The Vera C. Rubin Observatory has taken another step towards the first light, projected for some time in 2022. Its huge 3200 megapixel camera has just taken its first photo during laboratory tests at the SLAC National Accelerator Laboratory. The camera is the largest ever built, and its unprecedented power is the driving force behind the ten-year Observatory’s Legacy Survey of Space and Time (LSST).
When paired with the 8.4-meter main mirror, the camera is an incredible data-producing monstrosity. Its focal plane contains 189 separate charge-coupled devices (CCDs) that each capture 16 megapixels. Each 3200-megapixel image would require 378 ultra-high definition 4K TV screens to display.
Each image is so large that a single one captures an area of sky equivalent to 40 full moons. The team behind the camera says the image sensors are so powerful that it will be able to “see”
“This is a milestone for us,” said Vincent Riot, LSST Camera project manager at DOE’s Lawrence Livermore National Laboratory. “The focal plane will produce the images for the LSST, so it is the capable and sensitive eye of the Rubin Observatory.”
Steven Kahn, director of the SLAC observatory, said in a press release: “This achievement is among the most significant of the entire Rubin Observatory project. The completion of the LSST camera focal plane and its successful tests is a ‘huge victory by the camera team that will allow Rubin Observatory to deliver next generation astronomical science. “
For ten years, the observatory will capture over 20 terabytes of data every night. By the end of its 10-year survey, it will have produced 60 petabytes.
So much data will be produced, in fact, that there will be two 40GB high-speed fiber optic data lines to handle it. All this data will be transferred to the Archive Center in the United States. There it will be processed, stored and made available to the community.
All this image collection and processing will create the Rubin Observatory’s output: wide-field panoramic images of the southern sky, one every few nights for 10 years. All of those images will add up to a great ten-year video of the night sky.
This will be the Rubin Observatory’s main contribution to astronomy: the Legacy Survey of Space and Time (LSST). LSST will be a catalog of approximately 20 billion galaxies, more galaxies than there are humans. It will find all kinds of transient objects, such as asteroids whizzing around our Solar System, as well as distant supernovae. It will help map dark matter and dark energy, and also our Milky Way.
The camera’s sensor system consists of units called rafts. Each raft contains several sensors each and there are two types of rafts. 21 rafts contain nine sensors each and those 21 are responsible for image acquisition. Then there are four special rafts. They contain three sensors each and are responsible for focusing the camera and synchronizing with the rotation of the Earth.
“These specifications are simply astounding,” said Steven Ritz, project scientist for the LSST Camera at the University of California, Santa Cruz. “These unique features will enable the Rubin Observatory’s ambitious scientific program.”
“These data will improve our understanding of how galaxies have evolved over time and allow us to test our dark matter and dark energy models more deeply and precisely than ever before,” Ritz said. “The observatory will be a wonderful facility for a wide range of sciences, from detailed studies of our solar system to studies of distant objects towards the edge of the visible universe.”
It took the camera team several months to install the rafts on the focal plane. Rafts are very expensive equipment. Each can cost up to $ 3 million, and installation tolerances are extremely tight. The space between each raft is less than five human hairs wide. Imaging sensors can also break if touched.
Hannah Pollek is a mechanical engineer at SLAC who worked on sensor integration. In a press release he said: “The combination of high stakes and tight tolerances made this project very challenging. But with a versatile team we practically nailed each other. ”
To acquire these first images, the sensors were cooled to their operating temperature of -101 C (-150 F). Since the entire camera is not yet assembled, the team projected the images onto the focal plane with a 150-micron pinhole. The objects used for the test images were a head of Romanesco broccoli, the Flammarion engraving, a photo of Vera C. Rubin herself, a photographic collage of the LSST team members and a photographic collage of the logos of the LSST member institutions.
“Taking these images is an important achievement,” said Aaron Roodman of SLAC, the scientist responsible for assembling and testing the LSST camera. “With the rigorous specifications we have really pushed the limits of what is possible to exploit every square millimeter of the focal plane and maximize the science we can do with it.”
The next step is the assembly of the entire camera. The focal plane and cryostat will be inserted into the camera body, along with its three lenses. One of these lenses, with a diameter of 1.57 meters (5.1 feet), is believed to be the largest high-performance optical lens in the world. There is also the shutter and a filter change system. Overall, the camera will be the size of an SUV and will be assembled and ready for final testing by 2021. After that, it will be shipped to Chile.
“The completion of the camera is very exciting and we are proud to play such a central role in building this key component of the Rubin Observatory,” said JoAnne Hewett, SLAC chief research officer and associate laboratory director for fundamental physics. “It’s a milestone that takes us a big step towards exploring fundamental questions about the universe in ways we weren’t able to do before.”
One of the things that makes Vera C. Rubin’s Observatory so special is the fact that it shoots the same areas of the sky over and over in rapid succession. All this activity is also largely automated. This means it will spot transient objects and be able to alert other observers of things like supernovae. This will allow powerful telescopes coming online soon, such as the Extremely Large Telescope, to bring their power over them in a way that the Rubin Observatory cannot.
All of this exquisite image data will be accessible to the rest of us as well. In 2007, Google announced its involvement in the project. Although the LSST data will be available to researchers in a more raw form, Google wants to use its data expertise to make the LSST data more publicly accessible. They hope to provide digital coverage of things like supernovae, asteroids and distant galaxies.
The keywords of the Vera Rubin Observatory are “broad, deep and fast”. It will repeatedly scan the night sky with a wide field of view, with high resolution depth and do so quickly. There has never been anything like it.
And the fact that anyone with an internet connection will be able to share the findings and images means that the Rubin Observatory could inspire generations of future astronomers, much like the Hubble Space Telescope.