Difference: DCPToolsFITS (2 vs. 3)

Revision 32023-03-24 - GillesLandais

 
META TOPICPARENT name="IvoaDCP"

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Howto create FITS images/spectra to be VO-compatible

FITS format is a popular output used in astronomy for spectra and images. FITS recommendations when applied enable to make a clean mapping between FITS header and ObsCore DM.

Mapping FITS with ObsCore

Some Obscore items can be assigned by provider (i.e.: obsid, access_estimated_size, ..) and other can be detected in FITS using different keywords.
We can classify them into 3 categories (ordered by relevance):

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  1. WCS keywords
    Available for different topics (position, electromagnetics band..). WCS is a serialisation based on FITS keywords that make a bijection between a simple set of values and the true values (see the official document: https://fits.gsfc.nasa.gov/fits_wcs.html )
    An automated workflow requires all WCS keywords :
    i.e.: CRVAL, CTYPE, CRPIX, CDELT ,CUNIT, [CDi_j]
  2. NASA standards and extended keywords list
    See https://fits.gsfc.nasa.gov/
  3. Other keywords in usage
    Other keywords used FITS, not described by NASA

Proposed keywords grouped by topics

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Obscore Description Mandatory WCS possible Automated assignment possible NASA FITS standard keywords NASA FITS exended keywords Others keywords
dataproduct_type Data product (file content) primary type YES YES
dataproduct_subtype Data product specific type
calib_level Calibration level of the observation YES YES
target_name Object of interest YES YES OBJECT OBJNAME OBJECT, TARGET
target_class Class of the Target object as in SSA
obs_id Internal ID given by the ObsTAP service YES YES OBS-ID
obs_title Brief description of dataset in free format TITLE
obs_collection Name of the data collection YES YES
obs_creation_date Date when the dataset was created
obs_creator_name Name of the creator of the data
obs_creator_did IVOA dataset identifier given by the creator
obs_release_date Curation.releaseDateunitlessdateObservation release date (ISO 8601)
obs_publisher_did ID for the Dataset given by the publisher. YES YES
publisher_id IVOA-ID for the Publisher
bib_reference Service bibliographic reference
data_rights Public/Secure/Proprietary/
access_url URL used to access dataset YES YES
access_format Content format of the dataset YES YES
access_estsize Estimated size of dataset: in kilobytes YES YES
s_ra Right ascension YES YES RA, RA_NOM, RA_OBJ, RA_PNT, RA_SXS, RA_SCY,RA_SCZ RA, RA2000, RAOBJ, RA1950
s_dec Declination YES YES DEC, DEC_NOM, DEC_OBJ, DEC_PNT, DEC_SXS, DEC_SCY, DEC_SCZ DEC, DEC2000, DEC1950, DE2000, DE1950, DEOBJ
s_fov Estimated size of the covered region as the diameter of a containing circle YES YES FOV
s_region Sky region covered by the data product (expressed in ICRS frame) YES YES REGION
s_resolution Spatial resolution of data as FWHMof PSF YES YES
s_xel1 Number of elementsalong the first coordinate of the spatial axis YES YES (NAXIS)
s_xel2 Number of elementsalong the second coordinate of the spatial axis YES YES (NAXIS)
s_ucd UCD for the nature of the spatial axis
s_unit Unit used for spatial axis
s_resolution_min Resolution min value on spatial axis (FHWM of PSF)
s_resolution_max Resolution max value on spatial axis
s_calib_status Type of calibration along the spatial axis
s_stat_error Astrometric precision along the spatial axis
s_pixel_scale Sampling period in world coordinate units along the spatial axis
t_xel Number of elementsalong the time axis YES
t_refpos Time Axis Reference Position as defined in STC REC
t_min Start time inMJD YES DATE-OBS TIME-OBS TSTART, OBSSTART, OBS-DATE, DATE-OBS, DATEOBS, OBSDATE, MJDMJDOS, TIME
t_max Stop time in MJD YES TIME-END, DATE-END TSTOP, OBSEND, ENDOBS, ENDDATE, DATEEND
t_exptime Total exposure time YES EXPOSURE, EXPTIME, TELAPSE, ELAPTIME, ONTIME, LIVETIME EXPTIME, TEXP, OBSTIME, TIMEOBS
t_resolution Temporal resolution FWHM YES
t_calib_status Type of time coordinate calibration
t_stat_error Time coord statistical error
em_xel Number of elementsalong the spectral axis YES YES (NAXIS)
em_ucd Nature of the spectral axis
em_unit Units along the spectral axis
em_calib_status Type of spectral coord calibration
em_min start in spectral coordinates YES YES
em_max stop in spectral coordinates YES YES
em_res_power Value of the resolving power along the spectral axis. (R) YES YES
em_res_power_min Resolving power min value on spectral axis
em_res_power_max Resolving power max value on spectral axis
em_resolution Value of Resolution along the spectral axis
em_stat_error Spectral coord statistical error
o_ucd Nature of the observable axis YES
o_unit Units used for the observable values
o_calib_status Typeof calibration for the observable coordinate
