The Sun Radio Interferometer Space Experiment (SunRISE) Mission

Abstract:

SunRISE will provide an entirely new view on particle acceleration and transport in the inner heliosphere by localizing heliospheric radio emissions with the first low radio frequency interferometer in space. SunRISE will image and track the locations of decametric-hectometric (DH) Type II radio bursts from 0.1 MHz–25 MHz, relative to the structures of expanding CMEs, with the aim of constraining the acceleration mechanism relevant for producing solar energetic particles (SEPs). SunRISE will also image and track the locations of DH Type III radio bursts, with the aim of tracing the magnetic field topology from active regions into interplanetary space. Six small spacecraft, of 6U form factor, will fly in a supersynchronous geosynchronous Earth orbit (GEO) within about 10 km of each other, in a passive formation, forming a very long baseline interferometer (VLBI) observatory. The SunRISE observatory will image the Sun and heliosphere in a portion of the spectrum that is blocked by the ionosphere and cannot be observed from Earth. Key aspects that enable this mission concept are that only position knowledge of the spacecraft is required, not active control, and that the architecture involves a modest amount of on-board processing coupled with significant ground-based processing for navigation, position determination, and science analysis. SunRISE leverages more than 50 years of development in VLBI techniques, and mission-enabling advances in software-defined radios, GPS navigation and timing, and small spacecraft technologies, developed and flown over the past few years on DARPA High Frequency Research (DHFR), the Community Initiative for Continuing Earth Radio Occultation (CICERO), and the Mars Cube One (MarCO) missions, have made this mission feasible. The SunRISE mission involves utilizing commercial access to space, in which the SunRISE spacecraft will be carried to their target orbit as a secondary payload in conjunction with a larger host spacecraft intended for GEO.

The SunRISE mission began Phase B (Formulation) in 2020 June, with a planned review to assess readiness to proceed to Phase C (Development) in 2021Q2. This paper presents a summary of the SunRISE mission and its current status. Complementary abstracts are presented by J. Kasper, A. Romero-Wolf, and A. Hegedus.