Satellite Ground Segment Research Articles

Automated and Intelligent Satellite Mission Operations Experiences with the N2 Satellite Ground Segment and Future Directions

Automated and Intelligent Satellite Mission Operations Experiences with the N2 Satellite Ground Segment and Future Directions

정지궤도 해양위성 2호 지상시스템의 설계 및 구현

정지궤도 해양위성 2호 지상시스템의 설계 및 구현

SDN/NFV-enabled satellite communications networks: Opportunities, scenarios and challenges

In the context of next generation 5G networks, the satellite industry is clearly committed to revisit and revamp the role of satellite communications. As major drivers in the evolution of (terrestrial) fixed and mobile networks, Software Defined Networking (SDN) and Network Function Virtualisation (NFV) technologies are also being positioned as central technology enablers towards improved and more flexible integration of satellite and terrestrial segments, providing satellite network further service innovation and business agility by advanced network resources management techniques. Through the analysis of scenarios and use cases, this paper provides a description of the benefits that SDN/NFV technologies can bring into satellite communications towards 5G. Three scenarios are presented and analysed to delineate different potential improvement areas pursued through the introduction of SDN/NFV technologies in the satellite ground segment domain. Within each scenario, a number of use cases are developed to gain further insight into specific capabilities and to identify the technical challenges stemming from them.

Towards a critical design of an operational ground segment for an Earth observation mission

The ground segment for the future remote sensing mission Environmental Mapping and Analysis Program (EnMAP; www.enmap.org) is developed by the Earth Observation Center and the German Space Operations Center at the German Aerospace Center. The launch is scheduled for 2017. An operational satellite ground segment is a highly complex heterogeneous system which has to cope with different levels of criticality, novelty, specificity, and to be operated for many years. It consists of equipment, hard- and software as well as operators with their procedures. The strengths of the global coherence of the segment-wide approach bringing these aspects together is examined and not on the local details of segment-specific issues. However, the effects on two software-based elements of the ground segment are considered in more detail, namely the product library and the level 2geo processor. The development methodology and how the critical design of the complete ground segment finished its detailed design phase successfully was achieved is analyzed. As a measure of the maturity of the design, its stability across the project phases is proposed.

CNES solution for a reusable payload ground segment

The MYRIADE program of the French Space Agency (CNES) has been developed for research institutes proposing pertinent scientific space experiments. It is composed of a satellite bus with independent and configurable functional chains able to onboard a scientific payload of 50kg/60W for at least a 3-year duration. The CNES is responsible for the launch and the development of the satellite bus and the satellite ground segment, while the research institute manages the development of the payload and the payload ground segment.This paper aims at discussing the means to enhance the development of a payload ground segment for small missions as MYRIADE. The needs of this kind of experimental missions are very specific and to try developing a reusable segment has been often considered inefficient. However the lessons learnt from the previous missions show the key role played by the payload ground segment in the success of the mission and also demonstrate that a payload ground segment of a small mission is more complex than expected.After a presentation of the MYRIADE program, the ground segments of the three first CNES missions are compared. This analysis first highlights that 15 full time equivalent in average are required to develop a payload ground segment. This result is not compliant with the resources of the research institutes which are mainly devoted to the development of the payload. The comparison emphasises invariants in the functional architecture and operational concept independently of the mission that allow to provide a tested frame adapted to small missions. The engineering processes are also compared and a solution is proposed to introduce flexibility and efficiency in the development. The approach, compliant with the functional architecture presented before, consists in using tools developed for previous missions and thereby to limit the new developments for the mission specific functions. This proposition is currently tested at CNES with the TARANIS and MICROSCOPE missions: some reusable software and templates documents have been selected and developed to ease the work during all the development phases of the payload ground segment (A–D). The software set can be fully or partially integrated to manage all the common functions. The mission specificities are added either by configuration or add-on developments. The documentation set integrates the requirements common to most of the payload ground segments and the requirements to be completed with respect to the mission specificities. This process is virtuous since each mission adds new options to the software set and improves the engineering documents by the lessons learned.

