2. Software and Controls FITS Keyword Dictionary

2.1. Introduction

This report provides a list of FITS header keywords used by the Data Processing Subsystem when processing telescope data and generating FITS data products.

2.2. Acronyms

2.3. Standard FITS Keywords

Description:

Keywords for a basic FITS standard header. In many cases, the keywords and descriptions are taken verbatim from ‘Definition of the Flexible Image Transport System (FITS), Version 3.0’.

Table 2.3 Standard FITS Keywords Dictionary

Key	Keyword	Info	Type	HDU	Description
author	AUTHOR	Author(s) of data	String	any	The value field shall contain a character string identifying who compiled the information in the data associated with the header. This keyword is appropriate when the data originate in a published paper or are compiled from many sources.
bitpix	BITPIX	Bits per data value	Integer	any	The value field shall contain an integer. The absolute value is used in computing the sizes of data structures. It shall specify the number of bits that represent a data value.
blankkey		Descriptive comment	String	any	Columns 1-8 contain ASCII blanks. This keyword has no associated value. Columns 9-80 may contain any ASCII text. Any number of card images with blank keyword fields may appear in a header. Blank field supplies comments to FITS file, useful for aesthetic purposes to provide a break between groups of related keywords in the header.
blank	BLANK	Value used for undefined array elements	integer	primary	This keyword shall be used only in primary array headers or IMAGE extension headers with positive values of BITPIX (i.e., in arrays with integer data). Columns 1-8 contain the string, ‘BLANK ‘ (ASCII blanks in columns 6-8). The value field shall contain an integer that specifies the representation of array values whose physical values are undefined.
bscale	BSCALE	Linear factor in scaling equation	Float	any	This keyword shall be used, along with the BZERO keyword, when the array pixel values are not the true physical values, to transform the primary data array values to the true physical values they represent, using the equation: physical_value = BZERO + BSCALE * array_value. The value field shall contain a floating point number representing the coefficient of the linear term in the scaling equation, the ratio of physical value to array value at zero offset. The default value for this keyword is 1.0.
bunit	BUNIT	Physical units of the array values	String	any	The value field shall contain a character string, describing the physical units in which the quantities in the array, after application of BSCALE and BZERO, are expressed. The units of all FITS header keyword values, with the exception of measurements of angles, should conform with the recommendations in the IAU Style Manual. For angular measurements given as floating point values and specified with reserved keywords, degrees are the recommended units (with the units, if specified, given as ‘deg’
bzero	BZERO	Zero point in scaling equation	Float	any	This keyword shall be used, along with the BSCALE keyword, when the array pixel values are not the true physical values, to transform the primary data array values to the true values using the equation: physical_value = BZERO + BSCALE * array_value. The value field shall contain a floating point number representing the physical value corresponding to an array value of zero. The default value for this keyword is 0.0.
comment	COMMENT	Descriptive comment	String	any	This keyword shall have no associated value; columns 9-80 may contain any ASCII text. Any number of COMMENT card images may appear in a header.
date	DATE	Date of file creation	String	any	The date on which the HDU was created, in the format specified in the FITS Standard. The old date format was ‘yy/mm/dd’ and may be used only for dates from 1900 through 1999. The new Y2K compliant date format is ‘yyyy-mm-dd’ or ‘yyyy-mm-ddTHH:MM:SS[.sss]’.
datamax	DATAMAX	Maximum data value	Float	any	The value field shall always contain a floating point number, regardless of the value of BITPIX. This number shall give the maximum valid physical value represented by the array, exclusive of any special values.
datamin	DATAMIN	Minimum data value	Float	any	The value field shall always contain a floating point number, regardless of the value of BITPIX. This number shall give the minimum valid physical value represented by the array, exclusive of any special values.
date_obs	DATE-OBS	Date of the observation	String	any	The date of the observation, in the format specified in the FITS Standard. The old date format was ‘yy/mm/dd’ and may be used only for dates from 1900 through 1999. The new Y2K compliant date format is ‘yyyy-mm-dd’ or ‘yyyy-mm-ddTHH:MM:SS[.sss]’.
dobs	DOBSn	Date of the observation	String	any	Similar to DATE-OBS except primary keyword for BINTABLE vector and pixel list alike.
end	END	Marks the end of the header keywords		any	No associated value. Marks the logical end of the header. Columns 9-80 shall be filled with ASCII blanks.
extlevel	EXTLEVEL	Hierarchical level of the extension	Integer	extension	The value field shall contain an integer, specifying the level in a hierarchy of extension levels of the extension header containing it. The value shall be 1 for the highest level; levels with a higher value of this keyword shall be subordinate to levels with a lower value. If the EXTLEVEL keyword is absent, the file should be treated as if the value were 1. This keyword is used to describe an extension and should not appear in the primary header.
extend	EXTEND	Indicates whether the FITS file contain extensions	Boolean	primary	T or F indicating whether the FITS file is allowed to contain conforming extensions following the primary HDU. This keyword MUST NOT appear in XtensionFrame. Contains a logical value indicating whether the FITS file is allowed to contain conforming extensions following the primary HDU. This keyword may only appear in the primary header and must not appear in an extension header. If the value field is T then there may be conforming extensions in the FITS file following the primary HDU. This keyword is only advisory, so its presence with a value T does not require that the FITS file contains extensions, nor does the absence of this keyword necessarily imply that the file does not contain extensions.
nextend	NEXTEND	The number of standard extensions	Integer	primary	Number of standard extensions
extname	EXTNAME	Name of the extension	String	extension	The value field shall contain a character string, to be used to distinguish among different extensions of the same type, i.e., with the same value of XTENSION, in a FITS file. This keyword is used to describe an extension and should not appear in the primary header. The extension types are: SCI (science image), ERR (error image), DQ (data quality image), SAMP (number of sample), TIME (exposure time), EVENTS (photon event list), GTI (good time interval), WHT (weight image), CTX (context image).
extver	EXTVER	Version of the extension	Integer	extension	The value field shall contain an integer, to be used to distinguish among different extensions in a FITS file with the same type and name, i.e., the same values for XTENSION and EXTNAME. The values need not start with 1 for the first extension with a particular value of EXTNAME and need not be in sequence for subsequent values. If the EXTVER keyword is absent, the file should be treated as if the value were 1. This keyword is used to describe an extension and should not appear in the primary header.
gcount	GCOUNT	Group count	Integer	extension	The value field shall contain an integer that shall be used in any way appropriate to define the data structure, consistent with Eq. 5.2 in the FITS Standard. This keyword originated for use in FITS Random Groups where it specifies the number of random groups present. In most other cases this keyword will have the value 1. Must have the value 1 in the IMAGE, Table, and BINTABLE standard extensions.
groups	GROUPS	Indicates random groups structure	Boolean	extension	The value field shall contain the logical constant T. The value T associated with this keyword implies that random groups records are present.
history	HISTORY	Processing history of the data	String	any	This keyword shall have no associated value; columns 9-80 may contain any ASCII text. The text should contain a history of steps and procedures associated with the processing of the associated data. Any number of HISTORY card images may appear in a header.
instrume	INSTRUME	Name of instrument	String	any	The value field shall contain a character string identifying the instrument used to acquire the data associated with the header.
naxis	NAXIS	Number of axes	Integer	any	The value field shall contain a non-negative integer no greater than 999, representing the number of axes in the associated data array. A value of zero signifies that no data follow the header in the HDU. In the context of FITS ‘TABLE’ or ‘BINTABLE’ extensions, the value of NAXIS is always 2.
naxisn	NAXISn	Size along the axis n dimension	Integer	any	The value field of this indexed keyword shall contain a non-negative integer, representing the number of elements along axis n of a data array. The NAXISn must be present for all values n = 1,…,NAXIS, and for no other values of n. A value of zero for any of the NAXISn signifies that no data follow the header in the HDU. If NAXIS is equal to 0, there should not be any NAXISn keywords.
naxis1	NAXIS1	Size along the axis 1 dimension	Integer	any	Size along the axis 1 dimension
naxis2	NAXIS2	Size along the axis 2 dimension	Integer	any	Size along the axis 2 dimension
object	OBJECT	Name or type of observed object	String	any	The value field shall contain a character string giving a name or type of the object observed. Often ‘TARGNAME’ is used for target name, in which case ‘OBJECT’ can be used to specify the object category.
observer	OBSERVER	Observer who acquired the data	String	any	The value field shall contain a character string identifying who acquired the data associated with the header.
origin	ORIGIN	Organization responsible for the data	String	any	The value field shall contain a character string identifying the organization or institution responsible for creating the FITS file.
pcount	PCOUNT	Parameter Count	Integer	extension	The value field shall contain an integer that shall be used in any way appropriate to define the data structure, consistent with Eq. 5.2 in the FITS Standard. This keyword was originated for use with FITS Random Groups and represented the number of parameters preceding each group. It has since been used in ‘BINTABLE’ extensions to represent the size of the data heap following the main data table. In most other cases its value will be zero. Must have value of 0 for IMAGE and TABLE extensions. In BINTABLE, the value specifies the number of bytes that follow the main data table in the supplemental data area called the heap. This keyword is also used in the random groups structure to specify the number of parameters preceding each array in a group.
pscaln	PSCALn	Parameter scaling factor	Float	extension	This keyword is reserved for use within the FITS Random Groups structure. This keyword shall be used, along with the PZEROn keyword, when the nth FITS group parameter value is not the true physical value, to transform the group parameter value to the true physical values it represents, using the equation, physical_value = PZEROn + PSCALn * group_parameter_value. The value field shall contain a floating point number representing the coefficient of the linear term, the scaling factor between true values and group parameter values at zero offset. The default value for this keyword is 1.0.
ptypen	PTYPEn	Name of random groups parameter	String	extension	This keyword is reserved for use within the FITS Random Groups structure. The value field shall contain a character string giving the name of parameter n. If the PTYPEn keywords for more than one value of n have the same associated name in the value field, then the data value for the parameter of that name is to be obtained by adding the derived data values of the corresponding parameters. This rule provides a mechanism by which a random parameter may have more precision than the accompanying data array elements; for example, by summing two 16-bit values with the first scaled relative to the other such that the sum forms a number of up to 32-bit precision.
