Understanding the Sun's magnetic field related activity is far from complete as reflected in the limited ability to make
accurate predictions of solar variability. To advance our understanding of solar magnetism, the National Solar
Observatory (NSO) constructed the Synoptic Optical Long-term Investigations of the Sun (SOLIS) suite of instruments
to conduct high precision optical measurements of processes on the Sun whose study requires sustained observations
over long time periods. The Vector Spectromagnetograph (VSM), the principal SOLIS instrument, has been in operation
since 2003 and obtains photospheric vector data, as well as photospheric and chromospheric longitudinal magnetic field
measurements. Instrument performance is being enhanced by employing new, high-speed cameras that virtually freeze
seeing, thus improving sensitivity to measure the solar magnetic field configuration. A major operational goal is to
provide real-time and near-real-time data for forecasting space weather and increase scientific yield from shorter
duration solar space missions and ground-based research projects. The National Solar Observatory proposes to build two
near-duplicates of the VSM instrument and place them at international sites to form a three-site global VSM network.
Current electronic industry practice of short lifetime cycles leads to improved performance and reduced acquisition costs
but also to redesign costs and engineering impacts that must be minimized. The current VSM instrument status and
experience gained from working on the original instrument is presented herein and used to demonstrate that one can
dramatically reduce the estimated cost and fabrication time required to duplicate and commission two additional
instruments.
The Chromospheric Telescope (ChroTel) is a 10 cm robotic telescope to observe the full solar disk with a 2k × 2k CCD
at high temporal cadence. It is located at the Observatorio del Teide, Tenerife, Spain, next to the 70 cm German Vacuum
Tower Telescope (VTT). ChroTel contains a turret system that relays a stabilized image of the solar disk into a
laboratory within the VTT building. The control design allows a fully robotic operation. Observations are carried out in
three chromospheric wavelengths (CaK: 393 nm, Ha: 652 nm, HeI 1083 nm).
The Advanced Solar Technology Telescope (ATST) is a 4-m solar telescope being designed for high spatial, spectral and temporal resolution, as well as IR and low-scattered light observations. The overall limit of performance of the telescope is strongly influenced by the qualities of the site at which it is located. Six sites were tested with a seeing monitor and a sky brightness instrument for 1.5 to 2 years. The sites were Big Bear (California), Haleakala (Hawaii), La Palma (Canary Islands, Spain), Panguitch Lake (Utah), Sacramento Peak (New Mexico), and San Pedro Martir (Baja California, Mexico). In this paper we will describe the methods and results of the site survey, which chose Haleakala as the location of the ATST.
This paper addresses the issue of calibrating the Advanced Technology Solar Telescope for high-precision polarimetry, in particular of the optical train above the Gregorian station (where suitable calibration optics will be placed). Conventional techniques would not be adequate for this telescope given its large aperture. Here we explore two different methods that are currently being considered by the design team. The first one is the "sub-aperture" method, which uses small calibration optics above the primary mirror to calibrate a small sub-aperture of the system. This calibration is then extended to the full aperture by means of actual observations. The second method is based on analyzing the polarization observed in a spectral line with a peculiar Zeeman pattern, such as the FeII 614.9 nm line, which does not produce any intrinsic linear polarization. Numerical simulations are presented that show the robustness of both techniques and their respective advantages and disadvantages are discussed.
The mission of the ATST visible spectro-polarimeter (ViSP) is to provide precision measurements of the full state of polarization (Stokes parameters) simultaneously at diverse wavelengths in the visible spectrum and fully resolve (or nearly so) the profiles of spectrum lines originating in the solar atmosphere. We present the instrument science requirements, their flow down to instrument specifications, and a preliminary ViSP design. The ViSP spectrograph allows for reconfiguration while maintaining an immediately selectable configuration. We describe how the ViSP will utilize the ATST polarimetry facility.
The location of the Advanced Technology Solar Telescope (ATST) is a critical factor in the overall performance of the telescope. We have developed a set of instrumentation to measure daytime seeing, sky brightness, cloud cover, water vapor, dust levels, and weather. The instruments have been located at six sites for periods of one to two years. Here we describe the sites and instrumentation, discuss the data reduction, and present some preliminary results. We demonstrate that it is possible to estimate seeing as a function of height near the ground with an array of scintillometers, and that there is a distinct qualitative difference in daytime seeing between sites with or without a nearby lake.
