The observatory is located on the El Peñón peak of Cerro Pachón, a 2,682-meter-high (8,799 ft) mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

[20][21] The first on-sky observations with the engineering camera occurred on 24 October 2024,[22] while system first light is expected in July 2025 and full survey operations are aimed to begin later in 2025, due to COVID-related schedule delays.

[24] The renaming was enacted into United States law on 20 December 2019,[25] and announced at the 2020 American Astronomical Society winter meeting.

The name honors Rubin and her colleagues' legacy to probe the nature of dark matter by mapping and cataloging billions of galaxies through space and time.

[29] The fifth decadal report, Astronomy and Astrophysics in the New Millennium, was released in 2001,[30] and recommended the "Large-Aperture Synoptic Survey Telescope" as a major initiative.

It will also contribute to the study of the structure of the universe by observing thousands of supernovae, both nearby and at large redshift, and by measuring the distribution of dark matter through gravitational lensing.

All the data will be available through the National Virtual Observatory... providing access for astronomers and the public to very deep images of the changing night sky.

[17] The lead organizations are:[33] In May 2018, the United States Congress surprisingly appropriated much more funding than the telescope had asked for, in hopes of speeding construction and operation.

Making the primary mirror parabolic removes spherical aberration on-axis, but the field of view is then limited by off-axis coma.

The result is sharp images over a wide field of view, but at the expense of some light-gathering power due to the large tertiary mirror obscuring part of the optical path.

Making them out of the same piece of glass results in a stiffer structure than two separate mirrors, contributing to rapid settling after motion.

Such correction, which requires re-adjusting an additional element in the optical train, would be very difficult to achieve in the 5 seconds allowed between pointings, plus is a technical challenge due to the extremely short focal length.

[41] The Simonyi telescope uses an active optics system, with wavefront sensors at the corners of the camera, to keep the mirrors accurately figured and in focus.

The process occurs in three stages:[42] The precise shape and focus of the mirror assembly is estimated, and then corrected, by comparing the images on four sets of deliberately defocused CCDs (one in front of the focal plane and one behind, see figure at right).

One proceeds analytically, estimating a Zernike polynomial description of the current shape of the mirror, and from this computing a set of corrections to restore figure and focus.

[6] Repointing such a large telescope (including settling time) within 5 seconds requires an exceptionally short and stiff structure.

[44] Each spot on the sky is imaged with two consecutive 15 second exposures, to efficiently reject cosmic ray hits on the CCDs.

[49]Allowing for maintenance, bad weather and other contingencies, the camera is expected to take over 200,000 pictures (1.28 petabytes uncompressed) per year, far more than can be reviewed by humans.

[58] Each alert will include the following:[59]: 22 There is no proprietary period associated with alerts—they are available to the public immediately, since the goal is to quickly transmit nearly everything LSST knows about any given event, enabling downstream classification and decision making.

This avoids the need to download, then upload, huge quantities of data by allowing users to use the LSST storage and computation capacity directly.

[73] LSST, by itself, is estimated to be capable of detecting 62% of such objects,[74] and according to the United States National Academy of Sciences, extending its survey from ten years to twelve would be the most cost-effective way of finishing the task.

The main factors were the number of clear nights per year, seasonal weather patterns, and the quality of images as seen through the local atmosphere (seeing).

The site also needed to have an existing observatory infrastructure, to minimize costs of construction, and access to fiber optic links, to accommodate the 30 terabytes of data that LSST will produce each night.

The shell of the summit building was complete, and 2018 saw the installation of major equipment, including HVAC, the dome, mirror coating chamber, and the telescope mount assembly.

On 21 October 2014, the secondary mirror blank was delivered from Harvard to Exelis (now a subsidiary of Harris Corporation) for fine grinding.

The LSST pier is unusually large (16 m diameter), robust (1.25-meter-thick walls) and mounted directly to virgin bedrock,[109] where care was taken during site excavation to avoid using explosives that would crack it.

[124][125] Data is first sent via a $5 million dedicated encrypted network to a secret United States intelligence community facility in California.

This transfer uses multiple fiber optic cables from the base facility in La Serena to Santiago, Chile, then via two redundant routes to Miami, Florida, where it connects to existing high speed infrastructure.

For bright trails, the complete exposure could be ruined by a combination of saturation, crosstalk (far away pixels gaining signal due to the nature of CCD electronics), and ghosting (internal reflections within the telescope and camera) caused by the satellite trail, affecting an area of the sky significantly larger than the satellite path itself during imaging.

[132] Possible approaches to this problem would be a reduction of the number or brightness of satellites, upgrades to the telescope's CCD camera system, or both.