Getting Started with Kepler

1. Getting Started with Kepler Kepler Science & Guest Observer Offices Steve Bryson Douglas Caldwell Jessie Christiansen Michael Fanelli Michael Haas Jon Jenkins Karen Kinemuchi Jeffrey Kolodziejczak Pavel Machalek Fergal Mullally Jason Rowe Martin Still Susan Thompson Jeffrey Van Cleve January 11, 2011 e-mail: kepler-scienceoffice@lists.nasa.gov keplergo@mail.arc.nasa.gov

2. Agenda • What Kepler provides … • Spacecraft Idiosyncrasies – Doug Caldwell • Pixels to Photometry • Light Curve Systematics & Detrending • How you can be involved … • Opportunities and Support • How to Find Interesting Targets • Archival Products • User Documentation

3. Kepler Data: from Stars to Ground Module #3, consisting of 4 channels, died in Jan 2010. Kepler is a Schmidt telescope with a focal plane of 42 back-thinned CCDs each with two read-out amplifiers for a total of 84 detector channels. The photometer stares continuously for 3 months, then rotates 90º about the boresight. The CCD layout is four-fold symmetric, except for the center module, so rows and columns maintain their orientation on the sky. Mod 3 Kepler is continuously monitoring >150,000 stars in a 110 sq. degree field in Cygnus/Lyra. The mission is planned for 3.5 years. Three main types of data are available: Long cadence: 30-minute samples of >150K stars from 5 – 18th mag Short cadence: 1-minute samples of 512 stars Full-Frame Images: monthly snap shots of all active pixels in the focal plane

4. Kepler Data: from Stars to Ground Image motion: differential velocity aberration introduces target star motions up to ~0.5 pixel at the edges of the focal plane (top). Pointing drift has been greatly reduced since Q3 (bottom) 1) Stars to CCDs: Seasonal focus variations change the PSF width up to ±10% on some channels DVA motion over focal plane Scattered light & Optical ghosts – affect only 1-3% of focal plane. Pointing drift attitude error Q1 Q2 Q3 Attitude error (mpix) 10 30 50 70 Q4 Q5 Q6 Q7

5. Kepler Data: from Stars to Ground 2) CCDs to memory: Electronic ghosting (video crosstalk) occurs within modules. Peak signal level is about 1/200 of source signal Undershoot/overshoot occurs during readout with a median level of ~0.3%. Undershoot is corrected in SOC calibration Fine guidance sensor clocking crosstalk occurs on all channels, affecting ~15% of targets. FGS xtalk is corrected in calibration.Moiré pattern artifacts affect ~10-20% of the FOV at a level significant for Earth-size transit detections (≥0.02 DN/pixel/read)

6. Kepler Data: from the Stars to the Ground 3) Memory to storage to ground: Pixel values are requantized based on intrinsic noise level to reduce range from 23 bits to 16 bits. Requantized step size is designed such that quantization noise is <25% of intrinsic pixel noise (3% noise increase when RSS’d) SC pixels at mean intensities >20,000 e- show banding (below) as a result of requantization; however, the overall noise of the light curve is near the Poisson limit. RQ step size (DN) Raw pixel value near SC bias (DN) Subsequent compression is lossless – baseline image difference followed by Huffman coding – and reduces range to ~5 bits/pixel/long cadence. DMC decompresses and un-requantizes baseline image each 24 hrs Bits/pixel/cadence 4 6 8 10 12

7. Agenda • What Kepler provides … • Spacecraft Idiosyncrasies • Pixels to Photometry – Steve Bryson • Light Curve Systematics & Detrending • How you can be involved … • Opportunities and Support • How to Find Interesting Targets • Archival Products • User Documentation

8. Pixel Level Data Module 17 Output 2 Zoomed Image near HAT-P-7b HAT-P-7b LC pixels 6.6 x 6.6 millideg 28 pixels collected Black = no data 0.09 x 0.09 degrees 80 x 80 pixels 6400 pixels total Scaled to show faint detail 1.13 (h) x 1.22 (w) degrees

