1. Software and Controls Data Product Specifications II

1.1. Introduction

This report provides a list of the FITS data product files produced by the Data Processing Subsystem.

1.2. Acronyms

1.3. FITS-Standard Data Containers

1.3.1. Primary HDU (PHDU)

Description:

This is a basic model that defines the primary header data unit, or PHDU, of a FITS container. This model creates an empty storage container.

Format:

Position attribute ‘pos’ defines the order in the FITS header, where -1 is the last position, while 0 specifies no particular location. The last keyword in the header must be END, i.e. ‘pos: -1’.

File:

<inst>_phdu.fits

Table 1.1 Primary HDU: Basic FITS Primary Header Data Unit

#	Keyword	Value	HDU
1	simple	true	phdu
2	bitpix	8	phdu
3	naxis	2	phdu
4	naxis1	0	phdu
5	naxis2	0	phdu
-1	end		phdu

1.3.2. Extension HDU: Image

Description:

This is a basic model that defines an empty FITS storage container for an image extension. This base ‘image’ defines an area of 1024 columns and 1024 rows Position attribute ‘pos’ defines the order in the FITS header, where -1 is the last position, while 0 specifies no particular location.

Format:

The header keywords must follow the order shown, i.e. the first keyword must be XTENSION = ‘IMAGE ‘, the second BITPIX = 16, and so on. The last keyword in the header must be END.

File:

<inst>_bimg.fits

Table 1.2 Extension HDU: Basic FITS Image Extension

#	Keyword	Value	HDU
4	extend	true	phdu
1	xtension	IMAGE	hdu1
2	bitpix	8	phdu
3	naxis	2	phdu
4	naxis1	0	phdu
5	naxis2	0	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
-1	end		phdu
1	simple	true	phdu

1.3.3. Extension HDU: ASCII Table

Description:

This is a basic model that defines an empty FITS storage container for an ASCII table extension. An ASCII table can store catalogues and tables of data. Each row of the table has a fixed length of ASCII characters, divided into columns by TBCOLn. This base ‘table’ defines an area of ASCII text that has one column which is 80 characters wide and 100 rows deep. Position attribute ‘pos’ defines the order in the FITS header, where -1 is the last position, while 0 specifies no particular location.

Format:

The header keywords must follow the order shown, i.e. the first keyword must be XTENSION = ‘TABLE ‘, the second BITPIX = 16, and so on. The last keyword in the header must be END.

File:

<inst>_atbl.fits

Table 1.3 Extension HDU: Base ASCII Table

#	Keyword	Value	HDU
4	extend	true	phdu
1	xtension	TABLE	hdu1
2	bitpix	8	phdu
3	naxis	2	phdu
4	naxis1	0	phdu
5	naxis2	0	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
0	ttype1	TEXT	hdu1
0	tbcol1	1	hdu1
0	tform1	A80	hdu1
-1	end		phdu
1	simple	true	phdu

1.3.4. Extension HDU: Binary Table

Description:

This is a basic model that defines an empty FITS storage container for an binary table extension. This base ‘table’ defines storage for 1 column and 100 rows of integers, where each row has 1024 bytes in width. Position attribute ‘pos’ defines the order in the FITS header, where -1 is the last position, while 0 specifies no particular location.

Format:

The header keywords must follow the order shown, i.e. the first keyword must be XTENSION = ‘BINTABLE’, the second BITPIX = 16, and so on. The last keyword in the header must be END.

File:

<inst>_btbl.fits

Table 1.4 Extension HDU: Basic Binary Table Extension

#	Keyword	Value	HDU
4	extend	true	phdu
1	xtension	BINTABLE	hdu1
2	bitpix	8	phdu
3	naxis	2	phdu
4	naxis1	0	phdu
5	naxis2	0	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
9	ttype1	Col	hdu1
10	tform1	1024I	hdu1
11	tunit1	Counts	hdu1
-1	end		phdu
1	simple	true	phdu

1.4. Common Data Product Patterns

1.4.1. Base Exposure Primary HDU (PHDU)

Description:

This is a basic model that specifies baseline headers that are found in an GMT exposure. This ought to be inherited by all imaging and spectroscopy exposures.

Format:

TBC

File:

<inst>_phdu.fits

Table 1.5 Primary HDU: Base Exposure

#	Keyword	Value	HDU
0	date		phdu
0	iraf_tlm		phdu
0	nextend		phdu
0	origin		phdu
0	rootname		phdu
0	filename		phdu
0	filetype		phdu
0	telescop	GMT	phdu
0	instrume		phdu
0	equinox		phdu
0	proposid		phdu
0	pr_inv_l		phdu
0	pr_inv_f		phdu
0	pr_inv_m		phdu
0	targname		phdu
0	object		phdu
0	ra_targ		phdu
0	dec_targ		phdu
0	tequinox		phdu
0	expname		phdu
0	date_obs		phdu
0	time_obs		phdu
0	expstart		phdu
0	expend		phdu
0	exptime		phdu
0	nrptexp		phdu
0	crsplit		phdu
0	qualcom1		phdu
0	qualcom2		phdu
0	qualcom3		phdu
0	quality		phdu
0	postarg1		phdu
0	postarg2		phdu
0	eqnx_off		phdu
0	obstype		phdu
0	obsmode		phdu
0	photmode		phdu
0	sclamp		phdu
0	lamp_id		phdu
0	lamp_vol		phdu
0	subarray	F	phdu
0	detector		phdu
0	cmdgain		phdu
0	opt_elem		phdu
0	propaper		phdu
0	aperture		phdu
0	aper_fov		phdu
0	filter		phdu
0	cenwave		phdu
0	detamp		phdu
0	atodgain		phdu
0	rdnoise		phdu
0	detoffst		phdu
0	platesc		phdu
0	centera1		phdu
0	sizaxis1		phdu
0	sizaxis2		phdu
0	binaxis1		phdu
0	binaxis2		phdu
0	bpixtab		phdu
0	darkfile		phdu
0	pfltfile		phdu
0	dfltfile		phdu
0	lfltfile		phdu
0	ffltfile		phdu
0	phottab		phdu
0	apertab		phdu
0	ccdtab		phdu
0	atodtab		phdu
0	biasfile		phdu
0	shadfile		phdu
0	crrejtab		phdu
0	wavecal		phdu
0	sptrctab		phdu
0	disptab		phdu
0	lamptab		phdu
0	sdctab		phdu
0	xtractab		phdu
0	pctab		phdu
0	wcptab		phdu
0	itdstab		phdu
0	asn_id		phdu
0	asn_tab		phdu
0	meanexp		phdu
0	scalense		phdu
0	initgues		phdu
0	skysub		phdu
0	crsigmas		phdu
0	crradius		phdu
0	crthresh		phdu
0	badinpdq		phdu
0	rej_rate		phdu
0	crmask		phdu
0	pattern1		phdu
0	p1_shape		phdu
0	p1_purps		phdu
0	p1_npts		phdu
0	p1_pspac		phdu
0	p1_lspac		phdu
0	p1_angle		phdu
0	p1_frame		phdu
0	p1_orint		phdu
0	p1_centr		phdu
0	propttl1		phdu
0	obset_id		phdu
0	targdesc		phdu
0	pm_flag		phdu
0	parallax		phdu
0	pm_ra		phdu
0	pm_dec		phdu
0	pm_equin		phdu
0	pa_v3		phdu
0	airmass		phdu
0	gs1_ra		phdu
0	gs1_dec		phdu
0	gs1_mag		phdu
0	gs1_filt		phdu
0	gs1_eqnx		phdu
0	gs2_ra		phdu
0	gs2_dec		phdu
0	gs2_mag		phdu
0	gs2_filt		phdu
0	gs2_eqnx		phdu
0	gs3_ra		phdu
0	gs3_dec		phdu
0	gs3_mag		phdu
0	gs3_filt		phdu
0	gs3_eqnx		phdu
0	gs4_ra		phdu
0	gs4_dec		phdu
0	gs4_mag		phdu
0	gs4_filt		phdu
0	gs4_eqnx		phdu
0	proctime		phdu
0	history		phdu

1.4.2. Base Exposure Extension HDU (EHDU)

Description:

This is a basic model that specifies baseline headers that are found in an GMT exposure. This ought to be inherited by all imaging and spectroscopy exposures.

