Segment production for the Giant Magellan Telescope is well underway, with the off-axis Segment 1 completed, off-axis
Segments 2 and 3 already cast, and mold construction in progress for the casting of Segment 4, the center segment. All
equipment and techniques required for segment fabrication and testing have been demonstrated in the manufacture of
Segment 1. The equipment includes a 28 m test tower that incorporates four independent measurements of the segment's
figure and geometry. The interferometric test uses a large asymmetric null corrector with three elements including a 3.75
m spherical mirror and a computer-generated hologram. For independent verification of the large-scale segment shape,
we use a scanning pentaprism test that exploits the natural geometry of the telescope to focus collimated light to a point.
The Software Configurable Optical Test System, loosely based on the Hartmann test, measures slope errors to submicroradian
accuracy at high resolution over the full aperture. An enhanced laser tracker system guides the figuring
through grinding and initial polishing. All measurements agree within the expected uncertainties, including three
independent measurements of radius of curvature that agree within 0.3 mm. Segment 1 was polished using a 1.2 m
stressed lap for smoothing and large-scale figuring, and a set of smaller passive rigid-conformal laps on an orbital
polisher for deterministic small-scale figuring. For the remaining segments, the Mirror Lab is building a smaller, orbital
stressed lap to combine the smoothing capability with deterministic figuring.
The Giant Magellan Telescope (GMT) is 25 meter diameter extremely large ground based infrared/optical telescope
being built by an international consortium of universities and research institutions. It will be located at the Las
Campanas Observatory in Chile. The GMT primary mirror consists of seven 8.4 meter diameter borosilicate mirror
segments. Two seven segment Gregorian secondary mirror systems will be built; an Adaptive Secondary Mirror (ASM)
to support adaptive optics modes and a Fast-steering Secondary Mirror (FSM) with monolithic segments to support
natural seeing modes when the ASM is being serviced.
Wind excitation results in static deformation and vibration in the telescope structure that affects alignment and image
jitter performance. The telescope mount will reject static and lower frequency windshake, while each of the Faststeering
Secondary Mirror (FSM) segments will be used to compensate for the higher frequency wind-shake, up to 20
Hz. Using a finite element model of the GMT, along with CFD modeling of the wind loading on the telescope structure,
wind excitation scenarios were created to study the performance of the FSM and telescope against wind-induced jitter.
A description of the models, methodology and results of the analyses are presented.
The Giant Magellan Telescope active optics system is required to maintain image quality across a 20 arcminute diameter field of view. To do so, it must control the positions of the primary mirror and secondary mirror segments, and the figures of the primary mirror segments. When operating with its adaptive secondary mirror, the figure of the secondary is also controlled. Wavefront and fast-guiding measurements are made using a set of four probes deployed around the field of view. Through a set of simulations we have determined a set of modes that will be used to control fielddependent aberrations without degeneracies.
The Giant Magellan Telescope (GMT) is a 25.4-m diameter, optical/infrared telescope that is being built by an international consortium of universities and research institutions as one of the next generation of Extremely Large Telescopes. The primary mirror of GMT consists of seven 8.4 m borosilicate honeycomb mirror segments that are optically conjugate to seven corresponding segments in the Gregorian secondary mirror. Fabrication is complete for one primary mirror segment and is underway for the next two. The final focal ratio of the telescope is f/8.2, so that the focal plane has an image scale of 1.02 arcsec/mm. GMT will be commissioned using a fast-steering secondary mirror assembly comprised of conventional, rigid segments to provide seeing-limited observations. A secondary mirror with fully adaptive segments will be used in standard operation to additionally enable ground-layer and diffraction-limited adaptive optics. In the seeing limited mode, GMT will provide a 10 arcmin field of view without field correction. A 20 arcmin field of view will be obtained using a wide-field corrector and atmospheric dispersion compensator. The project has recently completed a series of sub-system and system-level preliminary design reviews and is currently preparing to move into the construction phase. This paper summarizes the technical development of the GMT sub-systems and the current status of the GMT project.
