Stephen L. Keil

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.

The Advanced Technology Solar Telescope: design and early construction

The National Solar Observatory’s (NSO) Advanced Technology Solar Telescope (ATST) is the first large U.S. solar telescope accessible to the worldwide solar physics community to be constructed in more than 30 years. The 4-meter diameter facility will operate over a broad wavelength range (0.35 to 28 μm ), employing adaptive optics systems to achieve diffraction limited imaging and resolve features approximately 20 km on the Sun; the key observational parameters (collecting area, spatial resolution, spectral coverage, polarization accuracy, low scattered light) enable resolution of the theoretically-predicted, fine-scale magnetic features and their dynamics which modulate the radiative output of the sun and drive the release of magnetic energy from the Sun’s atmosphere in the form of flares and coronal mass ejections. In 2010, the ATST received a significant fraction of its funding for construction. In the subsequent two years, the project has hired staff and opened an office on Maui. A number of large industrial contracts have been placed throughout the world to complete the detailed designs and begin constructing the major telescope subsystems. These contracts have included the site development, AandE designs, mirrors, polishing, optic support assemblies, telescope mount and coudé rotator structures, enclosure, thermal and mechanical systems, and high-level software and controls. In addition, design development work on the instrument suite has undergone significant progress; this has included the completion of preliminary design reviews (PDR) for all five facility instruments. Permitting required for physically starting construction on the mountaintop of Haleakalā, Maui has also progressed. This paper will review the ATST goals and specifications, describe each of the major subsystems under construction, and review the contracts and lessons learned during the contracting and early construction phases. Schedules for site construction, key factory testing of major subsystems, and integration, test and commissioning activities will also be discussed.

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.

Advanced Technology Solar Telescope project management

The Advanced Technology Solar Telescope (ATST) has recently received National Science Foundation (NSF) approval to begin the construction process. 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. This paper gives an overview of the project, and describes the project management principles and practices that have been developed to optimize both the projects success as well as meeting requirements of the projects funding agency.

Solar Mass Ejection Imager (SMEI)

The Solar Mass Ejection Imager (SMEI) experiment is designed to detect and measure transient plasma features in the heliosphere, including coronal mass ejections, shock waves, and structures such as streamers which corotate with the Sun. SMEI will provide measurements of the propagation of solar plasma clouds and high-speed streams which can be used to forecast their arrival at Earth from one to three days in advance. The white light photometers on the HELIOS spacecraft demonstrated that visible sunlight scattered from the free electrons of solar ejecta can be sensed in interplanetary space with an electronic camera baffled to remove stray background light. SMEI promises a hundred-fold improvement over the HELIOS data, making possible quantitative studies of mass ejections. SMEI measurements will help predict the rate of energy transfer into the Earths magnetospheric system. By combining SMEI data with solar, interplanetary and terrestrial data from other space and ground-based instruments, it will be possible to establish quantitative relationships between solar drivers and terrestrial effects. SMEI consists of three cameras, each imaging a 60 degree(s) X 3 degree(s) field of view for a total image size of 180 degree(s) X 3 degree(s). As the satellite orbits the earth, repeated images are used to build up a view of the entire heliosphere.

Flare Genesis Experiment

In January 1996, the Flare Genesis Experiment was carried for 19 days by a 29.4 M cu. ft helium-filled balloon in the stratosphere above Antarctica, during which over 14000 images of the Sun were recorded. Long-duration ballooning provides a relatively inexpensive means to observe the Sun under near-space conditions and to develop instrumentation and techniques that will be used on future solar space missions. The purpose of the flight was to improve understanding of the mechanisms involved in many different types of solar activity, particularly flares and solar filament eruptions. Achieving this goal demanded the development of a platform for an 80-cm F/1.5 optical telescope that would be stable to 10 arcseconds. In addition, we developed an image motion compensation system capable of holding the Suns image to better than the systems 0.2 arcsecond diffraction limit. Other key elements on board included a lithium-niobate Fabry-Perot etalon filter to provide a tunable 0.016-nm bandpass over a wide wavelength range, a fast 1534 X 1024-pixel Kodak CCD camera, and 180 GBytes of on-board storage. There was also a system for sending commands and receiving telemetry and a high-speed downlink for sending images during periods when the payload was in line of sight of the ground station. On- board computers provided a command and control system capable of near-autonomous operation. During most of the flight, contact with the payload was sporadic, so operation was primarily under autonomous control.