Calibrated Data Formats and Header Dictionaries

Fraser Watson

DKIST Data Center

January 18, 2019

REVISION SUMMARY:

Date: January 18, 2019
Revision:
Changes: Initial draft

Introduction

Calibrated DKIST data will be provided to the community along with a collection of relevant metadata that allows the science user to more efficiently extract information from the data. This document details the formats that calibrated DKIST data will be provided in, and lists the metadata that accompanies the data.

Dependence on SPEC-0122, DKIST Data Model

This document is based upon SPEC-0122 and any changes to SPEC-0122 will likely require changes to this document. The version of SPEC-0122 used as the base of this document is Revision A, August 2016.

Standards applying to calibrated data

Data formats

All DKIST data shall be delivered – combined with its metadata – across non DKIST-internal interfaces in a format compliant with the FITS 4.0 standard. The FITS 4.0 standard is defined at https://fits.gsfc.nasa.gov/standard40/fits_standard40aa-le.pdf.

For each dataset produced by the DKIST Data Center, an associated Advanced Scientific Data Format file (ASDF, Greenfield, Droettboom, and Bray, 2015) will be produced that allows the user to examine the data without downloading the full collection of FITS files that contain the science data. This file will be leveraged by the DKIST User Tools.

Compression

Calibrated DKIST FITS files will be stored and delivered with a RICE compression algorithm applied as described in Rice (1993).

Use of the World Coordinate System

All DKIST data and metadata shall be delivered using a coordinate system that complies with the World Coordinate System standard as defined in the FITS 4.0 standard and Thompson (2006).

All DKIST data and metadata shall be delivered with exactly two coordinate systems,

one relevant for solar data: Helioprojective Coordinates
one relevant for astronomical objects other than the Sun: Equatorial Coordinates

Some DKIST data will be of spectroscopic, or spectro-polarimetric nature. These types of data can be handled within the FITS standard for spectroscopic data.

Use of the Système Internationale d’Unités

All DKIST metadata delivered across a non DKIST-internal interface shall be in SI (base or derived) units.

FITS header dictionary

FITS required keywords

Key	Type	Method of derivation	Description
SIMPLE	String	None	Mandatory FITS keyword
BITPIX	Int	None	Mandatory keyword describing the number of bits per pixel in the data. Permitted values are: 8, 16, 32, 64, -32, -64.
NAXIS	Int	None	Number of axes in the associated data array.
NAXISn	Int	None	Number of elements along axis ‘n’.
END	String	None	Keyword marking the end of the header.

DKIST reserved keywords

Key	Type	Method of derivation	Description
BUNIT	String	Mode of raw values.	The physical unit of the data values after application of BZERO and BSCALE according to Pence (2010) (physical_value in BUNIT = BZERO + BSCALE× array_value.) Allowable units and prefixes are stated in Pence (2010), Tables 3, 4, and 5 (and anticipated to be typically ADU)
BZERO	Float	Calculation of new zero point in bit depth.	see Pence (2010), and BUNIT, default BZERO=0
BSCALE	Int	None	Number of axes in the associated data array.
BLANK	Int	None	Number of elements along axis ‘n’.
DATE	String	Time of HDU creation	UTC time of HDU creation.
DATE-OBS	String	Time of first frame used in creating calibrated frame.	UTC time of beginning of observations in calibrated frame.
DATE-BGN	String	Mode of raw values.	Start date / time of instrument program.
DATE-END	String	Mode of raw values.	End date / time of instrument program.
ORIGIN	String	Mode of raw values.	Organization responsible for creating the FITS file.
TELESCOP	String	Mode of raw values.	Telescope used to acquire data in the FITS file.
OBSERVAT	String	Mode of raw values.	The physical entity, located in a defined location, which provides the resources necessary for the installation of an instrument.
NETWORK	String	Mode of raw values.	Organizational entity of a series of instruments with similar characteristics or goals that operates in some coordinated manner or produces data with some common purpose.
INSTRUME	String	Mode of raw values.	Instrument used to acquire the data in the FITS file.
WAVELNTH	Float	Mode of raw values.	Coarse wavelength band, in nanometers, of observation.
OBSERVER	String	Mode of raw values.	The value field shall contain a character string identifying the DKIST operator who acquired the data associated with the header.
OBJECT	String	Mode of raw values.	A name for the observed object.
COMMENT	String	Mode of raw values.	Any comments regarding the FITS file.

