effective mission operations within the general framework ... money and time), the system engineering process .... typing approach consists of an early and quick.
Acia Asrrortuurrca Vol 39. No. l-4. pp 61-70. lY96 Copynght t 1997 Elsewer Scxence Ltd Prmted m Great Britam All nghts reserved 0094-5765!96 $I 5 00 + 0 00 SOO94-5765(%)00123-3
Pergamon PII:
COST-EFFECTIVE
MISSION OPERATIONS
J. C. van der Ha European Space Agency - European Space Operations Centre Robert-Bosch-Str. 5,64293 Darmstadt, Germany
M. H. Marshall & J. A. Landshof The John Hopkins University - Applied Physics Laboratory John Hopkins Rd., Laurel, MD 20723, USA
system engineering process”*‘: this is a consequence of the drive for overall life-cycle cost-effectiveness which cuts all across traditional barriers between the various mission components such as mission design, spacecraft and payload design, ground segment, mission operations and data analyses.
Abstract The present paper identifies and evaluates the various methodologies for performing costeffective mission operations within the general framework of the ‘Faster. Cheaper, and Better’ paradigm. Emphasis is placed on the mission system engineering process which represents the overall context in which life-cycle costeflectiveness must be measured. The paper analyzes the mission system engineering process in which ground system &sign and mission operations are petformed and illustrates how the characteristics of that environment determine their costs. The most Hective cost-saving management and engineering methods with relevance to mission operations will be evaluated. Specific characteristics will be highlighted by reference to APL’s interplanetary mission NEAR launched on February 17.1996. Keywords: Mission operations, engineering, cost-effectiveness, NEAR Copyright
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1997 Elsevier
It must also be recalled that in actual practice all decisions affecting mission operations costs are finalized well before the satellite is launched and most of these decisions are made outside the realm of operations during the mission, spacecmft and payload design. Furthermore, these decisions are often made with little awareness of their impact on mission operations. In order to achieve maximum costeffectiveness, all components of a mission system architecture (shown in Figure I) over its mission life-cycle must be designed in concert within the mission system engineering process.
system Science
This process identifies and analyses design options and resource allocations over the complete mission life-cycle and across all mission components. The distribution of facilities and activities over the different mission components is a central part of the system engineering process. Within the constraints prescribed by the limited resources (in particular. money and time), the system engineering process must determine the most efficient use of the available resources for achieving the mission objectives while observing the mission system architecture as a whole.
Ltd
INTRODUCTION The objective of the present Paper is to identify,
evaluate and organize the various methodologies which arc available at present for conducting cost-effective mission operations. It is evident that operations cost reductions in themselves are counterproductive if they would result in larger spacecraft design costs. Mission operations must be considered as an integral part of the mission
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MISSION OBJECTIVES
MISSION DESIGN
Figure 1. Components of a Space Mission System Architecture
MISSION PROGRAMMATICS
EFFECTIYE SCHEDULE
EFFICIENT DOCUMENTATION
of RISKS *RApiD F+ROTO-_G
MISSION SYSTEM ENGINEERING
SYSTEM - LEVEL IN’ERACTIONS
Table 1. Programmatic Features for Cost-Effective Onerations
The challenge of cost-effective mission design and implementation may be formulated as follows: ‘to increase effectiveness by optimizing performance and minimbkg risks within the prescribed resource limits’. General and absolute statements on how much or how little operations should cost can not be made: costs are mainly determined by the type and objectives of a mission, by the experiences and culture of the mission management and operations center and by the risks one is prepared (or forced) to accept. Another important characteristic of costcffective mission system design refers to the implementation schedule. It has been demonstrated by the NEAB and Clementine
missions that interplanetary missions with focused and valuable objectives can be launched within an interval of little more than 2 years after project approval. A short implementation schedule has tremendous repercussions on the ‘way of working and perhaps presents an even greater challenge than low-cost on its own. It also provides many crucial advantages above the conventional longer schedules: for instance, it provides more frequent mission opportunities for the user community and more advanced technology for the spacecraft designers. Indeed, it is one of the most critical ingredients of the ‘Faster, Cheaper, and Better’ philosophy!
