PARIS — The Russian government, which in late 2011 succeeded in returning its Glonass positioning, navigation and timing satellite constellation to fully operational status, plans to launch three more Glonass satellites in the first half of 2012 and to spend some 20.5 billion roubles ($642 million) on the program this year, the Russian space agency, Roscosmos, announced Jan. 17.

Despite the loss of three Glonass spacecraft in a December 2010 Proton rocket failure caused by a fueling error, Glonass is an acknowledged Russian space success story. The constellation, which briefly reached its full operational strength of 24 functioning satellites in 1996, suffered from Russia’s financial crisis and by 2002 had only eight fully functioning spacecraft in orbit.

Since then, the government has made Glonass a consistent investment priority. The earlier generation of satellites, with a design life of just three years, were replaced, starting in 2003, with the Glonass-M spacecraft, which are designed to function for seven years in medium Earth orbit.

In February 2011, the first next-generation satellite, called Glonass-K1, was launched. It has an operating life of 10 years in addition to offering more-accurate timing and more operating signals.

Roscosmos said that in the first half of 2012, two more Glonass-M and one Glonass-K spacecraft will be launched. A heavy-lift Proton rocket, which carries three Glonass spacecraft at a time, and two medium-lift Soyuz vehicles, each carrying a single Glonass, have been reserved for the near-term Glonass deployment.

In addition to the Glonass satellites, Russia has been investing in its SDCM Glonass-augmentation capability, whose design is similar to the U.S. Wide-Area Augmentation System, Europe’s Egnos and Japan’s MSAS. China is developing a similar architecture.

All these systems use terminals hosted on telecommunications satellites in higher geostationary orbit to verify the accuracy of the positioning, navigation and timing signals provided by constellations in lower orbit.

In December, a Russian Proton rocket launched the Loutch 5A data-relay satellite, which includes an SDCM Glonass-verification payload. Loutch 5A will operate at 16 degrees west in geostationary orbit. Two more Loutch satellites, to be positioned at 95 degrees east and 167 degrees east longitude, are scheduled for launch in 2012 and 2013.

ISS Reshetnev of Krasnoyarsk, Russia, the manufacturer of the Glonass satellites, said that of the 31 Glonass spacecraft currently in orbit, 24 are operational and in service, three are being commissioned, one is an in-orbit spare and two are in maintenance. The inaugural Glonass-K satellite launched in February is still being tested, Reshetnev said.

Peter B. de Selding was the Paris bureau chief for SpaceNews.