The M2 secondary mirror of the Vera C. Rubin Observatory, scheduled to be commissioned on-sky in 2024, will be the first active secondary mirror of 3.5m diameter in operation. Its substantial dimensions and advanced functionalities place it in league with the secondary mirrors of the upcoming 30m class telescopes. Characterizing its performance serves as a critical step towards comprehending and controlling the optics of the next generation of Extremely Large Telescopes (ELTs). This study focuses on testing and validating the M2 cell in the Observatory’s integration hall and at the Telescope Mount Assembly (TMA). We also report on the integration steps of the M2 cell onto the TMA itself, including installing the light baffle. During the testing campaign, the M2 cell is equipped with an aluminum mirror surrogate for safety reasons regarding the glass mirror. To ensure integrity when the thin glass mirror (10cm) is installed onto the telescope, the M2 support system must be actively controlled during any M2 cell movement. This prompted the development of a dedicated control system to enable closed loop mode for transporting the M2 cell with the glass mirror from the integration hall to the telescope. The tests in the integration hall were conducted with the M2 cell mounted on a rotating cart, allowing different orientations with respect to gravity as it will experience on the telescope. Upon reaching the telescope, static and dynamic tests are conducted at progressively higher telescope performance, increasing slewing speed, acceleration, and jerk. A significant novelty introduced by Rubin to astronomical instrumentation is the Verification & Validation architecture as part of the model-based Systems Engineering approach where requirements, test procedures and executions are merged into an interlaced and dynamic flow. This report presents the experimental results from the distinct test campaigns covering a wide range of M2 cell functionalities. These include characterization of actuator behavior in terms of maximum stroke and force limits, evaluation of closed-loop (active) and open-loop (passive) support system operation for the M2, system settling time and Force Balance response to different slewing speeds of the telescope.
Precision in optical alignment is crucial for optimizing image quality in astronomical telescopes, particularly for wide-field survey telescopes such as the Vera C. Rubin Observatory, which will conduct the Legacy Survey of Space and Time (LSST). This paper explores the deployment and efficacy of laser tracker technology, specifically the Leica AT960/930, in maintaining optical alignment of the Simonyi Survey Telescope within tens of microns. Initially suggested by Burge et al. in 2007, laser tracker technology has been instrumental in several major telescopes and is a cornerstone of operations at the Rubin Observatory, marking it as one of the first widefield telescopes to implement such advanced metrology. Here, we detail the process and outcomes of employing this technology in its integration, initial setup, and preliminary operations. In particular, we present detailed results on the structural flexure of the telescope at varying elevations, the effects of gravitational dynamics on the alignment of optical components, and the overall impact of azimuth and camera rotation on misalignments. Furthermore, our findings demonstrate that the operation of the laser tracker within the Active Optics System (AOS) allows realigning components within stringent tolerances in a single step, achieving near-perfect initial alignment. These capabilities demonstrate that we can achieve the necessary alignment for astronomical observations and establish a new benchmark for optical alignment in future large astronomical facilities.
The Vera C. Rubin Observatory is nearing completion, and we are embarking on a campaign to optimize the image quality during its upcoming 10-year optical survey. Here, we present the tools and methods we are implementing to disentangle and quantify the different sources of image degradation, as well as our plans to correct and mitigate as many of these different contributions to seeing as possible. The tools include an on-site Differential Image Motion Monitor (DIMM) for measuring atmospheric seeing, multiple 2D and 3D sonic anemometers for measuring in-dome wind speed and turbulence, and direct dome seeing monitors. We also implement a guider mode that allows data to be taken at 9Hz over small regions and a stuttered and streaked imaging mode that allows us to measure mount tracking and jitter and perform atmospheric tomography. Additionally, we use curvature wavefront sensing to estimate the residual wavefront error to support the telescope’s alignment and focus. This is the same algorithm that we will use for the Simonyi Survey Telescope. Many of these tools, as well as additional techniques to quantify the contribution of astigmatism to seeing, have been tested at the Auxiliary Telescope (AuxTel). This 1.2m telescope acts as a pathfinder for the Rubin Observatory. We present initial results and the creation of an image quality budget table for AuxTel to characterize and monitor significant sources of image quality degradation. We then discuss plans for implementing these techniques on the 8.4m Simonyi Survey Telescope.
The Vera C. Rubin Observatory is an integrated survey system, currently under construction in Chile, to accomplish a 10-year optical survey of the southern sky. The 8.4-meter Simonyi Survey Telescope mount is nearing completion and undergoing final verification and performance testing. Since the system is optimized for etendue, the telescope mount slewing performance is particularly critical to overall survey efficiency. For example, this high performance mount is required to slew 3.5 degrees, on the sky, and settle in a 4-second period. Here an account of the mount subsystem is presented and selected dynamic performance results from on-site testing are described.
