Nitric oxide, which reacts catalytically to destroy ozone, can be produced in great abundance in the middle atmosphere during energetic particle precipitation triggered by solar storms. During the Antarctic winter, the strong polar vortex can rapidly transport nitric oxide downward, and this process has been identified as a mechanism that can link ozone recovery in the upper stratosphere with solar activity. As part of the Sun Earth Connection programme at the British Antarctic Survey (BAS), a new, state-of-the-art microwave radiometer is being developed in collaboration with the Max-Planck Institute (MPI) and the Norwegian Polar Institute (NPI) to simultaneously measure profiles of ozone and nitric oxide between 30 and 80 km deep within the Antarctic polar vortex. Operating in the 250 GHz spectral region, the semi-autonomous instrument will be coupled to moderate- and high-resolution chirp spectrometers to provide simultaneous spectra of the nitric oxide and ozone. In addition, a second local oscillator will be used to periodically examine carbon monoxide at 230.538 GHz to infer the vertical descent rate within the Antarctic vortex. Here, we present the science rationale for the observation programme as well as the instrument specifications, design and performance.