9. Pipeline: Pixels to Planets CAL Pixel Level Calibrations TAD Select Pixels Raw Data Pixel Specification Calibrated Pixels PA Photometric Analysis Sums Pixels & Measures Centroids PDC Pre-search Data Conditioning Removes Systematic Errors Raw Light Curves & Centroids Corrected Light Curves TCEs: Threshold Crossing Events TPS Transiting Planet Search Diagnostic Metrics DV Data Validation

10. TAD: Find the “Optimal” Pixels that Maximize SNR • TAD: Pixels are selected that maximize the SNR of the calibrated sum • Use the measured PSF to create synthetic images with and without the target, so we know the signal and the noise of each pixel

11. TAD: Get the Optimal Pixels and More • TAD: Pixels are selected that maximize the SNR of the calibrated sum • Optimal aperture embedded in a halo for margin • Optimal aperture + halo define the pixels downlinked for each target

12. Pipeline: Pixels to Planets CAL Pixel Level Calibrations TAD Select Pixels Raw Data Pixel Specification Calibrated Pixels PA Photometric Analysis Sums Pixels & Measures Centroids PDC Pre-search Data Conditioning Removes Systematic Errors Raw Light Curves & Centroids Corrected Light Curves TCEs: Threshold Crossing Events TPS Transiting Planet Search Diagnostic Metrics DV Data Validation

13. CAL: Pixel Level Calibrations LDE Undershoot FGS Clocking Crosstalk Identify CR in Black + Black Level Correction 2D Black Correction LDE Undershoot Correction Gain + Nonlinearity Correction Raw Pixels ID CR & Remove from Smear Smear + Dark Current Correction Flat Field Correction Calibrated Pixels + Uncertainties

14. CAL: Pixel Level Calibrations Raw FFI Calibrated FFI

15. Pipeline: Pixels to Planets CAL Pixel Level Calibrations TAD Select Pixels Raw Data Pixel Specification Calibrated Pixels PA Photometric Analysis Sums Pixels & Measures Centroids PDC Pre-search Data Conditioning Removes Systematic Errors Raw Light Curves & Centroids Corrected Light Curves TCEs: Threshold Crossing Events TPS Transiting Planet Search Diagnostic Metrics DV Data Validation

16. PA: From Pixels to Photometry • PA: Create the flux light curve by summing pixels in the optimal aperture • First remove background from the pixels • Then remove cosmic rays from the pixels • Then sum optimal pixels to create flux light curve • Also compute pixel centroids at each observation • Systematics in the data • Focus variations due to thermal events • Pointing drift early in the mission 30 days 16 months

17. PA: Special Issues • Sometimes conventional photometry has problems • Saturated targets • Saturation is very complex and poorly modeled • So in early quarters some targets were poorly captured • Galaxies misclassified as stars • Solution: do your own photometry via target pixel files Example of a galaxy misclassified as a bright star TAD pixel selection Custom pixel selection

18. Agenda • What Kepler provides … • Spacecraft Idiosyncrasies • Pixels to Photometry • Light Curve Systematics & Detrending – Jeff Van Cleve • How you can be involved … • Opportunities and Support • How to Find Interesting Targets • Archival Products • User Documentation

19. Pipeline: Pixels to Planets CAL Pixel Level Calibrations TAD Select Pixels Raw Data Pixel Specification Calibrated Pixels PA Photometric Analysis Sums Pixels & Measures Centroids PDC Pre-search Data Conditioning Removes Systematic Errors Raw Light Curves & Centroids Corrected Light Curves TCEs: Threshold Crossing Events TPS Transiting Planet Search Diagnostic Metrics DV Data Validation

20. How PDC Works • PDC is designed to remove systematic errors by removing correlations (cotrending) between light curves and known system state variables such as: • Electronics board temperatures • Pointing and local image motion • Thermometers on or near optics (not currently used, but available) • Method used is Least Squares fit to the principal components of this set of time series • Simple filtering (detrending) cannot remove systematic noise on the same time scale as a transit without removing most of the transit, while cotrending can • PDC also removes light curve discontinuities caused by persistent damage of individual pixels by cosmic rays

