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Ultraviolet Coronagraph Spectrometer (UVCS)

ResourceID
spase://SMWG/Instrument/SOHO/UVCS

Description

The primary scientific goals of the UVCS (UltraViolet Coronagraph Spectrometer) are to: (1) locate and characterize the coronal source regions of the solar wind; (2) identify and understand the dominant physical processes that accelerate the solar wind; (3) understand how the coronal plasma is heated in solar wind acceleration regions; and, (4) increase our knowledge of the coronal phenomena that control the physical properties of the solar wind as determined by in situ measurements. The UVCS is intended to determine the primary plasma parameters of the solar corona from its base to as high as 10 Re. It is expected to measure signatures of both thermal and nonthermal processes: electron temperatures, effective temperatures of protons and several minor ions; electron and ion densities of O+5, Mg+9, Si+11, and Fe+11; and flow velocities of the electron/proton plasma and of O+5, Mg+9, and Si+11. The instrument consists of an occulted telescope and a high resolution spectrometer assembly. Three off-axis telescope mirrors focus co-registered images of the extended corona onto the three entrance slits of the spectrometer assembly. The spectrometer assembly consists of three sections. One is optimized for line profile measurements of H I Lyman alpha, with a range of 114.8--128.3 nm, extendable to 113.0 nm and 130.0 nm with grating motions. A second section is optimized for line intensity measurements of O VII (103.2 nm) and is also used to observe Si XII in second order (499 and 521 nm; first order range is 93.2--106.8 nm). The third section is used to measure polarized radiance of the visible corona. A filter with a bandpass of 450.0--600.0 nm is mounted in front of a photomultiplier tube. The EUV spectrometer sections use toroidal concave diffraction gratings in Rowland circle mounts that produce stigmatic imaging at the subject wavelengths. There are entrance slit changing mechanisms on each spectrometer. The detectors for the EUV are multi-anode microchannel arrays, each with 360 x 1024 pixels on 0.025 mm centers. The instantaneous field of view (FOV) of the instrument is the portion of the solar image that passes through the spectrometer entrance slits. Internal mirror motions are used to step the instantaneous FOV across the 141' x 40' FOV defined by the entrance aperture. Offset pointing adjustments can be used to extend the FOV for EUV measurements down to the solar limb, and also onto the solar disk for measurements of absolute spectral line intensities and positions. The UVCS can rotate its FOV about the sun-center to observe any segment of the corona within 10 solar radii. Twelve rotations of 30 degrees would build up a spectroscopic description of the full corona out to 5 solar radii, with additional data out to 10 solar radii. This information was taken from the article ``UVCS - the Ultraviolet Coronagraph Spectrometer for SOHO,'' by J. L. Kohl and G. Noci (Proceedings of the First SOHO Workshop, ESA SP-348, pp. 23-26, November 1992).

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Details

Version:2.0.0

Instrument

ResourceID
spase://SMWG/Instrument/SOHO/UVCS
ResourceHeader
ResourceName
Ultraviolet Coronagraph Spectrometer (UVCS)
AlternateName
UVCS
ReleaseDate
2019-05-05 12:34:56Z
Description

The primary scientific goals of the UVCS (UltraViolet Coronagraph Spectrometer) are to: (1) locate and characterize the coronal source regions of the solar wind; (2) identify and understand the dominant physical processes that accelerate the solar wind; (3) understand how the coronal plasma is heated in solar wind acceleration regions; and, (4) increase our knowledge of the coronal phenomena that control the physical properties of the solar wind as determined by in situ measurements. The UVCS is intended to determine the primary plasma parameters of the solar corona from its base to as high as 10 Re. It is expected to measure signatures of both thermal and nonthermal processes: electron temperatures, effective temperatures of protons and several minor ions; electron and ion densities of O+5, Mg+9, Si+11, and Fe+11; and flow velocities of the electron/proton plasma and of O+5, Mg+9, and Si+11. The instrument consists of an occulted telescope and a high resolution spectrometer assembly. Three off-axis telescope mirrors focus co-registered images of the extended corona onto the three entrance slits of the spectrometer assembly. The spectrometer assembly consists of three sections. One is optimized for line profile measurements of H I Lyman alpha, with a range of 114.8--128.3 nm, extendable to 113.0 nm and 130.0 nm with grating motions. A second section is optimized for line intensity measurements of O VII (103.2 nm) and is also used to observe Si XII in second order (499 and 521 nm; first order range is 93.2--106.8 nm). The third section is used to measure polarized radiance of the visible corona. A filter with a bandpass of 450.0--600.0 nm is mounted in front of a photomultiplier tube. The EUV spectrometer sections use toroidal concave diffraction gratings in Rowland circle mounts that produce stigmatic imaging at the subject wavelengths. There are entrance slit changing mechanisms on each spectrometer. The detectors for the EUV are multi-anode microchannel arrays, each with 360 x 1024 pixels on 0.025 mm centers. The instantaneous field of view (FOV) of the instrument is the portion of the solar image that passes through the spectrometer entrance slits. Internal mirror motions are used to step the instantaneous FOV across the 141' x 40' FOV defined by the entrance aperture. Offset pointing adjustments can be used to extend the FOV for EUV measurements down to the solar limb, and also onto the solar disk for measurements of absolute spectral line intensities and positions. The UVCS can rotate its FOV about the sun-center to observe any segment of the corona within 10 solar radii. Twelve rotations of 30 degrees would build up a spectroscopic description of the full corona out to 5 solar radii, with additional data out to 10 solar radii. This information was taken from the article ``UVCS - the Ultraviolet Coronagraph Spectrometer for SOHO,'' by J. L. Kohl and G. Noci (Proceedings of the First SOHO Workshop, ESA SP-348, pp. 23-26, November 1992).

Contacts
RolePersonStartDateStopDateNote
1.PrincipalInvestigatorspase://SMWG/Person/John.L.Kohl
2.PrincipalInvestigatorspase://SMWG/Person/J.Leonard.Culhane
InformationURL
Name
NSSDC's Master Catalog
URL
Description

Information about the Ultraviolet Coronagraph Spectrometer (UVCS) experiment on the SOHO mission.

InstrumentType
Spectrometer
InvestigationName
Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO
ObservatoryID