L4 Data Product

FITS HDU Structure

Image HDU array: (4,r,c), where r and c depend on cropping.

ERR HDU array: (1,4,r,c)

DQ HDU array: (4,r,c)

KL_THRU HDU array: (2,2,2)

CT_THRU HDU array: (2,2)

Below is an example.

Index	Name	Datatype	Array Size
0	Primary	None	0
1	Image	float32	(4, 54, 54)
2	ERR	float32	(1, 4, 54, 54)
3	DQ	uint16	(4, 54, 54)
4	KL_THRU	float32	(2, 2, 2)
5	CT_THRU	float32	(2, 2)

Header

Primary Header (HDU 0)

Keyword	Datatype	Example Value	Description
SIMPLE	bool	True	conforms to FITS standard
BITPIX	int	8	array data type
NAXIS	int	0	number of array dimensions
EXTEND	bool	True	Denotes FITS extensions
VISITID	str	0200001001001001001	The full visit ID assigned to this pointing
CDMSVERS	str	2.1.0	SSC CDMS pipeline build version used to generate L1
FSWDVERS	str	1.1.5.1	Record of the CGI FSW dictionary used to parse the telemetry
MOCK	bool	True	Only used for simulated data examples
TELESCOP	str	ROMAN	Telescope name
INSTRUME	str	CGI	Instrument designation
DETECTOR	str	EXCAM	Name of the detector
ORIGIN	str	DRP	Who is responsible for the data
FILETIME	str	2026-02-20T06:41:40.140828+…	When file was created
DATAVERS	int	1	Version of data (increments for reprocessing)
PROGNUM	str	02000	The Program ID in visit hierarchy (first 5 digits)
EXECNUM	str	01	The Execution Number in visit hierarchy (digits 6-7)
CAMPAIGN	str	001	The Pass/Campaign in visit hierarchy (digits 8-10)
SEGMENT	str	001	The Segment Number in visit hierarchy (digits 11-13)
OBSNUM	str	001	The Observation Number in visit hierarchy (digits 14-16)
VISNUM	str	001	The Visit number in visit hierarchy (digits 17-19)
CPGSFILE	str	campaign_020000100100100100…	Campaign-level XML containing the current visit
AUXFILE	str	aux_0200001001001001001.txt	An AUX file associated with this observation
VISTYPE	str	CGIVST_TDD_OBS	The visit file template used for this observation
TARGET	str	ScienceStar	Name of pointing target
RA	float	0.0	Planned RA
DEC	float	0.0	Planned DEC
EQUINOX	float	2000	J2000
RAPM	float	0.0	RA proper motion
DECPM	float	0.0	DEC proper motion
PSFREF	int	0	Whether this is a PSF reference observation or not
OPGAIN	str	1000	Planned EXCAM EM gain or “AUTO”
PHTCNT	str	AUTO	Whether photon counting mode is planned, or if set to “AUTO”. “FALSE” = Photon-counting mode not planned. “TRUE”=Photon-
FRAMET	str	30	Planned exposure time per frame or if set to “AUTO”. Taken from the observation plan
PA_V3	float	-999.0	Observatory position angle
PA_APER	float	-999.0	Position angle in the CGI aperture
SVB_1	float	-999.0	Sun unit vector in the body frame axis 1
SVB_2	float	-999.0	Sun unit vector in the body frame axis 2
SVB_3	float	-999.0	Sun unit vector in the body frame axis 3
ROLL	float	-999.0	S/C roll angle wrt the reference frame
PITCH	float	-999.0	S/C pitch angle wrt the reference frame
YAW	float	-999.0	S/C yaw angle wrt the reference frame
FILENAME	str	cgi_0200001001001001001_202…	The name of the file
OBSNAME	str	SCI	User-defined label for the associated observation plan
WBJ_1	float	-999.0	S/C angular momentum axis 1
WBJ_2	float	-999.0	S/C angular momentum axis 2
WBJ_3	float	-999.0	S/C angular momentum axis 3
KLIP_ALG	str	ADI

Image Header (HDU 1)

