Major Projects

The Advanced Solar Telescope (AST) is a future large-aperture facility that will probe magnetic structures on the Sun with unprecedented resolution. With the AST, the magnetic microstructure that is responsible for coronal heating and contributes to solar irradiance variability will be resolved in the spatial, temporal, and spectral domains.

When coupled to adaptive optics, the AST will be capable of breaking the 0.1 arcsec barrier in the visible and will provide the resolution needed to analyze the active magnetic microstructure. The large aperture is required to provide the photon counts needed to follow changes on short time scales. Models suggest that many of the physical processes controlling atmospheric heating and magnetic field stability occur on scales of ~ 70--100 km or ~ 0.1 arcsec, and that magnetic fibrils move at velocities of ~ 0.5--0.7 kms^-1 and have lifetimes of ~ 20 minutes. Achieving high temporal and spectral resolution simultaneously with the necessary signal-to-noise (S/N) ratio requires a high photon flux, which in turn requires a large-aperture telescope (~ 3 m), even for the Sun. It is unlikely that a solar telescope of such a large aperture will be deployed in space in the next two decades. In the visible, the AST will complement forthcoming missions such as SOLAR-B, which will have an aperture of 0.5 m and will operate over a wider field of view than the AST.

Critical diagnostics of the solar magnetic field in the low chromosphere and the corona reside in the thermal infrared, thereby adding a requirement for an all-reflective telescope and low-scattering optics.

NSO continues to work with the solar community to develop plans for an advanced solar telescope that will provide solar astronomers with the ability to go well beyond current ground- and space-based capabilities in the spatial, spectral, and temporal domains. During the Chicago AAS meeting, an interested-parties meeting for the AST was held with about 30 people in attendance. Issues concerning an AST management structure and development plan were discussed, with almost unanimous agreement that the AST should proceed as a collaboration between the university community and the national centers. NSO has prepared an AST science brochure for the Astronomy and Astrophysics Survey Committee, which is available at the NSO Web site. NSO continues to explore some of the technical issues involved in developing an AST. In addition to adaptive optics, near- and thermal-IR detectors are being developed which will be needed to fully exploit the AST and methods of integrating the adaptive optics with advanced Stokes polarimetry, narrow-band imaging and multi-lens arrays for simultaneous 2-D spatial and spectral imaging.

Seeing observations using the Seykora solar scintillation monitor continue at a number of sites. The construction of two new instruments is nearing completion. One is a Solar Dual Image Motion Monitor (S-DIMM), which will measure the differential motions of a point on the solar limb as seen by two telescopes 0.75 inch in diameter, 9 inches apart. Assuming Kolmogorov turbulence statistics, these measurements result in an estimate of the Fried parameter r_o. Two S-DIMMs will be constructed with the intent of locating one permanently at a lake site (for example, BBSO) to confirm the superiority of those sites for high-resolution observations with direct seeing measurements. The other will be movable among various other sites. The second instrument is a linear array of 9 solar scintillometers. The 36 scintillometer baselines vary in range from 1 cm to 22 meters. The correlation between the signals of pairs of scintillometers defines the properties of the shadow band pattern formed by the full Sun. From it the height variation of the atmospheric structure constant C_n² can be determined which in turn results in an estimate of the isoplanatic patch size. The device called SHAdow BAnd Ranger, or SHABAR, will be deployed initially at Sacramento Peak.

GONG

The Global Oscillation Network Group (GONG) is an international, community-based project designed to conduct a detailed study of the internal structure and dynamics of our closest star, the Sun, by measuring resonating waves that penetrate throughout the solar interior. In order to overcome the limitations of observations imposed by the day-night cycle at a single observatory, GONG is operating a six-station network of extremely sensitive and stable solar velocity mappers located around the Earth obtaining nearly continuous observations of the ``five-minute" pressure oscillations. GONG is also operating a distributed data reduction and analysis system to support the coordinated analysis of these data, and a data management system to archive and distribute the data products. GONG data are available to any qualified investigator whose proposal has been accepted; however, active membership in a GONG Scientific Team allows early access to the data and the collaborative scientific analysis that the teams conduct.

A Scientific Advisory Committee---consisting of P. Gilman (High Altitude Observatory), R. Noyes (Harvard-Smithsonian Center for Astrophysics), A. Title (Lockheed Martin Solar and Astrophysics Laboratory), J. Toomre (University of Colorado/Chair), and R. Ulrich (University of California, Los Angeles)---continues to provide overall scientific guidance to the project. In addition, a Data Management and Analysis Center Users' Committe---consisting of T. Appourchaux (ESA/ESTEC), S. Basu (Princeton), P. Stark (University of California, Berkeley), S. Korzennik (Harvard-Smithsonian Center for Astrophysics), J. Schou (Stanford University/Chair)—provides important community input to this critical part of the project.

