Exploring the Sun-heliosphere connection
Science questions
Mission overview
Status update

• Addresses ESA’s Cosmic Vision question “How does the solar system work?”
• Study plasma phenomena which occur throughout the
Universe
– Shocks, particle acceleration, magnetic reconnection, turbulence, etc.
– Also addresses Cosmic Vision question “What are the fundamental physical laws of the Universe?”
• Solar wind and energetic particles directly affect life on Earth
– Impact on space and ground-based assets
• Builds on European heritage: Ulysses and SoHO

In-situ density
1 2 3 4
Days
Solar Orbiter
Solar Orbiter
5 6

How and where do the solar wind plasma and magnetic field originate in the corona?
• Solar wind is variable and structured
• Originates in complex magnetic
“carpet”
• Small scale transient jets are common polar coronal hole coronal funnel
• Solar Orbiter will measure the spatial and temporal variability of the solar source and solar wind in unprecedented detail

• We need to measure the same parameter on the Sun and in space to make the link
– Heavy ion charge states and composition
– Magnetic polarity
– Energetic particles
H+
He+
• Solar Orbiter will make all of these measurements with both remote sensing and in situ instruments

How do solar transients drive heliospheric variability?
• How are substructures of coronal mass ejections related to interplanetary transients?
• How are CMEs processed as they travel from the Sun?
• Solar Orbiter will image CMEs and measure their evolution in the inner heliosphere

How do solar eruptions produce energetic particle radiation?
• Around 10% of coronal mass ejection energy is in accelerated particles
0.3 AU
• Understanding release and transport mechanisms requires going close to the Sun
1.0 AU
• Solar Orbiter will measure energetic particles within a mean free path of their acceleration site

How does the solar dynamo work?
• The unexplored poles are central to the operation of the Sun’s dynamo
• Solar Orbiter will provide the first accurate measurements of polar flows and magnetic fields

• Close to the Sun
• Out of the ecliptic
• Long duration observations of the same region
• Remote measurements of the Sun and corona
• In situ measurements of fields and particles
• It is this unique combination provided by Solar Orbiter that makes it possible to address the question of how the Sun creates and controls the heliosphere

Summary
Carefully optimised payload of ten remote sensing and in situ instruments
Launch: January 2017
Cruise Phase: 3 years
Nominal Mission: 3.5 years
Extended Mission: 2.5 years
Perihelion: 0.28 – 0.3 AU
Fast perihelion motion: solar features visible for almost complete rotation
Out of ecliptic: first good view of solar poles

• Three-axis stabilised, Sun pointing
• Heatshield at front
• Re-use of BepiColombo unit designs as practical
• Mass: 1750kg
• Power: 1100W
• Launch: ELV

In situ instruments
SWA
EPD
MAG
Solar wind analyser Chris Owen, UK
Energetic particle detector Javier Rodriguez-
Pacheco, Spain
Magnetometer Tim Horbury, UK
Sampling protons, electrons and heavy ions in the solar wind
Measuring timing and distribution functions of accelerated energetic particles
High-precision measurements of the heliospheric magnetic field
Studying local electromagnetic and electrostatic waves and solar radio bursts
RPW Radio and plasma wave analyser
Milan Maksimovic,
France
Remote sensing instruments
PHI
EUI
STIX
METIS
SoloHI
SPICE
Polarimetric and heliospheric imager
Sami Solanki,
Germany
Extreme ultraviolet imager Pierre Rochus,
Belgium
Spectrometer/telescope for imaging X-rays
Arnold Benz,
Switzerland
Multi-element telescope for imaging and spectroscopy
Solar Orbiter heliospheric imager
Spectral imaging of the coronal environment
Full-disc and high-resolution visible light imaging of the Sun
Studying fine-scale processes and large-scale eruptions
Studying hot plasmas and accelerated electrons
Ester Antonucci, Italy High-resolution UV and extreme UV coronagraphy
Russ Howard, US Observing light scattered by the solar wind over a wide field of view
Facility instrument,
ESA provided
Spectroscopy on the solar disc and corona

• ESA tasked external review committee to study scientific impact of NASA decision not to support SPICE and SIS
• Committee urged ESA to investigate ways to recover measurement capabilities of SIS and SPICE

• Returns 2D high resolution spectral images
– Intensity, Doppler shift, line width
– Complete temperature coverage from chromosphere to flaring corona
• Provides remote characterisation of plasma properties near the Sun
• Map outflow velocities and composition of surface features to solar wind structures

• Proposal exists for provision of SPICE instrument
• Retains Red Book capabilities
– Full on disk capabilities
– Off-limb up to 1.3 solar radii
– METIS augments this with off-limb spectroscopy beyond
1.3 solar radii
• All mission science goals achieved

• Measures supra-thermal heavy ions
• Part of EPD suite
• Covers energy range between solar wind and energetic particles
• Explores near-Sun ion pool, plus flares and shocks

• Proposal exists for provision of SIS instrument
• Retains Red Book capability
• All mission science goals achieved

High-latitude remote sensing
Perihelion remote sensing
High-latitude remote sensing
• Orbit: 150-168 days
• In situ instruments on at all times
• Three science “windows” of 10 days each
• All remote sensing instruments operational
• Observing strategies based on science targets
– Active regions, coronal hole boundaries, flares, high speed wind, polar structures
• Autonomous burst mode triggers for unpredictable events
• Telemetry and mass memory tailored to return planned instrument data volumes

• Many conjunctions will occur between Solar
Orbiter and Solar Probe
Plus
– Extends science return from both msisions
• Solar Probe Plus is not required for any Solar
Orbiter science goal

• Answers the Cosmic Vision question “How does the solar system work?”
• Unique combination of orbit and instruments
• Selected payload is optimised answer the most fundamental questions of solar and heliospheric physics
• Timely, mature and well studied mission with compelling scientific objectives