KEYWORDS: Space telescopes, Design and modelling, Telescopes, Observatories, Mirrors, James Webb Space Telescope, Space mirrors, Equipment, Astronomy, Coronagraphy
New development approaches, including launch vehicles and advances in sensors, computing, and software, have lowered the cost of entry into space, and have enabled a revolution in low-cost, high-risk Small Satellite (SmallSat) missions. To bring about a similar transformation in larger space telescopes, it is necessary to reconsider the full paradigm of space observatories. Here we will review the history of space telescope development and cost drivers, and describe an example conceptual design for a low cost 6.5 m optical telescope to enable new science when operated in space at room temperature. It uses a monolithic primary mirror of borosilicate glass, drawing on lessons and tools from decades of experience with ground-based observatories and instruments, as well as flagship space missions. It takes advantage, as do large launch vehicles, of increased computing power and space-worthy commercial electronics in low-cost active predictive control systems to maintain stability. We will describe an approach that incorporates science and trade study results that address driving requirements such as integration and testing costs, reliability, spacecraft jitter, and wavefront stability in this new risk-tolerant “LargeSat” context.
Aspera is the UV small-satellite mission to detect and map the warm-hot phase gas in nearby galaxy halo. Aspera was chosen as one of NASA's Astrophysics Pioneers missions in 2021 and employs a FUV long-slit spectrograph payload, optimized for low-surface brightness O VI emission line detection at 103-104 nm. The mission incorporates state-of-the-art UV technologies such as high-efficiency micro-channel plates and enhanced LiF coating to achieve a high level of diffuse-source sensitivity of the payload, down to 5.0E-19 erg/s/cm^2/arcsec^2. The combination of the high sensitivity and a 1-degree by 30-arcsecond long-slit field of view enables efficient 2D mapping of diffuse halo gas through step and stare concept observation. Aspera is presently in the critical design phase, with an expected launch date in mid-2025. This work provides a current overview of the Aspera payload design.
Aspera is an extreme-UV (EUV) Astrophysics small satellite telescope designed to map the warm-hot phase coronal gas around nearby galaxy halos. Theory suggests that this gas is a significant fraction of a galaxy’s halo mass and plays a critical role in its evolution, but its exact role is poorly understood. Aspera observes this warm-hot phase gas via Ovi emission at 1032 °A using four parallel Rowland-Circle-like spectrograph channels in a single payload. Aspera’s robust-and-simple design is inspired by the FUSE spectrograph, but with smaller, four 6.2 cm × 3.7 cm, off-axis parabolic primary mirrors. Aspera is expected to achieve a sensitivity of 4.3×10−19 erg/s/cm2/arcsec2 for diffuse Ovi line emission. This superb sensitivity is enabled by technological advancements over the last decade in UV coatings, gratings, and detectors. Here we present the overall payload design of the Aspera telescope and its expected performance. Aspera is funded by the inaugural 2020 NASA Astrophysics Pioneers program, with a projected launch in late 2024.
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