On the global geodetic observing system: Africa's preparedness and challenges

Space geodetic techniques and satellite missions play a crucial role in the determination and monitoring of geo-kinematics, Earth's rotation and gravity fields. These three pillars of geodesy provide the basis for determining the geodetic reference frames with high accuracy, spatial resolution and temporal stability. Space geodetic techniques have been used for the assessment of geo-hazards, anthropogenic hazards and in the design of early warning systems for hazard and disasters. In general, space geodesy provides products for Earth observation, science and influences many activities (e.g., building and management) in a modern society. In order to further promote the application of space geodetic methods to solving Earth science problems, the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) was commissioned as an important geodetic infrastructure that integrates different geodetic techniques (such as Global Navigation Satellite Systems, Very Long Baseline Interferometry, Satellite Laser Ranging, Interferometric Synthetic Aperture Radar and Doppler Orbitography and Radio-positioning Integrated by Satellite), models and analysis techniques for the purpose of ensuring long-term, precise monitoring of geodetic observables vital for monitoring Earth system processes. Since its inception, there has been considerable progress made towards setting up the infrastructure necessary for the establishment of the GGOS database. While the challenges that beleaguer the GGOS are acknowledged (at least at global level), the assessment of an attuned GGOS infrastructure in the African context is necessary, yet lacking. In the present contribution, (a) the African preparedness and response to the observing system is assessed, and (b) the specific scientific and technological challenges of establishing a regional GGOS hub for Africa are reviewed. Currently only South Africa has a fundamental geodetic observatory located at Hartebeesthoek, Pretoria. Other countries in Africa have shown interest to participate in global geodetic activities, in particular through interest in the development of a unified African geodetic reference frame (AFREF). In particular interest has been shown in the proposed African VLBI Network (AVN), which will be partially based on existing ex-telecommunication radio antennas. Several countries are investigating their participation in the AVN, including Kenya, Nigeria and Ghana.     

北斗三号短报文低轨卫星测控应用研究

针对低轨卫星星座测控管理的全球覆盖需求和测控链路资源需求,分析北斗三号全球导航系统短报文用于低轨卫星测控的基本能力,描述应用北斗三号全球短报文进行卫星测控的系统组成、工作流程及各部分功能,识别用于卫星测控管理的相关关键技术,并提出关键技术的初步解决途径,给出测控应用模式建议。     

The metric camera experiment on the first spacelab flight

In the first Spacelab Mission which will take place in Sept. Oct. 1983 a Metric Camera will be flown as part of the Earth observation payload. The camera will be a modified high quality Aerial Survey Camera.The hardware development is finished and the instrument is already integrated into Spacelab.The application of Metric Cameras in Space, an area which is neglected up to now, can effectively contribute to an improved cartographic coverage of the Earth. The Metric Camera Experiment is a first step to fill this gap which can be realized by utilizing the extended capacities of the Space Transportation System.The paper outlines the scientific objectives of the experiment, describes in detail the camera system and deals with the operation and control philosophy during the mission.     

How shall we live in space? Culture, law and ethics in spacefaring society

The US civilian space program is focused on planning for a new round of human missions beyond Earth orbit, to realize a ‘vision’ for exploration articulated by President George W. Bush. It is important to examine this ‘vision’ in the broader context of the global enterprise of 21st century space exploration. How will extending a human presence into the Solar System affect terrestrial society and culture? What legal, ethical and other value systems should govern human activities in space? This paper will describe the current environment for space policy making and possible frameworks for future space law, ethics and culture. It also proposes establishment of a World Space Conference to aid deliberations on the above.     

International coordination in the era of faster, better, cheaper

Space agencies around the world are seeking innovative approaches to reduce the time and expense of space-based activities, including observation of the Earth and acquisition of environmental data for Earth science research. As government budgets are squeezed, agencies search for innovative approaches to streamline program management, introduce new technology, and share costs with external partners. International cooperation has been a mainstay of Earth observation activity from the beginning of space exploration. It continues to be true that global problems require global solutions, and governments recognize the need to share the investment in understanding and monitoring the planet. Agencies need to carefully consider how changes in their program development and management practices might impact cooperative ventures. Improved communication, enhanced strategic planning, and coordinated rather than comprehensive missions are all tools agencies can use to maintain or improve partnerships.     