Format:

File:

<inst>_ehdu.fits

Table 1.6 Extension HDU: Base Exposure

#	Keyword	Value	HDU
0	extname		ehdu
0	extver		ehdu
0	iraf_tlm		ehdu
0	inherit		ehdu
0	expname		ehdu
0	bunit		ehdu
0	asn_mtyp		ehdu
0	wcsaxes		ehdu
0	crpix1		ehdu
0	crpix2		ehdu
0	crval1		ehdu
0	crval2		ehdu
0	ctype1		ehdu
0	ctype2		ehdu
0	cd1_1		ehdu
0	cd1_2		ehdu
0	cd2_1		ehdu
0	cd2_2		ehdu
0	ltv1		ehdu
0	ltv2		ehdu
0	ltm1_1		ehdu
0	ltm2_2		ehdu
0	ra_aper		ehdu
0	dec_aper		ehdu
0	pa_aper		ehdu
0	dispaxis		ehdu
0	cunit1		ehdu
0	cunit2		ehdu
0	orientat		ehdu
0	sunangle		ehdu
0	moonangl		ehdu
0	sun_alt		ehdu
0	refframe		ehdu
0	date_obs		ehdu
0	time_obs		ehdu
0	expstart		ehdu
0	expend		ehdu
0	exptime		ehdu
0	expflag		ehdu
0	rv_helio		ehdu
0	pattstep		ehdu
0	ncombine		ehdu
0	ngoodpix		ehdu
0	sdqflags		ehdu
0	goodmin		ehdu
0	goodmax		ehdu
0	snrmin		ehdu
0	snrmax		ehdu
0	snrmean		ehdu
0	softerrs		ehdu
0	meandark		ehdu
0	meanblev		ehdu
0	sporder		ehdu

1.4.3. Base Calibration Reference Table (CRT)

Description:

This is a basic model that specifies baseline headers for GMT calibration reference tables.

Format:

File:

<inst>_crt.fits

Table 1.7 Extension HDU: Base Calibration Reference Table

#	Keyword	Value	HDU
0	simple	T	phdu
0	bitpix	8	ehdu
0	naxis	2	ehdu
0	extend	T	phdu
0	filename		phdu
0	telescop	GMT	phdu
0	instrume		phdu
0	date		phdu
0	filetype		phdu
0	use_date		phdu
0	descrip		phdu
0	aperture		phdu
0	cenwave		phdu
0	end		ehdu
0	xtension	BINTABLE	ehdu
0	naxis1		ehdu
0	naxis2		ehdu
0	pcount	0	ehdu
0	gcount	1	ehdu
0	tfields		ehdu
0	extname		ehdu
0	extver	1	phdu
0	inherit	T	ehdu

1.5. Calibration and Reference File Data Products

1.5.1. Bias Frame (BIA)

Description:

This is an image of the electronic zeropoint-level of an instrument, obtained with all light sources turned off, the detector shutter closed, and zero-second (or shortest possible) integration time. Usually, multiple (>10) bias images are taken at the beginning and/or end of the night and combined into one image. The file for the combined bias frame has the ‘bia’ suffix; pre-combined bias frames have a ‘raw’ suffix. The combined bias image is removed from the science images, usually as the first step in the data reduction.

Format:

For both a single and multi-chip detector, the combined bias image is stored as an multi-extension file, with each set corresponding to each detector chip. If it is possible to change the binning mode of a detector, the binning factors are given by BINAXIS1 and BINAXIS2 header parameters. The bias image [SCI] and the error array [ERR] have raw detector data units (DN), such that GAIN * DN = electrons.

File:

<inst>_bia.fits

Table 1.8 Data Product HDU: Bias Frame

#	Keyword	Value	HDU
0	filetype	BIAS	phdu
0	extname	BIAS	phdu
0	obstype	IMAGING	phdu
0	filter	CLEAR	phdu
0	bunit	DN	phdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	IMAGE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.5.2. Dark Frame (DRK)

Description:

This image records the dark-current signal of an instrument, obtained with ambient light turned off, the detector shutter closed. Typically, multiple dark exposures are taken at the beginning and/or end of the night, using different integration time settings. After subtracting out the bias, the individual dark images are combined into one and normalized to 1 second. The file for the combined dark frame has the “drk” suffix; pre-combined dark frames have a “raw” suffix. When applying dark correction to a science image, the combined dark image is scaled to the exposure time of the science image and removed, usually either as the second (after bias subtraction) or third (after overscan correction, if relevant) step in the data reduction.

Format:

A combined dark image is stored as an MEF of the type shown in Figure 5-1 for an optical/UV detector, and Figure 5 2 for a NIR detector. When it is possible to change the binning mode of a detector, the binning factors are given by BINAXIS1 and BINAXIS2 header parameters. The dark image [SCI] and the error array [ERR] have raw detector data units per second (DN/sec), such that GAIN * DN = electrons/sec, for both UVIS and IR images. The header keyword EXPTIME = 1 is set to indicate the normalization.

Two flags in the [DQ] extension that potentially are present are 16 (hot pixels) and 128 (bad reference pixels, for IR detectors). Other, more permanent flags, e.g. dead and unstable pixels, should be stored in the bad pixel table (suffix “BPX”) file. IR detectors – For IR detectors, the SAMP and the TIME image extensions (see Figure 5 2) are used to calculate the total exposure times (TIME * SAMP) at each pixel. The SAMP extension gives the total number of retained input samples after image combination, and is an image. The TIME extension gives the total open shutter exposure time at that readout sequence and is a single value for all pixels, thus the exposure time is stored as a PIXVALUE keyword value and not as EXPTIME (=1.0).

NUMEXPOS is intended for NIR MEF, where the keyword in the phdu contains the number of sets.

PIXVALUE is used for the TIME extension, for image exposure time.

SAMP_SEQ, for NIR data, name the sampling sequence for a MULTIACCUM readout.

File:

<inst>_drk.fits

Table 1.9 Data Product HDU: Dark Frame

#	Keyword	Value	HDU
0	filetype	DARK	phdu
0	extname	DARK	phdu
0	obstype	IMAGING	phdu
0	filter	CLEAR	phdu
0	numexpos		phdu
0	bunit	DN/s	phdu
0	pixvalue		ehdu
0	exptime	1	ehdu
0	samp_seq		ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	IMAGE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.5.3. Dome Flat Field (DFL)

Description:

The dome-flat is an image that records the pixel-to-pixel response of a detector, using a bright artificial light source in the dome to provide the illumination. Dome flats contain wavelength-dependent information about the uniformity of the detector response. After bias and dark subtraction, the combined dome flat is divided into the science images for calibration.

Format:

A combined dome image is stored as an MEF of the type shown in Figure 5-1 for all optical/UV and NIR detectors, with only a single set of extension HDUs. The suffix “DFL” is used only for combined flat; individual raw flatfield images have the “RAW” suffix.

The median of the pixel value distribution is normalized to 1.

