Kepler: A Search for Terrestrial Planets
Kepler Archive Manual
KDMC-10008-001
March 15, 2011
Space Telescope Science Institute
3700 San Martin Drive
Baltimore, MD 21218
Prepared by: ________________________________________
Date __________
Susan E. Thompson, Science Office
Prepared by:
________________________________________ Date __________
Dorothy Fraquelli, MAST Archive Scientist
Approved by: _______________________________________
Date __________
Chris Middour, SOC Systems Engineer
Approved by:
_______________________________________ Date __________
Rick Thompson, Ground Segment Systems Engineer
Approved by: _______________________________________
Date __________
Cyrus
Chow, Mission Assurance
Approved by: _______________________________________ Date
__________
Ron
Gilliland, Co-Investigator, STScI
Approved by: _______________________________________ Date
___________
Michael Haas, Science
Office Director
Table of Contents
Table of Contents.................................................................................................................................................................................................................................. 3
Chapter 1 Introduction............................................................................................................................................. 4
1.1 Overview of Kepler.................................................................................................................................................................................................................... 4
1.2 Targets................................................................................................................................................................................................................................................ 5
1.3 Overview of Data Flow............................................................................................................................................................................................................. 6
1.4 Related Documents..................................................................................................................................................................................................................... 7
1.5 Overview of MAST....................................................................................................................................................................................................................... 8
1.6 User Support Services............................................................................................................................................................................................................... 8
1.7 Registering as a User.................................................................................................................................................................................................................. 9
1.8 Proprietary Data Periods..................................................................................................................................................................................................... 10
1.9 Getting Your Data...................................................................................................................................................................................................................... 11
1.10 Publication Acknowledgement..................................................................................................................................................................................... 11
Chapter 2 Kepler Data Products............................................................................................................................ 12
2.1 Introduction................................................................................................................................................................................................................................. 12
2.1.1 Overview of Data in the Archive.............................................................................................................................................................................. 12
2.1.2 Kepler Time System......................................................................................................................................................................................................... 12
2.1.3 FITS headers........................................................................................................................................................................................................................ 13
2.1.4 Disclaimer: File Formats will Change................................................................................................................................................................. 13
2.2 File Name Syntax........................................................................................................................................................................................................................ 13
2.3 Data in the Archive................................................................................................................................................................................................................... 14
2.3.1 Light Curve Files............................................................................................................................................................................................................... 14
2.3.2 Target Pixel Data............................................................................................................................................................................................................. 16
2.3.3 Full Frame Image............................................................................................................................................................................................................ 19
Chapter 3 Searching the Archive for Kepler Data................................................................................................ 20
3.1 The Kepler Catalogs as Presented at
MAST.......................................................................................................................................................... 20
3.2 The MAST Search Forms................................................................................................................................................................................................... 24
3.2.1
Kepler
Target Searches (e.g. objects to
observe)....................................................................................................................................... 25
3.2.2 Kepler Data Searches.................................................................................................................................................................................................. 36
3.2.3 FFI Search and Retrieval or Download.............................................................................................................................................................. 46
Appendices............................................................................................................................................................ 54
A.1: Kepler Light Curve File Headers.................................................................................................................................................................................... 55
A.2: Target Pixel File Headers.................................................................................................................................................................................................... 59
B.1: Full Frame Image (FFI)Primary
Header.................................................................................................................................................................. 64
B.2 Calibrated FFI Channel Header........................................................................................................................................................................................ 68
C.1: Glossary of Terms................................................................................................................................................................................................................... 70
C.2 Common Acronyms................................................................................................................................................................................................................. 72
Chapter 1 Introduction
Data from the Kepler mission are housed in the Archive at the Space Telescope Science Institute (STScI) and accessed through MAST (Multi-mission Archive at Space Telescope). The Kepler Input Catalog (KIC), Kepler Target Catalog (KTC), Characterization Table (CT) and Kepler Results Catalog (KRC) are also accessed through MAST. Products such as light curves and target pixel data are stored on spinning disk. General information about Kepler may be found at the Kepler Mission http://www.kepler.arc.nasa.gov/ and the Kepler GO Program http://keplergo.arc.nasa.gov/ web sites.
1.1 Overview of
Kepler
The Kepler mission is designed to survey a region of the Milky Way galaxy to detect and characterize Earth-size and smaller planets in or near the habitable zone by using the transit method of planetary detection. The expected lifetime of the mission is 3.5 to 6 years.
The Kepler telescope has
a 0.95-meter aperture and a 105 deg2 (about 12 degree diameter)
field-of-view (FOV). It is pointed at and records data from the same group of
stars for the duration of the mission.
The single instrument on board, a photometer, is an array of 42 CCDs
arranged in 21 modules of 2 CCDs each.
Each CCD has 2 outputs. The half-maximum bandpass is 435 to 845 nm, with
>1% relative spectral response as short as 420 nm and as long as 905
nm. Each 50x25 mm CCD has 2200x1024
pixels. The interval between reads of a given pixel of a CCD is composed of an
exposure time set to 6.019802903 s and a fixed readout time of 0.5189485261
seconds. All pixels are read out every
integration, and temporally summed in the Science Data Accumulator (SDA).
Mission and GO target lists determine which of those SDA summed pixels are read
out of the SDA and transmitted to the Solid State Recorder for later
downlink. On average 32 pixels are read
out of the SDA per target. The long cadence data are summed into onboard
memory for 30 minutes (270 integrations), while the short cadence data
are 1 minute sums (9 integrations).
Downlinks are expected to occur on an approximate monthly basis.
A star field near the galactic plane, centered on galactic coordinates l = 76.32°, b = +13.5° (RA=19h 22m 40s, Dec=+44° 30' 00'), is the “field.” Figure 1-1 shows the field with the Kepler FOV superimposed. The squares show the 5 square degree FOV of each of the 21 modules. The gaps between the modules are aligned so that about half of the 15 stars in the FOV brighter than mv=6 fall in these gaps. The 42 CCDs cover a four-way symmetrical pattern on the sky such that most of the same stars stay visible during the mission, even after a quarterly 90° roll. In addition, the orientation of the rows and columns of each module location on the sky is preserved for all roll orientations. The center module is only 180 degree symmetric. The roll is necessary to keep the solar arrays oriented towards the Sun and the radiator pointed towards deep space.
Kepler is in an Earth-trailing heliocentric
orbit with a period of 372.5 days. In this orbit the spacecraft slowly drifts
away from the Earth and is at a distance of over 0.5 AU after 3.5 years. The orbit permits continuous pointing on a
single region of the sky. Additional
advantages are the very stable pointing attitude and the avoidance of high
radiation dosage associated with an Earth orbit, but from time to time the
spacecraft is subject to solar flares.
1.2 Targets
At launch, ~150,000 targets were selected for observations by the the mission. As the downlink data rate drops, one or more target “down selects” may occur. The data for these no-longer-observed targets will become public within 2 to 4 months, depending on processing status.
Through MAST, users are able to search for existing targets
of potential interest, determine when specific observations are available
(consistent with proprietary restrictions) for access, and retrieve data. The
community may propose to monitor additional objects of any nature that are in
the Kepler FOV, such as variable stars or active galactic nuclei. In
general, proposals that duplicate the exoplanet project are not
allowed. See the Guest Observer
(GO) Program website (http://keplergo.arc.nasa.gov/)
for details on the proposal cycle.
1.3 Overview of Data Flow
Data are downloaded from the spacecraft (S/C) through the
Deep Space Network (DSN). The Mission
Operations Center (MOC) at LASP receives the data and telemetry packets that are
binned into files by data type. The data
are then sent to the Data Management Center (DMC) at STScI, where they are
archived. The data are then
decompressed, sorted by cadence (long or short) and pixel type (target,
background or collateral), and converted to FITS. The keyword values are
populated. At this point in processing,
the data are termed to be “original.”
The data are then sent to the Science Operations Center (SOC) at NASA
Ames, where detailed calibration is performed and light curves and target pixel
files are produced. The data are then
returned to the DMC for archiving. The total time for one cycle (data dump from
the S/C through archiving of the processed data) is nominally 4 months. For a
given target, archive users can access the original and calibrated pixel values
in the target pixel files or the integrated flux values in the light curves.
1.4 Related Documents
Documentation is available on-line for all archive holdings. The main archive page, http://archive.stsci.edu, provides links to a MAST tutorial, a general introduction to MAST and a "getting started" page. Each mission page has links to mission specific information, a mission specific "getting started" page and the MAST tutorial. The MAST Kepler page is located at http://archive.stsci.edu/kepler/. Other useful links for Kepler are http://kepler.nasa.gov/ , http://www.kepler.arc.nasa.gov/ and http://keplergo.arc.nasa.gov/ .
