I spent the day pottering around SHIRE today: replacing cables wrenched open by the pressure of the winter ice, and tying down loose cables against the wind.

SHIRE is an Imaging Riometer - an array of 64 antennas that listen to the sound of the most distant galaxies without actually giving a fig about them per se. By comparing the received galactic radio wave intensity on the ground with the intensity we'd expect if we were high in orbit, it's possible to work out how much of the signal has been absorbed by the ionosphere in between - and hence, determine how dense the ionosphere is.

'Riometer' is actually an acronym for 'Relative Ionospheric Opacity Meter'. The cosmic-noise method was an Australian invention, born in the CSIRO in 1953. Standard riometers use a single beam, but when they detect a fluctuating reading it's difficult to work out whether it's a stable density gradient that the earth is turning underneath, or a true temporal variation in the ionosphere. The Imaging Riometer gets around this difficulty by using a complex array of antennas, each of which measure a different portion of the sky, so that a 2-dimensional map of the ionosphere can be constructed. The first imaging riometer, IRIS, was used at the South Pole in 1987. SHIRE, the Southern Hemisphere Imaging Riometer Experiment, was installed at Davis in 1996.

self-portrait with imaging relative ionospheric opacity meter

In other news: happy birthday Mum!