The GONG stations are hosted by, and operate in close collaboration with, major international astronomical facilities: Big Bear Solar Observatory in California, the High Altitude Observatory's site on Mauna Loa in Hawaii, the Learmonth Solar Observatory in Western Australia, the Udaipur Solar Observatory in India, the Observatorio del Teide on Tenerife in the Canary Islands, and the Cerro Tololo Inter-American Observatory in Chile.

The project's Tucson-based operations staff maintains daily contact with the automatically operating site instruments checking the current state of the instruments and reviewing any informational messages generated by the real-time system. Each of the network instruments generates a 200 parameter database which is transmitted to the Tucson station once a day to facilitate the review and analysis of the functioning of the remote instruments, including fault diagnosis and the detection of performance anomalies and long-term trends. When problems occur or a quick response is required, the network operations ``on call" duty responder can be readily accessed via phone, fax, or e-mail. The instruments are also monitored locally by our collaborators at the host observatories.

The technical performance and reliability of the network continue to be excellent, with the daily sidelobe artifacts virtually invisible. Of all the possible images that could be obtained at the individual sites, less than 2% have been lost to equipment down-time, attributed primarily to scheduled maintenance, and many of these gaps were filled by images taken at adjacent sites.

The Data Management and Analysis Center (DMAC) completed the reduction of the raw data from GONG's first three years of operation: 35 36-day-long GONG months with a final fill factor of 0.84. Data reduction activities over the past year included an eight-month campaign to identify the mode frequencies in the initial 35 GONG-month run, and the reduction of magnetograms to synoptic maps for the entire data set. The data from these and other processing steps continue to be archived in the Data Storage and Distribution System, which is also responsible for the distribution of archived scientific data products to the community. Requests are typically received by email and via GONG's web site and most data distributions are satisfied by Internet transfers.

Since the GONG instruments were designed over a decade ago, local helioseismology and studies of the upper convection zone have become major research areas. These studies require better angular resolution, but promise rich scientific rewards from high duty-cycle observations of Doppler velocity, line strength, continuum intensity, and Zeeman splitting over a solar cycle.

Thus, we are developing a 1024² CCD camera system [GONG+], which has been installed at the Tucson facility and is providing full-resolution solar images to a prototype data acquisition system. Although we are still characterizing the system and analyzing data, calibration data indicate that the system performs well within our signal-to-noise goals and the instrument environment is much quieter than anticipated. The initial l-v diagrams, from time series acquired with the new system, show excellent response out to the optical cutoff of around l = 950. We plan for a February--June deployment schedule, with a fully operational network in place by mid-June 2000.

The project plans to collect full-resolution images on-site, and calibrate and merge the six-site high-resolution data set at the Tucson processing center. The added factor of sixteen resolution, in addition to the collection of continuous line-of-sight magnetograms, presents a formidable task for the current DMAC data reduction pipeline. Once merged, the data will be processed at the DMAC maintaining the current l coverage. To address the GONG+ processing limitation, the project will propose for another phase, GONG++, implementing a high-performance computing capability.

The GONG 1999 Annual Meeting was held in Tucson, March 22--24. With nearly ninety participants, the forum focused on works in progress, which address the physics of the moderate and high spherical harmonic degree modes, the data analysis methods needed to extract the appropriate description of their properties, and the physics of the solar interior that can be derived from them. The meeting also presented the opportunity to stimulate the work of the international GONG community in anticipation of the GONG+ high-resolution data. The meeting provided an opportunity for the Scientific Advisory Committee and the DMAC Users' Committee to meet. Representatives from all the sites were in attendance, providing an opportunity to discuss the installation and certification of the GONG+ camera system.

The project had the pleasure of hosting extended scientific visits for Sushant Tripathy (Udaipur Solar Observatory), Markus Roth (Kiepenheuer-Institut), Pier Francesco Moretti (University of Rome), and Oleg Ladenkov (Uzbek Academy of Sciences).

SOLIS

SOLIS (Synoptic Optical Long-term Investigations of the Sun) is a project to make optical measurements of processes on the Sun, the study of which requires well-calibrated, sustained observations over a long time period. The project was conceived in 1995, proposed to NSF in January 1996 as part of a ``Renewing NOAO" proposal, and received partial funding in January 1998. The design and construction phases will require three years and the 25-year operational phase will start by the end of FY 2001. The project was de-scoped at the request of the NSF when funding fell short of the request. A Science Advisory Group provides expert advice from a wide range of the user community. The High Altitude Observatory and NASA are active partners in SOLIS. The project is also sharing results and experience with other NSO projects including RISE/PSPT, GONG, and ISOON.

After de-scoping, SOLIS consists of three instruments that will initially be mounted on the top of the existing Kitt Peak Vacuum Telescope, pending availability of a superior, affordable site. The three full-disk instruments on a common mount are as follows: (1) a Vector Spectromagnetograph (VSM) to measure the strength and direction of the photospheric magnetic field, the line-of-sight component of the chromospheric magnetic field, and the spectral line characteristics of the helium chromosphere; (2) a Full Disk Patrol (FDP) that provides digital, one arcsec pixel images of the full disk showing the intensity and line-of-sight velocity in a number of spectrum lines at high cadence; (3) an Integrated Sunlight Spectrometer (ISS) which furnishes Sun-as-a-star spectra at both high and medium spectral resolutions with emphasis on high photometric precision and stability. A major component of SOLIS is data processing, distribution, and archiving.

