The Vera Rubin Observatory hosts a large (8.4 meter) wide-field (3.5 degree) survey telescope4. The Secondary Mirror (M2) Assembly6 and Camera5 utilize large hexapods3 to facilitate optical positioning relative to the Primary/Tertiary Mirror. These hexapods were designed, fabricated, assembled, tested and met all their requirements1. 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 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.
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 optical axis of a Nasmyth telescope should be perpendicular to the Elevation axis and pass through the rotational center of the Tertiary mirror turret rotator. Realized by aligning a laser beam to the rotational center of the two field derotators. A high precision Pentaprism mounted on the Tertiary mirror rotator deviates the laser beam by 90° defining the optical axis onto which the Primary and Secondary mirrors are mounted and aligned. We present method, procedure, tools and results for two examples of Nasmyth Telescopes; the 4.1m SOAR and the LSST's 1.2m Auxiliary Telescope.
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...
We describe the design and implementation of a fourth version of the TripleSpec near-infrared spectrograph (TSpec4). This version of the instrument was designed for and first implemented on the 4-m Blanco telescope on Cerro Tololo, and subsequently converted for use on the 4-m Southern Astrophysical Research (SOAR) Telescope on Cerro Pachon. Details of the changed opto-mechanical design and mounting arrangements are discussed. An updated data pipeline provides reduced spectra from the instrument. We describe the required modifications and the performance of both implementations of TSpec4.
The move from the Blanco to SOAR required changing from operation at a classical Cassegrain f/8 focus to operation at a Nasmyth f/16 focus. The SOAR mount also employs a rotator and required accommodation to a significantly different back-focal distance inside the instrument. These changes were implemented by modifying the instrument fore-optics which feeds light onto the slit at f/10.6. The spectrograph and slit viewer optics are unchanged. A dichroic reflects infrared light toward the instrument while passing visible light to a SOAR facility guider; this removes the shortest wavelengths from the spectra and in turn required modification of the data reduction pipeline.
As the telescopes have similar apertures, the performance of the instrument is similar on both, though on SOAR image quality is somewhat better and details of the instrument’s optical properties differ also. Flexure performance differs as well due to the different instrument locations.
The Southern Astrophysical Research (SOAR) 4.1m telescope, located in Cerro Pachón, Chile, has an active optics system that uses a Shack Hartmann wave front sensor to achieve optimal image correction and focus. This Calibration Wave Front Sensor (CWFS) has two detectors, one to acquire the star and the other to sense the wave front. In 2012 the acquisition camera failed, being replaced temporarily by an SBIG camera. We describe here a project to repair and upgrade the CWFS, extending the lifetime of this critical telescope component. The upgrade includes two new detectors and modifications to the existing software in order to communicate with the new cameras. Also, new mechanical supports were fabricated to mount the new cameras, and a new field flattener was designed for the acquisition camera. A laboratory rig with all the components was setup so to carry out extensive testing before installation on the telescope.
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 SOAR telescope was designed to have a bare Aluminum coating. This coating is performed in the Gemini-South sputtering facility. Two coatings have been done on the SOAR mirror (2004 and 2009). On both occasions, the reflectivity obtained for the UV-blue were lower than the reflectivity of the nominal bare Aluminum. Various tests have been done during 2018 and 2019, in order to reach a higher reflectivity in the UV, including changes in the coating recipe. We report here the progress to date, the performance that we have reached and the problems we have faced in this 8-meter coating facility.
The linear Atmospheric Dispersion Corrector has been operating at the SOuthern Astrophysical Research telescope since 2014. It was designed and built in collaboration between the University of North Carolina at Chapel Hill, and Cerro Tololo Inter-American Observatory. The device is installed in the elevation axis before the instruments mounted at the optical Nasmyth focus. It consists of two 300mm diameter sol-gel coated fused silica prisms, trombone mounted, which can be folded in or out of the beam. It is important for long slit spectroscopy, and essential for Multi-Object Slit spectroscopy. We present optical and mechanical designs, electronics and software control, and on-sky performance.
