simspec-EXPID.fits¶

Summary:: Input spectra to simulate with pixsim.
Naming Convention:: simspec-{EXPID}.fits, where {EXPID} is the 8-digit exposure ID.
Regex:: simspec-[0-9]{8}\.fits
File Type:: FITS, 2 GB

Contents¶

Number	EXTNAME	Type	Contents
HDU0	WAVE	IMAGE	Input wavelength vector
HDU1	FLUX	IMAGE	Input object spectra
HDU2	SKYFLUX	IMAGE	Input sky flux
HDU3	WAVE_B	IMAGE	Input wavelengths b-channel
HDU4	PHOT_B	IMAGE	Input object photons b-channel
HDU5	SKYPHOT_B	IMAGE	Input sky photons b-channel
HDU6	WAVE_R	IMAGE	Input wavelengths r-channel
HDU7	PHOT_R	IMAGE	Input object photons r-channel
HDU8	SKYPHOT_R	IMAGE	Input sky photons r-channel
HDU9	WAVE_Z	IMAGE	Input wavelengths z-channel
HDU10	PHOT_Z	IMAGE	Input object photons z-channel
HDU11	SKYPHOT_Z	IMAGE	Input sky photons z-channel
HDU12	TRUTH	BINTABLE	Truth metadata about the targets
HDU13	FIBERMAP	BINTABLE	Fibermap
HDU14	OBSCONDITIONS	BINTABLE	Observing conditions metadata
HDU15	TRUTH_BGS	BINTABLE	BGS-specific truth metadata
HDU16	TRUTH_ELG	BINTABLE	ELG-specific truth metadata
HDU17	TRUTH_STAR	BINTABLE	STAR-specific truth metadata
HDU18	TRUTH_WD	BINTABLE	WD-specific truth metadata

FITS Header Units¶

HDU0¶

EXTNAME = WAVE

Input wavelength vector. Simulation inputs are stored in header cards.

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type	Comment
NAXIS1	32001	int	Number of wavelength pixels
NIGHT	YYYYMMDD	str	Night of observation
EXPID	0	int	DESI exposure ID
TILEID	1	int	DESI tile ID
PROGRAM	dark	str	Program name
FLAVOR	science	str	Flavor of observation (arc, flat, science)
TELRA	0.0	float	Telescope pointing RA [degrees]
TELDEC	0.0	float	Telescope pointing Dec [degrees]
AIRMASS	1.0	float	Airmass at middle of exposure
EXPTIME	1000.0	float	Exposure time [sec]
SEEING	1.080542206764221	float	Seeing FWHM [arcsec]
MOONFRAC	0.4083473802955095	float	Moon illumination fraction 0-1; 1=full
MOONALT	-4.92578905244666	float	Moon altitude [degrees]
MOONSEP	135.3911422523808	float	Moon:tile separation angle [degrees]
DATE-OBS	2017-06-15T22:00:00	str	Start of exposure
MJD	58925.38986146489	float
SNR2FRAC	0.501188337802887	float
TRANSP	0.9904059171676636	float
SKY	1.0	float
RA	150.73	float
DEC	30.52	float
PASS	4	int
DOSVER	SIM	str
FEEVER	SIM	str
BUNIT	Angstrom	str	Wavelength unit
AIRORVAC	vac	str	Vacuum wavelengths

Data: FITS image [float64, 32001]

HDU1¶

EXTNAME = FLUX

Input object spectra.

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type	Comment
NAXIS1	32001	int
NAXIS2	5000	int
BUNIT	10**-17 erg/(s cm2 Angstrom)	str	Flux unit

Data: FITS image [float32, 32001x5000]

HDU2¶

EXTNAME = SKYFLUX

Input sky flux.

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type	Comment
NAXIS1	32001	int
NAXIS2	5000	int
BUNIT	10**-17 erg/(s cm2 Angstrom)	str	Flux unit

Data: FITS image [float32, 32001x5000]

HDU3¶

EXTNAME = WAVE_B

Input wavelengths b-channel [Angstrom].

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type	Comment
NAXIS1	11901	int

Data: FITS image [float64, 11901]

HDU4¶

EXTNAME = PHOT_B

Input object photons b-channel.

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type
NAXIS1	11901	int
NAXIS2	5000	int
BUNIT	photon	str

Data: FITS image [float32, 11901x5000]

HDU5¶

EXTNAME = SKYPHOT_B

Input object photons b-channel.

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type
NAXIS1	11901	int
NAXIS2	5000	int
BUNIT	photon	str

Data: FITS image [float32, 11901x5000]

HDU6¶

EXTNAME = WAVE_R

Input wavelengths r-channel [Angstrom].

