We present SLIDE , a pipeline that enables transient discovery in data from the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), using archival images from the Dark Energy Camera as templates for difference imaging. We apply this pipeline to the recently released Data Preview 1 (DP1; the first public release of Rubin commissioning data) and search for transients in the resulting difference images. The image subtraction, photometry extraction, and transient detection are all performed on the Rubin Science Platform. We demonstrate that SLIDE effectively extracts clean photometry by circumventing poor or missing LSST templates. We identified 29 previously unreported transients, 12 of which would not have been detected based on the DP1 DiaObject catalog. SLIDE will be especially useful for transient analysis in the early years of LSST, when template coverage will be largely incomplete or when templates may be contaminated by transients present at the time of acquisition. We present multiband light curves for a sample of known transients, along with new transient candidates identified through our search. Finally, we discuss the prospects of applying this pipeline during the main LSST survey. Our pipeline is broadly applicable and will support studies of all transients with slowly evolving phases.

Resulting from its unusual optical configuration, the Vera C. Rubin Observatory requires precise top-end assembly (TEA) thermal control. The three-mirror system locates the large camera, the secondary mirror (M2), the secondary mirror hexapod, the camera hexapod/rotator, and associated electronics on the TEA. Escaping heat, or overcooling, crosses the optical path three times potentially significantly degrading the image quality. Most observatories follow a common thermal control strategy. A central refrigeration system, composed of chillers and pumps, supplies non-precision temperature-controlled ethylene glycol/water (EGW) coolant through long pipes, to the observatory’s subsystems including the general ones (Facility Services, Telescope machinery, etc.) and the scientific instrumentation. The refrigeration for the instrumentation is provided by EGW cooled secondary systems. The common strategy is inadequate for this application. For this application, since overcooling is just as detrimental as escaping heat, TEA thermal control is needed to levels impractical with the common strategy. Consequently, a new system was developed to provide superior thermal control. An intermediate cooling stage was added directly under the telescope. Using local chillers, recirculation pumps, and mixing valves, coolant is provided to the TEA at precise temperatures and flow rates. This system itself is cooled by EGW from the central refrigeration system. The location of the Camera, etc. on the TEA, over the main primary tertiary mirror (M1M3), produces a critical leak risk to the optical system. Many glycol/water leaks at different observatories have damaged critical electronics and optics elements. Consequently, less toxic and corrosive Dynalene was chosen, rather than the more common EGW.

The Rubin Observatory Commissioning Camera (ComCam) is a scaled down (144 Megapixel) version of the 3.2 Gigapixel LSSTCam which will start the Legacy Survey of Space and Time (LSST), currently scheduled to start in 2024. The purpose of the ComCam is to verify the LSSTCam interfaces with the major subsystems of the observatory as well as evaluate the overall performance of the system prior to the start of the commissioning of the LSSTCam hardware on the telescope. With the delivery of all the telescope components to the summit site by 2020, the team has already started the high-level interface verification, exercising the system in a steadystate model similar to that expected during the operations phase of the project. Notable activities include a simulated "slew and expose" sequence that includes moving the optical components, a settling time to account for the dynamical environment when on the telescope, and then taking an actual sequence of images with the ComCam. Another critical effort is to verify the performance of the camera refrigeration system, and testing the operational aspects of running such a system on a moving telescope in 2022. Here we present the status of the interface verification and the planned sequence of activities culminating with on-sky performance testing during the early-commissioning phase.

The Rubin Observatory's Simonyi Survey Telescope M1M3 is a lightweight honeycomb 8.4 meter Ohara E-6 borosilicate glass mirror, cast by the University of Arizona (UofA) Mirror Lab. It combines primary and tertiary mirror surfaces, hence its acronym. Its control software might be referenced as a 3rd generation UofA mirror active control system - after the Multiple Mirror Telescope's (MMT) and the Large Binocular Telescope Observatory's (LBTO). The control software uses a combination of LabVIEW Field Programmable Gate Array (FPGA),(1) C++ ("back office"), and Python/Web (Graphical User Interface (GUI)/Engineering User Interface (EUI) to control the mirror. With the telescope's first light expected soon, details of control software evolution, performed changes, as well as new development and status are described.