WCS keywords

Key	Type	Method of derivation	Description
WCSAXESa	Int	Calculated from calibrated data.	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. (see also Pence et al. 2010) Possible values for a: “ “ (blank), or “A” through “Z” Default value: “ “ (blank, indicating the primary WCS name; “A” through “Z” indicate an alternate WCS)
WCSNAMEa	String	Calculated from calibrated data.	Name of the WCS (see Pence et al, 2010). The index a is present for an alternate WCS (see WCSAXESa)
CRPIXna	Float	Calculated from calibrated data.	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. DKIST pointing data will be relative to the boresight of the telescope defined by the WFC Context Viewer that will center an image of the GOS pinhole on its detector using a 10 nm wavelength band centered on 525 nm. The same pinhole image will be used by all instruments as reference for determining the pointing of the instrument in relation to the WFC Context Viewer. The index a is present for an alternate WCS (see WCSAXESa)
CRDATEna	String	Calculated from calibrated data.	Date of last update of CRPIXn and CDELTn value The index a is present for an alternate WCS (see WCSAXESa) The value will get updated upon realignment of the data source with the WFC Context Viewer (see CRPIXna)
CRVALna	Float	Calculated from calibrated data.	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. DKIST values for this entry will be determined at the wavelength of the WFC Context Viewer, which covers a band of 10 nm centered on 525 nm. The value will not be corrected for differential refraction of Earth’s atmosphere. The index a is present for an alternate WCS (see WCSAXESa)
CDELTna	Float	Calculated from calibrated data.	Pixel spacing along axis n (Thompson, 2006) The index a is present for an alternate WCS (see WCSAXESa)
CUNITna	String	Calculated from calibrated data.	The unit of the value contained in CDELTn (Thompson, 2006) The index a is present for an alternate WCS (see WCSAXESa)
CTYPEna	String	Calculated from calibrated data.	A string value labeling each coordinated axis. This keyword shall be used to describe image data axes, see e.g. Thompson (2006) This keyword shall be used to describe spectro-polarimeteric axes that the data may have; see also e.g. Section 5.2 in Greisen (2006) The index a is present for an alternate WCS (see WCSAXESa)
PCi_ja	Float	Calculated from calibrated data.	See e.g. Pence et al. (2010) The index a is present for an alternate WCS (see WCSAXESa)
LONPOLEa	Float	Calculated from calibrated data.	See Calabretta (2002) and Thompson (2006)
LATPOLEa	Float	Calculated from calibrated data.	See Calabretta (2002) and Thompson (2006)
TAZIMUTH	Float	Mean of raw values.	raw Telescope azimuth angle in [deg]
TELEVATN	Float	Mean of raw values.	raw Telescope elevation angle in [deg]
TELTRACK	String	Mode of raw values.	Tracking Mode of the Telescope. Possible values: “None, Fixed Solar Rotation Tracking, Differential Rotation Tracking, Scanning Motion (Random, or Grid, or Raster, or Spiral)”
TTBLANGL	Float	Mean of raw values.	Telescope Coude table angle
TTBLTRCK	String	Mode of raw values.	Coude table tracking mode. Values: (stepped) parallactic, fixed angle on Sun (e.g. N-S), fixed difference angle between coude and tel. azimuth, fixed coude table angle
CRDERna
CSDERna
DV

OCS ID keywords

Key	Type	FITS Comment	Method of derivation	Description
ID___001	String	DKISTFITSHeaderVersion	Mode of raw values.	Version of the DKIST FITS Header format
ID___002	String	FileID	Calculated from calibrated data.	Unique ID of this FITS file
ID___003	String	CheckSum	Calculated from calibrated data.	Checksum for data integrity verification.
ID___004	String	DataSetID	Mode of raw values.	Unique ID of the DataSet associated with these data.
ID___005	String	DataSetParametersID	Mode of raw values.	Unique ID of the DataSetParameters used to configure the InstrumentProgram associated with these data.
ID___006	String	DataSetParameterSequenceID	Mode of raw values.	Unique ID of the DataSetParameterSequence used to configure the InstrumentProgram associated with these data.
ID___007	String	InstrumentProgramID	Mode of raw values.	Unique ID of the InstrumentProgram associated with these data.
ID___008	String	InstrumentScriptID	Mode of raw values.	Unique ID identifying the instrument script that was executed to acquire this data.
ID___009	String	InstrumentProgramParametersID	Mode of raw values.	Unique ID of the parameters used to configure the InstrumentProgram associated with these data.
ID___010	String	ObservingProgramID	Mode of raw values.	Unique ID of the original ObservingProgram associated with the generation of these data.
ID___011	String	ObservingProgramAsRunID	Mode of raw values.	Unique ID of the ‘as run’ ObservingProgram associated with the generation of these data.
ID___012	String	ObservingScriptId	Mode of raw values.	Unique ID of the Observing Program Script used to acquire this data.
ID___013	String	ObservingProgramParametersID	Mode of raw values.	Unique ID of the OCS level parameters used to configure the ObservingProgram associated with these data.
ID___014	String	TelescopeParametersID	Mode of raw values.	Unique ID of the TCS level parameters used to configure the ObservingProgram associated with these data.
ID___015	String	ExperimentID	Mode of raw values.	Unique ID of the experiment associated with the generation of these data.
ID___016	String	ProposalID	Mode of raw values.	Unique ID of the proposal associated with the experiment associated with the generation of these data.
ID___017	String	InvestigatorID	Mode of raw values.	Unique ID identifying the Principal Investigator associated with the experiment.

