Solar Orbiter - October 2003 Solar Orbiter Status of Solar Orbiter Scientific Goals Spectrometer Update Richard Harrison Rutherford Appleton Laboratory

Solar Orbiter - October 2003

Solar Orbiter

Status of Solar Orbiter

Scientific Goals

Spectrometer Update

Richard Harrison

Rutherford Appleton Laboratory



Recent & On-Going Activities:

Payload Working Group

Science Definition Team

International Status

ESA Reconstruction of Science Programme


PAYLOAD WORKING GROUP Payload Working Group – established 2002, to address payload-

related challenges Remote Sensing (Chairs: R. Harrison and B. Fleck) In-Situ (Chairs: R. Wimmer-Schweingruber and R. Marsden)

Tasks: To study instrument feasibility, and produce payload definition documents

Reports delivered to ESA May/June 2003 – including a number of recommendations concerning, e.g. thermal loads, telemetry, low mass options, detectors.

No show stoppers



Baseline mission (SDT)

Instrument Mass

kg

Power

W

Rate

kbpsPlasma Package (SWA) 15.5 11 14

Fields Package (MAG +RPW + CRS) 11 13 5.8

Particles Package (incl. Neutrons,gammas & dust)

15 15 4.5

Visible Light Imager & Magnetograph (VIM)

30 25 20

EU Imager (3 telescopes incl. FSI) 30 25 20

EU Spectrometer 25 25 17

Spectrometer/Telescope Imaging X-rays (STIX)

4 4 0.2

Coronagraph (COR) 10 10 7

Total 140.5 128 88.5



SCIENCE DEFINITION TEAM

Chair: E. Marsch. reviewing the scientific goals of the mission as presently

understood refining these goals where needed prioritising them in order to achieve a well-balanced, and highly

focused scientific mission defining the sets of measurements needed (baseline and

minimum) to achieve the mission’s scientific goals, taking into account the output of the Payload Working Group

Output: Science Requirements Document to be completed by SDT in November 2003



INTERNATIONAL STATUS Solar Orbiter – ESA’s contribution to the International

Living with a Star (ILWS) programme US as well as European support in Payload Working

Group and Science Definition Team, anticipating some US-led instrumentation

NASA contribution to mission anticipated Solar Orbiter has been highlighted as important for

the US community in a number of documents, such as the Sun-Earth connection Roadmap and the Decadal report of the National Science Foundation



The ESA Science Programme – Reconstruction On-going activity – ESA committees and working groups

reassessing missions – urgent need to balance the books – i.e. ESA cannot afford all of the missions on its books.

Missions could go! The Missions:

BepiColombo Eddington GAIA Netlander LISA Solar Orbiter SMART-2 (LISA Pathfinder) Note: No JWST and Venus Express



The ESA Science Programme – Reconstruction Committee/Working Group Meetings:

SPC Sept 25 FPAG Sept 29-30, Oct 7-8 SSWG Oct 6-8 AWG Oct 7-9 SSAC Oct 7, 13-14 SPC Nov 5-6 Council Dec 10-11



The ESA Science Programme – Reconstruction UK Space Science Advisory Committee:

Assess UK priorities prior to ESA assessment; brief UK SPC delegates

18 Sept Meeting – top priority for UK (equal) = LISA, BepiColombo, Solar Orbiter, Eddington, GAIA (Eddington and BC lander are lowest of the high priorities!).