File:

<inst>_dfl.fits

Table 1.10 Data Product HDU: Dome Flat Field Frame

#	Keyword	Value	HDU
0	filetype	DOME FLAT	phdu
0	extname	FLT	phdu
0	obstype	IMAGING	phdu
0	filter	CLEAR	phdu
0	bunit	DN	phdu
0	lamp_id		phdu
0	lamp_vol		phdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	IMAGE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.5.4. Night Sky Flat Field (NFL)

Description:

A night-sky flatfield is an image that records the pixel-to-pixel response of a detector using sky observations. Night-sky flatfields contain wavelength-dependent information about the uniformity of the detector response. They are similar to twilight-sky flats (or “twiflats,” suffix TFL, Appendix B.01f), except they are taken in the middle of the night rather than near sunrise or sunset for twiflats. The images used to combine night-sky flats may sometimes be intended for other purposes, such as science images themselves. Often, night-sky flats are observed immediately surrounding the intended science images. Night-sky and twi-flats may be derived using different data processing procedures. After bias and dark subtraction, the combined flat is divided into the science images for calibration.

Format:

A combined night-sky flatfield image is stored as an MEF of the type shown in Figure 5-1 for all optical/UV and NIR detectors, with only a single set of extension HDUs. The suffix “NFL” is used only for combined flat; individual raw flatfield images have the “RAW” suffix.

Median of the pixel value distribution is normalized to 1.

File:

<inst>_nfl.fits

Table 1.11 Data Product HDU: Night-Sky Flat Field Frame

#	Keyword	Value	HDU
0	filetype	NIGHT SKY FLAT	phdu
0	extname	FLT	phdu
0	obstype	IMAGING	phdu
0	filter	CLEAR	phdu
0	bunit	DN	phdu
0	lamp_id		phdu
0	lamp_vol		phdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	IMAGE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.5.5. Twilight Flat Field (TFL)

Description:

A twilight sky-flat (or ‘twiflats’) is an image that records the pixel-to-pixel response of a detector using sky observations. Twiflats contain wavelength-dependent information about the uniformity of the detector response, and by definition are taken close to sunset or sunrise. The distinction between night-sky flatfield, dome flats, and twiflats should be made clear, as different data processing procedures are sometimes involved. After bias and dark subtraction, the combined flat is divided into the science images for calibration.

Format:

A combined twiflat image is stored as a multi-extension file for all optical/UV and NIR detectors, with only a single set of extension HDUs. The suffix ‘TFL’ is used only for combined flat; individual raw flatfield images have the ‘RAW’ suffix.

File:

<inst>_tfl.fits

Table 1.12 Data Product HDU: Twilight Flat Field Frame

#	Keyword	Value	HDU
0	filetype	TWILIGHT SKY FLAT	phdu
0	extname	FLT	phdu
0	obstype	IMAGING	phdu
0	filter	CLEAR	phdu
0	bunit	DN	phdu
0	lamp_id		phdu
0	lamp_vol		phdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	IMAGE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.5.6. Background Illumination Pattern (ILM)

Description:

This is an image of spatially variable background illumination pattern. Correcting for the background pattern involves dividing the illumination image from data. When the signal is low, the background illumination pattern file is sometimes constructed using multiple (potentially science) images with object rejection, or by smoothing the background illumination pattern image. Details of image combination and smoothing are stored under the header keyword HISTORY, or potentially in a data processing trailer file.

Format:

A background illumination file is stored as an MEF of the type shown in Figure 5 1 for all optical/UV and NIR detectors. The suffix “ILM” is used only for combined illumination file; individual raw flatfield images have the “RAW” suffix.

File:

<inst>_ilm.fits

Table 1.13 Data Product HDU: Background Illumination Pattern Frame

#	Keyword	Value	HDU
0	filetype	ILLUMINATION PATTERN	phdu
0	extname	ILM	phdu
0	obstype	IMAGING	phdu
0	filter	CLEAR	phdu
0	bunit	DN	phdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	IMAGE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.5.7. Bad Pixel Mask (MSK)

Description:

This is an image of all known, long-term, bad pixels for a detector. It is an image counterpart the “Bad Pixel Table (BPX)” discussed in Appendix B.02b. Transient hot pixels or cosmic rays detected during data reduction are stored in the data quality extension (DQ) of an MEF, or in the dark current reference file (file suffix “DRK”), depending on the purpose. The pixel values correspond to the data quality file as shown in Table 5-2.

Format:

The coordinate origin of the bad pixel image is at the lower left corner after trimming the overscan region. The types of bad pixels recorded and their code values are:

4 – dead pixels 8 – deviant zeroth read (NIR) or bad pixel in bias (UVIS) 32 – unstable (NIR) 512 – bad in flatfield

These values are reflected in the data quality extensions during data processing.

File:

<inst>_msk.fits

Table 1.14 Data Product HDU: Bad Pixel Mask Frame

#	Keyword	Value	HDU
0	filetype	STATIC BAD PIXEL MASK	phdu
0	extname	MSK	phdu
0	obstype	IMAGING	phdu
0	filter	CLEAR	phdu
0	bunit		phdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	IMAGE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.5.8. Post Flash Image (FLS)

Description:

A post-flash image corrects for the signal added to CCD exposures after a post-flash procedure. Correcting for post-flash signal involves: scaling the reference image in exposure time and gain to the science image, followed by image subtraction.

Format:

A post-flash reference is an MEF of the same FITS data structure, image dimension and binning factor, as the science image. Like the raw science image, it consists of both the physical and virtual overscan regions.

File:

<inst>_fls.fits

Table 1.15 Data Product HDU: Post Flash Image

#	Keyword	Value	HDU
0	filetype	POST FLASH	phdu
0	extname	FLS	phdu
0	obstype	IMAGING	phdu
0	filter	CLEAR	phdu
0	bunit	DN	phdu
0	detamp		phdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	IMAGE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.5.9. Analog to Digital Table (A2D)

Description:

This table provides a more detailed account of the A-to-D gain of a detector, i.e. number of actual counts (electrons) for each detected count (ADU) in an image, than provided in the image header keyword GAIN. This table is useful when the actual, measured, gain of a detector drifts with respect to an independent variable (REF_NAME), such as the exposure time, despite the nominal GAIN setting. The values of the independent variable are stored in the REF_VALUE array while the corresponding actual gain values are in ATOD.

Format:

File:

<inst>_a2d.fits

Table 1.16 Data Product HDU: Analog-to-Digital Table

#	Keyword	Value	HDU
0	filetype	ANALOG TO DIGITAL	phdu
0	extname	A2D	ehdu
1	xtension	BINTABLE	hdu1
9	ttype1	Col	hdu1
10	tform1	1024I	hdu1
0	tdisp1	A4	ehdu
11	tunit1	Counts	hdu1
0	ttype2	CMDGAIN	ehdu
0	tform2	I2	ehdu
0	tdisp2	I2.1	ehdu
0	tunit2	Integer	ehdu
0	ttype3	DETCHIP	ehdu
0	tform3	I1	ehdu
0	tdisp3	I1.1	ehdu
0	ttype4	NELEM	ehdu
0	tform4	I2	ehdu
0	tdisp4	I2.1	ehdu
0	ttype5	REF_NAME	ehdu
0	tform5	A12	ehdu
0	tdisp5	A12	ehdu
0	ttype6	REF_VALUE	ehdu
0	tform6	I2	ehdu
0	tdisp6	I2.1	ehdu
0	ttype7	ATODGAIN	ehdu
0	tform7	F5.2	ehdu
0	tdisp7	F5.2	ehdu
0	ttype8	DATESTAMP	ehdu
0	tform8	A10	ehdu
0	tdisp8	A10	ehdu
0	ttype9	TIMESTAMP	ehdu
0	tform9	A12	ehdu
0	tdisp9	A12	ehdu
0	ttype10	DESCRIP	ehdu
0	tform10	A67	ehdu
0	tdisp10	A67	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.5.10. Bad Pixel Table (BPX)

Description:

A bad pixel table contains a list on all known, long-term, bad pixels for a detector. This is the table counterpart of the “Static Bad Pixel Image (MSK)” discussed in Appendix B.01i. Transient hot pixels or cosmic rays detected during data reduction are stored in the data quality extension (DQ) of an MEF, or in the dark current reference file (file suffix “DRK”), depending on the purpose.