OCS configuration keywords

Key	Type	FITS Comment	Method of derivation	Description
DKIST001	String	OCSMode	Mode of raw values.	Mode the telescope was operated in: ‘Auto’: Data were acquired as part of a regular, automatic execution of an Observing Program ‘Manual’: Data were acquired executing either a part of an or a complete Observing Program manually.
DKIST002	String	ObservingProgramRunMode	Mode of raw values.	‘Full’: Data were acquired as part of a regular execution of an Observing Program ‘Test’: Data were acquired as part of a test execution of (parts of) an Observing Program
DKIST003	String	ObservingProgramTask	Mode of raw values.	Observing Task addressed by the Observing Program that led to the acquisition of this data. For calibrated data, ‘Observation’ is the only valid value.
DKIST004	String	InstrumentProgramTask	Mode of raw values.	Instrument Program Task addressed by the Instrument Program that led to the acquisition of this data. For calibrated data, ‘Observation’ is the only valid value.
DKIST005	String	FIDOConfiguration	Mode of raw values.	The DKIST FIDO configuration in the following format: [M9aStatus,CL2,CL2a,CL3,CL3a,CL4]
DKIST006	String	InstrumentHealthStatus	Worst health status form frames that made up the calibrated frame.	Worst health status of the instrument during data acquisition (Good, Ill, Bad)
DKIST007	Bool	EngineeringDataFlag	All DKIST007 values == 0.	0: Data belongs to a regular science experiment execution. 1: Data is ‘engineering’ data. Scientific value of data not guaranteed.
DKIST008	String	StartDateOfValidity	Mode of raw values.	Start of date range for validity of data, e.g.calibration data. Equal to NA, if not applicable (e.g. science data)
DKIST009	String	EndDateOfValidity	Mode of raw values.	End of date range for validity of data, e.g. calibration data. Equal to NA, if not applicable (e.g. science data)
DKIST010	Int	NumberOfRepeats	Mode of raw values.	Number (> 0) of repeated DataSetParametersequences within an InstrumentProgram. VBI/DL-NIRSP: Number of field scans to acquire for the observation: N=-1 (loop until interrupted), N>=1
DKIST011	Int	RepeatNumber	Mode of raw values.	Number (0 < RepeatNumber ≤ NumberOfRepeats) describing the current repetition of the DataSetParametersequence within an InstrumentProgram. VBI/DL-NIRSP: RepeatNumber = Current field scan repetition
DKIST012	Float	RepeatCadence	Mean of raw values.	Cadence, in seconds, of the DataSetParameterSequences VBI/DL-NIRSP: Cadence of field scans
DKIST013	Int	LightLevel	Mode of raw values.	Number of entries in the FITS table accompanying the data containing the value of the telescope light level during data acquisition.

Camera keywords

Key	Type	FITS Comment	Method of derivation	Description
CAM__001	String	CameraUniqueID	Mode of raw values.	Unique ID of camera used to acquire the data
CAM__002	Float	FPAExposureTime	Calculated from calibrated data.	Total duration of exposure to photons, in milliseconds, that resulted in the FPAs within the FPA-set contained in this FITS file.
CAM__003	Float	FPAFrameRate	Mode of raw values.	Average acquisition rate of FPAs, in Hertz
CAM__004	Float	CamExposureTime	Mode of raw values.	Duration of photosensitive sensor exposure to photons per single sensor read-out
CAM__005	Float	CamFrameRate	Mode of raw values.	Rate of photosensitive sensor read-outs
CAM__006	Int	ChipDimensionX	Mode of raw values.	Value describing the number photosensitive pixels on the camera sensor, in X direction
CAM__007	Int	ChipDimensionY	Mode of raw values.	Value describing the number photosensitive pixels on the camera sensor, in Y direction
CAM__008	Int	HardwareBinningX	Mode of raw values.	Value describing the binning performed in hardware in pixels, in X direction Equals 1 if disabled
CAM__009	Int	HardwareBinningY	Mode of raw values.	Value describing the binning performed in hardware in pixels, in Y direction Equals 1 if disabled
CAM__010	Int	SoftwareBinningX	Mode of raw values.	Binning performed by software in pixels, after hardware binning, in pixels, X Equals 1 if disabled
CAM__011	Int	SoftwareBinningY	Mode of raw values.	Binning performed by software in pixels, after hardware binning, in pixels, Y Equals 1 if disabled
CAM__012	Int	NumberOfFPAs	Sum of raw values.	Number of FullyProcessedAccumulators generated with the DataSetParameters
CAM__013	Int	CurrentFPA	Mean of raw values	Number N of the current FPA generated with the DataSetParameters 1 ≤ N ≤ NumberOfFPAs
CAM__014	Int	AccumulationsPerFPA	Mode of raw values.	Number of accumulations per FPA
CAM__015	Int	ROI1OriginX	Mode of raw values.	Region Of Interest 1 X - Origin coordinate in pixels
CAM__016	Int	ROI1OriginY	Mode of raw values.	Region Of Interest 1 Y - Origin coordinate in pixels
CAM__017	Int	ROI1SizeX	Mode of raw values.	Region Of Interest 1 X - Size in pixels
CAM__018	Int	ROI1SizeY	Mode of raw values.	Region Of Interest 1 Y - Size in pixels
CAM__019	Int	ROI2OriginX	Mode of raw values.	Region Of Interest 2 X - Origin coordinate in pixels Keyword not present, if not used
CAM__020	Int	ROI2OriginY	Mode of raw values.	Region Of Interest 2 Y - Origin coordinate in pixels Keyword not present, if not used
CAM__021	Int	ROI2SizeX	Mode of raw values.	Region Of Interest 2 X - Size in pixels Keyword not present, if not used
CAM__022	Int	ROI2SizeY	Mode of raw values.	Region Of Interest 2 Y - Size in pixels Keyword not present, if not used
CAM__023	Int	ROI3OriginX	Mode of raw values.	Region Of Interest 3 X - Origin coordinate in pixels Keyword not present, if not used
CAM__024	Int	ROI3OriginY	Mode of raw values.	Region Of Interest 3 Y - Origin coordinate in pixels Keyword not present, if not used
CAM__025	Int	ROI3SizeX	Mode of raw values.	Region Of Interest 3 X - Size in pixels Keyword not present, if not used
CAM__026	Int	ROI3SizeY	Mode of raw values.	Region Of Interest 3 Y - Size in pixels Keyword not present, if not used
CAM__027	Int	ROI4OriginX	Mode of raw values.	Region Of Interest 4 X - Origin coordinate in pixels Keyword not present, if not used
CAM__028	Int	ROI4OriginY	Mode of raw values.	Region Of Interest 4 Y - Origin coordinate in pixels Keyword not present, if not used
CAM__029	Int	ROI4SizeX	Mode of raw values.	Region Of Interest 4 X - Size in pixels Keyword not present, if not used
CAM__030	Int	ROI4SizeY	Mode of raw values.	Region Of Interest 4 Y - Size in pixels Keyword not present, if not used

