediate science with two telescopes.Qualification and tests of the 3T/4T mode.


Multimode interferometry

• Large field of view for science … and for alignment!

• Cophasing has no sense in multimode! • Coherencing with and accuracy of Lcoh/NSpCh

• Mlim (fringe tracking) Nph/speckle/frame, independent of D

• SNR increases as

• Differential Interferometry approach– Increased limiting magnitude and SNR

)arg()arg(~

.~

];[ with )()(~

2121*

21

²

];[

²2

VVVVII

ffVVI DBDBBDBDB

Image plane, 2D analysis, photon noise limitationBério et al., 1999, 2001

frameSpeckle NN

21.)( ChCh SNRSNRDISNR


Accuracy in visible multimode interferometryMourard et al., 2002

V2inst = 0.367 ± 0.005 and = 3.07 ± 0.06

Vega observed in June 2001• different nights (seeing)• different baselines• no reference star

V2 estimations• selection of correctly guided images• 9nm @ 645 nm• correction of centroiding effects• correction for the photon bias• instrumental corrections (flux ratio, pupil geometry)

Simultaneous adjustment of Vinstr and *


1-22-4 4-3

1

2

3

4

Pupil plane Modulation Transfer Function

-

+

1-2

1-3

2-3

2-4 4-3

1-4 2-3

1-31-3

1-42-3

D

b=2D

b/ -D/

+D/

VEGA, a 4 beams dispersedfringes combiner


Spectroscopic characteristics

Grating X- mode Spectral distance between red and blue cameras R1: 1800tr/mm R=35000 =6.7nm 18 nm R2: 300tr/mm R=5000 =40nm 140 nm R3: 100tr/mm R=1700 =120nm Not usable simultaneously

Parameters Red camera Blue camera min 0.58µm 0.45µm max 0.87µm 0.75µm ref 0.7µm 0.57µm

Slit width 61µm 50µm Maximum field of view (center of detector) 5.4’’ 4.2’’

Number of spectral channels 173 156 Internal magnification of the spectrograph

(between the slit and the image plane) 1.4 1.8


GI2T/REGAIN SPINNatural light

// ┴

//

┴

UMa (A1V), 650-680nm

SPIN experimentK. Perraut, J.B. Le Bouquin, D.

Mourard

Instrumental polarizationA&A 2006, in press.


New Generation Photon Counting Detectors (OCA/CRAL)

• Sensitivity : x 5

• Rate : x 2 (Algol) x 5 (CPNG)

• Volume : / 5

• Price : / 2,5


Current Software Screenshot


Expected performancesHypothesis for calculations:• For a V=0 star, the number of photons received is equal to N0=1000 ph/s/cm²/A

• Transmission in the visible QTotal=0.15% assuming– QCHARA = 0.03 (…)– QInstrument = 0.15 (13 mirrors @ 0.98 + 1 grating 0.6 + the slit 0.3) – QDetector = 0.3

• Exposure time t0=20ms, integration time=1800s

• Instrumental visibility of CHARA 0.8

• r0 estimations (for 650 nm) @ Mt Wilson. These informations have been extracted from the Nils Turner presentation in 2005:

– Median conditions, r0=8.0*(650/500)6/5=11.0 cm (seeing=1.25’’)– Excellent conditions, r0=15.0*(650/500)6/5=20.6 cm (seeing 0.7’’)


Limiting magnitude

30mn of integration. =650nm.SNR=10 on |VV2| with 1= 50 nm (40, 6.7) and 2= 0.4 nm (0.13, 0.02)


Signal to noise ratio

The calculations are made for a seeing of 1.25’’ and 30mn of integration time


Summary of performances(preliminary estimations)

Dispersed fringe mode (4 telescopes)– Highest spectral resolution: 35000

spectral channelsof0.02nm SNR=10 in 1800sMlimbetween 5.5 and 6.5 depending on seeing

conditions.

– Lowest spectral resolution: 1500 180 spectral channels of 0.4 nm SNR=10 in 1800s, Mlimbetween 8.5 and 9.5 depending on seeing

conditions.

– Simultaneous polarizations measurement


P Cygni on GI2T (1994) X- MRVakili et al., A&A 323, 1997

P Cygni V=5 GI2T94=0.3% Ti=180s, Vinstr=0.5 2=5nm, 1=0.3nm


Summary of the science cases• Fundamental stellar parameters• Stellar activity: spots and Doppler Imaging• Differential rotation and stellar inclination• Asteroseismology• Cepheids: distance scale and pulsating atmospheres• Mira stars and related objects• Active hot stars• Hot emission-line stars in binaries• Wolf Rayet stars

