1. 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 face-to-face meeting)
CL#
© 2016 California Institute of Technology. Government sponsorship acknowledged.

2. The HabEx STDT. (mostly)

3. HabEx Design Team at JPL

4. 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.

5. 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.

6. 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

7. 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

8. 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 face-to-face STDT meetings so far, weekly design team meetings
Interim report due late 2017, final report early 2019.

9. 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

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

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

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

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

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

15. 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

16. 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

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

18. 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 400nm
(stretch 250nm)

19. 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)

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

21. Coating options to extend UV below 120nm
Quantum Coatings Protected Silver
FSS99-500* *
Reflective coating options for telescope
Protected Silver
FSS 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: / ; 

22. 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

23. Telescope stability
Laser Metrology for Active Rigid Body Motion Control
Existing JPL technology, TRL-9 expected by 2019
Performance:
< 6 nm RMS Gauge 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

24. 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.

25. 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)

26. Starshade Trades Size Deployment Method
Depends strongly on IWA and longest desired wavelength of operation. IWA will be ~70 mas, max = 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

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

28. 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: nm
Diffraction limited at 400 nm
Spectral Resolution:
Moderate resolution spectroscopy, R~2000
FOV: 3 x 3 arcminute
9/24/2015

29. 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)

30. Work together - meet in the middle
LUVOIR
HabEx

31. 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

32. Yields: ExoEarths
Chris Stark 2015

33. 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: nm (stretch ~ nm)
LUVOIR
~9m segmented
16m segmented on axis
4-5 instruments (or instrument bays)
Starshade as a future option
DI λ: nm