Micro Electro-Mechanical Systems (MEMS) are currently being considered in the space sector due to its suitable level of performance for spacecrafts in terms of mechanical robustness with low power consumption, small mass and size, and significant advantage in system design and accommodation. However, there is still a lack of understanding regarding the performance and testing of these new sensors, especially in planetary robotics. This paper presents what is missing in the field: a complete methodology regarding the characterization and modeling of MEMS sensors with direct application. A reproducible and complete approach including all the intermediate steps, tools and laboratory equipment is described. The process of sensor error characterization and modeling through to the final integration in the sensor fusion scheme is explained with detail. Although the concept of fusion is relatively easy to comprehend, carefully characterizing and filtering sensor information is not an easy task and is essential for good performance. The strength of the approach has been verified with representative tests of novel high-grade MEMS inertia sensors and exemplary planetary rover platforms with promising results.

During the last year internal research activities have been carried out at ESTEC in the line of testing highgrade inertial sensors. This article shows the performance characterization of prototype Inertial Measurement Units (IMUs) in terms of facilities and methodologies within ESTEC, with focus on MEMS inertial sensors for planetary rovers. Specifically, this article shows the system level demonstration and capabilities of the test facilities of the ESTEC Automation & Robotics section as well as first performance results of MEMS inertial sensors for attitude estimation on typical planetary rover manoeuvres.

A recent ESA R&D activity, led by ÅAC, including SEA and DFKI, was undertaken to develop a miniaturised MEMS based inertial measurement unit (IMU) for use in rover navigation systems for planetary or lunar exploration missions. It has been part of the Technology Research Program (TRP) at ESTEC allocated in the Automation & Robot Section. The miniaturised IMU study showed the feasibility of such a unit by deriving requirements from the targeted missions, and showing how these can be met. The study was supported by developing, manufacturing and testing a functional breadboard demonstrator and by testing material mock-ups under target environmental conditions. This paper provides a brief introduction into the design options, the miniaturisation using ÅAC proprietary multi wafer packaging „via‟ technology and the results of the environmental tests. Another focus lies on the derivation of the requirements, and the testing of the IMU breadboard prototype.

We present a new manufacturing technology to produce multi-scale compliant feet for use with a novel climbing robot. Climbing robots for space exploration missions may allow scientists to explore environments too difficult for traditional wheeled designs. These climbing robot designs should be able to grasp or adhere to a variety of surface types at multiple angles in order to be effective. To adhere to multiple surfaces, biomimetic dry adhesives based on gecko feet have been proposed. These biomimetic dry adhesives work by using multi-scale compliant mechanisms to make intimate contact with different surfaces and adhere by using Van der Waals forces. Fabrication of these adhesives has frequently been challenging however, due to the difficulty in combining macro, micro and nanoscale compliance. We present here strategies for creating multi-scale compliant mechanisms from macro to nanoscale for use with bioinspired climbing robots for eventual use in space exploration.

Presented here is an examination of unstructured and structured (by anisotropic etching), monocrystalline silicon wafers coated with sputter deposited aluminum and chemical vapor deposited silicon dioxide for high solar reflectance and high thermal emittance, respectively. The topography of the samples was characterized with optical and scanning electron microscopy. Optical properties were examined with reflectance and transmittance spectroscopy, partly by usage of an integrating sphere. The measurement results were used to estimate the equilibrium temperature of the surfaces in space. The suitability of the surfaces with high solar reflectance and high thermal emittance to aid in the thermal control of miniaturized, highly integrated components for space applications is discussed. A silicon dioxide layer on a metal layer results in a slightly lower reflectance when compared to surfaces with only a metal layer, but might be beneficial for miniaturized space components and modules that have to dissipate internally generated heat into open space. Additionally, it is an advantage to microstructure the emitting surface for enhanced radiation of excess heat.

In this work, a gas valve using a microstructured silicon valve lid and a stainless steel valve seat clamped axially together in an aluminum cylinder is investigated. The difference in coefficient of thermal expansion of these components makes the valve open and close on a temperature change. A simple model accounting for elastic deformation of the system’s components is proposed to facilitate design of the valve. By means of a helium leak detector, a typical increase in flow rate from 1.0×10−8to1.0×10−4sccs gaseous helium under a pressure of up to 10bars was observed upon the increase of temperature from 12 to around 98°C, after a single breaking-in. Plastic deformation of the valve seat as a consequence of an imprint of the microstructured valve lid and contaminating particles was studied. Microscopy confirmed a tolerance for particles of up to a few micrometers in diameter. Larger particles were found to be a possible cause of failure.