The Vera Rubin Observatory hosts a large (8.4 meter) wide-field (3.5 degree) survey telescope(4). The Secondary Mirror (M2) Assembly(6) and Camera(5) utilize large hexapods(3) to facilitate optical positioning relative to the Primary/Tertiary Mirror. These hexapods were designed, fabricated, assembled, tested and met all their requirements(1). Unfortunately, both hexapods were damaged prior to integration. The camera hexapod was damaged from overheating induced separation of the low temperature grease into constituents. The M2 hexapod was damaged from water intrusion during shipping. In both cases the critical linear encoders/tapes interior to the hexapod actuators were affected. These encoders are used by the control system to determine the length of the actuator during hexapod operations. If these encoders require servicing while deployed on the telescope, the hexapod needs to be unloaded by removing its optical payload (camera or M2), and the hexapod disassembled. The hexapod actuator then needs to be disassembled and repaired. This procedure produces an unacceptable risk to equipment, and an excessive disruption of observing. To rectify this, the actuators were redesigned to allow on-telescope servicing of these encoders. The encoder to tape orientation was inverted, and an access cover was added. This facilitates servicing the encoder/tape while on the telescope, reducing the servicing time from days to minutes. To improve reliability, alterations were also applied to the electrical system. The limit switch wiring was rearranged, and the cabling to the hexapod legs was upgraded. Also, multiple software upgrades were incorporated to improve function, performance, and compatibility with the other observatory systems.

The construction of the Vera C. Rubin Observatory is well underway, and when completed the telescope will carry out a precision photometric survey, scanning the entire sky visible from Chile every three days. The photometric performance of the survey is expected to be dominated by systematics; therefore, multiple calibration systems have been designed to measure, characterize and compensate for these effects, including a dedicated telescope and instrument to measure variations in the atmospheric transmission over the LSST bandpasses. Now undergoing commissioning, the Auxiliary Telescope system is serving as a pathfinder for the development of the Rubin Control systems. This paper presents the current commissioning status of the telescope and control software, and discusses the lessons learned which are applicable to other observatories.

Rubin Observatory’s Commissioning Camera (ComCam) is a 9 CCD direct imager providing a testbed for the final telescope system just prior to its integration with the 3.2-Gigapixel LSSTCam. ComCam shares many of the same subsystem components with LSSTCam in order to provide a smaller-scale, but high-fidelity demonstration of the full system operation. In addition, a pathfinder version of the LSSTCam refrigeration system is also incorporated into the design. Here we present an overview of the final as-built design, plus initial results from performance testing in the laboratory. We also provide an update to the planned activities in Chile both prior to and during the initial first-light observations.

The Vera C. Rubin Observatory is currently under construction on Cerro Pachon, in Chile. It was designed to conduct a 10-year multi-band survey of the southern sky with frequent re-visits (with both an intra- and extra-night cadence) to identify transient and moving objects. The mirror cell assembly was designed in Tucson, Arizona by the Rubin Observatory engineering department, and was tested twice in Tucson. The first testing campaign was performed at CAID industries, where the mirror cell was fabricated, using a steel mirror surrogate that has the same geometry and mass of the glass mirror(2,4). The glass mirror is a single monolith that contains both the primary and tertiary mirrors on a single substrate. The testing results confirmed that the mirror support system was performing within the design specifications, and that it was safe to install the glass mirror on the cell. The second test campaign was performed at the Richard F. Caris Mirror Lab of the University of Arizona using the actual glass mirror(16). This test campaign was performed under the test tower, which contains a vibration insensitive interferometer to measure mirror figure. This confirmed the mirror support system could achieve proper optical surface figure control for both primary and tertiary mirrors. After successful test campaigns at CAID, and the mirror Lab, the mirror cell assembly was disassembled, packed and shipped to the Rubin Observatory site at the Cerro Pachon summit in Chile. Upon arrival, the mirror cell has been integrated with the mirror surrogate once again to perform the third test campaign that confirmed the system has arrived safe and operational to the summit This integrated system will be tested on the telescope mount assembly to verify that it still meets it requirements under the effects of variations in gravitational orientation, and dynamic (slewing) loads.

