Rubin's LSST (2019): The Plan for a 10-Year Movie of the Sky

Željko Ivezić and colleagues set out the design of the Legacy Survey of Space and Time (LSST) in a paper published in 2019: one telescope with a 3.2-gigapixel camera, imaging the entire southern sky every few nights for ten years. The Vera C. Rubin Observatory began that survey in mid-2026.

What was LSST built to answer?

Most telescopes study a few objects in depth. LSST was designed the other way around: a single survey that serves many sciences at once by imaging the whole visible sky, deep and often. The paper names four science drivers:

1. Probing dark energy and dark matter.
2. Taking an inventory of the Solar System.
3. Exploring the transient optical sky, everything that flares, fades or moves.
4. Mapping the Milky Way.

Each needs the same ingredients: a wide field of view, a big mirror and repeated visits, which is why one design can serve all four.

What the paper describes

• The telescope and camera. An 8.4-meter primary mirror (6.5 meters effective), a 9.6 square-degree field of view and a 3.2-gigapixel camera with six filters, ugrizy, covering 320 to 1,050 nanometers. The site is Cerro Pachón in northern Chile.
• The observing rhythm. A standard visit is a pair of 15-second exposures. With these repeats the system can image about 10,000 square degrees in one filter in three nights, reaching about magnitude 24.5 in a single visit.
• The main survey. About 90% of the time goes to a deep-wide-fast survey covering 18,000 square degrees about 800 times over 10 years. Stacking, or coadding, those images reaches about magnitude 27.5 in the r band.
• The data. A public database of about 32 trillion observations of some 40 billion objects.

How it works

Every few nights the telescope sweeps the southern sky. Software compares each new image with a reference template and flags anything that changed: a supernova, a moving asteroid, a flaring star. That produces up to about 7 million alerts per night. Meanwhile, stacking all the visits builds a deep map of the whole survey area. Each night yields about 10 terabytes of data.

Why it mattered

The paper is unusual. It was first posted to arXiv in 2008, when the project expected regular survey operations by 2022, and it was updated until its 2019 journal publication. It became the reference design for a whole decade of astronomy. LSST is the imaging heir of the Sloan Digital Sky Survey, scaled up for the time domain, and it is expected to help test ideas such as the hypothesized Planet Nine.

What we know now

The facility, now the NSF-DOE Vera C. Rubin Observatory, released its first images on 23 June 2025. Its Data Preview 1, from a commissioning camera, went to scientists a week later. First alerts followed in February 2026, and Rubin began its 10-year Legacy Survey of Space and Time in mid-2026 (announced 30 June 2026). During early test surveys it found more than 11,000 new asteroids. As of October 2026, Data Preview 2 is expected by the end of the year.

Who wrote it

Željko Ivezić, Steven M. Kahn, J. Anthony Tyson and a large team of collaborators wrote the paper for the LSST project. Semantic Scholar lists about 3,180 citations (October 2026).

Read the original

Ivezić, Ž., Kahn, S. M., Tyson, J. A., et al. (2019). “LSST: From Science Drivers to Reference Design and Anticipated Data Products.” The Astrophysical Journal 873, 111. doi:10.3847/1538-4357/ab042c

Free to read: arXiv preprint.