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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” - PowerPoint PPT Presentation
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MagEX: A Proposal for a Lunar-based X-ray Telescope
Steven SembayAndrew Read & Jenny Carter
Department of Physics and Astronomy
University of Leicester
• Lunar-based X-ray Astronomy – a short review
• The MagEX concept
Speculative 21st Century High Throughput
(>100 m2) 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’s 1 m2
Phase 2: 2010 10 m2
Phase 3: 2040 100 m2
XMM-Newton
0.45 m2 @ 1.5 keV
Launched: Dec 1999
Xeus
5 m2 @ 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 m2 / 956 kg
Chandra
XMM-Newton
0.45 m2 / 1,050 kg
X-ray Mirror Technologies – Resolution v Area density relation
Si Square Pore Optic
XEUSGeneration-X ??
~100 m2 / ~ 2-3 tonnes
Adaptive Optics
~ 5 m2 / ~ 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 J1242-11Stellar Capture Event
1) Network of wide area monitors for studying extra-solar system
transients and variables
Applications for small Lunar-based X-ray Telescopes
LEO Ext. OrbitMoon
Contiguous light curves NoYes
Particle background Lowest Highest
Thermal stability (poles)
Yes
X-ray background Low Low
GoodGood
Low
Highest
PoorThermal 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
Aq+ + 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 (< 20-30 kg)
wide field of view (~30°)
imaging capable (psf ~ 1.5 arcminutes FWHM)
detector energy resolution (~50 eV FWHM @ 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 sizeformed by holdingcurved plates(3cm x 3cm) in asegmented 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 onthe Radius of curvature of the optic and the Field of view.
D ~ 13 cm for R = 50 cm & fov = 30°
Optic of desired sizeformed by holdingcurved plates(3cm x 3cm) in asegmented 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 sensitivityGood energy resolutionGood 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 Exospherevia 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
(CCDs @ -100°C)
What do we expect to see?
PX-ray = α nsw usw nn
Efficiency factor α depends on solarwind 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)
uswnsw nn
Robertson & Cravens (2003, 2006)
Exosphere model (Hodges 1994)MHD model
X-ray power depends on SW densityand velocity and exosphere density
Predicted SWCX Maps – View from 50 RE
Proton flux as measured byWind and Ace spacecraft
Robertson & Cravens (2003) Robertson & Cravens (2006)
Model including the cusps
Average SW10 ksSrc 5.7 cts/sSky 126 cts/sInst. 3.1 cts/s
Average SW100 ksSrc 5.7 cts/sSky 126 cts/sInst. 3.1 cts/s
Storm SW1 ksSrc 75 cts/sSky 126 cts/sInst. 3.1 cts/s
Storm SW10 ksSrc 75 cts/sSky 126 cts/sInst. 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 simplecorrelation with SW flux as measured by ACE (Snowden, Kuntz, Carter, Sembay)
Aq+ + 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 andspatially highly variable as the SWflux varies and compresses the region
• SW heavy ion species can produceidentifiable lines in the X-ray spectrumso 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 ~ 105 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 ConditionsTrávniček et al. (2005)
Lunar Contribution
Polar Viewpoint
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 srEff. 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
Sensitivity to Auroral X-raysBright Event: 4th 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