This PDF file contains the front matter associated with SPIE Proceedings Volume 8836, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

This study is trying to evaluate different lens barrel material, caused lens stress OPD (Optical Path Different) in different temperature condition. The Cassegrain telescope's correct lens assembly are including as correct lens, lens mount, spacer, mount barrel and retainer. The lens barrel initial design is made by invar, but system mass limit is need to lightweighting to meet requirement. Therefore, the lens barrel material is tried to replace to lower density material, such as aluminum and titanium alloy. Meanwhile, the aluminum or titanium alloy material properties CTE (Coefficient of Thermal Expansion) are larger then invar. Thus, the high CTE material will introduce larger thermal stress into the optical system in different temperature condition. This article is analysis the correct lens assembly thermal stress and optical performance in different lens mount material. From above conditions, using FEM (Finite Element Method) and optical software, simulation and optimization the lens mount to achieve system mass requirement.

ASTRI is an Flagship Project led by the Italian National Institute of Astrophysics, INAF, strictly linked to the development of the ambitious Cherenkov Telescope Array, CTA. Primary goal of the ASTRI project is the design, production, installation and calibration of an end-to-end Small Size Telescope prototype, devoted to the investigation of the highest gamma-ray energy band, from a fraction of TeV up to 100 TeV and beyond. The telescope, named ASTRI SST-2M, is mainly characterized by an optical system in dual-mirror configuration and by a modular camera at the curved focal surface composed of a matrix of Silicon Photo-Multipliers photo-sensors. In this paper we present an overview of the mechanical, thermal and electrical concept design of the camera and of the related technological solutions adopted for the ASTRI SST-2M prototype.

Optomechanical design considerations are presented in the development of a fiber-delivered three degree-offreedom displacement measuring interferometer. The tool can be used to simultaneously calibrate the linear motion and rotational errors of a translating stage using a single measurement beam incident on a plane mirror target. This novel interferometer incorporates a quadrant photodiode to measure four spatially separated interference signals all within a single optical interference beam, otherwise known as differential wavefront sensing. In post processing, a weighted phase average is created over symmetrically adjacent pairings of detector elements to decouple and measure displacement and changes in pitch and yaw. Design considerations include a custom displacement interferometer architecture, mechanical analyses and qualification testing of a working prototype. This interferometer has the potential for providing multi-DOF calibrations for precision motion stages.

A simple geometrical fiber optic vibration sensor is designed and demonstrated using fiber optic fused 2x2 coupler that utilizes the principle of reflection intensity modulation. The rational output is used to avoid the effects of source signal power fluctuations and fiber bending losses. The calibrated 1mm linear region of the displacement characteristic curve of the sensor having high sensitivity of 2.1 mV/mm (0.36 a.u. /mm) is considered for vibration measurement. The experimental results show that the sensor is capable to measure the frequency up to 3500 Hz with ~0.03μm resolution of vibration amplitude over a dynamic range of 0-1mm. The SNR of the rational output is also improved with respect to the sensing signal. In comparison with dual-fiber and bifurcated-bundle fiber, this sensor eliminates the dark region and front slope which facilitates the easy alignment. The simplicity of design, non-contact measurement, high degree of sensitivity, economical along with advantages of fiber optic sensors are attractive attributes of the designed sensor that lend to real time monitoring and embedded applications.

Raytheon Space and Airborne Systems (SAS) has designed, built and tested a 3.3-inch diameter fast steering mirror (FSM) for space application. This 2-axis FSM operates over a large angle (over 10 degree range), has a very high servo bandwidth (over 3.3 Khz closed loop bandwidth), has nanoradian-class noise, and is designed to support microradian class line of sight accuracy. The FSM maintains excellent performance over large temperature ranges (which includes wave front error) and has very high reliability with the help of fully redundant angle sensors and actuator circuits. The FSM is capable of achieving all its design requirements while also being reaction-compensated. The reaction compensation is achieved passively and does not need a separate control loop. The FSM has undergone various environmental testing which include exported forces and torques and thermal vacuum testing that support the FSM design claims. This paper presents the mechanical design and test results of the mechanism which satisfies the rigorous vacuum and space application requirements.