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PROGRAMMATIC COST REDUCTION METHODS Programmatics refers to the ‘context’ in which a space mission system is designed, developed, tested, launched, and operated. It includes many elements for potential cost reduction which by necessity are out of the hands of the space system developers and operators. The entries identified in Table 1 represent the essential elements of the mission programmatics which generate an environment in which cost-effectiveness can be achieved.
Short Imdementation
Schedule
A short implemenrarion schedule means that the time between mission approval and launch is not more than 2 to 3 years (for small interplanetary missions). Such a schedule can normally be achieved only when the payload instruments are already available. A short schedule is beneficial for the user as it enhances ‘mission turnaround’ and it provides significant advantages in terms of the potential use of advanced technology both on-board and on-ground. For instance, computer hardware may be purchased fairly early in the development cycle without fear of obsolescence at the time of launch. A short schedule is also an effective cost reducer since indeed ‘time is money’ and not only in the sense that the total staff cost is essentially proportional to the implementation period. It is also a fact that the work must proceed much more efficiently under a fixed short schedule: when there are many years of implementation phase, it becomes too tempting to engage in many of the typical time-filling ‘rituals’ such as extensive studies, design refmements, unwarranted perfectionism, excessive documentation, and frequent reviews. Furthermore, it is easier to maintain staff morale and continuity of expertise over a short period of time. However, it must be recognized that a short implementation schedule is an enormous challenge and has severe repercussions on all mission implementation activities. Finally, it should also be admitted that the achievement of a short schedule imposes a considerable burden on the engineering staff who are expected to perform at peak level during at least two years: the danger of staff bum-out must
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be taken seriously and all possible precautions should be adopted. 1. Focused Objectives. The term focused objectives refers to the clarity of ‘what needs to be done’ so that cost savings will result from avoiding the waste of effort involved in working on the wrong issues. It is important that every participant knows the objectives to be accomplished in order that all can ‘pull in the same direction’. It is crucial to have well-defined and unambiguous objectives from the beginning of the project: clear mission objectives and a mature payload are the key enabling factors for allowing system-level requirements to be fixed early. A realistic implementation concept with adequate cost and schedule margins should be prepared and agreed. A reasonable potential for de-scoping or relaxation of mission objectives and/or system design requirements should be kept in reserve in order to have the necessary flexibility when financial, schedule and/or technical problems are encountered. A relatively low number (perhaps up to 5 or 6) of payload instruments facilitates the system and operations design by limiting the number of simultaneous constraints to be taken into account. Mature instruments allow to have early and realistic baseline models for the required payload resources in terms of power, on-board and onground data handling requirements as well as telemetry and command interactions, etc. 2. Acceptance of Risks. The phrase acceptance of risks expresses the fact that satellites are designed and operated with full a priori knowledge that anomalies and failures may occur. These events should be accepted as part of an overall cost-effective strategy: the attempt at eliminating the last few remaining elements of risk in design and operations is extremely expensive and there is a law of diminishing return. Perfection is never achievable and an estimated mission reliability increase from 0.95 to 0.96 may not be cost-effective for most (unmanned) missions if disproportionate extra costs were to be required. Small teams also represent a risk due to the fact that every person in the team is essentially indispensable within the tight cost and schedule constraints. Although a somewhat increased risk of in-orbit failures induced by the unavoidable shortcuts in the design and operations concepts should be accepted, the identification and assessment of the available risks must not be abandoned.
