Las Campanas Observatory (LCO) of the Carnegie Institution of Science has been operating in Chile for about 50 years, currently operating four main telescopes. Carnegie operates the two 6.5 meter Magellan telescopes on behalf of a partnership that includes a consortium of universities. The Magellan Telescopes were commissioned in 2000 and 2002 and offer the consortium users a suite of twelve instruments. In this paper we will first provide a brief description of the science, technical and administrative structure of the observatory. We will then present an updated review of the Magellan telescopes operations and maintenance. Details on status and performances of the instruments will be given. We will finally cover the operations of the duPont 2.5 meter and Swope 1 meter telescopes including the current and future collaboration with the two hemisphere surveys SDSS-IV and SDSS-V.
The Magellan Telescopes are a set of twin 6.5 meter ground based optical/near-IR telescopes operated by the Carnegie Institution for Science at the Las Campanas Observatory (LCO) in Chile. The primary mirrors are f/1.25 paraboloids made of borosilicate glass and a honeycomb structure. The secondary mirror provides both f/11 and f/5 focal lengths with two Nasmyth, three auxiliary, and a Cassegrain port on the optical support structure (OSS). The telescopes have been in operation since 2000 and have experienced several small earthquakes with no damage. Measurement of <i>in situ</i> response of the telescopes to seismic events showed significant dynamic amplification, however, the response of the telescopes to a survival level earthquake, including component level forces, displacements, accelerations, and stresses were unknown. The telescopes are supported with hydrostatic bearings that can lift up under high seismic loading, thus causing a nonlinear response. For this reason, the typical response spectrum analysis performed to analyze a survival level seismic earthquake is not sufficient in determining the true response of the structure. Therefore, a nonlinear transient finite element analysis (FEA) of the telescope structure was performed to assess high risk areas and develop acceleration responses for future instrument design. Several configurations were considered combining different installed components and altitude pointing directions. A description of the models, methodology, and results are presented.
The f/5 instrumentation suite for the Clay telescope was developed to provide the Magellan Consortium observer community with wide field optical imaging and multislit NIR spectroscopy capability. The instrument suite consists of several major subsystems including two focal plane instruments. These instruments are Megacam and MMIRS. Megacam is a panoramic, square format CCD mosaic imager, 0.4° on a side. It is instrumented with a full set of Sloan filters. MMIRS is a multislit NIR spectrograph that operates in Y through K band and has long slit and imaging capability as well. These two instruments can operate both at Magellan and the MMT. Megacam requires a wide field refractive corrector and a Topbox to support shutter and filter selection functions, as well as to perform wavefront sensing for primary mirror figure correction. Both the corrector and Topbox designs were modeled on previous designs for MMT, however features of the Magellan telescope required considerable revision of these designs. In this paper we discuss the optomechanical, electrical, software and structural design of these subsystems, as well as operational considerations that attended delivery of the instrument suite to first light.
The Magellan Baade and Clay telescopes regularly produce images of ~0.5" in natural seeing. We review efforts to
improve collimation, active optics response, and telescope guiding and pointing to optimize the performance of the
telescopes. Procedures have been developed to monitor and analyze image quality delivered by the imaging science
instruments. Improved models have been developed to correct for flexure of the telescope and primary mirror under
gravity loading. Collimation has been improved using a "two-probe" Shack-Hartman technique to measure field
aberrations. Field acquisition performance has been improved by implementing an open loop model for the primary
mirror control. Telescope pointing has been improved by regular monitoring and adjustments to improve acquisition
We have conducted extensive tests of both transmission and focal ratio degradation (FRD) on two integral field
units currently in use on the VIRUS-P integral field spectrograph. VIRUS-P is a prototype for the VIRUS
instrument proposed for the Hobby-Eberly Telescope at McDonald Observatory. All tests have been conducted
at an input f-ratio of F/3.65 and with an 18% central obscuration in order to simulate optical conditions on the
HET. Transmission measurements were conducted with narrow-band interference filters (FWHM: 10 nm) at 10
discrete wavelengths (337 to 600 nm), while FRD tests were made at 365 nm, 400 nm and 600 nm. The influence
of wavelength, end immersion, fiber type and length on both FRD and transmission is explored. Most notably,
we find no wavelength dependence on FRD down to 365 nm. All fibers tested are within the VIRUS instrument
specifications for both FRD and transmission. We present the details of our differential FRD testing method and
explain a simple and robust technique of aligning the test bench and optical fiber axes to within ±0.1 degrees.