Extreme Lightweight ZERODUR® Mirrors, analyzed and described in our recent series of papers, have been demonstrated via a representative 1.2m diameter mirror (88% isogrid lightweighted with f0>200Hz). The attributes of such mirrors are suitable for spaceflight in sizes form < 0.5m to > 4m, while the manufacturing approach is compatible with attractive mirror substrate cost and delivery schedules. We will review manufacturing approach together with recent data on the low magnitude and homogeneity of the coefficient of thermal expansion, and on the toughness of the material. Simple ways to specify these mirrors are summarized.

Polymer matrix composites (PMCs) have been well established in optomechanical systems for several decades. The other three classes of composites; metal matrix composites (MMCs), ceramic matrix composites (CMCs), and carbon matrix composites (CAMCs) are making significant inroads. The latter include carbon/carbon (C/C) composites (CCCs). The success of composites has resulted in increasing use in consumer, industrial, scientific, and aerospace/defense optomechanical applications. Composites offer significant advantages over traditional materials, including high stiffnesses and strengths, near-zero and tailorable coefficients of thermal expansion (CTEs), tailorable thermal conductivities (from very low to over twice that of copper), and low densities. In addition, they lack beryllium’s toxicity problems. Some manufacturing processes allow parts consolidation, reducing machining and joining operations. At present, PMCs are the most widely used composites. Optomechanical applications date from the 1970s. The second High Energy Astrophysical Observatory spacecraft, placed in orbit in 1978, had an ultrahigh-modulus carbon fiber-reinforced epoxy (carbon/epoxy) optical bench metering structure. Since then, fibers and matrix materials have advanced significantly, and use of carbon fiber-reinforced polymers (CFRPs) has increased steadily. Space system examples include the Hubble Space Telescope metering truss and instrument benches, Upper Atmosphere Research Satellite (UARS), James Webb Space Telescope and many others. Use has spread to airborne applications, such as SOFIA. Perhaps the most impressive CFRP applications are the fifty-four 12m and twelve 7m moveable ground-based ALMA antennas. The other three classes of composites have a number of significant advantages over PMCs, including no moisture absorption or outgassing of organic compounds. CCC and CMC components have flown on a variety of spacecraft. MMCs have been used in space, aircraft, military and industrial applications. In this paper, we review key PMC, MMC, CCC, and CMC optomechanical system materials, including properties, advantages, disadvantages, applications and future developments. These topics are covered in more detail in SPIE short courses SC218 and SC1078.

In carbon fiber reinforced plastic (CFRP) optomechanical structures, particularly when embodying reflective optics, angular stability is critical. Angular stability or warping stability is greatly affected by moisture absorption and thermal gradients. Unfortunately, it is impossible to achieve the perfect laminate and there will always be manufacturing errors in trying to reach a quasi-iso laminate. Some errors, such as those related to the angular position of each ply and the facesheet parallelism (for a bench) can be easily monitored in order to control the stability more adequately. This paper presents warping experiments and finite-element analyses (FEA) obtained from typical optomechanical sandwich structures. Experiments were done using a thermal vacuum chamber to cycle the structures from −40°C to 50°C. Moisture desorption tests were also performed for a number of specific configurations. The selected composite material for the study is the unidirectional prepreg from Tencate M55J/TC410. M55J is a high modulus fiber and TC410 is a new-generation cyanate ester designed for dimensionally stable optical benches. In the studied cases, the main contributors were found to be: the ply angular errors, laminate in-plane parallelism (between 0° ply direction of both facesheets), fiber volume fraction tolerance and joints. Final results show that some tested configurations demonstrated good warping stability. FEA and measurements are in good agreement despite the fact that some defects or fabrication errors remain unpredictable. Design guidelines to maximize the warping stability by taking into account the main dimensional stability contributors, the bench geometry and the optical mount interface are then proposed.

Glass has been ignored by most of the structural engineering community because of its brittle nature. Glass is an indispensable material in optical systems and sometimes safety, even human safety, depends upon optical glass elements to behave in a structurally reliable manner. One such occasion is to accommodate survey cameras in transport-class aircraft. Fortunately, glass has reliable structural properties and the methods for structural analysis and testing for glass have been well developed. Unfortunately, the glass suppliers have not chosen to publish the appropriate strength properties for many of their glasses. This paper describes the physics of the strength of glass and the engineering application of that physics to an airborne survey aircraft for the safety of its inhabitants.

