Synoptic Optical Long-term Investigations of the Sun (SOLIS) is a synoptic facility for solar observations over a long time frame that is funded by the

National Science Foundation The U.S. National Science Foundation (NSF) is an Independent agencies of the United States government#Examples of independent agencies, independent agency of the Federal government of the United States, United States federal government that su ...

(NSF) and designed and built by the

National Solar Observatory The National Solar Observatory (NSO) is a United States federally funded research and development center to advance the knowledge of the physics of the Sun. NSO studies the Sun both as an astronomical object and as the dominant external influen ...

(NSO). It is operated by the

NSO Integrated Synoptic Program (NISP) NSO or Nso may refer to: Computing * Nintendo Switch Online, online subscription service for the Nintendo Switch * NSO Group (Niv, Shalev, Omri), an Israeli phone spyware company Government and military * NATO Standardization Office * Nethe ...

. SOLIS is a single set of three instruments mounted on a common observing platform. The instruments are the 50 cm apertur
Vector Spectromagnetograph
(VSM), the 8 mm apertur

(ISS), and the 14 cm apertur

(FDP). The VSM telescope is a quasi- Ritchey-Chretien design with a primary mirror operating at f/1.6. The ~ 400 W of solar light from the primary is reflected by a secondary mirror fabricated from a single silicon crystal. The final f/6.6 full-disk solar image is focused on a spectrograph slit that is cooled by a flow of chilled water-propylene glycol solution. The mirrors are coated with protected silver. To improve the internal seeing, the VSM is sealed by 74 cm diameter, 6 mm thick fused silica window. Originally, it was filled with helium at about ambient pressure and temperature. In 2014, helium was replaced by nitrogen due to the increasing cost of helium. Due to this change, the image sharpness was slightly degraded. The VSM provides full-disk vector (strength and direction) maps of the

solar magnetic field The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light an ...

both in the

photosphere The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esc ...

and in the

chromosphere A chromosphere ("sphere of color", from the Ancient Greek words χρῶμα (''khrôma'') 'color' and σφαῖρα (''sphaîra'') 'sphere') is the second layer of a Stellar atmosphere, star's atmosphere, located above the photosphere and below t ...

on a daily basis, continuing the 40-year record of NSO magnetic field observations. The ISS obtains spectra of the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

integrated over the solar disk, so the Sun appears as it would as a much more distant

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

. The combination of data from the ISS and the VSM is useful for studies of

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

systems as it allows the modeling of the influence of a star's magnetic field on its

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

giving clues to the activity level that the exoplanets may be subject to. The FDP provides full-disk images of the Sun in a variety of spectral lines with a cadence as high as 10 seconds. SOLIS was located on top of the Vacuum Telescope building at

Kitt Peak National Observatory The Kitt Peak National Observatory (KPNO) is a United States astronomy, astronomical observatory located on Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono Oʼodham Nation, west-southwest of Tucson, Arizona. With ...

until July 2014, then temporarily moved to the

University of Arizona The University of Arizona (Arizona, U of A, UArizona, or UA) is a Public university, public Land-grant university, land-grant research university in Tucson, Arizona, United States. Founded in 1885 by the 13th Arizona Territorial Legislature, it ...

Agricultural Farm in Tucson until October 2017, and is now being permanently relocated to

Big Bear Solar Observatory Big Bear Solar Observatory (BBSO) is a university-based solar observatory in the United States. It is operated by New Jersey Institute of Technology (NJIT). BBSO has a clear-aperture Goode Solar Telescope (GST), which has no obscuration in th ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. Construction of the new SOLIS facility began in April of 2021, and was mostly completed by the end of that year. In December of 2021, the primary telescope mount was installed inside the newly constructed building. In September of 2024, the VSM and FDP were successfully installed on the main telescope mount. Once back to operations, SOLIS will provide unique observations of the Sun on a continuing basis for several decades to understand the solar activity cycle, sudden energy releases in the solar atmosphere, and

solar irradiance Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ( ...

changes and their relationship to global change.

SOLIS Gallery

File:Crews pour concrete footings, the first step in the construction of a permanent home of the NSF’s SOLIS instrument at Big Bear Solar Observatory in California.jpg, Crews pour concrete footings, the first step in the construction of a permanent home of the NSF’s SOLIS instrument at Big Bear Solar Observatory in California File:SOLIS on the shore of Big Bear Lake, California. White dome in the background is the Goode Solar Telescope.jpg, SOLIS on the shore of Big Bear Lake, California. White dome in the background is the Goode Solar Telescope File:SOLIS mount installation looking down.jpg, SOLIS mount installation looking down File:SOLIS Vector SpectroMagnetograph at Kitt Peak.jpg, The vector spectromagnetograph mounted on top of the Kitt Peak Synoptic Optical Long-term Investigations of the Sun (SOLIS) Tower, formerly the vacuum telescope tower.

References

{{Portal bar, California, Astronomy, Stars, Spaceflight, Outer space, Solar System, Education, Science Solar telescopes Solar observatories Optical telescopes Astronomical observatories in California National Science Foundation

SOLIS Gallery

See also

References