Polarization analysis and calibration keywords

Key	Type	FITS Comment	Method of derivation	Description
PAC__001	String	UpGOSLinPolarizer	Mode of raw values.	Value indicating status of Upper GOS Linear Polarizer slide. OutOfBeam, IDOfLinearPolarizerOpticsInBeam
PAC__002	Float	UpGOSLinPolarizerAngle	Mean of raw values.	Current Rotation Angle of the Linear Polarizer Optics. Keyword not present, if not used
PAC__003	String	UpGOSRetarder	Mode of raw values.	Value indicating status of Upper GOS Retarder slide. OutOfBeam, IDOfRetarderOpticsInBeam
PAC__004	Float	UpGOSRetarderAngle	Mean of raw values.	Current Rotation Angle of the Retarder Optics Keyword not present, if not used
PAC__005	Float	UpGOSRetarderTemp	Mode of raw values.	Current Temperature of the Retarder Optics Keyword not present, if not used
PAC__006	String	UpGOSLightSource	Mode of raw values.	Value indicating status of Upper GOS Light Source slide. OutOfBeam, IDOfBroadbandLightSourceInBeam
PAC__007	String	LoGOSObject	Mode of raw values.	Value indicating status of Lower GOS Slide Object. FieldStop, Dark, Pinhole, LineGrid, NonRedundantArray, InterferometerSphere, Occulter
PAC__008	Float	LoGOSFieldStopDia	Mean of raw values.	Aperture diameter of the Lower GOS FieldStop Keyword not present, if not used
PAC__009	Float	LoGOSPinholeDia	Mean of raw values.	Diameter of the Lower GOS Pinhole Keyword not present, if not used
PAC__010	String	LoGOSPinholeType	Mode of raw values.	Type of Lower GOS pinhole. Normal, Inverse Keyword not present, if not used
PAC__011	Float	LoGOSLineGridDist	Mean of raw values.	Distance between lines of the Lower GOS Line Grid. Keyword not present, if not used
PAC__012	String	LoGOSNRAType	Mode of raw values.	Type of the Non- RedundantArray Target Type AirForce, MultiPinhole Keyword not present, if not used
PAC__013	Float	LoGOSOcculterPosAngle	Mean of raw values.	Position angle of the Lower GOS Occulter Keyword not present, if not used
PAC__014	String	DKISTPolarizationCalX12ID	Mode of raw values.	Reference ID of the DKIST Polarization Calibration Data (Matrix for M1 and M2) valid for this data (PolCalX-matrices must be selected to be adequate for the wavelength range, and within a ‘valid date range’) Keyword not present, if not used
PAC__015	String	DKISTPolarizationCalX34ID	Mode of raw values.	Reference ID of the DKIST Polarization Calibration Data (Matrix for M3 and M4) valid for this data (PolCalX-matrices must be selected to be adequate for the wavelength range, and within a ‘valid date range’) Keyword not present, if not used
PAC__016	String	DKISTPolarizationCalX56ID	Mode of raw values.	Reference ID of the DKIST Polarization Calibration Data (Matrix for M5 and M6) valid for this data (PolCalX-matrices must be selected to be adequate for the wavelength range, and within a ‘valid date range’) Keyword not present, if not used
PAC__017	String	DKISTPolarizationCalXInstID	Mode of raw values.	Reference ID of the DKIST Polarization Calibration Data (Matrix for M7 to the instrument) valid for this data (PolCalX-matrices must be selected to be adequate for the wavelength range, and within a ‘valid date range’) Keyword not present, if not used

Adaptive Optics keywords

Key	Type	FITS Comment	Method of derivation	Description
AO___001	Int	HOAOFriedParameterVals	Sum of raw values.	Number of entries in the FITS table included in this file containing the value of Fried's parameter during data acquisition. Keyword not present, if not used
AO___002	Bool	HOAOLockStatus	All AO___002 values == 1.	Lock status of HOAO during data acquisition. 0: HOAO was unlocked for some duration of data acquisition 1: HOAO was locked for the complete duration of data acquisition Keyword not present, if not used
AO___003	Float	HOAOLockOffPointingX	Mode of raw values.	Current Lockpoint offpointing in X of the HOAO WFS in pixels relative to WFC Context Viewer defined telescope boresight
AO___004	Float	HOAOLockOffPointingY	Mode of raw values.	Current Lockpoint offpointing in Y of the HOAO WFS in pixels relative to WFC Context Viewer defined telescope boresight
AO___005	Float	LimbSensorRadialSetPos	Mode of raw values.	Radial set position with respect to the limb as seen at the sensing wavelength of the Limb Sensor = 0 indicates occulting at the limb > 0 indicates over-occulting, i.e. the limb is not visible < 0 indicates under-occulting i.e. the limb is visible Keyword not present, if not used
AO___006	Float	LimbSensorRate	Mode of raw values.	Frequency with which the Limb Sensor position is read out Keyword not present, if not used