Keyword	Datatype	Example Value	Description
XTENSION	str	IMAGE	Image extension
BITPIX	int	-64	array data type
NAXIS	int	3	number of array dimensions
NAXIS1	int	54	Raw data axis 1 size
NAXIS2	int	54	Raw data axis 2 size for SCI frames (1200) or ENG frames (2200)
NAXIS3	int	4	Length of third array dimension (axis 3)
PCOUNT	int	0	number of parameters
GCOUNT	int	1	number of groups
BUNIT	str	photoelectron/s	Physical unit of the array (brightness unit)
ARRTYPE	str	SCI	Whether it is the smaller SCI frame or full ENG frame
SCTSRT	str	2026-05-05T17:39:18	Spacecraft timestamp of first packet for this image frame in UTC
SCTEND	str	2026-05-05T17:40:18	Spacecraft timestamp of last packet for this image frame in UTC
FRMTYPE	str	NUM	Specifies which frame collection routine was used based on instrument EVRs
ISHOWFSC	int	0	Denotes whether the frames are collected as a part of the HOWFSC loop.
ISACQ	int	0	Denotes whether this frame was taken during acquisition
SPBAL	int	0	Denotes whether this frame was taken during speckle balance
ISFLAT	int	0	Denotes whether this frame was taken during the AAC flat activity
SATSPOTS	int	0	Denotes whether the frame contains satellite spots based on a combination of visit type and EXCAM collection command
STATUS	int	0	Housekeeping packet health check status
HVCBIAS	int	0	HV clock bias value. DAC value controlling EM-gain
OPMODE	str	NONE_DETON_0	EXCAM readout operational mode
EXPTIME	float	60.0	Commanded exposure time. Taken from telemetry on CGI
EMGAIN_C	float	1.0	Commanded gain
UNITYG	int	0	DAC value corresponding to unity gain
EMGAINA1	float	0.0	“Actual” gain calculation a1 coefficient
EMGAINA2	float	0.0	“Actual” gain calculation a2 coefficient
EMGAINA3	float	0.0	“Actual” gain calculation a3 coefficient
EMGAINA4	float	0.0	“Actual” gain calculation a4 coefficient
EMGAINA5	float	0.0	“Actual” gain calculation a5 coefficient
GAINTCAL	float	0.0	Calibration reference temperature for gain calculation
EXCAMT	float	0.0	EXCAM temperature from telemetry
EMGAIN_A	float	0.0	“Actual” gain computed from a1-a5 and calibration temperature
KGAINPAR	float	0.0	Calculated K-gain parameter (DN to electrons)
BLNKTIME	float	0.0	EXCAM commanded blanking time
BLNKCYC	int	0	Commanded blanking cycles
EXPCYC	int	0	Exposing stage duration (cycles)
OVEREXP	int	0	EXCAM over-illumination flag
NOVEREXP	float	0.0	Number of pixels overexposed /100
ISPC	int	0	Designated photon counting (telemetered value)
PROXET	float	0.0	Thermal strap interface, EXCAM ProxE heater
FCMLOOP	str	0	Control state of the FCM loop
FCMPOS	float	0.0	Coarse FCM position
FSMINNER	str	0	Control state of the FSM inner loop
FSMLOS	str	1	Control state of the FSM LOS loop
FSMPRFL	str	NFOV	FSM profile that has been loaded
FSMRSTR	int	0	Whether FSM raster is executing
FSMSG1	float	0.0	Average measurement in volts for strain gauge 1 over the last 1000 samples
FSMSG2	float	0.0	Average measurement in volts for strain gauge 2 over the last 1000 samples
FSMSG3	float	0.0	Average measurement in volts for strain gauge 3 over the last 1000 samples
FSMX	float	50.0	Derived FSM X position relative to home from strain gauge voltages and FSM transformation matrix
FSMY	float	50.0	Derived FSM Y position relative to home from strain gauge voltages and FSM transformation matrix
EACQ_ROW	float	0.0	Desired pixel row for most recent star acquisition via EXCAM acquisition method
EACQ_COL	float	0.0	Desired pixel col for most recent star acquisition via EXCAM acquisition method
SB_FP_DX	float	0.0	X pixels offset (from EXCAM center), from FPAM speckle balance alignment
SB_FP_DY	float	0.0	Y pixels offset (from EXCAM center), from FPAM speckle balance alignment
SB_FS_DX	float	0.0	X pixels offset (from EXCAM center), from FSAM speckle balance alignment
SB_FS_DY	float	0.0	Y pixels offset (from EXCAM center), from FSAM speckle balance alignment
DMZLOOP	str	0	Control state of the DM Zernike loop
