Showing papers presented at "IEEE Aerospace Conference in 2015"

SHERLOC: Scanning habitable environments with Raman & luminescence for organics & chemicals

Abstract: SHERLOC is an arm-mounted fluorescence and Raman spectrometer that was recently selected to be part of the payload for the next proposed NASA rover mission to Mars, scheduled for launch in 2020 SHERLOC enables non-contact, spatially resolved, high sensitivity detection and characterization of organics and minerals on the Martian surface The investigation goals are to assess past aqueous history, detect the presence and preservation potential of biosignatures, and support the selection of samples for caching and potential return to Earth

Automatic detection, classification and tracking of objects in the ocean surface from UAVs using a thermal camera

Abstract: The use of unmanned aerial vehicles (UAVs) that can operate autonomously in dynamic and dangerous operational environments are becoming increasingly common. In such operations, object detection, classification and tracking can often be one of the main goals. In recent years there has been an increased focus on embedded hardware that is both small and powerful, making UAV on-board data processing more viable. Being able to process the video feed on-board the UAV calls for fast and robust real-time algorithms for object identification and tracking. This paper discusses the development and implementation of a machine vision system for a low-cost fixed-wing UAV with a total flying weight of less than 4kg. The machine vision system incorporates the use of a thermal imaging camera and on-board processing power to perform real-time object detection, classification and tracking of objects in the ocean surface. The system is tested on thermal video data from a test flight, and is found to be able to detect 99;6% of objects of interest located in the ocean surface. Of the detected objects, only 5% were false positives. Furthermore, it classifies 93; 3% of the object types it is trained to classify correctly. The classifier is highly agile, allowing the user to quickly define which object characteristics that should be considered during classification, and what types of objects to classify. Finally, the system is found to successfully track 85% of the object types it is actively searching for in a real-time simulation test.

Risk-aware planetary rover operation: Autonomous terrain classification and path planning

Abstract: Identifying and avoiding terrain hazards (e.g., soft soil and pointy embedded rocks) are crucial for the safety of planetary rovers. This paper presents a newly developed ground-based Mars rover operation tool that mitigates risks from terrain by automatically identifying hazards on the terrain, evaluating their risks, and suggesting operators safe paths options that avoids potential risks while achieving specified goals. The tool will bring benefits to rover operations by reducing operation cost, by reducing cognitive load of rover operators, by preventing human errors, and most importantly, by significantly reducing the risk of the loss of rovers. The risk-aware rover operation tool is built upon two technologies. The first technology is a machine learning-based terrain classification that is capable of identifying potential hazards, such as pointy rocks and soft terrains, from images. The second technology is a risk-aware path planner based on rapidly-exploring random graph (RRG) and the A* search algorithms, which is capable of avoiding hazards identified by the terrain classifier with explicitly considering wheel placement. We demonstrate the integrated capability of the proposed risk-aware rover operation tool by using the images taken by the Curiosity rover.

Additive manufacturing for Aerospace

Abstract: Additive Manufacturing aka 3D printing opens up a whole new era for digital design and manufacturing. No longer is the aerospace engineering designer constrained by the ability to manufacture a component. The new philosophy is “if you can design it, we can produce it”. Yet there is a laundry list of caveats with the current state of the technology especially as it applies to aerospace applications and in particular, launch vehicles. Use of polymer based materials has caught hold in production tooling, yet use of polymers and metals for actual flight applications faces challenges until the technology catches up with the specific needs of the Aerospace industry. Launch vehicle applications may prove to be the bounding arena for aerospace applications. Consider the need for perfection in quality, temperature extremes from cryogenic commodities to rocket engine exhaust, shock and vibration conditions, and the grand size. However, given the variety of exquisite designs and low volume, aerospace applications are well suited for Additive Manufacturing. The challenges of today are already being solved and incorporated into the technology of tomorrow. It is simply a matter of time before AM finds not only a foot hold in aerospace but becomes the manufacturing tool of choice.

The OSIRIS-REx asteroid sample return mission

Abstract: In September of 2016, the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith EXplorer) spacecraft will depart for asteroid (101955) Bennu, and when it does, humanity will turn an important corner in the exploration of the Solar System. After arriving at the asteroid in the Fall of 2018, it will undertake a program of observations designed to select a site suitable for retrieving a sample that will be returned to the Earth in 2023. The third mission in NASA's New Frontiers program, OSIRIS-REx will obtain a minimum of 60 g of a primitive asteroid's surface, the largest sample of extra-terrestrial material returned to the Earth since the end of the Apollo lunar missions (Figure 1). OSIRIS-REx will also return a separate sample of the fine-grained surface material that is <1 mm in diameter.