The Vera C. Rubin Observatory is reaching the final stages of its construction and integration, advancing towards its 10-year Legacy Survey of Space and Time (LSST). One of the key milestones was the installation of the M1M3 Mirror Cell Assembly onto the Simonyi Survey Telescope’s (SST) Telescope Mount Assembly (TMA). The Cell Assembly actively supports the primary/tertiary mirror (M1M3), playing a crucial role in maintaining the glass safe and ensuring image quality. However, before the mirror glass installation, the Cell Assembly was installed on the TMA while supporting a steel surrogate M1M3 mirror. This surrogate closely mimics the glass mirror’s mass, center of gravity, and geometry. The M1M3 cell and surrogate were tested under conditions that simulate rapid field changes in the sky, which are essential for the observatory’s ambitious sky mapping schedule. These tests, extending from 1-100% of designed telescope slew velocities/accelerations, assessed the M1M3 active mirror support system, including the force balance system’s performance, the hardpoint behaviors, and the efficacy of the pneumatic figure control actuators. Preliminary results suggest the system meets operational requirements, ensuring safety and effectiveness at full speed.
The Simonyi Survey Telescope (formerly known as the Large Synoptic Survey Telescope) of the Rubin Observatory is an 8.4m telescope now in construction on Cerro Pachón, in Chile. This telescope has been designed to conduct a 10 years’ survey of the sky in which it will map the entire night sky every three nights. The Mirror Cell Assembly system is a 9x9m steel structure that provides positioning, support, figure correction and temperature control to the primary and tertiary mirror. It is composed of two main systems, the Support System and the Thermal Control System. The Support System provides positioning, support and figure control of the mirror as well as dynamic forces compensation. The Thermal Control System will control the bulk temperature and temperature variations throughout the mirror. The temperature variations produce thermal distortions of the mirror which produce image degrading distortion of the optical surface. Variations between the bulk temperature and the ambient degrade local seeing and can produce condensation. The mirror cell assembly was designed and build in Tucson, Arizona by the LSST engineering team, and was tested, to confirm correct integration, at the Richard F Caris Mirror Lab to confirm the optical performance of the system using the real glass mirror. After successful testing, the mirror cell assembly was disassembled, packed and shipped to the Cerro Pachón summit in Chile where it was integrated with the surrogate mirror, and installed on the telescope mount assembly (TMA) for system performance test. Once system performance test concluded, the mirror cell was transported to the maintenance level to remove the metal surrogate mirror, install the glass and coat. After coating the mirror, the mirror cell assembly will be integrated with the telescope mount assembly to conduct final testing and verification.
The Vera C. Rubin Observatory is an astronomical survey facility nearing completion in Chile. Its mission is to accomplish the 10-year Legacy Survey of space and Time (LSST) survey - a 6-color optical imaging survey of the southern sky. The science mission for the LSST resulted in demanding requirements for optical performance and system dynamics. Producing a Telescope and an Observatory meeting these requirements resulted in multiple technical challenges which were encountered and resolved during the design and construction of the project. Resolving these challenges has impacted the assembly and integration of the overall system. Analyses were performed and solutions were developed. This paper provides a general overview of these challenges and highlights some specific examples where resolutions were found and implemented.
The shipment of the LSST Camera from SLAC National Lab in California to Rubin Observatory in Chile was completed successfully in spring 2024 after extensive road and flight testing of the Camera’s shipping container. Prior to final shipment, two local driving tests and one full test shipment from California to Chile were completed with a mass simulator to validate the performance of the wire rope isolator system by collecting data on acceleration events and vibration modes. This paper presents the results from the second test drive as well as the final shipment of the LSST Camera and associated hardware to the observatory.
The Dutch Rubin Enhanced Atmospheric Monitor – DREAM – brings high-resolution, real-time information on all-sky transparency and cloud coverage to the Vera C. Rubin Observatory. Leveraging the MASCARA legacy, DREAM employs five wide-field cameras, pointing upward and in the four cardinal directions. It precisely measures the brightness of all bright stars (V < 8.4) with a cadence of 6.4 seconds. To disentangle instrumental and stellar brightness variations from transmission fluctuations, a comprehensive spatial-temporal calibration is applied. The resulting transmission variations are calibrated and processed to generate an all-sky image of transparency, providing the actual cloud cover at an approximate cadence of 30 seconds. DREAM also produces calibrated light curves for stars brighter than magnitude 8.4, extending the temporal coverage of the MASCARA southern hemisphere survey. Integrated and tested at Leiden Observatory in 2023, DREAM was shipped in November of the same year and installed in close proximity to the Vera C. Rubin Observatory. In its initial phase, DREAM supplies cloud coverage and transparency data to the Auxiliary Telescope. Once the LSST Camera of the Vera C. Rubin Observatory becomes operational, DREAM will play a crucial role in optimizing the survey strategy by providing input to the scheduler, particularly in non-photometric conditions.