pzeron	PZEROn	Parameter scaling zero point	Float	extension	This keyword is reserved for use within the FITS Random Groups structure. This keyword shall be used, along with the PSCALn keyword, when the nth FITS group parameter value is not the true physical value, to transform the group parameter value to the physical value. The value field shall contain a floating point number, representing the true value corresponding to a group parameter value of zero. The default value for this keyword is 0.0. The transformation equation is as follows: physical_value = PZEROn + PSCALn * group_parameter_value.
referenc	REFERENC	Bibliographic reference	String	any	The value field shall contain a character string citing a reference where the data associated with the header are published.
simple	SIMPLE	Indicates whether the file conforms to the standard	Boolean	primary	The SIMPLE keyword is required to be the first keyword in the primary header of all FITS files. The value field shall contain a logical constant with the value T if the file conforms to the standard. This keyword is mandatory for the primary header and is not permitted in extension headers. A value of F signifies that the file does not conform to this standard.
tbcoln	TBCOLn	Beginning column number	Integer	extension	The value field of this indexed keyword shall contain an integer specifying the column in which field n starts in an ASCII TABLE extension. For tables, The TBCOLn keywords must be present for all values n=1 … TFIELDS, and for no other values of n. The value contains an integer specifying the column in which field n starts. The first column of a row is numbered 1.
tdimn	TDIMn	Dimensionality of the array	String	extension	The value field of this indexed keyword shall contain a character string describing how to interpret the contents of field n as a multidimensional array, providing the number of dimensions and the length along each axis. The form of the value is not further specified by the Standard. A proposed convention is described in Appendix B.2 of the FITS Standard in which the value string has the format ‘(l,m,n…)’ where l, m, n,… are the dimensions of the array. The data are ordered such that the array index of the first dimension given (l) is the most rapidly varying and that of the last dimension given is the least rapidly varying.
tdispn	TDISPn	Display format	String	extension	The value field of this indexed keyword shall contain a character string describing the format recommended for the display of the contents of field n. If the table value has been scaled, the physical value shall be displayed. All elements in a field shall be displayed with a single, repeated format. For purposes of display, each byte of bit (type X) and byte (type B) arrays is treated as an unsigned integer. Arrays of type A may be terminated with a zero byte. Only the format codes in Table 8.6, discussed in section 8.3.4 of the FITS Standard, are permitted for encoding. The format codes must be specified in upper case. If the Bw.m, Ow.m, and Zw.m formats are not readily available to the reader, the Iw.m display format may be used instead, and if the ENw.d and ESw.d formats are not available, Ew.d may be used. The meaning of this keyword is not defined for fields of type P in the Standard but may be defined in conventions using such fields.
telescop	TELESCOP	Name of telescope	String	any	The value field shall contain a character string identifying the telescope used to acquire the data associated with the header.
tfields	TFIELDS	Number of columns in the table	Integer	extension	The value field shall contain a non-negative integer representing the number of fields in each row of a ‘TABLE’ or ‘BINTABLE’ extension. The maximum permissible value is 999.
tformn	TFORMn	Column data format	String	extension	The value field of this indexed keyword shall contain a character string describing the format in which field n is encoded in a ‘TABLE’ or ‘BINTABLE’ extension. The TFORMn keywords must be present for all values n=1…TFIELDS, and for no other values of n.
theap	THEAP	Offset to starting data heap address	Integer	extension	The value field of this keyword shall contain an integer providing the separation, in bytes, between the start of the main data table and the start of a supplemental data area called the heap. The default value, which is also the minimum allowed value, shall be the product of the values of NAXIS1 and NAXIS2. This keyword shall not be used if the value of PCOUNT is zero. A proposed application of this keyword is presented in Appendix B.1 of the FITS Standard.
tnulln	TNULLn	Value used to indicate undefined table element	String	extension	In ASCII ‘TABLE’ extensions, the value field for this indexed keyword shall contain the character string that represents an undefined value for field n. The string is implicitly blank filled to the width of the field. In binary ‘BINTABLE’ table extensions, the value field for this indexed keyword shall contain the integer that represents an undefined value for field n of data type B, I, or J. The keyword may not be used in ‘BINTABLE’ extensions if field n is of any other data type.
tscaln	TSCALn	Linear data scaling factor	Float	extension	This indexed keyword shall be used, along with the TZEROn keyword, when the quantity in field n does not represent a true physical quantity. The value field shall contain a floating point number representing the coefficient of the linear term in the equation, physical_value = TZEROn + TSCALn * field_value, which must be used to compute the true physical value of the field, or, in the case of the complex data types C and M, of the real part of the field with the imaginary part of the scaling factor set to zero. The default value for this keyword is 1.0. This keyword may not be used if the format of field n is A, L, or X.
ttypen	TTYPEn	Column name	String	extension	The value field for this indexed keyword shall contain a character String, giving the name of field n. It is recommended that only letters, digits, and underscore (hexadecimal code 5F, (‘_’) be used in the name. String comparisons with the values of TTYPEn keywords should not be case sensitive. The use of identical names for different fields should be avoided.
tunitn	TUNITn	Column units	String	extension	The value field shall contain a character string describing the physical units in which the quantity in field n, after any application of TSCALn and TZEROn, is expressed. The units of all FITS header keyword values, with the exception of measurements of angles, should conform with the recommendations in the IAU Style Manual. For angular measurements given as floating point values and specified with reserved keywords, degrees are the recommended units (with the units, if specified, given as ‘deg’).
tzeron	TZEROn	Column scaling zero point	Float	extension	This indexed keyword shall be used, along with the TSCALn keyword, when the quantity in field n does not represent a true physical quantity. The value field shall contain a floating point number representing the true physical value corresponding to a value of zero in field n of the FITS file, or, in the case of the complex data types C and M, in the real part of the field, with the imaginary part set to zero. The default value for this keyword is 0.0. This keyword may not be used if the format of field n is A, L, or X. This indexed keyword is used with TSCALn keyword to linearly scale the values in the table field n to transform them into physical values using: physical_value = TZEROn + TSCALn * field_value.
xtension	XTENSION	Marks beginning of new HDU	String	extension	Required to be the first keyword of all image (XTENSION= ‘IMAGE ‘)and table (XTENSION= ‘BINTABLE’ or XTENSION= ‘TABLE ‘) extensions. The value field shall contain a character string giving the name of the extension type. This keyword is mandatory for an extension header and must not appear in the primary header. For an extension that is not a standard extension, the type name must not be the same as that of a standard extension.
wcsaxes	WCSAXES	The number of axes in the WCS description	Integer	all	[integer; default: NAXIS, or larger of WCS indexes i or j]. Number of axes in the WCS description. This keyword, if present, must precede all WCS keywords except NAXIS in the HDU. The value of WCSAXES may exceed the number of pixel axes for the HDU.
ctypei	CTYPEia	Name of the coordinate axis	String	all	The value field shall contain a character string, giving the name of the coordinate represented by axis n. Any coordinate type that is not covered by the standard or an officially recognized FITS convention shall be taken to be linear. All non-linear coordinate system names must be expressed in ‘4–3’ form: the first four characters specify the coordinate type, the fifth character is a hyphen (‘-’), and the remaining three characters specify an algorithm code for computing the world coordinate value. Coordinate types with names of less than four characters are padded on the right with hyphens, and algorithm codes with less than three characters are padded on the right with blanks. Algorithm codes should be three characters.
ctype1	CTYPE1	Coordinate type for the x-axis	String	all	Coordinate type for the x-axis
ctype2	CTYPE2	Coordinate type for the y-axis	String	all	Coordinate type for the y-axis
ictypn	iCTYPn	Name of the coordinate axis	String	extension	Similar to CTYPEia except primary keyword for BINTABLE vector.
ictyn	iCTYna	Name of the coordinate axis	String	extension	Alternative keyword for iCTYPn for BINTABLE vector.
tctypn	TCTYPn	Name of the coordinate axis	String	extension	Similar to CTYPEia except primary keyword for pixel list.
tctyn	TCTYna	Name of the coordinate axis	String	extension	Alternative keyword for TCTYPn for pixel list.
cuniti	CUNITia	Units of CRVAL and CDELT	String	primary	Physical units of CRVAL and CDELT for axis i. Note that units should always be specified. Units for celestial coordinate systems defined in this Standard must be degrees.
icunin	iCUNIn	Units of CRVAL and CDELT	String	extension	Similar to CUNITia except primary keyword for BINTABLE vector.
icunn	iCUNna	Units of CRVAL and CDELT	String	extension	Same as iCUNIn except alternative keyword for BINTABLE vector.
tcunin	TCUNIn	Units of CRVAL and CDELT	String	pixel list	Similar to CUNITia except primary keyword for pixel list.
tcunn	TCUNna	Units of CRVAL and CDELT	String	extension	Same as iCUNIn except alternative keyword for pixel list.
crpixj	CRPIXja	Coordinate system reference pixel	Float	primary	The value field shall contain a floating point number, identifying the location of a reference point along axis n, in units of the axis index. This value is based upon a counter that runs from 1 to NAXISn with an increment of 1 per pixel. The reference point value need not be that for the center of a pixel nor lie within the actual data array. Use comments to indicate the location of the index point relative to the pixel.
jcrpxn	jCRPXn	Coordinate system reference pixel	Float	extension	Similar to CRPIXja except primary keyword for BINTABLE vector.
icrpn	jCRPna	Coordinate system reference pixel	Float	extension	Same as jCRPXn except alternative keyword for BINTABLE vector.
tcrpxn	TCRPXn	Coordinate system reference pixel	Float	all	Similar to CRPIXja except primary keyword for pixel list.
tcrpn	TCRPna	Coordinate system reference pixel	Float	extension	Same as jCRPXn except alternative keyword for pixel list.
crvali	CRVALia	Coordinate system value at reference pixel	Float	all	The value field shall contain a floating point number, giving the value of the coordinate specified by the CTYPEn keyword at the reference point CRPIXn. Units must follow the prescriptions of section 5.3 of the FITS Standard.
crval1	CRVAL1	x-coordinate value at reference pixel	Float	primary	x-coordinate value at reference pixel
crval2	CRVAL1	y-coordinate value at reference pixel	Float	primary	y-coordinate value at reference pixel
icrvln	iCRVLn	Coordinate system value at reference pixel	Float	extension	Similar to CRVALia except primary keyword for BINTABLE vector.