Weather station keywords

Key	Type	FITS comment	Method of derivation	Description
WS___001	Float	WeathWindSpeed	Mean of raw values.	DKIST Local Outside Wind Speed (m/s)
WS___002	Int	WeathWindDirection	Mean of raw values.	DKIST Local Outside Wind Direction North: 0 deg East: 90 deg South: 180 deg West: 270 deg
WS___003	Float	WeathOutsideTemperature	Mean of raw values.	DKIST Local Outside Tempertature (C)
WS___004	Float	WeathRelativeHumidity	Mean of raw values.	DKIST Local Outside Relative Humidity (%)
WS___005	Float	WeathDewPoint	Mean of raw values.	DKIST Local Outside Dew Point (C)
WS___006	Float	WeathBarometricPressure	Mean of raw values.	DKIST Local Outside Barometric Pressure (hPa)
WS___007	Float	WeathSkyBrightness	Mean of raw values.	DKIST Local Outside Sky Brightness (ppm)

VBI keywords

Key	Type	FITS Comment	Method of derivation	Description
VBI__001	Float	InterferenceFilterFWHM	Mean of raw values.	Full Width at Half Maximum spectral transmission. (nm)
VBI__002	Int	FilterWheelPosition	Mode of raw values.	Filterwheel position.
VBI__003	String	SpatialStepPattern	Mode of raw values.	Selected pattern with which the FieldOfView is sampled. Keyword not present, if not used
VBI__004	Int	NumberOfSpatialSteps	Mode of raw values.	Value indicating the number of images belonging to the scanned FieldOfView. Keyword not present, if not used
VBI__005	Int	CurrentSpatialStep	Mode of raw values.	Value indicating the current image position belonging to the scanned FieldOfView. 1 ≤ CurrentSpatialStep ≤ NumberOfSpatialSteps Keyword not present, if not used
VBI__006	Bool	Processed	Mode of raw values.	Value indicating whether the image has been processed by algorithms (e.g. reconstruction algorithms etc.) or not.

VTF keywords

Key	Type	FITS Comment	Method of derivation	Description
VTF__001	Float	FilterFWHM	Mean of raw values.	Full Width at Half Maximum spectral transmission at the current prefilter central wavelength.
VTF__002	Int	FilterWheelPosition	Mode of raw values	Filter wheel position of the current prefilter.
VTF__003	Float	WavelengthRangeMinimum	Min of VTF__003.	Minimum wavelength scanned within the current prefilter bandpass.
VTF__004	Float	WavelengthRangeMaximum	Max of VTF__004.	Maximum wavelength scanned within the current prefilter bandpass.
VTF__005	Int	NumberOfSpectralSteps	Sum of raw values.	Number of spectral steps performed by the FPI(s).
VTF__006	Int	CurrentSpectralStep	Mode of raw values.	Current spectral step in scan (1 ≤ CurrenSpectralStep ≤ NumberOfSpectralSteps)
VTF__007	Float	CurrentSpectralStepWaveL	Mean of raw values.	Wavelength at current spectral step.
VTF__008	Int	NumberOfImagesPerSpectralStep	Sum of raw values.	Number of images acquired at one particular spectral step (and modulation configuration)
VTF 009-049		Reserved for parameters describing the FPI configurations, TBD		Values of parameters describing the Fabry-Perot Etalon configurations (e.g. peak/central wavelengths, voltages, etc)
VTF 050-079		Reserved for parameters describing the Polarization Modulator configurations, TBD		Values of parameters that describe the modulation state in the SysOutput (t0, rate, state at t0, number of modulation states, number of accumulations per modulation state, modulation scheme, voltage for each discrete state, demodulation table, etc.)

