Building the Murchison Widefield Array radio telescope – Day 1

Today I got to go to the Murchison Radio-astronomy Observatory (MRO) for the first time, after more than 6 years communicating all things radio astronomy in Western Australia it’s very exciting and a great opportunity to get involved and hands on with building a radio telescope. Today I got to drive off road lots, dig holes, carry heavy stuff around and look the part in my high vis gear and Aussie bush hat, all of which certianly adds to the experience. Our main task for the next few days (or however long it takes) is to move and place several tonnes of mesh sheets (each about 5 metres by 2 metres) in specific locations. Each “tile” is made up of three sheets and we need 128 tiles in a precise configuration, which has been marked out in previous visits.

The mesh sheets are similar to the parabolic dish part of a normal “dish” antenna, only they’re flat. They have holes in them (hence the name “mesh”) but as radio waves have longer wavelengths than the holes are big, it means incoming radio waves don’t “see” the holes so the mesh sheet acts as if it’s a complete sheet of steel, reflecting the incoming radio waves on to the receiving dipole elements in the same way a mirror in an optical telescope reflects light on to the human light detector, the eye. The dipoles are to be placed on these tiles in a few weeks time by another group.

The ground is incredibly hard (it hasn’t changed in billions of years) and as the tiles need to be placed flat on an even surface, this means that any lumps, bumps or concrete hard termite mounds need to be broken up and cleared away along with any bush scrub (see picture). Today this was done with a crow bar, a shovel and a rake, tomorrow we’re hoping to borrow a sledge hammer… I hope. Once the ground is cleared of lumps, bumps and scrub the mesh sheets are placed precisely and held together with clips. In a few days time, once all 128 tiles are down (384 mesh sheets at 20 kilos each = approx. 9 tonne), we’ll start spot welding them together so that the 3 pieces in each tile perform as a single large sheet with current flowing through it to power the dipole elements.

At night we’re staying in Wooleen Homestead, which is about 80 kilometres from the MRO, meaning a bit of dirt track driving at the beginning and end of each day. We have 2 vehicles and the lead vehicle throws up an almighty dust cloud for the trailing vehicle to negotiate in addition to the roos, goats, cows and cattle grids. The homestead is located near an enormous dried out lake bed, which floods once every nine years and stretches away to the distant horizon. Wooleen Homestead is gorgeous, it feels very old with bits and pieces added on over the years. It used to be a cattle ranch but in recent years the owner has de-stocked the farm in favour of reviving the land and attracting tourists to the area. It’s well off the beaten track, approximately 300 km north east of Geraldton and several hours away from the nearest sealed road.ImageImageImage

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