The proposed COSMO facility consists of two major elements: A Large-aperture Coronagraph with its own pointing system and dome, and a solar-pointed spar for the supporting instrumentation in a smaller adjacent dome. The Large-aperture Coronagraph is a 1.5-m aperture refractor with two accompanying instruments: a narrow-band tunable filter polarimeter for synoptic measurements, and a fiber-fed spectropolarimeter for high-spectral-resolution observations. The supporting instruments are a white-light coronagraph to record the evolution of the electron scattered corona (K-corona), and a chromosphere and prominence magnetometer for disk and limb measurements of magnetic fields in the chromosphere and prominences using filter polarimetry. A conceptual sketch of the Large-aperture Coronagraph in its dome is shown below.

Proposed Suite of Instruments

The most important instrument in the COSMO suite is a large-aperture coronagraph with instrumentation to measure coronal magnetic fields. However, in order to exploit coronal magnetic field measurements to their full potential for advancing science they should be considered in the context of the ambient plasma environment. For this reason, crucial information on prominence magnetic fields and the dynamical conditions of the embedded plasma will be collected by two additional instruments: a white-light K-corona coronagraph and a prominence and filament magnetometer. These additional supporting instruments are designed to provide temporal and spatial resolutions that meet or exceed the temporal and spatial resolutions of the coronal magnetic field observations from the large-aperture coronagraph.

A brief description of the three main instruments follows.

Large-aperture Coronagraph - This solar telescope (Figure 9) performs coronal magnetometry using the coronal forbidden emission lines of Fe XIII at 1074.7 and 1079.8 nm and the He I chromospheric emission line at 1083.0 nm. This coronagraph will have an aperture of 1.5 m and a full FOV of 1 degree. Post-focus instrumentation includes a narrow band tunable filter able to observe the entire FOV, as well as a fiber-fed spectrograph capable of high spectral resolution line profile observations.

White-light K-coronagraph - This 20-cm aperture white-light coronagraph provides observations of CME formation and early acceleration. It replaces the 1970s-vintage Mauna Loa Mk4 system, the world's only ground-based white light coronameter, with modern technology that allows observations with improved spatial resolution, temporal resolution, FOV, and signal-to-noise ratio. Given the absence of a white-light coronagraph on the SDO spacecraft, the K-coronagraph will be an essential complement to space- and ground-based coronal instruments.

Chromosphere and Prominence Magnetometer - This supporting magnetometer is designed to observe the He I 587.6 and 1083 nm lines, and Hα, both on the solar disk and above the limb. This instrument, which we call "ChroMag," will have the ability to determine magnetic fields and LOS Doppler shifts.