Arrayed wide-field astronomical camera system for spectroscopic surveys on Extremely Large Telescopes: system architecture, proof-of-concept, and enabling technologies

Abstract

The next generation Extremely Large Telescopes (ELTs) are promising a profound transformation of humanity's understanding of the universe by opening our eyes to a myriad of previously unseen astronomical objects across cosmic space time. Some of the key observational contributions to this transformation will, once again, be made through large-scale ultradeep spectroscopic surveys. Such surveys will call for a wide-field system to expand field of view and correct atmospheric dispersion beyond what an uncorrected ELT is canonically capable of. Although the traditional monolithic form of field correctors served our needs very well on 2-to 8-m class telescopes, we recognize challenges around scaling this traditional design to the ELT level, and hence, as detailed here, present a fundamentally different architecture, called the arrayed wide-field astronomical corrector system or AWACS, for the ELTs of two-mirror construction. The AWACS accomplishes field expansion via an array of small units populated over a telescope's focal surface, compensating for field aberrations and atmospheric dispersion locally but simultaneously. The AWACS units share one common electro-opto-mechanical design, permitting cost-effective high-volume part manufacturing. We detail the architectural features and proof-of-concept on-sky demonstration of the AWACS. In addition, we highlight our recent development results of randomly nano-textured antireflective (AR) surface structures in terms of an immediately viable, super-broadband, high-performance AR solution for not only the AWACS optics, but also broader ranges of electro-optical devices, particularly those subjected to harsh environments such as high-power laser, cryogenic, and space systems. With continuous advances in other relevant fields, the AWACS is uniquely positioned to enable, either by itself or by complementing traditional correctors, wide-field multi-object spectroscopic surveys in the ELT era and beyond. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

UV to IR high-efficiency antireflective surface modification of freeform and cylindrical lenses for space platform optical instrumentation

“…Larger diameter surfaces result in the generation of more etch byproducts that slow the process, and have more center-to-edge uniformity variance. Overall, the results shown in Figure 2 are very consistent and meet the spectral transmission requirements of the system unit 14,15 .…”

“…Randomly-distributed anti-reflective nanostructures were fabricated on fused silica cylindrical lenses and freeform optical elements, using a plasma-assisted reactive-ion etching technique. We examined the transmission-enhancing impact of the random nanostructures on the surfaces before their use as components of an arrayed wide-field astronomical corrector unit 14,15 .…”

High-efficiency anti-reflective modification of freeform elements and cylindrical lenses for arrayed wide-field astronomical corrector units

“…The rARSS exhibits characteristics that are ideal to meet such a need. [21][22][23] To the best of our knowledge, research to date has primarily focused on assessing the optical transmission performance of random structures including some comparisons between lenses with thin film anti reflection (TFAR) and rARSS, 15,16,18 without investigating optical system-level effects. Potential scattering or wavefront distortions caused by the presence of rARSS-enhanced components in an optical system are not available in the existing literature.…”

“…Due to the large (22×) number of air-glass interfaces in each AWACS unit, it is critical to minimize the loss from Fresnel reflection and scattering over a broad wavelength range from 365 to 1000 nm. The rARSS exhibits characteristics that are ideal to meet such a need 21 – 23 …”