Format:

File:

<inst>_bpx.fits

Table 1.17 Data Product HDU: Bad Pixel Table

#	Keyword	Value	HDU
0	filetype	BAD PIXEL	phdu
0	extname	BPX	ehdu
1	xtension	BINTABLE	hdu1
9	ttype1	Col	hdu1
10	tform1	1024I	hdu1
0	tdisp1	A4	ehdu
0	ttype2	XPOS	ehdu
0	tform2	I5	ehdu
0	tdisp2	I5.1	ehdu
0	ttype3	YPOS	ehdu
0	tform3	I5	ehdu
0	tdisp3	I5.1	ehdu
0	ttype4	VALUE	ehdu
0	tform4	I4	ehdu
0	tdisp4	I4.1	ehdu
0	ttype5	DESCRIP	ehdu
0	tform5	A67	ehdu
0	tdisp5	A67	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
11	tunit1	Counts	hdu1

1.5.11. Detector Characteristics Table (DCT)

Description:

A detector can have several readout modes, distinguished by readout speed, gain, bias level, binning factor settings, which an observer may manually set to optimize observations. Each readout mode is associated with a set of calibrated values in gain, bias level, readnoise, saturation level, etc.. For example, faster readout speeds usually result in higher readnoise. This master table stores information that maps a selected readout mode setting with measured performance parameters.

Format:

In the FITS table, each row corresponds to a readout configuration. Each row is uniquely specified by the following parameters: the readout amplifiers configuration (AMPCONFIG), the detector chip (DETCHIP), speed of the readout (RDSPEED), commanded gain (CMDGAIN), commanded bias (CMDBIAS), and chip binning factors (BINAXIS1, BINAXIS2), as well as the date and time stamps (DATESTAMP, TIMESTAMP). The actual measured parameters for the readout modes are the bias levels (BIASA through BIASD), gain (ATODGNA through ATODGND), and readnoise (RDNOISEA through RDNOISED).

Table B-18 show an example where a detector chip is read out by 4 amplifiers (A-D), each amplifier reading out one quadrant. The AMPX and AMPY keywords indicate the dividing rows and columns of the quadrants. For example, For a 4096x4096 pixels in area, AMPX=2049 and AMPY=2049 indicate that the first quadrant runs from rows and columns 1-2048, while the fourth quadrant runs from 2049-4096 rows and columns.

File:

<inst>_dct.fits

Table 1.18 Data Product HDU: Detector Characteristics Table

#	Keyword	Value	HDU
0	filetype	DETECTOR CHARACTERISTICS	phdu
0	extname	DCT	phdu
9	ttype1	Col	hdu1
10	tform1	1024I	hdu1
0	tdisp1	A4	ehdu
0	ttype2	DETCHIP	ehdu
0	tform2	I1	ehdu
0	tdisp2	I1.1	ehdu
0	ttype3	RDSPEED	ehdu
0	tform3	A4	ehdu
0	tdisp3	A4	ehdu
0	ttype4	CMDGAIN	ehdu
0	tform4	I2	ehdu
0	tdisp4	I2.1	ehdu
0	ttype5	CMDBIASA	ehdu
0	tform5	F5	ehdu
0	tdisp5	F5.2	ehdu
0	ttype6	CMDBIASB	ehdu
0	tform6	F5	ehdu
0	tdisp6	F5.2	ehdu
0	ttype7	CMDBIASC	ehdu
0	tform7	F5	ehdu
0	tdisp7	F5.2	ehdu
0	ttype8	CMDBIASD	ehdu
0	tform8	F5	ehdu
0	tdisp8	F5.2	ehdu
0	ttype9	BINAXIS1	ehdu
0	tform9	I2	ehdu
0	tdisp9	I2.1	ehdu
0	ttype10	BINAXIS2	ehdu
0	tform10	I2	ehdu
0	tdisp10	I2.1	ehdu
0	ttype11	BIASA	ehdu
0	tform11	F5	ehdu
0	tdisp11	F5.2	ehdu
0	ttype12	BIASB	ehdu
0	tform12	F5	ehdu
0	tdisp12	F5.2	ehdu
0	ttype13	BIASC	ehdu
0	tform13	F5	ehdu
0	tdisp13	F5.2	ehdu
0	ttype14	BIASD	ehdu
0	tform14	F5	ehdu
0	tdisp14	F5.2	ehdu
0	ttype15	ATODGNA	ehdu
0	tform15	F5	ehdu
0	tdisp15	F5.2	ehdu
0	ttype16	ATODGNB	ehdu
0	tform16	F5	ehdu
0	tdisp16	F5.2	ehdu
0	ttype17	ATODGNC	ehdu
0	tform17	F5	ehdu
0	tdisp17	F5.2	ehdu
0	ttype18	ATODGND	ehdu
0	tform18	F5	ehdu
0	tdisp18	F5.2	ehdu
0	ttype19	RDNOISEA	ehdu
0	tform19	F5	ehdu
0	tdisp19	F5.2	ehdu
0	ttype20	RDNOISEB	ehdu
0	tform20	F5	ehdu
0	tdisp20	F5.2	ehdu
0	ttype21	RDNOISEC	ehdu
0	tform21	F5	ehdu
0	tdisp21	F5.2	ehdu
0	ttype22	RDNOISED	ehdu
0	tform22	F5	ehdu
0	tdisp22	F5.2	ehdu
0	ttype23	AMPA	ehdu
0	tform23	I6	ehdu
0	tdisp23	I6.1	ehdu
0	ttype24	AMPB	ehdu
0	tform24	I6	ehdu
0	tdisp24	I6.1	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	BINTABLE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
11	tunit1	Counts	hdu1

1.5.12. Cosmic Ray Rejection Parameter (CRR)

Description:

This table contains the parameters used to identify pixels affected by cosmic-rays (CR) when observed data images are split into multiple sub-exposures for the purpose. The affected pixels are marked for rejection in the data quality (DQ) extension of individual frames. The identification process begins by median-combining or minimum thresholding a list of CR-split images (FILTSCHEME) to estimate the background sky level (SKYSUB) and noise (SCALENSE) values. Those pixels above a certain threshold value given by CRTHRESH and CRSIGMAS are identified as being cosmic-ray hit. If CRMASK is set to ‘Y’, then the CR-hit pixels take on values given by BADINDPDQ in the DQ extension of the affected image. If CRRADIUS is specified, then neighboring pixels are also identified as being affected.

Format:

File:

<inst>_crr.fits

Table 1.19 Data Product HDU: Cosmic Ray Rejection Parameters

#	Keyword	Value	HDU
0	filetype	COSMIC RAY REJECTION	phdu
0	extname	CRR	phdu
1	xtension	BINTABLE	hdu1
9	ttype1	Col	hdu1
10	tform1	1024I	hdu1
0	tdisp1	I1.1	ehdu
0	ttype2	CRSPLIT	ehdu
0	tform2	I2	ehdu
0	tdisp2	I2.1	ehdu
0	ttype3	MEANEXP	ehdu
0	tform3	I2	ehdu
0	tdisp3	I2.1	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
11	tunit1	Counts	hdu1

1.5.13. Image Distortion Coefficients (IDC)

Description:

This reference table contains information on geometric distortion models for generic imaging detectors. More specifically, the table contains coefficients and values for a polynomial that maps the coordinates from a raw image (distorted) to an undistorted space and vice versa.

