Dual Wavelength Optical System for Multiple Quantum Communication Transmitters in Cubesat Platform

Quantum Key Distribution systems will play an important role in future networks for secure data communication. In order to provide a global coverage of a future Quantum Key Distribution service, satellites will be needed to bridge large distances. These satellite systems must be cost efficient to facilitate deployment since many network nodes will be needed. The CubeSat standard is frequently used for New Space projects as a versatile platform for satellite payloads. It is also chosen as a baseline for the construction of the system described in this paper. The DLR Institute of Communications and Navigation develops optical free space communication systems for scientific research in classical and quantum communications. In the OSIRIS4CubeSat (Optical Opace Infrared Downlink System for CubeSats) project a 1/3 U CubeSat laser-communication terminal for up to 100 Mbit/s downlinks was developed.1 This developement is adapted to be used for quantum communications tests with multiple transmitters in the scope of the project QUBE.2 Since the OSIRIS4CubeSat terminal was designed for C- and L-band wavelengths, a redesign of the optical system is needed to achieve polychromatic performance for C- and L-band and 850 nm. The optical system consists of a fiber collimator, a fine pointing assembly and an afocal telescope. Most important requirement of the latter is a similar magnification for all wavelengths to ensure coaligned beams pointing to the optical ground station (OGS). As the afocal telescope is used bidirectionally, it also needs to be optimized for the incident wave-front of the beacon laser from the OGS with respect to the beam shape at the tracking sensor which is used in the fine pointing assembly. These parameters are important for a correct pointing control. In addition to the laser terminal, a fiber-based wavelength division multiplexer (WDM) was specified for combining signals from three sources into one output fiber. It is based on cascaded thin film interference filters which are coupled to the fibers. Especially the propagation of 850 nm and C/L-band signals in one single mode fiber is critical. Therefore the types of optical fibers were selected with respect to the bend loss, to single mode propagation behaviour, polarisation integrity and optimal cladding diameter for production

Qualification of Inter-Satellite Link Laser Communication Terminals on CubeSats - CubeISL

Free Space Optical (FSO) communications on the rise to replace classic Radio-Frequency (RF) systems in many sectors of satellite communication. DLR has a long heritage in developing Laser Communication Terminals (LCT’s) for LEO satellites. Major requirement for the design of the terminals is the optical characterization. Beside the verification in the laboratory, the terminals must withstand the harsh conditions of launch and space and fulfil all functionalities. To characterize the LCT’s optical properties, DLR developed and built an Optical Ground Support Equipment (OGSE) which mirrors the functionalities of an Optical Ground Station (OGS), in a small scale, to test and adjust the LCT’s. This paper describes the setup of the OGSE and its capabilities. The success of the New Space move is based on short qualification and development times. Thus, DLR tailors common standards to the needs of the final mission. The paper describes the qualification approach with the example of the world’s smallest LCT OSIRIS4CubeSat (O4C). The next step is to transfer the technology from Direct-To-Earth (DTE) into the Inter-Satellite Link (ISL) domain in the CubeISL project. To reduce time and cost efforts for development and qualification, subsystems and processes were reused from O4C

Acquisition Concept for Inter-Satellite Communication Terminals on CubeSats

Free Space Optical (FSO) communication is gaining ground in satellite industry and an ideal supplement to classical radio data transmission. It offers solutions for global, high-rate and secure communication channels with compact designs and high cost- and performance-efficiency. Thus, German Aerospace Center (DLR) develops laser communication terminals for CubeSats and small satellites. DLR has a long heritage in developing FSO terminals for Low Earth Orbit (LEO) satellites in the Direct To Earth (DTE) scenario. The next step is to transfer this technology to Inter-Satellite Links (ISL). This paper presents DLR’s current development of an ISL laser communication terminal for CubeSats “CubeISL”. The optical terminal of CubeISL relies on the basic development of the “OSIRIS4CubeSat” (O4C) payload. To establish a link between the corresponding CubeISLterminals, DLR developed a search algorithm to acquire the laser of the partner terminal on the other satellite. The paper discusses the possibilities of different concepts based on the current design. CubeISL will be demonstrated in a mission with two 6U CubeSats. Beside the technical description of the payload design and the search and acquisition algorithm, the paper will also give an overview and an outlook to this demonstrator missio

OSIRIS4CubeSat - System Engineering with new Space approach from the development of a high data-rate optical communication payload to the demonstrator in a quasi-operational mission