The Evolvable Mars Campaign - study status

Abstract: NASA is developing a long-term strategy for achieving extended human missions to Mars in support of the policies outlined in the 2010 NASA Authorization Act and National Space Policy. The Authorization Act states that “A long term objective for human exploration of space should be the eventual international exploration of Mars.” Echoing this is the National Space Policy, which directs that NASA should, “By 2025, begin crewed missions beyond the moon, including sending humans to an asteroid. By the mid-2030s, send humans to orbit Mars and return them safely to Earth.” Further defining this goal, NASA's 2014 Strategic Plan identifies that “Our long-term goal is to send humans to Mars. Over the next two decades, we will develop and demonstrate the technologies and capabilities needed to send humans to explore the red planet and safely return them to Earth.” To accomplish these goals, NASA is employing a capability-driven approach to its human spaceflight strategy. This approach is based on developing a suite of evolving capabilities that provide specific functions to solve exploration challenges. These capabilities can be leveraged and reused, enabling more complex operations over time and exploration of more distant solar system destinations. The Evolvable Mars Campaign is an ongoing study identifying potential exploration options leading to sustainable human exploration of Mars. This campaign will leverage existing activities, adapt to capability developments, scientific discovery, and ever-changing programmatic environments. The results of this study will not produce “The Plan” for sending humans to Mars, but instead develop potential human Mars exploration strategies to inform NASA management on key decision options and investment priorities. This paper provides a summary of the 2014 study activities and key findings to date.

Phased Array Fed Reflector (PAFR) antenna architectures for space-based sensors

Abstract: Communication link and target ranges for satellite communications (SATCOM) and space-based sensors (e.g. radars) vary from approximately 400–1000 km for low earth orbits (LEO) to 35,800 km for geosynchronous orbits (GEO). At these long ranges, large antenna gains are required and most legacy systems use high gain reflectors with beams that are either fixed or mechanically steered. However, for some radio frequency (RF) sensor applications, mechanical beam scanning has inherent limitations.

X-ray pulsar navigation algorithms and testbed for SEXTANT

Abstract: The Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) is a NASA funded technology-demonstration. SEXTANT will, for the first time, demonstrate real-time, on-board X-ray Pulsar-based Navigation (XNAV), a significant milestone in the quest to establish a GPS-like navigation capability available throughout our Solar System and beyond. This paper describes the basic design of the SEXTANT system with a focus on core models and algorithms, and the design and continued development of the GSFC X-ray Navigation Laboratory Testbed (GXLT) with its dynamic pulsar emulation capability. We also present early results from GXLT modeling of the combined NICER X-ray timing instrument hardware and SEXTANT flight software algorithms.

Carbon nanomaterial-based wing temperature control system for in-flight anti-icing and de-icing of unmanned aerial vehicles

Abstract: Structural changes due to ice accretion are common causes for unmanned aerial vehicle incidents in Arctic regions. For fixed wing unmanned aerial vehicles (UAVs) the leading edge of airfoil surfaces is one of the primary surfaces exposed to these changes, causing a significant reduction in aerodynamic ability, i.e. decreasing lift and manoeuvrability, and increasing drag, weight, and consequently power consumption. Managing or altogether preventing ice accretion could potentially prevent icing related UAV incidents and increase the operability of UAVs. This paper addresses the issue of structural change, caused by ice accretion, on small UAVs by integrating a power control system and an electrically conductive carbon nano material based coating for temperature control of UAV airfoil surfaces. Performance assessment is achieved through extensive laboratory experiments, where various coating layouts have been investigated in various conditions, with temperatures ranging from +25° to −25°. The experimental setup consists of an Arduino microcontroller capable of controlling power delivery to the coating through feedback from thermocouples and a humidity sensor, sensing the surface temperature of the leading edge of the UAV wing and ambient humidity, respectively. Experiments reveal that a layout, where the coating covers the entire length of an wing is preferable, with the solution being highly capable of rapidly increasing the airfoil surface temperature (de-icing) when needed, and of maintaining an approximately constant airfoil surface temperature (anti-icing) when needed, all the while keeping power and energy consumption within weight and cost constraints imposed by the small scale of the UAV. The results represents a proof of concept by using an electrically conductive coating for de-icing and anti-icing of leading edge UAV airfoils.

