SOT-SP FITS Keywords
The following table lists the keywords found in the FITS headers for Level 0 SOT-SP data.
| Keyword | Type | Description |
|---|---|---|
CRPIX1 | Flt | Horizontal position of the reference pixel in the data, e.g., the center of the CCD [pixels] |
CRPIX2 | Flt | Vertical position of the reference pixel in the data, e.g., the center of the CCD [pixels] |
CRVAL1 | Flt | The wavelength of the reference pixel specified by CRPIX1 [Å] (e.g., 6302.0) |
CRVAL2 | Flt | Heliocentric coordinates (Y) of the reference pixel along the slit specified by CRPIX2 [arcsec] |
CDELT1 | Flt | Pixel scale in the dispersion (X) direction [Å/pixel] |
CDELT2 | Flt | Pixel scale in the slit (Y) direction [arcsec/pixel] |
CUNIT1 | Str | Unit of CRVAL1 (e.g., Angstrom) |
CUNIT2 | Str | Unit of CRVAL2 (e.g., arcsec) |
CTYPE1 | Str | Label of the first dimension of the data (e.g., Wavelength) |
CTYPE2 | Str | Label of the second dimension of the data (e.g., Solar-Y) |
CTYPE3 | Str | Label of the third dimension of the data (e.g., CCD side) |
CTYPE4 | Str | Label of the fourth dimension of the data (e.g., Stokes component) |
XSCALE | Flt | Step size of slit scanning [arcsec] |
YSCALE | Flt | Pixel scale in the slit (Y) direction [arcsec/pixel] |
XCEN | Flt | The heliocentric coordinate (X) at the slit position [arcsec] |
YCEN | Flt | The heliocentric coordinate (Y) at the center of the slit [arcsec] |
FOVX | Flt | The width of the field-of-view in the X direction, i.e., the slit width [arcsec] |
FOVY | Flt | The width of the field-of-view in the Y direction [arcsec] |
SPMAPCTR | Flt | Center position of slit scan with respect to scan mechanism center [scan steps] |
SPCCDIX0 | Int | Index of the 1st pixel in the CCD X-direction [pixel] |
SPCCDIX1 | Int | Index of the last pixel in the CCD X-direction [pixel] |
SPCCDIY0 | Int | Index of the 1st pixel in the CCD Y-direction [pixel] |
SPCCDIY1 | Int | Index of the last pixel in the CCD Y-direction [pixel] |
NSLITPOS | Int | Number of slit positions in an SP map [scan steps] |
SLITINDX | Int | Index number of slit position in map, ranges from 0 to NSLITPOS−1 [scan steps] |
NUM_SIDE | Int | Number of the CCD sides in use (1 if only left side, 2 if both left and right sides) |
SPNINT | Int | Number of integration cycles (between 1 and 16), where each cycle corresponds to 0.8 sec integration (half rotation of PMU) |
SP_EXTID | Int | SP extraction table ID (ranges between 1 and 15), determines ROI in spatial direction |
SCN_STEP | Int | Number of scan steps between positions at which data is collected |
SCN_SUM | Int | Number of slit positions summed before sending data to MDP |
SCN_RPT | Int | Number of scan repeats, with 0 indicating infinite repeats |
SPBSHFT | Int | Scaling (bit-shift) options: 0 indicates no scaling, 1 indicates Stokes I down by a factor of 2, 2 indicates Stokes I and V down by a factor of 2, and 3 indicates Stokes I, Q, U, and V down by a factor of 2 |
SLITPOS | Int | Position of slit with respect to scan mechanism center, software best estimate [scan steps] |
SLITENC | Int | Encoder position of SP scan mechanism, center is 2048 [scan steps] |
SPMAPINX | Int | Cumulative number of SP maps completed |
DOP_RCV | Int | Doppler shift compensation provided by MDP [m/s] |