1SVALID	int	1	Is LOWFSC 1s stats valid
Z2AVG	float	0.0	Avg Z2 value (tip) coefficient from previous second
Z2RES	float	0.0	Res Z2 value (tip) coefficient from previous second
Z2VAR	float	0.0	Var Z2 value (tip) coefficient from previous second
Z3AVG	float	0.0	Avg Z3 value (tilt) coefficient from previous second
Z3RES	float	0.0	Res Z3 value (tilt) coefficient from previous second
Z3VAR	float	0.0	Var Z3 value (tilt) coefficient from previous second
10SVALID	int	1	Is LOWFSC 10s stats valid
Z4AVG	float	0.0	Avg Z4 value (focus) coefficient for 10000 samples
Z4RES	float	0.0	Res Z4 value (focus) coefficient for 10000 samples
Z5AVG	float	0.0	Avg Z5 value (astigmatism) coefficient for 10000 samples
Z5RES	float	0.0	Res Z5 value (astigmatism) coefficient for 10000 samples
Z6AVG	float	0.0	Avg Z6 value (astigmatism) coefficient for 10000 samples
Z6RES	float	0.0	Res Z6 value (astigmatism) coefficient for 10000 samples
Z7AVG	float	0.0	Avg Z7 value (coma) coefficient for 10000 samples
Z7RES	float	0.0	Res Z7 value (coma) coefficient for 10000 samples
Z8AVG	float	0.0	Avg Z8 value (coma) coefficient for 10000 samples
Z8RES	float	0.0	Res Z8 value (coma) coefficient for 10000 samples
Z9AVG	float	0.0	Avg Z9 value (trefoil) coefficient for 10000 samples
Z9RES	float	0.0	Res Z9 value (trefoil) coefficient for 10000 samples
Z10AVG	float	0.0	Avg Z10 value (trefoil) coefficient for 10000 samples
Z10RES	float	0.0	Res Z10 value (trefoil) coefficient for 10000 samples
Z11AVG	float	0.0	Avg Z11 value (spherical) coefficient for 10000 samples
Z11RES	float	0.0	Res Z11 value (spherical) coefficient for 10000 samples
Z12AVG	float	0.0	Avg Z12 value (flux ref) coefficient for 10000 samples
Z13AVG	float	0.0	Avg Z13 value (shear X) coefficient for 10000 samples
Z14AVG	float	0.0	Avg Z14 value (shear Y) coefficient for 10000 samples
SPAM_H	float	0.0	SPAM absolute position of the H-axis in microns
SPAM_V	float	0.0	SPAM absolute position of the V-axis in microns
SPAMNAME	str	OPEN	Closest named SPAM position, calculated from SPAM_H/V keywords
SPAMSP_H	float	0.0	SPAM set point H. The default H position corresponding to the closest SPAM named position
SPAMSP_V	float	0.0	SPAM set point V. The default V position corresponding to the closest SPAM named position
FPAM_H	float	0.0	FPAM absolute position of the H-axis in microns
FPAM_V	float	0.0	FPAM absolute position of the V-axis in microns
FPAMNAME	str	HLC12_C2R1	Closest named FPAM position, calculated from FPAM_H/V and FPAM lookup table
FPAMSP_H	float	0.0	FPAM set point H. The default H position corresponding to the closest FPAM named position
FPAMSP_V	float	0.0	FPAM set point V. The default V position corresponding to the closest FPAM named position
LSAM_H	float	0.0	LSAM absolute position of the H-axis in microns
LSAM_V	float	0.0	LSAM absolute position of the V-axis in microns
LSAMNAME	str	NFOV	Closest named LSAM position, calculated from LSAM_H/V and LSAM lookup table
LSAMSP_H	float	0.0	LSAM set point H. The default H position corresponding to the closest LSAM named position
LSAMSP_V	float	0.0	LSAM set point V. The default V position corresponding to the closest LSAM named position
FSAM_H	float	0.0	FSAM absolute position of the H-axis in microns
FSAM_V	float	0.0	FSAM absolute position of the V-axis in microns
FSAMNAME	str	R1C1	Closest named FSAM position, calculated from FSAM_H/V and FSAM lookup table
FSAMSP_H	float	0.0	FSAM set point H. The default H position corresponding to the closest FSAM named position
FSAMSP_V	float	0.0	FSAM set point V. The default V position corresponding to the closest FSAM named position
CFAM_H	float	0.0	CFAM absolute position of the H-axis in microns
CFAM_V	float	0.0	CFAM absolute position of the V-axis in microns
CFAMNAME	str	1F	Closest named CFAM position, calculated from CFAM_H/V and CFAM lookup table