A reference description of Kepler may be found in the Kepler Instrument Handbook (KIH, KSCI-19033). The KIH describes the design, performance, and operational constraints of the Kepler hardware, and gives an overview of the pixel data sets available. A description of Kepler calibration is given in a series of SPIE papers published in 2010. Copies of both the KIH and the SPIE papers may be downloaded from MAST. They are located under the Documentation item in the left gutter of the MAST/Kepler home page (http://archive.stsci.edu/kepler/documents.html).
Science users should also consult the special ApJ Letters devoted to early Kepler science (April 2010, ApJL, Vol. 713 L79-L207). This volume contains a description of the mission design (Koch et al. L79), an overview of the processing pipeline (Jenkins et al. L87), how the first Kepler planets were found (Borucki et al. L126; Dunham et al. L136) and how these data may be used for asteroseismology (Gilliland et al. L160; Chaplin et al. L169).
Additional technical details regarding the data processing
and data qualities can be found in the Data Characteristics Handbook (DCH, KSCI-19040)
and the Data Release Notes (DRN, KSCI-19042 to KSCI-19049), which are located
in the left gutter of the MAST/Kepler home page. New Data Release Notes accompany the data for
each processing of each quarter.
1.5 Overview of MAST
The Multi-mission Archive at STScI supports a variety of astronomical data archives, with the primary focus on scientifically related data sets in the optical, ultraviolet, and near-infrared parts of the spectrum. See http://archive.stsci.edu/missions.html for a full list of the missions hosted by MAST and http://archive.stsci.edu/hlsp/index.html for the high-level science products, surveys, and catalog data distributed by MAST. MAST is a component of NASA's distributed Space Science Data Services (SSDS).
The staff of the Archive Sciences Branch and the Multi-mission Archive at STScI (MAST) provides:
- world-wide technical and scientific leadership in archive system design
- secure storage and reliable retrieval services for data from HST and all MAST-supported missions
- user-friendly and scientifically useful search and cross-correlation tools
- development and support for inter-archive communication and data transfer standards
- accurate and useful mission archive documentation
- helpful user support services with a 1 business day response time
MAST archives a variety of spectral and image data with a range of data characteristics. MAST provides a large suite of searches, including customized searches for each mission. It also provides several cross-mission search tools.
MAST also archives sets of community contributed High-Level Science Products (HLSPs). MAST actively solicits submission of High-Level Science Products related to our missions and we provide guidelines for contributing them to MAST.
The MAST Users Group provides essential user perspectives on archive operations and development, including suggesting priorities for short and long term operational and scientific enhancements to the archive.
User feedback is obtained via an annual survey. Send e-mail to archive@stsci.edu to participate in the next survey.
The archive website, http://archive.stsci.edu , is the best place to start learning about MAST and what it can do to enable your research. The web site should always be consulted for the most current information.
1.6 User Support Services
Archive Hotseat
Help or answers to any questions about archive issues may be obtained by sending e-mail to archive@stsci.edu, or by telephoning (410) 338-4547 Monday through Friday, 9 a.m. to 5 p.m. Eastern time.
The helpdesk staff will respond to questions concerning the archive and archive databases, and CDs, DVDs and hard disks provided by STScI. Helpdesk personnel also authorize accounts so that PIs and GOs can access their proprietary data. They will also provide advice concerning basic search strategies, and will investigate and document all problem reports. The archive helpdesk staff may not always know how to solve a problem, but they are responsible for finding out who does know the answer and for continuing to work with you until the problem is resolved. All initial communication from the user community to the archive should be directed to the archive helpdesk.
Questions and Comments
Communication regarding all aspects of the archive should normally be directed to the archive helpdesk (e-mail: archive@stsci.edu, or telephone (410) 338-4547). This will allow Archive staff to respond to your requests even when individual members of the group are away. If you feel your needs are not being adequately addressed through the helpdesk, place a message in the Suggestion Box located at http://archive.stsci.edu/suggestions.html.
1.7 Registering as a User
Registration is not required to search the archive and/or retrieve public data. Registration and authorization is required to retrieve proprietary data, even for the Kepler Principal Investigator (PI) and Guest Observers (GO). Only registered and authorized users can retrieve proprietary data. Register (create an archive account) by using the on-line form at http://archive.stsci.edu/registration. Alternatively, send e-mail to archive@stsci.edu. Within two working days of the receipt of your e-mail, you will be notified by e-mail of your registration as an archive user and you will be provided with a username and a password. Note: The password can be changed from the registration page.
For proprietary users of Kepler data, authorization is handled automatically via quarterly receipt of an XML document from the Kepler Science Office. Archive users who find they are denied access to their proprietary data should have the PI or GO on the proposal send e-mail to archive@stsci.edu stating the investigation ID and the identities of anyone who should be able to retrieve the data.
KASC members do not have access to proprietary data through MAST. Instead, they should work through the KASC data archive maintained by the Kepler Asteroseismic Science Consortium. See http://astro.phys.au.dk/KASC/ .
To access proprietary Kepler data with a MAST account, the contact information and the e-mail of the user’s archive account must match the contact information and e-mail provided to the Kepler Science Office. Users with existing archive accounts at STScI/MAST, created to retrieve data from other missions, do not need to create a new one. They may, however, need to update the contact information and/or change the e-mail address for the account. The GO office provides the MAST with the GO names and email addresses contained in the GO proposal. All information must match the MAST account information, or access will be denied. This means that a GO named Christopher E. Smith on the Kepler proposal, but registered as Chris Smith at the archive, will need to update his archive account contact information.
The direct link to the archive account update page is:
http://archive.stsci.edu/registration/index.html#acct_tools .
Near the bottom of the page is a section titled "How can I keep my account current?" In this section are links to
* Have your password sent to you
* Change your password
* Update your account information.
You will need your archive user name and password to access the Change Contact Info page.
These changes should be made BEFORE data are delivered to the MAST. This action is required because the links between the investigation ids and the proposer names are created before the data are ingested. If your data have already been delivered to MAST and you cannot access them, contact the archive help desk at archive@stsci.edu.
1.8 Proprietary Data Periods
The Guest Observer Office will notify GOs of the availability of their data. It is the responsibility of the GOs to fetch their data from the archive. Unlike exoplanet data, GO data have a public release date set to one year from the time the light curves are archived. See http://keplergo.arc.nasa.gov for more information on the proprietary period for GO targets.
Archived data for mission targets dropped from the planetary search program will generally be made public within 4 months after being dropped from the target list. All data are public one year after the end of data acquisition from the mission.
Table 1-1 – Data Release Timeline for Exoplanet
Program
|
Quarter |
Data Release Date* |
|
1 |
6/15/2010 |
|
2 |
2/02/2011 |
|
3 and 4 |
6/18/2012 |
|
5 and 6 |
6/18/2013 |
|
7 to 14 |
11/18/2013 |
Several types of Kepler data are non-proprietary. These are the collateral and background pixels files, the full frame images (FFIs) and the Kepler catalogs. The catalogs include the Kepler Input Catalog (KIC), the Characteristics Table (CT), the Kepler Target Catalog (KTC), and the Kepler Results Catalog (KRC). The catalogs contain metadata that will be staged through the Kepler archive interface at MAST. Information staged in these catalogs through MAST is public. The KRC is not yet available.
1.9 Getting Your Data
GOs on Kepler proposals and their authorized Co-Is may retrieve their data via the MAST Kepler Data Search and Retrieval form http://archive.stsci.edu/kepler/search.php . Entering the proposal id in the Investigation_ID field and clicking on the “Search” button will return a list of the data in the archive for that proposal. Select the data to retrieve by clicking on the boxes in the “Mark” column. Note: there is a “Mark All” box. Click on the “Submit” button. The Retrieval Options page will be displayed. Fill out the required information then click on the Submit button. E-mail will be sent acknowledging receipt of the retrieval request. A second e-mail will be sent when the data have been retrieved. If the data were retrieved to the staging disk, follow the directions in the e-mail to copy the data from staging. The data will remain on staging for a limited time before being automatically deleted. See Chapter 3 for more details on the MAST Kepler search forms and Chapter 5 for non-search based data retrieval.
1.10 Publication Acknowledgement
Publications based on Kepler data retrieved from MAST should carry the following acknowledgment, which is in addition to any acknowledgement required by the Kepler project.
"Some/all of the data presented in this paper were obtained from the Multimission Archive at the Space Telescope Science Institute (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NAG5-7584 and by other grants and contracts.”
See the MAST Data Use Policy http://archive.stsci.edu/data_use.html for the current MAST grant number.
This Kepler Archive Manual should be referenced as
D. Fraquelli
& S. E. Thompson, 2011, Kepler Archive Manual (KDMC-10008-001), http://archive.stsci.edu/kepler/documents.html.
Chapter 2 Kepler Data Products
2.1 Introduction
2.1.1 Overview of Data in the Archive
Kepler’s primary mission is to obtain flux time series of individual targets. As such, the majority of the Kepler science data is organized by target. Those interested in studying rapid time variable phenomenon will find the light curve files and/or the target pixel files of interest. Additionally, Kepler downloads and calibrates a single cadence of the entire Kepler field each month. These Full Frame Images (FFIs) are not target specific and can be downloaded within months of acquisition from their own search and download page at MAST.
Besides the astronomical data, Kepler archives much of the auxillary data that either directly or indirectly affects the astronomical data products. Engineering data describes the state of the instrument and the spacecraft during data collection. Focal plane characteristic models and ancillary engineering CCD data are used to calibrate and process the data. While available upon request, these data will be of less interest to the typical science user.
2.1.2 Kepler Time System
The readout time for each
recorded cadence is recorded as a Vehicle Time Code (VTC). This timestamp is
produced within 4 ms of the readout of the last pixel of the last frame of the
last time slice (see glossary). When the data is downloaded to Earth, the
Mission Operations Center converts VTC to Coordinated Universal Time (UTC),
correcting for leap seconds and any drift in the spacecraft clock, as measured
from telemetry. UTC times are converted to Barycentric Dynamical Time (TDB)
then to BJD to correct for the motion of the spacecraft around the center of
mass of the solar system.
TDB is a time system that does not include the leap seconds that bedevil
calculations of periods in the UTC system. TDB agrees with the time systems TDT
and TT to better than 2 ms at all time. See Eastman et al. (2010, PASP 122,
935) for a recent discussion of the various time systems common in astronomy.
Time stamps expressed in MJD or UTC are geocentric and not corrected to the TDB time system. Time is specified in the data files with an offset from BJD, either BJD-2400000.0 (light curve files) or BJD-2454833.0 (target pixel files). The units are clearly defined in the headers of these files. The SOC uses SPICE kernels, which are calculated from the S/C telemetry, to calculate barycentric corrections. For more information on the SPICE kernels and SPICE tools visit http://naif.jpl.nasa.gov/naif/.
The quoted times for any cadence are accurate to within ±50 ms. This requirement was developed so that knowledge of astrophysical event times is limited by the characteristics of the event, rather than the characteristics of the flight system, even for high SNR events. Users who require temporal accuracy of better than 1 minute should read the Kepler Data Characterization Handbook (Section 6) and the associated Kepler Data Release Notes carefully. These documents contain additional details regarding the times, including accuracy, corrections for readout time slice offsets, change in units, etc.
2.1.3 FITS headers
Kepler science data use the FITS (Flexible Image Transport System) format to comply with astronomical data standards. Data headers use standard FITS keywords to formulate the data definition and comply with all FITS recommended keyword usage current at the time of header design. The primary headers contain keywords inherited by all subsequent extensions. Primary header keywords specify data processing inputs, data quality, observational modes (long cadence, short cadence, FFI), target information etc. The primary header/data units (HDU) do not contain a data array. FITS headers for cadence science data are specified in Appendix A.
2.1.4 Disclaimer: File Formats will Change
Currently all data products do not conform to a uniform file format. The astronomical data products are all in FITS, while the auxillary data is available in a variety of forms. The key words and time systems are not universally consistent between all the data products. This document aims to describe the current state of the data products and not their future state.
Significant improvements will be made to the light curve, FFI and target pixel files in 2011. These improvements will provide consistency between the data products, add WCS solutions and make the information stored in the files more transparent. Data quality and processing flags will be added to enable the user to understand anomalies in the data and how the data was processed.
2.2 File Name Syntax
These
three components are concatenated as shown to form the file name. This is the name of the file on disk.
kplr<rootname>_<suffix>.<extension>
In the
archive, the data set name is the rootname.
Table 2-1 Science Data Filenames
|
Type
of Data |
Rootname* |
Suffix |
|
Calibrated
Light Curves: |
|
|
|
LC
calibrated light curves |
<kepler_id>-<stop_time>= |
llc |
|
SC
calibrated light curves |
<
kepler _id>-<stop_time>= |
slc |
|
Target
Pixel Data: |
|
|
|
LC Target
pixel data |
<
kepler _id>-<stop_time>= |
lpd-targ |
|
SC Target
pixel data |
<
kepler _id>-<stop_time>= |
spd-targ |
|
Full
Frame Image: |
|
|
|
FFI
original data |
<stop_time> |
ffi-orig |
|
FFI
calibrated data |
<stop_time> |
ffi-cal |
|
FFI Processing
history |
<stop_time> |
ffi-history |
|
FFI
uncertainty file |
<stop_time> |
ffi-uncert |
* All rootnames begin with kplr.
2.3 Data in the Archive
2.3.1 Light Curve Files
The corrected
(‘ap_corr_flux’) light-curve product generated by the PDC (Pre-search Data
Conditioning) pipeline module is designed to enable the Kepler planetary
transit search. Although significant effort has been expended to preserve the
natural variability of targets in the corrected light curves in order to enable
astrophysical exploitation of the Kepler data, it is not possible to perfectly
preserve stellar variability on long timescales with amplitudes comparable to
or smaller than the instrumental systematics. PDC currently is known to remove
or distort astrophysical features in a subset of the corrected light curves. In
those cases where PDC fails, or where the requirements of an astrophysical
investigation are in conflict with those for transit planet search, the
investigator should use the uncorrected (‘ap_raw_flux’) light-curve product,
for which basic calibration has been performed but correction for instrumental
systematics has not, instead of the PDC (‘ap_corr_flux’) light-curve product.
2.3.2 Target Pixel Data
For each target, Kepler only acquires the pixels contained within a predefined mask. These pixels are used to create the data found in the light curve files. Each target pixel file packages these pixels as a time series of images in a binary FITS table. The intent of these files is to provide the data necessary to perform photometry on the raw or calibrated data when needed (or desired) to understand (or improve) the automated results of the Kepler pipeline.
Primary Header
The primary header contains information pertaining to the entire file, such as target information and version processing information. This header contains information about which CCD was used to collect this data, which quarter the data was collected, and which Data Release notes apply to this processing of the data. The header also contains all KIC values as reference. We remind the user that the KIC is static and the values found in the FITS headers are currently not updated as better measurements are acquired. Appendix A.2a contains a description of all the keywords in this header.
Target Table Extension
The second extension contains pixel time series. It has 10 columns containing either an array of values or an array of images. The header defines these columns according to the FITS standard (see Pence et al. 2010 A&A, 524, A42). The keywords are explained in Appendix A.2b.
The image dimensions for each target varies, however all images contained in a single target pixel file will have the same dimensions. The location of the pixels on the specified CCD is provided in the header. World Coordinate System solutions will be added to these files in the near future.
The definition of each column in the target table extension is as follows:
TIME [64-bit floating point] – The time at the center of the cadence in BKJD. Kepler Barycentric Julian Day is a Julian day minus 2454833.0 (UTC=January 1, 2009 12:00:00) and corrected to be the arrival times at the barycenter of the Solar System. The pipeline uses the right ascension and declination of the object (found in the primary header), along with the location of the spacecraft at the time of the cadence to perform this calculation. This column can be converted to BJD using the following formula for each member of the series [i]:
BJD[i] = TIME[i] + BJDREFI + BJDREFF
= TIME[i] + 2454833.0,
where BJDREFI and BJEDREFF are given as keywords in the header.
TIMECORR [32-bit floating point] – The barycenter correction calculated by the pipeline plus the time slice correction. To convert the times in the first column to Julian Day use the following formula:
JD[i] = BJD[i] - TIMECORR[i] + time_slice_correction
= BJD[i] - TIMECORR[i] + (0.25 + 0.62(5- TIMSLICE))/(86400)
where TIMSLICE is given in the header.
CADENCENO [integer] – The cadence number is a unique integer that is incremented with each cadence.
RAW_CNTS [2D array of signed 32-bit integers] – One image per cadence of the raw counts measured in each pixel downloaded from Kepler. To restore the values contained in this column to those read off the photometer, subtract the “fixed offset” of 419400 or 219400, for LC or SC respectively, and add the mean black level (keyword MEANBLCK) times the number of readouts (keyword NREADOUT). Then, each count represents one Analog to Digital Unit.
FLUX [2D array of 32-bit floating point] – One image per cadence of the measured flux in each pixel after processing by the pipeline module CAL, the removal of the interpolated background, and the removal of cosmic rays. The units are electrons per second. See Quintana et al. (2010 SPIE, 7740, 77401X) on pixel level calibrations for more details on the processing. This column may be used, along with the optimal aperture, to reproduce the “ap_raw_flux” values found in the light curve file for this target. For each cadence one may sum the flux in the pixels contained in the optimal aperture to reproduce the “ap_raw_flux” value. Remember that, for now, the units of the light curve files are in electrons per cadence while the target pixel files have the units of electrons per second. To determine the number of seconds per cadence, multiply the value of the keyword INT_TIME by the value of the keyword NUM_FRM. (The value of INT_TIME is truncated for some files; the full value is 6.0198029 [s].)
FLUX_ERR [2D array of 32-bit floating point] – An image of the 1-sigma error in the measured flux as calculated by CAL in electrons per second. This error includes the error from the background subtraction. This per pixel error does not include the pixel-to-pixel correlated background errors that are included in the error columns of the light curve files.
FLUX_BKG [2D array of 32-bit floating point] – An image of the background flux subtracted from the data in electrons per second. The background flux is calculated by interpolating a 2 dimensional surface from approximately 4500 dedicated background pixels on each channel.
FLUX_BKG_ERR [2D array of 32-bit floating point] – An image of the error in the background flux. This per pixel error does not include the pixel-to-pixel correlated background errors that are included in the error columns of the light curve files.
COSMIC_RAYS [2D array of 32-bit floating point] – An image of the cosmic ray flux identified by the module PA. The units are electrons per second. For most cadences, this image will be an array of NaNs to indicate that there were no cosmic rays. The quality flag, bit 8, indicates when a cosmic ray falls in the optimal aperture.
QUALITY [32-bit integer] – Flags containing information about the quality of the data. The following table explains what activates each bit. See the Data Characteristics Handbook and Data Release notes for more details on Safe Modes, Coarse Point, Argabrightening and attitude tweaks. Unused bits are reserved for future use.
Table 2-3 – Bits for the Quality data column.
|
Bit |
Value |
Explanation |
|
1 |
1 |
Attitude Tweak |
|
2 |
2 |
Safe Mode |
|
3 |
4 |
Spacecraft is in Coarse Point |
|
4 |
8 |
Spacecraft is in Earth Point |
|
5 |
16 |
Reserved |
|
6 |
32 |
Reaction Wheel Desaturation Event |
|
7 |
64 |
Multi-Channel Argabrightening |
|
8 |
128 |
Cosmic Ray in Optimal Aperture pixel |
|
9 |
256 |
Manual Exclude. The SOC operator excluded this time period because of an anomaly. |
|
10 |
512 |
Reserved |
|
11 |
1024 |
Discontinuity identified between this cadence and the following one |
|
12 |
2048 |
Impulsive outlier removed after cotrending |
|
13 |
4096 |
Argabrightening
event on CCD mod/out detected |
Aperture Extension
2.3.3 Full Frame Image
A Full Frame Image (FFI) contains values for every pixel in each of the 84 channels. Up to three FFIs are taken each quarter and are used to confirm the proper orientation and placement of the detector on the sky and assess photometer health. FFIs are non-proprietary and calibrated FFIs are available to the public once the processing is complete, within a few months of acquisition. Both original and calibrated FFIs contain one extension per mod/out and have units of counts per cadence. A complete FFI dataset consists of 3 files, each with a filename like kplr<stop_time>_suffix. Tables 2-5 and 2-1 give details on the file names and data set.
The DMC process generates an FFI data file that contains the uncalibrated pixels (ffi-orig) and the processing log. The SOC produces the calibrated FFI image (ffi-cal) in units of electrons per cadence. FFIs include a temporary WCS solution for each channel using a linear transformation calculated from three reference stars in each mod/out. The current linear WCS solution is good to better than 2 pixels. See Appendix D.1.2 for a listing of the FFI data header.
Table 2-5 – FFI Data set and files
|
Data type |
File suffix |
Format |
|
FFI – original |
ffi-orig |
FITS image |
|
FFI – calibrated |
ffi-cal |
FITS image |
|
FFI Processing history file |
ffi-history |
FITS table (binary) |
Chapter 3 Searching the Archive for Kepler Data
Users can search for Kepler data in a multitude of ways. Common searches are based on position, time of observation, target name or kepler_id (Kepler Identifcation Number), but all catalog fields are searchable. MAST allows the upload of a file containing a list of up to 1000 kepler_id’s, coordinates and/or target names for desired searches. Cross correlation with catalogs may be allowed in the future. Please note kepler_id and target name are different identifiers. MAST makes this distinction so that users may enter, say, NGC 6791 or TrES-2, as the target name and the Resolver will return the coordinates. Existing Resolvers do not yet recognize kepler_id as a target name.
This chapter contains descriptions of the MAST Kepler Data Search and Retrieval form, the MAST Kepler Target Search form, and the Kepler Input Catalog (KIC), Characteristics Table (CT) and Kepler Target Catalog (KTC) as hosted by MAST, and the FOV table, which is MAST’s version of the KIC. The FOV table is a combination of the KIC and the CT, so it contains objects found in both catalogs. It is supplemented with additional fields of interest. Users intending to propose for Kepler time should search the FOV table for targets via the “Kepler Target Search” form. Users interested in existing data should use the “Kepler Data Search & Retrieval” form to search the archive catalog for data of interest. A search form is also provided for users who wish to search the original KIC.
3.1 The Kepler Catalogs as Presented at MAST
As of this writing, the Kepler catalogs at MAST consist of the Kepler Input Catalog (KIC), the FOV table, which is the Kepler Input Catalog modified by the Characteristics Table (CT) and supplemented by additional fields provide by MAST, and the Kepler Target Catalog (KTC) with additional fields from the archive catalog. The KIC, CT and KTC are provided by the Kepler Project. The FOV table is provided by MAST.
The Kepler Input Catalog contains information on approximately 13 million sources, most of which are visible in or nearby the Kepler FOV. Creation of the KIC is discussed in Brown et al. 2011 (arXiv:1102.0342v1). Each source has an identification number, called the kepler_id, and a position (RA and Dec). Additional fields may or may not have values for each source. Table 3-1 lists the fields in the FOV table, along with a short description of the field. The non-KIC fields in Table 3-1 are flagged as either provided by MAST or taken from the CT. See the MAST help files at http://archive.stsci.edu/search_fields.php?mission=kepler_fov for more details.
Facts about the KIC, CT and FOV table:
- The full KIC contains 13,161,029 rows (objects)
- The CT (and likewise the FOV table) contains 6,569,466 rows (about half of the KIC total)
- The number of FOV table entries considered on CCD for at least one season is 4,412,616 (about a third of the KIC total)
- The number of FOV table entries on CCD every season is 4,382,449.
The Kepler Target Catalog (KTC) contains all objects observed or scheduled for observation by Kepler. At launch, there were some 150,000 targets in the KTC. The KTC is updated on a quarterly basis and holds planned observation start and stop times for each target. The times are given in both Modified Julian Date (MJD) and standard date format (i.e., YYYY-MM-DD HH:MM:SS). Table 3-2 lists all columns of the KTC, including several from the archive catalog. For a given object, the kepler_id is the same in the KIC, the FOV table and the KTC. The one exception is for KIC targets observed with custom apertures: in this case, the kepler_id found in the KTC is not the same as the kepler_id found in the KIC. For more details on the columns see the MAST help files at http://archive.stsci.edu/search_fields.php?mission=kepler .
The Characteristics Table (CT) contains parameters indicating if a given kepler_id is observable (“on silicon” is the termed used by the Kepler Science Team) for each of the 4 seasons, as well as other characteristics. Not all sources in the KIC have values for all parameters. In fact, only about one third of the KIC entries are ever “on silicon.” Table 3-3 lists the CT parameters. MAST does not provide a direct search capability for the CT. Instead, the CT fields have been included in the FOV table, which contains only those objects that have entries in both the KIC and CT. The Kepler Target Search form is used to search the FOV table. Information about the CT parameters is given in the MAST help files, http://archive.stsci.edu/kepler/kepler_fov/help/search_help.html.
The Kepler Results Catalog (KRC) will be hosted at MAST, although no version or description of it is yet available. The KRC contains results obtained for the mission targets. The final KRC will not be received until at least 1 year after mission end. The format of the KRC has not yet been defined.
