  The Cassini mission offered us the opportunity to monitor the seasonal
evolution of Titan's atmosphere from 2004 to 2017, i.e. half a Titan year. The
lower part of the stratosphere (pressures greater than 10 mbar) is a region of
particular interest as there are few available temperature measurements, and
because its thermal response to the seasonal and meridional insolation
variations undergone by Titan remains poorly known. In this study, we measure
temperatures in Titan's lower stratosphere between 6 mbar and 25 mbar using
Cassini/CIRS spectra covering the whole duration of the mission (from 2004 to
2017) and the whole latitude range. We can thus characterize the meridional
distribution of temperatures in Titan's lower stratosphere, and how it evolves
from northern winter (2004) to summer solstice (2017). Our measurements show
that Titan's lower stratosphere undergoes significant seasonal changes,
especially at the South pole, where temperature decreases by 19 K at 15 mbar in
4 years.