Demonstrated and characterized here is a single use valve developed for high-pressure applications. Incorporated within the single use valve is a particle filter. The filter serves to remove any particle debris created by the activation process. The valve is solder sealed to be leakage proof. The solder is remelted to obtain activation of the valve. Local heater elements are incorporated on the valve surface together with solder wetting pads. The gas mass flow through the device was evaluated prior to sealing and after activation. The valve was functional at pressures of 100 bar, and opened in less than 10 s with an applied power of 13 W.

Thermal management is crucial for many microsystems and electronics applications (and that of miniaturized spacecraft is particularly demanding). This paper presents thermal modeling and scaling of a generic multiwafer silicon segment for placement in between two devices, or as a stage for a single one, in need of asymmetric thermal management. The unit is autonomous, i.e., it doesn't require any input signals or power. It comprises paraffin acting both as a heat sink, or thermal storage, and a material activating heat switches. The former mitigates heat bursts and accommodates power initially generated in, e.g., attached electronics, whereas the latter facilitates heat dissipation through heat guides during more intensive operation. Its function and physical properties are described in detail. A lumped thermal model has been constructed and implemented in the Simulink environment to investigate effects from: physical scaling of the unit, and change of its boundary temperature and coupling thereto, power generated, its emission and absorption properties and area fractions dedicated for passive devices, infrared (IR) emission, and heat guides on the unit's exterior, as well as fractional cross sections of paraffin, heat guides and other structural material in its interior. Conclusions, based on simulation results, are made and design rules based on the thermal modeling are presented. It was found that a 68 times 68 mm module could handle more than 10 W for 6 min in its heat sink mode alone. Subjected to 15 W for the same time, the module enters its active dissipation mode by closing its heat switches. A lateral increase and simultaneous vertical decrease of the unit's size resulted in overheating, whereas most scaling did not cause depletion of the heat sink. Changing the area fractions of various constituents also indicated operational stability with exception for excessive enlargement of passive heat guide material, exchanging structural material with paraffin, or severely limiting IR emission (by emitter area reduction or using low emission material), or using high absorbance material. Altering the boundary temperature and interface conductance proved to be means of biasing the system to various operating temperatures.

This paper presents system engineering parameters obtained from experiments, design analyses, and modelling of multifunctional microsystem modules for future spacecraft, made from bonded silicon and glass wafers. Specifically, it is shown that the 68times68 mm, mass 54 g silicon modules in aluminium frames can be used as structural elements for spacecraft. Random vibration analysis implies that the modules can survive peak accelerations and shocks.

The resilience and performance of carbon microcoil heaters made by laser-induced chemical vapor deposition (LCVD) to be used as an efficient means for increasing the specific impulse of cold/hot gas microthrusters were investigated. Two naked carbon coils and two tungsten coated carbon coils coated through LCVD were used in this experiment. Each pair of coated and uncoated carbon coils were heated resistively in a thermal cycling between 300-1173K and 973-1173K for 2 h in 0.000003 mbar and 2 bar N. The results show that at these temperatures the carbon microcoils and nitrogen propellant were compatible while the tungsten coated microcoils started degrading. It was observed that LVCD-deposited carbon and tungsten-coated carbon microcoils can withstand low to medium-high temperatures for extended periods of time during thermal cycling without showing signs of degradation.

This thesis explores the potential of multifunctional silicon-based microsystems for advanced nanospacecraft (AIN). Especially, multifunctional microsystems with the coexistant functions of communications and thermal management implemented in multilayer silicon stacks are approached with systems study. Host vehicles, composed of microsystems, including micro/nano-spacecraft and spherical rovers are contemplated with respect to future performance and implications, system level design, and breadboard realizations. A module of great importance, named the integrated communications and thermal management system for advanced or ICTM, symbolizes the achievements within the field of self-contained microsystems and is a prioritized entity throughout the thesis. The ICTM is natively placable onboard all types of highly miniaturized craft.The single AIN spacecraft and future clusters of these are investigated with respect to future full scale implementation of space systems designed and implemented with the distributed reconfigurable nanospacecraft cluster (DRNC) concept. Here, a true entanglement of microsystems technology (MST) and miniaturized spacecraft technology can revolutionize the applications, cost, and span of conceivable space missions.An intended communications scenario supporting a data rate of 1 Mbps, for the transmitter, is achieved during 6 minutes with a maximum continuous power dissipation of 10 W. Thermal simulations support the expectation, of a thermally biased ICTM, that the module is capable of supporting this energy burst, by using the mechanisms of heat storage and heat switches, and still fulfilling the requirements imposed by AIN type of spacecraft. In addition, multiple functional surfaces for the ICTM are evaluated with respect to equilibrium temperature and process compatibility. The tailored surfaces provide temperature control using micromachining methods.A design of a micromachined Ka-band front end with several MST enabled features is presented including e.g. vias, phase-shifters, and antennas. Similar antennas have been manufactured resulting in an evaluation of ring- and slot-antennas on silicon substrate. Based on a primitive version of the ICTM, a S-band patch antenna has been successfully implemented and characterized. Included in the thesis is a microthruster, an enabling technology for DRNC.

