The LISA Pathfinder Mission

LISA Pathfinder, formerly known as SMART-2, is the second of the European Space Agency’s Small Missions for Advance Research and Technology, and is designed to pave the way for the joint ESA/NASA Laser Interferometer Space Antenna (LISA) mission, by testing the core assumption of gravitational wave detection and general relativity: that free particles follow geodesics. The new technologies to be demonstrated in a space environment include: inertial sensors, high precision laser interferometry to free floating mirrors, and micro-Newton proportional thrusters. LISA Pathfinder will be launched on a dedicated launch vehicle in late 2011 into a low Earth orbit. By a transfer trajectory, the sciencecraft will enter its final orbit around the first Sun-Earth Lagrange point. First science results are expected approximately 3 months thereafter. Here, we give an overview of the mission including the technologies being demonstrated.     

伸缩机翼变形技术研究

变体飞机可以根据需要改变气动外形,以便在不同的飞行状态都能获得最佳的气动性能,提高飞机的任务适应能力。伸缩机翼变形技术在国外已经过几十年的研究和探索,是变体飞机技术的主要发展方向之一。本文综述了伸缩机翼技术的发展历史及国内外研究情况,阐述了伸缩机翼变形原理及其优缺点,提炼了设计伸缩机翼所涉及的关键技术,展望了伸缩机翼技术在飞机、导弹、地效翼飞行器以及飞行汽车等方面的应用前景。     

Comparative study of lunar mission requirements and onboard propulsion system performance

In recent years, the lunar explorer programs, suspended for a long time, have resumed again with the rapid development of low cost and high-level technologies. As a result, several nations have made a success of lunar exploration programs with their own orbiters. Unlike a satellite orbiting the earth, the optimal design of an onboard propulsion system of a lunar orbiter is a major issue because it is not simple to make the orbiter arrive accurately at another planet far from the earth. Hence, a close attention is required to select and develop an appropriate type of the onboard propulsion system based on given mission requirements of a lunar orbiter. To do this, this study first surveys several lunar orbiters launched since 1990 and their major mission requirements. Then, it summarizes the technical trends of the onboard propulsion systems of the recent lunar orbiters and their key design and performance specifications through trade-off studies. By comparing these features, the present study investigates which lunar mission requirements are critically important, and how they can effect on the overall performance of an onboard propulsion system. Based on these investigations the major objective of the present study intends ultimately to set up a fundamental baseline in selecting and developing an appropriate type of onboard propulsion system of a lunar orbiter.     

STEREO Ground Segment, Science Operations, and Data Archive

Vitally important to the success of any mission is the ground support system used for commanding the spacecraft, receiving the telemetry, and processing the results. We describe the ground system used for the STEREO mission, consisting of the Mission Operations Center, the individual Payload Operations Centers for each instrument, and the STEREO Science Center, together with mission support from the Flight Dynamics Facility, Deep Space Mission System, and the Space Environment Center. The mission planning process is described, as is the data flow from spacecraft telemetry to processed science data to long-term archive. We describe the online resources that researchers will be able to use to access STEREO planning resources, science data, and analysis software. The STEREO Joint Observations Program system is described, with instructions on how observers can participate. Finally, we describe the near-real-time processing of the “space weather beacon” telemetry, which is a low telemetry rate quicklook product available close to 24 hours a day, with the intended use of space weather forecasting.     

无人机编队飞行问题初探

回顾了国内外无人机的发展历史和近年来的发展趋势，简要介绍了无人机在军事、国民经济和科学技术方面的作用。分析了单架无人机执行任务时面临的问题和编队飞行的优势，介绍了国内外在无人机编队飞行方面的研究状况，同时对保证无人机编队飞行的关键技术进行了探讨和分析。     

On the Detectability and Use of Normal Modes for Determining Interior Structure of Mars

