File Naming Conventions and Data Products

JWST Data has unique names according to their relationship, within a proposal, with the observation mode and the members of an exposure and target. For a given association or exposure, the data also includes extension names according to the type of product.

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The naming convention for calibration products provides information about the program, exposure, instrument mode, as well as stages of calibration. At each stage of the calibration pipeline, the input data for a step is the calibration product produced by previous stages. In some cases, a given step of the calibration pipeline can produce other products that will not be used in subsequent steps and produced only when explicitly requested by the user. These are referred to as intermediate or optional products and are not stored in MAST.



Exposure file names

JWST science data files are FITS format files that in their first stages of processing contain only the values from a single exposure for a single detector. In the file name, a detector is defined to be a single Sensor Chip Assembly (SCA). These files are processed and combined with other exposures in stage 3 of the calibration pipeline.

The names of the exposure level data is constructed with information from the science header of the exposure, allowing users to map it to the observation in ther corresponding APT files:

jw<PPPPP><OOO><VVV>_<GGSAA>_<EEEEE>_<detector >_<suffix> .fits

where

  • PPPPP = Program ID
  • OOO = Observation number
  • VVV = Visit number
  • GG = Visit Group
  • S = Parallel Sequence id (1 prime, 2-5 parallel)
  • AA = Activity number (base 36)
  • EEEEE = Exposure number
  • <detector> = detector name; e.g. nrca1, nrclong, mirimage
  • <sufix> = product type; e.g. uncal, rate

For example, the filename for a long wavelength uncalibrated NIRCam exposure, taken with module A, would take the form "jw80500012009_01101_00012_nrcalong_uncal.fits."

The observation number from the APT proposal entry is preserved as the observation number in the science telemetry, making it easier for the proposer to determine the observation that gave rise to an individual exposure. Since the exposure number resets with each new activity, the visit group, parallel sequence ID, and activity are included to make it possible to trace the exposure to the commanding request. All the products of the calibration pipeline that derive from this exposure have this naming convention, with the file name suffix distinguishing the different file products in the data set.



Stage 1 and stage 2 data products

The values for the suffix field within the file name, correspond to the different stages of the calibration pipeline and are as defined in the Algorithms Documentation.  The input and output from each of stage 1 and stage 2 of the calibration pipeline steps are provided in Table 1.


Table 1. Standard and optional products for stage 1 and stage 2

StageModuleInput data suffixOutput
product
suffix
UnitsDescription
stage 0

_uncalDNRaw 4D (ncols x nrows x ngroups x nints) exposure data. Used as input to calwebb_detector1.

stage 1


calwebb_detector1

_uncal

_rateints

DN/s

3-D slope images for each integration. Each plane of the 3D cube is the result of an individual integration. Typically only of interest and used for time-series observations. Result of ramp fitting.

_rate

DN/s

2-D slope images derived after averaging of all countrate integrations within the exposure.

_ramp

DN

Optional-partial calibrated product. It is a corrected 4D exposure data. Processed up through jump detection step.

_fitopt

(various)

Optional product with fitting results from ramp_fit step

_trapsfilledDNOptional product. Charge trap state product produced by the persistence correction step.
_darkDNOptional product. This is a 4D corrected dark exposure data. Processed up to dark subtraction step.

stage 2 (imaging)





calwebb_image2

_rate

_cal


DN/s

Calibrated slope images per exposure

_i2d 


DN/s

Rectified calibrated slope images per exposure.

_bsub


DN/s

Background-subtracted image

_rateints

_calints


DN/sec

Calibrated slope images for each integration

_bsubints


DN/s

Per integration background-subtracted image

stage 2 (spectroscopy)





calwebb_spec2

_rate




 _cal


DN/s (non-IFU)

mJy/arcsec2 (IFU)

2D fully calibrated data. Data are averaged over all integrations.

_s3d


mJy/arcsec2

IFU: 3-D spectral cubes per exposure

_s2d

DN/s

non-IFU: 2-D  rectified (drizzled) slope image per exposure

 _x1d


(various)

Extracted 1-D spectra over all integrations

_bsubDN/s2D background-subtracted spectral data. Data are averaged over all integrations.
_cal_annn _crf
stage 3 product. Copy of _cal with DQ array updated by outlier_detection step

_rateints



_x1dints

(various)

Extracted 1-D spectra per integration

 _calints

DN/s

Calibrated slope images for each integration

_flat



Optional output for NIRSpec data. Provided the extracted and interpolated flat fields.

