MOSCOW, July 31: An upgraded Russian unmanned spacecraft successfully linked up with the International Space Station on Sunday on its second attempt to test a new docking system, Russia’s space agency said. The docking set aside doubts over the new Kurs-NA rendezvous system that will deliver astronauts and future cargoes to the orbital station after a botched first test when the equipment malfunctioned due to low temperatures earlier this week. (agencies)