### Solar Orbiter

### High-Resolution Mission to the Sun and Inner Heliosphere

######## Assessment Study Report

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# **July 2000**

**Foreword**

The Solar Orbiter Mission was proposed to ESA by an international team
of scientists led by E. Marsch in response to the call for mission
proposals for two flexible missions (F2 and F3) and submitted on January
27, 2000. In March 2000 ESA\'s Space Science Advisory Committee
recommended the Solar Orbiter for further study based on a
pre-assessment study performed in 1999 in the framework of ESA's Solar
Physics Planning Group activities.

This document is the result of the "delta" assessment study, carried out
by representatives of the European solar and heliospheric physics
communities, in close co-operation with ESA staff.

####### Study team members:

**E. Marsch**, Max-Planck-Institut für Aeronomie,

Katlenburg-Lindau, Germany

####### 

####### E. Antonucci, Osservatorio Astronomico di Torino, Italy

**P. Bochsler**, University of Bern, Switzerland

**J.-L. Bougeret**, Observatoire de Paris, Meudon, France

**R. Harrison**, Rutherford Appleton Laboratory, Chilton, UK

**R. Schwenn**, , Max-Planck-Institut für Aeronomie, Katlenburg-Lindau,
Germany

**J.-C. Vial**, University of Paris XI, Orsay, France

**ESA staff members:**

Study Scientists: **B. Fleck**, ESA/GSFC, Greenbelt, Maryland, USA

**R. Marsden**, ESA/ESTEC, Noordwijk, The Netherlands

Study Manager: **O. Pace**, ESA/ESTEC, Noordwijk, The Netherlands

Solar System Mission Coordinator: **M. Coradini**, ESA HQ, Paris, France

Valuable contributions and comments on the science objectives and
instrumentation were provided by:

**M. Collados**, Instituto de Astrofisica de Canarias, Spain

**C. Fröhlich**, Physikalisch-Metorologisches Observatorium, Davos,
Switzerland

**L. Gizon**, Stanford Univ., USA

**B. Lites**, High Altitude Observatory, Boulder, USA

**O. von der Lühe**, Kieperheuer Institut für Sonnenphysik, Freiburg,
Germany

**V. Martinez Pillet**, Instituto de Astrofisica de Canarias, Spain

**R.B. McKibben**, Univ. of Chicago, USA

**W. Schmidt**, Kieperheuer Institut für Sonnenphysik, Freiburg, Germany

**V. Bothmer**, University of Kiel, Germany

**R. Bruno**, Istituto Fisica Spazio Interplanetario del CNR, Roma,
Italy

**C. Chiuderi**, University of Florence, Italy

**A. Cacciani**, University of Rome, Italy

**L. Damé**, Service d\' Aéronomie du CNRS, Verrières-le-Buisson, France

**P. Hoyng**, SRON, Utrecht, The Netherlands

**O. Kjeldseth-Moe**, University of Oslo, Norway

**O. von der Lühe**, Kieperheuer Institut für Sonnenphysik, Freiburg,
Germany

**G. Mann**, Astrophysikalisches Institut Potsdam, Potsdam, Germany

**V. Martinez Pillet**, Instituto de Astrofisica de Canarias, Spain

**E. Priest**, University of St. Andrews, UK

**W. Schmutz**, Physikalisch-Metorologisches Observatorium, Davos,
Switzerland

**S. Solanki**, Max-Planck-Institut für Aeronomie, Lindau, Germany

**J. Stenflo**, Eidgenössische Technische Hochschule Zürich, Switzerland

**Table of Contents**

Foreword

1\. Executive Summary

2\. Solar Orbiter Goals

3\. Scientific Background

3.1 Status of the field and goals of Solar Orbiter

3.2 Key scientific objectives

3.2.1 Scientific rationale

3.2.2 Key goals for the near-Sun phase

3.2.3 Key goals for the out-of-ecliptic phase

3.3 Conclusions

4\. Particles and Fields Environment

4.1 Microstate of the interplanetary solar wind

4.2 Solar wind ions as tracers of coronal structures

4.3 Magnetohydrodynamic turbulence

4.4 Acceleration and transport of solar energetic particles

4.5 Neutral particles from the Sun

4.6 Circumsolar and interplanetary dust

4.7 Solar neutrons

4.8 Solar radio emission

5\. Morphology and activity of the Sun\'s magnetic field

5.1 Photospheric magnetic flux elements

5.2 Fine morphology and fast activity of coronal magnetic fields

6\. Detailed links between the photosphere, corona and inner heliosphere

6.1 Global solar corona and solar wind

6.2 Structure of the magnetic network and origin of the solar wind

6.3 Waves in the corona

7\. The Sun\'s polar regions and equatorial corona

7.1 The Sun\'s polar magnetic field and the dynamo

7.2 Coronal transients and their impact on the heliosphere

7.3 Solar luminosity variations

8\. Scientific Payload

8.1 Measurement requirements

8.2 *In-Situ* Heliospheric Instruments

8.2.1 Solar Wind Plasma Analyser (SWA)

8.2.2 Plasma Waves Analyser (PWA)

8.2.3 Magnetometers (MAG)

8.2.4 Energetic Particle Detector (EPD)

8.2.5 Dust Detector (DUD)

8.2.6 Radio Instruments

8.2.7 Neutral Particle Detector (NPD)

8.3 Remote sensing solar instruments

8.3.1 General considerations

8.3.2 Visible-light imager and magnetograph (VIM)

#  8.3.3 EUV spectrometer (EUS)

8.3.4 EUV imager and X-ray imager (EXI)

8.3.5 Ultraviolet and visible-light coronagraph (UVC)

8.3.6 Neutron and γ-ray detector (NGD)

8.3.7 Radiometer (RAD)

8.3.8 Other potential solar instruments

10\. System Design

10.1 Design requirements and drivers

10.2 Main System Design Features

10.2.1 Requirements and Constraints

10.2.2 Spacecraft Baseline Design

10.2.3 Thruster Positioning

10.2.4 Thermal Design

10.2.5 Power Supply

10.3 Data Collection/Dumping

10.4 Radiation

10.5 Mass Budgets

11\. Subsystem Design Description

11.1 Attitude and orbit control

11.2 Reaction Control System

11.3 Propulsion

11.4 Structure

11.5 Thermal C1ontrol

12\. Ground Systems and Operations

12.1 Ground segment facilities and services

12.2 Ground Stations and Communications Network

12.3 Mission Control Centre

12.4 Computer facilities and Network

12.5 The Flight Control Software System

12.6 Mission Operations Concept

12.7 Scientific Operations

13\. Management

13.1 F2/F3 Procurement Approach

13.2 Procurement Philosophy

13.3 Scientific Management and Instrument Selection

13.4 Industrial Management

13.5 Development Philosophy and Schedule

13.5.1 General

13.5.2 Payload Model Philosophy

13.5.3 Service Module Model Philosophy

13.5.4 Schedule

14\. Bibliography

15\. Mission and Spacecraft Summary