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Juhani Huovelin and Lauri Alha Observatory, University of Helsinki Finland

University of Helsinki. Spaceborne X-ray observations of the Sun and sky background : Analysis of data from the XSM onboard SMART-1. Juhani Huovelin and Lauri Alha Observatory, University of Helsinki Finland. J.Huovelin, Patras, 19th May 2006. SMART-1 The first European mission to

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Juhani Huovelin and Lauri Alha Observatory, University of Helsinki Finland

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  1. University of Helsinki Spaceborne X-ray observations of the Sun and sky background : Analysis of data from the XSM onboard SMART-1 Juhani Huovelin and Lauri Alha Observatory, University of Helsinki Finland J.Huovelin, Patras, 19th May 2006

  2. SMART-1 The first European mission to the Moon University of Helsinki • Project started in 1999 • Launch: 27 Sept. 2003. as a piggybag on Ariane 5 at Kourou, French Guiana • Mission: ~15 months cruise and 9 + 12months at Moon orbit (***) • Main task: Test of Solar electric propulsion (SEP) for future planetary missions (***) Controlled crash to Moon in September, 2006 J.Huovelin, Patras, 19th May 2006

  3. SMART-1 Space Craft (S/C) University of Helsinki Manufacturer: Swedish Space Corporation(SSC) • Volume: ~1 m x 1 m x 1 m • Mass: 370 kg • Primary propulsion: A plasma thruster: Sunlight  electric power by solar cells/panels  a strong electric field inside thruster engine  acceleration of ions from thruster  S/C acceleration • Fuel: 82 kg of Xenon-plasma • Thrust force: 70 mN (~weight of one A4 sheet of paper !) - Accelerated SMART-1 to Moon orbit in 1.5 years • Payload: 19 kg (7 instruments) J.Huovelin, Patras, 19th May 2006

  4. SMART-1 Payload University of Helsinki • 7 instruments operating during the whole mission • 10different scientific experiments • D-CIXS (Demonstration of a Compact Imaging X-ray Spectrometer) • XSM(X-ray Solar Monitor) • SPEDE (Spacecraft Potential Electron and Dust Experiment) • AMIE (Advanced Moon micro-Imager Experiment) • Laserlinkand OBAN • EPDP (Electric Propulsion Diagnostic Package) • KATE (Ka-Band TT&C Experiment) • RSIS (Radio-Science Investigations for SMART-1) • SIR (SMART-1 Infrared Spectrometer) J.Huovelin, Patras, 19th May 2006

  5. University of Helsinki SMART-1 Science and Technology WorkingTeam (STWT) B. Foing (ESA project scientist), J.L. Josset, M. Grande (D-CIXS), J. Huovelin (XSM), U. Keller, A. Nathues, G. Noci, A. Mälkki, Z. Sodnik, P. McMannamon STWT & STOC Flight Operations Team J.Huovelin, Patras, 19th May 2006

  6. SMART-1 University of Helsinki Demonstration of a Compact Imaging X-ray Spectrometer (D-CIXS) PI: Manuel Grande, (Rutherford Appleton Laboratory,) UK Science task of D-CIXS • Mapping of chemical elements on the Moon (Mg, Si, Al, Fe), • Absolute chemical abundances using XSM data J.Huovelin, Patras, 19th May 2006

  7. SMART-1 University of Helsinki D-CIXS observations • All detectors on a facet • observe at the same direction • with a ~8 degrees FoV • The effective area of a facet is ~5 cm2 Centre facet Credit: M. Grande et al. J.Huovelin, Patras, 19th May 2006

  8. Ca Fe Mg Al Si 1 keV 10 keV SMART-1 University of Helsinki D-CIXS observations of the Moon Credit: M. Grande et al. J.Huovelin, Patras, 19th May 2006

  9. SMART-1 X-ray Solar Monitor (XSM) I Task of XSM E XSM measures the X-ray spectrum of the whole Sun with good spectral and time resolution • Observations of the X-ray illumination on the sunlit Moon surface (= solar X-ray spectrum) - Needed for Moon science: determination of elemental abundances from X-ray fluorescence spectra measured by D-CIXS on SMART-1 - Very useful new information on the hot solar corona solar science - Also other applications: full sky X-ray background, including local intra-solar-system emission Today’s topic • X-ray spectroscopy of the Sun (and sky background) with XSM • Search of axion-related X-ray emission J.Huovelin, Patras, 19th May 2006