Gigapixel cameras using lens arrays can contain hundreds to thousands of precisely positioned optical components and thus require fast, reliable methods for optical assembly and alignment verification. Our first one-gigapixel prototype camera (AWARE-2) and our four-gigapixel camera currently under development (AWARE-10) need active alignment and performance measurement procedures during assembly to ensure high quality images. Here we describe the methods that we have developed to ensure proper positioning of all optical components in the AWARE-10 system and the resulting optomechanical design decisions. AWARE cameras employ a single monocentric objective lens that is shared by an array of smaller ”micro-cameras”, each composed of a set of smaller scale lenses. In AWARE-10, approximately two thousand pieces of individual optics must be aligned to a high level of accuracy in order to attain the desired optical resolution over four gigapixels. To guarantee proper alignment before final assembly, the objective lens and the micro-optics are checked separately. Using tools including auto-stigmatic microscopy, slanted edge MTF measurements, and flat field measurements, we can confirm the correct alignment of individual components before assembly. Optomechanical designs that incorporate the application of these alignment tools are described.

A fiber-optic sensor scheme, capable of the simultaneous measurement of pressure and temperature using two in-line Fiber Bragg Gratings (FBGs) is reported. Sensor head is configured by embedding the two FBGs with metal bellows, such that FBG1 is sensitive to both pressure and temperature, whereas FBG2 is only sensitive to temperature. High pressure sensitivity is achieved because of the lower spring rate in longitudinal direction to that of the large elastic modulus in transverse direction of the metal bellows. Pressure and temperature measurement is made by monitoring the shift of Bragg wavelengths of the FBGs corresponds to variation in pressure and temperature. From the test results, the obtained pressure and temperature sensitivities are 86 pm/psi and 9.17 pm/°C, over a dynamic range of 0-40 psi pressure, and 25-110°C temperature measurements respectively. The experimental results well agreed with the theoretical results and show good linearity. This simple design, economical and all fiber optic sensors can be used for liquid and gas pressure measurements, and under-water applications.

This paper is investigated to construct the self-developed fundamental capability which can apply to the opto-mechanical design and analysis in space telescope. The mounting mechanics is found to be a key issue to dramatically affect the optical performance in optical systems. Design and experiments are conducted to study the relationship between stresses and wavefront errors of the opto-mechanical systems by use of the interferometric measurement. Zernike polynomials and wavefront fitting is performed to study the mirror mounting mechanism. It is reported that mirror mounting stresses will severely affect the wavefront errors of the optical systems. Moreover, this investigation indicates that the external stresses will increase the wavefront errors, especially in the terms of astigmatism and trefoil. In addition, the transverse shear stress is more sensitive to degrade the optical performance in this opto-mechanical system design.

A new theoretical concept for stabilization of a line-of-sight through the use of the reaction between two inertial members is introduced. This concept is used to establish a mechanical configuration that will provide an immediate, real-time correction for platform rotational movement.

The advances in manufacturing techniques for lightweight mirrors, such as EXELSIS deep core low temperature fusion, Corning’s continued improvements in the Frit bonding process and the ability to cast large complex designs, combined with water-jet and conventional diamond machining of glasses and ceramics has created the need for more efficient means of generating finite element models of these structures. Traditional methods of assembling 400,000 + element models can take weeks of effort, severely limiting the range of possible optimization variables. This paper will introduce model generation software developed under NASA sponsorship for the design of both terrestrial and space based mirrors. The software deals with any current mirror manufacturing technique, single substrates, multiple arrays of substrates, as well as the ability to merge submodels into a single large model. The modeler generates both mirror and suspension system elements, suspensions can be created either for each individual petal or the whole mirror. A typical model generation of 250,000 nodes and 450,000 elements only takes 3-5 minutes, much of that time being variable input time. The program can create input decks for ANSYS, ABAQUS and NASTRAN. An archive/retrieval system permits creation of complete trade studies, varying cell size, depth, and petal size, suspension geometry with the ability to recall a particular set of parameters and make small or large changes with ease. The input decks created by the modeler are text files which can be modified by any text editor, all the shell thickness parameters and suspension spring rates are accessible and comments in deck identify which groups of elements are associated with these parameters. This again makes optimization easier. With ANSYS decks, the nodes representing support attachments are grouped into components; in ABAQUS these are SETS and in NASTRAN as GRIDPOINT SETS, this make integration of these models into large telescope or satellite models easier.