CFAMSP_H	float	0.0	CFAM set point H. The default H position corresponding to the closest CFAM named position
CFAMSP_V	float	0.0	CFAM set point V. The default V position corresponding to the closest CFAM named position
DPAM_H	float	-999.0	DPAM absolute position of the H-axis in microns
DPAM_V	float	-999.0	DPAM absolute position of the V-axis in microns
DPAMNAME	str	-999	Closest named DPAM calculated from DPAM_H/V and DPAM lookup table
DPAMSP_H	float	-999.0	DPAM set point H. The default H position corresponding to the closest DPAM named position
DPAMSP_V	float	-999.0	DPAM set point V. The default V position corresponding to the closest DPAM named position
DATETIME	str	-999	Time of preceding 1Hz HK packet in UTC
FTIMEUTC	str	-999	Frame time (correlated injected metadata with S/C timestamp) - UTC
MJDSRT	float	60722.0	Exposure start time (MJD)
MJDEND	float	60722.00069	Exposure end time (MJD)
FILE0	str	l0_file_name.fits	File name for the n-th science file used
DATALVL	str	L4	Data level: ‘L1’, ‘L2a’, L2b’, ‘L3’, ‘L4’, ‘TDA’, ‘CAL’
MISSING	int	0	Flagged if header keywords are missing
DESMEAR	bool	False	Desmearing used in L1→L2a pipeline (0/1)
CTI_CORR	bool	False	CTI correction applied to frame (0/1)
IS_BAD	bool	False	Frame deemed bad (0/1)
FWC_PP_E	float	0.0	Full well capacity, EM gain register (e-)
FWC_EM_E	float	0.0	Full well capacity, image area pixel (e-)
SAT_DN	float	0.0	DN saturation
RECIPE	str	{“name”: “l3_to_l4_pol”, “t…	DRP recipe and steps; paths to noise maps, calib
DRPVERSN	str	3.1	corgidrp version that produced this file
DRPCTIME	str	2026-02-20T06:41:40.326	When this file was saved
KGAIN_ER	float	0.0	Kgain error
RN	float	-999.0	Read noise (e-)
RN_ERR	float	-999.0	Read noise uncertainty (e-)
FRMSEL01	float	1.0	Bad Pixel Fraction < This Value. Doesn’t includ
FRMSEL02	bool	False	Are we selecting on the OVEREXP flag?
FRMSEL03	float	-999.0	tip rms (Z2VAR) threshold
FRMSEL04	float	-999.0	tilt rms (Z3VAR) threshold
FRMSEL05	float	-999.0	tip bias (Z2RES) threshold
FRMSEL06	float	-999.0	tilt bias (Z3RES) threshold
CD1_1	float	0.848048096156426	WCS: transform matrix element axis 1 (deg/pixel)
CD1_2	float	0.5299192642332049	WCS: matrix elem mixing axis 2 into 1 (deg/pixel)
CD2_1	float	-0.5299192642332049	WCS: matrix elem mixing axis 1 into 2 (deg/pixel)
CD2_2	float	0.848048096156426	WCS: transform matrix element axis 2 (deg/pixel)
CRPIX1	float	28.0	WCS: reference pixel position axis 1 (pixel)
CRPIX2	float	28.0	WCS: reference pixel position axis 2 (pixel)
CTYPE1	str	RA—TAN	WCS: coordinate type axis 1 (e.g. RA—TAN)
CTYPE2	str	DEC–TAN	WCS: coordinate type axis 2 (e.g. DEC–TAN)
CDELT1	float	0.0	WCS: pixel scale axis 1; deprecated if CD matrix
CDELT2	float	0.0	WCS: pixel scale axis 2; deprecated if CD matrix
CRVAL1	float	0.0	WCS: coordinate at reference pixel, axis 1 (deg)
CRVAL2	float	0.0	WCS: coordinate at reference pixel, axis 2 (deg)
PLTSCALE	float	21.8	Plate scale; pixel angular extent on-sky (mas/pix)
NORTHANG	float	-17.0	WCS: northang calculated from northangle of astrom cal and roll_offset between image frame and astrom cal frame (deg)
STARLOCX	float	27.0	X (column) position of the target star in the image (pixels)
STARLOCY	float	27.0	Y (row) position of the target star in the image (pixels)
NUM_FR	int	16	Number of frames combined
DRPNFILE	int	1	Num raw files used in pyKLIP
FILE_0	str	_INT1.fits	Name of file used in PYKLIP
PSFSUB	str	pyKLIP	PSF Subtraction Algo
PYKLIPV	str	2.8	pyKLIP version that was used
PSFPARAM	str	mode=ADI,annuli=1,subsect=1…	KLIP parameters
KLMODE0	str	1	KL Mode of slice 0
CTYPE3	str	STOKES	Flag indicating this is a polarimetry/ Stokes cube
CTCALFN	str	cgi_0200001001001001001_202…	Core throughput calibration file name
FLXCLF0	str	cgi_0200001001001001001_202…	POL0 flux calibration file name
FLXCLF45	str	cgi_0200001001001001001_202…	POL45 flux calibration file name
HISTORY	str	Marked 0 frames as bad: I…	Processing history

