This PDF file contains the front matter associated with SPIE Proceedings Volume 12676, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

NASA’s Habitable Worlds Observatory will consist of a segmented telescope and high contrast coronagraph to characterize exoplanets for habitability. Achieving this objective requires an ultra-stable telescope with wavefront stability of picometers in certain critical modes. The NASA funded Ultra-Stable Large Telescope Research and Analysis – Technology Maturation program continues to mature key component-level technologies for this new regime of “ultra-stable optical systems,” including active components like segment edge sensors, actuators and thermal hardware, passive components like low distortion mirrors and stable structures, and supporting capabilities like precision metrology. This paper will present an update to the latest results from hardware testbeds and simulations in the areas listed above. It will also contain a correction to previously published results of Ball’s Integrated Demo, which consists of a capacitive sensor and three actuators operating in closed loop.

UVO to Far-IR (UVO-FIR) mirror technology development project is a multiyear effort initiated in Fiscal Year (FY) 2022 to mature the Technology Readiness Level (TRL) of critical technologies required to enable ultra-stable telescope of the Habitable Worlds Observatory (HWO) mission. Accomplishments of 2022/23 include: building and correlating a new ‘as-built’ model of the 1.5-m ULE® AMTD-2 mirror, and extrapolating implications for achieving an ultra-stable wavefront for coronagraphy; implementing absolute gravity-sag characterization algorithms and demonstrating ability to compensate G-say via a CGH; using tailored stiffness process to design a mirror for a balloon mission whose only significant gravity sag as a function of elevation angle is coma (which can be eliminated via adjusting the secondary mirror); and as a community service, MSFC’s Center for Mirror System Characterization and Acceptance Testing (CfMSCAT) cryo-tested 7 different mirror technologies provided by industrial partners.

NASA’s Habitable Worlds Observatory will consist of a segmented telescope and high contrast coronagraph to characterize exoplanets for habitability. Achieving this objective requires an ultra-stable telescope with wavefront stability of picometers in certain critical modes. The Ultra-Stable Large Telescope Research and Analysis – Technology Maturation program has matured key component-level technologies as well as developed integrated modeling capability to predict performance in a flight system. ULTRASim is a stability simulation of an ultrastable telescope, including segment sensing and control of the primary mirror using actuators and edge sensors and global position control of the secondary and phased primary mirrors with laser metrology. New developments since previous publications include a capacitive edge sensing network and development of a control-structure interaction model.

Space interferometers could, in principle, exploit the relatively stable space environment and ease of baseline reconfiguration to collect measurements beyond the limitations of ground-based interferometers. In particular, a two-element interferometer could provide excellent uv-plane coverage over a few tens of low-Earth orbits. One of the challenges for free-flying interferometers is controlling the optical path distance with sub-wavelength accuracies despite the collectors flying up to hundreds of meters apart. This work considers two approaches: an artificial in-orbit laser guide star (LGS) that provides a phase reference for the space interferometer and fringe tracking on the science target itself. The two approaches (LGS vs. no LGS) would require different image processing techniques. In this work, we explore image processing with LGS phase residuals due to GPS uncertainties. We use GPS uncertainties from the GRACE-FO mission to simulate image retrieval with a 300 m baseline laser-guided space interferometer. This is done by fitting the slowly varying phase errors of complex visibility measurements. We also consider a 40 m baseline interferometer with visibility(-modulus)-only measurements. In this case, we simulate the bias in visibility due to fringe tracking in the presence of parasitic forces acting on the spacecraft. We then use a modified version of the Hybrid Input-Output phase retrieval algorithm for image reconstruction. We conclude that under our optimistic assumptions, both approaches could enable general imaging of a few large stars even with CubeSats, although an LGS would significantly improve the best resolution obtainable.

The 2020 Astrophysics decadal study’s choice for NASA’s next flagship mission to be developed is the Habitable Worlds Observer (HWO). HWO will have at its heart, a coronagraph, whose accommodation requires exceptional stability. Mechanical disturbances from micrometeoroid impact are one of the environmental effects that has been shown to degrade the performance of a coronagraphic telescope unacceptably. This paper introduces the problem of micrometeoroid induced disturbances on HWO and the mitigation options available. The paper will conclude with a discussion the development of for a potential shield.