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Responsible risk management should form an integral part of a cost-effective satellite design concept: the inherent risks should be evaluated before they are accepted or not as the outcome of a cost-benefit trade-off. Specific spacecraft autonomy characteristics (e.g., robust safe modes) should ensure satellite survival in case of on-board and on-ground anomalies. Finally, it should not be overlooked that many of the typical characteristics like a short low-cost implementation schedule, small and collocated teams, design simplicity and resource margins will in fact benefit the overall system reliability. 3. Rapid Proto-typing. A rapid prototyping approach consists of an early and quick implementation of a rough incomplete model representing the final product. This proto-type will subsequently be refined and completed in an iterated manner on the basis of the maturing requirements, the evolving system design baseline and the results of early stand-alone and interface tests. Conventional ‘waterfall’ approaches to system development are typically slow, cumbersome, and costly: Booch4 points out that they follow a ‘sacred, immutable process’ consisting of rigid definition, and sequential requirements specification development. preliminary design, detailed design, fabrication, and test phases. Each of these phases is usually driven by milestones based on deliveries from one team to another which enforces the ‘us against them’ attitude. Furthermore, the products of each phase are often ‘written in granite’ and serve as a costly-tochange input to the next phase. Rapid pro-typing methods are characterized by more tirne-effrcient and more flexible interactions between the various phases of a development cycle. They allow for a more natural incremental and iterated evolution in the requirements and design deli&ions resulting from intensive interactions between users and developers. Naturally, there are considerable risks in rapid proto-typing, but there is simply no alternative when faced with a two-year implementation schedule.
Effective & CornDetentTeams The presence of eficfive teams ensures that the effort concentrates on the right type of activities in addition to performing these in a capable
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manner. Knowledgeable and high-performance staff, with preferably previous project experience, should be recruited. A good strategy is to build up an in-house dedicated core team and to add the necessary specialized expertise by hiring external specialists whenever and for as long as needed. 1. Collocation of Teams. In order that the mission system engineering methodology can be executed in the most effective manner, it is essential that the design and operations teams (and preferably also representatives of the science or users team) are all integrated and collocated on a single site. This is crucial for generating the synergy required for effective system engineering. Collocation represents one of the key aspects of the NEAR mission implementation and operations at APL. The replacement of strictly formalized interfaces by more open communications leads to a faster and more effective flow of information. This also leads to an increase in mutual understanding without any of the traditional ‘us against them animosities. Collocation also offers natural training opportunities for operations staff in a cost-effective manner through participation in design and test activities. Finally, it is extremely beneficial to have the original design engineers collocated on the operations site after launch when contingencies develop. 2. Empowerment of Staff. Team members should be given the maximum possible empowerment meaning that decisional authority should be delegated down to the lowest possible level. A streamlined project organization has a minimum number of organizational baniers and a straightforward management structure in terms of hierarchy and reporting levels. This reduces overhead costs and is efficient as it helps to avoid or reduce misunderstandings and time delays. In this manner, the diffusion of responsibilities and accountabilities which is fairly common in large organizational structures may be eliminated. While project and program management do need adequate insight into the development and operations process, excessive reporting is counter-productive. 3. Efacient Team Interactions. The inherent complexity of a system is largely determined by the number and magnitude of the teams to be coordinated, especially if these are distributed over different organizations at various sites. Reductions in the complexity of an
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organizational structure in terms of the number and intensity of managerial and technical interfaces will be beneficial for the overall cost and reliability of the system. The important message here is that effective, efficient communications can best be established through team -to- team interfaces, rather than through the more typical team -to- management -to- team interfaces. Regular progress and coordination meetings also stimulate the necessary interactions within a team and serve as a means to inform all team members of the project status and the relevant on-going issues.
Mission
Svstem
Engineering
Perhaps the single most effective measure a project can take to lower the total cost of a space mission is to strongly endorse mission system it can only be implemented engineering: effectively through the full support of the project management. Someone ‘at the top’ must commit to deciding the allocation of resources between space mission elements based upon overall mission effectiveness criteria. Operations costs are strongly influenced by the degree to which operations considerations are taken into account in the design and development of the space system3. A spacecraft designed to be operable will be more reliable and will require fewer ground resources to operate. Effective design options should in general be preferred above optimal ones, since the latter are usually more time-consuming to define and more complex to implement for often just a marginal extra return. This is particularly true when attempting to design payload operational sequences under stringent resource constraints. ‘The better is the enemy of the good enough’ is a good maxim of low-cost design. 1. Concurrent Engineering. The simultaneous and interactive design and development of two or more parts of a system may be referred to as concurrent engineering. Communications between the teams involved must be intensive in order to be able to perform a meaningful concurrent engineering approach and to ensure that all points of view are given adequate attention. Cost effectiveness comes (indirectly) from the reduction in system complexity and from the enhancement of system reliability.