The ESA Science Programme – Reconstruction 7th October SPC/SSAC/Working Group Presentations

at ESTEC Each mission presented NASA and Japan present (NASA stressed support for LISA

and Solar Orbiter; Japan stressed support for BepiColombo)

No conclusions until November/December BUT, general feeling seems to be that Solar Orbiter is in

good shape (despite links to BepiColombo) Tone Peacock already contacted me to talk about next

phase of studies from PWG activity; industrial ‘payload integration’ ITT is out and due to start later in year…


Solar Orbiter Scientific Goals

Science Definition Team

Solar Orbiter ‘firsts’

Solar Orbiter rationale

Solar Orbiter Goals (Science Definition Team)

Underlying Questions


Science Definition Team (SDT)

Chair: E. Marsch. The SDT is currently: reviewing the scientific goals of the mission as

presently understood refining these goals where needed prioritising them in order to achieve a well-balanced,

and highly focused scientific mission defining the sets of measurements needed (baseline

and minimum) to achieve the mission’s scientific goals, taking into account the output of the Payload Working Group

Output: Science Requirements Document to be completed by SDT in November 2003


Solar Orbiter firsts

Explore the uncharted innermost regions of our solar system

Study the Sun from close-up (45 solar radii)

Fly by the Sun tuned to its rotation and examine the solar surface and the space above from a co-rotating vantage point

Provide images of the Sun’s polar regions from heliographic latitudes in excess of 30°


Solar Orbiter rationale

The Sun's atmosphere and heliosphere are - uniquely accessible domains of space, - excellent laboratories for detailed study of fundamental processes common to astrophysics and solar physics

Remote sensing and in-situ measurements, - much closer to the Sun than ever before, - combined with an out-of-ecliptic perspective,

promising to bring about major breakthroughs in solar and heliospheric physics


Main 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 Sun’s magnetized atmosphere

Probe the solar dynamo by observing the Sun’s high-latitude field, flows and seismic waves


Nature of the Inner Heliosphere

What is the character and radial evolution of solar wind structures in the inner heliosphere?

What is the nature of solar wind stream interactions in the inner heliosphere, and how does it depend on latitude?

What is the influence of CMEs on the structure of the inner heliosphere?

What is the nature of particle acceleration and transport in the near-Sun environment?

What is the role of shocks and flares in accelerating particles near the Sun?

How does the solar wind microstate evolve with radial distance?


Nature of the Inner Heliosphere

What are the sources and properties of dust in the inner heliosphere. Do Sun-grazing comets contribute to the dust?

What is the role played by the near-Sun dust for the interplanetary pick-up ions?

What are the fluxes and spectra of low-energy solar neutrons? Can one probe remotely nuclear reactions and ion acceleration

on the Sun? Is there a neutral solar wind, and what are its properties? How does the solar corona look like when being imaged by

energetic neutral atoms? How does the solar luminosity vary, and does it change

globally (depend on latitude)?


Linking Sun and Heliosphere

How does the evolution of the solar magnetic field affect the heliosphere at all scales?

What are the sources of the slow solar wind, and what is its temporal and spatial evolution?

What are the sources and the global dynamics of eruptive events and what are their effects on the inner heliosphere?

What are the relevant physical processes that lead to turbulence in the tenuous magnetofluid of the inner heliosphere, and how does this turbulence interact with heliospheric particles?

What is the solar source of the solar wind plasma (including that of CMEs) and energetic particles seen in the interplanetary medium (IPM)?

What regions at the Sun are the sources of the magnetic field lines in the IPM?


The Sun’s Atmosphere at all Latitudes

How is the polar high-speed wind generated and how does this relate to the polar plume phenomenon?

How does the structure and evolution of polar coronal hole regions project into the inner heliosphere?

What is the nature of coronal hole boundaries, how do they evolve and how do they project into the inner heliosphere?

What is the nature of fundamental processes in a stellar atmosphere, including wave activity from source to the corona, the physics of transient events and flux emergence, over all latitudes?


The Polar Magnetic field & Dynamo

How does the high-latitude field of the Sun evolve on a range of scales?

What are the properties of the Sun's surface and sub-surface meridional flow and differential rotation at high latitude, and how do these vary with time and position?

How do the average properties of granular and supergranular flows depend on latitude?

What are the properties of emerging flux at high latitudes? How is field removed from the solar surface around the

high-latitude polarity inversion regions? What are the signatures of the solar dynamo action near

the bottom of the convective envelope?


