Coding the JWST Calibration Pipeline(s)

2010 Calibration WorkshopRobert Jedrzejewski/STScI

JWST Calibration Pipeline Plan

• STScI will develop the calibration pipelines for JWST

• SI Teams will provide the calibration algorithms to be used in the calibration pipelines

• Experience from developing the HST Calibration Pipelines will help guide the design

HST Calibration Pipelines

• CALCOS • CALACS • CALWF3 • CALSTIS

/acs/calacs/acsccdacsccd.cblevdrift.cblevfit.cdoatod.cdobias.cdoblev.cdoccd.cdoflash.cfindblev.cfindover.cgetacsflag.cgetccdsw.cmainccd.c

/wf3/calwf3/wf3ccdblevdrift.cblevfit.cdoatod.cdobias.cdoblev.cdoccd.cdoflash.cfindblev.cfindover.cgetccdsw.cgetflags.cmainccd.cwf3ccd.c

/stis/calstis/cs1blevdrift.cblevfit.cdoatod.cdobias.cdoblev.cfindblev.cfindover.cgetflags1.c

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JWST Observing Modes

JWST has 4 science instruments, each of which can be used in several ways for science

NIRSpec

Multi-Object Spectroscopy

Long-slit spectroscopy

Integral Field Spectroscopy

MIRI

Imaging

Coronography

Long-slit Spectroscopy

Integral Field Spectroscopy

FGS-TFI

Imaging

Coronography

Non-redundant Mask Imaging

NIRCam

Imaging

Coronography

Grism Spectroscopy

Instruments share several common modes!

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Calibration flow

All JWST data is a representation of a celestial scene, as processed by the OTE and instrument to create an image on the detector The detector turns that image into a digital dataset (imperfectly!)

JWSTOTE

InstrumentDetector

Data

CelestialScene

Image formedby telescope

Image/spectrumformed by instrument

Photons go this way

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Decomposing the Calibration Pipeline

DetectorCalibration

InstrumentCalibration

ImagingCalibration

SpectroscopicCalibration

CoronographicCalibration

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Detector Calibration

The detector calibration is simplified because we will only have 2 types of detectors on JWST 15 Hawaii 2RG HgCdTe detectors on NIRCam, NIRSpec,

FGS/TFI 3 Si:As detectors on MIRI

The description of the calibration steps will be the same for either detector type E.g., Both types of detectors have a Reference Pixel

Correction step The best algorithm for doing the correction will often be different

for different instruments It’s unlikely that the Reference Pixel Correction will be the

same for Si:As and HgCdTe detectors And often the same

The Nonlinearity Correction algorithm may well be the same for all detectors – we’ll see

JWST Calibration Pipelines or Pipeline?

caljwstcalDetector

calNearIRDetector calMidIRDetector

calcalImaging calSpectroscopy calCoronography

calInstrument

No more CALxxx

• Since we will develop the JWST calibration pipelines in parallel, we can share code much more easily

• The functionality shared among the instrument pipelines makes it advantageous to design modules that calibrate generic effects, rather than instrument-specific effects

• But the overall driver is the BEST calibration – we will not force the calibration steps to be the same for each instrument.

Summing Up

• We can take advantage of the fact that JWST instruments share identical detectors to have the calibration pipelines share much of the detector calibration code

• We can use the fact that several observing modes are shared by JWST instruments to have the calibration pipelines share significant amounts of instrument calibration code

• It makes more sense to think of CALJWST instead of CALSTIS/CALACS/CALNICA/CALWF3/CALCOS

• If a pipeline module needs to be different for different instruments, it will be