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type	Comment
NAXIS1	10581	int

Data: FITS image [float64, 10581]

HDU7¶

EXTNAME = PHOT_R

Input object photons r-channel.

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type
NAXIS1	10581	int
NAXIS2	5000	int
BUNIT	photon	str

Data: FITS image [float32, 10581x5000]

HDU8¶

EXTNAME = SKYPHOT_R

Input object photons r-channel.

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type
NAXIS1	10581	int
NAXIS2	5000	int
BUNIT	photon	str

Data: FITS image [float32, 10581x5000]

HDU9¶

EXTNAME = WAVE_Z

Input wavelengths z-channel [Angstrom].

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type	Comment
NAXIS1	11996	int

Data: FITS image [float64, 11996]

HDU10¶

EXTNAME = PHOT_Z

Input object photons z-channel.

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type
NAXIS1	11996	int
NAXIS2	5000	int
BUNIT	photon	str

Data: FITS image [float32, 11996x5000]

HDU11¶

EXTNAME = SKYPHOT_Z

Input object photons z-channel.

Required Header Keywords¶

Required Header Keywords Table

KEY	Value	Type
NAXIS1	11996	int
NAXIS2	5000	int
BUNIT	photon	str

Data: FITS image [float32, 11996x5000]

HDU12¶

EXTNAME = TRUTH

Required Header Keywords¶

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	109	int	length of dimension 1
NAXIS2	5000	int	length of dimension 2

Required Data Table Columns¶

Name	Type	Units	Description
TARGETID	int64		Unique DESI target ID
MOCKID	int64		TODO: description needed
TRUEZ	float32		TODO: description needed
TRUESPECTYPE	char[10]		TODO: description needed
TEMPLATETYPE	char[10]		TODO: description needed
TEMPLATESUBTYPE	char[10]		TODO: description needed
TEMPLATEID	int32		TODO: description needed
SEED	int64		TODO: description needed
MAG	float32		TODO: description needed
MAGFILTER	char[15]		TODO: description needed
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_W1	float32	nanomaggy	WISE flux in W1 (AB)
FLUX_W2	float32	nanomaggy	WISE flux in W2 (AB)
FLUX_W3	float32		TODO: description needed
FLUX_W4	float32		TODO: description needed

HDU13¶

EXTNAME = FIBERMAP

Map of which fibers are on which targets. See See DESI_SPECTRO_DATA/NIGHT/EXPID/fibermap-EXPID.

Required Header Keywords¶

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	334	int	length of dimension 1
NAXIS2	5000	int	length of dimension 2
NIGHT	20200316	str	Night of observation YEARMMDD
EXPID	10	int	DESI exposure ID
TILEID	28408	int	DESI tile ID
PROGRAM	GRAY	str	program [dark, bright, …]
FLAVOR	science	str	Flavor [arc, flat, science, zero, …]
TELRA	150.73	float	Telescope pointing RA [degrees]
TELDEC	30.52	float	Telescope pointing dec [degrees]
AIRMASS	1.34693655042678	float	Airmass at middle of exposure
EXPTIME	757.8536680645208	float	Exposure time [sec]
SEEING	1.080542206764221	float	Seeing FWHM [arcsec]
MOONFRAC	0.4083473802955095	float	Moon illumination fraction 0-1; 1=full
MOONALT	-4.92578905244666	float	Moon altitude [degrees]
MOONSEP	135.3911422523808	float	Moon:tile separation angle [degrees]
DATE-OBS	2020-03-17T09:21:24.031	str	Start of exposure