Advances in mirror fabrication are making very large space based telescopes possible. In many applications, only monolithic mirrors can meet the performance requirements. The existing and near-term planned heavy launch vehicles place a premium on lowest possible mass, and then available payload shroud sizes limit near term designs to 4 meter class mirrors. Practical 8 meter class and beyond designs could encourage planners to include larger shrouds, if it can be proven that such mirrors can be manufactured. These two factors, lower mass and larger mirrors, present the classic optimization problem. There is a practical upper limit to how large of a mirror can be supported by a purely kinematic mount system handling both operational and launch loads. This paper shows how the suspension system and mirror blank need to be designed simultaneously. We will also explore the concepts of auxiliary support systems which act only during launch and disengage on orbit. We will define required characteristics of these systems and show how they can substantially reduce the mirror mass.

The paper is aimed at obtaining the optimum isostatic mount configuration for a ZERODUR® primary mirror with a predesigned lightweight configuration on the back for a space Cassegrain telescope. The finite element analysis and Zernike polynomial fitting based on the Taguchi method are applied to the whole optimization process. Under the integrated optomechanical analysis, three isostatic mounts are bonded to the center of gravity of the mirror. Geometrical control factors and levels have been selected to minimize the optical aberrations under self-weight loading. The optimum isostatic mount with the least induced astigmatism value is finally attained under the Taguchi method.

Launching a precision optical instrument, such as a laser, into space presents a challenge due to the harsh structural and acoustic coupled loads that result from the launch vehicle engines. Special precautions must be implemented to protect the payload and attenuate the high frequency random vibration environment while still maintaining accurate alignment and beam pointing. Fibertek has designed, analyzed, and tested novel Ti6Al4V flexures for isolating a space laser from a high g-load random vibration launch environment. Detailed finite element analysis was done to verify structural integrity of flight hardware by assessing the applied loads, load paths, and critical failure modes. Experimental data validated the modeling and the overall conclusions.

Lens positioning accuracy and manufacturing cost are two main concerns for optomechanical engineers looking for solutions to reduce costs while meeting stringent optical and environmental requirements. Minimizing optical component positioning errors generally translates into significant cost increases. To maximize the precision-to-cost ratio, there are significant advantages in having both an accurate optomechanical tolerance calculation method and an effective technique to mount and align lenses. This paper presents a tool that has been developed at INO to easily perform complex optomechanical statistical tolerancing using Monte Carlo simulation to reduce manufacturing and alignment costs. This tolerancing method provides a more realistic prediction of optical component errors compared to the classical worst case and root sum square calculations. In addition, precision alignment using elastomeric lens mounting is presented. Thermal stability and often overlooked factors for effective alignments are discussed. Results of tests performed on real optical assemblies are presented for tolerancing, thermal stability and alignment performance. The use of these methods can considerably reduce cost while efficiently ensuring compliance with requirements.

This paper highlights a mounting solution for miniature, high aspect ratio Zinc Selenide (ZnSe) optics capable of sustaining high vibration loads and cryogenic temperatures. The GOES-R Advanced Baseline Imager (ABI) optical design requires ZnSe filters that have a significantly higher-than-standard aspect ratio. The thin structure, along with the material properties of ZnSe, lead to a filter that is very delicate. The mounting technique minimizes stresses induced over thermal extremes, while maintaining sufficient preload for launch loads. The filters are mounted to metallic housings using a spring loaded retainer and compliant materials. Detailed analysis of the mounting and an understanding of the unique material properties enables the design to be successful. Special attention is given to materials passing through glass transition temperatures. This design was qualified through extensive thermal cycling and vibration testing, and exhibited performance acceptable for production.

Kirkpatrick-Baez (K-B) mirrors ^[1] are sophisticated x-ray micro- and nano-focusing tools for synchrotron radiation applications. A prototype of a modular x-ray K-B mirror mount system has been designed and tested at an optics testing beamline, 1-BM at the Advanced Photon Source (APS), Argonne National Laboratory (ANL). This compact, costeffective modular mirror mount system is designed to meet challenging mechanical and optical specifications for producing high positioning resolution and stability for various scientific applications with focused hard x-ray beams down to the 100-nanometer scale. The optomechanical design of the modular x-ray K-B mirror mount system as well as the preliminary test results of its precision positioning performance are presented in this paper.

