TDP1 Ground System Design

This paper illustrates the historical development of the TDP-1 ground segment, the system as implemented and operational experience, as well as an outlook to future programs. Aim of the project TDP-1 – Technology Demonstration Payload No.1 - is the demonstration of a data relay service, using an optical High Data Rate Inter-Satellite Link (ISL) between a Laser Communication Terminal (LCT) flown on a low earth orbiting satellite (LEO-LCT) and a second LCT (GEO-LCT) placed on the geostationary communication satellite AlphaSat (of INMARSAT) . The LCT planning system consists of one geostationary satellite (GEO) and up to five low orbiting satellites (LEO) which are also referred to as customers. The main task of GEO within this system is to serve as service provider for the LEOs and one optional optical ground station (OGS). The service consists of an optical data link between the Laser Communication Terminals (LCT) of the satellites (inter-satellite-link,ISL) and a link from a satellite to a ground station (space-to-ground-link, SGL). DLR’s Operations Center (GSOC) role in the TDP-1 program includes design, development and integration of ground infrastructure and operations of the satellites and ground stations. GSOC already gained experience operating Laser Terminals in test scenarios on the TerraSAR spacecraft. This knowledge was be used to develop the TDP-1 operations concept. One major task is the planning of the laser connections and the required coordination between all parties. This paper will illustrate the development from the first activities at GSOC in connection with laser data transfer through the design of the TDP-1 system to an outlook at the EDRS operations concept

EDRS-C – Challenging Way of Bringing the Second Orbital Node into Space

The European Data Relay System (EDRS), also known as the SpaceDataHighway, is designed to provide commercial data relay service to spacecraft in low earth orbit (LEO). It offers high data rates and short response times and uses optical and Ka-band links for two-way data transmissions. The project was established by the European Space Agency ESA in frame of the Advanced Research in Telecommunications Systems program (ARTES-7). ESA is also acting as an anchor customer contributing LEO missions from their Copernicus Program. The EDRS project was organized as a public private partnership (PPP) with the industrial prime contractor Airbus Defence and Space. Airbus owns, operates and provides commercial services for the SpaceDataHighway. With EDRS-A, the first orbital node of the system started routine operations in late 2016. It is a hosted payload on the Eutelsat 9B spacecraft and is operated by the German Space Operations Center (GSOC) in a mostly automated way. In a second step, EDRS-C, a complete satellite has been added. This time, GSOC is responsible for both, platform and payload operations. GSOC's work for EDRS-C was organized in two parts. The first part covered the preparation and execution of the LEOP as well as the in-orbit tests of platform and payload. The payload consists of 3 elements, the data relay equipment for EDRS, The HYLAS 3 Ka-band communication payload of Avanti, and ESA's Next Generation Radiation Monitor NGRM. The spacecraft is a 3-ton-class SmallGEO platform built by OHB Bremen, Germany, which was already operated by GSOC during the maiden flight, the Hispasat Advanced Generation 1 (HAG1) mission in 2017. For EDRS-C, the challenge was not only to perform another LEOP and IOT, but also to have the next project phase in view, the routine operations for platform and payload. The second part comprised the development and implementation of the ground segment for EDRS-C, and the execution of mission operations for the 15 years routine phase. It was initially planned to do this in parallel to the LEOP and IOT preparations, but after coordination with the customer, a step-by-step approach was agreed. This approach allowed concentrating on the LEOP and IOT tasks in order to gain a timely launch readiness. As a consequence, the routine phase related components and operational products had to be completed in parallel to the already ongoing IOT operations. This paper will give an overview of the EDRS-C mission and emphasize the challenges of the step-wise approach to prepare LEOP, IOT, and routine phase operation. It explains the integration of the new satellite with different technology into the existing SpaceDataHighway network, delivers an insight into the project management approach at GSOC for the different work tasks and contracts, and illustrates the harmonization of the EDRS-A and C payload operations. EDRS-C was launched in August 2019. The in-orbit test phase for platform and payload was completed successfully and the operational services could be started in 2020, so this paper can provide an up-to-date status of the mission. In addition, an outlook is given to adaptations and improvements of GSOC's ground segment components in preparation of further extension of the SpaceDataHighway fleet

