ND Filter Spectroscopy Data Product

FITS HDU Structure

Index	Name	Datatype	Array Size
0	Primary	None	0
1	Image	float32	(9, 19, 4)
2	ERR	float32	(1, 9, 19, 4)
3	DQ	uint16	(9, 19, 4)

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	-999	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	2026-03-23T21:21:34.232644+…	When file was created
DATAVERS	int	1	Version of data (increments for reprocessing)
PROGNUM	str	-999	The Program ID in visit hierarchy (first 5 digits)
EXECNUM	str	-999	The Execution Number in visit hierarchy (digits 6-7)
CAMPAIGN	str	-999	The Pass/Campaign in visit hierarchy (digits 8-10)
SEGMENT	str	-999	The Segment Number in visit hierarchy (digits 11-13)
OBSNUM	str	-999	The Observation Number in visit hierarchy (digits 14-16)
VISNUM	str	-999	The Visit number in visit hierarchy (digits 17-19)
CPGSFILE	str	-999	Campaign-level XML containing the current visit
AUXFILE	str	-999	An AUX file associated with this observation
VISTYPE	str	-999	The visit file template used for this observation
TARGET	str	-999	Name of pointing target
RA	float	-999.0	Planned RA
DEC	float	-999.0	Planned DEC
EQUINOX	float	2000.0	J2000
RAPM	float	-999.0	RA proper motion
DECPM	float	-999.0	DEC proper motion
PSFREF	int	0	Whether this is a PSF reference observation or not
OPGAIN	str	-999	Planned EXCAM EM gain or “AUTO”
PHTCNT	str	-999	Whether photon counting mode is planned, or if set to “AUTO”. “FALSE” = Photon-counting mode not planned. “TRUE”=Photon-
FRAMET	str	-999	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	-999	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
COMMENT	str	Simulation-specific metadat…	FITS comment keyword

Image Header (HDU 1)