Table 3-1 Fields in the FOV Table as Displayed by MAST
|
Field name |
Description |
|
kepler_id |
Kepler identification number |
|
2mass_id* |
2MASS catalog ID, a sexagesimal, equatorial position-based source name in the form: hhmmssss+ddmmsss[ABC...] |
|
tmid% |
KIC provided 2 MASS designation, which is a unique identification number defined during 2MASS final processing, and known as the pts_kpy/cntr. See the User's Guide to the 2Mass All Sky Data Release, at http://www.ipac.caltech.edu/2mass/releases/allsky/doc/explsup.html for information on the pts_key/cntr field. |
|
ra* |
Right ascension of object in hours |
|
dec |
Declination of object in decimal degrees |
|
pmra |
Proper Motion in right ascension |
|
pmdec |
Proper Motion in declination |
|
umag |
U magnitude |
|
gmag |
G magnitude |
|
rmag |
R magnitude |
|
imag |
I magnitude |
|
zmag |
Z magnitude |
|
gredmag |
GRed magnitude |
|
d51mag |
D51 magnitude |
|
Jmag |
2MASS J magnitude |
|
Hmag |
2MASS H magnitude |
|
Kmag |
2MASS K magnitude |
|
kepmag |
Kepler magnitude |
|
scpid |
ID from the SCPKEY table |
|
altid |
ID from an alternate source |
|
altsource |
Source of alternate ID |
|
Star/gal ID |
Star/galaxy indicator. |
|
blend |
Is object a blend |
|
variable |
Is object variable |
|
Data Availability flag |
2= data in archive, 1 = planned to be observed or observed with no data in archive, 0 = not observed or planned to be observed |
|
teff |
Derived effective temperature |
|
logg |
Derived surface gravity |
|
metallicity |
Derived metallicity (Fe/H) |
|
E(B-V) |
Derived excess reddening E(B-V) |
|
A_v |
Derived extinction Av |
|
radius |
Estimate stellar radius |
|
cq |
Source of Kepler-band magnitude |
|
pq |
Photometry quality indicator |
|
aq |
Astrophysics quality indicator |
|
Catalog key |
Link to CATKEY table |
|
SCP key |
Link SCPKEY table |
|
parallax |
Parallax in arcseconds |
|
Gal Lon |
Galactic longitude |
|
Gal Lat |
Galactic latitude |
|
pmtotal |
Proper motion in arcsec/year |
|
g-r color |
(G-R) color |
|
J-K color |
(J-K) color |
|
g-K color |
(G-K) color |
|
degree_ra |
Right Ascension in decimal degrees |
|
+sky_group_id |
The channel where the target falls in season 2. Values will range from 1 to 84. |
|
+crowding |
The fraction of light in the aperture due to the target star. 1 means all the light is from the target, 0 implies all background. 0.5 means half the light is due to the target. This value is not intended for use in data analysis. |
|
Seasons_on_CCD |
Number of seasons a target is on the detector |
|
Contamination* |
Measure of light contamination defined as 1-crowding. 0 implies no contamination, 1 implies all background. This value is not intended for use in data analysis. |
|
Edge_Distance_0* |
The shortest distance to the detector edge for season 0 in pixels. |
|
Edge_Distance_1* |
The shortest distance to the detector edge for season 1 in pixels. |
|
Edge_Distance_2* |
The shortest distance to the detector edge for season 2 in pixels. |
|
Edge_Distance_3* |
The shortest distance to the detector edge for season 3 in pixels. |
|
+Channel_season_0 |
Integer channel number for season 0. |
|
+Channel_season_1 |
Integer channel number for season 1. |
|
+Channel_season_2 |
Integer channel number for season 2. |
|
+Channel_season_3 |
Integer channel number for season 3. |
|
+Column_season_0 |
Column number for season 0. |
|
+Column_season_1 |
Column number for season 1. |
|
+Column_season_2 |
Column number for season 2. |
|
+Column_season_3 |
Column number for season 3. |
|
+Module_season_0 |
Integer module number for season 0. |
|
+Module_season_1 |
Integer module number for season 1. |
|
+Module_season_2 |
Integer module number for season 2. |
|
+Module_season_3 |
Integer module number for season 3. |
|
+Output_season_0 |
Integer output number per module for season 0. |
|
+Output_season_1 |
Integer output number per module for season 1. |
|
+Output_season_2 |
Integer output number per module for season 2. |
|
+Output_season_3 |
Integer output number per module for season 3. |
|
+Row_season_0 |
Row number for season 0. |
|
+Row_season_1 |
Row number for season 1. |
|
+Row_season_2 |
Row number for season 2. |
|
+Row_season_3 |
Row number for season 3. |
* Field added/modified by MAST.
% 2MASS id provided in the KIC
+ Field taken from the Characteristics Table.
|
Column |
Description |
|
Kepler Id |
Running Kepler ID number |
|
Investigation_id |
Investigation ID assigned by Project |
|
+Pep_id |
Unique integer value assigned by DMC |
|
+Dataset Name |
Dataset name for the exposure |
|
+Quarter |
The quarter in which the exposure was made. |
|
*RA(J2000) |
RA in decimal degrees |
|
+Dec(J2000) |
Dec in decimal degrees |
|
Target Type |
Cadence – LC or SC |
|
Actual Observation Start Time |
Actual start time |
|
Actual Observation End Time |
Actual end time |
|
+Release Date |
Date when data become public. |
|
+Generation_date |
Date file was ingested into archive |
|
+data_rel |
Release Notes |
Table 3-2 Fields in the Kepler Target Catalog (KTC) as Displayed by
MAST
+ Field taken from data in the Kepler archive
* Field added by MAST
Table 3-3 Parameters in the Characteristics Table (CT) at MAST
|
Column |
Description |
Values |
|
Kepler ID |
The kepler id |
integer |
|
Channel season 0 |
Integer channel number for season 0. |
1-84 |
|
Channel season 1 |
Integer channel number for season 1. |
1-84 |
|
Channel season 2 |
Integer channel number for season 2. |
1-84 |
|
Channel season 3 |
Integer channel number for season 3. |
1-84 |
|
Column season 0 |
Column number for season 0. |
20 to1043 |
|
Column season 1 |
Column number for season 1. |
-201 to 1111 |
|
Column season 2 |
Column number for season 2. |
-225 to 1094 |
|
Column season 3 |
Column number for season 3. |
-225 to 1094 |
|
Module season 0 |
Integer module number for season 0. |
2-24 |
|
Module season 1 |
Integer module number for season 1. |
2-24 |
|
Module season 2 |
Integer module number for season 2. |
2-24 |
|
Module season 3 |
Integer module number for season 3. |
2-24 |
|
Output season 0 |
Integer output number per module for season 0. |
1-4 |
|
Output season 1 |
Integer output number per module for season 1. |
1-4 |
|
Output season 2 |
Integer output number per module for season 2. |
1-4 |
|
Output season 3 |
Integer output number per module for season 3. |
1-4 |
|
Row season 0 |
Row number for season 0. |
-225 to 1094 |
|
Row season 1 |
Row number for season 1. |
-225 to 1094 |
|
Row season 2 |
Row number for season 2. |
-225 to 1094 |
|
Row season 3 |
Row number for season 3. |
-225 to 1094 |
|
Skygroup ID |
The module/output where the target falls. Values will range from 1 to 84. |
1-84 |
|
Crowding Value |
The fraction of light in the aperture due to the target star. 1 means all the light is from the target, 0 implies all background. 0.5 means half the light is due to the target. |
0 - 1 |
|
Availability flag |
2= data in archive, 1 = planned to be observed or observed with no data in archive, 0 = not observed or planned to be observed |
0,1,2 |
3.2 The MAST Search Forms
MAST provides separate forms for searching for targets to observe (ie, exploring the FOV table) and for locating Kepler data in the archive. Each form serves a different purpose. Searches of the FOV table are done in support of proposal preparation. Called Kepler Target Searches or Kepler FOV searches, these searches of the FOV table are via MAST’s Kepler Target Search form, and are used to find targets to observe with Kepler or to find astronomical information about the targets. Searches of the archive for existing data are called Kepler Data Searches, are done using MAST’s Kepler Data Search and Retrieval form and are based on the archive catalog and the KTC. These searches are done to locate and retrieve data from the archive. The forms function in the same manner, but the search fields are different because the underlying catalogs and database contain different information. The kepler_id is the same in both forms.
Additional MAST forms exist. These include an FFI search, http://archive.stsci.edu/kepler/ffi/search.php and the previously mentioned KIC search, http://archive.stsci.edu/kepler/kic10/search.php . Check the “Search & Retrieval” menu on MAST’s Kepler home page, http://archive.stsci.edu/kepler/ , for a current list of search and download options.
MAST provides standard forms, that is, forms that look and operate the same from mission to mission. On the "standard form", the top section consists of a place to enter a target name or coordinates and a Resolver. If a
target name is entered, the coordinates will be resolved using SIMBAD or NED and these coordinates will be used in the search. The user can also choose the search radius (the default is 0.02 arcmin). Note the Resolver uses a standard MAST hierarchy, whose order is NED, SIMBAD, etc. The user can select a Resolver from the pull down menu. One of the options is ‘Don’t Resolve.’
Note the "file upload form" link near the top right of the form. Clicking on the link brings up a version of the standard form that allows the upload of a user created file. The file must be an ASCII text file or table with one entry per line with one or more fields (e.g. RA and Dec) separated with one of the allowed delimiters. Searches are allowed on coordinates, target name or kepler_id. Other fields are allowed in the file, but are not searchable. Up to 5000 lines are allowed. Several coordinate formats and delimiters are allowed. Check the on-line help for information. The name of the file is the name the file has on the user’s disk. A browse button is provided.
The middle section of the search page contains mission specific fields, which can be used to qualify the search. For Kepler, four user-specified fields are provided. The menu (down arrow) next to each of these fields contains a complete list of the table columns. Select the desired field to add it to the search form. For more information about each field click on the link "Field Descriptions". This brings up a page of all the available columns, in tabular form. The table lists the database column name, the label, a description, an example or range of valid values in that field, and the data type.
The
third section provides output options for the search results. On the left side is a list of columns that is
displayed by default. Columns can be
removed by highlighting that column and clicking on the “remove” button to the
right. Columns are added by choosing columns from the “select” box and clicking
the “add” button to the left of the “select” box. Change the order by clicking on field in the
output columns box and click on the “up” or “down” buttons to the right.
