FAQ's

Questions and Answers

This is the FAQ for the public. Would you prefer the scientist FAQ? Feel free to ask a new question.

Frequently Asked Questions


Q: What is the LSST?

A: The Large Synoptic Survey Telescope is a revolutionary facility which will produce an unprecedented wide-field astronomical survey of our universe using an 8.4-meter ground-based telescope. The LSST leverages innovative technology in all subsystems: the camera (3200 Megapixels, the world’s largest digital camera), telescope (simultaneous casting of the primary and tertiary mirrors; two aspherical optical surfaces on one substrate), and data management (30 Terabytes of data nightly, nearly instant alerts issued for objects that change in position or brightness). This innovation on all fronts has attracted some prominent donors who are innovators in technology, institutional members, and hundreds of other scientists.


Q: What does “Synoptic” mean?

A: Our use of the word derives from the greek word “Synopsis” and refers to looking at all aspects of something. The LSST is a synoptic survey in several ways: billions of objects will be imaged in six colors in an unprecedented large volume of our universe. This survey over half the sky also records the time evolution of these sources: the first motion picture of our universe.


Q: Why do we need the LSST?

A: From its mountaintop site in Chile, the LSST will image the entire visible sky every few nights, thus capturing changes and opening up the time-domain window to the observable universe. Ultimately, in 10 years of observing, the goal is to record the greatest movie ever made. The LSST data will reveal The New Sky to scientists and the public with manifold implications for science. Billions of objects in our universe will be seen for the first time and monitored over time. Outstanding mysteries in astronomy and physics will be uniquely addressed. With a thousand-fold increase in capability over current facilities, LSST is likely to make unexpected discoveries.


Q: Why did you choose to build the telescope in Chile?

A: The decision to place LSST on Cerro Pachón in Chile was made by an international site selection committee based on a competitive process that is described here. In short, modern telescopes are located in sparsely populated areas (to avoid light pollution), at high altitudes and in dry climates (to avoid cloud cover). In addition to those physical concerns, there are infrastructure issues. The ten best candidate sites in both hemispheres were studied by the site selection committee. Cerro Pachón was the overall winner in terms of quality of the site for astronomical imaging and available infrastructure. The result will be superb deep images from the ultraviolet to near infrared over the vast panorama of the entire southern sky.


Q: When will LSST be ready?

A: The LSST received its federal construction start in 2014 and will achieve engineering first light five years after that. Full science operations for the ten-year survey will begin two years after engineering first light. In addition to successful reviews by funding agencies, significant milestones have already been reached, including the casting of the primary and tertiary mirrors.


Q: How can LSST help teach my students science content in the classroom?

A: Students learn best when they are engaged in authentic investigations! We will provide an increasing number of investigative modules which you can use in your classroom to supplement existing curricula or to create your own units. The science themes of LSST encompass astronomy, physics, chemistry, earth/space science, mathematics and technology. Our discoveries will be the foundation for our educational materials.


Q: Will LSST educational materials help me teach my science standards?

A: LSST educational materials will be based in and will clearly specify National and State science, math and technology standards that are met by the activity. Our materials will enhance 21st century workforce skills, incorporate inquiry and problem solving, and ensure continual assessment embedded in instruction.


Q: How can LSST educational materials help me be a better teacher?

A: LSST educational materials will provide access to sound scientific principles using engaging activities that are age appropriate and conceptually accurate. We are modeling our materials after “Understanding by Design” and will provide you with overarching concepts, essential questions, knowledge and skills, assessments, and lesson plans. Background information for teachers will be embedded within our educational modules; we envision online discussions and training for educators.


Q: What role will there be for amateur astronomers, since everything will have been discovered by LSST? What’s left for us to find?

A: While discovery space may be closed by LSST and its predecessors, overwhelming new opportunities will open for follow-up. LSST saturates at magnitude 16, well within the reach of many well-equipped amateurs. Tens of thousands of alerts per night will point to surprises to be understood and monitored. In addition, the open database will provide a limitless playground for data mining and exploring.


Q: Who is involved with LSST?

A: Meet the team here and see a list of the current institutional members.


Q: Why build an entirely new telescope for this task?