We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the solar system, exploring the transient optical sky, and mapping the Milky Way. LSST will be a large, wide-field ground-based system designed to obtain repeated images covering the sky visible from Cerro Pachón in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg 2 field of view, a 3.2-gigapixel camera, and six filters ( ugrizy ) covering the wavelength range 320–1050 nm. The project is in the construction phase and will begin regular survey operations by 2022. About 90% of the observing time will be devoted to a deep-wide-fast survey mode that will uniformly observe a 18,000 deg 2 region about 800 times (summed over all six bands) during the anticipated 10 yr of operations and will yield a co-added map to r ∼ 27.5. These data will result in databases including about 32 trillion observations of 20 billion galaxies and a similar number of stars, and they will serve the majority of the primary science programs. The remaining 10% of the observing time will be allocated to special projects such as Very Deep and Very Fast time domain surveys, whose details are currently under discussion. We illustrate how the LSST science drivers led to these choices of system parameters, and we describe the expected data products and their characteristics.

The Large Synoptic Survey Telescope (LSST) Commissioning Camera (ComCam) is a smaller, simpler version of the full LSST camera (LSSTCam). It uses a single raft of 9 (instead of twenty-one rafts of 9) 4K x 4K LSST Science CCDs, has the same plate scale, and uses the same interfaces to the greatest extent possible. ComCam will be used during the Project’s 6-month Early Integration and Test period beginning in 2020. Its purpose is to facilitate testing and verification of system interfaces, initial on-sky testing of the telescope, and testing and validation of Data Management data transfer, infrastructure and algorithms prior to the delivery of the full science camera.

The Large Synoptic Survey Telescope (LSST) large field of view is achieved through a three-lens camera system and a three-mirror optical system comprised of a unique 8.4-meter diameter monolithic primary/tertiary mirror (M1M3) and a 3.4-meter diameter secondary mirror (M2)(1). The M2 is a 100mm thick meniscus convex asphere. The M2 Assembly includes a welded steel cell and a support system comprised of 72 axial and 6 tangential electromechanical actuators to control the mirror figure. The M2 Assembly (including optical polishing and integrated optical testing) is being fabricated by Harris Corporation in Rochester, NY. The summary status of this system and results are presented.

The Large Synoptic Survey Telescope(1) (LSST) is an altitude-azimuth mounted three mirror telescope and camera. The primary (M1) and tertiary (M3) mirrors are integrated into a single, monolithic borosilicate substrate 8.42 m diameter. The annular secondary (M2) mirror is located above the M1M3 mirror and the camera is nested inside the M2. The M1M3 mirror is supported on a mirror cell by two independent systems: one system is for Active Mode and the other for Static Mode. During observing, or Active Mode(2), the M1M3 mirror is supported by an array of 156 support and figure control actuators consisting of 268 pneumatic cylinders that react to gravity and inertial loads and provide figure error correction. Load cells on the actuators measure forces that are communicated to the M1M3 control system. However, the figure actuators do not define the mirror position. This is defined with six axially stiff linear actuators called hardpoints(3) arranged in a hexapod pattern to restrain rigid body motion of the mirror in a kinematic fashion. By adjusting the length of each hardpoint, the mirror can be adjusted in all six degrees of freedom with respect to the cell. Displacement sensors and load cells on the hardpoints communicate displacements and forces to the control system, which processes the telemetry and issues force corrections to the figure actuators to zero out any loads and moments on the hardpoints. In Static Mode, the M1M3 mirror is no longer supported by figure actuators and the position sensing of the hard point hexapod is inactive. A second support system consisting of 288 wire rope isolators called Static Supports come into play. The static supports mechanically capture the mirror whether in Active or Static Mode and in the event the mirror experiences motion beyond the active motion range in any direction. The static supports also safely support the mirror during seismic events for all elevation angles. In active mode, the static supports do not contact the mirror and thus, do not affect the mirror positioning or figure. This paper focuses on the detailed design, development, testing, integration, and current status of the M1M3 pneumatic figure actuators.

