The Terrestrial Planet Finder Coronagraph will rely heavily on modeling and analysis throughout its mission lifecycle. Optical modeling is especially important, since the tolerances on the optics as well as scattered light suppression are critical for the mission's success. The high contrast imaging necessary to observe a planet orbiting a distant star requires new and innovative technologies to be developed and tested, and detailed optical modeling provides predictions for evaluating design decisions. It also provides a means to develop and test algorithms designed to actively suppress scattered light via deformable mirrors and other techniques. The optical models are used in conjunction with structural and thermal models to create fully integrated optical/structural/thermal models that are used to evaluate dynamic effects of disturbances on the overall performance of the coronagraph. The optical models we have developed have been verified on the High Contrast Imaging Testbed. Results of the optical modeling verification and the methods used to perform full three-dimensional near-field diffraction analysis are presented.

The Coronagraph version of the Terrestrial Planet Finder (TPF) mission relies on a large-optics, space-born observatory, which requires extreme stability of the optics in the presence of thermal and dynamic disturbances. The structural design requires balancing of stringent constraints on launch packaging with unusually tight response requirements for thermal and dynamic environments. The minimum-mission structural model (pre-phase A, point design) includes a deployable, pre-tensioned membrane sun-shield and solar-sail, a 10m long deployable secondary support structure, and a light-weighted 6m diameter monolithic glass primary mirror. We performed thermal distortion and dynamic response analyses in order to demonstrate feasibility, quantify critical sensitivities, and to identify potential problems that might need to be addressed early on.

The Terrestrial Planet Finder (TPF) employs an aggressive coronagraph designed to obtain better than 1e-10 contrast inside the third Airy ring. Minute changes in low-order aberration content scatter significant light at this position. One implication is the requirement to control low-order aberrations induced by motion of the secondary mirror relative to the primary mirror; sub-nanometer relative positional stability is required. We propose a 6-beam laser truss to monitor the relative positions of the two mirrors. The truss is based on laser metrology developed for the Space Interferometry Mission.

A Darwin precursor breadboard, comprising both fine lateral and longitudinal metrology sensors was designed, built and partially tested. The lateral metrology sensor was designed and built by TNO TPD and more than meets the imposed requirements. The longitudinal metrology sensor consists of a dual wavelength interferometer with an integrated delay line for optical path stabilisation. Here TNO TPD supplied the delay line and implemented the optical path difference stabilisation control. Experiments under ambient conditions show that noise reduction up to five orders of magnitude is achievable.

This paper describes a unique experimental facility designed to measure damping of materials at cryogenic temperatures for the Terrestrial Planet Finder (TPF) mission at the Jet Propulsion Laboratory. The test facility removes other sources of damping in the measurement by avoiding frictional interfaces, decoupling the test specimen from the support system, and by using a non-contacting measurement device. Damping data reported herein are obtained for materials (Aluminum, Aluminum/Terbium/Dysprosium, Titanium, Composites) vibrating in free-free bending modes with low strain levels (< 10-6 ppm). The fundamental frequencies of material samples are ranged from 14 to 202 Hz. To provide the most beneficial data relevant to TPF-like precision optical space missions, the damping data are collected from room temperatures (around 293 K) to cryogenic temperatures (below 40 K) at unevenly-spaced intervals. More data points are collected over any region of interest. The test data shows a significant decrease in viscous damping at cryogenic temperatures. The cryogenic damping can be as low as 10-4 %, but the amount of the damping decrease is a function of frequency and material. However, Titanium 15-3-3-3 shows a remarkable increase in damping at cryogenic temperatures. It demonstrates over one order of magnitude increase in damping in comparison to Aluminum 6061-T6. Given its other properties (e.g., good stiffness and low conductivity) this may prove itself to be a good candidate for the application on TPF. At room temperatures, the test data are correlated well with the damping predicted by the Zener theory. However, large discrepancies at cryogenic temperatures between the Zener theory and the test data are observed.

As part of the James Webb Space Telescope (JWST) materials working group, a novel cryogenic dilatometer was designed and built at NASA Jet Propulsion Laboratory to help address stringent coefficient of thermal expansion (CTE) knowledge requirements. Previously reported results and error analysis have estimated a CTE measurement accuracy for ULE of 1.7 ppb/K with a 20K thermal load and 0.1 ppb/K with a 280K thermal load. Presented here is a further discussion of the cryogenic dilatometer system and a description of recent work including system modifications and investigations.

