The composition of current and former committees can be found here. Elections are held in Hilary term each year, and any member of the society can run for any position. Each committee serves for one year. Being on the committee is an enriching experience, allowing you to meet a variety of different people and gain experience for your CV. More detail about the positions can be found in the constitution.
Site design by Sophie Dillon, 2013. Background image credit: NASA, ESA, and M. Livio and the Hubble 20th Anniversary Team (STScI)