It’s the first night of the 2009 Undergraduate ALFALFA workshop, and I’ve spent the last several hours here in the control room, running the ALFALFA observations (designated as project A2010). Usually, I participate in our observations remotely, from the EGG workroom in Ithaca. But here, I am more acutely aware that I’m in control of something really big, and that when I click “Point,” I’m moving around a dome on a 900-ton platform suspended 450 feet in the air.
Usually, when folks picture a typical “night of observing” at a telescope, they think of a scientist in a labcoat looking through the eyepiece of a telescope, pointing from object to object, making notations on a sheet of paper. There are a few things about this picture that aren’t quite right for ALFALFA, the least of which is the fact that I’m bundled up in cozy flannel pajama pants and a polar fleece vest, rather than a starchy labcoat. As radio astronomers, we don’t look through an eyepiece, since the light we’re detecting is invisible to the human eye. Fortunately, it’s visible to the telescope, so our data can be written to disk and used later (that eliminates the sheet of paper as well, which is handy since we’re making 14 recordings every time a second ticks by).
The key difference, though, between the ALFALFA survey and this common picture is that we aren’t pointing the telescope over and over again. Since we’re conducting a survey, searching for clumps of hydrogen somewhere out there in the Universe, we want to look at every spot in our survey region at least once (our goal is twice). It’s sort of like shading in the pictures in a coloring book: we’ve outlined a region on the sky, and now we want to fill that in. We do so methodically, filling in one stripe at a time, instead of dashing all over the place. As a result, I’m not moving the telescope much at all tonight; I’m not looking at one portion of the sky before moving on to another one. Instead, I’ve pointed the telescope once and only once, at the very beginning of the observation, and as the Earth rotates and different portions of the night sky move overhead, the hardware and software detects and records the signal at each position. Honestly, the rotation of the Earth does most of the work for us! Tomorrow night I’ll point at a slightly different spot at the beginning, and slowly but surely, the ALFALFA survey will start to come together. It turns out that the area of the sky that ALFALFA will cover adds up to about one-sixth of the whole sky, so we’ve got our work cut out for us!
Since I’m not pointing the telescope over and over again, I’m having a pretty quiet night. Writing this blog post is the most excitement I’ve had in hours! Fortunately, that means nothing has gone wrong with our observation — a quiet night is a good night, as far as ALFALFA is concerned. As the time passes, I keep a detailed log of the observations, and keep an eye on lots of fun plots reported to me by the telescope, just to make sure that everything looks as it should. By the time I go to bed, I’ll have added about 8 hours to the four thousand or so it will take to finish the project. Tomorrow night, Sabrina and I will be back here in the control room, filling in another section of the local Universe for the ALFALFA survey.