The Giant Magellan Telescope (GMT) will feature two Gregorian secondary mirrors, an adaptive secondary mirror (ASM) and a fast-steering secondary mirror (FSM). The FSM has an effective diameter of 3.2 m and consists of seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment contains a tip-tilt capability for fast guiding to attenuate telescope wind shake and mount control jitter. This tiptilt capability thus enhances performance of the telescope in the seeing limited observation mode. The tip-tilt motion of the mirror is produced by three piezo actuators. In this paper we present a simulation model of the tip-tilt system which focuses on the piezo-actuators. The model includes hysteresis effects in the piezo elements and the position feedback control loop.
The Fast-steering Secondary Mirror (FSM) of Giant Magellan Telescope (GMT) consists of seven 1.1 m diameter circular segments with an effective diameter of 3.2 m, which are conjugated 1:1 to the seven 8.4 m segments of the primary. Each FSM segment contains a tip-tilt capability for fast guiding to attenuate telescope wind shake and mount control jitter by adapting axial support actuators. Breakaway System (BAS) is installed for protecting FSM from seismic overload or other unknown shocks in the axial support. When an earthquake or other unknown shocks come in, the springs in the BAS should limit the force along the axial support axis not to damage the mirror. We tested a single BAS in the lab by changing the input force to the BAS in a resolution of 10 N and measuring the displacement of the system. In this paper, we present experimental results from changing the input force gradually. We will discuss the detailed characteristics of the BAS in this report.
The Fast-Steering Secondary Mirror (FSM) of Giant Magellan Telescope (GMT) consists of seven 1.1m diameter segments with effective diameter of 3.2m. Each segment is held by three axial supports and a central lateral support with a vacuum system for pressure compensation. Both on-axis and off-axis mirror segments are optimized under various design considerations. Each FSM segment contains a tip-tilt capability for guiding to attenuate telescope wind shake and mount control jitter. The design of the FSM mirror and support system configuration was optimized using finite element analyses and optical performance analyses. The design of the mirror cell assembly will be performed including sub-assembly parts consisting of axial supports, lateral support, breakaway mechanism, seismic restraints, and pressure seal. . In this paper, the mechanical results and optical performance results are addressed for the optimized FSM mirror and mirror cell assembly, the design considerations are addressed, and performance prediction results are discussed in detail with respect to the specifications
The Giant Magellan Telescope (GMT) will be equipped with two Gregorian secondary mirrors; a fast-steering secondary mirror (FSM) for seeing-limited operations and an adaptive secondary mirror (ASM) for adaptive optics observing modes. The FSM has an effective diameter of 3.2 m and is comprised of seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary mirror. Each FSM segment has a tip-tilt capability for fast guiding to attenuate telescope wind shake and jitter. The FSM is mounted on a two-stage positioning system; a macro-cell that positions the entire FSM segments as an assembly and seven hexapod actuators that position and drive the individual FSM segments. In this paper, we present a technical overview of the FSM development status. More details in each area of development will be presented in other papers by the FSM team.
The Fast Steering Secondary Mirror (FSM) for the Giant Magellan Telescope (GMT) will have seven 1.05 m diameter circular segments and rapid tip-tilt capability to stabilize images under wind loading. In this paper, we report on the assembly, integration, and test (AIT) plan for this complex opto-mechanical system. Each fast-steering mirror segment has optical, mechanical, and electrical components that support tip-tilt capability for fine coalignment and fast guiding to attenuate wind shake and jitter. The components include polished and lightweighted mirror, lateral support, axial support assembly, seismic restraints, and mirror cell. All components will be assembled, integrated and tested to the required mechanical and optical tolerances following a concrete plan. Prior to assembly, fiducial references on all components and subassemblies will be located by three-dimensional coordinate measurement machines to assist with assembly and initial alignment. All electronics components are also installed at designed locations. We will integrate subassemblies within the required tolerances using precision tooling and jigs. Performance tests of both static and dynamic properties will be conducted in different orientations, including facing down, horizontal pointing, and intermediate angles using custom tools. In addition, the FSM must be capable of being easily and safely removed from the top-end assemble and recoated during maintenance. In this paper, we describe preliminary AIT plan including our test approach, equipment list, and test configuration for the FSM segments.
