The receiver we use for our observations, ALFA (more details here), is back in use after being out of commission for a month and a half for service. ALFA was put back into place at the beginning of the month and has been working ever since; we’ve been observing over the last two weeks and things seem to be mostly working.
Servicing ALFA is no simple task. You want to get the receiver into the shop so that it can be tinkered and twiddled with easily, but it’s installed in a dome that is suspended 400 ft above the dish of the telescope and kept chilled to very cold temperatures (well below freezing). You want to have a very good reason for needing to service the receiver. There’s the hassle of uninstalling and reinstalling the receiver, but also the risk that every time you let it warm up to room temperature when it’s in the shop that it might not cool back down without breaking. Then there’s also all of the observing time you lose while the receiver is in the shop. (Of course, Arecibo was still being used for observations, it’s just that any of the projects using ALFA – including us – couldn’t observe.) In this case, ALFA was taken down for servicing because several programs that use the receiver needed it be to improved and tweaked a little bit so that they could actually make the observations they wanted.
Unfortunately, like with everything, once you fix one problem, another appears. In this case, one of the beams of ALFA has been acting up. Fortunately, it seems like this isn’t a problem that will require ALFA coming off the telescope again to fix. Instead, it seems to be something that can be fixed while ALFA is installed in the dome, allowing the problem to be worked on during telescope maintenance time without impacting observations.