Date: Thu, 28 Mar 2024 09:58:07 -0400 (EDT) Message-ID: <752143322.947.1711634287686@ploutercf.stsci.edu> Subject: Exported From Confluence MIME-Version: 1.0 Content-Type: multipart/related; boundary="----=_Part_946_1704107016.1711634287684" ------=_Part_946_1704107016.1711634287684 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Content-Location: file:///C:/exported.html
The keywords listed below are required, recommended or optional for all = FITS files headers: either the primary (P) or extension (E) HDUs, for all f= iles that contain spectra. Recommended keywords, if absent, will be compute= d and inserted prior to ingest; suggested keywords would be beneficial to a= rchival users if present. Headers must also include the <= a class=3D"external-link" href=3D"https://www.aanda.org/index.php?option=3D= com_article&access=3Dstandard&Itemid=3D129&url=3D/articles/aa/f= ull_html/2010/16/aa15362-10/T30.html" rel=3D"nofollow">basic structural FIT= S keywords and the list of common keywords.
The following table(s) of HLSP metadata, to be included in science produ= cts, are color-coded:
Required | |
Recommended | |
Suggested |
One-dimensional spectra are commonly organized as an image or as a table= (or a table row); two-dimensional spectral images may contain multiple spe= ctra. Spectra may be represented in a FITS IMAGE or a BINTABLE extension. These cases are d= iscussed below.
Keyword | HDU | Notes | |
---|---|---|---|
APERTURE |
P or E | Name of aperture used for exposure | |
DETECTOR |
P or E | ID of detector used for exposure | |
DISPRSR |
P or E | Name of dispersive element used, or <=
/span>'MULTI ' if more than one defined the passband. |
|
DISPR
| P or E | Name(s) of dispersive element(s) used for exposu=
re if more than one was used, with nn (zero-padded) incrementing from 1. Note that this information can alternatively be repr=
esented in a PROVENANCE extension. See Provenance Metadata for details. |
|
XPOSURE |
P or E | Effective exposure duration in seconds, exclusiv= e of dead time |
In this case, spectral pixel values are stored in an image array (primar= y or extension), and header keywords contain the parameters of the dispersi= on relation (i.e., mapping of pixel to wavelength). Multiple arrays would b= e used to contain concomitant quantities, such as variance and data quality= .
Keyword | HDU | Notes | ||||
---|---|---|---|---|---|---|
BUNIT |
P or E | Brightness unit for array values, e.g., er=
g/cm2/s/Angstrom or Jy for flux density |
||||
CDi_j |
P or E | Transformation matrix between pixel axis&n=
bsp;j=
code> and intermediate coordinate axis i . The indicies range from 1 to the value of NAXIS . Note: if the alterna=
tive PCi_j=
notation is used, these keywords must not appear in the header. |
||||
CDELT |
P or E | Increment of the world coordinate at the referen=
ce point for axis i , in units of deg/pixel. Used i=
n conjunction with PC notation for transformation matrix; ignored for CD no=
tation. |
||||
CRPIX |
P or E | Location of the reference point in the image for=
axis j<=
/code> , in array pixel units. |
||||
CRVAL |
P or E | World coordinate value at the reference location=
for axis
|
CTYPE |
P or E | World coordinate type for axis =
i <=
/em>. |
|
CUNITi |
P or E | Physical units of CRVAL for axis i =
strong>. Note: units for celestial coordinate systems m=
ust be degrees. |
||||
PCi_j |
P or E | Alternative to CD notation for transforming pixe=
l axis j to intermediate coordin=
ate axis i . Must be used with CDi_j keywords are present. |
||||
RADESYS |
P or E | Mnemonic for celestial coordinate reference syst=
em (typically 'FK5 '<=
/span> or the preferred 'ICRS '), if applicable. |
||||
WCSAXES |
P or E | Number of axes in WCS description, which may exc= eed the number of pixel array axes |
Only the keywords common to all spectra are required. However, certain c=
ontent is required or suggested for fields (columns) in the table. The foll=
owing specific field names are suggested, and would appear as values of the=
TTYPEn
keywords in the table header. Units s=
hould be specified, where applicable, with the TUNITn
keywords. Note that spectra may be organized such that the values =
for each field run sequentially with row number; alternatively each table r=
ow may contain a spectrum, where non-scalar table cells contain 1-D arrays.=
Field Name | Notes | |
---|---|---|
FLAGS |
Data quality (binary) flags, with zero indicating no anthologies |
|
FLUX =
|
Could also be called "FLUX_DENSITY "=
or something similar, depending upon the quantity stored. Flux(es) for the=
associated wavelength(s), in units of the value of the TUNIT =
keyword for this column. |
|
VARIANCE |
Variance in the flux(es) at the associated wavel= ength(s) | |
WAVELENGTH<=
/code> |
Wavelength(s) for the associated flux(es), in un=
its of the TUNIT keyword for this column. |