Next generation space avionics: layered system implementation

Advances in electronics over the past decade have produced major improvements in the power and flexibility of computer systems. Unfortunately current avionics systems for space applications typically have not leveraged these COTS advantages. A decade ago, the state-of-the-art for avionics systems made a step change to the Integrated Modular Avionics (IMA) used in the Boeing 777. This next generation avionics architecture is not based upon traditional Byzantine redundancy structures, but on a truth-based scheme where each element knows when an internal failure occurs and removes itself from the system. IMA utilizes a lock-step microprocessor design that communicates to a COTS Backplane for input/output, and to a Virtual Backplane/spl trade/ (a reliable high-speed serial bus) for intra-system communication. The system functions are implemented using a time and space partitioned operating system. The entire system provides the simplicity of a simplex system, implements the highest level of reliability providing complete flexibility to reconfigure both software applications and hardware interfaces, allows for rapid prototyping using low-cost COTS hardware, and is easily expandable beyond the initial point implementation. As the only 5/sup th/ generation avionics architecture, the concepts incorporated into Honeywell's IMA are ideally suited to be the backbone of the next generation Space Exploration Program avionics architectures.     

Next generation test support systems for the aircraft life cycle

The objective of this paper is to present the experience of EADS in using a common test support system for integration and qualification testing, aircraft ground equipment (AGE), in-service software maintenance facilities (ISMF) and ground crew training. EADS uses its test support system AIDASS (Advanced Integrated Data Acquisition and Stimulation System) in different phases of the aircraft life cycle. AIDASS is comprised of a real-time front-end system and a standard PC for the user interface. The EADS test support system is used in almost all phases of the aircraft life cycle, for instance, for integration and verification testing, as aircraft ground equipment, for in-service software maintenance and training of ground crews. This test support system is used for the software maintenance in the TORNADO program at different airforces in Europe. The airforces also share test setups with industry     

Next generation digital GPS receiver

The architecture and technology features of the next-generation (NGR) digital GPS (Global Positioning System) receiver manufactured by Collin are described. The project's objective was to develop an advanced GPS receiver chipset with high antijam capabilities. The program, initiated in 1985, has provided the technology for miniature receiver products for both unmanned and manned vehicle applications. A two-channel version of the receiver is in full-scale development for tactical missile applications. A five-channel version is being tested and evaluated as a drop-in replacement for RCVR-3A, the US Department of Defense standard high dynamic receiver. The NGR design started with the digital signal processing architecture developed for the Defense Advanced Research Project Agency (DARPA) hand-held GPS receiver. Enhancements were made to improve the antijam and signal acquisition performance. Producible, qualifiable and cost-effective silicon monolithic microwave integrated circuits and semicustom digital technologies were used to develop the core GPS chipset. A system design approach was established to permit reuse of mature and validated GPS software     

Next generation GOES satellite power subsystem

Hughes space and communications was awarded a contract in January 1998 from NASA's Goddard Space Flight Center for the design, manufacture, integration and launch of two next generation geostationary operational environmental satellites (GOES) and options for two additional satellites. The satellites measure weather phenomena as the primary mission and X-rays and charged particles as the secondary missions. This paper describes the GOES electrical power subsystem (EPS) requirements, architecture, hardware and energy balance analysis. As of this writing, the design of the EPS has completed the critical design review phase and the hardware has entered the manufacturing phase     

Unmanned space vehicle navigation by GPS

In this paper, flight-path deviation in the navigation of unmanned space vehicles by global positioning system (GPS) is analyzed. A new method to calculate flight-path deviation by means of coordinate transforming is presented and the software of navigation and control is designed. This software is practical and effective for navigation by GPS with some characteristics including high-speed, high accuracy, real-time positioning and the use of digital mapping technique     

Next generation functional test program development system

While superior-quality functional board test has been a goal for most high reliability electronics manufacturers, the time and effort for generating such test programs using today's tools and processes makes this difficult to achieve in a cost effective manner. This paper will introduce a revolutionary approach to functional board test program development that combines the comprehensiveness of software-based simulation with the speed and simplicity of hardware emulation. The result is a functional Test Program Set development system that can produce high fault coverage, diagnostic test programs in a fraction of the time it takes using traditional techniques, and at a lower unit cost. In this paper we will first provide a brief background on the strengths and weaknesses of current software and hardware TPS development techniques-simulation hot mock-up. Next, the new approach is described in detail and contrasted against the existing techniques. Finally, actual experience to date using a prototyped system is presented     

