KEPLERDiscovery Mission # 10

William Borucki, PINASA Ames

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KEY QUESTIONS:

• Are terrestrial planets common or rare?• How many are in the habitable zone?• What are their sizes & distances?• Dependence on stellar properties

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SCIENTIFIC GOALS

• Determine the frequency of terrestrial and larger planets in or near the habitable zone of a wide variety of stellar spectral types

• Determine the distribution of sizes and semi-major axes of these planets

• Identify additional members of each photometrically discovered planetary system using complementary techniques

• Determine the distributions of semi-major axis, albedo, size, and density of short-period giant planets

• Estimate the frequency of planets orbiting multiple star systems

• Determine the properties of those stars that harbor planetary systems

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KNOWN EXTRASOLAR PLANETS

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DOPPLER VELOCITY MEASURMENTS

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INFORMATION OBTAINED FROM PLANETARY TRANSITS

Star

Planet

Planetary Orbit

From transit data obtain: Duration, depth, orbital period and inclination. Derive planet sizes and orbital radii (when combine with stellar information)

From ensemble of planetary systems: Estimates frequency of planet formation for inner planets. Distribution of planetary sizes, orbital sizes, co-planarity, effects of Jovian planets.

Additional science: Expect 24 large planets in outer orbits (ground based follow up.) Stellar activity (star spot cycles, p-mode oscillations, white light flaring, etc.) Frequency of Maunder minimums and the implications for the Sun and Earth’s climate. Stellar rotation rates, limb darkening. Extreme-mass-ratio eclipsing binaries.

4/97

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GEOMETRY FOR TRANSIT PROBABILITY

2) Solid angle of 4πd*/D for all πossible πole πositionsfor any given LOS

3) Geometric Transit Probability = d*/D

2π2d*/D

1) Range of Pole Positions = d*D/2

D/2 Orbital radius

d*

StellarDiameter

5/96

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Use transit photometry to detect Earth-size planets • 0.95 meter aperture provides enough photons • Observe for several years to detect the pattern of transits • Monitor stars continuously to avoid missing transits• Use heliocentric orbit

Get statistically valid results by monitoring 100,000 stars • Use wide field of view telescope • Use a large array of CCD detectors

21 CCD Modules are the Heart of the Kepler Mission

MISSION DESIGN

KEPLER: A Wide FOV Telescope that Monitors 100,000 Stars for 4 years with Enough Precision to Find Earth-size Planets in the HZ

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REQUIRED SENSITIVITY•∆L/L = area Earth/area Sun = 1/12,000 = 8x10-5

•Require total noise to be <2x10-5 for 4-sigma detection in 6.5 hours

•Three sources of noise and their contributions:- Stellar variability:<1x10-5, typically for the Sun on timescale of ~1/2 day- Shot noise:1.4x10-5, in 6.5 hr for mv=12 solar-like star and 0.95-meter aperture - Instrument noise: <1x10-5, including detector dark current, electronics read noise,

thermal effects, spacecraft pointing jitter, and shutterless operation.

•Detector of choice: array of 42–2kx1k CCDs with 27µm pixels and dual readout- Thinned, back-illuminated, anti-reflection coated

•Limiting bright magnitude of mv=9 and full-well depth of 106 e-requires:- Defocus image to 5 pixel square and readout every 3 seconds.

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MEASUREMENT TECHNIQUE•Use differential photometry (common mode rejection):

- Brightness of each star is re-normalized to the ensemble of thousands of stars in each half of each CCD & readout with a single amplifier;

•Transits only last several hours: - Long term photometric stability not necessary;

•Defocus the star image to five pixel square: - Mitigates saturation (109 e-/hr) and sensitivity to motion;

•Control pointing to 3 millipixels (0.01 arc sec); - Star images remain on the same group of pixels, eliminates

effects of inter-pixel variations in sensitivity;•Operate CCDs near full-well capacity:

- Dark current and read-noise effects become negligible; •Place the photometer in a heliocentric orbit (SIRTF-like):

- Provides for a very stable thermal and stray light environment.