Format:

The format for the image distortion coefficient table is shown in Table B-22. The header keyword NORDER indicates the order of the polynomial and the number of coefficients used in the transformation.

File:

<inst>_idc.fits

Table 1.20 Data Product HDU: Image Distortion Coefficients

#	Keyword	Value	HDU
0	filetype	DISTORTION COEFFICIENTS	phdu
0	extname	IDC	phdu
1	xtension	BINTABLE	hdu1
0	norder		ehdu
0	parity		ehdu
9	ttype1	Col	hdu1
10	tform1	1024I	hdu1
0	tdisp1	I1.1	ehdu
0	ttype2	DIRECTION	ehdu
0	tform2	I2	ehdu
0	tdisp2	I2.1	ehdu
0	ttype3	FILTER	ehdu
0	tform3	A10	ehdu
0	tdisp3	A10	ehdu
0	ttype4	XSIZE	ehdu
0	tform4	I5	ehdu
0	tdisp4	I5.1	ehdu
0	tunit4	pixel	ehdu
0	tdesc4	Raw image size in X-direction	ehdu
0	ttype5	YSIZE	ehdu
0	tform5	I5	ehdu
0	tdisp5	I5.1	ehdu
0	tunit5	pixel	ehdu
0	tdesc5	Raw image size in Y-direction	ehdu
0	ttype6	XREF	ehdu
0	tform6	F10	ehdu
0	tdisp6	F10.6	ehdu
0	tunit6	pixel	ehdu
0	tdesc6	X position of reference point	ehdu
0	ttype7	YREF	ehdu
0	tform7	F10	ehdu
0	tdisp7	F10.6	ehdu
0	tunit7	pixel	ehdu
0	tdesc7	Y position of reference point	ehdu
0	ttype8	THETA	ehdu
0	tform8	F10	ehdu
0	tdisp8	F10.6	ehdu
0	tunit8	arcsec	ehdu
0	tdesc8	Scale of square corrected pixel	ehdu
0	ttype9	V2REF	ehdu
0	tform9	F10	ehdu
0	tdisp9	F10.6	ehdu
0	tunit9	arcsec	ehdu
0	tdesc9	V2 position of reference point [Axis name TBC]	ehdu
0	ttype10	V3REF	ehdu
0	tform10	F10	ehdu
0	tdisp10	F10.6	ehdu
0	tunit10	arcsec	ehdu
0	tdesc10	V3 position of reference point [Axis name TBC]	ehdu
0	ttype11	CX10	ehdu
0	tform11	F10.6	ehdu
0	tdisp11	F10.6	ehdu
0	tdesc11	Distortion coefficients for X position	ehdu
0	ttype12	CX11	ehdu
0	tform12	F10.6	ehdu
0	tdisp12	F10.6	ehdu
0	tdesc12	Distortion coefficients for X position	ehdu
0	ttype13	CY10	ehdu
0	tform13	F10.6	ehdu
0	tdisp13	F10.6	ehdu
0	tdesc13	Distortion coefficients for Y position	ehdu
0	ttype14	CY11	ehdu
0	tform14	F10.6	ehdu
0	tdisp14	F10.6	ehdu
0	tdesc14	Distortion coefficients for Y position	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
11	tunit1	Counts	hdu1

1.5.14. Photometric Calibration (PHT)

Description:

This reference file contains photometry keywords and calibrated values: PHOTMODE, PHOTFLAM, PHOTFNU, PHOTZPT, PHOTPLAM, PHOTBW for an instrument camera and filter combination used in an observation. If the science image has units in [DN sec-1], multiplying the pixel value by PHOFLAM or PHOTFNU yields absolute source fluxes in [ergs sec^-1 cm^-2 Ang^-1] or [Jy], respectively.

Format:

The photometry parameters file consists the columns shown in Table B-26. The PHOTMODE string is a comma-separated string of: instrument name, camera name/number, and filter or grating name. The HISTORY keyword in the HDU header or a trailer file contains detailed information on the calibration files used to derive the photometric parameters.

File:

<inst>_pht.fits

Table 1.21 Data Product HDU: Photometric Calibration

#	Keyword	Value	HDU
0	filetype	PHOTOMETRIC CALIBRATION	phdu
0	extname	PHT	ehdu
1	xtension	BINTABLE	hdu1
9	ttype1	Col	hdu1
10	tform1	1024I	hdu1
0	tdisp1	A19	ehdu
0	tdesc1	Instrument observing mode	ehdu
0	ttype2	PHOTFLAM	ehdu
0	tform2	E10	ehdu
0	tdisp2	E10.5	ehdu
0	tunit2	ergs/cm^2/Ang/DN	ehdu
0	tdesc2	Inverse sensitivity	ehdu
0	ttype3	PHOTFNU	ehdu
0	tform3	E10	ehdu
0	tdisp3	E10.5	ehdu
0	tunit3	Jy sec DN^-1	ehdu
0	tdesc3	Inverse sensitivity	ehdu
0	ttype4	PHOTPLAM	ehdu
0	tform4	E10	ehdu
0	tdisp4	E10.5	ehdu
0	tunit4	Angstrom	ehdu
0	tdesc4	Inverse sensitivity	ehdu
0	ttype5	PHOTBW	ehdu
0	tform5	E10	ehdu
0	tdisp5	E10.5	ehdu
0	tunit5	Angstrom	ehdu
0	tdesc5	Bandwidth	ehdu
0	ttype6	PHOTZPT	ehdu
0	tform6	E10	ehdu
0	tdisp6	E10.5	ehdu
0	tunit6	mag	ehdu
0	tdesc6	Photometric zeropoint	ehdu
0	ttype7	DATESTAMP	ehdu
0	tform7	A10	ehdu
0	tdisp7	A10	ehdu
0	tdesc7	Date stamp	ehdu
0	ttype8	TIMESTAMP	ehdu
0	tform8	A12	ehdu
0	tdisp8	A12	ehdu
0	tdesc8	Time stamp	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
11	tunit1	Counts	hdu1

1.5.15. Aperture Throughput Table (APT)

Description:

This is a table containing the wavelength-dependent transmission of each aperture with respect to a nominated reference aperture.

Format:

The columns consist of: Aperture ID, number of elements in the throughput array, wavelength array, array of system throughput at corresponding wavelength, pedigree (datestamp) of reference data, and description. The suffix ‘APT’ is used to denote the file type.