o_stat_error Statistical error on the Observable axis
pol_xel Number of elements along the polarization axis YES
pol_states List of polarization states present in the data file YES POL, STOKES
instrument_name The name of the instrument used for the observation YES INSTRUME INSTRUME
facility_name Name of the facility used for this observation YES TELESCOP FACILITY, TELESCOP
dataproduct_subtype Data product specific type
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Obscore Description Mandatory WCS possible Automated assignment possible NASA FITS standard keywords NASA FITS exended keywords Others keywords
dataproduct_type Data product (file content) primary type YES YES
dataproduct_subtype Data product specific type
calib_level Calibration level of the observation YES YES
target_name Object of interest YES YES OBJECT OBJNAME OBJECT, TARGET
target_class Class of the Target object as in SSA
obs_id Internal ID given by the ObsTAP service YES YES OBS-ID
obs_title Brief description of dataset in free format TITLE
obs_collection Name of the data collection YES YES
obs_creation_date Date when the dataset was created
obs_creator_name Name of the creator of the data
obs_creator_did IVOA dataset identifier given by the creator
obs_release_date Curation.releaseDateunitlessdateObservation release date (ISO 8601)
obs_publisher_did ID for the Dataset given by the publisher. YES YES
publisher_id IVOA-ID for the Publisher
bib_reference Service bibliographic reference
data_rights Public/Secure/Proprietary/
access_url URL used to access dataset YES YES
access_format Content format of the dataset YES YES
access_estsize Estimated size of dataset: in kilobytes YES YES
s_ra Right ascension YES YES RA, RA_NOM, RA_OBJ, RA_PNT, RA_SXS, RA_SCY,RA_SCZ RA, RA2000, RAOBJ, RA1950
s_dec Declination YES YES DEC, DEC_NOM, DEC_OBJ, DEC_PNT, DEC_SXS, DEC_SCY, DEC_SCZ DEC, DEC2000, DEC1950, DE2000, DE1950, DEOBJ
s_fov Estimated size of the covered region as the diameter of a containing circle YES YES FOV
s_region Sky region covered by the data product (expressed in ICRS frame) YES YES REGION
s_resolution Spatial resolution of data as FWHMof PSF YES YES
s_xel1 Number of elementsalong the first coordinate of the spatial axis YES YES (NAXIS)
s_xel2 Number of elementsalong the second coordinate of the spatial axis YES YES (NAXIS)
s_ucd UCD for the nature of the spatial axis
s_unit Unit used for spatial axis
s_resolution_min Resolution min value on spatial axis (FHWM of PSF)
s_resolution_max Resolution max value on spatial axis
s_calib_status Type of calibration along the spatial axis
s_stat_error Astrometric precision along the spatial axis
s_pixel_scale Sampling period in world coordinate units along the spatial axis
t_xel Number of elementsalong the time axis YES
t_refpos Time Axis Reference Position as defined in STC REC
t_min Start time inMJD YES DATE-OBS TIME-OBS TSTART, OBSSTART, OBS-DATE, DATE-OBS, DATEOBS, OBSDATE, MJDMJDOS, TIME
t_max Stop time in MJD YES TIME-END, DATE-END TSTOP, OBSEND, ENDOBS, ENDDATE, DATEEND
t_exptime Total exposure time YES EXPOSURE, EXPTIME, TELAPSE, ELAPTIME, ONTIME, LIVETIME EXPTIME, TEXP, OBSTIME, TIMEOBS
t_resolution Temporal resolution FWHM YES
t_calib_status Type of time coordinate calibration
t_stat_error Time coord statistical error
em_xel Number of elementsalong the spectral axis YES YES (NAXIS)
em_ucd Nature of the spectral axis
em_unit Units along the spectral axis
em_calib_status Type of spectral coord calibration
em_min start in spectral coordinates YES YES
em_max stop in spectral coordinates YES YES
em_res_power Value of the resolving power along the spectral axis. (R) YES YES
em_res_power_min Resolving power min value on spectral axis
em_res_power_max Resolving power max value on spectral axis
em_resolution Value of Resolution along the spectral axis
em_stat_error Spectral coord statistical error
o_ucd Nature of the observable axis YES
o_unit Units used for the observable values
o_calib_status Typeof calibration for the observable coordinate
o_stat_error Statistical error on the Observable axis
pol_xel Number of elements along the polarization axis YES
pol_states List of polarization states present in the data file YES POL, STOKES
instrument_name The name of the instrument used for the observation YES INSTRUME INSTRUME
facility_name Name of the facility used for this observation YES TELESCOP FACILITY, TELESCOP
dataproduct_subtype Data product specific type
 

Validator tools

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Tools like the CDS fits validator (based on Saada) checks the VO-compatibility according to WCS and a keyword list based on the FITS extended keywords.

http://cdsarc.unistra.fr/vizier.submit/fitsvalidator.html

The service was built in the VizieR ingestion context. The background process is similar as the VizieR web service provided for authors.