ViSP keywords

Key	Type	FITS Comment	Method of derivation	Description
ViSP_001	Int	ArmID	Mode of raw values.	Identifier for ViSP arm that generated the data: 1, 2, 3
ViSP_002	Float	ArmPosition	Mean of raw values.	Angular position of the arm.
ViSP_003	Float	ArmFocus	Mean of raw values.	Location of the focus stage of the arm.
ViSP_004	String	FilterID	Mode of raw values.	Unique ID of the filter in use
ViSP_005	Float	FilterWavelength	Mean of raw values.	Central wavelength of filter in use
ViSP_006	Float	FilterFWHM	Mean of raw values.	Full Width at Half Maximum spectral transmission at the current filter central wavelength in use
ViSP_007	String	PolarimeterMode	Mode of raw values.	Polarimeter Mode with which these data were acquired: Full Stokes, Stokes-I, Other(?)
ViSP_008	String	ModulatorID	Mode of raw values.	Unique identifier of the modulator.
ViSP_009	String	ModulationType	Mode of raw values.	The type of motion used by the modulator: “discrete, continuous”
ViSP_010	String	ModulatorT0	Mode of raw values.	Reference time for the Modulator motion. Unit is TBD.
ViSP_011	Float	ModulationRate	Mean of raw values.	Rate at which states are to be acquired, in Hertz.
ViSP_012	Int	ModulationStateNumAtT0	Mean of raw values.	Integer number identifier corresponding to the particular state defined by the position of the modulator at its reference time.
ViSP_013	Int	ModulationStateAngAtT0	Mean of raw values.	Modulator angle corresponding to the modulation state at T0.
ViSP_014	Int	NumberOfStates	Mode of raw values.	Number of states to be acquired: NumberOfStates ≥ 1
ViSP_015	Int	CurrentStateNumber	Mode of raw values.	Number of the current state: 1 ≤ CurrentStateNumber ≤ NumberOfStates
ViSP_016	String	GratingID	Mode of raw values.	Unique identifier of the grating in use.
ViSP_017	Float	GratingConstant	Mean of raw values.	Grating constant.
ViSP_018	Float	GratingBlazeAngle	Mean of raw values.	Grating blaze angle.
ViSP_019	Float	GratingAngle	Mean of raw values.	Grating angle with respect to incident beam.
ViSP_020	String	SlitID	Mode of raw values.	UniqueID of the slit assembly in use
ViSP_021	Float	SlitWidth	Mean of raw values.	Width of the slit in use
ViSP_022	Float	SlitSteppingSize	Mean of raw values.	Single step size of the slit for this observation Keyword not present, if not used
ViSP_023	Float	SlitScanVelocity	Mean of raw values.	Slit move velocity for this observation [ViSP intensity mode only] Keyword not present, if not used
ViSP_024	Int	NumberOfSpatialSteps	Mean of raw values.	Value indicating the number of images belonging to the scanned FieldOfView. Keyword not present, if not used
ViSP_025	Int	CurrentSpatialStep	Mean of raw values.	Value indicating the current image position belonging to the scanned FieldOfView. 1≤CurrentSpatialStep≤NumberOfSpatialSte ps Keyword not present, if not used
ViSP_026	Float	SlitSelectorPosition	Mode of raw values.	Position of the slit selector stage.
ViSP_027	Float	SlitTranslationPosition	Mode of raw values.	Position of the slit translation stage.
ViSP_028	Float	FoldMirrorPosition	Mode of raw values.	Position of the fold mirror stage.
ViSP_029	String	ViSPSoftwareVersion	Mode of raw values.	Version of the ViSP Instrument Software

DL-NIRSP keywords

Key	Type	FITS Comment	Method of derivation	Description
DLN__001	String	ArmID	Mode of raw values.	Identifier for DL-NIRSP arm that generated the data: VIS, JBand, HBand
DLN__002	Float	ArmPosition	Mean of raw values.	Angular position of the arm.
DLN__003	Float	ArmFocus	Mean of raw values.	Location of the focus stage of the arm.
DLN__004	String	FilterID	Mode of raw values.	Unique ID of the filter in use
DLN__005	Float	FilterWavelength	Mean of raw values.	Central wavelength of filter in use
DLN__006	Float	FilterFWHM	Mean of raw values.	Full Width at Half Maximum spectral transmission at the current filter central wavelength in use
DLN__007	String	PolarimeterMode	Mode of raw values.	Polarimeter Mode with which these data were acquired: Full Stokes, Stokes-I, Other(?)
DLN__008	String	ModulatorID	Mode of raw values.	Unique identifier of the modulator.
DLN__009	String	ModulationType	Mode of raw values.	The type of motion used by the modulator: “discrete, continuous”
DLN__010	String	ModulatorT0	Mode of raw values.	Reference time for the Modulator motion. Unit is TBD.
DLN__011	Float	ModulationRate	Mean of raw values.	Rate at which states are to be acquired, in Hertz.
DLN__012	Int	ModulationStateNumAtT0	Mean of raw values.	Integer number identifier corresponding to the particular state defined by the position of the modulator at its reference time.
DLN__013	Int	ModulationStateAngAtT0	Mean of raw values.	Modulator angle corresponding to the modulation state at T0.
DLN__014	Int	NumberOfStates	Mode of raw values.	Number of states to be acquired: NumberOfStates ≥ 1
DLN__015	Int	CurrentStateNumber	Mode of raw values.	Number of the current state: 1 ≤ CurrentStateNumber ≤ NumberOfStates
DLN__016	String	GratingID	Mode of raw values.	Unique identifier of the grating in use.
DLN__017	Float	GratingConstant	Mean of raw values.	Grating constant.
DLN__018	Float	GratingBlazeAngle	Mean of raw values.	Grating blaze angle.
DLN__019	Float	GratingAngle	Mean of raw values.	Grating angle with respect to incident beam.
DLN__020	Int	NumberOfDataCycles	Mode of raw values.	The number of data cycles that should occur for each mosaic tile. A data cycle can be a single or multiple modulation states. A modulation cycle is defined in discrete sampling by the collection of state values. In continuous sampling, it is defined as one half-rotation of the modulator.
DLN__021	String	CoAddMode	Mean of raw values.	Defines how data were coadded by the detector. Values are defined as follows: State: All coadded exposures for a single state are acquired prior to progressing to the next modulation state (discrete modulation). Sequence: The full discrete modulation sequence is cycled through a number of times equivalent to the number of coadds. Half-rotation: States of the first half rotation are coadded with comparable states of the second half rotation. None: All exposures are saved without coadding.
DLN__022	String	FeedOpticsFRatio	Mean of raw values.	Configuration of the DL-NIRSP Feed Optics: F/24, F/62
DLN__023	String	IFUInBeam	Mean of raw values.	Value indicating BiFOIS-IFU that was used for this observation: IFU-36, IFU-72
DLN__024	String	SlitMode	Mean of raw values.	Value indicating whether DL-NIRSP was operated in single- or multi-slit configuration: Single, All
DLN__025	Int	SlitSelection	Mean of raw values.	Identifier of the slit used when DL-NIRSP is operated in single slit mode: 1,2,3,4,5 Keyword not present, if not used
DLN__026	String	SpatialStepPattern	Mode of raw values.	Selected pattern with which the FieldOfView is sampled. Keyword not present, if not used
DLN__027	Bool	DitherMode	Mode of raw values.	Boolean indicating whether the DL-NIRSP dithering mode was activated or not. When enabled, a sub-unit field shift is used between successive completed FieldSamples: 0, 1
DLN__028	Int	NumberOfSpatialStepsX	Mode of raw values.	Value indicating the number of images in horizontal direction belonging to the scanned FieldOfView. Keyword not present, if not used
DLN__029	Float	StepCenterPositionX	Mode of raw values.	Angular position of the center position in the horizontal direction of the field scan given in units of the field scanning mirror motorized stage. Default position will be a property updated when the instrument is co-aligned with other instruments using a GOS target.
DLN__030	Float	StepSizeX		Angular step size in the horizontal direction given in units of the field scanning mirror motorized stage. Default value will be calculated according to IFU, slits, and feed optics selection.
DLN__031	Int	CurrentSpatialStepX		Value indicating the current image position in horizontal direction belonging to the scanned FieldOfView. 1 ≤ CurrentSpatialStepX ≤ NumberOfSpatialStepsX Keyword not present, if not used
DLN__032	Int	NumberOfSpatialStepsY		Value indicating the number of images in vertical direction belonging to the scanned FieldOfView. Keyword not present, if not used
DLN__033	Float	StepCenterPositionY		Angular position of the center position in the vertical direction of the field scan given in units of the field scanning mirror motorized stage. Default position will be a property updated when the instrument is co-aligned with other instruments using a GOS target.
DLN__034	Float	StepSizeY		Angular step size in the vertical direction given in units of the field scanning mirror motorized stage. Default value will be calculated according to IFU, slits, and feed optics selection.
DLN__035	Int	CurrentSpatialStepY		Value indicating the current image position in vertical direction belonging to the scanned FieldOfView. 1 ≤ CurrentSpatialStepY ≤ NumberOfSpatialStepsY Keyword not present, if not used

