The Habitable Exoplanet Imaging Mission (HabEx): Exploring our neighboring planetary systems. Community Chairs: Scott Gaudi (OSU/JPL) & Sara Seager (MIT) Study Scientist: Bertrand Mennesson (JPL) Study Manager: Keith Warfield (JPL) (This presentation extracted from material presented by Scott Gaudi, Keith Warfield, Gary Kuan, and HabEx STDT members at Nov. 10-11 face-to-face meeting) CL#16-5499 © 2016 California Institute of Technology. Government sponsorship acknowledged.

The HabEx STDT. (mostly)

HabEx Design Team at JPL

HabEx General Goals. Optimal means: Constraints include: “Develop an optimal mission concept for characterizing the nearest planetary systems, and detecting and characterizing a handful of ExoEarths.” “Given this optimal concept, maximize the general astrophysics science potential without sacrificing the primary exoplanet science goals.” Optimal means: Maximizing the science yield while maintaining feasibility, i.e., adhering to to expected constraints. Constraints include: Cost, technology (risk), time to develop mission. Thus some primary lower-level goals include: Identify and quantify what science yields are desired and optimal. Identify and quantify the range of potential constraints.

HabEx Science Goals. Exploration-based: How many unique planetary systems can we explore in great detail, determine “their story”, including finding and characterizing potential habitable worlds? HabEx will explore N systems as systematically and completely as possible. Leverage abundant pre-existing knowledge about our nearest systems, acquire as much additional information as possible. Take the first step into the unknown! Search for Potentially Habitable Worlds Detect and characterize a handful of potentially habitable planets. Search for signs of habitability and biosignatures. Optimized for exoplanet imaging, but will still enable unique capabilities to study a broad range of general astrophysics topics.

Exploration approach: The case of 40 Eridani A Constraining the presence of a habitable planet K0 star at 5 pc distance; B and C components orbit each other 80 away HZ lies at 0.13 separation. An earth mass planet there: Would induce 12 cm/sec of stellar reflex motion Has a 0.4% probability of ever transiting Would induce 0.5 as of stellar astrometric wobble Won’t lens background stars (galactic latitude -38°) In direct imaging, an Earth analog here would: Appear at R magnitude 27.6, and with contrast to the star of 310-10 Be separated from the star by 3 resolution elements as seen by a 3 meter telescope observing in V band Provide photons enabling its discovery *and* spectral measurements of its physical/chemical/biological? conditions

Fiscal and technical constraints From Keith Warfield’s study of past decadal missions: “All past missions prioritized by the Decadal Survey were thought to be under $ 3B” Only allowed  3 “tooth fairies”, i.e. major technology development activities Paul Hertz ~$ 7B of free energy in NASA astrophysics budget through 2035; HabEx study goal is to not use it all

HabEx Overview Exploring our nearest planetary systems. Detect and characterize potentially habitable planets, search for signs of habitability and biosignatures. Enable a broad range of general astrophysics. Study started spring 2016. 3 face-to-face STDT meetings so far, weekly design team meetings Interim report due late 2017, final report early 2019.

Planets with comparable brightness have very different spectra Cloud Sulfur species Venus Cool Neptune CH4 CH4 3-bar Earth CH4 Scaled Brightness CH4 O3 O3 Rayleigh Mars Surface Oxides SO2 Wavelength [nm] Ty Robinson

Earth observed in the optical Feng, Robinson, et al. (in prep.)

