Hydrocarbon conversion and synthesis gas production are two components of the power production process that require significant development and exploration in the advanced energy arena. To remain within our current fueling infrastructure, it is imperative that an efficient and reliable mechanism to facilitate these components of the power production process is developed for automotive applications. A honeycomb monolith rhodium based catalyst has been identified as a potential fuel reformer element for use in automotive hydrocarbon fuel conversion. Using the novel and minimally invasive SpaciMS (Spatially resolved capillary inlet Mass Spectroscopy), developed at Oak Ridge National Laboratories, and an internal temperature acquisition system, the impact of fuel inlet space velocity on the operating rhodium based catalytic fuel reformer of interest was parametrically studied. In situ temperature and species profiles of the catalyst during steady state operation were produced. The data acquired through these experiments was then used to demonstrate analytic capability by conducting thermodynamic analyses on the operating fuel reformer. Experimental and analytical results can be used in development of design considerations for fuel conversion systems.