This paper discusses the design, manufacture and cryogenic testing of a Lightweight Athermal SLMS Innovative Telescope (LASIT) under a Schafer funded Internal REsearch and Development program. The 25 cm aperture, 10X magnification LASIT is of Cassegrain design with structural components manufactured from carbon fiber reinforced silicon carbide (Cesic), while the primary mirror uses silicon lightweight mirror system (SLMS) technology. A fourteen pound, dimensionally stable telescope is the result. LASIT cryogenic testing will be performed at NASA/MSFC under Schafer's Space Act Agreement later this year.

Large Space based IR are presently under development. These telescopes are placed on the L2 Lagrangian point and will operate in far infrared range. EADS-ASTRIUM is manugacturing HERSCHEL telescope and will extend its technology to the SPICA Telescope. HERSCHEL operates in the spectral range between 80 and 670 μm wavelength and is devoted to astronomical investigations in the far-infrared, sub-millimetre and millimetre wavelength range. ASTRIUM has been awarded by ESA to manufacture tgeh 3,5m all SiC telescope. The concept for the HERSCEL telescope is based on an axisymetric, 3,5-m-diameter Cassegrain design. The driving requirements are the large diameter (3,5m) especially for the manufacturing aspects, the WFE which has to be kept below 6μrms, the operational temperatuer (70k) which brings distortionas wrt ambient environment, and finally the mass to keep below 300kg. This Development is part of the ESA HERSCHEL PLANK program. SPICA Telescope driving requirements are also the large diameter (3,5m) especially critical for the manufacturing aspects, the WFE which has to be kept below 350nmrms, and the operational temperature (4,5K) which requires to master the distortions wrt ambient environment. Telescope will operate in the 5 to 200 μm wavelength range. ASTRIUM has been awarded by Sumitomo and ISAS to study the faisability of teh 3,5m all SiC telescope. The main features developed in this paper are: The final design and the recent manufacturing developments of the HERSHEL telescope and the expected performances of such a telescope in space environment The preliminary design of the SPICA telescope and teh predicted performances which are taking advantage from the Silicone Carbide properties developed for HERSCHEL telescope, especially considering the homogeneity inside the structure its stability from abient to the operational temperature range (4,5K). The study shows that the Silicone Carbide Telescope design can fulfil the mechanical and optical requirements, in a passive way without actuators.

The James Web Space Telescope (JWST) is a large, infrared-optimized space telescope scheduled for launch in 2011. System-level verification of critical optical performance requirements will rely on integrated modeling to a considerable degree. In turn, requirements for accuracy of the models are significant. The size of the lightweight observatory structure, coupled with the need to test at cryogenic temperatures, effectively precludes validation of the models and verification of optical performance with a single test in 1-g. Rather, a complex series of steps are planned by which the components of the end-to-end models are validated at various levels of subassembly, and the ultimate verification of optical performance is by analysis using the assembled models. This paper describes the critical optical performance requirements driving the integrated modeling activity, shows how the error budget is used to allocate and track contributions to total performance, and presents examples of integrated modeling methods and results that support the preliminary observatory design. Finally, the concepts for model validation and the role of integrated modeling in the ultimate verification of observatory are described.

Accurately predicting optical performance for any of the near-term concepts proposed under NASA's Origins missions is a uniquely challenging task, and one that has served to highlight a number of areas of necessary advancement in the field of computer-aided engineering analysis. The strongly coupled nature of these classes of problems combined with unprecedented levels of required optical precision demand a solution approach that is itself fundamentally integrated if accurate, efficient analyses, capable of pointing the way towards improved designs are to be achieved. Recent development efforts have served to lay the foundation for an entirely new finite element-based analytical capability; one that is open, highly extensible, is Matlab-hosted, and which utilizes NASTRAN syntax to describe common-model multidisciplinary analyis tasks. Capabilities currently under development, a few of which will be highlighted here, will soon capture behavioural aspects of coupled nonlinear radiative heat transfer, structures, and optics problems to a level of accuracy and performance not yet achieved for these classes of problems, in an environment that will greatly facilitate future research, development, and technical oversight efforts.