SAM (Soar Adaptive-optics Module), the SOAR (Southern Observatory for Astrophysical Research) GLAO facility is in service since 2011, with a UV, 355nm Laser Guide Star (LGS). The atmospheric wavefront error is therefore measured at 355nm and the star images are corrected in the visible range (BVRI bands). An ADC is required for High Resolution imaging at low telescope elevation, especially at shorter wavelengths of the visible spectrum. The ADC is based on 80mm diameter rotating prisms. This compact unit, fully automated, can be inserted or removed from the tightly constrained SAM collimated beam space-envelope, it adjusts to the parallactic angle and corrects the atmospheric dispersion. Here we present the optical and opto-mechanical design, the control design, the operational strategy and performance results obtained from extensive use in on-sky HR Speckle Imaging.
The f/8 RC-Cassegrain Focus of the Blanco Telescope at Cerro Tololo Inter-American Observatory, hosts two new instruments: COSMOS, a multi-object spectrograph in the visible wavelength range (350 – 1030nm), and ARCoIRIS, a NIR cross-dispersed spectrograph featuring 6 spectral orders spanning 0.8 – 2.45μm. Here we describe a calibration lamp unit designed to deliver the required illumination at the telescope focal plane for both instruments. These requirements are: (1) an f/8 beam of light covering a spot of 92mm diameter (or 10 arcmin) for a wavelength range of 0.35μm through 2.5μm and (2) no saturation of flat-field calibrations for the minimal exposure times permitted by each instrument, and (3) few saturated spectral lines when using the wavelength calibration lamps for the instruments. To meet these requirements this unit contains an adjustable quartz halogen lamp for flat-field calibrations, and one hollow cathode lamp and four penray lamps for wavelength calibrations. The wavelength calibration lamps are selected to provide optimal spectral coverage for the instrument mounted and can be used individually or in sets. The device designed is based on an 8-inch diameter integrating sphere, the output of which is optimized to match the f/8 calibration input delivery system which is a refractive system based on fused-silica lenses. We describe the optical design, the opto-mechanical design, the electronic control and give results of the performance of the system.
In recent years the V. M. Blanco 4-m telescope at Cerro Tololo Inter-American Observatory (CTIO) has been renovated for use as a platform for a completely new suite of instruments: DECam, a 520-megapixel optical imager, COSMOS, a multi-object optical imaging spectrograph, and ARCoIRIS, a near-infrared imaging spectrograph. This has had considerable impact, both internally to CTIO and for its wider community of observers. In this paper, we report on the performance of the renovated facility, ongoing improvements, lessons learned during the deployment of the new instruments, how practical operations have adapted to them, unexpected phenomena and subsequent responses. We conclude by discussing the role for the Blanco telescope in the era of LSST and the new generation of extremely large telescopes.
TripleSpec 4 (TS4) is a near-infrared (0.8um to 2.45um) moderate resolution (R ~ 3200) cross-dispersed spectrograph
for the 4m Blanco Telescope that simultaneously measures the Y, J, H and K bands for objects reimaged
within its slit. TS4 is being built by Cornell University and NOAO with scheduled commissioning in 2015.
TS4 is a near replica of the previous TripleSpec designs for Apache Point Observatory's ARC 3.5m, Palomar
5m and Keck 10m telescopes, but includes adjustments and improvements to the slit, fore-optics, coatings and
the detector. We discuss the changes to the TripleSpec design as well as the fabrication status and expected
sensitivity of TS4.