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SCIENCE DRIVER

Statistically valid result for abundance of Earth-size planets in habitable zone

Expected # of planets found, assuming one planet of a given size & semi-major axis per star and random orientation of orbital planes.

# of

Pla

net D

etec

tions

Orbital Semi-major Axis (AU)

10000

1000

100

10

1 0.2 10 1.40.4 1.20.80.6 1.6

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Stellar Occultations & High-Precision CCD Photometry•Timothy Brown, HAO, UCAR •Edward Dunham, Lowell Obs.•John Geary, SAO •Ronald Gilliland, STScI•Steve Howell, U. Cal., Riverside•Jon M. Jenkins, SETI InstituteDoppler Velocity Planet Searches•William Cochran, UTexas•David Latham, CfA, SAO•Geoff Marcy, U. Cal., BerkeleyStellar Variability•Gibor Basri, U. Cal., Berkeley•Andrea Dupree, CfA, SAO•Dmiter Sasselov, CfA, Harvard

Theoretical Studies•Alan Boss, Carneige Institute Wash.•Jack Lissauer, NASA AmesMission Operations•Donald Brownlee, U. of Washington•Yoji Kondo, NASA GSGCGeneral Overview•John Caldwell, York U.•David Morrison, NASA Ames •Tobias Owen, Univ. Hawaii•Harold Reitsema, Ball Aerospace Co.•Jill Tarter, SETI InstituteEducation and Public Outreach•Edna DeVore, SETI Institute •Alan Gould, Lawrence Hall of Science

William J. Borucki, PI, and David Koch, Deputy PI

SCIENCE TEAM

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OPERATIONS ORGANIZATIONScience Ops Center - Ames

• Scientific direction• Select target stars• Manage Instrument• Diff. ensemble photometry• Stellar light curves• Transit search• Candidate planet list• Direct follow-up observing• Final planet determination

ComplementaryObserving - SAO/UA/UC-B

• Stellar classification• Elim. false positives - low resolution

spectroscopy• Stellar properties• Giant planet mass - high resolution

spectroscopyData ManagementCenter - STScI• Calibrate data• Archive data• Difference images• HST follow-up• PSP and DAP

Education PublicOutreach - LHS/SETI

• Formal education• Informal education• Public outreach

DSN

Mission Ops Center- Honeywell

• Cmd/control spacecraft• DSN scheduling• Acquire all data• Engr. data archive• Anomaly response

Sustaining Engneering- Ball Aerospace• Manage MOC• Ensure spacecraft health/safety• Anomaly resolution

Rawdata

Cmd/data

Calibrated dataTarget list

Results

Stellardata

Observ-ingrequest

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EDUCATIONAL & PUBLIC OUTREACH

Lessons, simulations — Website — Information, data

Informal• New GEMS strand: Space Science “ Finding New Worlds”

• FOSS Teacher workshops• Space Place activities• Hands On Universe Planet-finding for high school

• Kepler-CAM (Underserved/ minority colleges)

• Multi-media planetarium program (large dome)• Interactive planetarium program (small dome)• Kepler CD-ROM• Exhibit Orrery Transit Model

• Amateur Astronomers -kit -ephemerides-TransitSearch

• Broadcast television program

• STARDATE radio programs

Public OutreachFormal

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SCHEDULE & MISSION STATUS

Bill Borucki

CDRPhase B

Phase C/DPhase E

06 07 08 09 10 11 12 130502 03

PDRSRR

04

Launch

CY01

ATP End normaloperations

End extendedoperations

Phase F

CCD Detectors are arriving from both vendors

Optics are on order

Preparing for the first major review

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VALIDATION OF DISCOVERIES

Signal to Noise Ratio (SNR) > 7 to rule out statistical fluctuations

Three or more transits to confirm orbital characteristics

Light curve depth, shape, and duration

Image subtraction to identify signals from background stars

Radial velocityMedium resolution to rule out stellar companionsHigh resolution to measure mass of giant planets

High spatial resolution to identify extremely close background stars