S unrise iii : Instrument, Mission, Data, and First Results

Abstract S unrise iii is a stratospheric balloon-borne solar observatory with a 1 m diameter telescope and three postfocus instruments, along with an image stabilisation system, all within a protective gondola. It samples the lower solar atmosphere, from the solar surface to the middle chromosphere, at a resolution approaching 50 km on the Sun. S unrise iii flew successfully for 6.5 days suspended from a zero-pressure stratospheric balloon from northern Sweden to northwestern Canada in 2024 July, gathering around 200 TB of data. The present issue of the Astrophysical Journal Letters focuses on the first scientific results from the data collected during that flight. This Letter introduces this Focus Issue, providing a very brief overview of the capabilities of the instrumentation, the flight, and of the gathered data. Challenges for the measurements, data reduction, and interpretation are also briefly touched upon. The Letter ends with an overview of the first set of science results obtained from these data, as presented in the current Focus Issue.