MOSCOW, March 31. /TASS/. The first launch of Russia’s Proton-M carrier rocket this year is scheduled for the end of May, Chief Designer for Launch Vehicles and Ground Infrastructure Alexander Medvedev said on Friday.

"The first launch is planned for the end of May," the chief designer said.

The launch of an EchoStar 21 spacecraft was planned back last year but was delayed over problems found in the engines of a Proton-M carrier rocket.

A total of seven Proton carrier rocket launches are planned until the end of this year under the federal space program and in the interests of commercial customers.

Russia’s State Space Corporation Roscosmos earlier recalled for tests all the engines mounted on the second and the third stages of Proton-M carrier rockets and produced at the Voronezh Mechanical Factory.

According to Roscosmos, a more expensive solder failing to meet the requirements specification was used by the factory as part of the engine production.

Roscosmos also gave instructions to replace the engines produced by this factory and mounted on the third stages of Soyuz-U and Soyuz-FG carrier rockets intended for launches to the International Space Station. The engines had to be replaced after an accident with a Soyuz-U carrier rocket on December 1, 2016, which resulted in the crash of a Progress MS-04 space freighter.

After Roscosmos officials visited the Voronezh Mechanical Factory on January 20, Factory Director Ivan Koptev resigned of his own free will over the unsatisfactory work and quality of the enterprise’s output.