SOI Logo MDI Lev1.5 Keyword Descriptions


The following keywords are found in the image headers, record.rdb, and overview.fits files of the MDI lev1.5 data. In most cases, the keywords are described, as opposed to defined mathematically. For more precise definitions or questions, please contact MDI.

Level 1.5 Keywords

KEYWORD		DEFINITION
---------	-------------------------------------------------------
ABS_MIN		Minimum of the absolute values of the data
AUTHOR		FITS keyword.  
AVG_FLUX	TOT_FLUX divided by NPIXFLUX.
B0      	Heliographic coordinate of the sub-observation point in 
		degrees.
BFITZERO	Magnetogram zero offset.
BITPIX  	Mandatory FITS data type. Must be second keyword 
		in header. 
BLANK   	Undefined integer pixels are set to this value. 
		Missing float pixels are set to NaN (not a number). 
		FITS only.
BLDVER00	Level 0 software version number.
BLDVER01	Level 1 software version number.
BLDVER15	Level 1.5 software version number.
BSCALE  	Scaling factor to convert data to float.  FITS only.
BUNIT   	Physical units of the data. For example, m/s.
BZERO   	Offset applied to true pixel values.  FITS only.
	        physical_value = fits_pixel_value*bscale + bzero
CADENCE 	Time step in seconds between adjacent data samples.
CALTBLS		Calibration files pathname.
CDELT1		SolarSoft keyword.  Same as XSCALE.
CDELT2          SolarSoft keyword.  Same as YSCALE.
CENTER_X	X0 + 1.0
CENTER_Y	Y0 + 1.0
CMPERRS 	Number of compression errors.
COMMENT		Comment, usually a reference to online documentation 
		and source of data.
CONFORMS	Used by gather_info to determine time step.
CRPIX1		SolarSoft keyword.  Disk center x-coordinate, lower 
		left = (1,1).
CRPIX2		SolarSoft keyword.  Disk center y-coordinate, lower 
		left = (1,1).
CTYPE1		SolarSoft keyword.  X-axis is EW on disk in arcsec from 
		disk center.
CTYPE2          SolarSoft keyword.  Y-axis is NS on disk in arcsec from 
		disk center.
DATAFILE	SOI data file name. Generated by the vds library.  
DATAKIND	Pointer to keyword list.  Not fully implemented.
DATAKURT	Kurtosis (4th moment of the data distribution).
DATAMAX 	Maximum data value in units specified by BUNIT.
DATAMEAN	Mean value of data in units specified by BUNIT.
DATAMEDN	Approximation of data median - may not be accurate.  	                             
DATAMIN 	Minimum data value in units specified by BUNIT.
DATANAME	Dataname is currently left blank
DATASIGN	Sign convention. The value is -1 for velocity data, 
		which signifies the convention that positive is in 
		the redshift direction (away from the observer).
DATASKEW        3rd moment of the data distribution.
DATAVALS	Number of non-missing values in data record.
DATA_RMS	RMS value of data in units specified by BUNIT.
DATE    	File creation date.                    
DATE-OBS	Date of T_OBS in UT as DD/MM/YY.      
DATE_OBS	UT start time of obs in CCSDS format 
		(e.g.1996-03-19T23:07:02.000Z) 
DFNAME0		
DNAME0  	Descriptive name of the first variable in a data set 
		(currently the only variable). 
DNOTE0  	Comment field for var 0. 
DPC     	8- or 10-character version of data product code.
DPC_CONF	Indicates whether the DPC is a conforming or 
		non-conforming DPC.
DPC_CROP	Crop radius in CCD pixels.   
DPC_FORM	Image format. Possibilities are, 'Cropped', 'Raster 
		Compressed'.
DPC_OBSR	DPC description. For example, 
		'HR_Filtergram' / High-Resolution Filtergram.
DPC_ORGN	Origin of data. Possibilities are 'Space', 'Sim', 'Grnd'
DPC_RATE	Data channel. Possibilities are 'High-Rate' (160kbps) 
		or 'Low-Rate' (5kbps).
DPC_SMPL	Sample period in seconds.