The twin 6.5m Magellan Telescopes have been in routine operations at the Las Campanas Observatory in the Chilean
Andes since 2001 and 2002 respectively. The telescopes are owned and operated by Carnegie for the benefit of the
Magellan consortium members (Carnegie Institution of Washington, Harvard University, the University of Arizona,
Massachusetts Institute of Technology, and the University of Michigan). This paper provides an up to date review of the
scientific, technical, and administrative structure of the 'Magellan Model' for observatory operations. With a modest
operations budget and a reasonably small staff, the observatory is operated in the "classical" mode, wherein the visiting
observer is a key member of the operations team. Under this model, all instrumentation is supplied entirely by the
consortium members and the various instrument teams continue to play a critical support role beyond initial deployment
and commissioning activities. Here, we present a critical analysis of the Magellan operations model and suggest lessons
learned and changes implemented as we continue to evolve an organizational structure that can efficiently deliver a high
scientific return for the investment of the partners.
The Hobby-Eberly Telescope (HET) is an innovative large telescope of 9.2 meter aperture, located in West Texas at
McDonald Observatory. The HET operates with a fixed segmented primary and has a tracker which moves the four-mirror
corrector and prime focus instrument package to track the sidereal and non-sidereal motions of objects. The
HET has been taking science data for nearly a decade. Recent work has improved performance significantly, replacing
the mirror coatings and installing metrology equipment to provide feedback that aids tracking and alignment of the
primary mirror segments. The first phase of HET instrumentation included three facility instruments: the Low
Resolution Spectrograph (LRS), the Medium Resolution Spectrograph (MRS), and High Resolution Spectrograph
(HRS). The current status of these instruments is briefly described.
A major upgrade of HET is in progress that will increase the field of view to 22 arcminutes diameter, replacing the
corrector, tracker and prime focus instrument package. This wide field upgrade will feed a revolutionary new integral
field spectrograph called VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX).
VIRUS is a facility instrument that consists of 150 or more copies of a simple unit integral field spectrograph. In total
VIRUS will observe 34,000 spatial elements simultaneously, and will open up wide-area surveys of the emission-line
universe for the first time. We describe the HET wide field upgrade and the development of VIRUS, including results
from testing the prototype of the VIRUS unit spectrograph.
VIRUS is a planned integral-field instrument for the Hobby-Eberly Telescope (HET). In order to achieve a large field-of-view and high grasp at reasonable costs, the approach is to replicate integral-field units (IFU) and medium sized spectrographs many times. The Astrophysical Institute Potsdam (AIP) contributes to VIRUS with the development and testing of the IFU prototype. While the overall project is presented by Hill et al.<sup>1</sup>, this paper describes the opto-mechanical design and the manufacture of the fiber-based IFU subsystem. The initial VIRUS development aims to produce a prototype and to measure its performance. Additionally, techniques will be investigated to allow industrial replication of the highly specific fiber-bundle layout. This will be necessary if this technique is to be applied to the next generation of even larger astronomical instrumentation.
We present the design of, and the science drivers for, the <b>V</b>isible <b>I</b>ntegral-field <b>R</b>eplicable <b>U</b>nit <b>S</b>pectrograph (<b>VIRUS</b>). This instrument is made up of 145 individually small and simple spectrographs, each fed by a fiber integral field unit. The total VIRUS-145 instrument covers ~30 sq. arcminutes per observation, providing integral field spectroscopy from 340 to 570 nm, simultaneously, of 35,670 spatial elements, each 1 sq. arcsecond on the sky. This corresponds to 15 million resolution elements per exposure. VIRUS-145 will be mounted on the Hobby-Eberly Telescope and fed by a new wide-field corrector with 22 arcminutes diameter field of view. VIRUS represents a new approach to spectrograph design, offering the science multiplex advantage of huge sky coverage for an integral field spectrograph, coupled with the engineering multiplex advantage of >100 spectrographs making up a whole. VIRUS is designed for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) which will use baryonic acoustic oscillations imprinted on the large-scale distribution of Lyman-α emitting galaxies to provide unique constraints on the expansion history of the universe that can constrain the properties of dark energy.
The Hobby-Eberly Telescope (HET) is an innovative large telescope of 9.2 meter aperture, located in West Texas at McDonald Observatory. The HET operates with a fixed segmented primary and has a tracker which moves the four-mirror corrector and prime focus instrument package to track the sidereal and non-sidereal motions of objects. The HET has been taking science data for six years. Work over the past two years has improved performance significantly, replacing the mirror coatings and installing metrology equipment to provide feedback that aids tracking and alignment of the primary mirror segments. The first phase of HET instrumentation includes three facility instruments: the Low Resolution Spectrograph (LRS), the Medium Resolution Spectrograph (MRS), and High Resolution Spectrograph (HRS). The current status of these instruments is described. A major upgrade of HET is planned that will increase the field of view to 22 arcminutes diameter, replacing the corrector, tracker and prime focus instrument package. This wide field upgrade will feed a revolutionary new integral field spectrograph called VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX).