Key component of Baseline Payload

Required for basic plasma diagnostic capability on Orbiter, for a range of scientific questions

Proposed next-generation CDS led from RAL has been proposed at PPARC SOI

Proto-consortium has met three times – full meetings in 2001, 2002 and wavelength meeting in 2003

Pre-proposal to PPARC due at end of October

EUV Spectrometer: Update


Instrument Mass

kg

Power

W

Rate

kbpsPlasma Package (SWA) 15.5 11 14

Fields Package (MAG +RPW + CRS) 11 13 5.8

Particles Package (incl. Neutrons,gammas & dust)

15 15 4.5

Visible Light Imager & Magnetograph (VIM)

30 25 20

EU Imager (3 telescopes incl. FSI) 30 25 20

EU Spectrometer 25 25 17

Spectrometer/Telescope Imaging X-rays (STIX)

4 4 0.2

Coronagraph (COR) 10 10 7

Total 140.5 128 88.5

Baseline Payload (SDT)


The Need for a Spectrometer

• This is the best we can do now: EUV imaging to 0.5 arcsec (350 km) and EUV spectroscopy to 2-3 arcsec. We know that the solar atmosphere is composed of fine-scale structures and must aim to develop appropriate tools. Our target is spectroscopy at ~70 km (0.5 arcsec at 0.2 AU, 0.1 arcsec at 1 AU).


The EUS Instrument Requirements

Spatial Resolving Element (pixel) 0.5 arcsec 75 km at perihelion

Spectral Resolving Element (pixel) 0.01-0.02 Å/ pixel lower the better

Field of View (minimum) 34 x 34 arcmin2 AR size at perihelion

Exposure time (minimum) <1 s

Maximum Exposure Time Few 100 s cosmic ray limit

Wavelength Bands 170-220 Å580-630 Å> 912 Å

Prime bands f romTenerif e meeting

Pointing To anywhere on Sun and low corona

• SDT Resolution = 150 km target

• Spectral resolution critical – polar flows

• Wavelength bands – lines from chromosphere, transition region & corona is a major driver from the community

• Pointing – payload bolted together, common pointing JOP approach


The EUS Instrument Requirements

Other Factors Which Influence the Design


The EUS Instrument Environment

1. Thermal Loads

149 day cycle = 2,142 to 34,275 W/m2 (0.8 to 0.2 AU).

Need to address thermal balance for high load values and for variation of thermal input.

We must validate the designs through extensive modelling. Can we define test activities and facilities which could be used for such testing? What about optical degradation?



2. Particle Environment at 0.2 AU

Cosmic Rays:- Non-solar cosmic rays about the same as for SOHO, or less.

Solar Wind:- Projecting naively from 1 AU values (~10 p/m3) we might expect 250 p/m3 in ‘normal’ conditions at 0.2 AU, with v ~ 400 km/s. Thus, we expect 106 hits/cm2.s (25x SOHO flux). Is this a worry? Perhaps not so much if the detectors are ‘buried’ (don’t view space directly) and if the protons are low enough energy (will be plenty of 100 keV protons, for example). (Note: 109 direct proton hits ‘will kill a CCD’ - not so an APS…)

Neutrons:- We might expect to see some. 15 min half life means that we may expect them - possibly only from flares but more often than for 1 AU. Concern over their cross section at the silicon lattice relative to protons. Needs investigation.



2. Particle Environment at 0.2 AU (continued…)

Flares and shock (CME) particles:- Dose difficult to predict. Could argue that the chance of being hit by a flare proton(/neutron) ‘beam’ is the same as for, e.g. SOHO. What about from larger shocks? Would suggest that there is a greater chance of seeing energetic particles, but hard to calculate.

Note: Hadrons can cause damage to the silicon lattice which causes traps that can ‘steal’ charge which can be transferred to other parts of the image. The APS minimises the problem by not transferring charge.

Note: What about particle effects on optical surfaces? See CDS proton-gold coating study (subsurface bubbling).


