After the remarkable achievement by the COBE FIRAS team, revealing that the CMB spectrum was extremely close to a perfect blackbody with T=2.725±0.001 K, the primary concern is if this spectrum presents distortions, as predicted by the standard cosmological model. Measurement of these distortions provides a powerful tool for investigating the termal history of the Universe. 

The Tenerife Microwave Spectrometer (TMS) is a ground-based instrument planned to map and measure the spectrum of the Cosmic Microwave Background from frequencies 10 to 20 GHz. The proposed system shall measure the spectrum of the sky emissions, reaching a sensitivity level of 10-26 W m-2 Hz-1 sr-1 in sub-bands of 1 GHz after integration periods of 1000h. 

This instrument is currently in an early stage of design. In this presentation, I will try to explain the requirements that are to be instigated to achieve the scientific goals and the architecture and design proposed.