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

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

Possible timeline for evolution of effective area of X-ray Astronomy Satellites (Gorenstein 1990) Phase 1: Late 1990’s1 m 2 Phase 2: m 2 Phase 3: m 2 XMM-Newton 0.45 m 1.5 keV Launched: Dec 1999 Xeus 5 m 1.0 keV Launch: 2020’s? 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

0.075 m 2 / 956 kg Chandra XMM-Newton 0.45 m 2 / 1,050 kg X-ray Mirror Technologies – Resolution v Area density relation

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

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. Far-UV Camera/Spectrograph carried on Apollo 16 If not LARGE then how about SMALL?

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

Applications for small Lunar-based X-ray Telescopes LEOExt. OrbitMoon Contiguous light curves NoYes Particle backgroundLowestHighest Thermal stability (poles) Yes X-ray backgroundLow Good Low Highest Poor 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? 1) Network of wide area monitors for studying extra-solar system transients and variables

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

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: Magnetosheath Explorer in X-rays MagEX X-ray Telescope is compact (< 50 cm side) low mass (< kg) wide field of view (~30°) imaging capable (psf ~ 1.5 arcminutes FWHM) detector energy resolution (~50 eV 600 eV)

MagEX: Magnetosheath Explorer in X-rays 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 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.

Optic Technology 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 Slumped Glass Micropore Optics: Wide field of view & low mass ~ 30 cm

Optic Technology 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° Optic of desired size formed by holding curved plates (3cm x 3cm) in a segmented bracket. Total mass ~ 1 kg D ~ 13cm Channel width = 20µm Slumped Glass Micropore Optics: Wide field of view & low mass ~ 30 cm

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

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

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

What do we expect to see? P X-ray = α n sw u sw n n Efficiency factor α depends on solar wind ion and target neutral composition α ~ 9.4 x eV cm 2 (slow wind) α ~ 3.3 x eV cm 2 (fast wind) u sw n swn Robertson & Cravens (2003, 2006) Exosphere model (Hodges 1994)MHD model X-ray power depends on SW density and velocity and exosphere density

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

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

Detection of SWCX by XMM (30’ diam. fov) 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)

A q+ + B → A (q-1)+* + B + A (q-1)+* → A (q-1)+ + hν SWCX: Heavy solar wind ion in collision with neutral target atom or molecule 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 Primary Science Goals

The tenuous lunar atmosphere (surface density ~ 10 5 cm -3, exponential scale height ~ 40 km) is a significant source of SWCX X-rays. X-ray emission as function of view angle Solar wind density in vicinity of Moon 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 - Average Solar Conditions Trávniček et al. (2005) Lunar Contribution Polar Viewpoint

Intensity ~ 10 4 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 sr Eff. Area of Telescope ~ 5 cm 2 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) ~ cts s -1 Sensitivity to Auroral X-rays Bright Event: 4 th May 1998 ~ 80 MagEX resolution elements

Concluding Remarks o MagEX will provide the first global view of the dynamical interaction of the Solar wind with the Earth’s magnetosheath and the lunar atmosphere o 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. MagEX: Magnetosheath Explorer in X-rays