SOLAR ORBITER A Mission Overview Joachim Woch MPS, Katlenburg-Lindau

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SOLAR ORBITER A Mission OverviewJoachim
WochMPS, Katlenburg-Lindau

• Scientific Goals
• Baseline Mission Profile
• Scientific Reference Payload
• Schedule

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What is unique about this mission?

• Not a single feature rather a combination of
  specials
• orbit ? closest to Sun ever, with corotation
  periods and out of ecliptic
• suite of remote sensing instruments working as an
  ensemble doing coordinated measurements
• combined with a comprehensive in situ package
• allows to trace solar processes from the
  photosphere through the corona into the
  interplanetary medium close to the Sun

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Top level scientific goals

• With Solar Orbiter we will, for the first time
• Determine the properties, dynamics and
  interactions of plasma, fields and particles in
  the near-Sun heliosphere
• Investigate the links between the solar surface,
  corona and inner heliosphere
• Explore, at all latitudes, the energetics,
  dynamics and fine-scale structure of the Suns
  magnetized atmosphere
• Probe the solar dynamo by observing the Suns
  high-latitude field, flows and seismic waves

Combination of Remote Sensing In-Situ science
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Solar Orbiter

• Solar Orbiter Firsts
• Study the Sun from close-up (48 solar radii or
  0.22 AU) at high resolution
• Explore the uncharted innermost regions of our
  solar system
• Fly by the Sun and examine the solar surface and
  the space above from a nearly co-rotating vantage
  point
• Provide images of the Suns polar regions from
  heliographic latitudes as high as 35

• Solar Orbiter will open a new research chapter,
  because
• the payload suite and the orbit are unique
• No solar imaging mission has yet come close to
  the Sun or climbed out of the ecliptic
• ? unprecedented views
• ? exploration and potential discoveries

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Comparison with solar missions

• In the Solar Orbiter time-frame (with launch in
  2015)
• SOHO, TRACE, Ulysses missions will be over
• STEREO, Solar-B missions likely to be complete
• Solar Dynamics Observatory (SDO) should still be
  operational
• Kuafu possibly operational
• ground based observation facilities certainly
  operational
• ? opportunities for stereoscopic observations

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Measuring polar magnetic field

• Solar Orbiter will allow us to study the
• magnetic structure and evolution of the polar
  regions,
• detailed flow patterns in the polar regions,
• development of magnetic structures, using
  local-area helioseismology at high latitudes.

Model magnetogram of the simulated solar cycle.
The sun viewed from a latitude of 30 north of
the ecliptic (courtesy Schrijver)
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Resolving fundamental scales
SOHO/EIT
TRACE Solar Orbiter 1850
km pixels 350 km pixels
75 km pixels
Due to proximity, Solar Orbiter will resolve
scales such as the photon mean free path,
barometric scale height and flux tube diameter in
the photosphere ( 150 km)
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Baseline mission profile

• Launch date (current baseline) May 2015
• (backup opportunity in Jan 2017)
• Launch by Soyuz-Fregat 2-1b
• Cruise phase (3.4 yrs)
• Chemical Propulsion
• Gravity Assist Manoeuvres (Venus, Earth)
• Science phase
• 32 resonant orbit with Venus (period 149.8 days)
• Total mission duration, incl. extended phase
  (2015) 10 yrs
• Minimum perihelion distance 48 solar radii (0.22
  AU)
• Maximum solar latitude 34 (in extended phase)

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SEP vs. Chemical (Ballistic) mission

• Science phase orbits can be reached using either
  high specific impulse (solar electric) or low
  specific impulse (chemical) propulsion
• Solar Electric Propulsion
• Short cruise phase (1.8 yrs)
• Commonality with BepiColombo
• Increased complexity (SEP module to be
  jettisoned)
• Development risk
• Chemical Propulsion
• Lower development risk
• Longer cruise phase (3.4 yrs)
• Chemical propulsion (ballistic) mission launched
  has better mass margins
• Science operations possible during cruise phase

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CP Profile launch opportunities

• Ballistic transfers
• 3.4 yr - Oct 2013
• 3.4 yr - May 2015
• 4.1 yr - Jan 2017
• 3.4 yr - Aug 2018
• Inclination raising phase almost identical for
  all launch dates.
• 2017 different from 2013-2015-2018 43 resonance
  initial orbit ? 32, orbit reached only 3 month
  before 2018 scenario ? longer mission
  duration

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Baseline (chemical) mission - 2015 launch
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Baseline (chemical) mission - 2015 launch
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Baseline (chemical) mission - 2015 launch
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Baseline (chemical) mission - 2015 launch
Transfer Phase
Science Phase
Extended Mission
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Mission profile vs. solar cycle
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Science payload / SO status