Required Data Table Columns¶

Name	Type	Units	Description
TARGETID	int64		Unique DESI target ID
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
SECONDARY_TARGET	int64		TODO: description needed
TARGET_RA	float64	deg	Barycentric right ascension in ICRS
TARGET_DEC	float64	deg	Barycentric declination in ICRS
TARGET_RA_IVAR	float64	deg-2	TODO: description needed
TARGET_DEC_IVAR	float64	deg-2	TODO: description needed
BRICKID	int64		Brick ID from tractor input
BRICK_OBJID	int64		Imaging Surveys OBJID on that brick
MORPHTYPE	char[4]		Imaging Surveys morphological type from Tractor
PRIORITY	int32		Target current priority
SUBPRIORITY	float64		Random subpriority [0-1) to break assignment ties
REF_ID	int64		Tyc11,000,000+Tyc210+Tyc3 for Tycho-2; `sourceid` for Gaia DR2
PMRA	float32	10**-3 arcsec yr-1	proper motion in the +RA direction (already including cos(dec))
PMDEC	float32	10**-3 arcsec yr-1	Proper motion in the +Dec direction
REF_EPOCH	float32	yr	Reference epoch for Gaia/Tycho astrometry. Typically 2015.5 for Gaia
PMRA_IVAR	float32	10**+6 arcsec-2 yr2	Inverse variance of PMRA
PMDEC_IVAR	float32	10**+6 arcsec-2 yr2	Inverse variance of PMDEC
RELEASE	int16		Imaging surveys release ID
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_W1	float32	nanomaggy	WISE flux in W1 (AB)
FLUX_W2	float32	nanomaggy	WISE flux in W2 (AB)
FLUX_IVAR_G	float32	nanomaggies**-2	Inverse variance of FLUX_G (AB)
FLUX_IVAR_R	float32	nanomaggies**-2	Inverse variance of FLUX_R (AB)
FLUX_IVAR_Z	float32	nanomaggies**-2	Inverse variance of FLUX_Z (AB)
FLUX_IVAR_W1	float32	nanomaggies**-2	Inverse variance of FLUX_W1 (AB)
FLUX_IVAR_W2	float32	nanomaggies**-2	Inverse variance of FLUX_W2 (AB)
FIBERFLUX_G	float32	nanomaggies	Predicted g-band flux within a fiber of diameter 1.5 arcsec from this object in 1 arcsec Gaussian seeing
FIBERFLUX_R	float32	nanomaggies	Predicted r-band flux within a fiber of diameter 1.5 arcsec from this object in 1 arcsec Gaussian seeing
FIBERFLUX_Z	float32	nanomaggies	Predicted z-band flux within a fiber of diameter 1.5 arcsec from this object in 1 arcsec Gaussian seeing
FIBERFLUX_W1	float32	nanomaggies	TODO: description needed
FIBERFLUX_W2	float32	nanomaggies	TODO: description needed
FIBERTOTFLUX_G	float32	nanomaggies	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	nanomaggies	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	nanomaggies	Predicted z-band flux within a fiber of diameter 1.5 arcsec from all sources at this location in 1 arcsec Gaussian seeing
FIBERTOTFLUX_W1	float32	nanomaggies	TODO: description needed
FIBERTOTFLUX_W2	float32	nanomaggies	TODO: description needed
MW_TRANSMISSION_G	float32		Milky Way dust transmission in LS g-band
MW_TRANSMISSION_R	float32		Milky Way dust transmission in LS r-band
MW_TRANSMISSION_Z	float32		Milky Way dust transmission in LS z-band
EBV	float32	mag	Galactic extinction E(B-V) reddening from SFD98
PHOTSYS	char[1]		‘N’ for the MzLS/BASS photometric system, ‘S’ for DECaLS
OBSCONDITIONS	int32		Bitmask of allowed observing conditions
NUMOBS_INIT	int64		Initial number of observations for target calculated across target selection bitmasks and OBSCONDITIONS
PRIORITY_INIT	int64		Target initial priority from target selection bitmasks and OBSCONDITIONS
NUMOBS_MORE	int32		Number of additional observations needed
HPXPIXEL	int64		HEALPixel containing this location at NSIDE=64 in the NESTED scheme
FIBER	int32		Fiber ID on the CCDs [0-4999]
PETAL_LOC	int32		Petal location [0-9]
DEVICE_LOC	int32		Device location on focal plane [0-523]
LOCATION	int32		Location on the focal plane PETAL_LOC*1000 + DEVICE_LOC
FIBERSTATUS	int32		Fiber status mask. 0=good
OBJTYPE	char[3]		Object type: TGT, SKY, NON, BAD
LAMBDA_REF	float32	Angstrom	Requested wavelength at which targets should be centered on fibers
FIBERASSIGN_X	float32	mm	Fiberassign expected CS5 X location on focal plane
FIBERASSIGN_Y	float32	mm	Fiberassign expected CS5 Y location on focal plane
FA_TARGET	int64		Targeting bit internally used by fiberassign (linked with FA_TYPE)
FA_TYPE	byte		Fiberassign internal target type (science, standard, sky, safe, suppsky)
NUMTARGET	int16		Total number of targets that this positioner covered
FIBER_RA	float64	deg	RA of actual fiber position
FIBER_DEC	float64	deg	DEC of actual fiber position
FIBER_RA_IVAR	float32	deg-2	TODO: description needed
FIBER_DEC_IVAR	float32	deg-2	TODO: description needed
PLATEMAKER_X	float32	mm	TODO: description needed
PLATEMAKER_Y	float32	mm	TODO: description needed
PLATEMAKER_RA	float32	deg	TODO: description needed
PLATEMAKER_DEC	float32	deg	TODO: description needed
NUM_ITER	int32		Number of positioner iterations
SPECTROID	int32		Hardware ID of spectrograph (not used)
BRICKNAME	char[8]		Brick name from tractor input
LAMBDAREF	float64		TODO: description needed
DELTA_X	float64	mm	CS5 X requested minus actual position
DELTA_Y	float64	mm	CS5 Y requested minus actual position

