1. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Prospects for X-ray astronomy from the lunar surface Steven Sembay Co-I of the EPIC-MOS X-ray camera on XMM-Newton Jenny Carter, Michael Collier, George Fraser and Steve Snowden Department of Physics and Astronomy, University of Leicester, Leicester, UK. Laboratory for Geospace Physics, NASA/GSFC, Greenbelt, USA. X-ray Astrophysics Laboratory, NASA/GSFC, Greenbelt, USA.

2. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Why would you place an X-ray telescope on the lunar surface? What would be its scientific goals? What design would you employ? XEUS: 2020+? ~5 m 2 XMM: 1999-? ~0.5 m 2

3. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Speculative 21 st Century High Throughput (>100 m 2 ) Lunar X-ray Observatory Science Goals include: Large scale structure of the universe to z>=2 through survey of cluster Fe emission Evolution of accretion disk in AGN to z>=2 through study of Fe fluoresence line c.f. Gorenstein, P. 1990, High throughput X-ray telescope on a lunar base, in “Astrophysics from the Moon; Proceedings of the Workshop”, AIP, 207, 382

4. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Lunar X-ray Observatory (LXO) on a more practical scale…. X-ray telescopes which are small instrument packages that can be delivered via an astronaut program or on a soft lander… i.e. one part of a much larger scientific payload.

5. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Science Goals of an LXO: Primary: Study of solar wind interaction with the lunar atmosphere and the terrestrial magnetosheath via soft X-ray emission from the solar wind charge exchange (SWCX) process Secondary: All-sky monitor for extra-solar system transient objects

6. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany A soft X-ray spectrum of the SWCX spectrum from a comet taken with Suzaku demonstrates the need for spectral resolution to distinguish the different constituents of the (variable) solar wind. A q+ + B → A (q-1)+* + B + A (q-1)+* → A (q-1) + hν SWCX Mechanism: Heavy solar wind ion in collision with neutral target atom or molecule Process first detected in X-ray emission from comets: Rosat/HRI Image GSFC/MPE Porter et al. in prep

7. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Lunar-Based Soft X-ray Science Objectives: Sites of SWCX emission: Comets Planetary atmospheres…including the lunar atmosphere Geocoronal neutrals at the terrestrial magnetosheath Inter-stellar neutral atoms within the heliosphere and at the heliospheric boundary

8. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Soft X-ray background (0.1<E<1.5 keV) has substantial structure from contributions from beyond Solar System sources, namely… 1)Unresolved background from AGN 2)Extended Galactic Halo at 10 6.5 K 3)Irregular distribution from 10 6 K plasma in lower Galactic Halo 4)The Local Hot Bubble, a 10 6 K plasma filling a cavity in the Galactic disk surrounding the Sun. Only in the last decade (from ~1997) has strong/variable emission due to SWCX from terrestrial and inter-planetary sources been recognised as a significant contribution in measurements of the diffuse X-ray background. The soft X-ray sky: diffuse emission

9. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Correlation of the strength of the solar wind and the strength of the soft X-ray emission as seen by ROSAT (1990’s) in low Earth orbit. ROSAT Long Term Enhancements (LTE) in background attributed to SWCX with interplanetary and geocoronal neutrals. This correlation allows remote sensing of the strength of the solar wind using soft X-ray fluxes as a proxy. Correlation of Soft X-ray Flux (ROSAT) with Solar Wind

10. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany XMM-EPIC detection of SWCX during observation of Hubble Deep Field North Snowden, Collier and Kuntz, 2004, ApJ, 610, 1182

11. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany A Lunar X-ray Observatory properly placed on the Moon will be able to observe soft X-ray emission from the interaction of the solar wind with both the lunar atmosphere and the magnetosheath. The Moon is located in a prime spot to study SWCX

12. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany FOV of an observatory on the lunar surface with a fixed look angle will sweep past the densest part of the magnetosheath each month. Configuration for observations during lunar night. Scanning of magnetosheath over the lunar orbit…

13. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany A model of the strength of the magnetospheric SWCX emission as a function of position around the Earth (at origin) (Robertson & Cravens 2003). This is NOT a static picture: soft X-ray imaging can be used to study the dynamical interaction between the magnetosheath and the solar wind. Magnetosheath contribution….

14. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Simulation of the soft X-ray emission as a function of Position in the lunar sky. (Trávniček et al. 2005) Lunar atmosphere contribution…. Suggests optimum location to provide greatest contrast is polar position with view zenith angle ~ 90 0

15. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Secondary (“Added Value”) Science Goals: An LXO as an all-sky-monitor to study time-domain astrophysics in the soft X-ray regime…

16. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Secondary (“Added Value”) Science Goals: An LXO as an all-sky-monitor to study time-domain astrophysics in the soft X-ray regime…One example… Stellar Capture events by super-massive black holes in the centre of galaxies Soft X-ray flares lasting weeks-months L > 10 43 erg s -1 Rate every ~ 10 4 – 10 5 years / galaxy Only handful detected so far by chance Chandra/CXC/M.Weiss RX J1242-11

17. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Secondary (“Added Value”) Science Goals: An LXO as an all-sky-monitor to study time-domain astrophysics in the soft X-ray regime…One example… Statistics on the frequency and luminosity function of these events will give strong constraints on the mass distribution of SMBHs (with M < 10 8-9 M solar ) and the co- evolution of SMBHs with their host galaxies. Chandra/CXC/M.Weiss RX J1242-11

18. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Telescope proposal and design: Lunar X-ray Observatory (LXO)

19. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Program: Concept Studies for Lunar Sortie Science Opportunities solicitation within NASA Research Announcement: Research Opportunities in Space and Earth Sciences (ROSES) – 2006 Title of Investigation: Lunar-Based Soft X-ray Science PI: Michael Collier PI Institution: NASA/Goddard Space Flight Center Collaborators: Univ. of Kansas, Univ. of Leicester UK, Acad. Sci. Czech Rep. Current Status: NASA has budgeted ~$750K for 5-10 concept studies which are expected to take 6-9 months duration. Proposal has been submitted. Expect result spring 2007.

20. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany LSSO concept similar to…. ALSEP: Apollo Lunar Surface Experiment Package Apollo 16 experiments Image: www.myspacemuseum.com Jim Lovell (CMDR Apollo 13) practising Image: en.wikipedia.com RTG Central Station Passive Seismic Experiment

21. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Mass < 40 kg (self-contained power system, i.e. solar cells + battery) Mass < 20 kg (external PSU common to multiple experiments) Power < 70W if actively cooled with Thermal Electric Cooler (TEC) Power < 20-30W if passively cooled and operated during lunar night. Lunar X-ray Observatory (LXO): example configuration Basic Constraints based on ALSEP experience: Mass < 40 kg Power < 75W

22. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Competing Technologies for LXO Detector

23. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Competing Technologies for LXO Detector Solid state detectors have sufficient energy resolution to spectrally resolve individual solar wind ions

24. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Slumped Microchannel Plate: Compact/Lightweight X-ray Optics Eye structure of a Lobster MCP optic for LOBSTER ASM R = 70 cm (f = 37.5 cm) Single module fov = 30 0 x 30 0 Univ. of Leicester

25. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany LOBSTER optic designed for primary science goal as an ASM so optimises telescope grasp (fov x effective area) For LXO we would enhance soft X-ray sensitivity: f = 50 cm gives useful 9 0 x 9 0 fov in a compact form. Eff. Area of nickel- coated glass MCP optic of varying focal lengths

26. Steve Sembay (sfs5@star.le.ac.uk) To Moon and Beyond: DGLR International Symposium 14-16 March 2007, Bremen, Germany Summary: The moon is an ideal location for soft X-ray astrophysics, both for studying Solar System SWCX processes directly and for helping to decouple this emission from Cosmic astrophysical sources. The LXO is practical (the technology is mature and well understood) and is relatively low cost because it is piggy-backing onto a larger program (NASA’s Vision for Space Exploration).