WFIRST Coronagraph Instrument (CGI) Status
Feng Zhao, CGI Deputy Project Manager
John Trauger, CGI Instrument Scientist
Jet Propulsion Laboratory
California Institute of Technology
July 29, 2018
Copyright 2018 California Institute of Technology. Government sponsorship acknowledged Page 1
Outline
• WFIRST Coronagraph Instrument (CGI) re-cap
• CGI current capabilities
• CGI Participating Scientists Programs (PSP)
• Summary
2
WFIRST Coronagraph Instrument (CGI)
• Coronagraph (CGI) is the 2nd instrument on WFIRST,
– Exo-planet direct imaging technology demonstration
– Participating Scientists Programs (PSP)
• Coronagraph instrument is managed by JPL
– Instrument Project Manager: Peg Frerking
– Deputy Instrument Project Manager: Feng Zhao
• Other coronagraph partner institutions:
– NASA centers:
• GSFC (responsible for integral field spectrograph)
– Industry:
• Northrup Grumman Xinetics (deformable mirror)
• Boston Micromachines Corp (deformable mirror)
• e2v (Electron Multiplying CCD – EMCCD)
– Science Investigations Teams (SIT):
• SIT #1 PI: Bruce Macintosh, Stanford University
• SIT #2 PI: Maggie Turnbull, SETI Institute
– Coronagraph Adjutant Scientist (CAS):
• Jeremy Kasdin, Princeton University
– Science Center:
• IPAC/Caltech, STScI
– Potential International Partners:
• Germany -- Max Planck Institute of Astronomy (mask filter wheels)
• UK – e2v (EMCCD)
• Japan – JAXA (polarization module)
• France – LAM/CNES (Super-polished coronagraph optics)
Page 3
CGI Functional Overview
4
• Active components
• Fast Steering Mirror (FSM) for line of sight control
• Focus Correction Mechanism (FocM) for focus control
• Deformable mirrors (DM1, DM2) for wavefront control
• Control loops
• High order wavefront sensing and control (HOWFS/C) for achieving starlight suppression
• Low order wavefront sensing and control (LOWFS/C) for continuously maintaining starlight suppression
OAP5 OAP6 OAP7 OAP8
OAP1
OAP2
OAP3 Fold Mirror
OAP4
Integral
Field
Spectro
graph
IFS/Img
Selector
Focus
Correction
Mechanism
Fast
Steering
Mechanism
Deformable
Mirror 2
1 kHz
5 m
Hz
5 m
Hz
LOCAMLow Order
Wavefront
Sensing/
Control
DICAM
IFS
CA
M
High Order
Wavefront
Sensing/
Control
Deformable
Mirror 1
Collimated
Light From
Telescope
Pupil
Plane
Mask
Focal Plane
Mask
Lyot
Stop
Filter
Wheel
Field
Stop
DI –
narrow
Spectro
scopyopen
open DI – wide
Active Wavefront sensing and control enables CGI ~1000x deeper starlight suppression than previous space coronagraphs
OAP = Off-Axis Parabolic [Mirror]
DI = Direct Imaging
Status Since WIETR Report
• CGI has passed Systems Requirement Review (SRR) in May 2018!
• WFIRST in in Phase B
• The Coronagraph Instrument is a technology demonstration only
• Reduction in modes and science center role (descoping)
• Requirements established using standard engineering practice
• Model uncertainty factors (MUFs)
• Margins and reserves
• Design to be “starshade ready” to support possible starshade rendezvous mission
(pending Decadal recommendation)
• Participating Scientists Programs (PSP)
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Operations Scenario #6 (OS6) Simulations --
Speckle Field Time Series
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Default cadence & thermal stepsize
0 20 40 60 80 100 120Hours
-300
-200
-100
0
100
200
300
Default cadence & short thermal stepsize
0 20 40 60 80 100 120
-300
-200
-100
0
100
200
300
Short cadence & thermal stepsize
0 20 40 60 80 100 120
-300
-200
-100
0
100
200
300
Z4
(p
m R
MS
)Z
4 (p
m R
MS
)Z
4 (p
m R
MS
)
η UMa 47 UMa
2 hour timestep & 60 s thermal timestep
2 hour timestep & 10 s thermal timestep
10 min timestep & 10 s thermal timestep
Hours
Red = η UMa Blue = 47 UMa0 h 132 h
No Optical MUFs With Optical MUFs
Includes: static aberrations (surface errors & polarization), high and low order
wavefront control, thermally-induced wavefront aberration & pupil position
changes, deformable mirror thermal drift, pointing & wavefront jitter, stellar
diameters & colors
Lo
g10(c
on
tra
st)
This OS6 simulated time series data available at
wfirst.ipac.caltech.edu
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Target Star Roll 1
- Reference Star
Target Star Roll 2
- Reference Star
Angular Differential
Image (Target only)
No optical
MUFs
With optical
MUFs
1 x 10-8
3.5 λ/D
3 x 10-9
4.5 λ/D
Field incident on detector shown. Detector effects not included
Differential Imaging
CGI Filters
• Post-WIETR descope: number of color filters (and associated coronagraph masks)
reduced
• No change in the number of slots in the filter wheel
8
Wavelength (nm)
Fu
ll D
isk A
lbedo
Log
10(κ
)
Karkoschka (1994)
14
3
Hα
2
CGI Operating Modes
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CGI Filters
λcenter
(nm)BW Channel Masks Working Angle
Can use w/ linear
polarizers
StarlightSuppression
Region
2 660 18% IFS SPC 3-9 λ/D 130°
2 660 18% Imager SPC 3-9 λ/D Y 130°
3 760 18% Imager SPC 3-9 λ/D Y 130°
4 825 10% Imager HLC 3-9 λ/D Y 360°
4 825 10% IFS HLC 3-9 λ/D 360°
Three Required Technology Demonstration Modes:
Other possible modes with required masks and filters:
3 primary Tech Demo Modes identified in CGI requirements.Other mask combinations exist and can be used during participating
Scientists program.
