Ground-based demonstration of the European Laser Timing (ELT) experiment

Area of Science:

• Metrology and fundamental physics research
• Optical frequency standards
• Time and frequency transfer

Background:

• Current microwave-based clock comparison systems (GPS, TWSTFT) face limitations.
• Advancements in optical frequency standards necessitate improved time transfer links.
• The European Laser Timing (ELT) is an optical link concept for the Atomic Clock Ensemble in Space (ACES) mission.

Purpose of the Study:

• To assess the feasibility of the ELT optical time transfer link.
• To evaluate key components and functionalities of the ELT system before space deployment.
• To validate the performance of a proposed space-based clock comparison technique.

Main Methods:

• A ground-based feasibility study was conducted at the Geodetic Observatory Wettzell.
• Utilized ordinary satellites equipped with laser reflectors.
• Implemented an independent detection port and laser pulse timing unit with a separate time scale for evaluation.

Main Results:

• The study successfully evaluated critical aspects of the ELT time transfer link.
• Demonstrated the capability to time tag laser pulses detected by a single-photon avalanche diode (SPAD).
• Confirmed the potential for precise ranging information using a corner cube retro-reflector (CCR).

Conclusions:

• The ground-based feasibility study validates the ELT concept for future space missions.
• The results support the development of advanced optical time transfer systems for metrology and fundamental physics.
• This research paves the way for enhanced precision in distributed time scales and clock comparisons.