May 19, 2007: Both India and Pakistan are using radar aerostats (blimps) to fill in the many gaps in the radar coverage of their mutual border. India is getting theirs from Israel, while the United States is providing aerostats to Pakistan. India already has two aerostats, bought three years ago, and is getting four more. It needs a total of 13 to cover all its borders. Pakistan is getting six L-88 Aerostat Systems. Indias decision to move ahead on its aerostat system is, in part, motivated by the recent success of LTTE rebels in Sri Lanka, using single engine commercial aircraft to bomb military targets (without much success, but the potential of such low flying aircraft was demonstrated.)

Aerostat systems use a 100-250 foot long, helium filled, unmanned blimp equipped with radar and other sensors. The larger of these blimps are more than twice the size as the more familiar advertising blimps. An aerostat is designed to always turn into the wind and stay in the same place. An aerostat is unpowered, and secured by a cable that can keep the aerostat in position at its maximum altitude of 15,000 feet. At that altitude, a large aerostat can carry a two ton payload. The cable also supplies power, which means the blimp can stay up for about 30 days at a time before it has to be brought down for maintenance on its radars. Often, two radars are carried. One is a surveillance radar, the other is a precision track and illumination radar (PTIR). The surveillance radar provides long-range coverage (nearly 400 kilometers), while the PTIR, which is a steerable system capable of tracking multiple targets, can focus in on items of interest.

Aerostat systems cost varies from $5 million, to over $100 million each, depending on the size of the aerostat and the capabilities of the radar and other sensors. Aerostats work. Kuwait had one in 1990, and the ground radar spotted the Iraqis as soon as they crossed the border. The U.S. uses dozens of aerostat systems in Iraq and Afghanistan, to guard bases.