The Sunrise Chromospheric Infrared Spectro-Polarimeter SCIP: an instrument for SUNRISE III

TL;DR

The Sunrise Chromospheric Infrared Spectro-Polarimeter (SCIP) is a new instrument on the Sunrise III solar observatory, enabling high-resolution, sensitive magnetic and velocity measurements in the near-infrared spectrum of the Sun.

Contribution

Development of SCIP, a novel spectro-polarimeter for Sunrise III, with high spatial, spectral, and polarimetric resolution for solar magnetic field studies.

Findings

Achieved a polarimetric sensitivity of 0.03% with 10 s integration.

Designed optical and mechanical systems for high-precision polarization detection.

Enabled observations of solar magnetic fields in near-infrared wavelengths.

Abstract

The Sunrise balloon-borne solar observatory is equipped with a one-meter aperture optical telescope, offering a unique platform for uninterrupted seeing-free observations across ultraviolet, visible, and infrared wavelengths from altitudes higher than 33 km. For the third flight of the upgraded Sunrise observatory conducted in 2024, now called Sunrise III, a new spectro-polarimeter called the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) was developed for observing near-infrared wavelength ranges around 770 nm and 850 nm. These wavelength ranges contain many spectral lines, including two of the Ca II infrared triplet, K I D1 and D2 lines, and multiple Fe I lines, that are sensitive to solar magnetic fields and velocities in the photosphere and chromosphere. SCIP consists of a grating spectrograph in which polarimetric measurements are conducted using a rotating waveplate as a modulator and polarizing beam splitters placed in front of the cameras. The spatial and spectral resolutions are 0.21" and 1x10^5, respectively, and a polarimetric sensitivity of 0.03% (1sigma) of the continuum intensity is achieved with a 10 s integration time per a resolution element. To achieve high-precision detection of small polarization signals, we carefully designed the optical and mechanical systems, polarization components, control electronics, and onboard data processing. Together with the other post-focus instrumentation developed for Sunrise III, the Sunrise Ultraviolet Spectropolarimeter and Imager and the visible imaging spectro-polarimeter Tunable Magnetograph, SCIP provides novel observations that help elucidate energy transfer and time-dependent phenomena across the solar photosphere and chromosphere.