GLONASS, Russia's Global Navigation Satellite System, is critical not just for Russian strategic interests, but also those of India.

The system requires 18 satellites for continuous navigation services covering the entire territory of the Russian Federation, and 24 satellites to provide services worldwide.

The satellites orbit in three planes, with eight satellites in each plane. Six satellites are kept in reserve, two in each plane. 

In the event of a satellite failing, a reserve is positioned to fill the slot. This can take between several days and several weeks – depending on how far the reserve satellite is from the position it needs to assume.

Russia currently has a total of 23 operational GLONASS satellites in orbit, with an additional eight satellites undergoing in orbit tests or maintenance.

A Glonass-M satellite was launched on November 28, 2011 The satellite was deployed in the third orbital plane of the constellation.

A Glonass-M satellite was launched on October 3, 2011 using a Soyuz-2.1b Launcher from the Plesetsk launch site. The launcher, equipped with a Fregat boost stage, successfully placed the satellite in its correct  orbit.

A Glonass-K satellite was successfully launched on February 26, 2011. The Glonass-K has a life of 10-12 years.

In December 2010, an attempt to launch three more GLONASS-M satellites failed after the rocket carrying them deviated from its path and plunged into the Pacific Ocean northwest of Hawaii.

Three Glonass satellites were successfully launched on a Proton M rocket on Thursday, September 2, 2010.

A Proton M carrier rocket bearing three Glonass satellites was launched from the Baikonur space center in Kazakhstan on early Tuesday, March 2, 2010.

Six new GLONASS satellites were added to the network in 2008 and three more on December 14, 2009.

GLONASS satellites transmit two types of signal: a standard precision (SP) signal and an obfuscated high precision (HP) signal.

The system requires 18 satellites for continuous navigation services covering the entire territory of the Russian Federation, and 24 satellites to provide services worldwide.

At peak efficiency, the SP signal offers horizontal positioning accuracy within 57-70 meters, vertical positioning within 70 meters, velocity vector measuring within 15 cm/s, and timing within 1 µs, all based on measurements from four satellite signals simultaneously.

The more accurate HP signal is available for authorized users, such as the Russian Military.

Russia initiated modernization of the GLONASS system with the launch of GLONASS-M satellites which have better signal characteristics and a longer design life of 7-8 years. (Earlier GLONASS satellites had a design life of just 3 years). 

A low mass third generation GLONASS-K satellite with a guaranteed lifespan of 10 years will be succeed  the GLONASS-M satellite. 

The  935-kg GLONASS-K uses the the new Ekspress-1000 platform developed by NPO PM design bureau (later renamed ISS Reshetnev) and uses a lighter, standardized unpressurized bus. 

The satellite five navigation signals - four in the special L1 and L2 bands and one for civilian applications in the L3 band. The satellite will facilitate more accurate navigation.

A follow-up version of the GLONASS-K, the  GLONASS-K2, will introduce a new type of navigation signal with so-called code-protected selection. The first K2 satellite is expected to be launched in 2013.

Under an agreement with India signed in January 2004, Russian Space Agency (RSA) committed to make the system operational with 24 satellites by 2010. A constellation of 18 GLONASS satellites not only provide full coverage to Russian they also cover India.

During a December 2005 summit between Indian Prime Minister Manmohan Singh and Russian President Vladimir Putin, it was agreed that India would share some of the development costs of the GLONASS-K series.

On December 21, 2010, during the visit of Russian President Dmitry Medvedev to India for the annual summit, Russia and India signed a agreement to share high precision signals.

Earlier, during the visit to New Delhi by Russian PM Vladimir Putin on March 12, 2010, a preliminary agreement was inked to allow India access to the military signals of the GLONASS system. [ via Aviation Week]

India is the first country that has been given access to the military signal. 

On August 25, while speaking at the Bengaluru Space Expo 2010,  Brahmos CEO Sivathanu Pillai said that the BrahMos missiles was equipped with Glonass receivers to acquire and effectively engage targets. He said the receivers performed reliably and consistently.