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single system engineer should have full responsibility for the mission system design and be able to initiate and resolve the relevant trades. In order that operational capabilities and constraints will receive the attention required, it is necessary that one or more experienced operations staff participate in the system design, implementation and test activities. In the case of NEAR, two out of the eight operations engineers worked directly with the spacecraft designers in order to enhance spacecraft operability and to document the spacecraft -to- ground system interfaces’. A
2. Efficient Documentation. There has been a clear tendency in large space missions for documentation to become an end in itself. What counts in the end, however, is the fact that the system itself is in good shape rather than the documentation. The growth in documentation is strongly related to the increasing management complexity of large space missions. Every management layer and every interface between two teams typically levies its documentation requirements, mainly as a ‘self-protection’ occur. mechanism in case problems Documentation should be written only in as far as it supports the design activities while requiring a minimum of engineering time. The decision on specific engineering the necessity of documentation should perhaps be left up to the engineering team leaders, not to program management. Documentation is useful for documenting and maintaining requirements and design baselines. As such it would follow the design process, rather than drive this process as would be the case in a traditional environment with strictly sequential development phases. It is crucial that documents should be kept as concise and as compact view-graph style as possible: documentation turns out to be very effective! It is also essential that spacecraft operations manuals (and also perhaps space-to-ground segment interface documents) are written by the operations staff in consultations with the design engineers. This is an extremely valuable training exercise and leads to a better product since design engineers are understandably not aware of and not interested in the specific operations point of view. 3. System-Level Trades. Design tradeoffs must be conducted at the system-level, consisting of spacecraft, payload, ground system
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and operations, rather than within one or two particular elements of the overall system’. Trades in system design and life-cycle costs, risks, reliability and operability should be performed as early as feasible during the mission design phase. All teams involved in the project should be represented in management coordination
missions
meetings and design reviews in order to be able to identify and execute the relevant trade-offs. Significant savings may be generated by systemlevel trades due to the fact that it allows to select the overall cost-optima1 system design solution rather than just a ‘parochial’ optimal one.
MISSION SYSTEM DESIGN
SPACECRAFT SYSTEM DESIGN
GROUND
SYSTEM
OPERATIONS CONCEPT
SKILLED TEAM .
RESOURCE MARGINS
OPERABILITY .
ON-BOARD AUTONOMY
OFF-THE- SHELF MULTI-MISSION INFBAsTBucTuBE ADHEBENCE to STANDARDS
ADVANCED TECHNOLOGY
TEST & OPERATIONS AUTOMATION
Table 2. Svstem Design Features for Achieving Low Life-Cvcle Cost
SYSTEM DESIGN COST REDUCTION METHODS Table 2 provides a summary of the three elements of the mission system design which are most relevant to operations costs: they form the environment for trade studies to be conducted during the life-cycle system engineering process.
