The balloon-borne 1m solar telescope SUNRISE III lifted off for the third time on early morning July 10, 2022, from Esrange Space Center, the Swedish Space Agency's (SSC) balloon and rocket base in Kiruna, Sweden. It is equipped with the new image stabilization system developed and constructed by the Leibniz Institute for Solar Physics (KIS) in Freiburg, to ensure the high precision of the telescope operation.
The Sunrise III westward flight of 4 to 6 days will be at a stratospheric altitude of about 35 km along the Arctic Circle. In the first few hours after launch, the balloon passes through air layers with widely varying temperatures, so that equilibrium must first be re-established thereafter. During this time, all systems are powered up and tested so that scientific observations can begin quickly. During the flight, the balloon is in contact with the control center in Kiruna via a satellite-based system, from where the observations are controlled and monitored. The observation data itself will be stored on board and will have to be recovered with the telescope after a parachute landing, probably in northern Canada.
As in the already very successful flights of SUNRISE I and II in 2009 and 2013, Leibniz Institute for Solar Physics (KIS) again provided the image stabilization and autofocus (Correlating Wavefront Sensor, CWS). Technical advances allowed the KIS team, led by project scientist Dr. Thomas Berkefeld, to make extensive improvements with a new optical and electronic setup for the image stabilization. To reduce a typical nacelle oscillation of one degree to an acceptable residual oscillation of 0.005 arc seconds (a factor of 700,000), a two-stage system is used: Coarse image stabilization is performed by a telescope nacelle supplied by the Johns Hopkins Applied Physics Laboratory, USA, and fine stabilization is performed by a system developed by KIS consisting of a very fast camera, control computer, and tilting mirror, which corrects image wobble 8000 times per second. For comparison: 0.005 arcseconds is about the size of a 1-cent coin at a distance of 400 km.
The launch of the telescope had to be postponed several times due to delivery delays of the balloon - the ongoing congestion of many container ports also affects scientific research - and later due to unfavorable weather conditions on site in Kiruna. The technical and scientific teams from Germany, Spain, Japan and the USA thus had plenty of time to prepare all systems and the scientific instruments for their mission. During launch preparations and during the flight, the KIS scientists and engineers in Kiruna provide extensive support.
Flying north of the Arctic Circle in summer allows uninterrupted observations for 24 hours a day (midnight sun). The launch is just in time for this, since according to NASA's wind forecasts, a launch after July 10 would cause the balloon to drift too far south and the Sun would set for Sunrise after all, which would not only interrupt the time series but also require renewed thermal stabilization afterwards.
The goal of the Sunrise III mission is to study the outer solar atmosphere with a series of enhanced and new instruments. On board are one spectropolarimeter each for the ultraviolet (Max Planck Institute for Solar System Research, Göttingen), the visible (Spanish consortium) and for the near infrared (National Astronomical Observatory of Japan) wavelength range of light, with which the various layers of the Sun's chromosphere and its magnetic field can be studied with a high temporal cadence at maximum image sharpness. To this end, scientists from the participating institutes submitted a large number of observing proposals during the mission preparation phase, which were evaluated, prioritized, and combined into a tightly timed observing schedule for the entire mission.
Since at a flight altitude of 35 km almost no atmospheric disturbances such as air turbulence occur any more, SUNRISE III will have an optimal image quality. The so-called spatial resolution of the telescope is so high that it would allow a pair of car headlights to be perceived as separate from a distance of 5000 km. Because most of the ozone layer is below 35 km, SUNRISE can also observe in the ultraviolet wavelength range, which is otherwise only possible with much smaller and more expensive solar telescopes from space.
It is planned to perform, as far as possible, coordinated simultaneous observations with other ground-based and space telescopes, including the 1.5m solar telescope GREGOR of the KIS on Tenerife, thus scientifically complementing the observations of SUNRISE III.
The balloon-borne solar observatory Sunrise III is a mission of the Max Planck Institute for Solar System Research (MPS, Germany) and the Johns Hopkins Applied Physics Laboratory (APL, USA). A Spanish consortium, the National Astronomical Observatory of Japan (NAOJ, Japan) and the Leibniz Institute for Solar Physics (KIS, Germany) are significantly involved in the mission. The Spanish consortium is led by the Instituto de Astrofísica de Andalucía (IAA, Spain) and includes the Instituto Nacional de Técnica Aeroespacial (INTA), the Universitat de València (UV), the Universidad Politécnica de Madrid (UPM) and the Instituto de Astrofísica de Canarias (IAC). Other partners include NASA's Wallops Flight Facility Balloon Program Office (WFF-BPO) and the Swedish Space Corporation (SSC). Sunrise III is being funded by the Max Planck Foundation, NASA under grant #80NSSC18K0934, the Spanish FEDER/AEI/MCIU (RTI2018-096886-C5) and a "Center of Excellence Severo Ochoa" award to the IAA-CSIC (SEV -2017-0709) as well as the ISAS/JAXA Small Mission of Opportunity program and JSPS KAKENHI JP18H05234.
Dr. Thomas Berkefeld, (Project Manager), Thomas.Berkefeld@~@leibniz-kis.de
Prof. Dr. Svetlana Berdyugina (Managing Director Leibniz Institute for Solar Physics), svetlana.berdyugina@~@leibniz-kis.de
Dr. Reiner Volkmer, (Head of the Solar Telescopes Group), Reiner.Volkmer@~@leibniz-kis.de, 0761-3198-401
Leibniz Institute for Solar Physics (KIS): www.leibniz-kis.de
The SUNRISE telescope on the hook of the crane vehicle just before the launch (left), the mission balloon ready to be released (center) and in flight just after the launch (right). Image: KIS, A. Bell.
The launch of the Sunrise III telescope into the stratosphere. Video: KIS, A.Bell.
Sunrise III mission rising to the stratosphere... before its termination a few hours later. Images: KIS, A. Bell.