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 steady state 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.
KEYWORDS: Observatories, System integration, Imaging systems, Data processing, Data acquisition, Control systems, Cameras, Telescopes, Image processing, Software development
The Rubin Observatory has entered its latter stages of the construction effort with system integration, test and commissioning. All system elements are coming together including components of the telescope, the science camera and software systems for control and data processing. In this paper we report on the progress, status, plans and schedule for integrating the system elements into a fully functional observatory to carry out the 10-year Legacy Survey of Space and Time.
In the last couple of years, the Rubin telescope and site subsystem has made tremendous progress and overcome a few challenges. The insulated cladding on the dome is done and work is now focused on finishing the louvers, weatherproof cladding, interior work, light baffles, and the final fabrications. This has been done concurrently with the installation of the telescope mount, now mostly complete and approaching the beginning of functional testing in September-October, 2022. While work is being done on these two major subsystems, other major components and systems are being integrated and tested in a system spread configuration: M1M3 & M2 mirrors, the camera hexapod/rotator and the control software, including elements of the active optics control and the commissioning camera. Finally, the calibration system - an important contributor to achieving the exquisite photometry required by the Legacy Survey of Space and Time (LSST) - is being finalized.
The Vera C. Rubin Observatory (Rubin Obs) (formerly Large Synoptic Survey Telescope - LSST) is an 8.4-m telescope, now under construction in Chile. In the last couple of years, the telescope has achieved tremendous progress, though like many other projects, progress has been curtailed for over six months due to the worldwide pandemic. This paper provides the high-level status of each of the telescope's subsystem. The summit facility (Cerro Pachon) and base facility (La Serena) have been substantially completed. The dome is expected to be finished by October of 2021, which will also allow the completion of integration and testing of the Telescope Mount Assembly (TMA). The integration and verification of the TMA is planned to be completed by the end of 2021. The two mirror systems, M1M3 and M2, have been fully tested under interferometers, showing they both satisfy their performance requirement, and both have been received at the summit facility. The M2 mirror has been successfully coated with protected aluminum, which is the first scientific coating produced by the new Rubin coating plant. The M1M3 mirror is planned to be coated with the same plant at the beginning of 2022. The auxiliary telescope and its principal spectrograph instrument, which will allow for real-time atmospheric characterization, has been commissioned. The Rubin environment awareness system (EAS), which includes the DIMM, weather station, all-sky camera, and facility environmental control, is operational. Significant progress has been made on the software for all of the above-mentioned subsystems, as well as the comprehensive telescope control system and the telescope operator interfaces.
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.
The Vera C. Rubin Observatory is a joint NSF and DOE construction project with facilities distributed across multiple sites. These sites include the Summit Facility on Cerro Pachón, Chile; the Base Facility in La Serena, Chile; the Project and Operations Center in Tucson, AZ; the Camera integration and testing laboratories at SLAC National Accelerator Laboratory in Menlo Park, CA; and the data support center based at the National Center for SuperComputing Applications at Urbana-Champaign, IL. The Rubin Observatory construction Project has entered its system integration and testing phase where major subsystem components are coming together and being tested and verified at a system level for the first time. The system integration phase of the Project requires a closely coordinated and organized plan to merge, manage, and be able to adapt the complex set of subsystems and activities across the entire observatory as real effects are discovered. In this paper we present our strategy to successfully complete integration, test and commissioning of the systems making up the Rubin Observatory. We include discussion on (i) our strategy for integration activities and the verification of requirements (ii) a brief summary of construction status at the time of this paper, (iii) early integration activities that are used to mitigate risks including the use of the Rubin Observatory's commissioning camera (ComCam), planning for the integration, testing and verification of the primary science instrument - LSSTCam, and lastly, (v) Science Verification through short concentrated survey-like campaigns. Throughout this paper we identify where key performance metrics are addressed that directly impact the Rubin Observatory's 10{year Legacy Survey of Space and Time (LSST) science capabilities - e.g. image quality, telescope dynamics, alert latency, etc...
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.
