================================== spectra-SURVEY-PROGRAM-PIXNUM.fits ================================== :Summary: DESI spectra grouped by nested healpix number :Naming Convention: ``spectra-SURVEY-PROGRAM-PIXNUM.fits``, where ``SURVEY`` is *e.g.* ``main`` or ``sv1``, ``PROGRAM`` is *e.g.* ``bright`` or ``dark`` and ``PIXNUM`` is the HEALPixel number. :Regex: ``spectra-(cmx|main|special|sv1|sv2|sv3)-(backup|bright|dark|other)-[0-9]+\.fits`` :File Type: FITS, 408 MB Spectra files contain non-coadded spectra for multiple targets observed on multiple individual exposures and cameras. The format can contain any arbitrary set of targets, though the standard DESI spectroscopic pipeline outputs are grouped either by a single petal of a given tile, or all targets on a single healpix. Tile-based spectra can be grouped in multiple ways across exposures and nights; see the top-level :doc:`SPECPROD/tiles/ <../../../index>` description for an overview of the per-tile GROUPTYPE and GROUPID options. Healpix-based spectra are grouped by SURVEY and PROGRAM. Science analyses may release spectra in other groups, e.g. all the spectra selected for a particular analysis. Please see :doc:`coadd files ` for a coadded version of the same spectra in a very similar format. The FIBERMAP table contains metadata about each target, with one row per target per exposure. The corresponding SCORES table contains quantities measured from the spectra, also with one row per target per exposure. The spectra themselves are in a set of image HDUs for the FLUX, IVAR (inverse variance), MASK, and spectral RESOLUTION, each prefixed with a spectrograph camera name, e.g. B, R, or Z for DESI, though the format in general could support other numbers and names of cameras for other instruments. A row of each image HDU correponds to the target from the same row index of the FIBERMAP and SCORES HDUs. See the end of :doc:`tile-based spectra ` for examples of reading this file format. Note: the table below is the order in which these HDUs appear in DESI spectroscopic pipeline output, but the order is arbitrary and they should be read by name not by number. Contents ======== ====== ============ ======== =================== Number EXTNAME Type Contents ====== ============ ======== =================== HDU00_ IMAGE Empty HDU01_ FIBERMAP BINTABLE fibermap table HDU02_ SCORES BINTABLE scores table HDU03_ B_WAVELENGTH IMAGE Wavelength array of b-channel spectra HDU04_ B_FLUX IMAGE Flux of b-channel spectra HDU05_ B_IVAR IMAGE Inverse variance of b-channel spectra HDU06_ B_MASK BINTABLE Mask of b-channel spectra HDU07_ B_RESOLUTION IMAGE Resolution matrices of b-channel spectra HDU08_ R_WAVELENGTH IMAGE Wavelength array of r-channel spectra HDU09_ R_FLUX IMAGE Flux of r-channel spectra HDU10_ R_IVAR IMAGE Inverse variance of r-channel spectra HDU11_ R_MASK BINTABLE Mask of r-channel spectra HDU12_ R_RESOLUTION IMAGE Resolution matrices of r-channel spectra HDU13_ Z_WAVELENGTH IMAGE Wavelength array of z-channel spectra HDU14_ Z_FLUX IMAGE Flux of z-channel spectra HDU15_ Z_IVAR IMAGE Inverse variance of z-channel spectra HDU16_ Z_MASK BINTABLE Mask of z-channel spectra HDU17_ Z_RESOLUTION IMAGE Resolution matrices of z-channel spectra ====== ============ ======== =================== FITS Header Units ================= HDU00 ----- HEALPixel keywords. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ======== ================ ==== ============================================== KEY Example Value Type Comment ======== ================ ==== ============================================== SPGRP healpix str Spectral grouping method SPGRPVAL 26371 int Grouping value = healpixel number HPXPIXEL 26371 int Nested nside=64 healpixel number HPXNSIDE 64 int Healpix nside HPXNEST True str Healpix nested? (vs. ring) SURVEY main str DESI Survey (sv1, sv3, main...) PROGRAM bright str DESI Program (dark, bright, ...) CHECKSUM 8DPU9BMR8BMR8BMR str HDU checksum updated 2021-07-19T17:59:29 DATASUM 0 str data unit checksum updated 2021-07-19T17:59:29 ======== ================ ==== ============================================== Empty HDU. HDU01 ----- EXTNAME = FIBERMAP Fibermap table with per-target metdata. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ======== ================ ==== ============================================== KEY Example Value Type Comment ======== ================ ==== ============================================== NAXIS1 413 int Width of table in bytes NAXIS2 1031 int Number of rows in table CHECKSUM U9Fia89iV8Cia89i str HDU checksum DATASUM 3589169610 str data unit checksum ======== ================ ==== ============================================== Required Data Table Columns ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Propagated from the FIBERMAP HDU of the input :doc:`cframe files `. .. rst-class:: columns ===================== ======= ============ ========================================================================================================================= Name Type Units Description ===================== ======= ============ ========================================================================================================================= TARGETID int64 Unique DESI target ID PETAL_LOC int16 Petal location [0-9] DEVICE_LOC int32 Device location on focal plane [0-523] LOCATION int64 Location on the focal plane PETAL_LOC*1000 + DEVICE_LOC FIBER int32 Fiber ID on the CCDs [0-4999] FIBERSTATUS int32 Fiber status mask. 0=good TARGET_RA float64 deg Barycentric right ascension in ICRS TARGET_DEC float64 deg Barycentric declination in ICRS PMRA float32 mas yr^-1 proper motion in the +RA direction (already including cos(dec)) PMDEC float32 mas yr^-1 Proper motion in the +Dec direction REF_EPOCH float32 yr Reference epoch for Gaia/Tycho astrometry. Typically 2015.5 for Gaia LAMBDA_REF float32 Angstrom Requested wavelength at which targets should be centered on fibers FA_TARGET int64 Targeting bit internally used by fiberassign (linked with FA_TYPE) FA_TYPE binary Fiberassign internal target type (science, standard, sky, safe, suppsky) OBJTYPE char[3] Object type: TGT, SKY, NON, BAD FIBERASSIGN_X float32 mm Fiberassign expected CS5 X location on focal plane FIBERASSIGN_Y float32 mm Fiberassign expected CS5 Y location on focal plane PRIORITY int32 Target current priority SUBPRIORITY float64 Random subpriority [0-1) to break assignment ties OBSCONDITIONS int32 Bitmask of allowed observing conditions RELEASE int16 Imaging surveys release ID BRICKID int32 Brick ID from tractor input BRICK_OBJID int32 Imaging Surveys OBJID on that brick MORPHTYPE char[4] Imaging Surveys morphological type from Tractor FLUX_G float32 nanomaggy Flux in the Legacy Survey g-band (AB) FLUX_R float32 nanomaggy Flux in the Legacy Survey r-band (AB) FLUX_Z float32 nanomaggy Flux in the Legacy Survey z-band (AB) FLUX_IVAR_G float32 nanomaggy^-2 Inverse variance of FLUX_G (AB) FLUX_IVAR_R float32 nanomaggy^-2 Inverse variance of FLUX_R (AB) FLUX_IVAR_Z float32 nanomaggy^-2 Inverse variance of FLUX_Z (AB) MASKBITS int16 Bitwise mask from the imaging indicating potential issue or blending REF_ID int64 Tyc1*1,000,000+Tyc2*10+Tyc3 for Tycho-2; “sourceid” for Gaia DR2 REF_CAT char[2] Reference catalog source for star: “T2” for Tycho-2, “G2” for Gaia DR2, “L2” for the SGA, empty otherwise GAIA_PHOT_G_MEAN_MAG float32 mag Gaia G band magnitude GAIA_PHOT_BP_MEAN_MAG float32 mag Gaia BP band magnitude GAIA_PHOT_RP_MEAN_MAG float32 mag Gaia RP band magnitude PARALLAX float32 mas Reference catalog parallax BRICKNAME char[8] Brick name from tractor input