File:

<inst>_apt.fits

Table 1.22 Data Product HDU: Aperture Throughput Table

#	Keyword	Value	HDU
0	filetype	APERTURE THROUGHPUT TABLE	phdu
0	obstype	SPECTROSCOPIC	phdu
1	xtension	TABLE	hdu1
0	extname	APT	ehdu
0	ttype1	TEXT	hdu1
0	tform1	A80	hdu1
0	tdisp1	A19	ehdu
0	tdesc1	Aperture name	ehdu
0	ttype2	NELEM	ehdu
0	tform2	I6	ehdu
0	tdisp2	I6.1	ehdu
0	tunit2		ehdu
0	tdesc2	Number of data points in throughput array	ehdu
0	ttype3	WAVELENGTH	ehdu
0	tform3	E12	ehdu
0	tdisp3	E12.7	ehdu
0	tunit3	Angstrom	ehdu
0	tdesc3	Reference wavelength array	ehdu
0	ttype4	THROUGHPUT	ehdu
0	tform4	F6	ehdu
0	tdisp4	F6.4	ehdu
0	tunit4	percent	ehdu
0	tdesc4	Total system throughput at each wavelength	ehdu
0	ttype5	DATESTAMP	ehdu
0	tform5	A67	ehdu
0	tdisp5	A67	ehdu
0	tunit5	date	ehdu
0	tdesc5	Date stamp	ehdu
0	ttype6	DESCRIP	ehdu
0	tform6	A67	ehdu
0	tdisp6	A67	ehdu
0	tdesc6	Description of reference data	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	80	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
0	tbcol1	1	hdu1

1.6. Science and Operations Data Products

1.6.1. Raw Data (RAW)

Description:

This is the first FITS data product produced by the DPS after receiving data from an instrument, where the data are in their unprocessed image state. To arrive at this stage, the DPS:

• Packaged the raw instrument data stream into FITS binary data format,

• Parsed the telemetry stream to obtain meta data and to assign FITS header information,

• Created a FITS file with the “raw” suffix, without regard to how the data would subsequently be used,

At this stage, the file suffix does not yet reflect the intended purpose of the data. The purpose is only apparent after additional data processing when another suffix (e.g. “bia”, “drk”, “dfl”, etc.) would replace the “raw” suffix. The raw FITS file is stored permanently into the data archive.

Format:

The default file format for an UVIS CCD is shown in Figure 5-1 and discussed in Section 5.2.3, whereas for an NIR array, the format is shown in Figure 5-2 of Section 5.2.4.

File:

<inst>_raw.fits

Table 1.23 Data Product HDU: Raw Data

#	Keyword	Value	HDU
0	filetype	RAW	phdu
0	extname	RAW	phdu
0	obstype	IMAGING	phdu
0	filter	CLEAR	phdu
0	bunit	DN	phdu
1	xtension	IMAGE	hdu1
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.6.2. Wavelength Calibration Exposure (WAV)

Description:

This is an image containing 2-D spectral lines as observed from a spectral calibration light source, where the spectrum is dispersed along one dimension while spatial information is along the other dimension. This file is used to determine the wavelength solution of a corresponding science data spectral image. The spatial and dispersion directions might not necessarily be perfectly orthogonal, nor aligned with the detector pixel directions.

Format:

The 2-D lamp spectral image is stored as a multi-extension file. The suffix ‘WAV’ is used to denote the file type.

File:

<inst>_wav.fits

Table 1.24 Data Product HDU: Wavelength Calibration Exposure

#	Keyword	Value	HDU
0	filetype	WAVELENGTH CALIBRATION SPECTRAL IMAGE	phdu
0	extname	WAV	phdu
0	obstype	SPECTROSCOPIC	phdu
0	filter	CLEAR	phdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	1024	hdu1
5	naxis2	1024	hdu1
-1	end		hdu1
4	extend	true	phdu
1	xtension	IMAGE	hdu1
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1

1.6.3. Template Calibration Lamp Spectra Table (LMP)

Description:

The template calibration table contains spectra of the calibration lamp obtained at different operating voltage levels. These spectra are used to create template spectra or images, from which wavelength corrections can be determined, and wavelength solution determined.

Format:

The lamp spectral calibration table is stored as a multi-extension file. The suffix ‘LMP’ is used to denote the file type.

File:

<inst>_lmp.fits

Table 1.25 Data Product HDU: Template Calibration Lamp Spectra Table

#	Keyword	Value	HDU
0	filetype	TEMPLATE CAL LAMP SPECTRA TABLE	phdu
0	obstype	SPECTROSCOPIC	phdu
1	xtension	TABLE	hdu1
0	extname	LMP	ehdu
0	ttype1	TEXT	hdu1
0	tform1	A80	hdu1
0	tdisp1	A20	ehdu
0	tdesc1	Name of calibration lamp that is on	ehdu
0	ttype2	LAMPVOLT	ehdu
0	tform2	F6	ehdu
0	tdisp2	F6.2	ehdu
0	tunit2	voltage	ehdu
0	tdesc2	Spectral calibration lamp voltage setting	ehdu
0	ttype3	NELEM	ehdu
0	tform3	I10	ehdu
0	tdisp3	I10	ehdu
0	tunit3		ehdu
0	tdesc3	Number of data points in spectrum	ehdu
0	ttype4	Flux	ehdu
0	tform4	F8	ehdu
0	tdisp4	F8.4	ehdu
0	tunit4	counts	ehdu
0	tdesc4	Lamp flux	ehdu
0	ttype5	DATESTAMP	ehdu
0	tform5	A67	ehdu
0	tdisp5	A67	ehdu
0	tdesc5	Date stamp	ehdu
0	ttype6	DESCRIP	ehdu
0	tform6	A67	ehdu
0	tdisp6	A67	ehdu
0	tdesc6	Description of reference data	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	80	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
0	tbcol1	1	hdu1

1.6.4. Jitter File (JIF)

Description:

This data product contains information on how the telescope behaved during an observation. Observation log files, sometimes called “jitter” files, record telemetries on pointing, jitter, guiding, open-loop tracking, laser operations, etc., during an observation. Observation log files are produced by the DPS; the information to produce the log files come by way of querying different data sources: the acquisition and guiding wavefront sensors, the mount control system, the telescope control system, on-instrument wavefront sensor, science instruments, etc.. Observation log files share the same rootname (Figure 6-2) as the main observation data except with the suffixes “_jit” or “_jif” (see Table 6-4).

The exact contents of this file is TBD, but generally speaking, this file contains a 2-D histogram of time-averaged telescope pointing excursion during an observation, stored in an image format. The amount of time averaging depends on the source of the data and the observing mode (natural seeing vs. adaptive optics) involved. The FITS header contains keywords providing information regarding the file structure, observation details, background light, telescope control system, jitter summary, problem flags, and warnings. The header values for extension 1+ will inherit keywords from the primary HDU.

Format:

Content TBD

File:

<inst>_jif.fits

Table 1.26 Data Product HDU: Telescope Jitter Image

#	Keyword	Value	HDU
0	filetype	JITTER HISTOGRAM	phdu
0	extname	JIF	phdu
0	xtension	IMAGE	ehdu

1.6.5. Telescope Jitter File (JIT)

1.6.6. Aperture Description Table (APD)

Description:

The aperture description table describes the geometries of the apertures (size, orientation) and their offsets (in arcsec) from a reference position.

Format:

Each row of the table contains the aperture name, size (length and width) of the aperture, offset from the center of aperture to the center of a reference (which is named in the header), and the orientation of the aperture’s y-axis relative to a coordinate system that is fixed to the, ground, the telescope, or the instrument rotator, depending on the mounting location [TBD].

