======================= exposures-SPECPROD.fits ======================= :Summary: File containing metadata about individual DESI exposures. There are two tables. The first is per-exposure and the second is per-camera per-exposure. The per-exposure table includes observational information as well as derived quantities estimating the observational depth for each target class, quoted in seconds of effective, idealized observing time. The second provides similar information on a per-camera basis. :Naming Convention: ``exposures-{SPECPROD}.fits``, where ``{SPECPROD}`` is the official name of the full reduction, *e.g.* ``everest``. :Regex: ``exposures-[a-z0-9_-]+\.fits`` :File Type: FITS, 19 MB Contents ======== ====== ========= ======== =================== Number EXTNAME Type Contents ====== ========= ======== =================== HDU0_ IMAGE Empty HDU1_ EXPOSURES BINTABLE Per-exposure metadata HDU2_ FRAMES BINTABLE Per-camera per-exposure metadata ====== ========= ======== =================== FITS Header Units ================= HDU0 ---- This HDU has no non-standard required keywords. Empty HDU. HDU1 ---- EXTNAME = EXPOSURES Binary table containing metadata about individual DESI exposures. This includes observational information as well as derived quantities estimating the observational depth for each target class, quoted in seconds of effective, idealized observing time. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ===================== KEY Example Value Type Comment ====== ============= ==== ===================== NAXIS1 337 int Number of columns NAXIS2 3912 int Number of exposure rows ====== ============= ==== ===================== Required Data Table Columns ~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. rst-class:: columns ====================== ======== ============= ================================= Name Type Units Description ====================== ======== ============= ================================= NIGHT int32 Observing night EXPID int32 DESI Exposure number TILEID int32 DESI Tile ID TILERA float64 deg RA of tile given in fiberassign file TILEDEC float64 deg DEC of tile given in fiberassign fileDEC of tile given in fiberassign file MJD float64 Modified Julian Date when shutter was opened for this exposure. SURVEY char[7] Survey name PROGRAM char[6] Program name FAPRGRM char[*] Fiberassign program name FAFLAVOR char[*] Fiberassign flavor name EXPTIME float64 s Length of time shutter was open. EFFTIME_SPEC float64 s Effective exposure time for nominal conditions derived from the TSNR2 fits to the spectroscopy GOALTIME float64 s Goal for total effective exposure time for the tile GOALTYPE char[6] The intended observing conditions for the tile MINTFRAC float64 Minimum fraction of GOALTIME acceptable for considering a tile complete AIRMASS float32 Average airmass during this exposure. EBV float32 Galactic extinction E(B-V) reddening from SFD98_ SEEING_ETC float64 arcsec Average FWHM atmospheric seeing during this exposure as measured by ETC. EFFTIME_ETC float64 s Effective exposure time for nominal conditions inferred from ETC data TSNR2_ELG float64 ELG template (S/N)^2 summed over B,R,Z TSNR2_QSO float64 QSO template (S/N)^2 summed over B,R,Z TSNR2_LRG float64 LRG template (S/N)^2 summed over B,R,Z TSNR2_LYA float64 LYA template (S/N)^2 summed over B,R,Z TSNR2_BGS float64 BGS template (S/N)^2 summed over B,R,Z TSNR2_GPBDARK float64 GPBDARK template (S/N)^2 summed over B,R,Z TSNR2_GPBBRIGHT float64 GPBBRIGHT template (S/N)^2 summed over B,R,Z TSNR2_GPBBACKUP float64 GPBBACKUP template (S/N)^2 summed over B,R,Z LRG_EFFTIME_DARK float64 s Effective exposure time for nominal dark conditions inferred for LRG targets ELG_EFFTIME_DARK float64 s Effective exposure time for nominal dark conditions inferred for ELG targets BGS_EFFTIME_BRIGHT float64 s Effective exposure time for nominal bright conditions inferred for BGS targets LYA_EFFTIME_DARK float64 s Effective exposure time for nominal dark conditions inferred for LYA targets GPB_EFFTIME_DARK float64 s Effective exposure time for nominal dark conditions inferred for GPB targets GPB_EFFTIME_BRIGHT float64 s Effective exposure time for nominal bright conditions inferred for GPB targets GPB_EFFTIME_BACKUP float64 s Effective exposure time for nominal backup conditions inferred for GPB targets TRANSPARENCY_GFA float64 Average airmass during this exposure as measured by GFA. SEEING_GFA float64 arcsec Average FWHM atmospheric seeing during this exposure as measured by GFA. FIBER_FRACFLUX_GFA float64 Fraction of the flux entering the fiber relative to nominal 1.1" seeing using the PSF inferred from the GFAs FIBER_FRACFLUX_ELG_GFA float64 Fraction of the flux entering the fiber relative to nominal 1.1" seeing using the PSF inferred from the GFAs for a source with an ELG profile (0.45" exponential galaxy profile) FIBER_FRACFLUX_BGS_GFA float64 Fraction of the flux entering the fiber relative to nominal 1.1" seeing using the PSF inferred from the GFAs for a source with a BGS profile (deV profile, half light radius of 1.5") FIBERFAC_GFA float64 Fraction of light entering a fiber relative to expectations for 1.1" seeing, transparency 1, for an object with a PSF profile, measured by comparing the flux integrated over a 107 micron diameter circle on the GFA images centered at the PlateMaker expectations for where stars should land. FIBERFAC_ELG_GFA float64 Same as FIBERFAC_GFA except for an ELG profile FIBERFAC_BGS_GFA float64 Same as FIBERFAC_GFA except for a BGS profile AIRMASS_GFA float64 Average airmass during this exposure as measured by GFA. SKY_MAG_AB_GFA float64 mag arcsec^-2 Sky background in the GFA passband, measured from the GFA backgrounds. SKY_MAG_G_SPEC float64 mag arcsec^-2 Sky background measured in the spectroscopy integrated over the DECam g passband, AB mags. SKY_MAG_R_SPEC float64 mag arcsec^-2 Sky background measured in the spectroscopy integrated over the DECam r passband, AB mags. SKY_MAG_Z_SPEC float64 mag arcsec^-2 Sky background measured in the spectroscopy integrated over the DECam z passband, AB mags. EFFTIME_GFA float64 s Effective exposure time for nominal conditions inferred from GFA data EFFTIME_DARK_GFA float64 s Effective exposure time for nominal dark conditions inferred from GFA data EFFTIME_BRIGHT_GFA float64 s Effective exposure time for nominal bright conditions inferred from GFA data EFFTIME_BACKUP_GFA float64 s Effective exposure time for nominal backup conditions inferred from GFA data ====================== ======== ============= ================================= .. _SFD98: https://ui.adsabs.harvard.edu/abs/1998ApJ...500..525S/abstract HDU2 ---- EXTNAME = FRAMES Binary table containing metadata about individual DESI exposures per camera. This includes observational information as well as derived quantities estimating the observational depth for each target class, quoted as TSNR2_*. TSNR2_* can be converted to EFFTIME using the desispec_ function *desispec.tsnr.tsnr2_to_efftime(tsnr2,target_type)*. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ===================== KEY Example Value Type Comment ====== ============= ==== ===================== NAXIS1 167 int Number of columns NAXIS2 111720 int Number of per-camera per-exposure rows ====== ============= ==== ===================== Required Data Table Columns ~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. rst-class:: keywords =============== ======== ====== =========== Name Type Units Description =============== ======== ====== =========== NIGHT int32 Observing night EXPID int32 DESI Exposure number TILEID int32 DESI Tile ID TILERA float64 deg RA of tile given in fiberassign file TILEDEC float64 deg DEC of tile given in fiberassign file MJD float64 Modified Julian Date when shutter was opened for this exposure. EXPTIME float32 s Length of time shutter was open. AIRMASS float32 Average airmass during this exposure. EBV float32 Galactic extinction E(B-V) reddening from SFD98_ SEEING_ETC float64 arcsec Average FWHM atmospheric seeing during this exposure as measured by ETC. EFFTIME_ETC float64 s Effective exposure time for nominal conditions derived from exposure ETC data CAMERA char[2] Camera identifier. Passband and SPECGRPH ([brz][0-9]). TSNR2_GPBDARK float64 GPBDARK template (S/N)^2 summed over B,R,Z TSNR2_ELG float64 ELG template (S/N)^2 summed over B,R,Z TSNR2_GPBBRIGHT float64 GPBBRIGHT template (S/N)^2 summed over B,R,Z TSNR2_LYA float64 LYA template (S/N)^2 summed over B,R,Z TSNR2_BGS float64 BGS template (S/N)^2 summed over B,R,Z TSNR2_GPBBACKUP float64 GPBBACKUP template (S/N)^2 summed over B,R,Z TSNR2_QSO float64 QSO template (S/N)^2 summed over B,R,Z TSNR2_LRG float64 LRG template (S/N)^2 summed over B,R,Z TSNR2_ALPHA float32 Scaling factor on the CCD readnoise component to the TSNR2 SURVEY char[7] Survey name GOALTYPE char[6] The intended observing conditions for the tile FAPRGRM char[*] PROGRAM in fiberassign file FAFLAVOR char[*] FLAVOR in fiberassign file MINTFRAC float64 Minimum fraction of GOALTIME acceptable for considering a tile complete GOALTIME float64 s Goal for total effective exposure time for the tile =============== ======== ====== =========== .. _SFD98: https://ui.adsabs.harvard.edu/abs/1998ApJ...500..525S/abstract .. _desispec: https://github.com/desihub/desispec/blob/720153babcf85dd93530252b0c1f631d48edfc0d/py/desispec/tsnr.py#L1140 Notes and Examples ================== This file is based on the ``guadalupe`` production. There are minor type differences for these columns in both HDU1 and HDU2: ``FAPRGRM``, ``FAFLAVOR``, ``EBV``, ``EFFTIME_ETC``. Type warnings about these columns should be ignored.