Creating Gateway Alliances Using WS-PGRADE/gUSE - Science Gateways for Distributed Computing Infrastructures - page 254

The CMB maps are built starting from the CMB power spectrum with synfast
code being part of the HEALPix package.

￿

CMB is combined with foregrounds having their own frequency-dependent
intensities, and the

￿

final sky is convolved with the beam pattern for each of the
detectors considered in the simulation.

The map is contaminated by introducing instrumental noise, which is computed
and added to the

￿

“ observed ” sky signal, and therefore the TOD are built.

In order to speed up the calculations, we can assume a perfect overlap between
samples in two consecutive scan circles of the spacecraft when it remains in the
same pointing position. In this way the sky signal is always the same for all the 60
scan circles corresponding to the same pointing position, and we can therefore
simulate it only once.
The workflow we design and deploy in the STARnet portal is presented in
Fig. 18.4 . It implements the LevelS pipeline and produces a TOD simulation
starting from a set of initial cosmological and instrumental parameters designed by
the user. The TOD data are also processed to produce a map of the sky as observed
by the instruments.

Fig. 18.4 LevelS workflow: LevelS pipeline is designed as a workflow and implemented in the
STARnet portal. The workflow starts with the simulation of the cosmic microwave background on
the basic of a set of cosmological parameters selected by the user, and produces both time-ordered
data and PNG images representing the sky observed at different stages of the pipeline