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About this book

This book includes a selection of 30 reviewed and enhanced manuscripts published during the 15th SpaceOps Conference held in May 2018 in Marseille, France. The selection was driven by their quality and relevance to the space operations community. The papers represent a cross-section of three main subject areas:

Mission Management – management tasks for designing, preparing and operating a particular mission Spacecraft Operations – preparation and implementation of all activities to operate a space vehicle (crewed and uncrewed) under all conditions Ground Operations – preparation, qualification, and operations of a mission dedicated ground segment and appropriate infrastructure including antennas, control centers, and communication means and interfaces

This book promotes the SpaceOps Committee’s mission to foster the technical interchange on all aspects of space mission operations and ground data systems while promoting and maintaining an international community of space operations experts.

Table of Contents

Frontmatter

Mission Design and Mission Management

Frontmatter

Implementing Next-Generation Relay Services at Mars in an International Relay Network

Nearly all data acquired by vehicles on the surface of Mars is returned to Earth via Mars orbiters—more than 1.7 TB so far. Successful communication between the various spacecraft is achieved via the careful implementation of internationally recognized CCSDS telecommunications protocols and the use of planning and coordination services provided by NASA’s Mars Program Office and the Multimission Ground Systems and Services (MGSS) Program at the Jet Propulsion Laboratory in Pasadena, CA. This modern Mars relay network has evolved since its inception in 2004 with the addition and loss of several missions, but it has fundamentally remained unchanged. Ground interfaces between the various spacecrafts’ mission operation centers on Earth remain largely unique for each participant; each mission maintains its own interfaces with deep-space communications networks (e.g., DSN, ESTRACK), which are similar but still unique; and relay sessions at Mars require careful ground planning, coordination, and implementation. This paper will discuss the existing architecture and consider how several technologies may be applied to the next generation of relay services at Mars. Ultimately, these are expected to lead to the implementation of a delay- and disruption-tolerant network at Mars, a precursor to becoming a major element in an emerging Solar System Internetwork. This chapter, which derives material from a paper the authors delivered at the SpaceOps 2018 conference [1], will discuss several of these pending technologies, which are predicted to be necessary for the next generation of relay activities at Mars.

Roy E. Gladden, Greg J. Kazz, Scott C. Burleigh, Daniel Wenkert, Charles D. Edwards

Space Mobile Network Concepts for Missions Beyond Low Earth Orbit

The space mobile network (SMN) is an architectural framework that will allow for quicker, more efficient and more easily available space communication services, providing user spacecraft with an experience similar to that of terrestrial mobile network users. While previous papers have described SMN concept using examples of users in low Earth orbit, the framework can also be applied beyond the near-Earth environment. This chapter details how SMN concepts such as user-initiated services, which will enable users to request access to high-performance link resources in response to real-time science or operational events, would be applied in and beyond the near-Earth regime. Specifically, this work explores the application of user-initiated services to direct-to-Earth (DTE), relay, and DTE/relay hybrid scenarios in near-Earth, lunar, martian, and other space regimes.

David J. Israel, Christopher J. Roberts, Robert M. Morgenstern, Jay L. Gao, Wallace S. Tai

Creating a NASA Deep Space Optical Communications System

We expect data rates from deep space missions to increase by approximately one order of magnitude per decade for the next 50 years. The first order of magnitude improvement will come from existing plans for radio frequency (RF) communications including enhancements to both spacecraft and Deep Space Network (DSN) facilities. The next two orders of magnitude are predicted to come from the introduction of deep space optical communications. Studies indicate that optical receive apertures of between 8 and 12 m are desired. The large cost of dedicated receive telescopes makes this method unrealistic—at least in the near-term. The cost of large optical ground terminals is driven primarily by the cost of the optics and by the cost of a stable structure for the telescope. We propose a novel hybrid design in which existing DSN 34 m beam waveguide (BWG) radio antennas can be modified to include an 8 m equivalent optical primary. By utilizing a low-cost segmented spherical mirror optical design, pioneered by the optical astronomical community, and by exploiting the already existing extremely stable large radio aperture structures in the DSN, we can minimize both of these cost drivers for implementing large optical communications ground terminals. Two collocated hybrid RF/optical antennas could be arrayed to synthesize the performance of an 11.3 m receive aperture to support more capable or more distant space missions or used separately to communicate with two optical spacecraft simultaneously. NASA is currently building six new 34 m BWG antennas in the DSN. The final two are planned to be built at the DSN Goldstone, California, and Canberra complexes. We are now investigating building these last two antennas as RF/optical hybrids. By delaying their operational dates by two years, we would be able to add the 8 m optical receive capability for these two antennas while fitting within existing budgetary constraints. This paper, which derives material from a paper the authors delivered at the SpaceOps 2018 conference [1], describes the hybrid antenna design, the technical challenges being addressed, and plan for using this concept, together with ongoing work on optical flight terminals, to infuse operation optical communications into deep space missions. All included figures are reproduced here with permission of the American Institute of Aeronautics and Astronautics (AIAA) the publishers of the transactions of SpaceOps.

Leslie J. Deutsch, Stephen M. Lichten, Daniel J. Hoppe, Anthony J. Russo, Donald M. Cornwell

Concept of Operations for the Gateway

NASA has outlined a phased approach to expand human presence deeper into the solar system starting with the Moon. Phase 1 of this plan begins in the 2020s with missions in cislunar space and assembly of the Gateway. The Gateway is an evolvable, flexible, and modular space platform in lunar orbit. It can support initial crewed missions of 30 days, with the potential to increase mission duration for later missions. When the Gateway is uncrewed, robotic science missions will be performed. The Gateway allows astronauts to practice the skills and test technologies needed for months and years beyond low Earth orbit. A key to success for these deep space missions will be carefully coordinated operations by ground support, flight crew, and autonomous spacecraft. Lockheed Martin Space is designing Gateway concepts as part of NASA’s NextSTEP study contract. Additional operational considerations will be made to accommodate science payloads that would use the Gateway as a communication relay, platform for in-space or remote robotic missions to the lunar surface, and remote experiments during untended periods. The Gateway is modular in design to incorporate international cargo and logistics modules, additional habitat modules, and perhaps crewed lunar landers. These operational considerations are also being designed into the system. Working through the operational practices and relationships between the crew and ground control at the Gateway will provide the groundwork for future missions to Mars requiring more autonomy, such as Mars Base Camp missions. For example, robotic operations on the lunar surface, conducted by scientist astronauts, are directly translated to the exploration of the Martian surface by rovers and unmanned aerial vehicles from a Mars orbital platform. As preparations are made for missions to Mars, more autonomy will be required and the interactions between the crew, ground, and autonomous spacecraft systems need to be refined.

