CoRoT-9b is the first temperate transiting exoplanet. With a semi-major axis of 0.41 AU 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. CoRoT-9b is thus the most promising planet known to date to probe its nearby environment with an accurate transit light curve. Up to 2014, there will be only two opportunities to observe a transit of CoRoT-9b with Spitzer. We will observe the first one in June 2010 with Spitzer. Here we propose to observe the second one, that will occur in July 2011 during the Cycle 7. This new observation will increase the probability for satellite detection and allow any detection of rings based on the June-2010 transit to be confirmed. The Spitzer/IRAC light curve will also allow the search for Transit Timing Variations 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 July 2011. Observable CoRoT-9b transits being extremely rare, opportunities should not be missed. The program we propose here is the last chance to secure this transit observation before year 2014.