The Giant Magellan Telescope (GMT) will be equipped with two Gregorian secondary mirrors: a fast-steering mirror (FSM) system for seeing-limited operations and an adaptive secondary mirror (ASM) for adaptive optics observing modes. The FSM has an effective diameter of 3.2 m and is comprised of seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment has a tip-tilt capability for fast guiding to attenuate telescope wind shake and jitter. To verify the tip-tilt performance at various orientations, we performed tiptilt tests using a conceptual prototype of the FSM (FSMP) which was developed at KASI for R&D of key technologies for FSM. In this paper, we present configuration, methodology, results, and lessons from the FSMP test which will be considered in the development of FSM.
The Giant Magellan Telescope (GMT) will be featured with two Gregorian secondary mirrors, an adaptive secondary mirror (ASM) and a fast-steering secondary mirror (FSM). The FSM has an effective diameter of 3.2 m and built as seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope sub-apertures and fast guiding to attenuate telescope wind shake and mount control jitter. This tip-tilt capability thus enhances performance of the telescope in the seeing limited observation mode. As the first stage of the FSM development, Phase 0 study was conducted to develop a program plan detailing the design and manufacturing process for the seven FSM segments. The FSM development plan has been matured through an internal review by the GMTO-KASI team in May 2016 and fully assessed by an external review in June 2016. In this paper, we present the technical aspects of the FSM development plan.
The Miniature Exoplanet Radial Velocity Array (MINERVA) is a U.S.-based observational facility dedicated to the discovery and characterization of exoplanets around a nearby sample of bright stars. MINERVA employs a robotic array of four 0.7-m telescopes outfitted for both high-resolution spectroscopy and photometry, and is designed for completely autonomous operation. The primary science program is a dedicated radial velocity survey and the secondary science objective is to obtain high-precision transit light curves. The modular design of the facility and the flexibility of our hardware allows for both science programs to be pursued simultaneously, while the robotic control software provides a robust and efficient means to carry out nightly observations. We describe the design of MINERVA, including major hardware components, software, and science goals. The telescopes and photometry cameras are characterized at our test facility on the Caltech campus in Pasadena, California, and their on-sky performance is validated. The design and simulated performance of the spectrograph is briefly discussed as we await its completion. New observations from our test facility demonstrate sub-mmag photometric precision of one of our radial velocity survey targets, and we present new transit observations and fits of WASP-52b—a known hot-Jupiter with an inflated radius and misaligned orbit. The process of relocating the MINERVA hardware to its final destination at the Fred Lawrence Whipple Observatory in southern Arizona has begun, and science operations are expected to commence in 2015.
We present the science motivation, design, and on-sky test data of a high-throughput fiber coupling unit suitable for automated 1-meter class telescopes. The optical and mechanical design of the fiber coupling is detailed and we describe a flexible controller software designed specifically for this unit. The system performance is characterized with a set of numerical simulations, and we present on-sky results that validate the performance of the controller and the expected throughput of the fiber coupling. This unit was designed specifically for the MINERVA array, a robotic observatory consisting of multiple 0.7 m telescopes linked to a single high-resolution stabilized spectrograph for the purpose of exoplanet discovery using high-cadence radial velocimetry. However, this unit could easily be used for general astronomical purposes requiring fiber coupling or precise guiding.
The Zwicky Transient Facility (ZTF) is a synoptic optical survey for high-cadence time-domain astronomy. Building
upon the experience and infrastructure of the highly successful Palomar Transient Factory (PTF) team, ZTF will survey
more than an order of magnitude faster than PTF in sky area and volume in order to identify rare, rapidly varying optical
sources. These sources will include a trove of supernovae, exotic explosive transients, unusual stellar variables,
compact binaries, active galactic nuclei, and asteroids. The single-visit depth of 20.4 mag is well matched to
spectroscopic follow-up observations, while the co-added images will provide wide sky coverage 1.5 – 2 mag deeper
than SDSS. The ZTF survey will cover the entire Northern Sky and revisit fields on timescales of a few hours, providing
hundreds of visits per field each year, an unprecedented cadence, as required to detect fast transients and
variability. This high-cadence survey is enabled by an observing system based on a new camera having 47 deg<sup>2</sup> field of
view – a factor of 6.5 greater than the existing PTF camera - equipped with fast readout electronics, a large, fast
exposure shutter, faster telescope and dome drives, and various measures to optimize delivered image quality. Our
project has already received an initial procurement of e2v wafer-scale CCDs and we are currently fabricating the camera
cryostat. International partners and the NSF committed funds in June 2014 so construction can proceed as planned to
commence engineering commissioning in 2016 and begin operations in 2017. Public release will allow broad utilization
of these data by the US astronomical community. ZTF will also promote the development of transient and variable
science methods in preparation for the seminal first light of LSST.