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.
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.
MDI Lev1.5 Keyword Descriptions