Clicking on the “reset” button will restore the default output columns
settings. The output can be sorted by up
to three columns. Note the following
behavior when a sort option is used. If
the upload contains more than 200 entries, the order of entries from the
uploaded file is maintained. If
the upload file contains less than 200 entries, the order in the uploaded file
is not preserved. A ‘null’ option
is available if no sorting is desired.
When the no sort option is specified, the results are returned in the
order in which they are stored in the database and for Kepler, this means in
order of kepler_id.
The output format can be specified using the “Output Format” menu in the lower right of the form. Formats include HTML, comma separated value text, Excel spread sheet, and VO table format. The HTML format will give access to useful links and retrieval options. Since the astrophysical fields in the KIC are not populated for every object, searches that direct the results to an output file should use the Excel Spreadsheet output, or one of the CSV outputs that use a character (i.e., comma or semi-colon) as the delimiter. Use of a space delimited CSV format can result in non-interpretable results.
Output coordinates are displayed in sexagesimal by default, but decimal degrees or decimal hours can be specified. Click on the headings for additional help.
3.2.1
Kepler Target Searches (e.g. objects to observe)
Figure 3.1 shows the Kepler Target Search form located at http://archive.stsci.edu/kepler/kepler_fov/search.php
The form allows searches based on kepler_id, position, target name and/or physical characteristics, where the available physical characteristics provided in the FOV table are taken from the KIC. Note: since there are ~7 million objects in the catalog searched by this form, it is not a good idea to submit an unqualified search. Indeed, such a search is likely to time out, with no results returned.
There are 3 fields on or available through the Kepler Target Search form, which are not listed in Table 3-1 or Table 3-3, above. These fields are calculated from KIC or CT fields that are given above.
Min. Distance from Edge: The user may enter a value in pixels. The output value is calculated from the row and column values for each season and restricts the search to targets at least this number of pixels from the detector edge.
Seasons Target on CCD: The user may enter a given season, all or accept the default of any to define when or how often a target is on silicon. The returned values for this field are determined from the various channel, output, module, row and column fields in the CT. The planned start date for each season is given in Table 3-4. The seasons are numbered from 0 to 3, with 0 corresponding to Summer.
Table 3-4 Planned
Start Date for Seasons
|
Year |
Spring |
Summer |
Fall |
Winter |
|
Quarters |
1,5,9,13 |
2,6,10,14 |
3,7,11,15 |
4,8,12 |
|
Season |
3 |
0 |
1 |
2 |
|
2009 |
May 13 |
Jun 18 |
Sep 17 |
Dec 17 |
|
2010 |
Mar 19 |
Jun 23 |
Sep 23 |
Dec 22 |
|
2011 |
Mar 24 |
Jun 27 |
Sep 29 |
Dec 29 |
|
2012 |
Mar 29 |
Jun 28 |
Oct 1 |
|
Contamination: 1 – Crowding, where the Crowding value is taken from the CT. Contamination is a floating-point number between 0 and 1 representing the fraction of light in the aperture due to the target star. A value of 0 means all the light is from the target, 1 implies all background. 0.5 means half the light is due to the target. The user may enter a value for contamination or leave it unspecified. Contamination may be added via one of the user-specified field elements.
The contamination value is NOT to be used to correct Kepler flux light curves. The values currently at MAST are intended only to facilitate the selection of isolated stars as targets. The contamination parameter for an aperture is defined as the ratio of the flux due to the target and the flux from all sources in that aperture. The contamination parameter currently on MAST is for a 21 x 21 pixel (83.6" x 83.6") square aperture centered on the target. This large aperture is not the same as the photometric aperture used to create the Kepler flux light curves. The photometric aperture is usually (but not always) much smaller.
The contamination value
relevant to a specific flux light curve can be substantially different from the
predictive value provided at MAST. It varies from season to season because of
changes in photometric aperture size, the pixel response function, optical throughput,
and other position-dependent characteristics of the focal plane. The aperture
for Kepler photometry is approximately defined before data collection, but is
not finalized until post-processing is complete. The contamination values at
MAST will be updated to provide a better metric for selecting isolated targets,
but they should never be used for correction and analysis of Kepler flux light
curves.
The Kepler Project will
make crowding and contamination values appropriate for the photometric apertures
available to users by 2012, both on MAST and in the FITS file headers. If
contamination values for Kepler targets are needed sooner, please send requests
to kepler-scienceoffice@lists.nasa.gov.
Also, the crowding
metric used by the SOC pipeline to produce the PDC light curves can be
determined by dividing the median of the PDC light curve by the median of the
PA light curve (median (ap_corr_flux)/median(ap_raw_flux)).
Example Target Searches
See Figure 3-1 as an example of how to use the MAST Target Search Form. The Contamination, Teff and Log G fields have values entered to qualify the search. Note the use of carets, < and >, to provide starting or ending values. Also note the input in the “Log_G” field, 3.0..3.5, which specifies a range of values starting with 3.0 and ending with 3.5. A User-specified field, “R_Mag”, was used to qualify the R magnitude of the search. Finally, in the “Output Columns” box, a number of fields were removed to make the results more readable. This search was executed and the results are shown in Figure 3-2. More information on general usage of MAST search forms is provided in the on-line MAST tutorial, which is accessible via the (Help) link in the top right corner of form.
Figure 3‑1 MAST Kepler Target Search Form
Figure 3‑2 Results of Target Search
The results in Figure 3-2 are in the default HTML form. Clicking on the column name at the top of a column will sort the input by that column. A second click will order the sort in the opposite direction. A click on the column name link at the bottom of the results will bring up a page that describes the column.
Other output formats are available and can be specified on the Search Form, see Figure 3-1, in the lower right. Consult the on-line tutorial for additional details.
Example Target Searches: Use Case 1
Upload a target list, e.g. of coordinate values. Return all objects within the default search radius having contaminations of less than 0.15. Include the 2MASS_ID in the output.
Start by creating a file that contains a table or list of coordinate values. The file must be an ASCII text file with either one entry per line (i.e., a target name, a Data ID, or a set of coordinates) or a table, with the values separated by one of the allowed delimiters (tab, comma, vertical bar or semicolon). Additional information may be available in the file/table. Only one entry per line is extracted. The file is created on the user’s disk. Below is the file that was input in this example.
3830833, 18 58 29.93, +38 56 54.1
8547781, 19 05 40.22, +44 37 26.4
5127321, 19 54 09.98, +40 13 40.4
8540791, 18 50 24.70, +44 38 39.9
12207020, 19 21 59.33, +50 49 27.1
8581320, 19 54 22.80, +44 40 20.4
9667235, 19 52 56.74, +46 21 01.0
To upload the file, go the Kepler Target Search form, http://archive.stsci.edu/kepler/kepler_fov/search.php , and click on the “file upload form” link in the upper right corner of the form. This will bring up a similar looking MAST search form. Note the “Local File Name (required)” form element on the left hand side. Click on the “Browse” button next to the field to locate the file on the user’s disk. Select the appropriate file from the user’s computer and click open. Enter the location and name of the file in the form element. Next, indicate the delimiter used in the file or table. In this case, comma (,) is the delimiter. Next, indicate which column holds the RA values, in this case column 2, and which column holds the DEC values, in this case, column 3. To add a contamination qualifier, the field needs to be added to the form. Go to “User-specified field 1” and click on the down arrow. A list of fields to add will be displayed. Scroll down to Contamination and click on it. Enter the qualifier, <0.15, in the box labeled “Field Descriptions.” Adjust the output columns and select the output format. In this example, the output columns will be Kepler ID, 2Mass ID, RA, Dec and contamination, and the results will be displayed to the screen as comma-separated values. (The contamination field was added to the output columns via the “add” box below the Output Column form element.) Figure 3.3 shows the Kepler Target Search form with the above information specified. Click the “Search” button to begin the search.
The results, as displayed to the screen, are shown below Figure 3.3. Note the 5th object in the input file did not return a result, because the contamination value was larger than the specified limit. 
Figure 3-3 Use Case 1 Target Search Form Setup |
Kepler_ID,2MASS ID,RA (J2000),Dec (J2000),Contamination integer,string,ra,dec,float 3830833,18582992+3856541,18 58 29.93,+38 56 54.1,0.008 5127321,19540999+4013403,19 54 09.98,+40 13 40.4,0.080 8540791,18502471+4438399,18 50 24.70,+44 38 39.9,0.011 12207020,19215932+5049271,19 21 59.33,+50 49 27.1,0.009 no rows found 9667235,19525673+4621009,19 52 56.74,+46 21 01.0,0.044 9667235,19525673+4621009,19 52 56.74,+46 21 01.0,0.044 |
Table
3-5 Results for Use Case 1
Example Target Searches: Use Case 2
Return a list of all cool white dwarfs with large proper motions in the Kepler field of view: Teff < 7000K, log g >=5.0, and mu >0.5 arcsec/year.
