An ultra-compact spectrometer for space weather monitoring

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1 An ultra-compact spectrometer for space weather monitoring Amy Keesee West Virginia University Smallsats for Space Weather Research and Forecasting 4 August 2017; Washington, DC

2 Acknowledgements Drew Elliott, Greg Lusk, Julianne McIlvaine, Earl Scime West Virginia University Matt Dugas, Steve Ellison, Joseph Tersteeg Advanced Research Corporation Alex Barrie, Amy Rager, Suzanne Smith Goddard Space Flight Center Supported by the NASA Heliospheric Technology and Instrument Development for Science (H-TIDeS) Program, the Department of Energy STTR Program, and the WVU PSCoR Program U.S. Patent No. 9,502,229

3 Outline Motivation Spectrometer design Component fabrication and testing Next steps

Space weather monitoring of ~kev particles needed Solar wind Particles have thermal energies ~1.5-10 kev. Schrijver et al.

4 Space weather monitoring of ~kev particles needed Solar wind Particles have thermal energies ~ kev. Schrijver et al. [2015] describe need for electron and ion spectrometers to monitor 1-30 kev energies. Magnetosphere Thomsen et al. [2013] showed that 5-10 kev electrons are responsible for most spacecraft surface charging on LANL geosynchronous satellites. Surface charging is likely to occur during high levels of geomagnetic activity when satellites are on the night side (eclipse); satellite anomalies have been shown to correlate with these conditions [Choi et al., 2011]. Fraction With Potential < -100 V LANL-02A Kp [Thomsen et al., 2013]

Heliophysics Roadmap defines constellation missions that require identical instrumentation Geospace Dynamics Constellation (GDC) mission: 4-6 platforms Magnetospheric Constellation (MagCon) and

5 Heliophysics Roadmap defines constellation missions that require identical instrumentation Geospace Dynamics Constellation (GDC) mission: 4-6 platforms Magnetospheric Constellation (MagCon) and Magnetosphere Constellation and Tomography (MagCaT): 20 spacecraft Constellations of satellites have tremendous potential and mission concepts have appeared in previous roadmaps, but implementation faces a major obstacle: How to manufacture, integrate and test large numbers of instruments and subsystems within reasonable cost and schedule is a new challenge. The traditional implementation of heliophysics missions is incompatible with constellation builds, and partnering with industry for multiple-copy builds should be explored.

We are developing a plasma spectrometer that meets small and multi payload requirements Collimator Ions or electrons ~5-20 kev Voltages < 100V DC (no sweeping); 100% duty cycle Volume < 2 cm cubed

6 We are developing a plasma spectrometer that meets small and multi payload requirements Collimator Ions or electrons ~5-20 kev Voltages < 100V DC (no sweeping); 100% duty cycle Volume < 2 cm cubed Effective collection area scales linearly with instrument length or width Manufacturing process like computer chips Energy Analyzer Scime et al., JGR, 2016 US Patent 9,502,229 Solid State Detector (SSD)

Energy analyzer bands have DC bias for 100% duty cycle Biases of 0-100V can be applied in a pattern to the bands to create energy passbands of 5-20 kev

7 Energy analyzer bands have DC bias for 100% duty cycle Biases of 0-100V can be applied in a pattern to the bands to create energy passbands of 5-20 kev (10.7 V channel for 20 kev ions) No high voltage, no sweeping One bounce light blocking r =80 µm, R= 300 mm E = qr V 2 r E = 1875 V Scime et al., JGR, 2016

Energy analyzer layers will be stacked to increase signal Biases of 0-100V can be applied in a pattern to the bands to create energy passbands of 5-20 kev (10.

8 Energy analyzer layers will be stacked to increase signal Biases of 0-100V can be applied in a pattern to the bands to create energy passbands of 5-20 kev (10.7 V channel for 20 kev ions) Each layer connected electrically so the same bias is applied to all EA bands vertically 1.5 cm Particles through a vertical column of bands will be incident on a vertical SSD pixel 1.0 cm 1.75 cm Scime et al., JGR, 2016

9 Initial collimator fabrication and testing has been performed Scime et al., JGR, 2016

5 µm bonding mismatch Narrowing to 17 µm limits transmission efficiency to 20% from expected 49% Process could be

10 Collimator fabrication demonstrated challenges in manufacturing process DRIE to fabricate 28 x 28 µm apertures spaced by 40 µm Two wafers bonded together to achieve 1.5 x 1.5 angular acceptance, < 1.5 µm bonding mismatch Narrowing to 17 µm limits transmission efficiency to 20% from expected 49% Process could be tweaked to minimize narrowing effect and other process variations but recent improvements eliminate this step entirely Scime et al., JGR, 2016

11 Updated design to an Integrated collimator and analyzer Eliminates additional processing steps Eliminates need for separate device that must be aligned to the energy analyzer.

12 Initial energy analyzer fabrication has been performed DRIE to fabricate 60 µm wide plates with 80 µm gap in 350 µm thick highly-conductive silicon on insulating baseplate Undercutting prevents fabrication of thinner plates Scime et al., JGR, 2016

13 Initial energy analyzer testing has been performed A bias of 26.6 V applied to one band; 5 kev electron beam detected Energy resolution approximately 20% Scime et al., JGR, 2016

14 Energy analyzer stack test has been performed

15 SSD with thinned contacts used for the detector No high voltage required 5 kev detection threshold for ions Energy resolving detector provides noise reduction Electronics under development Tindall et al., IEEE Trans. Nuc. Sci., 2008

16 SSD electronics tested with alpha particles 4 pixel test detector Amptek A250 charge sensitive preamplifier; DP5 digital pulse processor Flight test planned on RockSat ASIC likely to be used in future

17 Next steps Funded by DoE STTR to manufacture a combined collimator-energy analyzer Submitted proposal to NASA to build a prototype UCPS, bringing spectrometer to TRL 6 Submitted proposal to NASA to fly a CubeSat that includes a collimated SSD for flight testing of components Different detector could be used for lower energy range Design additions could be made to add mass resolution or detect neutral atoms

18 Key Points Sugar-cube sized space plasma instrument. Manufacturing process modeled completely on chip manufacturing. Defective instruments are thrown away. Scalable wafer scale manufacturing. 12 units per 100 mm wafer. 100 Volts needed to measure 20 kev particles. No MCPs, no high voltages, no sweeping power supplies. Fully solid state instrument. Resistant to impact, environmental conditions, and vibration. Use 10 to gain factor of 10 in sensitivity. Arrange in an arc/scanning platform for angular coverage. Energy resolving SSSD along with energy selection provides for background rejection in space.

Miniaturized In-Situ Plasma Sensors Applications for NSF Small Satellite program. Dr. Geoff McHarg

Miniaturized In-Situ Plasma Sensors Applications for NSF Small Satellite program Dr. Geoff McHarg National Science Foundation Small Satellite Workshop- CEDAR June 2007 FalconSat-3 Physics on a small satellite