To substantially upgrade the Blanco telescope a new Dark Energy Camera (DECam)5 was developed. The Blanco telescope was commissioned in 1974 before the benefits of modern heavy instruments were foreseen. Consequently, the mass of DECam is greater than the original instrument payload. DECam was installed on the Blanco in 20121, 2. The telescope mount was rebalanced about the declination assembly by redesigning the Cassegrain cage to accommodate a significant increase in balancing mass. Finite element analysis was used to both determine the structural integrity of the new telescope configuration and to predict the effects of this added mass on the relative displacement between the primary and secondary mirrors. The counterweight system is described.
In an inauspicious start to the ultimately very successful installation of the Dark Energy Camera on the V. M. Blanco 4- m telescope at CTIO, the light-weighted Cer-Vit 1.3-m-diameter secondary mirror suffered an accident in which it fell onto its apex. This punched out a central plug of glass and destroyed the focus and tip/tilt mechanism. However, the mirror proved fully recoverable, without degraded performance. This paper describes the efforts through which the mirror was repaired and the tip/tilt mechanism rebuilt and upgraded. The telescope re-entered full service as a Ritchey- Chrétien platform in October of 2013.
KEYWORDS: Telescopes, Cameras, Mirrors, Control systems, Current controlled current source, Content addressable memory, Forward error correction, Actuators, Camera shutters, Chlorine
The Dark Energy Camera (DECam) is a new prime focus, wide-field imager for the V. M. Blanco 4-m telescope at CTIO. Instrumentation includes large, five-lens optical corrector mounted on hexapod mechanism for fine adjustment, filters, and a 519 Megapixel camera vessel; all integrated in a cage similar to the existing telescope prime focus structure. Currently Blanco allows a flip of this structure such that the f/8 secondary mirror, mounted on the back of the cage, points towards the primary mirror for Ritchey-Chretien observations. DECam will maintain this capability by attaching the existing F/8 mirror cell to the front of the new cage. Installation of this 8,600 kg instrument required the removal from the telescope of the primary mirror, the removal of the old prime focus assembly, and fine adjustment of large, over-constrained mechanisms followed by reassembly. A large facility shutdown was scheduled for this upgrade and several tools, fixtures, monitoring systems and procedures were developed in order to identify and then recover the optical alignment of the system, to control the distribution of stresses during tuning of the installation and to maintain the balance of the telescope with significant added mass. The final goal has been to maintain high performance of the telescope for both the existing f/8 Ritchey-Chretien focus mounted instruments and the new DECam instrument now in commissioning. The challenges presented in handling large elements, real-time monitoring, alignment, verification and feedback are described.
The Dark Energy Camera (DECam) has been installed on the V. M. Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. This major upgrade to the facility has required numerous modifications to the telescope and improvements in observatory infrastructure. The telescope prime focus assembly has been entirely replaced, and the f/8 secondary change procedure radically changed. The heavier instrument means that telescope balance has been significantly modified. The telescope control system has been upgraded. NOAO has established a data transport system to efficiently move DECam's output to the NCSA for processing. The observatory has integrated the DECam highpressure, two-phase cryogenic cooling system into its operations and converted the Coudé room into an environmentally-controlled instrument handling facility incorporating a high quality cleanroom. New procedures to
ensure the safety of personnel and equipment have been introduced.
The adaptive module of the 4-m SOAR telescope (SAM) has been tested on the sky by closing the loop on
natural stars. Then it was re-configured for operation with low-altitude Rayleigh laser guide star in early 2011.
We describe the performance of the SAM LGS system and various improvements made during one year of on-sky
tests. With acceptably small LGS spots of 1.6′′ the AO loop is robust and achieves a resolution gain of almost
two times in the I band, under suitable conditions. The best FWHM resolution so far is 0.25′′ over the 3′ field
of the CCD imager.
The V. M. Blanco 4-m telescope at Cerro Tololo Inter-American Observatory is undergoing a number of improvements
in preparation for the delivery of the Dark Energy Camera. The program includes upgrades having potential to deliver
gains in image quality and stability. To this end, we have renovated the support structure of the primary mirror,
incorporating innovations to improve both the radial support performance and the registration of the mirror and telescope
top end. The resulting opto-mechanical condition of the telescope is described. We also describe some improvements to
the environmental control. Upgrades to the telescope control system and measurements of the dome environment are
described in separate papers in this conference.
