# L1-IFS Data model

## File: CSST_IFS_CUBE_{OBJ_id}_{VER_cube}_{LIN/LOG}_{STM_cube}.fits

### File contents


| HDU  | data                    | note       |
|------|-------------------------|------------|
| HDU0 | None                    | PrimaryHDU |
| HDU1 | FLUX                    | ImageHDU   |
| HDU2 | IVAR                    | ImageHDU   |
| HDU3 | MASK                    | ImageHDU   |
| HDU4 | EXP_NUM                 | ImageHDU   |
| HDU5 | LSF                     | ImageHDU   |
| HDU6 | WEIGHT_MARTIX           | ImageHDU   |
| HDU7 | rRSS_FILE_LIST          | BinTableHDU|


### HDU0

| keyword | value | comment       | fill value    | type | module       |
|---------|:------|---------------|---------------|------|--------------|
| SIMPLE  | True  | Fits standard | True          | bool |csst_ifs_cube |

### HDU0

#### Header of `csst_ifs_cube`

| keyword   | value                 | comment                                           | fill value   | type | module                   |
|-----------|:----------------------|---------------------------------------------------|--------------|------|--------------------------|
| RSS_VER   |: R6100                | version of RSS code                               | RXXXX        |str   | csst_ifs_cube            |
| CUB_VER   |: C6100                | version of CUBE code                              | CXXXX        |str   | csst_ifs_cube            |
| COV_VER   |: C6100                | version of CUBE code                              | CXXXX        |str   | csst_ifs_cube            |
| LSF_VER   |: C6100                | version of CUBE code                              | CXXXX        |str   | csst_ifs_cube            |
| FLUXUNIT  |: '1E-17 erg/s/cm2/A/arcsec2' | unit of flux                               | '1E-17 erg/s/cm2/A/arcsec2'|str   | csst_ifs_cube |
| FLUXSCALE |: 1                    | Intensity unit scaling                            | 1            |I8    | csst_ifs_cube            |
| FLUXZERO  |: 0                    | Intensity zeropoint                               | 0            |I8    | csst_ifs_cube            |
|TELESCOP	|: CSST                 | Telescope used to acquire data		            | CSST         |str   | csst_ifs_cube            |
|INSTRUMENT	|: IFS                  | Identifier for instrument used to acquire data    | IFS          |str   | csst_ifs_cube            |
|OBJID      |: 174053.8-534326'     | ID of Object(in the form of HHMMSS.S+DDMMSS)      | hhmmss.sddmmss|str  | csst_ifs_cube            |
|NEXP       |: 50                   | number of science exposures combined              | 0            |I8    | csst_ifs_cube            |
|EXPTIME    |: 60000                | Total exposure time                               | 0            |f32   | csst_ifs_cube            |
|MJDMIN     |: 2459955.2275463      | Minimum OBS MJD across all exposures              | -9999        |f32   | csst_ifs_cube            |
|MJDMAX     |: 2459955.39282407     | Maximum OBS MJD across all exposures              | -9999        |f32   | csst_ifs_cube            |
|MJDMED     |: 2459955.34074074     | Median OBS MJD across all exposures               | -9999        |f32   | csst_ifs_cube            |
|WCSCAL_VER |: A6101                | Version of WCS calibration	                    | AXXX         |str   | csst_ifs_cube            |
|WCSCAL_P	|:                      | file for WCS calibration 	                        |  "?"         |str   | csst_ifs_cube            |
|RADECSYS	|: FK5                  | Frame of reference of coordinates                 | FK5          |str   | csst_ifs_cube            |
|EQUINOX    |: 2000.0               |                                           	　  | 2000.0       |str   | csst_ifs_cube            |
|OBJRA	    |: 265.22407917         |Object R.A. (J2000 deg.)                           | -9999        |f32   | csst_ifs_cube            |
|OBJDEC     |: -53.72406389         |Object Dec. (J2000 deg.)                           | -9999        |f32   | csst_ifs_cube            |
|CENRA	    |: 265.2240087483441    |Plate center R.A. (J2000 deg.)	R4	                | -9999        |f32   | csst_ifs_cube            |
|CENDEC	    |: -53.72410555664603   |Plate center Dec. (J2000 deg.)	R4	                | -9999        |f32   | csst_ifs_cube            |
|CTYPE3	    |: 'LIN'                | The type of wavelength array                      | 'LIN'        |str   | csst_ifs_cube            |
|CRPIX3	    |:1.0                   | Starting pixel	                                | -9999        |f32   | csst_ifs_cube            |
|CRVAL3	    |: 3500.0               | The central wavelength wv0 of first pixel 	    | -9999        |f32   | csst_ifs_cube            |
|CD3_3	    |: 1.75                 | wavelength dispersion per pixel	                | -9999        |f32   | csst_ifs_cube            |
|CUNIT3	    |: 'Angstrom'           | unit of wavelength                                | 'Angstrom'   |str   | csst_ifs_cube            |
|CRPIX1	    |: 49.0                 | Reference pixel	                                | -9999        |f32   | csst_ifs_cube            |
|CRPIX2	    |: 52.0                 | Reference pixel	                                | -9999        |f32   | csst_ifs_cube            |
|CRVAL1	    |: 265.22407917         | RA of reference point	                            | -9999        |f32   | csst_ifs_cube            |
|CRVAL2     |: -53.72406389	        | Dec of reference point	                        | -9999        |f32   | csst_ifs_cube            |
|CD1_1	    |: -2.7777777777777E-05 | Coordinate transformation matrix element	        | -9999        |f32   | csst_ifs_cube            |
|CD1_2	    |: 0.0                  | Coordinate transformation matrix element	        | -9999        |f32   | csst_ifs_cube            |
|CD2_1	    |: 0.0                  | Coordinate transformation matrix element	        | -9999        |f32   | csst_ifs_cube            |
|CD2_2	    |: 2.7777777777778E-05  | Coordinate transformation matrix element	        | -9999        |f32   | csst_ifs_cube            |
|CTYPE1     |: 'RA---TAN'	        | Declination, gnomonic projection	                | 'RA---TAN'   |str   | csst_ifs_cube            |
|CTYPE2     |: 'DEC--TAN'	        | Declination, gnomonic projection	                | 'DEC--TAN'   |str   | csst_ifs_cube            |
|CUNIT1	    |: 'deg'                | Units of coordinate increment and value	        | 'deg'        |str   | csst_ifs_cube            |
|CUNIT2	    |: 'deg'                | Units of coordinate increment and value	        | 'deg'        |str   | csst_ifs_cube            |
|EBVGAL     |: 0	                | Galactic reddening E(B-V)	                        | -9999        |f32   | csst_ifs_cube            |
|CHECKSUM   |: 0                    |checksum                                           | 1            |I8    | csst_ifs_cube            |