Exoplanet Exploration Program, Planet Detection Test-bed: Latest results of planet light detection in the presence of starlight

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Exoplanet Exploration Program, Planet Detection
Test-bed Latest results of planet light
detection in the presence of starlight

• Andrew J. Booth, Stefan R. Martin, Frank Loya,
• Jet Propulsion Laboratory, California Institute
  of technology

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Summary

• Test-bed goals
• Introduction to the Planet Detection test-bed
  (PDT)
• Additions to Test-bed since 2006
• Nulling performance
• Planet detections
• Future plans

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Test-bed Goals

• Lab simulation for a near infrared terrestrial
  exoplanet characterization mission
• 10um, dual nulling interferometer
• X-array Emma, formation flying
• Other testbeds deal with
• formation flying
• broadband nulling
• PDT emulates 4 beam nulling and cross combining
  for
• Optical arrangements
• Control systems
• Planet signal extraction

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Test-bed Goals

• Detect planet signal at 1061 contrast ratio
  with star with SNR 3
• Stable nulls of 1051
• Local zodiacal light at 10-4 of star mean better
  nulls superfluous
• Extra 1001 contrast ratio below null depth
  obtained by
• Chopping planet signal - interferometrically
• Rotation of array through 360º and averaging

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Introduction to the PDT
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Introduction to the PDT

• Null starlight
• Chop cross combiner optical path from fringe peak
  on one side of star to fringe peak on other side
  of star (star at inflection point)
• Planet signal is difference in flux on two sides
  of chop

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Introduction to PDT
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Test-bed updates since 2006

• Closed loop tip-tilt (few 10Hz) and shear (few
  Hz) servos with detectors working at 850nm

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Test-bed updates since 2006

• Fringe tracking at 2.5um, 1Hz
• Star thermal source
• Control signal is difference of two beam combiner
  outputs
• One for each nuller and cross combiner
• laser metrology tracking at 1.5um, 100Hz
• Up stream and down stream from beam train mid
  point

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Test-bed updates since 2006

• Phase plates
• Path matching at nulling and fringe tracking
  wavelengths
• Nullers
• Null at 10um
• Fringe signal inflection point at 2.5um
• Cross combiner
• Chop 10um fringe peak to trough
• Chop from 2.5um inflection point to inflection
  point

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Test-bed updates since 2006

• Planet input optics with optical path modulation
  to allow simulation of array rotations

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Nulling performance

• Short term (100s) null depth
• Max null depth 1.61061
• Mean null depth 91051 (goal better than 1051)
• Short term noise due to poor metrology tracking

peak
shutter
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Nulling performance

• Long term null stability
• Drift of lt few 1061 over 104s (goal better
  than lt1051)

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Planet Detection

• Linear dual Bracewell array configuration
• Planet at 0.1urad from star (1AU at 50pc)

Time (sec)
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Planet Detection

• Normalized cross correlation of data with
  templates

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Simulated Emma Array planet signal

• Simulated Emma array planet signal
• Array ratio 61, radius 60m, planet at 0.375urad

Normalized planet chopped signal
Array Rotation (degrees)
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Future Plans

• Emma array simulations
• Broad band nulling from Ar-arc source with
  dispersed dectection
• Will allow further 10x sensitivity improvement
  using wavelength fitting of fringe rotation data,
  allowing planet detection at realistic 107
  contrast ratios.