A first order single surface analysis indicates that, to enable coronagraphic detection and characterization of exo-Earth planets, near angle scatter must be considered when specifying optical surfaces for a potential Habitable World Observatory. Based on arbitrary error budget allocations and using Rayleigh-Rice Vector Scatter Theory, Generalized Harvey-Shack Scalar Scatter Theory, and Greynolds Approximation, ‘placeholder’ specifications for the primary mirror are derived: Static Surface Roughness < 1 nm rms, and Dynamic Surface Roughness < 1 pm PV. These specifications will change once error budget allocations are defined. Analysis does not include scatter from more than just the primary mirror, coating structure, edges, contamination, micrometeoroid impacts, etc.

DUET is an embodiment of an astronomical telescope without mirrors or lenses. All optics are diffractive. The primary objective is a gossamer membrane annular Gabor Zone Cone which has the characteristic of focusing by wavelength. The secondary is a very high resolution spectrometer. The annulus primary has a diameter sufficiently wide so that the spectral separation of the parent star is resolved to cm/sec Doppler shift as needed to detect Earth analogs in the 10 pc "Neighborhood." Proximate stars are removed by the dual dispersion method permitted with a precise secondary spectrometer. Residual photons detected after coronagraphy come from the exoplanetary system and are natively spectrographic. The optical train allows for new types of coronagraphy, because of a natural bandpass spectral separation. Two types of coronagraph are proposed. The physical embodiment presumes in-space construction. The large primary is delivered as a ribbon on mandrels and is installed over a network of active trusses.

The PolyOculus technology, developed by CREOL’s Astrophonics group, creates a large-area-equivalent telescope using fiber optics and a photonic lantern to link several semi-autonomous, small, inexpensive, commercial-off-theshelf telescopes. The Original PolyOculus Array, OPA, will use seven, Celestron 11” telescopes with iOptron centralbalanced equatorial mounts (CEM 70) to create a ~0.75m equivalent optical telescope for spectroscopic follow up observations of astronomical events. This telescope array will include 7 acquisition and guiding systems (one per telescope) to appropriately center and finely focus objects in the telescopes’ field of view along with an atmospheric dispersion corrector for each unit. That light will then be sent through single, multimode, optical fibers (one fiber per telescope) and to a photonic lantern where the light from all seven telescopes will be combined then sent to a spectrograph. The photonic lantern has demonstrated over 91% efficiency in combined optical light. The Original PolyOculus Array will be commissioned and operated at Mount Laguna Observatory in southern California. OPA will be the prototype to an eventual, more numerous PolyOculus driven array and other future PolyOculus arrays with different applications.

The PRIMA (Probe Far-Infrared Mission for Astrophysics) system will be a 1.8 meter, multi-mode, cryogenic, far-infrared space-based observatory consisting of a collecting afocal telescope followed by multiple spectrometer and imager instruments. The afocal telescope collects light from targets across a total field of view that is selectable by means of two different internal scan mirrors, one each for the spectrometers and the imagers. The primary and secondary mirrors are common to both instrument groups, and working with an angular field offset between instruments. The optics after the secondary and up to the scan mirrors are separate. The telescope provides two separate collimated and demagnified beams emerging from the scan mirrors to the spectrometer and imager instrument groups. Design-driving factors include the need to demagnify the entrance beam to fit a heritage scan mirror, and the need for an accessible field stop located clear of any mirror. This paper describes the requirements, configuration trade and development, preliminary optical design, and performance analysis of the telescope.