ERR Header (HDU 2)

Keyword	Datatype	Example Value	Description
XTENSION	str	IMAGE	Image extension
BITPIX	int	-64	array data type
NAXIS	int	4	number of array dimensions
NAXIS1	int	54	Raw data axis 1 size
NAXIS2	int	54	Raw data axis 2 size for SCI frames (1200) or ENG frames (2200)
NAXIS3	int	4	Length of third array dimension (axis 3)
NAXIS4	int	1
PCOUNT	int	0	number of parameters
GCOUNT	int	1	number of groups
EXTNAME	str	ERR	FITS extension name
TRK_ERRS	bool	False	Whether individual errors are tracked (T/F)
LAYER_1	str	combined_error	Type of error reported in this error slice
BUNIT	str	photoelectron	Physical unit of the array (brightness unit)
KGAINPAR	float	0.0	Calculated K-gain parameter (DN to electrons)
KGAIN_ER	float	0.0	Kgain error
RN	float	-999.0	Read noise (e-)
RN_ERR	float	-999.0
DESMEAR	bool	False	Desmearing used in L1→L2a pipeline (0/1)
HISTORY	str	Interpolated over 0 bad pi…	Processing history

DQ Header (HDU 3)

Keyword	Datatype	Example Value	Description
XTENSION	str	IMAGE	Image extension
BITPIX	int	16	array data type
NAXIS	int	3	number of array dimensions
NAXIS1	int	54	Raw data axis 1 size
NAXIS2	int	54	Raw data axis 2 size for SCI frames (1200) or ENG frames (2200)
NAXIS3	int	4	Length of third array dimension (axis 3)
PCOUNT	int	0	number of parameters
GCOUNT	int	1	number of groups
BSCALE	int	1	Linear factor in scaling equation. Needed for non-standard FITS data types
BZERO	int	32768	Offset for 16-bit unsigned data type (FITS format determined)
EXTNAME	str	DQ	FITS extension name

KL_THRU Header (HDU 4)

Keyword	Datatype	Example Value	Description
XTENSION	str	IMAGE	Image extension
BITPIX	int	-64	array data type
NAXIS	int	3	number of array dimensions
NAXIS1	int	2	Raw data axis 1 size
NAXIS2	int	2	Raw data axis 2 size for SCI frames (1200) or ENG frames (2200)
NAXIS3	int	2	Length of third array dimension (axis 3)
PCOUNT	int	0	number of parameters
GCOUNT	int	1	number of groups
UNITS	str	Separation: EXCAM pixels. K…
EXTNAME	str	KL_THRU	extension name
COMMENT	str	array of shape (N,n_seps,2)…

CT_THRU Header (HDU 5)

Keyword	Datatype	Example Value	Description
XTENSION	str	IMAGE	Image extension
BITPIX	int	-64	array data type
NAXIS	int	2	number of array dimensions
NAXIS1	int	2	Raw data axis 1 size
NAXIS2	int	2	Raw data axis 2 size for SCI frames (1200) or ENG frames (2200)
PCOUNT	int	0	number of parameters
GCOUNT	int	1	number of groups
UNITS	str	Separation: EXCAM pixels. C…
EXTNAME	str	CT_THRU	extension name
COMMENT	str	KLIP Throughput as a functi…