• Instruments to be selected via a competetive
  process based on an AO open to the international
  scientific community
• Philosophy
• Resource-efficient instrumentation (e.g.,
  remote-sensing instruments to be "1 metre, 1
  arcsec resolution" class)
• Science Management Plan calls for proposals to be
  submitted via relevant funding agencies
• ESA Solar Orbiter Instrument AO
• Foreseen for release end of 2007 / beginning 2008
  after final decision by SPC on SO implementation
  (Nov 2007)
• Letters of Intent to Propose were due Sept 15th,
  2006
• ? Consolidation - Heat Shield / System Study
  Phase
• Project Instr. Teams Iterations on technical
  (thermal) issues
• SO Mission Consolidation

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Reference payload
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Visible-light Imager and Magnetograph (VIM)
High-resolution images (75 km pixels),
Dopplergrams (helioseismology) and magnetograms
of the photosphere
Vector magnetograph consisting of - 125 mm
diameter Gregorian telescope - 15 mm diameter
full disc telescope (refractor) - Filtergraph
optics (two 50 mm Fabry-Perot etalons)
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Visible-light Imager and Magnetograph
(VIM)Overview

• Measurement of
• velocity fields using Doppler effect
• magnetic fields using Zeeman effect
• Magnetograph imagery in narrow (5 pm FWHM )
  spectral bands around a visible spectral line at
  different polarisation states ? line of sight
  (LOS) velocity ? magnetic field vector
• Time resolution 1 minute (5 ? x 4
  polarisations)
• Spatial resolution
• 1 arc-sec with 0.5 arc-sec sampling ? 125 mm (_at_
  500nm)
• Field 2.7 (angular diameter of sun at 0.22 AU)
• Split in 2 instruments HRT for resolution and
  FDT for field
• Stringent LOS stability 0.02 arc-sec over 10 s
  (differential photometry) ? internal Image
  Stabilisation System

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Extreme UV Spectrometer (EUS)
Principle scientific goal determine the plasma
density, temperature, element/ion abundances,
flow speeds and structure of the solar atmosphere
using spectroscopic observations of emission
lines in the UV/EUV. High-res. plasma diagnostics
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Extreme UV Spectrometer (EUS)

• Instrument Concept
• - off-axis normal incidence system (NIS)
• - Single paraboloid primary mirror reflects
  portion of solar image \\\into a spectrometer
• - Spectrometer utilises toroidal variable line
  spaced (TVLS) grating (normal incidence
  configuration)
• - The solar image is scanned across the
  spectrometer slit by motions of the primary
  mirror.
• - The wavelength selections are geared to the
  bright solar lines in the extreme ultraviolet
  (EUV) emitted by a broad range of plasma
  temperatures within the solar atmosphere.
• - Wavelength bands under consideration 170-220
  Å, 580-630 Å and gt912 Å, to obtain spectral
  information from the corona, transition region
  and chromosphere,

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Extreme UV Imager (EUI)

• Principal scientific goals
• provide EUV images with at least a factor 2
  higher spatial resolution than currently
  available, in order to reveal the fine-scale
  structure of coronal features
• provide full-disc EUV images of the Sun in order
  to reveal the global structure and irradiance of
  inaccessible regions such as the "far side" of
  the Sun and the polar regions
• study the connection between in-situ and
  remote-sensing observations. High-resolution
  imaging of the corona.

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Extreme UV Imager (EUI)

• Instrument Concept
• - High Resolution Imager (HRI) and a Full Sun
  Imager (FSI))
• - HRI comprises up to three telescopes in
  different wavelength bands (resources
  permitting).
• - Both the quiet Sun network regions and the
  coronal loops will be observed..
• The wavelength choices for the reference design
  were 30.4, 17.1 and 13.3 nm covering temperatures
  from 5 104 K to 1.6 107 K.
• FSI is based on a single telescope concept. This
  will provide a global insight into changes in the
  solar atmosphere and in addition will provide
  context information for other instruments. The
  operating wavelength for the reference design is
  TBD in the range 13.3 - 30.4 nm.

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Coronagraph (COR)

• Principal scientific goals
• Investigate the evolution of the magnetic
  configuration of streamers in order to test the
  hypothesis of magnetic reconnection as one of the
  main processes leading to the formation of the
  slow solar wind during the quasi
  helio-synchronous phases of the orbit
• Measure the longitudinal extent of coronal
  streamers and coronal mass ejections from an
  out-of ecliptic vantage point. These data are
  essential to determine the magnetic flux carried
  by plasmoids and coronal mass ejections in the
  heliosphere
• Investigate the large-scale structure of the
  F-corona (the dust) and the cometary sources of
  the dust near the Sun. This will provide
  important information for the in-situ instruments
  in the payload that measure plasma and dust.

