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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]

Abstract: In view of the severe steam channeling in the steam flooding of super heavy reservoir, lab experiment on steam channeling control were carried out. The combination of nitrogen foam and thermoset blocking agent was tested to seal steam channeling, in which thermoset blocking agent plugs big pore throats, while nitrogen foam adjusts steam absorption profile. The optimized foam formulation has a resistance factor of over 30 at 300 °C, can plug low oil saturation areas selectively, and applies to the plugging of high permeability zones in super-heavy oil reservoirs. Thermoset blocking agent, which would consolidate at 120 °C in 4 h and consolidate at 150 °C in 2 h, can provide effective plugging during dynamic steam flooding. The best steam channeling control mode was determined using parallel tube model. By the combination of nitrogen foam and thermoset blocking agent, the recovery rate is 5.7% higher than the application of nitrogen foam only, with the overall sweeping efficiency reaching up to 60.8%. In 2011, the mode was used in the steam flooding in Shan-56 reservoir. The water cut drops 10.2%, the wellhead temperature of producer drops more than 15 °C, the oil production of the well group increases over 28 tons per day, the valid period of a single cycle is up to 198 days, and the oil production increases 2 562 t, showing significant improvement in steam flooding. [Copyright &y& Elsevier]

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]

Abstract: High-precision time synchronization between satellites and ground stations plays the vital role in satellite navigation system. Laser time transfer (LTT) technology is widely recognized as the highest accuracy way to achieve time synchronization derived from satellite laser ranging (SLR) technology. Onboard LTT payload has been designed and developed by Shanghai Astronomical Observatory, and successfully applied to Chinese Beidou navigation satellites. By using the SLR system, with strictly controlling laser firing time and developing LTT data processing system on ground, the high precise onboard laser time transfer experiment has been first performed for satellite navigation system in the world. The clock difference and relative frequency difference between the ground hydrogen maser and space rubidium clocks have been obtained, with the precision of approximately 300ps and relative frequency stability of 10E−14. This article describes the development of onboard LTT payload, introduces the principle, system composition, applications and LTT measuring results for Chinese satellite navigation system. [Copyright &y& Elsevier]

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]