  10. SMART-1 XSM specifications 1.5 mm Instrument Detector: - HPSi PIN, diameter 2mm - X-ray photon counter - Circular Field-of-View, 52o radius - Entrance filter: 25 micron Be - Aperture stop, Au, inner diameter 1.5 mm - Electromagetic shutter, 0.4 mm W (Tungsten) Features - Energy range: 1.5 - 20 keV (effective range) - Energy resolution: ~250 eV @ 6 keV (2003) ~350 eV @ 6 keV (2006) • Effective area (on-axis): 0.0145 cm2 Data Counts sampled to energy spectra: - 1 spectrum/16 s (512 energy channels) Sensor unit - Dimensions: 81 x 40 x 26 mm3 - Mass: approx. 190 g - Box material: Aluminium - Contents: Detector Cooler (Peltier) Front end electronics Shutter mechanism Calibration source (55Fe+Ti) J.Huovelin, Patras, 19th May 2006

  11. SMART-1 XSM sensitivity On- Axis effective area Sensitivity: 1cps ~ 10-9 W/m2 J.Huovelin, Patras, 19th May 2006

  12. SMART-1 XSM observations 2004-5 • Observations of sky background • 129 hours total • one field covers 1/5 of the whole sky • different offsets from the Sun • Includes all targets, X-ray sky background + possible axion-related X-ray emission • Observations of the Sun • - 351 h total (78933 sp. !) • 42 full flares • 20 partial flares • Flare coverage: B2 – M2 • + periods of quiescence (with • axion-induced emission ?) J.Huovelin, Patras, 19th May 2006

  13. A flare with XSM SMART-1 J.Huovelin, Patras, 19th May 2006

  14. SMART-1 Observations of the Sun 1. Sensitivity 160 s exposure at quiescence, 1-2 x 10-7 W/m2 160 s exposure of a C5 flare, 5 x 10-6 W/m2 J.Huovelin, Patras, 19th May 2006

  15. SMART-1 Observations of the Sun 2.Rising phase of an X-flare 16 s exposure of a flare 15th January, 2005 Flux (1-8 Å)= 10-5 W/m2 (M1 level, a few minutes after onset) Analysis: Indicative of filling–up of spectrum with densely populated line emission, or (non-thermal ?) continuum emission. Temperature > 20 MK. J.Huovelin, Patras, 19th May 2006

  16. SMART-1 Observations of the Sun 3. Flare spectra and models exposure time: 16 s • Model: thermal bremsstrahlung + lines • C1.5 flare: T = 17 MK (from BS model) • Fe K-alpha vs. K-beta visible and strong enough for • comparative temperature analysis • - Coronal abundances for several elements below 5 keV J.Huovelin, Patras, 19th May 2006

  17. SMART-1 Observations of the Sun 3. Flare spectra and models exposure time: 16 s • Model: thermal bremsstrahlung + lines • C 5 flare: T = 20 MK (from BS model) • Fe K-alpha vs. K-beta visible and strong enough for • comparative temperature analysis • - Coronal abundances for several elements below 5 keV J.Huovelin, Patras, 19th May 2006

  18. SMART-1 Question 1 WHAT DO WE EXPECT TO SEE, AND WHERE ? • Axion-induced X-ray emission 1. In the Solar corona • best visible during quiescence (or quiescent regions) • How to distinguish from the solar X-ray spectrum ? • 2. At ~ 5 RSun away from the Sun • visible all the time • how to distinguish from the sky X-ray background ? • 3. Elsewhere in the Solar System • how to minimise other sources of X-rays and background ? •  e.g. measurements of emission between a S/C and a celestial body that is a weak emitter of X-rays J.Huovelin, EGU 2006

  19. SMART-1 Question 2 • X-ray emission from axions in the solar system originated in the Sun At which energies we expect to see such emission ? • What is the expected spectral disribution ? • What is the strength of the expected emission ? J.Huovelin, EGU 2006