The InSight mission to Mars is well underway and will be the first mission to acquire seismic data from a planet other than Earth. In order to maximise the science return of the InSight data, a multifaceted approach will be needed that seeks to investigate the seismic data from a series of different frequency windows, including body waves, surface waves, and normal modes. Here, we present a methodology based on globally-averaged models that employs the long-period information encoded in the seismic data by looking for fundamental-mode spheroidal oscillations. From a preliminary analysis of the expected signal-to-noise ratio, we find that normal modes should be detectable during nighttime in the frequency range 5–15 mHz. For improved picking of (fundamental) normal modes, we show first that those are equally spaced between 5–15 mHz and then show how this spectral spacing, obtained through autocorrelation of the Fourier-transformed time series can be further employed to select normal mode peaks more consistently. Based on this set of normal-mode spectral frequencies, we proceed to show how this data set can be inverted for globally-averaged models of interior structure (to a depth of \(\sim 250~\mbox{km}\)), while simultaneously using the resultant synthetically-approximated normal mode peaks to verify the initial peak selection. This procedure can be applied iteratively to produce a “cleaned-up” set of spectral peaks that are ultimately inverted for a “final” interior-structure model. To investigate the effect of three-dimensional (3D) structure on normal mode spectra, we constructed a 3D model of Mars that includes variations in surface and Moho topography and lateral variations in mantle structure and employed this model to compute full 3D waveforms. The resultant time series are converted to spectra and the inter-station variation hereof is compared to the variation in spectra computed using different 1D models. The comparison shows that 3D effects are less significant than the variation incurred by the difference in radial models, which suggests that our 1D approach represents an adequate approximation of the global average structure of Mars.     

The Scientific Measurement System of the Gravity Recovery and Interior Laboratory (GRAIL) Mission

The Gravity Recovery and Interior Laboratory (GRAIL) mission to the Moon utilized an integrated scientific measurement system comprised of flight, ground, mission, and data system elements in order to meet the end-to-end performance required to achieve its scientific objectives. Modeling and simulation efforts were carried out early in the mission that influenced and optimized the design, implementation, and testing of these elements. Because the two prime scientific observables, range between the two spacecraft and range rates between each spacecraft and ground stations, can be affected by the performance of any element of the mission, we treated every element as part of an extended science instrument, a science system. All simulations and modeling took into account the design and configuration of each element to compute the expected performance and error budgets. In the process, scientific requirements were converted to engineering specifications that became the primary drivers for development and testing. Extensive simulations demonstrated that the scientific objectives could in most cases be met with significant margin. Errors are grouped into dynamic or kinematic sources and the largest source of non-gravitational error comes from spacecraft thermal radiation. With all error models included, the baseline solution shows that estimation of the lunar gravity field is robust against both dynamic and kinematic errors and a nominal field of degree 300 or better could be achieved according to the scaled Kaula rule for the Moon. The core signature is more sensitive to modeling errors and can be recovered with a small margin.     

天基与地基测量数据融合技术在靶场的应用

随着GPS技术的发展,靶场的测控也在逐步由地基测控网过渡到天地结合的一体化综合测控网。如何将天基测量数据同靶场现有的高精度测量带测量数据融合处理,近年成为数据处理的热点话题。本文就某具体任务,对天基和地基测量数据融合技术的方法和工程应用作了详细介绍,给出了初步的结论,提出了天基测量数据在工程应用时应注意的问题和有待进一步分析的问题。     

The ARTEMIS Mission

The Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon??s Interaction with the Sun (ARTEMIS) mission is a spin-off from NASA??s Medium-class Explorer (MIDEX) mission THEMIS, a five identical micro-satellite (hereafter termed ??probe??) constellation in high altitude Earth-orbit since 17 February 2007. By repositioning two of the five THEMIS probes (P1 and P2) in coordinated, lunar equatorial orbits, at distances of ??55?C65 R _E geocentric (??1.1?C12 R _L selenocentric), ARTEMIS will perform the first systematic, two-point observations of the distant magnetotail, the solar wind, and the lunar space and planetary environment. The primary heliophysics science objectives of the mission are to study from such unprecedented vantage points and inter-probe separations how particles are accelerated at reconnection sites and shocks, and how turbulence develops and evolves in Earth??s magnetotail and in the solar wind. Additionally, the mission will determine the structure, formation, refilling, and downstream evolution of the lunar wake and explore particle acceleration processes within it. ARTEMIS??s orbits and instrumentation will also address key lunar planetary science objectives: the evolution of lunar exospheric and sputtered ions, the origin of electric fields contributing to dust charging and circulation, the structure of the lunar interior as inferred by electromagnetic sounding, and the lunar surface properties as revealed by studies of crustal magnetism. ARTEMIS is synergistic with concurrent NASA missions LRO and LADEE and the anticipated deployment of the International Lunar Network. It is expected to be a key element in the NASA Heliophysics Great Observatory and to play an important role in international plans for lunar exploration.     