File:

<inst>_apd.fits

Table 1.27 Data Product HDU: Aperture Description Table

#	Keyword	Value	HDU
0	filetype	APERTURE DESCRIPTION TABLE	phdu
1	xtension	TABLE	hdu1
0	extname	APT	ehdu
0	ttype1	TEXT	hdu1
0	tform1	A80	hdu1
0	tdisp1	A20	ehdu
0	tdesc1	Name of aperture	ehdu
0	ttype2	WIDTH1	ehdu
0	tform2	F8	ehdu
0	tdisp2	F8.5	ehdu
0	tunit2	arcsec	ehdu
0	tdesc2	Width along axis 1	ehdu
0	ttype3	WIDTH2	ehdu
0	tform3	F8	ehdu
0	tdisp3	F8.5	ehdu
0	tunit3	arcsec	ehdu
0	tdesc3	Width along axis 2	ehdu
0	ttype4	ANGLE	ehdu
0	tform4	F10	ehdu
0	tdisp4	F10.3	ehdu
0	tunit4	degrees	ehdu
0	tdesc4	Orientation of long or y-axis of aperture	ehdu
0	ttype5	OFFSET1	ehdu
0	tform5	F12	ehdu
0	tdisp5	F12.5	ehdu
0	tunit5		ehdu
0	tdesc5	Offset from reference position in axis 1	ehdu
0	ttype6	OFFSET2	ehdu
0	tform6	F12	ehdu
0	tdisp6	F12.5	ehdu
0	tunit6		ehdu
0	tdesc6	Offset from reference position in axis 2	ehdu
0	ttype7	DATESTAMP	ehdu
0	tform7	A67	ehdu
0	tdisp7	A67	ehdu
0	tdesc7	Date stamp	ehdu
0	ttype8	DESCRIP	ehdu
0	tform8	A67	ehdu
0	tdisp8	A67	ehdu
0	tdesc8	Description of reference data	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	80	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
0	tbcol1	1	hdu1

1.6.7. 2D_Spectrum_Distortion_Correction_Table (SDC)

Description:

This table consists of a set of WCS information used to rectify and linearize observed spectra in a 2-D image. Each set of WCS corresponds to a spectral order for a long slit spectrum, spectrum aperture ID for an integral field or multi-slit/fiber spectral image.

Format:

The columns of the table are: optical element, central wavelength, spectral order, the pixel position of the center of the spectrum, and the WCS information of the output rectified spectra.

File:

<inst>_sdc.fits

Table 1.28 Data Product HDU: 2D Spectrum Distortion Correction

#	Keyword	Value	HDU
0	filetype	2-D SPECTRUM DISTORTION CORRECTION TABLE	phdu
1	xtension	TABLE	hdu1
0	extname	SDC	ehdu
0	ttype1	TEXT	hdu1
0	tform1	A80	hdu1
0	tdisp1	A20	ehdu
0	tdesc1	Spectroscopic element in the grating wheel	ehdu
0	ttype2	CENWAVE	ehdu
0	tform2	F8	ehdu
0	tdisp2	F8.2	ehdu
0	tunit2	Angstrom	ehdu
0	tdesc2	Central wavelength	ehdu
0	ttype3	SPORDER	ehdu
0	tform3	I3	ehdu
0	tdisp3	I3	ehdu
0	tunit3		ehdu
0	tdesc3	Spectral order	ehdu
0	ttype4	APERTURE	ehdu
0	tform4	A20	ehdu
0	tdisp4	A20	ehdu
0	tunit4		ehdu
0	tdesc4	Spectral aperture ID	ehdu
0	ttype5	WCENTER	ehdu
0	tform5	F10	ehdu
0	tdisp5	F10.3	ehdu
0	tunit5	pixel	ehdu
0	tdesc5	Nominal pixel (along dispersion direction) corresponding to center of spectrum	ehdu
0	ttype6	NPIX1	ehdu
0	tform6	I5	ehdu
0	tdisp6	I5	ehdu
0	tunit6	pixel	ehdu
0	tdesc6	Number of axis 1 pixels in rectified image	ehdu
0	ttype7	NPIX2	ehdu
0	tform7	I5	ehdu
0	tdisp7	I5	ehdu
0	tdesc7	Number of axis 1 pixels in rectified image	ehdu
0	ttype8	CRPIX1	ehdu
0	tform8	I5	ehdu
0	tdisp8	I5	ehdu
0	tunit8	pixel	ehdu
0	tdesc8	Axis 1 coordinate a reference pixel in rectified image	ehdu
0	ttype9	CRPIX2	ehdu
0	tform9	I5	ehdu
0	tdisp9	I5	ehdu
0	tunit9	pixel	ehdu
0	tdesc9	Axis 2 coordinate a reference pixel in rectified image	ehdu
0	ttype10	CRVAL1	ehdu
0	tform10	F10	ehdu
0	tdisp10	F10.3	ehdu
0	tunit10	Angstrom	ehdu
0	tdesc10	Axis 1 value at reference pixel in rectified image	ehdu
0	ttype11	CRVAL2	ehdu
0	tform11	F12	ehdu
0	tdisp11	F12.5	ehdu
0	tunit11	arcsec	ehdu
0	tdesc11	Axis 2 value at reference pixel in rectified image	ehdu
0	ttype12	CDELT1	ehdu
0	tform12	F8	ehdu
0	tdisp12	F8.4	ehdu
0	tunit12	Angstrom/pixel	ehdu
0	tdesc12	Axis 1 pixel spacing in rectified image	ehdu
0	ttype13	CDELT2	ehdu
0	tform13	F8	ehdu
0	tdisp13	F8.5	ehdu
0	tunit13	arcsec/pixel	ehdu
0	tdesc13	Axis 2 pixel spacing in rectified image	ehdu
0	ttype14	DATESTAMP	ehdu
0	tform14	A67	ehdu
0	tdisp14	A67	ehdu
0	tdesc14	Date stamp	ehdu
0	ttype15	DESCRIP	ehdu
0	tform15	A67	ehdu
0	tdisp15	A67	ehdu
0	tdesc15	Description of reference data	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	80	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
0	tbcol1	1	hdu1

1.6.8. Dispersion Coefficients Table (DSP)

Description:

This table consists of dispersion coefficients of a nominal, calibrated, dispersion solution, to apply to extracted 1-D spectra.

Format:

The columns of the table are: optical element (e.g. grating), central wavelength, spectral order, aperture ID, reference aperture name, and coefficients to a dispersion function.

File:

<inst>_dsp.fits

Table 1.29 Data Product HDU: Dispersion Coefficients Table

#	Keyword	Value	HDU
0	filetype	DISPERSION COEFFICIENTS TABLE	phdu
1	xtension	TABLE	hdu1
0	extname	DSP	ehdu
0	ttype1	TEXT	hdu1
0	tform1	A80	hdu1
0	tdisp1	A20	ehdu
0	tdesc1	Spectroscopic element in the grating wheel	ehdu
0	ttype2	CENWAVE	ehdu
0	tform2	F8	ehdu
0	tdisp2	F8.2	ehdu
0	tunit2	Angstrom	ehdu
0	tdesc2	Central wavelength	ehdu
0	ttype3	SPORDER	ehdu
0	tform3	I3	ehdu
0	tdisp3	I3	ehdu
0	tunit3		ehdu
0	tdesc3	Spectral order	ehdu
0	ttype4	APERTURE	ehdu
0	tform4	A20	ehdu
0	tdisp4	A20	ehdu
0	tunit4		ehdu
0	tdesc4	Spectral aperture ID	ehdu
0	ttype5	REF_APER	ehdu
0	tform5	A12	ehdu
0	tdisp5	A12	ehdu
0	tunit5		ehdu
0	tdesc5	Name of reference aperture	ehdu
0	ttype6	WCENTER	ehdu
0	tform6	F10	ehdu
0	tdisp6	F10.3	ehdu
0	tunit6	pixel	ehdu
0	tdesc6	Nominal pixel (along dispersion direction) corresponding to center of spectrum	ehdu
0	ttype7	NCOEFF	ehdu
0	tform7	I2	ehdu
0	tdisp7	I2	ehdu
0	tdesc7	Number of coefficients in dispersion solution	ehdu
0	ttype8	COEFF	ehdu
0	tform8	E10	ehdu
0	tdisp8	E10.7	ehdu
0	tunit8		ehdu
0	tdesc8	Dispersion solution coefficients	ehdu
0	ttype9	DATESTAMP	ehdu
0	tform9	A67	ehdu
0	tdisp9	A67	ehdu
0	tdesc9	Date stamp	ehdu
0	ttype10	DESCRIP	ehdu
0	tform10	A67	ehdu
0	tdisp10	A67	ehdu
0	tdesc10	Description of reference data	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	80	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
0	tbcol1	1	hdu1

1.6.9. 1D Spectrum Trace Table (1DT)

Description:

This table defines the spectral trace prior to extracting 1-D spectrum. If a spectrum is dispersed mostly along the x-axis, then the table consists of y-displacements of the spectrum as a function of x that defines the spectral trace.