The HET is a modified Arecibo-style telescope with a segmented spherical primary and a four-mirror spherical
aberration corrector (SAC). Objects are tracked by driving the SAC along the focal sphere of the primary. In the original
design of the telescope the alignment of the SAC was to be maintained passively. In practice, this could not be done to
specifications, leading to degraded imaging quality. We have developed a metrology system to actively control the
alignment of the SAC. An autocollimator maintains the optical axis of the SAC normal to the primary mirror beneath it.
An absolute distance measuring interferometer (DMI) monitors the SAC/primary mirror distance, maintaining focus.
Both systems work at a wavelength of 1.5 microns, well above the operating wavelength of current or planned science
instruments and therefore do not interfere with observations. The performance of the system is measured via Hartmann
Several upgrades are implemented in the primary mirror control system, including calibration of individual edge
sensors, new control system software, and a new method of setting and controlling the overall radius of curvature of the
primary array. New techniques were developed to efficiently piston the segments onto the proper sphere radius.
A major performance upgrade for the Hobby-Eberly Telescope (HET) is in the conceptual design phase. The extensive upgrade will include a wide field optical corrector, a new HET tracker with increased payload capacity, and improved telescope pointing and tracking accuracy. The improvements will support the HET Dark Energy Experiment (HETDEX), which seeks to characterize the evolution of dark energy by mapping the imprint of baryonic oscillations on the large scale structure of the Universe. HETDEX will use the increased field-of-view and payload to feed an array of approximately 145 fiber-fed spectrometers, called VIRUS for "Visible Integral field Replicable Unit Spectrograph". The new corrector will have a science field-of-view diameter of 18 arcminutes, in contrast to the original corrector's 4 arcminute field, a twenty-fold increase in area. A new HET tracker with increased payload capacity will be designed to support the wide field corrector. Improved pointing and tracking will be accomplished using new autocollimation and distance measuring metrology combined with real-time wavefront sensing and correction. The upgrade will maintain operation of the current suite of facility instruments, consisting of low, medium, and high resolution spectrometers.
We investigate the role of industrial replication in the construction of the next generation of spectrographs for large telescopes. In this paradigm, a simple base spectrograph unit is replicated to provide multiplex advantage, while the engineering costs are amortized over many copies. We argue that this is a cost-effective approach when compared to traditional spectrograph design, where each instrument is essentially a one-off prototype with heavy expenditure on engineering effort. As an example of massive replication, we present the design of, and the science drivers for, the Visible IFU Replicable Ultra-cheap Spectrograph (VIRUS). This instrument is made up of 132 individually small and simple spectrographs, each fed by a fiber integral field unit. The total VIRUS-132 instrument covers ~29 sq. arcminutes per observation, providing integral field spectroscopy from 340 to 570 nm, simultaneously, of 32,604 spatial elements, each 1 sq. arcsecond on the sky. VIRUS-132 will be mounted on the 9.2 m Hobby-Eberly Telescope and fed by a new wide-field corrector with a science field in excess of 16.5 arcminutes diameter. VIRUS represents a new approach to spectrograph design, offering the science multiplex advantage of huge sky coverage for an integral field spectrograph, coupled with the engineering multiplex advantage of >102 spectrographs making up a whole.
The Hobby-Eberly Telescope (HET) is a fixed-elevation, 9.2-m telescope with a spherical primary mirror and a tracker at prime focus to follow astronomical objects. The telescope was constructed for $13.9M over the period 1994-1997. A series of extensive engineering upgrades and corrective actions have been completed recently, resulting in significantly improved delivered image quality and increased operational efficiency. The telescope's Spherical Aberration Corrector (SAC) optics were recoated with a highly reflective and durable broadband coating at Lawrence Livermore National Laboratory. The software mount model that maintains optical alignment of the SAC with the 11-m primary mirror array was recalibrated and improved. The acquisition and guiding optics for both the High Resolution Spectrograph (HRS) and the Low Resolution Spectrograph (LRS) were reworked and improved, allowing for better focus and SAC alignment monitoring and control. Recoating of the primary mirror segment array was begun. Telescope images of 0.82 arcseconds have been recorded for sustained periods in preliminary testing following the engineering upgrade, an improvement of 50% over previous best performance. Additional engineering upgrades are scheduled to consolidate these performance gains and to continue improving delivered image quality, throughput, and telescope operational efficiency. The HET is now capable of the science performance for which it was designed.