The Large Synoptic Survey Telescope is an 8.4m telescope now in construction on Cerro Pachon, in Chile. This telescope is designed to conduct a 10-year survey of the southern sky in which it will map the entire night sky every few nights. In order to achieve this goal, the telescope mount has been designed to achieve high accelerations that will allow the system to change the observing field in just 2 seconds. These rapid slews will subject the M1M3 mirror to high inertial and changing gravitational forces that has to be actively compensated for in order to keep the mirror safe, aligned, and properly figured during operations. The LSST M1M3 active support system is composed of six "hard point" actuators and 156 pneumatic actuators. The hard points define the mirror position in the mirror cell (with little or no applied force) and hold that position while observing in order to maintain the alignment of the telescope optics. The pneumatic actuators provide the force-distributed mirror support plus a known (static) figure correction as well as dynamic optical figure optimizations coming from other components of the Active Optics System. Optimizing this mirror support system required the introduction of innovative control concepts in the control loops (Inner and Outer). The Inner Loop involves an extensive pressure control loop to ensure precise force feedback for each pneumatic actuator while the Outer Loop includes telescope motion sensors to provide the real-time feedback to compensate for the changing external inertial and gravitational forces. These optimizations allow the mirror support system to maximize the hard point force-offloading while keeping the glass safe when slewing and during seismic events.

The Large Synoptic Survey Telescope (LSST) primary/tertiary (M1M3) mirror cell is a 25-ton, 9-meter x 9-meter x 2- meter steel weldment that supports the 19-ton borosilicate M1M3 monolith mirror on the telescope and acts as the lower vessel of the coating chamber when optically coating the mirror surfaces. The M1M3 telescope mirror cell contract was awarded to CAID Industries, Inc., of Tucson, Arizona in October 2015. After the mirror cell final acceptance in October 2017, the integration of the mirror support system started. The M1M3 cell assembly with the surrogate mirror will take place in a dedicated controlled-environment area at CAID Industries. All components of the mirror support system that were developed and tested by the LSST Telescope and Site M1M3 team at the NOAO offices in Tucson have been moved to CAID premises and have been integrated into the cell by a team of LSST, CAID and Richard F. Caris Mirror lab personnel. After completion of the cell integration and its assembly with the surrogate, a test phase that includes zenith and offzenith testing for the mirror support system will be carried by the LSST team. These tests aim to verify that the active support system components, mirror control, and software are performing as expected and the mirror support system is safe for the next step, the M1M3 cell to borosilicate glass assembly and tests at the RFC Mirror Lab of the University of Arizona.

This paper describes the status and details of the large synoptic survey telescope(1,2,3) mount assembly (TMA). On June 9th, 2014 the contract for the design and build of the large synoptic survey telescope mount assembly (TMA) was awarded to GHESA Ingenieria y Tecnologia, S. A. and Asturfeito, S. A. The design successfully passed the preliminary design review on October 2, 2015 and the final design review January 29, 2016. This paper describes the detailed design by subsystem, analytical model results, preparations being taken to complete the fabrication, and the transportation and installation plans to install the mount on Cerro Pachon in Chile. This large project is the culmination of work by many people and the authors would like to thank everyone that has contributed to the success of this project.

The Large Synoptic Survey Telescope (LSST) is currently under construction and upon completion will perform precision photometry over the visible sky at a 3-day cadence. To meet the stringent relative photometry goals, LSST will employ multiple calibration systems to measure and compensate for systematic errors. This paper describes the design and development of these systems including: a dedicated calibration telescope and spectrograph to measure the atmospheric transmission function, a collimated beam projector to characterize the spatial dependence of the LSST transmission function and a flat-field screen illumination system to measure the high-frequency variations in the global system response function.

