A Space Coronagraph Mission for Exoplanet Imaging and ...

Status and Challenges:A Space Coronagraph Mission for Exoplanet Imagingand SpectroscopyJohn Trauger, JPL / CaltechMeeting of the ExoPAG – Seattle – 8 January 2011!(c) 2009 California Institute of Technology. Government sponsorship acknowledged

Rally around the science• The Astro2010 calls for consensus on exoplanet mission readiness.• Rally around a compelling science mission with high readiness, elsecede the future of exoplanet missions to the next decadal survey.• The astrophysics of exoplanet systems is the compelling science ofthe coming decade, i.e., direct imaging and spectroscopy.• A successful concept also supports general astrophysics (UV-visibleimaging and spectroscopy) in the post-Hubble area.• A coronagraph mission serves a broad range of astrophysics, sincecoronagraph is in essence one selectable observing mode in a verystable general astrophysics space telescope.

Exoplanet Discovery SpaceAsterisks: known exoplanetsCurves: instrument capabilitiesColors: photometry bandsBlobs: regions of high likelihoodfor detection of Jupiter-twins andEarth-twins orbiting the nearest100 AFGK stars3

Exoplanet Discovery Space– Ground-based imaging observations – .beta Pictoris bLagrange et al. 2010HR8799 b,c,d,eMarois et al. 20104

Exoplanet Discovery Space– Hubble ACS coronagraph observations –Fomalhaut bKalas et al. 20086

Conceptual observatory:ACCESS = one of severalrepresentative 1.5-meter spacecoronagraphs!

Exoplanet Discovery Space– Extrapolation from 1.5 to 4 meter telescope aperture –“TPF”10

High readiness by 2014• Let’s not miss our last best chance for exoplanets at the mid-decade.• Compelling science, not the specific coronagraph design, is thejustification for an exoplanet mission.• Only high TRL coronagraph systems will be relevant in the middecadedecision.• Fish or cut bait: there will always be a “better idea” in the comingyear – holding out for “better” may defeat our opportunity for amission in the coming decade.• The general astrophysics community does not understand – and isreluctant to endorse – high-contrast coronagraphs, hence we havean obligation to provide coherent and constructive discourse withour colleagues.

Exoplanet Mission Readiness Checklist✓ Coronagraph performance✓ Telescope thermal and dynamic stability✓ Telescope pointing control✓ Optical wavefront control and stability✓ Method for speckle / planet discrimination✓ Photon-counting imaging sensors✓ End-to-end performance models✓ End-to-end laboratory validations

ExoplanetCoronagraphReadinessContrastInner working angleSpectral bandwidthThroughputWavefront Sensing and ControlLaboratory validations

The demonstrated state of exoplanet coronagraphyLyot coronagraph demonstrations and goalsContrast demonstrations with metallic and metal+dielectric Lyot masks:IWA = 3 λ/D, 20% BW, C = 2.7 e-9 (ACCESS, 2009)IWA = 4 λ/D, 10% BW, C = 6 e-10 (TPF-C M2, 2008)Milestone #1 for the hybrid Lyot TDEM program is:IWA = 3 λ/ D, 20% BW, C < 1e-9 (TDEM, 2011)• Profiled metal+dielectric layerscontrol complex (amplitude andphase) wavefront• Optimized design for improved contrast(3e-10) at 3 λ/D over 20% bandwidth,and throughput (60%) is the goal of a2010-11 TDEM program.!"#$,-$! %#!,-$! %"!,-$! %&!,-$! %)!"#$%&+$!'(!!!!"#$%""&!'(!!!!!!!!""&%")*!'(!!!!!!!!")*%&$&!'(!!!!!!!!&$&%&*+!'(!!!!!!!!!&*+%&+$!'(!!!,-$! %-$!14

The demonstrated state of exoplanet coronagraphyPupil mapping demonstrationsThe pupil mapping (PIAA) coronagraph has achievedIWA = 2 λ/D, monochromatic, C = 3e-8with the Generation 1 PIAA mirrors now on the HCITtestbed (Kern et al. 2010). Generation 2 mirrors,designed for 20% bandwidths (Guyon 2008) havebeen manufactured by Tinsley and are now active onon the Ames testbed (Belikov 2010)blocked star location(half-plane blocked by aknife-edge occulter)15