The National Solar Observatory in collaboration with the High-Altitude
Observatory is developing a new solar polarimeter, the Diffraction Limited Spectro-Polarimeter. In conjunction with a new high-order adaptive optics system at the NSO Dunn Solar Telescope, the DLSP design facilitates very high angular resolution observations of solar vector magnetic fields. This project is being carried out in two phases. As a follow-on to the successful completion of the first phase, the ongoing DLSP Phase II implements a high QE CCD camera system, a ferro-electric liquid crystal modulator, and a new opto-mechanical system for polarization calibration. This paper documents in detail the development of the modulator system and its performance, and presents preliminary results from an engineering run carried out in combination with the new NSO high-order AO system.
A diffraction limited spectro-polarimeter is under construction at the National Solar Observatory in collaboration with the High Altitude Observatory. The scientific objective of the project is to measure the magnetic fields on the Sun up to the diffraction limit of the Dunn Solar Telescope. The same instrument would also measure the magnetic field of large sunspots or sunspot groups with reasonable spatial resolution. This requires a flexible image scale which cannot be obtained with the current Advanced Stokes Polarimeter (ASP) without loosing 50% of the light. The new spectro-polarimeter is designed in such a way that the image scale can be changed without loosing much light. It can work either in high-spatial resolution mode (0.09 arcsec per pixel) with a small field of view (FOV: 65 arcsec) or in large FOV mode (163 arcsec) with low-spatial resolution (0.25 arcsec per pixel). The phase-I of this project is to design and build the spectrograph with flexible image scale. Using the existing modulation, calibration optics of the ASP and the ASP control and data acquisition system with ASP-CHILL camera, the spectrograph was tested for its performance. This paper will concentrate on the performance of the spectrograph and will discuss some preliminary results obtained with the test runs.
Bruce Lites, David Elmore, Kim Streander, David Akin, Tom Berger, Dexter Duncan, Chris Edwards, Barbara Francis, Chris Hoffmann, Noah Katz, Michael Levay, Dnyanesh Mathur, William Rosenberg, Ericka Sleight, Theodore Tarbell, Alan Title, Darrel Torgerson
As a Japanese National space mission with international collaboration, Solar-B (2005 launch) will carry a spectro- polarimeter (SP) to be operated in visible light to obtain the first high angular resolution, precision measurements of solar vector magnetic fields from space. The SP is part of the Focal Plane Package (FPP) fed by a diffraction-limited 50-cm optical telescope. The SP will be operated exclusively at the photospheric 630 nm Fe I lines. It features a rotating, low-order crystalline quartz retarder for polarization modulation and a reflecting Littrow spectrograph design that is shortened by using diffraction from the 12micrometers wide slit to fill the grating. Polarization analysis is accomplished by a modified Savart plate beam splitter. A custom CCD detector with two active areas, one for each beam from the beam splitter, allows continuous high duty-cycle sampling of polarization. The spectrograph slit will sample a 0.16 x 164 arcsec2 rectangle of the solar image, which may be scanned across the slit by up to +/- 160 arcsec in order to build up vector magnetic field maps of the solar photosphere. Along with simultaneous, co-spatial imaging and polarimetry with the filter imagers of the FPP, the SP will provide a precise view of active and quiet solar magnetic fields that control the structure, dynamics, and energetics of the upper solar atmosphere.
We describe a ground-based eclipse instrument for measuring solar coronal polarization brightness and intensity, and the calibration procedures for this instrument. We present coronal measurements from the February 26, 1998 total solar eclipse observed at Curacao, N.A.. The instrument employs a liquid crystal variable retarder for analysis of coronal broad band linear polarization and collects data on an array detector spanning a 6.5 solar radius field of view. Polarization calibration of the liquid crystal variable retarder utilizes the tangential orientation of coronal polarization to calculate retardance values.
A new Stokes polarimeter for high spatial resolution quantitative measurement of magnetic fields at multiple heights in the solar atmosphere has been constructed by the National Center for Atmospheric Research and the National Solar Observatory. The instrument uses the Vacuum Tower Telescope at Sunspot, New Mexico, and its existing horizontal spectrograph, universal birefringment filter, and image motion stabilization system. The polarimeter uses a rotating retarder polarization modulator with polarization calibration optics. Multiple paired CCDs are used for detection followed by video processing to produce spatial maps of the full state of polarization in restricted regions of the solar spectrum. Two spectral regions encompassing lines sensitive to the Zeeman effect, which form in the photosphere and low chromosphere, are recorded simultaneously. Significant developments include: construction of the new telescope post focus optical arrangement, creation of a polarization model for the telescope, construction of high-speed, low-noise solid state cameras, and construction of computer hardware for receiving and processing high-rate 12-bit digital data.
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