The Large Synoptic Survey Telescope (LSST) has a 10 degrees square field of view which is achieved through a 3 mirror optical system comprised of an 8.4 meter primary, 3.5 meter secondary (M2) and a 5 meter tertiary mirror. The M2 is a 100mm thick meniscus convex asphere. The mirror surface is actively controlled by 72 axial electromechanical actuators (axial actuators). Transverse support is provided by 6 active tangential electromechanical actuators (tangent links). The final design has been completed by Harris Corporation. They are also providing the fabrication, integration and testing of the mirror cell assembly, as well as the figuring of the mirror. The final optical surface will be produced by ion figuring. All the actuators will experience 1 year of simulated life testing to ensure that they can withstand the rigorous demands produced by the LSST survey mission. Harris Corporation is providing optical surface metrology to demonstrate both the quality of the optical surface and the correctablility produced by the axial actuators.

The Large Synoptic Survey Telescope (LSST) primary/tertiary (M1M3) mirror cell assembly supports both on-telescope operations and off-telescope mirror coating. This assembly consists of the cast borosilicate M1M3 monolith mirror, the mirror support systems, the thermal control system, a stray light baffle ring, a laser tracker interface and the supporting steel structure. During observing the M1M3 mirror is actively supported by pneumatic figure control actuators and positioned by a hexapod. When the active system is not operating the mirror is supported by a separate passive wire rope isolator system. The center of the mirror cell supports a laser tracker which measures the relative position of the camera and secondary mirror for alignment by their hexapods. The mirror cell structure height of 2 meters provides ample internal clearance for installation and maintenance of mirror support and thermal control systems. The mirror cell also functions as the bottom of the vacuum chamber during coating. The M1M3 mirror has been completed and is in storage. The mirror cell structure is presently under construction by CAID Industries. The figure control actuators, hexapod and thermal control system are under developed and will be integrated into the mirror cell assembly by LSST personnel. The entire integrated M1M3 mirror cell assembly will the tested at the Richard F Caris Mirror Lab in Tucson, AZ (formerly Steward Observatory Mirror Lab).

The Large Synoptic Survey Telescope (LSST) is a large (8.4 meter) wide-field (3.5 degree) survey telescope, which will be located on the Cerro Pachon summit in Chile. Both the Secondary Mirror (M2) Cell Assembly and Camera utilize hexapods to facilitate optical positioning relative to the Primary/Tertiary (M1M3) Mirror. A rotator resides between the Camera and its hexapod to facilitate tracking. The final design of the hexapods and rotator has been completed by Moog CSA, who are also providing the fabrication and integration and testing. Geometric considerations preclude the use of a conventional hexapod arrangement for the M2 Hexapod. To produce a more structurally efficient configuration the camera hexapod and camera rotator will be produced as a single unit. The requirements of the M2 Hexapod and Camera Hexapod are very similar; consequently to facilitate maintainability both hexapods will utilize identical actuators. The open loop operation of the optical system imposes strict requirements on allowable hysteresis. This requires that the hexapod actuators use flexures rather than more traditional end joints. Operation of the LSST requires high natural frequencies, consequently, to reduce the mass relative to the stiffness, a unique THK rail and carriage system is utilized rather than the more traditional slew bearing. This system utilizes two concentric tracks and 18 carriages.

The Large Synoptic Survey Telescope (LSST) is an 8.4 meter, 3.5 degree, wide-field survey telescope. The survey mission requires a short slew, settling time of 5 seconds for a 3.5 degree slew. Since it does not include a fast steering mirror, the telescope has stringent vibration limitations during observation. Meeting these requirements will be facilitated by a stiff compact Telescope Mount Assembly (TMA) riding on a robust pier and by added damping. The TMA must also be designed to facilitate maintenance. The design is an altitude over azimuth welded and bolted assembly fabricated from mild steel.