The PRobe Infrared Mission for Astrophysics (PRIMA) will be a multi-mode, cryogenic, far-infrared space-based observatory consisting of a 1.8 meter collecting telescope followed by multiple spectrometer and imager instruments. There is a Fourier Transform Module (FTM) that is optionally inserted between the telescope and Far-Infrared Enhanced Survey Spectrometer (FIRESS), which consists of an objective group that receives the collimated beam from the scan mirror and creates a focus at the slit for all spectrometers. A total of four spectrometers, working in different spectral bands, disperse the light and create a focus at FPAs. Most commonly, imaging spectrometers work at 1:1 magnification between slit and FPA, but in PRIMA the magnification of the four spectrometers ranges from 0.6x to 1.8x. The non-unity magnification led to a configuration trade for the spectrometer optics, and required the use of low-order Zernike aspheres (freeform surfaces) to achieve the requirements on wavefront error, keystone error, and smile. This paper describes the requirements, configuration trade and development, preliminary optical design, and performance analysis of FIRESS.

Spectral distortions in the cosmic microwave background open a new window to the structure, content, and evolution of the universe. Detecting the expected signals at the few part-per-billion level requires background-limited sensitivity with careful control of instrumental signatures. PHOENIX is a Probe-class mission to map the CMB and diffuse astrophysical foregrounds at microwave through far-IR wavelengths. I describe the scientific goals and instrument design for the PHOENIX mission and use detailed time-ordered simulations to evaluate the projected instrument performance.

In previous work we demonstrated the feasibility of a new plasma process based on electron beam-generated plasmas in SF₆ environments that effectively passivates the surface of aluminum mirror samples for applications in the UV/O/IR (ultraviolet/optical/infrared) by removing the native oxide layer and producing an AlF₃ passivation layer with tunable thickness. This process provides good results in terms of far ultraviolet reflectivity, environmental stability, uniformity, polarization aberration, surface roughness, and does not require elevated substrate temperatures or ultra-high vacuum conditions. In this communication we show that, in addition to these characteristics, Al mirrors can be passivated faster with NF₃ than with SF₆ over a wide range of process parameters without the loss of optical performance independent of the working-gas choice adopted for the plasma.

Astronomical space telescopes to study astrophysical phenomena from the far ultraviolet (FUV) to the near infrared (NIR) will require mirror coatings with high reflectance over this entire spectral region. While coatings for the optical and NIR part of the spectrum are fairly well developed with proven performance, the FUV range has presented significant challenges, particularly below 120nm. Recent developments in electron-beam (e-Beam) generated plasma treatment in a SF₆ environments has enabled the effective passivation of aluminum (Al) coatings for applications in the FUV, by native oxide removal and the formation of a AlF₃ passivation layer which could be tuned to any desired AlF₃ thickness. These results have been produced through a collaboration between the Goddard Space Flight Center (GSFC) and the Naval Research Laboratory (NRL). The passivation experiments have been carried out using the Large Area Plasma Processing System (LAPPS) at NRL using bare aluminum samples and provided by the coating group at GSFC. This novel procedure has demonstrated improved Al mirrors with state-of-the-art FUV reflectivity (e.g. R=91% at 121.6nm). In this paper, we will be reporting on environmental testing, micro-roughness, as well as polarization studies of these E-beam treated samples. These characterizations are being done in order to advance the Technology Readiness Level (TRL) for these Al+AlF₃ mirror coatings produced at LAPPS. The ultimate goal is to demonstrate the promise of using this coating technology to deliver reflectance performance plus stability and uniformity over a large area for a future IR/O/UV space telescope observatory.

Randomly distributed anti-reflective nanostructures were fabricated on both surfaces of cylindrical lenses and freeform optical surfaces, using a plasma assisted reactive-ion etching technique. Spectral transmission of an average 98% was measured across the range 340-800 nm. Mid-band full-angle directional scatter measurements show a difference of six orders-of-magnitude in transmission intensity between specular and off-specular angles. Measurements before and after the etching process show little to no wavefront distortion for the cylindrical lenses. As the nanostructures are etched into the optical surface their thermal and mechanical shock resilience is high, as verified by our prior work on fused silica windows.