icrvn	iCRVna	Coordinate system value at reference pixel	Float	extension	Alternative keyword for iCRVLn for BINTABLE vector.
tcrvln	TCRVLn	Coordinate system value at reference pixel	Float	pixel list	Similar to CRVALia except primary keyword for pixel list.
tcrvn	TCRVna	Coordinate system value at reference pixel	Float	pixel list	Alternative keyword for iCRVLn for pixel list.
cdelti	CDELTi	Coordinate increment along axis	Float	primary	The value field shall contain a floating point number giving the partial derivative of the coordinate specified by the CTYPEn keywords with respect to the pixel index, evaluated at the reference point CRPIXn, in units of the coordinate specified by the CTYPEn keyword. These units must follow the prescriptions of section 5.3 of the FITS Standard.
icdltn	iCDLTn	Coordinate increment along axis	Float	extension	Similar to CDELTi except primary keyword for BINTABLE vector.
icden	iCDEna	Coordinate increment along axis	Float	extension	Alternative keyword for iCDLTn for BINTABLE vector.
tcdltn	TCDLTn	Coordinate increment along axis	Float	pixel list	Similar to CDELTi except primary keyword for pixel list.
tcden	TCDEna	Coordinate increment along axis	Float	pixel list	Alternative keyword for TCDLTn for pixel list.
crotai	CROTAi	Coordinate system rotation angle	Float	primary	This keyword is used to indicate a rotation from a standard coordinate system described by the CTYPEn to a different coordinate system in which the values in the array are actually expressed. Rules for such rotations are not further specified in the Standard; the rotation should be explained in comments. The value field shall contain a floating point number giving the rotation angle in degrees between axis n and the direction implied by the coordinate system defined by CTYPEn. Further use of this keyword is deprecated, in favor of the newer formalisms that use the CDi_j or PCi_j keywords to define the rotation.
icrotn	iCROTn	Coordinate system rotation angle	Float	extension	Similar to CROTAi except primary keyword for BINTABLE vector.
tcrotn	TCROTn	Coordinate system rotation angle	Float	pixel list	Similar to CROTAi except primary keyword for pixel list.
pci_j	PCi_ja	Coordinate transformation coefficient	Float	primary	[floating point; defaults: 1.0 when i = j, 0.0 otherwise]. Linear transformation matrix between pixel axes j and intermediate coordinate axes i. The PCi_j matrix must not be singular.
ijpcn	ijPCna	Coordinate transformation coefficient	Float	extension	Similar to PCi_ja except this is keyword for BINTABLE vector.
tpcn_k	TPCn_ka	Coordinate transformation coefficient	Float	pixel list	Similar to PCi_ja except this is keyword for pixel list.
tpn_k	TPn_ka	Coordinate transformation coefficient	Float	pixel list	Similar to PCi_ja except this is also keyword for pixel list.
cdi_j	CDi_ja	Linear transformation matrix between axes i and j	Float	primary	[floating point; defaults: 0.0, but see below]. Linear transformation matrix (with scale) between pixel axes j and intermediate coordinate axes i. This nomenclature is equivalent to PCi j when CDELTi is unity. The CDi_j matrix must not be singular. Note that the CDi_j formalism is an exclusive alternative to PCi_j, and the CDi_j and PCi_j keywords must not appear together within an HDU.
cd1_1	CD1_1	Projection of unit vector of axis 1 of one coordinate system with respect to axis 1 of the other coordinate system	Float	primary	When two coordinate axes are rotated with respect to each other, e.g. North with respect to x-axis, this keyword gives the projection of unit vector of axis 1 (e.g. N) of one system with respect to the axis 1 (e.g. x) of the other.
cd1_2	CD1_2	Projection of unit vector of axis 1 of one coordinate system with respect to axis 2 of the other coordinate system	Float	primary	When two coordinate axes are rotated with respect to each other, e.g. North with respect to x-axis, this keyword gives the projection of unit vector of axis 1 (e.g. N) of one system with respect to the axis 2 (e.g. y) of the other.
cd2_1	CD2_1	Projection of unit vector of axis 2 of one coordinate system with respect to axis 1 of the other coordinate system	Float	primary	When two coordinate axes are rotated with respect to each other, e.g. South with respect to x-axis, this keyword gives the projection of unit vector of axis 2 (e.g. S) of one system with respect to the axis 1 (e.g. x) of the other.
cd2_2	CD2_2	Projection of unit vector of axis 2 of one coordinate system with respect to axis 2 of the other coordinate system	Float	primary	When two coordinate axes are rotated with respect to each other, e.g. South with respect to y-axis, this keyword gives the projection of unit vector of axis 2 (e.g. S) of one system with respect to the axis 2 (e.g. y) of the other.
ijcdn	ijCDna	Linear transformation matrix between axes i and j	Float	extension	Similar to CDi_ja except this is keyword for BINTABLE vector.
tcdn_k	TCDn_ka	Linear transformation matrix between axes i and j	Float	extension	Similar to CDi_ja except this is keyword for pixel list.
tcn_k	TCn_ka	Linear transformation matrix between axes i and j	Float	extension	Similar to CDi_ja except this is also a keyword for pixel list.
pvii_m	PVIi_ma	Value for intermediate WCS axis i	Float	primary	[floating point]. Numeric parameter values for intermediate world coordinate axis i, where m is the parameter number. Leading zeros must not be used, and m may have only values in the range 0 through 99, and that are defined for the particular non-linear algorithm.
ipvn_m	iPVn_ma	Value for intermediate WCS axis i	Float	extension	Similar to PVi_ma except this is keyword for BINTABLE vector.
ivn_m	iVn_ma	Value for intermediate WCS axis i		extension	This is equivalent to iPVn_ma.
tpvn_m	TPVn_ma	Value for intermediate WCS axis i	Float	pixel list	Similar to PVi_ma except this is keyword for pixel list.
tvn_m	TVn_ma	Value for intermediate WCS axis i	Float	pixel list	This is equivalent to TPVn_ma.
ivn_x	iVn_Xa	Coordinate parameter array	Float	extension	Coordinate parameter array for BINTABLE vector.
psi_m	PSi_ma	Parameters for for intermediate WCS axis i	String	primary	[character]. Character-valued parameters for intermediate world coordinate axis i, where m is the parameter number. Leading zeros must not be used, and m may have only values in the range 0 through 99, and that are defined for the particular non-linear algorithm.
ipsn_m	iPSn_ma	Parameters for for intermediate WCS axis i	String	extension	Sn_ma) Similar to PSi_ma except this is keyword for BINTABLE vector.
isn_m	iSn_ma	Parameters for for intermediate WCS axis i	String	extension	This is equivalent to PSi_ma
tpsn_m	TPSn_ma	Parameters for for intermediate WCS axis i	String	pixel list	Sn_ma) Similar to PSi_ma except this is keyword for pixel list.
tsn_m	TSn_ma	Parameters for for intermediate WCS axis i	String	pixel list	This is equivalent to TPSn_ma
crderi	CRDERi	Random error in coordinate i	Float	primary	[floating point; default: 0.0]. Random error in coordinate i, which must be non-negative.
icrdn	ICRDna	Random error in coordinate i	Float	extension	Similar to CRDERi except this is keyword for BINTABLE vector.
tcrdn	TCRDna	Random error in coordinate i	Float	pixel list	Similar to CRDERi except this is keyword for pixel list.
csyeri	CSYERi	Systematic error in coordinate i	Float	primary	[floating point; default: 0.0]. Systematic error in coordinate i, which must be non-negative.
icsyn	ICSYna	Systematic error in coordinate i	Float	extension	SYna) Similar to CSYERi except this is keyword for BINTABLE vector.
tcsyn	TCSYna	Systematic error in coordinate i	Float	pixel list	SYna) Similar to CSYERi except this is keyword for pixel list.
wcstn	WCSTna	WCS cross-reference target for BINTABLE vector	String	extension	WCS Cross-reference target for BINTABLE vector
wcsxn	WCSXna	WCS cross-reference for BINTABLE vector	String	extension	WCS Cross-reference for BINTABLE vector
wcsname	WCSNAMEa	Name of the world world coordinate system	String	primary	[character; default for a: ’ ’ (i.e., blank, for the primary WCS, else a character A through Z that specifies the coordinate version]. Name of the world coordinate system represented by the WCS keywords with the suffix a. Its primary function is to provide a means by which to specify a particular WCS if multiple versions are defined in the HDU.
wcsnn	WCSNna	Name of the world world coordinate system	String	extension	Similar to WCSNAMEa except this is keyword for BINTABLE vector.
wcsn	WCSna	Name of the world world coordinate system	String	pixel list	Similar to WCSNAMEa except this is keyword for pixel list.
twcsn	TWCSna	Name of the world world coordinate system	String	pixel list	This is equivalent to WCSna.
radesys	RADESYSa	Reference frame of equatorial or ecliptic coordinates	String	any	[character; default: FK4, FK5, or ICRS: see below]. Name of the reference frame of equatorial or ecliptic coordinates, whose value must be one of those specified in Table 24 of ‘FITS Standard’ document. The default value is FK4 if the value of EQUINOXa < 1984.0, FK5 if EQUINOXa >= 1984.0, or ICRS if EQUINOXa is not given.
radecsys	RADECSYS	Reference frame of equatorial or ecliptic coordinates	String	any	The exact same definition as RADESYSa
raden	RADEna	Reference frame of equatorial or ecliptic coordinates	String	extension	Similar to RADESYSa except this is keyword for BINTABLE vector and pixel list alike.
equinox	EQUINOXa	Equinox of celestial coordinate system	Float	any	The value field shall contain a floating point number giving the equinox in years for the celestial coordinate system in which positions are expressed. The interpretation of epoch depends upon the value of RADESYSa if present: Besselian if the value is FK4 or FK4-NO-E, Julian if the value is FK5; not applicable if the value is ICRS or GAPPT.
equin	EQUIna	Equinox of celestial coordinate system	Float	extension	Similar to EQUINOXa except this is keyword for BINTABLE vector and pixel list alike.