Cryo-NIRSP keywords

Key	Type	FITS Comment	Method of derivation	Description
CRSP_001	Int	ArmID	Mode of raw values.	Identifier for Cryo-NIRSP arm that generated the data: Spectro-Polarimeter, Context Viewer
CRSP_002	Float	ArmPosition	Mean of raw values.	Angular position of the arm.
CRSP_003	Float	ArmFocus	Mean of raw values.	Location of the focus stage of the arm.
CRSP_004	String	FilterID	Mode of raw values.	Unique ID of the filter in use
CRSP_005	Float	FilterWavelength	Mean of raw values.	Central wavelength of filter in use
CRSP_006	Float	FilterFWHM	Mean of raw values.	Full Width at Half Maximum spectral transmission at the current filter central wavelength in use
CRSP_007	String	PolarimeterMode	Mode of raw values.	Polarimeter Mode with which these data were acquired: Full Stokes, Stokes-I, Other(?)
CRSP_008	String	ModulatorID	Mode of raw values.	Unique identifier of the modulator.
CRSP_009	String	ModulationType	Mode of raw values.	The type of motion used by the modulator: “discrete, continuous”
CRSP_010	String	ModulatorT0	Mode of raw values.	Reference time for the Modulator motion. Unit is TBD.
CRSP_011	Float	ModulationRate	Mean of raw values.	Rate at which states are to be acquired, in Hertz.
CRSP_012	Int	ModulationStateNumAtT0	Mean of raw values.	Integer number identifier corresponding to the particular state defined by the position of the modulator at its reference time.
CRSP_013	Int	ModulationStateAngAtT0	Mean of raw values.	Modulator angle corresponding to the modulation state at T0.
CRSP_014	Int	NumberOfStates	Mode of raw values.	Number of states to be acquired: NumberOfStates ≥ 1
CRSP_015	Int	CurrentStateNumber	Mode of raw values.	Number of the current state: 1 ≤ CurrentStateNumber ≤ NumberOfStates
CRSP_016	String	GratingID	Mode of raw values.	Unique identifier of the grating in use.
CRSP_017	Float	GratingConstant	Mean of raw values.	Grating constant.
CRSP_018	Float	GratingBlazeAngle	Mean of raw values.	Grating blaze angle.
CRSP_019	Float	GratingAngle	Mean of raw values.	Grating angle with respect to incident beam.
CRSP_020	String	SlitAssemblyID	Mode of raw values.	UniqueID of the slit assembly in use
CRSP_021	Float	SlitWidth	Mean of raw values.	Width of the slit in use
CRSP_022	Float	SlitSteppingSize	Mean of raw values.	Single step size of the slit for this observation Keyword not present, if not used
CRSP_023	Float	SlitSteppingVelocity	Mean of raw values.	Slit move velocity for this observation [ViSP intensity mode only]. Keyword not present, if not used
CRSP_024	Int	NumberOfSpatialSteps	Mean of raw values.	Value indicating the number of images belonging to the scanned FieldOfView. Keyword not present, if not used
CRSP_025	Int	CurrentSpatialStep	Mean of raw values.	Value indicating the current image position belonging to the scanned FieldOfView. 1≤CurrentSpatialStep≤NumberOfSpatialSteps. Keyword not present, if not used
CRSP_026	String	SpatialStepPattern	Mode of raw values.	Selected pattern (scan direction) with which the FieldOfView is sampled. Keyword not present, if not used
CRSP_027	String	PickOffMirrorPosition	Mode of raw values.	Value indicates the position of the Pick Off Mirror used for this observation.
CRSP_028	String	AttenuationFilterID	Mode of raw values.	ID of Attenuation Filter in beam. Keyword not present, if not used
CRSP_029	String	ContextViewerFilterWheel1	Mode of raw values.	Value indicates the named position active in the Cryo-NIRSP Context Viewer Filterwheel 1
CRSP_030	String	ContextViewerFilterWheel1	Mode of raw values.	Value indicates the named position active in the Cryo-NIRSP Context Viewer Filterwheel 2