The EDRS mission and its operational experiences to date from GSOC perspective

Since 2016, the European Data Relay System (EDRS) – also known as SpaceDataHighway – is serving as a geostationary (GEO) relay system offering unique laser communication services for satellites of the low earth orbit (LEO). As the satellite market evolves, today´s LEO satellites produce more accurate, more precise, and more detailed data, and thus struggle with the task of bringing huge amounts of data to ground. EDRS offers a convenient solution to that challenge by its data transfer service via its GEO nodes to ground. In addition to this basic concept, the EDRS mission also involves the technology of optical communication: the space-to-space link is performed in optical frequencies by the means of so-called Laser Communication Terminals (LCTs), offering a secure and high-speed data transfer. Currently, EDRS consists of two nodes: EDRS-A is a hosted payload on the Eutelsat-9B satellite which was launched in January 2016. It was complemented by the satellite EDRS-C, launched in August 2019, dedicated for the EDRS mission. Both payloads, as well as the EDRS-C satellite platform, are operated by the German Space Operations Center (GSOC), which is part of the German Aerospace Center (DLR). The EDRS program itself is a public-private partnership between ESA and Airbus Defence and Space as the industrial prime contractor. The LCTs are manufactured by TESAT Spacecom, while the 3-ton-class SmallGEO platform built by OHB is the satellite bus for EDRS-C. In addition to the LCTs, which are the prime payloads on both nodes, GSOC also operates a Ka-Band relay antenna as supplementing part of the EDRS mission, a Ka-Band transponder for AVANTI Communications, as well as a radiation monitor of ESA as secondary payloads. The EDRS system is capable of performing up to 200 communication links with LEO satellites per node and per day. Until mid of 2023, though, the EDRS mission will consist of seven LEO customer satellites, as well as one Ka-band customer antenna (ColKa) on the Columbus module of the International Space Station ISS. All of them are using the EDRS service either via laser communication or the secondary Ka-band antenna. The high numbers of possible links as well as customer satellites pose a challenging task to the control centers at GSOC. For this reason, both LCTs are controlled using an automated operations engine, which is designed to supervise the complete cycle of telecommand uplink and execution as well as reaction monitoring of telemetry, giving GSOC permanent control and awareness. The system has proven to be very robust, is routinely used and led to over 60.000 successful optical links until mid of 2022. This paper gives an overview over the EDRS mission and shows how GSOC organises and performs EDRS-A and EDRS-C operations. It also describes how both operations evolved during the course of the project, which harmonisations were performed, and gives an outlook on how the future of the program might look from a GSOC perspective

EDRS - Betrieb der Datenautobahn im Weltall

Das Europäische Datenrelaissatellitensystem (European Data Relay Satellite System, EDRS) ist eine kommerzielle Raumfahrtmission mit dem Ziel, niedrig fliegenden Satelliten eine einzigartige Hochgeschwindigkeits-Datenverbindung zum Boden anzubieten. Dies wird am heutigen Satellitenmarkt immer wichtiger: Durch die ständig anwachsende Anzahl an Satelliten im Orbit kombiniert mit ebenfalls ansteigenden Datenmengen, welche zur Erde übertragen werden müssen, werden immer höhere Datenübertragungsraten benötigt. Diese Datenmengen werden klassischerweise über Bodenstationen im Radiofrequenzbereich (z.B. Ka-, S-, oder X-Band) zur Erde übertragen. Die Zeit eines Überfluges über einer Bodenstation ist jedoch auf wenige Minuten begrenzt. Darüber hinaus muss abgewartet werden, bis der Satellit eben diese Bodenstation überfliegt – was im Fall von zeitkritischen Daten den Nutzen schmälern oder sie gänzlich unbrauchbar machen kann. An diesen zwei Problemen setzt das Konzept von EDRS an: Satelliten im geostationären Erdorbit dienen als Relais-Station, und sind somit für niedrig fliegende Satelliten für nahezu die Hälfte ihres Orbits erreichbar. Zusätzlich wird die Datenübertragung von Satellit zu Satellit per Laser durchgeführt, was eine schnelle Datenrate und eine hohe Abhörsicherheit ermöglicht. Aktuell besteht EDRS aus zwei geostationären Knoten: EDRS-A ist eine Nutzlast auf dem Eutelsat-9B Satelliten, welcher 2016 gestartet wurde. Drei Jahre später hatte EDRS-C seinen Launch. Dieser besteht im Gegensatz zu EDRS-A aus einem eigeneständigen, dedizierten Satelliten. Beide Komponenten werden vom Deutschen Raumfahrtkontrollzentrum (German Space Operations Center, GSOC) betrieben, welches Teil des Deutschen Zentrums für Luft- und Raumfahrt (DLR) ist. Das EDRS Programm selbst ist ein Public Private Partnership zwischen der ESA und Airbus Defence and Space als Hauptvertragspartner der Industrie. Die für die Datenverbindung benutzten Laser Communication Terminals (LCTs) wurden von der Firma TESAT Spacecom entwickelt und hergestellt. Beim Satellitenbus von EDRS-C handelt es sich um die SmallGEO Plattform, welche von OHB produziert wird. Zusätzlich zur Hauptnutzlast, bestehend aus den LCTs, ist noch ein Ka-Band Transponder sowie ein Strahlungsmonitor Teil der EDRS Mission. Das EDRS System ist in der aktuellen Form in der Lage, bis zu 200 Datenverbindungen pro niedrig fliegendem Satellit pro Tag zu unterstützen. Bis Anfang nächsten Jahres werden sieben Kunden-Satelliten sowie eine Ka-band Antenne auf dem Columbus-Modul der Internationalen Raumstation ISS den Service von EDRS genutzt haben. Diese hohe Anzahl an Nutzern und die hohen technischen und organisatorischen Anforderungen stellen den Betrieb am GSOC vor hohe Herausforderungen. Dieses Paper gibt einen Überblick über die EDRS Mission, mit einem Fokus auf das Betriebskonzept und dessen Entwicklungen aus Perspektive des GSOC

Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks

无线传感器网络，作为全球未来十大技术之一，集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术，可实时感知、采集、处理、传输网络分布区域内的各种信息数据，在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议，并针对大规模的无线传感器网络设计了一种树状路由协议，它根据节点地址信息来形成路由，从而简化了复杂繁冗的路由表查找和维护，节省了不必要的开销，提高了路由效率，实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR（AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位：工学硕士院系专业：信息科学与技术学院通信工程系_通信与信息系统学号：2332007115216

The different roles of the DLR German Space Operations Center in recent Laser Communication Projects

Laser communication is of growing importance for space programs and is utilized in several recent satellite missions, since it offers the advantages of high data rates over long distances. Since 2007, the German Space Operations Center (GSOC) of the German Aerospace Center (DLR) is involved in a number of projects in which laser communication plays a significant role, such as TerraSAR-X, TDP-1, EDRS-A and the upcoming EDRS-C. The role performed by GSOC is different for each of these missions, thus it covers a broad portfolio of operational experience in laser communication. For TerraSAR-X, a low earth orbit (LEO) satellite, GSOC performs the satellite as well as all payload operations. TerraSAR-X is equipped with a Laser Communication Terminal (LCT) as secondary payload, which is capable of inter-satellite (ISL) as well as space-to-ground links (SGLs). The development of these LCTs is led by the Space Administration of DLR, funded by the Federal Ministry for Economic Affairs and Energy, and performed by TESAT Spacecom GmbH. In contrast, EDRS-A is a hosted payload on a geostationary (GEO) satellite and the first step in the European Data Relay System, which will soon be supported by a second relay terminal, EDRS-C. The relay system offers LEO satellites more possibilities for high speed data downlinks via laser. It is a commercially used service with quite demanding requirements concerning the availability of this downlink. For EDRS-A, GSOC fulfills the role of the LCT payload control center. For EDRS-C, the task of GSOC is extended to dedicated satellite operations including the LCT payload. To address the demanding requirements, all processes on GSOC side are completely automated. ESA´s TDP-1 (Technology Demonstration Payload No.1) project is the proof-of-concept for EDRS. It is a collaboration between DLR, ESA, and TESAT-Spacecom. The mission involves LCTs installed as secondary payloads on board a variety of LEO and GEO satellites as well as on ground, allowing for ISLs as well as for SGLs. Here, GSOC fulfills the role of the Mission Control Center, which includes collection of orbit and availability data, calculation of feasible link slots, scheduling of customer link requests, and generation of operational products for the LCT payloads of the involved spacecraft. One important aspect of this advanced concept is the connection to multiple control centers or associated facilities (like TECO, INMARSAT, ESOC), which is a necessary prerequisite for successful laser communication between different satellite projects. This paper gives an overview of the operational concepts of GSOC within the four mentioned projects, with a focus on our involvement in the TDP-1 program

The TDP-1 Mission Control Center and ist current operational experience

TDP-1 is a quasi-operational technology demonstration payload, designed to prove the concept of data transfer between low-orbit observation satellites and earth via a geostationary relay satellite in between the communication chain. This detour allows to significantly increase transferable data volume at reduced latency time, and is performed with the help of Laser Communication Terminals (LCTs) on board the low-orbit as well as the geostationary satellite, from which the data is immediately downlinked via Ka-Band. In this framework, TDP-1 is the successful precursor mission for the forthcoming European Data Relay Satellite System (EDRS). A dedicated operational concept has been developed by DLR GSOC as TDP1 Mission Control Center. The concept is based on heritage programs TerraSAR-X and NFIRE and includes all necessary tasks and steps like calculation of feasible link slots based on satellite orbit and availability data, scheduling of customer link requests, and generation of operational products for the involved spacecrafts to execute the links. This paper gives an overview of the current Mission Control Center System Design of the TDP-1 program and its operational experiences

