Guidelines for spectroscopic data products
The table below contains the minimum set of information ('data items') requested for 1D spectrum headers (example header). Providing these metadata in the FITS header and mapping it to the appropriate data items will enable users to fully characterise the data and to query for this information. For each data item the table includes a description and a FITS header keyword suggestion. Keywords may assume different names as long as there is a one-to-one correspondence. The colour of each line indicates whether that item is:
| required | , | highly recommended | or | optional |
| Data item | Description | FITS keyword | |
|---|---|---|---|
| Curation | |||
| Facility | The observatory or facility where the data was obtained | ORIGIN | |
| Telescope | Telescope name. Please use the TELESCOPE key values from the raw frames (if present) | TELESCOP | |
| Creator | Name of PI/Co-I | PI-COI | |
| Collection | Proposal ID (identifier of the original proposal) or Name of Data Collection | PROG_ID | |
| Photometric calibration | (uncalibrated, relative, absolute) | FLUXCAL | |
| Astrometric calibration | (uncalibrated, relative, absolute) | SPATCAL | |
| Software reference | Description of software/pipeline used for processing (e.g. MVM, IRAF, etc.), with version | PROCSOFT | |
| Bibliographic reference | Please use a format like 2006A&A...454..423V | BIBREF | |
| Signal to noise ratio | Signal to noise ratio | SN | |
| Instrument | |||
| Instrument name | Please use the instrument values from the raw frames or as specified in the proposal | INSTRUME | |
| Filter name | Please use the filter values from the raw frames or as specified in the proposal | FILTER | |
| Dispersive element | Please use the relevant values from the raw frames or as specified in the proposal | GRISM | |
| Instrument mode | Instrument mode (partly identifying optical path) as specified in the proposal(1) | INS_MODE | |
| Resolving power | Instrument resolving power (spectral resolution, R) e.g. 115000 | INST_RES | |
| Observation | |||
| Technique of observation | (IFU, Echelle, Long Slit, MOS, ...)(1) | OBSTECH | |
| Total exposure time | Total exposure time [s] | TEXPTIME | |
| Unit of pixel values | (erg/cm2/s/A, ...) | BUNIT | |
| Minimum flux | Min. physical value across image in BUNIT | DATAMIN | |
| Maximum flux | Max. physical value across image in BUNIT | DATAMAX | |
| Effective gain | Detector sensitivity in no. of electrons/count | GAIN | |
| Number of frames | Number of combined frames | NCOMBINE | |
| Comments | Further explanations about this data product | COMMENT | |
| Target | |||
| Target name | Target name | OBJECT | |
| RA of the target | Right Ascension of target (sky position from where spectrum was extracted) | RA_TARG | |
| Dec of the target | Declination of target (sky position from where spectrum was extracted) | DEC_TARG | |
| Target position error | Positional uncertainty of target coordinates ["] | ERR_TARG | |
| Equinox | Equinox of reference coordinate system | EQUINOX | |
| Reference frame | Frame of reference for equatorial coordinate system (FK5, ICRS) | RADECSYS | |
| Reference catalogue | Reference source for target position (GSC2, USNO, ...) | ASTRCAT | |
| Spatial accuracy | RMS Error in reference source ["] | ASTRERR | |
| WCS | |||
| NAXIS1 | Number of bins along axis 1 | NAXIS1 | |
| CD1_1 | Linear transformation matrix element 1,1 | CDELT1/CD1_1 | |
| CRPIX1 | Pixel coordinate of reference point | CRPIX1 | |
| CRVAL1 | Coordinate value of reference point | CRVAL1 | |
| CTYPE1 | Main axis type(2) | CTYPE1 | |
| CUNIT1 | Unit of main axis | CUNIT1 | |
| Spectral reference system | Frame of reference for spectral coordinates (TOPOCENT, HELIOCEN, BARYCENT, ...)(2) | SPECSYS | |
| Characterisation | |||
| Start date time | Observation start date time of first exposure [MJD] | MJDSTART | |
| Stop date time | Observation end date time of last exposure [MJD] | MJDEND | |
| RA of slit centre | RA of slit centre | RA_SLIT | |
| Dec of slit centre | Dec of slit centre | DEC_SLIT | |
| Slit centre position error | Error in slit centre position ["] | ERR_SLIT | |
| Slit width | Slit width ["] | SLIT_WID | |
| Slit length | Slit length ["] | SLIT_LEN | |
| Slit orientation | Slit orientation [deg] (N=0, E=90) | SLIT_ROT | |
| Seeing | Atmospheric seeing condition ["] | SEEING | |
| Seeing error | Atmospheric seeing error ["] | SEEINERR | |
| Average spectral resolution | Average spectral resolution (R) e.g. 40000 | SPEC_RES | |
(1) An explicit list may appear here at a later time
(2) See 'Representations of spectral coordinates in FITS', Greisen, E.W. et al. 2006A&A...446..747G