Texture-specific elemental analysis of rocks and soils with PIXL: The Planetary Instrument for X-ray Lithochemistry on Mars 2020

Abstract: PIXL (Planetary Instrument for X-ray Lithochemistry) is a micro-focus X-ray fluorescence instrument for examining fine scale chemical variations in rocks and soils on planetary surfaces. Selected for flight on the science payload for the proposed Mars 2020 rover, PIXL can measure elemental chemistry of tiny features observed in rocks, such as individual sand grains, veinlets, cements, concretions and crystals, using a 100 µm-diameter, high-flux X-ray beam that can be scanned across target surfaces.

Continuum robots for space applications based on layer-jamming scales with stiffening capability

Abstract: Continuum robots, which have continuous mechanical structures comparable to the flexibility in elephant trunks and octopus arms, have been primarily geared toward the medical and defense communities. In space, however, NASA projects these robots to have a place in irregular inspection routines. The inherent compliance and bending of these continuum arms are especially suitable for inspection in obstructed spaces to ensure proper equipment functionality. In this paper, we propose a new solution that improves on the functionality of previous continuum robots, via a novel mechanical scaly layer-jamming design. Layer-jamming assisted continuum arms have previously required pneumatic sources for actuation, which limit their portability and usage in aerospace applications. This paper combines the compliance of continuum arms and stiffness modulation of the layer jamming mechanism to design a new hybrid layer jamming continuum arm. The novel design uses an electromechanical actuation which eliminates the pneumatic actuation therefore making it compact and portable.

A family of CMOS analog and mixed signal circuits in SiC for high temperature electronics

Abstract: This paper describes the simulation and test results of a family of analog and mixed signal circuits in silicon carbide CMOS technology at temperatures of 300°C and above. As SiC and wide bandgap devices in general grow in popularity for efficient and stable operation in high temperature and harsh environment applications, CMOS SiC integrated circuits can open up a new frontier of opportunity for miniaturization and system dependability. The building block circuits presented here can serve as the basis of rugged SiC system-on-chips for extreme environment applications.

NASA's Asteroid Redirect Mission concept development summary

Abstract: This paper summarizes key findings of Asteroid Redirect Mission pre-formulation concept development efforts, including mission architecture and design drivers, flight system concepts and trades, advanced solar electric propulsion component and system options, and asteroid capture option trades and risk reduction efforts This paper also provides a summary of concept development findings with a focus on extensibility to future mission applications and risk reduction and early testing of astronaut extra-vehicular activities

Microwave and millimeter-wave ranging for coherent distributed RF systems

Abstract: Microwave and millimeter-wave ranging systems, waveforms, and experimental results are described for coherent distributed RF systems applications. Measured results show that coherent distributed systems operating at carrier frequencies with coherence at λ/10 are possible well into the millimeter-wave regime by using widely separated two-tone ranging waveforms. The two-tone waveform in the context of continuous-wave ranging is introduced. A method for overcoming the range-ambiguous output of the matched filter processing is described. Microwave and millimeter-wave ranging measurements are shown and compared to the Cramer-Rao lower bound for range accuracy.

Software Defined Radio (SDR) architecture to support multi-satellite communications

Abstract: Software Defined Radio (SDR) is a key area to realise new software implementations for adaptive and reconfigurable communication systems without changing any hardware device or feature. A review on efficient use of limited bandwidth and increasing distributed satellite missions can lead to the need for a generic yet configurable communication platform that can handle multiple signals from multiple satellites with various modulation techniques, data rates and frequency bands that must be compatible to typical small satellite requirements. SDR is beneficial for space applications as it can provide the flexibility and re-configurability and this is driven by fast development times, new found heritage, reduced cost, and low mass Commercial Off-The-Shelf (COTS) components. The implementation of a combined System-On-Chip (SoC) and SDR communication platform enables additional reduction in cost as well as mass. This paper proposes a SDR architecture in which Field Programmable Gate Array (FPGA) System-on-Chip (SoC) is paired with a Radio Frequency (RF) programmable transceiver SoC to solve back-end and front-end re-configurability challenges respectively. The test-bed is aimed at implementing the signal processing software functions in both the dual-core ARM processors and associated FPGA fabric. The distribution of the functions between the FPGA fabric and dual-processor is based on profiling experiments using signal processing blocks, implemented on the development platform, in order to identify where bottlenecks exist. This paper discusses further the results from the new multi-signal / multi-satellite pipeline architecture and the subsequent bandwidth, data rate and processing requirements. Aspects of implementing and testing signal processing chains needed for CubeSat Telecommand, Telemetry and Control (TT&C) are presented together with initial results. Thus the proposed technology not only contributes for a lightweight and portable ground station but also for an on-board satellite transceiver.