DPC_STR 	10-character version of data product code. For example, 
		'0x40483D00'.            
DSDS_UID	Database ID.
DSIGN0  	Sign convention of first variable (currently the only 
		variable).
DSNAME  	SSSC data set name prog:mdi,level:lev1.5,series:
		hr_M_1024x500_01h[35855].
DTYPE   	Data type.  V=dopplergram B=magnetic field C=continuum 
		M=modulation     
DUNIT0  	Currently blank. should be copy of DATANAME for each var. 
DVALS0  	Number of non-missing values in all records in a data 
		set.
D_MAX0  	Maximum value of all records in a data set.              
D_MEAN0 	Mean value of all records in a data set.      
D_MIN0  	Minimum value of all records in a data set.  
D_RMS0  	RMS value of all records in a data set.     
D_VARS  	Number of variables in a data set.         
EARTH_B0	Heliographic Latitude of the center of the earth.  
EARTH_CR	Heliographic rotation number for EARTH_L0.    
EARTH_D 	Sun-center to Earth-center distance in AU.                                  
EARTH_DT	Delay time between T_OBS and T_EARTH 
		(T_EARTH = T_OBS + EARTH_DT). 
EARTH_L0	Heliographic Longitude of the center of the earth. 
EARTH_R0	Radius of the Sun in arc seconds, as viewed from earth.
EARTH_VN	"Northward" velocity of Earth in m/s. Positive is in 
		direction of solar north.
EARTH_VR	Radial velocity of Earth in m/s. Positive direction 
		toward the Sun.
EARTH_VW	"Westward" velocity of Earth in m/s. Positive is in 
		direction of Earth's orbit.  
END     	Mandatory FITS.  Marks the end of the FITS header.
EPH_QUAL	Status value returned by soho_ephemeris. 0 means the 
		ephemeris data is good.
FD_SCALE	Nominal full-disk plate scale = 1.97784.   
FNDLMBAN	Angle between y-axis and major-axis in degrees. 
FNDLMBMA	Major-axis length in pixels.            
FNDLMBMI	Minor-axis length in pixels.           
FNDLMBXC	X-center of image in pixels.          
FNDLMBYC	Y-center of image in pixels.         
HISTORY		Comment field, usually with a comment about 
		processing history.
HR_MAG  	Magnification factor of the high-resolution magnetograms 
		with respect to the full-
		disk images. The current value is 3.267. 
I_DREC		Record ID number.
IM_SCALE       	Nominal pixel scale in arc-seconds/pixel. 
		IM_SCALE = FD_SCALE/MAGNIFY
INSTRUME	MDI.    
INTERVAL	Integration time in seconds. 
ITIME   	GONG keyword. Same as CADENCE.
L0      	Heliographic coordinate of the sub-observation point in 
		degrees.
MAGNIFY 	Magnification factor used. The value is 1 for all images 
		other than high-resolution magnetograms, in which case 
		it takes on the value of HR_MAG.
MDIREF  	T_REF as a number. 
MDI_X0  	Full Disk Image x-center in pixels. Value taken from 
		pointing info. 
MDI_Y0  	Full Disk Image y-center in pixels. Value taken from 
		pointing info.
MEAN_FLD	Sum of B over pixels within radius (.95 * R_SUN) 
		divided by NPIXFLUX.
MISSPKTS	Number of missing packets.     
MISSVALS	Number of missing values in data record. 
NAXIS   	Mandatory. Number of axes. Must be third keyword in header. 
NAXIS1  	Mandatory. Size of first dimension. Must follow NAXIS 
		in header.
NAXIS2  	Mandatory. Size of second dimension. Must follow NAXIS1 
		in header.
NPIXFLUX	Number of pixels within radius .95 * R_SUN.
OBS_B0  	Heliographic Latitude of the observer's disk center. 
OBS_CR  	Carrington rotation number for OBS_L0.  
OBS_DIST	Distance of observer to Sun center in AU.
OBS_L0  	Heliographic Longitude of the observer's disk center. 
OBS_MODE	DPC description. For example, 
		'HR_Filtergram' / High-Resolution Filtergram. 