Aluminum (Al) mirrors are conventionally protected with metal-fluoride coatings (e.g., MgF₂, LiF, or AlF₃) immediately after deposition to prevent oxidation and preserve its far-ultraviolet (FUV) spectral efficiency. However, the resulting FUV reflectance of the aluminum reflector is limited by the metal-fluoride overcoat film index of refraction, morphology, stoichiometry, and its absorption cut-off in the lower end of the FUV spectra. Cryolite (sodium hexafluoroaluminate, Na₃AlF₆) emerges as a potential candidate to preserve the aluminum FUV reflectance due to its relatively lower index of refraction in the visible to ultraviolet; therefore, allowing for the thin-film design of highly spectral efficient reflectors over a wide spectral range. We investigate the use of cryolite in aluminum reflector FUV coating design. The deposited aluminum reflector overcoated with cryolite will be examined in terms of spectral efficiency and environmental durability. The deposited cryolite overcoat will be evaluated in terms of optical constants and structural properties. Preliminary results have shown that the use of cryolite as an overcoat to protect aluminum would yield unprecedented results as an optimal Hydrogen Lyman-alpha (HLyα) spectral line reflector, with experimental reflectance values >96%.

The Sun-Earth Lagrange point L4 is the most stable location among the five Lagrange points at 1 AU. The L4 mission affords a clear and wide-angel view of the Sun-Earth line for the study of the Sun-Earth, Sun-Moon, and Sun-Mars connections from remote-sensing observations. The L4 mission will significantly contribute to advancing heliophysics science, improving the capability of space weather forecasting, and extending space weather studies beyond near-Earth space. This presentation outlines the importance of L4 observations and advocates comprehensive and coordinated observations of the heliosphere at multi-points including other planned L1 and L5 missions. In addition, conceptual designs are provided for an optical telescope for solar H-alpha and photospheric magnetic field observation, and a EUV telescope for solar corona.

High-resolution white light observations of the solar corona over a large field of view (FOV) are crucial for understanding the structure and evolution of large coronal structures, including coronal mass ejections. With current telescopes for imaging the corona and inner heliosphere, there is a tradeoff between spatial resolution and the FOV; coronagraphs typically provide high-resolution (<1 arcminute) imaging over a relatively small region while heliospheric imagers are designed with a wide FOV, sacrificing spatial resolution for coverage. Incorporating a scanning system enables the conservation of high spatial resolution while adding the ability to map over a large field of regard; however, with conventional optical designs, this would require large/complex gimbaled systems, which are risky for space-based instrumentation. The Coronal and Heliospheric imaging with Achromatic Metasurfaces Pathfinder (CHAMP) aims to address this need, consisting of a visible light telescope which uses novel achromatic metasurface Risley prisms (MRPs) to create high-resolution, wide-FOV maps of the solar corona in a small form factor. With this design, optical beam steering is achieved by rotating two MRPs relative to each other using rotational stages, eliminating the need for gimbaled systems. Here we describe the CHAMP instrument concept and efforts to develop multi-layer achromatic MRPs which perform across a wide bandpass (∼100 nm) in the visible light regime.

The Nancy Grace Roman Space Telescope (“Roman”) was prioritized by the 2010 Decadal Survey in Astronomy & Astrophysics and is NASA’s next flagship observatory. Launching no earlier than 2026, Roman will explore the nature of dark energy, as well as expand the census of exoplanets in our galaxy via microlensing. Roman will also demonstrate key technology needed to image and spectrally characterize extra-solar planets. Roman’s large field of view, agile survey capabilities, and excellent stability enable these scientific objectives, yet present unique challenges for the design, test, and verification of its optical system. The Roman optical system comprises an optical telescope assembly (OTA) and two instruments: the primary science wide-field instrument (WFI) and a technology demonstration coronagraph instrument (CGI), and the instrument carrier (IC), which meters the OTA to each instrument. This paper presents a status of the optical system hardware as it begins integration and test (I&T), as well as describes key optical test, alignment, and verification activities as part of the I&T program.

