kepler discovery mission # 10 william borucki, pi nasa 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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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 4π */ d D for all possible pole positions for any given LOS
3) = */ Geometric Transit Probability d D
2π2 */d D
1) = Range of Pole Positions*d
/2D
/2D 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
Det
ecti
ons
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 ORGANIZATION
Science 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
spectroscopy
Data 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
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