VR-OOS: The DLR's virtual reality simulator for telerobotic on-orbit servicing with haptic feedback

Abstract: The growth of space debris is becoming a severe issue that urgently requires mitigation measures based on maintenance, repair, and de-orbiting technologies. Such on-orbit servicing (OOS) missions, however, are delicate and expensive. Virtual Reality (VR) enables the simulation and training in a flexible and safe environment, and hence has the potential to drastically reduce costs and time, while increasing the success rate of future OOS missions. This paper presents a highly immersive VR system with which satellite maintenance procedures can be simulated interactively using visual and haptic feedback. The system can be used for verification and training purposes for human and robot systems interacting in space. Our framework combines unique realistic virtual reality simulation engines with advanced immersive interaction devices. The DLR bimanual haptic device HUG is used as the main user interface. The HUG is equipped with two light-weight robot arms and is able to provide realistic haptic feedback on both human arms. Additional devices provide vibrotactile and electrotactile feedback at the elbow and the fingertips. A particularity of the realtime simulation is the fusion of the Bullet physics engine with our haptic rendering algorithm, which is an enhanced version of the Voxmap-Pointshell Algorithm. Our haptic rendering engine supports multiple objects in the scene and is able to compute collisions for each of them within 1 msec, enabling realistic virtual manipulation tasks even for stiff collision configurations. The visualization engine ViSTA is used during the simulation to achieve photo-realistic effects, increasing the immersion. In order to provide a realistic experience at interactive frame rates, we developed a distributed system architecture, where the load of computing the physics simulation, haptic feedback and visualization of a complex scene is transferred to dedicated machines. The implementations are presented in detail and the performance of the overall system is validated. Additionally, a preliminary user study in which the virtual system is compared to a physical test bed shows the suitability of the VR-OOS framework.

Mars conjunction crewed missions with a reusable hybrid architecture

Abstract: A new crew Mars architecture has been developed that provides many potential benefits for NASA-led human Mars moons and surface missions beginning in the 2030s or 2040s. By using both chemical and electric propulsion systems where they are most beneficial and maintaining as much orbital energy as possible, the Hybrid spaceship that carries crew round trip to Mars is pre-integrated before launch and can be delivered to orbit by a single launch. After check-out on the way to cis-lunar space, it is refueled and can travel round trip to Mars in less than 1100 days, with a minimum of 300 days in Mars vicinity (opportunity dependent). The entire spaceship is recaptured into cis-lunar space and can be reused. The spaceship consists of a habitat for 4 crew attached to the Hybrid propulsion stage which uses long duration electric and chemical in-space propulsion technologies that are in use today. The hybrid architecture's con-ops has no in-space assembly of the crew transfer vehicle and requires only rendezvous of crew in a highly elliptical Earth orbit for arrival at and departure from the spaceship. The crew transfer vehicle does not travel to Mars so it only needs be able to last in space for weeks and re-enter at lunar velocities. The spaceship can be refueled and resupplied for multiple trips to Mars (every other opportunity). The hybrid propulsion stage for crewed transits can also be utilized for cargo delivery to Mars every other opportunity in a reusable manner to pre-deploy infrastructure required for Mars vicinity operations. Finally, the Hybrid architecture provides evolution options for mitigating key long-duration space exploration risks, including crew microgravity and radiation exposure.

Integrity and authenticity of ADS-B broadcasts

Abstract: We propose a novel approach to provide authenticity and integrity of Automatic Dependent Surveillance-Broadcast (ADS-B) messages. We employ a key-management schema for authentication and rely on a key-edhashed message authentication code (HMAC) for integrity. Our approach avoids scalability and compatibility issues, as we neither change the packet format nor its size.

