sky-EXPID

Summary:

Raw data from the two DESI Sky Cameras, with one fpack-compressed HDU for each camera.

Naming Convention:

sky-EXPID.fits.fz, where EXPID is the zero-padded 8-digit exposure ID.

Regex:

sky-[0-9]{8}\.fits\.fz

File Type:

FITS, 70 MB

Contents

Number	EXTNAME	Type	Contents
HDU0	SKY	Empty HDU	Header keywords only
HDU1	SKYCAM1	Compressed IMAGE	Sky camera frames
HDU2	SKYCAM1T	BINTABLE	Metadata about each frame
HDU3	SKYCAM0	Compressed IMAGE	Sky camera frames
HDU4	SKYCAM0T	BINTABLE	Metadata about each frame

The SKYCAMERA data will be 3D[nframes, ny, nx] such that data[i] is the 2D sky camera frame number i. Row i of the SKYCAM[01]T table will contain the metadata about that frame, e.g. the DATE-OBS and EXPTIME.

FITS Header Units

HDU0

EXTNAME = SKY

This HDU contains header keywords only.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
MODULE	SKY	str	Image Sources/Component
EXPID	118526	int	Exposure number
FRAMES	7	int	Number of Frames in Archive
TILEID	4403	int	DESI Tile ID
FLAVOR	science	str	Observation type
PURPOSE	Main Survey	str	Purpose of observing night
PROGRAM	DARK	str	Program name
NIGHT	20220113	int	Observing night
ACQTIME	None	Unknown	[s] acqusition image exposure time
GUIDTIME	None	Unknown	[s] guider GFA exposure time
FOCSTIME	None	Unknown	[s] focus GFA exposure time
SKYTIME	60.0	float	[s] sky camera exposure time (acquisition)
REQRA	170.239	float	[deg] Requested right ascension (observer input
REQDEC	-7.093	float	[deg] Requested declination (observer input)
DELTARA	None	Unknown	[arcsec] Offset], right ascension, observer inp
DELTADEC	None	Unknown	[arcsec] Offset], declination, observer input
FOCUS	946.6,-231.6,-83.4,-18.3,9.8,139.4	str	Telescope focus settings
TRUSTEMP	12.267	float	[deg] Average Telescope truss temperature (only
PMIRTEMP	11.675	float	[deg] Average primary mirror temperature (nit,e
SKYDEC	-7.102329	float	[deg] Telescope declination (pointing on sky)
SKYRA	170.24163	float	[deg] Telescope right ascension (pointing on sk
TARGTDEC	-7.102329	float	[deg] Target declination (to TCS)
TARGTRA	170.24163	float	[deg] Target right ascension (to TCS)
ACQCAM	GUIDE0,GUIDE2,GUIDE3,GUIDE5,GUIDE7,GUIDE8	str	Acquisition cameras used
GUIDECAM	GUIDE0,GUIDE2,GUIDE3,GUIDE5,GUIDE7,GUIDE8	str	Guide cameras used for t
FOCUSCAM	FOCUS1,FOCUS4,FOCUS6,FOCUS9	str	Focus cameras used for this exposure
SKYCAM	SKYCAM0,SKYCAM1	str	Sky cameras used for this exposure
ADC1PHI	None	Unknown	[deg] ADC 1 angle
ADC2PHI	None	Unknown	[deg] ADC 2 angle
HEXPOS	None	Unknown	Hexapod position
DOSVER	trunk	str	DOS software version
CONSTVER	DESI:CURRENT	str	Constants version
ARCHIVE	/exposures/desi/20220113/00118526/sky-00118526.fits.fz	str
CHECKSUM	1m7R3m7P1m7P1m7P	str	HDU checksum updated 2022-01-14T11:14:08
DATASUM	0	str	data unit checksum updated 2022-01-14T11:14:08

Empty HDU.