21. What PDC Does Well • PDC works well on >70% of stars >90% of the time for its primary purpose: cleaning up light curves for transit detections • Quarters with several flight system anomalies (Safe Mode, Loss of Fine Point, pointing tweaks) are difficult because of the number and diversity of discontinuities

22. PDC Emphasizes Transits While Sometimes Distorting Astrophysical Signals • A Least-squares (LS) fitting of systematic errors (cotrending) to an incomplete model can minimize the bulk RMS of a light curve by transferring signal power from real astrophysical signals into false high-frequency noise • Users will need to be cautious when their phenomena of interest are much shorter (<1 h) or much longer (>5 d) than a transit, or have complex light curves with multiple extrema on transit time scales (such as eclipsing and contact binaries)

23. PDC Sometimes Adds Noise PDC-induced high frequency noise is more noticeable for bright stars, where it can dominate shot noise

24. Present Expedients and Future Progress • For diverse science, how you process the data can depend on what you are looking for • In the near term, users are invited to use the engineering data and intermediate Pipeline products provided as the Data Release Notes Supplement to do their own cotrending of uncorrected light curves • In the middle term, users may also wish to cotrend data using principal components derived from an ensemble of reference light curves for each channel, after a Quarter goes public • In the long term, we are developing the Maximum A Posterior (MAP) method described in Monday’s talk (103.02) and poster (140.08) to provide PDC with constraints on the magnitudes and signs of the fit coefficients to prevent overfitting and high-frequency noise • The legacy solution would be to make an off-line Pipeline available to users, pending availability of resources

25. The Joy of MAP: An Example • Blue line is mean-removed, normalized flux • Green line is a robust fit to the blue line, showing signal artifact and high-frequency • noise in the fit • Red line is the MAP fit to the blue line, showing gradual trend to be removed • Both robust fit & MAP use light curve ensemble as cotrending basis in this example

26. Agenda • What Kepler provides … • Spacecraft Idiosyncrasies • Pixels to Photometry • Light Curve Systematics & Detrending • How you can be involved … • Opportunities and Support – Martin Still & Mike Fanelli • How to Find Interesting Targets • Archival Products • User Documentation

27. GUEST OBSERVER • PROGRAM • Annual Program • PURPOSE: provide the whole community with competitive access to Kepler through a peer-reviewed science competition • 3,000 long cadence targets available every quarter • 25 short cadence targets are available every month • Successful US proposals are funded by NASA grants • URL: keplergo.arc.nasa.gov • E-mail: keplergo@mail.arc.nasa.gov • Martin’s Slides go here

28. GUEST OBSERVER PROGRAM • Director’s Discretionary Targets • PURPOSE: provide rapid response to community demand for Kepler targets • Targets of Opportunity • Pilot studies for the main GO program • Follow-up of old Kepler targets • Reinstatement of dropped targets • 100 targets available every quarter • Successful proposals are not funded by NASA grants • URL: keplergo.arc.nasa.gov • E-mail: keplergo@mail.arc.nasa.gov • Martin’s Slides go here

29. KEPLER ASTEROSEISMOLOGY SCIENCE CONSORTIUM • KASC is an unfunded consortium of (currently ~440) asteroseismologists. • KASC receives 1700 targets per quarter to investigate stellar “seismic” activity: • Solar-like oscillations • Pulsations in open clusters • β Cephei stars • d Scuti stars • roAp stars • Cepheid variables • B stars • Red giants • Pulsations in binary stars • g Doradus stars • Compact pulsators • Miras and semi-regulars • RR Lyrae stars • KASC is an open consortium, membership is free • apply onlineat: astro.phys.au.dk/KASC/