The Giant Magellan Telescope (GMT) is one of Extremely large telescopes, which is 25m in diameter featured with two Gregorian secondary mirrors, an adaptive secondary mirror (ASM) and a fast-steering secondary mirror (FSM). The FSM is 3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to the seven 8.4m segments of the primary. The guiding philosophy in the design of the FSM segment mirror is to minimize development and fabrication risks ensuring a set of secondary mirrors are available on schedule for telescope commissioning and early operations in a seeing limited mode. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope subapertures and fast guiding to attenuate telescope wind shake and mount control jitter, thus optimizing the seeing limited performance of the telescope. The final design of the FSM mirror and support system configuration was optimized using finite element analyses and optical performance analyses. The optical surface deformations, image qualities, and structure functions for the gravity print-through cases, thermal gradient effects, and dynamic performances were evaluated. The results indicated that the GMT FSM mirror and its support system will favorably meet the optical performance goals for residual surface error and the FSM surface figure accuracy requirement defined by encircled energy (EE80) in the focal plane. The mirror cell assembly analysis indicated an excellent dynamic stiffness which will support the goal of tip-tilt operation.
The preliminary design of the 25 m Giant Magellan Telescope (GMT) has been completed. This paper describes the design of the optics, structure and mechanisms, together with the rationales that lead to the current design. Analyses that were conducted to verify structure and optical performance are summarized. Science instruments will be mounted within the telescope structure. A common instrument de-rotator is provided to compensate for field rotation caused by the alt-az tracking of the telescope. The various instrument stations and provisions for mounting instruments are described. Post-PDR development plans for the telescope are presented.
The Giant Magellan Telescope (GMT) Fast Steering Secondary Mirror (FSM) is one of the GMT two Gregorian secondary mirrors. The FSM is 3.2 m in diameter and built as seven 1.06 m diameter circular segments. The conceiving philosophy used on the design of the FSM segment mirror is to minimize development and fabrication risks ensuring a set of secondary mirrors are available on schedule for telescope commissioning and early operations in a seeing limited mode, thereby mitigating risks associated with fabrication of the Adaptive Secondary Mirrors (ASM). This approach uses legacy design features from the Magellan Telescope secondary mirrors to reduce such risks. The final design of the substrate and support system configuration was optimized using finite element analyses and optical performance analyses. The optical performance predictions of the FSM are based on a substrate with a diameter of 1.058m (on-axis), 1.048m (off-axis), a depth of 120mm, and a face plate thickness of 20mm leading to a mass of approximately 90kg. The optical surface deformations, image qualities, and structure functions for the axial and lateral gravity print-through cases, thermal gradient effects, and dynamic performances were evaluated. The results indicated that the GMT FSM mirror and its support system will favorably meet the optical performance goals for residual surface error and the FSM surface figure accuracy requirement defined by encircled energy in the focal plane. The mirror cell assembly analysis indicated an excellent dynamic stiffness which will support the goal of 20 Hz tip-tilt motion.
Like many telescope projects today, the 24.5-meter Giant Magellan Telescope (GMT) is truly a complex system. The primary and secondary mirrors of the GMT are segmented and actuated to support two operating modes: natural seeing and adaptive optics. GMT is a general-purpose telescope supporting multiple science instruments operated in those modes. GMT is a large, diverse collaboration and development includes geographically distributed teams.
The need to implement good systems engineering processes for managing the development of systems like GMT becomes imperative. The management of the requirements flow down from the science requirements to the component level requirements is an inherently difficult task in itself. The interfaces must also be negotiated so that the interactions between subsystems and assemblies are well defined and controlled.