Quality control in integrated navigation systems

Real-time estimation of parameter sin dynamic systems, which becomes increasingly important in the field of high-precision navigation, requires real-time testing of the models underlying the navigation system. A real-time recursive testing procedure than can be used in conjunction with the Kalman filter algorithm is presented, along with diagnostic tools for inferring the detectability of particular model errors. The testing procedure consists of detection, identification, and adaptation. It can accommodate model errors in the measurement model and dynamic model of the integrated navigation system and is optimal in the uniformly-most-powerful-invariant sense     

Electric space propulsion systems

Active development of electric thrustors began 10 years ago. Today, several kinds of thrustors have achieved efficiencies above 90 % and lifetimes of several thousand hours. The following article derives the basic theory of electric thrust production at constant exhaust velocity, and at variable exhaust velocity programmed for optimum vehicle performance. Electrothermal or arcjet; electrostatic or ion; and electrodynamic or plasma thrustors are described. At the present time, ion thrustors of the electron bombardment and of the surface ionization types are the most promising systems. Electric power in space may be generated by solar cells or nuclear-electric generators. It is expected that the incore thermionic converter will eventually be the preferred system. A variety of missions with electric propulsion systems appear feasible and highly desirable, among them orbital station keeping, attitude control, planetary probes, solar and out-of-the-ecliptic probes, deep-space probes, and manned Mars and Venus exploration. For each mission, a careful systems-design study must be made, which will provide the optimum selection of thrustor type, thrust level, exhaust velocity, thrust program, power source, trajectory, and flight plan.     

INMARSAT integrity channels for global navigation satellite systems

The transmission of integrity information using a signal format compatible with the Global Positioning System (GPS) and relayed through a geostationary satellite repeater, which will be critical in achieving high integrity and availability of global navigation by satellite is discussed. The inclusion of navigation repeaters designed to fulfil this function, the next generation of INMARSAT spacecraft, INMARSAT-3 is examined. The global navigation satellite system (GNSS) integrity channel (GIC) will employ pseudorandom codes in the same family as, but distinct from, the codes reserved by GPS. The data format of the basic integrity channel is designed to convey user range error information for 24 to 40 satellites. A closed-loop timing compensation technique will be used at the uplinking Earth station, to make the signal's clock and carrier Doppler variations identical to those that would result from an onboard signal source. Therefore, the INMARSAT-3 satellites will increase the number of useful navigation satellites available to any user, and can also function as sources of precise timing. There is also a possibility that wide area differential corrections can be carried on the same signal     

GPS modeling for designing aerospace vehicle navigation systems

The complexity of the design of a Global Positioning System (GPS) user segment, as well as the performance demanded of the components, depends on user requirements such as total navigation accuracy. Other factors, for instance the expected satellite/vehicle geometry or the accuracy of an accompanying inertial navigation system can also affect the user segment design. Models of GPS measurements are used to predict user segment performance at various levels. Design curves are developed which illustrate the relationship between user requirements, the user segment design, and component performance     

EDISON: The next generation infrared space observatory

EDISON, a large-aperture, radiatively-cooled telescope, is proposed as the major international mission to follow the current generation of cryogenically-cooled infrared space telescopes. It is being studied at present as a 2.5–3.5 m mixed radiatively- and mechanically-cooled facility optimized to investigate the wavelength range 3–100+ m. This paper outlines the status of the project, discusses some aspects of a smaller-aperture precursor mission, and describes a portion of the baseline science mission.     

Short-range radio navigation systems: current status and prospects

The problems of the development of short-range navigation aids as integrated multifunctional systems for the near future while implementing them in poorly equipped regions, ice-breaker fleets, and on remote oil platforms are discussed. Conclusions are drawn about the reasonability of utilization for those purposes of various modifications of the existing integrated short-range navigation systems. These systems provide highly accurate operation, have a convenient ρ-&thetas; coordinate system, and are capable in some cases of providing the additional functions     

New architectures for space power systems

Electric power generation and conditioning have experienced revolutionary development over the past two decades. Furthermore, new materials such as high energy magnets and high temperature superconductors are either available or on the horizon. Our work is based on the premise that new technologies are an important driver of new power system concepts and architectures. This observation is borne out by the historical evolution of power systems both in terrestrial and aerospace applications. This paper introduces new approaches to designing space power systems by using several new technologies. Two new architectures are introduced: the current source current intensive system and the articulate system. Basic characteristics of these systems have been investigated. Some aspects of the articulate system architecture, as discussed in this paper can be implemented in the short term. Flexible AC transmission systems which are now undergoing rapid development and implementation, can be regarded as a subset of the family of control methodologies which constitute the realm of articulate systems     