mjd_obs	MJD-OBS	Modified Julian Date of observation	Float	primary	[floating point; default: DATE-OBS if given, other- wise no default]. Modified Julian Date (JD – 2,400,000.5) of the observation, whose value corresponds (by default) to the start of the observation, unless another interpretation is explained in the comment field. No specific time system (e.g. UTC, TAI, etc.) is defined for this or any of the other time-related keywords. It is recommended that the TIMESYS keyword, as defined in Appendix B be used to specify the time system.
mjdobn	MJDOBn	Modified Julian Date of observation	Float	extension	Similar to MJD_OBS except this is keyword for BINTABLE vector and pixel list alike.
lonpole	LONPOLEa	Longitude relative to celestial north pole	Float	any	[floating point; default: φ0 if δ0 >= θ0, φ0 + 180 deg otherwise]. Longitude in the native coordinate system of the celestial system’s north pole. Normally, φ0 is zero unless a non-zero value has been set for PVi 1a, which is associated with the longitude axis. This default applies for all values of θ0, including θ0 = 90 deg, although the use of non-zero values of θ0 are discouraged in that case.
lonpn	LONPna	Longitude relative to celestial north pole	Float	extension	Similar to LONPOLEa except this is keyword for BINTABLE vector and pixel list alike.
latpole	LATPOLEa	Latitude relative to celestial north pole	Float	any	[floating point; default: 90 deg, or no default if (θ0, δ0, φp-φ0) = (0, 0, ±90 deg)]. Latitude in the native coordinate system of the celestial system’s north pole, or equivalently, the latitude in the celestial coordinate system of the native system’s north pole. May be ignored or omitted in cases where LONPOLEa completely specifies the rotation to the target celestial system.
latpn	LATPna	Latitude relative to celestial north pole	Float	extension	Similar to LATPOLEa except this is keyword for BINTABLE vector and pixel list alike.
cnamei	CNAMEia	Spectral coordinate description	String	any	[character; default: ’ ’ (i.e. a linear, undefined axis)]. Spectral coordinate description which must not exceed 68 characters in length.
icpnan	ICNAna	Spectral coordinate description	String	extension	Similar to CNAMEia except this is keyword for BINTABLE vector.
tcnan	TCNAna	Spectral coordinate description	String	pixel list	Similar to CNAMEia except this is keyword for pixel list.
restfrq	RESTFRQa	Rest frequency of spectral feature of interest	Float	any	[floating point; default: none]. Rest frequency of the of the spectral feature of interest. The physical unit must be Hz.
restfreq	RESTFREQ	Rest frequency of spectral feature of interest	Float	any	This keyword is identical to RESTFRQa.
rfrqn	RFRQna	Rest frequency of spectral feature of interest	Float	extension	Similar to RESTFRQa except this is keyword for BINTABLE vector and pixel list alike.
restwav	RESTWAVa	Vacuum rest wavelength of the spectral feature of interest	Float	any	[floating point; default: none]. Vacuum rest wavelength of the spectral feature of interest. The physical unit must be m.
rwavn	RWAVna	Vacuum rest wavelength of the spectral feature of interest	Float	extension	Similar to RWAVna except this is keyword for BINTABLE vector and pixel list alike.
date_avg	DATE-AVG	Calendar date of the mid-point of observation	String	any	[character; default: none]. Calendar date of the mid-point of the observation, expressed in the same way as the DATE-OBS keyword.
davgn	DAVGn	Calendar date of the mid-point of observation	String	extension	Similar to DATE-AVG except this is keyword for BINTABLE vector and pixel list alike.
mjd_avg	MJD-AVG	MJD of the mid-point of the observation	Float	any	[floating point; default: none]. Modified Julian Date (JD – 2,400,000.5) of the mid-point of the observation.
mjdan	MJDAn	MJD of the mid-point of the observation	Float	extension	Similar to MJD-AVG except this is keyword for BINTABLE vector and pixel list alike.
specsys	SPECSYSa	Reference frame of spectral axis coordinate	String	any	[character; default: none]. The reference frame in use for the spectral axis coordinate(s). Valid values are given F2W in Table 27 of the ‘FITS Standard’ document.
specn	SPECna	Reference frame of spectral axis coordinate	String	extension	Similar to SPECna except this is keyword for BINTABLE vector and pixel list alike.
ssysobs	SSYSOBSa	Constant spectral reference frame over the range of non-spectral WCS		any	[character; default: TOPOCENT]. The spectral reference frame that is constant over the range of the non-spectral world coordinates. Valid values are given in Table 27 of the ‘FITS Standard’ document.
sobsn	SOBSna	Constant spectral reference frame over the range of non-spectral WCS	String	extension	Similar to SSYSOBSa except this is keyword for BINTABLE vector and pixel list alike.
obsgeo_x	OBSGEO-X	X-coordinate of geocentric reference frame relative to standard	Float	any	[floating point; default: none]. X-coordinate (in meters) of a Cartesian triplet that specifies the location, with respect to a standard, geocentric terrestrial reference frame, where the observation took place. The coordinate must be valid at the epoch MJD-AVG or DATE-AVG.
obsgxn	OBSGXn	X-coordinate of geocentric reference frame relative to standard	Float	extension	Similar to OBSGEO-X except this is keyword for BINTABLE vector and pixel list alike.
obsgeo_y	OBSGEO-Y	Y-coordinate of geocentric reference frame relative to standard	Float	any	[floating point; default: none]. Y-coordinate (in meters) of a Cartesian triplet that specifies the location, with respect to a standard, geocentric terrestrial reference frame, where the observation took place. The coordinate must be valid at the epoch MJD-AVG or DATE-AVG.
obsgyn	OBSGYn	Y-coordinate of geocentric reference frame relative to standard	Float	extension	Similar to OBSGEO-Y except this is keyword for BINTABLE vector and pixel list alike.
obsgeo_z	OBSGEO-Z	Z-coordinate of geocentric reference frame relative to standard	Float	any	[floating point; default: none]. Z-coordinate (in meters) of a Cartesian triplet that specifies the location, with respect to a standard, geocentric terrestrial reference frame, where the observation took place. The coordinate must be valid at the epoch MJD-AVG or DATE-AVG.
obsgzn	OBSGZn	Z-coordinate of geocentric reference frame relative to standard	Float	extension	Similar to OBSGEO-Z except this is keyword for BINTABLE vector and pixel list alike.
ssyssrc	SSYSSRCa	Reference frame of systemic velocity of observed source	Float	any	[character; default: none]. Reference frame for the value expressed in the ZSOURCEa keyword to document the systemic velocity of the observed source. Value must be one of those given in Table 27 in the ‘FITS Standard’ document except for SOURCE.
ssrcn	SSRCna	Reference frame of systemic velocity of observed source	Float	extension	Similar to SSYSSRCa except this is keyword for BINTABLE vector and pixel list alike.
velosys	VELOSYSa	Relative radial velocity between observer and selected standard of rest	Float	any	[floating point; default: none]. Relative radial velocity between the observer and the selected standard of rest in the direction of the celestial reference coordinate. Units must be m/s. The CUNITia keyword is not used for this purpose since the WCS version a might not be expressed in velocity units.
vsysn	VSYSna	Relative radial velocity between observer and selected standard of rest	Float	extension	Similar to VELOSYSa except this is keyword for BINTABLE vector and pixel list alike.
zsource	ZSOURCEa	Redshift of source	Float	any	[floating point; default: none]. Radial velocity with respect to an alternative frame of rest, expressed as a unitless redshift (i.e., velocity as a fraction of the speed of light in vacuum). Used in conjunction with SSYSSRCa to document the systemic velocity of the observed source.
zsoun	ZSOUna	Redshift of source	Float	extension	Similar to ZSOURCEa except this is keyword for BINTABLE vector and pixel list alike.
velangl	VELANGLa	Space velocity vector angle of source	Float	any	[floating point; default:+90.]. In the case of relativistic velocities (e.g., a beamed astrophysical jet) the transverse velocity component is important. This keyword may be used to express the orientation of the space velocity vector with respect to the plane of the sky. See Appendix A of reference Greisen et al. (2006) for further details.
vangn	VANGna	Space velocity vector angle of source	Float	extension	Similar to VELANGLa except this is keyword for BINTABLE vector and pixel list alike.

2.4. Supplemental FITS Keywords

Description:

Supplemental keywords for FITS headers. These keywords are not found the FITS Standard. The keywords and descriptions in some cases are derived, sometimes inherited verbatim, from the ‘Introduction to the HST Data Handbooks’, Data Handbooks from WFC3, STIS, etc., ‘ESO Data Interface Control Document (GEN-SPE-ESO-19400-0794)’, and Chandra’s ‘ASC FITS Designers’ Guide ASC-FITS-2.1.0’

Table 2.4 Supplemental FITS Keywords Dictionary

Key	Keyword	Info	Type	HDU	Description
proposid	PROPOSID	Proposal ID	String	any	Proposal ID
propttln	PROPTTLn	Proposal title	String	any	Proposal ID
pi_coi	PI_COI	Names of PI and CO-Is (Initials and Surname)	String	any	(PI-COI) The PI or Co-I’s initials followed by his/her surname
pr_inv_l	PR_INV_L	Last name of the principle investigator	String	any	Last name of the principle investigator
pr_inv_f	PR_INV_F	First name of the principle investigator	String	any	First name of the principle investigator
pr_inv_m	PR_INV_M	Middle name of the principle investigator	String	any	Middle name of the principle investigator
sun_alt	sun_alt	Altitude of the sun	Float	any	Altitude of the sun above horizon
sunangle	SUNANGLE	Angle between sun and z-axis	Float	any	Angle between sun and z-axis
moonangl	MOONANGL	Angle between moon and z-axis	Float	any	Angle between moon and z-axis
refframe	REFFRAME	Guide star catalog version	String	any	Guide star catalog version
time_obs	TIME-OBS	UT time of start of observation (hh:mm:ss)	String	any	UT time of start of observation (hh:mm:ss)
expstart	EXPSTART	Exposure start time (Modified Julian Date)	Float	any	Exposure start time (Modified Julian Date)
expend	EXPEND	Exposure end time (Modified Julian Date)	Float	any	Exposure end time (Modified Julian Date)
exptime	EXPTIME	On-detector, open-shutter, integration time (seconds)	Float	any	Provides the integration time in seconds. Although not a standard use, EXPTIME is commonly used to calculate the flux of a source via: Flux = ADU / EXPTIME. It is advisable to respect this usage. Under this definition, when multiple images are combined into one, EXPTIME is sometimes used with NCOMBINE to reflect the type of combining operation: if the images are summed then EXPTIME is the total open shutter integration, summed over all the sub-exposures, but with NCOMBINE=1. If N subexposures are averaged together into 1, then EXPTIME is the average exposure time, and with NCOMBINE = N. The purpose of defining NCOMBINE in this way is to facilitate the calculation of image statistics.
