  There is a lack of exoplanets with sizes similar to Neptune orbiting their
host stars with periods $\lesssim 3$ days -- hence the name
``sub-Jovian/Neptune desert''. Recently, several exoplanets have been confirmed
to reside in the desert transforming it into a ``savanna'' with several
``giraffe'' planets (such as LTT 9779 b and TOI-674 b). The most prominent
scenarios put forward for the explanation of the formation of the desert are
related to the stellar irradiation destroying the primary atmosphere of certain
specific exoplanets. We aim to present three targets (LTT 9779 b, TOI-674 b and
WASP-156 b) which, when observed at wide wavelength ranges in infrared (IR),
could prove the presence of these processes, and therefore improve the theories
of planetary formation/evolution. We simulate and analyse realistic light
curves of the selected exoplanets with PLATO/NCAM and the three narrow-band
filters of Ariel (VISPhot, FGS1 and FGS2) based on TESS observations of these
targets. We improved the precision of the transit parameters of the three
considered planets from the TESS data. We find that the combination of the
three narrow-band filters of Ariel can yield inner precision of $\lesssim
1.1\%$ for the planetary radii. Data from the three telescopes together will
span decades, allowing the monitoring of changes in the planetary atmosphere
through radius measurements. The three selected ``giraffe'' planets can be
golden targets for Ariel, whereby the loss of planetary mass due to stellar
irradiation could be studied with high precision, multi-wavelength
(spectro-)photometry.