This paper will provide an overview of the systems engineering processes and tools implemented for the GMT project during the preliminary design phase. This will include requirements management, documentation and configuration control, interface development and technical risk management. Because of the complexity of the GMT system and the distributed team, using web-accessible tools for collaboration is vital. To accomplish this GMTO has selected three tools: Cognition Cockpit, Xerox Docushare, and Solidworks Enterprise Product Data Management (EPDM). Key to this is the use of Cockpit for managing and documenting the product tree, architecture, error budget, requirements, interfaces, and risks. Additionally, drawing management is accomplished using an EPDM vault. Docushare, a documentation and configuration management tool is used to manage workflow of documents and drawings for the GMT project. These tools electronically facilitate collaboration in real time, enabling the GMT team to track, trace and report on key project metrics and design parameters.
The Giant Magellan Telescope (GMT) is a 25.4-m optical/infrared telescope constructed from seven 8.4-m primary
mirror segments. The collecting area is equivalent to a 21.6-m filled aperture. The instrument development program was
formalized about two years ago with the initiation of 14-month conceptual design studies for six candidate instruments.
These studies were completed at the end of 2011 with a design review for each. In addition, a feasibility study was
performed for a fiber-feed facility that will direct the light from targets distributed across GMT's full 20 arcmin field of
view simultaneously to three spectrographs. We briefly describe the features and science goals for these instruments, and
the process used to select those instruments that will be funded for fabrication first. Detailed reports for most of these
instruments are presented separately at this meeting.
The GMT (Giant Magellan Telescope) is a large ground-based telescope for astronomical research at optical and infrared
wavelengths. The telescope is enclosed inside an Enclosure that rotates to follow the tracking of the telescope. The
Enclosure is equipped with adjustable shutters and vents to provide maximum ventilation for thermal control while
protecting the telescope from high wind loads, stray light, and severe weather conditions. The project will be built at Las
Campanas Observatory in Chile on Cerro Las Campanas. The first part of this paper presents the wind tunnel test data as
well as CFD (Computational Fluid Dynamics) study results for the GMT Enclosure. The wind tunnel tests include
simulations for: a) Topography, b) Open Enclosure (all the shutters and vents open), and c) Closed Enclosure (all the
vents and shutters closed). The CFD modeling was carried out for a wide range of conditions such as low and high wind
speeds at various wind directions, and for the fully open and partially open Enclosure. The second part of this paper
concerns the thermal effects of the Enclosure steel members. The wind speed and member sizes have been studied in
relation to the required time to reach a defined temperature inside the Enclosure. This is one of the key performance
characteristics of the Enclosure that can affect "Dome Seeing" significantly. The experimental data and theoretical
predications have been used to identify the areas inside the Enclosure that need to be ventilated. The Enclosure thermal
control strategy has been determined and an optimized system has been designed based on the final results.
The Giant Magellan Telescope (GMT) is a 25-meter optical/infrared extremely large telescope that is being built by an
international consortium of universities and research institutions. It will be located at the Las Campanas Observatory,
Chile. The GMT primary mirror consists of seven 8.4-m borosilicate honeycomb mirror segments made at the Steward
Observatory Mirror Lab (SOML). Six identical off-axis segments and one on-axis segment are arranged on a single
nearly-paraboloidal parent surface having an overall focal ratio of f/0.7. The fabrication, testing and verification
procedures required to produce the closely-matched off-axis mirror segments were developed during the production of
the first mirror. Production of the second and third off-axis segments is underway.
GMT incorporates a seven-segment Gregorian adaptive secondary to implement three modes of adaptive-optics
operation: natural-guide star AO, laser-tomography AO, and ground-layer AO. A wide-field corrector/ADC is available
for use in seeing-limited mode over a 20-arcmin diameter field of view. Up to seven instruments can be mounted
simultaneously on the telescope in a large Gregorian Instrument Rotator. Conceptual design studies were completed for
six AO and seeing-limited instruments, plus a multi-object fiber feed, and a roadmap for phased deployment of the GMT
instrument suite is being developed.