FITS (Nasa) recomendations

 
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Note: NASA FITS url: https://fits.gsfc.nasa.gov/fits_dictionary.html , HEASARC URL : https://heasarc.gsfc.nasa.gov/docs/fcg/ (idem than FITS)
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Tools like the CDS fits validator (based on Saada) checks the VO-compatibility according to WCS and a keyword list based on the FITS extended keywords.

https://cdsarc.cds.unistra.fr/vizier.submit/fitsvalidator.html

FITS (Nasa) recomendations

 
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Obscore Description Mandatory WCS possible Automated assignment possible NASA FITS standard keywords NASA FITS exended keywords Others keywords
dataproduct_type Data product (file content) primary type YES YES
dataproduct_subtype Data product specific type
calib_level Calibration level of the observation YES YES
target_name Object of interest YES YES OBJECT OBJNAME OBJECT, TARGET
target_class Class of the Target object as in SSA
obs_id Internal ID given by the ObsTAP service YES YES OBS-ID
obs_title Brief description of dataset in free format TITLE
obs_collection Name of the data collection YES YES
obs_creation_date Date when the dataset was created
obs_creator_name Name of the creator of the data
obs_creator_did IVOA dataset identifier given by the creator
obs_release_date Curation.releaseDateunitlessdateObservation release date (ISO 8601)
obs_publisher_did ID for the Dataset given by the publisher. YES YES
publisher_id IVOA-ID for the Publisher
bib_reference Service bibliographic reference
data_rights Public/Secure/Proprietary/
access_url URL used to access dataset YES YES
access_format Content format of the dataset YES YES
access_estsize Estimated size of dataset: in kilobytes YES YES
s_ra Right ascension YES YES RA, RA_NOM, RA_OBJ, RA_PNT, RA_SXS, RA_SCY,RA_SCZ RA, RA2000, RAOBJ, RA1950
s_dec Declination YES YES DEC, DEC_NOM, DEC_OBJ, DEC_PNT, DEC_SXS, DEC_SCY, DEC_SCZ DEC, DEC2000, DEC1950, DE2000, DE1950, DEOBJ
s_fov Estimated size of the covered region as the diameter of a containing circle YES YES FOV
s_region Sky region covered by the data product (expressed in ICRS frame) YES YES REGION
s_resolution Spatial resolution of data as FWHMof PSF YES YES
s_xel1 Number of elementsalong the first coordinate of the spatial axis YES YES (NAXIS)
s_xel2 Number of elementsalong the second coordinate of the spatial axis YES YES (NAXIS)
s_ucd UCD for the nature of the spatial axis
s_unit Unit used for spatial axis
s_resolution_min Resolution min value on spatial axis (FHWM of PSF)
s_resolution_max Resolution max value on spatial axis
s_calib_status Type of calibration along the spatial axis
s_stat_error Astrometric precision along the spatial axis
s_pixel_scale Sampling period in world coordinate units along the spatial axis
t_xel Number of elementsalong the time axis YES
t_refpos Time Axis Reference Position as defined in STC REC
t_min Start time inMJD YES DATE-OBS TIME-OBS TSTART, OBSSTART, OBS-DATE, DATE-OBS, DATEOBS, OBSDATE, MJDMJDOS, TIME
t_max Stop time in MJD YES TIME-END, DATE-END TSTOP, OBSEND, ENDOBS, ENDDATE, DATEEND
t_exptime Total exposure time YES EXPOSURE, EXPTIME, TELAPSE, ELAPTIME, ONTIME, LIVETIME EXPTIME, TEXP, OBSTIME, TIMEOBS
t_resolution Temporal resolution FWHM YES
t_calib_status Type of time coordinate calibration
t_stat_error Time coord statistical error
em_xel Number of elementsalong the spectral axis YES YES (NAXIS)
em_ucd Nature of the spectral axis
em_unit Units along the spectral axis
em_calib_status Type of spectral coord calibration
em_min start in spectral coordinates YES YES
em_max stop in spectral coordinates YES YES
em_res_power Value of the resolving power along the spectral axis. (R) YES YES
em_res_power_min Resolving power min value on spectral axis
em_res_power_max Resolving power max value on spectral axis
em_resolution Value of Resolution along the spectral axis
em_stat_error Spectral coord statistical error
o_ucd Nature of the observable axis YES
o_unit Units used for the observable values
o_calib_status Typeof calibration for the observable coordinate
o_stat_error Statistical error on the Observable axis
pol_xel Number of elements along the polarization axis YES
pol_states List of polarization states present in the data file YES POL, STOKES
instrument_name The name of the instrument used for the observation YES INSTRUME INSTRUME
facility_name Name of the facility used for this observation YES TELESCOP FACILITY, TELESCOP
dataproduct_subtype Data product specific type
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  • FITS recommendation based on keywords :

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Note: NASA FITS url: https://fits.gsfc.nasa.gov/fits_dictionary.html , HEASARC URL : https://heasarc.gsfc.nasa.gov/docs/fcg/ (idem than FITS)

 
 
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