expflag	EXPFLAG	Exposure interrupt indicator	String	any	Exposure interrupt indicator
qualcom1	QUALCOM1	Data quality comment 1	String	any	Data quality comment 1
qualcom2	QUALCOM2	Data quality comment 2	String	any	Data quality comment 2
qualcom3	QUALCOM2	Data quality comment 3	String	any	Data quality comment 3
quality	QUALITY	Data quality summary	String	any	Data quality summary
institut	INSTITUT	Institutions of the PI/Co-I	String		Institutions of the PI/Co-I
targname	TARGNAME	Target name	String	any	This keyword is more specifically used to define target name, versus OBJECT, which might be used to describe target category. This keyword never specifies target category.
targdesc	TARGDESC	Target description	String	any	Target description is used to describe a target more generally than its category.
ra_targ	RA_TARG	Right ascension of the target in mean places of equinox	Float	any	Right ascension of the target in mean places of equinox
dec_targ	DEC_TARG	Declination of the target in mean places of equinox	Float	any	Declination of the target in mean places of equinox
ecl_long	ECL_LONG	Ecliptic longitude of target (deg)	Float	any	Ecliptic longitude of target (deg)
ecl_lat	ECL_LAT	Ecliptic latitude of target (deg)	Float	any	Ecliptic latitude of target (deg)
gal_long	GAL_LONG	Galactic longitude of target (deg)	Float	any	Galactic longitude of target (deg)
gal_lat	GAL_LAT	Galactic latitude of target (deg)	Float	any	Galactic latitude of target (deg)
tequinox	TEQUINOX	Equinox of the target	Float	any	Equinox of the target
rv_helio	rv_helio	Target heliocentric radial velocity	Float	any	Target heliocentric radial velocity
pm_flag	PM_FLAG	Does this target have proper motion?	true	any	Does this target have proper motion
pm_ra	PM_RA	Target proper motion in RA	Float	any	Target proper motion in RA
pm_dec	PM_DEC	Target proper motion in DEC	Float	any	Target proper motion in DEC
pm_eqnx	PM_EQUIN	Equinox of target proper motion	String	any	Equinox of target proper motion, from proposal
parallax	PARALLAX	Target parallax	Float	any	Target parallax
gsn_id	GSn_ID	ID of the guide star	Float	any	ID of the guide star
gsn_ra	GSn_RA	Right ascension of the guide stars in mean places of equinox	Float	any	Right ascension of the guide stars in mean places of equinox
gsn_dec	GSn_DEC	Declination of the guide stars in mean places of equinox	Float	any	Declination of the guide stars in mean places of equinox
gsn_mag	GSn_MAG	Guide star magnitude	Float	any	Guide star magnitude
gsn_filt	GSn_FILT	Passband of guide star magnitude	String	any	Passband of guide star magnitude
gsn_eqnx	GSnEQNOX	Equinox of the guidestars	Float	any	Equinox of the guidestars
gs1_id	GS1_ID	ID of the guide star 1	Float	any	ID of the guide star 1
gs1_ra	GS1_RA	Right ascension of the guide star 1 in mean places of equinox	Float	any	Right ascension of the guide star 1 in mean places of equinox
gs1_dec	GS1_DEC	Declination of the guide star 1 in mean places of equinox	Float	any	Declination of the guide star 1 in mean places of equinox
gs1_mag	GS1_MAG	Guide star 1 magnitude	Float	any	Guide star 1 magnitude
gs1_filt	GS1_FILT	Passband of guide star 1 magnitude	String	any	Passband of guide star 1 magnitude
gs1_eqnx	GS1EQNOX	Equinox of the guidestar 1	Float	any	Equinox of the guidestar 1
gs2_id	GS2_ID	ID of the guide star 2	Float	any	ID of the guide star 2
gs2_ra	GS2_RA	Right ascension of the guide star 2 in mean places of equinox	Float	any	Right ascension of the guide star 2 in mean places of equinox
gs2_dec	GS2_DEC	Declination of the guide star 2 in mean places of equinox	Float	any	Declination of the guide star 2 in mean places of equinox
gs2_mag	GS1_MAG	Guide star 2 magnitude	Float	any	Guide star 2 magnitude
gs2_filt	GS1_FILT	Passband of guide star 2 magnitude	String	any	Passband of guide star 2 magnitude
gs2_eqnx	GS2EQNOX	Equinox of the guidestar 2	Float	any	Equinox of the guidestar 2
gs3_id	GS3_ID	ID of the guide star 3	Float	any	ID of the guide star 3
gs3_ra	GS3_RA	Right ascension of the guide star 3 in mean places of equinox	Float	any	Right ascension of the guide star 3 in mean places of equinox
gs3_dec	GS3_DEC	Declination of the guide star 3 in mean places of equinox	Float	any	Declination of the guide star 3 in mean places of equinox
gs3_mag	GS1_MAG	Guide star 3 magnitude	Float	any	Guide star 3 magnitude
gs3_filt	GS1_FILT	Passband of guide star 3 magnitude	String	any	Passband of guide star 3 magnitude
gs3_eqnx	GS3EQNOX	Equinox of the guidestar 3	Float	any	Equinox of the guidestar 3
gs4_id	GS4_ID	ID of the guide star 4	Float	any	ID of the guide star 4
gs4_ra	GS4_RA	Right ascension of the guide star 4 in mean places of equinox	Float	any	Right ascension of the guide star 4 in mean places of equinox
gs4_dec	GS4_DEC	Declination of the guide star 4 in mean places of equinox	Float	any	Declination of the guide star 4 in mean places of equinox
gs4_mag	GS1_MAG	Guide star 4 magnitude	Float	any	Guide star 4 magnitude
gs4_filt	GS1_FILT	Passband of guide star 4 magnitude	String	any	Passband of guide star 4 magnitude
gs4_eqnx	GS4EQNOX	Equinox of the guidestar 4	Float	any	Equinox of the guidestar 4
pa_v3	PA_V3	Position angle of the V3 axis.	Float	any	Position angle of the V3 axis. The V3-axis vector points toward the origin of the instrument aperture (deg), from the center of the focal plane; it is analogous to HST PA_V3.
ra_off	RA_OFF	Telescope offset in RA from target position for observation	Float	any	Telescope offset in RA from target position for observation
dec_off	DEC_OFF	Telescope offset in DEC from target position for observation	Float	any	Telescope offset in DEC from target position for observation
eqnx_off	EQNX_OFF	Equinox of the offset, in case different from target equinox	Float	any	Equinox of the offset, in case different from target equinox
postarg1	POSTARG1	Telescope Offset in axis 1 direction (usually x)	Float	any	Telescope Offset in axis 1 direction (usually x)
postarg2	POSTARG2	Telescope Offset in axis 2 direction (usually y)	Float	any	Telescope Offset in axis 2 direction (usually y)
xoffset	XOFFSET	Telescope Offset in X from target position for observation	Float	any	Telescope Offset in X from target position for observation
yoffset	YOFFSET	Telescope Offset in Y from target position for observation	Float	any	Telescope Offset in Y from target position for observation
totexpt	TOTEXPT	Total exposure time	Float	any	Total exposure time
sci_cat	SCI_CAT	Science category (e.g. unresolved stellar pop, galaxy structure.	String	any	Science category (e.g. unresolved stellar pop, galaxy structure.
sci_kwd	SCI_KWD	Scientific keywords (e.g. Black Holes, Galaxy Bulges, Galaxy Formation and Evolution, etc.	String	any	Scientific keywords (e.g. Black Holes, Galaxy Bulges, Galaxy Formation and Evolution, etc.
timesys	TIMESYS	Time system used	String	any	Time system used
utc	UTC	Time in seconds elapsed since midnight of start of exposure	Float	any	Gives the time in seconds elapsed since midnight of the start of the exposure as known to TCS. The time on TCS is synchronized with the observatory time system via a dedicated time module. In practice, MJD-OBS, UTC, and LST, provide for a redundant consistency check mechanism in case of malfunction.
lst	LST	Local Sidereal Time, in seconds elapsed since midnight of the start of the exposure as known to the TCS.	Float	any	Local Sidereal Time, in seconds elapsed since midnight of the start of the exposure as known to the TCS.
iraf_tlm	IRAF-TLM	(IRAF-TLM) Time of last modification	String	any	(IRAF-TLM) Time of last modification
filename	FILENAME	Name of file	String	any	Name of file
filetype	FILETYPE	Type of data found in data file (SCI, CALIB, RAW, etc.)	String	any	Type of data found in data file (SCI, CALIB, RAW, etc.)
rootname	ROOTNAME	Rootname of the observation set	String	any	Rootname of the observation set
imagetyp	IMAGETYP	Type of exposure identifier (e.g. EXT)	String	any	Type of exposure identifier (e.g. EXT)
primesi	PRIMESI	Instrument designated as prime [DELETE?]	String	any	Instrument designated as prime [DELETE?]
origfile	ORIGFILE	Original file name	String	any	Records the original file name, as assigned at the instrument workstation. This is an alternative file name.
arcfile	ARCFILE	Archive file name	String	any	Provides the name under which the file is stored in the archive
checksum	CHECKSUM	Exposure integrity checksum	String	any	Provides a Cyclic Redundant Check (CRC) calculation for each HDU. It uses the ASCII encoded 1’s complement algorithm.
datasum	DATASUM	Data integrity checksum	String	any	Gives the checksum calculated for the data sections only. For dataless records, this keyword should be set to ‘0’.
inherit	INHERIT	Indicates whether header of primary HDU is inherited into extensions	Boolean	primary	Used to indicate that the keywords from the header of the primary HDU should be inherited into the extension.