This paper illustrates an athermal mounting for a Zinc Selenide (ZnSe) optic in an AlBeMet housing for use at cryogenic temperatures. The GOES-R Advanced Baseline Imager (ABI) instrument beamsplitter utilizes this design and the difficulty is the significant delta in the coefficient of thermal expansion (CTE) between the housing and the optic. The high discrepancy in CTE is exacerbated by a large thermal range from an ambient assembly to cryogenic operational temperature. The assembly utilizes CTE matched clips bonded to the optic using a well controlled bondline. The clips are attached to an optimized spacer of a high CTE material that is used to reduce the CTE mismatch. The spacers are coupled to a four flexure design that is symmetric in both axes. The net effect reduces the apparent CTE between the optic and the housing in a space constrained mounting. The flexures allow the final small amount of expansion room that the assembly requires as it goes over a large temperature swing. This design was qualified through extensive thermal cycling and vibration testing, and exhibited performance acceptable for production.

The Interface Region Imaging Spectrograph (IRIS) is a NASA SMall Explorer (SMEX) mission launched onboard a Pegasus™ booster on June 27, 2013. The spacecraft and instrument were designed and built at the Lockheed Martin Space Systems Company. The primary mission goal is to learn how the solar atmosphere is energized. IRIS will obtain high-resolution UV spectra and images in space (0.4 arcsec) and time (1s), focusing on the chromosphere and transition region of our sun, which is a complex interface region between the photosphere and corona. The IRIS instrument uses a Cassegrain telescope to feed a dual spectrograph and slit-jaw imager, which operate in the 133-141 nm and 278-283 nm wavelengths, respectively. Within the spectrograph there are sixteen optics, each requiring subtle mounting features to meet exacting surface figure and stability requirements. This paper covers the opto-mechanical design for the most challenging optic mounts, which include the Collimator, UV Fold Mirrors, and UV Gratings. Although all mounts are unique in size and shape, the fundamental design remains the same. The mounts are highly kinematic, thermally matched, and independent of friction. Their development will be described in detail, starting with the driving requirements and an explanation of the underlying design philosophy.

Space and launch environments demand robust, low mass, and thermally insensitive mechanisms and optical mount designs. The rotating prism mechanism (RPM), a component of the stabilized dispersive focal plane system (SDFPS), is a spectral disperser mechanism that enables the SDFPS to deliver spectroscopic or direct imaging functionality using only a single optical path. The RPM is a redundant, vacuum-compatible, self-indexing, motorized mechanism that provides robust, athermalized prism mounting for two sets of matching prisms. Each set is composed of a BK7 and a CaF₂ prism, both 70 mm in diameter. With the prism sets separated by 1 mm, the RPM rotates the two sets relative to one another over a 180° range, and maintains their alignment over a wide temperature range (190-308K). The RPM design incorporates self-indexing and backlash prevention features as well as redundant motors, bearings, and drive trains. The RPM was functionally tested in a thermal vacuum chamber at 210K and <1.0x10^-6 mbar, and employed in the top-level SDFPS system testing. This paper presents the mechanical design, analysis, alignment measurements, and test results from the prototype RPM development effort.

Focal Plane Arrays (FPA) consisting of multiple Sensor Chip Assemblies (SCA) in a precision aligned mosaic are being increasingly used in optical instruments requiring large format detectors. The Joint Milli-Arcsecond Pathfinder Survey Mission (JMAPS) requires very precise positional alignment and stability of its 2 x 2 SCA mosaic at operational temperatures to meet its precision sky mapping mission requirements. Key performance requirements include: detector active area co-planarity, in-plane alignment, and thermal stability. This paper presents an overview of the JMAPS Focal Plane Array Assembly, its alignment and thermal-mechanical stability requirements, and associated test-validated performance in a cryogenic vacuum environment.

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) has an optical prescription which terminates at two focal plane arrays for each module. The instrument will operate at 37K after experiencing launch loads at 293K. The focal plane array housings (FPAHs), including stray light baffles (SLBs) must accommodate all associated thermal and mechanical stresses. In addition, the stray light baffles must be installed in situ on the previously assembled flight modules. The main purpose of the FPAH SLBs is to effectively attenuate mission limiting stray light on the focal planes. This paper will provide an overview of the NIRCam stray light baffle design, mechanical and optical analysis, hardware implementation and test results.

