LBTI Technical Update

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LBTI Technical Update
Topics Beamcombiner work NIC design
progress MMT prototyping activities
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The LBTI-UBC Optical Design
deformable secondary
deformable secondary
f/15 telescope foci
beamcombiner
8.4 m LBT primary
14.4 m separation
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LBTI design

• Discrete cold dewars
• External Rigid Structure
• General Purpose (Universal) Beam Combiner (UBC)?
• Three Camera Ports
• Nulling and Imaging Camera (NIC) is the only
  camera at the moment.
• Integrated Wavefront Sensors

UBC
Side Camera
Wavefront Sensors
NIC
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LBTI Parts
Parent Ellipse Mirror
vacuum bellows
rough cryostat housing
Mirror being polished
cryostat housing machined
center metering structure
metering structure edge-on
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LBTI Components
Fast Pathlength Corrector
4 K Mech. Cooler
SiC Mirror
Systems Engineer Tom Connors checks whether we
have left enough room for the binocular eyepiece
Left UBC Cryostat
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LBTI Structure in lab
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Optical Alignment Preparation
LBTI strongback as it would be seen from above
the LBT
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Fringes formed in late October 2006. Measured
end-to-end optical quality Pupil Mirrors need to
be improved Other mirrors are within spec (l/10
)? Measured vibration effects on phase Need to
improve measurement scheme with 4D interferometer
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LBTI-NIC requirements

• Four separate channels Wavelength Detector F
  OV
• Nulling 8-13 µm SiAs 256x256 7.7
• N band Fizeau 8-13 µm SiAs 256x256 7.7
• LM band Fizeau 3-5 µm HAWAII-1 10
• phase sensing channel 2-2.4 µm PICNIC 10
• Channels require separate intermediate focal and
  pupil planes for coronagraphy or nulling
  techniques.
• Require a reflective design for broadband (2-10
  µm) operations
• Split off NIR light after beam combination for
  phase control
• Require multiple dichroics in design to get right
  wavelength to right detector
• Each channel will be capable of low resolution
  (R100-300) spectroscopy

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NIC Optical Design
Side
Side View
In-Plane View
UBC focal Plane
N band Camera
DRS detector
Nulling Interferometer
HAWAII detector
L and M band Camera (LMIRCam)?
Each channel uses a pair of aspheric toroidal
mirrors to form intermediate image and pupil
planes
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Nulling Channel
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N band imaging
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LMIRCam
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Phase Sensing
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LBTI Structure
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MIRAC4 prototype for NIC

• MIRAC4 was tested out in October 2006 at MMT.
• Detector is a 256x256 DRS array identical to NIC
• Electronics are identical to NIC.
• Same use of Pulse tube for cooling
• Similar filter complement

First light image from MIRAC4 on MMT

• See electronic noise in the current system
• The detector has variable offset and crosstalk
  artifacts.

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BLINC phase sensing testing in February 2007

• BLINC is being used to prototype our phase
  correction for the LBTI.

Quick look tool from BLINC phase control showing
the phase variations on-sky.
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What we could do with a partial LBT

• Tertiaries only tests
• Measure the power spectral density of phase
  variations
• Measure differential image stability
• Use the phase sensor and FPC to stabilize the
  phase

• Single arm AO tests
• Test throughput
• Measure and refine emissivity
• Integrate the wavefront sensor with the
  interferometer
• Measure image quality (Strehl)?
• Measure image stability (vibrations)?
• Test Fast Pathlength Corrector (FPC) performance
• Carry out single aperture nulling
• Implement phase sensing using FPC tip-tilt for
  feedback
• Test AO-Telescope-Interferometer communication

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My choice of topics

• AO status and schedule
• Vibration characterization
• Installing LBTI and NIC

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