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Coronagraph (COR)

• Instrument Concept
• - COR is an externally occulted telescope for
  broad-band polarisation imaging of the visible
  K-corona and for narrow-band imaging of the UV
  corona in the H I Lyman-a, 121.6 nm, line
• annular field of view between 1.2 and 3.5 solar
  radii, when the Solar Orbiter perihelion is 0.22
  AU.
• off-axis Gregorian telescope
• The UV Lyman- a line is separated with
  multilayer mirror coatings and (optionally) EUV
  transmission filters (optimized for 30.4 nm)
• The visible light channel includes an achromatic
  polarimeter, based on electro-optically modulated
  liquid crystals.

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Solar Wind Plasma Analyser (SWA)

• Principal scientific goals
• provide observational constraints on kinetic
  plasma properties for a fundamental and detailed
  theoretical treatment of all aspects of coronal
  heating
• investigate charge- and mass-dependent
  fractionation processes of the solar wind
  acceleration process in the inner corona
• correlate comprehensive in-situ plasma analysis
  and compositional tracer diagnostics with
  spacebased and ground-based optical observations
  of individual stream elements.

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Solar Wind Plasma Analyser (SWA)

• Instrument Concept
• A Proton/a-particle Sensor (PAS) with the
  principal aim to investigate the velocity
  distribution of the major ionic species at a time
  resolution equivalent to the ambient proton
  cyclotron frequency. The sensor is Sun pointing.
• An Electron Analyser System (EAS) consisting of
  two (three optional if resources allow) sensors
  to cover nearly 4p ?ster of viewing space and to
  allow the determination of the primary moments of
  the electron velocity distribution with high
  temporal resolution.
• A Heavy Ion Sensor (HIS) which allows the
  independent determination of the major charge
  states of oxygen and iron and a coarse mapping of
  the three-dimensional velocity distribution of
  some prominent minor species. Also, pick-up ions
  of various origins, such as Si, etc.) should be
  measured. The sensor is Sun pointing.

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Radio and Plasma Wave Analyser (RPW)

• Principal scientific goals
• Provide measurements of both the electric field
  and magnetic field in a broad frequency band
  (typically from a fraction of a Hertz up to
  several tens of MHz) covering characteristic
  frequencies in the solar corona and
  interplanetary medium.
• Measurements of both electrostatic and
  electromagnetic waves provide different
  diagnostics
• - Electrostatic waves provide in-situ
  information in the vicinity of the spacecraft
• - Electromagnetic waves provide extensive
  remote-sensing of energetic phenomena in the
  solar corona and interplanetary medium.

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Magnetometer (MAG)

• Principal scientific goals
• Provide vector measurements of the solar wind
  magnetic field with high resolution (better than
  1 nT) at sub-second sampling.
• The MAG instrument will enable the investigation
  of
• - The link between coronal structures and their
  signatures in the solar wind
• - Kinetic effects in the solar wind plasma
• - Large-scale structures in the solar wind,
  e.g., coronal mass ejections
• - MHD waves and turbulence.

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Energetic Particle Detector (EPD)

• Principal scientific goals
• Determine in-situ the generation, storage,
  release and propagation of different species of
  solar energetic particles in the inner
  heliosphere
• Identify the links between magnetic activity and
  acceleration on the Sun of energetic particles,
  by virtue of combined remote-sensing of their
  source regions and in-situ measurements of their
  properties
• Characterize gradual (typically CME-related) and
  impulsive (typically flare-related) particle
  events and trace their spatial and temporal
  evolution near the Sun.
• Measure energetic pick-up particles originating
  from the interaction of the Solar Wind with
  near-Sun dust.
• In order to achieve these goals, measurements
  should be acquired at high time resolution
  (capable of up to 1 s, during high flux
  situations), with as complete an angular coverage
  as possible in order to resolve particle
  pitch-angle distributions.

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Observational Strategies

• Prime Science Periods
• 10 days around perihelion and/or highest
  latitudes
• highest data rates dumped to onboard memory
• instruments run autonomous in pre-defined mode
  sequences
• pointing by pre-defined s/c orientation
  maneuvers
• burst mode triggering, re-orientation triggering
  under consideration
• Cruise Phase
• CP allows for science observations during the
  transfer period
• possibilities (data rates, length of observation
  intervals...) TBD
• Aphelion Segments during Science and Extended
  Phase
• TBD
• so far, only observation opportunities for in
  situ instruments at low data rates are foreseen
• ? we have to strongly push to open opportunities
  for remote sensing instruments and define
  reasonable low data rate modes

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Schedule - Planning assumptions

• Sept 2006 Letters of Intent to Propose
• to Nov 2007 Mission Consolidation Phase
• Nov 2007 SPC Decision
• thereafter AO release
• 2008 SPC approval of payload
• 2008 Start of definition phase (18 months)
• 2010 Start of implementation phase (tbc)
• May 2015 Launch