Global astrometry is the measurement of stellar positions and motions. These are typically characterized by five parameters, including two position parameters, two proper motion parameters, and parallax. The Space Interferometry Mission (SIM) will derive these parameters for a grid of approximately 1300 stars covering the celestial sphere to an accuracy of approximately 4uas, representing a two orders of magnitude improvemnt over the most precise current star catalogues. Narrow angle astrometry will be performed to a 1uas accuracy. A wealth of scientific information will be obtained from these accurate measurements encompassing many aspects of both galactic and extragalactic science. SIM will be subject to a number of instrument errors that can potentially degrade performance. Many of these errors are systematic in that they are relatively static and repeatable with respect to the time frame and direction of the observation. This paper and its companion define the modeling of the contributing factors to these errors and the analysis of how they impact SIM's ability to perform astrometric science.

In this paper, we present an optimal open-loop slew trajectory algorithm developed at GSFC for the so-called "Yardstick design" of the James Webb Space Telescope (JWST). JWST is an orbiting infrared observatory featuring a lightweight, segmented primary mirror approximately 6 meters in diameter and a sunshield approximately the size of a tennis court. This large, flexible structure will have significant number of lightly damped, dominant flexible modes. With very stringent requirements on pointing accuracy and image quality, it is important that slewing be done within the required time constraint and with minimal induced vibration in order to maximize observing efficiency. With reaction wheels as control actuators, initial wheel speeds as well as individual wheel torque and momentum limits become dominant constraints in slew performance. These constraints must be taken into account when performing slews to ensure that unexpected reaction wheel saturation does not occur, since such saturation leads to control failure in accurately tracking commanded motion and produces high frequency torque components capable of exciting structural modes. A minimum-time constraint is also included and coupled with reaction wheel limit constraints in the optimization to minimize both the effect of the control torque on the flexible body motion and the maneuver time. The optimization is on slew command parameters, such as maximum slew velocity and acceleration, for a given redundant reaction wheel configuration and is based on the dynamic interaction between the spacecraft and reaction wheel motion. Analytical development of the slew algorithm to generate desired slew position, rate, and acceleration profiles to command a feedback/feed forward control system is described. High-fidelity simulation and experimental results are presented to show that the developed slew law achieves the objectives.

The Space Technology 7 (ST7) experiment will perform an on-orbit system-level validation of two specific Disturbance Reduction System technologies: a gravitational reference sensor employing a free-floating test mass and a set of micronewton colloidal thrusters. The ST7 Disturbance Reduction System (DRS) is designed to maintain the spacecraft's position with respect to a free-floating test mass to less than 10 nm/√Hz over the frequency range of 1 to 30 mHz. This paper presents the overall design and analysis of the spacecraft drag-free and attitude controllers. These controllers close the loop between the gravitational sensors and the micronewton colloidal thrusters. There are five control modes in the operation of the ST7 DRS, starting with the attitude-only mode and leading to the science mode. The design and analysis of each of the control modes as well as the mode transition strategy are presented.

High and low intensity dynamic environments experienced by a spacecraft during launch and on-orbit operations, respectively, induce structural loads and motions, which are difficult to reliably predict. Structural dynamics in low- and mid-frequency bands are sensitive to component interface uncertainty and non-linearity as evidenced in laboratory testing and flight operations. Analytical tools for prediction of linear system response are not necessarily adequate for reliable prediction of mid-frequency band dynamics and analysis of measured laboratory and flight data. A new MATLAB toolbox, designed to address the key challenges of mid-frequency band dynamics, is introduced in this paper. Finite-element models of major subassemblies are defined following rational frequency-wavelength guidelines. For computational efficiency, these subassemblies are described as linear, component mode models. The complete structural system model is composed of component mode subassemblies and linear or non-linear joint descriptions. Computation and display of structural dynamic responses are accomplished employing well-established, stable numerical methods, modern signal processing procedures and descriptive graphical tools. Parametric sensitivity and Monte-Carlo based system identification tools are used to reconcile models with experimental data and investigate the effects of uncertainties. Models and dynamic responses are exported for employment in applications, such as detailed structural integrity and mechanical-optical-control performance analyses.

