a search for earth-size planets borucki – page 1 kepler; data validation and follow up...
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A Search for Earth-size Planets
Borucki – Page 1
KEPLER; Data Validation and Follow Up Observations
CoRoT SymposiumW.J. Borucki& the Kepler
Team 5 February 2009
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Key
Ground Segment Roadmap
Functional Interface
Primary Command Flow
Primary Telemetry Flow
Project Scheduling
Services
Navigation (NAV)JPL
Deep Space Mission Systems
Mission Operations Center
LASP
Data Management CenterSTScI
Flight Planning CenterBATC
Science Operations Center
ARC
Stellar Classification
Program
Mission Management
OfficeARC
Science OfficeARC
Follow-up Observing Program
BATC LASP
ARCJPL
Sci TeamSTScI
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Black level correction
Quarterly Processing
DMC
Ground-basedFollow up Observing
SOC Smear, flat field, dark current, nonlinearity, cosmic ray correction
OAP and DIA photometry to generate flux time
series
Pre-search data conditioning to remove
systematic errors
Transiting and reflected- light planet searchFocal Plane
Characterization
Data Validation
SOC data store
SOC Data Store
Photometer performance assessment
SOC data store
SOC Data Store
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Methods of Data ValidationUsing Kepler Data
• Rule out statistical fluctuations in the data, accept only signals that show 3 or more transits and that have a total signal-to-noise ratio that exceeds 7 sigma.
• To rule out small stellar companions of the target star, check for secondary eclipses and determine if the transit characteristics are appropriate for a planetary companion. Modeling effort will be used to distinguish stellar binaries from stars with planets.
• Check for background binaries that are in the target aperture; measure the movement of the image centroid before, during, and after the transit. This test is expected to rule out the hundreds of binary signals expected from background stars. The precision of the measurement depends on the stellar fluxes and positions but can be better than 0.01 pixel; i.e., 0.04”.
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Ground-based Follow Upto Eliminate False-Positive Events
Those candidates that pass DV are examined using ground-based telescopes and radial velocity spectrometers.
1. Medium precision RV is used to rule out any remaining stellar companions.
2. High spatial resolution imaging is used to check for nearby stars that are in the aperture. (apertures depend on magnitude but are ~ 36 sq arc sec.)
3. If no confounding stars present, then the candidate observed with a large telescope such as Keck, HET, or Willilam Herschel for high precision observations to get the planet mass or an upper limit to it.
4. If there are some stars in the aperture, then the photometric observations are employed to look for the transit by one of the confounding stars. (Includes AO & HST observations for Earth-size candidates.)
5. If transit signal is not due to confounding stars, then the candidate is sent to a large telescope such as Keck, HET, or William Herschel for high precision observations to get the planet mass or an upper limit to it.
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Coordination of Ground-basedFollow Up Observations
• Candidate Follow up
– Algorithm ranks several hundred candidates to set their priority
– Observers assemble to discuss & agree on targets
– Target information (RA, dec, mag, SpT, variability, ephemeris) sent to coordination website
• Coordination Web Site
– Organized by follow-up target and by observation request
– Contains all the information on the targets as requested by observers
– Contains intermediate results from observations and whatever compact, reduced data sets are required by the Follow up Observers Group
– Voluminous data is referenced by links to observers’ home facilities
• Coordination data base
– Operated by the Follow-up Coordinator to schedule and track status of observations requested by the PI and Science Team
• Results returned to Science Office• Science team meets to discuss results & make announcements
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DATA RELEASE POLICY
Figure 1. Relation between the times the data are returned from the spacecraft and when they are released.
Beginning of science operations (30 days after launch)
0
A ll data released
Data released:
End of nominal mission
Data produced:
1 yr
2 yrs
3 yrs
4 yrs
4.5 yrs
0
1 yr
2 yrs
3 yrs
3.5 yrs
All discoveries are released after the team meets to discuss the evidence and NASA HQ is informed.Pixel-level data and light curves are released with each discovery.