GRAVITY

Frank Eisenhauer (Max-Planck-Institute for extraterrestrial Physics) Ten Years of VLTI Conference, Garching, Germany, 26 October 2011

GRAVITY: Observing the Universe in Motion

100 102 104 106

maximum distance from Earth (pc)

single season campaign

three year program

ten year large program

astrometric signal exo-Jupiter/Uranus

orbit of exo-Jupiter/Uranus

proper motionsmassive star cluster

detection of intermediatemass BH in GCs/Arches

detection of SR/GR effects in cusp star orbits

SgrA* flare dynamics

detection of ‘dark halo’ around SgrA*

stellar motions in nuclei of nearby galaxies

binary dynamics

gas flows in AGN

lensing

3d dynamics of nuclear star cluster

imaging jets/disks in YSOs & CBs

evolution outflows in YSOs & micro-QSOs

GRAVITY: Observing the Universe in Motion

Setting the Scale – just to scare … 6 RS

Earth Orbit

RS ~ 10 µas

1 Schwarzschild radius =

a coin on the moon

Phase Referenced Imaging & Astrometry

2”

GC

Phase Referenced Imaging & Astrometry

2”

GC

Contrast (B) <-> FourierTransform (Image)

GRAVITY Astrometry & Imaging

Beam Combiner IR Adaptive Optics

Adaptive Optics

Adaptive Optics Adaptive Optics

Metrology

Metrology Metrology

Metrology

Metrology

Metrology

Metrology

Metrology

Beam stabilization

Beam stabilization Beam stabilization

Beam stabilization

Beam stabilization

Beam stabilization Beam stabilization

Beam stabilization

Adaptive Optics

Wavefront-Sensor

Interferometric Beam

PRIMA Star Separator Light from telescope

Brander, Hippler et al., Clenet et al. 2010

SELEX / ESO development of Infrared Avalanche Photo Diode array:

Adaptive Optics and Fringe Tracking Detectors

Finger et al. 2010

2.75 e- @ 5.8 ms

Brander, Hippler et al., Clenet et al. 2010

Beam Combiner Instrument

Fiber Couplers

Fiber Control Unit

Acquisition Camera Spectrometers

Integrated Optics Beam Combiners

Metrology Injection Units

Haug, Thiel et al.

Guiding system

Single Mode Instrument

Fluoride glass fibers (OHANA) • optimum throughput in K-band • possibility to measure in unpolarized light = sensitivity Perrin, Perraut, Jacou et al.

2”

GC

Fiber control

Perrin et al.

Integrated Optics Optical equivalent of electronic integrated circuits

Jacou et al. 2010, Perraut et al.

Visible laser

Integrated Optics

Jacou et al. 2010, Perraut et al.

0,0000

0,1000

0,2000

0,3000

0,4000

0,5000

0,6000

0,7000

0,8000

2000 2050 2100 2150 2200 2250 2300 2350 2400

FHD PECVD

Average throughput: 59%

K-band operation Cryogenic operation

Spectrometers

Straubmeier et al. 2010

Fringe Tracker – Kalmann Control

Menu, Choquet , Fedou, Dembet, et al.

Fringe Tracker

Choquet et al. 2010

Fringetracking testbed @ LESIA

Lab data

Narrow Angle Astrometry

2”

GC

Interferometric Astrometry

10 µas 500 µm

5 nm

Interferometric Baseline

Lacour et al.

Interferometric Baseline

Lacour et al.

Narrow Angle Baseline

Stable realization of the narrow angle baseline

Calibration of the narrow angle baseline

Lacour, Kervella et al.

500 µm

Interferometric Astrometry

Lacour et al.

Pupil Errors For perfect tip-tilt correction

For simultaneous tilt error

Interferometric Astrometry

Lacour et al.

Align your fibers (angles) well, and actuate both pupils with the same actuator -> Telescope pointing error / common tip/tilt does not hurt too much

Interferometric Astrometry

Lacour et al.

Acquire well, and actuate tip/tilt of both fibers with same actuator -> Pupil error does not hurt too much

Control pupil such that fiber pupils are fixed on metrology reference Minimize Tip/Tilt and guiding errors

Tilt Control Atmosphere VLTI Tunnel

Pfuhl et al., Amorim et al. 2010,

Acquisition and guiding camera

Pupil Control

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

39.000 41.400 43.800 46.200 48.600 51.000 53.400 55.800 58.200 60.600 63.000OPL [m]

late

ral p

upil

[mm

]

lateral y [mm]lateral x [mm]

y = -0.029x - 0.3663

-2.4

-2.2

-2

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

39.000 44.000 49.000 54.000 59.000OPL [m]

long

itudi

nal p

upil

[m]

Amorim et al. 2010, Pfuhl et al.

2”

GC

Fibercoupler

Tip-Tilt-Piston-Actuator

Pupil-Actuator

X,Y,Z Stages

Rotation Stages Shutters

Pfuhl et al. 2010

Laser Metrology

Rabien et al. 2008, Bartko et al. 2010, Gillessen et al.

GRAVITY Key Figures

Fringe Tracking: • UTs: K~10 mag • ATs: K~7 mag

Milestones: • Final design in 2011/12 • Installation at the telescope in 2014

Astrometry: • few 10 µas in 5 minutes

Interferometric Imaging: • UTs: K~16, ATs: K~13 in 100s • SNR(V) = 10 for visibility • σ(φ) = 0.1 rad for referenced phase

Thank you very much for your attention