HBA installation progress — 19-Jul-2011

Today, the last few tiles were put on the field, thus completing the antenna deployment. Although there were only three to go it, it was by no means an easy day and repair work, high winds and torrential rain main the going slow, difficult and risky.

The main problem was the high wind speeds, which was unusually blowing in from the south east. The speeds were generally pretty strong, with gusts up to 15 m/s. Typically a LOFAR station would have stopped work under those circumstances, but we pressed on, despite the fact that everything was being done 1.5 metres higher as well, because of the frameset mounts.

To make things easier for us, we moved the unfolding station in close to the two tiles in the east storage stack.

The first tile (location H30) managed to go on okay in a small lull. This was probably just as well, as this was the most exposed tile. Once in place, we could then deploy the framesets in locations H42 and H31. There was a small pause as the last frameset went in as we smiled at the moment. Then we wiped the rain from our faces and headed over to prepare the penultimate tile.

This second one was more challenging and there were several occasions where the tile would rise alarmingly in the blustery conditions. With stress levels at a maximum, the tile lurched into place and we quickly got the cover on and locked it down.

We figured we didn't have enough time to complete the final tile repair work before lunch, and the weather was being uncooperative, so we spent the next while putting in additional O-rings to ensure that the covers on deployed tiles were all locked down okay.

After lunch, came the tile we'd all be dreading. This one had been damaged during transit and we needed to effect repairs on at least 3, if not more, of the cells. The main concern was that we'd need to dismantle most of the tile to get the work done — not good, as the rain was coming and going and we were concerned about exposed electronics.

Again, we moved the unfolding station right next to the tile and then set to work. We were lucky to have Stuart Keenan to hand, as he could quickly and expertly conduct the repair work on the damaged side of the tile, while the rest of the team continued the fitting work on the other side. As we completed cell repairs, we quickly set and check the polarisation and then get the cover down. In the end, rain exposure was minimal and we had the tile prepared ready for the final lift.

Like the previous one, this also proved difficult. Access was limited as we were now pushed into the easternmost corner and vehicle manoeuvring was severely restricted. That meant it was one of our longest reaches to get the tile into place and the wind was not cooperating.

Using loading straps — at 2+ metres high, it was out of easy arms reach — we held the tile down as much as we could and drove it into place. With about 1 metre to go, there was a strong gust and the tile swung violently to one side, but we managed to steady it and get it lowered into place. We quickly slid on the cover and locked it down.

The last was definitely the most challenging and the relief at having got this major phase of the work done was considerable. It was the riskiest part of the entire construction phase and we managed it without too many problems and we completed it on schedule too. The final status is, of course, as follows:

To everyone who took part in the deployment of the tiles: thank you! Some photographs of this final stage will be posted here on the web log in the morning. And then we get to start the next phase of the project!