The partner institutions have made firm commitments for approximately 45% of the funds required to build the
telescope. Project Office efforts are currently focused on advancing the telescope and enclosure design in preparation for
subsystem- and system-level preliminary design reviews which are scheduled to be completed in the first half of 2013.
The Giant Magellan Telescope (GMT), one of several next generation Extremely Large Telescopes (ELTs), is a 25.4
meter diameter altitude over azimuth design set to be built at the summit of Cerro Campanas at the Las Campanas
Observatory in Chile. The primary mirror consists of 7 individual 8.4 meter diameter segments resulting in an equivalent
collecting area of a 21.5 meter diameter single mirror. The telescope structure, optics and instrumentation has a rotating
mass of approximately 1250 metric tons and stands approximately 40 meters tall. This paper reports the results of our
ongoing preliminary design and development of the GMT structure and its major mechanical and opto-mechanical
components. A major recent redesign of the Gregorian Instrument Rotator (GIR) resulted in significant changes to the
telescope structure and several mechanisms. Design trade studies of various aspects of the main structure, hydrostatic
bearing system, main axes drives, M2 positioner, M3 subsystem and the corrector-ADC subsystem have refined the
preliminary design in these areas.
The Giant Magellan Telescope (GMT) Fast-steering secondary mirror (FSM) is one of the GMT two Gregorian
secondary mirrors. The FSM is 3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to
the seven 8.4m segments of the primary. A parametric study and optimization of the FSM mirror blank and central
lateral flexure design were performed. For the optimized FSM configuration, the optical image qualities and structure
functions for the axial and lateral gravity print-through cases, thermal gradient effects, and dynamic performances will be
discussed. This paper reports performance predictions of the optimized FSM. To validate our lateral flexure design
concept, mechanical and optical tests were conducted on test mirrors installed with two different lateral flexures.
Cerro Las Campanas located at Las Campanas Observatory in Chile has been selected as the site for the Giant Magellan
Telescope. We report results obtained since the commencement, in 2005, of a systematic site testing survey of potential
GMT sites at LCO. Seeing data have been obtained at three potential sites, and are compared with identical data taken at
the site of the twin Magellan 6.5m telescopes. In addition, measurements of the turbulence profile of the free-atmosphere
have been collected. Co. Las Camapanas and the Magellan site are nearly identical in their seeing statistics, and
apparently their average ground-layer characteristics.
Cerro Las Campanas located at Las Campanas Observatory (LCO) in Chile has been selected as the site for the Giant
Magellan Telescope. We report results obtained since the commencement, in 2005, of a systematic site testing survey of
potential GMT sites at LCO. Atmospheric precipitable water vapor (PWV) adversely impacts mid-IR astronomy
through reduced transparency and increased background. Prior to the GMT site testing effort, little was known regarding
the PWV characteristics at LCO and therefore, a multi-pronged approach was used to ensure the determination of the
fraction of the time suitable for mid-IR observations. High time resolution monitoring was achieved with an Infrared
Radiometer for Millimeter Astronomy (IRMA) from the University of Lethbridge deployed at LCO since September of
2007. Absolute calibrations via the robust Brault method (described in Thomas-Osip et al.1) are provided by the
Magellan Inamori Kyocera Echelle (MIKE), mounted on the Clay 6.5-m telescope on a timescale of several per month.
We find that conditions suitable for mid-IR astronomy (PWV < 1.5 mm) are concentrated in the southern winter and
spring months. Nearly 40% of clear time during these seasons have PWV < 1.5mm. Approximately 10% of these nights
meet our PWV requirement for the entire night.
The 25-meter Giant Magellan Telescope (GMT) is one of the next generation of extremely large ground-based
optical/infrared telescopes. GMT is currently under development by a consortium of major US and international
university and research institutions. The telescope will be located at the Las Campanas Observatory in Chile. The GMT
Project is mid-way through its Design Development Phase. This paper summarizes the organizational structure and
status of the GMT Project and recent progress in the technical development of the various GMT subsystems.
