A.J.Booth et al., Planet Detection Testbed 1

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

A.J.Booth et al., Planet Detection Testbed 2

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 106:1 contrast ratio with star with SNR 3

Stable nulls of 105:1– Local zodiacal light at ~10-4 of star mean better nulls superfluous

Extra 100:1 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

Star laser source

Planet source

Star thermal source

Detector

pinholes

Cross-combiner

Nuller 1

Nuller 2π

π

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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

Tip-tilt laser source

Star source

π

nuller

Tip-tilt detector

Tip-tilt detector

Shear detector

Shear detector

Shear mirror

Tip-tilt mirror

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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

Star laser source

Planet source

Star thermal source

Detector

pinholes

Cross-combiner

Nuller 1

Nuller 2π

π

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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

Star laser source

Planet source

Star thermal source

Detector

pinholes

Cross-combiner

Nuller 1

Nuller 2π

π

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Nulling performance Short term (100s) null depth

– Max null depth 1.6×106:1

– Mean null depth 9×105:1 (goal: better than 105:1)

– Short term noise due to poor metrology tracking

0 50 100 150 200 25010

-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Time (secs)

Flu

x

peak

shutter

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Nulling performance

Long term null stability– Drift of < few 106:1 over 104s (goal : better than <105:1)

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 1000010

-8

10-6

10-4

10-2

100

102

time(s)

log

null

shutter

peak

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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 6:1, radius 60m, planet at 0.375urad

Array Rotation (degrees)Nor

mal

ized

pla

net c

hopp

ed s

igna

l

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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.