Microsystem interfaces to the macroscopic surroundings and within the microsystems themselves are formidable challenges that this thesis makes an effort to overcome, specifically for enabling a spacecraft based entirely on microsystems. The NanoSpace-1 nanospacecraft is a full-fledged satellite design with mass below 10 kg. The high performance with respect to mass is enabled by a massive implementation of microsystem technology – the entire spacecraft structure is built from square silicon panels that allow for efficient microsystem integration. The panels comprise bonded silicon wafers, fitted with silicone rubber gaskets into aluminium frames. Each module of the spacecraft is added in a way that strengthens and stiffens the overall spacecraft structure. The structural integrity of the silicon module as a generic building block has been successfully proven. The basic design (silicon, silicone, aluminium) survived considerable mechanical loads, where the silicon material contributed significantly to the strength of the structural element. Structural modeling of the silicon building blocks enables rapid iterative design of e.g. spacecraft structures by the use of pertinent model simplifications. Other microsystem interfaces treats fluidic, thermal, and mechanical functions. First, solder sealing of microsystem cavities was demonstrated, using screen-printed solder and localized resistive heating in the microsystem interface. Second, a dismountable fluidic microsystem connector, using a ridged silicon membrane, intended for monopropellant thruster systems, was developed. Third, a thermally regulated microvalve for minute flows, made by a silicon ridge imprint in a stainless steel nipple, was investigated. Finally, particle filters for gas interfaces to microsystems, or between parts of fluidic microsystems, were made from sets of crossed v-grooves in the interface of a bonded silicon wafer stack. Filter manufacture, mass flow and pressure drop characterization, together with numeric modeling for filter design, was performed. All in all this reduces the weight and volume when microsystems are interfaced in their applications.

This thesis explores the potential of multifunctional silicon-based microsystems for advanced nanospacecraft (AIN). Especially, multifunctional microsystems with the coexistant functions of communications and thermal management implemented in multilayer silicon stacks are approached with systems study. Host vehicles, composed of microsystems, including micro/nano-spacecraft and spherical rovers are contemplated with respect to future performance and implications, system level design, and breadboard realizations. A module of great importance, named the integrated communications and thermal management system for advanced or ICTM, symbolizes the achievements within the field of self-contained microsystems and is a prioritized entity throughout the thesis. The ICTM is natively placable onboard all types of highly miniaturized craft.The single AIN spacecraft and future clusters of these are investigated with respect to future full scale implementation of space systems designed and implemented with the distributed reconfigurable nanospacecraft cluster (DRNC) concept. Here, a true entanglement of microsystems technology (MST) and miniaturized spacecraft technology can revolutionize the applications, cost, and span of conceivable space missions.An intended communications scenario supporting a data rate of 1 Mbps, for the transmitter, is achieved during 6 minutes with a maximum continuous power dissipation of 10 W. Thermal simulations support the expectation, of a thermally biased ICTM, that the module is capable of supporting this energy burst, by using the mechanisms of heat storage and heat switches, and still fulfilling the requirements imposed by AIN type of spacecraft. In addition, multiple functional surfaces for the ICTM are evaluated with respect to equilibrium temperature and process compatibility. The tailored surfaces provide temperature control using micromachining methods.A design of a micromachined Ka-band front end with several MST enabled features is presented including e.g. vias, phase-shifters, and antennas. Similar antennas have been manufactured resulting in an evaluation of ring- and slot-antennas on silicon substrate. Based on a primitive version of the ICTM, a S-band patch antenna has been successfully implemented and characterized. Included in the thesis is a microthruster, an enabling technology for DRNC.

With the miniaturization of spacecraft the need for efficient, accurate and low-weight attitude control systems is becoming evident. To this end, the cold/hot gas microthruster system of this paper incorporates carbon microcoils—deposited via laser-induced chemical vapor deposition—for heating the propellant gas (nitrogen) before the nozzle inlet. By increasing the temperature of the propellant gas for such a system, the specific impulse (Isp) of the microthruster will increase. The benefits of a higher Isp are lower propellant mass, higher thrust and shorter burning times. Therefore, the feasibility of achieving this increase with the carbon microcoils is investigated. The carbon microcoils have been characterized experimentally with respect to their electrothermal performance, i.e. resistance, temperature, parasitic heat losses and degradation in ambient. The resulting heat losses from the heater and the heated gas have been estimated through a combination of experiments, numerical simulation and approximate analytical expressions. At high powers, degradation of the carbon material leads to coil failure in ambient where trace oxygen was present. Thus, the next generation of carbon microcoils to be tested will have a protective coating to extend their lifetime. Theoretical modeling showed that an increase in the propellant gas temperature from 300 to 1200 K and a corresponding two-fold increase in the Isp can be achieved if 1.0 W of power is supplied to each coil in a three-coil thruster. These simulation results show that if the coils are capable of dissipating 1 W of heat at 1700 K coil temperature, the doubling of the Isp may be achieved. Comparing to the electrothermal characterization results we find that the carbon coils can survive at 1700 K if protected, and that they can be expected to reach 1700 K at power below 1 W.

