## SPIRE Spectrometer HPDP: re-gridded hyper-spectral cubes
##
## Mapping observations re-gridded to remove high resolution spectra 
##
## Rosalind Hopwood
## ESAC SPIRE Instrument and Calibration Scientist
##
## 12th December 2016, v1
##

# Description of HPDP

There are 22 SPIRE Spectrometer mapping observations that suffer from one or
more individual spectra that have higher than expected spectral resolution.
In the Herschel Science Archive, the final standard product generation (SPG)
produced hyper-spectral cubes (cubes) reports the highest resolution of all
the spectra included when projecting the cube. This value is stored in the 
top-level metadata, with the FITS keyword ACTRES. The best spectral resolution
expected for high-resolution SPIRE Spectrometer data is 1.18448225 GHz, which
is representative for nearly all the spatial-pixels of any spectral cube where
one or more of the constituent spectra have degraded resolution. This is due
to the large number of spectra projected into any given cube and because the
degraded spectra are always towards the outer ring of either of the 
Spectrometer bolometer detector arrays. For both of these reasons the 22
mapping observations in question can be re-gridded without change to the
majority of their spatial pixels, although one or more pixels (of low quality)
can be lost at the edge of the map. 

As there is minimal change or loss of data when re-projecting mapping
observations with the degraded resolution spectra omitted, and as the value
of ACTRES in the associated standard pipeline products is not representative
of the associated cubes as a whole, the mapping observations that suffer from
one or more degraded spectra have been re-gridded to be provided as HPDPs. The
new cubes, therefore, all report an actual unpadded spectral resolution of
1.18448225 GHz in their metadata.

The spectra used to create the new cubes were reduced with HIPE version 14.1,
using spire_cal_14_3.

The cubes are extended-source calibrated in standard Spectrometer surface
brightness units of W/m2/Hz/sr and presented in the same format as their HSA
counterpart. There are four cubes per observation affected: Naive projected,
convolution projected (CP), and apodized versions of these. All 22
observations were taken in high-resolution mode.

Each product is provided as a gzipped FITS file, which are named with the 
convention:

“OBSID_correctedActualRes_PROJECTIONCube_SSW.fits.gz”
“OBSID_correctedActualRes_PROJECTIONCube_apod_SSW.fits.gz”
where
OBSID is the observation identification number
PROJECTION is either “naive” or “cp”

The files size ranges from 1.1 MB to 28.7 MB.

# Purpose
These data have been made available to avoid confusion over their science
readiness, and spectral resolution, and the need to re-project the cubes before
they can be analysed.

# Caveats
There are two Spectrometer bolometer detector arrays (the long wavelength, SLW,
and short wavelength, SSW, arrays). Not all of the observations reprocessed
suffered degraded resolution spectra for both arrays. Where only one array was
affected, only one re-gridded HPDP cube is offered. A list of the reprocessed
observations and which array was affected are below, where True indicates a
HPDP exists.

#OBSID,SLW,SSW
1342192173,False,True
1342192174,False,True
1342192175,False,True
1342204898,False,True
1342204920,True,True
1342214827,True,True
1342214841,True,True
1342214846,False,True
1342228703,True,True
1342243631,False,True
1342243632,False,True
1342243633,False,True
1342243634,False,True
1342243635,False,True
1342243636,False,True
1342243637,False,True
1342245851,True,True
1342262908,False,True
1342262909,False,True
1342262913,False,True
1342262916,False,True
1342265845,False,True