Three Glonass-M spacecraft Cosmos 2459 (Glonass 731), Cosmos 2461 (Glonass 735) and Cosmos 2460 (Glonass 732) were added to the Russian global navigation satellite system. They were launched by a Proton-M rocket with a Block DM upper stage from Baikonur on 01 March 2010 at 21:19 UT. Each spacecraft has a mass of 1360 kg and are designed to last seven years. The GLONASS system requires satellites in three orbital planes and global service requires 24 satellites. As of 01 March 2010 the constellation consisted of 18 operational satellites. These recent additions to the constellation will occupy the third plane, orbital slots 22, 24, and 23, respectively.