HDU1

EXTNAME = SKYCAM1

Contains the raw data from multiple exposures of SkyCam1, normally taken concurrently with a DESI spectrograph exposure. Each raw image contains spots from the ETC fibers whose total flux is a measure of relative sky brightness in the r band. Use the desietc.sky module to reduce these images and measure sky fiber fluxes.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	8	int	width of table in bytes
NAXIS2	14329	int	number of rows in table
ZTILE3	1	int	size of tiles to be compressed
BZERO	32768	int	offset data range to that of unsigned short
BSCALE	1	int	default scaling factor
EXPID	118526	int	Exposure number
FRAMES	7	int	Number of Frames in Archive
TILEID	4403	int	DESI Tile ID
FIBASSGN	/data/tiles/SVN_tiles/004/fiberassign-004403.fits.gz	str	Fiber assign
FLAVOR	science	str	Observation type
SEQUENCE	_Split	str	OCS Sequence name
PURPOSE	Main Survey	str	Purpose of observing night
PROGRAM	DARK	str	Program name
PROPID	2020B-5000	str	Proposal ID
OBSERVER	Jessica Chellino, Corentin Ravoux	str	Names of observers
LEAD	Martin Landriau	str	Lead observer
INSTRUME	DESI	str	Instrument name
OBSERVAT	KPNO	str	Observatory name
OBS-LAT	31.96403	str	[deg] Observatory latitude
OBS-LONG	-111.59989	str	[deg] Observatory east longitude
OBS-ELEV	2097.0	float	[m] Observatory elevation
TELESCOP	KPNO 4.0-m telescope	str	Telescope name
CORRCTOR	DESI Corrector	str	Corrector Identification
NIGHT	20220113	int	Observing night
TIMESYS	UTC	str	Time system used for date-obs
DATE-OBS	2022-01-14T11:04:17.933414	str	[UTC] Observation data and start time
MJD-OBS	59593.46131867	float	Modified Julian Date of observation
ST	11:14:42.9462	str	Local Sidereal time at observation start (HH:MM
SKYTIME	60.0	float	[s] sky camera exposure time (acquisition)
REQRA	170.239	float	[deg] Requested right ascension (observer input
REQDEC	-7.093	float	[deg] Requested declination (observer input)
DELTARA	None	Unknown	[arcsec] Offset], right ascension, observer inp
DELTADEC	None	Unknown	[arcsec] Offset], declination, observer input
FOCUS	946.6,-231.6,-83.4,-18.3,9.8,139.4	str	Telescope focus settings
TRUSTEMP	12.267	float	[deg] Average Telescope truss temperature (only
PMIRTEMP	11.675	float	[deg] Average primary mirror temperature (nit,e
EPOCH	2000.0	float	Epoch of observation
EQUINOX	None	Unknown	Equinox of selected coordinate reference frame
MOUNTAZ	176.725567	float	[deg] Mount azimuth angle
MOUNTDEC	-7.102329	float	[deg] Mount declination
MOUNTEL	50.883914	float	[deg] Mount elevation angle
MOUNTHA	-2.081118	float	[deg] Mount hour angle
SKYDEC	-7.102329	float	[deg] Telescope declination (pointing on sky)
SKYRA	170.24163	float	[deg] Telescope right ascension (pointing on sk
TARGTDEC	-7.102329	float	[deg] Target declination (to TCS)
TARGTRA	170.24163	float	[deg] Target right ascension (to TCS)
USEETC	T	bool	ETC data available if true
ACQCAM	GUIDE0,GUIDE2,GUIDE3,GUIDE5,GUIDE7,GUIDE8	str	Acquisition cameras used
GUIDECAM	GUIDE0,GUIDE2,GUIDE3,GUIDE5,GUIDE7,GUIDE8	str	Guide cameras used for t
FOCUSCAM	FOCUS1,FOCUS4,FOCUS6,FOCUS9	str	Focus cameras used for this exposure
SKYCAM	SKYCAM0,SKYCAM1	str	Sky cameras used for this exposure
ADC1PHI	None	Unknown	[deg] ADC 1 angle
USESKY	T	bool	DOS Control: use Sky Monitor
USEFOCUS	T	bool	DOS Control: use focus
HEXPOS	None	Unknown	Hexapod position
HEXTRIM	0.0,0.0,0.0,0.0,0.0,0.0	str	Hexapod trim values
USEROTAT	T	bool	DOS Control: use rotator
ROTOFFST	138.8	float	[arcsec] Rotator offset
ROTENBLD	T	bool	Rotator enabled
ROTRATE	0.513	float	[arcsec/min] Rotator rate
USEGUIDR	T	bool	DOS Control: use guider
USEDONUT	T	bool	DOS Control: use donuts
RADESYS	FK5	str	Coordinate reference frame of major/minor axes
SHAPE	2047,3072	str
DOSVER	trunk	str	DOS software version
OCSVER	1.2	float	OCS software version
CONSTVER	DESI:CURRENT	str	Constants version
INIFILE	/data/msdos/dos_home/architectures/kpno/desi.ini	str	DOS Configuration
ADCPHI2	None	Unknown
ROI	None	Unknown
ROIWIDTH	None	Unknown
GEXPMODE	None	Unknown	GFA readout mode (loop/normal)
DEVICEID	None	Unknown	GFA device id (serial number)
REQTIME	1860.0	float	[s] Requested exposure time
CHECKSUM	CPA0EN50CNA0CN30	str	HDU checksum updated 2022-01-14T11:14:08
DATASUM	4223421838	str	data unit checksum updated 2022-01-14T11:14:08