proctime	PROCTIME	Pipeline processing time (MJD)	Float	any	Pipeline processing time (MJD)
obstype	OBSTYPE	Observation type - imaging or spectroscopic	String	any	Observation type - imaging or spectroscopic
obsmode	OBSMODE	Operating mode	String	any	Operating mode
sclamp	SCLAMP	Lamp status, NONE or name of lamp which is on	String	any	Lamp status, NONE or name of lamp which is on
nrptexp	NRPTEXP	Number of repeat exposures in set: default 1	Integer	any	Number of repeat exposures in set: default 1
subarray	SUBARRAY	Data from a subarray (T) or full frame (F)	Boolean	any	Data from a subarray (T) or full frame (F)
detector	DETECTOR	Detector name in use	String	any	Detector name in use
filter	FILTER	Filter name selected from filter wheel	String	any	Filter name selected from filter wheel
filt_id	FILT_ID	Filter ID selected from filter wheel	String	any	Filter ID selected from filter wheel
camera	Camera	Camera name or number in use	String	any	Camera name or number in use
aperture	APERTURE	Aperture name	String	any	Aperture name
aper_fov	APER_FOV	Aperture field of view	String	any	Aperture field of view
focus	FOCUS	Instrument focus setting	String	any	Instrument focus setting
propaper	PROPAPER	Aperture specified in an observing proposal	String	any	Aperture specified in an observing proposal
dirimage	DIRIMAGE	Direct image for grism or prism exposure	String	any	Direct image for grism or prism exposure
niter	NITER	Number of exposure iterations	Integer	any	Number of exposure iterations
nsamp	NSAMP	Number of MULTIACCUUM ramp samples	Integer	any	Number of MULTIACCUUM ramp samples
nread	NREAD	Number of MULTIACCUUM initial and final readouts	Integer	any	Number of MULTIACCUUM initial and final readouts
readout	READOUT	Detector readout rate (FAST, SLOW)	String	any	Detector readout rate (FAST, SLOW)
samp_seq	SAMP_SEQ	MULTIACUUM exposure time sequence name	String	any	MULTIACUUM exposure time sequence name
sampzero	SAMPZERO	MULTIACUUM sample time of the zeroth read (sec)	Float	any	MULTIACUUM sample time of the zeroth read (sec)
subtype	SUBTYPE	Size/type of subarray	String	any	Size/type of subarray
crsplit	CRSPLIT	Number of cosmic ray split exposures	Integer	any	Number of cosmic ray split exposures
cenwave	CENWAVE	Proposed central wavelength of spectrum	Integer	any	Proposed central wavelength of spectrum
dqicorr	DQICORR	Flag for data quality check initialization	String	any	Flags for initializing and performing data quality checking procedures
blevcorr	BLEVCORR	Flag for subtracting bias level measured from overscan (UVIS) or reference pixels (IR)	String	any	Flag for subtract bias level measured from overscan (UVIS) or reference pixels (IR)
illmcorr	ILLMCORR	Flag for subtracting background illumination	String	any	Flag for subtracting background illumination
crcorr	CRCORR	Flag to combine observations to reject/identify cosmic rays hits	String	any	Flag to combine observations to reject/identify cosmic rays hits
darkcorr	DARKCORR	Flag to subtract dark image	String	any	Flag to subtract dark image
flatcorr	FLATCORR	Flag to apply flat field to data	String	any	Flag to apply flat field to data
photcorr	PHOTCORR	Flag to populate photometric header keywords	String	any	Flag to populate photometric header keywords
drizcorr	DRIZCORR	Flag to apply drizzle processing	String	any	Flag to apply drizzle processing
nlincorr	NLINCORR	Flag to correct for detector non-linearities	String	any	Flag to correct for detector non-linearities
rptcorr	RPTCORR	Flag to combine individual repeat observations	String	any	Flag to combine individual repeat observations
unitcorr	UNITCORR	Flag to convert to count rates (see also BUNIT)	String	any	Flag to convert to count rates (see also BUNIT)
zsigcorr	ZSIGCORR	Flag to apply zero read signal correction	String	any	Flag to apply zero read signal correction
zoffcorr	ZOFFCORR	Flag to subtract MULTIACCUM zero read	String	any	Flag to subtract MULTIACCUM zero read
atodcorr	ATODCORR	Flag to correct for analog to digital conversion errors	String	any	Flag to correct for analog to digital conversion errors
biascorr	BIASCORR	Flag to subtract bias image	String	any	Flag to subtract bias image
expscorr	EXPSCORR	Flag to process individual observations after CR-reject	String	any	Flag to process individual observations after CR-reject
flshcorr	FLSHCORR	Flag to apply post flash correction	String	any	Flag to apply post flash correction
shadcorr	SHADCORR	Flag to apply shutter shading correction	String	any	Flag to apply shutter shading correction
wavecorr	WAVECORR	Flag to use wavecal to adjust wavelength zeropoint	String	any	Flag to use wavecal to adjust wavelength zeropoint
x1dcorr	X1DCORR	Flag to perform 1-D spectral extraction	String	any	Flag to perform 1-D spectral extraction
backcorr	BACKCORR	Flag to perform background subtraction (sky and interorder)	String	any	Flag to perform background subtraction (sky and interorder)
helcorr	HELCORR	Flag to convert to heliocentric wavelengths	String	any	Flag to convert to heliocentric wavelengths
dispcorr	DISPCORR	Flag to apply 2-D dispersion solutions	String	any	Flag to apply 2-D dispersion solutions
fluxcorr	FLUXCORR	Flag to convert to absolute flux units	String	any	Flag to convert to absolute flux units
ctecorr	CTECORR	Flag to correct for CCD charge transfer inefficiency	String	any	Flag to correct for CCD charge transfer inefficiency
x2dcorr	X2DCORR	Flag to rectify 2-D spectral image	String	any	Flag to rectify 2-D spectral image
imstat	IMSTAT	Flag to calculate image statistics	String	any	Flag to calculate image statistics
bpixtab	BPIXTAB	Bad pixel table	String	extension	Bad pixel table
ccdtab	CCDTAB	Detector calibration parameters	String	any	Detector calibration parameters
crrejtab	CRREJTAB	Cosmic ray rejection parameter table	String	extension	Cosmic ray rejection parameter table
oscntab	OSCNTAB	Table containing overscan (UVIS) or reference (IR) pixel locations	String	any	Table containing overscan (UVIS) or reference (IR) pixel locations
pixrejtab	CRREJTAB	Cosmic ray rejection parameters	String	any	Cosmic ray rejection parameters
darkfile	DARKFILE	Superdark image file name	String	any	Superdark image file name
tdarkfil	TDARKFIL	Temperature dependent dark file name	String	any	Temperature dependent dark file name
pfltfile	PFLTFILE	Pixel to pixel flatfield file name	String	any	Pixel to pixel flatfield file name
dfltfile	DFLTFILE	Delta flatfield file name	String	any	Delta flatfield file name
lfltfile	LFLTFILE	Low order flat file	String	any	Low order flat file
tfltfile	TFLTFILE	Temperature dependent flat file	String	any	Temperature dependent flat file
ffltfile	FFLTFILE	Fringe correction flat file	String	any	Fringe correction flat file
maskfile	MASKFILE	Mask image file name	String	any	Mask image file name
noisefil	NOISEFIL	Detector read noise file name	String	any	Detector read noise file name
nlinfile	NLINFILE	Detector nonlinearities file	String	any	Detector nonlinearities file
graphtab	GRAPHTAB	Graph table	String	any	Graph table
comptab	COMPTAB	Components table	String	any	Components table
idctab	IDCTAB	Image distortion correction table	String	any	Image distortion correction table
phottab	PHOTTAB	Photometric throughput table	String	any	Photometric throughput table
apertab	APERTAB	Relative aperture throughput table	String	any	Relative aperture throughput table
dettab	DETTAB	Detector calibration parameters	String	any	Detector calibration parameters
dgeofile	DGEOFILE	Distortion correction image	String	any	Distortion correction image
mdriztab	MDRIZTAB	MultiDrizzle parameter file	String	any	MultiDrizzle parameter file
driztab	DRIZTAB	Drizzle parameter file when not using MultiDrizzle	String	any	Drizzle parameter file when not using MultiDrizzle
atodtab	ATODTAB	Analog to digital correction file	String	any	Analog to digital correction file
biasfile	BIASFILE	Superbias image file name	String	any	Superbias image file name
flshfile	FLSHFILE	Post flash correction file name	String	any	Post flash correction file name
shadfile	SHADFILE	Shutter shading correction file	String	any	Shutter shading correction file
wavecalf	WAVECALF	Wavelength image file name	String	any	Wavelength image file name
sptrctab	SPTRCTAB	Spectrum trace table	String	any	Spectrum trace table
disptab	DISPTAB	Dispersion coefficient table	String	any	Dispersion coefficient table
lamptab	LAMPTAB	Template calibration lamp spectra table	String	any	Template calibration lamp spectra table
pctab	PCTAB	Photometry correction table	String	any	Photometry correction table
sdctab	SDCTAB	2-D spatial distortion correction table	String	any	2-D spatial distortion correction table
xtractab	XTRACTAB	Parameters for 1-D spectral extraction tab	String	any	Parameters for 1-D spectral extraction tab
wcptab	WCPTAB	Wavelength calibration parameter table	String	any	Wavelength calibration parameter table
meanexp	MEANEXP	Reference exposure time for parameters	Float	any	Reference exposure time for parameters
scalense	SCALENSE	Multiplicative scale factor applied to noise	Float	any	Multiplicative scale factor applied to noise
initgues	INITGUES	Initial guess method (MIN or MED)	String	any	Initial guess method (MIN or MED)