  20. SMART-1 Question 3 HOW COULD SMART-1 HELP IN THIS ? 1. In the Solar corona • XSM observations of the Sun during coronal quiescence • Accurate modelling of coronal X-ray emission and surrounding sky spectrum (very wide FoV !) needed • 2. Towards ~ 5 RSun away from the Sun • All off-Sun observations with XSM • Accurate modelling of sky background far away from the • Sun, and study of deviations for different off-Sun angles • 3. Elsewhere in the Solar System • XSM observations of the sky background. • - D-CIXS observations of the Moon ? J.Huovelin, Patras, 19th May 2006

  21. Solar X-ray spectrum • Date: 30 June 2005 • Exp. time: 960 s • off-axis/Sun: 9 deg • Count rate: 250 cps • Flux (2-10 keV): 7.1 10-8 W/m2 • Model: • Thin thermal plasma (Sun) • Broken powerlaw (sky/bkg) SMART-1 1. XSM observations of quiescent solar corona J.Huovelin, Patras, 19th May 2006

  22. Solar X-ray spectrum • Date: 06 Jan 2006 • Exp. time: 1120 s • off-axis/Sun: 3 deg • Count rate: 48 cps • Flux (2-10 keV): 1.1 10-8 W/m2 • Model: • Thin thermal plasma (Sun) • Broken powerlaw (sky/bkg) SMART-1 1. XSM observations of quiescent solar corona J.Huovelin, Patras, 19th May 2006

  23. Solar X-ray spectrum • Date: 25 Mar 2006 • Exp. time: 1600 s • off-axis/Sun: 9-12 deg • Count rate: 74 cps • Flux (2-10 keV): 1.8 10-8 W/m2 • Model: • Thin thermal plasma (Sun) • Broken powerlaw (sky/bkg) SMART-1 1. XSM observations of quiescent solar corona J.Huovelin, Patras, 19th May 2006

  24. SMART-1 X-ray sky observationwith XSM 3.4 h integration (762 spectra) • Average signal rate (1-20 keV): ~ 1 cps • Fit result (Note: includes all X-ray sources in a 2.4 sterad sky field): • Flux (E, keV) = 111.0 x E –1.06 x exp(-E/11.7) photons/cm2/s/keV • Flux (2-10keV) = 8 x 10-7 erg/cm2/s (~ 1/5 of full sky) • Estimate: ~ 4 x 10-6 erg/cm2/sfor full sky (TBC by analysis of all data) • ~ 3.3* 10-7 erg/cm2/s/sr average J.Huovelin, Patras, 19th May 2006

  25. Solar X-ray spectrum • Date: 21 June 2004 • Exp. time: 4416 s • off-axis/Sun: 53-54 deg • Count rate: 0.7 cps • Flux (2-10 keV): 5.3 10-10 W/m2 • Model: • Broken powerlaw (sky/bkg) SMART-1 2. XSM observations towards ~ 5 RSun away from the Sun J.Huovelin, Patras, 19th May 2006

  26. SMART-1 3. Observations elsewhere in the Solar System • Solar X-ray spectrum • Date: 13 June 2004 • Exp. time: 20752 s • off-axis/Sun: 75-79 deg • Count rate: 1.0 cps • Flux (2-10 keV): 8.0 10-10 W/m2 • Model: • Broken powerlaw (sky/bkg) J.Huovelin, Patras, 19th May 2006

  27. SMART-1 Conclusions • There may be weak signs on some residual emissionat some energies • Interpretation: may be due to inaccurate modelling of • - Solar X-ray spectrum • - Sky X-ray background spectrum • However, it is possible to derive an upper limit to the axion-related component. • - Reliable, since instrument background very low J.Huovelin, Patras, 19th May 2006

  28. SMART-1 Future ? • Idea: XSM observation towards the Moon before SMART-1 crashes on the Moon • Possible to make accurate quantitative analysis of the observation • Large FoV, thus large volume of space between S/C and Moon surface  compensates for the small size of detector • Future space missions with our involvement (for more data): • Chandrayaan-1 (ISRO): Moon mission on 2007-8 with XSM2 • BepiColombo (ESA): Mercury mission (2013-20) with SIXS and MIXS X-ray instruments (similar task as for SMART-1 D-CIXS/XSM) J.Huovelin, Patras, 19th May 2006

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