Data: FITS image [int16 (compressed), 3072x2047x7]

HDU2

EXTNAME = SKYCAM1T

A table of timestamps and instrument parameters for each SkyCam0 exposure stored in HDU SKYCAM1.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	144	int	width of table in bytes
NAXIS2	7	int	number of rows in table
CHECKSUM	S14XT04US04US04U	str	HDU checksum updated 2022-01-14T11:14:08
DATASUM	136958306	str	data unit checksum updated 2022-01-14T11:14:08

Required Data Table Columns

Name	Type	Units	Description
EXPTIME	float64		TODO: description needed
REQTIME [1]	float64		TODO: description needed
NIGHT	int64		TODO: description needed
DATE-OBS	char[26]		TODO: description needed
TIME-OBS	char[15]		TODO: description needed
MJD-OBS	float64		TODO: description needed
OPENSHUT	char[*]		TODO: description needed
ST	char[*]		TODO: description needed
HEXPOS	char[4]		TODO: description needed
GAMBNTT	char[4]		TODO: description needed
GFPGAT	char[4]		TODO: description needed
GFILTERT	char[4]		TODO: description needed
GCOLDTEC	char[4]		TODO: description needed
GHOTTEC	char[4]		TODO: description needed
GCCDTEMP	char[4]		TODO: description needed
GCAMTEMP	char[4]		TODO: description needed
GHUMID2	char[4]		TODO: description needed
GHUMID3	char[4]		TODO: description needed

[1] (1,2)