HDU14¶

EXTNAME = OBSCONDITIONS

Table with a single row defining the observing conditions for this exposure, e.g. SEEING, AIRMASS, lunar conditions.

Required Header Keywords¶

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	115	int	length of dimension 1
NAXIS2	1	int	length of dimension 2

Required Data Table Columns¶

Name	Type	Units	Description
EXPID	int32		Exposure ID
MJD	float64	d	Modified Julian Date
EXPTIME	float32	s	Exposure time
TILEID	int32		Tile ID
SNR2FRAC	float32		TODO: description needed
AIRMASS	float32		Airmass
SEEING	float32	arcsec	Atmospheric seeing FWHM
TRANSP	float32		Transparency [0-1]; 0=no photons
SKY	float32		TODO: description needed
PROGRAM	char[6]		DESI program name (e.g. DARK/GRAY/BRIGHT)
NIGHT	char[8]		Night ‘YEARMMDD’
FLAVOR	char[7]		Exposure flavor (e.g. science or calib)
MOONFRAC	float64		Moon illumination fraction [0-1]; 1=full moon
MOONALT	float64	deg	Moon altitude
MOONSEP	float64	deg	Separation angle between moon and center of tile
RA	float64	deg	Right ascension
DEC	float64	deg	Declination
PASS	int16		tiling pass number

TODO: define if AIRMASS etc. are at middle of exposure, averaged, etc.

HDU15¶

EXTNAME = TRUTH_BGS

Truth metadata that are specific to BGS targets.

Required Header Keywords¶

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	56	int	length of dimension 1
NAXIS2	262	int	length of dimension 2

Required Data Table Columns¶

Name	Type	Description
TARGETID	int64	Unique DESI target ID
OIIFLUX	float32	TODO: description needed
HBETAFLUX	float32	TODO: description needed
EWOII	float32	TODO: description needed
EWHBETA	float32	TODO: description needed
D4000	float32	TODO: description needed
VDISP	float32	TODO: description needed
OIIDOUBLET	float32	TODO: description needed
OIIIHBETA	float32	TODO: description needed
OIIHBETA	float32	TODO: description needed
NIIHBETA	float32	TODO: description needed
SIIHBETA	float32	TODO: description needed
TRUEZ_NORSD	float32	TODO: description needed

HDU16¶

EXTNAME = TRUTH_ELG

Truth metadata that are specific to ELG targets.

Required Header Keywords¶

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	56	int	length of dimension 1
NAXIS2	4225	int	length of dimension 2

Required Data Table Columns¶

Name	Type	Description
TARGETID	int64	Unique DESI target ID
OIIFLUX	float32	TODO: description needed
HBETAFLUX	float32	TODO: description needed
EWOII	float32	TODO: description needed
EWHBETA	float32	TODO: description needed
D4000	float32	TODO: description needed
VDISP	float32	TODO: description needed
OIIDOUBLET	float32	TODO: description needed
OIIIHBETA	float32	TODO: description needed
OIIHBETA	float32	TODO: description needed
NIIHBETA	float32	TODO: description needed
SIIHBETA	float32	TODO: description needed
TRUEZ_NORSD	float32	TODO: description needed

HDU17¶

EXTNAME = TRUTH_STAR

Truth metadata that are specific to STAR targets.

Required Header Keywords¶

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	20	int	length of dimension 1
NAXIS2	106	int	length of dimension 2

Required Data Table Columns¶

Name	Type	Description
TARGETID	int64	Unique DESI target ID
TEFF	float32	TODO: description needed
LOGG	float32	TODO: description needed
FEH	float32	TODO: description needed

HDU18¶

EXTNAME = TRUTH_WD

Truth metadata that are specific to White Dwarf targets.

Required Header Keywords¶

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	16	int	length of dimension 1
NAXIS2	1	int	length of dimension 2

Required Data Table Columns¶

Name	Type	Description
TARGETID	int64	Unique DESI target ID
TEFF	float32	TODO: description needed
LOGG	float32	TODO: description needed