Modern satellite missions like CubeSat-missions are characterized by extremely short development time and significant low resource requirements. This can only be reached by reducing classical standards to necessary levels, tailored down for the respective mission. It leads to a rethinking of system engineering in modern space missions following the new space approach, which tailors down the standard processes to a minimum but reasonable level. The Optical Communication Systems Group (OCS) of DLR develops solutions to break the bottleneck caused by limited data-rates of traditional RF-communication systems with Free-Space-Optics (FSO) technologies for earth orbiting platforms. Therefore DLR started 10 years ago the OSIRIS (Optical Space InfraRed downlInk System) program which concentrates on research and development of laser communication terminals for Low-Earth-Orbit (LEO) satellites. The development speed in laser communication accelerated in the last years due to the availability of compact and low-cost flying platforms like pico- and nanosatellites. Therefore OCS follows the new space approach to shorten development times and finish projects much earlier compared to traditional space missions. The OSIRIS4CubeSat (O4C) project has the goal to develop a high data-rate optical communication payload for CubeSats and demonstrates it in a quasi-operational scenario. The development of the payload is in close collaboration with Tesat-Spacecom who sells O4C under the name 'CubeLCT' as a commercial product. Beside the payload development, the functionality of O4C will be demonstrated in a direct to earth downlink from a CubeSat to an Optical Ground Station. Thus, the payload will fly in the PIXL-1 mission on a 3U CubeSat built by GomSpace. After the Launch and Early Operational Phase (LEOP) the satellite will be hand over to German Space Operation Center (GSOC) to demonstrate for the first a time a commanding of a CubeSat by a professional Ground System. The ambitious path from the development of the payload, which started from scratch, to a quasi-operational mission, shows the necessity of a working system engineering to observe all requirements, coordinate the different teams and manage the interfaces to the stakeholder. This paper describes the system engineering based on the new space approach for a modern CubeSat mission. In the beginning of the project the overall requirements for the whole project were defined. This includes the technical requirements for the payload, to ensure the functionality depending on the extreme environmental conditions in space and the requirements for the satellite. Furthermore the operational requirements were defined. Additionally to the internal requirements the needs of the commercialization partner and the possible launch opportunities had to be considered. Beside the requirements, the single work packages were defined to distinguish the several tasks and visualise the interfaces and connections in a work breakdown structure (WBS). Based on the WBS the technical teams for the development were formed. During the concept development and the integration of the payload, the system engineering had to monitor the requirements and coordinate the different technical teams with all their interfaces. Even though the teams were separated in optics, mechanics, electronics and software, their tasks were strongly connected. Beside the internal interface coordination the system engineering had to coordinate the communication on technical level to the external stakeholders like contractee (Tesat), satellite manufacturer (GomSpace), launch provider and operator (GSOC). This paper gives an overview over the processes in the OSIRIS4CubeSat project which represents modern system engineering following the new space approach

OSIRIS Optical Communication Demonstration on CubeSat

With the increasing need for higher data rates on small LEO spacecraft, highly compact laser communication systems are required to overcome the limitations in the downlink channel. The group of Optical Communication Systems (OCS) at the Institute of Communications and Navigation of the German Aerospace Center (DLR) is working on the program OSIRIS (Optical Space Infrared Downlink System). DLR is closely cooperating with Tesat Spacecom for the industrial application of the OSIRIS technology. CubeSat missions have been seen as technology demonstration missions in the past, but made its way to both scientific as well as commercial missions especially in the framework of Earth Observation and Remote Sensing. Increasing capabilities of small scale sensor systems raised the need for higher data rates in the Direct To Earth (DTE) channel also for CubeSat missions. In the cooperation between DLR and Tesat, the first demonstrator has been developed that will be launched in 2018 to demonstrate the performance of the technology. Therefore, OSIRIS heritage from previous missions has been optimized for the application on a CubeSat. Especially size, weight and power have been taken into account, but also the compatibility to different CubeSat bus interfaces, and influences from a mass manufacturing point of view. The optimization leads to a payload weight of 350 grams and a volume of 0,3 CubeSat units. With an electrical powerconsumption of 8 W, the optical communication payload enables downlink data rates of up to 100 Mbps. This paper will give an overview over the OSIRIS payload and the design constraints, the foreseen mission scenario as well as an investigation on the data throughput together with the commercial application CubeL envisaged after the demonstration mission