The Giant Magellan Telescope (GMT) Mirror cells provide positioning, support, with active optics compensation, and
thermal control of the seven 8.4 meter primary mirror segments. Each mirror cell is a large steel welded structure, and in
the case of the outer off axis segments, is designed to be interchangeable for any one of the 6 possible mirror positions.
The mirror support and active optics compensation are provided through a series of single axis and three axis pneumatic
actuators that control the force used to support the mirror at a total of 165 positions and allows for support of the mirror
in any one of the six positions. Mirror positioning is provided by a stiff hexapod actuator system between the mirror and
the mirror cell. Mirror thermal control is provided by a series of fans that pressurize the mirror cell and condition the air
before it is directed into the mirror through 1700 nozzles.
Cerro Las Campanas located at Las Campanas Observatory (LCO) in Chile has been selected as the site for the Giant
Magellan Telescope. We report results obtained since the commencement, in 2005, of a systematic site testing survey of
potential GMT sites at LCO. Meteorological (cloud cover, temperature, pressure, wind, and humidity) and DIMM
seeing data have been obtained at three potential sites, and are compared with identical data taken at the site of the twin
Magellan 6.5m telescopes. In addition, measurements of the turbulence profile of the free-atmosphere above LCO have
been collected with a MASS/DIMM. Furthermore, we consider photometric quality, light pollution, and precipitable
water vapor (PWV). LCO, and Co. Las Campanas in particular, have dark skies, little or no risk of future light pollution,
excellent seeing, moderate winds, PWV adequate for mid-IR astronomy during a reasonable fraction of the nights, and a
high fraction of clear nights overall. Finally, Co. Las Campanas meets or exceeds all the defined science requirements.
The Giant Magellan Telescope (GMT) is a 24.5m diameter optical/infrared telescope. Its seven 8.4m primary mirrors
give it a collecting area equivalent to a 21.4m filled aperture. The ten GMT partners are constructing the telescope at the
Las Campanas Observatory in Chile with first light planned for the end of 2018. In this paper, we describe the plans for
the first-generation focal plane instrumentation for the telescope. The GMTO Corporation has solicited studies for
instruments capable of carrying out the broad range of objectives outlined in the GMT Science Case. Six instruments
have been selected for 14 month long conceptual design studies. We briefly describe the features of these instruments
and give examples of the major science questions that they can address.
The design of the adaptive optics (AO) system for the GMT is currently being developed. The baseline system is
planned around a segmented adaptive secondary mirror (ASM), with elements similar in size to current ASM's for 8 m
telescopes. A facility wavefront sensing system is planned to provide AO correction at several science instrument ports.
The AO system will contain a subsystem dedicated to controlling the relative phases between the seven segments of the
GMT aperture. The anticipated modes include natural guide star, laser tomography, and ground layer adaptive optics. A
cooled optical relay is described to provide baffling and reimaging of the focal plane to the various science ports. The
laser projection system will use six beacons on an adjustable radius to support both diffraction-limited and ground layer
correction modes. Modeling work, as well as science instrument design development will be integrated with this design
effort to develop a concept that provides efficient diffraction-limited performance and seeing-improved capabilities for
The GMT adaptive secondary mirror (ASM) is based on a "segmented" concept following the primary segment layout:
seven 1.05m diameter circular, independent adaptive mirrors are fed by the primaries and focus to the main telescope
focal stations. The adaptive unit's design is based on the consolidated thin mirror, contactless technology already
employed in several units (MMT, LBT, Magellan, VLT and one of the proposed E-ELT M4 designs), but nevertheless
the mirror's topology reveals several design challenges. In particular, the off-axis units are strongly aspheric and
therefore they require aspheric shaping of both thin mirror surfaces and of the thick reference body. The strong tilt of the
off-axis units forced us to consider a peculiar fine positioning hexapod design, maximizing its stiffness and also
implementing a special design of the last three rings of actuators to remain within the prescribed obstruction. From the
control point of view, the actuator density of the adaptive mirrors is remarkably lower than in all previous units: 672
actuators with 36mm spacing compared to 30mm typical separation adopted so far. This choice is validated by static and
dynamic performance computation though a sophisticated numerical simulator based on a full state space model
incorporating mechanics, control and fluid dynamics. The control system fulfills the dimensional constraints of the unit.