Kathleen Coderre, Christine Edwards, Tim Cichan, Danielle Richey, Nathan Shupe, David Sabolish, Steven Ramm, Brent Perkes, Jerome Posey, William Pratt, Eileen Liu

Ariane 6 Launch System Operational Concept Main Drivers

The European launchers belonging to the Ariane and Vega families are leaders on the commercial launch services market, with demonstrated high reliability after a very lengthy run of successful flights. Ariane 6 is the next-generation heavy-lift European launch system in the Ariane family. It is being developed with the objectives of providing users with high mass lift-capability performance, mission versatility, operational flexibility, high launch rate and low launch service cost. The European Space Agency (ESA), in its role as Launch System Architect (LSA), is in charge of ensuring the coherence between the launcher and the launch base and of verifying the launch system performance to reach those objectives. With this goal, the Launch System Architect (ESA), the launcher prime (ArianeGroup) and the launch base prime (CNES) are working together on building up an optimised launch operations plan. The launch operations plan starts with the arrival at the launch range of the launcher elements and the spacecraft to be launched together with its support ground equipment. It ends with the post-flight analysis, the launch facilities’ revalidation and their reconfiguration for the following launch. To ensure that the above-mentioned challenging set of objectives is met, the launch preparation and launch operations concept (“Operational Concept” or CONOPS) will be designed taking the mission cost as the main driver and pursuing the same service quality and reliability as that provided by Ariane 5 today. Therefore, with a view to customer needs, the CONOPS is being constantly optimised to minimise waste. The optimisation of CONOPS is being done while complying with the safety requirements imposed by the applicable law and regulations which ultimately constitute a guarantee of operational system robustness. This paper presents the drivers established to build the Ariane 6 Operational Concept, the related trade-offs performed and the rationale for the selected choices. Lastly, some aspects of the preliminary operations plan resulting from the CONOPS exercise are compared with former Ariane operations plans to show differences and highlight improvements with respect to users’ expectations.

Pier Domenico Resta, Julio A. Monreal, Benoît Pouffary, Sonia Lemercier, Aline Decadi, Emilie Arnoud

LUMIO: An Autonomous CubeSat for Lunar Exploration

The Lunar Meteoroid Impact Observer (LUMIO) is one of the four projects selected within ESA’s SysNova competition to develop a small satellite for scientific and technology demonstration purposes to be deployed by a mothership around the Moon. The mission utilizes a 12U form-factor CubeSat which carries the LUMIO-Cam, an optical instrument capable of detecting light flashes in the visible spectrum to continuously monitor and process the meteoroids impacts. In this chapter, we will describe the mission concept and focus on the performance of a novel navigation concept using Moon images taken as byproduct of the LUMIO-Cam operations. This new approach will considerably limit the operations burden on ground, aiming at autonomous orbit-attitude navigation and control. Furthermore, an efficient and autonomous strategy for collection, processing, categorization, and storage of payload data is also described to cope with the limited contact time and downlink bandwidth. Since all communications have to go via a lunar orbiter, all commands and telemetry/data will have to be forwarded to/from the mothership. This will prevent quasi-real-time operations and will be the first time for CubeSats as they have never flown without a direct link to Earth. This chapter was derived from a paper the authors delivered at the SpaceOps 2018 conference [1].

Stefano Speretta, Angelo Cervone, Prem Sundaramoorthy, Ron Noomen, Samiksha Mestry, Ana Cipriano, Francesco Topputo, James Biggs, Pierluigi Di Lizia, Mauro Massari, Karthik V. Mani, Diogene A. Dei Tos, Simone Ceccherini, Vittorio Franzese, Anton Ivanov, Demetrio Labate, Leonardo Tommasi, Arnoud Jochemsen, Jānis Gailis, Roberto Furfaro, Vishnu Reddy, Johan Vennekens, Roger Walker

Use of Terrain-Based Analysis in Mission Design, Planning and Modeling of Operations of a Lunar Exploration Rover

The starting point for planning planetary surface exploration missions begins with deciding upon a landing site. TeamIndus, who participated in the Google Lunar XPRIZE (GLXP) competition to soft-land a Lander on the Moon, had to perform detailed studies on the terrain at the chosen landing area to ensure that the mission’s objectives were achievable. The main objectives of the mission were: (i) to achieve a stable and soft-landing of the Lunar Lander (HHK-1) and (ii) to operate a surface exploration Rover over a distance of at least 500 m with the Lander serving as a communication relay between earth and the Rover. Two aspects of terrain analysis are discussed in this chapter: (i) design inputs used for antenna design on the Lander and the Rover, and (ii) terrain and line-of-sight (LoS)-based reachability analysis to the 500-m periphery from touchdown coordinates carried out for the Rover and its use in path planning. Lunar Reconnaissance Orbiter (LRO)-Narrow-Angle Camera (NAC) SDNDTM data product served as the source dataset for this analysis. The results brought out firm recommendations to increase the antenna height on both the Lander and the Rover, and thereby extend the range of the Rover communication on the lunar surface. A global path planning (GPP) methodology incorporating the above analysis is laid out considering that the landing point is localized to within 20 m of known landmarks on the selenographic map constituted by LRO-NAC images of the landing area. This feature-based landmark map once overlaid on a derived LoS hazard map is used to perform a grid-based cost minimization for deriving waypoints for reaching a destination at 500 m from the Lander.

M. S. Menon, A. Kothandhapani, N. S. Sundaram, S. Nagaraj, A. Gopalan

The Evolution of Interface Specification for Spacecraft Command and Control

This paper describes an evolution from a traditional satellite commanding interface control document (ICD) to a service suite which provides real-time propagation and validation of interface changes. TEL handling, elucidation, modification, and investigation service (THEMIS) is the DigitalGlobe next-generation software suite which provides runtime validation of satellite tasking built by mission planning systems and spacecraft engineers. It enables more efficient management of multiple baselines and changes through the lifecycle of a constellation mission. Through THEMIS, developers, spacecraft engineers, and system engineers view, edit, and manage revisions of the spacecraft tasking interface. The interface specification is represented in JavaScript Object Notation (JSON) format and configuration management is provided through a GitHub repository. Once generated, the ICDs are used in real-time operations. This approach has reduced interface interpretation errors by having a single service able to validate commanding generated by multiple sources against any interface baseline.

