SDSS is a multi-object spectroscopic survey, meaning that it can analyze the light of multiple objects simultaneously using its spectrographs. To do that, light from multiple objects needs to be guided from the focal plane of the telescope, where it is focused, to the spectrographs that sit at the back of the telescope. This is done using optical fibers – thin cables of glass or plastic, that are very efficient at carrying light from one point to another. SDSS can obtain spectra of up to 1000 objects at a time, by using up to 1000 optical fibers. These fibers need to placed in exactly the right place so as to capture the light of each individual object for which we would like to get a spectrum for. In SDSS, this is done using aluminum plates, called plug plates. Each plate contains up to 1000 holes, drilled to be in exactly the right place so as to collect the light of the required astronomical objects. Up to date, SDSS has drilled over 10,000 plates, each covering a unique part of the sky, and each enabling the collection of spectra of hundreds of unique astronomical objects.
This video shows the process of drilling an SDSS plate:
Then, optical fibers are plugged into each of these holes, manually, by our dedicated team of observers. Each day, five to ten plates will be plugged, so that they are ready to be used for observations that night. The following video shows this process happening: