Risaku Toda

Thin films with ultra-low thermal expansion.

Ultra-low coefficient of thermal expansion (CTE) is an elusive property, and narrow temperature ranges of operation and poor mechanical properties limit the use of conventional materials with low CTE. We structured a periodic micro-array of bi-metallic cells to demonstrate ultra-low effective CTE with a wide temperature range. These engineered tunable CTE thin film can be applied to minimize thermal fatigue and failure of optics, semiconductors, biomedical sensors, and solar energy applications.

A normally latched, large-stroke, inchworm microactuator

This paper presents the successful demonstration of a large-stroke, high-precision inchworm microactuator. The actuator is capable of zero-power latching, or forcibly maintaining its position by using pre-stressed spring load. The actuator is driven by a combination of a PZT-stack actuator unit for slider thrust and electrostatic comb-drive units for slider grip. Incremental step size is precisely adjustable to the tens of nanometers level by controlling the PZT-stack actuator voltage. The observed minimum step size was 59 nm/cycle. Large stroke is obtained by repeating the operation sequence numerous times. A large-stroke actuation exceeding 600 µm has been demonstrated. There is no conceivable limit to the stroke except for the length of the slider and external load.

Zero-Power Latching, Large-Stroke, High-Precision Linear Microactuator for Lightweight Structures in Space

This paper presents the successful demonstration of a latching-type, large-stroke, high-precision linear microactuator. The microactuator is capable of zero-power latching, or forcibly maintaining its position by using pre-stressed spring load. The actuator is driven by a combination of PZT actuator for slider thrust and electrostatic comb drive for slider grip. Incremental step size is precisely adjustable to tens of nanometer level by controlling PZT actuator voltage. Large stroke is obtained by repeating the operation sequence numerous times. Large stroke exceeding 600μm has been demonstrated. There is no conceivable limit to the stroke except for the length of the slider and external load.

Development of sample verification system for sample return missions

This paper describes the development of a proof-of-concept sample verification system (SVS) for in-situ mass measurement of planetary rock and soil sample in future robotic sample return missions. Our proof-of-concept SVS device contains a 10 cm diameter pressure sensitive elastic membrane placed at the bottom of a sample canister. The membrane deforms under the weight of accumulating planetary sample. The membrane is positioned in proximity to an opposing substrate with a narrow gap. The deformation of the membrane makes the gap to be narrower, resulting in increased capacitance between the two nearly parallel plates. Capacitance readout circuitry on a nearby printed circuit board (PCB) transmits data via a low-voltage differential signaling (LVDS) interface. The fabricated SVS proof-of-concept device has successfully demonstrated approximately 1pF/gram capacitance change.1, 2

Application specific electrode-integrated nanotube cathodes (ASINCs) for miniature analytical instruments for space exploration

JPL has developed high performance cold cathodes using arrays of carbon nanotube bundles that routinely produce > 15 A/cm2 at applied fields of 5 to 8 V/μm without any beam focusing. They have exhibited robust operation in poor vacuums of 10-6 to 10-4 Torr- a typically achievable range inside hermetically sealed microcavities. A new double-SOI process to monolithically integrate gate and additional beam tailoring electrodes has been developed. These electrodes are designed according to application requirements making carbon nanotube field emission sources application specific (Application Specific electrode-Integrated Nanotube Cathodes or ASINCs). ASINCs, vacuum packaged using COTS parts and a reflow bonding process, when tested after 6-month shelf life have shown little emission degradation. Lifetime of ASINCs is found to be affected by two effects- a gradual decay of emission due to anode sputtering, and dislodging of CNT bundles at high fields (> 10 V/μm). Using ASINCs miniature X-ray tubes and mass ionizers have been developed for future XRD/XRF and miniature mass spectrometer instruments for lander missions to Venus, Mars, Titan, and other planetary bodies.

Development of Latching Type Large Vertical-Travel Microactuator

This paper describes design, fabrication and preliminary characterization of a proof-of-concept vertical-travel microactuator, providing linear motion and high precision positioning in space. The microactuator is capable of providing latching function when it is un-powered to maintain its position. The microactuator consists of two opposing comb drive actuator dies, a slider and bulk PZT actuators sandwiched between the dies. The slider is inserted between clutches. Comb drives are connected to the clutches to engage/disengage clutching. Sequential activation of the comb drives (in-plane motion) and the PZT actuator (out-of-plane motion) provides cumulative linear travel of the slider. The novelty of the slider insertion approach include (1) post-fabrication engagement of comb teeth enabling thick wafer DRIE process for comb drive actuators and (2) stressed tethers enabling zero-power latching. A test device was fabricated and assembled. By applying 100V∼300V DC to the electrostatic comb drive, lateral actuation of clutches was observed. Vertical actuation by PZT was also confirmed using WYKO RST plus interferometer.Copyright

Experimental results with the BiBlade sampling chain for comet surface sampling

The BiBlade sampling chain has been developed for use in a potential Comet Surface Sample Return mission in a touch-and-go mission architecture. This paper describes the BiBlade sampling chain, an implementation of the system and experimental results. The system includes a BiBlade sampling tool, a robotic arm, a sample measurement system, a sample transfer system, and simulants.

FiSI: Fiberscope sample imaging system for robotic comet surface sample return missions

This paper discusses the Fiberscope Sample Imaging (FiSI) system currently being developed for a potential robotic comet surface sample return mission. In this mission concept, the spacecraft would perform touch-and-go maneuver at a small body to collect a comet surface sample. Immediately after the sample is captured the FiSI would perform in situ verification of the comet sample. Sample volume would be estimated and images of the collected sample acquired and evaluated. If the captured sample volume were deemed insufficient, the sample collection maneuver would be re-attempted, multiple times if necessary, until a baseline sample volume was positively confirmed. This repeatability would improve the potential science outcome of the sample return mission. Our proof-of-concept FiSI hardware consists of nine imaging fiberscopes integrated into a single bundle. The nine fiberscopes are designed to provide wide swath coverage of overlapping fields of view within a sample measurement station. The achieved image resolution is in excess of 4 linepair/mm at 20 mm working distance. Surface color and texture of a comet sample simulant would clearly be discernible at this fidelity. The distal end of these fiberscopes are designed to tolerate harsh temperature and radiation environments near a comet while sensitive electronics and optical components at the proximal end can be placed in a more benign electronics bay of the notional spacecraft. An early FiSI prototype was tested in a -50°C chamber and showed no image degradation. To study the FiSI proof-of-concept system response in a microgravity-like environment, a preliminary experiment was attempted using a neutral buoyancy sample. The test result was consistent with Monte Carlo simulation.

Lunar Surface Operation Testbed (LSOT)

This paper describes a high fidelity mission concept systems testbed at JPL, called Lunar Surface Operations Testbed (LSOT). LSOT provides a unique infrastructure that enables mission concept studies designers to configure and demonstrate end-to-end surface operations using existing JPL mission operations and ground support tools, Lander, robotic arm, stereo cameras, flight software, and soil simulant (regolith), in a high fidelity functional testbed. This paper will describe how LSOT was used to support the MoonRise mission concept study. MoonRise: Lunar South Pole-Aitken Basin Sample Return Mission would place a lander in a broad basin near the moons South Pole and return approximately two pounds of lunar materials to Earth for study. MoonRise was one of three candidate missions competing to be selected as the third mission for NASAs New Frontiers Program of Solar System Explorations. LSOT was used to demonstrate JPLs extensive experience and understanding of the MoonRise Lander capabilities, design maturity, surface operations systems engineering issues, risks and challenges.

Atmospheric electron-induced X-ray spectrometer (AEXS) development

The progress in the development of the Atmospheric Electron X-ray Spectrometer (AEXS) is described. The AEXS is a surface analysis tool based on excitation of characteristic X-ray fluorescence (XRF) spectra from samples in ambient atmospheres using a focused electron beam. Operation in ambient atmospheres with moderate-to-high spatial resolution in comparison to similar instruments is obtained through the use of a thin electron transmissive membrane to isolate the vacuum of the electron probe, obviating the need for the samples to be drawn into the probe vacuum. Our initial setup consisted of an actively pumped chamber from within which the electrons were transmitted -not a portable instrument. The instrument that has been assembled and used to acquire XRF spectra in our laboratory during the past two years consists of a 20 keV electron tube sealed with a SiN membrane and requires no active pumping -a big step towards the development of a stand-alone instrument. The microprobe was used to perform elemental analysis of NIST and USGS standards, with good agreement with the certified composition for samples in up to about 90 Torr-cm thick atmosphere, and for resolving the composition of mm-sized mineral grains in inhomogeneous samples, a big improvement over the several cm-scale spatial resolution of the APXS instrument that flew on NASAs MER mission.