# Presentation: 899753

## Solar Orbiter 

- E. Marsch, R. Schwenn, E. Antonucci, P. Bochsler,
- J.-L. Bougeret, B. Fleck, R. Harrison, R. Marsden, J.-C. Vial

**A High Resolution Mission to the Sun an Inner Heliosphere**

## Background

**The Solar Orbiter (SO), developed from InterHelios, was presented at ”A Crossroads for European Solar and Heliospheric Physics” and was endorsed by ESA’s Solar Physics Planning Group (SPPG).**
**ESA conducted a pre-assessment study for SO in 1999.**
**Additional mission scenarios, such as polar orbits and/or closer approaches to the Sun, were discarded for technical reasons. **
**Technical feasibility of SO demonstrated.**
**SO was one of about 40 responses to the Call for Proposals for the next two “flexi-missions” (F2 and F3) within ESA’s Scientific Programme.**
**On 1 March 2000, ESA’s Space Science Advisory Committee (SSAC) selected SO, among 5 other proposals, for an assessment study.**
**Next selection round (for definition phase) in September 2000.**
**Given the realistic cost estimates, international partners (e.g. NASA, ISAS, RSA or other national agencies) are needed. **

## Solar Physics after SOHO: New Goals

**Unravel couplings between all layers of the solar atmosphere**
- make multi-wavelength simultaneous observations at very high spatial resolution!
**Disentangle spatial and temporal variations in the solar wind**
- choose orbit enabling S/C co-rotation with the Sun!
**Uncover missing links for understanding the solar dynamo**
- observe the Sun from high latitudes!

## Novel Measurements

**Observe all layers of the solar atmosphere at  high spatial resolution (< 40 km) from near the Sun (45 R******** ).**
**Separate spatial and temporal variations in the solar wind from quasi-corotational orbit (1.3******** per day).**
**Enable first observations of the polar regions of the Sun from out-of-ecliptic vantage points (up to 38******** in heliographic latitude).**

## Coverage of Solar and Heliospheric Physics

**Interior**
**Dynamo**** ******** image solar poles and determine magnetic field**
**Photosphere and Chromosphere**
**Luminosity**** ******** measure irradiance changes (at high latitudes)**
**Flux tubes**** ********  resolve small-scale magnetic elements (<100 km)**
**Corona**
**Loops**** ******** imaging and spectroscopic diagnostics of the building blocks of the corona**
**Flares**** ******** measure radio emissions, particles, and neutrons**
**Heliosphere**
**Streams**** ******** separate structures from turbulence and waves**

## Scientific Payload

**Solar Instruments**
**Visible-light imager and magnetograph**
**EUV / X-ray imager**
**EUV spectrometer**
**UV and visible-light coronagraph**
**Neutron and ********-ray detector**
**Radiometer**

**Heliospheric Instruments**
**Solar wind plasma analyzer**
**Plasma wave analyzer**
**Magnetometer**
**Energetic particle detector**
**Neutral particle detector**
**Dust detector**
**Radio spectrometer**
**Coronal radio sounding experiment**

##           Key Goals for the Near Sun Phase

- solar magnetic field  - structure and evolution at the fundamental scale of magnetic elements, providing new insights into magnetoconvection
- coronal heating processes - in the transition region and at the coronal base, at a much finer scale (< 100 km) than previously possible
- coronal and interplanetary disturbances  -  magnetic flux tubes, magnetic activity, flares, eruptive prominences and coronal mass ejections
- evolution of solar active regions  -  sunspots, loops, and prominences.
- plasma  and  electromagnetic fields - coronal streamer belt and coronal holes  extending to the near-ecliptic regions  (slow and fast solar wind)
- energetic particles close to the Sun  -  origin, acceleration and transport
- near-Sun dust  -  origin and spatial distribution
- coronal radio emission  -  and particles originating from the same source

##    Key Goals for theOut-of-Ecliptic Phase

- nature and evolution of the solar polar coronal holes, as well as their boundaries
- origin of solar  wind streams at intermediate and high latitudes
- coronal mass ejections: their global distribution, longitudinal extent, onset and propagation
- magnetic field structure and evolution, in particular over the poles where it is poorly known
- working of the solar dynamo, including the reversals of the polar field
- dynamics and rotation of the solar corona near the poles
- magnitude and nature of the solar luminosity variations
- global coronal waves and their effects over the poles
- acceleration of the solar wind over the poles by Doppler-velocity measurements.

## Solar Instrumentation

##    Heliospheric Instrumentation

## Mission Characteristics

**Orbit**
**inclination: variable (heliographic): ****0 ******** i ******** 38******
**perihelion: down to ****45 R******** **
**S/C platform**
**3-axis stabilized, Sun-pointing, better than 3 arcsec/15 min**
**Launch date: 2009, compatible with F2/F3**
**Lifetime: total ******** 7 years**
**cruise: ******** 2 years**
**scientific: ******** 5 years (nominal ******** 3 years + extended ******** 2 years)**
**Payload: solar-remote package + in-situ package**
**Mass: S/C ******** 1500 kg, P/L ******** 100 kg**
**Data rate: 70 kbit/s (Ka-band)**

## Spacecraft Overview

**Total mass: 1510 kg**
**Dimensions: 3 m x 1.2 m x 1.6 m**
**3-axis stabilized**
**pointing stability better than ****	****	****	****	****	****	****3 arcsec / 15 min**
**Solar Electric Propulsion (SEP):**
**4 x 0.15 N stationary plasma thrusters**
**Deployable and rotatable Cruise solar ****	****	****	****	****arrays, jettisoned after last SEP ****	****	****	****	****	****thrusting**
**Deployable and tiltable Orbit solar arrays,****	****	****	****	****	****16% GaAs cells, 84% OSR.**
**4 X-band LGAs, omni coverage, for TT&C.**
**One Ka-band HGA, 1.5 m dia., for telemetry after Cruise.**

## Trajectory

**Perihelion Radius**

**Solar Latitude wrt Solar Equator**

## Modes of Operation

## Telemetry Capabilities

## Programmatics

**Mission managed and financed mainly by ESA, with strong international collaboration (e.g. NASA).**
**PI-type mission, instruments supplied by community.**
**Cost estimate (pre-assessment study): 232 Meuro.**
**Maximum use of available technology, of-the-shelf (in 2004), or from the proposed Mercury Orbiter Cornerstone “Bepi-Colombo”.**
**Launcher: Soyuz-Fregat type.**
**S/C and science operations performed with a single ground station, e.g. by ESOC.**
**Seeking international partners for second and third ground station, in order to increase science telemetry.**
**Design lifetime compatible with a 7-year mission.**

##       Summary: Solar Orbiter will ...

**explore ****unknown territory**** near the Sun**
**provide unprecedented ****high-resolution observations**** of the Sun ****(******** 40 km)**
**provide the first images of the ****solar poles**
**correlate in-situ with remote-sensing measurements at ****45 R******** from a ****quasi-co-rotational**** vantage point**
**be ****technically feasible**** (using electric propulsion)**
**be the next logical step and ****open new grounds**** in solar and heliospheric physics!**