A number of future space based science instruments key to NASA's Origins program require exceptionally large and precise support structures. The scale of these structures and stringency of their dimensional stability will present a number of challenges in the ground verification testing stage of their development and deployment. This paper will discuss a number of the unique challenges involved in developing validation procedures for these structures. It will also describe a novel approach to the development and validation of nonlinear component models of the structural mechanics. This "Component in the Loop" approach offers the ability to directly measure the in situ coupled behavior of a structural component as part of the ex situ component testing process. This testing methodology would allow the coupled system level response of the larger structure to be assessed without the need for assuming particular nonlinear component model forms. The proposed method is not limited to conducting virtual system tests. Feedback functions can be specifically designed to maximize the sensitivity of the output with respect to uncertain parameter(s). Maximum sensitivity is desired to accurately characterize the parameter in question, which is fundamental in model updating procedures.

The Galaxy Evolution Explorer is an orbiting space telescope that will collect information on star formation by observing galaxies and stars in ultraviolet wavelengths. The optical bench supporting detectors and related optical components used an interesting and unusual passive thermal compensation technique to accommodate thermally-induced focal length changes in the optical system. The proposed paper will describe the optical bench thermal compensation design including concept, analysis, assembly and testing results.

The use of true-membrane reflectors holds the promise of increasing the size of space-based apertures by decreasing payload mass and reducing launch volumes, but figure acquisition and maintenance of the thin, deployed structure present significant control challenges. The ability to manage both the static and dynamic aberrations defines the utility of these compliant mirrors for resolving quality images. The scope of the current study consists of characterizing the non-linear dynamic behavior of membrane reflectors to visible-optics quality under realistic support and loading scenarios. The basis for quality in the finite element model (FEM) deformed shape predictions is established both by comparing FEM and analytical solutions for linear static problems and by studying the convergence of eigen solutions. Most of the results are shown, too, to be within a previously determined range of optically-accurate solutions. The topographical difference between linear and non-linear dynamic solutions is characterized and correlated to support and loading regimes for eventual inclusion in closed-loop-control schemes. The objective of this paper is thus to study the non-linear characteristics of the dynamic behavior of membrane optics as the basis for future work in system identification and figure control.

The use of an elastic memory composite member (EMC) as the active element in deployable optical instruments has tremendous potential. Elastic memory composite mechanisms can remove the need for mechanical latches and remove the post deployed microdynamic instabilities associated with them while providing a low shock, controlled deployment. Additionally, elastic memory composite mechanisms are lightweight, simple, and have a very low coefficient of thermal expansion, which are also desirable properties for deployable optical systems. This paper describes an effort that has been done to explore this possibility. A mechanical latching actuator in an existing precision deployable optical testbed was replaced by an EMC self-locking actuator. Feasibility was assessed through a detailed design and fabrication exercise followed by experimental evaluation of a prototype actuator system in the ground-based deployable optics testbed.

Good wavefront quality, easy to align, and stable mounts are desired requirements for any optical system. Small variations in design parameters of mounts can radically diminish these qualities and performance of an optical system if tolerances of mounts don’t match optical requirements. We present design considerations required to create a stable ball knuckle mount with 5 degrees of freedom for a secondary mirror. Our system also required a rigid hub-mounted primary mirror with minimal optical deformation. Wavefront figure will be traced during design development of each mount. Overall final optical alignment was stable in 2 gravity vectors.

A novel tip-tilt mechanism has been designed which is capable of aligning a small 1-inch optic with one arc second resolution. This mechanism performs this function without the aid of a piezoelectric device or other electronic technology. The optic is bonded to a three bipod mount in series with a spring-loaded flexure. Three manually adjustable differential screws drive the flexure. The bipod/flexure arrangement allows highly accurate and stable adjustment. This paper will give an overview of the design, and present laboratory data and analysis quantifying the adjustment resolution of the mechanism. Material and surface coating selection is also presented.