TOWARDS THE UTILIZATION OF OPTICAL GROUND-TO-SPACE LINKS FOR LOW EARTH ORBITING SPACECRAFT

The microwave spectrum has become a highly limited resource in satellite communications owing to an ever increasing demand for bandwidth and capacity. Therefore, a shift to the exploitation of optical carrier frequencies is currently underway. Focusing on high-rate transmissions of payload data from remote sensing satellites, operational systems, like the well-known European Data Relay Satellite system, are based on optical inter-satellite links. Besides, direct-to-earth free-space optical communications from low Earth orbiting spacecraft hold high potential for upcoming space missions through lower complexity. In that regard, we study the viability of the ground-to-space beacon laser signal of optical ground stations to be additionally modulated with tele-command tokens. Such an optical return channel could be variously put into use, e.g. to trigger automatic repeat requests of payload data downlinks, for jamming-free control of the spacecraft or for high-rate software uploads to its on-board processor. A particular challenge is posed by the unequal fading behavior of the optical channel regarding the down- and uplinks, which cover asymmetric optical pathways through the atmosphere. We define the end-to-end architecture of the communication chain including the transmitter on ground and the space-based receiver. Special attention is given to compatibility with established space data and system standards. Moreover, we examine the effects on the scheduling of satellite control, resulting from a constrained availability of the optical uplink due to cloud blockages. Our analysis aims at the employment of available space protocols for bidirectional optical communications with low earth orbiting spacecraft. Further on, we consider the adoption of upcoming standards to account for the optical fading channel. Certain applications like immediate automatic-repeat-requests for the downlink will require novel, optimized protocols

Towards the utilization of optical ground-to-space links for low earth orbiting spacecraft

The microwave spectrum has become a highly limited resource in satellite communications owing to an ever increasing demand for bandwidth and capacity. Therefore, a shift to the exploitation of optical carrier frequencies is currently underway. Focusing on high-rate transmissions of payload data from remote sensing satellites, operational systems, like the well-known European Data Relay Satellite system, are based on optical inter-satellite links. Besides, direct-to-earth free-space optical communications from low Earth orbiting spacecraft hold high potential for upcoming space missions through lower complexity. In that regard, we study the viability of the ground-to-space beacon laser signal of optical ground stations to be additionally modulated with tele-command tokens. Such an optical return channel could be variously put into use, for example to trigger automatic repeat requests of payload data downlinks, for jamming-free control of the spacecraft or for high-rate software uploads to its on-board processor. A particular challenge is posed by the unequal fading behavior of the optical channel regarding the down- and uplinks, which cover asymmetric optical pathways through the atmosphere. We define the end-to-end architecture of the communication chain including the transmitter on ground and the space-based receiver. Special attention is given to compatibility with established space data and system standards. Moreover, we examine the effects on the scheduling of satellite control, resulting from a constrained availability of the optical uplink due to cloud blockages. Our analysis aims at the employment of available space protocols for bidirectional optical communications with low earth orbiting spacecraft. Further on, we consider the adoption of upcoming standards to account for the optical fading channel. Certain applications like immediate automatic-repeat-requests for the downlink will require novel, optimized protocols

Four years operations of Inter-satellite and SpaceGround Optical links

During the past four years, the laser communication terminal on board of Alphasat GEO-stationary satellite has achieved the successful execution of more than 1300 optical links which implies more than 24.000 tasks for the planning system. This laser terminal in combination with a Ka-Band system constitutes the TDP1 technology demonstrator. Approximately half of the links were inter-satellite optical links, using the Sentinels low orbit satellites of the EU Copernicus program (S1A, S1B, S2A and S2B) as communication partner with the aim of supporting in orbit commissioning activities and TDP1 experimentation purposes. The other half of the links used the transportable adaptive optical ground station of the DLR (T-AOGS [2]) located currently at Tenerife, Spain as counter terminal. These optical satellite to ground links prepare the way not only to GEO feeder links, but also for connecting the space segment to HAPs, airborne terminals or LEO direct to earth links. In contrast to pure inter satellite links the satellite to ground links involve the atmosphere and local weather conditions. Adopting the operational concept established for inter satellite links, a certain percentage of the planned links cannot be conducted (e.g. due to clouds). The conducted links were used to characterizing the T-AOGS, characterize the atmospheric conditions as well as optimize and test coding schemes. Most of the tasks executed by the LCTs and the Ka-Band have been based in the TESAT input delivered to the MCC (operated by DLR GSOC), further processed and finally transferred to the spacecraft control center