The LSST Camera is a complex, highly integrated instrument for the Vera C. Rubin Observatory. Now that the assembly is complete, we present the highlights of the LSST Camera assembly: successful installation of all Raft Tower Modules (RTM) into the cryostat, integration of the world’s largest lens with the camera body, and successful integration and testing of the shutter and filter exchange systems. While the integration of the LSST Camera is a story of success, there were challenges faced along the way which we present: component failures, late design changes, and facility infrastructure issues.
The LSST Camera is the sole instrument for the Vera C. Rubin Observatory and consists of a 3.2 gigapixel focal plane mosaic with in-vacuum controllers, dedicated guider and wavefront CCDs, a three-element corrector whose largest lens is 1.55m in diameter, six optical interference filters covering a 320–1050 nm bandpass with an out-of-plane filter exchange mechanism, and camera slow control and data acquisition systems capable of digitizing each image in 2 seconds. In this paper, we describe the verification testing program performed throughout the Camera integration and results from characterization of the Camera’s performance. These include an electro-optical testing program, measurement of the focal plane height and optical alignment, and integrated functional testing of the Camera’s major mechanisms: shutter, filter exchange system and refrigeration systems. The Camera is due to be shipped to the Rubin Observatory in 2024, and plans for its commissioning on Cerro Pachon are briefly described.
The Filter Exchange System (FES) of the Legacy Survey of Space and Time camera (LSSTCam) for the Vera C. Rubin Observatory has been integrated into the camera assembly before shipping to Chile. It holds five 75-cm filters weighing 25.5 to 38 kg. The main requirement for the FES is to perform each exchange in under 90s, with 100-μm positioning in the focal plane, while operating within the envelope of the camera body. The FES is split into three motorized subsystems: the Carousel stores the filters and rotates the selected filter to the standby position, the Autochanger moves the filter between the standby position and the focal plane, and the Loader can be mounted on the camera body to swap filters in and out during daytime, allowing the use of the full 6-filter set of LSSTCam. The locking mechanisms are also motorized, and their designs and qualifications account for seisms up to magnitude 7. Additional design constraints come from the temperature range at the Observatory and the cleanliness requirements for the filters and lenses. Programmable Logic Controllers enforce the safety equations of the system, and the control of the FES has been integrated into the overall Camera Control System software. After assembly of a full-scale prototype, the FES has been assembled and tested in France on a test-stand simulating telescope attitude, then integrated into the camera body at SLAC National Accelerator Laboratory. It meets its required performances, including an average exchange time of 83s.
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