The demonstrated state of exoplanet coronagraphyShaped pupil coronagraph experiments with HCITShaped pupil maskFocal plane maskHigh contrast fieldAt left, the transmittance profile of a representative shaped pupil apodization(black indicates opaque, white indicates clear). At center, the corresponding“bowtie” image plane mask. This “Ripple 3” design achieved 2.4e-9 contrast in10% bandwidth averaged over the 4-10 λ/D dark field (outlined) on the HCIT.(Belikov et al. 2007)

The demonstrated state of exoplanet coronagraphy!"#$%&'!%&$"(')%&%*+,&+-.'•!•!•!/.+0"12+0"3'#%&%*+,&+-.'45+66'7**"&'8%&97*,'+*,6":'.7,.'$.&%;,.-;$:'075-67#7$%*'D'%='3"E7#"0B''•! 4"#%*31%&3"&'5+090'7*0$+66"3'+$'/+6%5+&:';0"3'$%'75+,"'"(%-6+*"$0'+*3'#%5-+*7%*0'3%8*'$%'D1F'GH3'7*'$."'*"+&17*=&+&"3';07*,'+3+->E"'%->#0I'•! J%;&$.1%&3"&'5+09'$"0$"3'7*'$."'E70726"'%*'$."'K)LM'7*'FNNO'?PDN 1Q' %E"&'DNR'STA'–! C"*"&+>%*'FB'•! M"#.*%6%,7#+6'3"E"6%-5"*$'U*+*#"3'$.&%;,.'V/WV'+*3'4SLW'-&%,&+50'•! L5-&%E"3'3"U*7>%*'%='$."'#"*$"&'''?XN'Y5'Z['\'Y5A'•! V#.&%5+>#'?,%+6'DN 1]' %E"&'FNR'STA'4"&+2

The demonstrated state of exoplanet coronagraphyVisible nuller coronagraph• VNC development is active atGSFC (Lyot et al.) and at JPL(Sandhu et al.)• Segmented MEMS DMs fromboth Boston Micromachines andIRIS-AO are under consideration.• Spatial filters, consisting of abundle of 1000 single modefibers coupled with lenslet arrays,are now being perfected andtested.• Starlight suppression of 1e-8 hasbeen demonstrated in laser light(Lyot et al. 2010).18

All coronagaphs require deformable mirrorsfor precise wavefront controlHCIT experiments have been carried out withXinetics DMs. Fused silica facesheet is polishednominally to λ/100 rms. Surface figure (openloop) has been shown to be settable to 0.05 nmrms and stable to 0.01 nm rms over periods of 6hours or more in a vacuum testbed environment.Protoflight qualification is in progress at JPL.MEMS DMs manufacturedby Boston Micromachines(left) and IRIS-AO (right)can be configured witheither continuous orsegmented mirrorfacesheets. MEMS DMs areactively in use in alltestbeds other than HCIT.

The demonstrated state of exoplanet coronagraphy• Laboratory verified performance provides objective criteria forcomparisons among the representative coronagraph types.• Demonstrated raw contrast, spectral bandwidth, inner workingangle, throughput, cost/complexity, can be used to inform ahigh fidelity exoplanet mission simulation.20

Exoplanet Discovery Space– Performances goal for the coming three years) –21

Exoplanet Discovery Space– Extrapolation from 1.5 to 4 meter telescope aperture –“TPF”22

Next three years are critical forconcept validation• Advances in demonstrated contrast, spectral bandwidth, innerworking angle, and nulling algorithms by 2014.• Laboratory validation of performance models, including pointingcontrol methods and strategies for planet/speckle discrimination.• Validation of high contrast imaging, wavefront control, and specklediscrimination with a flight-configured coronagraph instrument in aflight simulating environment.• Develop a compelling exoplanet reference science missiongrounded on validated coronagraph performance models.23

Next three years are critical forbuilding consensus in the exoplanet community• The past few years have seen good progress, spurred on byinstitutional investments as well as NASA programs.• Thanks to NASA for the ASMCS and TDEM programs, which enabledthe community to set relevant and timely goals (milestones) that arefresh and current in the thinking of the exoplanet community.• But! Are the research and development enabled by NASA programs(SAT, APRA) adequate to bring exoplanet technologies to a readinesslevel that justifies the endorsement of the astronomy community?• We need to rally our community around a compelling exoplanetreference science mission grounded on validated coronagraphperformance models.24

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