4.4. Meta data and FITS keywords to help identify spectroscopy slices

As mentioned in Section 2.3, PACS spectroscopy observations are sliced by the pipeline on wavelength and position, so the cubes and tables are provided "sliced"; therefore there may be several FITS file "slices" provided in the lowest-level directory for each type of product provided. If you are interacting with an observation on disc, rather than within HIPE, it is necessary to inspect the FITS keywords of your particular cube or table "slice" to identify what is unique about that cube or table. In the table below we list the keywords to focus on to identify what part of an observation each sliced product comes from: the wavelength range, and raster position for mapping observations. Note that pointed observations have a single pointing and so only one position slice. Note also that mosaic cubes (provided for mapping observations) are the combination of a raster, and hence will not have the "rasterId" Meta datum. More keywords indicating the observing mode for PACS spectroscopy observations can be found in Table 2.4 and Table 2.5. If you cannot find a Meta datum/keyword in your FITS file, it means that that particular Meta datum/keyword is not relevant for that product.

Table 4.2. The Meta data and FITS keywords in the Level 2 and higher cubes and tables to identify what is unique about that particular "slice number". Note that mosaic cubes are the combination of a raster, and hence will not have raster-related keywords.

Mean wavelength Slice number Raster line,column sequence
Meta datum meanWavelength / lineDescription sliceNumber rasterId
FITS keyword MEANWAVE / LINEINFO SLICENUM RASID