Microwave radiometer

The microwave radiometer enables us to gain a better understanding of the chemistry and physics of the polar middle atmosphere, 35–90km above the ground, and how it affects climate.

For example, huge amounts of energy and matter released from the Sun during solar storms can cause energetic electrons and protons to enter our atmosphere. As well as producing beautiful displays of aurora, these energetic particles interact with atmospheric gases to produce reactive chemicals such as nitric oxide (NO) that in turn affects ozone in the stratosphere and mesosphere.

Electrons from the Earth’s radiation belts are more likely to enter the atmosphere above Halley, making it an excellent location to study changes in NO, ozone and other trace gases. The radiometer allows us to measure these chemicals remotely from the ground and continuously, around the clock, in all but the very worst weather conditions.

The radiometer has been operating at Halley since early 2013, having previously been deployed at the Norwegian Troll station, Antarctica and in Andøya, northern Norway. The radiometer is a complex and unique instrument, custom-built for BAS using state-of-the-art components from around the world. Expert engineers, both on-site at Halley and in Cambridge, aim to keep the system running continuously and at optimum performance.

The radiometer has an incredibly sensitive superconducting detector that works at a temperature of 4K (-269°C) – easily the coldest place at Halley! The instrument is located in the double caboose (C6), close to the main station buildings, and points up at the sky above Halley through a south-facing window in the side of the caboose.

It measures microwaves that are emitted naturally by the molecules making up the atmosphere. Each molecule has a unique microwave spectral fingerprint and, by tuning the radiometer to different frequencies, we can figure out which chemicals are up there and how much occurs at each height.

The processed radiometer data are analysed in Cambridge using computer models and other observations from Halley and polar-orbiting spacecraft that measure the electrons and protons.

The ultimate goal is to further understanding of the processes that lead to climate variability in the polar regions and globally – highly relevant for UK environmental science and collaborative research at an international level in which BAS plays a key role.