Measurement systems such as systems based on interferometric combination of beams of light, require highly accurate alignment of optical components such as mirrors to achieve fringes. Moreover, the stability of such alignment mechanisms must be even higher. Alignment devices based on flexures provide accurate alignment with excellent resolution, without play or hysteresis. TNO TPD developed mechanisms for adjustment of mirrors in two degrees of freedom, meaning two rotations, and used these mechanisms in setups to achieve picometer stability. The paper describes the design process and the development of a set of alignment mechanisms. Theoretical and practical aspects are mentioned. First the design aspects for designing stable mounts are given, and then two mechanisms are described. The mechanisms consist of a monolithic adjustment mount for a mirror that is made by wire erosion in such a way that the mirror can rotate about two axes. Adjustment screws in combination with a lever and a gear provide easy and accurate adjustment of the rotation of the mirror. The combination of flexures result in a virtual point of rotation that is positioned on the centre of the mirror surface. In this case, the optical path length of the deflected light path will not change. Two degree of freedom rotation mechanisms have a generic design, so the design can be used in multiple instruments. The measurement systems show high stability of the components.

A number of concepts using the principle of the refraction of light have been developed to steer light beams. Refractive beam steering concepts involve the use of optical wedges in order to deviate a light beam. This principle is ideally suited for steering laser light since dispersion is minimal due to the monochromatic nature of the laser. The methods used to form the optical wedge and the means developed to adjust it are what distinguish the various concepts and have resulted in many patents over the years for their innovators. A new concept called a Lubricated Adjustable Optical Wedge (LAOW) has been recently developed that does not require complicated mechanical systems to form the wedge and provide the adjustment necessary to deviate the light beam. An optical wedge is formed using plano-convex and plano-concave lenses that are contacted together using a thin film of transparent index matching lubricant between the spherical surfaces. The forces of capillary action and surface tension provide the sole means of keeping the lens elements together. This technique has demonstrated a repeatability ≤±0.12 arc seconds in beam deviation angle.

The objective of this project is to dynamically align a Michelson interferometer. This interferometer is designed to measure the spatial coherence of light sources. In order to obtain accurate coherence measurements, many parameters within the interferometer must be controlled with high precision. Once such parameter is the angle of inclination between mirrors in the interferometer. To introduce a well controlled and variable amount of tilt between the mirrors, we propose here a new dynamic alignment method employing a position sensitive device. A theoretical angular precision of 1 microrad was desired and an experimental angular precision of 2 microrads was obtained.

The accurate measurement of the orientation of optical parts and systems is a pressing problem for upcoming space missions, such as stellar interferometers, requiring the knowledge and maintenance of positions to the sub-arcsecond level. Theodolites, the devices commonly used to make these measurements, cannot provide the needed level of accuracy. This paper describes the design, construction, and testing of an interferometer system to fill the widening gap between future requirements and current capabilities. A Twyman-Green interferometer mounted on a 2 degree of freedom rotation stage is able to obtain sub-arcsecond, gravity-referenced tilt measurements of a sample alignment cube. Dubbed a 'theoferometer', this device offers greater ease-of-use, accuracy, and repeatibility than conventional methods, making it a suitable 21st-century replacemnt for the theodolite.

A mirror mount for adjusting and holding half-inch diameter optics is described. The intended environment for the mount is that of flight Military Lasers. This operational environment includes varying static and dynamic loading, temperatures, and pressures. The mount is angle adjustable in two orthogonal directions, though is not a true gimbal mount. Its most unique characteristics are small package size, locking features that do not impose crosstalk on the adjusted position, and extreme ruggedness and stability over the stated environment. Design and performance information is presented.

For many applications involving polarized light, it is important that the azimuthal angle of a polarization optic (i.e. polarizer, retarder, etc...) be accurately aligned to a physical datum or to an eigenaxis of another polarization optic. A simple opto-mechanical tool for azimuthal alignment can be used to perform accurate alignments and consists of two "rotatable" mounts. One mount holds a polarizer, while the other holds a half-wave retarder. The method of swings is used to aid in the azimuthal alignment of the polarization optic and is illustrated using the Poincare Sphere. Additionally, imperfections in polarization optics are discussed.

Ritchey-Chretien type or Cassegrain type has been widely used for earth-observing space camera. As most earth-observing cameras are required to scan the wide area in a single path, they generally have a wider field of view, compared to the ground-based telescope. However, the alignment of Cassegrain or RC telescope with a wide-field of view is not easy. One reason is that it has a central hole in the primary mirror so that it is difficult to find an optical axis. Another reason is that it can introduce much off-axis aberration such as coma and astigmatism, when it is aligned at on-axis with zero-coma condition. In this paper, we calculate the alignment accuracy using a conventional method for a RC type telescope of which diameter is 300 mm and field of view is 2.08 degrees. We suggest that the most effective alignment method for wide field of view system is a computer-aided alignment. With this method, it was found that the variation of rms wavefront error of the telescope over the entire field of view was less than 10 %.