SDacecraftSvstem Design The spacecraft system design represents a critical driver for operations costs. It is therefore important that operational capabilities and constraints are examined during the spacecraft design process as part of the system engineering process. The complexity of spacecraft operations control should be minimized: this refers to the number of tele-commands, number of states, number of conditional relationships, number of flight rules, and the frequency and lengths of station contacts. The complexity of ‘one-of-akind’ control functions like operations
commissioning, initializations and calibrations should he reduced as much as possible. Design. 1. Robust Spacecraft Spacecraft design robustness refers to the inherent flexibility, versatility and/or resilience of the spacecraft system design. Although this is largely an ‘intangible’ characteristic, it is extremely important, especially during and after in-orbit failures: the absence or presence of robustness may well be decisive for mission failure or success. Sometimes, relatively minor changes in spacecraft or instrument design can significantly simplify operations and thereby save costs. For example, attitude control, thermal and subsystem design robustness may power eliminate the need for complex maneuver sequence preparation and monitoring. 2. Resource Margins. Spacecraft resource marginsrefer to the reserves in the onboard resources during critical operations phases. This includes on-board power and thermal capabilities, data storage and throughput, RF signal strength, as well as processor memory and
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speed. During the design phase, adequate spacecraft resource margins are essential in providing ‘room’ for performing design tradeoffs. Sufficient resources should be available at all times during operations in order to avoid the introduction of complex constraints in the design of sequences. The provision of sufficient resource margins may allow the detailed management of the on-board resources to be eliminated or to be performed autonomously on-board. on-board Large memories and processor speeds will facilitate the use of complex on-board stored command sequences and the automation of instrument data collection sequences. Margins always enhance the flexibility in devising an operations concept and they increase the number of options available for implementation of the operations concept. Furthermore, margins in the on-board resources are extremely effective in reducing the probability that an anomaly occurs and may limit the resulting damage if one does occur. 3. Design for Operability. Spacecraft operability refers to the ‘ease’ with which it can be operated with savings generated through the implementation of a simpler operations concept. Operability is closely related to the availability of resource margins and design robustness but addresses different aspects, for instance, telemetry and tele-command interfaces and mode transitions. When operability issues are addressed early in the design process, they can normally be fulfilled at no or insignificant extra expenditure and lead to rather straightforward and sensible design choices. Too often, however, operability issues are ignored or relegated to the mission operations team in order to save spacecraft development costs. In fact, these trades should come naturally as part of the concurrent engineering process if the system engineering concept is taken seriously. After the spacecraft has been launched, the operability may be enhanced only to a very limited extent, i.e. by means of ground system and on-board software modifications. 4. On-Board Autonomy. When a spacecraft is able to perform certain operations functions on its own without direct support from ground, one refers to on-board autonomy. One of the prime objectives of the system engineering process is to design and develop spacecraft systems that require minimal operations support. Perhaps the most obvious way to reduce
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operations cost is to build a spacecraft that does not require any control from ground (but the corresponding complications in spacecraft design and their costs should not be ignored in a meaningful system design trade-off!). The degree of on-board autonomy to be implemented depends largely on the characteristics of a specific mission and should be determined through the system engineering process.
Ground
System Design
1. Re-Use of Existing Facilities. In order to save the resources required for the development and validation of a new mission (from control system, it is advantageous reliability and schedule points of view) to re-use existing software and hardware elements. In addition, a number of nice-to-have features may come along with the existing infrastructure at no extra cost. Existing capabilities, however, are not all cases: cost-efficient in necessarily maintenance and personnel costs associated with outdated and inefficient facilities can negate their advantage. A detailed analysis will also be necessary to determine whether the existing element in question indeed is capable of performing the required functions, whether the interfaces with other system elements are compatible. Usually, the main implementation challenge will be in the tailoring and integration of the various existing elements coming from different heritages into an effective working system and in the subsequent validation of the integrated system. 2. Commercial Off -TheShelf Elements. Commercial 08 -The- Shelf (COTS) hardware and software elements designate capabilities which can be purchased on the commercial market_ This option should always be examined for applicability on a cost-efficiency basis. In fact, it may be worthwhile to reformulate existing support requirements in order to adapt them to the available COTS capabilities. Alternatively, COTS elements may be adapted or tailored to the requirements at hand at a lower cost than new developments. In the case of the NEAR ground system, the core control system containing generic telemetry and tele-command functions and interfaces is an offthe-shelf system’. There are, however, a few major shortcomings of COTS systems:
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1. COTS elements for space mission applications are not like the shrink-wrapped products of the truly commercial (in particular, PC) marketplace. Also the efforts of customization for each application should be considered in the total cost.
staffing during test, launch, and mission operations. Two individual systems may be required in order to be able to support simultaneous pre-launch I & T and operations preparations.
2. Many capabilities that are required for operating a complex and unique space mission are often not found in the COTS offerings: straightforward telemetry, tracking, and control functions for a commercial communications satellite are significantly different from those for a unique planetary exploration mission with mission planning and command complex sequence development.
