Indian Armed Forces have used imagery from ISRO civil satellites since the early 1990s.

Most civil satellites can be used for military purposes. Someone just has to analyze the data, which is a lot of grunt work. Most militaries use commercially available imagery from satellites. Western analysts have managed to keep track of Chinese missile and nuclear submarine deployment using Google Earth! 

Imagery from the TES satellite launched in 2001 using PSLV-C3 has been used by the Indian Military. The satellite provides sub 1m resolution in the visual spectrum. 

RISAT-2, launched in  with an Israeli X-Band SAR has the most advanced surveillance capabilities amongst Indian satellites in orbit.  The 300 kg can take 1 m resolution images at night and through clouds.

DRDO Chief Saraswat's announcement signals India's decision not to be coy about its military satellite program. The shift in policy probably stems from the knowledge that its military satellite program will not attract US sanctions against ISRO as would have happened in the past.

“We are looking at launching one or two satellites every year to fulfill the requirements of all three military formations,” Saraswat said.

“Once these satellites are operational, we will be able to see troop movements along the borders,” he added. “The key is high-resolution images with precision.

“The army, the navy and the air force have varied requirements, and it won’t be appropriate to give the numbers.

"Data and commands can be sent through these satellites to cruise missiles.”

The satellites will be developed and launched by ISRO based on requirements projected by the armed forces.

The satellite is being developed with a budget of Rs 100 crore by theDefense Electronics Research Laboratory (DLRL) under the Defense Research and Development Organization (DRDO).

The existence of the project was revealed on Tuesday, February 2010 by DLRL director G. Bhoopathy.

"We are in the process of designing and developing a spacecraft fitted with an intelligent sensor that will pick up conversations and communications across the borders," he told reporters in Bangalore before the start of the first international conference on electronic warfare (EWCI 2010).

The satellite will feature a Synthetic Aperture Radar (SAR) and be used for imaging and communication. It will be capable of detecting conversations and espionage activities in the region.

“The satellite will orbit Earth at 500 km. and cover hostile regions in the area by passing on surveillance data to intelligence agencies,” G. Bhoopathy, DRDL director told AW&ST in November 2010.

The satellite will be launched in the lower earth orbit — about 500 km above the earth — on board the polar satellite launch vehicle (PSLV).

The satellite, which will be operational by 2014, will also serve as a test bed for anti-satellite weapon development.

A dedicated satellite to facilitating Naval communication and network centric warfare will be launched into geostationary orbit by ISRO in FY 2012-13. [via PIB]

Defense Minister, AK Antony announced the project during Senior Naval  Officers Conference in New Delhi on October 22, 2009. The satellite was initially planned to be launched in 2010, but the project has been delayed.

The satellite will facilitate networking of IN warships, submarines and aircraft among themselves as well as with operational centres ashore through high-speed data-links, allowing Maritime threats to be detected and shared in real-time to ensure swift reaction.

The multi-band satellite will weigh 2,330 kg. (5,137 lb.).

The satellite will provide coverage over a 600 x 1,000 nm area of the Indian Ocean Region (IOR), which India considers to be its primary area of responsibility in terms of maritime security.

The project cost is Rs 950 crore. 

The first dedicated IAF communication satellite is scheduled for launch in FY 2013-14, after the Navy satellite due to be launched in 2012-13. [via PIB]

The satellite was initially scheduled to be launched in July 2009, according to a PTI report on November 18, 2008. In early January 2009, the IAF Chief said the IAF satellite will be launched in 2010. Later, it was reported that the satellite would be launched in 2011-12, 

The launch schedule of both the Navy and IAF satellites got disrupted due to back-to-back failures of the GSLV in 2010.

According to IAF Chief Fali H. Major, the satellite will serve as the air force's eye in the skies. It will link up the six AWACS that the IAF is acquiring with each other as well as other ground and airbased radars.