Development and characteristics of African Satellite Augmentation System (ASAS) network

This paper reports on an African Satellite Augmentation System (ASAS) Space and Ground Segments as an integration part of Global Satellite Augmentation System (GSAS) for enhanced Traffic Control and Management (TCM) globally at sea, on the ground (road and railway vehicles) and in the air. The ASAS network can be used as solely systems for covering and providing TCM and Safety and Security service for entire African Continent and Middle East region, according to the International Maritime Organization (IMO), its Global Maritime Distress and Safety System (GMDSS) and International Civil Aviation Organization (ICAO) recommendations and requirements. Since 1995 few commercial Regional Satellite Augmentation System (RSAS) networks have been projected and developed to utilize Communication, Navigation and Surveillance (CNS) service for Maritime Traffic Control (MTC), Land Traffic Control (LTC) and Air Traffic Control (ATC), including for improved Safety and Security in all transportation systems. The proposed Space Segment of Geostationary Earth Orbit (GEO) constellation and Ground Segment of ASAS network are discussed, and areas examined where further investigations are needed. Specific issues related to these challenges are concluded and a set of solutions is proposed to maximize the availability of ASAS network capacity to the user applications.

ENVISAT radar altimeter measurements over continental surfaces and ice caps using the ICE-2 retracking algorithm

This study presents the first results obtained with the ENVISAT satellite radar altimeter RA-2 over lands and ice caps. As radar altimetry was firstly devoted to ocean study, this paper starts with a detailed description of the radar altimetry principle over continental surfaces: a general formulation of the radar altimeter echoes according to different surface types is given and the retracking procedure ICE-2, specially implemented on the ENVISAT satellite ground segment to provide output parameters over continents, is clearly presented. The ENVISAT RA-2 datasets processed with the ICE-2 procedure are then mapped given an overall description of the output parameters over various surfaces. The behaviour of these ENVISAT altimetric parameters are analysed and related to main land surface characteristics such as surface/volume echo, specularity, roughness…. Apart from few unexpected signals which will need to be further investigated, the new ENVISAT dataset confirms the potential of inland altimetry and provides a new opportunity to monitor continental surfaces. The Ku band measurements confirm previous results recently obtained with the altimeters on board ERS or Topex–Poseidon and offer a temporal continuity. The S band altimeter measurements are in accordance with theoretical expected ones and confirm previous Topex–Poseidon observations in C band. The S band and the use of the dual-frequency thus bring new capabilities for altimetric applications with important deliveries for temporal evolution survey. For instance, S band will be used over continents to better detect wetlands located under vegetated areas or to better quantify wave penetration in terrestrial snowpack to accurately retrieve snow depth evolution. Over ice sheets, the dual-frequency S and Ku band waveforms parameters will provide a more accurate height estimation as it will be possible to quantify the error on height measurements induced by snowpack structure change over time. This will then provide a more confident survey of the ice sheets surface topography evolution. The combination and complementarities with the other altimetry missions such as ERS, Topex–Poseidon and Jason look already promising and offer a 10-year span dataset for continental altimetry applications.

A uni-directional satellite paging system for land mobile users

A satellite ground segment which is capable of supporting a uni-directional paging service for land mobile users is described. The system is configured around existing satellites and the VHF wide-area paging network. A suitable transmission format is proposed which employs multi-level frequency shift keying, dual time diversity and Reed-Solomon forward error correction. The anticipated performance of the transmission format is discussed. Proposed implementations of the mobile paging receiver and transmitter data-formatting modulation equipment are presented.

Shuttle Communication Systems Compatibility and Performance Testing

The Shuttle communications system consists of major space and ground elements. The space elements include the Orbiter, Tracking and Data Relay Satellite, payload and extravehicular astronaut communications subsystems. The Spaceflight Tracking and Data Network, relay satellite ground segment, and the Air Force Satellite Control Facility make up the major ground elements of the communications system. The compatibility and performance of each of these major elements functioning as a complete system must be certified prior to operational missions. Unique Shuttle communication channels employing spread spectrum techniques, high rate data (50 Mbits/s), convolutional encoding, and unbalanced quadriphase modulation must be evaluated on an end-to-end RF (radio frequency) system basis. To accomplish the necessary communication system compatibility and performance tests, NASA has established the ESTL (Electronic Systems Test Laboratory) at the Lyndon B. Johnson Space Center. This paper discusses the Shuttle communication systems compatibility and performance testing which is being accomplished at the ESTL. The system test philosophy for the complex communications channels is described in terms of the major phases which include early breadboard system design evaluation tests, system verification tests with prototype hardware and system certification testing with qualifiable (flight) hardware. The system hardware configuration, facility requirements, test and evaluation techniques and operational approaches required to accomplish each major phase of testing are reviewed. Results of recently completed space-to-space and space-space-to-ground system tests are presented. Test techniques and measurement accuracies proven over 10 years of system evaluation experience unique to the ESTL are reviewed. Techniques used in relating experimental system performance and predicted system performance (based on hardware math models), and conclusions regarding effectiveness of system level testing of such complex hardware are addressed.