Phys.org April 26, 2021
Microwave-based satellite–ground links cannot fully satisfy the requirements of metrology, navigation, positioning, and very long baseline interferometers. Researchers in China investigated the possibility of an optical-based satellite–ground link, where the transferred carriers are pulsed lasers, resulting in a link with a high time resolution and a large ambiguous range. They analyzed the parameters of satellites in different orbits and concluded that high-orbit links enable more stable time–frequency comparison or dissemination by taking advantage of the long duration, a large common view range, and the lower relativistic effects. They performed a 16 km free-space transfer experiment to simulate links in the loss, noise, and delay effects. The link exhibited an instability and an approximately 10 fs time deviation with an average loss of 72 dB, corresponding to the loss of a satellite–ground link at geostationary earth orbit. Based on these results, they expect that the instability of the time–frequency transfer via a GEO link might reach 10−18 at 10,000 s…read more. Open Access TECHNICAL ARTICLEÂ
Satellite–ground optical time–frequency dissemination diagram with different orbit types… Credit: Optica Vol. 8, Issue 4, pp. 471-476 (2021)Â