Starshade Rendezvous Probe MissionSara Seager (MIT), Jeremy Kasdin (Princeton), Co-PIsAndrew Gray (JPL), Study LeadAndrew Romero-Wolf (JPL), Jeff Booth (JPL) and the Starshade Probe Team
2.4 m diameter
aperture
26 m
The starshade contrast and inner working
angle are largely decoupled from the
telescope aperture size
Outer working angle only limited by the
detector
Retargeting requires starshade slews of days
to a couple of weeks
At the cost of a Probe, a starshade can be launched in time to rendezvous with WFIRST, taking advantage of the existing telescope and coronagraph instrument to reach Earth-like planet levels of contrast on ten or so nearby stars
Starshade Rendezvous Probe Mission
Probing our Nearest Sun-Like Star Neighbors
Image credit: JPL
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Starshade Concept• Originated in the 1960s by L. Spitzer• Revisited each decade since
Exo-S Probe Study (2013-2015)• The Dedicated Mission, a 30 m starshade and 1.1 m
telescope co-launches• The Rendezvous Mission, 34 m starshade launches and
meets up with WFIRST
Other Related Studies (2015-2016)• Extended Probe Study (2015), 20 m• Starshade Readiness Working Group (2016)
Starshade Rendezvous Probe Mission (2017-2019)• Selected to update the Exo-S Rendezvous Mission
concept study
Overview
Exoplanet Direct Imaging Landscape
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Adapted from plot by Vanessa Bailey
Starshade + WFIRST• Can reach down to Earth-size planets in Earth-like orbits
about sun-like stars
TESS/JWST Transiting Exoplanets• Transiting rocky planet atmospheres limited to small red
dwarf stars• Earth-sun analogs are not possible: low probability for an
Earth-orbit planet to transit and too small atmosphere superimposed on the host star
ELTs for M Dwarf Stars• Capable of direct imaging for M dwarf star rocky planets
in reflected light
Space-based direct imaging is the natural and essential next step—the next frontier for discovery in exoplanet science
Science Objectives
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1. Habitability & Planetary
Systems
Objective 1a: Habitability and Biosignature Gases.
Determine whether super-Earth size or smaller exoplanets
in the habitable zone exist around the nearest sunlike stars
and have signatures of oxygen and water vapor in their
atmospheres.
Objective 1b: The Nearest Solar System Analogs
Detect and characterize planets orbiting the nearest sun-
like stars.
2. Exozodiacal Dust
Objective 2: Brightness of Zodiacal Dust Disks. Establish if
the zodiacal cloud of our inner solar system is representative of
the population of our nearest neighbor stars.
3. Giant Exoplanet Atmospheres
Objective 3: Giant Planet Atmosphere Metallicity. Determine
the metallicity of known cool giant planets to examine trends with
planetary mass and orbital semi-major axis, and to determine if
these trends are consistent with our solar system.
Perform a “deep dive”, an intense, long integration of the 10 nearest sun-like stars with imaging and spectra for targets amenable to multiple visits to constrain orbits
1. Habitability and Planetary System Architectures
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The Deep Dive Approach
Initial ReconnaissanceFirst visit evaluates zodiacal dust brightness and detection of any exoplanets present
Orbit Determination Revisits to determine if planets are in the habitable zone of a star
Spectral CharacterizationDeep integration triggered by habitable zone exoplanet candidates. Any other planets in the field of view will also be spectroscopically characterized
JSimulation of the Solar System at 6 pc, 60 deg incl., and 1 day integration time
The sensitivity to discover and characterize Earth-like exoplanet candidates drives the observatory requirements
Credit: S. Hildebrandt
1. Habitability and Planetary System Architectures
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R=50
Starshade + WFIRST-CGI has the capability to take spectral measurements of exoplanet atmospheres
Requirements set using Earth as a model to enable the characterization of a wide class of planets
SRP BANDS
Image Credit: Aki Roberge
Planet Yield
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Discovery of a variety of exoplanets expected
All detected planets can be spectrally characterized (including for water vapor and oxygen)
Metallicity investigation yields another ~10 Jupiters
Parameter ValueAg 0.2Planet Radius 0.8–1.4 REarth
Habitable Zone (0.95–1.67) √Lsun
Solar System Zodi 1Exozodi 4.5
Earth-like planet input values
2. Exozodiacal Dust
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Main objective is to obtain 10 samples of exozodiacal dust disk brightness
Inform the HabEx deep dive and statistical distribution of warm dust disk brightness
Potentially observe the influence of planets in high dust environments
Simulated dust disk in the presence of a 5 ME exoplanet with 1 AU orbit (Stark & Kuchner 2008). r is the dust density and s is the grain size.