Developing a CubeSat Model-Based System Engineering (MBSE) reference model — Interim status #2

Abstract: Model-Based Systems Engineering (MBSE) is the formalized application of modeling to support key systems engineering tasks for addressing requirements, design, analysis, validation, and verification. The International Council on Systems Engineering (INCOSE) established the MBSE Initiative to promote, advance, and institutionalize the practice of MBSE. As part of this effort, the INCOSE Space Systems Working Group (SSWG) has been investigating the applicability of MBSE for designing CubeSats. Our application of MBSE is enabled by the graphical modeling language Systems Modeling Language (SysML). SysML is used to model all aspects of a system either directly or through interfaces with other models. SysML diagrams are used to describe requirements, structures, behaviors, and parametrics from the system down to the component level. Requirements and design are contained in the model rather than in a series of independent engineering artifacts. The CubeSat Reference Model provides the logical architecture. The logical elements can be reused as a starting point for a mission-specific CubeSat logical architecture, followed by the physical architecture and the CubeSat development. Our prior work established the CubeSat Reference Model domain as consisting of the stakeholders, CubeSat enterprise, external environment, and external constraints, with the CubeSat enterprise consisting of space and ground segments. The CubeSat enterprise architecture has been refined to accommodate an external service providing CubeSat transportation to a launch site, integration into a launch vehicle, launch, and deployment. It has also been refined to accommodate a CubeSat project developing its own ground station or operating with an existing ground station that provides uplink and downlink services. Space and ground subsystems had been identified in our prior work. Use cases have now been established to further define the subsystem capabilities. It has been recognized that there are two modeling efforts. One is the SSWG developing a CubeSat Reference Model with its logical architecture. The other is a team eventually taking the CubeSat Reference Model as a basis for its mission-specific logical and physical architectures. Therefore, there are two categories of stakeholders. A stakeholder is any entity that has an interest in the system. The stakeholders for the CubeSat Reference Model include INCOSE, the Object Management Group (OMG), regulatory agencies, and the university teams that will be using the CubeSat Reference Model. We are exploring having NASA, NOAA, and FCC regulations contained within their own SysML models and connecting those models to our CubeSat Reference Model. The stakeholders for the mission-specific CubeSat model are those with an interest in the mission-specific CubeSat space and ground system. Typical stakeholders for a space and ground system include sponsor, user, operator, project manager, project engineer, developer, and tester. The list of stakeholders for a university CubeSat project is much smaller. We are collaborating with OMGs Space Domain Task Force (SDTF) to adopt the CubeSat Reference Model as an OMG specification.

Virtual hand-button interaction in a generic virtual reality flight simulator

Abstract: Flight simulators with a physical mock-up are dependent on the aircraft type and have high costs. In order to overcome high cost issues, a generic virtual reality flight simulator is designed. Virtual buttons are used without a physical mock-up to make the virtual reality flight simulator independent of the aircraft type. The classic virtual hand metaphor is employed to interact with the virtual objects. This paper examines the virtual hand-button interaction in the generic virtual reality flight simulator where no haptic feed-back is provided. The effect of the collision volume of a virtual button during the virtual hand-button interaction is determined. It is concluded that a change in the collision volume within aircraft design limits, does not have a significant impact on the interaction. We also investigate different virtual hand avatars. We find that the accuracy of hand-button interaction depends on the hand avatar rather than the collision volume. Representing a smaller part of the hand avatar results in less efficient interaction. This shows the size and shape of hand avatars plays a major role in the virtual reality simulator design. This finding contributes to the various virtual reality applications which exploit the virtual hand metaphor.

Design and demonstration of the Mars Organic Molecule Analyzer (MOMA) on the ExoMars 2018 rover

Abstract: The Mars Organic Molecule Analyzer (MOMA) investigation is a key astrobiology experiment scheduled to launch on the joint ESA-Roscosmos ExoMars 2018 rover mission. MOMA will examine the chemical composition of geological samples acquired from depths of up to two meters below the martian surface, where fragile organic molecules may be protected from destructive cosmic radiation and/or oxidative chemical reactions. The heart of the MOMA mass spectrometer subsystem (i.e., MOMA-MS) is a miniaturized linear ion trap (LIT) that supports two distinct modes of operation to detect: i) volatile and semi-volatile, low-to-moderate mass organics (≤500 Da) via pyrolysis coupled with gas chromatography mass spectrometry (pyr/GCMS); and, ii) more refractory, moderate-to-high mass compounds (up to 1000 Da) via laser desorption (LDMS) at ambient Mars pressures. Additionally, the LIT mass analyzer enables selective ion trapping via multi-frequency waveform ion excitation (e.g., stored waveform inverse Fourier transform, or SWIFT), and structural characterization of complex molecules using tandem mass spectrometry (MS/MS). A high-fidelity Engineering Test Unit (ETU) of MOMA-MS, including the LIT subassembly, dual-gun electron ionization source, micropirani pressure gauge, solenoid-driven aperture valve, redundant detection chains, and control electronics, has been built and tested at NASA GSFC under relevant operational conditions (pressure, temperature, etc.). Spaceflight qualifications of individual hardware components and integrated subassemblies have been validated through vibration, shock, thermal, lifetime, and performance evaluations. The ETU serves as a pathfinder for the flight model buildup, integration and test, as the ETU meets the form, fit and function of the flight unit that will be delivered to MPS in late 2015. To date, the ETU of MOMA-MS has been shown to meet or exceed all functional requirements, including mass range, resolution, accuracy, instrumental drift, and limit-of-detection specifications, thereby enabling the primary science objectives of the MOMA investigation and ExoMars 2018 mission.

