March 23, 2021 - The first completed filter for the Rubin Observatory LSST Camera has arrived at SLAC National Accelerator Laboratory! The r-band filter was delivered to SLAC on March 12th, marking an exciting milestone for the LSST Camera team.
The r-band filter is one of six filters that will be used in the LSST Camera; each filter is optimized to collect light within a specific range of the electromagnetic spectrum. Each filter is about 30 inches (76 cm) in diameter and weighs about 90 lbs (41 kg). The filters are labeled u, g, r, i, z, and y; each transmits light from a segment of the electromagnetic spectrum progressing from the ultra-violet (u) to the near-infrared (y). The r-band filter, which covers a spectral band near the center of this range, will be one of the filters used most often during the Legacy Survey of Space and Time (LSST). It will also be particularly useful for testing the camera because standard optical techniques can be used to verify the optical performance of the camera when this filter is in place.
From its raw-material state to its recent delivery, the r-band filter has acquired an enviable travel record. The raw material for the substrate, procured in New York State, was shipped to Aix-en-Provence, France, where it was shaped and polished. Then, the substrate was sent to Westford, Massachusetts, where the filter coating was applied. From there, the filter traveled to the Lawrence Livermore National Laboratory (LLNL) in California to be installed in its frame, and finally the finished filter was sent to SLAC, in Menlo Park, CA.
At SLAC, the r-band filter will be stored in a special container until the rest of the filters arrive. This is the same storage container that will be used at the Rubin Observatory in Chile, to safely store filters that are not in use, since the filter carousel can only accommodate five of the six filters at any given time. The other filters will arrive at SLAC over the next couple of months; two are currently being installed in their frames at LLNL, and the other three are still with the coating vendor. Installation of all the filters in the filter exchanger, which is also at SLAC, is expected to take place at the end of 2021. After thorough testing, the camera and all its components, including the filters, will be meticulously packed and shipped to Chile in early 2022.
Links
[1] https://gallery.lsst.org/bp/#/folder/9294619/119691980