Left: 8-meter monolithic mirror telescope (credit: MSFC Advanced Concepts Office)
Right: 16-meter segmented mirror telescope (credit: Northrop Grumman Aerospace Systems & NASA/STScI)
What is ATLAST?
The Advanced Technology Large Aperture Space Telescope (ATLAST) is a NASA strategic mission concept study for the next generation of UVOIR space observatory. ATLAST will have a primary mirror diameter in the 8m to 16m range that will allow us to perform some of the most challenging observations to answer some of our most compelling astrophysical questions. We have identified two different telescope architectures, but with similar optical designs, that span the range in viable technologies. The architectures are a telescope with a monolithic primary mirror and two variations of a telescope with a large segmented primary mirror. The concepts invoke heritage from HST and JWST design, but also take significant departures from these designs to minimize complexity, mass, or both. ATLAST will have an angular resolution that is 5 - 10 times better than the James Webb Space Telescope (JWST) and a sensitivity limit that is up to 2000 times better than the Hubble Space Telescope (HST).
Why should we build ATLAST?
The greatest leaps in our understanding of the universe typically follow the introduction of radically new observational capabilities that bring previously unobserved phenomena into view. Some, such as the unambiguous detection of life on an Earth-like planet orbiting another star, will be profound yet conceivable. Others are entirely beyond our imagination. All forever change our view of our place in the universe. ATLAST is envisioned as a flagship mission of the 2025 - 2035 period, designed to address one of the most compelling questions of our time. Is there life else where in our Galaxy? It will accomplish this by detecting"biosignatures" (such as molecular oxygen, ozone, water, and methane) in the spectra of terrestrial exoplanets.
But ATLAST is more than just a "life-finder". ATLAST will have the performance required to reveal the underlying physics that drives star formation and to trace the complex interactions between dark matter, galaxies, and the intergalactic medium. Because of the large leap in observing capabilities that ATLAST will provide, we cannot fully anticipate the diversity or direction of the investigations that will dominate its use - just as the creators of HST did not foresee its pioneering roles in characterizing the atmospheres of Jupiter-mass exoplanets or measuring the acceleration of cosmic expansion using distant supernovae. ATLAST will have the versatility to far outlast the scientific vision of current-day astronomers.
Objectives of our NASA Strategic Mission Concept Study
We have produced a road map of the key technology developments required to enable ATLAST. Two of the concepts, the 8m monolithic mirror telescope and the 16.8m segmented mirror telescope, span the range of UVOIR observatories that are enabled by NASA's proposed space launch system (SLS) vehicle. The 8m ATLAST offers the inherent advantages of a monolithic aperture telescope in terms of high-contrast imaging and superb wavefront control. The 16m ATLAST represents a pathway to truly large apertures in space and uses the largest extrapolation of a JWST-like chord-fold primary mirror packaging. However, the ATLAST mission is not solely dependent on Ares V. Our third concept, a 9.2m segmented telescope, is compatible with an Evolved Expendable Launch Vehicle (EELV) and also adopts JWST design heritage. The ATLAST technology development plan is supported with funding from NASA's Astrophysics Strategic Mission Concept Study program, the Goddard Space Flight Center, the Marshall Space Flight Center, the Jet Propulsion Laboratory (Caltech) and related programs at Northrop Grumman Aerospace Systems and Ball Aerospace and Technology Corp.
The rapid progress on lightweight mirror technology that enabled the JWST is already being extended using new materials and processes, such as silicon carbide, corrugated and/or nanolaminate mirrors. Combined with advances in closed-loop wave front control of active optics and very large launch vehicles, the ATLAST concepts are affordable for the 2020 era if the technological development continues appropriately. The focus of our study was to identify the designs and technologies that enable the most cost-effective approaches. Consequently, our technology development plan is based on a comprehensive comparison of options for mirror fabrication, wavefront sensing and control, optical design, thermal analysis, pointing control, science instrument capabilities and a roadmap to bring these to high technological readiness levels for flight in the 2020 decade.
