MOSCOW, July 31 (Reuters) - The head of Russia"s Roscosmos space agency said on Saturday that pressure in a Russian service module on the International Space Station had dropped as a result of an air leak. Pressure had fallen over a two-week period before a Russian research module, the Nauka, threw the station out of control when its engines fired shortly after docking on Thursday, but Roscosmos head Dmitry Rogozin said the two events were not linked. The fall in pressure was a result of a known minor air leak in an isolated transfer chamber of the Zvezda service module and pressure will be raised in the next 24 hours, Roscosmos said in a statement. "It was an expected and not a "sharp" drop in the still problematic Zvezda and it is not linked to the research module," Rogozin tweeted in response to media reports. Pressure in the service module dropped on July 29, the day the Nauka research module docked, to about one third of its level on July 14 but would be increased, Rogozin tweeted. The air leak in the Zvezda module, which provides living quarters for crew members and life support systems, was detected last year. It poses no danger to the crew but persists despite attempts to fix it by sealing cracks. Russia said on Friday that a software glitch, and possible lapse in human attention, were to blame for an emergency caused by inadvertently reignited jet thrusters of the Nauka research module. read more On Saturday, Russian crew entered the research module after the air was tested and cleaned, Rogozin tweeted. Russia held a scientific council meeting on Saturday to discuss the future use of the Russian segment of the space station, which was sent into orbit in 1998 and is supposed to work until 2028. "The chief constructors council noted after considering the current condition of the Russian ISS segment that the use of the Russian ISS segment after 2024 creates additional risks due to the ageing of equipment," Roscosmos said.