From my first post on medium, you can read some about the big-picture science of why we’re in Antarctica getting ready to operate our telescopes from a high-altitude balloon. We’re among several groups directly observing the early universe to make measurements that will tell us about the physics that powered the big bang.

To see this glow from the aftermath of the big bang, we have three telescopes that are sensitive to light waves at a frequency of 95 GHz, and three more that are sensitive to light waves at 150 GHz. For comparison, cell phones communicate using lower frequency 1 GHz waves, and regular visible light we see with our eyes is at much higher frequencies, roughly 600,000 GHz. This means that our observing frequencies are too high to borrow conventional cell phone technology, and too low to borrow conventional optics technology, so we need to build our own detectors and telescopes.

The detectors and telescopes our collaboration built together are among the most sensitive microwave systems ever built, which is necessary to see the faint polarized light signature that contains information about the big bang. We want to be really sure that we are truly seeing that signal, and not accidentally seeing a systematic error in our instrument. For my PhD thesis, I worked with a group at Case in Cleveland to build an optical component, called a half-wave plate, that will help us do that. This device lets us select on the fly which polarization state each of our detectors is sensing. That way, we can repeatedly make maps of the sky in both polarization states with each individual detector, and be sure that we really are seeing polarized light from the early universe and not accidentally just seeing systematic error in the instrument.

So, here it is! The top picture shows a half-wave plate, mounted in its rotation mechanism, installed in front of one of our telescopes. The round dark-colored circle is the plate itself (the version built for 150 GHz light), which fills the entire aperture of the telescope (about a foot in diameter). The rotation mechanism is how we change which polarization state each detector is looking at. Rotating the plate rotates the light. The bottom picture shows me sitting by one of the plates built for 95 GHz light.

Since we have six telescopes, we built six (plus some spares!) of these optical devices. My PhD thesis describes how this was done, and all the research and development that it took for us to figure out how to make them work. Here’s a picture of all six of the rotation mechanisms on the bench before we installed them.

Now that we’re here, we finally got to install them in the instrument this past week, and get them ready to really fly and really enable our measurement of the early universe. Here’s a picture of Johanna, another grad student who worked with me on building this system, working on the installation towards the end of the process. Looks great!

Go Spider!