Download HabEx`s Three Graces of general asrophysics: Paul Scowen

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)
© 2016 California Institute of Technology. Government sponsorship acknowledged.
CL#16-5499
The HabEx STDT.
(mostly)
HabEx Design Team at JPL
Name
Keith Warfield
Bertrand Mennesson
Gary Kuan
Stefan Martin
Joel Nissen
Rhonda Morgan
Stuart Shaklan
Doug Lisman
David Webb
Eugene Serabyn
John Krist
Alina Kiessling
Bala Balasubramanian
Phil Stahl
Steve Warwick
Shouleh Nikzad
John Hennessy
Fang Shi
Role
Study Lead
Study Center Scientist
Design Lead
Optics Lead
Systems & Structures; Stability
DRM & science yield
starshade & coronagraph expert
Starshade expert
Starshade expert
coronagraph expert
coronagraph expert
associate center scientist
coatings expert
MSFC - Telescope
Northrup Grumman - Starshade expert
Detectors Lead
detectors expert
LOWFSC expert consultant
jpl.nasa.gov
HabEx General Goals.
1. “Develop an optimal mission concept for characterizing the nearest
planetary systems, and detecting and characterizing a handful of
ExoEarths.”
2. “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
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
Fiscal and technical constraints
• ~$ 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
Scaled Brightness
Sulfur species
Venus
Cool Neptune
CH4 CH4
3-bar Earth
O3
O3
Rayleigh
Mars
SO2
Surface Oxides
Wavelength [nm]
Ty Robinson
CH4
CH4
Earth observed in the optical
Feng, Robinson, et al. (in prep.)
Why go into the near-IR
Ty Robinson
O3
H2O H O
2
O2
H2O
O2
H2O
O2
CO2
H2O
H2O
H2O
CO2
Why go into the UV for HZ planets
Venus
Earth
CO2
Ty Robinson
O3
Mars
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.
Science driver
Hubble Constant
Escape Fraction
Cosmic Baryon Cycle
Massive Stars/Feedback
Stellar Archaeology
Dark Matter
observation
wavelength
spatial resolution
spectral resolution FOV
aperture effective aperture exp. time
image Cepheid variable
stars in SN Ia host galaxies
UV imaging of star
forming galaxies
optical-near-IR (!.6
micron)
UV, preferably down
to 912A
diffraction limited
diffraction limited
preferred
N/A
3'
>=4m
R ~ 1000-3000
few arcmin >=4m
spectroscopy of
absorption lines in
background QSO or
galaxies; UV imaging
UV imaging and
spectroscopy of massive
stars in the Galaxy and
nearby galaxies
UV, imaging down to
115nm sufficient,
spectroscopy down to
92nm preferred
10mas
R=1,000-40,000
(grating turret)
10'
>6m
UV, 120-160nm
spectroscopy; 1101000nm imaging
R=10,000
10-30'
>4m
N/A
10'
4-8m
?
10'
>=8m
diffraction limited;
0.04" at 300nm
resolved photometry of
individual stars in nearby
galaxies
optical (500-1000nm) diffraction limited
integrated photometry +
radial velocities and
proper motions of stars in
Local Group dwarf
galaxies
optical (500-1000nm) diffraction limited
other
20 ks/galaxy
few ks/galaxy
>3x10^4 cm^2 in
the UV - implies
10% (throughput +
DQE) in the UV for
a 6m telescope
300-2000s
100
hours/galaxy
MOS capabilities
beneficial over a field as
large as 20x20'
large number of broad,
medium and narrow filter
bands; spectroscopic
angular resolution 5 mas
this science can be done
with smaller aperture
telescopes, but a
significant jump in
capability occurs at
around 8m
astrometric accuracy of
<40 m arcsec/yr
-> 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 – 1m
– (stretch: 90nm – 2m)
•
•
•
•
•
•
Starshade(s)
Active vs. passive stability
Coronagraph
10 arcmin^2 imager
30,000 spectrograph
Diffraction limited @ 400nm
– (stretch 250nm)
jpl.nasa.gov
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)
jpl.nasa.gov
Effect of Coronagraph Type, mirror coatings
John Krist & Stefan Martin
jpl.nasa.gov
Coating options to extend UV below 120nm
Reflective coating options for telescope
• Protected Silver
Quantum Coatings Protected Silver
FSS99-500*
– FSS99-600 from
Quantum Coatings or
similar, TRL-9
• Standard Protected
Aluminum
– Aluminum with MgF2
overcoat, like HST,
TRL-9
*http://www.quantumcoating.com/fss99
• 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
jpl.nasa.gov
Exo-C Coronagraph Low-Order Sensitivity
Contrast change with 100 pm RMS WFE (550 nm)
10-7
10-7
10-8
Spherical
10-9
Coma
10-9
Coma
10-10
Focus
Trefoil
-11
10
PIAA
10-8
RMS contrast
RMS contrast
Spherical
HLC
Astigmatism
10-12
10-10
Focus Trefoil
Astigmatism
10
-11
Tilt
10-12
Tilt
10-13
10-13
IWA
10-14
2
4
6
/D
lλ/D
8
10
12
2
10-7
VVC
charge 4
RMS contrast
Coma
Astigmatism
Trefoil
-12
10
10
12
14
VVC
charge 6
Trefoil
10-10
10-11
Astigmatism
10-12
Focus
10-13
10-14
8
/D
lλ/D
10-9
Tilt
10-11
6
IWA
10-8
RMS contrast
10-8
10-10
4
10-7
Spherical
10-9
IWA
10-14
Coma
Spherical
10-13
Tilt
IWA
2
10-14
4
6
8
/D
lλ/D
10
12
14
2
Focus
4
6
8
l/D
λ/D
10
12
14
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
jpl.nasa.gov
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)
TRADE STATEMENT: Recommend a 4m exoplanet direct detection architecture for HabEx study concept development
Description
Architecture Trades
MUSTS
Technical
M1
M2
M3
M4
Can search the HZ of XX nearby stars
Can spectrally characterize planets from 400nm -1000nm
Can spectrally characterize planets to >RXX resolution
Operational for 5 years or more
Schedule
M5
Ready for KDP-A by 2025
Evaluation
Cost
M6
Total estimated cost will be less than $XXB
WANTS (DISCRIMINATORS)
Weights
Technical
W1
W2
W3
W4
W5
Spectrally characterize to XXnm in IR
Spectrally characterize to XXnm in UV
Minimize number of new technologies
Maximize characterization of all planet types
Maximize characterization of HZs
Schedule
W6
Reach TRL 5 at earliest possible date
Cost
Risk Evaluation
W7
Minimize cost
RISKS
R1
R2
R3
OPPORTUNITIES
O1
O2
25
1
2
3
4
5
Starshade Only
Corongraph
Only
S&C
2 Starshades
S & 10-9C
Starshade Trades
• Size
– 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 followon) 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
28
Waveband: 120nm – 1m
Detectors
• UV spectrograph: (100nm – 350nm)
– micro-channel plate
• General Astrophysics Imager: (150nm – 2m)
– CCD (high TRL)
– HgCdTe (high TRL)
• Coronagraph & Starshade: (150nm - 1m)
– micro-channel plate (high TRL, GALEX) ?
– EMCCD (WFIRST), (250nm – 1m)
– HgCdTe (1m - 1.7m) (current devices are too noisy)
jpl.nasa.gov
Work together - meet in the middle
30
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
31
Yields: ExoEarths
Chris Stark 2015
Interpolation
• HabEx
•
•
•
•
•
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
33
jpl.nasa.gov