skysub	SKYSUB	Sky value subtracted (MODE or NONE)	String	any	Sky value subtracted (MODE or NONE)
skysum	SKYSUM	Sky level from the sum of all constituent images	Float	any	Sky level from the sum of all constituent images
crsigmas	CRSIGMAS	Statistical rejection criteria	String	any	Statistical rejection criteria
crradius	CRRADIUS	Rejection propagation radius (pixels)	Float	any	Rejection propagation radius (pixels)
crthresh	CRTHRESH	Rejection propagation threshold	Float	any	TBC
badinpdq	BADINPDQ	Data quality flag bits to reject	Integer	any	Data quality flag bits to reject
rej_rate	REJ_RATE	Rate at which pixels are affected by cosmic rays	Float	any	Rate at which pixels are affected by cosmic rays
crmask	CRMASK	Flag CR-rejected pixels in input files (T/F)	Boolean	any	Flag CR-rejected pixels in input files (T/F)
mdrizsky	MDRIZSKY	Sky value computed by MultiDrizzle		any	Sky value computed by MultiDrizzle
photmode	PHOTMODE	Observation configuration mode for photometric calibration	String	any	Observation configuration mode for photometric calibration
photflam	PHOTFLAM	Inverse sensitivity, ergs/cm^2/Ang/electron	Float	any	Inverse sensitivity, ergs/cm^2/Ang/electron
photfnu	PHOTFNU	Inverse sensitivity, Jy*sec/electron	Float	any	Inverse sensitivity, Jy*sec/electron
photzpt	PHOTZPT	Magnitude zero point	Float	any	Magnitude zero point
photplam	PHOTPLAM	Pivot wavelength (Angstroms)	Float	any	Pivot wavelength (Angstroms)
photbw	PHOTBW	RMS bandwidth of filter plus detector (Angstroms)	Float	any	RMS bandwidth of filter plus detector (Angstroms)
pattern1	PATTERN1	Primary pattern type	String	any	Primary pattern type: DITHER-BOX-MIN (4-step sampling), DITHER-LINE (2-point sampling) DITHER-LINE-3PT (3-point sampling), DITHER-BOX (4 point box sampling), GAP-LINE (2-point dithering over interchip gap) MOSAIC-LINE (full frame offset that uses single set of guide stars)
p1_shape	P1_SHAPE	Primary pattern shape	String	any	Primary pattern shape
p1_purps	P1_PURPS	Primary pattern purpose	String	any	Primary pattern purpose
p1_npts	P1_NPTS	Number of points in primary pattern	Integer	any	Number of points in primary pattern
p1_pspac	P1_PSPAC	Point spacing for primary pattern (arc-sec)	Float	any	Point spacing for primary pattern (arc-sec)
p1_lspac	P1_LSPAC	Line spacing for primary pattern (arc-sec)	Float	any	Line spacing for primary pattern (arc-sec)
p1_angle	P1_ANGLE	Angle between sides of parallelogram pattern (deg)	Float	any	Angle between sides of parallelogram pattern (deg)
p1_frame	P1_FRAME	Coordinate frame of primary pattern	String	any	Coordinate frame of primary pattern
p1_orint	P1_ORINT	Orientation of pattern to coordinate frame (deg)	Float	any	Orientation of pattern to coordinate frame (deg)
p1_centr	P1_CENTR	Center pattern relative to pointing (yes/no)	String	any	Center pattern relative to pointing (yes/no)
pattern2	PATTERN2	Secondary pattern type	String	any	Primary pattern type: DITHER-BOX-MIN (4-step sampling), DITHER-LINE (2-point sampling), DITHER-LINE-3PT (3-point sampling), DITHER-BOX (4 point box sampling), GAP-LINE (2-point dithering over interchip gap), MOSAIC-LINE (full frame offset that uses single set of guide stars)
p2_shape	P2_SHAPE	Secondary pattern shape	String	any	Secondary pattern shape
p2_purps	P2_PURPS	Secondary pattern purpose	String	any	Secondary pattern purpose
p2_npts	P2_NPTS	Number of points in secondary pattern	Integer	any	Number of points in secondary pattern
p2_pspac	P2_PSPAC	Point spacing for secondary pattern (arc-sec)	Float	any	Point spacing for secondary pattern (arc-sec)
p2_lspac	P2_LSPAC	Line spacing for secondary pattern (arc-sec)	Float	any	Line spacing for secondary pattern (arc-sec)
p2_angle	P2_ANGLE	Angle between sides of parallelogram pattern (deg)	Float	any	Angle between sides of parallelogram pattern (deg)
p2_frame	P2_FRAME	Coordinate frame of secondary pattern	String	any	Coordinate frame of secondary pattern
p2_orint	P2_ORINT	Orientation of pattern to coordinate frame (deg)	Float	any	Orientation of pattern to coordinate frame (deg)
p2_centr	P2_CENTR	Center pattern relative to pointing (yes/no)	String	any	Center pattern relative to pointing (yes/no)
pattstep	PATTSTEP	Position number of this point in the pattern	Integer	any	Position number of this point in the pattern
detamp	DETAMP	Detector amplifier readout configuration	String	any	Detector amplifier readout configuration
detoffst	DETOFFST	Commanded detector bias offset	String	any	Commanded detector bias offset
cmdgain	CMDGAIN	Commanded A-to-D conversion gain of detector	Float	any	Commanded A-to-D conversion gain of detector
detofsab	DETOFSAB	Commanded detector bias offset for amps A&B	Integer	any	Commanded detector bias offset for amps A&B
detofscd	DETOFSCD	Commanded detector bias offset for amps C&D	Integer	any	Commanded detector bias offset for amps C&D
detofsta	DETOFSTA	Commanded detector bias offset for amplifier A	Integer	any	Commanded detector bias offset for amplifier A
detofstb	DETOFSTB	Commanded detector bias offset for amplifier B	Integer	any	Commanded detector bias offset for amplifier B
detofstc	DETOFSTC	Commanded detector bias offset for amplifier C	Integer	any	Commanded detector bias offset for amplifier C
detofstd	DETOFSTD	Commanded detector bias offset for amplifier D	Integer	any	Commanded detector bias offset for amplifier D
atodgain	ATODGAIN	Measured analog-to-digital conversion gain	Float	any	Measured analog-to-digital conversion gain
atodgna	ATODGNA	Measured gain for amplifier A	Float	any	Measured gain for amplifier A
atodgnb	ATODGNB	Measured gain for amplifier B	Float	any	Measured gain for amplifier B
atodgnc	ATODGNC	Measured gain for amplifier C	Float	any	Measured gain for amplifier C
atodgnd	ATODGND	Measured gain for amplifier D	Float	any	Measured gain for amplifier D
rdnoise	RDNOISE	Detector readnoise parameter	Float	any	Detector readnoise parameter
readnsa	READNSA	Measured readnoise for amplifier A	Float	any	Measured readnoise for amplifier A
readnsb	READNSB	Measured readnoise for amplifier B	Float	any	Measured readnoise for amplifier B
readnsc	READNSC	Measured readnoise for amplifier C	Float	any	Measured readnoise for amplifier C
readnsd	READNSD	Measured readnoise for amplifier D	Float	any	Measured readnoise for amplifier D
biasleva	BIASLEVA	Bias level for amplifier A	Float	any	Bias level for amplifier A
biaslevb	BIASLEVB	Bias level for amplifier B	Float	any	Bias level for amplifier B
biaslevc	BIASLEVC	Bias level for amplifier C	Float	any	Bias level for amplifier C
biaslevd	BIASLEVD	Bias level for amplifier D	Float	any	Bias level for amplifier D
det_chp	DET_CHP	Detector chip number	Integer	any	Detector chip number
det_temp	DET_TEMP	Detector temperature	Float	any	Detector temperature
asn_id	ASN_ID	Unique identifier assigned to association	String	any	Unique identifier assigned to association
asn_tab	ASN_TAB	Name of the association file	String	any	Name of the association file
asn_mtyp	ASN_MTYP	Role of the member in the association	String	any	Role of the member in the association
expname	EXPNAME	Exposure identifier	String	extension	Exposure identifier
ltv1	LTV1	Offset in X to subsection start	Float	any	Offset in X to subsection start
ltv2	LTV2	Offset in Y to subsection start	Float	any	Offset in Y to subsection start
ltm1_1	LTM1_1	Reciprocal of sampling rate in X	Float	any	Reciprocal of sampling rate in X
ltm2_2	LTM2_2	Reciprocal of sampling rate in Y	Float	any	Reciprocal of sampling rate in Y
pa_aper	PA_APER	Position angle of reference aperture center (deg)	Float	any	Position angle of reference aperture center (deg)
orientat	ORIENTAT	Position angle of image Y-axis (degrees East of North)	Float	any	Position angle of image Y-axis (degrees East of North)
ra_aper	RA_APER	Right ascension of aperture reference position	Float	any	Right ascension of aperture reference position
dec_aper	DEC_APER	Declination of aperture reference position	Float	any	Declination of aperture reference position
ncombine	NCOMBINE	Number of image sets combined, such as during CR rejection, or for any other purpose	Integer	any	Number of image sets combined, such as during CR rejection, or for any other purpose. See EXPTIME description to note how the use of NCOMBINE may depend on EXPTIME when summing or averaging over multiple sub-exposures into one. Because there are ambiguities about what NCOMBINE may mean, to be more specific about the type of combining operation, prefer NCOMBSUM, NCOMBAVG, NCOMBMED, and promote the use of NCOMBINE that adheres to the definition given in EXPTIME when used in a science data HDU.
ncombsum	NCOMBSUM	Number of image sets combined via summing over N sub-exposures into one final exposure.	Integer	any	Number of image sets combined via summing over N sub-exposures into one final exposure.
ncombavg	NCOMBAVG	Number of image sets combined via averaging over N sub-exposures into one final exposure.	Integer	any	Number of image sets combined via averaging over N sub-exposures into one final exposure.
ncombmed	NCOMBMED	Number of image sets combined via median combining N sub-exposures into one final exposure.	Integer	any	Number of image sets combined via median combining N sub-exposures into one final exposure.