Development of laser terminals for satellite-based QKD on CubeSat platforms

Satellite-based Quantum Key Distribution (QKD) plays an important role in future quantum safe networks to overcome the limited transmission range of fiber based QKD. Recent missions demonstrated the feasibility of this technique paving the way for future projects. CubeSats provide a cost-efficient way for testing new QKD technologies in space and pose a promising and scalable platform for future constellation. The DLR Institute of Communication and Navigation (DLR-KN) develops terminals for satellite QKD systems. Within the scope of the project QUBE, a 1/3U sized terminal is developed for space-to-ground QKD experiments. The terminal will set up a multi wavelength downlink, providing a classical synchronization and a quantum channel. Its functionality is verified in a ground-to-ground link and the launch of the 3U CubeSat is planned for 2024. During the mission, core technologies for future QKD technologies are tested in space. Follow up projects at DLR-KN aim at the development and integration of bigger telescopes in CubeSats leading to an increased antenna gain, enabling full QKD implementation. Based on the QUBE system, a terminal breadboard with an aperture diameter of 85mm is developed within the QuNET project. The paper presents an overview of the system concept, a detailed insight into the optics design, the concept for the optomechanics and the implementation of the pointing assembly. The parallel development of the subsequent QUBE-II terminal exploits the gathered experience and lessons learned from the QUBE mission and QuNET breadboard development. The QUBE-II terminal will enable full space-to-ground QKD implementation with a CubeSat and will additionally provide an optical data up- and downlink. QUBE-II will be launched at the end of 2025

Miniaturized Optical Intersatellite Communication Terminal - CubeISL

The increasing request for higher data rates and the technical limitations of traditional radio-frequency channels in intersatellite communication requires solutions to overcome these obstacles. German Aerospace Center (DLR) has a long heritage in optical air-to-ground and space-to-ground transmission. Due to its high data rates, resistance against interferences and being free from regulations like from the International Telecommunication Union (ITU), Free Space Optical communication (FSO) provides solutions to overcome the challenges for satellite communication. Based on the developments in the OSIRIS4CubeSat project, DLR transfers the technology of laser communication on CubeSats from Direct to Earth (DTE) into the intersatellite domain. Therefore, the project CubeISL started with the goal to develop an optical intersatellite for CubeSats. This paper discusses possible mission scenarios where CubeISL terminals can be used, the research results of a feasibility analysis and the required technical adaptions, which will be realized in the near future

DLR's Optical Communication Terminals für CubeSats

Free space optical communication (FSO) overcomes the challenges of traditional RF-communication in space. With its high data-rates, robustness against electromagnetic influences and being free from organizational regulations, FSO provides solutions for high-rated Direct to Earth (DTE) and Intersatellite (ISL) communication. With the raising CubeSat market and the increasing number of satellite constellations, the request for compact and efficient designs increases as well. Thus, German Aerospace Center (DLR) developed the world’s smallest laser communication terminal for CubeSats (OSIRIS4CubeSat, O4C). O4C is flying on the CubeL satellite in the PIXL-1 mission. The payload itself has a modular design which allows to transfer the technology into other fields of satellite communication. The basic payload can be adapted and/or extended by different subsystems to provide solutions for intersatellite communication or Quantum Key Distribution (QKD). This paper gives an overview of the first results of the PIXL-1 mission. After the Launch and Early Orbit Phase (LEOP) the first contact between the laser terminal and DLR’s Transportable Optical Ground Station (TOGS) could be established. Afterwards, further experiments were done to demonstrate the performance of the O4C terminal. Furthermore, this paper shows the ongoing and upcoming developments. Based in the O4C dedicated terminals towards higher data rates, optical intersatellite links and QKD on CubeSats are and will be developed

Update on DLR's OSIRIS program and first results of OSIRISv1 on Flying Laptop

Optical satellite links have gained increasing attention throughout the last years. Especially for the application of optical satellite downlinks. Within the OSIRIS program, DLR's Institute of Communications and Navigation develops optical terminals and systems which are optimized for small satellites. After the successful qualification and launch of two precursor terminals, DLR currently develops OSIRISv3, a 3rd generation OSIRIS terminal with up to 10 Gbps downlink rate, and OSIRIS4Cubesat, a miniaturized version optimized for Cubesat Applications. The University of Stuttgart's Institute of Space Systems develops small satellites, which are used to demonstrate novel technologies in the Space domain. Together, DLR and University of Stuttgart integrated the first OSIRIS generation onboard the Flying Laptop satellite, which was launched in July 2017 and has been successfully operated since. This paper will give an overview about DLR's OSIRIS program. Furthermore, it will show first results of OSIRISv1 on Flying Laptop. Therefore, the Flying Laptop satellite and OSIRISv1 will be explained. Preliminary results from the validation campaign, where optical downlinks have been demonstrated, will be given. © 2019 SPIE. Downloading of the abstract is permitted for personal use only