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Science Product Core Keywords

The keywords listed below are required or recommended in all FITS files (and in some cases, all FITS extensions) of any type that contain images, spectra, light curves, and other similar science products. Recommended keywords, if absent, will be derived and inserted prior to ingest.

HLSP Metadata Color Codes
The following table(s) of HLSP metadata, to be included in science products, are color-coded:

Required

Recommended

Suggested

The extension column refers to the primary (P) header or, for multi-extension (MEF) files, one or more extensions (E). Depending upon the organization of the data (e.g., if image data arrays appear in an extension), any given Primary keyword may instead belong in an Extension.


KeywordHDUNotes

DATE-BEGP or EISO-8601 formatted DateTime string for start of an observation (or, the start of the first observation of a combined product), in the time system specified by TIMESYS. May use MJD-BEG in addition or instead. For catalogs, this time should reflect the time of the earliest observation of the entries.

DATE-ENDP or EISO-8601 formatted DateTime for end of an observation (or, the end of the last observation of a combined product), in the time system specified by TIMESYS. May use MJD-END in addition or instead. For catalogs, this time should reflect the time of the latest observation of the entries.

DOIPDigital Object Identifier for the HLSP data collection

EQUINOXEEquinox of the celestial coordinate system. This keyword must not be used if RADESYS = 'ICRS'

HLSPIDPThe identifier (acronym) for this HLSP collection

HLSPLEADPFull name of HLSP project lead

HLSPNAMEPTitle for HLSP project, long form

HLSPTARGPDesignation of the target(s) or field(s) for this HLSP

HLSPVERPVersion identifier for this HLSP product

INSTRUMEPDesignation of instrument used for this observation

LICENSEPLicense for use of these data, with the value 'CC BY 4.0'

LICENURLPData license URL, with the value 'https://creativecommons.org/licenses/by/4.0/'

MJD-BEGP or EStart time of observation (or, the start of the first observation of a combined product), expressed as MJD. May use DATE-BEG in addition or instead. For catalogs, this time should reflect the time of the earliest observation of the entries.

MJD-ENDP or EEnd time of exposure (or, the end of the last observation of a combined product), expressed as MJD, in the time system specified by TIMESYS. May use DATE-END in addition or instead. For catalogs, this time should reflect the time of the earliest observation of the entries.

MJD-MIDP or EMid-time of exposure (or, the mid-point of a series of observations), expressed as MJD, in the time system specified by TIMESYS. May use DATE-AVG in addition or instead. For catalogs, this time should reflect the time of the earliest observation of the entries.

OBSERVATPObservatory used to obtain this observation.

PROPOSIDPObservatory program/proposal identifier, if applicable

REFERENCPBibliographic identifier (ADS bibcode) for reference where these data were published

TELAPSEP or ETime elapsed between start- and end-time of observation

TELESCOPPDesignation of telescope used for this observation

TIMESYSP or ECharacter string code (see FITS Standard) for time scale of time-related keywords. Ex: 'UTC'

XPOSUREP or EDuration of exposure, exclusive of dead time

Although observation time-stamps can be specified in MJD or as ISO-8601 date-time strings, be consistent: all of one or the other; or include both types.

Data Simulations

Generally, data simulations should include the same metadata that apply to the data product that is being simulated. However, it is essential that users of the simulations (including software applications) be able to distinguish between simulated and observed data. Therefore all simulated data must include the following keyword in the primary header (PHDU) in FITS files:

  • SIMULATD= T

Special Considerations for FITS Keywords

  • Note that the lists in this chapter do not include the basic structural FITS keywords (SIMPLE, NAXIS, etc.) that are required for valid FITS HDUs. Most FITS writing applications already know how to insert structural keywords into FITS headers.
  • Keyword records listed in this chapter are arranged alphabetically by name for ease of reference; contributor teams may choose the order of most keywords.
  • Deprecated FITS keywords (such as EPOCH) must not be used.
  • The FITS Standard allows for continued-string (or long-string) keyword records. These are string-valued keywords, with values that are too long to be defined within the character limitation of a single keyword record. This feature must not be used with any of the keywords designated as mandatory or reserved in the FITS Standard, but otherwise may be used without restriction in HLSP science files.

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