The Giant Magellan Telescope (GMT) will be one of the next class of extremely large segmented mirror telescopes. The GMT will utilize two Gregorian secondary mirrors, and Adaptive Secondary Mirror (ASM) and a Fast-steering Secondary Mirror (FSM). The FSM consists of six off-axis mirrors surrounding a central on-axis circular segment. The segments are 1.1 m in diameter and conjugated 1:1 to the seven 8.4 m segments of the primary. A prototype of the FSM mirror (FSMP) has been developed, analyzed and tested in order to demonstrate the mechanical and optical responses of the mirror assembly when subjected to structural and thermal loadings. In this paper, the mechanical and thermal performances of the FSMP were evaluated by performing finite element analyses (FEA) in NX Nastran. The deformation of the mirror’s lateral flexure was measured when the FSMP was axially loaded and the temperature response of the mirror assembly was measured when exposed to a sample thermal environment. In order to validate the mirror/lateral flexure design concept, the mechanical, optical and thermal measurements obtained from the tests conducted on mirrors having two different lateral flexures were compared to the responses calculated by FEA.

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.

The fast steering mirror (FSM) is a key element in astronomical telescopes to provide real-time angular correction of line-of-sight error due to telescope jitter and wind-induced disturbance. The Giant Magellan Telescope (GMT) will utilize a FSM as secondary mirror under unfavorable wind conditions that excites the telescope at the lowest resonance frequency around 8Hz. A flexure in the center of the mirror constrains lateral displacements, while still allowing tip-tilt motion to steer. Proper design of this central flexure is challenging to meet lateral loading capability as well as angular and axial flexibility to minimize optical surface distortion forced by redundant constraints at the flexure. We have designed the lateral flexure and estimated its performance from a variety of design case studies in a finite element analysis tool. A carefully designed finite element model at the sub-system level including the flexure, lightweight mirror and 3 point axial supports allows evaluating whether the designed flexure is qualified within specifications. In addition, distorted surface maps can be achieved as a function of forces that could be induced in telescope operation or due to misalignment errors during assembling. We have also built a test set-up to validate the finite element analysis results. Optical quality was measured by a phase shifting interferometer in various loading conditions and the measurements were decomposed by standard Zernike polynomials to concentrate specific surface shapes and to exclude low order shapes as measurement uncertainties.

In this report the study of direct recording of the surface relief gratings on amorphous chalcogenide thin (2.5-5μm) films is presented by three different recording setups. Recording was performed on As₂S₃ by 532nm wavelength laser light. Additionally the evolution of surface relief in dependence from the recording time and polarization has been investigated in detail. The mechanism of the direct recording of surface relief on amorphous chalcogenide films based on the photo-induced plasticity has been discussed.

We present a conceptual design for a high-resolution optical spectrograph appropriate for mounting at Cassegrain on a large aperture telescope. The design is based on our work for the Gemini High Resolution Optical Spectrograph (CUGHOS) project. Our design places the spectrograph at Cassegrain focus to maximize throughput and blue wavelength coverage, delivering R=40,000 resolving power over a continuous 320–1050 nm waveband with throughputs twice those of current instruments. The optical design uses a two-arm, cross-dispersed echelle format with each arm optimized to maximize efficiency. A fixed image slicer is used to minimize optics sizes. The principal challenge for the instrument design is to minimize flexure and degradation of the optical image. To ensure image stability, our opto-mechanical design combines a cost-effective, passively stable bench employing a honeycomb aluminum structure with active flexure control. The active flexure compensation consists of hexapod mounts for each focal plane with full 6-axis range of motion capability to correct for focus and beam displacement. We verified instrument performance using an integrated model that couples the optical and mechanical design to image performance. The full end-to-end modeling of the system under gravitational, thermal, and vibrational perturbations shows that deflections of the optical beam at the focal plane are <29 μm per exposure under the worst case scenario (<10 μm for most orientations), with final correction to 5 μm or better using open-loop active control to meet the stability requirement. The design elements and high fidelity modeling process are generally applicable to instruments requiring high stability under a varying gravity vector.