EUS - Concept & Initial Design Strategy

Two design concepts now under discussion

Off-axis single mirror NI telescope with VLS grating (Roger Thomas)

Wolter II GI telescope with VLS grating (Luca Poletto)


EUS Web site http://www.orbiter.rl.ac.uk

1. Concept document (‘Blue Book’)

2. Technical notes (TN1 - Wavelength selection; TN2 - Orbiter goals; TN3 - Optical design requirements; TN4 - Detector requirements etc…)

3. Meeting reports, including ppt talks.

4. Contact info., links, Solar Orbiter information, notes/documents...


The EUS Instrument The consortium

Rutherford Appleton Laboratory, UK

Mullard Space Science Laboratory, UK

Birmingham University, UK

Max Planck, Lindau, Germany

Padua University, Italy

Goddard Space Flight Center, USA

Oslo University, Norway

IAS, Orsay, France

NRL, Washington, USA

Scientific CoI Groups – e.g. UCLAN, Armagh, Aberystwyth …


EUS Design Comparisons

I = intensity of line [erg.cm-2.s-1.ster-1]. Want to convert to measured intensity, M [count.s-1]

M = (Iλ/hc) (abA/f2) ε [count.s-1]

λ = wavelength of line

h = Planck’s constant [6.626 x 10-34 Js]

c = Speed of light [3 x 108 ms-1]

ab = Dimensions of slit [m2]

A = Aperture area [m2]

f = Focal length [m]

ε = Efficiency product (εt x εg x εf x εm x εd) (i.e. efficiency product of telescope, grating, filter, scan mirror, detector)

Compare different designs to CDS, i.e. an existing instrument that works! Tabulate the function (abA/f2)ε.


EUS Design Comparisons

EUS7 EUS5 EUS8 CDSAperture 100mmx100mm 100mx100mm 50mmx50mm 3430 mm2

A 0.01 m2 0.01 m2 0.025 m2 0.0034 m2

Total Length 1400mm 1400mm 1400mm Slit 2.6μmx5.3mm 3.0μmx3.7mm 2.1μmx8.6mm 25μmx3mmSlit 0.5“ x 650“ 0.53“ x 650“ 0.5“ x 2048“ 2“x240“Slit 75km x 97500km 80km x 98113km 75km x 307200km 1,500 km x 180,000 km

Resolution (λ) 0.0128 Å/pixel 0.0147 Å/pixel 0.0133 Å/pixel 0.08 & 0.14 Å/pixelResolution (λ) 2.56 Å/mm 2.95 Å/mm 2.66 Å/mm 3.17 & 5.56 Å/mmλ range* 50 Å 64 Å 52 Å 73 &120 ÅResolution (x)** 0.25 arcsec/pix 0.16 arcsec/pix 0.5 arcsec/pix 1.68 arcsec/pix

Plate scale 20 μm/arcsec 31.5 μm/arcsec 10 μm/arcsec 12.5 μm/arcsecFOV 1024“ (17.1’) 650“ (10.81’) 2048“ (34.1’) 240“ (4’)a 5 μm 5 μm 5 μm 21 μmb 5 μm 5 μm 5 μm 21 μmεt 0.04 0.04 0.04 0.25εm - - - 0.80εf 0.2 0.2 0.2 -εg 0.07 (SERTS) 0.07 0.07 0.02εd 0.4 0.4 0.4 0.13Eff product, ε 2.24 x 10-4 2.24 x 10-4 2.24 x 10-4 5.2 x 10-4

Eff. Area (A ε) 2.24 x 10-6 2.24 x 10-6 5.6 x 10-6 1.8 x 10-6

f 1.072 m 1.176 m 0.886 m 2.57 m(abA/f2)ε 4.87 x 10-17 4.05 x 10-17 1.78 x 10-16 1.2 x 10-16

* assumes 4kx4k, 5 micron pixels (CDS has 1024 pixels)** ignores PSF

Documents

Solar Orbiter - October 2003 Solar Orbiter Status of Solar Orbiter Scientific Goals Spectrometer Update Richard Harrison Rutherford Appleton Laboratory