Optional

HDU3

EXTNAME = SKYCAM0

Contains the raw data from multiple exposures of SkyCam0, normally taken concurrently with a DESI spectrograph exposure. Each raw image contains spots from the ETC fibers whose total flux is a measure of relative sky brightness in the r band. Use the desietc.sky module to reduce these images and measure sky fiber fluxes.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	8	int	width of table in bytes
NAXIS2	14329	int	number of rows in table
ZTILE3	1	int	size of tiles to be compressed
BZERO	32768	int	offset data range to that of unsigned short
BSCALE	1	int	default scaling factor
EXPID	118526	int	Exposure number
FRAMES	7	int	Number of Frames in Archive
TILEID	4403	int	DESI Tile ID
FIBASSGN	/data/tiles/SVN_tiles/004/fiberassign-004403.fits.gz	str	Fiber assign
FLAVOR	science	str	Observation type
SEQUENCE	_Split	str	OCS Sequence name
PURPOSE	Main Survey	str	Purpose of observing night
PROGRAM	DARK	str	Program name
PROPID	2020B-5000	str	Proposal ID
OBSERVER	Jessica Chellino, Corentin Ravoux	str	Names of observers
LEAD	Martin Landriau	str	Lead observer
INSTRUME	DESI	str	Instrument name
OBSERVAT	KPNO	str	Observatory name
OBS-LAT	31.96403	str	[deg] Observatory latitude
OBS-LONG	-111.59989	str	[deg] Observatory east longitude
OBS-ELEV	2097.0	float	[m] Observatory elevation
TELESCOP	KPNO 4.0-m telescope	str	Telescope name
CORRCTOR	DESI Corrector	str	Corrector Identification
NIGHT	20220113	int	Observing night
TIMESYS	UTC	str	Time system used for date-obs
DATE-OBS	2022-01-14T11:04:17.933414	str	[UTC] Observation data and start time
MJD-OBS	59593.46131867	float	Modified Julian Date of observation
ST	11:14:42.9462	str	Local Sidereal time at observation start (HH:MM
SKYTIME	60.0	float	[s] sky camera exposure time (acquisition)
REQRA	170.239	float	[deg] Requested right ascension (observer input
REQDEC	-7.093	float	[deg] Requested declination (observer input)
DELTARA	None	Unknown	[arcsec] Offset], right ascension, observer inp
DELTADEC	None	Unknown	[arcsec] Offset], declination, observer input
FOCUS	946.6,-231.6,-83.4,-18.3,9.8,139.4	str	Telescope focus settings
TRUSTEMP	12.267	float	[deg] Average Telescope truss temperature (only
PMIRTEMP	11.675	float	[deg] Average primary mirror temperature (nit,e
EPOCH	2000.0	float	Epoch of observation
EQUINOX	None	Unknown	Equinox of selected coordinate reference frame
MOUNTAZ	176.725567	float	[deg] Mount azimuth angle
MOUNTDEC	-7.102329	float	[deg] Mount declination
MOUNTEL	50.883914	float	[deg] Mount elevation angle
MOUNTHA	-2.081118	float	[deg] Mount hour angle
SKYDEC	-7.102329	float	[deg] Telescope declination (pointing on sky)
SKYRA	170.24163	float	[deg] Telescope right ascension (pointing on sk
TARGTDEC	-7.102329	float	[deg] Target declination (to TCS)
TARGTRA	170.24163	float	[deg] Target right ascension (to TCS)
USEETC	T	bool	ETC data available if true
ACQCAM	GUIDE0,GUIDE2,GUIDE3,GUIDE5,GUIDE7,GUIDE8	str	Acquisition cameras used
GUIDECAM	GUIDE0,GUIDE2,GUIDE3,GUIDE5,GUIDE7,GUIDE8	str	Guide cameras used for t
FOCUSCAM	FOCUS1,FOCUS4,FOCUS6,FOCUS9	str	Focus cameras used for this exposure
SKYCAM	SKYCAM0,SKYCAM1	str	Sky cameras used for this exposure
ADC1PHI	None	Unknown	[deg] ADC 1 angle
USESKY	T	bool	DOS Control: use Sky Monitor
USEFOCUS	T	bool	DOS Control: use focus
HEXPOS	None	Unknown	Hexapod position
HEXTRIM	0.0,0.0,0.0,0.0,0.0,0.0	str	Hexapod trim values
USEROTAT	T	bool	DOS Control: use rotator
ROTOFFST	138.8	float	[arcsec] Rotator offset
ROTENBLD	T	bool	Rotator enabled
ROTRATE	0.513	float	[arcsec/min] Rotator rate
USEGUIDR	T	bool	DOS Control: use guider
USEDONUT	T	bool	DOS Control: use donuts
RADESYS	FK5	str	Coordinate reference frame of major/minor axes
SHAPE	2047,3072	str
DOSVER	trunk	str	DOS software version
OCSVER	1.2	float	OCS software version
CONSTVER	DESI:CURRENT	str	Constants version
INIFILE	/data/msdos/dos_home/architectures/kpno/desi.ini	str	DOS Configuration
ADCPHI2	None	Unknown
ROI	None	Unknown
ROIWIDTH	None	Unknown
GEXPMODE	None	Unknown	GFA readout mode (loop/normal)
DEVICEID	None	Unknown	GFA device id (serial number)
REQTIME	1860.0	float	[s] Requested exposure time
CHECKSUM	SLfNTKfKSKfKSKfK	str	HDU checksum updated 2022-01-14T11:14:09
DATASUM	4278834758	str	data unit checksum updated 2022-01-14T11:14:09

Data: FITS image [int16 (compressed), 3072x2047x7]

HDU4

EXTNAME = SKYCAM0T

A table of timestamps and instrument parameters for each SkyCam0 exposure stored in HDU SKYCAM0.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	144	int	width of table in bytes
NAXIS2	7	int	number of rows in table
CHECKSUM	dFIceCHbdCHbdCHb	str	HDU checksum updated 2022-01-14T11:14:09
DATASUM	3066928412	str	data unit checksum updated 2022-01-14T11:14:09

Required Data Table Columns

Name	Type	Units	Description
EXPTIME	float64		TODO: description needed
REQTIME [1]	float64		TODO: description needed
NIGHT	int64		TODO: description needed
DATE-OBS	char[26]		TODO: description needed
TIME-OBS	char[15]		TODO: description needed
MJD-OBS	float64		TODO: description needed
OPENSHUT	char[*]		TODO: description needed
ST	char[*]		TODO: description needed
HEXPOS	char[4]		TODO: description needed
GAMBNTT	char[4]		TODO: description needed
GFPGAT	char[4]		TODO: description needed
GFILTERT	char[4]		TODO: description needed
GCOLDTEC	char[4]		TODO: description needed
GHOTTEC	char[4]		TODO: description needed
GCCDTEMP	char[4]		TODO: description needed
GCAMTEMP	char[4]		TODO: description needed
GHUMID2	char[4]		TODO: description needed
GHUMID3	char[4]		TODO: description needed