The OTA for the Nancy Grace Roman Space Telescope includes the primary mirror, secondary mirror, and aft optics for guiding light into the Wide Field Instrument and the Coronagraph Instrument. The telescope is taking shape as the tested optical mirror assemblies are integrated. The assemblies have been thermal cycled to the cold temperatures for infrared operation, load tested to launch loads, vibration tested, and optically tested. Testing included launch-level vibration testing of the 2.4-meter light-weighted primary mirror assembly. In addition, the telescope control electronics (TCE) box has been fully assembled and the environmental testing of the TCE is progressing. Pictures and descriptions of the integration and test progress are provided, along with performance results measured at these levels of assemblies. Planning and test equipment preparation for the telescope thermal vacuum testing continues including plans to take advantage of the large dynamic range available with focus diversity phase retrieval and a Shack-Hartmann wavefront sensor for the gravity-sagged primary mirror.

The Cold Module (CM) is a fundamental collection of components within the Wide Field Instrument (WFI) on NASA’s Nancy Grace Roman Space Telescope. The CM consists of components necessary prior to Focal Plane System (FPS) integration, including the hexapod adjustment mechanism for the focal plane, the optical element selection mechanism, the optical metering support structure, and a cold enclosure. The CM has completed a challenging integration and test process in preparation for the FPS. This paper will summarize the design and execution of the integration and test campaign for the CM as well as the verification effort to this point.

The Wide Field Instrument (WFI) on NASA’s Roman Space Telescope has eight filters on a large filter wheel that are key to enabling the science missions of the observatory. These filters have completed their journey from individual components to fully integrated elements in the optical element wheel assembly (EWA), and have been characterized in terms of their transmittance, wavefront impact, and other key performance characteristics. This paper will summarize their capabilities and performance, demonstrating their ability to deliver top-quality science on orbit.

SPHEREx is a Medium Explorer astrophysics mission that requires a wide-field cryogenic short-wave infrared (SWIR) to mid-wave infrared (MWIR) telescope. The SPHEREx telescope has been designed and built at Ball Aerospace based on a JPL optical prescription and system architecture. The telescope has a 20cm entrance pupil, three freeform aluminum mirrors, a dichroic beam splitter furnished by Caltech, and forms two images in the SWIR and MWIR spectral bands. The “all-aluminum” architecture combined with a cryogenic space environment defines the opto-mechanical design approach for this system. Ball Aerospace performed developmental testing on a flight-like aluminum engineering development mirror for cryogenic surface figure and measured the differential thermal expansion of structural and optical aluminum materials. These development tests validated aspects of the athermal design prior to system-level integration and test. The telescope alignment process uses a laser tracker and system wavefront error (WFE) data to determine the adjustment of two mirrors and a focal plane assembly optical simulator (FPAOS). The FPAOS provides a retroreflection of interferometer light from each image location and an athermal focus position. The FPAOS was used in place of the SWIR band focal plane during system alignment and was moved to the MWIR focal plane interface to validate WFE performance in both bands. A cryogenic system WFE test was conducted to validate SWIR band performance at operational temperatures, and a post-vibrational WFE test demonstrates flight readiness. The SPHEREx telescope has been tested, delivered, and is ready for the next level of system integration.

The Europa Imaging System (EIS) combines a Narrow-Angle Camera (NAC) and a Wide-Angle Camera (WAC) to explore Jupiter’s Icy moon Europa. EIS is designed to address high-priority geology, composition, ice shell and ocean science objectives with the challenges of imaging in a wide range of scenarios spanning fast, low-altitude flybys with rapidly changing geometry and illumination to high-altitude imaging of faint scenes. Images for both EIS cameras are taken with a 10-μm pixel-pitch, 4096×2048 frontside illuminated CMOS image sensor. To perform color pushbroom imaging, the NAC and WAC both have six 32-row broadband stripe filters. The WAC is an F/5.75, 46-mm focal length, 8- lens refractive telescope with a 48° × 24° FOV and an IFOV of 218-μrad, achieving 11-m pixel scale from a 50-km altitude over a 44-km-wide swath. The along-track FOV provides 3-line (forward, nadir, and aft) pushbroom stereo swaths enabling digital topographic models with 32-m spatial scale and 4-m vertical precision. In order to perform over a 400- 1050 nm bandwidth in the extreme radiation environment surrounding Europa, the design contains 4 different materials: fused silica, CaF2, and two radiation resistant glasses. Each lens, except the exposed front surface of Lens 1 (L1), is coated with a proprietary antireflective (AR) coating, which has been tested for durability and performance in varying temperature and radiation environments. The 25-mm thick fused silica L1 plays dual roles in the WAC telescope design to also protect the CMOS sensor from the intense radiation of the Jovian environment. The optomechanical design maintained the optical alignment through thermal and vibration environmental testing. The WAC was delivered to NASA’s Jet Propulsion Laboratory (JPL) and integrated to the Europa Clipper spacecraft in summer 2022.

