SULIS* Mission Concept
Determining the magnetic field of the solar corona is critical to answering fundamental scientific questions about the nature of solar eruptive events driving space weather at Earth. Space weather sources are solar flares, Coronal Mass Ejections (CMEs), solar energetic particles, and geomagnetic disturbances. SULIS will be a flagship UK space science mission, which will lead a step-change in human understanding of the key physics that governs the nature of the Sun-Earth environment, through innovative 6U CubeSat technology. SULIS will place three pairs of formation-flying coronagraphs within CubeSats in 1AU orbits around the Sun. The sunward occulting CubeSat of each pair will observe the solar disk and, uniquely, act as an external occulter for the anti-sunward coronagraph CubeSat, which will observe the extended corona. Each CubeSat pair will fly in formation, the first pair in Earth orbit and the other two pairs drifting away, ahead of and behind Earth in its orbit, for a mission lifetime of 10 years.
The aim of SULIS is to understand the Sun’s link to the inner heliosphere via revolutionary UK-led technology. For international relevance, SULIS will not only be the first UK-led space science mission, it will provide unprecedented measurements of the magnetic field of the corona answering fundamental questions that underpin the sources of space weather. This aligns perfectly with the UK Space Innovation and Growth Strategy. SULIS offers bespoke technology demonstration testing smart CubeSat optical communication, multi-purpose radiation-hardened PhotoVoltaic (PV) cells invoking power-by-light technology.
Despite the hazards of space weather to terrestrial infrastructure (UK National Risk Register for Civil Emergencies, 2017), routine monitoring of space weather is limited to two ageing scientific missions (SOHO & STEREO; RAL Space scientists are PIs on both).
*SULIS is the name of a mythological British goddess of the Sun
SULIS has three key objectives:
I) Provide the first direct measurements of the 3D coronal magnetic field (unique science).
II) Provide eclipse-quality imaging of the extended solar corona (out to 5 solar radii) for deeper understanding of fundamental science underpinning space weather.
III) Demonstrate UK-led future technologies (i.e, smart CubeSat’s; radiation-hardened solar; laser optical communications).
Instrument 1 (Coronagraph): A coronagraphic high-resolution multichannel spectrometer together with a state-of-the-art broadband hyperspectral imager for observing the off-disk extended corona. The high-resolution spectrometer element of this instrument has been developed through an STFC PRD grant (ST/N002962/1). An accompanying novel hyperspectral imager is included, which is linked to the development of the PanCam instrument on ExoMars (e.g. ST/G003114/1). The visible coronagraph will be hosted on the anti-sunward coronagraph CubeSat of each pair, with the sunward CubeSat being an occulter to mimic a solar eclipse.
Instrument 2 (Spectropolarimeter): Bespoke 99-slit, massively-multiplexed coronal spectropolarimeter for uniquely measuring 3D magnetic field vectors in the corona close to the Sun. Prof Lin (PI of the DL-NIRSP instrument on DKIST) has secured $2 million of NSF funding (2018) to develop a TRL-4 prototype designed to fit into 6U CubeSat’s. The disk-imaging near-IR spectropolarimeter will be uniquely hosted on the sunward occulting CubeSat of each pair.
UK Solar/Heliophysics Physics: The UK has consistently played a pivotal internationally leading role in solar/heliophysics science missions over the last 6 decades, for example SOHO, Coriolis, STEREO, Hinode, SDO, GOES, Solar Orbiter. Several of these involve instrument PIs from STFC RAL Space, MSSL and Imperial College London. The UK has the largest number of active solar physics researchers in Europe. A study** of the NASA Astrophysics Data System (ADS) showed that, for the year 2015, the UK was top in Europe and 4th in the world behind USA, China and Russia for solar/heliophysics publications. SULIS will build on and demonstrate this strength and legacy of UK space leadership.
The success of the UK solar physics community is due to many internationally-recognised leading-experts in several subdisciplines. SULIS PI Dr. Scullion, from the Solar Physics Group at Northumbria, is an expert in imaging spectropolarimetry, reflected in his leading roles on several observing campaigns, time awarded on major ground-based facilities, and impressive publication record (e.g., Nature publication 2012, Nature Communications publication 2017). Co-PI Dr. Morgan is Head of Solar System Physics at Aberystwyth and is an expert on the detection and tracking of CME’s in coronagraph data. Awarded the Eilir Hedd Morgan memorial prize for Contribution to Welsh Science and has led and had major roles within several international collaborations. He is PI on a STFC PRD project to develop new instrumentation for observing the solar corona.
Li-Fi Communications OCRG, Northumbria University: This research group is headed by Prof. Zabih Ghassemlooy a world leading expert on VLC+. Prof. Zabih Ghassemlooy was the vice-chair of EU Cost Action IC1101 from 2006-2008, vice-chairman of the Institute for Electrical and Electronic Engineering (IEEE: the world’s largest technical professional organization for the advancement of technology) from 2008-2011.
SULIS provides an exciting opportunity to strengthen the collaborative relationship between STFC and the UK space industry. The UK’s growing space sector is a core part of the government’s Industrial Strategy, which aims to bring together the UK’s world-class research base with business investment.
Opportunity to Influence National Strategies, Policies and Funding: Severe space weather is a medium- to high-likelihood event in the UK National Risk Register. The Space Weather Preparedness Strategy (2015) describes the risk to the UK from severe space weather, prepared by BEIS. Government departments must plan for this risk, including military, energy, civil aviation, and transport in general. Development of new infrastructure (e.g. HS2) must consider the impact of space weather through the advice of The Cosmic Radiation Advisory Group. Through SULIS, STFC will influence many policy-enforcing agencies and future large-scale infrastructure planning by the UK Government.
**Schrijver, C. J., 2016, “Publication Statistics on the Sun and Heliosphere”, Solar Physics, 291, 1267
+Zabih Ghassemlooy et al., 2017, “Visible Light Communications: Theory and Applications”, CRC Press, ISBN 9781498767538