Eric Brenner, Ron Bolton, Chris Ostrum, A. Marquis Gacy

Exploring the Benefits of a Model-Based Approach for Tests and Operational Procedures

Traditional practices to specify tests and procedures for satellite manufacturing activities rely on handwritten specification in Word or PDF documents, provided as inputs for validation and verification activities (V&V) such as on-board software validation, functional chain validation, and assembly, integration, and test validation. Several optimizations of the V&V process have already been identified, and new tools and practices are progressively deployed in operational projects, but with a limited impact on planning. In complement to these works, and based on a large background in model-based system engineering (MBSE), Thales Alenia Space has started to define a new approach to introduce more formalism in the test and procedure activities, especially using the open-source Capella modeling tool and its associated methodology, Arcadia. This work performed through R&D activities has allowed to highlight MBSE benefits and to define an end-to-end MBSE approach to handle tests and procedures specifications, which seems promising to reduce costs and planning for new spacecraft design and test activities.

R. de Ferluc, F. Bergomi, G. Garcia

The Power of High-Fidelity, Mission-Level Modeling and Simulation to Influence Spacecraft Design and Operability for Europa Clipper

NASA’s planned Europa Clipper mission seeks to assess the habitability of Jupiter’s moon Europa, which exhibits strong evidence of an ocean of liquid water underneath its icy crust. The sheer number of unique instruments, all of which require quiescent environments in order to operate, compounded with Jupiter’s distance from the Sun and Earth, makes this planned mission challenging and resource-constrained. High-fidelity, mission-level simulations that model the spacecraft, ground, and environment from launch to end of mission with a given trajectory and mission plan have been employed early in the project life cycle to better understand the interactions between various components of the mission and how design changes impact the entire system. These simulations have already resulted in tangible benefits to the project by providing vital input to key spacecraft trades, assessing impacts to operability, and quantifying how well the scientific objectives of the mission can be achieved. Improvements to simulation performance and to the process by which information defining the system is gathered and built into models used by simulations have the potential to further expand the scope of their use on Europa Clipper and future missions.

Eric W. Ferguson, Steve S. Wissler, Ben K. Bradley, Pierre F. Maldague, Jan M. Ludwinski, Chistopher R. Lawler

Attitude Control Optimization of a Two-CubeSat Virtual Telescope in a Highly Elliptical Orbit

This paper investigates a novel approach for attitude control of two satellites acting as a virtual telescope. The Virtual Telescope for X-Ray Observations (VTXO) is a mission exploiting two 6U CubeSats operating in a precision formation. The goal of the VTXO project is to develop a space-based, X-ray imaging telescope with high angular resolution precision. In this scheme, one CubeSat carries a diffractive lens and the other one carries an imaging device to support a focal length of 100 m. In this mission, the attitude control algorithms are required to keep the two spacecraft in alignment with the Crab Nebula observations. To meet this goal, the attitude measurements from the gyros and the star trackers are used in an extended Kalman filter, for a robust hybrid controller, and the energy and accuracy of attitude control are optimized for this mission using neural networks and multi-objective genetic algorithm.

Reza Pirayesh, Asal Naseri, Fernando Moreu, Steven Stochaj, Neerav Shah, John Krizmanic

Ground Systems and Networks

Frontmatter

The Cassini/Huygens Navigation Ground Data System: Design, Implementation, and Operations

The highly successful Cassini/Huygens mission conducted almost 20 years of scientific research in both its journey across the solar system and its 13-year reconnaissance of the Saturnian system. This operational effort was orchestrated by the Cassini/Huygens Spacecraft Navigation team on a network of computer systems that met a requirement for no more than two minutes of unplanned downtime a year (99.9995% availability). The work of spacecraft navigation involved rigorous requirements for accuracy and completeness carried out often under uncompromising critical time pressures and resulted from a complex interplay between several teams within the Cassini Project, conducted on the Ground Data System. To support the Navigation function, a fault-tolerant, secure, high-reliability/high-availability computational environment was necessary to support operations data processing. This paper discusses the design, implementation, re-implementation, and operation of the Navigation Ground Data System. Systems analysis and performance tuning based on a review of science goals and user consultation informed the initial launch and cruise configuration requirements, and then those requirements were subsequently upgraded for support of the demanding orbital tour of the Saturn System. Configuration management was integrated with fault-tolerant design and security engineering, according to cornerstone principles of Confidentiality, Integrity, and Availability, and strategic design approaches such as Defense in Depth, Least Privilege, and Vulnerability Removal. Included with this approach were security benchmarks and validation to meet strict confidence levels. The implementation of this computational environment incorporated a secure, modular system that met its reliability metrics and experienced almost no downtime throughout tour operations.

R. M. Beswick

Ground Enterprise Transformation at NESDIS

This paper describes major changes in the architecture and capability of the Ground Enterprise that operates and sustains the National Oceanic and Atmospheric Administration’s (NOAA’s) weather satellites. Operated by NOAA’s National Environmental Satellite Data and Information Service (NESDIS), the Ground Enterprise supports satellite systems in both polar and geosynchronous orbits. These include the legacy Polar Operational Environmental Satellite (POES) and Geostationary Operational Environmental Satellite (GOES) systems as well as the new Geostationary Operational Environmental Satellite Series R (GOES-R) and Joint Polar Satellite System (JPSS) systems. Additionally, NESDIS participates with domestic and international partners in satellite operations, product generation, and distribution involving a variety of platforms. Analysis over the last three years defined an evolved architecture for the Ground Enterprise that integrates its elements together for greater effectiveness and efficiency. Based on common services, the evolved architecture complements the strengths of the new GOES-R and JPSS ground systems with investments to modernize the remainder of the existing infrastructure and exploit new technologies. These changes will enable the Ground Enterprise to process and distribute new sources of data with greater agility, flexibility, and efficiency at reduced cost. They also provide economies of scale across the entire enterprise and enable more straightforward implementation of security measures. This paper describes the translation of the architecture analysis into time-phased investment plans. These plans address the migration to a set of enterprise algorithms based on common physics implementations, a modernized data archive potentially leveraging the cloud, shared product generation, and distribution services for more efficient operations, and a mission science network to promote greater collaboration across the science community. The paper also describes the status of initial investments in mission support tools.