The Segment Alignment Maintenance System (SAMS) is a control system to maintain the alignment of the 91 segment Hobby-Eberly Telescope (HET) primary mirror array. The system was developed by Blue-Line Engineering (Colorado Springs, CO) and NASA-Marshall Space Flight Center (Huntsville-Al). The core of the system is a set of 480 inductive edge sensors which measure relative shear between adjacent segments. The relative shear is used to calculate segment tip/tilt and piston corrections. Although the system has dramatically improved the performance of the HET it does not meet its error budget due to thermal drifts in the sensors. The system is now sufficiently stable that it routinely requires only one primary mirror alignment at the beginning of the night. We describe methods to calibrate this sensor drift.
The Mirror Alignment Recovery System (MARS) is a Shack-Hartmann based sensor at the center of curvature (CoC) of the Hobby-Eberly Telescope (HET) spherical primary mirror used to align the 91 mirror segments. The instrument resides in a CoC tower next to the HET dome, a location which provides a challenging set of problems including wind shake and seeing from two different domes. The system utilizes an internal light source to illuminate the HET and a reference mirror to provide focused spot locations from a spherical surface. A custom lenslet array is sized to the HET pupil image, matching a single hexagonal lenslet to each mirror segment. Centroids of the HET mirror segment spots are compared to the reference spot locations to measure tip/tilt misalignments of each segment. A MARS proof-of-concept (POC) instrument, tested on the telescope in 2001, utilized a commercial wavefront sensor from Adaptive Optics Associates. The final system uses the same concept, but is customized for optimal performance on the HET.
MARS replaces previous burst-antiburst alignment techniques and provides a more intuitive method of aligning the primary mirror for telescope operators. The POC instrument has improved median HET stack sizes by 0.3" EE50, measured at the CoC tower. The current alignment accuracy is 0.14" rms (0.28" rms on the sky), resolution is 0.014", measurement precision is 0.027" rms, and segment capture range is ± 5". With continuing improvements in HET dome ventilation and the addition of software customized for removal of tower motion during measurement, the alignment accuracy is expected to reach approximately 0.04" rms in the final MARS, to be installed in late 2002.
The Hobby-Eberly Telescope (HET) is a fixed-elevation, 9.2-m telescope with a spherical primary mirror and a tracker at prime focus to follow astronomical objects. The telescope was constructed for $13.9M over the period 1994-1997. A number of telescope performance deficiencies were identified and corrected following construction. Remaining problems included: 1) Dome seeing, 2) inadequate initial mirror segment alignment accuracy, and 3) mirror segment misalignment with time. The HET Completion Project was created in May 2001 to attack these problems and to identify and solve the next tier of problems. To address dome seeing, large louvers were installed and in operation by May 2002. Efforts are also underway to eliminate or suppress heat sources within the dome environment. To address segment alignment accuracy, a prototype Shack-Hartmann device, the Mirror Alignment Recovery System (MARS), was built and is in routine use at HET. The Segment Alignment Maintenance System (SAMS) is in early operation and has markedly improved telescope performance. Two Differential Image Motion Monitor (DIMM) telescopes were brought into regular operation in July 2001 to quantify atmospheric seeing at HET. As these improvements have been implemented, telescope image quality has improved significantly. Plans are in place to address additional performance issues.
A sensing and control system for maintaining the optical alignment of the ninety-one 1-meter diameter hexagonal segments forming the Hobby-Eberly Telescope (HET) primary mirror array has been developed by NASA - Marshall Space Flight Center (Huntsville, AL) and Blue Line Engineering (Colorado Springs, CO) and implemented. This Segment Alignment Maintenance System (SAMS) employs 480 edge sensors to measure the relative shear motion between each segment edge pair and compute individual segment tip, tilt and piston position errors. Error information is sent to the HET primary mirror control system, which then corrects the physical position of each segment every 90 seconds. On-site installation of the SAMS sensors, ancillary electronics and software was completed in September 2001. Since that time, SAMS has undergone engineering testing. The system has operated almost nightly, improving HET's overall operational capability and image quality performance. SAMS has not yet, however, demonstrated performance at the specified levels for tip, tilt, piston and Global Radius of Curvature (GRoC) maintenance. Additional systems development and <i>in situ </i>calibration are expected to bring SAMS to completion and improved operation performance by the end of this year.