The infrared sensors group at the Pacific Northwest National Laboratory (PNNL) is focused on the science and technology of remote and in-situ chemical sensors for detecting proliferation and countering terrorism. To support these vital missions, PNNL is developing frequency-modulation techniques for remote probing over long optical paths by means of differential-absorption light detecting and ranging (LIDAR). This technique can easily monitor large areas, or volumes, that could only be accomplished with a large network of point sensors. Recently, PNNL began development of a rugged frequency-modulation differential-abosrption LIDAR (FM-DIAL) system to conduct field experiments. To provide environmentla protection for the system and facilitate field deployments and operations, a large, well insulated, temperature controlled trailer was specified and acquired. The trailer was outfitted with a shock-mounted optical bench, an electronics rack, a liquid nitrogen Dewar, and a power generator. A computer-controlled gimbal-mounted mirror was added to allow the telescope beam to be accurately pointed in both the vertical and horizontal plane. This turned out to be the most complicated addition, and is described in detail. This paper provides an overview of the FM-DIAL system and illustrates innovative solutions developed to overcome several alignment and stability issues encountered in the field.

The European Southern Observatory (ESO) is presently developing the PRIMA facility (Phase Referenced Imaging and Microarcsecond Astronomy). PRIMA will enable the observation of very faint celestial objects. A key element in this facility is the Star Separator that has been designed and is being built by TNO TPD in the Netherlands. This Star Separator makes it possible in principle to simultaneously observe two objects, the guide star and the faint object, with one telescope. The separation of the faint object and the guide star is case dependent i.e. the separation between the two objects depends on the observation direction. This necessitates the use of a very accurate and stable pointing mechanism. The required repeatability of such mechanism is < 0.5 arcsec while its resolution should be < 0.1 arcsec. By using a statically determined fully elastic guiding and actuation mechanism in combination with closed loop driven piezos the realization of such mechanism was successful. A unique feature of the mechanism is that only the guiding/actuating mechanism needed to be designed. The rest is readily available from piezo suppliers. This makes this pointing mechanism a true low budget solution with excellent performance.

Homothetic mapping is a technique that combines the images from several telescopes so that it looks like as though they came form a single large telescope. This technique enables a much wider interferometric field of image than current techniques can provide. To investigate the feasibility, a research testbed is build know as Delft Testbed interferometer (DTI). DTI simulates a configuration of three telescopes collecting light of a set of 3 stars. The stars are simulated by coupling light of a Xenon light source into three fibres, which illuminate a parabolic mirror. The light that is used has wavelengths of 500 nm - 800 nm. The light of the three telescopes will be combined in such a way that the beam arrangement in the pupil plane corresponds with the telescope arrangement and the Optical Path Difference (OPD) is minimized for the three beams. To achieve white light fringes with high visibility, the mechanical testbed that is 2 m x 1 m x 0.5 m in size, requires stable mounting of components. This paper describes the mounting of the diamond turned off-axis parabolic mirrors of 200 mm in diameter and 240 mm flat mirrors; furthermore, it describes components like the telescopes and the active controllable components for repositioning of the beam arrangement. Mechanisms were developed for alignment of piezo actuators and for delay lines. The delay lines can also be used to compensate pupil rotation. Test results demonstrate that the test setup is highly stable for temperature as well as for airflow, although the system is placed in a non-thermally controlled lab. This allows measurements of nm, in presence of μm disturbances.

TNO TPD, in cooperation with Micromega-Dynamics, SRON, Dutch Space and CSL, has designed a compact breadboard cryogenic delay line for use in future space interferometry missions. The work is performed under ESA contract in preparation for the DARWIN mission. The breadboard (BB) delay line is representative of a flight mechanism, with all materials and processes used being flight representative. The delay line has a single stage voice coil actuator for Optical Path Difference (OPD) control, driving a two-mirror cat's eye. Magnetic bearings provide frictionless and wear free operation with zero-hysteresis. Overall power consumption is below the ESA specification of 2.5 W. The power dissipated on the optical bench at 40 K is considerably less than the maximum allowable 25 mW. The design of the BB delay line has been completed. Verification testing, including functional testing at 40 K, is planned to start in the 4th quarter of 2004. The current design could also be adapted to the needs of the TPF-I mission.