Format:

The dispersion column consists: Optical element, central wavelength, aperture ID for multi-fiber/slit spectra, the reference position of the aperture on a 2-D spectral image, spectral order, and an array of y-displacements of the spectrum as a function of nominal dispersion position (often x-position).

File:

<inst>_1dt.fits

Table 1.30 Data Product HDU: 1D Spectrum Trace Table

#	Keyword	Value	HDU
0	filetype	2-D SPECTRUM DISTORTION CORRECTION TABLE	phdu
1	xtension	TABLE	hdu1
0	extname	1DT	ehdu
0	ttype1	TEXT	hdu1
0	tform1	A80	hdu1
0	tdisp1	A20	ehdu
0	tdesc1	Spectroscopic element in the grating wheel	ehdu
0	ttype2	CENWAVE	ehdu
0	tform2	F8	ehdu
0	tdisp2	F8.2	ehdu
0	tunit2	Angstrom	ehdu
0	tdesc2	Central wavelength	ehdu
0	ttype3	APERTURE	ehdu
0	tform3	A20	ehdu
0	tdisp3	A20	ehdu
0	tunit3		ehdu
0	tdesc3	Spectral aperture ID	ehdu
0	ttype4	SPORDER	ehdu
0	tform4	I3	ehdu
0	tdisp4	I3	ehdu
0	tunit4		ehdu
0	tdesc4	Spectral order	ehdu
0	ttype5	A1CENTER	ehdu
0	tform5	F10	ehdu
0	tdisp5	F10.3	ehdu
0	tunit5	pixel	ehdu
0	tdesc5	Nominal pixel (along dispersion direction) corresponding to wavelength center of spectrum	ehdu
0	ttype6	A2CENTER	ehdu
0	tform6	F10	ehdu
0	tdisp6	F10.4	ehdu
0	tunit6	pixel	ehdu
0	tdesc6	Nominal pixel corresponding to spatial center of spectrum	ehdu
0	ttype7	A2DISPL	ehdu
0	tform7	F10	ehdu
0	tdisp7	F10.4	ehdu
0	tunit7		ehdu
0	tdesc7	Spectral displacement along axis 2	ehdu
0	ttype8	DATESTAMP	ehdu
0	tform8	A67	ehdu
0	tdisp8	A67	ehdu
0	tdesc8	Date stamp	ehdu
0	ttype9	DESCRIP	ehdu
0	tform9	A67	ehdu
0	tdisp9	A67	ehdu
0	tdesc9	Description of reference data	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	80	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
0	tbcol1	1	hdu1

1.6.10. 1D Spectral Extraction Parameter Table (1DX)

Description:

This table describes the science and background extraction apertures and the functions used in extractions.

Format:

The extraction apertures are defined by the height of the box (EXTRSIZE, BK1SIZE, BK2SIZE), the extraction algorithm (XTRACALG, polynomial function), and functional coefficients (SLTCOEFF, BKTCOEFF).

File:

<inst>_1dx.fits

Table 1.31 Data Product HDU: 1D Spectral Extraction Parameter Table

#	Keyword	Value	HDU
0	filetype	1-D SPECTRAL EXTRACTION PARAMETER TABLE	phdu
1	xtension	TABLE	hdu1
0	extname	1DX	ehdu
0	ttype1	TEXT	hdu1
0	tform1	A80	hdu1
0	tdisp1	A20	ehdu
0	tdesc1	Spectroscopic element in the grating wheel	ehdu
0	ttype2	CENWAVE	ehdu
0	tform2	F8	ehdu
0	tdisp2	F8.2	ehdu
0	tunit2	Angstrom	ehdu
0	tdesc2	Central wavelength	ehdu
0	ttype3	APERTURE	ehdu
0	tform3	A20	ehdu
0	tdisp3	A20	ehdu
0	tunit3		ehdu
0	tdesc3	Spectral aperture ID	ehdu
0	ttype4	SPORDER	ehdu
0	tform4	I3	ehdu
0	tdisp4	I3	ehdu
0	tunit4		ehdu
0	tdesc4	Spectral order	ehdu
0	ttype5	EXTRSIZE	ehdu
0	tform5	F8	ehdu
0	tdisp5	F8.3	ehdu
0	tunit5	pixel	ehdu
0	tdesc5	Height of spectrum extraction box	ehdu
0	ttype6	NCOEFFSL	ehdu
0	tform6	I3	ehdu
0	tdisp6	I3	ehdu
0	tunit6		ehdu
0	tdesc6	Number of coefficients in solution to slit tilt correction	ehdu
0	ttype7	SLTCOEFF	ehdu
0	tform7	E8	ehdu
0	tdisp7	E8.6	ehdu
0	tunit7		ehdu
0	tdesc7	Spectrum extraction coefficients	ehdu
0	ttype8	BK1SIZE	ehdu
0	tform8	F8	ehdu
0	tdisp8	F8.3	ehdu
0	tunit8	pixel	ehdu
0	tdesc8	Height of background extraction box 1	ehdu
0	ttype9	BK2SIZE	ehdu
0	tform9	F8	ehdu
0	tdisp9	F8.3	ehdu
0	tunit9	pixel	ehdu
0	tdesc9	Height of background extraction box 2	ehdu
0	ttype10	BK1OFFST	ehdu
0	tform10	F8	ehdu
0	tdisp10	F8.3	ehdu
0	tunit10	pixel	ehdu
0	tdesc10	Offset of background extraction box 1 from spectrum	ehdu
0	ttype11	BK2OFFST	ehdu
0	tform11	F8	ehdu
0	tdisp11	F8.3	ehdu
0	tunit11	pixel	ehdu
0	tdesc11	Offset of background extraction box 2 from spectrum	ehdu
0	ttype12	NCOEFFBK	ehdu
0	tform12	I3	ehdu
0	tdisp12	I3	ehdu
0	tunit12		ehdu
0	tdesc12	Number of coefficients in solution to slit tilt correction	ehdu
0	ttype13	BKTCOEFF	ehdu
0	tform13	E8	ehdu
0	tdisp13	E8.6	ehdu
0	tunit13		ehdu
0	tdesc13	Background extraction coefficients	ehdu
0	ttype14	BACKORD	ehdu
0	tform14	I3	ehdu
0	tdisp14	I3	ehdu
0	tunit14		ehdu
0	tdesc14	Order of polynomial fit to background	ehdu
0	ttype15	XTRACALG	ehdu
0	tform15	A20	ehdu
0	tdisp15	A20	ehdu
0	tdesc15	Extraction algorithm to use	ehdu
0	ttype16	DATESTAMP	ehdu
0	tform16	A67	ehdu
0	tdisp16	A67	ehdu
0	tdesc16	Date stamp	ehdu
0	ttype17	DESCRIP	ehdu
0	tform17	A67	ehdu
0	tdisp17	A67	ehdu
0	tdesc17	Description of reference data	ehdu
1	simple	true	phdu
2	bitpix	16	hdu1
3	naxis	2	hdu1
4	naxis1	80	hdu1
5	naxis2	100	hdu1
-1	end		hdu1
4	extend	true	phdu
6	pcount	0	hdu1
7	gcount	1	hdu1
8	tfields	1	hdu1
0	tbcol1	1	hdu1

1.7. References