Optimal core baseline design and observing strategy for probing the
  astrophysics of reionization with the SKA
  With the first phase of the Square Kilometre Array (SKA1) entering into its
final pre-construction phase, we investigate how best to maximise its
scientific return. Specifically, we focus on the statistical measurement of the
21 cm power spectrum (PS) from the epoch of reionization (EoR) using the low
frequency array, SKA1-low. To facilitate this investigation we use the recently
developed MCMC based EoR analysis tool 21CMMC (Greig & Mesinger). In light of
the recent 50 per cent cost reduction, we consider several different SKA core
baseline designs, changing: (i) the number of antenna stations; (ii) the number
of dipoles per station; and also (iii) the distribution of baseline lengths. We
find that a design with a reduced number of dipoles per core station (increased
field of view and total number of core stations), together with shortened
baselines, maximises the recovered EoR signal. With this optimal baseline
design, we investigate three observing strategies, analysing the trade-off
between lowering the instrumental thermal noise against increasing the field of
view. SKA1-low intends to perform a three tiered observing approach, including
a deep 100 deg$^{2}$ at 1000 h, a medium-deep 1000 deg$^{2}$ at 100 h and a
shallow 10,000 deg$^{2}$ at 10 h survey. We find that the three observing
strategies result in comparable ($\lesssim$ per cent) constraints on our EoR
astrophysical parameters. This is contrary to naive predictions based purely on
the total signal-to-noise, thus highlighting the need to use EoR parameter
constraints as a figure of merit, in order to maximise scientific returns with
next generation interferometers.