Keyword	Datatype	Example Value	Description
XTENSION	str	IMAGE	Image extension
BITPIX	int	-32	array data type
NAXIS	int	3	number of array dimensions
NAXIS1	int	4	wave, OD, x, y
NAXIS2	int	19	length of wavelength grid
NAXIS3	int	9	number of dithers
PCOUNT	int	0	number of parameters
GCOUNT	int	1	number of groups
BUNIT	str		Physical unit of the array (brightness unit)
ARRTYPE	str	SCI	Whether it is the smaller SCI frame or full ENG frame
SCTSRT	str	2025-02-16T00:00:00	Spacecraft timestamp of first packet for this image frame in UTC
SCTEND	str	2025-02-16T00:00:00	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	-999	Denotes whether the frames are collected as a part of the HOWFSC loop.
ISACQ	int	-999	Denotes whether this frame was taken during acquisition
SPBAL	int	-999	Denotes whether this frame was taken during speckle balance
ISFLAT	int	-999	Denotes whether this frame was taken during the AAC flat activity
SATSPOTS	int	-999	Denotes whether the frame contains satellite spots based on a combination of visit type and EXCAM collection command
STATUS	int	-999	Housekeeping packet health check status
HVCBIAS	int	-999	HV clock bias value. DAC value controlling EM-gain
OPMODE	str	-999	EXCAM readout operational mode
EXPTIME	float	-999.0	Commanded exposure time. Taken from telemetry on CGI
EMGAIN_C	float	-999.0	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	1.0	“Actual” gain computed from a1-a5 and calibration temperature
KGAINPAR	float	-999.0	Calculated K-gain parameter (DN to electrons)
BLNKTIME	float	-999.0	EXCAM commanded blanking time
BLNKCYC	int	-999	Commanded blanking cycles
EXPCYC	int	-999	Exposing stage duration (cycles)
OVEREXP	int	0	EXCAM over-illumination flag
NOVEREXP	float	-999.0	Number of pixels overexposed /100
ISPC	int	0	Designated photon counting (telemetered value)
PROXET	float	-999.0	Thermal strap interface, EXCAM ProxE heater
FCMLOOP	str	-999	Control state of the FCM loop
FCMPOS	float	-999.0	Coarse FCM position
FSMINNER	str	-999	Control state of the FSM inner loop
FSMLOS	str	-999	Control state of the FSM LOS loop
FSMPRFL	str	-999	FSM profile that has been loaded
FSMRSTR	int	-999	Whether FSM raster is executing
FSMSG1	float	-999.0	Average measurement in volts for strain gauge 1 over the last 1000 samples
FSMSG2	float	-999.0	Average measurement in volts for strain gauge 2 over the last 1000 samples
FSMSG3	float	-999.0	Average measurement in volts for strain gauge 3 over the last 1000 samples
FSMX	float	-999.0	Derived FSM X position relative to home from strain gauge voltages and FSM transformation matrix
FSMY	float	-999.0	Derived FSM Y position relative to home from strain gauge voltages and FSM transformation matrix
EACQ_ROW	float	-999.0	Desired pixel row for most recent star acquisition via EXCAM acquisition method
EACQ_COL	float	-999.0	Desired pixel col for most recent star acquisition via EXCAM acquisition method
SB_FP_DX	float	-999.0	X pixels offset (from EXCAM center), from FPAM speckle balance alignment
SB_FP_DY	float	-999.0	Y pixels offset (from EXCAM center), from FPAM speckle balance alignment
SB_FS_DX	float	-999.0	X pixels offset (from EXCAM center), from FSAM speckle balance alignment
SB_FS_DY	float	-999.0	Y pixels offset (from EXCAM center), from FSAM speckle balance alignment
DMZLOOP	str	-999	Control state of the DM Zernike loop
1SVALID	int	-999	Is LOWFSC 1s stats valid
Z2AVG	float	-999.0	Avg Z2 value (tip) coefficient from previous second
Z2RES	float	-999.0	Res Z2 value (tip) coefficient from previous second
Z2VAR	float	-999.0	Var Z2 value (tip) coefficient from previous second
Z3AVG	float	-999.0	Avg Z3 value (tilt) coefficient from previous second
Z3RES	float	-999.0	Res Z3 value (tilt) coefficient from previous second
Z3VAR	float	-999.0	Var Z3 value (tilt) coefficient from previous second
10SVALID	int	-999	Is LOWFSC 10s stats valid
Z4AVG	float	-999.0	Avg Z4 value (focus) coefficient for 10000 samples
Z4RES	float	-999.0	Res Z4 value (focus) coefficient for 10000 samples
Z5AVG	float	-999.0	Avg Z5 value (astigmatism) coefficient for 10000 samples
Z5RES	float	-999.0	Res Z5 value (astigmatism) coefficient for 10000 samples
Z6AVG	float	-999.0	Avg Z6 value (astigmatism) coefficient for 10000 samples
Z6RES	float	-999.0	Res Z6 value (astigmatism) coefficient for 10000 samples
Z7AVG	float	-999.0	Avg Z7 value (coma) coefficient for 10000 samples
Z7RES	float	-999.0	Res Z7 value (coma) coefficient for 10000 samples
Z8AVG	float	-999.0	Avg Z8 value (coma) coefficient for 10000 samples
Z8RES	float	-999.0	Res Z8 value (coma) coefficient for 10000 samples
Z9AVG	float	-999.0	Avg Z9 value (trefoil) coefficient for 10000 samples
Z9RES	float	-999.0	Res Z9 value (trefoil) coefficient for 10000 samples
Z10AVG	float	-999.0	Avg Z10 value (trefoil) coefficient for 10000 samples
Z10RES	float	-999.0	Res Z10 value (trefoil) coefficient for 10000 samples
Z11AVG	float	-999.0	Avg Z11 value (spherical) coefficient for 10000 samples
Z11RES	float	-999.0	Res Z11 value (spherical) coefficient for 10000 samples
Z12AVG	float	-999.0	Avg Z12 value (flux ref) coefficient for 10000 samples
Z13AVG	float	-999.0	Avg Z13 value (shear X) coefficient for 10000 samples
Z14AVG	float	-999.0	Avg Z14 value (shear Y) coefficient for 10000 samples
SPAM_H	float	26250.4	SPAM absolute position of the H-axis in microns
