  We present a time-resolved experimental study of the temperature effect on
the coherence of traveling polariton condensates. The simultaneous detection of
their emission both in real- and reciprocal-space allows us to fully monitor
the condensates' dynamics. We obtain fringes in reciprocal-space as a result of
the interference between polariton wavepackets (WPs) traveling with the same
speed. The periodicity of these fringes is inversely proportional to the
spatial distance between the interfering WPs. In a similar fashion, we obtain
interference fringes in real-space when WPs traveling in opposite directions
meet. The visibility of both real- and reciprocal-space interference fringes
rapidly decreases with increasing temperature and vanishes. A theoretical
description of the phase transition, considering the coexistence of condensed
and non-condensed particles, for an out of equilibrium condensate such as ours
is still missing. Yet a comparison with theories developed for atomic
condensates allows us to infer a critical temperature for the BEC-like
transition when the visibility goes to zero.
