With a new software release of the GTC Control System that was implemented as of October 2011,
a number of changes to the FITS headers took place. The following table provides a listing and
description of these modifications.
| Keyword | Example entry | Comment |
| APPLYPRE | true | Reordering applied or not |
| ARCHID | 141289 | unique image number |
| CD1_1 | 6.15197399589511E-05 | for astrometric calibration, Not yet filled |
| CD1_2 | -3.47495197988005E-05 | for astrometric calibration, Not yet filled |
| CD2_1 | -3.47495197988005E-05 | for astrometric calibration, Not yet filled |
| CD2_2 | -6.15197399589511E-05 | for astrometric calibration, Not yet filled |
| CRPIX1 | 462.5 | for astrometric calibration, Not yet filled |
| CRPIX2 | 995. | for astrometric calibration, Not yet filled |
| CRVAL1 | 328.053157852889 | for astrometric calibration, Not yet filled |
| CRVAL2 | 2.41799503858528 | for astrometric calibration, Not yet filled |
| CTYPE1 | RA---TAN | for astrometric calibration, Not yet filled |
| CTYPE2 | RA---TAN | for astrometric calibration, Not yet filled |
| DATE-OBS | 2011-09-27T21:39:31:281 | Time when starts the first exposure |
| ELAPSHUT | 1.466 | Total elapsed time |
| EQUINOX | 2000. | for astrometric calibration |
| EXTNAME | GTC FRAME | Extension written by GTC pipeline |
| FILSTAT | COMMITED | ? |
| GAIN | 0.95 | Gain (e-/adu) |
| GAINTYPE | GAIN_x9_5 | Gain mode requested by user |
| GTCPRGID | GTC3-11BIACMEX | Program Id |
| HEIGHT | 2348 | Telescope height above sea level (m) |
| INSMODE | Instrument Mode | |
| LATITUDE | 28762000 | Telescope latitude (degrees), +28:45:43.2 |
| LONGITUD | 17877639 | Telescope longitude (degrees), +17:52:39.5 |
| LOOPSHIF | 0 | Charge Shuffling: Num times -numshifts- is repeated |
| NAXIS1 | 1024 | length of data axis 1 |
| NAXIS2 | 2051 | length of data axis 2 |
| OBSCLASS | Science | Observation Class |
| OBSERVAT | ORM | Observatory (IRAF style) |
| ORIGFILE | Oct16_042857.fits | Original file name |
| RADESYS | FK5 | for astrometric calibration, Not yet filled |
| RSPEED | 200 | Readout Speed Khz; now is a number (was SPEED_200) |
| SIMTYPE | 0 | Unknown |
| SIMVAL | 0 | Unknown |
| TELESCOP | GTC | Telescope |
| TFBANDW | 12.4312877655029 | filter bandwidth after offset correction, in Angstrom |
| TFID | TF_RED | Tunable Filter identifier |
| TFTEMP | TF temperature | |
| TFWAVEL | 9127.95339211425 | filter wavelength after offset correction |