A parametric study of space transfer/upper propulsion stages

For Space Transportation System (i.e. Space Shuttle) launched satellites destined for a Geosynchronous Earth Orbit (GEO), there is a need for cost-effective, versatile propulsion systems to provide the perigee burn, i.e. to boost the satellite from Low Earth Orbit (LEO) to Geosynchronous Transfer Orbit (GTO). Surveys of commercial spacecraft activities and future GEO satellite requirements indicate that a spacecraft propulsion system that will provide the perigee burn for a broad range of future commercial satellites would have an excellent market potential.Parametric studies to investigate and define attractive perigee-burn upper propulsion systems (i.e. an Upper Propulsion Stage, or a UPS) are presented. The feasibility and payload capacilities that could be provided by a UPS assembled from essentially off-the-shelf components and subsystems, and the benefits that could be achieved by using major subsystems specifically tailored for the application are presented. The results indicate that attractive UPS configurations can be defined using either off-the-shelf or optimized major subsystems.     

Earth observation from space – The issue of environmental sustainability

Remote sensing scientists work under assumptions that should not be taken for granted and should, therefore, be challenged. These assumptions include the following:1. Space, especially Low Earth Orbit (LEO), will always be available to governmental and commercial space entities that launch Earth remote sensing missions.2. Space launches are benign with respect to environmental impacts.3. Minimization of Type 1 error, which provides increased confidence in the experimental outcome, is the best way to assess the significance of environmental change.4. Large-area remote sensing investigations, i.e. national, continental, global studies, are best done from space.5. National space missions should trump international, cooperative space missions to ensure national control and distribution of the data products.At best, all of these points are arguable, and in some cases, they're wrong. Development of observational space systems that are compatible with sustainability principles should be a primary concern when Earth remote sensing space systems are envisioned, designed, and launched. The discussion is based on the hypothesis that reducing the environmental impacts of the data acquisition step, which is at the very beginning of the information stream leading to decision and action, will enhance coherence in the information stream and strengthen the capacity of measurement processes to meet their stated functional goal, i.e. sustainable management of Earth resources. We suggest that unconventional points of view should be adopted and when appropriate, remedial measures considered that could help to reduce the environmental footprint of space remote sensing and of Earth observation and monitoring systems in general. This article discusses these five assumptions in the context of sustainable management of Earth's resources. Taking each assumption in turn, we find the following:(1) Space debris may limit access to Low Earth Orbit over the next decades.(2) Relatively speaking, given that they're rare event, space launches may be benign, but study is merited on upper stratospheric and exospheric layers given the chemical activity associated with rocket combustion by-products.(3) Minimization of Type II error should be considered in situations where minimization of Type I error greatly hampers or precludes our ability to correct the environmental condition being studied.(4) In certain situations, airborne collects may be less expensive and more environmentally benign, and comparative studies should be done to determine which path is wisest.(5) International cooperation and data sharing will reduce instrument and launch costs and mission redundancy. Given fiscal concerns of most of the major space agencies – e.g. NASA, ESA, CNES – it seems prudent to combine resources.     

Measuring performance: Moving NASA Earth science products into the mainstream user community

Demonstrating performance of the applications of Earth observation satellite-based science data products and services is increasingly a requirement of government research agencies. We present efforts from the NASA-funded Earth Observing System Data and Information System's Synergy Project to measure performance in the development of applications from NASA research and development projects. We summarize challenges in monitoring performance and share our experience in evolving metrics over a 5-year project life. We demonstrate how to adapt project management processes and metrics from the information technology (IT) industry to Earth observation applications research and development. A roadmap for adapting IT processes and developing metrics and examples of quantitative and qualitative metrics are provided. Our findings suggest that designing and implementing these IT metrics will enhance project success, as defined by the degree of penetration of NASA products into the user community and level of non-NASA funding secured.     

