Small-ELF (SELF) is a 3.5-meter telescope currently entering the manufacturing phase and will serve as a technology precursor for the much larger telescope named ELF (Exo-Life Finder). The primary objective of the proposed design approach is to to radically improve the system’s capabilities for the detection of biomarkers and life in the atmospheres of exoplanets while keeping costs well below the current flagship observatories and thus maintaining cost-effectiveness. This is achieved through innovative approaches in motion and shape control, machine learning, and the integration of tensegrity techniques. SELF's manufacturing phase will commence in 2024-2025, with detailed design and manufacturing specifics outlined in this paper. To further mitigate technical risks, a small 0.25-meter prototype named MicroELF is also being designed and built in 2024. MicroELF incorporates the proposed optical and mechanical design to allow varying degrees of freedom for each component and utilizes distributed aperture principles akin to SELF. The degrees of freedom in MicroELF are controllable based on optical image feedback and a machine learning model. The paper details the optomechanical complexity of MicroELF, designed for successful construction and demonstration within 2024. SELF and MicroELF, as technology demonstrators, address prevalent cost and scalability challenges in existing telescopes, intending to introduce a novel paradigm in large telescope structural design.
The constantly increasing needs for astronomical imaging of ever fainter objects as well as for imaging the Earth from space require much higher angular resolution and dynamic range than current optical telescopes can deliver. Mirrors are the key elements of these systems; but they are technologically difficult to improve because they must maintain an exceedingly precise shape while resisting deformations (for example from gravity and/or variable wind loads) in the open environments in which they must operate. Our interdisciplinary novel technology will establish a new paradigm: we will shape thin, very smooth, “fire-polished,” lightweight glass to a predetermined curvature and generate dynamically controlled stiffness by using the addressable energy of electroactive polymers (EAPs) to resist environmental deformations – making what we call a “Live” Mirror.
Small-ELF is a 3.5-meter telescope currently in development that will serve as a technology demonstrator for the much larger telescope named ELF (Exo-Life Finder). The ELF is proposed to be built with a minimum effective diameter of 12- meters and is designed to be scalable to a much larger size. The primary objective of the proposed design approach is to radically improve the system’s capabilities for direct imaging of exoplanets while keeping costs well below the current flagship observatories. The basic optical design of Small-ELF consists of an annulus of 15 primary mirror sub-apertures, mounted on an alt-az configuration. As a technology demonstrator, the mechanical design of Small-ELF intends to deliver a versatile and reliable experimental platform to implement and verify several new techniques: the use of a tensegrity-based configuration for a light-weight supporting structure, the use of tensioned ropes to actively adjust the telescope geometry, methods of accommodating sub-apertures of significant weight variations, and methods of controlling and mitigating vibrations associated with light-weighted structures through active and passive damping systems. The design also adopts techniques for efficient precision manufacturing and cost control. The unique optical layout and application of tensegrity produce significant weight and subsequent cost reductions. This technology demonstrator tackles the cost and scalability problem faced by most existing telescopes and intends to open a new chapter in large telescope structural design methodology.
The small ExoLife Finder (sELF) telescope is a 3.4m diameter fixed pupil tracking Fizeau interferometer. Its design relies on several new technologies the ELF-PLANETS consortium has championed that will enable large narrow-field optical coronagraphic direct imaging. These distinguish it from other segmented aperture telescopes by its light weight, low cost, and its capability to create a coronagraphic point spread function with the telescope pupil, ahead of the secondary optics. This diffractive control emphasizes high dynamic range imaging in the presence of a bright central star in a narrow field-of-view. Its optomechanical design uses elements of tensegrity combined with thin (2mm thick by 0.5m diameter) off-axis parabola segments to decrease both the optical payload and mechanical structural mass. The sELF optomechanical design has been completed and contracts for construction in the Canary Islands will be tendered during the 1st quarter of 2023
An enclosure design concept is proposed for a large ground-based optical telescope in the 20- to 30-metre class. The proposed configuration differs from the enclosures for existing large telescopes. Current large telescope enclosure designs have inherent inefficiencies which may be substantially magnified if these designs are scaled. Dynamic analysis studies show that motion requirements for the mechanical components of existing enclosures may be too stringent for next-generation enclosures and that these requirements should be revisited. The proposed enclosure design uses a spherical base structure with a rotating inclined cap. This design improves upon some of the mechanical, structural and operational inefficiencies of current spherical enclosures with conventional shutters. The design also offers potential advantages in the protection of the telescope from wind buffeting forces. Wind loading is expected to be one of the most significant factors governing the design of a next-generation large telescope. The enclosure design includes features which are expected to improve the air flow characteristics in and around the enclosure. Preliminary computational fluid dynamics (CFD) studies have been performed in order to analyze the effect of various enclosure details and components on the flow patterns. Future comparative and detailed CFD studies on the enclosure and telescope are proposed. A plan for practical validation of the results of CFD analysis is presented, in order to better understand the benefits of CFD in predicting the effects of wind buffeting on next-generation large telescopes.
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