centera1	CENTERA1	Subarray axis 1 center point in unbinned detector pix	Integer	any	Subarray axis 1 center point in unbinned detector pix
centera2	CENTERA2	Subarray axis 2 center point in unbinned detector pix	Integer	any	Subarray axis 2 center point in unbinned detector pix
sizaxis1	SIZAXIS1	Subarray axis 1 size in unbinned detector pixels	Integer	any	Subarray axis 1 size in unbinned detector pixels
sizaxis2	SIZAXIS2	Subarray axis 2 size in unbinned detector pixels	Integer	any	Subarray axis 2 size in unbinned detector pixels
binaxis1	BINAXIS1	Axis 1 bin size in unbinned detector pixels	Integer	any	Axis 1 bin size in unbinned detector pixels
binaxis2	BINAXIS1	Axis 2 bin size in unbinned detector pixels	Integer	any	Axis 2 bin size in unbinned detector pixels
sampnum	SAMPNUM	MULTIACCUM sample number	Integer	any	MULTIACCUM sample number
samptime	SAMPTIME	Total integration time (sec)	Float	any	Total integration time (sec)
deltatim	DELTATIM	Integration time of this sample (sec)	Float	any	Integration time of this sample (sec)
routtime	ROUTTIME	UT time of array readout (MJD)	Real	any	UT time of array readout (MJD)
ngoodpix	NGOODPIX	Number of good pixels	Integer	any	Number of good pixels
sdqflags	SDQFLAGS	Serious data quality flags	Integer	any	Serious data quality flags
goodmin	GOODMIN	Minimum value of good pixels	Float	any	Minimum value of good pixels
goodmax	GOODMAX	Maximum value of good pixels	Float	any	Maximum value of good pixels
snrmin	SNRMIN	Minimum signal-to-noise of good pixels	Float	any	Minimum signal-to-noise of good pixels
snrmax	SNRMAX	Maximum signal-to-noise of good pixels	Float	any	Maximum signal-to-noise of good pixels
snrmean	SNRMEAN	Mean value of signal-to-noise of good pixels	Float	any	Mean value of signal-to-noise of good pixels
softerrs	SOFTERRS	Number of soft error pixels (DQF1)	Integer	any	Number of soft error pixels (DQF1)
meandark	MEANDARK	Average dark level subtracted	Float	any	Average dark level subtracted
meanblev	MEANBLEV	Average bias level subtracted	Float	any	Average bias level subtracted
meanflsh	MEANFLSH	Mean number of counts in post flash exposure	Float	any	Mean number of counts in post flash exposure
operator	OPERATOR	Name of telescope operator	String	any	Name of telescope operator
focleng	FOCLENG	Telescope focal length [m]	Float	any	Telescope focal length [m]
focscale	FOCSCALE	Telescope focal scale [arcsec/mm]	Float	any	Telescope focal scale [arcsec/mm]
focvalue	FOCVALUE	Telescope M2 setting [mm]	Float	any	Telescope M2 setting [mm]
p_angbeg	P_ANGBEG	Parallactic angle at beginning of exposure (deg)	Float	any	Parallactic angle at beginning of exposure (deg)
p_angend	P_ANGEND	Parallactic angle at end of exposure (deg)	Float	any	Parallactic angle at end of exposure (deg)
trck_ra	TRCK_RA	Tracking rate in RA (mas/sec)	Float	any	Tracking rate in RA (mas/sec)
trck_dec	TRCK_DEC	Tracking rate in DEC (mas/sec)	Float	any	Tracking rate in DEC (mas/sec)
trckstat	TRCKSTAT	Tracking status	Status	any	Tracking status
airmass	AIRMASS	Airmass at the center of exposure	Float	any	Airmass at center of exposure, sec(zenith angle)
airm_beg	AIRM_BEG	Airmass at start of exposure	Float	any	Airmass at start of exposure, sec(zenith angle)
airm_end	AIRM_END	Airmass at end of exposure	Float	any	Airmass at end of exposure, sec(zenith angle)
tel_alt	TEL_ALT	Telescope altitude at start (deg) of exposure	Float	any	Telescope altitude at start (deg) of exposure
tel_az	TEL_AZ	Telescope azimuth at start (deg) of exposure	Float	any	Telescope azimuth at start (deg) of exposure
geo_elev	GEO_ELEV	Telescope elevation above sea level [m]	Float	any	Telescope elevation above sea level [m]
moonphas	MOONPHAS	Moon phase	Float	any	Moon phase
seeing	SEEING	Atmospheric seeing	Float	any	Atmospheric seeing
wind_spd	WIND_SPD	Average wind speed during observation [km/hr]	Float	any	Average wind speed during observation [km/hr]
wind_dir	WIND_SPD	Average wind direction during observation [deg]	Float	any	Average wind direction during observation [deg]
humidity	HUMIDITY	Average relative humidity during observation [%]	Float	any	Average relative humidity during observation [%]
pressure	PRESSURE	Average atmospheric pressure during observation [mm]	Float	any	Average atmospheric pressure during observation [mm]
ambtemp	AMBTEMP	Average ambient temperature during observation [C]	Float	any	Average ambient temperature during observation [C]
ins_id	INS_ID	Instrument control software ID	String	any	Instrument control software ID
ics_vers	ICS_VERS	Instrument control software version and installation date	String	any	Instrument control software version and installation date
adc_stat	ADC_STAT	ADC status	String	any	ADC status
adc_pos	ADC_POS	ADC position	String	any	ADC position
ins_oper	INS_OPER	Instrument operator	String	any	Instrument operator
disp_pa	DISP_PA	Disperser, grating or grism, position angle (N=0, E=90) [deg]	String	any	Disperser, grating or grism, position angle (N=0, E=90) [deg]
disp_nam	GRAT_NAM	Name of disperser, grating or grism	String	any	Name of disperser, grating or grism
disp_id	DISP_ID	ID of disperser, grating, or grism.	String	any	Grating ID
dispers	DISPERS	Grating or grism dispersion (Angstrom/mm)	Float	any	Grating or grism dispersion (Angstrom/mm)
disp_wav	DISP_WAV	Disperser, grating or grism, central wavelength (Angstrom)	String	any	Disperser, grating or grism, central wavelength (Angstrom)
dispaxis	DISPAXIS	Dispersion axis: 1= axis 1, 2 = axis 2, none	String	any	Dispersion axis: 1 = axis 2, 2 = axis 2, none
lamp_id	LAMP_ID	Lamp ID	String	any	Lamp ID
lamp_vol	LAMP_VOL	Lamp voltage status	Float	any	Lamp voltage status
ins_mode	INS_MODE	Instrument mode used	String	any	Instrument mode used
ins_temp	INS_TEMP	Instrument temperature (C)	Float	any	Instrument temperature (C)
ins_optp	INS_OPTP	Instrument optical pathway name	String	any	Instrument optical pathway name
opt_elem	OPT_ELEM	Optical element in use	String	any	Optical element in use, e.g. disperser name
slit_wid	SLIT_WID	Slit width [arcsec]	Float	any	Slit width [arcsec]
slit_len	SLIT_LEN	Slit length [arcsec]	Float	any	Slit length [arcsec]
slit_pa	SLIT_PA	Slit position angle [deg]	Float	any	Slit position angle [deg]
slit_ra	SLIT_RA	Slit right ascension [deg]	Float	any	Slit right ascension [deg]
slit_dec	SLIT_DEC	Slit declination [deg]	Float	any	Slit declination [deg]
sporder	SPORDER	Spectral order	Integer	any	Spectral order
platesc	PLATESC	Detector plate scale [arcsec]		any	Detector plate scale [arcsec]
guidsta1	GUIDSTA1	Telescope autoguider 1 status	String	any	Telescope autoguider 1 status
guid_ra1	GUID_RA1	Telescope autoguider 1 right ascension	Float	any	Telescope autoguider 1 right ascension
guid_dc1	GUID_DC1	Telescope autoguider 1 declination	Float	any	Telescope autoguider 1 declination
guidsta2	GUIDSTA2	Telescope autoguider 2 status	String	any	Telescope autoguider 2 status
guid_ra2	GUID_RA2	Telescope autoguider 2 right ascension	Float	any	Telescope autoguider 2 right ascension
guid_dc2	GUID_DC2	Telescope autoguider 2 declination	Float	any	Telescope autoguider 2 declination
guidsta3	GUIDSTA3	Telescope autoguider 3 status	String	any	Telescope autoguider 3 status
guid_ra3	GUID_RA3	Telescope autoguider 3 right ascension	Float	any	Telescope autoguider 3 right ascension
guid_dc3	GUID_DC3	Telescope autoguider 3 declination	Float	any	Telescope autoguider 3 declination
phas_sta	PHAS_STA	Telescope phasing camera status	String	any	Telescope phasing camera status
phas_ra	PHAS_RA	Telescope phasing camera right ascension	Float	any	Telescope phasing camera right ascension
phas_dec	PHAS_DEC	Telescope phasing camera declination	Float	any	Telescope phasing camera declination
obs_pid	OBS_PID	Program ID corresponding to observing block	String	any	Program ID corresponding to Observing block
obs_id	OBS_ID	Observing block ID	Integer	any	Observing block ID
obs_name	OBS_NAME	Observing block name	String	any	Observing block name
obs_grp	OBS_GRP	Observing block group (linked blocks)	String	any	Observing block group (linked blocks)
obs_seqn	OBS_SEQN	Sequence number in observing block template	Integer	any	Sequence number in an observing block template
obset_id	OBSET_ID	Observation set ID	String	any	Observation set ID
tpl_id	TPL_ID	Observing template ID	Float	any	Observing template ID
tpl_name	TPL_name	Observing template name	String	any	Observing template name
tpl_seqn	TPL_SEQN	Template sequence number within block	Integer	any	Template sequence number within block
tpl_nexp	TPL_NEXP	Number of exposures within sequence template	Integer	any	Number of exposures within sequence template
tpl_expn	TPL_EXPN	Exposure number within template	Integer	any	Exposure number within template
dpr_catg	DPR_CATG	Data product file, data product category	String	any	Data product file, data product category [TBC]
dpr_type	DPR_TYPE	Data product file, observation type	String	any	Data product file, Observation type [TBC]
dpr_tech	DPR_TECH	Data product file, observation technique	String	any	Gives the technique used for the observation and can take on more than one value. The values should be separated with commas, from general to specific. [TBC]
tlmin	TLMINn	Minimum legal values for a column	Float	extension	Minimum legal values for a column
tlmax	TLMAXn	Maximum legal values for a column	Float	extension	Maximum legal values for a column
pixvalue	PIXVALUE	Value of all the pixels in an uniform image	Float	any	When all pixels in an image are of a single value, that value is stored as PIXVALUE and the HDU has no binary data section. The use of PIXVALUE is not allowed for a SCI extension.
tdescn	TDESCn	Column description	String	extension	The value field of this indexed keyword contains a character string that describes the content of the table column.
use_date	USE_DATE	Use this file for obs taken on or after this date	String	all	Use this file for observations taken on or after the date specified in the value field. This is used e.g. in instrument or calibration reference tables.

2.5. References