The biosphere 2 project and its potential role in assisting space exploration

Space Biospheres Ventures is developing technologies for its Biosphere 2 project — a 3 acre materially closed ecological system with human habitat, intensive agriculture and five wilderness biomes — and other life-support testbeds for space habitats in microgravity and the Moon and Mars, as well as for ecological research pertinent to the biosphere of Earth. These include soil bed reactors for air purification and biomass production; aquatic waste processing systems; real-time analytic systems; and computer systems of control and management. A space policy pursuing joint Earth and ‘space biospheres’ objectives and implications is discussed.     

Assuring the sustainability of space activities

The growth of new space systems and the continued creation of orbital debris could in a few years make activities in Earth orbit unsustainable, so finding cost-effective ways to sustain space activities in Earth orbit is essential. Because outer space activities serve the needs of the military–intelligence, civil, and commercial communities, each with their own requirements, creating the necessary international agreements for reaching and maintaining a condition of sustainability will not be easy. This paper summarizes the primary issues for the international space community regarding our future ability to reap the benefit of space systems in Earth orbit. It explores several of the efforts to develop international agreements that would lead to or support the sustainability of space activities and examines the benefits and drawbacks of each approach. In particular, it reviews progress within the UN COPUOS, and examines the EU's proposal for an international Code of Conduct for Outer Space Activities. It also notes the need for states to establish or expand their own space legal infrastructure to conform to the UN treaties and guidelines for space activities.     

Options for space — proposal for a programme

Because of the physical scale of human operations at present, we need to extend them into the Solar System for sustainability and into interstellar space for knowledge. Stabilizing the population on Earth, as well as reducing poverty, is vital, as is a more environmentally appropriate demographic transition than the historical one. Space assets can contribute most to strategic threats in areas like power and minerals and can also assist global education. Such public interest is important as education, but it is vital to remember that a certain level of precision in materials and engineering is needed before ideas become realizable. The crucial step is to turn the space environment to an open market and override the present government monopoly constraint. As a start, a Center for International Space Industrialization Research (CSIR) is to be set up as a model for the better understanding of the issues involved, thus making a case for strategic investment for space assets.     

Tropical Earth Resources Satellite: is the investment warranted?

All existing and planned Earth observation satellites have near-polar orbits (hence global coverage), but the Tropical Earth Resources Satellite (TERS) will have a true equatorial orbit at 1681 km. The TERS, conceived for the equatorial countries and Indonesia in particular, complements the existing and planned remote sensing satellites and will enable the monitoring of critical processes, such as food production, conservation of the national environment and land usage. The swath-width of the high resolution multispectral instrument can be pointed anywhere between latitude 10°N and 10°S, offering the tropical countries an opportunity to observe any part of their territory four times a day during daylight. A forward looking cloud sensor detects which areas are free of clouds and the pushbroom optical instrument will be pointed to specific clear areas. It is expected that the benefits of the monitoring capability warrant the investment in TERS.     

Space and the fate of humanity

Current growth and consumption rates on Earth cannot be sustained into the future. Space technology is already a vital tool in the management of the planet and we should look at it to mitigate some of the problems we face. However, this should not include colonization of interstellar space. Rather we should focus on using solar energy from space and on mining asteroids, both of which would be feasible if the Moon was developed as a space base and power station. The most difficult and expensive part of getting into space is escaping Earth's gravity - something that could be avoided once a presence was established on the Moon. A lunar base would also provide the obvious site from which to reach GEO, travel to Mars or back to Earth and, ultimately, to explore the further reaches of the Solar System.     

Analysis on coverage ability of BeiDou navigation satellite system for manned spacecraft

To investigate the service ability of the BeiDou Navigation Satellite System (BDS) for manned spacecraft, both the current regional and the future-planned global constellations of BDS are introduced and simulated. The orbital parameters of the International Space Station and China׳s Tiangong-1 spacelab are used to create the simulation scenario and evaluate the performance of the BDS constellations. The number of visible satellites and the position dilution (PDOP) of precision at the spacecraft-based receiver are evaluated. Simulation and analysis show quantitative results on the coverage ability and time percentages of both the current BDS regional and future global constellations for manned-space orbits which can be a guideline to the applications and mission design of BDS receivers on manned spacecraft.     

