KEYWORDS: Telescopes, Mirrors, James Webb Space Telescope, Space operations, Mirror structures, Thermal modeling, Thermal efficiency, Space telescopes, Off axis mirrors, Infrared telescopes
Some concepts for a future large IR/O/UV space telescope include a James Webb Space Telescope (Webb) style sunshade for thermal stability. This will bias the telescope cold and complicate one key advantage that a 6m high-contrast imaging telescope could have: operating and testing at room temperature. Early concepts of LUVOIR-B, a segmented, off-axis 8-meter aperture concept developed the Large Mission Concept Study Teams, predict more than 5kW of heat would be needed to bring the telescope to operating temperature. These room-temperature telescopes invite configurations that could take more advantage of solar heating. This paper explores architecture options and identifies some technologies, their maturation requirements, and risks.
KEYWORDS: Telescopes, Space operations, Sun, Space telescopes, Thermal modeling, Data modeling, Stray light control, MATLAB, Solar system, Solar energy
Starting with a conceptual thermal model of LUVIOR-A, provided by NASA/Goddard Space Flight Center, alternate concepts of operations are explored. A candidate technology was identified to use solar power for rough first stage heating. That innovation reimagines what functions a solar array can have in a large telescope architecture. By combining electricity generation, stray-light control, and thermal control into one agile deployable structure, the heater power requirements could be improved by reducing the inefficiency of solar power conversion.
Interferometric testing of large-sized optics in a thermal vacuum environment poses challenges not normally found in an optical metrology lab. Unless the test equipment is thermal-vacuum compatible, it must be installed in an ambient environment with the test item viewed through a window in the thermal-vacuum chamber. Limitations in chamber port size preclude normal-incidence viewing of the full aperture of large-sized optical elements. This necessitates the use of a mechanical translation of the test item to acquire multiple overlying interferograms. The interferograms are then concatenated in order to produce a full-aperture surface map of the test item. This is then used to confirm surface deformation of the entire test mirror. This paper will discuss the challenges, solutions, and results of a series of thermalvacuum tests performed on a large-scale (>40cm) silicon carbide mirror at ambient temperatures.
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