Spacecraft databases can readily be designed with the objective to be reused during the operations phase. Operations staff should actively participate in the spacecraft integration tests for familiarization and training purposes. In the case of the NEAR mission, the control system developed for spacecraft integration and testing served as a (separate) proto-type for the operations control system required after launch. After launch, the I & T system will be reconfigured as a backup operational system’.
3. Adherence to Standards. Standards ‘means of refer to commonly accepted implementation’. The use of standards reduces costs through the avoidance of superfIuous duplication of development efforts. Therefore, the use of standards has found widespread application in all major space agencies, in particular in multi-mission environments. As a prime example, the packet telemetry and telecommand data interface standards developed under the auspices of the Consultative Committee on Space Data Sranaizrds (CCSDS), which have proven to be extremely effective, may be mentioned. The CCSDS consists of telemetry and tele-command data transfer and processing experts from ESA, NASA, and NASDA. Standardization of on-board subsystems and interfaces (for instance, micro-processors and data interface buses) has also proven to be a favorable factor for spacecraft as well ground segment development costs. Standards should be adopted whenever they result in a more cost-effective implementation or when there is a potential need of cross-support. The potential use of standards for a particular project should be studied with care as incompatibilities may arise with specific existing or commercial off -the- shelf items. 4. Test & Operations CommonaWes. It is advantageous to build systems that achieve simplicity through the use of common architectures. Many spacecraft Integration and Test (I&T) functions are duplicated in the mission operations system and vice versa. Why should these capabilities be developed twice? The use of a common system design for mission operations and I&T saves resources not only in the design and development of the ground system, but also in training of personnel and
ODerations Concern There exist a number of cost saving features which can be implemented within the operations realm itself without affecting the rest of the system. Pre-launch development of ground segment facilities and operations processes, team build-up and training, and system testing are significant mission cost items. Analyses and trades of the available options should be performed during the operations concept development within the framework of the mission system engineering process. 1. Small & Skilled Team. The most significant post-launch cost item for most missions is personnel. Therefore, costeffectiveness requires the number of operations staff to be minim&d by building spacecraft and ground systems that require minimum support. Reductions in personnel may also be achieved merely by paying attention to the type and capabilities of staff hired and the changes in skills needed during different phases of the mission. As teams become smaller, the competence and scope of individual members becomes more important. Small teams can not afford to have members with specialized or limited skills; every team member must contribute significantly to the overall productivity of the team. Operations staff should preferably have a multi-disciplinary inclination. For maximum system-level effectiveness, they may be cross-trained to be able to perform any potential operations activity as well as associated administrative chores.
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Operators should be given a variety of related tasks, which keeps staff challenged and interested in the tasks they are performing and, if so required by the circumstances, allows them to transgress the boundaries of their direct responsibility. 2. Multi-Mission Infrastructure. The repeated use of a standard mission control infrastructure for a number of different missions is an obvious and common approach for implementing low-cost ground systems. There are significant of advantages in terms implementation effort, testing and operators training. A multi-mission environment usually provides a readily available common back-up control system which may be shared between a number of missions. Also staff may be re-used efficiently on sequential and even on parallel projects. It should also be mentioned, however, that the cost and schedule for a multi-mission control system implementation are in general significantly higher than those for a missiondedicated system. This is a consequence of the many ‘generic’ requirements which must be anticipated. Therefore, a sufficient number of missions should be available in order that the initial investments can be amortized. ESA’s operations center ESOC has systematically developed and maintained a multimission operations infrastructure: only three different control systems have been used in ESOC for the operations support of about 30 satellites over the past 20 years. Diverse missionspecific support requirements have in general been incorporated by more or less extensive tailoring of the baseline core system. 3. Advanced Technology Tools. Advanced fechndogy tools refer to the powerful capabilities of existing hardware and software facilities: these should be utilized whenever applicable by the operations staff in their monitoring, control, and assessment tasks. Operations costs can be reduced dramatically through enhancement of staff productivity. Any cost savings, however, must be traded off against the costs for development, validation and training involved with the installation and use of the tools. Present state-of-the-art software tools are well capable of providing immediate interpretations of large complex data sets and allow easy visualizations of spacecraft and other properties by means of graphics and mimic displays.
