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.
This paper reports on progress and plans for all meta-components of the Large Synoptic Survey Telescope (LSST) observatory control system (OCS). After an introduction to the scope of the OCS we discuss each meta- component in alphabetical order: application, engineering and facility database, maintenance, monitor, operator- remote, scheduler, sequencer, service abstraction layer and telemetry. We discuss these meta-components and their relationship with the overall control and operations strategy for the observatory. At the end of the paper, we review the timeline and planning for the delivery of these items.
Construction of the Large Synoptic Survey Telescope system involves several different organizations, a situation that poses many challenges at the time of the software integration of the components. To ensure commonality for the purposes of usability, maintainability, and robustness, the LSST software teams have agreed to the following for system software components: a summary state machine, a manner of managing settings, a flexible solution to specify controller/controllee relationships reliably as needed, and a paradigm for responding to and communicating alarms. This paper describes these agreed solutions and the factors that motivated these.
The LSST communications middleware is based on a set of software abstractions; which provide standard interfaces for common communications services. The observatory requires communication between diverse subsystems, implemented by different contractors, and comprehensive archiving of subsystem status data. The Service Abstraction Layer (SAL) is implemented using open source packages that implement open standards of DDS (Data Distribution Service1) for data communication, and SQL (Standard Query Language) for database access. For every subsystem, abstractions for each of the Telemetry datastreams, along with Command/Response and Events, have been agreed with the appropriate component vendor (such as Dome, TMA, Hexapod), and captured in ICD's (Interface Control Documents).The OpenSplice (Prismtech) Community Edition of DDS provides an LGPL licensed distribution which may be freely redistributed. The availability of the full source code provides assurances that the project will be able to maintain it over the full 10 year survey, independent of the fortunes of the original providers.
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 Pachón 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) 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.
As astronomical instruments have increased in complexity, cost and production time, sharing a major instrument
between telescopes has become an attractive alternative to duplication. This requires solving technical and logistical
problems of transportation, transferring operational support knowledge between on-site staffs, and developing effective
responses to in-service problems at a different site. The infrared camera NEWFIRM has been operated for two years on
the 4-m Mayall telescope of Kitt Peak National Observatory in Arizona. We have recently temporarily moved it to the 4-
m Blanco telescope of Cerro Tololo Interamerican Observatory in Chile for a limited period of operation. We describe
here our solutions to the challenges involved in relocating this major in-service cryogenic instrument, with an emphasis
on "lessons learned" to date.
The WIYN High Resolution Infrared Camera (WHIRC) has been a general-use instrument at the WIYN telescope on
Kitt Peak since 2008. WHIRC is a near-infrared (0.8 - 2.5 μm) camera with a filter complement of J, H, Ks broadband
and 10 narrowband filters, utilizing a 2048 × 2048 HgCdTe array from Raytheon's VIRGO line, developed for the
VISTA project. The compact on-axis refractive optical design makes WHIRC the smallest near-IR camera with this
capability. WHIRC is installed on the WIYN Tip-Tilt Module (WTTM) port and can achieve near diffraction-limited
imaging with a FWHM of ~0.25 arcsec at Ks with active WTTM correction and routinely delivers ~0.6 arcsec FWHM
images without WTTM correction. During its first year of general use operation at WIYN, WHIRC has been used for
high definition near-infrared imaging studies of a wide range of astronomical phenomena including star formation
regions, stellar populations and interstellar medium in nearby galaxies, high-z galaxies and transient phenomena. We
discuss performance and data reduction issues such as distortion, pupil ghost, and fringe removal and the development of
new tools for the observing community such as an exposure time calculator and data reduction pipeline.
The LSST middleware design is based on a set of software abstractions; which provide standard interfaces for common communications services. The observatory requires communication between many subsystems, and comprehensive archiving of subsystem status data. Control commands as well as health and status data from across the observatory must be stored to support both the science data analysis, and trending analysis for the early detection of hardware anomalies.
The Service Abstraction Layer (SAL) is implemented using open source packages that implement open standards of DDS (Data DistributionService) for data communication and SQL for storage.
Designs for the automatic generation of code, documentation, and subsystem simulation, are being developed. Abstractions for the Telemetry datastreams, each with customized data structures, Command/Response, and the Logging and Alert messages are described.
