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.
KEYWORDS: Mirrors, Field programmable gate arrays, LabVIEW, Telescopes, Control systems, Observatories, Human-machine interfaces, Control systems design, Telecommunications, Actuators, Borosilicate glass
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 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.
The Vera C. Rubin observatory will be performing numerous studies and high cadence surveys. In order to perform the surveys most efficiently, the observations need to be planned in an optimal way, taking into account numerous atmospheric effects such as the current weather conditions and cloud cover. Building on the heritage from the MASCARA station, the DREAM team is developing the cloud & transmission monitoring system. The DREAM station is an upgraded version of the MASCARA station, which has been already been successfully operational on La Palma, Canary Islands, Spain, and La Silla, Chile. Using a set of wide-field cameras, nearly the full local sky is imaged every 6.4 seconds. Using calibrated brightness measurements of all bright stars (V < 8.4) in the field of view, the transmission and extinction is monitored, at a 30-60 seconds cadence. DREAM is currently being assembled and tested in the Netherlands and is expected to be deployed on-site by the end of 2022.
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 is now under construction on Cerro Pachon in Chile. This ground-based facility is designed to conduct the Legacy Survey of Space and Time (LSST), which is a decade-long time-domain optical survey of the night sky. The system aberrations introduced by temperature gradients, hysteresis and other non-predictable errors can prevent the telescope from delivering a consistently high-quality image over its 3.5 degrees field of view, necessary to the LSST scientific goals. Therefore, the active optics system (AOS) uses a combination of an open-loop and a closed-loop correction. The AOS open-loop is planned to correct for typical gravity variations while the AOS closed-loop will correct the real-time (within 30s) system aberrations. The components used for this task consist mainly of: two mirrors with active support systems (M1M3 and M2), two hexapods and curvature wavefront sensors integrated to the focal plane of the science detector. By the beginning of 2019, both M1 and M3 mirrors had been extensively tested using interferometry techniques, providing necessary measurements to refine our Finite Element models. This will help to achieve higher image quality when integrating all mirrors on the telescope. Progress has also been made on the active optics pipeline, which allows for conversion of the wavefront sensor images into corrective data for the mirrors and hexapods. In this paper, we will present the main results from the mirror testing as well as predicted performance of the AOS using these results. Finally, we will discuss the test plan for commissioning the AOS on the telescope.
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...
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.
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