Recently, I’ve posted only secondhand on the Vera Rubin Observatory, via its implications and our expectations. It’s time to get caught up on the progress at the Cerro Pachon peak.
The dome is practically built; the telescope mount works (with a dummy mirror, made of steel). In the past weeks, the secondary mirror, then the primary mirror were just installed and checked out. As the VRO staff say, “we have a telescope”. Of course, glass alone will tell us nothing. The LSST Camera, from SLAC, was built and shipped; it is in storage in Chile for the time being.
ComCam (Commissioning Camera) was mounted on the telescope. For test purposes, ComCam is a similar but far simpler version of LSSTCam. Given that this is a one-of-a-kind, custom system, extensive testing and adjustment is needed to make things work out. ComCam, then, is an active, electronic counterpart to the steel dummy mirror. Several months will elapse with checkout and testing of an end-to-end system. Assuming no real issues are found, the main camera will be swapped in very late-‘24 or early-‘25.
ComCam is not the size and weight of an SUV; the real LSSTCam is. ComCam puts representative pixels at various places around the field of view, to check for any issues. It has ‘only’ 144 megapixels. LSSTCam will fill the field of view, with 3.2 gigapixels (that’s 3,200 megapixels). By comparison, consumer cameras are one-hundred to one-thousand times lower in pixel count. With a 3.2 gigapixel field, alignment is critical- even a tiny ‘misfocus’ will be visible… and the telescope will repoint itself at speeds unlike any previous telescope of this size. That is, the Rubin telescope will “slew” from one spot on the sky, to another, in a rapid pace to maximize its surveying ability. Neither cam must slip out of alignment.
It’s been a long ordeal. We made it through the pandemic halt of operations, we made it through the realignment of NOAO (National Optical Astronomy Observatory) into NOIR. We just made it through mountain snowfalls and Chile’s September holidays. The Vera Rubin Observatory will see engineering first light- actual pixels on the sky, gathering actual starlight. And then after that, science first light- verification of LSSTCam in a full-up telescope. When the Legacy Survey of Space and Time begins, photons (including comet and asteroid ones) will come in a a rate unlike any previous telescope. We’re preparing on our end for this asteroid avalanch.