A: Because no existing telescope can do what the LSST will do. The LSST is different from other ground-based telescopes in that it is a wide-field survey telescope and camera that can move quickly around the sky and image everything over and over. We describe it as Wide-Fast-Deep. That combination is unique: wide field of view (10 square degrees), short exposures (pairs of 15-second exposures), and sensitive camera (24th magnitude single images, 27th magnitude stacked). LSST is far more than a telescope. With its 3200 Megapixel camera, supercomputer, and giant data processing, analysis, and distribution system, the LSST facility will produce an entirely new view of our universe enabling unforeseen explorations of discovery.


Q: Why should the general public care about the LSST?

A: LSST has been designed as a public facility from the beginning, with deep color imaging and multi-dimensional data products made available quickly over the internet. We are planning to involve the public, including students, in exploring The New Sky. In addition to innovative portals like Google Sky or World Wide Telescope, we intend to develop research projects that can be done by students in classroom settings, at home, and via science museums with the the public. In addition, we’re paying attention to citizen science projects like e.g. Galaxy Zoo. Supercomputers will continuously transform LSST imaging data into a revolutionary four dimensional space-time landscape of color and motion, offering exciting possibilities for exploration and discovery by curious minds of all ages.


Q: Why an 8-meter mirror with a 3 degree field? Couldn’t a smaller telescope or an array of smaller telescopes do the same science in a somewhat longer time?

A: Some of the science can’t be done at all with a smaller telescope, or group of small telescopes. For instance, the near-Earth object (NEO) survey is looking for things that won’t sit still for a long exposure. An exposure longer than 10 or 20 seconds becomes ineffective, and so finding the vast majority of NEOs which are small and faint requires a telescope that can collect a lot of light in 10 or 20 seconds. Similarly, longer exposures on a smaller telescope will not help characterize faint transient objects lasting only seconds. In an array of smaller telescopes, longer exposures would be required (to reach sky-noise limit) as well as multiple Gigapixel cameras. Some of the science can be done on a smaller telescope in a longer time, but consider the numbers: The speed with which you can survey an area of sky for objects of a given faintness is proportional to throughput (collecting area times field of view in meters squared degrees squared). The LSST enables totally new windows on the universe because it has such a high throughput. For most of the exciting explorations of our universe, the total time would increase from 5 years to 50 years if the LSST were shrunk to 4 meters and a 2-degree field of view. There is real value in being able to complete the project in less than several generations!


Q: Why not a space mission?

A: A few of the very deep probes of the universe would benefit somewhat from the higher angular resolution available in space. But they also require huge samples of objects over a wide area of sky (large volume of the universe.) This Wide-Deep capability is hard to obtain in space. And the Wide-Fast-Deep capability would be lost: space telescopes have small collecting area compared to what can be built on the ground, leading to long exposures and loss of timing information. Since all of LSST’s science goals can be achieved from the ground, we must weigh the incremental benefit against the drawbacks. The science that drives the need for the LSST requires ultra deep and rapid wide-field imaging at optical wavelengths—a mission best achieved on the ground at a superb site.


Q: Where does LSST rank among the many proposed national scientific facilities?

A: Over the past decade six national reports have ranked LSST highly. This is because LSST is uniquely capable of attacking some of the greatest mysteries in astronomy and physics. National committees studying options for the next generation facility have recommended LSST for its capability to study many fundamental questions in astronomy and physics all at the same time. Rather than building separate facilities to study near-Earth asteroids, or the outer solar system, or how our galaxy was formed, or the nature of energetic explosions in the universe, or the mysterious dark matter and dark energy, LSST has a sufficient light grasp (throughput) to undertake all these scientific programs simultaneously from the same Wide-Fast-Deep survey.


Q: Will it be possible to subscribe to real time alerts of LSST discoveries?

A: Yes. Web alert pages and auto email alert services enabled by our data centers via the Virtual Observatory will permit users to custom filter alerts based on a number of classification parameters.


Q: Will the full resolution, full depth image data be available to download?

A: Yes. There will be a range of data products and download portals.


Q: Will LSST imaging data be available world-wide for scientific use?

A: LSST alerts and educational programs will be available world-wide; images and catalogs are available to scientists in the US and Chile and to international institutions that are supporting LSST operations.


Q: I’d like to support the LSST project. Who should I contact?

A: You can contact us by emailing "contact" at "lsst.org". The LSST Project solicits your input on the technical and scientific choices that we face. Share your views with us! Please make specific reference to technical documents or presentations when appropriate, so we can be sure to route your comments to the relevant people. Consider also browsing our team page.