* Raytheon "JLENS" program could get boost * Tethered aerostats would feed into existing defenses * Aerostats work in pairs, may stay aloft 30 days By Jim Wolf WASHINGTON, Feb 1 (Reuters) - A pair of big, blimp-like craft, moored to the ground and flying as high as 10,000 feet (3,000 metres), are to be added to a high-tech shield designed to protect the Washington D.C. area from air attack, at least for a while.