7.5.3.2: Specifications for DEIMOS Overall Grouping table extension

The overall grouping table serves as the master table for all elements of a single CCD readout.

7.5.3.2.1: The Grouping FITS Header

Here follows a draft schematic for the contents of the FITS header:

XTENSION= 'TABLE   '           / ASCII table extension
BITPIX  =                    8 / number of bits per data pixel
NAXIS   =                    2 / always 2 for a FITS table
NAXIS1  =                  102 / number of chars needed to describe members
NAXIS2  =                    4 / number of member HDUs in the group
PCOUNT  =                    0 / required FITS extension keyword
GCOUNT  =                    1 / required FITS extension keyword
TFIELDS =                    5 / Number of columns in the table

EXTNAME = 'GROUPING'           / This table describes a group
EXTVER  =                    1 / Unique index of this grouping table in file
GRPNAME = 'DEIMOS_Data'        / Is this really a good value to use here?
DATE    = 'dd/mm/yy'           / Date of construction of grouping table
CTIME   = 'WkD CcYy Mon Dt Hr:Mn:Ss TZn' / Time of construction of table

TBCOL1  =                    1 / First character in column 1
TFORM1  = 'A8'                 / Fortran 77 format of column 1
TTYPE1  = 'MEMBER_XTENSION'    / To find member HDUs by reference

TBCOL2  =                    9 / First character in column 2
TFORM2  = 'A24'                / Fortran 77 format of column 2
TTYPE2  = 'MEMBER_NAME'        / To find member HDUs by reference

TBCOL3  =                   33 / First character in column 3
TFORM3  = 'I3'                 / Fortran 77 format of column 3
TTYPE3  = 'MEMBER_VERSION'     / To find member HDUs by reference

TBCOL4  =                   36 / First character in column 4
TFORM4  = 'A3'                 / Fortran 77 format of column 4
TTYPE4  = 'MEMBER_URI_TYPE'    / To find member HDUs in other FITS files

TBCOL5  =                   39 / First character in column 5
TFORM5  = 'A64'                / Fortran 77 format of column 5
TTYPE5  = 'MEMBER_LOCATION'    / To find member HDUs in other FITS files

END

The header is padded with ASCII blanks such that it consists of a positive integer multiple of 2880 bytes (36 card images of 80 characters).

The value of the keyword GRPNAME deserves further scrutiny. Other kinds of FITS groups for DEIMOS data may become desirable; e.g., groups which relate calibration exposures to sky exposures. It may also be desirable to insert other kinds of documentary data using additional standard and/or DEIMOS-specific keywords. The DATE keyword presents an obvious problem as we enter a new century, but the FITS community has not yet developed an alternative scheme.

7.5.3.2.2: The Grouping FITS data table

In an actual FITS data table there need be no character denoting the boundaries between the various columns. The following schematic representation of a DEIMOS grouping table inserts the character `|' for readability. This follows the table layout given above:

TABLE  |DEIMOS_Image_Group      |  1|   |
TABLE  |DEIMOS_Input_Catalog    |  1|   |
TABLE  |DEIMOS_SlitMask         |  1|   |
TABLE  |DEIMOS_Hardware         |  1|   |

The table is padded with ASCII blanks such that it consists of a positive integer multiple of 2880 bytes.

Note that all these tables reside in the same file as the grouping table, so the URI and location fields are blank.

The EXTNAMEs for the DEIMOS tables deserve further scrutiny. See the discussion in the documents that define the tables.

Back to the DEIMOS home page.

Steve Allen <sla@ucolick.org>

$Date: 1996/03/13 21:29:36 $