Development of Resilient Time and Frequency Distribution from Low Earth Orbit using Nanosatellites

该项目将评估由专门的低地球轨道(LEO)纳米卫星组成的大型星座提供的、覆盖全球27/4的替代定位、导航和授时服务的可行性。与具有中地球轨道(MEOS)卫星的成熟全球导航卫星系统(GNSS)相比，来自LEO纳米卫星星座的测距信号的分布为PNT提供了一些潜在的优势。它使APNT系统能够：-提高对地面有意和无意干扰的恢复能力；-提供可用于验证和增强基于GNSS的PVT解决方案的冗余PVT解决方案，以抵御欺骗企图和恶劣的电磁传播条件；--提供备用PVT解决方案，以防因任何系统故障而导致全球停机(例如，2016年1月的全球定位系统或2019年7月的伽利略系统，参见：https://insidegnss.com/lessons-to-be-learned-from-galileo-signal-outage/)；-通过利用将以相对较低的成本在星座中部署的纳米卫星的能力以及它们利用已有的在较高高度轨道上飞行的全球导航卫星系统卫星的能力，以具有成本效益的方式获得类似全球导航卫星系统的服务。为了评估这种全球导航卫星系统服务的可行性，该项目将研究目前的技术水平，详细阐述具有成本效益的系统的初步设计和制约因素，并部署实验室概念演示，以评估向地面最终用户接收器提供的全球导航卫星系统服务的质量。

This project will assess the feasibility of an alternative Positioning, Navigation and Timing (aPNT) service with 27/4 global coverage, provided by a large constellation of dedicated Low Earth Orbit (LEO) nanosatellites. Compared to well-established Global Navigation Satellite Systems (GNSS) with satellites in Medium Earth Orbits (MEOs), the distribution of ranging signals from a constellation of nanosatellites in LEO offers a few potential advantages for PNT.It enables the aPNT system to: -- Improve resilience to on-ground intentional and unintentional interference; -- Deliver a redundant PVT solution that can be used to validate and enhance the PVT solution based on GNSSs against spoofing attempts and harsh electromagnetic propagation conditions; -- Provide a back-up PVT solution in case of any global outage due to any system failure (e.g., GPS in January 2016 or Galileo in July 2019, see: https://insidegnss.com/lessons-to-be-learned-from-galileo-signal-outage/); -- Give access to a GNSS-like service in a cost-effective manner by leveraging the ability of nanosatellites to be deployed in a constellation at relatively low cost as well as their capability to exploit already existing GNSS satellites flying at higher-altitude orbits.To assess the feasibility of such aPNT service, the project will study the current state of the art, elaborate the preliminary design and constraints of a cost-effective system, and deploy a laboratory concept demonstration to assess the quality of the aPNT service to the end user receiver on ground..