3,200MP Old Survey Space-Time (LSST) Camera Under Final Tests: Digital Imaging Review

The world’s largest digital camera is undergoing final assembly and testing before being shipped to the Vera Rubin Observatory in Chile next year. The camera, dubbed the Legacy Survey of Space and Time (LSST), will capture half of the southern night sky every three days at a resolution of 3200 megapixels.

Just over 14 months ago, the camera’s creators, the Department of Energy’s SLAC National Accelerator Laboratory, successfully tested the camera ahead of a planned installation in Chile in 2022. The camera’s sensor is an array of 189 individual image sensors. The sensors are charge-coupled devices (CCDs) that each capture a 16-megapixel image. While SLAC is building the camera, the Department of Energy’s Brookhaven National Laboratory assembles square units of nine sensors, called scientific pontoons, then sends them to SLAC for final assembly. Each raft costs up to $3 million. As you can tell, a lot of different teams and a lot of money were involved in the project.

Earlier this month, the team marked a new milestone when both LSST camera-cooling systems have successfully worked together in time since January. The camera produces about 10 times more heat than other astronomical cameras. There are two separate cooling systems, a “cold” system that keeps the pontoon’s electronics running and a “cryo” system that cools the 189 CCDs for the cam.

Image credit: LSST / DOE

After the successful testing of the cooling systems, the LSST Camera team will now perform a full suite of photovoltaic tests to improve focal plane performance, which includes CCDs, reading electronics and thermal systems, and then run a series of verification tests that include semi-finished operating conditions. The tests will collect approximately six weeks of data and test for factors such as propagation, readout noise, dark or hot pixels or bars, gain, crosstalk, linearity, brighter, and any charge transfer inefficiencies.

When photographing the southern half of the night sky every three days, the camera will record images every 15 seconds. This means that each week, scientists will have a complete, wide-ranging picture of the sky and that astronomers, astrophysicists and cosmologists can not only view very distant and dim objects with incredible sharpness, but also see how the sky changes over time thanks to a regular and consistent image database.

“We’ll see fainter objects than people have seen before in an area of ​​the sky,” said astrophysicist Aaron Rodman, chief scientist for assembly and testing of the cameras. “People have done profound things, but they were in small areas of heaven.”

Image credit: SLAC

The LSST camera has six rotating filters that can be switched depending on the prevailing sky conditions and the target subject. Filters allow the operator to photograph different wavelengths of light. The camera itself, as we saw last year, is great. It is 1.65 m (5.5 in) wide and 3 m (9.8 in) long. It weighs approximately 2,800 kg (6,200 lb). The camera has a field of view of 3.5 degrees and pixels as small as 10 µm can record 0.2 arcseconds. The image area itself has a diameter of 64 cm (25.2 in). You can read the in-depth technical features of the camera here.

The optics attached to the sensor array are equally impressive. The LSST lens was delivered in 2019 and includes a massive 1.57 m (5.1 in) optical lens and a smaller 1.2 m (3.9 in) L-2 lens. In 2019, the L-1 was touted as one of the largest, if not the biggest, high-performance lenses.

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