The detection of the transiting extrasolar planet CoRoT-9b has just been reported (Deeg et al. 2010). With a semi-major axis of 0.41 astronomical unit on a quasi-circular orbit, this is the first transiting planet far enough from its parent star to have an extended Hill sphere (3.5 million kilometers in radius), as needed to form and sustain rings and satellites. Here we propose to observe a full transit of CoRoT-9b in front of its parent star to significantly improve the accuracy on the transit light curve as provided by the CoRoT satellite and to probe the nearby environment of the planet. Up to 2014, there will be only two opportunities to observe a transit of CoRoT-9b with Spitzer: the first one in June 2010, and the second will not happen before July 2011. Those rare events should not be missed. Here we propose Director Discretionary Time observations to observe the transit of June 2010, 17th. The primary aim of these observations will be the search for rings and satellites. The Spitzer/IRAC light curve will also allow the search for Transit Timing Variations (TTV) and Transit Duration Variations (TDV) potentially due to additional bodies in this planetary system, as well as a significant refinement of the system parameters, together with the photometric and spectroscopic ground-based campaign that we will simultaneously conduct in June 2010.