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| CRISP (instrument) | |
|---|---|
| Name | CRISP |
| Caption | CRISP at the Swedish 1-m Solar Telescope |
| Type | Fabry–Pérot imaging spectropolarimeter |
| Operator | Institute for Solar Physics |
| Telescope | Swedish 1-m Solar Telescope |
| Wavelength | Visible and near-infrared |
| Detector | CCD |
| First light | 2008 |
| Status | Operational |
CRISP (instrument) is a high-resolution imaging spectropolarimeter installed at the Swedish 1-m Solar Telescope on the island of La Palma in the Canary Islands. It was developed to enable detailed studies of solar photospheric and chromospheric structure by combining rapid tunable spectroscopy with full Stokes polarimetry, supporting investigations across multiple spectral lines such as Hα, Ca II and Fe I. CRISP has played a major role in observational campaigns that involved institutions like the Institute for Solar Physics, the University of Oslo, and the Institute for Solar Physics, Royal Swedish Academy of Sciences.
CRISP was conceived to deliver diffraction-limited imaging spectroscopy and polarimetry for the study of fine-scale solar phenomena including sunspots, penumbral filaments, umbral dots, spicules, and magnetic reconnection events. It serves key science programs affiliated with the European Space Agency mission planning and ground-based networks such as the Global Oscillation Network Group by providing high temporal, spectral, and spatial resolution necessary to resolve dynamics on granular and sub-granular scales. The instrument complements spaceborne facilities like Hinode (solar observatory) and Solar Dynamics Observatory by supplying spectrally resolved, high-cadence measurements at visible wavelengths.
CRISP is based on a dual Fabry–Pérot interferometer design employing two tunable etalons in a telecentric configuration, enabling narrowband imaging with high spectral purity and rapid wavelength tuning. The optical train was engineered to work with the adaptive optics system of the Swedish 1-m Solar Telescope to approach the diffraction limit at visible wavelengths. Typical spectral resolution reaches R ~ 100,000 depending on the chosen line, while spatial resolution approaches 0.14 arcseconds under good seeing. Detectors are high-speed, low-noise CCDs synchronized with liquid crystal modulators for polarimetric modulation. The mechanical layout and control electronics were developed in collaboration with engineering groups at the Royal Institute of Technology (KTH) and instrument teams affiliated with the University of Oslo.
Key components include a pair of high-finesse Fabry–Pérot etalons, prefilters for order suppression, a polarimetric package with nematic liquid crystals, beam splitters, and high-frame-rate CCD cameras. The etalons are temperature- and pressure-stabilized and are mounted in a telecentric focal plane to minimize field-dependent wavelength shifts, an approach informed by designs used at the German Vacuum Tower Telescope and other European facilities. The polarimeter employs modulators and analyzers optimized for full Stokes measurements, enabling studies of Zeeman signatures in lines such as Fe I 630.2 nm and Ca II 854.2 nm. Cryogenic or cooled detector housings and custom electronics ensure low dark current and high duty cycles, similar to systems developed at the Max Planck Institute for Solar System Research.
CRISP supports fast spectral scans, long time-series, and dual-line observing modes, permitting trade-offs between spectral sampling, temporal cadence, and spatial coverage. Observers commonly use modulation schemes synchronized with exposure sequences to obtain Stokes I, Q, U, and V. Typical programs exploit multi-line setups to probe photospheric and chromospheric layers simultaneously, coordinated with campaigns involving Hinode (solar observatory), Interface Region Imaging Spectrograph, and ground-based networks. Observing strategies include speckle reconstruction priors to post-facto correct seeing, multi-object multi-frame blind deconvolution pipelines shared with other solar instruments, and adaptive optics locking to sunspot or granulation features.
Calibration routines address cavity errors, flat-fielding, etalon blueshift, and polarimetric calibration using calibration units and telescope models developed for the Swedish 1-m Solar Telescope. Data reduction pipelines perform demodulation, image restoration via Multi-Object Multi-Frame Blind Deconvolution, wavelength calibration with solar atlases and telluric lines, and inversion-ready output for radiative transfer codes like SIR and NICOLE. Performance assessments published by collaborating groups demonstrate polarimetric sensitivity approaching 10^-3 of the continuum and spectral sampling sufficient for reliable inversion of magnetic field vectors in active regions. Long-term stability studies were carried out in coordination with maintenance teams at the Observatorio del Roque de los Muchachos.
CRISP observations have contributed to breakthroughs in understanding magneto-convective processes, penumbral filamentation, umbral microstructure, photospheric oscillations, chromospheric heating, and rapid magnetic flux emergence. Notable results include resolved measurements of opposite-polarity patches at granular scales, mapping of chromospheric fibrils in unprecedented detail, and high-cadence detection of small-scale reconnection events linked to Ellerman bombs and UV bursts observed by Interface Region Imaging Spectrograph. CRISP data have been central to studies published in journals associated with the American Astronomical Society and used in comparative analyses with data from Solar Orbiter.
The instrument was developed through a collaboration involving the Institute for Solar Physics, the University of Oslo, the Royal Swedish Academy of Sciences, and engineering partners across Europe. Development milestones included prototype testing at the Swedish 1-m Solar Telescope and iterative upgrades to etalons and polarimetric components informed by campaigns coordinated with Hinode (solar observatory) teams. Funding and technical support were provided by national research councils and European consortia, and the CRISP team has maintained active data-sharing and software collaborations with groups at the Max Planck Institute for Solar System Research, University of Oslo, and Korea Astronomy and Space Science Institute.
Category:Solar telescopes Category:Spectropolarimeters