Prototyping a New Telescope Design for Unprecedented Survey Speed in the Infrared

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Our Universe is full of fireworks. Events like colliding neutron stars are not only spectacular but can explain how heavy elements like gold were created. However, like fireworks hidden by their own smoke, scientist can only “hear” their gravitational waves. Astronomers in addition need to “see” the flash of light to know exactly where these explosions are, their colors and their secrets. Fortunately, infrared light penetrates the obscuring material. To catch these events before they fade, we need an infrared camera that records larger sections of the sky in one image than what is available at present. In the system being developed under this award, the entire telescope will be cryogenically cooled so that it doesn't emit a glow in infrared light. This project will build a quarter-scale prototype of a 1m diameter telescope that is planned for use in the Antarctic where the infrared sky is much darker. Such a system will be an infrared complement to the Vera Rubin Observatory. The team will integrate education and research by supporting undergraduate engineering and astronomy students working directly on this technology development. Graduate students will conduct demonstration science under the supervision of the project scientist. This project will develop a new infrared telescope that will utilize a pair of fused silica meniscus lenses placed symmetrically about the pupil to correct for the aberrations introduced by the spherical primary. This geometry achieves low chromatic aberration to deliver diffraction limited images at focal ratios as fast as f/1.2, without requiring dissimilar glasses. The convex fused silica second element is strong enough to support atmospheric pressure, enabling a fully cryogenic optical path through its use as the dewar window. The only warm surfaces seen by the detector are the transparent first element and a thin annulus at the pupil stop, which is configured as a low emissivity narcissus mirror. Key goals of the prototype are to confirm the predicted low thermal background, high throughput and good image quality at f/2 using a 250 mm aperture. A 2.5 μm cutoff Teledyne H2RG detector will cover a 17.8 deg2 field of view with 7.4 arcsec/pixel sampling. Three undergraduate students will be involved in demonstrating key technologies. These include measures to keep the entrance window above dew point, high precision focus and tilt control via thermal expansion of the primary mirror support bipods, and a novel detector readout mode for higher observing efficiency and enhanced dynamic range. This project advances the goals of the Windows on the Universe Big Idea.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.