30. PARTICIPATING SCIENTIST PROGRAM • Participating Scientists serve as members of the Kepler Science Team and participate in Science Team activities, such as exoplanet data processing and analysis, transit candidate follow-up and characterization, and publication • Exoplanet statistics and theory • Sub-Neptune size planets • Multi-planet systems • Planet atmospheres • Asteroseismology • Stellar activity • Eclipsing and interacting binaries • Cluster astrophysics • The deadline for cycle 2 PSP proposals is Feb 11, 2011. Proposal instructions and element details are provided in the NASA Research Announcement: • URL: keplerscience.arc.nasa.gov/PSP.shtml • E-mail: douglas.m.hudgins@nasa.gov

31. ASTROPHYSICS DATA ANALYSIS PROGRAM (ADAP) • From Feb 1, 2011 the Kepler archive at MAST (http://archive.stsci.edu/kepler) will have available for the whole community 165,000 light curves with 130 days of near-continuous monitoring (Q0, Q1 & Q2) • Analysis of archived Kepler data can be funded through NASA’s Astrophysical Data Analysis Program, designed to support continued science using NASA mission data sets. Possible topics include: • Exoplanets • Asteroseismology • Stellar activity and evolution • Binary stars • Stellar and extragalactic accretion • The expected deadline for 2011 ADAP proposals is May 14, 2011. Proposal instructions and element details for the 2011 ADAP cycle will be released in early February 2011. Details about the 2010 ADAP program are provided in the NASA Research Announcement NNH10ZDA001N-ADAP on NSPIRES. • URL: http://nspires.nasaprs.com • E-mail: douglas.m.hudgins@nasa.gov

33. KEPLER COMMUNITY SERVICES • Kepler Guest Observer Office • URL: http://keplergo.arc.nasa.gov • E-mail: keplergo@mail.arc.nasa.gov • Kepler Science Office • E-mail: kepler-scienceoffice@lists.nasa.gov • Kepler archive at MAST • URL: http://archive.stsci.edu/kepler • E-mail: archive@stsci.edu • Kepler Users’ Panel • URL: http://nspires.nasaprs.com • E-mail: kepler-users-panel@lists.nasa.gov

34. Agenda • What Kepler provides … • Spacecraft Idiosyncrasies • Pixels to Photometry • Light Curve Systematics & Detrending • How you can be involved … • Opportunities and Support • How to Find Interesting Targets – Mike Fanelli • Archival Products • User Documentation

35. Selecting Targets For Observation The Kepler field-of-view, as seen in a full-frame image taken during commissioning • The challenge: • Classify & catalog sources • Identify appropriate targets for a wide range of astrophysical investigations

36. Creating a Source Catalog ► Need a comprehensive catalog describing source positions, motions, brightness, colors & classifications ► Primary classification source: optical observing program of the FOV carried out by the Kepler Science Team ► Photometry obtained in Sloan g,r,i,z broad-band filters + D51 narrow-band filter (a surface gravity diagnostic) ► Calibrated data compiled into the Kepler Input Catalog ► ~4.4 million cataloged sources located within the detector footprint

37. The Kepler Input Catalog Contents of the “KIC” ► Unique source identifications – expressed as KIC # (sometimes KepID) ►Federated with 2MASS JHK photometry, also uses USNO-B catalog ►Astrometry from 2MASS, USNO-B ►Star/galaxy separation using the 2MASS extended source catalog ► Estimation of source contamination (“crowding”) at the Kepler pixel scale ►Calibrated Kepler magnitudes (Kp) = flux as seen through theKepler photometer ► Source locations in the FOV, defined using focal plane models ► Estimates of Teff, log_g (for dwarf / giant separation), [Fe/H], E(B-V) ► Single epoch data – NO information on source variability KIC algorithms document: www.cfa.harvard.edu/kepler/kic/algorithms/algorithms.ps

38. MAST Target Search KIC search engine: archive.stsci.edu/kepler/kepler_fov/search.php input parameter search criteria Example: All sources with 15.0 < Kp < 16.0 Teff < 4000 K Log g > 4.0 multiple output formats