Steven R. Petersen

CNES Mission Operations System Roadmap: Towards Rationalisation and Efficiency with ISIS

In the middle of the two thousand, CNES was operating around 15 space vehicles, using five different mission operations systems. The rationale was that each spacecraft type or product line had its own mission operations system, so as to have an optimised system for each kind of vehicle. This was leading to ‘local’ optima. This paper aims at showing how CNES has chosen to improve its global efficiency for mission operations system development and for spacecraft operations. In order to find a better development and operations cost optimisation, as well as an optimisation of the organisation of its space operations, CNES studied by about 2006 the development of a new mission operations system that must be usable for all the future missions operated at CNES. The decision to achieve this development was taken in 2010. This new system is developed in the frame of the CNES ISIS project (Initiative for Space Innovative Standard). The ISIS project aims at optimising the CNES space systems development by standardising for CNES missions the platforms together with the mission operations system. The payload and the payload operations and data system are out of the scope of the ISIS project as they are specific to each mission. ISIS only deals with the interfaces towards the payload world. The whole ISIS project is achieved in partnership with two spacecraft manufacturers: TAS (Thales Alenia Space) and ADS (Airbus Defence and Space). The new mission operations ground system is called LP CCC ISIS (French acronym for ISIS command control centre product line). The paper explains how the ISIS project was born at CNES, the rationale of the project, the area and mission types it covers and the objectives it follows in order to perfectly understand the context in which the LP CCC ISIS is being developed. The ISIS project description also gives the rationale for optimising the space systems development and unifying the operations concept at CNES. This project is designed as the follow-on of the successful CNES/TAS (Thales Alenia Space) mini-satellites product line called PROTEUS. The main PROTEUS concepts are recycled in ISIS and are completed with all the CNES, TAS and ADS past experience in various space systems development and operations. The paper shows the major role given to various CCSDS and ECSS standards in this process. The context being explained, the paper addresses then the objectives of the LP CCC ISIS (for instance better performances to anticipate the evolution of the space systems, more automation to reduce operations costs and securing at defence missions level). It also addresses the various foreseen uses of the LP CCC ISIS which are not limited to mission operations system but also cover, for instance, test bench for instrument and satellites AIT (assembly, integration and tests) or remote analysis toolbox for on-call operators. This is due to the will to optimise software developments in all fields connected with satellites monitoring and control. Thereafter are described the main concepts on which the LP CCC ISIS relies and how they help fulfil the various objectives assigned to this new product. The main topic here is about service-oriented architecture (SOA), CCSDS Mission Operation standard and splitting of the software into components. This is completed with a high-level technical description of the LP CCC ISIS, showing all the functions covered by the software, how they are organised and what is to be done when the LP CCC ISIS is to be adapted to a new mission. The industrial organisation for development and integration/qualification phases will be described. This will highlight the expected benefits from this new product line. For instance, it will be shown how different systems for different uses can be built from the LP CCC ISIS components or the advantages of using the LP CCC ISIS software in various contexts and not only in mission operations system. The paper will give an overview of the development planning and of client missions at CNES for the LP CCC ISIS. A first evaluation of the benefits those missions have seen by using the ISIS standard and the LP CCC ISIS will be exposed, considering that CNES is only in assembly and tests phase as the first launch has not yet been achieved. The paper touches on the links with the European Ground System Common Core (EGS-CC) initiative. EGS-CC fulfils similar objectives and thus exchanges have taken place between the two initiatives. CNES is a member from the beginning of the EGS-CC steering board and of the EGS-CC system engineering team.

Paul Gélie, Helene Pasquier, Yves Labrune

Return Link Service Provider (RLSP) Acknowledgement Service to Confirm the Detection and Localization of the SAR Galileo Alerts

The French Space Agency, CNES, has contributed to the international Cospas/Sarsat program since its creation in 1982. This program is a cooperation of 43 states and agencies committed to detecting and locating radio beacons activated by persons, aircraft or vessels in distress. Within this consortium, the return link service provider, RLSP, will be the facility responsible for the establishment of the return link messages and their coordination with the Galileo system, interfacing on one side with the Cospas/Sarcat system and on the other side with the Galileo Ground Mission Segment (GMS). The first version of the RLSP will enable the return link service provision including the acknowledgement service separated into two types: Type1—system acknowledgement (Galileo sends message automatically when the alert has been received and located), Type 2—rescue coordination centres (RCC) acknowledgement (RLSP transmits the message after authorization from the responsible RCC). Through the acknowledgement service provision, the RLSP will play a very important role in the Cospas/Sarsat network, because for the first time ever, it will be possible to send feedback messages to the beacons that sent a distress, thus completing the cycle with the beacons. Considering these functionalities and interfaces to put in place with Galileo and Cospas/Sarsat networks, the European Commission entrusted the CNES in order to manage the development of the whole system and also to operate the RLSP with high levels of objectives. After a brief recall of the RLSP functions and Cospas/Sarsat system, this paper will present the numerous technologies and methods put in place to guarantee the performances and the high availability of the system (99.95%) in order to ensure operations on a 7 d/24 h basis. The infrastructure and COTS used or developed to design the RLSP functionalities will be described. Design concepts such as redundancy, scalability, virtualization, real time/non-real time, the database and the Web server will be detailed. The paper will highlight the integration of all these components and their interfaces with external entities. The GMS communicates through a ciphered network, the Cospas/Sarsat network via a VPN, and the rescue coordination centres using the Internet. More than 250 RCC across the world will connect to the RLSP website to acknowledge distress beacons. By consequence, the architecture is a key to the success of this project. A security tradeoff involving national and international actors was made between the architecture and security measures so that the RLSP can be connected to both a closed secured environment such as Galileo, and also to the outside world via the Internet. The main outcomes of this tradeoff will be exposed in article and presentation. This paper will demonstrate how the CNES concepts of operations, with the RLSP, will address the European Commission’s high-level objectives mentioned here above which makes the RLSP state-of-the-art in modern technology. Finally, the paper will conclude with some important lessons learned from the accreditation, integration and qualification phases and the first months in operations of this system.