The UN and space — 1990 review

In its 44th session the United Nations passed resolutions endorsing International Space Year and the United Nations Conference on Environment and Development, both scheduled for 1992. Together they provide for global efforts to understand and protect the Earth and its environment. N. Jasentuliyana, Director of the Outer Space Affairs Division at the UN, outlines their significance.     

Advancing Earth observation from space: A global challenge

Global Earth observation goes well beyond taking pictures of the Earth from space. Earth observation aims to identify and characterize planetary-scale processes that occur in the Earth interior or the world's oceans, at the Earth's surface or within the global atmosphere, on the basis of weak signals that may be detected in space. This is a truly challenging task that requires the dedicated efforts of professionals and firm public support commitments. The article reveals the scope of global Earth observation, highlights the technical and managerial challenges involved in undertaking it and discusses ways of making it more effective. Competent international cooperation and cost-sharing arrangements are essential for the ultimate success of existing and future activities in this field.     

Canada and the International Space Station program: overview and status

The twelve months since IAF 2000 have been perhaps the most exciting, challenging and rewarding months for Canada since the beginning of our participation in the International Space Station program in 1984. The highlight was the successful launch, on-orbit check out, and the first operational use of Canadarm2, the Space Station Remote Manipulator System, between April and July 2001. The anomalies encountered and the solutions found to achieve this success are described in the paper. The paper describes, also, the substantial progress that has been made, during the twelve months since IAF 2000, by Canada as it continues to complete work on all flight-elements of its contribution to the International Space Station and as we transition into real-time Space Station operations support and Canadian utilization. Canada's contribution to the International Space Station is the Mobile Servicing System (MSS), the external robotic system that is key to the successful assembly of the Space Station, the maintenance of its external systems, astronaut EVA support, and the servicing of external science payloads. The MSS ground segment that supports MSS operations, training, sustaining engineering, and logistics activities is reaching maturity. The MSS Engineering Support Center and the MSS Sustaining Engineering Facility are providing real-time support for on-orbit operations, and a Canadian Payloads Telescience Operations Center is now in place. Mission Controllers, astronauts and cosmonauts from all Space Station Partners continue to receive training at the Canadian Space Agency. The Remote Multi Purpose Room, one element of the MSS Operations Complex, will be ready to assume backroom support in 2002. Canada has completed work on identifying its Space Station utilization activities for the period 2000 through 2004. Also during the past twelve months the CSA drafted and is proceeding with the approval of a Canadian Space Station Commercialization Policy. Canadian astronauts have now participated in three ISS assembly missions--Julie Payette on STS-96, Marc Garneau on STS-97, and Chris Hadfield on STS-100 in April 2001 during which he performed Canada's first EVA and the successful installation of the Space Station Remote Manipulator System.     

Designing nonuniform satellite systems for continuous global coverage using equatorial and polar circular orbits

We present a method for designing nonuniform satellite systems for continuous global coverage using a combination of equatorial and near-polar satellite segments in circular orbits. Equations are derived to determine the basic design parameters of the satellite system itself and the conditions of its closure at the joint of near-polar and equatorial segments. We analyze specific features of near-polar and equatorial satellite systems and their advantages and disadvantages compared with existing classes of near-polar phased and kinematically correct satellite systems. We estimate the minimum required number of spacecrafts in satellite systems for a given fold of coverage and present calculated dependences for classes of near-polar phased and equatorial satellite systems with different types of closure. For the class of kinematically correct satellite systems, we analyze the characteristics of systems with a minimum spacecraft flight height and reveal that the number of satellites in the orbital plane depends on the flight height for different folds of coverage. We bring examples of the best near-polar equatorial satellite systems of global coverage for different folds and a class of satellite systems with a fixed number of spacecrafts and orbital planes in them.     

Activities of the COSPAR Panel on Exploration supporting the Global Exploration Roadmap

The Global Exploration Roadmap (GER) is driven by several goals and objectives that include space science, the search for life as well as preparatory science activities to enable human space exploration. The Committee on Space Research (COSPAR), through its Commissions and Panels provides an international forum that supports and promotes space exploration worldwide. COSPAR's Panel on Exploration (PEX) investigates a stepwise approach of preparatory research on Earth and in Low Earth Orbit (LEO) to facilitate a future global space exploration program. We summarize recent activities and workshops of PEX in support of the GER.