This report covers months eight through nineteen (9/98--8/99) of the planned forty-two month design, construction, testing, and startup phases of the 25-year SOLIS project. During the report period most of the project effort was devoted to design of the mounting, instruments, and software. By the end of the report period, most of the design work was completed and the project is now well into the construction and testing phases.

Three reviews of the project involving outside experts took place during the report period. The first, February 2--3, 1999 focused on project management. The committee recognized that the project had made good progress under difficult conditions (mainly a result of hiring delays) but identified a number of ways in which the management approach needed to be strengthened. The main outcome was to develop, jointly with other NOAO projects, standard tools and techniques for managing SOLIS and other NOAO programs. The second review, April 14--16, 1999 was a technical review of hardware and software designs. For some aspects of the project, this was a conceptual design review, while for others, it was a critical review. This situation resulted from the very different paces of the various parts of the project. This review was successful and provided valuable advice from community experts. The third exercise involved the SOLIS Science Advisory Group (SAG) centered around the time of a meeting of the group on June 1, 1999. This review produced a prioritized list of the data products to be provided by SOLIS. In addition to these reviews, numerous smaller scale reviews of specific aspects of the SOLIS system were held throughout the year. Some of these involved only project personnel and others took advantage of non-project NOAO personnel.

In addition to preparation of these reviews and regular status reports for the NSO staff, the SOLIS SAG, NOAO, and NSF, the project conducted a number of major activities: (1) Procurement of long-lead time items by Requests for Proposal and other contracting or purchasing means. Some significant examples were the SOLIS mounting (bids now being reviewed), the ISS spectrograph and CCD camera (delivered and now undergoing testing), a very large grating for the VSM (delivered and tested), the large entrance window for the VSM (delivery imminent), fabrication of the telescope optics for the VSM (recently initiated), polarization modulators for the VSM (delivered and under test), the custom high-speed CCD cameras for the VSM (prototype expected in early FY 2000), the fast tip-tilt mirror driver for the FDP and VSM (delivered and tested), and the Storage Area Network for handling data from the instrument (recently initiated). (2) Analytic and laboratory studies and tests as part of the design activities. Some examples include the polarization modulator for the VSM, in-house construction of achromatic wave-plates for the FDP, testing of new algorithms for calibrating data from the VSM, and testing various software communication strategies. (3) Preparation of final design drawings and documents.

FY 2000 will see the peak of the current solar activity cycle and also of SOLIS construction activity. Major emphasis will be on assembly, testing, and debugging of the hardware and software components of SOLIS. Development of calibration and reduction algorithms will be accelerated by the imminent arrival of a Data Scientist. Preliminary observations and cross calibrations using the ISS should be well underway. The SOLIS funded staff will reach its peak of 12 FTE with additions from the NSO and ETS bases augmenting this roster. We do not yet know the fate of a proposal to NSF by the High Altitude Observatory of NCAR/UCAR that incorporates construction of two additional VSM instruments, but if we are to take full advantage of our present excellent team of engineers and technicians, this possibility needs to be resolved soon.

RISE/PSPT

The Precision Solar Photometric Telescope (PSPT) project consists of a network of three specialized telescopes to provide high photometric precision and high spatial resolution full-disk solar images in the CaII K line and two other continuum wavelengths. These images can be used to study the irradiance contribution of various solar features, ranging in size from small magnetic field elements to large active regions, and to characterize the global temperature structure. FY 1999 witnessed completion of the third RISE/PSPT telescope, which will operate at NSO/SP. The other two telescopes forming the PSPT network are in Hawaii and Italy. The NSO will seek funds to operate the PSPT for at least a full eleven years to provide data for all phases of the solar cycle.

SOAR

The goal of the SOAR project is the construction of a 4.3-m telescope on Cerro Pachón, with first light occurring in late 2002. The partners in the project are CNPq (Brazil), the University of North Carolina, Michigan State University, and NOAO. During this past year, several significant milestones were achieved: the primary mirror blank was fused at Corning; contracts were let to RSI for the telescope mount and to Raytheon for the active optics system; design of the facility was completed by M3 Architecture and Engineering; excavation activities were begun for the telescope pier on Cerro Pachón; and the utility line work was completed, with all conduits and pipes for water, electricity, and communications in place as of the end of the fiscal year. Procurement of the enclosure, which will be fabricated in Brazil, is in progress.

SOAR staff members worked with Brooke Gregory (CTIO) during May in Tucson to define the Calibration Wave-Front Sensor (CWFS) Package for SOAR. SOAR has also joined a consortium to obtain MIT/LL CCDs. The SOAR TCS will be based on LabVIEW, and contracts have been let to Patrick Wallace (RAL) and Mike Ashe (Imaginatics) to develop software.