As a part of the ESA deep space mission to mercury -BepiColombo -investigations of mercury´s surface layer using a push-broom thermal infrared imaging spectrometer (MERTIS) with a high spectral resolution is planned. One of the scientific goals is the measurement of Christiansen Features which are emissivity maxima resulting from rapid changes in the real part of the mineral´s refractive index. Their positions within the spectral range of 7-14µm deliver information about mineralogical compositions. For these measurement MERTIS needs to have a high spectral resolution of 90nm. The planet will be mapped with a resolution of 500m and a S/N ratio of at least 100. For the measurement of the surface radiation a micro-bolometer detector array will be used. A detectivity of 1.0E9 is required. High sensitive TIR systems commonly use cooled detectors with a large mass budget and high electrical power consumption. One of the challenges of MERTIS is the use of an uncooled micro-bolometer detector. The development of MERTIS is currently in an early phase but a breadboard concept will be presented. Special attention is payed to the first of two phases of the breadboard concept:-The Radiometric Breadboard (RAB) has been configured for the development of the opto-electronical components and for the investigation of radiometric calibration methods and algorithms. The design of the RAB is already a spectrometer configuration but it cannot reach the performance the technical and scientific requirements demand.-The Spectro-Radiometric Breadboard (SRB) will be implemented for investigations of the performances of the optics and detector of MERTIS. Relevant components have to be developed and validated particularly in the spectral domain. The SRB will be the prototype of MERTIS.