_bsubintsDN/s3D background-subtracted spectral data. Each plane of 3D cube is result for individual integrations.
_calints _annn _crfints
stage 3 product. Copy of _cal with DQ array updated by outlier_detection step



Association file names

Associations capture the relationship between exposures that are to be combined by design to form a single product. Association data products result from the combination of multiple exposures like dithers or mosaics and are generated by the stage 3 of the calibration pipeline.  These products will have a file name that includes the astronomical source and observation parameters that would help users to map these with the proposed observation. 

The format for the file name of an association has all alphabetic characters in lower case, underscores are only used to delineate between major fields, and dashes can be used as separators for optional fields. Just as for Stage 2, the suffix distinguishes the different file products of Stage 3 of the calibration pipeline:

jw<PPPPP>-<AC_ID>_x[<“t”TargetID  | “s”SourceID> ](-<"epoch”X>)_<science_instrument>_<optical_elements>(-<subarray>)_ <suffix>(-<ACT_ID>).fits

where

  • PPPPP =  is the program ID
  •  AC_ID = association candidate (AC) ID which can take the following values
    • "o"oo0
    •  "c"cccc
    •  "a"aaaa
    • "r"rrrr
  • “t”TargetID  | “s”SourceID,  either TargetID or SourceID must be present
    • TargetID = The standard target name is a 3 digit Target ID (usually imaging target)
    • SourceID = The standard source name is a 5 digit Source ID (usually spectral MSA target)
  • "epoch”X = The text "epoch" followed by a single digit indicating the epoch number
  •  science_instrument = The designator for the science instrument, i.e. nircam, miri, etc.    
  • optical_elements> = A single or "-" separated list of optical elements alphabetically (filters).   
  • subarray = Optional indicator of the subarray.   
  • suffix = The product type suffix.  See Link to the JCCWG confluence page listing product types.    

In this case, the EPOCH is an optional parameter that is used for observations of the same target that are taken at different epochs.



Stage 3 data products

Table 2 is the Input exposure level data coming from stage 2 and their stage 3 products separated by the modules as described in the Stages of Processing article.


Table 2. Standard and optional products for stage 3 of the calibration pipeline

Data
stage
ModuleInput
suffix
DescriptionOutput
suffix

Description

stage 3 imaging




calwebb_image3

_cal

All _cal files in an association




_i2d


2D rectified and combined image.

_cat
Source catalog, in .ecsv format
_crfDN/sCopy of _cal with DQ array updated by outlier_detection step
_segm
Segmentation map
stage 3 spectroscopy





calwebb_spec3




_cal




All _cal files in an association




_crf

DN/s

Copy of _cal with DQ array updated by outlier_detection step

_x1d

flux

Extracted 1-D spectra from combined exposures.

_s3d


3D rectified and combined spectral cube. For IFU modes and spectral mapping observations.

_s2d


non-IFU: 2D rectified and combined spectral image.

_calint

All _calint files in an association

_crfints


Same as _calints but with updated CR flags

_x1dints

net, flux

Extracted 1-D spectra per integration

stage 3 coronagraphic



calwebb_coron3






_calints





All _cal files in an association



_crf


Copy of _cal with DQ array updated by outlier_detection step

_psfstack

3D stack of PSF images. Output of stack_refs step. One _psfstack product per associated target.

_i2d

2D combined and resampled science target image. Output of resample step. One _i2d product per associated target

_crfints


Same as _calints but with updated CR flags

_annn_psfsub


psf subtracted

_annn_psfalign


4D array of PSF images aligned to individual integrations of science target images. Output of align_refs step. One _psfalign product per target input.

stage 3 Time Series Observations




calwebb_tso3





_cal


  
All_cal files in an association


_s2d


2D resampled+combined spectroscopic image 1 product per source

_crfDN/sCopy of _cal with DQ array updated by outlier_detection step

_phot

mag

Imaging photometry, in ecsv format.

_whtlt


.

 Spectroscopic white-light curve, in ecsv format.

 _calints All _calint files in an association_crfintsDN/s3D calibrated data with DQ array updated by outlier_detection step. Copy of _calints input.

stage 3 Aperture Masking Interferometry



calwebb_ami3



_cal



All_cal files in an association

_annn_ami


Output of ami_analize step. One per exposure

_amiavg


Table of averaged fringe parameters for PSF reference or science target exposures. Output of ami_average step.

_aminorm


Final single product for the target corrected by the calibrator




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