SLAC 3,200-megapixel camera: World's largest digital camera

SLAC is leading the construction of the 3,200-megapixel camera, which will be the size of a small car and weigh more than 3 tons. 

The digital camera will be the largest ever built, allowing LSST to create an unprecedented archive of astronomical data that will help researchers study the formation of galaxies, track potentially hazardous asteroids, observe exploding stars and better understand mysterious dark matter and dark energy, which make up 95 percent of the universe. 

Credit: SLAC National Accelerator Laboratory

Plans for the construction of the world's largest digital camera at the Department of Energy's SLAC National Accelerator Laboratory have reached a major milestone.

The 3,200-megapixel centerpiece of the Large Synoptic Survey Telescope (LSST), which will provide unprecedented details of the universe and help address some of its biggest mysteries, has received key "Critical Decision 2" approval from the DOE.

"This important decision endorses the camera fabrication budget that we proposed," said LSST Director Steven Kahn.

"Together with the construction funding we received from the National Science Foundation in August, it is now clear that LSST will have the support it needs to be completed on schedule."

Science operations are scheduled to begin in 2022 with LSST taking digital images of the entire visible southern sky every few nights from atop a mountain called Cerro Pachón in Chile.

It will produce the widest, deepest and fastest views of the night sky ever observed.

Over a 10-year time frame, the observatory will detect tens of billions of objects, the first time a telescope will catalogue more objects in the universe than there are people on Earth, and will create movies of the sky with details that have never been seen before.

LSST will generate a vast public archive of data, approximately 6 million gigabytes per year, that will help researchers study the formation of galaxies, track potentially hazardous asteroids, observe exploding stars and better understand dark matter and dark energy, which make up 95 percent of the universe but whose nature remains unknown.

"The telescope is a key part of the long-term strategy to study dark energy and other scientific topics in the United States and elsewhere," said David MacFarlane, SLAC's director of particle physics and astrophysics.

"SLAC places high priority on the successful development and construction of the LSST camera, and is very pleased that the project has achieved this major approval milestone."

This is a rendering of the LSST observatory (foreground) atop Cerro Pachón in Chile. 

When LSST starts taking images of the entire visible southern sky in 2022, it will produce the widest, deepest and fastest views of the night sky ever observed. 

Over a 10-year time frame, LSST will image several tens of billions of objects and create movies of the sky with unprecedented detail. 

Credit: Large Synoptic Survey Telescope Project Office

The LSST team can now move forward with the development of the camera and prepare for the "Critical Decision 3" review process next summer, the last requirement before actual fabrication of the camera can begin.

Components of the camera, which will be the size of a small car and weigh more than 3 tons, will be built by an international collaboration of labs and universities, including DOE's Brookhaven National Laboratory, Lawrence Livermore National Laboratory and SLAC, where the camera will be assembled and tested.

"Many excellent, hard-working people have been developing LSST for a long time and it is gratifying to see the quality of their efforts being recognized by the DOE approval," said Steve Ritz of the University of California, Santa Cruz, the lead scientist of the camera project. "We are all excited about the amount of great science that LSST will enable."

Cherenkov Telescope Array (CTA): CHEC a cutting-edge camera

This colourful piece of electronics is a photomultiplier module for the CHEC camera undergoing testing. 

Credit: Fabricio Sousa/SLAC

Key components for a new type of camera that will collect only the faintest, fastest flashes of light in the night sky are being assembled and tested now at SLAC.

Their eventual destination: the first Compact High-energy Camera (CHEC), which will be installed in a prototype telescope for the Cherenkov Telescope Array (CTA).

The CTA is a ground-based gamma-ray observatory currently under development by an international consortium with more than 1000 members from 27 countries.

The CTA will detect ultra-high-energy gamma rays, which are beyond even the reach of the Fermi Gamma-ray Space Telescope.

Current plans call for the observatory to comprise two separate arrays, one in the Northern Hemisphere and one in the Southern Hemisphere, totaling more than 100 telescopes of three different sizes.

The telescopes are now under development. Researchers at SLAC are testing modules of electronic components for the first CHEC camera, which will be installed on a prototype telescope later this year.

But most gamma rays from cosmic sources are blocked by the Earth's atmosphere. What will the camera be looking at?

'Seeing' Gamma Rays
Gamma rays are the most energetic form of electromagnetic radiation – energetic enough they cause showers of secondary particles when they hit the atmosphere.

The particles race toward the ground so fast they break the speed of light in our atmosphere.

This is considerably slower than the speed of light in a vacuum, but still speedy enough to cause them to emit a form of radiation called Cherenkov radiation.

All 32 of the photomultiplier modules for the CHEC camera. 

Credit: Tobias Jogler/SLAC

"It's really just light – bluish light," said Stefan Funk, an astrophysicist at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), a joint SLAC-Stanford institute.

Its a faint blue light that flashes on and off in about five nanoseconds: "If we had nanosecond eyes, we could see it," he said.

Unfortunately we don't have nanosecond eyes, and neither do CCD cameras, which are the type of camera generally used at observatories to collect light. That's where the CHEC camera comes in.

Nanosecond Eyes
Each CHEC camera contains modules of customized electronic components, beginning with photomultipliers.

A photomultiplier can capture a single photon, or particle of light, and amplify its signal for a detector to read.

But the real heart of each module is a special integrated circuit chip called a TARGET chip, developed at the University of Hawaii in collaboration with SLAC researchers.

Each TARGET chip can read the signals from 16 individual pixels on a photomultipliers one billion times a second, fast enough to capture the flashes of Cherenkov light.

"The prototype camera we're building uses 32 modules, each with a 64-pixel photomultiplier and four TARGET chips," said KIPAC postdoctoral researcher Luigi Tibaldo.

"It will be installed on a prototype of the smallest telescope," which represents the majority of instruments needed for the arrays; the TARGET chips are also under consideration for some of the mid-sized telescopes under development.

This adds up to around 60 telescopes to equip, making cost an important factor in the design.

Luigi Tibaldo of SLAC (center) and collaborators Shigeki Hirose of the University of Nagoya (left) and Mark Bryan of the University of Amsterdam (right) in Building 84, where they're testing the photomultiplier modules for the CHEC camera. 

Credit: Fabricio Sousa/SLAC

To address this issue, the modules can easily be mass-produced, Funk said.

Their colleague Gary Varner of the University of Hawaii works with industry partners to create the TARGET chips and the photomultipliers are supplied by Hamamatsu Photonics, a Japanese firm.