Design and flight testing of an integrated solar powered UAV and WSN for remote gas sensing

Abstract: This paper describes a generic and integrated solar powered remote Unmanned Air Vehicles (UAV) and Wireless Sensor Network (WSN) gas sensing system. The system uses a generic gas sensing system for CH 4 and CO 2 concentrations using metal oxide (MoX) and non-dispersive infrared sensors, and a new solar cell encapsulation method to power the UASs as well as a data management platform to store, analyse and share the information with operators and external users. The system was successfully field tested at ground and low altitudes, collecting, storing and transmitting data in real time to a central node for analysis and 3D mapping. The system can be used in a wide range of outdoor applications, especially in agriculture, bushfires, mining studies, opening the way to a ubiquitous low cost environmental monitoring. A video of the bench and flight test performed can be seen in the following link https://www.youtube.com/watch?v=Bwas7stYIxQ.

A cognitive radio system for improving the reliability and security of UAS/UAV networks

Abstract: This paper describes a system based on cognitive radio technology to improve the reliability and security of wireless communications of unmanned aerial systems and vehicles (UAS/UAV) networks UAS/UAV networks can experience problems with connectivity and thus with data reception and delivery Since UAS/UAV are mobile, their connectivity is dynamic; thus, link status changes are more frequent than for traditional networks Specifically, link losses due to jamming, interference, fading, and multipath are common problems Another factor is the way the radio spectrum is used at each specific location The availability of specific spectrum frequency bands can vary from one location to another, thus making it crucial for aircraft to be frequency agile to maintain connectivity

SpaceFibre: A multi-Gigabit/s interconnect for spacecraft onboard data handling

Abstract: SpaceFibre is a spacecraft onboard data link and network technology being developed by University of Dundee for the European Space Agency (ESA), which runs over both copper and fibre optic cables. Initially targeted at very high data rate payloads such as Synthetic Aperture Radar (SAR) and multi-spectral imaging instruments, SpaceFibre is capable of fulfilling a wider set of spacecraft onboard communications applications because of its inbuilt QoS and FDIR capabilities and its backwards compatibility with the ubiquitous SpaceWire technology. SpaceFibre operates at 2.5 Gbits/s providing 12 times the throughput of a SpaceWire link with current flight qualified technology and allowing data from multiple SpaceWire devices to be concentrated over a single SpaceFibre link. This substantially reduces cable harness mass and simplifies redundancy strategies. The innovative QoS mechanism in SpaceFibre provides concurrent bandwidth reservation, priority and scheduled QoS. This simplifies spacecraft system engineering through integrated quality of service (QoS), which reduces system engineering costs and streamlines integration and test. Novel integrated FDIR support provides galvanic isolation, transparent recovery from transient errors, error containment in virtual channels and frames, and “Babbling Idiot” protection. SpaceFibre enhances onboard network robustness through its inherent FDIR and graceful degradation techniques incorporated in the network hardware. This simplifies system FDIR software, reducing development and system validation time and cost. SpaceFibre includes low latency event signalling and time distribution with broadcast messages. This enables a single network to be used for several functions including: transporting very high data rate payload data, carrying SpaceWire traffic, deterministic delivery of command/control information, time distribution and event signalling. SpaceFibre is backwards compatible with existing SpaceWire equipment at the packet level allowing simple interconnection of SpaceWire devices into a SpaceFibre network and enabling that equipment to take advantage of the QoS and FDIR capabilities of SpaceFibre.

Updated population and risk assessment for airbursts from near-earth objects (NEOs)

Abstract: We present a new analysis of airburst risk based on updated estimates for the population of undiscovered NEOs, taking into account the enhanced damage potential of directed airbursts. We define airbursts as events in which small (meters to tens-of-meters in diameter) asteroids deposit most of their energy in the atmosphere as large bolides and where the total energy is comparable to or greater than small nuclear explosions (>0.1 kilotons of TNT). Our tens-of-meter population estimate from optical surveys is now much closer to bolide frequency estimates, resolving most of an earlier discrepancy. Our Tunguska-class (∼40 meters) population estimate has doubled, and Chelyabinsk-class (∼20 meters) has increased by a factor of 2.6. Uncertainty in this population remains quite large, and can only be unambiguously reduced by expanded surveys focused on objects in the tens-of-meters size range. The assessed risk from this population is also increasing for two reasons. First, airbursts are significantly more damaging than assumed in the original risk assessments, because for typical impact geometries they more efficiently couple energy to the surface than nuclear explosions of the same energy. Second, the greater numbers mean that they are more frequent than previously thought. We review the evidence that asteroid airbursts are more damaging than nuclear explosions, and provide arguments that such events are more frequent.

Human exploration of Phobos

Abstract: This study developed, analyzed, and compared mission architectures for human exploration of Mars' moons within the context of an Evolvable Mars Campaign. METHODS: All trades assumed conjunction class missions to Phobos (approximately 500 days in Mars system) as it was considered the driving case for the transportation architecture. All architectures assumed that the Mars transit habitat would remain in a high-Mars orbit (HMO) with crewmembers transferring between HMO and Phobos in a small crew taxi vehicle. A reference science/exploration program was developed including performance of a standard set of tasks at 55 locations on the Phobos surface. Detailed EVA timelines were developed using realistic flight rules to accomplish the reference science tasks using exploration systems ranging from jetpacks to multi-person pressurized excursion vehicles combined with Phobos surface and orbital (L1, L4/L5, 20 km distant-retrograde-orbit [DRO]) habitat options. Detailed models of propellant mass, crew time, science productivity, radiation exposure, systems and consumables masses, and other figures of merit were integrated to enable quantitative comparison of different architectural options. Options for prestaging assets using solar electric propulsion versus delivering all systems with the crew were also evaluated. Seven discrete mission architectures were evaluated. RESULTS: The driving consideration for habitat location (Phobos surface versus orbital) was radiation exposure, with an estimated reduction in cumulative mission radiation exposure of up to 34% (versus a Mars orbital mission) when the habitat is located on the Phobos surface, compared with only 3% to 6% reduction for a habitat in a 20-km DRO. The exploration utility of lightweight unpressurized excursion vehicles was limited by the need to remain within 20 minutes of solar particle event radiation protection combined with complex guidance, navigation, and control systems required by the nonintuitive and highly-variable gravitational environment. Two-person pressurized excursion vehicles as well as mobile surface habitats offer significant exploration capability and operational benefits compared with unpressurized extravehicular activity (EVA) mobility systems at the cost of increased system and propellant mass. Mechanical surface translation modes (ie, hopping) were modeled and offered potentially significant propellant savings and the possibility of extended exploration operations between crewed missions. Options for extending the use of the crew taxi vehicle were examined, including use as an exploration asset for Phobos surface exploration (when combined with an alternate mobility system) and as an EVA platform, both on Phobos and for contingency EVA on the Mars transit habitat. CONCLUSIONS: Human exploration of Phobos offers a scientifically meaningful first step towards human Mars surface missions that develops and validates transportation, habitation, and exploration systems and operations in advance of the Mars landing systems.

Meteorological path planning using dynamic programming for a solar-powered UAV

Abstract: Solar-powered Unmanned Aerial Vehicles (SUAV) designed for Low-Altitude Long-Endurance (LALE) applications provide potential multi-day continuous flight capability, but are generally prone to local meteorological impediments such as rain, strong winds or reduced solar irradiance. This paper therefore presents METPASS, the Meteorology-aware Trajectory Planning and Analysis Software for Solar-powered UAVs. METPASS optimizes large-scale solar-powered UAV missions using a detailed consideration of meteorological effects: An optimal trajectory is found on a 3-D grid for given departure and arrival points by applying a Dynamic Programming approach and a cost function that considers environmental hazards, winds, solar radiation, aircraft parameters and flight time. The cost function is evaluated based on a kinematic and energetic UAV system model and forecast data from the European Centre for Medium-Range Weather Forecasts (ECMWF). The trajectory-planning environment is applied to an envisioned fully autonomous and solar-powered crossing of the North Atlantic Ocean by AtlantikSolar, a 5.6m-wingspan SUAV developed at ETH Zurich. Results based on historical ECMWF weather data from 2012 and 2013 show that properly pre-optimized routes allow the Atlantic crossing even in case of significant global cloud coverage and that optimal routes can reduce the required flight time by up to 50% (from 106h to 52h) by exploiting wind conditions.

Random forests for industrial device functioning diagnostics using wireless sensor networks

Abstract: In this paper, random forests are proposed for operating devices diagnostics in the presence of a variable number of features. In various contexts, like large or difficult-to-access monitored areas, wired sensor networks providing features to achieve diagnostics are either very costly to use or totally impossible to spread out. Using a wireless sensor network can solve this problem, but this latter is more subjected to flaws. Furthermore, the networks' topology often changes, leading to a variability in quality of coverage in the targeted area. Diagnostics at the sink level must take into consideration that both the number and the quality of the provided features are not constant, and that some politics like scheduling or data aggregation may be developed across the network. The aim of this article is (1) to show that random forests are relevant in this context, due to their flexibility and robustness, and (2) to provide first examples of use of this method for diagnostics based on data provided by a wireless sensor network.

On the identifiability of noise statistics and adaptive KF design for robust GNSS carrier tracking

Abstract: Carrier synchronization is of paramount importance in any communications or positioning system. Mass-market Global Navigation Satellite System (GNSS) receivers typically implement traditional carrier tracking techniques based on well-established phase-locked loop architectures, which are only reliable in quite benign propagation conditions. Under nonnominal harsh propagation conditions, the signal may be affected by shadowing, strong fading, multipath or severe ionospheric scintillation, and thus, traditional architectures are not valid anymore and there exists an actual need for robust tracking solutions. Several approaches to overcome the conventional PLL limitations have appeared during the last decade, being the Kalman filter (KF) based architectures the most promising research line. The main drawback of standard KFs is the assumption of perfectly known process and measurement noise statistics, a knowledge that is always constrained by the system model accuracy. Beyond heuristic solutions, a general framework for the design of adaptive KFs correctly dealing with both process and measurement noises, that would be of capital importance for the practitioner, has not been established. The main goal of this contribution is to provide a clear answer to this fundamental question. It is shown that the main driver on the KF performance is not the adjustment of the measurement noise but the adequate tuning of the process noise statistics. Within this framework, a comprehensive discussion is given for the correct design of adaptive KF architectures for robust carrier tracking applications, where the key idea is to use two independent noise statistics estimation strategies to sequentially adapt both parameters. The design choice is supported by a discussion on the identifiability of the noise statistics' parameters. Simulation results are provided showing the need of fully adaptive solutions, and the achieved performance gain of KF-based architectures when compared to traditional tracking loops.

NISAR spacecraft concept overview: Design challenges for a proposed flagship dual-frequency SAR mission

Abstract: NISAR (NASA-ISRO Synthetic Aperture Radar) would be the inaugural collaboration between National Aeronautics and Space Administration (NASA) and Indian Space Research Organization (ISRO) on an Earth Science mission, which would feature an L-Band SAR instrument and an S-Band SAR instrument. As partners, NASA and ISRO would each contribute different engineering elements to help achieve the proposed scientific objectives of the mission. ISRO-Vikram Sarabhai Space Centre would provide the GSLV-Mark II launch vehicle, which would deliver the spacecraft into the desired orbit. ISRO-Satellite Centre would provide the spacecraft based on its I3K structural bus, a commonly used platform for ISRO's communication satellite missions, which would provide the resources necessary to operate the science payload. NASA would augment the spacecraft capabilities with engineering payload systems to help store, and transmit the large volume of science data. The combination of two SAR instruments on one platform would challenge the capabilities of both ISRO and NASA. The following are some of the challenges that will be discussed in the paper. The desire to operate both radars simultaneously would lead to a several-kilowatt power system design. The need to point the radar antenna to within a tenth of a degree would drive the attitude control system design. At peak rates, each instrument would produce data at gigabit per second speeds, which would drive the data transfer and storage capabilities. Furthermore, these data volumes would require the transition from an X-Band telecommunication system to Ka-Band, which could support multi-gigabit data rates.