XICHANG, Sichuan Province - Chinese scientists are to conduct a laser-ranging test between the relay satellite of the Chang'e-4 lunar probe and an observatory on the ground, which might help lay the foundation for space-based gravitational wave detection.The relay satellite Queqiao, or Magpie Bridge, which was launched Monday, will fly to a halo orbit around the second Lagrangian point (L2) of the Earth-Moon system. It will be a communication link between controllers on Earth and the Chang'e-4 lunar probe, which is expected to soft-land on the far side of the Moon at the end of this year.Chinese scientists will also conduct a laser-ranging test with the satellite at a maximum distance of 460,000 km, a record distance for an experiment of its kind, said Zhang Lihua, manager of the relay satellite project.China has reportedly accomplished its first successful lunar laser-ranging, with a 1.2-meter telescope at southwest China's Yunnan Observatories on Jan. 22 this year, when scientists measured the distance between the Moon and the Earth, based on the signals of laser pulses reflected by the lunar retro-reflector planted by the U.S. Apollo mission more than 40 years ago.Scientists calculated the time a laser pulse takes to travel from a ground station to the retro-reflector on the Moon and back again to get a measurement.Just a few countries, including the United States, France and China, have successfully harnessed the lunar laser-ranging technology.The Queqiao satellite, carrying a reflector developed by Sun Yat-sen University, is expected to extend laser-ranging to a new record distance.As the satellite will fly at a constant high speed, it will be extremely hard for the laser beam from the ground to target the reflector on the satellite about 460,000 km away.Luo Jun, an academician of the Chinese Academy of Sciences and president of Sun Yat-sen University, has proposed a space science program to detect gravitational waves. Laser-ranging is a necessary technology for that detection. rubber bracelets canadablue silicone wristbandsblue rubber bracelet meaningcustom made bracelets ukorder rubber bracelets cheap
As part of China's efforts to press ahead with smart city development and build itself into a technology-driven economy, the country will hold the fourth China Smart City International Expo in Shenzhen from Aug 21 to 23.According to organizers, more than 400 enterprises and organizations related to smart cities are expected to attend the expo, which will be held at the Shenzhen Convention and Exhibition Center. The exhibition area for this year's expo will cover 30,000 square meters.The annual event will feature exhibitions, forums, signing ceremonies on project cooperation and other activities, with the aim of providing a platform for governments, enterprises and institutions from across the world to share their experiences in smart city building and carry out cooperation in the field.An international forum on smart city development in the Guangdong-Hong Kong-Macao Greater Bay Area will invite politicians and business leaders from the world's three other bay areas, who will discuss their experiences in the sector, providing insights for China's development.Another forum on engineering management in smart city development will be held on the sidelines of the expo.Shenzhen epitomizes the country's reform and opening-up efforts over the past 40 years and the city has led the country in smart city development, said Feng Kui, director of the academic committee of the China Center for Urban Development and one of the event organizers.We are going to hold the expo in Shenzhen because we want to showcase our country's achievements over 40 years of reform and opening-up, especially in smart city building, he said at the event's press conference on Tuesday.We hope to demonstrate Shenzhen's efforts, and the country's exploration and innovation in smart city development.The event is co-organized by the China Center for Urban Development, the Shenzhen municipal government, Ping An Insurance and the Smart City Development Alliance.It is the fourth year for the expo to be held. More than 500 exhibitors showcased their achievements in smart city development over the previous three years, with the cumulative visitor count reaching 300,000.