OBS_R0  	Apparent semi-diameter of Sun in arc seconds from SOHO.                               
OBS_TYPE	Observable code determined from DPC.
OBS_VN  	"Northward" velocity of observer in m/s. Positive is 
		in direction of solar north.  
OBS_VR  	Radial velocity of observer in m/s. Positive direction 
		is away from the Sun.
OBS_VW  	"Westward" velocity of observer in m/s. Positive is in 
		direction of Earth's orbit.  
OBT_TIME	Local On Board Time of start of data.  
ORIENT  	The orientation of the Sun's image in the file/array is 
		defined by a character string indicating the "side" of 
		the Sun (with an assumed position angle of 0) that corresponds
		to the origin and x-axis used for the pointing and scale
		parameters. This string contains 4 characters from the set
		N,S,E,W and tells the "corner" for the (0,0) pixel and the
		corner for the (xmax,0) pixel. In the soho nominal image
		orientation, with P_ANGLE corretion applied, this would be "SESW".   
ORIGIN  	Organization that created the FITS file. SOHO-SOI.
PIXLENX 	Pixel x-dimension. 1.0 for SOI.        
PIXLENY 	Pixel y-dimension. 1.0 for SOI.       
PLATE_X		Pixel x-coordinate of image center.  
		0.5*({cols,rows} - 1) for reconstructed 2-d images.
PLATE_Y		Pixel y-coordinate of image center.  
		0.5*({cols,rows} - 1) for reconstructed 2-d images.
PROTOCOL	Conforming dataset file format.      
P_ANGLE 	Angular location of the solar north pole on the image 
		after mappings have been performed.
ROLL_TBL	Name of roll angle table from which P_ANGLE, SOLAR_P and 
		SOLAR_P0 are interpolated; "none" if no table is used; 
		"not used" if a table is specified but the interpolation 
		failed for any reason.
ROLL_UPD	Last modification time of the roll angle table; blank if 
		ROLL_TBL is "none" or "not used".
QUALITY 	Status summary, 0 == no known problems.  
RUNTIME 	Date data was processed. Format yyyy.mm.dd_hh:mm:ss_UT
R_SUN   	Semi_major axis length of the apparent solar image when 
		plotted with square image elements. 
SEMIDIAM	Semi-diameter in radians. 
SIMPLE  	Mandatory. File type. Mandatory in primary header. Must 
		be F(alse) if the file does not conform to the FITS 
		standard, otherwise T(rue). Must be first keyword in 
		header.  
SITE    	'md' for MDI.           
SIZERRS 	Potential number of size errors from compressed data 
		(used as a quality flag).              
SOLAR_B0	Same as OBS_B0 - Heliographic Latitude of the observer's 
		disk center. 
SOLAR_P 	Original position angle of the solar north pole measured
		eastward (counterclockwise) from plate "north" (degrees). 
SOLAR_P0	Same as SOLAR_P - position angle of the Solar North pole.
SOURCE  	Database data source prog:mdi,level:lev1[2],series:
		4b4a2d00_01h[35855]:sel[53]. 
SQID    	Sequence ID.  
S_ANGLE 	Position angle of S_MAJOR axis. Default is 0 for MDI. 
S_MAJOR 	Scale for semi-major axis of squished Earth-based images. 
		Default is 1 for MDI.  
S_MINOR 	Scale for semi-minor axis of squished Earth-based images. 
		Default is 1 for MDI. 
TBLXYUPD	Pointing table last modification date. 
TELESCOP	SOHO.                                      
TIME-OBS	Time of T_OBS in UT as hh:mm:ss.ss.  
TOT_FLUX	Sum of |B| over pixels within radius .95 * R_SUN.
T_BLOCK 	Specifies time increment that the dataset is stored (or 
		blocked) in.  
T_EARTH 	Time of observation had it occured on Earth. 
		T_EARTH = T_OBS + EARTH_DT. 
T_EPOCH 	Epoch for this time series.     
T_FIRST 	UT start time of observation (center of averaging 
		interval).
T_LAST  	UT end time of observation (center of averaging 
		interval). 
T_OBS  		Actual (center) of integration time.
T_REC   	Intended observation time.
