Page 1 2011 Jan 11 – AAS Splinter Session - Getting Started with Kepler Getting Started with...

Page 12011 Jan 11 – AAS Splinter Session - Getting Started with Kepler

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: [email protected] [email protected]


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


Kepler Data: from Stars to Ground

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:1. Long cadence: 30-minute samples of >150K stars from 5 – 18th mag2. Short cadence: 1-minute samples of 512 stars3. Full-Frame Images: monthly snap shots of all active pixels in the focal plane

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

Module #3, consisting of 4 channels, died in Jan 2010.



1) Stars to CCDs: Seasonal focus variations change the PSF width up to ±10% on some channels

Scattered light & Optical ghosts – affect only 1-3% of focal plane.

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)

Q1 Q2 Q3

Q4 Q5 Q6 Q7

Att

itud

e er

ror

(mpi

x) 1

0

30

5

0

70

DVA motion over focal plane

Pointing drift attitude error



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 artifactsaffect ~10-20% of the FOV at a level significant for Earth-size transit detections (≥0.02 DN/pixel/read)


Kepler Data: from the Stars to the Ground

RQ

ste

p si

ze (

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 B

its/p

ixe

l/cad

enc

e

4

6 8

10

12

baseline image each 24 hrs

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.


Agenda

• What Kepler provides …– Spacecraft Idiosyncrasies

– Pixels to Photometry – Steve Bryson







0.09 x 0.09 degrees80 x 80 pixels6400 pixels total

HAT-P-7b LC pixels

Zoomed Image near HAT-P-7b

6.6 x 6.6 millideg28 pixels collectedBlack = no data

Scaled to show faint detail1.13 (h) x 1.22 (w) degrees

Module 17 Output 2

Pixel Level Data


CALPixel LevelCalibrations

PAPhotometric

Analysis

Sums Pixels & Measures Centroids

TPSTransiting Planet

Search

PDCPre-search Data

Conditioning

Removes Systematic Errors

RawData

TCEs:Threshold Crossing Events

CorrectedLight Curves

CalibratedPixels

Raw LightCurves & Centroids

DVData Validation

Diagnostic Metrics

Pipeline: Pixels to Planets

TADSelect Pixels

PixelSpecification


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


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



PAPhotometric

Analysis



Search

PDCPre-search Data

Conditioning


RawData



CalibratedPixels


DVData Validation

Diagnostic Metrics


TADSelect Pixels

PixelSpecification


2D Black Correction

Identify CR in Black +

Black Level Correction

Gain + Nonlinearity Correction

ID CR & Remove

from Smear

LDE Undershoot Correction

Smear + Dark Current

Correction

Raw Pixels

Flat Field Correction

Calibrated Pixels + Uncertainties

945 950 955 960 965 970 975

235

240

245

250

255

260

265

270

275

LDE Undershoot

FGS Clocking Crosstalk

CAL: Pixel Level Calibrations


CAL: Pixel Level Calibrations

Raw FFI Calibrated FFI



PAPhotometric

Analysis



Search

PDCPre-search Data

Conditioning


RawData



CalibratedPixels


DVData Validation

Diagnostic Metrics


TADSelect Pixels

PixelSpecification


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

16 months

30 days


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


Agenda



– Light Curve Systematics & Detrending – Jeff Van Cleve







PAPhotometric

Analysis



Search

PDCPre-search Data

Conditioning


RawData



CalibratedPixels


DVData Validation

Diagnostic Metrics


TADSelect Pixels

PixelSpecification


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


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


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)


PDC Sometimes Adds Noise

PDC-induced high frequency noise is more noticeable for bright stars, where it can dominate shot noise


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


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


Agenda




• How you can be involved …– Opportunities and Support – Martin Still & Mike Fanelli





• Martin’s Slides go here

GUEST OBSERVERPROGRAM

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: [email protected]


• Martin’s Slides go here

GUEST OBSERVER PROGRAM

Director’s Discretionary Targets

PURPOSE: provide rapid response to community demand for Kepler targets

oTargets of OpportunityoPilot studies for the main GO programoFollow-up of old Kepler targetsoReinstatement of dropped targets

•100 targets available every quarter

Successful proposals are not funded by NASA grants

URL: keplergo.arc.nasa.gov

E-mail: [email protected]


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 Scuti stars• roAp stars• Cepheid variables• B stars• Red giants• Pulsations in binary stars Doradus stars• Compact pulsators• Miras and semi-regulars• RR Lyrae stars

• KASC is an open consortium, membership is free

• apply online at: astro.phys.au.dk/KASC/


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.shtmlE-mail: [email protected]


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.comE-mail: [email protected]



KEPLER COMMUNITY SERVICES

• Kepler Guest Observer OfficeURL: http://keplergo.arc.nasa.govE-mail: [email protected]

• Kepler Science OfficeE-mail: [email protected]

• Kepler archive at MASTURL: http://archive.stsci.edu/keplerE-mail: [email protected]

• Kepler Users’ PanelURL: http://nspires.nasaprs.comE-mail: [email protected]


Agenda





– How to Find Interesting Targets – Mike Fanelli




Selecting Targets For Observation

The challenge:

Classify & catalog sources

Identify appropriate targets for a wide range of astrophysical investigations

The Kepler field-of-view, as seen in a full-frame image

taken during commissioning


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


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 the Kepler 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


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


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


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)


GALEX − Kepler Source Match


Agenda






– Archival Products – Susan Thompson



Introduction to the Kepler Archive

Light Curve Files

Target Pixel Files

Full Frame Image

Data at MAST -- Multimission Archive at STScIhttp://archive.stsci.edu/kepler



• 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



• 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)


Target Pixel Files

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



• 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


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.


Kepler Data Search

http://archive.stsci.edu/kepler/data_search/search.php



Retrieving Data

• To obtain a username and password (or use anonymous for public data)– http://archive.stsci.edu/registration/registration_form.html

• You must highlight target pixel files or FFI if that is what you wish to retrieve


Future Data Releases

• February 1, 2011 : All Q2 exoplanet data will go public

• April 2011 : Q3 GO targets will be public

You are here


Agenda







– User Documentation – Jessie Christiansen


User Documentation

The following documentation can be obtained from the Kepler MAST Documents page: http://archive.stsci.edu/kepler/documents.html

• Kepler Instrument Handbook – photons to pixels– Description of hardware – design, performance, operational

constraints– Updated bi-annually

• Kepler Data Processing Handbook – pixels to photometry– Description of science processing pipeline, including theoretical

basis of the algorithms used– Updated with each new release of the SOC Pipeline

• Kepler Archive Manual – photometry to you– Description of data available through MAST, including file formats

and availability– Updated with each new release of the SOC Pipeline


User Documentation

The following documentation can be obtained from the Kepler MAST Data Release page: http://archive.stsci.edu/kepler/data_release.html

• Kepler Data Characteristics Handbook – phenomena in photometry– Description of all instrumental/systematic phenomena identified in

the data– Updated with identification of new phenomena

• Kepler Data Release Notes – brief newsletter accompanying each data release– Dynamic set of tables and figures documenting phenomena

identified during each processing of each quarter of data– Supplement: tar ball of files for use in user analysis and cotrending

of the data, including ancillary engineering data

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