The Education and Public Outreach Program for NASA��s Dawn Mission

The Dawn mission??s Education and Public Outreach (E/PO) program takes advantage of the length of the mission, an effort to maintain level funding, and the exceptional support of the science and engineering teams to create formal and informal educational materials that bring STEM content and modes of thinking to students of all ages. With materials that are based on researched pedagogical principles and aligned with science education standards, Dawn weaves together many aspects of the mission to engage students, teachers, and the general public. E/PO tells the story of the discovery of the asteroid belt, uncovers principles of physics behind the ion propulsion that powers the spacecraft, and explains what we can learn from the instrumentation and how the mission??s results will expand our understanding of the origins of the solar system. In this way, we not only educate and inform, we build anticipation and expectation in the general public for the spacecraft??s arrival at Vesta in 2011 and three years later at Ceres. This chapter discusses the organization, strategies, formative assessment and dissemination of these materials and activities, and includes a section on lessons learned.     

Future fighter fable: a day in the life of a future fighter-how dowe get there from here?

The intent of this tongue-in-cheek paper is to stimulate thought about technologies that may be included in future weapons systems and how the weapon system developer is impacted today. It explores a day in the life of a future generation fighter aircraft (year 2015-2025 time-frame). The scenario starts from the perspective of the ground crew awaiting the return of their future fighters: the new A/F-2, “Thunderchief II”-to a dispersed operations location (DOL) from a combat air patrol (CAP) mission in the fictitious country of Crad. A nonrestrictive technology view is assumed, tempered with as much realism as one can logically include in the scenario, with some of today's evolving technology thrusts     

Orbit Design for the THEMIS Mission

THEMIS, NASA’s fifth Medium Class Explorer (MIDEX) mission will monitor the onset and macro-scale evolution of magnetospheric substorms. It is a fleet of 5 small satellites (probes) measuring in situ the magnetospheric particles and fields while a network of 20 ground based observatories (GBOs) monitor auroral brightening over Northern America. Three inner probes (～1 day period, 10 R_E apogee) monitor current disruption and two outer probes (～2 day and ～4 day period, 20 R_E and 30 R_E apogees respectively) monitor lobe flux dissipation. In order to time and localize substorm onsets, THEMIS utilizes Sun–Earth aligned conjunctions between the probes when the ground-based observatories are on the nightside. To maintain high recurrence of conjunctions the outer orbits have to be actively adjusted during each observation season. Orbit maintenance is required to rearrange the inner probes for dayside observations and also inject the probes into their science orbits after near-simultaneous release from a common launch vehicle. We present an overview of the orbit strategy, which is primarily driven by the scientific goals of the mission but also represents a compromise between the probe thermal constraints and fuel capabilities. We outline the process of orbit design, describe the mission profile and explain how mission requirements are targeted and evaluated. Mission-specific tools, based on high-fidelity orbit prediction and common magnetospheric models, are also presented. The planning results have been verified by in-flight data from launch through the end of the first primary science seasons and have been used for mission adjustments subject to the early scientific results from the coast phase and first tail season.     

ARTEMIS Mission Design

The ARTEMIS mission takes two of the five THEMIS spacecraft beyond their prime mission objectives and reuses them to study the Moon and the lunar space environment. Although the spacecraft and fuel resources were tailored to space observations from Earth orbit, sufficient fuel margins, spacecraft capability, and operational flexibility were present that with a circuitous, ballistic, constrained-thrust trajectory, new scientific information could be gleaned from the instruments near the Moon and in lunar orbit. We discuss the challenges of ARTEMIS trajectory design and describe its current implementation to address both heliophysics and planetary science objectives. In particular, we explain the challenges imposed by the constraints of the orbiting hardware and describe the trajectory solutions found in prolonged ballistic flight paths that include multiple lunar approaches, lunar flybys, low-energy trajectory segments, lunar Lissajous orbits, and low-lunar-periapse orbits. We conclude with a discussion of the risks that we took to enable the development and implementation of ARTEMIS.     

