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

Southwest Research Institute NSF Conference on Small Satellites 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 NSF Conference on Small Satellites 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) (  X  ~ 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 NSF Conference on Small Satellites Particle Experiment for Planetary Exploration (PEPE) on Deep Space-I Developed as outgrowth of Dave Young’s Internal Research project at SwRI, 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, 5W dual spectrometer with LEF TOF measurement included

Southwest Research Institute NSF Conference on Small Satellites Miniature -15kV Power Supply

Southwest Research Institute NSF Conference on Small Satellites Flight Model – Ready for Cal

Southwest Research Institute NSF Conference on Small Satellites 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 ~0.4G field; Prime target electron energy from 0.1 to 100 eV Radius of curvature of ESA plates ~5mm. ESA Analyzer gap < 1 mm With analyzer ratio of ~7, application of 1kV ESA voltage would allow viewing of 7 keV electrons; Sensor the size of 35 mm film can; pre-amp boom and electronics box presently occupies more macroscopic scale.

Southwest Research Institute NSF Conference on Small Satellites

Southwest Research Institute NSF Conference on Small Satellites A Very Small & Very Black Inner Tophat Electrode

Southwest Research Institute NSF Conference on Small Satellites TECHS Sensor Elements

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

Southwest Research Institute NSF Conference on Small Satellites

Southwest Research Institute NSF Conference on Small Satellites 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 kV (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 NSF Conference on Small Satellites IES Sensor Design

Southwest Research Institute NSF Conference on Small Satellites Rosetta Ion and Electron Sensor Parameters. Parameter Value Energy Range1 eV/e to 30 keV/e Resolution (DE/E)0.04 ScanMode-dependent Angle Range (FOV) 90 x 360º (2.8p sr) Resolution (e - )5 x 22.5º (16 azimuthal x 16 polar) Resolution (ions)5 x 45º (16 azimuthal x 7 polar) Temporal resolution3D distribution 3 s Geometric factor Total (ions) 5 x 10-4 cm 2 -sr-eV/eV count/ion Per 45º sector (ions)6 x 10-5 cm2 sr eV/eV count/ion Total (e - )5 x 10-4 cm2 sr eV/eV count/electron Per 22.5º sector (e - )3 x 10-5 cm2 sr eV/eV count/electron Mass1040 g Volume1297 cm 3 Dimensions Sensor:73 mm dia x 101 mm Electronics box:139 x 121 x 64 mm Power1850 mW Downlink data rate bit s-1

Southwest Research Institute NSF Conference on Small Satellites

Southwest Research Institute NSF Conference on Small Satellites A MagCon 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 NSF Conference on Small Satellites Micro-Satellite Architectural Diagram

Southwest Research Institute NSF Conference on Small Satellites Final Draco Bench-Top Configuration CDPU Mag Sensor Mag Electronics IES Elec. EPS Electronics

Southwest Research Institute NSF Conference on Small Satellites 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!