3. Metallicity of Known Giant Exoplanet Atmospheres
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Objective is to test the correlation of metallicity in giant exoplanet atmospheres with planet properties: mass and semi-major axis
Adapted from Wakeford+, 2017
Credit N. Lewis and B. MacIntosh
Observation Model
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WFIRST and StarshadeWFIRST Starshade Accommodations
• Starshade Acquisition Camera
– Used to acquire the starshade beacon after retargeting
• Formation Control Sensing and Commanding
– CGI LOWFS used for sensing offsets by capturing pupil plane images of out-of-science band starlight S-band radio
• S-band radio link
• Coronagraph filters
– Five custom filters in CGI
– 3 26% imaging bands
– 2 20% bands in IFS, R50 spectroscopy• WFIRST participates in rendezvous, formation control, and
science
• The starshade team has flowed requirements to WFIRST through an Interface Requirements Document (IRD)
The Starshade• Petal subsystem• Inner disk subsystem• Petal Launch Restraint Unfurl System (PLUS)
Requirement DescriptionThreshold
Value
Starlight SuppressionInstrument contrast 1×10-10
Solar Scatter Lobe brightness visual magnitude
V ≥ 25 mags
Lateral Formation Sensing & Control
Later position sensor accuracy that supports ±1 m control
≤ ±30 cm
Petal Shape Pre-launch accuracy ≤ ±70 µm
On-orbit thermal stability
≤ ±80 µm
Petal Position Pre-launch accuracy ≤ ±300 µm
On-orbit thermal stability
≤ ±200 µm
Driving RequirementsInner Working Angle ≤ 103 mas
Contrast (at IWA) ≤ 10-10
Flux Sensitivity: scattered light from starshade < background
Mission Duration: starshade must maintain thermal and mechanical stability for 3 years
Science Payload: Starshade
Starshade Technology Gaps
(1) Starlight Suppression
Suppressing diffracted light from on-axis
starlight and optical modeling (S-2)
Suppressing scatted light off petal
edges from off-axis Sunlight (S-1)
Positioning the petals to high accuracy, blocking on-axis starlight,
maintaining overall shape on a highly stable structure (S-5)
Fabricating the
petals to high
accuracy (S-4)
(2) Formation Sensing
(3) Deployment Accuracy
and Shape Stability
Sensing the lateral offset
between the spacecraft (S-3)
S-# corresponds to ExEP
Starshade Technology Gap
(http://exoplanets.nasa.gov/e
xep/technology/gap-lists)16
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J F M A M J J A S O N D
J F M A M J J A S O N D
Epsilon Indi A
Altair
Delta Pavonis
Procyon A
Sirius A
Omicron 2 Eridani
Epsilon Eridani
82 Eridani
Tau Ceti
J F M A M J J A S O N D J F M A M J J A S O N D
J F M A M J J A S O N D J F M A M J J A S O N D
Spacecraft
Events and Maneuvers
Contact with DSN 34 meter antenna 2 hours/day, 3 days/week; 4 days/week during maneuversDSN
Science
Laun
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Rend
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TCM
1 L
+3
2029 2030
Cumulative Science Delta-v
TCM
2 L
+30
Science Maneuvers
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3 9 21 27
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Dis
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2031+
15 22 33
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Star
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Summary
Starshade Rendezvous Probe opens a new frontier: the possibility of detecting Earth-like exoplanets orbiting nearby sun-like stars in the next decade
Starshade Probe will provide the first direct imaging examination of planetary systems in our nearest sun-like stars, including their habitable zones, giant exoplanets, and warm dust disks, opening a new frontier
Starshade Probe will determine whether the metallicity and mass of known gas giant exoplanets follows the correlation observed in our own solar system, fueling planetary formation studies
Beyond its science objectives, Starshade Probe will be an invaluable demonstration of technology and operations for future missions
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Probing our Nearest Sun-Like Star Neighbors
Image credit: JPL