Why go into the near-IR Ty Robinson H2O O3 H2O H2O O2 O2 CO2 H2O H2O

Why go into the UV for HZ planets Venus Earth CO2 O3 Mars Ty Robinson

Earth twins 4-m HabEx Coronagraph 5 pc λ/Δλ = 7 Ty Robinson

Venus twins 4-m HabEx Starshade 5 pc λ/Δλ = 7 Ty Robinson

General Astrophysics Consider what will be or has been available: HST JWST, WFIRST Ground-based ELTs UV for >2.5m aperture provides a novel capability Paul Scowen

General Astrophysics Themes. Hubble Constant Escape Fraction Cosmic Baryon Cycle Massive Stars & Feedback Stellar Archaeology Dark Matter HabEx’s Three Graces of general asrophysics: Paul Scowen, Rachel Somerville, Dan Stern

General Astrophysics Capabilities Matrix. -> UV Spectrometer and UVOIR imager. HabEx’s Three Graces of general asrophysics: Paul Scowen, Rachel Somerville, Dan Stern

HabEx configuration for 4 meter monolith First architecture option 4-meter monolithic primary mirror, off-axis, unobscured Waveband: 120nm – 1mm (stretch: 90nm – 2mm) Starshade(s) Active vs. passive stability Coronagraph 10 arcmin^2 imager 30,000 spectrograph Diffraction limited @ 400nm (stretch 250nm)

Assessing UV compatibility with coronagraph: polarization effects Effects of telescope f number and mirror coatings Considered: f/1.5 , f/2.0 , f/2.5 Coating: Protected Silver Coating (all optics) Standard Protected Aluminum coating on Telescope optics (PM, SM, TM) and protected silver coating on all other optics Coronagraph Architecture (chosen for convenience & sensitivity): Hybrid Lyot Coronagraph (HLC) design from Exo-C probe study Vector Vortex charge 6 design Analysis: Two linear polarization states (+45deg, -45deg) input to Telescope Wavefront phase and amplitude maps at exit pupil passed as input to coronagraph Coronagraph Analysis: Electric Field Conjugation (EFC), PROPER, Deformable Mirror (DM)

Effect of Coronagraph Type, mirror coatings John Krist & Stefan Martin

Coating options to extend UV below 120nm Quantum Coatings Protected Silver FSS99-500* *http://www.quantumcoating.com/fss99 Reflective coating options for telescope Protected Silver FSS99-600 from Quantum Coatings or similar, TRL-9 Standard Protected Aluminum Aluminum with MgF2 overcoat, like HST, TRL-9 UV Enhanced Protected Aluminum Aluminum with MgF2/LiF overcoats, in development, ~TRL-3 Aluminum with AlF3/LiF overcoats, in development, ~TRL-3 Kunjithapatham Balasubramanian ; John Hennessy ; Nasrat Raouf ; Shouleh Nikzad ; Michael Ayala ; Stuart Shaklan ; Paul Scowen ; Javier Del Hoyo and Manuel Quijada " Aluminum mirror coatings for UVOIR telescope optics including the far UV ", Proc. SPIE 9602, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VII, 96020I (September 22, 2015); doi:10.1117/12.2188981; http://dx.doi.org/10.1117/12.2188981

Exo-C Coronagraph Low-Order Sensitivity Contrast change with 100 pm RMS WFE (550 nm) HLC Spherical PIAA Spherical Coma Coma Focus Trefoil Focus Astigmatism Trefoil Astigmatism Tilt Tilt IWA IWA λ/D λ/D IWA Spherical VVC charge 4 VVC charge 6 Trefoil Coma Tilt Astigmatism Trefoil Astigmatism Focus Coma Spherical IWA Tilt λ/D Focus λ/D

Telescope stability Laser Metrology for Active Rigid Body Motion Control Existing JPL technology, TRL-9 expected by 2019 Performance: < 6 nm RMS Gauge Noise @ 1 kHz < 5 nm/°C Thermal Drift 10mK temp stability < 50 pm gauge error drift Stuart Shaklan, Metrology System for the Terrestrial Planet Finder Coronagraph , Proceedings of SPIE Vol. 5528 Low order wavefront sensor would supply information on a restricted set of disturbances