M. Fontanier, H. Ruiz, C. Scaleggi

Automated Techniques for Routine Monitoring and Contingency Detection of LEO Spacecraft Operations

The flight control teams of two low Earth orbit missions at EUMETSAT present an overview of the automated tools and methodologies being used to analyse and report on spacecraft health including trend analysis, data mining and outlier detection. A qualitative analysis of the techniques is provided based on in-flight experience, and proposals for future development of such toolsets are presented. This paper focuses on the experiences of the Copernicus Sentinel-3 and EPS MetOp flight control teams in using the EUMETSAT CHART framework, which allows engineers to define automated reports and perform ad hoc analysis on large data sets with multiple input sources. Arguments are also presented regarding whether or not it may be appropriate for future missions to consider applying some of these techniques directly on-board as an extension of the currently in-place FDIR mechanisms.

Ed Trollope, Richard Dyer, Tiago Francisco, James Miller, Mauro Pagan Griso, Alessandro Argemandy

The Added Value of Advanced Feature Engineering and Selection for Machine Learning Models in Spacecraft Behavior Prediction

This paper describes the approach of one of the top ranked prediction models at the Mars Express Power Challenge. Advanced feature engineering methods and information mining from the Mars Express Orbiter open data constitute an important step during which domain knowledge is incorporated. The available data describes the thermal subsystem power consumption and the operational context of the Mars Express Orbiter. The power produced by the solar panels and the one consumed by the orbiter’s platform are well known by operators, as opposed to the power consumption of the thermal subsystem which reacts to keep subsystems at a given range of working temperatures. The residual power is then used for scientific observation. This paper presents an iterative and interactive pipeline framework which uses machine learning to predict, with more accuracy, the thermal power consumption. The prediction model, along with the estimation of the thermal power consumption, also provides insight into the effect of the context which could help operators to exploit spacecraft resources, thereby prolonged mission life.

Ying Gu, Gagan Manjunatha Gowda, Praveen Kumar Jayanna, Redouane Boumghar, Luke Lucas, Ansgar Bernardi, Andreas Dengel

The EnMAP Mission Planning System

The Environmental Monitoring and Analysis Program mission (EnMAP) is a German hyperspectral Earth observation mission, currently scheduled for launch in 2020. The EnMAP Mission Planning System (MPS), developed and operated by the German Space Operations Center (GSOC), is one of the 15 subsystems constituting the EnMAP ground segment. Its main task is to compile and maintain a conflict-free timeline for routine operations that does not violate any constraints of the spacecraft (e.g. regarding power or onboard memory); this timeline will regularly be commanded to the spacecraft. This paper gives an overview of the current EnMAP MPS design, including the special requirements of the EnMAP mission, the components of the MPS and its most important external interfaces. The design of the EnMAP MPS largely builds on our experience gathered during the TerraSAR-X/TanDEM-X mission and has been developed further. Novel technologies include the Reactive Planning Framework, which particularly stands out due to its high responsiveness to user input. Particular attention is furthermore paid to the inclusion of cloud coverage and sunglint information into the planning process—two challenges which are specific to EnMAP observing in the optical and near-infrared part of the spectrum.

Thomas Fruth, Christoph Lenzen, Elke Gross, Falk Mrowka

Recommendations Emerging from an Analysis of NASA’s Deep Space Communications Capacity

During 2016–2017, NASA’s Space Communications and Navigation (SCaN) Office chartered a study of Deep Space Network (DSN) communications capacity relative to projected future mission demand over the next 30 years. In this paper, an expanded version of the one presented at SpaceOps 2018, we briefly describe the methodology used to analyze capacity versus demand over such a broad timeframe, summarize key findings emerging from the analysis, and discuss the associated recommendations [1]. Performing the analysis entailed: identifying key factors shaping the anticipated future mission set, identifying several alternative future mission set scenarios consistent with these factors, and then analyzing each mission set scenario in terms of required antenna capacity, downlink and uplink capabilities, and spectrum as a function of time. On the basis of these aggregate requirements, DSN loading simulations were then conducted that examined how well each of the postulated mission sets could load up onto the DSN’s “in-plan” architecture. To the extent that capacity shortfalls emerged during these baseline simulations, architectural solutions to the shortfalls were then postulated and tested via additional simulations. In general, the trend analyses and baseline loading simulations indicated a significant progression in challenges over the next three decades. In the current decade, the DSN appeared to be operating very close to capacity. The first projected human exploration mission and its secondary payload launch opportunities for cubeSats traveling beyond GEO contributed to this loading. As a consequence, the main challenge appeared to be managing peak asset contention periods. In the next decade, the DSN continued to operate close to capacity but also began transitioning to more frequent human mission support. Upgrading for, and operating, a human-rated system while continuing to meet robotic mission customer requirements emerged as the key challenge. In the 2030s and beyond, simulations suggested a need for fundamentally new capability and capacity. The high data rates and long link distances characteristic of human Mars exploration drove requirements far beyond what is currently “in-plan.” The key challenge then became determining the most cost-effective combination of RF and optical assets for communicating with the postulated human Mars assets while still providing for the needs of all the other missions across the solar system. Various link budgets, visibility, and loading analyses ultimately suggested that the human Mars exploration demands of the 2030s could best be addressed with two cross-linked RF-optical areostationary relays (or an areostationary relay and deep space habitat) providing a dual “trunk link” to an array of 2-to-3 additional 34 m beam waveguide antennas and an ~8.5 m optical antenna at each DSN Complex. The dual “trunk link” would enable the same amount of total data return to Earth as a single trunk link at twice the data rate, but with only half the required array size on the ground, assuming use of Multiple Spacecraft Per Antenna (MSPA) techniques. MSPA techniques, including a Multiple Uplink Per Antenna (MUPA) technique currently under investigation, also showed promise for reducing asset contention in the decades prior to human Mars exploration.

Douglas S. Abraham, Bruce E. MacNeal, David P. Heckman, Yijiang Chen, Janet P. Wu, Kristy Tran, Andrew Kwok, Carlyn-Ann Lee

Statistical Methods for Outlier Detection in Space Telemetries

Satellites monitoring is an important task to prevent the failure of satellites. For this purpose, a large number of time series are analyzed in order to detect anomalies. In this paper, we provide a review of such analysis focusing on methods that rely on features extraction. In particular, we set up features based on fixed functional bases (Fourier, wavelets, kernel bases...) and databased bases (PCA, KPCA). The outlier detection methods we apply on those features can be distance- or density-based. Those algorithms will be tested on real telemetry data.

