Interstellar heliospheric probe/heliospheric boundary explorer mission—a mission to the outermost boundaries of the solar system

Abstract

The Sun, driving a supersonic solar wind, cuts out of the local interstellar medium a giant plasma bubble, the heliosphere. ESA, jointly with NASA, has had an important role in the development of our current understanding of the Suns immediate neighborhood. Ulysses is the only spacecraft exploring the third, out-of-ecliptic dimension, while SOHO has allowed us to better understand the influence of the Sun and to image the glow of The IHP/HEX Team.Exp Astron (2009) 24:9-46 interstellar matter in the heliosphere. Voyager 1 has recently encountered the innermost boundary of this plasma bubble, the termination shock, and is returning exciting yet puzzling data of this remote region. The next logical step is to leave the heliosphere and to thereby map out in unprecedented detail the structure of the outer heliosphere and its boundaries, the termination shock, the heliosheath, the heliopause, and, after leaving the heliosphere, to discover the true nature of the hydrogen wall, the bow shock, and the local interstellar medium beyond. This will greatly advance our understanding of the heliosphere that is the best-known example for astrospheres as found around other stars. Thus, IHP/HEX will allow us to discover, explore, and understand fundamental astrophysical processes in the largest accessible plasma laboratory, the heliosphere.

Interstellar hydrogen ionization in the heliosheath

“…It is also important to quantitatively determine how absence of measurable electron fluxes by the Voyager 2 plasma instrument beyond the termination shock constrains possible effective temperatures and velocity distributions of electrons. In the longer term, in situ measurement of electrons should be among top priorities for the future Interstellar Probe mission [ Mewaldt and Liewer , ; McNutt et al , , ; Gruntman , ; Fiehler and McNutt, ; Wimmer‐Schweingruber et al , ; McNutt et al , ].…”

Future Exploration of the Outer Heliosphere and Very Local Interstellar Medium by Interstellar Probe

“…In 2006, a design study of the Interstellar Heliopause (IHP) mission concept (Wimmer-Schweingruber and McNutt 2009a ; Wimmer-Schweingruber et al. 2009b ) was conducted as a Technology Reference Study (TRS) under the Science Payload & Advanced Concepts Office at ESA. The IHP concept consisted of a 517 kg spacecraft assuming solar sails to reach 200 au in 25 years, and outlined the required development of enabling technologies.…”

STELLA—Potential European contributions to a NASA-led interstellar probe

“…An international meeting on this topic was held at ISSI in Beijing in November 2019. Numerous mission white papers have been submitted to ESA (Wimmer-Schweingruber et al, 2009;Wimmer-Schweingruber, 2013;Wimmer-Schweingruber, 2019) and laid the ground work for the STELLA mission proposal (Barabash and Wimmer-Schweingruber, 2022). The necessarily long duration and ensuing cost of such a mission strongly suggest a coordinated NASA-ESA effort.…”

“…A 498-page study led by the Johns Hopkins University (JHU)/Applied Physics Laboratory (APL) provides a detailed account of the science goals and questions, the mission concept, scientific and technical implementation, as well as programmatics and concepts for the managements of such a 50-year mission (McNutt et al, 2021). The white paper reported here draws heavily from that study, as well as from white papers submitted previously to the European Space Agency (ESA) (Wimmer-Schweingruber et al, 2009;Wimmer-Schweingruber, 2013;Wimmer-Schweingruber, 2019) in response to its Cosmic Vision and Voyage 2050 calls for proposals, and the STELLA proposal submitted to ESA's 13 December 2021 call for a medium-size mission opportunity (Barabash and Wimmer-Schweingruber, 2022). In line with the JHU/APL study, STELLA is a proposal for a substantial European contribtion to a NASA-led Interstellar Probe (ISP) that would reach 350 au after 50 years (Brandt et al, 2022).…”