The Korea Astronomy and Space Science Institute is working on a project, the Republic of Korea Imaging Test System shortly called ROKITS, which is an optical system that aims to study the formation and occurrence of the aurora. The main objective is to gain insights into the changes occurring in the atmosphere, particularly the upper atmosphere, due to external energy sources from outside the Earth. Additionally, the system will investigate the feasibility of detecting atmospheric waves, specifically atmospheric gravity waves, which spread from the lower atmosphere. To achieve these scientific goals, 90 degrees of a wide field of view and a very narrow bandwidth of filters in a specific wavelength are required, and this paper will present information on the optical design and related analysis.

The Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE C) is a high-altitude balloon-borne observatory that used a vector vortex coronagraph to image dust and debris disks around nearby stars, as well as develop and test technology necessary for direct imaging of exoplanets from a flight platform. The balloon flight environment presents several challenges: an ambient pressure and temperature of approximately 4 Torr and 220-240 K, combined with significant and varying solar irradiance, lead to time-dependent and anisotropic thermal deformation of the optics and their supporting structure. In order to characterize how these effects limit the ultimate performance of the mission, we present a finite-element model of the flight instrument, implemented in Thermal Desktop, which takes into account the interactions with the environment. We present the comparison of this thermal model with flight data.

The objective of thisstudy was to assess the tolerance sensitivity of various aperture sizes in the Ritchey–Chrétien telescope employed in remote sensing instruments. A comparative analysis was performed to identify the optimal system specification considering different aperture sizes and marginal tolerances. The results were then utilized in the Formosat– 8 satellite program to determine the most suitable aperture size for fabricating the mirror components and establish the tolerances budget for the system alignment of the Formosat–8 satellite remote sensing instrument.

In this paper, the results of designing a visible and infrared optical system with the same effective focal length are presented. The basic form is the three-mirror anastigmat (TMA) structure that can minimize major aberrations such as spherical, comma, and astigmatism and is an optical system that can secure a relatively wide field of view. The ray incident onto the optical system passes through three mirrors, is divided into infrared and visible bands by a beam splitter, and is incident on the focal plane array (FPA). Typically, in the case of a visible optics system, the stop of the optical system is placed near the primary mirror to be designed to have a minimum size. However, the stop is placed in front of the FPA to minimize thermal stray light owing to the internal temperature in the infrared channel.

The Lunar Terrain Imager (LUTI), comprising two identical optical systems, serves as a primary payload on the Korean Pathfinder Lunar Orbiter spacecraft. This high-resolution camera is specifically designed to capture lunar surface images and facilitate the identification of potential landing sites for future missions. Leveraging the capabilities of the camera will significantly enhance our understanding of lunar geology, morphology, and evolution, laying a strong foundation for future lunar exploration. This paper introduces the configuration and features of the proposed LUTI camera, a highresolution electro-optical camera. It details the assembly and alignment process, presents performance measurement results, and elucidates its optical characteristics. Through precise alignment and calibration, this camera achieves a required swath width of > 8 km at an altitude of 100 km, providing a broader coverage of the lunar terrain. Its advanced components, including a sun shield and a Cassegrain-type telescope with hyperbolic mirrors, contribute significantly to its high-resolution imaging capabilities. Performance measurement results confirm that the LUTI camera meets the required specifications, including achieving a 10 % performance level for its modulation transfer function. The detailed imagery captured by the LUTI camera lays a strong foundation for future scientific research on the Moon, enabling researchers to conduct in-depth studies and investigations of lunar features and phenomena.