人工智能在卫星任务规划中的应用

智能规划与调度是实现卫星自主规划其飞行任务的关键。将人工智能方法应用于卫星的任务规划,以执行对地观测任务为例,将任务规划问题归于组合优化问题,建立了相应的数学模型,并应用Hopfield神经网络算法进行求解,结果表明,该方法可用于单个仪器的任务规划。     

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     

Combined heat and power: how much carbon and energy canmanufacturers save?

In this paper we analyze the potential for CHP in US manufacturing. We use typical efficiencies of today's available CHP technologies to estimate the technical potential for the frozen technology case. We find that if manufacturers in 1994 had self-generated all their steam and electric needs with existing cost-effective CHP technologies, they could have reduced carbon equivalent (=12/44 carbon dioxide) emissions by up to 30 million metric tons of carbon (MtC) or nearly 20 percent, and energy use by nearly an Exajoule (EJ). With growth in manufacturing and expected improvements in CHP technologies, this technical potential could be much larger. However, without environmental regulatory reform and innovation-oriented utility restructuring policies, actual CHP installed by US manufacturers could fall far short     

X-33 redundancy management system

The X-33 is an unmanned advanced technology demonstrator with a mission to validate new technologies for the next generation of Reusable Launch Vehicles. Various system redundancies are designed in the X-33 to enhance the probability of successfully completing its mission in the event of faults and failures during flight. One such redundant system is the Vehicle and Mission Computer that controls the X-33 ea, and manages the avionics subsystems. Historically, redundancy management and applications such as flight control and vehicle management tended to be highly coupled. One of the technologies that the X-33 will demonstrate is the Redundancy Management System (RMS) that uncouples the applications from the redundancy management details, in the same way that real-time operating systems have uncoupled applications from task scheduling, communication and synchronization details     

Solar power system options for the Radiation and TechnologyDemonstration spacecraft

The Radiation and Technology Demonstration (RTD) Mission has the primary objective of demonstrating high-power (10 kilowatts) electric thruster technologies in Earth orbit. This paper discusses the conceptual design of the RTD spacecraft photovoltaic (PV) power system and mission performance analyses. These power system studies assessed multiple options for PV arrays, battery technologies and bus voltage levels. To quantify performance attributes of these power system options, a dedicated Fortran code was developed to predict power system performance and estimate system mass. The low-thrust mission trajectory was analyzed and important Earth orbital environments were modeled. Baseline power system design options are recommended on the basis of performance, mass and risk/complexity. Important findings from parametric studies are discussed and the resulting impacts to the spacecraft design and cost     

Realization of an optimized wing camber by using formvariable flap structures

According to market research predictions, a large growth in the number of passengers as well as airfreight volume can be expected for the civil transport aircraft industry. This will lead to an increased competition between aircraft manufacturers. To stay competitive it will be essential to improve the efficiency of new generation of aircraft. Transonic wings of civil aircraft with their fixed geometry offer an especially large potential for improvement. Such fixed geometry wings are optimized for only one design point, characterized by the following parameters: altitude, mach number and aircraft weight. Since these vary permanently during the mission of the aircraft the wing geometry is rarely optimal. As aerodynamic investigations have shown, one possibility to compensate for this major disadvantage lies in the chordwise and spanwise differential variation of the wing camber for mission duration. This paper describes the design of a flexible flap system for an adaptive wing to be used in civil transport aircraft that allows both a chordwise as well as a spanwise differential camber variation during flight. Since both lower and upper skins are flexed by active ribs, the camber variation is achieved with a smooth contour and without any additional gaps. This approach for varying the wing's camber is designed to be used for replacement and enhancement of a given flap system. In addition, the kinematics of the rib structure allows for adaptation of the profile contour to different types of aerodynamic and geometric requirements.