Nathan E. Dalrymple

Design and development of the Advanced Technology Solar Telescope (ATST)

High-resolution studies of the Suns magnetic fields are needed for a better understanding of solar magnetic fields and the fundamental processes responsible for solar variability. The generation of magnetic fields through dynamo processes, the amplification of fields through the interaction with plasma flows, and the destruction of fields are still poorly understood. There is still incomplete insight as to what physical mechanisms are responsible for heating the corona, what causes variations in the radiative output of the Sun, and what mechanisms trigger flares and coronal mass ejections. Progress in answering these critical questions requires study of the interaction of the magnetic field and convection with a resolution sufficient to observe scales fundamental to these processes. The 4m aperture Advanced Technology Solar Telescope (ATST) will be a unique scientific tool, with excellent angular resolution, a large wavelength range, and low scattered light. With its integrated adaptive optics, the ATST will achieve a spatial resolution nearly 10 times better than any existing solar telescope. Building a large aperture telescope for viewing the sun presents many challenges, some of the more difficult being Heat control and rejection Contamination and scattered light control Control of telescope and instrument polarization Site selection This talk will present a short summary of the scientific questions driving the ATST design, the design challenges faced by the ATST, and the current status of the developing design and siting considerations

Advanced Technology Solar Telescope: a progress report

The four-meter Advanced Technology Solar Telescope (ATST) will be the most powerful solar telescope and the worlds leading resource for studying solar magnetism that controls the solar wind, flares, coronal mass ejections and variability in the Suns output. Development of a four-meter solar telescope presents many technical challenges (e.g., thermal control of the enclosure, telescope structure and optics). We give a status report of the ATST project (e.g., system design reviews, instrument PDR, Haleakala site environmental impact statement progress) and summarize the design of the major subsystems, including the telescope mount assembly, enclosure, mirror assemblies, wavefront correction, and instrumentation.

Advanced Technology Solar Telescope: conceptual design and status

The Advance Technology Solar Telescope (ATST) has finished its conceptual design stage, submitted a proposal for construction funding and is working towards a system level preliminary design review later this year. The current concept (including integrated adaptive optics and instrumentation) will be reviewed with concentration on solutions to the unique engineering challenges for a four meter solar telescope that have been previously presented. The overall status will be given with a concentration on near term milestones and impact on final completion targeted in 2012.

Technical challenges of the Advanced Technology Solar Telescope

The 4m Advance Technology Solar Telescope (ATST) will be the most powerful solar telescope in the world, providing a unique scientific tool to study the Sun and possibly other astronomical objects, such as solar system planets. We briefly summarize the science drivers and observational requirements of ATST. The main focus of this paper is on the many technical challenges involved in designing a large aperture solar telescope. The ATST project has entered the design and development phase. Development of a 4-m solar telescope presents many technical challenges. Most existing high-resolution solar telescopes are designed as vacuum telescopes to avoid internal seeing caused by the solar heat load. The large aperture drives the ATST to an open-air design, similar to night-time telescope designs, and makes thermal control of optics and telescope structure a paramount consideration. A heat stop must reject most of the energy (13 kW) at prime focus without introducing internal seeing. To achieve diffraction-limited observations at visible and infrared wavelengths, ATST will have a high order (order 1000 DoF) adaptive optics system using solar granulation as the wavefront sensing target. Coronal observations require occulting in prime focus, a Lyot stop and contamination control of the primary. An initial set of instruments will be designed as integral part of the telescope. First telescope design and instrument concepts will be presented.

The Advanced Technology Solar Telescope enclosure

Telescope enclosure design is based on an increasingly standard set of criteria. Enclosures must provide failsafe protection in a harsh environment for an irreplaceable piece of equipment; must allow effective air flushing to minimize local seeing while still attenuating wind-induced vibration of the telescope; must reliably operate so that the dome is never the reason for observatory down time; must provide access to utilities, lifting devices and support facilities; and they must be affordable within the overall project budget. The enclosure for the Advanced Technology Solar Telescope (ATST) has to satisfy all these challenging requirements plus one more. To eliminate so-called external dome seeing, the exterior surfaces of the enclosure must be maintained at or just below ambient air temperature while being subjected to the full solar loading of an observing day. Further complicating the design of the ATST enclosure and support facilities are the environmental sensitivities and high construction costs at the selected site - the summit of Haleakala on the island of Maui, Hawaii. Previous development work has determined an appropriate enclosure shape to minimize solar exposure while allowing effective interior flushing, and has demonstrated the feasibility of controlling the exterior skin temperature with an active cooling system. This paper presents the evolution of the design since site selection and how the enclosure and associated thermal systems have been tailored to the particular climatic and terrain conditions of the site. Also discussed are load-reduction strategies that have been identified through thermal modeling, CFD modeling, and other analyses to refine and economize the thermal control systems.