The design has completed the feasibility phase, including the cost estimate. The choice of making the GMT adaptive
secondary mirrors similar to the already existing ones strongly reduces the implementation risks and allows shortening
the remaining design path.
Modeling adaptive optics (AO) systems is crucial to understanding their performance and a key aid in their
design. The Giant Magellan Telescope (GMT) is planning three AO modes at first light: natural guide star AO,
ground-layer AO and laser tomography AO. This paper describes how a modified version of YAO, an open-source
general-purpose AO simulation tool written in Yorick, is used to simulate the GMT AO modes. The simulation
tool was used to determine the piston segment error for the GMT. In addition, we present a comparison of
different turbulence simulation approaches.
Las Campanas Observatory has been designated as the location for the Giant Magellan Telescope (GMT).
We report results obtained since the commencement, in 2005, of a systematic site testing campaign at LCO.
Meteorological (cloud cover, temperature, pressure, wind, and humidity) and DIMM seeing data have been
obtained at three potential sites, and are compared with identical data taken at the site of the twin Magellan
6.5m telescopes. In addition, measurements of the turbulence profile of the free-atmosphere above LCO have
been collected with a MASS/DIMM. We examine the contribution to the seeing arising from turbulence in the
ground layer (defined here as below an altitude of 500 m) through the difference between the turbulence integrals
in the full atmosphere (as measured by DIMM) and in the free atmosphere (as measured by MASS). Additionally,
we consider photometric quality, light pollution, and precipitable water vapor at LCO.
The Giant Magellan Telescope (GMT) is being developed by a consortium of major US and international educational
and research institutions. The 25 meter next-generation telescope will be located at Las Campanas Observatory in Chile.
The project has completed the conceptual design of the telescope and enclosure and is currently in the Design
Development Phase leading up to construction. Various refinements have been made to the telescope structure since the
Conceptual Design. These include the modification of the upper truss structure to reduce image blur due to wind shake
and the design of a 9 meter rotator for large Gregorian instruments. An integral field spectrograph has been added to the
candidate list of first-generation instruments. The primary mirror for GMT consists of seven 8.4 meter diameter
segments. The first of the six, highly aspheric, off-axis segments has been cast and generated at the University of
Arizona SOML with completion of the mirror expected in 2009. The metrology for polishing the segments is currently
being installed in the new test tower at SOML. Verification tests that independently measure the mirror figure have been
designed and are also being implemented. This paper summarizes the overall design and recent progress in the technical
development of GMT and in characterizing the site.
The conceptual design phase for the Giant Magellan Telescope (GMT) has been completed and the project is continuing
the development of the telescope structure and instrumentation. The upper truss of the telescope has been revised to
reduce the tilt of the secondary mirror assembly, which was the major contributor to image blur caused by windshake of
the structure. A factor of 5-10 reduction is obtained in the static analysis. The generation of the first 8.4 m off-axis
mirror blank for GMT is nearing completion. The metrology for grinding and polishing the mirror to its final figure has
been designed and is being constructed. Multiple, independent tests are provided to verify the final mirror figure and
insure mirror-to-mirror repeatability. Loose abrasive grinding and polishing of the mirror is ready to start with mirror
completion expected in early 2009. GMT instruments mount in the telescope below the primary mirror. The candidate
list of first generation instruments is provided. Las Campanas Observatory has been selected as the site for GMT.