Wave induced energetic particle generation and space plasma modeling

An increasing number of high-resolution spacecraft observations provide access to details of energetic electron and ion velocity-space distribution structures. Since resonant wave-particle interaction processes depend considerably on the distribution function details, space plasma modeling is of particular interest for studies of a variety of plasma environments as planetary magnetospheres, the interplanetary medium or solar flares. After summarizing the most popular particle acceleration processes we focus on wave-powered energization mechanisms induced by Landau interaction and demonstrate from a time-evolutionary scenario that power-law distributions, highly favored by observations in recent years, are generated resonantly by an Alfvén wave spectrum and possibly saturate. This process is further stimulated in non-uniform magnetic field configurations where multiple wave packets at different phase velocities provide the energy source for a continuous acceleration process. Moreover, in this conjunction we demonstrate that in particular κ-distributions are a consequence of a generalized entropy concept, favored by nonextensive statistics, which provides the missing link for power-law plasma models from fundamental physics. With regard to in situ space observations examples are provided illuminating that for non-thermal plasma characteristics the particular structure of the velocity-space distribution dominates as regulating mechanism for the wave-particle interaction process over effects related to changes in space plasma parameters. This revised version was published online in August 2006 with corrections to the Cover Date.     

Micromechanical gyros & accelerometers for digital navigation & control systems

There is no general consensus of opinion about the future of micromechanical gyroscopes and accelerometers. According to the pessimistic estimation, micromechanical gyroscopes and accelerometers have attained the limit of their accuracy. However, optimists believe that micromechamical gyroscopes will soon occupy the niche of fiber-optical gyroscopes and the latter will press laser gyroscopes. The present-day development of micromechanical gyroscopes and accelerometers is aimed at improving the basic and minor parameters: sensitivity, bias, offset, drift, resolution, scale factor, and its non-linearity. High level of performance is provided by application of high technology. This is devoted to the development and manufacturing of silicon-glass micromechanical sensors of encapsulated-type with digital output processing. The key technological processes allowing production of micromechanical encapsulated sensors with vacuum insides are considered and the features of their design are described. The methods for maintaining high reliability of encapsulated micromechanical gyroscopes with inner getter structure are discussed. ASIC designs for control and processing of micromechanical sensor outputs allow their accuracy, which is part of modern integrated systems, to be considerably improved. Also considered are various assemblies and packaging of the ASIC and micromechanical sensor as a single product.     

Testing autonomous systems for deep space exploration

NASA is moving into an era of Increasing spacecraft autonomy. However, before autonomy can be routinely utilized, we must develop techniques for providing assurance that the system will perform correctly in flight. We describe why autonomous systems require advanced verification techniques, and offer some management and technical techniques for addressing the differences. Autonomous goal-driven spacecraft require advances in verification techniques because optimization (e.g., planning and scheduling) algorithms are at the core of much of autonomy. It Is the nature of such algorithms that over much of the input space an intuitively small change in the input results in a correspondingly small change in the output: This type of response typically leads one to conclude, quite reasonably, that if the two responses are correct, those responses between them will probably also be correct. However, there are certain regions in the input space where a small change in the input will result in a radically different output: One is not so inclined to conclude that all responses in these transition zones are likely to be correct. We believe, for two reasons, that these transition zones are one place where autonomous systems are likely to fail. First, boundary conditions, often a rich source of faults, are highly exercised in the transition zones, and so increase the likelihood of faults. Second, within the transition zone the algorithm outputs are likely to appear unusual, and, since the outputs of the algorithm become inputs to the remainder of the system, the whole system is probably pushed outside of its nominal usage profile: historically shown to be another good source of faults. We close with a discussion of risk management. Autonomous systems have many well-known management risk factors. Risk management and quality concerns must be pervasive, throughout all team members and the whole life-cycle of the project.     

Confluence of navigation, communication, and control in distributedspacecraft systems

This research details the development of technologies and methodologies that enable distributed spacecraft systems by supporting integrated navigation, communication, and control. Operating at the confluence of these critical functions produces capabilities needed to realize the promise of distributed spacecraft systems, including improved performance and robustness relative to monolithic space systems. Navigation supports science data association and data alignment for distributed aperture sensing, multipoint observation, and co-observation of target regions. Communication enables autonomous distributed science data processing and information exchange among space assets. Both navigation and communication provide essential input to control methods for coordinating distributed autonomous assets at the interspacecraft system level and the intraspacecraft affector subsystem level. A technology solution to implement these capabilities, the Crosslink Transceiver, is also described. The Crosslink Transceiver provides navigation and communication capability that can be integrated into a developing autonomous command and control methodology for distributed spacecraft systems. A small satellite implementation of the Crosslink Transceiver design is detailed and its ability to support broad distributed spacecraft mission classes is described