PAGE CONTENTS
Objectives
The objective of the project was to advance optical communication standards by analysing and validating optical ranging techniques based on CCSDS draft pink sheets. It focused on evaluating both asynchronous and synchronous telemetry ranging approaches, including their performance, requirements, and potential improvements through simulation and analysis.
A key goal was to design and implement a breadboard testbed to experimentally verify performance predictions and demonstrate technical feasibility. The project also aimed to provide validated results to support CCSDS standardisation, contributing to a reference implementation in the CCSDS Yellow Book. Additionally, it targeted achieving more than a tenfold improvement in ranging accuracy compared to RF systems and reaching Technology Readiness Level (TRL) 4.
Benefits
Compared with existing systems that rely on separate communication and ranging units, this approach reduces system complexity, Size, Weight, and Power (SWaP), and integration effort. It offers much higher precision than conventional Radio Frequency (RF)-based ranging and enables more accurate real-time tracking and trajectory determination. Its scalability makes it adaptable to different mission profiles, while CCSDS O3K alignment improves interoperability and future market potential. In addition, the project provides a validated reference implementation that creates a strong basis for future standardization and commercial optical terminal development.
Features
The product combines high-speed optical communication and high-resolution ranging in one architecture, using the physical layer of the CCSDS O3K signal for distance measurement without affecting data transmission. It supports scalable data rates from 0.625 to 10 Gbps and delivers very high reporting cadence, up to 100 kHz, for dense real-time ranging data. The solution was validated experimentally across multiple test cases and demonstrated sub-nanometer precision in stable conditions. It is also suitable for high-dynamic missions such as LEO and lunar applications.
Challenges
The main challenges identified concern performance degradation under non-ideal conditions and system configuration dependencies. While the system achieves extremely high precision in stable, low-attenuation scenarios, atmospheric turbulence significantly impacts measurement accuracy, reducing precision to decimeter levels.
Additionally, absolute measurement error varies with transmitter speed and frame structure, requiring careful optimisation of system parameters. Maintaining high accuracy across different operating conditions and configurations, while ensuring reliable identifier correlation, remains a key challenge. Balancing high data rates with measurement trueness and robustness is also critical for consistent real-time ranging performance.
System Architecture
The system architecture is based on a bidirectional free-space optical link between a ground station and a spacecraft. On both sides, Microchip SERDES transceivers generate and process the high-speed communication signal, which is interfaced to the optical domain through SFP+ optical modules. These modules provide the connection between the electrical communication hardware and the optical transmission path.
To emulate realistic operational conditions during development and testing, the propagation channel between the ground station and spacecraft is represented by a fibre-based atmospheric turbulence simulator. This simulator uses intensity modulators to reproduce the effects of atmospheric disturbances on the optical signal, including fluctuations that would occur in a real free-space link. Such an architecture enables controlled laboratory validation of both communication and ranging performance under representative channel conditions, while preserving the same signal structure and hardware interfaces intended for the final system.
Plan
The project plan was structured around key development and review phases. It began with the Preliminary Design Review (PDR), confirming requirements and the initial technical concept.
The Detailed Design Review (DDR) validated the complete design of the optical ranging solution and breadboard. The Test Readiness Review (TRR) marked the transition to verification, confirming readiness for performance testing.
The final phase concluded with the Final Review (FR), where test results, technical feasibility, and project outcomes were assessed, including inputs for CCSDS reference documentation.
Current Status
The project has progressed from concept to a validated technology demonstrator. Its main achievement is the successful development and testing of a system enabling simultaneous optical communication and ranging based on the CCSDS O3K standard. The demonstrator was verified under simulated atmospheric turbulence for MEO, GEO, and Deep Space scenarios, as well as in laboratory noise conditions.
Testing confirmed extremely high precision under stable links, with sub-nanometer repeatability, while maintaining acceptable performance under turbulence. The core functionality has therefore been demonstrated, and the project can be considered completed at the demo stage, providing a basis for further operational development and refinement.
