Strange satelites in the french sky

It was a clear night of july in The Motte d'Aveillans, a little village near Grenoble in France. I was staring at the sky for satelites with my Girlfriend and her brother, lying in the grass. It is common to see non-geostationary satelites in the sky at night when the sun reflects on their panels and they move rather quickly in the sky as little dots. We saw some 10 satelites that night but one of them is to remain in our memories. We don't know how or why nor whether it was an optical illusion, but all of a sudden, looking at one of these satelites, it changed direction from a 90 degrees angle and drew a square and several other polygones before changing direction for a last time and moving towards the horizon to dissapear in the light of the nearby city.
 We never told anyone about this strange satelite until a few days ago when I heard a similar story from a friend of mine living in Vendee (France) and who is a professional astronomer. I thought he would have an answer to that phenomenon, since he is the kind of guy who can point randomly to a star and name it and since he knows a lot about astrophysics and space exploration, but he couldn't say what it was exactly. We are quiet sure it wasn't a plane since it was moving to quickly into the sky and was too high to be one. The only possible explanation we have found is that some satelites we never heard of can very quickly modify their trajectory through the sky. If this is not the case, then it is still an Unidentified Flying Object to us and, without being a strong believer of extra terrestrial phenomenon, I have some doubt whether this object in the sky was human made.
Date is approximate.  PD