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APXS on Mars Science Laboratory – First Results From Post-landing
Checkout
C. S. Dickinson1, R. Gellert2, P. Dietrich1 and D. Hiemstra1
1MacDonald Dettwiler & Associates, 2University of Guelph
International Workshop on Instrumentation for Planetary Missions Greenbelt, MD 10. – 12. Oct. 2012
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• Payload contribution to MSL program by the Canadian Space Agency • PI: Dr. Ralf Gellert, University of Guelph, Canada • Prime contractor MacDonald Dettwiler & Associates (MDA) • Scientific design and engineering support by University of Guelph, Canada • Scientific design based on the successful MER design by Max-Plank Institute
for Chemistry, Mainz, Germany
MSL APXS Background
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First generation: Sojourner rover on Mars
Pathfinder Mission (1997)
APXS Flight Lineage
Second generation: Rover Spirit and Opportunity on MER Mission (2004 - now)
Third generation: Rover Curiosity on MSL
Mission (2012 - ??)
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MSL APXS Detector • Silicon drift detector (SDD) to detect x-rays induced by radioactive source • 244Cm source generating α particles and x-rays Two modes • PIXE: Particle induced x-ray emission
– α particles eject inner shell electrons, resulting in characteristic x-ray emission
– Best yield for low-Z elements • XRF: X-ray induced fluorescence
– X-rays (14 keV, 18 keV) eject inner shell electrons, resulting in characteristic x-ray emission
– Best yield for high-Z elements Application • Elemental analysis of rocks, soils. • Essential geological data
Principle of APXS
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Sensitivity of PIXE and XRF Mode
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• Activated Peltier cooler for SDD (∆T ~ -30C) Increased operating temperature up to -5° C (before -40° C) Allows tactical daytime operation (before: only nighttime) Improved resolution < 150 eV during night
• Shorter sample-detector distance Possible by discarding alpha channel Increased sensitivity by factor of 3 Decreased data acquisition by factor 5 ( now 10 min to 2 hours )
• Added standard XRF 244Cm sources Increased sensitivity for high-Z elements by factor of 2
• On-board basaltic rock slab for calibration. • Extended energy range to 25 keV (before 17 keV) • Various SW enhancements, proximity mode, SW update,..
MSL APXS Changes and Improvements
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MER APXS versus MSL APXS
MSL APXS is ~ 6 times faster than MER Able to measure at ~ 0 C during day ! MER needed -40C ! Additionally higher scatter peaks and extended energy
We are about 10 times faster than the MER APXS and can take good data during the day 0 2 4 6 8 10 12 14 16 18 20 22 24 26
1E-3
0.01
0.1
1
10
100
ClS
P
Na
Mg
Al
Si
KTi
Ca
Mn
ZnNi
Fe
sensitivity: Msl to MER x3 x6 x 10
high energy scatter peaks
Cts/
s
Energy keV
BCR-1 MER lab @ -40C BCR-2 MSL PFM @ 0C with TEC on
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Calibration approach similar to previous generation (MER) • Calibration in laboratory using various basalts, minerals, sediments,
well defined mixtures and chemical compounds • Two independent analysis approaches ( MER empirical and from first
principles) • On Mars re-calibration possible using the flight calibration target
(basaltic rock slab)
MSL APXS Calibration
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MSL APXS Specifications
Parameter Value
Sources 30 mCi of conventional sealed 244Cm + 30 mCi of α emitting 244Cm
Sample distance ~ 20 mm, standoff possible
Sample size in contact 17 mm ∅
Energy range 0.7 keV to 25 keV
Resolution (FWHM) 143 eV, T< -20° C
Operating temperature -130° C to -5° C(*)
Power dissipation 8 W, incl. 3 W Peltier
Mass sensor head 362 g
Mass calibration target 114 g
Mass electronics 1166 g
(*) Up to 10°C with degraded resolution
JPL provided contact sensor
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MSL APXS Design
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MSL APXS Flight Instrument
Calibration target (basaltic rock)
Sensor head
Electronics box
All deliverables underwent successful qualification, including 2x life PQV
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Curiosity Sampling Turret
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Curiosity Turret: APXS View
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Calibration target on Curiosity (sol34) • Red lines (S, Cl) are from dust on calibration target • Ar line is from atmosphere, Zr from collimator • Black lines are known calibration target lines
First Data from Mars
At night FWHM ~ 145eV. During day FWHM 180-250eV → acceptable and good science in 20 minutes during day All science design goals verified
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APXS spectrum of rock Jake Matijevic (sol46)
And More Data from Mars
0 1 2 3 4 5 6 7 8 9 10 11 12 13
0.01
0.1
1
10
BrZn
Ni
Fe
Mn
Cr
Ti
CaKCl
S
P
Si
Mg
Al
Na
coun
ts p
er s
econ
d
Energy [keV]
sol34 Caltarget sol46 JakeMatijevic
Jake Matijevic compared to calibration target: • Low in Mg, Fe • High in Na, Al, Si, K • Very low in Ni • S, Cl, Br are likely from
soil or dust on surface of rock
• Quite different from basalts measured with MER Spirit APXS in Gusev Crater
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• Many (!) people contributed to the success of MSL APXS • Funding for MSL APXS was provided by the Canadian Space Agency • Funding for the science team comes from CSA, NASA and the University of Guelph
Acknowledgements