Clémentine Barreyre, Loic Boussouf, Bertrand Cabon, Béatrice Laurent, Jean-Michel Loubes

Mission Execution

Frontmatter

In-Orbit Experience of the Gaia and LISA Pathfinder Cold Gas Micro-propulsion Systems

This paper presents in-flight experience of the cold gas micro-propulsion systems (MPS) used on-board the Gaia and LISA Pathfinder spacecraft. Gaia is an ESA Science cornerstone mission which is tasked with mapping one billion stars in the Milky Way to unprecedented precision. It is also expected to discover and chart 100,000’s of new objects including near-earth asteroids, exoplanets, brown dwarfs and quasars. The Gaia spacecraft was designed and built by Airbus Defence and Space. After a flawless launch on 19 Dec 2013, it was brought the circa 1.5 million km into L2 via a Soyuz Fregat burn. Additional delta-V was realized via a sequence of technically demanding orbit transfer manoeuvres using on-board chemical thrusters in thrust vectoring mode. Since early 2014, Gaia has been operating in a halo orbit around the second Sun-Earth Lagrange point that provides the stable thermal environment without Earth eclipses needed for the payload to function accurately. Starting in parallel to this and lasting six months, the spacecraft was fully commissioned and brought gradually up to the highest operational mode. The unique rate stability requirements for Gaia’s science mode (the standard deviation of its rate error is equivalent to one rotation every 420 years) lead to a high number of bespoke units, including a 106 CDD focal plane assembly, telescope-in-the-loop AOCS control and a cold gas micro-propulsion system which was developed by Thales Alenia Space Italia (TAS-I) and Leonardo Company. Continuously compensating for the solar radiation pressure torque in order to maintain an undisturbed scanning-law of the celestial sphere, a 3-year data set of MPS housekeeping telemetry was collected that offers the unique opportunity to characterize long-term performance of this novel fine pointing actuation system (thrust range 1 μN to 1000 μN at 0.1 μN resolution) in thermally stable conditions. Planned disturbances such as station keeping manoeuvres using coarse chemical propulsion as well as unplanned disturbances due to environmental effects such as micro-meteoroid impact also help characterize the cold gas system performance under stress due to sudden increase in thrust demand. LISA Pathfinder (LPF) is an ESA mission that demonstrates technologies needed for a planned ESA gravitational wave observatory. The LPF spacecraft, designed and built by Airbus Defence and Space, places two test masses in a nearly perfect gravitational free-fall, and controls and measures their relative motion with unprecedented accuracy. The laser interferometer measures the relative position and orientation of the masses to an accuracy of less than 0.01 nanometres, a technology shown to be sensitive enough to detect gravitational waves by the planned follow-on ESA mission, the Laser Interferometer Space Antenna (LISA). Launched on 03 Dec 2015, LPF reached its operational orbit around L1 in early 2016 where it underwent payload commissioning. The same MPS used by Gaia was selected for LPF fine attitude control to realize the extremely accurate free-fall trajectory of its test masses. After reaching the destination orbit, the propulsion module was separated. Since this point, the MPS was also the main actuator for station keeping manoeuvres where the cold gas thrusters are operated in “open-loop” realizing demanded forces. Approaching its nominal end of mission lifetime, LPF carried out dedicated test operations to characterize MPS performance under non-nominal conditions. The aim of this paper is to present the in-flight results that have been derived from post-processing of the Gaia and LPF housekeeping telemetry archives in terms of micro-thruster performances. MPS off-nominal events that have been encountered in-flight on individual or both spacecraft will be presented as well as mitigation actions that have been put in place to restore nominal conditions.

Jonas Marie, Federico Cordero, David Milligan, Eric Ecale, Philippe Tatry

The Cassini Mission: Reconstructing Thirteen Years of the Most Complex Gravity-Assist Trajectory Flown to Date

Cassini launched in 1997 and completed its prime mission, its Equinox first extended mission, and its Solstice second extended mission. Since its arrival at Saturn in 2004, Cassini completed almost 300 orbits around the planet. Over the span of the mission, significant improvements were made to all the major satellites ephemeris and to Saturn gravitational and pole models. These improvements have enabled better trajectory reconstructions throughout the timeframe of the mission, although using about one hundred different models of the Saturn system. Now that the mission is over, the paper reports on the uniform reconstruction of the entire Cassini orbital mission, which uses one consistent Saturn system model and satellite ephemerides throughout. We discuss the challenges of undertaking this task and comparison strategies for choosing the best and greatest Cassini trajectory for its very final delivery.

Julie Bellerose, Duane Roth, Zahi Tarzi, Sean Wagner

Resurrecting NEOSSat: How Innovative Flight Software Saved Canada’s Space Telescope

After on-orbit failure of its magnetometer and all torque rods, the NEOSSat microsatellite has recovered operations through the use of novel attitude determination and control algorithms. Attitude determination without the magnetometer was restored through the creation of a new attitude sensor from onboard GPS sensors. Desaturation without the torque rods was achieved through an innovative new control mode to orient the satellite’s internal residual dipole for optimal momentum dumping. Now operational based on a minimal sensor and actuator suite, NEOSSat has regained the performance necessary to accomplish its space surveillance missions with only a modest duty cycle reduction and adjustments to spacecraft operation planning. This paper, summarizing the NEOSSat mission and the unique flight software upgrades that enabled its recovery, expands the body of knowledge in GPS-based attitude determination and momentum management strategies for satellites.

Viqar Abbasi, Natasha Jackson, Michel Doyon, Ron Wessels, Pooya Sekhavat, Matthew Cannata, Ross Gillett, Stuart Eagleson

New Ways to Fly an Old Spacecraft: Enabling Further Discoveries with Kepler’s K2 Mission

The Kepler spacecraft revolutionized the field of exoplanet discovery during its prime mission and expanded upon that with its K2 extended mission following the failure of a second reaction wheel. While the K2 mission demonstrated that the Kepler spacecraft was still able to perform high-resolution photometry and find exoplanets, there were still many challenges to be faced from aging hardware, the increasing distance from the Earth and the desire to make the mission last as long as possible. This paper, which derives material from a paper the authors delivered at the SpaceOps 2018 conference [1], will review several examples of these challenges, the solutions that were devised and their outcomes with regard to improving performance, extending the mission lifetime, and demonstrating the cost-effectiveness of a small mission operations team.