NEWFIRM is the wide-field infra-red mosaic camera just delivered and commissioned on the Mayall 4-m telescope
on Kitt Peak. As with other major instrumentation projects, the software was part of a design, development,
implementation and delivery strategy. In this paper, we describe the final implementation of the NEWFIRM
software from acquisition within a MONSOON controller environment, directed by the observation control system,
to the quick-look functionality at the telescope and final delivery of standardized data products via the pipeline.
NEWFIRM is, therefore, the culmination of several years of design and development effort on several fronts.
We present the design overview and on-telescope performance of the WIYN High Resolution Infrared Camera
(WHIRC). As a dedicated near-infrared (0.8-2.5 μm) camera on the WIYN Tip-Tilt Module (WTTM), WHIRC will
provide near diffraction-limited imaging with a typical FWHM of ~0.25". WHIRC uses a 2048 x 2048 HgCdTe array
from Raytheon's VIRGO line, which is a spinoff from the VISTA project. The WHIRC filter complement includes J, H
KS, and 10 narrowband filters. WHIRC's compact design makes it the smallest near-IR camera with this capability. We
determine a gain of 3.8 electrons ADU-1 via a photon transfer analysis and a readout noise of ~27 electrons. A measured
dark current of 0.23 electrons s-1 indicates that the cryostat is extremely light tight. A plate scale of 0.098" pixel-1 results
in a field of view (FOV) of ~3' x 3', which is a compromise between the highest angular resolution achievable and the
largest FOV correctable by WTTM. Measured throughput values (~0.33 in H-band) are consistent with those predicted
for WHIRC based on an elemental analysis. WHIRC was delivered to WIYN in July 2007 and was opened for shared
risk use in Spring 2008. WHIRC will be a facility instrument at the WIYN telescope enabling high definition near-infrared
imaging studies of a wide range of astronomical phenomena including star formation regions, proto-planetary
disks, stellar populations and interstellar medium in nearby galaxies, and supernova and gamma-ray burst searches.
The Mayall 4-meter telescope on Kitt Peak is a successful and productive telescope now approaching its thirtieth anniversary. Originally designed at 150 inches, built at 158 inches, and with an effective aperture or 3.81m, it is from the generation of thick mirror, equatorially mounted telescopes. At a moderate altitude site, the Mayall had in the past upheld the prejudice that ground-based observing delivers about 1" seeing at best, and that it is no surprise to be considerably fuzzier. Changes in engineering, computer control, and our understanding of telescope seeing, have led to the new generation of lightweight mirrors with complex active support and advanced thermal control, running on altitude-azimuth mounts inside compact, low-volume enclosures. Such telescopes routinely deliver sub-arcsecond seeing, often down below 0.5" even from 'traditional' sites, and even sharper from higher and more remote sites to which access has been developed over recent decades. Nevertheless, what we have learned can be successfully applied to older telescopes: the Mayall telescope is a case in point, since it now regularly provides sub-arcsecond image quality. We discuss the significant improvements in thermal management and active control of the Mayall system over the last several years, as well as the difficulty of evaluating such changes, especially separating different effects. We also discuss future adjustments to and tuning of existing sub-systems, possible changes to the telescope environment, and planned new features. It takes effort and continual attention to detail, but older facilities can still be world class.
We have recently commissioned an active-optics upgrade for Kitt Peak National Observatory's 4 m Mayall telescope. The active-optics upgrade project is based largely on the CTIO 4 m upgrade and consists of three principle subsystems: (1) the 4 m Active Primary Support, (2) secondary mirror articulation and (3) a dedicated wavefront sensing system.
A framework for the construction of network services for observation planning and execution is presented. The framework is implemented using portable public domain software packages, and its components present a simple, self-descriptive application programming interface. Typical components are functionally independent units which can provide services to local/remote clients either via direct connections, or via a WWW gateway. A remote user or software-agent can query a component in order to discover the command set supported.
The complexity of modern astronomical instrumentation generates a large amount of status information for the operators to assess. In practice there is far more information than an individual can assimilate. In order to make optimum use of complex systems such as the WIYN active primary mirror system, it is essential that any system events which may impact on the quality of data be reported in a timely and comprehensible manner. Using toady's powerful workstations we can support the use of real-time visualization of telescope functions and system status. We have developed an interface to the commanding and status layers which allows us to take advantage of the anticipated potential for 3D, photorealistic, and virtual display technologies.