The Murchison Widefield Array
Last week I was up in Geraldton again at a project meeting of the Murchison Widefield Array (MWA) team. I'm not on the team, but I was invited along anyway, and I picked up a lot over the four days of the meeting. It's a pretty cool project but, like all projects, it has it's problems.
Basically, the MWA is a telescope with no moving parts. It's a series of dipoles which sit on the ground on top of a mesh groundscrren, sixteen dipoles making up one "tile". At the moment, there are 32 tiles up at Boolardy station with plans for 512 sometime in the next couple of years. The dipoles on each tile are connected to a beamformer which does some funky stuff to the signals before sending the data on to a receiver. Each receiver takes the inputs from 8 beamfomers, does some more funky stuff and sends the data on to the correlator.
What this all adds up to is a telescope which is steered electronically. In a conventional interferometer, to look at a different part of the sky you have to move all your telescopes and then adjust the delays added to each signal so that the wavefronts of the signals all line up (it's kind of like the Youngs slit experiment). With this sort of telescope, the dipoles can "see" most of the sky at once, and to make an image of the patch you are interedted in, you can adjust the delays in electronics to steer the beam. This is one of several SKA demonstrator telescopes which are testing out technologies and methods in preparation for the Square Kilometre Array.
It's all very interesting stuff and after spending a day in the lab annoying the engineers I think I understand it a whole lot better. There's still a lot I don't know though, but that's half the fun of research!