39. Mining the Kepler Input Catalog ►Primary information source for target identification ► Excellent search engine at MAST ► Users can also download the KIC as a text file from MAST, be aware of caveats as described on the MAST page ► Users must carefully check selected target lists – artifacts exist in the KIC ► Use the KIC overlay tool provided by skyview.gsfc.nasa.gov; Details on Guest Observer webpage keplergo.arc.nasa.gov under “Tools” Diffraction spikes flagged as KIC entries 2x2 arcminute extracts from the DSS2 red images, with KIC entries overlain using the tool noted above Multiple KIC entries in galaxy core

40. Expanding the Target Knowledge Base ► The KIC is optimized to identify cool (FGKM) dwarf stars for transit searches ► Users wanting to explore a broader range of science need sources: e.g., eclipsing binaries,pulsators, hot stars, accretors, compact stars, galaxies, active nuclei ► Kepler full-frame images provide a user resource for new source identification One FFI is obtained each month; all FFIs are available at MAST ► A number of community efforts are underway to expand knowledge of sources within the FOV: ☼GALEX (UV) / Kepler Cross Match Catalog: developed by MAST ☼ UKIRT – deep J-band survey: includes Kepler FOV; Courtesy Phil Lucas ROE, see keplergo.arc.nasa.gov/Tools ☼ All Sky Automated Survey - Kepler – variable stars in the Kepler field: www.astrouw.edu.pl/asas/kepler/kepler.html ☼ Variable Star Catalog – derived using 8 commissioning FFIs [see 201.06] ☼ Observing Campaigns: spring/summer 2011: U-band; deep (to ~21 mag) optical g,r,i, bands + Hα ☼ Other multiwavelength surveys: visit HEASARC, IPAC archives (NStED)

41. GALEX − Kepler Source Match

42. Agenda • What Kepler provides … • Spacecraft Idiosyncrasies • Pixels to Photometry • Light Curve Systematics & Detrending • How you can be involved … • Opportunities and Support • How to Find Interesting Targets • Archival Products – Susan Thompson • User Documentation

43. Introduction to the Kepler Archive Light Curve Files Target Pixel Files Full Frame Image • Data at MAST -- Multimission Archive at STScI • http://archive.stsci.edu/kepler

44. Introduction to the Kepler Archive • Data Products at the MAST • Light Curve Files (_llc and _slc) • LC is a quarter long • SC is a month long • Calibrated Aperture photometry (PA) • Detrended light curve (PDC) • Centroids • Target Pixel Files • Full Frame Images

45. Introduction to the Kepler Archive • Data Products at the MAST • Light Curve Files (_llc and _slc) • Target Pixel Files (_lpd-targ and _spd-targ) NEW! • Contains pixel information for one target. • RAW counts • Calibrated Pixels • Background Pixels • Cosmic Rays • Quality Flags • Aperture used by PA • Full Frame Images (_ffi-cal)

46. Target Pixel Files • Contains the pixels for each cadence. • Shows aperture used for photometry • Barycentered time (BKJD) • Flux in e-/sec

47. Introduction to the Kepler Archive • Data Products at the MAST • Light Curve Files (_llc and _slc) • Target Pixel Files (_lpd-targ and _spd-targ) • Full Frame Images (_ffi-cal) • Full readout of the CCDs each month • 84 extensions, one for each mod/out • https://archive.stsci.edu/kepler/ffi/search.php http://archive.stsci.edu/kepler

48. Getting Kepler Data • FTP download of gzipped tar files • Each contains subset of public data • Dropped Targets for Quarters 0-3 • Public Data from Quarters 0-3 • other public data • http://archive.stsci.edu/pub/kepler/lightcurves/tarfiles/ • Anonymous ftp • archive.stsci.edu • cd /pub/kepler/lightcurves/tarfiles • Data Search Page • Good to search for individual or groups of data.

49. Kepler Data Search http://archive.stsci.edu/kepler/data_search/search.php