ESA’s Asteroid Impact Mission (AIM) is both a Technology Mission of Opportunity, and a mission to greatly improve our understanding of asteroid physical properties and their response to a hypervelocity impact event on their surface. The AIM mission is combined with the Double Asteroid Redirection Test (DART). Both missions complement one another in a joint asteroid impact test and observation campaign called Asteroid Impact & Deflection Assessment (AIDA). The Thermal InfraRed Imager (TIRI) is Thermal IR imager of the AIM mission. It has been conceived to pursue both scientific and technology development goals. Indeed, on one side, it will be used to determine physical parameters of the Didymos surface, such as temperature, thermal inertia, chemical composition, as well as the shape of the surface rocks. On the other side, TIRI is supposed to aid the spacecraft navigation, by means of the analysis of TIR imagery. The successful demonstration of TIR based navigation would be of enormous value, as it would enable active navigation irrespective of the specific illumination conditions of the target object. A European consortium, led by cosine measurement systems B.V. and including GMV-Romania and GMV-Portugal, has been in charge of the execution of the TAIM (Thermal Asteroid Impact Mission) project, whose output is the preliminary design of TIRI (Thermal InfraRed Imager).