The Global Pool

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The Global Pool
list of active and potential calibrators

• AstroWise Workshop
• 20-11-2006

2
The Global Pool

• Why
• Calibration refinement
• What
• Astrometric calibration
• Photometric calibration
• How
• DB storage
• Global processing

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Why a global pool

• Higher precision
• Astrometric reference frame
• Large errors on dense catalogs
• Small errors on sparse catalogs
• Photometric calibration grid
• New calibrators
• Increase density of astrometric grid
• Build secondary photometric standards

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What is the global pool

• Data store of (potential) calibrators
• Source Pool
• Ever growing
• Source extractions
• Positions
• Fluxes
• Catalog
• Predefined slice from the Source Pool
• Calibrators
• Catalog with calibration status sources

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Actions on global pool

• Use
• Astrom input reference catalog
• Photom input standard star catalog
• Add
• SAssociate single chip/global catalogs
• Validate
• Check reliability of information
• Modify
• Derive new values

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How to build the global pool

• Filled with known calibrators
• USNO, GSC, Hipparcos, ... (weights)
• Landolt, SDSS, etc.
• Adding potential candidates
• Selections from the standard pipeline processing
• One or more characteristics
• Position measurements
• Flux measurements
• Evaluating candidates
• Deriving new calibrators

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Filling the global pool (1)

• At calibration pipeline processing
• Astrometric pipeline
• Calibration source extractions
• Overlap source extractions
• Other high SNR extractions (stellar objects)
• Multiple extraction of same source
• Re-run of pipeline
• Reobservation of sky area
• Associations of same source (association lists)

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Filling the global pool (2)
calibrator
extraction
extraction
extraction
Pipeline Associate
Pipeline Associate
Pool Source
Ingest Associate
Physical source
calibrator
candidate
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Filling the global pool (3)
Identity unique id per physical
source Origin external, measured,
derived Position measured or derived
positions Positional error Signal signal/flux/mag
nitude Signal error Astrom weight 0 1 Photom
weight 0 1 Quality unknown, calibrated Version
1 N Variable y/n Proper motion y/n Status unk
nown, validated, calibrator Flags TBD Obsdate Chi
pid filtid
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Filling the global pool (4)

• Calibrator
• Reference calibrator
• Original calibration data
• Multiple source extractions
• New calibrator
• Derived calibration data
• Multiple source extractions
• Potential calibrator
• No calibration data
• Multiple source extractions

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Deriving calibrators (1)

• Evaluate a given source (verify())
• Determine candidate status
• Stable (proper motion, variable, ...)
• High SNR information
• Enough measurements
• Promote/demote to/from calibrator
• Model description of instrument
• Large time interval processing

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Deriving calibrators (2)

• Model description Astrometric
• Optical path modelling
• Independent parametrization from standard
  pipeline processing
• History on extracted source information
• Association information
• Multiple pointings
• Multiple filters

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Deriving calibrators (3)

• Create new entry in Source Pool
• New derived information
• Status calibator
• Quality calibrated
• Weight 0 1 (errors)
• Demote older calibrator entry
• Last best?
• History of calibration

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Deriving calibrators (4)
Id1 seqnr1 Statuscalibrator Obsdate
20030405 Id1 seqnr2 Statusunknown Obsdate
20051201 Id1 seqnr3 Status unknown Obsdate
20051204 Id1 seqnr4 Statusunknown Obsdate
20060101 Id1 seqnr5 Status unknown Obsdate
20060523 Id1 seqnr6 Statuscalibrator Obsdate
20060723 Id1 seqnr7 Status unknown Obsdate
20061010 Id1 seqnr8 Status unknown Obsdate
20061011 Id2 seqnr1 Statuscalibrator Obsdate
20030405 Id2 seqnr2 Statusunknown Obsdate
20040909 Id2 seqnr3 Status unknown Obsdate
20041001 Id2 seqnr4 Statusunknown Obsdate
20041230 Id2 seqnr5 Status unknown Obsdate
20050305 Id2 seqnr6 Statusunknown Obsdate
20050809 Id2 seqnr7 Status calibrator Obsdate
20060723 Id2 seqnr8 Status unknown Obsdate
20061120 Id3 seqnr1 Status unknown Obsdate
20060402 Id3 seqnr2 Status unknown Obsdate
20060505 Id3 seqnr3 Status calibrator Obsdate
20060723
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Calibration consquences

• Every N months a new calibrator set
• Regenerate all calibrated data
• Regenerate all extractions that added to the
  Source Pool
• Iterative process
• Calibration refinement throughout observing

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Global Pool
Virtual sky of calibrators