Coordination within the remote sensing payload on the Solar Orbiter mission

Abstract

Context. To meet the scientific objectives of the mission, the Solar Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing (RS) instruments designed for joint operations with inter-instrument communication capabilities. Indeed, previous missions have shown that the Sun (imaged by the RS instruments) and the heliosphere (mainly sampled by the IS instruments) should be considered as an integrated system rather than separate entities. Many of the advances expected from Solar Orbiter rely on this synergistic approach between IS and RS measurements. Aims. Many aspects of hardware development, integration, testing, and operations are common to two or more RS instruments. In this paper, we describe the coordination effort initiated from the early mission phases by the Remote Sensing Working Group. We review the scientific goals and challenges, and give an overview of the technical solutions devised to successfully operate these instruments together. Methods. A major constraint for the RS instruments is the limited telemetry (TM) bandwidth of the Solar Orbiter deep-space mission compared to missions in Earth orbit. Hence, many of the strategies developed to maximise the scientific return from these instruments revolve around the optimisation of TM usage, relying for example on onboard autonomy for data processing, compression, and selection for downlink. The planning process itself has been optimised to alleviate the dynamic nature of the targets, and an inter-instrument communication scheme has been implemented which can be used to autonomously alter the observing modes. We also outline the plans for in-flight cross-calibration, which will be essential to the joint data reduction and analysis. Results. The RS instrument package on Solar Orbiter will carry out comprehensive measurements from the solar interior to the inner heliosphere. Thanks to the close coordination between the instrument teams and the European Space Agency, several challenges specific to the RS suite were identified and addressed in a timely manner.

Metis: the Solar Orbiter visible light and ultraviolet coronal imager

“…-Role of magnetic field lines in channelling the coronal wind. Solar Orbiter remote sensing and in situ instruments, as well as observations obtained by simultaneous space missions dedicated to heliophysics, will complement the Metis observations and facilitate our understanding of the scientific questions being addressed, as discussed in the papers devoted to the Solar Orbiter joint science (Auchére et al 2019;Horbury et al 2019a).…”

The Solar Orbiter EUI instrument: The Extreme Ultraviolet Imager

“…The EUI Full Sun Imager (FSI) will be imaging alternatively in the 17.4 nm and 30.4 nm EUV pass-bands, with a 3.8 • × 3.8 • FOV, corresponding to (14.3 R ) 2 at 1 AU and still (4.0 R ) 2 at perihelion. This FOV is unprecedentedly large for a coronal EUV imager and will have a significant overlap (Auchère et al 2020) with the Solar Orbiter coronagraph Metis (Antonucci et al 2020).…”

“…Full operation of the remotesensing instrument package of Solar Orbiter, including EUI, will be restricted to three periods of ten days per 168 days orbit, corresponding to perihelion and to maximal solar latitude north and south. In between these three periods, EUI will take part in a program of much reduced, synoptic remote sensing observations (Auchère et al 2020).…”

“…The EUI science planning is strongly rooted in the overall Solar Orbiter planning process (see Zouganelis et al 2020;Auchère et al 2020 for a full description). Here we focus on some EUI specific aspects.…”

“…The ESA Solar Orbiter mission is designed to determine how the Sun creates and controls the heliosphere (Garcia-Marirrodriga et al 2020). The spacecraft will bring a combination of in situ (Horbury et al 2020) and remote-sensing instruments (Auchère et al 2020) out of the ecliptic (>30 • ) and close to the Sun (<0.3 AU), to answer the following four questions (Müller et al 2020): 1. What drives the solar wind and where does the coronal magnetic field originate?…”