T_REF   	Local on-board time (LOBT) stamp.
T_START 	Beginning time of first image in a data set.          
T_STOP  	Just past ending time of last image in a data set.   
VCOR1   	Observer's velocity in m/s.                         
VDS_VERS	VDS version number.                               
X0		Distance along x-axis to center of solar disk from first 
		pixel center in array pixels
		X0 = [(MDI_X0 - 511.5 - X_OPAXIS)*MAGNIFY - X_OFFSET + 
		512.0]/X_SCALE - 0.5  
XCEN    	The location of the x-center of the image array on the 
		Sun measured in arc-seconds from the center of the Sun's 
		disk, positive is to the West (North).    
XSCALE  	XSCALE = X_SCALE * IM_SCALE
XY_FROM 	Source of pointing information. 
XY_QUAL 	Status value returned by mdi_pointing. 0 means the 
		pointing data is good. 
X_OFFSET	Sampled field of view origin distance from full field of 
		view origin. Units are CCD pixels.  These offsets are 
		always non-negative. They are zero in full-disk, full CCD 
		field of view case. There is some small correction (see 
		gather_xy_rsun) in vw_V case. In the extracted image 
		cases, these parameters are determined from COFF 
		parameter.  For binned data where the center of the lower 
		left bin is offset from the center of the lower left pixel 
		in the CCD X_OFFSET is computed as that distance in pixels 
		divided by the binning. I.e. for flux budget it is 3.5/8.0.
X_OPAXIS	Instrument field of view axis (i.e. optical axis) 
		arc-seconds from the center of the Sun's disk, plus to the 
		West (North).location wrt full disk magnification 
		instrument ccd center.  This is the current HR center 
		location on the fd optical axis on the ccd. in fd case 
		this is 0.0, 0.0 in hr it is (516.6-511.5) and 
		(573.0-511.5) for X,Y, i.e. (5.1, 61.5).  
X_SCALE 	CCD pixels per bin. X{Y}_SCALE are the size of image 
		elements in units of CCD pixels where the pixels are each 
		of angular size IM_SCALE. If the pixels are rectangular 
		X_SCALE, Y_SCALE, and IM_SCALE should form a consistent 
		set. For MDI these scale factors for X and Y include the 
		high-res vs. full disk and the binning information.                         
Y0      	Distance along y-axis to center of solar disk from first 
		pixel center in array pixels.  
		Y0 = [(MDI_Y0 - 511.5 - Y_OPAXIS)*MAGNIFY - Y_OFFSET + 
		512.0]/Y_SCALE - 0.5                       
YCEN    	The location of the y-center of the image array on the 
		Sun measured in arc-seconds from the center of the Sun's 
		disk, positive is to the West (North).        
YSCALE  	YSCALE = Y_SCALE * IM_SCALE  
Y_OFFSET	Sampled field of view origin distance from full field of 
		view origin. Units are CCD pixels.  These offsets are 
		always non-negative. They are zero in full-disk, full CCD 
		field of view case.  There is some small correction (see 
		gather_xy_rsun) in vw_V case. In the extracted image 
		cases, these parameters are determined from COFF parameter. 
		For binned data where the center of the lower left bin is 
		offset from the center of the lower left pixel in the CCD 
		X_OFFSET is computed as that distance in pixels divided 
		by the binning. I.e. for flux budget it is 3.5/8.0.
Y_OPAXIS	Instrument field of view axis (i.e. optical axis) 
		location wrt full disk magnification instrument ccd center. 
		This is the current HR center location on the fd optical 
		axis on the ccd. in fd case this is 0.0, 0.0 in hr it is 
		(516.6-511.5) and (573.0-511.5) for X,Y, i.e. (5.1, 61.5).  
Y_SCALE 	CCD pixels per bin. X{Y}_SCALE are the size of image 
		elements in units of CCD pixels where the pixels are each 
		of angular size IM_SCALE. If the pixels are rectangular 
		X_SCALE, Y_SCALE, and IM_SCALE should form a consistent 
		set. For MDI these scale factors for X and Y include the 
		high-res vs. full disk and the binning information.  


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