Free Access

Table 2

OIFITS main header keywords.

Keyword Type Req? Description Example

SIMPLE T yes Standard FITS format
BITPIX %d yes Number of bits per data pixel
NAXIS %d yes Number of data axes1 0
EXTEND T yes Extensions may be present
ORIGIN %s yes Institution responsible for file creation ESO
DATE %s yes Date the HDU was written 2015-01-13T16:12:56.57
DATE-OBS %s yes Start date of observation 2014-10-15T18:33:26.06
CONTENT %s yes Must contain only the string “OIFITS2”2 OIFITS2
AUTHOR %s no As defined in FITS norm
DATASUM %s no HDU datasum6
CHECKSUM %s no HDU checksum6

Keywords set to “MULTI” for heterogenous content of the OIFITS (see text)

TELESCOP %s yes A generic identification of the ARRAY3 CHARA
INSTRUME %s yes A generic identification of the instrument3 VEGA
OBSERVER %s yes Who acquired the data3 S.M.Eisenstein
OBJECT %s yes Object Identifier3 HD123456
INSMODE %s yes Instrument mode3 Low_JHK
REFERENC %s no Bibliographic reference3 2001PASP..112.1133P
PROG_ID %s no Program ID3 094.A-1234
PROCSOFT %s no Versioned Data Reduction Software3,4 pndrs 2.6
OBSTECH %s no Technique of observation3,5 SCAN, ABCD-PH, PH_REF...

Suggested supplementary keywords for “atomic” observations (see text)

RA %f no Target Right Ascension at mean EQUINOX (deg)
DEC %f no Target Declination at mean EQUINOX (deg)
EQUINOX %.1f no Standard FK5 (years) 2000.0
RADECSYS %s no Coordinate reference frame FK5
SPECSYS %s no Reference frame for spectral coord. TOPOCENTR
TEXPTIME %f no Maximum elapsed time for data point (s)
MJD-OBS %.8f no Start of observations (MJD)
MJD-END %.8f no End of observations (MJD)
BASE_MIN %f no Minimum projected baseline length (m) 16.01
BASE_MAX %f no Maximum projected baseline length (m) 100.12
WAVELMIN %f no Minimum wavelength (nm) 1200
WAVELMAX %f no Maximum wavelength (nm) 1600
NUM_CHAN %d no Total number of spectral channels 32
SPEC_RES %f no Reference spectral resolution (λ/ Δλ) 30
VIS2ERR %f no Representative V2 error (%) 5
VISPHERR %f no Representative Diff. Vis. Phase error (deg) 1
T3PHIERR %f no Representative Closure Phase error (deg) 1

Notes. Keywords in bold face are standard FITS keywords. The type column gives the format, where %s is string, %d is an integer number and %.xf is a real value with x decimal digits. The third column indicates whether the keyword is required or not.


Should be “0” unless a FITS image or cube is present after the main header.


Mandatory. Identifies the FITS file as an OIFITS version 2 file.


These are bookkeeping keywords. Some of them can be inferred from the headers of the tables contained in the OIFITS file. If the file is of “atomic” type (see text), all these keywords must be filled up by the relevant value. If the OIFITS acts as a container for heterogenous data and thus more than one value of the keyword would be needed, use “MULTI”.


Data Reduction Software (DRS) with version identification.


Identifiers for OBSTECH are not standardized here.


See Sect. 4.

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.