The original use case specified a proper motion of greater than 1 arcsec/year. However, there are no objects in the KIC that meet the temperature and gravity criteria that also have a listed proper motion of more than 1 arcsec/year. Before proceeding with the modified use case, the reader should note there are many thousands of objects in the KIC for which no temperature, surface gravity or proper motion information is provided. The situation for the FOV table is similar, but for fewer objects. Also, users of the KIC should become familiar with the accuracy and limitations of the values reported in this catalog (see http://www.cfa.harvard.edu/kepler/kic/kicindex.html) before searching for specific types of objects.
For the modified use case, the temperature and surface gravity criteria are entered on the search form. The total proper motion field is added as a “User-specified field” and added to the “Output Columns” menu. Most of the default columns have been removed from the “Output Columns” menu, and the order of the remaining values has been changed. The “Sort By” fields have been set to have the primary sort be done on the total proper motion, with the higher values displayed first. The secondary sort is on temperature and the tertiary search is on surface gravity. The “Output Format” is an HTML table. Finally, to allow the search to run more quickly, the “Seasons Target on CCDs” has been set to “unspecified”. This field may be added to the “Output Columns” if the information is needed. Click on “Search.”
Figure 3-4 Search Form for Use Case 2
Figure 3-5 Search Results for Use Case 2
Example Target Searches: Use Case 3
Return the E(B-V)'s of all the KIC objects, whether they fall on the Kepler detectors or not.
This use case cries out for CASJobs (see Section 3.2.4) because of the number of records that will be returned. However, the CASJobs interface for Kepler is not yet available. Using the standard MAST/Kepler search form, while possible, will drive your graduate student insane. There are some 7 million records in the FOV table, more than 13 million in the KIC, and the maximum number of results returned per search is 15001. This means some 438 searches, or more, would be required to cover the full Kepler FOV. MAST allows access to the catalog via scripts and http get requests. On-line help is available through the MAST services link on the MAST/Kepler home page. Taking advantage of the module/output structure of the Kepler detectors, http get requests may be issued for each mod/out. Below is an example of such a request. It is set up for mod/out 2.1, qualifies the “seasons target on CCD” as “unspecified,” and requests the kepler_id and E(B_V) values be returned in a comma separated variable (CSV) format. Using this get request reduces the number of searches to 84, one for each mod/out. http://archive.stsci.edu/kepler/kepler_fov/search.php?kct_module_season_0_value=2&kct_output_season_0_value=1&seasons=unspecified&max_records=400000&selectedColumnsCsv=kic_kepler_id,kic_ebminusv&outputformat=CSV&action=Search
A partial list of the output is listed here. The number of returned records for this get request is 101876 Kepler_ID,E(B-V)
integer,float
1862390,
1862391,
1862398,
1862400,
1862405,
1862421,
1862425,
1862437,
1862445,
1862446,
1862456,
1862458,
1862461,
1862462,
1862465,
1862467,
1862471,
1862472,
1862473,0.230
1862474,
1862475,
1862476,
1862479,
1862482,
1862485,
1862489,0.156
As can be seen, a significant number of the KIC entries do not have E(B-V) values. Perhaps a better search would be “give me the E(B-V)'s, where they exist, of all the KIC objects, whether they fall on the Kepler detectors or not.” A check of the column help shows the range of E(B-V) in the KIC is 0.001 to 0.521. This allows us to add a simple qualifier to the get request: E(B-V) > 0, which is written as =%3E0.0 in the get request, below. The “%3E” is used for the > in the get request. Note the = sign must also be included in the qualifier. If it is not included, no qualification will be done on the E(B-V) value. A partial list of the output for the modified get request is listed below. The Ra, Dec and 2MASS id have been added to the output columns.
http://archive.stsci.edu/kepler/kepler_fov/search.php?kct_module_season_0_value=2&kct_output_season_0_value=1&seasons=unspecified&kic_ebminusv=%3E0.0&max_records=400000&selectedColumnsCsv=kic_kepler_id,kic_ebminusv,kic_degree_ra,kic_dec,kic_2mass_id&outputformat=CSV&action=Search
Kepler_ID,E(B-V),RA (J2000),Dec (J2000),2MASS ID
integer,float,ra,dec,string
1862473,0.230,19 20 10.42,+37 22 28.2,19201041+3722282
1862489,0.156,19 20 11.50,+37 23 49.8,19201150+3723498
1862518,0.130,19 20 13.05,+37 22 27.1,19201304+3722270
1862519,0.168,19 20 13.06,+37 23 34.2,19201305+3723342
If the user truly wants to search the KIC, he will have to use the CasJobs interface when it becomes available. This is because the mod/out values are not in the KIC, so the work around we used with the get request search of the FOV table will not work for the KIC.
3.2.2 Kepler Data Searches
Users wishing to search for and/or retrieve Kepler data should use the Data Search and Retrieval Form, which is available at http://archive.stsci.edu/kepler/data_search/search.php . The features of this form are similar to those of the Target Search Form and function in the same way. On-line help is available. The search for data is a search using information from the archive tables, the FOV table and the KTC.
Figure 3-6 shows the Data Search and Retrieval Form set up for a very simple search, with only the Kepler ID as a qualifier. The results of this search are shown in Figure 3-7.
In the Search Results Form, note the “Mark” column, which is used to indicate the data to retrieve. When it is highlighted in yellow, the data are proprietary. Proprietary data may only be retrieved by the PI of the proposal for which the data were taken, and any authorized co-Is. The release date column, at the far right, shows when these data become public. To send a retrieval request for these data, click the “Mark” boxes or click on “Mark all”, as shown in Figure 3-8, then click on “Submit marked data for retrieval from STDAS.” This will open up the Retrieval Options page, as shown in Figure 3-9.
The Retrieval Options Form is used for retrieval of public and proprietary data, and for anonymous retrievals of public data. For proprietary data, the user must enter their archive account username and password. For public or non-proprietary data, an archive account or anonymous retrieval is available. Enter anonymous for the “Archive Username” and your e-mail for the “Archive Password”. For all requests, even anonymous, a valid e-mail account is necessary in order for the archive to send status information regarding the retrieval request.
Under Delivery Options, indicate how the data should be delivered. If requesting “FTP” delivery, fill out the boxes on the right side of the page, giving the name of the receiving computer, the location for the data, and a valid account name and password. Click on “Send retrieval request to ST-DADS.” The page shown in Figure 3-10 is displayed.
Some error checking is done for data that are to be ftp’ed, to ensure access to the computer and location for the data. A confirming e-mail is sent if the checks pass. If there is a problem, an e-mail reporting the problem is sent to the user.
If the “Stage” option is selected, the retrieved data are written to an Archive staging disk. The user is responsible for ftp’ing the data from the staging disk. After clicking on “Submit”, the page shown in Figure 3-10 is displayed.
For all retrievals, e-mail is sent confirming the retrieval request was received, where the data will be placed and what datasets will be retrieved. After the retrieval is complete, a second e-mail is sent listing the files that were delivered. If the “Stage” option was used, the location of the data is sent.
Standard ftp is used to retrieve data from the staging disk. Users are advised to issue bin (for binary) and, if using mget, prompt (to turn off prompting). Attempting to ftp the data from the staging disk before the retrieval is complete will result in incomplete datasets. The ftp should not be started until after the completion e-mail has been received.
Figure 3‑6 The MAST
Data Search and Retrieval Form
Figure 3‑7 Data Search
Results
Figure 3-8 Marked Datasets
for Retrieval
Figure 3-9 Retrieval Options Page
Figure 3‑10 Confirmation Page
Example Data Searches
All searches for Kepler data are, by definition, searches of the FOV table and will use the MAST Data Search & Retrieval form, http://archive.stsci.edu/kepler/data_search/search.php . The ultimate purpose of a data search is retrieval of data from the archive. Check the fields listed in the “Output Columns” box. Also check the format in the “Output Format” box. By default, search results are given as a html table.
Example Data Searches: Use Case 1
I’m a Kepler GO and I want to download my data.
This is a simple procedure. Starting at the main MAST web site, http://archive.stsci.edu/ , under “Mission Search” in the bar across the upper portion on the page, select “Kepler Data.” This will take you to the Kepler Data Search & Retrieval form, http://archive.stsci.edu/kepler/data_search/search.php.
Put the investigation id for your GO proposal in the box labeled “Investigation_ID.” You should include a wild card on both ends of the investigation id, in case one or more of your targets are shared with another investigation. For example, enter %GO20025% instead of GO20025. Figure 3-11 shows the Data Search & Retrieval, qualified as stated and Figure 3-12 shows the results page. Follow the instructions in section 3.2.2 to retrieve the data.
Example Data Searches: Use Case 2
I want to know if there are Kepler data in the archive for cool giant stars.
