This is not the ESA (European Space Agency) logo. It is the three letters "e", "s" and "a" in Arial font. It is intended to be used in place of a flag in lists of space missions etc. Due to copyright concerns, the real ESA logo seems to be repeatedly removed when used in these situations.
<a href="https://en.wikipedia.org/wiki/User:SpaceListsTemplate" class="extiw" title="wikipedia:User:SpaceListsTemplate">SpaceListsTemplate</a> at <a href="https://en.wikipedia.org/wiki/" class="extiw" title="wikipedia:">English Wikipedia</a>
Transferred from <span class="plainlinks"><a class="external text" href="https://en.wikipedia.org">en.wikipedia</a></span> to Commons.