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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]

Abstract Space debris laser ranging with a 4.2 W double-pulse 532 nm picosecond laser at a pulse repetition frequency of 1 kHz was achieved at the Shanghai satellite laser ranging (SLR) station, which receiving telescope was 60 cm. Space debris' radar cross sections were from 2 m2 to 12 m2, and ranging precision was up to centimeters. A compound regenerative amplifier was used to realize double pulses output with pulse space of 4.1 ns. Double pulses would have the same detection ability as the equal energy single pulse. A 500 μm diameter avalanche photo-diode detector with less than 10 kHz dark noise and a quantum efficiency of 40% at 532 nm was developed to improve the measurement capability. And also a spectral filter with high efficiency and narrow bandwidth were applied. Basing on the Shanghai SLR system, the laser ranging to space debris with picosecond laser at 1 kHz was successfully implemented for the first time among the global SLR stations. The results showed that the ranging precision root-mean-square can be achieved about 5 cm. It will be very useful to monitor and study the space debris. [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]

The article reports on the April 8, 2012 end of the Environmental Satellite (Envisat) mission. A discussion of range measurements to the satellite that allowed determination of the attitude and the spin period of Envisat during seven months of 2013 which were performed by Satellite Laser Ranging (SLR) stations, and found the spin axis of the satellite is 2.52 meters and causes the meter-scale oscillations of the range measurements between the ground SLR system and the satellite, is presented.

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 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]