Plasma Instrument Miniaturization and Integration Approaches and Limitations

Plasma Instrument Miniaturization and Integration: Approaches and Limitations C. J. Pollock, R. Torbert, and D. T. Young Southwest Research Institute

Plasma Instrument Miniaturization and Integration: Approaches and Limitations - Functional Guidelines - Measurement Focus - Sensor vs Electronics - System Integration -Examples of Low Resource Flight or Prototype Instruments - PEPE - IES - TECHS - MOSS -Limitations and Pitfalls: - It takes an aperture - It often takes high voltage Southwest Research Institute

Functional Guidelines Measurement Focus • Disciplined approach that focuses narrowly on priority science • Sensor technologies for disparate plasma regimes: • Langmuir Probe – Temperature and density of thermal plasma • Segmented Faraday Cup/RPA: High Mach # flowing plasma • Curved Plate ESA: Low mach number, structured plasma distributions Sensor vs Electronics • In some cases there are limitations to sensor size reduction (aperture size dictates signal) (DA X DW ~ A 1 A 2/L 2) • Other times, the electronics may be irreducible (high voltage circuits) System Integration vs Modularity(? ) • A high degree of functional integration is helpful to minimize resource consumption and unintended functional redundancy; • Still, developmental modularity allows parallel development, often critical for small budget/short time scale flight development Southwest Research Institute

Particle Experiment for Planetary Exploration (PEPE) on Deep Space-I • Developed as outgrowth of Dave Young’s Internal Research project at Sw. RI, entitled: Miniaturized, Optimized Smart Spectrometer (MOSS) • Designed as a low resource, high performance electron and ion composition spectrometer • Design principals include: • Innovative use of materials to reduce mass (ESAs are plated plastic) • Tight integration of electronics and sensor • Ions and electrons share entrance aperture • ~5 kg, 5 W dual spectrometer with LEF TOF measurement included Southwest Research Institute

Miniature -15 k. V Power Supply Southwest Research Institute

Flight Model – Ready for Cal Southwest Research Institute

Thermal Electron Capped Hemisphere Spectrometer (TECHS) • Developed to target thermal electron fluxes in Earth’s ionosphere; • Extreme miniaturization of tophat ESA necessary to measure low energy electrons in Earth’s ~0. 4 G field; • Prime target electron energy from 0. 1 to 100 e. V • Radius of curvature of ESA plates ~5 mm. • ESA Analyzer gap < 1 mm • With analyzer ratio of ~7, application of 1 k. V ESA voltage would allow viewing of 7 ke. V electrons; • Sensor the size of 35 mm film can; • pre-amp boom and electronics box presently occupies more macroscopic scale. Southwest Research Institute

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A Very Small & Very Black Inner Tophat Electrode Southwest Research Institute

TECHS Sensor Elements Southwest Research Institute

E-box and Boom Not So Small (room for improvement) Southwest Research Institute

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Ion an Electron Sensor (IES) on Rosetta • This was an exercise in extreme resourse conservation, patterned on the PEPE development. • Dual, shared aperture ion and electron tophats with FOV deflection • No time of flight (read: no ion composition) • Tightly integrated but no modularity (difficult to troubleshoot and repair) • Good performance obtained; • Flight resource requirements: 1. 25 kg; 1. 8 Watts • Severe compromises sometimes required. In IES, for example, to save power, the 1 st HV step on the z-style MCP stack is 2. 5 k. V (for both electron and ion stacks), and the stacks are enabled and commanded in common; • This is scary (perhaps less so for those with rocket background); It has worked well on orbit. Southwest Research Institute

IES Sensor Design Southwest Research Institute

Rosetta Ion and Electron Sensor Parameters. Parameter Value Energy Range 1 e. V/e to 30 ke. V/e Resolution (DE/E) 0. 04 Scan Mode-dependent Angle Range (FOV) 90 x 360º (2. 8 p sr) Resolution (e-) 5 x 22. 5º (16 azimuthal x 16 polar) Resolution (ions) 5 x 45º (16 azimuthal x 7 polar) Temporal resolution 3 D distribution 3 s Geometric factor Total (ions) 5 x 10 -4 cm 2 -sr-e. V/e. V count/ion Per 45º sector (ions) 6 x 10 -5 cm 2 sr e. V/e. V count/ion Total (e-) Per 22. 5º sector (e-) Mass Volume Dimensions Sensor: Electronics box: Power Downlink data rate Southwest Research Institute 5 x 10 -4 cm 2 sr e. V/e. V count/electron 3 x 10 -5 cm 2 sr e. V/e. V count/electron 1040 g 1297 cm 3 73 mm dia x 101 mm 139 x 121 x 64 mm 1850 m. W 5 - 250 bit s-1

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A Mag. Con System Concept • Magnetometer, e and i+ plasma spectrometer, energetic particles • A 3 -instrument suite, integrated with a single central c&dh • Instruments are sensors with bare bones co-located support circuitry; • C&DH system that holds all possible command functions; • C&DH system holds all possible signal processing functions; Southwest Research Institute

Micro-Satellite Architectural Diagram Southwest Research Institute

Final Draco Bench-Top Configuration CDPU IES Elec. Mag Sensor Mag Electronics EPS Electronics Southwest Research Institute

Conclusions • Significant miniaturization in capable plasma instrumentation is possible; • Limitations exist, however: • Aperture size sets limits on sensor miniaturization • HV requirements set limits on certain electronics miniaturization • Minimum resource plasma instruments and instrument suites can be focused on limited science goals • Minimum resource/limited capability instrument suites can also be fielded for constellation-class payloads • Continual investment in instrument & advanced technology development is a must! Southwest Research Institute