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Debris laser ranging (DLR) is receiving considerable attention as an accurate and effective method of determining and predicting the orbits of space debris. This paper reports some technologies of DLR, such as the high pulse repetition frequency (PRF) laser pulse, large-aperture telescope, telescope array, multi-static stations receiving signals. DLR with a picosecond laser at the Shanghai Astronomical Observatory is also presented. A few hundred laps of space debris laser-ranging measurements have been made. A double-pulse picosecond laser with an average power of 4.2 W, a PRF of 1 kHz, and a wavelength of 532 nm has been implemented successfully in DLR, it's the first time that DLR technology has reached a ranging precision at the sub-decimeter level. In addition, the characteristics of the picosecond-pulse-width laser transmission with the advantages of transmission in laser ranging were analyzed. With a mode of the pulse-burst picosecond laser having high average power, the DLR system has tracked small debris with a radar cross-section (RCS) of 0.91 m2 at a ranging distance up to 1726.8 km, corresponding to an RCS of 0.1 m2 at a distance of 1000 km. These works are expected to provide new technologies to further improve the performance of DLR. [ABSTRACT FROM AUTHOR]

The Time Transfer by Laser Link (T2L2) project allows for the synchronization of remote ultrastable clocks over intercontinental distances. The principle is derived from the satellite laser ranging technology with a dedicated space equipment designed to record arrival times of laser pulses at the satellite. The space segment was launched in 2008 as a passenger instrument on the ocean altimetry satellite Jason 2. For the first time, we have conducted by the end of 2016 a dedicated time transfer comparison campaign between Global Positioning System and T2L2 over intercontinental distances. The campaign was carried out between two laboratories in Europe and two in China. The campaign has demonstrated a consistency of the time transfer techniques at the 1-ns level, together with the confirmation of a subnanosecond level for continental distances. [ABSTRACT FROM AUTHOR]

Laser time transfer is of great significance in timing and global time synchronization. However, the temperature drift may occur and affect the delay of the electronics system, optic generation and detection system. This paper proposes a post-processing method for the compensation of temperature-induced system delay, which does not require any changes to the hardware setup. The temperature drift and time stability of the whole system are compared with and without compensation. The results show that the propagation delay drift as high as 240 ps caused by temperature changes is compensated. The temperature drift coefficient was diminished down to ~0.05 ps/°C from ~20.0 ps/°C. The system precision was promoted to ~2 ps from ~11 ps over a time period of 80,000 s. This method performs significant compensation of single-photon laser time transfer system propagation drift and will help to establish an ultra-stable laser time transfer link in space applications. [ABSTRACT FROM AUTHOR]

The mission of Chinese Space station is underway in China and the different type of clock systems will be carried and high stability and accuracy of time transfer is demanded. Laser Time Transfer (LTT) will be implemented between ground and Space Station and the LTT payload is being developed by Shanghai Astronomical Observatory (SHAO) with the time comparison single shot precision of 60ps, stability of less than 1ps @ 300s, and 1ps @ 1day. This paper will introduce the progress of LTT payload, including the design of the detector and timer, the optical design, testing results of the system stability and the future developments of this project. [ABSTRACT FROM AUTHOR]

The mission of Tiangong2 is the China's second manned space laboratory for further verifying the space rendezvous and docking technology and a series of space tests. The Laser Retro-reflector Array (LRA) for Satellite Laser Ranging (SLR) is designed to evaluate the precision of orbit determination and the global SLR measurements are performed under the support of ILRS with the coordination of SHAO and CSU and lots of laser data are obtained and used for centimeters-level precise orbit determination. Additionally, Laser Radar Retro-reflector Array (LRRA) is also designed for space rendezvous and docking mission. Because of its large size, the SLR station will receive echoes from the both arrays. The effective reflection area calculation model of LRA relative to ground station is established, and the influence of LRRA on the observation of LRA is also analyzed in this presentation. It makes the guidance for the acquisition of high precision observation data, and the scientific suggestions for the development of the LRRA in future. [ABSTRACT FROM AUTHOR]