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MagEX: A Proposal for a Lunar-based X-ray Telescope

MagEX: A Proposal for a Lunar-based X-ray Telescope. Steven Sembay Andrew Read & Jenny Carter Department of Physics and Astronomy University of Leicester. Lunar-based X-ray Astronomy – a short review The MagEX concept. “High Throughput X-ray Telescope on a Lunar Base”

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MagEX: A Proposal for a Lunar-based X-ray Telescope

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  1. MagEX: A Proposal for a Lunar-based X-ray Telescope Steven Sembay Andrew Read & Jenny Carter Department of Physics and Astronomy University of Leicester • Lunar-based X-ray Astronomy – a short review • The MagEX concept

  2. “High Throughput X-ray Telescope on a Lunar Base” Paul Gorenstein, 1990, in “Astrophysics from the Moon”, AIP Speculative 21st Century High Throughput (>100 m2) Lunar X-ray Observatory

  3. Phase 1: Late 1990’s 1 m2 XMM-Newton 0.45 m2 @ 1.5 keV Launched: Dec 1999 Phase 2: 2010 10 m2 Xeus 5 m2 @ 1.0 keV Launch: 2020’s? Phase 3: 2040 100 m2 Possible timeline for evolution of effective area of X-ray Astronomy Satellites (Gorenstein 1990) Existing technology (1990’s) implied ~400 ton facility Economic Argument: Assuming an existing lunar industrial infrastructure, cheaper to construct on the Moon than launch from Earth

  4. 0.45 m2 / 1,050 kg XMM-Newton Chandra 0.075 m2 / 956 kg X-ray Mirror Technologies – Resolution v Area density relation

  5. Generation-X ?? ~100 m2 / ~ 2-3 tonnes Adaptive Optics X-ray Mirror Technologies – Resolution v Area density relation ~ 5 m2 / ~ 1,296 kg XEUS Si Square Pore Optic

  6. If not LARGE then how about SMALL? Far-UV Camera/Spectrograph carried on Apollo 16 In the foreseeable future the “industrial” argument for lunar-based Large X-ray telescopes has been weakened by advances in mirror technology, although large space observatories would benefit from increased lift capacity generated by a space exploration programme.

  7. RX J1242-11 Stellar Capture Event Chandra/CXC/M.Weiss Applications for small Lunar-based X-ray Telescopes 1) Network of wide area monitors for studying extra-solar system transients and variables Analogue: SuperWASP wide-field optical monitor

  8. Applications for small Lunar-based X-ray Telescopes 1) Network of wide area monitors for studying extra-solar system transients and variables Moon LEO Ext. Orbit Contiguous light curves Yes No Yes Particle background Low Lowest Highest X-ray background Highest Low Low Thermal stability (poles) Good Poor Good Thermal stability (equator) Poor Case must be made on economic grounds. Is a network of simple X-ray Telescopes “piggybacking” on lunar (e.g.) missions cheaper than a dedicated spacecraft?

  9. Solar Wind Charge X-rays: Heavy solar wind ions in collision with neutral target atoms Aq+ + B → A(q-1)+* + B+ A(q-1)+*→ A(q-1)+ + hν Applications for small Lunar-based X-ray Telescopes 2) Remote sensing of the Terrestrial environment e.g. X-ray Emission from the SWCX process in the Magnetosheath

  10. MagEX:MagnetosheathExplorer inX-rays Program: Concept Studies for Lunar Sortie Science Opportunities solicitation within NASA Research Announcement: Research Opportunities in Space and Earth Sciences (ROSES) – 2006 PI: Michael Collier (NASA/GSFC) NASA/GSFC, Univ. of Kansas, Univ. of Leicester UK, Acad. Sci. Czech Rep. MagEX X-ray Telescope is compact (< 50 cm side) low mass (< 20-30 kg) wide field of view (~30°) imaging capable (psf ~ 1.5 arcminutes FWHM) detector energy resolution (~50 eV FWHM @ 600 eV)

  11. MagEX:MagnetosheathExplorer inX-rays Program: Concept Studies for Lunar Sortie Science Opportunities solicitation within NASA Research Announcement: Research Opportunities in Space and Earth Sciences (ROSES) – 2006 PI: Michael Collier (NASA/GSFC) Collaborators: Univ. of Kansas, Univ. of Leicester UK, Acad. Sci. Czech Rep. Proposal was funded (US) by NASA for a technical feasibility study, result due Autumn 2008 Awaiting result of an application to STFC for UK funding to support this study

  12. ~ 30 cm Optic Technology Slumped Glass Micropore Optics: Wide field of view & low mass Optic PSF: ~ 1.5’ FWHM (Lab Measurement) Optic of desired size formed by holding curved plates (3cm x 3cm) in a segmented bracket. Total mass ~ 1 kg Channel width = 20µm