…see detailed presentation by Philippe on Thursday…


Functional analysis of VEGA

SLIT MODULE

ANAMORPHOSIS OPTICS

COLLIMATINGOPTICS

DISPERSIVE OPTICS

POLARIZATION MODULE

SPECTROGRAPHINTERFACE OPTICS

CALIBRATION /ALIGNMENT

UNIT

CHARA

BEAM COMPRESSION

PICKING OPTICS

BEAM CONFIGURATION

CHARA/SOURCES SELECTION

FOCUSING OPTICS

NEUTRAL DENSITIES

CAMERA OPTICS

DETECTOR


Implantation

49 84 23

42.5

38.5

IR

V6

V5

181.5

OPL COMPENSATION FACILITY

S1 S2 TABLE

W1 W2 TABLE

E1 E2 TABLE

BEAM SAMPLER

METROLOGY TABLE

EXIT PUPIL LOCATION

V4

V3 V2 V1

BEAM REDUCER

BEAM COMBINATION LABORATORY

POSSIBLE LOCATION OF VEGA ELECTRONICS

49.5

FLUOR

MIRC

CHARA IRC

59

44 46.5

ELECTRONICS

36

POSSIBLE LOCATION OF VEGA PICK UP MIRRORS

INTERFACE OPTIC TABLE

59

VISIBLE TABLE

SOURCES TABLE

28

135

35.5

28

96 78

72

SPECTRO


Preliminary design of the picking optic

Note: will certainly be considered as an element of CHARA


Design of the Interface optics

Side view

Top view

Sources


Remarks

• The 4 cat’s eye have been designed in order to minimize the difference of longitudinal pupil distances (M2 of BCP) and to match the ZOPD plan of CHARA (longitudinal position of cat’s eye).

• We do not need a longitudinal dispersion correction.


Adjusting the pupil location

Beams of CHARA : S1, S2, W1, W2, E2, E1

Entrance beams in VEGA : V1, V2, V3, V4

S1

V4 V3

V1

S2 W1 W2 E2 E1

V2

Dv = 3’’

Df = 23’’

Dt = 46’’

V1Mbs = 38.5’’

Position of the 1st beam reducer mirror

Exit pupil location

VC = 360.5’’

Focale of the mirror F= 50’’


Chromatic Optical Path Difference

• We take the pessimistic hypothesis of L=100 m due to the differential air path in the delay lines.

• The chromatic optical path difference is given by = L(n- n) = L(1-n/n)

• The contrast loss due to this chromatic OPD is given by C = 1 - sin(/lc)/ (/lc) where lc represents the coherence length: lc = ²/ = R.

• In the case of VEGA, the lowest spectral resolution is R = 1700. At =0.6 µm, it means that the bandwidth of each spectral channel is about =0.35 nm. So, the chromatic OPD inside a spectral channel is only =0.4 µm.

• The contrast loss due to the chromatic OPD is then negligible and the use of a chromatic OPD compensator can be avoided.


The spectrograph

1) Entrance optic

2) Slit module

3) Collimator optic

4) Grating

5) Camera M1s

7) Detector output6) Camera M2s

8) Slit viewer


Control system of VEGA



Provisional schedule2006 2007


Costs and manpower kEuros

HardwareInterface Optics (IOP) 53,0Spectrograph (SPE) 23,0Instrument Control Electronics (ICE) 6,0

Software 10,0AIT Tools 19,5Manpower (contract) 75,0Travels, Missions & Shipment 93,7Sub-Total 280,2

20 % Margin for Contingency 56,0

336,2

Costs

TOTAL

Men.Years

ManpowerAstronomers/Scientists 4,1Management 0,6System Engineering 0,3Optics 1,9Mechanics 1,3Control Electronics 1,3Software 3,0

Sub-Total 12,620 % Margin for Contingency 2,5

15,1

FTEs

TOTAL

• Equipment = 110k€• Additional manpower = 2 men.year (1.5 software, 0.5 mechanical) but mechanic ok and a solution is searched for the software • Mission: certainly overestimated

• Already obtained this year: 35k€• In 2006: request from ANR for 3 years (deadline 20th march)

• This table includes the additional manpower required and corresponds to the 2 years of development.

• This does not include the CHARA participation, that has to be defined if the project is accepted.


ParticipantsUniversité de Nice, LUAN, NiceArmando Domiciano (Science)Slobodan Jankov (Science)Romain Petrov (Science)

Observatoire de Paris, LESIA, ParisVincent Coudé du Foresto (Science)Pierre Kervella (Science)Antoine Mérand (Science)Chantal Stehlé (Science)

Max Planck Institute, BonnKarl-Heinz Hoffmann (Science)Dieter Schertl (Science)Gerd Weigelt (Science)

Observatoire de Ondrejov, PraguePetr Harmanec (Science)Pavel Koubsky (Science)

Observatoire de la Côte d’Azur GEMINI, GrasseAlain Blazit (Science, Detector)Daniel Bonneau (Science, System)Sandra Bosio (Mechanic)Yves Bresson (Optic)Olivier Chesneau (Science)Jean-Michel Clausse (Software)François Hénault (Managem., System)Yves Hughes (Mechanic)Stéphane Lagarde (System)Aurélie Marcotto (Optic)Philippe Mathias (Science)Guy Merlin (Software, Electronic)Denis Mourard (Science, System)Nicolas Nardetto (Science)Alain Roussel (Mechanic)Philippe Stee (Science)

Observatoire de Grenoble, LAOG, GrenobleKarine Rousselet-Perraut (Sci., Sys.)Jean-Baptiste LeBouquin (Sci., Syst.)

Observatoire de Lyon, CRAL LyonPaul Berlioz-Arthaud (Science)Renaud Foy (Science)Isabelle Tallon-Bosc (Science, System)Michel Tallon (Science, System)Eric Thiébaut (Science, Detector)

Our wish is also to develop, through this project, a partnership with the CHARA group (and others also if wished and possible) for the scientific exploitation.

Documents

CHARA Collaboration Year-Two Science Review D. Mourard VEGA and CHARA VEGA and CHARA Denis Mourard Observatoire de la Côte d’Azur, Dépt GEMINI Proposal