The third flight of the SUNRISE balloon-borne solar observatory

IGLESIAS, F. A; SUNRISE III TEAM

Buenos Aires

Conferencia; XI COLAGE; 2018

Asociación Latinoamericana de Geofísica

The SUNRISE mission is a balloon-borne, stratospheric solar observatory fed by a 1 m Gregory-type reflector telescope. The combination of the large aperture, the unique observing conditions in terms of low atmospheric absorption and seeing, and the state-of-the-art instrumentation, has been essential for the great success of the first two SUNRISE flights in 2009 and 2013. One of the main goals of SUNRISE is the determination of faint solar magnetic fields at the highest spatial resolution. This is crucial to understand the dynamics and origin of the many phenomena present in the solar atmosphere. During the two first flights, SUNRISE investigated the magnetic fields only in solar photosphere, by acquiring high-spatial-resolution, spectropolarimetric measurements of the iron 525.02 nm spectral line using the imaging magnetograph IMaX. In addition, diffraction-limited, narrow-band images of the photosphere and part of the chromosphere were obtained in the UV between 214 and 397.6 nm, using the filter imager SuFI. Both IMaX and SuFI obtained numerous remarkable results which were, however, mainly restricted to the photosphere and the lower chromosphere. As a consequence, SUNRISE findings led to many open questions related to the influence of the observed small-scale dynamical features, in the higher layers of the atmosphere.The third science flight of SUNRISE, planned for 2021 and described in this poster, will include a new gondola and completely renewed payload to allow focusing on the small-scale magnetic phenomena occurring not only in the photosphere but also in the lower and higher chromosphere. Two new grating spectropolarimeters and an upgraded IMaX instrument are planned to cover the spectral range from 313 to 854 nm in selected spectral bands. The ultraviolet spectropolarimeter and Imager SUSI, is a slit-scan spectrograph based on an Echelle grating that also includes a slit-jaw imager and covers the 313 to 430 nm spectral range. SUSI aims to acquire high-cadence spectropolarimetric data in the UV to both reduce the effects of instrumental jitter and facilitate the implementation of a novel slit-scan, image restoration technique. The chromospheric infrared spectropolarimeter SCIP is a slit-scan, Echelle-grating-based spectropolarimeter that includes a slit-jaw imager and covers the 765 to 854 nm wavelength range. The new version of IMaX, IMaX+, is a collimated, double-pass Fabry-Pérot filtergraph that can measure polarization in the 517 to 525 nm spectral range. The new payload will make the third SUNRISE science flight unique in basically two aspects. Firstly, SUSI will be able to explore the magnetic, temperature and velocity fields using the UV region below 430 nm, which is poorly known because it has not been covered by other solar observatory to date. The SUSI UV bands will also probe many (10 to 100) magnetically sensitive spectral lines simultaneously, this increases the information input of the inversion process which translates in to a larger signal to noise ratio of the inferred quantities. Secondly, the ability to perform co-spatial, simultaneous co-observations with the three instruments (including spectropolarimetry in the UV and infrared) will allow probing magnetic fields and other relevant atmospheric parameters all the way from the photosphere to the higher chromosphere; this is critical to understand energy transport processes among others.