In this study, we investigated the impact of ghost images on the modulation transfer function (MTF) of a Korsch-type telescope using nonsequential ray-tracing simulations and the experimental measurements of the knife-edge method with a collimator and light source targets. Our findings showed that ghost images introduce a directional bias into the edge spread function depending on the field position, which affects the line spread function and MTF. Furthermore, our measurement results demonstrated that ghost images can significantly affect the MTF on the edge field of the green channel. The ghost-to-signal ratio in the multispectral (MS) green channel was approximately 2.5%, which is approximately 0.25% higher than that in the panchromatic channel. To estimate the impact of ghost images in the MS green channel, we performed a parametric analysis using a nonsequential ray-tracing simulation, exploring potential strategies, such as adjusting the window thickness, the distance between the detector and the window, the transmittance of the window surface, and the reflectance of the detector surface. By comparing the positions and intensities of the ghost images obtained from the simulations with those measured experimentally, we identified the simulation input parameters that best reproduced the measured results. Our study provides valuable insight into the importance of managing ghost images when designing and operating Korsch-type telescopes to achieve the optimal image quality.

We propose an alignment strategy that includes optimization criteria and appropriate targets to achieve satisfactory performance both on the ground and in space. The performance of a space telescope can vary significantly based on its assembly and alignment on the ground and its operation in space. Simulations were conducted to study the effects of gravity on a Korsch-type telescope with 0° astigmatism in the primary mirror. The results indicated that gravity influenced overall performance and led to an imbalance in performance across different fields. We propose three optimization criteria: overall, balanced, and good performance in both ground- and space-based environments. To meet these criteria, the telescope was optimized under the influence of gravity. Consequently, the selected optimization target successfully met the criteria by achieving good and balanced performance on the ground and in space. However, typical optimization targets, such as minimizing and designing the RMS wavefront error, are unable to fulfill all three criteria. Therefore, our alignment strategy offers a suitable solution that considers gravitational effects.

Space telescopes are exposed to extreme hot and cold temperature variations in the space environment depending on their orbit conditions. These temperature variations cause a significant effect on the opto-mechanical structures and lead to the final optical performance degradation. The development of space optical telescopes must achieve a thermally stable and reliable system through thermal analysis for on-orbit temperature prediction and thermal control design maintaining all components within their operating/survival temperature limits during entire mission phases. In this paper, we report the analysis results of passive and active thermal design for the ROKITS mission based on on-orbit thermal analysis taking into account the worst hot and cold conditions in the space environment using thermal analysis program - Thermal Desktop®, SINDA/FLUINT®.

New mission concepts that are under consideration by NASA call for the design and implementation of Far Ultraviolet (FUV) polarizer technologies that have not been developed yet. A team that includes members from the NASA Goddard Space Flight Center (GSFC), Arizona State University (ASU), and Woodruff Consulting, worked on the design and development of a polarizer design that produce very high extinction ratios in the FUV spectral range (100-200 nm). This polarizer consists of reflecting light through a series of mirrors from a combination of two silicon carbide (SiC) and two lithium fluoride (LiF) crystals positioned at angles of incidence (relative to surface normal) close to the average LiF Brewster’s angle in the FUV. The output is a highly linearly polarized beam. This polarizer concept was fabricated and tested in the existing McPherson 225 Vacuum Ultraviolet (VUV) spectrometer located in the Optics Branch at NASAGSFC. Initial testing using a MgF₂ crystal at the Brewster’s angle as an analyzer has shown that this design can produce state-of-the-art extinction ratios at the Hydrogen Lyman-Alpha (Ly-α) wavelength of 121.6 nm, and that the measured extinction ratio of the two crossed polarizers, ≈114, is mostly limited by the MgF₂ analyzer. A polarizer with such a performance at this wavelength has never been reported and it signifies a breakthrough in FUV polarization technology. The levels of effectiveness paired with the polarizer’s compact design allows for a new polarizer capability that would one day be implemented in a future FUV spectropolarimetry space mission.