The COronal Solar Magnetism Observatory (COSMO) is a proposed facility with unique capabilities for magnetic field measurements in the solar atmosphere and corona to increase our understanding of solar physics and space weather. The observatory underwent a preliminary design review (PDR) in 2015. This paper summarizes the systems engineering plan for this facility as well as a preliminary overview of the concept of operations. In particular we detail the flow of science requirements to engineering requirements, and discuss an overview of requirements management, documentation management, interface control and overall verification and compliance processes. Operationally, we discuss the categories of operational modes, as well as an overview of a daily operational cycle.
The Coronal Solar Magnetism Observatory Large Coronagraph (COSMO-LC) is a 1.5 meter Lyot coronagraph dedicated to measuring magnetic fields and plasma properties in the solar corona. The COSMO-LC will be able to observe coronal emissions lines from 530-1100 nm using a filtergraph instrument. COSMO-LC will have a 1 degree field of view to observe the full solar corona out to 1 solar radius beyond the limb of the sun. This presented challenges due to the large Etendue of the system. The COSMO-LC spatial resolution is 2 arc-seconds per pixel (4k X 4k). The most critical part of the coronagraph is the objective lens that is exposed to direct sunlight that is five orders of magnitude brighter than the corona. Therefore, it is key to the operation of a coronagraph that the objective lens (O1) scatter as little light as possible, on order a few parts per million. The selection of the material and the polish applied to the O1 are critical in reducing scattered light. In this paper we discuss the design of the COSMO-LC and the detailed design of the O1 and other key parts of the COSMO-LC that keep stray light to a minimum. The result is an instrument with stray light below 5 millionths the brightness of the sun 50 arc-seconds from the sun. The COSMO-LC has just had a Preliminary Design Review (PDR) and the PDR design is presented.
The Chromosphere and Prominence Magnetometer (ChroMag) is conceived with the goal of quantifying the intertwined dynamics and magnetism of the solar chromosphere and in prominences through imaging spectro- polarimetry of the full solar disk. The picture of chromospheric magnetism and dynamics is rapidly developing, and a pressing need exists for breakthrough observations of chromospheric vector magnetic field measurements at the true lower boundary of the heliospheric system. ChroMag will provide measurements that will enable scientists to study and better understand the energetics of the solar atmosphere, how prominences are formed, how energy is stored in the magnetic field structure of the atmosphere and how it is released during space weather events like flares and coronal mass ejections. An integral part of the ChroMag program is a commitment to develop and provide community access to the "inversion" tools necessary for the difficult interpretation of the measurements and derive the magneto-hydrodynamic parameters of the plasma. Measurements of an instrument like ChroMag provide critical physical context for the Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS) as well as ground-based observatories such as the future Advanced Technology Solar Telescope (ATST).
The COSMO K-Coronagraph is scheduled to replace the aging Mk4 K-Coronameter at the Mauna Loa Solar
Observatory of the National Center for Atmospheric Research in 2013. We present briefly the science objectives and
derived requirements, and the optical design. We single out two topics for more in-depth discussion: stray light, and
performance of the camera and polarimeter.
The Coronal Solar Magnetism Observatory (COSMO) is a facility dedicated to measuring magnetic
fields in the corona and chromosphere of the Sun. It will be located on a mountaintop in the Hawaiian
Islands and will replace the current Mauna Loa Solar Observatory (MLSO). COSMO will employ a
suite of instruments to determine the magnetic field and plasma conditions in the solar atmosphere and
will enhance the value of data collected by other observatories on the ground (SOLIS, ATST, FASR)
and in space (SDO, Hinode, SOHO, GOES, STEREO, DSCOVR, Solar Probe+, Solar Orbiter). The
dynamics and energy flow in the corona are dominated by magnetic fields. To understand the
formation of Coronal Mass Ejections (CMEs), their relation to other forms of solar activity, and their
progression out into the solar wind requires measurements of coronal magnetic fields. The COSMO
suite includes the Large Coronagraph (LC), the Chromosphere and Prominence Magnetometer
(ChroMag) and the K-Coronagraph. The Large Coronagraph will employ a 1.5 meter fuse silica singlet
lens and birefringent filters to measure magnetic fields out to two solar radii. It will observe over a
wide range of wavelengths from 500 to 1100 nm providing the capability of observing a number of
coronal, chromospheric, and photospheric emission lines. Of particular importance to measuring
coronal magnetic fields are the forbidden emission lines of Fe XIII at 1074.7 nm and 1079.8 nm. These
lines are faint and require the very large aperture. NCAR and NSF have provided funding to bring the
COSMO Large Coronagraph to a preliminary design review (PDR) state by the end of 2013.
An increasing number of astronomical applications depend on the measurement of polarized light. For example, our
knowledge of solar magnetism relies heavily on our ability to measure and interpret polarization signatures introduced
by magnetic field. Many new instruments have consequently focused considerable attention on polarimetry. For solar
applications, spectro-polarimeters in particular are often designed to observe the solar atmosphere in multiple spectral
lines simultaneously, thus requiring that the polarization modulator employed is efficient at all wavelengths of interest. We
present designs of polarization modulators that exhibit near-optimal modulation characteristics over broad spectral ranges.
Our design process employs a computer code to optimize the efficiency of the modulator at specified wavelengths. We
will present several examples of modulator designs based on rotating stacks of Quartz waveplates and Ferroelectric Liquid
Crystals (FLCs). An FLC-based modulator of this design was recently deployed for the ProMag instrument at the Evans
Solar Facility of NSO/SP. We show that this modulator behaves according to its design.
Measuring magnetic fields in the solar corona requires a large aperture telescope with exceptionally low levels of
scattered light. For internally-occulted coronagraphs the main source is scattering from dust or microroughness on the
primary lens or mirror. We show refracting primaries offer significantly lower levels for both sources. To observe
magnetic fields in the solar corona with scientifically interesting spatial and temporal resolutions, a 1 meter aperture or
larger is required. For a long time such large-scale refractors have been deemed impractical or impossible to construct
due to gravitational deformation of the lens. We present the results of finite-element and optical analyses of the
gravitational deformation, stress-induced birefringence, and absorptive heating of a (see manuscript)1.5 meter f/5 fused silica lens.
These studies demonstrate the traditional objections to large refractors are unfounded and large refracting primaries have
We are constructing a spectro-polarimeter using the 40-cm coronagraph at the Evans Solar Facility of the National
Solar Observatory in Sunspot, NM for the purpose of measuring the vector magnetic field in prominences and
filaments. The Prominence Magnetometer (ProMag) is comprised of a polarization modulation package and a
spectrograph. The modulation optics are located at the prime focus of the coronagraph along with calibration
optics and a beamsplitter that creates two beams of orthogonal Stokes states. The spectrograph resides at the
coude focus of the coronagraph. The polarizations of the two chromospheric lines of neutral helium, at 587.6 nm
and 1083.0 nm, are to be observed simultaneously. We present details of the design of the spectro-polarimeter.
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.