The design, manufacture and support of the primary mirror segments for the GMT build on the successful primary mirror systems of the MMT, Magellan and Large Binocular telescopes. The mirror segment and its support system are based on a proven design, and the experience gained in the existing telescopes has led to significant refinements that will provide even better performance in the GMT. The first 8.4 m segment has been cast at the Steward Observatory Mirror Lab, and optical processing is underway. Measurement of the off-axis surface is the greatest challenge in the manufacture of the segments. A set of tests that meets the requirements has been defined and the concepts have been developed in some detail. The most critical parts of the tests have been demonstrated in the measurement of a 1.7 m off-axis prototype. The principal optical test is a full-aperture, high-resolution null test in which a hybrid reflective-diffractive null corrector compensates for the 14 mm aspheric departure of the off-axis segment. The mirror support uses the same synthetic floatation principle as the MMT, Magellan, and LBT mirrors. Refinements for GMT include 3-axis actuators to accommodate the varying orientations of segments in the telescope.
The Giant Magellan Telescope (GMT) is a collaborative effort between universities and research institutions to build a next-generation extremely large telescope for astronomical research at optical and infrared wavelengths. The GMT enclosure is cylindrical in shape and stands approximately 65 meters high. The telescope rotates independently of the enclosure down to a minimum elevation angle of 25°. This paper covers the decisions made during the conceptual design phase of the GMT enclosure, including an understanding of the facilities systems.
The Giant Magellan Telescope (GMT) is being developed by a consortium of universities and research institutions to address the science goals set forth in the National Academy of Sciences most recent Decadal Survey. The telescope will be located in northern Chile and used for astronomical research at wavelengths from the atmospheric UV cut-off through the mid-IR. The GMT is designed with a segmented primary mirror consisting of seven 8.4 meter diameter mirrors and will have a collecting area equal to a filled aperture 21.9 meter telescope and the diffraction limited performance of a 24.5 meter telescope in the IR. The design builds on technology in the areas of structures, mirror fabrication, adaptive optics, and instrumentation developed for the current generation 6.5 m and 8.4 m telescopes. The GMT Project has recently completed its Conceptual Design Phase. This paper summarizes the telescope and enclosure concepts, site evaluation, and the GMT program.
The Giant Magellan Telescope (GMT) is a joint project of a consortium of universities and research institutions to build and operate a 21.5-m equivalent aperture astronomical telescope for use at visible and IR wavelengths. This paper briefly summarizes the science goals for the project and provides an overview of the preliminary telescope and enclosure concepts and site test program. The telescope is a Gregorian design with a fast, f/0.7, primary mirror that allows a compact and stiff mount structure. The 25.3-meter diameter primary mirror consists of six off-axis 8.4-meter circular mirrors arranged in a hexagon around a center 8.4-meter mirror. The Gregorian secondary mirror is adaptive allowing two-mirror, wide-field adaptive optics. Several corrector designs have been studied for wide-field applications and one such design is shown. Instruments being considered for GMT provide a wide range of scientific capabilities. Instruments mount below the primary mirror on an instrument platform. Instrument mounting and servicing provisions are summarized.
The partners in the Magellan Telescopes have formed a core group to collaborate in a project whose goal is the design and construction of one or more 20-meter class telescopes. The conceptual design for the unit telescope is being developed and the status of the work is described here. The design is based on a segmented primary mirror consisting of six off-axis 8.4-meter mirrors arranged in a hexagon. Various concepts with additional mirrors filling in the center have been investigated. An adaptive Gregorian secondary mirror combines the beams in the telescope. The mirrors will be mounted in a single fully-steerable alt-az mount. Survey and testing of prospective sites is underway in Chile.
Commissioning of the two 6.5-meter Magellan telescopes is nearing completion at the Las Campanas Observatory in Chile. The Magellan 1 primary mirror was successfully aluminized at Las Campanas in August 2000. Science operations at Magellan 1 began in February 2001. The second Nasmyth focus on Magellan 1 went into operation in September 2001. Science operations on Magellan 2 are scheduled to begin shortly.