Architecture – Initial Round Aperture trade STDT selected 4m unobscured and 6.5m on-axis telescope designs for study Decision based partly on an assessment of science per dollar, partly on an assessment current industry mirror capabilities, and JWST leverage value GA instrument trade STDT general astrophysics members identified 6 high-value instruments for evaluation by the whole STDT Discussions within the STDT reduced the instruments for evaluation to two: UV spectrograph and a UV/VIS/NIR camera Both instruments sent to Team X for rough design Team X identified new technologies, liens generated on the flight system and operations, and cost for both candidates STDT will select the best option for integration into the concept design L2 assumed as the orbit Earth trailing/leading limits life and starshades must co-launch Earth orbits are unattractive due to thermal and field-of-regard considerations L2 orbit size remains a small trade. Presently assuming a WFIRST-like orbit.

Architecture – Second Phase 5 unique architectures (so far) being evaluated for 4m design Additional variations based on extended bandpass (both in the blue and the red) Will repeat for 6.5m when we reach that design Using high-level assessments for performance, cost and risk Using Stark’s yield analysis (performance), ghosting the CATE (cost), counting new technologies (risk)

Starshade Trades Size Deployment Method Depends strongly on IWA and longest desired wavelength of operation. IWA will be ~70 mas, max = 1.0-1.7 m Currently working starshade sizing which is a function of the above and the desired bandpass Starshade must fit in 5m fairing to allow second (or follow-on) launches Minimizing dry mass will extend the delta-V and improve yield Deployment Method Will also evaluate NGAS and JPL deployment methods for use in the 4m and 6.5m concepts Overall concept cost and technical readiness will be the criteria

Team X Results – UV Spectrograph Study leads to mass, power, dimensional constraints for the mission architecture

Camera Study Requirements Imager (“HabEx Workhorse Camera”) 2 channel – UV/optical and near-IR – with a suite of filters. Spectrometer (“HabEx UV Instrument”; see 1817 Study Report) Slit spectroscopy A micro-shutter array (as per NIRSpec on JWST). Again, covering UV, optical, and near-IR wavelengths. Spectral Range: 150-2000 nm Diffraction limited at 400 nm Spectral Resolution: Moderate resolution spectroscopy, R~2000 FOV: 3 x 3 arcminute 9/24/2015

Waveband: 120nm – 1mm UV spectrograph: (100nm – 350nm) Detectors UV spectrograph: (100nm – 350nm) micro-channel plate General Astrophysics Imager: (150nm – 2mm) CCD (high TRL) HgCdTe (high TRL) Coronagraph & Starshade: (150nm - 1mm) micro-channel plate (high TRL, GALEX) ? EMCCD (WFIRST), (250nm – 1mm) HgCdTe (1mm - 1.7mm) (current devices are too noisy)

Work together - meet in the middle LUVOIR HabEx

Difference between LUVOIR and HabEx? Both LUVOIR and HabEx have two primary science goals Habitable exoplanets & biosignatures Broad range of general astrophysics The two architectures will be driven by difference in focus For LUVOIR, both goals are on equal footing. LUVOIR will be a general purpose “great observatory”, a successor to HST and JWST in the ~ 8 – 16 m class HabEx will be optimized for exoplanet imaging, but also enable a range of general astrophysics. It is a more focused mission in the ~ 4 – 8 m class Similar exoplanet goals, differing in quantitative levels of ambition HabEx will explore the nearest stars to “search for” signs of habitability & biosignatures via direct detection of reflected light LUVOIR will survey more stars to “constrain the frequency” of habitability & biosignatures and produce a statistically meaningful sample of exoEarths The two studies will provide a continuum of options for a range of futures

Yields: ExoEarths Chris Stark 2015

Interpolation HabEx LUVOIR 4m monolith off axis 6.5m segmented on or off axis 2-3 instruments (coronagraph, up to 2 GA instruments) Likely starshade(s) DI λ: 400-1000 nm (stretch ~200-1700nm) LUVOIR ~9m segmented 16m segmented on axis 4-5 instruments (or instrument bays) Starshade as a future option DI λ: 400- 2500 nm