  Context: NASA recently announced an extended mission for TESS. As a result it
is expected that the southern ecliptic hemisphere will be re-observed
approximately two years after the initial survey. Aims: We aim to explore how
TESS re-observing the southern ecliptic hemisphere will impact the number and
distribution of mono-transits discovered during the first year of observations.
This simulation will be able to be scaled to any future TESS re-observations.
Methods: We carry out an updated simulation of TESS detections in the southern
ecliptic hemisphere. This simulation includes realistic Sector window-functions
based on the first 11 sectors of SPOC 2 min SAP lightcurves. We then extend
this simulation to cover the expected Year 4 of the mission when TESS will
re-observed the southern ecliptic fields. For recovered monotransits we also
look at the possibility of predicting the period based on the coverage in the
TESS data. Results: We find an updated prediction of 339 monotransits from the
TESS Year 1 southern ecliptic hemisphere, and that approximately 80% of these
systems (266/339) will transit again in the Year 4 observations. The Year 4
observations will also contribute new monotransits not seen in Year 1,
resulting in a total of 149 monotransits from the combined Year 1 and Year 4
data sets. We find that 75% (189/266) of recovered Year 1 monotransits will
only transit once in the Year 4 data set. For these systems we will be able to
constrain possible periods, but period aliasing due to the large time gap
between Year 1 and Year 4 observations means that the true period will remain
unknown with further spectroscopic or photometric follow-up.

Earth and Planetary Astrophysics