Prime Minister Dmitry Medvedev on Friday issued an official reprimand to the head of Russia\'s space agency Roscosmos after a series of embarrassing rocket launch failures. The official reprimand essentially represents a warning to Roscosmos chief Vladimir Popovkin that he faces the sack if he does not rectify the stated shortcomings in his work. \"The head of the federal space agency Vladimir Popovkin must be given a reprimand for improperly carrying out his professional duties,\" said the document signed by Medvedev and released by the Russian government. Russia on July 2 suffered one of its worst space failures of recent years when a Proton-M rocket carrying a navigation satellite exploded shortly after launch from the Baikonur cosmodrome in Kazakhstan. That failure came after a string of botched unmanned launches in the last two years seriously tarnished the reputation of the Russian space programme. After the withdrawal of the US shuttle, Russia is now the sole nation capable of transporting humans to the International Space Station (ISS). Popovkin, a former defence ministry official, has been in charge of Roscosmos since April 2011.