Transcript ppt - GLAST at SLAC

GSSC Data Servers for DC2
Tom Stephens
GSSC Database Programmer
June 27-29, 2005 - DC2 Software Workshop - 1
Data To Be Served
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LAT Photon Data (FT1)
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LAT Pointing, Livetime and Mode History Data (FT2)
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Gamma-ray Burst Data
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LAT Source Catalog
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Pulsar Ephemeredes (D4)
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Calibration Database (CALDB)
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LAT Event Data (FT0) – maybe
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Data Access
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Data access to the scientific data will be provided via the
GSSC’s website at
http://glast.gsfc.nasa.gov/ssc/data/access/DC2
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Web page will provide
– Link to download Source Catalog
– Link to Burst Data website
– Link to download CALDB files
– Link to LAT Event, Photon, and Pointing database interface
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Nothing there at the moment
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Source Catalog and Pulsar Ephem.
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The LAT source catalog and Pulsar Ephemeredes database
are each a single FITS file.
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The link on the main data access page will point directly to
the FITS file for downloading.
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Users may download it and use it as they desire.
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Gamma-ray Burst Data
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We will provide data for each burst “detected”
“Detected” means that the burst crossed the GBM and/or LAT
sensitivity threshold
For each burst a designation will be generated of the form
“DC2-YYMMDDFFF” indicating that it is a DC2 burst and
giving its time in the DC2 data set
For each burst, a “Burst Data Package” will be constructed
containing the GBM and LAT data for the time period and
position of the burst
Information about each burst will be made accessible through
a website listing the bursts and basic burst data
– What would you like to see?
– This will include a link to the data package.
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CALDB
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The Calibration Database is a set of FITS data files stored in a
predefined directory structure
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This will be packaged into a single tarball and the link on the
main data page will provide access to download the data
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Once downloaded the user can unpack the data into the
appropriate location in their science tools installation
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For DC2 this will only be the LAT calibration files.
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LAT Photon & Pointing Data
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Access to this data is provided by a set of custom data
servers developed at the GSSC
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The link on the main data access page will take you to the
data server web interface at
http://glast.gsfc.nasa.gov/cgi-bin/ssc/DC2/LATDataQuery.cgi
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This page will allow you query the Photon and Pointing (and
Event if it is available) data simultaneously
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Allowed selection criteria are
– Object name or position (RA, Dec)
– Size of search area
– Time
– Energy
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Selection Criteria – Position
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Select center point for search region
– J2000, B1950, or galactic coordinates in comma separated list
– Or enter name of object and choose Simbad name resolver
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Choose shape of region
– Circle – must specify radius
– Box – must specify width, height and rotation angle in comma
separated list
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Default is circular region with 15° radius in J2000 coordinates
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If nothing entered in position field, an all-sky search is
performed
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Selection Criteria – Time
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May choose from Gregorian date, MJD or Mission Elapsed
Time formats. The default is Gregorian date.
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May specify start time and optionally end time in comma
separated list
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If no end time specified, returns start time + 6 months or until
end of data set which ever is less.
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If no times specified, last 6 months of data returned
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Special keyword “START” and “END” provided representing
the first and last data entries currently in the database.
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Selection Criteria – Energy & DB
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Energy
– Units are in MeV
– Can specify a lower and optional upper energy limit in comma
separated list.
– If nothing is specified, will return all events from entire energy range
of the LAT.
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Database Choice
– May select from any combination of Event, Photon and Spacecraft
database via checkboxes at bottom of page
– Searches are performed simultaneously
– Default is Photon and Spacecraft
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Box Searches – How to Implement
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Option 1 – Simple RA/Dec boxes
– Easy to implement as limits on the coordinates – width and height
translate to simple offsets from the central position
– Not truly rectangular regions on the sky – degenerate to triangles at
the poles
– Implementing in other coordinate systems not as easy with current
data file definitions (only RA & Dec in FT1 file)
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Option 2 – Rectangular regions projected onto sky
– More difficult to implement (but it’s just math and computers are fast)
– Width and height would determine vertices of box and then project
box onto celestial sphere to define region
– Region are true spherical rectangles and would convert to a
rectangular image when using a tangential projection to create maps.
– Much easier to implement rotations and searches in other coordinate
systems (i.e. galactic)
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Query Submission Screenshot
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Submission Response
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Once the query parameters are submitted the system quickly
returns with a response
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Result depends on the type of query
– All sky query with only a cut on time
• The page will indicate that the query is complete, give the query ID
number and provide a link to the query results page
• The data for all-sky searches is pre-packaged in one week intervals and
an all sky query returns a list of the files covering the time period
requested.
– All other queries
• The page will indicate the estimated amount of time until the query
completes, give the query ID number and provide a link to the query
results page.
• Will also provide an opportunity to enter an e-mail address to be notified
when query is done (mainly for event data as the searches may be long)
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Submission Response Screenshot
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Query Results
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Following the link on the previous page will take you to the
results page
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This page presents the following information about the query
results
– The query ID
– The query parameters used to extract the data
– The estimated time remaining (if any) until the query is finished
– A table of the available data files from the query with their size and
number of events contained and a link to begin downloading the files
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It also provides
– Another opportunity to enter your e-mail if the wait is still long
– A field to enter the query ID of a different query to get its results.
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Users will use the links provided to download the files to their
computers.
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Query Results – What You Get
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Time range only searches
– List of files, each covering ~one week of all-sky data, that cover the
time range specified by the selection criteria
– There will be more data than you asked for at the beginning and end
of the time period as no cuts are made on the data.
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All other searches
– List of files containing the data requested.
– Broken up into smaller files if the data volume gets large
• Currently set to limit file size to ~200 MB – no real impact on DC2
• Should this be set to a higher or lower limit?
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Query Results Screenshot
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Single CPU Performance
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Single CPU Performance
Searches on the
Galactic Center
Searches on Galactic
Anti-center region
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Event Data
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The content of the event database is still ill-defined
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We may have an “event” database for DC2 but
– It will not have 10-100x the number of events as the photon database
– It will have the same entries but with more data than just the standard
FT1 event summary data. Probably a cleaned up version of the Merit
Ntuple
• Duplicates removed (i.e. don’t need Energy and log(Energy))
• Variable stored in proper formats – not everything as a double
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Access provided by the same interface as the Photon data
but by checking the Event data box instead of or in addition
to the Photon data box at the bottom of the page.
June 27-29, 2005 - DC2 Software Workshop - 20
Discussion
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Additional data products
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Contents of burst page data table
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Additional search parameters for LAT photon and event
database
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Box search implementation
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(no?) Need for Event database prototype
June 27-29, 2005 - DC2 Software Workshop - 21