NameCGI
Filterλcenter
(nm)BW Channel Masks
WorkingAngle
Can use w/ linear
polarizers
StarlightSuppression
Region
Imaging w/ Narrow FoV 1 575 10% Imager HLC 3-9 λ/D Y 360°
Spectroscopy 3 760 18% IFS SPC 3-9 λ/D 130°
Imaging w/ Wide FoV 4 825 10% Imager SPC disk 6.5-20 λ/D Y 360°
CGI Low-noise Detectors
Item Requirement@5 yearsCBE
(5 years)Margin
Total Noise@165K (σ2)
575 nm Band 1 41.0 e--px-1–hr-1 @6s 19.6 52.2%
760 nm Band 3 3.7 e--px-1–hr-1 @80s 2.8 24.3%
825 nm Band 4 28.1 e--px-1–hr-1 @10s 11.0 60.9%
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Item RequirementCBE
(5 years)Margin
Total Noise@165K (σ2) 158.8 e--s-1 126.7 19.8%
Read 5 e- 4
CIC <0.1 e--pixel-1-fr-1 0.03
Dark <1 e--pixel-1-s-1 <0.00056
Full Well 25,000 e- 29,200 16.8%
Frame rate 1000 frames-s-1 1961 96%
Latency 0.5 ms 0.25 96%
Bits 14 14
Science Cameras (Direct imaging and IFS)
Engineering Camera (LOWFS)
e2v 1K X 1K Electron Multiplying CCDs
For all cameras, running at different modes
Infusing New Wavefront Sensing & Control
algorithms
• CGI is an actively controlled instrument, performance driven by both hardware
(masks, DMs) and algorithms/software (DM solutions)
• CGI plans to fly the most capable flight-ready processor, optimized with both CPU
and FPGAs
• WFIRST supports CGI software uploads during Phase E
• Welcome new algorithms development from future PSP teams
• CGI maintains an ops testbed during Phase E, that can proof-test new algorithms
before upload
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CGI is a Pathfinder for Direct Imaging and
Spectroscopy of Earth-like Exoplanets
12
Courtesy of V. Bailey
• NASA envisions a Participating Scientist Program
(PSP) that engages the general exoplanet community
in high-contrast direct imaging astronomy.
• Due to budget constraints, there will not be a
traditional General Observer support program for the
CGI — instead, the PSP will work with the CGI
project to develop science target priorities,
observing strategies, data processing algorithms,
and data analysis.
• The PSP team is intended to be in place before launch
and to fully participate in the 18-month tech demo
program.
• Following initial CGI commissioning and a successful
technology demonstration in the first 18 months of
operations, the PSP may guide additional CGI
observations during years 1.5-2.5.
• “If warranted,” science observations in years 2.5-5
with an augmented PSP (with further community
selections) or full a GO program.
Participating Scientist Program
CGI
Direct Imaging of Exoplanets: 2018Direct Imaging of Exoplanets: 2018
Direct imaging and spectroscopy of young self-luminous exoplanets have been
achieved from ground and space observatories. Direct imaging of mature cool
exoplanets in reflected starlight is currently beyond the reach of conventional
techniques, as illustrated by the estimated brightness of a sample of known radial
velocity exoplanets.
Plot generator: Bailey & Meshkat 2017
CGI pioneers coronagraph technologiesCGI pioneers coronagraph technologies
Early estimates of the CGI flux ratio curves for three observing configurations (direct
imaging at short and long wavelengths, and integral field spectroscopy) are based on
currently demonstrated static and dynamic testbed performance and observatory
optical disturbance models provided by the WFIRST project.
Plot generator: Bailey & Meshkat 2017
CGI sensitivity for circumstellar disksCGI sensitivity for circumstellar disks
Early estimate of the CGI sensitivity for imaging of low-luminosity disks associated
with a V=5 star. Surface brightness is represented in terms of flux ratios per imaging
resolution element. Comparisons are made with previously-imaged disks in visible
scattered light, and with HST instrument sensitivities.
J. Debes 2018
Summary
• CGI is pioneering all elements of an advanced coronagraph in space
• CGI team is making excellent progress
CGI current performance estimates would result in exciting science through
participating Scientists programs
• CGI is a Pathfinder for Direct Imaging and Spectroscopy of Earth-like Exoplanets
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