The World's Largest Digital Camera Will Shoot the Stars 3.2 Gigapixels at a Time

By Andrew Tarantola on at

We may be on the verge of an astronomical renaissance. Once complete, the Large Synoptic Survey Telescope hunt for dark energy and matter throughout the Southern sky from its perch atop Cerro Pachon in Chile while producing a staggering 60 petabyte public data archive. Now, we just need to figure out how to pay for it.

The Large Synoptic Survey Telescope (LSST) has been a long time coming. The Association of Universities for Research in Astronomy (AURA) and the National Optical Astronomy Observatory (NOAO) have been lobbying for such a wide-field survey telescope since the early 1990s and In 2010, the National Research Council voted the LSST its "highest-priority ground-based instrument" in its Astronomy and Astrophysics Decadal Survey. Already backed by 36 institutions and a variety of private financiers—even Bill Gates has donated $10 million—the LSST is awaiting the start of construction, which should begin in 2014, pending a $400 million grant by the National Science Foundation.

When it begins operating around 2022, the LSST will revolutionise our understanding of the universe through an unprecedented decade-long survey of the Southern sky. The LSST itself is an 8.4 metre ground-based telescope employing a 3200 MP camera and innovative triple-lens design. The LSST features an extraordinary 3.5-degree wide field of view, much wider than other similar-sized ground-based observatories. For reference, the moon takes up about half a degree (or .2 square degrees) when viewed from Earth. When paired with the telescope's relatively short double 15-second exposures and 3.2 Gigapixel sensor, the LSST will be 1000 times more capable than existing facilities.

It will scan a 20,000 square degree swath of the sky every few days—generating roughly 20 TB of data each night. "We actually move very quickly. Within five seconds, we can move from one piece of sky 3 1/2 degrees over and get ready for another exposure." William Gressler, senior optical engineer for the LSST, said. In all the, the LSST will snap a pair of 15-second exposures every twenty seconds, imaging every spot in the sky nearly a thousand times over a ten year span.

"The surveys that are being proposed for the LSST will provide the data sets a vast variety of astronomers will use to answer fundamentally different questions about the universe," Martha Haynes of Cornell University told NPR. Scientists hope to identify billions of new objects throughout the universe, as well as stuff that can't be seen directly, like dark matter and dark energy. These surveys will also make for one cool time-lapse video when complete.

At the heart of this telescope lies the world's largest digital camera. And by "largest" we're talking humungous, like the size of a VW Beetle. The camera assembly is 1.6 metres tall, 3 metres long, and weighs 2800 kilograms. A 64 cm diameter array of 16MP silicon detectors will comprise its 32GP sensor and will work in tandem with the telescope's large aperture to produce an estimate 200,000 extremely detailed images of the night sky every year.

To ensure that these images are distortion-free, the LSST will rely on a triple-mirror design. The primary mirror is 8.4 metres wide, the secondary mirror behind it will be 3.4 metres wide, and the 5 metre wide tertiary mirror will actually sit in a hole cut from the primary. In fact, the primary and tertiary mirrors are being cut from a single piece of "M1M3 monolith" glass.

Managing the torrent of data may be the most most challenging aspect of the system. The estimated 20TB nightly dump is far beyond the review capabilities of even the most dedicated research assistant. So the LSST will feature cutting-edge data mining technology, harnessing more than 150 petaflops of computing power to do the job.

All of the data, both the 60PB of raw and the 15PB of cataloged data, will be made available to the public. Look for Google Sky to get a serious upgrade come 2032.

[LSST - NOAO - AURA - Wikipedia - Image: Todd Mason / LSST corp]