Set up the Data Search & Retrieval form by putting the temperature and log g ranges in the “Temperature” and “Log G” boxes. Adjust the “Output Columns” and check the “Output Format.” Click “Search” to initiate the search. See Figure 3-13 for the qualified form and Figure 3-14 for the search results. There are proprietary data included in the search results. Unless you are authorized to retrieve these data, any request for them will be denied. To eliminate proprietary date from the results, return to the Data Search & Retrieval page and add a qualification in the “Release Date” box. An example entry is “< 2010-Dec-03.” Fewer results are returned, but all are public and may be retrieved.
Figure 3-11 Use case 1 qualified
search form
Figure 3-12 Use case 1
search results
Figure 3-13 Use case 2
qualified search form
Figure 3-14 Partial list of
search results for use case 2
3.2.3 FFI Search and Retrieval or Download
Kepler Full Frame Image (FFI) data are public. To search for a particular FFI, use the MAST/Kepler FFI Search page at http://archive.stsci.edu/kepler/ffi/search.php. The amount of metadata for FFIs is limited, with “start time”, “end time” and “quarter” being the main fields. Note that “quarter” was not available for FFIs prior to quarter 6. This will change when the FFIs are reprocessed. An example of the FFI Search form is given below in Figure 3-15.
To simply download the existing FFIs, go the http://archive.stsci.edu/pub/kepler/ffi/, either directly or from the MAST/Kepler home page. Click on the filename to download the file.
To display FFIs, without downloading them, go to the FFI display tool, either from the MAST/Kepler home page or directly at http://archive.stsci.edu/kepler/ffi_display.php. The opening page of this tool is shown in Figure 3-16, below.
Figure 3-16 Standard FFI
Search interface
Figure 3-16 MAST’s FFI Display Tool Opening Page
3.2.4 The
Kepler-GALEX Crossmatch
The Kepler-GALEX
cross match (KGxmatch) was created to mitigate the problem of selecting blue
objects from the KIC/FOV tables by providing GALEX magnitudes as a substitute
for u-band photometry, a value that does not exist in the KIC. Although GALEX observations do not cover the
entire Kepler field of view, there is sufficient coverage to warrant performing
a cross match.
MAST cross
matched the GALEX Release #6 “mcat” catalog, with the FOV table version of the
KIC. Our positional results are
contained in two Kepler/Cross matched tables described below.
No
extensive list of cross matched objects observed
by two missions is likely to be perfect. Our tables use as the criterion for matching the angular separation between
positions of objects in the KIC and GALEX catalogs, and this criterion alone is
not always sufficient. For example, the best apparent match to a KIC entry may
be a GALEX catalog entry for which the closest match is some other KIC entry.
To accommodate such ambiguities, MAST has generated two catalogs: a Complete
(alternatively, “KGMatch”) and an Accurate (“GoldStandard”) table.
The Complete
table gives all possible GALEX matches to each KIC entry within a search radius
of 5". This table in general gives multiple matches (and reverse matches),
ranked by increasing separation. The Complete table returns possible GALEX
matches of Kepler entries out to 5”, and vice versa; all potential matches are
ranked by distance from the Kepler entries.
The Accurate
table gives all unique matches for search radii out to 2.5", both in the
KIC-to-GALEX and GALEX-to-KIC match directions. Although this table is incomplete
- because it misses those rare correct matches to GALEX entries with
coordinates just beyond the 2.5” search radius - the matchings are unambiguous.
Note that while this table is designated “Accurate”, it can occasionally
generate a false match if the correct match is to a Kepler entry that has a
GALEX entry (and vice versa) that does not have the very closest coordinates.
Such errors are common in crowded fields and for data collated from different
bandpasses and at the edge of detectors where field distortions are greatest.
Note
also that both tables are subject to the greatest errors for GALEX AIS (all
sky) survey tiles, for which the exposures are short. There are 81 GALEX sky
tiles (each a circle of radius ~0.6o) that overlap the Kepler FOV, of which 79 were observed in both FUV and NUV bands.
The user can expect that most GALEX objects will have both magnitudes
represented. Users should note that the number of matched objects is limited by
both the incomplete GALEX areal coverage and the brighter faint magnitude limit
relative to the KIC’s.
Kepler-GALEX
Crossmatch interface form
MAST
provides two interfaces to the KGxmatch results. The tables may also be downloaded by ftp from
the gutter of the MAST/Kepler homepage.
One
interface is a standard MAST web form that allows search of either the complete
or the accurate table, accessible at http://archive.stsci.edu/kepler/kgmatch/search.php.
An example of this form is given in Figure 3-17. A portion of the results from the indicated
search is shown in Figure 3-18. This
interface will be familiar to most MAST users, and with the aid of a field
description page, usage should be almost self-explanatory. The table allows
uploading of target coordinates, and requires
checking of either the Complete or Accurate table box. The default is Accurate.
This form
is recommended for relatively simple queries that do not require more filter
conditions than those fields exhibited on the form. The returned fields include
fluxes and colors from GALEX, SCP-Sloan, and 2MASS missions. The output is
available in several formats.
Figure 3-17 Standard MAST interface for the
kepler-GALEX cross match tables
Figure 3-18 The Kepler/GALEX Crossmatch interface form and a results
page. This example shows a
request for all Kepler/GALEX
matches within a rectangular sky region from the “Accurate” table part of the
results listing.
The
CasJobs implementation
MAST
has adapted the “CasJobs” tool constructed at Johns Hopkins University and put
it into use for serving long and complicated requests to GALEX tables in the
archive and now for the Kepler-GALEX crossmatch tables. Use of this tool,
accessible at http://mastweb.stsci.edu/kplrcasjobs/,
requires a one-time registration unless users have registered for the
MAST/CasJobs tool already, e.g. for bulk queries of GALEX data.
Use of
the Casjobs form is recommended for users who wish to build their own more
complicated queries using SQL and/or who want to leave their results for future
work, e.g. for further cross-correlations with other catalogs or to
collaborators. Because many users may
not be familiar with SQL, this tool includes its own general help page, GO help
page, and SQL tutorial. It is necessary to read the help pages to avoid common
pitfalls, e.g. forgetting to change the ‘context’ tab (which points to a
database table) from kepler to the user’s own database
area (“MyDB”). Figure 3-19 exhibits the “Query” page of the
CasJobs/Kepler.
Because
many users may not be experienced in SQL, a few SQL sample queries are shown in
the indicated tab. The user can customize these examples to return more refined
lists. Use of this query requires consultation of the column names of interest.
These can be found in the kepler context tab and in the “Column Descriptions”
Quick Link at the top of the GOHelp page.
Figure 3-19 The
Kepler/GALEX CasJob form. This page can be used to
formulate sophisticated queries
to constrain a class objects. This example
shows a comment-annotated query for selection of matching
objects around a designated area in the sky
from the Complete table.
3.2.5 Alternate Methods for Downloading Data
As there are archive users who do not wish to search for Kepler data, but rather simply download, say, all the public data, or their GO data, MAST provides some alternative means for downloading data. See the “Search & Retrieval” menu item in the left hand gutter of the MAST Kepler home page for a complete list of search and retrieval options.
Public Data Download
Files tarred by quarter:
Kepler's public data have been staged in a directory area that is available through anonymous ftp or through a browser. For each quarter, the public files are tarred, by type, into one of three tarfiles. Within a quarter, data may be public for one of the following reasons.
- Dropped Target data
- Published Target data
- Other public data (e.g., the proprietary period has expired)
These
data are found at http://archive.stsci.edu/pub/kepler/lightcurves/tarfiles/
and are also available via anonymous ftp from archive.stsci.edu in directory cd
/pub/kepler/lightcurves/tarfiles.
A
set of wget scripts is also provided that, when executed, will download the
public light curves. These scripts are located in the same directory as the
tarfiles, http://archive.stsci.edu/pub/kepler/lightcurves/tarfiles/.
Consult the README file in their directory for details of the scripts.
Individual Public Light Curve Files
All public data are also online as
individual files. To see the directory through a browser go to http://archive.stsci.edu/pub/kepler/lightcurves/.
Note
the data have been grouped by the first four digits of the Kepler ID, e.g.
0007, 0008....0129. Under each of these directories, there is a directory for
each public Kepler ID, where all public Kepler lightcurves will be stored.
For
instance, as of July 26, 2010, there are two datasets to be found in the
directory: http://archive.stsci.edu/pub/kepler/lightcurves/0104/010480861/,
each corresponding to a different quarter.
The
path to these data via anonymous ftp is the same as for the public tar files:
ftp
archive.stsci.edu
login as anonymous
cd /pub/kepler/lightcurves
Proprietary Data Download
As with the public data, MAST provides an ftp download option for proprietary data. In this case, data are collected by investigation id and access control is applied to the directories. Only users who are authorized to access the data for a given investigation can download data from these directories. See section 1.7 for information on registering to receive your proprietary data.
To access the data:
ftp archive.stsci.edu
login with archive username and password
ftp> cd /pub/kepler/tarfiles