  13. ~ 30 cm Optic Technology Slumped Glass Micropore Optics: Wide field of view & low mass R = 50 cm FOV = 30° Focal Plane geometric area depends on the Radius of curvature of the optic and the Field of view. D ~ 13 cm for R = 50 cm & fov = 30° D ~ 13cm Optic of desired size formed by holding curved plates (3cm x 3cm) in a segmented bracket. Total mass ~ 1 kg Channel width = 20µm

  14. Detector Technology Wide area CCDs provide: Soft X-ray sensitivity Good energy resolution e2V, BI/FI CCD, 6.1 cm x 6.1 cm Good spatial resolution Near-contiguous detection plane Hamamatsu, BI CCD, 6.7 cm x 3.2 cm

  15. Observational Goals Primary and Unique… Study of the dynamical interaction of the solar wind with the Earth’s magnetosheath on global scales via observations of X-ray emission from the Solar Wind Charge Exchange Process Additional Goals…. Study of the interaction of the solar wind with the Lunar Exosphere via X-ray emission from SWCX Monitoring of Terrestrial Auroral soft X-ray emission

  16. Telescope in Lunar night for half the orbit Lunar location provides a natural Platform for Earth observations Lunar distance to Earth is well matched to size of SWCX emitting region and FOV (30°) of MagEX Optimum view of region AND optimum operating conditions (CCDs @ -100°C)

  17. What do we expect to see? Robertson & Cravens (2003, 2006) Efficiency factor α depends on solar wind ion and target neutral composition α ~ 9.4 x 10-16 eV cm2 (slow wind) α ~ 3.3 x 10-16 eV cm2 (fast wind) PX-ray = α nsw usw nn X-ray power depends on SW density and velocity and exosphere density nsw nn usw MHD model Exosphere model (Hodges 1994)

  18. Proton flux as measured by Wind and Ace spacecraft Predicted SWCX Maps – View from 50 RE Robertson & Cravens (2006) Robertson & Cravens (2003) Model including the cusps

  19. Telescope Simulation Average SW 100 ks Src 5.7 cts/s Sky 126 cts/s Inst. 3.1 cts/s Average SW 10 ks Src 5.7 cts/s Sky 126 cts/s Inst. 3.1 cts/s Storm SW 1 ks Src 75 cts/s Sky 126 cts/s Inst. 3.1 cts/s Storm SW 10 ks Src 75 cts/s Sky 126 cts/s Inst. 3.1 cts/s

  20. Enhancement in X-rays seen before spike in SW density measured by ACE at L1! Ongoing global studies of XMM-Newton detections of SWCX show no simple correlation with SW flux as measured by ACE (Snowden, Kuntz, Carter, Sembay) Detection of SWCX by XMM (30’ diam. fov)

  21. Primary Science Goals • SWCX X-rays map the global interaction of the SW with the bow-shock and magnetosphere • X-ray emitting region is temporally and spatially highly variable as the SW flux varies and compresses the region • SW heavy ion species can produce identifiable lines in the X-ray spectrum so the composition of this component of the SW can be mapped on large scales. • X-ray observations can simultaneously help test models of the exospheric density distribution SWCX: Heavy solar wind ion in collision with neutral target atom or molecule Aq+ + B → A(q-1)+* + B+ A(q-1)+*→ A(q-1)+ + hν

  22. Trávniček et al. (2005) Lunar Contribution The tenuous lunar atmosphere (surface density ~ 105 cm-3, exponential scale height ~ 40 km) is a significant source of SWCX X-rays. Polar Viewpoint X-ray emission as function of view angle Lunar atmosphere component strongly dependant on view angle: varies from ~ 0 – 35 keV cm-2 s-1 sr-1 c.f. Magnetosheath ~ 5-10 keV cm-2 s-1 sr-1 Solar wind density in vicinity of Moon - Average Solar Conditions

  23. Sensitivity to Auroral X-rays Bright Event: 4th May 1998 Intensity ~ 104 cts cm-2 s-1 sr-1 Region ~ 0.3° x 0.3° (6x6 pixels for 3’ psf) In range 2-12 keV. Chandra observations suggest ~ 30% of cts in hard band (2-10 keV) ~ 70% of cts in soft band (0.1-2 keV) Estimated count rate in MagEX: Solid angle at Moon ~ 2.7 x 10-5 sr Eff. Area of Telescope ~ 5 cm2 Auroral (bright) rate ~ 3.1 cts s-1 c.f. rates in same size sold angle Sky bgd ~ 0.03 cts s-1 Sheath (storm) ~ 0.015 cts s-1 ~ 80 MagEX resolution elements

  24. MagEX:MagnetosheathExplorer inX-rays • Concluding Remarks • MagEX will provide the first global view of the dynamical interaction of the Solar wind with the Earth’s magnetosheath and the lunar atmosphere • The Moon is an ideal location for looking back at the Earth because the geometry of the Earth-Moon system, the size and brightness of the X-ray emitting region under study and the technology of the MagEX telescope are all well-matched.

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