Solar Orbiter

1. Solar Orbiter • Status of Solar Orbiter • Scientific Goals • Spectrometer Update • Richard Harrison • Rutherford Appleton Laboratory

2. Status of Solar Orbiter • Recent & On-Going Activities: • Payload Working Group • Science Definition Team • International Status • ESA Reconstruction of Science Programme

3. Status of Solar Orbiter 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

4. Baseline mission (SDT)

5. Status of Solar Orbiter 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

6. Status of Solar Orbiter 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

7. Status of Solar Orbiter 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

8. Status of Solar Orbiter 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

9. Status of Solar Orbiter 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!).

10. Status of Solar Orbiter 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…

11. Solar Orbiter Scientific Goals • Science Definition Team • Solar Orbiter ‘firsts’ • Solar Orbiter rationale • Solar Orbiter Goals (Science Definition Team) • Underlying Questions

12. 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

13. 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°

14. 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

15. 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

16. 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?

17. 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)?

18. 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?

19. 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?

20. 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?

21. EUV Spectrometer: Update • 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

22. Baseline Payload (SDT)

23. 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).

24. The EUS Instrument Requirements • 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

25. The EUS Instrument Requirements Other Factors Which Influence the Design

26. 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?

27. The EUS Instrument Environment 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.

28. The EUS Instrument Environment 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).

29. 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)

30. 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...

31. 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 …

32. 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 xεf 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.

33. EUS7 EUS5 EUS8 CDS Aperture 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 25μmx3mm Slit 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/pixel Resolution (λ) 2.56 Å/mm 2.95 Å/mm 2.66 Å/mm 3.17 & 5.56 Å/mm λ range* 50 Å 64 Å 52 Å 73 &120 Å Resolution (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/arcsec FOV 1024“ (17.1’) 650“ (10.81’) 2048“ (34.1’) 240“ (4’) a 5 μm 5 μm 5 μm 21 μm b 5 μm 5 μm 5 μm 21 μm εt 0.04 0.04 0.04 0.25 εm - - - 0.80 εf 0.2 0.2 0.2 - εg 0.07 (SERTS) 0.07 0.07 0.02 εd 0.4 0.4 0.4 0.13 Eff 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 EUS Design Comparisons * assumes 4kx4k, 5 micron pixels (CDS has 1024 pixels) ** ignores PSF