Data Center keywords

Key	Type	Method of derivation	Description
DSETID	String	Data Center process	Unique ID of the dataset to which the frame belongs
FRAMEVOL	Float	Data Center process	Size of the frame on disk
AVALABLE	String	Data Center process	Availability status of the frame (Available, Degraded, Lost, Removed)
PROCTYPE	String	Data Center process	Controlled value list representing the degree of processing the frame has undergone since receipt at the DKIST data center.
RRUNID	String	Data Center process	Unique ID of the Recipe Run that produced the frame
DATASUM	String	Data Center process	The value field of the DATASUM keyword shall consist of a character string that should contain the unsigned-integer value of the 32-bit ones’ complement checksum of the data records in the HDU (i.e., excluding the header records).
CHECKSUM	String	Data Center process	A 16-character ASCII string that forces the 32-bit ones’ complement checksum accumulated over the entire FITS HDU to equal negative 0 (all 32 bits equal to 1). See Appendix J of the FITS 4.0 standard.
HISTORY	String	Data Center process	The processing provenance of the data, including code modules, libraries, and associated versions. Any number of HISTORY fields may appear in the header.

Compression keywords

Key	Type	Method of derivation	Description
ZIMAGE	String	Data Center process	This keyword must have the logical value T. It indicates that the FITS binary table extension contains a compressed image and that logically this extension should be interpreted as an image and not as a table.
ZCMPTYPE	String	Data Center process	The value field of this keyword shall contain a character string giving the name of the algorithm that must be used to decompress the image. Currently, values of GZIP 1, GZIP 2, RICE 1, PLIO 1, and HCOMPRESS 1 are reserved, and the corresponding algorithms are described in a later section of this document. The value RICE ONE is also reserved as an alias for RICE 1.
ZBITPIX	Int	Data Center process	The value field of this keyword shall contain an integer that gives the value of the BITPIX keyword in the uncompressed FITS image.
ZNAXIS	Int	Data Center process	The value field of this keyword shall contain an integer that gives the value of the NAXIS keyword in the uncompressed FITS image.
ZNAXISn	Int	Data Center process	The value field of these keywords shall contain a positive integer that gives the value of the NAXISn keywords in the uncompressed FITS image.
ZTILEn	Int	Data Center process	The value of these indexed keywords (where n ranges from 1 to ZNAXIS) shall contain a positive integer representing the number of pixels along axis n of the compression tiles. Each tile of pixels is compressed separately and stored in a row of a variable-length vector column in the binary table. The size of each image dimension (given by ZNAXISn) is not required to be an integer multiple of ZTILEn, and if it is not, then the last tile along that dimension of the image will contain fewer image pixels than the other tiles. If the ZTILEn keywords are not present then the default ’row by row’ tiling will be assumed such that ZTILE1 = ZNAXIS1, and the value of all the other ZTILEn keywords equals 1. The compressed image tiles are stored in the binary table in the same order that the first pixel in each tile appears in the FITS image; the tile containing the first pixel in the image appears in the first row of the table, and the tile containing the last pixel in the image appears in the last row of the binary table.
ZNAMEn ZVALn	String Int	Data Center process	These pairs of optional array keywords (where n is an integer index number starting with 1) supply the name and value, respectively, of any algorithm-specific parameters that are needed to compress or uncompress the image. The value of ZVALn may have any valid FITS datatype. The order of the compression parameters may be significant, and may be defined as part of the description of the specific decompression algorithm.
ZMASKCMP	String	Data Center process	Used to record the name of the image compression algorithm that was used to compress the optional null pixel data mask.
ZSIMPLE	String	Data Center process	The value field of this keyword must contain the value of the original SIMPLE keyword in the uncompressed image.
ZHECKSUM	String	Data Center process	The value field of this keyword must contain the value of the original CHECKSUM keyword in the uncompressed image.
ZDATASUM	String	Data Center process	The value field of this keyword must contain the value of the original DATASUM keyword in the uncompressed image.

Dataset keywords

Key	Type	Description
DNAXIS	Ine	The number of axes in the dataset
DNAXISn	Int	The length of the nth dataset axis
DTYPEn	String	The physical types of the axis
DPNAMEn	String	The name of the pixel axes
DWNAMEn	String	The name of the world axes
DUNITn	String	Physical unit for the nth axis of the dataset
DEAXES	Int	Extra axes not in the FITS arrays
DAAXES	Int	Number of non-unity dimensions in the array
DINDEXk	Int	index of this slice in the kth dataset axis

Public DKIST Operations Information

OPS-DC-SPEC-0214