targets-dr3

Summary:: DESI target selection files contain a single binary table covering the entire footprint. They contain the variables used by target selection (e.g. fluxes), variables needed by fiber assignment (e.g. RA, DEC), and variables needed for traceability (e.g. TARGETFLAG, TARGETID).
Naming Convention:: TBD, let’s try targets-{source}-{version}.fits where source is where the input data came from (e.g. ‘dr1’, ‘dr2’) and version is the code version that wrote this, preferably a git tag of desitargets.
Regex:: targets-dr[0-9]+-v?[0-9]+\.[0-9]+(\.[0-9]+|)\.fits
File Type:: FITS

Contents

Number	EXTNAME	Type	Contents
HDU0	PRIMARY	IMAGE	Blank
HDU1	TARGETS	BINTABLE	Target selection table

EXTNAME = PRIMARY

Empty HDU.

EXTNAME = TARGETS

Required Header Keywords Table

KEY	Example Value	Type	Comment
EXTNAME	TARGETS	str	name of this binary table extension
DEPNAM00	desitarget	str
DEPVER00	0.1.0	str	desitarget.__version__
DEPNAM01	desitarget-git	str
DEPVAL01	0.1.0	str	git revision
DEPNAM02	tractor-files	str
DEPVER02	/project/projectdirs/cosmo/data/legacysurvey/dr1/tractor	str	input directory

Name	Type	Description
BRICKID	int32	Brick ID from tractor input
BRICKNAME	char[8]	Brick name from tractor input
BRICK_OBJID	int32	OBJID (unique to brick, but not to file)
BRICK_PRIMARY	logical	should always be True
TYPE	char[4]	tractor object type
RA	float64	Right ascension [degrees]
RA_IVAR	float32	Inverse variance of RA
DEC	float64	Declination [degrees]
DEC_IVAR	float32	Inverse variance of DEC
DECAM_FLUX	float32[6]	DECam flux from tractor input (ugrizY)
DECAM_MW_TRANSMISSION	float32[6]	Milky Way dust transmission ([0-1] ugrizY)
WISE_FLUX	float32[4]	WISE flux (W1, W2, W3, W4)
WISE_MW_TRANSMISSION	float32[4]	Milky Way transmission
SHAPEEXP_R	float32	Half-light radius of exponential model (>0)
SHAPEDEV_R	float32	Half-light radius of deVaucouleurs model (>0)
TARGETID	int64	Unique targeting ID
DESI_TARGET	int64	DESI (dark time program) target selection bitmask
BGS_TARGET	int64	BGS (bright time program) target selection bitmask
MWS_TARGET	int64	MWS (bright time program) target selection bitmask

In general, the above format contains:

Columns that were used by target selection (e.g. DECAM_FLUX)
Columns needed by fiber assignment (e.g. RA, DEC)
Columns needed for traceability (e.g. BRICKNAME, TARGETID, DESI_TARGET, BGS_TARGET, MWS_TARGET)

TARGETID, DESI_TARGET, BGS_TARGET and MWS_TARGET are created by target selection; the rest are passed through from the original input tractor files

See http://legacysurvey.org for more details about the columns from input tractor files