We present a progress report on the SOAR Adaptive Module, SAM, including some results of tests of the Natural
Guide Star mode: image correction in the visible, performance estimates, and experiments with lucky imaging.
We have tested methods to measure the seeing and the AO time constant from the loop data and compared
the results to those of the stand-alone site monitor. Measurements of the instrument throughput and telescope
vibrations are given. We report progress on the Laser Guide Star system implementation, including tests of the
UV laser, test of the beam transfer optics with polarization control. We present the designs of the laser launch
telescope and laser wavefront sensor.
The installation and commissioning of a new laser cutter facility in La Serena, Chile is a cooperative effort between Gemini Observatory and the Cerro Tololo Inter-American Observatory. This system enables the cutting of aluminum and carbon fiber slit masks for three multi-object spectrographs operating in Chile: GMOS-S, Flamingos-2, and Goodman spectrograph. Selection of the new laser cutter tool was based on slit mask specifications developed for two materials. Prior to the commissioning all slit mask production was performed at Gemini's Northern base facility with a similar laser cutter system. The new facility supports two observatories and enhances the capabilities for both. This paper will discuss the observatory arrangement with respect to mask data tracking and handling. The laser system and facility will be discussed along with mask cutting performance, process development and manufacturing methods.
The SOAR Adaptive Module (SAM) will compensate ground-layer atmospheric turbulence, improving image
resolution in the visible over a 3'x3' field and increasing light concentration for spectroscopy. Ground layer
compensation will be achieved by means of a UV (355nm) laser guide star (LGS), imaged at a nominal distance
of 10km from the telescope, coupled to a Shack-Hartmann wave front sensor (WFS) and a bimorph deformable
mirror. Unique features of SAM are: access to a collimated space for filters and ADC, two science foci, built-in
turbulence simulator, flexibility to operate at LGS distances of 7 to 14 km as well as with natural guide stars
(NGS), a novel APD-based two-arm tip-tilt guider, a laser launch telescope with active control on both pointing
and beam transfer. We describe the main features of the design, as well as operational aspects. The goal is to
produce a simple and reliable ground layer adaptive optics system. The main AO module is now in the integration
and testing stage; the real-time software, the WFS, and the tip-tilt guider prototype have been tested. SAM
commissioning in NGS mode is expected in 2009; the LGS mode will be completed in 2010.
The CTIO V. M. Blanco 4-m telescope is to be the host facility for the Dark Energy Survey (DES), a large area optical
survey intended to measure the dark energy equation of state parameter, w, to a precision of ˜ 5%. The survey is
expected to take 5 years and use a new 520 megapixel CCD prime focus imaging system: the Dark Energy Camera
(DECam). In preparation for the arrival of DECam, we plan numerous upgrades to the telescope, including a new
telescope control system optimized for programmed and queued survey observations, modifications to the telescope
itself to improve reliability and performance, extended real-time telemetry of site and facility characteristics, and a
distributed observer interface allowing for on- and off-site observations and real time quality control. These upgrades
are specifically motivated by the scientific goals of the DES but will also improve community use of the telescope.
The Infrared Side Port Imager ISPI is a facility infrared imager for
the CTIO Blanco 4-meter telescope. ISPI has the following capabilities: 1-2.4 micron imaging with an 2K x 2K HgCdTe array, 0.3
arcsec/pixel sampling matched to typical f/8 IR image quality of ~0.6
arcsec and a 10.5 x 10.5 arcmin field of view. First light with ISPI
was obtained on September 24 2002, and since January 2003 ISPI has
been in operation as a common user instrument. In this paper we discuss operational aspects of ISPI, the behavior of the array and we report on the performance of ISPI during the first one and half year of operation.