K. A. Larson, K. M. McCalmont-Everton, C. A. Peterson, S. E. Ross, J. Troeltzsch, D. Wiemer

Incorporating Lessons Learned from Past Missions for InSight Activity Planning and Sequencing

The NASA’s InSight mission will place a lander on Mars in November 2018. During the first 90 days after landing on Mars, InSight will deploy two primary instruments on the surface: a seismometer and a heat probe. InSight will be operated daily at the Jet Propulsion Laboratory (JPL) during this time with a strict tactical timeline of 10 h. To support this rapid turnaround, significant automation is being developed to decrease human effort and increase operational efficiency. During tactical operations, science planning on InSight will be performed using the JPL APGen planning software, along with a novel Graphical User Interface (GUI) developed specifically for InSight, SPImaster. Every JPL mission invariably develops its own software for surface operations. This results in missions with smaller development budgets, such as the Phoenix lander mission, developing or utilizing operations software which is difficult to work with, resulting in issues during the lifetime of the mission. Fortunately, InSight has taken a more multi-mission approach in the development of the operations software and has been able to create software with all of the necessary features found on larger Flagship missions, at a fraction of the cost. The project has been able to do this by investing in multi-mission software tools and sharing code with other missions, such as the Europa Clipper project. Building off of the lessons learned from the Phoenix lander, Mars Science Laboratory (MSL), and Mars Exploration Rover (MER) missions, InSight developed a multi-mission system design, from which both small and large projects can learn. This paper, which derives material from a paper the authors delivered at the SpaceOps 2018 conference (Ridenhour et al. in 2018 SpaceOps Conference, SpaceOps Conferences (AIAA 2018-2552), 2018 [1]), describes the InSight planning software and compares its use to planning software developed for the MSL, MER, and Phoenix missions. All included figures are reproduced here with the permission of the American Institute of Aeronautics and Astronautics (AIAA), the publishers of the transactions of SpaceOps.

Forrest Ridenhour, C. Lawler, K. Roffo, M. Smith, S. Wissler, P. Maldague

Mars Aerobraking Operations for ExoMars TGO: A Flight Dynamics Perspective

This paper aims at giving a flight dynamics perspective on ExoMars Trace Gas Orbiter aerobraking operations, discussing the main challenges for both navigation and spacecraft commanding, describing the work-flow of activities within an operation cycle and presenting some results from the successful campaign, together with the most important lessons learnt.

F. Castellini, G. Bellei, B. Godard

Operations Design, Test and In-Flight Experience of the Sentinels Optical Communications Payload (OCP)

The Copernicus Sentinel-1 and Sentinel-2 Earth Observation missions are the first in history to use a LEO to GEO optical communications (i.e. laser) link to routinely downlink stored science data to the ground. The start of routine operations with EDRS A has represented a major milestone for both of the Sentinels missions and is the culmination of more than two years of intense and sustained operational validation activities by the FCTs. This chapter provides a summary of validation and test activities that have been performed during the Sentinel-1 and 2 satellite commissioning, then with Alphasat and finally with EDRS A, to achieve the current operational state. This chapter also describes how the OCPs are accommodated on the Sentinel-1 and Sentinel-2 satellites and the on-board services each OCP requires. The basic principles of how the OCPs on the LEO and GEO spacecraft establish a communications link with each other are also described. Each Sentinel spacecraft executes between 9 and 12 OCP communications links per day. The timing of these links is scheduled by the Sentinels Payload Data Ground Segment (PDGS) with the EDRS A service provider. The PDGS provides the link timing information to the Sentinels Flight Operations Segment (FOS) at ESOC where the Sentinels Mission Planning System has a dedicated function that is used to determine the necessary telecommand parameters for uplink and execution. We will describe the end-to-end link planning concept and process, highlighting the data exchange interfaces and will explain what telecommand parameters the OCP requires to execute a link and how they are calculated. The start of routine OCP operations with EDRS A has also introduced an extra level of operational complexity into the daily operations working practice of both Sentinel-1 and 2. Next, we will describe the impact of the routine OCP operations on the following operational areas; mission planning operations; orbit maintenance operations; collision avoidance operations; anomaly recovery operations; general operations working practice. The chapter will also focus on the operation lessons learned. We will also summarize the benefits to each mission of optical communications, showing how the use of optical communications, together with X-band ground station downlinks, has been used to maximize the data output of the missions. Finally, we will describe how the OCPs will be used in the future on both Sentinel-1 and Sentinel-2.

I. Shurmer, F. Marchese, J. Morales

Ant-Based Mission Planning for Constellations: A Generic Framework Applied to EO and Data Relay Missions

The earth observation market is growing rapidly, along with the missions’ complexity. Therefore, automated mission planning systems are being designed, allowing for operators to simply specify their intentions on a high level. In this paper, we propose an automated mission planning system based on the ants' foraging mechanism and apply it to two different mission planning problems, from an earth imaging and a data relay mission, investigating the system's ability to be generalized. We compare the planning process for the two problems and generalize on the type of planning problems the system can address.

Evridiki V. Ntagiou, Roberto Armellin, Claudio Iacopino, Nicola Policella, Alessandro Donati

Operational Benefit of a 3D Printer in Future Human Mars Missions—Results from Analog Simulation Testing

The remote nature of human missions to Mars requires a different paradigm for how operations should be performed. In particular, there is a need for greater independence from Earth, and the ability to adapt to evolving scenarios: needs that can potentially be assisted by integrating 3D printing technology into a Mars mission. A 3D printer can enable the production, repair, and modification of tools on Mars to address needs that arise. A series of experiments were carried out on the AMADEE-18 Mars Analog Simulation to investigate the potential benefit of integrating a printer into operations. AMADEE-18 was a one-month-long activity which provided a high-fidelity test environment, including communication delays between simulated Mars and Earth. The experiments involved production, repair, and modification of custom-designed geological sampling tools using a 3D printer inside the Mars habitat. A set of modular procedures were used to integrate 3D printing into the flight plan and compare the operational performance between Earth-led and Mars-led operations. 17 planned printing runs were complete, with execution times recorded, and subjective feedback collected. The results showed the difficulty in scheduling 3D printing operations, with the requirement for numerous small tasks spread out over an extended period. It was identified that Earth-led operations were superior with regard to crew workload, as they provided a more convenient way to manage these small, infrequent tasks. In addition to the planned prints, there were 13 unplanned prints completed, including a vital replacement clip for an EVA suit, showing the adaptability and utility granted by a 3D printer. The geological sampling tool used in the experiments was a hybrid of printed plastic and high-quality printed metal produced on “Earth”. This hybrid design was shown to be successful and presents an avenue for future research. In addition to the field tests during the AMADEE-18 mission, a study about the contamination in geological samples caused by the 3D printed tools was performed. Therefore, the size distribution of the abrasion from the 3D printed plastic tools was assessed and their form characterized.