SPAM_V	float	27254.4	SPAM absolute position of the V-axis in microns
SPAMNAME	str	SPEC	Closest named SPAM position, calculated from SPAM_H/V keywords
SPAMSP_H	float	26250.4	SPAM set point H. The default H position corresponding to the closest SPAM named position
SPAMSP_V	float	27254.4	SPAM set point V. The default V position corresponding to the closest SPAM named position
FPAM_H	float	61507.8	FPAM absolute position of the H-axis in microns
FPAM_V	float	25612.4	FPAM absolute position of the V-axis in microns
FPAMNAME	str	ND225	Closest named FPAM position, calculated from FPAM_H/V and FPAM lookup table
FPAMSP_H	float	-999.0	FPAM set point H. The default H position corresponding to the closest FPAM named position
FPAMSP_V	float	-999.0	FPAM set point V. The default V position corresponding to the closest FPAM named position
LSAM_H	float	36936.3	LSAM absolute position of the H-axis in microns
LSAM_V	float	29389.3	LSAM absolute position of the V-axis in microns
LSAMNAME	str	SPEC	Closest named LSAM position, calculated from LSAM_H/V and LSAM lookup table
LSAMSP_H	float	36936.3	LSAM set point H. The default H position corresponding to the closest LSAM named position
LSAMSP_V	float	29389.3	LSAM set point V. The default V position corresponding to the closest LSAM named position
FSAM_H	float	24087.0	FSAM absolute position of the H-axis in microns
FSAM_V	float	12238.0	FSAM absolute position of the V-axis in microns
FSAMNAME	str	R1C2	Closest named FSAM position, calculated from FSAM_H/V and FSAM lookup table
FSAMSP_H	float	24087.0	FSAM set point H. The default H position corresponding to the closest FSAM named position
FSAMSP_V	float	12238.0	FSAM set point V. The default V position corresponding to the closest FSAM named position
CFAM_H	float	2329.2	CFAM absolute position of the H-axis in microns
CFAM_V	float	24002.7	CFAM absolute position of the V-axis in microns
CFAMNAME	str	3F	Closest named CFAM position, calculated from CFAM_H/V and CFAM lookup table
CFAMSP_H	float	2329.2	CFAM set point H. The default H position corresponding to the closest CFAM named position
CFAMSP_V	float	24002.7	CFAM set point V. The default V position corresponding to the closest CFAM named position
DPAM_H	float	26824.2	DPAM absolute position of the H-axis in microns
DPAM_V	float	1261.3	DPAM absolute position of the V-axis in microns
DPAMNAME	str	PRISM3	Closest named DPAM calculated from DPAM_H/V and DPAM lookup table
DPAMSP_H	float	26824.2	DPAM set point H. The default H position corresponding to the closest DPAM named position
DPAMSP_V	float	1261.3	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	cgi_0200001001001001001_202…	File name for the n-th science file used
DATALVL	str	CAL	Data level: ‘L1’, ‘L2a’, L2b’, ‘L3’, ‘L4’, ‘TDA’, ‘CAL’
MISSING	int	0	Flagged if header keywords are missing
RN	float	100.0	Read noise (e-)
DESMEAR	bool	True	Was desmear applied to this frame?
CTI_CORR	bool	False	Was CTI correction applied to this frame?
IS_BAD	bool	False	Was this frame deemed bad?
RECIPE	str	{“name”: “l2b_nd_spec_cal”,…	DRP recipe and steps; paths to noise maps, calibrations
DRPVERSN	str	3.2.1	corgidrp version that produced this file
DRPCTIME	str	2026-03-23T21:21:34.236	When this file was saved
FWC_PP_E	float	-999.0	Full well capacity, EM gain register (e-)
FWC_EM_E	float	-999.0	Full well capacity, image area pixel (e-)
SAT_DN	float	-999.0	DN saturation
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
KGAIN_ER	float	0.0	Kgain error
RN_ERR	float	0.0	Read noise uncertainty (e-)
WAVLEN0	float	753.83	Central wavelength of narrowband filter used for zero-point (nm)
WV0_X	float	513.0132225061535	X pixel coordinate of wavelength zero-point source (broadband filter frame)
WV0_XERR	float	0.003017876546780365	Uncertainty in X pixel coordinate of wavelength zero-point
WV0_Y	float	503.4096061588887	Y pixel coordinate of wavelength zero-point source (broadband filter frame)
WV0_YERR	float	0.005249243937480492	Uncertainty in Y pixel coordinate of wavelength zero-point
WV0_DIMX	int	1024	X dimension of the detector frame used for wavelength zero-point
WV0_DIMY	int	1024	Y dimension of the detector frame used for wavelength zero-point
DRPNFILE	int	12	# of files used to create this processed frame
DATATYPE	str	NDSpectroscopy	Calibration data type
ODFLAG	bool	False	Flag for OD variation above threshold
HISTORY	str	Frames cropped and bias sub…	Processing history

ERR Header (HDU 2)

Keyword	Datatype	Example Value	Description
XTENSION	str	IMAGE	Image extension
BITPIX	int	-32	array data type
NAXIS	int	4	number of array dimensions
NAXIS1	int	4	wave_err, OD_err, x_err, y_err
NAXIS2	int	19	length of wavelength grid
NAXIS3	int	9	number of dithers
NAXIS4	int	1	Length of fourth array dimension (axis 4)
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	-999	Physical unit of the array (brightness unit)
KGAINPAR	float	-999.0	Calculated K-gain parameter (DN to electrons)
KGAIN_ER	float	0.0	Kgain error
RN	float	100.0	Read noise (e-)
RN_ERR	float	0.0	Read noise uncertainty (e-)
DESMEAR	bool	True	Was desmear applied to this frame?
HISTORY	str	Added error term: prescan_b…	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	4	wave, OD, x, y
NAXIS2	int	19	length of wavelength grid
NAXIS3	int	9	number of dithers
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