TNO TPD, in close cooperation with Micromega-Dynamics and Dutch Space, has developed an advanced Optical Delay Line (ODL) for use in PRIMA, GENIE and other ground based interferometers. The delay line design is modular and flexible, which makes scaling for other applications a relatively easy task. The developed technology can also be applied in future cryogenic space interferometers, such as DARWIN, and TPF-I. The ODL has a single linear motor actuator for Optical Path Difference (OPD) control, driving a two-mirror cat's eye with SiC mirrors and CFRP structure. Magnetic bearings provide frictionless and wear free operation with zero-hysteresis. The delay line has been assembled and is currently being subjected to a comprehensive test program.

The current design of the Space Interferometry Mission (SIM) employs a 19 laser-metrology-beam system (also called L19 external metrology truss) to monitor changes of distances between the fiducials of the flight system's multiple baselines. The function of the external metrology truss is to aid in the determination of the time-variations of the interferometer baseline. The largest contributor to truss error occurs in SIM wide-angle observations when the articulation of the siderostat mirrors (in order to gather starlight from different sky coordinates) brings to light systematic errors due to offsets at levels of instrument components (which include corner cube retro-reflectors, etc.). This is the external metrology wide-angle field-dependent error. Physics-based model of field-dependent error at single metrology gauge level is developed and linearly propagated to errors in interferometer delay. General formulation of delay error sensitivity to various error parameters is developed. The essence of the linear error model is contained in an errormapping matrix. A corresponding Zernike component matrix approach is developed in parallel with its advantages discussed. As a first example, dihedral error model is developed for the corner cubes (CC) attached to the siderostat mirrors. Average and worst case residual errors are computed when various orders of field-dependent terms are removed from the delay error. These serve as guidelines for arriving at system requirements given the error budget allocation. Highlights of the non-common vertex error (NCVE) model are shown as a second example followed by discussions.

A kinematic mount has been designed to support two Silicon Carbide-based spherical mirrors during cryogenic testing at the Goddard Space Flight Center. The mirrors are flight representative test mirrors for the NIRSpec Instrument of the James Webb Space Telescope (JWST), provided by Galileo Avionica of Florence, Italy. One is cold-pressed Silicon Carbide (SiC) and one is Carbon reinforced Silicon Carbide (C/SiC); both are coated in a SiC-based chemical vapor deposit. Each is lightweighted and has an integral mount on the rear surface. The integral mount is used as an interface to the kinematic mount, which is designed to support the mirrors during cryogenic testing while minimizing distortions induced by CTE mismatch among the materials. Additionally, an alternative "simply supported" mount is used to hold the mirrors around the outer edge of the optical surface. This eliminates the bending of the integral mount under the weight of the mirror and evaluates the effectiveness of the kinematic mount. The mirrors were analyzed for optical performance during testing from room temperature to 20K using Finite Element Analysis (FEA) with MSC/NASTRAN 2001. Predicted surface figure error (SFE) based on the removal of bias, tilt, and power was calculated using an in-house Matlab script for spherical mirrors. SFE was verified using the SigFit optical post-processing program to provide Zernike polynomial input for analysis with the Zemax optical software. The results show that the kinematic mount induces minimal figure error on the optical surface.

Future spaceborne astronomy missions will require telescopes with increasingly greater resolving power, driving the dimensions of the optics to a significant size. Fully integrated observatory verification becomes problematic as the systems approach or exceed the size of the test facilities required to control environmental factors (temperature, vibration, etc). Such tests also require extremely precise test optics. Under such conditions, system verification will start to rely on analytical propagation of ground test data to in-situ performance. Reliable analytical predictions must be grounded in a thorough characterization of system uncertainty. A methodology is proposed to experimentally characterize uncertainty using component test data and integrated system models. The approach relies on uncertainty propagation techniques to identify critical uncertainties and bound the resulting performance predictions, and test data (on the component, subsystem, and if possible system levels) to confirm probabilistic models. The methodology is demonstrated on the Mid-Deck Active Control Experiment (MACE), an articulated flexible test article.