The ability to deliver high-quality images is maintained at all times by the simultaneous operation of the primary mirror support system, the primary mirror thermal control system, and a real-time active optics system, based on a Shack-Hartmann image analyzer. Residual aberrations in the delivered image (including focus) are typically 0.10-0.15” fwhm, and real images as good as 0.25” fwhm have been obtained at optical wavelengths.
The mount points reliably to 2” rms over the entire sky, using a pointing model which is stable from year to year. The tracking error under typical wind conditions is better than 0.03” rms, although some degradation is observed under high wind conditions when the dome is pointed in an unfavorable direction.
Instruments used at Magellan 1 during the first year of operation include two spectrographs previously used at other telescopes (B&C, LDSS-2), a mid-infrared imager (MIRAC) and an optical imager (MAGIC, the first Magellan-specific facility instrument). Two facility spectrographs are scheduled to be installed shortly: IMACS, a wide-field spectrograph, and MIKE, a double echelle spectrograph.
The Magellan active optics system has been operating continuously on the Baade 6.5-m since the start of science operations in February 2001. The active optical elements include the primary mirror, with 104 actuators, and the secondary mirror, with 5 positional degrees of freedom. Shack-Hartmann (SH) wavefront sensors are an integral part of the dual probe guiders. The probes function interchangeably, with either probe capable of guiding or wavefront sensing. In the course of most routine observing stars brighter than 17th magnitude are used to apply corrections once or twice per minute. The rms radius determined from roughly 250 SH spots typically ranges between 0.05" and 0.10". The spot pattern is analyzed in terms of a mixture of 3 Zernike polynomials (used to correct the secondary focus and decollimation) and 12 bending modes of the primary mirror (used to compensate for residual thermal and gravitational distortions). Zernike focus and the lowest order circularly symmetric bending mode, known affectionately as the "conemode," are sufficiently non-degenerate that they can be solved for and corrected separately.
Construction of the Magellan Project 6.5 meter telescopes is in progress. The enclosure for the first telescope is complete along with the auxiliary building that will house the coatings plant. The mount for the first telescope was shipped to Las Campanas Observatory in October 1997. Currently the telescope is being installed in its enclosure and will be cabled up and under test in the first half of 1998. Primary mirror #1 is being polished by the University of Arizona and will tested on its supports in the telescope cell prior to shipping in Chile in early 1999. The work of re-building the oven for casting the second Magellan mirror has just started. The development of the first suite of science instruments that will include visible band and 1 - 2.5 micron infrared multi-object spectrometers is underway. A two channel Echelle spectrometer is also planned. This paper summarizes the progress to date.
The WIYN 3.5 Meter Telescope enclosure was designed to minimize the effects of dome seeing. A combination of strategies is being used to achieve this goal including a well ventilated telescope chamber, low thermal inertia construction, active ventilation using fans, and utilization of surface coatings to control radiation losses. This paper presents the design approach and preliminary thermal measurements of the facility.
The WIYN Observatory is a joint project of the University of Wisconsin, Indiana University, Yale University and the National Optical Astronomy Observatories to build a 3.5 meter ground-based telescope on Kitt Peak, Arizona. The observatory is currently under construction and nearing completion. This paper presents the current status of the project.
The University of Wisconsin-Indiana University-National Optical Astronomy Observatories ('WIN') 3.5-m aperture telescope project's design concepts and development status are assessed. The WIN telescope employs a wide field of view in order to take advantage of recent advancements in multiobject fiber-optic spectroscopy. A novel support system is under development for the borosilicate honeycomb primary mirror blank which acts solely on the mirror's rear surface; mirror temperature will be actively controlled. The WIN telescope's control system will use a distributed, easily expanded and upgraded network of microprocessors connected to a master computer via serial bus.