EBV float32 mag Galactic extinction E(B-V) reddening from SFD98 FLUX_W1 float32 nanomaggy WISE flux in W1 (AB) FLUX_W2 float32 nanomaggy WISE flux in W2 (AB) FLUX_IVAR_W1 float32 nanomaggy^-2 Inverse variance of FLUX_W1 (AB) FLUX_IVAR_W2 float32 nanomaggy^-2 Inverse variance of FLUX_W2 (AB) FIBERFLUX_G float32 nanomaggy Predicted g-band flux within a fiber of diameter 1.5 arcsec from this object in 1 arcsec Gaussian seeing FIBERFLUX_R float32 nanomaggy Predicted r-band flux within a fiber of diameter 1.5 arcsec from this object in 1 arcsec Gaussian seeing FIBERFLUX_Z float32 nanomaggy Predicted z-band flux within a fiber of diameter 1.5 arcsec from this object in 1 arcsec Gaussian seeing FIBERTOTFLUX_G float32 nanomaggy Predicted g-band flux within a fiber of diameter 1.5 arcsec from all sources at this location in 1 arcsec Gaussian seeing FIBERTOTFLUX_R float32 nanomaggy Predicted r-band flux within a fiber of diameter 1.5 arcsec from all sources at this location in 1 arcsec Gaussian seeing FIBERTOTFLUX_Z float32 nanomaggy Predicted z-band flux within a fiber of diameter 1.5 arcsec from all sources at this location in 1 arcsec Gaussian seeing SERSIC float32 Power-law index for the Sersic profile model (MORPHTYPE=”SER”) SHAPE_R float32 arcsec Half-light radius of galaxy model (>0) SHAPE_E1 float32 Ellipticity component 1 of galaxy model for galaxy type MORPHTYPE SHAPE_E2 float32 Ellipticity component 2 of galaxy model for galaxy type MORPHTYPE PHOTSYS char[1] 'N' for the MzLS/BASS photometric system, 'S' for DECaLS PRIORITY_INIT int64 Target initial priority from target selection bitmasks and OBSCONDITIONS NUMOBS_INIT int64 Initial number of observations for target calculated across target selection bitmasks and OBSCONDITIONS SV1_DESI_TARGET [1]_ int64 DESI (dark time program) target selection bitmask for SV1 SV1_BGS_TARGET [1]_ int64 BGS (bright time program) target selection bitmask for SV1 SV1_MWS_TARGET [1]_ int64 MWS (bright time program) target selection bitmask for SV1 SV1_SCND_TARGET [1]_ int64 Secondary target selection bitmask for SV1 DESI_TARGET int64 DESI (dark time program) target selection bitmask BGS_TARGET int64 BGS (Bright Galaxy Survey) target selection bitmask MWS_TARGET int64 Milky Way Survey targeting bits SCND_TARGET int64 Target selection bitmask for secondary programs PLATE_RA float64 deg Barycentric Right Ascension in ICRS to be used by PlateMaker PLATE_DEC float64 deg Barycentric Declination in ICRS to be used by PlateMaker NUM_ITER int64 Number of positioner iterations FIBER_X float64 mm CS5 X location requested by PlateMaker FIBER_Y float64 mm CS5 Y location requested by PlateMaker DELTA_X float64 mm CS5 X requested minus actual position DELTA_Y float64 mm CS5 Y requested minus actual position FIBER_RA float64 deg RA of actual fiber position FIBER_DEC float64 deg DEC of actual fiber position EXPTIME float64 s Length of time shutter was open PSF_TO_FIBER_SPECFLUX float64 fraction of light from point-like source captured by 1.5 arcsec diameter fiber given atmospheric seeing NIGHT int32 EXPID int32 DESI Exposure ID number MJD float64 Modified Julian Date when shutter was opened for this exposure TILEID int32 Unique DESI tile ID ===================== ======= ============ ========================================================================================================================= .. [1] Optional HDU02 ----- EXTNAME = SCORES Scores / metrics measured from the spectra for use in QA and systematics studies. These are propagated from the input :doc:`cframe SCORES HDU `. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ======================= KEY Example Value Type Comment ====== ============= ==== ======================= NAXIS1 488 int width of table in bytes NAXIS2 1031 int number of rows in table ====== ============= ==== ======================= Required Data Table Columns ~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. rst-class:: columns ===================== ======= ===== ============================================================ Name Type Units Description ===================== ======= ===== ============================================================ TARGETID int64 Unique DESI target ID SUM_RAW_COUNT_B float64 Sum of raw counts in B camera MEDIAN_RAW_COUNT_B float64 Median of raw counts in B camera MEDIAN_RAW_SNR_B float64 Median(raw signal/noise) in B camera SUM_FFLAT_COUNT_B float64 Sum of fiber-flatfielded counts B camera MEDIAN_FFLAT_COUNT_B float64 Median of fiber-flatfielded counts in B camera MEDIAN_FFLAT_SNR_B float64 Median(S/N) of fiberflatfielded counts in B camera SUM_SKYSUB_COUNT_B float64 Sum of sky-subtracted counts in B camera MEDIAN_SKYSUB_COUNT_B float64 Median of sky-subtracted counts in B camera MEDIAN_SKYSUB_SNR_B float64 Median(S/N) of sky-subtracted counts in B camera SUM_CALIB_COUNT_B float64 Sum of calibrated flux in B camera MEDIAN_CALIB_COUNT_B float64 Median of calibrated flux in B camera MEDIAN_CALIB_SNR_B float64 Median(S/N) of calibrated flux in B camera TSNR2_GPBDARK_B float64 template (S/N)^2 for dark targets in guider pass band on B TSNR2_ELG_B float64 ELG B template (S/N)^2 TSNR2_GPBBRIGHT_B float64 template (S/N)^2 for bright targets in guider pass band on B TSNR2_LYA_B float64 LYA B template (S/N)^2 TSNR2_BGS_B float64 BGS B template (S/N)^2 TSNR2_GPBBACKUP_B float64 TSNR2_QSO_B float64 QSO B template (S/N)^2 TSNR2_LRG_B float64 LRG B template (S/N)^2 SUM_RAW_COUNT_R float64 Sum of raw counts in R camera MEDIAN_RAW_COUNT_R float64 Median of raw counts in R camera MEDIAN_RAW_SNR_R float64 Median(raw signal/noise) in R camera SUM_FFLAT_COUNT_R float64 Sum of fiber-flatfielded counts R camera MEDIAN_FFLAT_COUNT_R float64 Median of fiber-flatfielded counts in R camera MEDIAN_FFLAT_SNR_R float64 Median(S/N) of fiberflatfielded counts in R camera SUM_SKYSUB_COUNT_R float64 Sum of sky-subtracted counts in R camera MEDIAN_SKYSUB_COUNT_R float64 Median of sky-subtracted counts in R camera MEDIAN_SKYSUB_SNR_R float64 Median(S/N) of sky-subtracted counts in R camera SUM_CALIB_COUNT_R float64 Sum of calibrated flux in R camera MEDIAN_CALIB_COUNT_R float64 Median of calibrated flux in R camera MEDIAN_CALIB_SNR_R float64 Median(S/N) of calibrated flux in R camera TSNR2_GPBDARK_R float64 template (S/N)^2 for dark targets in guider pass band on R TSNR2_ELG_R float64 ELG R template (S/N)^2 TSNR2_GPBBRIGHT_R float64 template (S/N)^2 for bright targets in guider pass band on R TSNR2_LYA_R float64 LYA R template (S/N)^2 TSNR2_BGS_R float64 BGS R template (S/N)^2 TSNR2_GPBBACKUP_R float64 TSNR2_QSO_R float64 QSO R template (S/N)^2 TSNR2_LRG_R float64 LRG R template (S/N)^2 SUM_RAW_COUNT_Z float64 Sum of raw counts in Z camera MEDIAN_RAW_COUNT_Z float64 Median of raw counts in Z camera MEDIAN_RAW_SNR_Z float64 Median(raw signal/noise) in Z camera SUM_FFLAT_COUNT_Z float64 Sum of fiber-flatfielded counts Z camera MEDIAN_FFLAT_COUNT_Z float64 Median of fiber-flatfielded counts in Z camera MEDIAN_FFLAT_SNR_Z float64 Median(S/N) of fiberflatfielded counts in Z camera SUM_SKYSUB_COUNT_Z float64 Sum of sky-subtracted counts in Z camera MEDIAN_SKYSUB_COUNT_Z float64 Median of sky-subtracted counts in Z camera MEDIAN_SKYSUB_SNR_Z float64 Median(S/N) of sky-subtracted counts in Z camera SUM_CALIB_COUNT_Z float64 Sum of calibrated flux in Z camera MEDIAN_CALIB_COUNT_Z float64 Median of calibrated flux in Z camera MEDIAN_CALIB_SNR_Z float64 Median(S/N) of calibrated flux in Z camera TSNR2_GPBDARK_Z float64 template (S/N)^2 for dark targets in guider pass band on Z TSNR2_ELG_Z float64 ELG Z template (S/N)^2 TSNR2_GPBBRIGHT_Z float64 template (S/N)^2 for bright targets in guider pass band on Z TSNR2_LYA_Z float64 LYA Z template (S/N)^2 TSNR2_BGS_Z float64 BGS Z template (S/N)^2 TSNR2_GPBBACKUP_Z float64 TSNR2_QSO_Z float64 QSO Z template (S/N)^2 TSNR2_LRG_Z float64 LRG Z template (S/N)^2 ===================== ======= ===== ============================================================ HDU03 ----- EXTNAME = B_WAVELENGTH 1D array of B-camera wavelengths in Angstrom, in vacuum (not in air), in the rest frame of the solar system barycenter. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ===================== KEY Example Value Type Comment ====== ============= ==== ===================== NAXIS1 2751 int Number of wavelengths BUNIT Angstrom str ====== ============= ==== ===================== Data: FITS image [float64, 2751] HDU04 ----- EXTNAME = B_FLUX 2D array of calibrated spectral flux of dimension ``[nspec, nwave]`` in units of 1e-17 erg / (s cm2 Angstrom). ``nspec`` is the number of fibers per camera. ``nwave`` in the length of the wavelength array. The spectra of all fibers share the same wavelength grid, given in HDU B_WAVELENGTH. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============================ ==== ===================== KEY Example Value Type Comment ====== ============================ ==== ===================== NAXIS1 2751 int ``nwave`` number of wavelengths NAXIS2 1031 int ``nspec`` number of spectra BUNIT 10**-17 erg/(s cm2 Angstrom) str ====== ============================ ==== ===================== Data: FITS image [float32, 2751x1031] HDU05 ----- EXTNAME = B_IVAR Inverse variance of flux (1/sigma^2) in units of (10^{-17} erg/s/cm2/A)^-2. Uncertainties comprise statistical uncertainties from the error propagation of the initial CCD pixel variance, the calibration uncertainties, plus an additional term on bright sky lines to account for the imperfect sky subtraction. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ================================= ==== ===================== KEY Example Value Type Comment ====== ================================= ==== ===================== NAXIS1 2751 int ``nwave`` number of wavelengths NAXIS2 1031 int ``nspec`` number of spectra BUNIT 10**+34 (s2 cm4 Angstrom2) / erg2 str ====== ================================= ==== ===================== Data: FITS image [float32, 2751x1031] HDU06 ----- EXTNAME = B_MASK Mask of spectral data; 0=good. See the :doc:`bitmask documentation ` page for the definition of the bits. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ========================================== KEY Example Value Type Comment ====== ============= ==== ========================================== NAXIS1 2751 int ``nwave`` number of wavelengths NAXIS2 1031 int ``nspec`` number of spectra BZERO 2147483648 int offset data range to that of unsigned long BSCALE 1 int default scaling factor ====== ============= ==== ========================================== Data: FITS image [int32 (compressed), 2751x1031] HDU07 ----- EXTNAME = B_RESOLUTION Resolution matrix stored as a 3D sparse matrix, modeling the per-fiber non-Gaussian effective line-spread-function resolution. See the :doc:`frame RESOLUTION HDU ` documentation for details about using this HDU. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ===================== KEY Example Value Type Comment ====== ============= ==== ===================== NAXIS1 2751 int ``nwave`` number of wavelengths NAXIS2 11 int ``ndiag`` number of diagonals NAXIS3 1031 int ``nspec`` number of spectra ====== ============= ==== ===================== Data: FITS image [float32, 2751x11x1031] A sparse resolution matrix may be created for spectrum ``i`` with:: from desispec.resolution import Resolution R = Resolution(data[i]) Or using lower-level scipy.sparse matrices:: import scipy.sparse import numpy as np nspec, ndiag, nwave = data.shape offsets = ndiag//2 - np.arange(ndiag, dtype=int) R = scipy.sparse.dia_matrix((data[i], offsets), shape=(nwave, nwave)) HDU08 ----- EXTNAME = R_WAVELENGTH 1D array of R-camera wavelengths in Angstrom, in vacuum (not in air), in the rest frame of the solar system barycenter. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ===================== KEY Example Value Type Comment ====== ============= ==== ===================== NAXIS1 2326 int number of wavelengths BUNIT Angstrom str ====== ============= ==== ===================== Data: FITS image [float64, 2326] HDU09 ----- EXTNAME = R_FLUX 2D array of calibrated spectral flux of dimension ``[nspec, nwave]`` in units of 1e-17 erg / (s cm2 Angstrom). ``nspec`` is the number of fibers per camera. ``nwave`` in the length of the wavelength array. The spectra of all fibers share the same wavelength grid, given in HDU R_WAVELENGTH. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============================ ==== ===================== KEY Example Value Type Comment ====== ============================ ==== ===================== NAXIS1 2326 int ``nwave`` number of wavelengths NAXIS2 1031 int ``nspec`` number of spectra BUNIT 10**-17 erg/(s cm2 Angstrom) str ====== ============================ ==== ===================== Data: FITS image [float32, 2326x1031] HDU10 ----- EXTNAME = R_IVAR Inverse variance of flux (1/sigma^2) in units of (10^{-17} erg/s/cm2/A)^-2. Uncertainties comprise statistical uncertainties from the error propagation of the initial CCD pixel variance, the calibration uncertainties, plus an additional term on bright sky lines to account for the imperfect sky subtraction. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ================================= ==== ===================== KEY Example Value Type Comment ====== ================================= ==== ===================== NAXIS1 2326 int ``nwave`` number of wavelengths NAXIS2 1031 int ``nspec`` number of spectra BUNIT 10**+34 (s2 cm4 Angstrom2) / erg2 str ====== ================================= ==== ===================== Data: FITS image [float32, 2326x1031] HDU11 ----- EXTNAME = R_MASK Mask of spectral data; 0=good. See the :doc:`bitmask documentation ` page for the definition of the bits. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ========================================== KEY Example Value Type Comment ====== ============= ==== ========================================== NAXIS1 2326 int ``nwave`` number of wavelengths NAXIS2 1031 int ``nspec`` number of spectra BZERO 2147483648 int offset data range to that of unsigned long BSCALE 1 int default scaling factor ====== ============= ==== ========================================== Data: FITS image [int32 (compressed), 2326x1031] HDU12 ----- EXTNAME = R_RESOLUTION Resolution matrix stored as a 3D sparse matrix, modeling the per-fiber non-Gaussian effective line-spread-function resolution. See the :doc:`frame RESOLUTION HDU ` documentation for details about using this HDU. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ===================== KEY Example Value Type Comment ====== ============= ==== ===================== NAXIS1 2326 int length of data axis 1 NAXIS2 11 int length of data axis 2 NAXIS3 1031 int length of data axis 3 ====== ============= ==== ===================== Data: FITS image [float32, 2326x11x1031] HDU13 ----- EXTNAME = Z_WAVELENGTH 1D array of Z-camera wavelengths in Angstrom, in vacuum (not in air), in the rest frame of the solar system barycenter. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ===================== KEY Example Value Type Comment ====== ============= ==== ===================== NAXIS1 2881 int ``nwave`` number of wavelengths BUNIT Angstrom str ====== ============= ==== ===================== Data: FITS image [float64, 2881] HDU14 ----- EXTNAME = Z_FLUX 2D array of calibrated spectral flux of dimension ``[nspec, nwave]`` in units of 1e-17 erg / (s cm2 Angstrom). ``nspec`` is the number of fibers per camera. ``nwave`` in the length of the wavelength array. The spectra of all fibers share the same wavelength grid, given in HDU Z_WAVELENGTH. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============================ ==== ===================== KEY Example Value Type Comment ====== ============================ ==== ===================== NAXIS1 2881 int ``nwave`` number of wavelengths NAXIS2 1031 int ``nspec`` number of spectra BUNIT 10**-17 erg/(s cm2 Angstrom) str ====== ============================ ==== ===================== Data: FITS image [float32, 2881x1031] HDU15 ----- EXTNAME = Z_IVAR Inverse variance of flux (1/sigma^2) in units of (10^{-17} erg/s/cm2/A)^-2. Uncertainties comprise statistical uncertainties from the error propagation of the initial CCD pixel variance, the calibration uncertainties, plus an additional term on bright sky lines to account for the imperfect sky subtraction. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ================================= ==== ===================== KEY Example Value Type Comment ====== ================================= ==== ===================== NAXIS1 2881 int ``nwave`` number of wavelengths NAXIS2 1031 int ``nspec`` number of spectra BUNIT 10**+34 (s2 cm4 Angstrom2) / erg2 str ====== ================================= ==== ===================== Data: FITS image [float32, 2881x1031] HDU16 ----- EXTNAME = Z_MASK Mask of spectral data; 0=good. See the :doc:`bitmask documentation ` page for the definition of the bits. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ========================================== KEY Example Value Type Comment ====== ============= ==== ========================================== NAXIS1 2881 int ``nwave`` number of wavelengths NAXIS2 1031 int ``nspec`` number of spectra BZERO 2147483648 int offset data range to that of unsigned long BSCALE 1 int default scaling factor ====== ============= ==== ========================================== Data: FITS image [int32 (compressed), 2881x1031] HDU17 ----- EXTNAME = Z_RESOLUTION Diagonals of z-channel resolution matrix. Resolution matrix stored as a 3D sparse matrix, modeling the per-fiber non-Gaussian effective line-spread-function resolution. See the :doc:`frame RESOLUTION HDU ` documentation for details about using this HDU. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ====== ============= ==== ===================== KEY Example Value Type Comment ====== ============= ==== ===================== NAXIS1 2881 int ``nwave`` number of wavelengths NAXIS2 11 int ``ndiag`` number of diagonals NAXIS3 1031 int ``nspec`` number of spectra ====== ============= ==== ===================== Data: FITS image [float32, 2881x11x1031] Notes and Examples ================== The format supports arbitrary channel names as long as for each channel {X} there is a set of HDUs named {X}_WAVELENGTH, {X}_FLUX, {X}_IVAR, {X}_MASK, {X}_RESOLUTION. For the SURVEY=cmx m33 tile (TILEID=80615) tile and all the SURVEY=sv1 tiles (except TILEID=80971-80976, the dc3r2 ones), proper-motion correction was applied at the :doc:`fiberassign ` design step; thus the following columns can have different values than in the :doc:`desitarget products `: ``TARGET_RA``, ``TARGET_DEC``, ``REF_EPOCH``, ``PLATE_RA``, ``PLATE_DEC``, and ``PLATE_REF_EPOCH``. For targets with a non-zero proper motion, ``FIBER_RA`` and ``FIBER_DEC`` refer to the position at the reference epoch (but note that the proper-motion correction has been applied at the time of the observation, it is just not recorded in ``FIBER_RA`` and ``FIBER_DEC``).