KEYWORDS: Large Synoptic Survey Telescope, Imaging systems, System integration, Cameras, Telescopes, Observatories, Data processing, Interfaces, Control systems, Computing systems
The Commissioning Phase of the LSST Project is the final stage in the combined NSF and DOE funded LSST construction project. The LSST commission phase is planned to start early in 2020 and be completed near the end of 2022, ending with the LSST Observatory system ready to start survey operations. Commissioning includes the assembly of the three principal subsystems (Telescope, Camera and Data Management) into the LSST Observatory System and the integration and test (AI&T) efforts as well as the science verification activities. The LSST System AI&T and Commissioning Plan is driven by a combination of engineering and scientifically oriented activities to show compliance with technical requirements and readiness to conduct science operations (acquiring data, processing data, and serving data and derived data products to users). LSST System AI&T and Commissioning will be carried out over four phases of activity: Phase-0) Pre-commissioning preparations (work breakdown structure; Phase-1) Early System AI&T with a commissioning camera (ComCam); Phase-2) Full System AI&T when the LSST Science Camera is shipped to Chile, integrated on the telescope and the data management system (DMS) is exercised with full scale data; and Phase-3) Science Validation where a series of mini-surveys are used to characterize the system with respect to the survey performance specifications in the SRD/LSR and functionality of the, leading to operations readiness. The Science Validation Phase concludes with an Operations Readiness Review (ORR).
The LSST System Assembly, Integration and Test and Commissioning effort has been planned out over several phases The first phase of commissioning under Early AI&T is designed to test and verify the system level interfaces using ComCam – a 144Mpixel imager utilizing the same control components as the full science camera. During this period, the telescope active optics system will be brought into compliance with system requirements; the scheduler will be exercised and all safety checks verified for autonomous operation; and early DM algorithm testing will be performed with on-sky data from ComCam using a commissioning computing cluster at the Base Facility.
The second phase of activities under Full System AI&T is designed to complete the technical integration of the three principal subsystems and EPO, show full compliance with system level requirements as detailed in the Observatory System Specifications and system level interface control documents, and provide full scale data for further DM/EPO software and algorithmic testing and development. System level requirements that flow directly to subsystems without any further derivation will be tested for compliance, at the subsystem level and below, under the supervision of Project Systems Engineering. This document includes the general approach and goals for these tests. It is expected that roughly four (4) months into the Full System AI&T phase the telescope and camera will be fully integrated and routinely producing science grade images over the full field of view (FOV), at which point “System First Light” will be declared. Following System First Light will be an intensive data acquisition period design to test the image processing pipelines and validate the derived science products that are to be delivered by the LSST survey.
The third and final phase of activities under Science Validation is designed to fully characterize the system performance specifications detailed in LSST System Requirements Document and the range of demonstrated performance per the LSST Science Requirements. These activities are based on the measured “On-Sky” performance and informed simulations of the LSST system.
In this paper we describe the inputs and assumptions to the commissioning plan, a summary of the activities in each phase, management strategies and expected outcomes.
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.
We present the design and lab performance of the Parallel Imager for Southern Cosmology Observations (PISCO), a photometer for the 6.5 m diameter Magellan telescopes that produces gl, rl, il, and zl band images simulta- neously within a 9 arcminute field of view. This design provides efficient follow-up observations of faint sources, particularly galaxy clusters and supernovae. Simultaneous imaging speeds the observing cadence by at a factor
of ~ 3 (including optical losses) compared to other photometric imagers. Also, the determination of color (flux
ratio between bands) is relatively immune to time variations in gray opacity due to clouds, so observations can
proceed in less than optimal conditions. First light is expected in September 2014 2014.
KEYWORDS: Control systems, Sensors, Telescopes, Data archive systems, Antennas, Human-machine interfaces, Bolometers, Data acquisition, Detection and tracking algorithms, Data storage
We present the software system used to control and operate the South Pole Telescope. The South Pole Telescope is
a 10-meter millimeter-wavelength telescope designed to measure anisotropies in the cosmic microwave background
(CMB) at arcminute angular resolution. In the austral summer of 2011/12, the SPT was equipped with a new
polarization-sensitive camera, which consists of 1536 transition-edge sensor bolometers. The bolometers are read
out using 36 independent digital frequency multiplexing (DfMux) readout boards, each with its own embedded
processors. These autonomous boards control and read out data from the focal plane with on-board software
and firmware. An overall control software system running on a separate control computer controls the DfMux
boards, the cryostat and all other aspects of telescope operation. This control software collects and monitors
data in real-time, and stores the data to disk for transfer to the United States for analysis.
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