To use the high mass fraction of silicon material in a nanosatellite based on microelectromechanical systems, part of the structural function has been assigned to the flat silicon stacks embracing these systems. Three modules for destructive testing in bending, warping, and shearing cases were built with 68 x 68 x 1 mm silicon stacks bonded in aluminium frames by in situ casting of silicone rubber. A special module of the same size was built with strain gauges of Nichrome. Elastic deformation tests on this and simulations using finite element analysis were performed for bending, warping, and shearing loads of up to 80,40, and 99 N, respectively. The correlation between simulations and experimental measurements was good with deviation of about 30%. The results show that the rubber works well as a mechanical interface between the stiff and brittle silicon stacks and their weaker and ductile aluminium frames. Its thickness influences the stress in the silicon stack significantly. The silicon stack stiffens the module by a factor of 46 and lowers the stress in its frame 24 times in shearing mode, which is the most relevant loading case for the satellite framework. Thus, the concept of using flat silicon panels as structural elements is fully feasible.

Spacecraft on interplanetary missions or advanced satellites orbiting the Earth all require propulsion systems to complete their missions. Introducing microelectromechanical systems technology to the space industry will not only reduce size and weight of the propulsion system, but can also increase the performance of the mission.Fluid handling systems are used in chemical and electric propulsion. Some components incorporated in a fluidic handling system are presented and evaluated in this work.Microsystems are very sensitive to contamination. Reliable, robust, and easily integrated filters were modeled, manufactured, and experimentally verified.A fluid connector, designed to withstand large temperature variations and aggressive propellants was manufactured and characterized. Similar designs was also be used as a thermally activated minute valve.The feasibility of a cold gas system for precise attitude control has been demonstrated. Steps towards improving the performance (from specific im-pulse 45 s) have been taken, by the integration of suspended heater elements.For electric propulsion, two thermally regulated flow restrictors have been characterized. These devices can fine-tune the propellant flow to e.g. an ion engine.A single-use valve using a soldered seal has also been successfully dem-onstrated within a pressure range of 5 to 100 bar.The microsystem-based propulsion systems of tomorrow’s spacecraft need to be demonstrated in space, in order to gain necessary credibility.

Microsystem interfaces to the macroscopic surroundings and within the microsystems themselves are formidable challenges that this thesis makes an effort to overcome, specifically for enabling a spacecraft based entirely on microsystems. The NanoSpace-1 nanospacecraft is a full-fledged satellite design with mass below 10 kg. The high performance with respect to mass is enabled by a massive implementation of microsystem technology – the entire spacecraft structure is built from square silicon panels that allow for efficient microsystem integration. The panels comprise bonded silicon wafers, fitted with silicone rubber gaskets into aluminium frames. Each module of the spacecraft is added in a way that strengthens and stiffens the overall spacecraft structure. The structural integrity of the silicon module as a generic building block has been successfully proven. The basic design (silicon, silicone, aluminium) survived considerable mechanical loads, where the silicon material contributed significantly to the strength of the structural element. Structural modeling of the silicon building blocks enables rapid iterative design of e.g. spacecraft structures by the use of pertinent model simplifications. Other microsystem interfaces treats fluidic, thermal, and mechanical functions. First, solder sealing of microsystem cavities was demonstrated, using screen-printed solder and localized resistive heating in the microsystem interface. Second, a dismountable fluidic microsystem connector, using a ridged silicon membrane, intended for monopropellant thruster systems, was developed. Third, a thermally regulated microvalve for minute flows, made by a silicon ridge imprint in a stainless steel nipple, was investigated. Finally, particle filters for gas interfaces to microsystems, or between parts of fluidic microsystems, were made from sets of crossed v-grooves in the interface of a bonded silicon wafer stack. Filter manufacture, mass flow and pressure drop characterization, together with numeric modeling for filter design, was performed. All in all this reduces the weight and volume when microsystems are interfaced in their applications.

This work forms part of the development of a framework for semantic extraction in road traffic monitoring. In this paper we develop a scene, object and event model based on regions in the ground plane. The model is formally specified using the Güting spatio-temporal formalism for moving regions and Z notation. The result is domain-independent knowledge representation that supports reasoning about time-varying regions and that is expressed in an accessible mathematical formalism.

Dynamic Simulation of an Asymmetric Thermal Management Segment for Multilayered Silicon Microsystems