Celeste: paving the way towards Positioning, Navigation and Timing in Low Earth Orbit (LEO-PNT)

Marco Anhileri

Positioning, Navigation, and Timing (PNT) services enabled by Global Navigation Satellite Systems are foundational to the functioning of modern society. Despite the significant impact of PNT in economy and society, GNSS systems face well-documented limitations. Low Earth Orbit (LEO) satellites have emerged as a promising solution to address these challenges. ESA’s LEO-PNT initiative, is named Celeste, in honour of Galileo Gaillei’s daughter. Celeste includes the on-going In-Orbit Demonstrator (IOD) phase and the upcoming In-Orbit Preparatory (IOP) phase. Celeste IOD aims at demonstrating services with final users and at validating enabling technologies such as frequency-diverse signal generation and transmission, on-board orbit determination and time synchronization, and advanced small satellite platforms, to demonstrate the feasibility and benefits of augmenting existing GNSS with a LEO-based layer. The next phase, the Celeste In-Orbit Preparatory (IOP) phase will encompass the development of pre-operational technologies, their industrialisation and in-orbit validation. ESA is working with the European Union towards defining a potential EU LEO-PNT operational system in complement to EGNOS and Galileo. This Celeste IOP phase will be instrumental in shaping future EU LEO-PNT and also to support industry for commercial opportunities.