M. Müller, S. Gruber, M. D. Coen, R. Campbell, D. Kim, B. Morrell

Ethological Approach of the Human Factors from Space Missions to Space Operations

Benefits of using the ethological approach in space field were first demonstrated on short-duration human missions then developed in the perspective of long-term missions for manned Mars exploration and Lunar village. We investigated a large panel of real and simulated situations (space shuttle, orbital stations, parabolic flights, bed rests, water immersion, confined chambers, Arctic expedition, and Antarctic bases) for better understanding the human adaptation to isolation, confinement, and autonomy. New goals of application are to propose complementary tools and an efficient method that assess positive actions of operators who cope with routine works and unexpected events while minimizing human factor (HF) risks in interactive space operations. As a preliminary study, we applied the ethological method for HF assessment within the interaction operators/systems during the satellite’s control-command operations. The question is on how the operators optimize their relationship with the system in which they interact as positive human dependability for the success of missions. The proposed method, based on the observation, description, and quantification of spontaneous spatial-motor actions, is to check the relevant behavioral indicators in operational situations. We give details about the tools and examples of analyses performed inside the network operations center (COR), at the Toulouse Space Center, in France. Observational data focused on interactions, actions, positions, displacements, distances, and orientations of the observed subjects in satellite’s post-launch situation on one side, and in routine situation on the other side. We completed the analyses during training procedures (Pleiades tests). The preliminary results support the relevance and report the opportunity of such an approach in next space operations. We emphasize the relationships between human behavior and human factor.

C. Tafforin, S. Michel, G. Galet

Enhanced Awareness in Space Operations Using Web-Based Interactive Multipurpose Dynamic Network Analysis

The dynamic network analysis (DNA) interactive visualization tool is a graph-based visualization tool that gives space operations staff the ability to comprehend complex relationships at stake in many different kinds of problems. The added value of DNA is exposed through different use cases applied to spacecraft operations. Operations engineers have shown an enhanced level of awareness when being able to visualize the dynamics of their problems. Tables, text, and numbers represent the way we communicate, but graph layouts and images represent, more efficiently, the way we think and mind map problems. Also, graphs represents patterns that our eyes are made to detect easily. By enabling the sharing of these mind maps and their semantics, we show how spacecraft issues can be detected earlier and, thanks to better insight, how they are solved more efficiently.

Redouane Boumghar, Rui Nuno Neves Madeira, Alessandro Donati, Ioannis Angelis, José Fernando Moreira Da Silva, Jose Antonio Martinez Heras, Jonathan Schulster

Space Education and Awareness in South Africa—Programmes, Initiatives, Achievements, Challenges and Issues

South Africa’s involvement in the Space Science started at the dawn of the “Space Age”. Before this, South Africa had been involved in astronomy since 1820, when the first permanent astronomical observatory (and scientific institution) in the southern hemisphere was completed at the Cape of Good Hope. Despite this rich history, South Africa has unfortunately, for various reasons, not been able to fully exploit the benefits of space technology and its applications to meet the challenges—it faces. One reason in particular is lack of awareness and understanding by planners, decision-makers and users about the potential benefits of space technology in planning and implementation of socio-economic development plans. In recent years, South Africa has made the development and cultivation of a domestic space industry a priority, citing the critical roles that space science, technology and innovation play in economic growth and socio-economic development. However, to ensure a long-term viable space programme and a growing space industry, it is imperative that South Africa builds the necessary capacity to support such an industry—hence, the need to create awareness and an appreciation for STEM-based careers at all levels of society which, for our school-going population, is likely to translate into an increase in the uptake and appreciation of science, technology, engineering and mathematics (STEM). In South Africa, the Department of Science and Technology (DST) plays a leading role in the implementation of space science and technology activities. Current space-related projects include the Satellite Build Programme; Operation Phakisa and the CubeSats Development Programme. There are also a number of local programmes and initiatives to promote space education and awareness. These are initiated, supported and implemented by various organizations, from the DST and its agencies through to the private sector and industry, as well as non-governmental and non-profit organizations. With regard to reaching out to schools, the DST conducts Space Weeks and other science festivals, as well as numerous initiatives by the local Radio Amateurs Clubs working with schools on high-altitude ballooning projects. Nonetheless, it has been noted that although there are much effort and resources expended on STEM awareness, there is notable lack of its intended impact. The role of educators/teaching staff will therefore be addressed focusing on their contribution to the goals of such STEM programmes. This paper discusses the various space-based STEM programmes that have been put in place to promote space education awareness and the contribution made by various role players. Furthermore, this paper will showcase a concept for a new approach to space awareness activities and its potential to drive STEM awareness programmes in the country. Lastly, this paper aims to recognize the achievements of South Africa in promoting space education and awareness in the country and the related issues and impediments to pursue these programmes. The paper also emphasizes the importance of introducing space education programmes in schools not only for the children but for the teachers in particular.

S. G. Magagula, J. Witten

Educational Outreach and International Collaboration Through ARISS: Amateur Radio on the International Space Station

The Amateur Radio on the International Space Station (ARISS) payload was first deployed and operated on the International Space Station (ISS) about two weeks after the first ISS expedition crew arrived on ISS. It has been continuously operational since that time. This makes ARISS the first operational payload and first educational outreach program on the ISS (Bauer et al. in Proceedings from the World Space Congress) [1]; (Conley et al. in Proceedings from the World Space Congress) [2]. ARISS provides a unique, once in a lifetime, educational opportunity for youth to conduct a ten-minute question and answer interview directly with crew members on board ISS. This is accomplished using the ARISS amateur radio systems on ISS, through the support of ISS crew members that have obtained their amateur radio licenses and through hundreds of ARISS international volunteers around the world. These volunteers mentor the schools, help set up ham radio equipment in the schools, and then prepare the students to coïnduct the contact with the ISS crew. ARISS, an international working group consisting almost entirely of dedicated volunteers, partners with the National Aeronautics and Space Administration (NASA), the Center for the Advancement of Science in Space (CASIS), and the other ISS international space agencies to engage the schools and students in educational opportunities that enable them to explore space and learn about wireless technology.

Frank H. Bauer, David Taylor, Rosalie A. White, Oliver Amend
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