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Sophisticated software tools exist for high-level command preparations by the spacecraft analyst. Off-the-shelf database tools are extremely effective in handling large telemetry files and spacecraft databases. Animation facilities for visualization of spacecraft attitude motion have proven to be extremely valuable during spacecraft design as well as in preparing maneuvers during operations. 4. Ground System Automation. The term auromution refers to the automatic and unattended performance of operations tasks by on-ground hardware and software facilities. Automation of many routine and tedious planning and control functions is expected to become a promising means for reducing operations costs in the near future. Once this method has been demonstrated to be robust and reliable, significant savings will result from the reduction or elimination of operations staff, in particular outside normal work hours. While totally automated operations may in general not be feasible for complex scientific missions, routine planning and scheduling functions are often already automated to a large extent. The use of high-level command languages reduces operations control efforts, as do integrated databases, graphical user interfaces, and automatic report generation and transmission capabilities. In any case, however, automation should preferably be implemented only gradually over time and only after routine operational experience has been established for a particular mission. The next logical step in operations automation will consist of systems that autonomously receive, ~rrocess, interpret, and respond to spacecraft telemetry. Automated monitoring of telemetry may not only alert an operator to an out-of-bounds co.tdition, it may spawn a complicated process: for instance, it may advise the operator what to do (i.e., retrieve a contingency plan from a database), or even take limited action itself depending on the nature and severity of the anomaly. Spacecraft data trending and analysis can be highly automated, generating formatted reports and delivering them electronically to the correct parties at the appropriate times (e.g., at shift changes).
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CONCLUSIONS The main results and conclusions
of the work presented here may be summarized as follows: The importance of the mission system engineering process as the environment in which meaningful mission life-cycle costeffectiveness can be achieved has been emphasized and illustrated by examples. A systematic breakdown of the various existing concepts and methodologies for conducting cost-effective mission operations has been carried ous the two principal areas identified and studied are: a) programmatks which includes project management and the ‘cultural’ characteristics of the environment in which operations activities are performed ; b) mission system design which refers to the concurrent and interactive design of spacecraft, ground segment, and operations within the mission system engineering process. A number of specific experiences and recommendations which have been proven to be effective in actual missions have been presented and discussed in detail. The results presented may be expected to be useful when developing cost-effective operations concepts for future missions under severe cost and schedule constraints
REFERENCES 1.
Space Mission Analysis and Design, Second Edition, Edited by Larson, W.J. & Wertz, J.R., Microcosm, Inc. & Kluwer Academic Publishers, 1992.
2.
Reducing Space Mission Costs, Edited by J.R. Wertz & Larson, W.J., Microcosm, Inc. C Kluwer Academic Publishers, 1996.
3.
Ledbetter, K.W., ‘Mission Operations Costs for Scientific Spacecraft: The Revolution That is Needed’, Acta Astronautica, Vol. 35, 1995, pp. 465-473.
4.
Booth, G., Object Oriented Design with Applications, The Benjamin / Cummings Publishing Company, Inc., Redwood City, California, 199 1.
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5. Landshof, J.A., Harvey, R.J., & Marshall, M.H., ‘Concurrent Engineering: Spacecraft and Mission Operations System Design’, Third International Symposium on Space Mission Operations and Data Systems, NASA Conference Proceedings 328 1, Greenbelt, MD, November 15- 18, 1994, pp. 1391-1397. P. & Fatig, M., ‘Mission Ondrus, Second Engineering’, International Symposium on Space Mission Operations and Data Systems Proceedings, November 16-20, 1992, JPL 93-5. pp. 313-318. Marshall, M H., Cameron, G.E., & Landshof, J.A. &., ‘The NEAR Mission Operations System’, Acta Astronautica, Vol. 35, 1995, pp. 501-506.