We briefly describe the SOAR Optical Imager (SOI), the first light instrument for the 4.1m SOuthern Astronomical Research (SOAR) telescope now being commissioned on Cerro Pachón in the mountains of northern Chile. The SOI has a mini-mosaic of 2 2kx4k CCDs at its focal plane, a focal reducer camera, two filter cartridges, and a linear ADC. The instrument was designed to produce precision photometry and to fully exploit the expected superb image quality of the SOAR telescope over a 5.5x5.5 arcmin2 field with high throughput down to the atmospheric cut-off, and close reproduction of photometric pass-bands throughout 310-1050 nm. During early engineering runs in April 2004, we used the SOI to take images as part of the test program for the actively controlled primary mirror of the SOAR telescope, one of which we show in this paper. Taken just three months after the arrival of the optics in Chile, we show that the stellar images have the same diameter of 0.74" as the simultaneously measured seeing disk at the time of observation. We call our image "Engineering 1st Light" and in the near future expect to be able to produce images with diameters down to 0.3" in the R band over a 5.5' field during about 20% of the observing time, using the tip-tilt adaptive corrector we are implementing.
The SOAR Telescope, near completion on Cerro Pachon - Chile, will carry Instrument Support Modules (ISMs) mounted at the two Nasmyth foci. Each ISM has three focal stations and is capable of making rapid instrument changes between them. Both ISMs also carry a Comparison Lamp System (CLS), guider and an acquisition camera, which are shared between the three instruments. One ISM supports IR instruments. The other is used for "Optical" instruments operating at wavelengths below 900nm. Beam steering mechanisms direct light from the SOAR science field or the CLS to the instrument in use. In the IR-ISM, light is sent to the lateral ports by dichroic mirrors which reflect IR and transmit wavelengths from 400-900nm to the guider. In the Optical-ISM, light is directed to the lateral ports by the use of first surface pick-off mirrors. Guiding is done off-axis. During operation, both ISMs can be rotated by 360° and must carefully control differential flexure between the guider and focal planes. A method of accurate relative flexure measurement has been developed where the ISM is rotated on its handling cart while carrying instrument mass simulators which reproduce its nominal payloads. In this paper, the ISM and its support sub-modules are described. Results of flexure measurements and tests of the CLS are provided.
The SOAR Optical Imager (SOI) is the commissioning instrument for the 4.2-m SOAR telescope, which is sited on Cerro Pachón, and due for first light in April 2003. It is being built at Cerro Tololo Inter-American Observatory, and is one of a suite of first-light instruments being provided by the four SOAR partners (NOAO, Brazil, University of North Carolina, Michigan State University). The instrument is designed to produce precision photometry and to fully exploit the expected superb image quality of the SOAR telescope, over a 6x6 arcmin field. Design goals include maintaining high throughput down to the atmospheric cut-off, and close reproduction of photometric passbands throughout 310-1050nm. The focal plane consists of a two-CCD mosaic of 2Kx4K Lincoln Labs CCDs, following an atmospheric dispersion corrector, focal reducer, and tip-tilt sensor. Control and data handling are within the LabVIEW-Linux environment used throughout the SOAR Project.
The new operations model for the CTIO Blanco 4-m telescope will use a small suite of fixed facility instruments for imaging and spectroscopy. The Infrared Side Port Imager, ISPI, provides the infrared imaging capability. We describe the optical, mechanical, electronic, and software components of the instrument. The optical design is a refractive camera-collimator system. The cryo-mechanical packaging integrates two LN2-cooled dewars into a compact, straightline unit to fit within space constraints at the bent Cassegrain telescope focus. A HAWAII 2 2048 x 2048 HgCdTe array is operated by an SDSU II array controller. Instrument control is implemented with ArcVIEW, a proprietary LabVIEW-based software package. First light on the telescope is planned for September 2002.
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